builder: fixed a problem with multiple process build cases

Signed-off-by: deadprogram <ron@hybridgroup.com>

.circleci/config.yml

@@ -68,14 +68,17 @@ commands:
     steps:
       - restore_cache:
           keys:
-            - llvm-source-11-v1
+            - llvm-source-11-v2
       - run:
           name: "Fetch LLVM source"
           command: make llvm-source
       - save_cache:
-          key: llvm-source-11-v1
+          key: llvm-source-11-v2
           paths:
-            - llvm-project
+            - llvm-project/clang/lib/Headers
+            - llvm-project/clang/include
+            - llvm-project/lld/include
+            - llvm-project/llvm/include
   build-wasi-libc:
     steps:
       - restore_cache:
@@ -154,12 +157,15 @@ commands:
       - llvm-source-linux
       - restore_cache:
           keys:
-            - llvm-build-11-linux-v2-assert
+            - llvm-build-11-linux-v3-assert
       - run:
           name: "Build LLVM"
           command: |
             if [ ! -f llvm-build/lib/liblldELF.a ]
             then
+              # fetch LLVM source
+              rm -rf llvm-project
+              make llvm-source
               # install dependencies
               sudo apt-get install cmake ninja-build
               # hack ninja to use less jobs
@@ -167,9 +173,10 @@ commands:
               chmod +x /go/bin/ninja
               # build!
               make ASSERT=1 llvm-build
+              find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
             fi
       - save_cache:
-          key: llvm-build-11-linux-v2-assert
+          key: llvm-build-11-linux-v3-assert
           paths:
             llvm-build
       - run: make ASSERT=1
@@ -218,12 +225,15 @@ commands:
       - llvm-source-linux
       - restore_cache:
           keys:
-            - llvm-build-11-linux-v2-noassert
+            - llvm-build-11-linux-v3-noassert
       - run:
           name: "Build LLVM"
           command: |
             if [ ! -f llvm-build/lib/liblldELF.a ]
             then
+              # fetch LLVM source
+              rm -rf llvm-project
+              make llvm-source
               # install dependencies
               sudo apt-get install cmake ninja-build
               # hack ninja to use less jobs
@@ -231,9 +241,10 @@ commands:
               chmod +x /go/bin/ninja
               # build!
               make llvm-build
+              find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
             fi
       - save_cache:
-          key: llvm-build-11-linux-v2-noassert
+          key: llvm-build-11-linux-v3-noassert
           paths:
             llvm-build
       - build-wasi-libc
@@ -287,29 +298,36 @@ commands:
             - go-cache-macos-v2-{{ checksum "go.mod" }}
       - restore_cache:
           keys:
-            - llvm-source-11-macos-v1
+            - llvm-source-11-macos-v2
       - run:
           name: "Fetch LLVM source"
           command: make llvm-source
       - save_cache:
-          key: llvm-source-11-macos-v1
+          key: llvm-source-11-macos-v2
           paths:
-            - llvm-project
+            - llvm-project/clang/lib/Headers
+            - llvm-project/clang/include
+            - llvm-project/lld/include
+            - llvm-project/llvm/include
       - restore_cache:
           keys:
-            - llvm-build-11-macos-v2
+            - llvm-build-11-macos-v3
       - run:
           name: "Build LLVM"
           command: |
             if [ ! -f llvm-build/lib/liblldELF.a ]
             then
+              # fetch LLVM source
+              rm -rf llvm-project
+              make llvm-source
               # install dependencies
               HOMEBREW_NO_AUTO_UPDATE=1 brew install cmake ninja
               # build!
               make llvm-build
+              find llvm-build -name CMakeFiles -prune -exec rm -r '{}' \;
             fi
       - save_cache:
-          key: llvm-build-11-macos-v2
+          key: llvm-build-11-macos-v3
           paths:
             llvm-build
       - restore_cache:

Makefile

@@ -152,9 +152,9 @@ gen-device-stm32: build/gen-device-svd
 
 
 # Get LLVM sources.
-$(LLVM_PROJECTDIR)/README.md:
+$(LLVM_PROJECTDIR)/llvm:
 	git clone -b xtensa_release_11.0.0 --depth=1 https://github.com/tinygo-org/llvm-project $(LLVM_PROJECTDIR)
-llvm-source: $(LLVM_PROJECTDIR)/README.md
+llvm-source: $(LLVM_PROJECTDIR)/llvm
 
 # Configure LLVM.
 TINYGO_SOURCE_DIR=$(shell pwd)
@@ -226,8 +226,6 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=microbit            examples/microbit-blink
 	@$(MD5SUM) test.hex
-	$(TINYGO) build -size short -o test.hex -target=microbit-v2         examples/microbit-blink
-	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/pininterrupt
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10040            examples/serial
@@ -256,6 +254,10 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=microbit-s110v8     examples/echo
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=microbit-v2         examples/microbit-blink
+	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=microbit-v2-s113v7  examples/microbit-blink
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nrf52840-mdk        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10031            examples/blinky1
@@ -288,6 +290,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.gba -target=gameboy-advance     examples/gba-display
 	@$(MD5SUM) test.gba
+	$(TINYGO) build -size short -o test.hex -target=grandcentral-m4     examples/blinky1
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=itsybitsy-m4        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=feather-m4          examples/blinky1
@@ -334,6 +338,10 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=p1am-100            examples/blinky1
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=atsame54-xpro       examples/blinky1
+	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=feather-m4-can      examples/blinky1
+	@$(MD5SUM) test.hex
 	# test pwm
 	$(TINYGO) build -size short -o test.hex -target=itsybitsy-m0        examples/pwm
 	@$(MD5SUM) test.hex
@@ -374,6 +382,10 @@ ifneq ($(AVR), 0)
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino -scheduler=tasks  examples/blinky1
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=arduino-mega1280    examples/blinky1
+	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=arduino-mega1280    examples/pwm
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=arduino-nano        examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=digispark           examples/blinky1

README.md

@@ -43,13 +43,14 @@ See the [getting started instructions](https://tinygo.org/getting-started/) for
 
 You can compile TinyGo programs for microcontrollers, WebAssembly and Linux.
 
-The following 55 microcontroller boards are currently supported:
+The following 57 microcontroller boards are currently supported:
 
 * [Adafruit Circuit Playground Bluefruit](https://www.adafruit.com/product/4333)
 * [Adafruit Circuit Playground Express](https://www.adafruit.com/product/3333)
 * [Adafruit CLUE](https://www.adafruit.com/product/4500)
 * [Adafruit Feather M0](https://www.adafruit.com/product/2772)
 * [Adafruit Feather M4](https://www.adafruit.com/product/3857)
+* [Adafruit Feather M4 CAN](https://www.adafruit.com/product/4759)
 * [Adafruit Feather nRF52840 Express](https://www.adafruit.com/product/4062)
 * [Adafruit Feather STM32F405 Express](https://www.adafruit.com/product/4382)
 * [Adafruit ItsyBitsy M0](https://www.adafruit.com/product/3727)
@@ -77,6 +78,7 @@ The following 55 microcontroller boards are currently supported:
 * [Game Boy Advance](https://en.wikipedia.org/wiki/Game_Boy_Advance)
 * [Makerdiary nRF52840-MDK](https://wiki.makerdiary.com/nrf52840-mdk/)
 * [Makerdiary nRF52840-MDK USB Dongle](https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/)
+* [Microchip SAM E54 Xplained Pro](https://www.microchip.com/developmenttools/productdetails/atsame54-xpro)
 * [nice!nano](https://docs.nicekeyboards.com/#/nice!nano/)
 * [Nintendo Switch](https://www.nintendo.com/switch/)
 * [Nordic Semiconductor PCA10031](https://www.nordicsemi.com/eng/Products/nRF51-Dongle)

builder/build.go

@@ -52,14 +52,17 @@ type BuildResult struct {
 // key, avoiding the need for recompiling all dependencies when only the
 // implementation of an imported package changes.
 type packageAction struct {
-	ImportPath      string
-	CompilerVersion int // compiler.Version
-	InterpVersion   int // interp.Version
-	LLVMVersion     string
-	Config          *compiler.Config
-	CFlags          []string
-	FileHashes      map[string]string // hash of every file that's part of the package
-	Imports         map[string]string // map from imported package to action ID hash
+	ImportPath       string
+	CompilerVersion  int // compiler.Version
+	InterpVersion    int // interp.Version
+	LLVMVersion      string
+	Config           *compiler.Config
+	CFlags           []string
+	FileHashes       map[string]string // hash of every file that's part of the package
+	Imports          map[string]string // map from imported package to action ID hash
+	OptLevel         int               // LLVM optimization level (0-3)
+	SizeLevel        int               // LLVM optimization for size level (0-2)
+	UndefinedGlobals []string          // globals that are left as external globals (no initializer)
 }
 
 // Build performs a single package to executable Go build. It takes in a package
@@ -127,20 +130,30 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 	var packageJobs []*compileJob
 	packageBitcodePaths := make(map[string]string)
 	packageActionIDs := make(map[string]string)
+	optLevel, sizeLevel, _ := config.OptLevels()
 	for _, pkg := range lprogram.Sorted() {
 		pkg := pkg // necessary to avoid a race condition
 
+		var undefinedGlobals []string
+		for name := range config.Options.GlobalValues[pkg.Pkg.Path()] {
+			undefinedGlobals = append(undefinedGlobals, name)
+		}
+		sort.Strings(undefinedGlobals)
+
 		// Create a cache key: a hash from the action ID below that contains all
 		// the parameters for the build.
 		actionID := packageAction{
-			ImportPath:      pkg.ImportPath,
-			CompilerVersion: compiler.Version,
-			InterpVersion:   interp.Version,
-			LLVMVersion:     llvm.Version,
-			Config:          compilerConfig,
-			CFlags:          pkg.CFlags,
-			FileHashes:      make(map[string]string, len(pkg.FileHashes)),
-			Imports:         make(map[string]string, len(pkg.Pkg.Imports())),
+			ImportPath:       pkg.ImportPath,
+			CompilerVersion:  compiler.Version,
+			InterpVersion:    interp.Version,
+			LLVMVersion:      llvm.Version,
+			Config:           compilerConfig,
+			CFlags:           pkg.CFlags,
+			FileHashes:       make(map[string]string, len(pkg.FileHashes)),
+			Imports:          make(map[string]string, len(pkg.Pkg.Imports())),
+			OptLevel:         optLevel,
+			SizeLevel:        sizeLevel,
+			UndefinedGlobals: undefinedGlobals,
 		}
 		for filePath, hash := range pkg.FileHashes {
 			actionID.FileHashes[filePath] = hex.EncodeToString(hash)
@@ -191,6 +204,25 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 					return errors.New("verification error after compiling package " + pkg.ImportPath)
 				}
 
+				// Erase all globals that are part of the undefinedGlobals list.
+				// This list comes from the -ldflags="-X pkg.foo=val" option.
+				// Instead of setting the value directly in the AST (which would
+				// mean the value, which may be a secret, is stored in the build
+				// cache), the global itself is left external (undefined) and is
+				// only set at the end of the compilation.
+				for _, name := range undefinedGlobals {
+					globalName := pkg.Pkg.Path() + "." + name
+					global := mod.NamedGlobal(globalName)
+					if global.IsNil() {
+						return errors.New("global not found: " + globalName)
+					}
+					name := global.Name()
+					newGlobal := llvm.AddGlobal(mod, global.Type().ElementType(), name+".tmp")
+					global.ReplaceAllUsesWith(newGlobal)
+					global.EraseFromParentAsGlobal()
+					newGlobal.SetName(name)
+				}
+
 				// Try to interpret package initializers at compile time.
 				// It may only be possible to do this partially, in which case
 				// it is completed after all IR files are linked.
@@ -206,6 +238,38 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 					return errors.New("verification error after interpreting " + pkgInit.Name())
 				}
 
+				if sizeLevel >= 2 {
+					// Set the "optsize" attribute to make slightly smaller
+					// binaries at the cost of some performance.
+					kind := llvm.AttributeKindID("optsize")
+					attr := mod.Context().CreateEnumAttribute(kind, 0)
+					for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
+						fn.AddFunctionAttr(attr)
+					}
+				}
+
+				// Run function passes for each function in the module.
+				// These passes are intended to be run on each function right
+				// after they're created to reduce IR size (and maybe also for
+				// cache locality to improve performance), but for now they're
+				// run here for each function in turn. Maybe this can be
+				// improved in the future.
+				builder := llvm.NewPassManagerBuilder()
+				defer builder.Dispose()
+				builder.SetOptLevel(optLevel)
+				builder.SetSizeLevel(sizeLevel)
+				funcPasses := llvm.NewFunctionPassManagerForModule(mod)
+				defer funcPasses.Dispose()
+				builder.PopulateFunc(funcPasses)
+				funcPasses.InitializeFunc()
+				for fn := mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
+					if fn.IsDeclaration() {
+						continue
+					}
+					funcPasses.RunFunc(fn)
+				}
+				funcPasses.FinalizeFunc()
+
 				// Serialize the LLVM module as a bitcode file.
 				// Write to a temporary path that is renamed to the destination
 				// file to avoid race conditions with other TinyGo invocatiosn
@@ -236,7 +300,13 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 				if err != nil {
 					return err
 				}
-				return os.Rename(f.Name(), bitcodePath)
+
+				// Rename may fail if another process is trying to write to
+				// the same file.  However, in this case, the failure is
+				// acceptable because the result of the other process can be
+				// used.
+				os.Rename(f.Name(), bitcodePath)
+				return nil
 			},
 		}
 		jobs = append(jobs, job)
@@ -430,7 +500,7 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		job := &compileJob{
 			description: "compile extra file " + path,
 			run: func(job *compileJob) error {
-				result, err := compileAndCacheCFile(abspath, dir, config.CFlags(), config)
+				result, err := compileAndCacheCFile(abspath, dir, config.CFlags(), config.Options.PrintCommands)
 				job.result = result
 				return err
 			},
@@ -449,7 +519,7 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 			job := &compileJob{
 				description: "compile CGo file " + abspath,
 				run: func(job *compileJob) error {
-					result, err := compileAndCacheCFile(abspath, dir, pkg.CFlags, config)
+					result, err := compileAndCacheCFile(abspath, dir, pkg.CFlags, config.Options.PrintCommands)
 					job.result = result
 					return err
 				},
@@ -603,6 +673,12 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 		transform.ApplyFunctionSections(mod) // -ffunction-sections
 	}
 
+	// Insert values from -ldflags="-X ..." into the IR.
+	err = setGlobalValues(mod, config.Options.GlobalValues)
+	if err != nil {
+		return err
+	}
+
 	// Browsers cannot handle external functions that have type i64 because it
 	// cannot be represented exactly in JavaScript (JS only has doubles). To
 	// keep functions interoperable, pass int64 types as pointers to
@@ -617,21 +693,8 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 
 	// Optimization levels here are roughly the same as Clang, but probably not
 	// exactly.
-	var errs []error
-	switch config.Options.Opt {
-	case "none", "0":
-		errs = transform.Optimize(mod, config, 0, 0, 0) // -O0
-	case "1":
-		errs = transform.Optimize(mod, config, 1, 0, 0) // -O1
-	case "2":
-		errs = transform.Optimize(mod, config, 2, 0, 225) // -O2
-	case "s":
-		errs = transform.Optimize(mod, config, 2, 1, 225) // -Os
-	case "z":
-		errs = transform.Optimize(mod, config, 2, 2, 5) // -Oz, default
-	default:
-		return errors.New("unknown optimization level: -opt=" + config.Options.Opt)
-	}
+	optLevel, sizeLevel, inlinerThreshold := config.OptLevels()
+	errs := transform.Optimize(mod, config, optLevel, sizeLevel, inlinerThreshold)
 	if len(errs) > 0 {
 		return newMultiError(errs)
 	}
@@ -653,6 +716,71 @@ func optimizeProgram(mod llvm.Module, config *compileopts.Config) error {
 	return nil
 }
 
+// setGlobalValues sets the global values from the -ldflags="-X ..." compiler
+// option in the given module. An error may be returned if the global is not of
+// the expected type.
+func setGlobalValues(mod llvm.Module, globals map[string]map[string]string) error {
+	var pkgPaths []string
+	for pkgPath := range globals {
+		pkgPaths = append(pkgPaths, pkgPath)
+	}
+	sort.Strings(pkgPaths)
+	for _, pkgPath := range pkgPaths {
+		pkg := globals[pkgPath]
+		var names []string
+		for name := range pkg {
+			names = append(names, name)
+		}
+		sort.Strings(names)
+		for _, name := range names {
+			value := pkg[name]
+			globalName := pkgPath + "." + name
+			global := mod.NamedGlobal(globalName)
+			if global.IsNil() || !global.Initializer().IsNil() {
+				// The global either does not exist (optimized away?) or has
+				// some value, in which case it has already been initialized at
+				// package init time.
+				continue
+			}
+
+			// A strin is a {ptr, len} pair. We need these types to build the
+			// initializer.
+			initializerType := global.Type().ElementType()
+			if initializerType.TypeKind() != llvm.StructTypeKind || initializerType.StructName() == "" {
+				return fmt.Errorf("%s: not a string", globalName)
+			}
+			elementTypes := initializerType.StructElementTypes()
+			if len(elementTypes) != 2 {
+				return fmt.Errorf("%s: not a string", globalName)
+			}
+
+			// Create a buffer for the string contents.
+			bufInitializer := mod.Context().ConstString(value, false)
+			buf := llvm.AddGlobal(mod, bufInitializer.Type(), ".string")
+			buf.SetInitializer(bufInitializer)
+			buf.SetAlignment(1)
+			buf.SetUnnamedAddr(true)
+			buf.SetLinkage(llvm.PrivateLinkage)
+
+			// Create the string value, which is a {ptr, len} pair.
+			zero := llvm.ConstInt(mod.Context().Int32Type(), 0, false)
+			ptr := llvm.ConstGEP(buf, []llvm.Value{zero, zero})
+			if ptr.Type() != elementTypes[0] {
+				return fmt.Errorf("%s: not a string", globalName)
+			}
+			length := llvm.ConstInt(elementTypes[1], uint64(len(value)), false)
+			initializer := llvm.ConstNamedStruct(initializerType, []llvm.Value{
+				ptr,
+				length,
+			})
+
+			// Set the initializer. No initializer should be set at this point.
+			global.SetInitializer(initializer)
+		}
+	}
+	return nil
+}
+
 // functionStackSizes keeps stack size information about a single function
 // (usually a goroutine).
 type functionStackSize struct {

builder/cc.go

@@ -17,7 +17,6 @@ import (
 	"strings"
 	"unicode"
 
-	"github.com/tinygo-org/tinygo/compileopts"
 	"github.com/tinygo-org/tinygo/goenv"
 	"tinygo.org/x/go-llvm"
 )
@@ -57,7 +56,7 @@ import (
 //   depfile but without invalidating its name. For this reason, the depfile is
 //   written on each new compilation (even when it seems unnecessary). However, it
 //   could in rare cases lead to a stale file fetched from the cache.
-func compileAndCacheCFile(abspath, tmpdir string, cflags []string, config *compileopts.Config) (string, error) {
+func compileAndCacheCFile(abspath, tmpdir string, cflags []string, printCommands bool) (string, error) {
 	// Hash input file.
 	fileHash, err := hashFile(abspath)
 	if err != nil {
@@ -68,14 +67,12 @@ func compileAndCacheCFile(abspath, tmpdir string, cflags []string, config *compi
 	buf, err := json.Marshal(struct {
 		Path        string
 		Hash        string
-		Compiler    string
 		Flags       []string
 		LLVMVersion string
 	}{
 		Path:        abspath,
 		Hash:        fileHash,
-		Compiler:    config.Target.Compiler,
-		Flags:       config.CFlags(),
+		Flags:       cflags,
 		LLVMVersion: llvm.Version,
 	})
 	if err != nil {
@@ -124,10 +121,17 @@ func compileAndCacheCFile(abspath, tmpdir string, cflags []string, config *compi
 	flags := append([]string{}, cflags...)                                   // copy cflags
 	flags = append(flags, "-MD", "-MV", "-MTdeps", "-MF", depTmpFile.Name()) // autogenerate dependencies
 	flags = append(flags, "-c", "-o", objTmpFile.Name(), abspath)
-	if config.Options.PrintCommands {
-		fmt.Printf("%s %s\n", config.Target.Compiler, strings.Join(flags, " "))
+	if strings.ToLower(filepath.Ext(abspath)) == ".s" {
+		// If this is an assembly file (.s or .S, lowercase or uppercase), then
+		// we'll need to add -Qunused-arguments because many parameters are
+		// relevant to C, not assembly. And with -Werror, having meaningless
+		// flags (for the assembler) is a compiler error.
+		flags = append(flags, "-Qunused-arguments")
 	}
-	err = runCCompiler(config.Target.Compiler, flags...)
+	if printCommands {
+		fmt.Printf("clang %s\n", strings.Join(flags, " "))
+	}
+	err = runCCompiler(flags...)
 	if err != nil {
 		return "", &commandError{"failed to build", abspath, err}
 	}

builder/library.go

@@ -136,7 +136,7 @@ func (l *Library) load(target, cpu, tmpdir string) (job *compileJob, err error)
 				var compileArgs []string
 				compileArgs = append(compileArgs, args...)
 				compileArgs = append(compileArgs, "-o", objpath, srcpath)
-				err := runCCompiler("clang", compileArgs...)
+				err := runCCompiler(compileArgs...)
 				if err != nil {
 					return &commandError{"failed to build", srcpath, err}
 				}

builder/tools.go

@@ -9,8 +9,8 @@ import (
 )
 
 // runCCompiler invokes a C compiler with the given arguments.
-func runCCompiler(command string, flags ...string) error {
-	if hasBuiltinTools && command == "clang" {
+func runCCompiler(flags ...string) error {
+	if hasBuiltinTools {
 		// Compile this with the internal Clang compiler.
 		headerPath := getClangHeaderPath(goenv.Get("TINYGOROOT"))
 		if headerPath == "" {
@@ -23,17 +23,8 @@ func runCCompiler(command string, flags ...string) error {
 		return cmd.Run()
 	}
 
-	// Running some other compiler. Maybe it has been defined in the
-	// commands map (unlikely).
-	if cmdNames, ok := commands[command]; ok {
-		return execCommand(cmdNames, flags...)
-	}
-
-	// Alternatively, run the compiler directly.
-	cmd := exec.Command(command, flags...)
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	return cmd.Run()
+	// Compile this with an external invocation of the Clang compiler.
+	return execCommand(commands["clang"], flags...)
 }
 
 // link invokes a linker with the given name and flags.

compileopts/config.go

@@ -118,6 +118,27 @@ func (c *Config) Scheduler() string {
 	return "coroutines"
 }
 
+// OptLevels returns the optimization level (0-2), size level (0-2), and inliner
+// threshold as used in the LLVM optimization pipeline.
+func (c *Config) OptLevels() (optLevel, sizeLevel int, inlinerThreshold uint) {
+	switch c.Options.Opt {
+	case "none", "0":
+		return 0, 0, 0 // -O0
+	case "1":
+		return 1, 0, 0 // -O1
+	case "2":
+		return 2, 0, 225 // -O2
+	case "s":
+		return 2, 1, 225 // -Os
+	case "z":
+		return 2, 2, 5 // -Oz, default
+	default:
+		// This is not shown to the user: valid choices are already checked as
+		// part of Options.Verify(). It is here as a sanity check.
+		panic("unknown optimization level: -opt=" + c.Options.Opt)
+	}
+}
+
 // FuncImplementation picks an appropriate func value implementation for the
 // target.
 func (c *Config) FuncImplementation() string {
@@ -163,7 +184,7 @@ func (c *Config) AutomaticStackSize() bool {
 // CFlags returns the flags to pass to the C compiler. This is necessary for CGo
 // preprocessing.
 func (c *Config) CFlags() []string {
-	cflags := append([]string{}, c.Options.CFlags...)
+	var cflags []string
 	for _, flag := range c.Target.CFlags {
 		cflags = append(cflags, strings.ReplaceAll(flag, "{root}", goenv.Get("TINYGOROOT")))
 	}
@@ -184,7 +205,7 @@ func (c *Config) CFlags() []string {
 func (c *Config) LDFlags() []string {
 	root := goenv.Get("TINYGOROOT")
 	// Merge and adjust LDFlags.
-	ldflags := append([]string{}, c.Options.LDFlags...)
+	var ldflags []string
 	for _, flag := range c.Target.LDFlags {
 		ldflags = append(ldflags, strings.ReplaceAll(flag, "{root}", root))
 	}

compileopts/options.go

@@ -2,6 +2,7 @@ package compileopts
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 )
 
@@ -10,6 +11,7 @@ var (
 	validSchedulerOptions     = []string{"none", "tasks", "coroutines"}
 	validPrintSizeOptions     = []string{"none", "short", "full"}
 	validPanicStrategyOptions = []string{"print", "trap"}
+	validOptOptions           = []string{"none", "0", "1", "2", "s", "z"}
 )
 
 // Options contains extra options to give to the compiler. These options are
@@ -26,11 +28,11 @@ type Options struct {
 	PrintCommands bool
 	Debug         bool
 	PrintSizes    string
+	PrintAllocs   *regexp.Regexp // regexp string
 	PrintStacks   bool
-	CFlags        []string
-	LDFlags       []string
 	Tags          string
 	WasmAbi       string
+	GlobalValues  map[string]map[string]string // map[pkgpath]map[varname]value
 	TestConfig    TestConfig
 	Programmer    string
 }
@@ -73,6 +75,12 @@ func (o *Options) Verify() error {
 		}
 	}
 
+	if o.Opt != "" {
+		if !isInArray(validOptOptions, o.Opt) {
+			return fmt.Errorf("invalid -opt=%s: valid values are %s", o.Opt, strings.Join(validOptOptions, ", "))
+		}
+	}
+
 	return nil
 }
 

compileopts/target.go

@@ -31,7 +31,6 @@ type TargetSpec struct {
 	BuildTags        []string `json:"build-tags"`
 	GC               string   `json:"gc"`
 	Scheduler        string   `json:"scheduler"`
-	Compiler         string   `json:"compiler"`
 	Linker           string   `json:"linker"`
 	RTLib            string   `json:"rtlib"` // compiler runtime library (libgcc, compiler-rt)
 	Libc             string   `json:"libc"`
@@ -244,7 +243,6 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 		GOOS:      goos,
 		GOARCH:    goarch,
 		BuildTags: []string{goos, goarch},
-		Compiler:  "clang",
 		Linker:    "cc",
 		CFlags:    []string{"--target=" + triple},
 		GDB:       []string{"gdb"},

compiler/compiler.go

@@ -23,7 +23,7 @@ import (
 // Version of the compiler pacakge. Must be incremented each time the compiler
 // package changes in a way that affects the generated LLVM module.
 // This version is independent of the TinyGo version number.
-const Version = 6 // last change: fix issue 1304
+const Version = 9 // last change: implement reflect.New()
 
 func init() {
 	llvm.InitializeAllTargets()
@@ -298,7 +298,7 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 		c.dibuilder.Finalize()
 	}
 
-	return c.mod, nil
+	return c.mod, c.diagnostics
 }
 
 // getLLVMRuntimeType obtains a named type from the runtime package and returns
@@ -2258,14 +2258,20 @@ func (b *builder) createConst(prefix string, expr *ssa.Const) llvm.Value {
 		} else if typ.Info()&types.IsString != 0 {
 			str := constant.StringVal(expr.Value)
 			strLen := llvm.ConstInt(b.uintptrType, uint64(len(str)), false)
-			objname := prefix + "$string"
-			global := llvm.AddGlobal(b.mod, llvm.ArrayType(b.ctx.Int8Type(), len(str)), objname)
-			global.SetInitializer(b.ctx.ConstString(str, false))
-			global.SetLinkage(llvm.InternalLinkage)
-			global.SetGlobalConstant(true)
-			global.SetUnnamedAddr(true)
-			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-			strPtr := b.CreateInBoundsGEP(global, []llvm.Value{zero, zero}, "")
+			var strPtr llvm.Value
+			if str != "" {
+				objname := prefix + "$string"
+				global := llvm.AddGlobal(b.mod, llvm.ArrayType(b.ctx.Int8Type(), len(str)), objname)
+				global.SetInitializer(b.ctx.ConstString(str, false))
+				global.SetLinkage(llvm.InternalLinkage)
+				global.SetGlobalConstant(true)
+				global.SetUnnamedAddr(true)
+				global.SetAlignment(1)
+				zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
+				strPtr = b.CreateInBoundsGEP(global, []llvm.Value{zero, zero}, "")
+			} else {
+				strPtr = llvm.ConstNull(b.i8ptrType)
+			}
 			strObj := llvm.ConstNamedStruct(b.getLLVMRuntimeType("_string"), []llvm.Value{strPtr, strLen})
 			return strObj
 		} else if typ.Kind() == types.UnsafePointer {

compiler/compiler_test.go

@@ -62,6 +62,7 @@ func TestCompiler(t *testing.T) {
 		"string.go",
 		"float.go",
 		"interface.go",
+		"func.go",
 	}
 
 	for _, testCase := range tests {
@@ -84,11 +85,16 @@ func TestCompiler(t *testing.T) {
 			mod, errs := CompilePackage(testCase, pkg, program.Package(pkg.Pkg), machine, compilerConfig, false)
 			if errs != nil {
 				for _, err := range errs {
-					t.Log("error:", err)
+					t.Error(err)
 				}
 				return
 			}
 
+			err = llvm.VerifyModule(mod, llvm.PrintMessageAction)
+			if err != nil {
+				t.Error(err)
+			}
+
 			// Optimize IR a little.
 			funcPasses := llvm.NewFunctionPassManagerForModule(mod)
 			defer funcPasses.Dispose()

compiler/func.go

@@ -25,14 +25,13 @@ func (c *compilerContext) createFuncValue(builder llvm.Builder, funcPtr, context
 		// Closure is: {context, function pointer}
 		funcValueScalar = funcPtr
 	case "switch":
-		sigGlobal := c.getTypeCode(sig)
 		funcValueWithSignatureGlobalName := funcPtr.Name() + "$withSignature"
 		funcValueWithSignatureGlobal := c.mod.NamedGlobal(funcValueWithSignatureGlobalName)
 		if funcValueWithSignatureGlobal.IsNil() {
 			funcValueWithSignatureType := c.getLLVMRuntimeType("funcValueWithSignature")
 			funcValueWithSignature := llvm.ConstNamedStruct(funcValueWithSignatureType, []llvm.Value{
 				llvm.ConstPtrToInt(funcPtr, c.uintptrType),
-				sigGlobal,
+				c.getFuncSignatureID(sig),
 			})
 			funcValueWithSignatureGlobal = llvm.AddGlobal(c.mod, funcValueWithSignatureType, funcValueWithSignatureGlobalName)
 			funcValueWithSignatureGlobal.SetInitializer(funcValueWithSignature)
@@ -50,6 +49,19 @@ func (c *compilerContext) createFuncValue(builder llvm.Builder, funcPtr, context
 	return funcValue
 }
 
+// getFuncSignatureID returns a new external global for a given signature. This
+// global reference is not real, it is only used during func lowering to assign
+// signature types to functions and will then be removed.
+func (c *compilerContext) getFuncSignatureID(sig *types.Signature) llvm.Value {
+	sigGlobalName := "reflect/types.funcid:" + getTypeCodeName(sig)
+	sigGlobal := c.mod.NamedGlobal(sigGlobalName)
+	if sigGlobal.IsNil() {
+		sigGlobal = llvm.AddGlobal(c.mod, c.ctx.Int8Type(), sigGlobalName)
+		sigGlobal.SetGlobalConstant(true)
+	}
+	return sigGlobal
+}
+
 // extractFuncScalar returns some scalar that can be used in comparisons. It is
 // a cheap operation.
 func (b *builder) extractFuncScalar(funcValue llvm.Value) llvm.Value {
@@ -71,7 +83,7 @@ func (b *builder) decodeFuncValue(funcValue llvm.Value, sig *types.Signature) (f
 		funcPtr = b.CreateExtractValue(funcValue, 1, "")
 	case "switch":
 		llvmSig := b.getRawFuncType(sig)
-		sigGlobal := b.getTypeCode(sig)
+		sigGlobal := b.getFuncSignatureID(sig)
 		funcPtr = b.createRuntimeCall("getFuncPtr", []llvm.Value{funcValue, sigGlobal}, "")
 		funcPtr = b.CreateIntToPtr(funcPtr, llvmSig, "")
 	default:

compiler/interface.go

@@ -46,6 +46,7 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 		var references llvm.Value
 		var length int64
 		var methodSet llvm.Value
+		var ptrTo llvm.Value
 		switch typ := typ.(type) {
 		case *types.Named:
 			references = c.getTypeCode(typ.Underlying())
@@ -69,22 +70,25 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 		if _, ok := typ.Underlying().(*types.Interface); !ok {
 			methodSet = c.getTypeMethodSet(typ)
 		}
-		if !references.IsNil() || length != 0 || !methodSet.IsNil() {
-			// Set the 'references' field of the runtime.typecodeID struct.
-			globalValue := llvm.ConstNull(global.Type().ElementType())
-			if !references.IsNil() {
-				globalValue = llvm.ConstInsertValue(globalValue, references, []uint32{0})
-			}
-			if length != 0 {
-				lengthValue := llvm.ConstInt(c.uintptrType, uint64(length), false)
-				globalValue = llvm.ConstInsertValue(globalValue, lengthValue, []uint32{1})
-			}
-			if !methodSet.IsNil() {
-				globalValue = llvm.ConstInsertValue(globalValue, methodSet, []uint32{2})
-			}
-			global.SetInitializer(globalValue)
-			global.SetLinkage(llvm.LinkOnceODRLinkage)
+		if _, ok := typ.Underlying().(*types.Pointer); !ok {
+			ptrTo = c.getTypeCode(types.NewPointer(typ))
 		}
+		globalValue := llvm.ConstNull(global.Type().ElementType())
+		if !references.IsNil() {
+			globalValue = llvm.ConstInsertValue(globalValue, references, []uint32{0})
+		}
+		if length != 0 {
+			lengthValue := llvm.ConstInt(c.uintptrType, uint64(length), false)
+			globalValue = llvm.ConstInsertValue(globalValue, lengthValue, []uint32{1})
+		}
+		if !methodSet.IsNil() {
+			globalValue = llvm.ConstInsertValue(globalValue, methodSet, []uint32{2})
+		}
+		if !ptrTo.IsNil() {
+			globalValue = llvm.ConstInsertValue(globalValue, ptrTo, []uint32{3})
+		}
+		global.SetInitializer(globalValue)
+		global.SetLinkage(llvm.LinkOnceODRLinkage)
 		global.SetGlobalConstant(true)
 	}
 	return global
@@ -341,7 +345,7 @@ func (b *builder) createTypeAssert(expr *ssa.TypeAssert) llvm.Value {
 		commaOk = b.createRuntimeCall("interfaceImplements", []llvm.Value{actualTypeNum, methodSet}, "")
 
 	} else {
-		globalName := "reflect/types.type:" + getTypeCodeName(expr.AssertedType) + "$id"
+		globalName := "reflect/types.typeid:" + getTypeCodeName(expr.AssertedType)
 		assertedTypeCodeGlobal := b.mod.NamedGlobal(globalName)
 		if assertedTypeCodeGlobal.IsNil() {
 			// Create a new typecode global.

compiler/symbol.go

@@ -139,6 +139,17 @@ func (c *compilerContext) getFunction(fn *ssa.Function) llvm.Value {
 		for _, attrName := range []string{"noalias", "nonnull"} {
 			llvmFn.AddAttributeAtIndex(0, c.ctx.CreateEnumAttribute(llvm.AttributeKindID(attrName), 0))
 		}
+	case "runtime.sliceAppend":
+		// Appending a slice will only read the to-be-appended slice, it won't
+		// be modified.
+		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
+		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
+	case "runtime.sliceCopy":
+		// Copying a slice won't capture any of the parameters.
+		llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("writeonly"), 0))
+		llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
+		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0))
+		llvmFn.AddAttributeAtIndex(2, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
 	case "runtime.trackPointer":
 		// This function is necessary for tracking pointers on the stack in a
 		// portable way (see gc_stack_portable.go). Indicate to the optimizer
@@ -355,16 +366,18 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
 
 		// Set alignment from the //go:align comment.
 		var alignInBits uint32
-		if info.align < 0 || info.align&(info.align-1) != 0 {
+		alignment := c.targetData.ABITypeAlignment(llvmType)
+		if info.align > alignment {
+			alignment = info.align
+		}
+		if alignment <= 0 || alignment&(alignment-1) != 0 {
 			// Check for power-of-two (or 0).
 			// See: https://stackoverflow.com/a/108360
 			c.addError(g.Pos(), "global variable alignment must be a positive power of two")
 		} else {
 			// Set the alignment only when it is a power of two.
-			alignInBits = uint32(info.align) ^ uint32(info.align-1)
-			if info.align > c.targetData.ABITypeAlignment(llvmType) {
-				llvmGlobal.SetAlignment(info.align)
-			}
+			alignInBits = uint32(alignment) ^ uint32(alignment-1)
+			llvmGlobal.SetAlignment(alignment)
 		}
 
 		if c.Debug && !info.extern {

compiler/testdata/func.go

@@ -0,0 +1,12 @@
+package main
+
+func foo(callback func(int)) {
+	callback(3)
+}
+
+func bar() {
+	foo(someFunc)
+}
+
+func someFunc(int) {
+}

compiler/testdata/func.ll

@@ -0,0 +1,47 @@
+; ModuleID = 'func.go'
+source_filename = "func.go"
+target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i686--linux"
+
+%runtime.funcValueWithSignature = type { i32, i8* }
+
+@"reflect/types.funcid:func:{basic:int}{}" = external constant i8
+@"main.someFunc$withSignature" = linkonce_odr constant %runtime.funcValueWithSignature { i32 ptrtoint (void (i32, i8*, i8*)* @main.someFunc to i32), i8* @"reflect/types.funcid:func:{basic:int}{}" }
+
+declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
+
+define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}
+
+define hidden void @main.foo(i8* %callback.context, i32 %callback.funcptr, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  %0 = call i32 @runtime.getFuncPtr(i8* %callback.context, i32 %callback.funcptr, i8* nonnull @"reflect/types.funcid:func:{basic:int}{}", i8* undef, i8* null)
+  %1 = icmp eq i32 %0, 0
+  br i1 %1, label %fpcall.throw, label %fpcall.next
+
+fpcall.throw:                                     ; preds = %entry
+  call void @runtime.nilPanic(i8* undef, i8* null)
+  unreachable
+
+fpcall.next:                                      ; preds = %entry
+  %2 = inttoptr i32 %0 to void (i32, i8*, i8*)*
+  call void %2(i32 3, i8* %callback.context, i8* undef)
+  ret void
+}
+
+declare i32 @runtime.getFuncPtr(i8*, i32, i8* dereferenceable_or_null(1), i8*, i8*)
+
+declare void @runtime.nilPanic(i8*, i8*)
+
+define hidden void @main.bar(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  call void @main.foo(i8* undef, i32 ptrtoint (%runtime.funcValueWithSignature* @"main.someFunc$withSignature" to i32), i8* undef, i8* undef)
+  ret void
+}
+
+define hidden void @main.someFunc(i32 %arg0, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}

compiler/testdata/interface.ll

@@ -3,23 +3,24 @@ source_filename = "interface.go"
 target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
 target triple = "i686--linux"
 
-%runtime.typecodeID = type { %runtime.typecodeID*, i32, %runtime.interfaceMethodInfo* }
+%runtime.typecodeID = type { %runtime.typecodeID*, i32, %runtime.interfaceMethodInfo*, %runtime.typecodeID* }
 %runtime.interfaceMethodInfo = type { i8*, i32 }
 %runtime._interface = type { i32, i8* }
 %runtime._string = type { i8*, i32 }
 
-@"reflect/types.type:basic:int" = linkonce_odr constant %runtime.typecodeID zeroinitializer
-@"reflect/types.type:pointer:basic:int" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:basic:int", i32 0, %runtime.interfaceMethodInfo* null }
-@"reflect/types.type:pointer:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:named:error", i32 0, %runtime.interfaceMethodInfo* null }
-@"reflect/types.type:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null }
-@"reflect/types.type:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{Error() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null }
+@"reflect/types.type:basic:int" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* null, i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:basic:int" }
+@"reflect/types.type:pointer:basic:int" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:basic:int", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
+@"reflect/types.type:pointer:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:named:error", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
+@"reflect/types.type:named:error" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:named:error" }
+@"reflect/types.type:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{Error() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:interface:{Error:func:{}{basic:string}}" }
 @"func Error() string" = external constant i8
 @"reflect/types.interface:interface{Error() string}$interface" = linkonce_odr constant [1 x i8*] [i8* @"func Error() string"]
-@"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{String:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null }
-@"reflect/types.type:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{String() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null }
+@"reflect/types.type:pointer:interface:{Error:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{Error:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
+@"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:interface:{String:func:{}{basic:string}}", i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* null }
+@"reflect/types.type:interface:{String:func:{}{basic:string}}" = linkonce_odr constant %runtime.typecodeID { %runtime.typecodeID* bitcast ([1 x i8*]* @"reflect/types.interface:interface{String() string}$interface" to %runtime.typecodeID*), i32 0, %runtime.interfaceMethodInfo* null, %runtime.typecodeID* @"reflect/types.type:pointer:interface:{String:func:{}{basic:string}}" }
 @"func String() string" = external constant i8
 @"reflect/types.interface:interface{String() string}$interface" = linkonce_odr constant [1 x i8*] [i8* @"func String() string"]
-@"reflect/types.type:basic:int$id" = external constant i8
+@"reflect/types.typeid:basic:int" = external constant i8
 @"error$interface" = linkonce_odr constant [1 x i8*] [i8* @"func Error() string"]
 
 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
@@ -51,7 +52,7 @@ entry:
 
 define hidden i1 @main.isInt(i32 %itf.typecode, i8* %itf.value, i8* %context, i8* %parentHandle) unnamed_addr {
 entry:
-  %typecode = call i1 @runtime.typeAssert(i32 %itf.typecode, i8* nonnull @"reflect/types.type:basic:int$id", i8* undef, i8* null)
+  %typecode = call i1 @runtime.typeAssert(i32 %itf.typecode, i8* nonnull @"reflect/types.typeid:basic:int", i8* undef, i8* null)
   br i1 %typecode, label %typeassert.ok, label %typeassert.next
 
 typeassert.ok:                                    ; preds = %entry

compiler/testdata/slice.ll

@@ -60,7 +60,7 @@ entry:
   ret { i32*, i32, i32 } %7
 }
 
-declare { i8*, i32, i32 } @runtime.sliceAppend(i8*, i8*, i32, i32, i32, i32, i8*, i8*)
+declare { i8*, i32, i32 } @runtime.sliceAppend(i8*, i8* nocapture readonly, i32, i32, i32, i32, i8*, i8*)
 
 define hidden { i32*, i32, i32 } @main.sliceAppendSlice(i32* %ints.data, i32 %ints.len, i32 %ints.cap, i32* %added.data, i32 %added.len, i32 %added.cap, i8* %context, i8* %parentHandle) unnamed_addr {
 entry:
@@ -85,4 +85,4 @@ entry:
   ret i32 %copy.n
 }
 
-declare i32 @runtime.sliceCopy(i8*, i8*, i32, i32, i32, i8*, i8*)
+declare i32 @runtime.sliceCopy(i8* nocapture writeonly, i8* nocapture readonly, i32, i32, i32, i8*, i8*)

compiler/testdata/string.go

@@ -1,5 +1,13 @@
 package main
 
+func someString() string {
+	return "foo"
+}
+
+func zeroLengthString() string {
+	return ""
+}
+
 func stringLen(s string) int {
 	return len(s)
 }

compiler/testdata/string.ll

@@ -3,6 +3,10 @@ source_filename = "string.go"
 target datalayout = "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128"
 target triple = "i686--linux"
 
+%runtime._string = type { i8*, i32 }
+
+@"main.someString$string" = internal unnamed_addr constant [3 x i8] c"foo", align 1
+
 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
 
 define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
@@ -10,6 +14,16 @@ entry:
   ret void
 }
 
+define hidden %runtime._string @main.someString(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret %runtime._string { i8* getelementptr inbounds ([3 x i8], [3 x i8]* @"main.someString$string", i32 0, i32 0), i32 3 }
+}
+
+define hidden %runtime._string @main.zeroLengthString(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret %runtime._string zeroinitializer
+}
+
 define hidden i32 @main.stringLen(i8* %s.data, i32 %s.len, i8* %context, i8* %parentHandle) unnamed_addr {
 entry:
   ret i32 %s.len

goenv/goenv.go

@@ -171,8 +171,9 @@ func getGoroot() string {
 	switch runtime.GOOS {
 	case "linux":
 		candidates = []string{
-			"/usr/local/go", // manually installed
-			"/usr/lib/go",   // from the distribution
+			"/usr/local/go",     // manually installed
+			"/usr/lib/go",       // from the distribution
+			"/snap/go/current/", // installed using snap
 		}
 	case "darwin":
 		candidates = []string{

interp/compiler.go

@@ -25,6 +25,7 @@ type function struct {
 // basicBlock represents a LLVM basic block and contains a slice of
 // instructions. The last instruction must be a terminator instruction.
 type basicBlock struct {
+	phiNodes     []instruction
 	instructions []instruction
 }
 
@@ -135,6 +136,15 @@ func (r *runner) compileFunction(llvmFn llvm.Value) *function {
 				default:
 					panic("unknown number of operands")
 				}
+			case llvm.Switch:
+				// A switch is an array of (value, label) pairs, of which the
+				// first one indicates the to-switch value and the default
+				// label.
+				numOperands := llvmInst.OperandsCount()
+				for i := 0; i < numOperands; i += 2 {
+					inst.operands = append(inst.operands, r.getValue(llvmInst.Operand(i)))
+					inst.operands = append(inst.operands, literalValue{uint32(blockIndices[llvmInst.Operand(i+1)])})
+				}
 			case llvm.PHI:
 				inst.name = llvmInst.Name()
 				incomingCount := inst.llvmInst.IncomingCount()
@@ -337,7 +347,13 @@ func (r *runner) compileFunction(llvmFn llvm.Value) *function {
 				// This error is handled when actually trying to interpret this
 				// instruction (to not trigger on code that won't be executed).
 			}
-			bb.instructions = append(bb.instructions, inst)
+			if inst.opcode == llvm.PHI {
+				// PHI nodes need to be treated specially, see the comment in
+				// interpreter.go for an explanation.
+				bb.phiNodes = append(bb.phiNodes, inst)
+			} else {
+				bb.instructions = append(bb.instructions, inst)
+			}
 		}
 	}
 	return fn

interp/interp_test.go

@@ -13,9 +13,9 @@ import (
 func TestInterp(t *testing.T) {
 	for _, name := range []string{
 		"basic",
+		"phi",
 		"slice-copy",
 		"consteval",
-		"map",
 		"interface",
 	} {
 		name := name // make tc local to this closure

interp/interpreter.go

@@ -33,6 +33,50 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 	lastBB := -1 // last basic block is undefined, only defined after a branch
 	var operands []value
 	for instIndex := 0; instIndex < len(bb.instructions); instIndex++ {
+		if instIndex == 0 {
+			// This is the start of a new basic block.
+			// There may be PHI nodes that need to be resolved. Resolve all PHI
+			// nodes before continuing with regular instructions.
+			// PHI nodes need to be treated specially because they can have a
+			// mutual dependency:
+			//   for.loop:
+			//     %a = phi i8 [ 1, %entry ], [ %b, %for.loop ]
+			//     %b = phi i8 [ 3, %entry ], [ %a, %for.loop ]
+			// If these PHI nodes are processed like a regular instruction, %a
+			// and %b are both 3 on the second iteration of the loop because %b
+			// loads the value of %a from the second iteration, while it should
+			// load the value from the previous iteration. The correct behavior
+			// is that these two values swap each others place on each
+			// iteration.
+			var phiValues []value
+			var phiIndices []int
+			for _, inst := range bb.phiNodes {
+				var result value
+				for i := 0; i < len(inst.operands); i += 2 {
+					if int(inst.operands[i].(literalValue).value.(uint32)) == lastBB {
+						incoming := inst.operands[i+1]
+						if local, ok := incoming.(localValue); ok {
+							result = locals[fn.locals[local.value]]
+						} else {
+							result = incoming
+						}
+						break
+					}
+				}
+				if r.debug {
+					fmt.Fprintln(os.Stderr, indent+"phi", inst.operands, "->", result)
+				}
+				if result == nil {
+					panic("could not find PHI input")
+				}
+				phiValues = append(phiValues, result)
+				phiIndices = append(phiIndices, inst.localIndex)
+			}
+			for i, value := range phiValues {
+				locals[phiIndices[i]] = value
+			}
+		}
+
 		inst := bb.instructions[instIndex]
 		operands = operands[:0]
 		isRuntimeInst := false
@@ -103,27 +147,24 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 			default:
 				panic("unknown operands length")
 			}
-			break // continue with next block
-		case llvm.PHI:
-			var result value
-			for i := 0; i < len(inst.operands); i += 2 {
-				if int(inst.operands[i].(literalValue).value.(uint32)) == lastBB {
-					incoming := inst.operands[i+1]
-					if local, ok := incoming.(localValue); ok {
-						result = locals[fn.locals[local.value]]
-					} else {
-						result = incoming
-					}
+		case llvm.Switch:
+			// Switch statement: [value, defaultLabel, case0, label0, case1, label1, ...]
+			value := operands[0].Uint()
+			targetLabel := operands[1].Uint() // default label
+			// Do a lazy switch by iterating over all cases.
+			for i := 2; i < len(operands); i += 2 {
+				if value == operands[i].Uint() {
+					targetLabel = operands[i+1].Uint()
 					break
 				}
 			}
+			lastBB = currentBB
+			currentBB = int(targetLabel)
+			bb = fn.blocks[currentBB]
+			instIndex = -1 // start at 0 the next cycle
 			if r.debug {
-				fmt.Fprintln(os.Stderr, indent+"phi", inst.operands, "->", result)
+				fmt.Fprintln(os.Stderr, indent+"switch", operands, "->", currentBB)
 			}
-			if result == nil {
-				panic("could not find PHI input")
-			}
-			locals[inst.localIndex] = result
 		case llvm.Select:
 			// Select is much like a ternary operator: it picks a result from
 			// the second and third operand based on the boolean first operand.
@@ -155,7 +196,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				// which case this call won't even get to this point but will
 				// already be emitted in initAll.
 				continue
-			case strings.HasPrefix(callFn.name, "runtime.print") || callFn.name == "runtime._panic" || callFn.name == "runtime.hashmapGet":
+			case strings.HasPrefix(callFn.name, "runtime.print") || callFn.name == "runtime._panic" || callFn.name == "runtime.hashmapGet" || callFn.name == "os.runtime_args":
 				// These functions should be run at runtime. Specifically:
 				//   * Print and panic functions are best emitted directly without
 				//     interpreting them, otherwise we get a ton of putchar (etc.)
@@ -163,6 +204,9 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				//   * runtime.hashmapGet tries to access the map value directly.
 				//     This is not possible as the map value is treated as a special
 				//     kind of object in this package.
+				//   * os.runtime_args reads globals that are initialized outside
+				//     the view of the interp package so it always needs to be run
+				//     at runtime.
 				err := r.runAtRuntime(fn, inst, locals, &mem, indent)
 				if err != nil {
 					return nil, mem, err
@@ -328,7 +372,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 					return nil, mem, r.errorAt(inst, err)
 				}
 				actualType := actualTypePtrToInt.Operand(0)
-				if actualType.Name()+"$id" == assertedType.Name() {
+				if strings.TrimPrefix(actualType.Name(), "reflect/types.type:") == strings.TrimPrefix(assertedType.Name(), "reflect/types.typeid:") {
 					locals[inst.localIndex] = literalValue{uint8(1)}
 				} else {
 					locals[inst.localIndex] = literalValue{uint8(0)}
@@ -415,74 +459,6 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 					return nil, mem, r.errorAt(inst, errors.New("could not find method: "+signature.Name()))
 				}
 				locals[inst.localIndex] = r.getValue(method)
-			case callFn.name == "runtime.hashmapMake":
-				// Create a new map.
-				hashmapPointerType := inst.llvmInst.Type()
-				keySize := uint32(operands[1].Uint())
-				valueSize := uint32(operands[2].Uint())
-				m := newMapValue(r, hashmapPointerType, keySize, valueSize)
-				alloc := object{
-					llvmType:   hashmapPointerType,
-					globalName: r.pkgName + "$map",
-					buffer:     m,
-					size:       m.len(r),
-				}
-				index := len(r.objects)
-				r.objects = append(r.objects, alloc)
-
-				// Create a pointer to this map. Maps are reference types, so
-				// are implemented as pointers.
-				ptr := newPointerValue(r, index, 0)
-				if r.debug {
-					fmt.Fprintln(os.Stderr, indent+"runtime.hashmapMake:", keySize, valueSize, "->", ptr)
-				}
-				locals[inst.localIndex] = ptr
-			case callFn.name == "runtime.hashmapBinarySet":
-				// Do a mapassign operation with a binary key (that is, without
-				// a string key).
-				if r.debug {
-					fmt.Fprintln(os.Stderr, indent+"runtime.hashmapBinarySet:", operands[1:])
-				}
-				mapPtr, err := operands[1].asPointer(r)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-				m := mem.getWritable(mapPtr.index()).buffer.(*mapValue)
-				keyPtr, err := operands[2].asPointer(r)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-				valuePtr, err := operands[3].asPointer(r)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-				err = m.putBinary(&mem, keyPtr, valuePtr)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-			case callFn.name == "runtime.hashmapStringSet":
-				// Do a mapassign operation with a string key.
-				if r.debug {
-					fmt.Fprintln(os.Stderr, indent+"runtime.hashmapBinarySet:", operands[1:])
-				}
-				mapPtr, err := operands[1].asPointer(r)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-				m := mem.getWritable(mapPtr.index()).buffer.(*mapValue)
-				stringPtr, err := operands[2].asPointer(r)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-				stringLen := operands[3].Uint()
-				valuePtr, err := operands[4].asPointer(r)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
-				err = m.putString(&mem, stringPtr, stringLen, valuePtr)
-				if err != nil {
-					return nil, mem, r.errorAt(inst, err)
-				}
 			default:
 				if len(callFn.blocks) == 0 {
 					// Call to a function declaration without a definition

interp/memory.go

@@ -640,288 +640,6 @@ func (v pointerValue) toLLVMValue(llvmType llvm.Type, mem *memoryView) (llvm.Val
 	return gep, nil
 }
 
-// mapValue implements a Go map which is created at compile time and stored as a
-// global variable.
-// The value itself is only used as part of an object (object.buffer). Maps are
-// reference types aka pointers, so it can only be used as a pointerValue, not
-// directly.
-type mapValue struct {
-	r           *runner
-	pkgName     string
-	size        uint32 // byte size of runtime.hashmap
-	hashmap     llvm.Value
-	keyIsString bool
-	keys        []interface{} // either rawValue (for binary key) or mapStringKey (for string key)
-	values      []rawValue
-	keySize     uint32
-	valueSize   uint32
-}
-
-type mapStringKey struct {
-	buf  pointerValue
-	size uint64
-	data []uint64
-}
-
-func newMapValue(r *runner, hashmapPointerType llvm.Type, keySize, valueSize uint32) *mapValue {
-	size := uint32(r.targetData.TypeAllocSize(hashmapPointerType.ElementType()))
-	return &mapValue{
-		r:         r,
-		pkgName:   r.pkgName,
-		size:      size,
-		keySize:   keySize,
-		valueSize: valueSize,
-	}
-}
-
-func (v *mapValue) len(r *runner) uint32 {
-	return v.size
-}
-
-func (v *mapValue) clone() value {
-	// Return a copy of mapValue.
-	clone := *v
-	clone.keys = append([]interface{}{}, clone.keys...)
-	clone.values = append([]rawValue{}, clone.values...)
-	return &clone
-}
-
-func (v *mapValue) asPointer(r *runner) (pointerValue, error) {
-	panic("interp: mapValue.asPointer")
-}
-
-func (v *mapValue) asRawValue(r *runner) rawValue {
-	panic("interp: mapValue.asRawValue")
-}
-
-func (v *mapValue) Uint() uint64 {
-	panic("interp: mapValue.Uint")
-}
-
-func (v *mapValue) Int() int64 {
-	panic("interp: mapValue.Int")
-}
-
-// Temporary struct to collect data before turning this into a hashmap bucket
-// LLVM value.
-type mapBucket struct {
-	m       *mapValue
-	tophash [8]uint8
-	keys    []rawValue // can have up to 8 keys
-	values  []rawValue // can have up to 8 values, len(keys) == len(values)
-}
-
-// create returns a (pointer to a) buffer structurally equivalent to
-// runtime.hashmapBucket.
-func (b *mapBucket) create(ctx llvm.Context, nextBucket llvm.Value, mem *memoryView) llvm.Value {
-	// Create tophash array.
-	int8Type := ctx.Int8Type()
-	tophashValues := make([]llvm.Value, 8)
-	for i := range tophashValues {
-		tophashValues[i] = llvm.ConstInt(int8Type, uint64(b.tophash[i]), false)
-	}
-	tophash := llvm.ConstArray(int8Type, tophashValues)
-
-	// Create next pointer (if not set).
-	if nextBucket.IsNil() {
-		nextBucket = llvm.ConstNull(llvm.PointerType(int8Type, 0))
-	}
-
-	// Create data for keys.
-	var keyValues []llvm.Value
-	for _, key := range b.keys {
-		keyValue, err := key.rawLLVMValue(mem)
-		if err != nil {
-			panic(err)
-		}
-		keyValues = append(keyValues, keyValue)
-	}
-	if len(b.keys) < 8 {
-		keyValues = append(keyValues, llvm.ConstNull(llvm.ArrayType(int8Type, int(b.m.keySize)*(8-len(b.keys)))))
-	}
-	keyValue := ctx.ConstStruct(keyValues, false)
-	if checks && uint32(b.m.r.targetData.TypeAllocSize(keyValue.Type())) != b.m.keySize*8 {
-		panic("key size invalid")
-	}
-
-	// Create data for values.
-	var valueValues []llvm.Value
-	for _, value := range b.values {
-		v, err := value.rawLLVMValue(mem)
-		if err != nil {
-			panic(err)
-		}
-		valueValues = append(valueValues, v)
-	}
-	if len(b.values) < 8 {
-		valueValues = append(valueValues, llvm.ConstNull(llvm.ArrayType(int8Type, int(b.m.valueSize)*(8-len(b.values)))))
-	}
-	valueValue := ctx.ConstStruct(valueValues, false)
-	if checks && uint32(b.m.r.targetData.TypeAllocSize(valueValue.Type())) != b.m.valueSize*8 {
-		panic("value size invalid")
-	}
-
-	// Create the bucket.
-	bucketInitializer := ctx.ConstStruct([]llvm.Value{
-		tophash,
-		nextBucket,
-		keyValue,
-		valueValue,
-	}, false)
-	bucket := llvm.AddGlobal(b.m.r.mod, bucketInitializer.Type(), b.m.pkgName+"$mapbucket")
-	bucket.SetInitializer(bucketInitializer)
-	bucket.SetLinkage(llvm.InternalLinkage)
-	bucket.SetUnnamedAddr(true)
-	return bucket
-}
-
-func (v *mapValue) toLLVMValue(hashmapType llvm.Type, mem *memoryView) (llvm.Value, error) {
-	if !v.hashmap.IsNil() {
-		return v.hashmap, nil
-	}
-
-	// Create a slice of buckets with all the keys and values in the hashmap.
-	var buckets []*mapBucket
-	var bucket *mapBucket
-	for i, key := range v.keys {
-		var data []uint64
-		var keyValue rawValue
-		switch key := key.(type) {
-		case mapStringKey:
-			data = key.data
-			keyValue = newRawValue(v.keySize)
-			// runtime._string is {ptr, length}
-			for i := uint32(0); i < v.keySize/2; i++ {
-				keyValue.buf[i] = key.buf.pointer
-			}
-			copy(keyValue.buf[v.keySize/2:], literalValue{key.size}.asRawValue(v.r).buf)
-		case rawValue:
-			if key.hasPointer() {
-				return llvm.Value{}, errors.New("interp: todo: map key with pointer")
-			}
-			data = key.buf
-			keyValue = key
-		default:
-			return llvm.Value{}, errors.New("interp: unknown map key type")
-		}
-		buf := make([]byte, len(data))
-		for i, p := range data {
-			buf[i] = byte(p)
-		}
-		hash := v.hash(buf)
-
-		if i%8 == 0 {
-			bucket = &mapBucket{m: v}
-			buckets = append(buckets, bucket)
-		}
-		bucket.tophash[i%8] = v.topHash(hash)
-		bucket.keys = append(bucket.keys, keyValue)
-		bucket.values = append(bucket.values, v.values[i])
-	}
-
-	// Convert these buckets into LLVM global variables.
-	ctx := v.r.mod.Context()
-	var nextBucket llvm.Value
-	for i := len(buckets) - 1; i >= 0; i-- {
-		bucket = buckets[i]
-		bucketValue := bucket.create(ctx, nextBucket, mem)
-		nextBucket = bucketValue
-	}
-	firstBucket := nextBucket
-	if firstBucket.IsNil() {
-		firstBucket = llvm.ConstNull(mem.r.i8ptrType)
-	} else {
-		firstBucket = llvm.ConstBitCast(firstBucket, mem.r.i8ptrType)
-	}
-
-	// Create the hashmap itself, pointing to these buckets.
-	hashmapPointerType := llvm.PointerType(hashmapType, 0)
-	hashmap := llvm.ConstNamedStruct(hashmapType, []llvm.Value{
-		llvm.ConstPointerNull(hashmapPointerType), // next
-		firstBucket, // buckets
-		llvm.ConstInt(hashmapType.StructElementTypes()[2], uint64(len(v.keys)), false), // count
-		llvm.ConstInt(ctx.Int8Type(), uint64(v.keySize), false),                        // keySize
-		llvm.ConstInt(ctx.Int8Type(), uint64(v.valueSize), false),                      // valueSize
-		llvm.ConstInt(ctx.Int8Type(), 0, false),                                        // bucketBits
-	})
-
-	v.hashmap = hashmap
-	return v.hashmap, nil
-}
-
-// putString does a map assign operation, assuming that the map is of type
-// map[string]T.
-func (v *mapValue) putString(mem *memoryView, stringBuf pointerValue, stringLen uint64, valuePtr pointerValue) error {
-	if !v.hashmap.IsNil() {
-		return errMapAlreadyCreated
-	}
-
-	value := mem.load(valuePtr, v.valueSize)
-	stringValue := mem.load(stringBuf, uint32(stringLen)).asRawValue(v.r)
-	if stringValue.hasPointer() {
-		panic("interp: string contains pointer")
-	}
-
-	// TODO: avoid duplicate keys
-	v.keys = append(v.keys, mapStringKey{stringBuf, stringLen, stringValue.buf})
-	v.values = append(v.values, value.asRawValue(v.r))
-	v.keyIsString = true
-
-	return nil
-}
-
-// putBinary does a map assign operation for binary data (e.g. [3]int etc). The
-// key must not contain pointer values.
-func (v *mapValue) putBinary(mem *memoryView, keyPtr, valuePtr pointerValue) error {
-	if !v.hashmap.IsNil() {
-		return errMapAlreadyCreated
-	}
-
-	key := mem.load(keyPtr, v.keySize)
-	value := mem.load(valuePtr, v.valueSize)
-
-	// Sanity checks.
-	if v.keySize != key.len(mem.r) || v.valueSize != value.len(mem.r) {
-		// This is a bug (not unhandled input), so panic.
-		panic("interp: key or value size mismatch")
-	}
-	if v.keyIsString {
-		panic("cannot put binary keys in string map")
-	}
-
-	// TODO: avoid duplicate keys
-	v.keys = append(v.keys, key.asRawValue(v.r))
-	v.values = append(v.values, value.asRawValue(v.r))
-
-	return nil
-}
-
-// Get FNV-1a hash of this string.
-//
-// https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash
-func (v *mapValue) hash(data []byte) uint32 {
-	var result uint32 = 2166136261 // FNV offset basis
-	for _, c := range data {
-		result ^= uint32(c)
-		result *= 16777619 // FNV prime
-	}
-	return result
-}
-
-// Get the topmost 8 bits of the hash, without using a special value (like 0).
-func (v *mapValue) topHash(hash uint32) uint8 {
-	tophash := uint8(hash >> 24)
-	if tophash < 1 {
-		// 0 means empty slot, so make it bigger.
-		tophash++
-	}
-	return tophash
-}
-
-func (v *mapValue) String() string {
-	return "<map keySize=" + strconv.Itoa(int(v.keySize)) + " valueSize=" + strconv.Itoa(int(v.valueSize)) + ">"
-}
-
 // rawValue is a raw memory buffer that can store either pointers or regular
 // data. This is the fallback data for everything that isn't clearly a
 // literalValue or pointerValue.

interp/testdata/basic.ll

@@ -65,6 +65,12 @@ entry:
   call void @modifyExternal(i32* bitcast (void ()* @willModifyGlobal to i32*))
   store i16 7, i16* @main.exposedValue2
 
+  ; Test switch statement.
+  %switch1 = call i64 @testSwitch(i64 1) ; 1 returns 6
+  %switch2 = call i64 @testSwitch(i64 9) ; 9 returns the default value -1
+  call void @runtime.printint64(i64 %switch1)
+  call void @runtime.printint64(i64 %switch2)
+
   ret void
 }
 
@@ -87,3 +93,22 @@ entry:
   store i16 8, i16* @main.exposedValue2
   ret void
 }
+
+define i64 @testSwitch(i64 %val) {
+entry:
+  ; Test switch statement.
+  switch i64 %val, label %otherwise [ i64 0, label %zero
+                                      i64 1, label %one
+                                      i64 2, label %two ]
+zero:
+  ret i64 5
+
+one:
+  ret i64 6
+
+two:
+  ret i64 7
+
+otherwise:
+  ret i64 -1
+}

interp/testdata/basic.out.ll

@@ -25,6 +25,8 @@ entry:
   store i16 5, i16* @main.exposedValue1
   call void @modifyExternal(i32* bitcast (void ()* @willModifyGlobal to i32*))
   store i16 7, i16* @main.exposedValue2
+  call void @runtime.printint64(i64 6)
+  call void @runtime.printint64(i64 -1)
   ret void
 }
 
@@ -44,3 +46,24 @@ entry:
   store i16 8, i16* @main.exposedValue2
   ret void
 }
+
+define i64 @testSwitch(i64 %val) local_unnamed_addr {
+entry:
+  switch i64 %val, label %otherwise [
+    i64 0, label %zero
+    i64 1, label %one
+    i64 2, label %two
+  ]
+
+zero:                                             ; preds = %entry
+  ret i64 5
+
+one:                                              ; preds = %entry
+  ret i64 6
+
+two:                                              ; preds = %entry
+  ret i64 7
+
+otherwise:                                        ; preds = %entry
+  ret i64 -1
+}

interp/testdata/interface.ll

@@ -6,7 +6,7 @@ target triple = "x86_64--linux"
 
 @main.v1 = global i1 0
 @"reflect/types.type:named:main.foo" = private constant %runtime.typecodeID { %runtime.typecodeID* @"reflect/types.type:basic:int", i64 0, %runtime.interfaceMethodInfo* null }
-@"reflect/types.type:named:main.foo$id" = external constant i8
+@"reflect/types.typeid:named:main.foo" = external constant i8
 @"reflect/types.type:basic:int" = external constant %runtime.typecodeID
 
 
@@ -21,7 +21,7 @@ entry:
 define internal void @main.init() unnamed_addr {
 entry:
   ; Test type asserts.
-  %typecode = call i1 @runtime.typeAssert(i64 ptrtoint (%runtime.typecodeID* @"reflect/types.type:named:main.foo" to i64), i8* @"reflect/types.type:named:main.foo$id", i8* undef, i8* null)
+  %typecode = call i1 @runtime.typeAssert(i64 ptrtoint (%runtime.typecodeID* @"reflect/types.type:named:main.foo" to i64), i8* @"reflect/types.typeid:named:main.foo", i8* undef, i8* null)
   store i1 %typecode, i1* @main.v1
   ret void
 }

interp/testdata/map.ll

@@ -1,74 +0,0 @@
-target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
-target triple = "armv6m-none-eabi"
-
-%runtime._string = type { i8*, i32 }
-%runtime.hashmap = type { %runtime.hashmap*, i8*, i32, i8, i8, i8 }
-
-@main.m = global %runtime.hashmap* null
-@main.binaryMap = global %runtime.hashmap* null
-@main.stringMap = global %runtime.hashmap* null
-@main.init.string = internal unnamed_addr constant [7 x i8] c"CONNECT"
-
-declare %runtime.hashmap* @runtime.hashmapMake(i8, i8, i32, i8* %context, i8* %parentHandle)
-declare void @runtime.hashmapBinarySet(%runtime.hashmap*, i8*, i8*, i8* %context, i8* %parentHandle)
-declare void @runtime.hashmapStringSet(%runtime.hashmap*, i8*, i32, i8*, i8* %context, i8* %parentHandle)
-declare void @llvm.lifetime.end.p0i8(i64, i8*)
-declare void @llvm.lifetime.start.p0i8(i64, i8*)
-
-define void @runtime.initAll() unnamed_addr {
-entry:
-  call void @main.init(i8* undef, i8* null)
-  ret void
-}
-
-define internal void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
-entry:
-; Test that hashmap optimizations generally work (even with lifetimes).
-  %hashmap.key = alloca i8
-  %hashmap.value = alloca %runtime._string
-  %0 = call %runtime.hashmap* @runtime.hashmapMake(i8 1, i8 8, i32 1, i8* undef, i8* null)
-  %hashmap.value.bitcast = bitcast %runtime._string* %hashmap.value to i8*
-  call void @llvm.lifetime.start.p0i8(i64 8, i8* %hashmap.value.bitcast)
-  store %runtime._string { i8* getelementptr inbounds ([7 x i8], [7 x i8]* @main.init.string, i32 0, i32 0), i32 7 }, %runtime._string* %hashmap.value
-  call void @llvm.lifetime.start.p0i8(i64 1, i8* %hashmap.key)
-  store i8 1, i8* %hashmap.key
-  call void @runtime.hashmapBinarySet(%runtime.hashmap* %0, i8* %hashmap.key, i8* %hashmap.value.bitcast, i8* undef, i8* null)
-  call void @llvm.lifetime.end.p0i8(i64 1, i8* %hashmap.key)
-  call void @llvm.lifetime.end.p0i8(i64 8, i8* %hashmap.value.bitcast)
-  store %runtime.hashmap* %0, %runtime.hashmap** @main.m
-
-  ; Other tests, that can be done in a separate function.
-  call void @main.testNonConstantBinarySet()
-  call void @main.testNonConstantStringSet()
-  ret void
-}
-
-; Test that a map loaded from a global can still be used for mapassign
-; operations (with binary keys).
-define internal void @main.testNonConstantBinarySet() {
-  %hashmap.key = alloca i8
-  %hashmap.value = alloca i8
-  ; Create hashmap from global.
-  %map.new = call %runtime.hashmap* @runtime.hashmapMake(i8 1, i8 1, i32 1, i8* undef, i8* null)
-  store %runtime.hashmap* %map.new, %runtime.hashmap** @main.binaryMap
-  %map = load %runtime.hashmap*, %runtime.hashmap** @main.binaryMap
-  ; Do the binary set to the newly loaded map.
-  store i8 1, i8* %hashmap.key
-  store i8 2, i8* %hashmap.value
-  call void @runtime.hashmapBinarySet(%runtime.hashmap* %map, i8* %hashmap.key, i8* %hashmap.value, i8* undef, i8* null)
-  ret void
-}
-
-; Test that a map loaded from a global can still be used for mapassign
-; operations (with string keys).
-define internal void @main.testNonConstantStringSet() {
-  %hashmap.value = alloca i8
-  ; Create hashmap from global.
-  %map.new = call %runtime.hashmap* @runtime.hashmapMake(i8 8, i8 1, i32 1, i8* undef, i8* null)
-  store %runtime.hashmap* %map.new, %runtime.hashmap** @main.stringMap
-  %map = load %runtime.hashmap*, %runtime.hashmap** @main.stringMap
-  ; Do the string set to the newly loaded map.
-  store i8 2, i8* %hashmap.value
-  call void @runtime.hashmapStringSet(%runtime.hashmap* %map, i8* getelementptr inbounds ([7 x i8], [7 x i8]* @main.init.string, i32 0, i32 0), i32 7, i8* %hashmap.value, i8* undef, i8* null)
-  ret void
-}

interp/testdata/map.out.ll

@@ -1,20 +0,0 @@
-target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
-target triple = "armv6m-none-eabi"
-
-%runtime.hashmap = type { %runtime.hashmap*, i8*, i32, i8, i8, i8 }
-
-@main.m = local_unnamed_addr global %runtime.hashmap* @"main$map"
-@main.binaryMap = local_unnamed_addr global %runtime.hashmap* @"main$map.1"
-@main.stringMap = local_unnamed_addr global %runtime.hashmap* @"main$map.3"
-@main.init.string = internal unnamed_addr constant [7 x i8] c"CONNECT"
-@"main$map" = internal global %runtime.hashmap { %runtime.hashmap* null, i8* getelementptr inbounds ({ [8 x i8], i8*, { i8, [7 x i8] }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } }, { [8 x i8], i8*, { i8, [7 x i8] }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } }* @"main$mapbucket", i32 0, i32 0, i32 0), i32 1, i8 1, i8 8, i8 0 }
-@"main$mapbucket" = internal unnamed_addr global { [8 x i8], i8*, { i8, [7 x i8] }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } } { [8 x i8] c"\04\00\00\00\00\00\00\00", i8* null, { i8, [7 x i8] } { i8 1, [7 x i8] zeroinitializer }, { { [7 x i8]*, [4 x i8] }, [56 x i8] } { { [7 x i8]*, [4 x i8] } { [7 x i8]* @main.init.string, [4 x i8] c"\07\00\00\00" }, [56 x i8] zeroinitializer } }
-@"main$map.1" = internal global %runtime.hashmap { %runtime.hashmap* null, i8* getelementptr inbounds ({ [8 x i8], i8*, { i8, [7 x i8] }, { i8, [7 x i8] } }, { [8 x i8], i8*, { i8, [7 x i8] }, { i8, [7 x i8] } }* @"main$mapbucket.2", i32 0, i32 0, i32 0), i32 1, i8 1, i8 1, i8 0 }
-@"main$mapbucket.2" = internal unnamed_addr global { [8 x i8], i8*, { i8, [7 x i8] }, { i8, [7 x i8] } } { [8 x i8] c"\04\00\00\00\00\00\00\00", i8* null, { i8, [7 x i8] } { i8 1, [7 x i8] zeroinitializer }, { i8, [7 x i8] } { i8 2, [7 x i8] zeroinitializer } }
-@"main$map.3" = internal global %runtime.hashmap { %runtime.hashmap* null, i8* getelementptr inbounds ({ [8 x i8], i8*, { { [7 x i8]*, [4 x i8] }, [56 x i8] }, { i8, [7 x i8] } }, { [8 x i8], i8*, { { [7 x i8]*, [4 x i8] }, [56 x i8] }, { i8, [7 x i8] } }* @"main$mapbucket.4", i32 0, i32 0, i32 0), i32 1, i8 8, i8 1, i8 0 }
-@"main$mapbucket.4" = internal unnamed_addr global { [8 x i8], i8*, { { [7 x i8]*, [4 x i8] }, [56 x i8] }, { i8, [7 x i8] } } { [8 x i8] c"x\00\00\00\00\00\00\00", i8* null, { { [7 x i8]*, [4 x i8] }, [56 x i8] } { { [7 x i8]*, [4 x i8] } { [7 x i8]* @main.init.string, [4 x i8] c"\07\00\00\00" }, [56 x i8] zeroinitializer }, { i8, [7 x i8] } { i8 2, [7 x i8] zeroinitializer } }
-
-define void @runtime.initAll() unnamed_addr {
-entry:
-  ret void
-}

interp/testdata/phi.ll

@@ -0,0 +1,31 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+@main.phiNodesResultA = global i8 0
+@main.phiNodesResultB = global i8 0
+
+define void @runtime.initAll() {
+  call void @main.init()
+  ret void
+}
+
+; PHI nodes always use the value from the previous block, even in a loop. This
+; means that the loop below should swap the values %a and %b on each iteration.
+; Previously there was a bug which resulted in %b getting the value 3 on the
+; second iteration while it should have gotten 1 (from the first iteration of
+; %for.loop).
+define internal void @main.init() {
+entry:
+  br label %for.loop
+
+for.loop:
+  %a = phi i8 [ 1, %entry ], [ %b, %for.loop ]
+  %b = phi i8 [ 3, %entry ], [ %a, %for.loop ]
+  %icmp = icmp eq i8 %a, 3
+  br i1 %icmp, label %for.done, label %for.loop
+
+for.done:
+  store i8 %a, i8* @main.phiNodesResultA
+  store i8 %b, i8* @main.phiNodesResultB
+  ret void
+}

interp/testdata/phi.out.ll

@@ -0,0 +1,9 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64--linux"
+
+@main.phiNodesResultA = local_unnamed_addr global i8 3
+@main.phiNodesResultB = local_unnamed_addr global i8 1
+
+define void @runtime.initAll() local_unnamed_addr {
+  ret void
+}

main.go

@@ -13,11 +13,13 @@ import (
 	"os/exec"
 	"os/signal"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strings"
 	"sync/atomic"
 	"time"
 
+	"github.com/google/shlex"
 	"github.com/mattn/go-colorable"
 	"github.com/tinygo-org/tinygo/builder"
 	"github.com/tinygo-org/tinygo/compileopts"
@@ -28,6 +30,7 @@ import (
 	"tinygo.org/x/go-llvm"
 
 	"go.bug.st/serial"
+	"go.bug.st/serial/enumerator"
 )
 
 var (
@@ -240,15 +243,12 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 	return builder.Build(pkgName, fileExt, config, func(result builder.BuildResult) error {
 		// do we need port reset to put MCU into bootloader mode?
 		if config.Target.PortReset == "true" && flashMethod != "openocd" {
-			if port == "" {
-				var err error
-				port, err = getDefaultPort()
-				if err != nil {
-					return err
-				}
+			port, err := getDefaultPort(strings.FieldsFunc(port, func(c rune) bool { return c == ',' }))
+			if err != nil {
+				return err
 			}
 
-			err := touchSerialPortAt1200bps(port)
+			err = touchSerialPortAt1200bps(port)
 			if err != nil {
 				return &commandError{"failed to reset port", result.Binary, err}
 			}
@@ -264,9 +264,9 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 			fileToken := "{" + fileExt[1:] + "}"
 			flashCmd = strings.ReplaceAll(flashCmd, fileToken, result.Binary)
 
-			if port == "" && strings.Contains(flashCmd, "{port}") {
+			if strings.Contains(flashCmd, "{port}") {
 				var err error
-				port, err = getDefaultPort()
+				port, err = getDefaultPort(strings.FieldsFunc(port, func(c rune) bool { return c == ',' }))
 				if err != nil {
 					return err
 				}
@@ -665,41 +665,66 @@ func windowsFindUSBDrive(volume string, options *compileopts.Options) (string, e
 }
 
 // getDefaultPort returns the default serial port depending on the operating system.
-func getDefaultPort() (port string, err error) {
-	var portPath string
+func getDefaultPort(portCandidates []string) (port string, err error) {
+	if len(portCandidates) == 1 {
+		return portCandidates[0], nil
+	}
+
+	var ports []string
 	switch runtime.GOOS {
-	case "darwin":
-		portPath = "/dev/cu.usb*"
-	case "linux":
-		portPath = "/dev/ttyACM*"
 	case "freebsd":
-		portPath = "/dev/cuaU*"
-	case "windows":
-		ports, err := serial.GetPortsList()
+		ports, err = filepath.Glob("/dev/cuaU*")
+	case "darwin", "linux", "windows":
+		var portsList []*enumerator.PortDetails
+		portsList, err = enumerator.GetDetailedPortsList()
 		if err != nil {
 			return "", err
 		}
 
-		if len(ports) == 0 {
-			return "", errors.New("no serial ports available")
-		} else if len(ports) > 1 {
-			return "", errors.New("multiple serial ports available - use -port flag")
+		for _, p := range portsList {
+			ports = append(ports, p.Name)
 		}
 
-		return ports[0], nil
+		if ports == nil || len(ports) == 0 {
+			// fallback
+			switch runtime.GOOS {
+			case "darwin":
+				ports, err = filepath.Glob("/dev/cu.usb*")
+			case "linux":
+				ports, err = filepath.Glob("/dev/ttyACM*")
+			case "windows":
+				ports, err = serial.GetPortsList()
+			}
+		}
 	default:
 		return "", errors.New("unable to search for a default USB device to be flashed on this OS")
 	}
 
-	d, err := filepath.Glob(portPath)
 	if err != nil {
 		return "", err
-	}
-	if d == nil {
+	} else if ports == nil {
 		return "", errors.New("unable to locate a serial port")
+	} else if len(ports) == 0 {
+		return "", errors.New("no serial ports available")
 	}
 
-	return d[0], nil
+	if len(portCandidates) == 0 {
+		if len(ports) == 1 {
+			return ports[0], nil
+		} else {
+			return "", errors.New("multiple serial ports available - use -port flag, available ports are " + strings.Join(ports, ", "))
+		}
+	}
+
+	for _, ps := range portCandidates {
+		for _, p := range ports {
+			if p == ps {
+				return p, nil
+			}
+		}
+	}
+
+	return "", errors.New("port you specified '" + strings.Join(portCandidates, ",") + "' does not exist, available ports are " + strings.Join(ports, ", "))
 }
 
 func usage() {
@@ -812,6 +837,52 @@ func handleCompilerError(err error) {
 	}
 }
 
+// This is a special type for the -X flag to parse the pkgpath.Var=stringVal
+// format. It has to be a special type to allow multiple variables to be defined
+// this way.
+type globalValuesFlag map[string]map[string]string
+
+func (m globalValuesFlag) String() string {
+	return "pkgpath.Var=value"
+}
+
+func (m globalValuesFlag) Set(value string) error {
+	equalsIndex := strings.IndexByte(value, '=')
+	if equalsIndex < 0 {
+		return errors.New("expected format pkgpath.Var=value")
+	}
+	pathAndName := value[:equalsIndex]
+	pointIndex := strings.LastIndexByte(pathAndName, '.')
+	if pointIndex < 0 {
+		return errors.New("expected format pkgpath.Var=value")
+	}
+	path := pathAndName[:pointIndex]
+	name := pathAndName[pointIndex+1:]
+	stringValue := value[equalsIndex+1:]
+	if m[path] == nil {
+		m[path] = make(map[string]string)
+	}
+	m[path][name] = stringValue
+	return nil
+}
+
+// parseGoLinkFlag parses the -ldflags parameter. Its primary purpose right now
+// is the -X flag, for setting the value of global string variables.
+func parseGoLinkFlag(flagsString string) (map[string]map[string]string, error) {
+	set := flag.NewFlagSet("link", flag.ExitOnError)
+	globalVarValues := make(globalValuesFlag)
+	set.Var(globalVarValues, "X", "Set the value of the string variable to the given value.")
+	flags, err := shlex.Split(flagsString)
+	if err != nil {
+		return nil, err
+	}
+	err = set.Parse(flags)
+	if err != nil {
+		return nil, err
+	}
+	return map[string]map[string]string(globalVarValues), nil
+}
+
 func main() {
 	if len(os.Args) < 2 {
 		fmt.Fprintln(os.Stderr, "No command-line arguments supplied.")
@@ -831,13 +902,13 @@ func main() {
 	target := flag.String("target", "", "LLVM target | .json file with TargetSpec")
 	printSize := flag.String("size", "", "print sizes (none, short, full)")
 	printStacks := flag.Bool("print-stacks", false, "print stack sizes of goroutines")
+	printAllocsString := flag.String("print-allocs", "", "regular expression of functions for which heap allocations should be printed")
 	printCommands := flag.Bool("x", false, "Print commands")
 	nodebug := flag.Bool("no-debug", false, "disable DWARF debug symbol generation")
 	ocdOutput := flag.Bool("ocd-output", false, "print OCD daemon output during debug")
-	port := flag.String("port", "", "flash port")
+	port := flag.String("port", "", "flash port (can specify multiple candidates separated by commas)")
 	programmer := flag.String("programmer", "", "which hardware programmer to use")
-	cFlags := flag.String("cflags", "", "additional cflags for compiler")
-	ldFlags := flag.String("ldflags", "", "additional ldflags for linker")
+	ldflags := flag.String("ldflags", "", "Go link tool compatible ldflags")
 	wasmAbi := flag.String("wasm-abi", "", "WebAssembly ABI conventions: js (no i64 params) or generic")
 
 	var flagJSON, flagDeps *bool
@@ -867,6 +938,19 @@ func main() {
 	}
 
 	flag.CommandLine.Parse(os.Args[2:])
+	globalVarValues, err := parseGoLinkFlag(*ldflags)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	var printAllocs *regexp.Regexp
+	if *printAllocsString != "" {
+		printAllocs, err = regexp.Compile(*printAllocsString)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+	}
 	options := &compileopts.Options{
 		Target:        *target,
 		Opt:           *opt,
@@ -879,23 +963,17 @@ func main() {
 		Debug:         !*nodebug,
 		PrintSizes:    *printSize,
 		PrintStacks:   *printStacks,
+		PrintAllocs:   printAllocs,
 		PrintCommands: *printCommands,
 		Tags:          *tags,
+		GlobalValues:  globalVarValues,
 		WasmAbi:       *wasmAbi,
 		Programmer:    *programmer,
 	}
 
-	if *cFlags != "" {
-		options.CFlags = strings.Split(*cFlags, " ")
-	}
-
-	if *ldFlags != "" {
-		options.LDFlags = strings.Split(*ldFlags, " ")
-	}
-
 	os.Setenv("CC", "clang -target="+*target)
 
-	err := options.Verify()
+	err = options.Verify()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err.Error())
 		usage()

main_test.go

@@ -13,7 +13,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"runtime"
-	"sort"
 	"strings"
 	"sync"
 	"testing"
@@ -29,41 +28,43 @@ const TESTDATA = "testdata"
 var testTarget = flag.String("target", "", "override test target")
 
 func TestCompiler(t *testing.T) {
-	matches, err := filepath.Glob(filepath.Join(TESTDATA, "*.go"))
-	if err != nil {
-		t.Fatal("could not read test files:", err)
+	tests := []string{
+		"alias.go",
+		"atomic.go",
+		"binop.go",
+		"calls.go",
+		"cgo/",
+		"channel.go",
+		"coroutines.go",
+		"float.go",
+		"gc.go",
+		"init.go",
+		"init_multi.go",
+		"interface.go",
+		"json.go",
+		"map.go",
+		"math.go",
+		"print.go",
+		"reflect.go",
+		"slice.go",
+		"sort.go",
+		"stdlib.go",
+		"string.go",
+		"structs.go",
+		"zeroalloc.go",
 	}
 
-	dirMatches, err := filepath.Glob(filepath.Join(TESTDATA, "*", "main.go"))
-	if err != nil {
-		t.Fatal("could not read test packages:", err)
-	}
-	if len(matches) == 0 || len(dirMatches) == 0 {
-		t.Fatal("no test files found")
-	}
-	for _, m := range dirMatches {
-		matches = append(matches, filepath.Dir(m)+string(filepath.Separator))
-	}
-
-	sort.Strings(matches)
-
 	if *testTarget != "" {
 		// This makes it possible to run one specific test (instead of all),
 		// which is especially useful to quickly check whether some changes
 		// affect a particular target architecture.
-		runPlatTests(*testTarget, matches, t)
+		runPlatTests(*testTarget, tests, t)
 		return
 	}
 
 	if runtime.GOOS != "windows" {
 		t.Run("Host", func(t *testing.T) {
-			runPlatTests("", matches, t)
-			if runtime.GOOS == "darwin" {
-				runTest("testdata/libc/filesystem.go", "", t,
-					nil, nil)
-				runTest("testdata/libc/env.go", "", t,
-					[]string{"ENV1=VALUE1", "ENV2=VALUE2"}, nil)
-			}
+			runPlatTests("", tests, t)
 		})
 	}
 
@@ -72,26 +73,26 @@ func TestCompiler(t *testing.T) {
 	}
 
 	t.Run("EmulatedCortexM3", func(t *testing.T) {
-		runPlatTests("cortex-m-qemu", matches, t)
+		runPlatTests("cortex-m-qemu", tests, t)
 	})
 
 	if runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
 		// Note: running only on Windows and macOS because Linux (as of 2020)
 		// usually has an outdated QEMU version that doesn't support RISC-V yet.
 		t.Run("EmulatedRISCV", func(t *testing.T) {
-			runPlatTests("riscv-qemu", matches, t)
+			runPlatTests("riscv-qemu", tests, t)
 		})
 	}
 
 	if runtime.GOOS == "linux" {
 		t.Run("X86Linux", func(t *testing.T) {
-			runPlatTests("i386--linux-gnu", matches, t)
+			runPlatTests("i386--linux-gnu", tests, t)
 		})
 		t.Run("ARMLinux", func(t *testing.T) {
-			runPlatTests("arm--linux-gnueabihf", matches, t)
+			runPlatTests("arm--linux-gnueabihf", tests, t)
 		})
 		t.Run("ARM64Linux", func(t *testing.T) {
-			runPlatTests("aarch64--linux-gnu", matches, t)
+			runPlatTests("aarch64--linux-gnu", tests, t)
 		})
 		goVersion, err := goenv.GorootVersionString(goenv.Get("GOROOT"))
 		if err != nil {
@@ -104,27 +105,72 @@ func TestCompiler(t *testing.T) {
 			// below that are also not supported but still seem to pass, so
 			// include them in the tests for now.
 			t.Run("WebAssembly", func(t *testing.T) {
-				runPlatTests("wasm", matches, t)
+				runPlatTests("wasm", tests, t)
 			})
 		}
 
 		t.Run("WASI", func(t *testing.T) {
-			runPlatTests("wasi", matches, t)
-			runTest("testdata/libc/env.go", "wasi", t,
-				[]string{"--env", "ENV1=VALUE1", "--env", "ENV2=VALUE2"}, nil)
-			runTest("testdata/libc/filesystem.go", "wasi", t, nil, []string{"--dir=."})
+			runPlatTests("wasi", tests, t)
 		})
 	}
+
+	// Test a few build options.
+	t.Run("build-options", func(t *testing.T) {
+		if runtime.GOOS == "windows" {
+			// These tests assume a host that is supported by TinyGo.
+			t.Skip("can't test build options on Windows")
+		}
+		t.Parallel()
+
+		// Test with few optimizations enabled (no inlining, etc).
+		t.Run("opt=1", func(t *testing.T) {
+			t.Parallel()
+			runTestWithConfig("stdlib.go", "", t, &compileopts.Options{
+				Opt: "1",
+			}, nil, nil)
+		})
+
+		// Test with only the bare minimum of optimizations enabled.
+		// TODO: fix this for stdlib.go, which currently fails.
+		t.Run("opt=0", func(t *testing.T) {
+			t.Parallel()
+			runTestWithConfig("print.go", "", t, &compileopts.Options{
+				Opt: "0",
+			}, nil, nil)
+		})
+
+		t.Run("ldflags", func(t *testing.T) {
+			t.Parallel()
+			runTestWithConfig("ldflags.go", "", t, &compileopts.Options{
+				Opt: "z",
+				GlobalValues: map[string]map[string]string{
+					"main": {
+						"someGlobal": "foobar",
+					},
+				},
+			}, nil, nil)
+		})
+	})
 }
 
-func runPlatTests(target string, matches []string, t *testing.T) {
+func runPlatTests(target string, tests []string, t *testing.T) {
 	t.Parallel()
 
-	for _, path := range matches {
-		path := path // redefine to avoid race condition
-		t.Run(filepath.Base(path), func(t *testing.T) {
+	for _, name := range tests {
+		name := name // redefine to avoid race condition
+		t.Run(name, func(t *testing.T) {
 			t.Parallel()
-			runTest(path, target, t, nil, nil)
+			runTest(name, target, t, nil, nil)
+		})
+	}
+	if target == "wasi" || target == "" {
+		t.Run("filesystem.go", func(t *testing.T) {
+			t.Parallel()
+			runTest("filesystem.go", target, t, nil, nil)
+		})
+		t.Run("env.go", func(t *testing.T) {
+			t.Parallel()
+			runTest("env.go", target, t, []string{"first", "second"}, []string{"ENV1=VALUE1", "ENV2=VALUE2"})
 		})
 	}
 }
@@ -141,10 +187,28 @@ func runBuild(src, out string, opts *compileopts.Options) error {
 	return Build(src, out, opts)
 }
 
-func runTest(path, target string, t *testing.T, environmentVars []string, additionalArgs []string) {
+func runTest(name, target string, t *testing.T, cmdArgs, environmentVars []string) {
+	options := &compileopts.Options{
+		Target:     target,
+		Opt:        "z",
+		PrintIR:    false,
+		DumpSSA:    false,
+		VerifyIR:   true,
+		Debug:      true,
+		PrintSizes: "",
+		WasmAbi:    "",
+	}
+	runTestWithConfig(name, target, t, options, cmdArgs, environmentVars)
+}
+
+func runTestWithConfig(name, target string, t *testing.T, options *compileopts.Options, cmdArgs, environmentVars []string) {
+	// Get the expected output for this test.
+	// Note: not using filepath.Join as it strips the path separator at the end
+	// of the path.
+	path := TESTDATA + "/" + name
 	// Get the expected output for this test.
 	txtpath := path[:len(path)-3] + ".txt"
-	if path[len(path)-1] == os.PathSeparator {
+	if path[len(path)-1] == '/' {
 		txtpath = path + "out.txt"
 	}
 	expected, err := ioutil.ReadFile(txtpath)
@@ -165,19 +229,8 @@ func runTest(path, target string, t *testing.T, environmentVars []string, additi
 	}()
 
 	// Build the test binary.
-	config := &compileopts.Options{
-		Target:     target,
-		Opt:        "z",
-		PrintIR:    false,
-		DumpSSA:    false,
-		VerifyIR:   true,
-		Debug:      true,
-		PrintSizes: "",
-		WasmAbi:    "",
-	}
-
 	binary := filepath.Join(tmpdir, "test")
-	err = runBuild("./"+path, binary, config)
+	err = runBuild("./"+path, binary, options)
 	if err != nil {
 		printCompilerError(t.Log, err)
 		t.Fail()
@@ -191,6 +244,7 @@ func runTest(path, target string, t *testing.T, environmentVars []string, additi
 	if target == "" {
 		cmd = exec.Command(binary)
 		cmd.Env = append(cmd.Env, environmentVars...)
+		cmd.Args = append(cmd.Args, cmdArgs...)
 	} else {
 		spec, err := compileopts.LoadTarget(target)
 		if err != nil {
@@ -200,13 +254,16 @@ func runTest(path, target string, t *testing.T, environmentVars []string, additi
 			cmd = exec.Command(binary)
 		} else {
 			args := append(spec.Emulator[1:], binary)
-			cmd = exec.Command(spec.Emulator[0], append(args, additionalArgs...)...)
+			cmd = exec.Command(spec.Emulator[0], args...)
 		}
 
 		if len(spec.Emulator) != 0 && spec.Emulator[0] == "wasmtime" {
+			// Allow reading from the current directory.
+			cmd.Args = append(cmd.Args, "--dir=.")
 			for _, v := range environmentVars {
 				cmd.Args = append(cmd.Args, "--env", v)
 			}
+			cmd.Args = append(cmd.Args, cmdArgs...)
 		} else {
 			cmd.Env = append(cmd.Env, environmentVars...)
 		}

src/device/sam/atsame5x-bitfields.go

@@ -0,0 +1,71 @@
+// Hand created file. DO NOT DELETE.
+// atsamd51x bitfield definitions that are not auto-generated by gen-device-svd.go
+
+// +build sam,atsame5x
+
+// These are the supported pchctrl function numberings on the atsamd51x
+// See http://ww1.microchip.com/downloads/en/DeviceDoc/SAM_D5xE5x_Family_Data_Sheet_DS60001507F.pdf
+// table 14-9
+
+package sam
+
+const (
+	PCHCTRL_GCLK_OSCCTRL_DFLL48     = 0 // DFLL48 input clock source
+	PCHCTRL_GCLK_OSCCTRL_FDPLL0     = 1 // Reference clock for FDPLL0
+	PCHCTRL_GCLK_OSCCTRL_FDPLL1     = 2 // Reference clock for FDPLL1
+	PCHCTRL_GCLK_OSCCTRL_FDPLL0_32K = 3 // FDPLL0 = 3 // 32KHz clock for internal lock timer
+	PCHCTRL_GCLK_OSCCTRL_FDPLL1_32K = 3 // FDPLL1 = 3 // 32KHz clock for internal lock timer
+	PCHCTRL_GCLK_SDHC0_SLOW         = 3 // SDHC0 = 3 // Slow
+	PCHCTRL_GCLK_SDHC1_SLOW         = 3 // SDHC1 = 3 // Slow
+	PCHCTRL_GCLK_SERCOMX_SLOW       = 3 // GCLK_SERCOM[0..7]_SLOW = 3
+	PCHCTRL_GCLK_EIC                = 4
+	PCHCTRL_GCLK_FREQM_MSR          = 5 // FREQM Measure
+	PCHCTRL_GCLK_FREQM_REF          = 6 // FREQM Reference
+	PCHCTRL_GCLK_SERCOM0_CORE       = 7 // SERCOM0 Core
+	PCHCTRL_GCLK_SERCOM1_CORE       = 8 // SERCOM1 Core
+	PCHCTRL_GCLK_TC0                = 9
+	PCHCTRL_GCLK_TC1                = 9  // TC0, TC1
+	PCHCTRL_GCLK_USB                = 10 // USB
+	PCHCTRL_GCLK_EVSYS0             = 11
+	PCHCTRL_GCLK_EVSYS1             = 12
+	PCHCTRL_GCLK_EVSYS2             = 13
+	PCHCTRL_GCLK_EVSYS3             = 14
+	PCHCTRL_GCLK_EVSYS4             = 15
+	PCHCTRL_GCLK_EVSYS5             = 16
+	PCHCTRL_GCLK_EVSYS6             = 17
+	PCHCTRL_GCLK_EVSYS7             = 18
+	PCHCTRL_GCLK_EVSYS8             = 19
+	PCHCTRL_GCLK_EVSYS9             = 20
+	PCHCTRL_GCLK_EVSYS10            = 21
+	PCHCTRL_GCLK_EVSYS11            = 22
+	PCHCTRL_GCLK_SERCOM2_CORE       = 23 // SERCOM2 Core
+	PCHCTRL_GCLK_SERCOM3_CORE       = 24 // SERCOM3 Core
+	PCHCTRL_GCLK_TCC0               = 25
+	PCHCTRL_GCLK_TCC1               = 25 // TCC0, TCC1
+	PCHCTRL_GCLK_TC2                = 26
+	PCHCTRL_GCLK_TC3                = 26 // TC2, TC3
+	PCHCTRL_GCLK_CAN0               = 27 // CAN0
+	PCHCTRL_GCLK_CAN1               = 28 // CAN1
+	PCHCTRL_GCLK_TCC2               = 29
+	PCHCTRL_GCLK_TCC3               = 29 // TCC2, TCC3
+	PCHCTRL_GCLK_TC4                = 30
+	PCHCTRL_GCLK_TC5                = 30 // TC4, TC5
+	PCHCTRL_GCLK_PDEC               = 31 // PDEC
+	PCHCTRL_GCLK_AC                 = 32 // AC
+	PCHCTRL_GCLK_CCL                = 33 // CCL
+	PCHCTRL_GCLK_SERCOM4_CORE       = 34 // SERCOM4 Core
+	PCHCTRL_GCLK_SERCOM5_CORE       = 35 // SERCOM5 Core
+	PCHCTRL_GCLK_SERCOM6_CORE       = 36 // SERCOM6 Core
+	PCHCTRL_GCLK_SERCOM7_CORE       = 37 // SERCOM7 Core
+	PCHCTRL_GCLK_TCC4               = 38 // TCC4
+	PCHCTRL_GCLK_TC6                = 39
+	PCHCTRL_GCLK_TC7                = 39 // TC6, TC7
+	PCHCTRL_GCLK_ADC0               = 40 // ADC0
+	PCHCTRL_GCLK_ADC1               = 41 // ADC1
+	PCHCTRL_GCLK_DAC                = 42 // DAC
+	PCHCTRL_GCLK_I2S0               = 43
+	PCHCTRL_GCLK_I2S1               = 44
+	PCHCTRL_GCLK_SDHC0              = 45 // SDHC0
+	PCHCTRL_GCLK_SDHC1              = 46 // SDHC1
+	PCHCTRL_GCLK_CM4_TRACE          = 47 // CM4 Trace
+)

src/examples/pwm/arduino-mega1280.go

@@ -0,0 +1,12 @@
+// +build arduino_mega1280
+
+package main
+
+import "machine"
+
+var (
+	// Configuration on an Arduino Uno.
+	pwm  = machine.Timer3
+	pinA = machine.PH3 // pin 6 on the Mega
+	pinB = machine.PH4 // pin 7 on the Mega
+)

src/machine/board_arduino_mega1280.go

@@ -0,0 +1,104 @@
+// +build arduino_mega1280
+
+package machine
+
+// Return the current CPU frequency in hertz.
+func CPUFrequency() uint32 {
+	return 16000000
+}
+
+const (
+	AREF Pin = NoPin
+	LED  Pin = PB7
+
+	A0  Pin = PF0
+	A1  Pin = PF1
+	A2  Pin = PF2
+	A3  Pin = PF3
+	A4  Pin = PF4
+	A5  Pin = PF5
+	A6  Pin = PF6
+	A7  Pin = PF7
+	A8  Pin = PK0
+	A9  Pin = PK1
+	A10 Pin = PK2
+	A11 Pin = PK3
+	A12 Pin = PK4
+	A13 Pin = PK5
+	A14 Pin = PK6
+	A15 Pin = PK7
+
+	// Analog Input
+	ADC0  Pin = PF0
+	ADC1  Pin = PF1
+	ADC2  Pin = PF2
+	ADC3  Pin = PF3
+	ADC4  Pin = PF4
+	ADC5  Pin = PF5
+	ADC6  Pin = PF6
+	ADC7  Pin = PF7
+	ADC8  Pin = PK0
+	ADC9  Pin = PK1
+	ADC10 Pin = PK2
+	ADC11 Pin = PK3
+	ADC12 Pin = PK4
+	ADC13 Pin = PK5
+	ADC14 Pin = PK6
+	ADC15 Pin = PK7
+
+	// Digital pins
+	D0  Pin = PE0
+	D1  Pin = PE1
+	D2  Pin = PE4
+	D3  Pin = PE5
+	D4  Pin = PG5
+	D5  Pin = PE3
+	D6  Pin = PH3
+	D7  Pin = PH4
+	D8  Pin = PH5
+	D9  Pin = PH6
+	D10 Pin = PB4
+	D11 Pin = PB5
+	D12 Pin = PB6
+	D13 Pin = PB7
+	D14 Pin = PJ1
+	D15 Pin = PJ0
+	D16 Pin = PH1
+	D17 Pin = PH0
+	D18 Pin = PD3
+	D19 Pin = PD2
+	D20 Pin = PD1
+	D21 Pin = PD0
+	D22 Pin = PA0
+	D23 Pin = PA1
+	D24 Pin = PA2
+	D25 Pin = PA3
+	D26 Pin = PA4
+	D27 Pin = PA5
+	D28 Pin = PA6
+	D29 Pin = PA7
+	D30 Pin = PC7
+	D31 Pin = PC6
+	D32 Pin = PC5
+	D33 Pin = PC4
+	D34 Pin = PC3
+	D35 Pin = PC2
+	D36 Pin = PC1
+	D37 Pin = PC0
+	D38 Pin = PD7
+	D39 Pin = PG2
+	D40 Pin = PG1
+	D41 Pin = PG0
+	D42 Pin = PL7
+	D43 Pin = PL6
+	D44 Pin = PL5
+	D45 Pin = PL4
+	D46 Pin = PL3
+	D47 Pin = PL2
+	D48 Pin = PL1
+	D49 Pin = PL0
+	D50 Pin = PB3
+	D51 Pin = PB2
+	D52 Pin = PB1
+	D53 Pin = PB0
+)

src/machine/board_atsame54-xpro.go

@@ -0,0 +1,330 @@
+// +build atsame54_xpro
+
+package machine
+
+import (
+	"device/sam"
+	"runtime/interrupt"
+)
+
+// Definition for compatibility, but not used
+const RESET_MAGIC_VALUE = 0x00000000
+
+const (
+	LED    = PC18
+	BUTTON = PB31
+)
+
+const (
+	// https://ww1.microchip.com/downloads/en/DeviceDoc/70005321A.pdf
+
+	// Extension Header EXT1
+	EXT1_PIN3_ADC_P     = PB04
+	EXT1_PIN4_ADC_N     = PB05
+	EXT1_PIN5_GPIO1     = PA06
+	EXT1_PIN6_GPIO2     = PA07
+	EXT1_PIN7_PWM_P     = PB08
+	EXT1_PIN8_PWM_N     = PB09
+	EXT1_PIN9_IRQ       = PB07
+	EXT1_PIN9_GPIO      = PB07
+	EXT1_PIN10_SPI_SS_B = PA27
+	EXT1_PIN10_GPIO     = PA27
+	EXT1_PIN11_TWI_SDA  = PA22
+	EXT1_PIN12_TWI_SCL  = PA23
+	EXT1_PIN13_UART_RX  = PA05
+	EXT1_PIN14_UART_TX  = PA04
+	EXT1_PIN15_SPI_SS_A = PB28
+	EXT1_PIN16_SPI_SDO  = PB27
+	EXT1_PIN17_SPI_SDI  = PB29
+	EXT1_PIN18_SPI_SCK  = PB26
+
+	// Extension Header EXT2
+	EXT2_PIN3_ADC_P     = PB00
+	EXT2_PIN4_ADC_N     = PA03
+	EXT2_PIN5_GPIO1     = PB01
+	EXT2_PIN6_GPIO2     = PB06
+	EXT2_PIN7_PWM_P     = PB14
+	EXT2_PIN8_PWM_N     = PB15
+	EXT2_PIN9_IRQ       = PD00
+	EXT2_PIN9_GPIO      = PD00
+	EXT2_PIN10_SPI_SS_B = PB02
+	EXT2_PIN10_GPIO     = PB02
+	EXT2_PIN11_TWI_SDA  = PD08
+	EXT2_PIN12_TWI_SCL  = PD09
+	EXT2_PIN13_UART_RX  = PB17
+	EXT2_PIN14_UART_TX  = PB16
+	EXT2_PIN15_SPI_SS_A = PC06
+	EXT2_PIN16_SPI_SDO  = PC04
+	EXT2_PIN17_SPI_SDI  = PC07
+	EXT2_PIN18_SPI_SCK  = PC05
+
+	// Extension Header EXT3
+	EXT3_PIN3_ADC_P     = PC02
+	EXT3_PIN4_ADC_N     = PC03
+	EXT3_PIN5_GPIO1     = PC01
+	EXT3_PIN6_GPIO2     = PC10
+	EXT3_PIN7_PWM_P     = PD10
+	EXT3_PIN8_PWM_N     = PD11
+	EXT3_PIN9_IRQ       = PC30
+	EXT3_PIN9_GPIO      = PC30
+	EXT3_PIN10_SPI_SS_B = PC31
+	EXT3_PIN10_GPIO     = PC31
+	EXT3_PIN11_TWI_SDA  = PD08
+	EXT3_PIN12_TWI_SCL  = PD09
+	EXT3_PIN13_UART_RX  = PC23
+	EXT3_PIN14_UART_TX  = PC22
+	EXT3_PIN15_SPI_SS_A = PC14
+	EXT3_PIN16_SPI_SDO  = PC04
+	EXT3_PIN17_SPI_SDI  = PC07
+	EXT3_PIN18_SPI_SCK  = PC05
+
+	// SD_CARD
+	SD_CARD_MCDA0   = PB18
+	SD_CARD_MCDA1   = PB19
+	SD_CARD_MCDA2   = PB20
+	SD_CARD_MCDA3   = PB21
+	SD_CARD_MCCK    = PA21
+	SD_CARD_MCCDA   = PA20
+	SD_CARD_DETECT  = PD20
+	SD_CARD_PROTECT = PD21
+
+	// I2C
+	I2C_SDA = PD08
+	I2C_SCL = PD09
+
+	// CAN
+	CAN0_TX = PA22
+	CAN0_RX = PA23
+
+	CAN1_STANDBY = PC13
+	CAN1_TX      = PB12
+	CAN1_RX      = PB13
+
+	CAN_STANDBY = CAN1_STANDBY
+	CAN_TX      = CAN1_TX
+	CAN_RX      = CAN1_RX
+
+	// PDEC
+	PDEC_PHASE_A = PC16
+	PDEC_PHASE_B = PC17
+	PDEC_INDEX   = PC18
+
+	// PCC
+	PCC_I2C_SDA    = PD08
+	PCC_I2C_SCL    = PD09
+	PCC_VSYNC_DEN1 = PA12
+	PCC_HSYNC_DEN2 = PA13
+	PCC_CLK        = PA14
+	PCC_XCLK       = PA15
+	PCC_DATA00     = PA16
+	PCC_DATA01     = PA17
+	PCC_DATA02     = PA18
+	PCC_DATA03     = PA19
+	PCC_DATA04     = PA20
+	PCC_DATA05     = PA21
+	PCC_DATA06     = PA22
+	PCC_DATA07     = PA23
+	PCC_DATA08     = PB14
+	PCC_DATA09     = PB15
+	PCC_RESET      = PC12
+	PCC_PWDN       = PC11
+
+	// Ethernet
+	ETHERNET_TXCK  = PA14
+	ETHERNET_TXEN  = PA17
+	ETHERNET_TX0   = PA18
+	ETHERNET_TX1   = PA19
+	ETHERNET_RXER  = PA15
+	ETHERNET_RX0   = PA13
+	ETHERNET_RX1   = PA12
+	ETHERNET_RXDV  = PC20
+	ETHERNET_MDIO  = PC12
+	ETHERNET_MDC   = PC11
+	ETHERNET_INT   = PD12
+	ETHERNET_RESET = PC21
+
+	PIN_QT_BUTTON   = PA16
+	PIN_BTN0        = PB31
+	PIN_ETH_LED     = PC15
+	PIN_LED0        = PC18
+	PIN_ADC_DAC     = PA02
+	PIN_VBUS_DETECT = PC00
+	PIN_USB_ID      = PC19
+)
+
+// UART0 aka USBCDC pins
+const (
+	USBCDC_DM_PIN = PA24
+	USBCDC_DP_PIN = PA25
+)
+
+// UART pins
+const (
+	// Extension Header EXT1
+	UART_TX_PIN = PA04 // TX : SERCOM0/PAD[0]
+	UART_RX_PIN = PA05 // RX : SERCOM0/PAD[1]
+
+	// Extension Header EXT2
+	UART2_TX_PIN = PB16 // TX : SERCOM5/PAD[0]
+	UART2_RX_PIN = PB17 // RX : SERCOM5/PAD[1]
+
+	// Extension Header EXT3
+	UART3_TX_PIN = PC22 // TX : SERCOM1/PAD[0]
+	UART3_RX_PIN = PC23 // RX : SERCOM1/PAD[1]
+
+	// Virtual COM Port
+	UART4_TX_PIN = PB25 // TX : SERCOM2/PAD[0]
+	UART4_RX_PIN = PB24 // RX : SERCOM2/PAD[1]
+)
+
+// I2C pins
+const (
+	// Extension Header EXT1
+	SDA0_PIN = PA22 // SDA: SERCOM3/PAD[0]
+	SCL0_PIN = PA23 // SCL: SERCOM3/PAD[1]
+
+	// Extension Header EXT2
+	SDA1_PIN = PD08 // SDA: SERCOM7/PAD[0]
+	SCL1_PIN = PD09 // SCL: SERCOM7/PAD[1]
+
+	// Extension Header EXT3
+	SDA2_PIN = PD08 // SDA: SERCOM7/PAD[0]
+	SCL2_PIN = PD09 // SCL: SERCOM7/PAD[1]
+
+	// Data Gateway Interface
+	SDA_DGI_PIN = PD08 // SDA: SERCOM7/PAD[0]
+	SCL_DGI_PIN = PD09 // SCL: SERCOM7/PAD[1]
+
+	SDA_PIN = SDA0_PIN
+	SCL_PIN = SCL0_PIN
+)
+
+// SPI pins
+const (
+	// Extension Header EXT1
+	SPI0_SCK_PIN = PB26 // SCK: SERCOM4/PAD[1]
+	SPI0_SDO_PIN = PB27 // SDO: SERCOM4/PAD[0]
+	SPI0_SDI_PIN = PB29 // SDI: SERCOM4/PAD[3]
+	SPI0_SS_PIN  = PB28 // SS : SERCOM4/PAD[2]
+
+	// Extension Header EXT2
+	SPI1_SCK_PIN = PC05 // SCK: SERCOM6/PAD[1]
+	SPI1_SDO_PIN = PC04 // SDO: SERCOM6/PAD[0]
+	SPI1_SDI_PIN = PC07 // SDI: SERCOM6/PAD[3]
+	SPI1_SS_PIN  = PC06 // SS : SERCOM6/PAD[2]
+
+	// Extension Header EXT3
+	SPI2_SCK_PIN = PC05 // SCK: SERCOM6/PAD[1]
+	SPI2_SDO_PIN = PC04 // SDO: SERCOM6/PAD[0]
+	SPI2_SDI_PIN = PC07 // SDI: SERCOM6/PAD[3]
+	SPI2_SS_PIN  = PC14 // SS : GPIO
+
+	// Data Gateway Interface
+	SPI_DGI_SCK_PIN = PC05 // SCK: SERCOM6/PAD[1]
+	SPI_DGI_SDO_PIN = PC04 // SDO: SERCOM6/PAD[0]
+	SPI_DGI_SDI_PIN = PC07 // SDI: SERCOM6/PAD[3]
+	SPI_DGI_SS_PIN  = PD01 // SS : GPIO
+)
+
+// USB CDC identifiers
+const (
+	usb_STRING_PRODUCT      = "SAM E54 Xplained Pro"
+	usb_STRING_MANUFACTURER = "Atmel"
+)
+
+var (
+	usb_VID uint16 = 0x03EB
+	usb_PID uint16 = 0x2404
+)
+
+// UART on the SAM E54 Xplained Pro
+var (
+	// Extension Header EXT1
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM0_USART_INT,
+		SERCOM: 0,
+	}
+
+	// Extension Header EXT2
+	UART2 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM5_USART_INT,
+		SERCOM: 5,
+	}
+
+	// Extension Header EXT3
+	UART3 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM1_USART_INT,
+		SERCOM: 1,
+	}
+
+	// EDBG Virtual COM Port
+	UART4 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM2_USART_INT,
+		SERCOM: 2,
+	}
+)
+
+func init() {
+	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM0_2, UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM5_2, UART2.handleInterrupt)
+	UART3.Interrupt = interrupt.New(sam.IRQ_SERCOM1_2, UART3.handleInterrupt)
+	UART4.Interrupt = interrupt.New(sam.IRQ_SERCOM2_2, UART4.handleInterrupt)
+}
+
+// I2C on the SAM E54 Xplained Pro
+var (
+	// Extension Header EXT1
+	I2C0 = I2C{
+		Bus:    sam.SERCOM3_I2CM,
+		SERCOM: 3,
+	}
+
+	// Extension Header EXT2
+	I2C1 = I2C{
+		Bus:    sam.SERCOM7_I2CM,
+		SERCOM: 7,
+	}
+
+	// Extension Header EXT3
+	I2C2 = I2C{
+		Bus:    sam.SERCOM7_I2CM,
+		SERCOM: 7,
+	}
+
+	// Data Gateway Interface
+	I2C3 = I2C{
+		Bus:    sam.SERCOM7_I2CM,
+		SERCOM: 7,
+	}
+)
+
+// SPI on the SAM E54 Xplained Pro
+var (
+	// Extension Header EXT1
+	SPI0 = SPI{
+		Bus:    sam.SERCOM4_SPIM,
+		SERCOM: 4,
+	}
+
+	// Extension Header EXT2
+	SPI1 = SPI{
+		Bus:    sam.SERCOM6_SPIM,
+		SERCOM: 6,
+	}
+
+	// Extension Header EXT3
+	SPI2 = SPI{
+		Bus:    sam.SERCOM6_SPIM,
+		SERCOM: 6,
+	}
+
+	// Data Gateway Interface
+	SPI3 = SPI{
+		Bus:    sam.SERCOM6_SPIM,
+		SERCOM: 6,
+	}
+)

src/machine/board_feather-m4-can.go

@@ -0,0 +1,142 @@
+// +build feather_m4_can
+
+package machine
+
+import (
+	"device/sam"
+	"runtime/interrupt"
+)
+
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0xf01669ef
+
+// GPIO Pins
+const (
+	D0  = PB17 // UART0 RX/PWM available
+	D1  = PB16 // UART0 TX/PWM available
+	D4  = PA14 // PWM available
+	D5  = PA16 // PWM available
+	D6  = PA18 // PWM available
+	D7  = PB03 // neopixel power
+	D8  = PB02 // built-in neopixel
+	D9  = PA19 // PWM available
+	D10 = PA20 // can be used for PWM or UART1 TX
+	D11 = PA21 // can be used for PWM or UART1 RX
+	D12 = PA22 // PWM available
+	D13 = PA23 // PWM available
+	D21 = PA13 // PWM available
+	D22 = PA12 // PWM available
+	D23 = PB22 // PWM available
+	D24 = PB23 // PWM available
+	D25 = PA17 // PWM available
+)
+
+// Analog pins
+const (
+	A0 = PA02 // ADC/AIN[0]
+	A1 = PA05 // ADC/AIN[2]
+	A2 = PB08 // ADC/AIN[3]
+	A3 = PB09 // ADC/AIN[4]
+	A4 = PA04 // ADC/AIN[5]
+	A5 = PA06 // ADC/AIN[10]
+)
+
+const (
+	LED       = D13
+	NEOPIXELS = D8
+)
+
+// UART0 aka USBCDC pins
+const (
+	USBCDC_DM_PIN = PA24
+	USBCDC_DP_PIN = PA25
+)
+
+const (
+	UART_TX_PIN = D1
+	UART_RX_PIN = D0
+)
+
+const (
+	UART2_TX_PIN = A4
+	UART2_RX_PIN = A5
+)
+
+// I2C pins
+const (
+	SDA_PIN = D22 // SDA: SERCOM2/PAD[0]
+	SCL_PIN = D21 // SCL: SERCOM2/PAD[1]
+)
+
+// SPI pins
+const (
+	SPI0_SCK_PIN = D25 // SCK: SERCOM1/PAD[1]
+	SPI0_SDO_PIN = D24 // SDO: SERCOM1/PAD[3]
+	SPI0_SDI_PIN = D23 // SDI: SERCOM1/PAD[2]
+)
+
+// CAN pins
+const (
+	CAN0_TX = PA22
+	CAN0_RX = PA23
+
+	CAN1_STANDBY = PB12
+	CAN1_TX      = PB14
+	CAN1_RX      = PB15
+	BOOST_EN     = PB13 // power control of CAN1's TCAN1051HGV (H: enable)
+
+	CAN_STANDBY = CAN1_STANDBY
+	CAN_S       = CAN1_STANDBY
+	CAN_TX      = CAN1_TX
+	CAN_RX      = CAN1_RX
+)
+
+// USB CDC identifiers
+const (
+	usb_STRING_PRODUCT      = "Adafruit Feather M4 CAN"
+	usb_STRING_MANUFACTURER = "Adafruit"
+)
+
+var (
+	usb_VID uint16 = 0x239A
+	usb_PID uint16 = 0x80CD
+)
+
+var (
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM5_USART_INT,
+		SERCOM: 5,
+	}
+
+	UART2 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM0_USART_INT,
+		SERCOM: 0,
+	}
+)
+
+func init() {
+	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM5_2, UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM0_2, UART2.handleInterrupt)
+
+	// turn on neopixel
+	D7.Configure(PinConfig{Mode: PinOutput})
+	D7.High()
+}
+
+// I2C on the Feather M4.
+var (
+	I2C0 = &I2C{
+		Bus:    sam.SERCOM2_I2CM,
+		SERCOM: 2,
+	}
+)
+
+// SPI on the Feather M4.
+var (
+	SPI0 = SPI{
+		Bus:    sam.SERCOM1_SPIM,
+		SERCOM: 1,
+	}
+)

src/machine/board_microbit-v2.go

@@ -5,11 +5,6 @@ package machine
 // The micro:bit does not have a 32kHz crystal on board.
 const HasLowFrequencyCrystal = false
 
-const (
-	LED  = P13
-	LED1 = LED
-)
-
 // Buttons on the micro:bit v2 (A and B)
 const (
 	BUTTON  Pin = BUTTONA

src/machine/board_nucleol432kc.go

@@ -13,20 +13,53 @@ const (
 	LED_GREEN   = PB3
 )
 
-// UART pins
 const (
+	// Arduino Pins
+	A0 = PA0
+	A1 = PA1
+	A2 = PA3
+	A3 = PA4
+	A4 = PA5
+	A5 = PA6
+	A6 = PA7
+	A7 = PA2
+
+	D0  = PA10
+	D1  = PA9
+	D2  = PA12
+	D3  = PB0
+	D4  = PB7
+	D5  = PB6
+	D6  = PB1
+	D7  = PC14
+	D8  = PC15
+	D9  = PA8
+	D10 = PA11
+	D11 = PB5
+	D12 = PB4
+	D13 = PB3
+)
+
+const (
+	// UART pins
 	// PA2 and PA15 are connected to the ST-Link Virtual Com Port (VCP)
 	UART_TX_PIN = PA2
 	UART_RX_PIN = PA15
-)
 
-// I2C pins
-const (
+	// I2C pins
 	// With default solder bridge settings:
 	//    PB6 / Arduino D5 / CN3 Pin 8 is SCL
 	//    PB7 / Arduino D4 / CN3 Pin 7 is SDA
 	I2C0_SCL_PIN = PB6
 	I2C0_SDA_PIN = PB7
+
+	// SPI pins
+	SPI1_SCK_PIN = PB3
+	SPI1_SDI_PIN = PB5
+	SPI1_SDO_PIN = PB4
+	SPI0_SCK_PIN = SPI1_SCK_PIN
+	SPI0_SDI_PIN = SPI1_SDI_PIN
+	SPI0_SDO_PIN = SPI1_SDO_PIN
 )
 
 var (
@@ -40,15 +73,20 @@ var (
 		RxAltFuncSelector: 3,
 	}
 	UART1 = &UART0
-)
 
-var (
 	// I2C1 is documented, alias to I2C0 as well
 	I2C1 = &I2C{
 		Bus:             stm32.I2C1,
 		AltFuncSelector: 4,
 	}
 	I2C0 = I2C1
+
+	// SPI1 is documented, alias to SPI0 as well
+	SPI1 = &SPI{
+		Bus:             stm32.SPI1,
+		AltFuncSelector: 5,
+	}
+	SPI0 = SPI1
 )
 
 func init() {

src/machine/machine_atmega1280.go

@@ -0,0 +1,931 @@
+// +build avr,atmega1280
+
+package machine
+
+import (
+	"device/avr"
+	"runtime/interrupt"
+	"runtime/volatile"
+)
+
+const irq_USART0_RX = avr.IRQ_USART0_RX
+
+const (
+	portA Pin = iota * 8
+	portB
+	portC
+	portD
+	portE
+	portF
+	portG
+	portH
+	portJ
+	portK
+	portL
+)
+
+const (
+	PA0 = portA + 0
+	PA1 = portA + 1
+	PA2 = portA + 2
+	PA3 = portA + 3
+	PA4 = portA + 4
+	PA5 = portA + 5
+	PA6 = portA + 6
+	PA7 = portA + 7
+	PB0 = portB + 0
+	PB1 = portB + 1
+	PB2 = portB + 2
+	PB3 = portB + 3
+	PB4 = portB + 4
+	PB5 = portB + 5
+	PB6 = portB + 6
+	PB7 = portB + 7
+	PC0 = portC + 0
+	PC1 = portC + 1
+	PC2 = portC + 2
+	PC3 = portC + 3
+	PC4 = portC + 4
+	PC5 = portC + 5
+	PC6 = portC + 6
+	PC7 = portC + 7
+	PD0 = portD + 0
+	PD1 = portD + 1
+	PD2 = portD + 2
+	PD3 = portD + 3
+	PD7 = portD + 7
+	PE0 = portE + 0
+	PE1 = portE + 1
+	PE3 = portE + 3
+	PE4 = portE + 4
+	PE5 = portE + 5
+	PE6 = portE + 6
+	PF0 = portF + 0
+	PF1 = portF + 1
+	PF2 = portF + 2
+	PF3 = portF + 3
+	PF4 = portF + 4
+	PF5 = portF + 5
+	PF6 = portF + 6
+	PF7 = portF + 7
+	PG0 = portG + 0
+	PG1 = portG + 1
+	PG2 = portG + 2
+	PG5 = portG + 5
+	PH0 = portH + 0
+	PH1 = portH + 1
+	PH3 = portH + 3
+	PH4 = portH + 4
+	PH5 = portH + 5
+	PH6 = portH + 6
+	PJ0 = portJ + 0
+	PJ1 = portJ + 1
+	PK0 = portK + 0
+	PK1 = portK + 1
+	PK2 = portK + 2
+	PK3 = portK + 3
+	PK4 = portH + 4
+	PK5 = portH + 5
+	PK6 = portH + 6
+	PK7 = portH + 7
+	PL0 = portL + 0
+	PL1 = portL + 1
+	PL2 = portL + 2
+	PL3 = portL + 3
+	PL4 = portL + 4
+	PL5 = portL + 5
+	PL6 = portL + 6
+	PL7 = portL + 7
+)
+
+// getPortMask returns the PORTx register and mask for the pin.
+func (p Pin) getPortMask() (*volatile.Register8, uint8) {
+	switch {
+	case p >= PA0 && p <= PA7:
+		return avr.PORTA, 1 << uint8(p-portA)
+	case p >= PB0 && p <= PB7:
+		return avr.PORTB, 1 << uint8(p-portB)
+	case p >= PC0 && p <= PC7:
+		return avr.PORTC, 1 << uint8(p-portC)
+	case p >= PD0 && p <= PD7:
+		return avr.PORTD, 1 << uint8(p-portD)
+	case p >= PE0 && p <= PE6:
+		return avr.PORTE, 1 << uint8(p-portE)
+	case p >= PF0 && p <= PF7:
+		return avr.PORTF, 1 << uint8(p-portF)
+	case p >= PG0 && p <= PG5:
+		return avr.PORTG, 1 << uint8(p-portG)
+	case p >= PH0 && p <= PH6:
+		return avr.PORTH, 1 << uint8(p-portH)
+	case p >= PJ0 && p <= PJ1:
+		return avr.PORTJ, 1 << uint8(p-portJ)
+	case p >= PK0 && p <= PK7:
+		return avr.PORTK, 1 << uint8(p-portK)
+	case p >= PL0 && p <= PL7:
+		return avr.PORTL, 1 << uint8(p-portL)
+	default:
+		return avr.PORTA, 255
+	}
+}
+
+// PWM is one PWM peripheral, which consists of a counter and two output
+// channels (that can be connected to two fixed pins). You can set the frequency
+// using SetPeriod, but only for all the channels in this PWM peripheral at
+// once.
+type PWM struct {
+	num uint8
+}
+
+var (
+	Timer0 = PWM{0} // 8 bit timer for PB7 and PG5
+	Timer1 = PWM{1} // 16 bit timer for PB5 and PB6
+	Timer2 = PWM{2} // 8 bit timer for PB4 and PH6
+	Timer3 = PWM{3} // 16 bit timer for PE3, PE4 and PE5
+	Timer4 = PWM{4} // 16 bit timer for PH3, PH4 and PH5
+	Timer5 = PWM{5} // 16 bit timer for PL3, PL4 and PL5
+)
+
+// Configure enables and configures this PWM.
+//
+// For the two 8 bit timers, there is only a limited number of periods
+// available, namely the CPU frequency divided by 256 and again divided by 1, 8,
+// 64, 256, or 1024. For a MCU running at 16MHz, this would be a period of 16µs,
+// 128µs, 1024µs, 4096µs, or 16384µs.
+func (pwm PWM) Configure(config PWMConfig) error {
+
+	switch pwm.num {
+	case 0, 2: // 8-bit timers (Timer/counter 0 and Timer/counter 2)
+		// Calculate the timer prescaler.
+		// While we could configure a flexible top, that would sacrifice one of
+		// the PWM output compare registers and thus a PWM channel. I've chosen
+		// to instead limit this timer to a fixed number of frequencies.
+		var prescaler uint8
+		switch config.Period {
+		case 0, (uint64(1e9) * 256 * 1) / uint64(CPUFrequency()):
+			prescaler = 1
+		case (uint64(1e9) * 256 * 8) / uint64(CPUFrequency()):
+			prescaler = 2
+		case (uint64(1e9) * 256 * 64) / uint64(CPUFrequency()):
+			prescaler = 3
+		case (uint64(1e9) * 256 * 256) / uint64(CPUFrequency()):
+			prescaler = 4
+		case (uint64(1e9) * 256 * 1024) / uint64(CPUFrequency()):
+			prescaler = 5
+		default:
+			return ErrPWMPeriodTooLong
+		}
+
+		if pwm.num == 0 {
+			avr.TCCR0B.Set(prescaler)
+			// Set the PWM mode to fast PWM (mode = 3).
+			avr.TCCR0A.Set(avr.TCCR0A_WGM00 | avr.TCCR0A_WGM01)
+		} else {
+			avr.TCCR2B.Set(prescaler)
+			// Set the PWM mode to fast PWM (mode = 3).
+			avr.TCCR2A.Set(avr.TCCR2A_WGM20 | avr.TCCR2A_WGM21)
+		}
+	case 1, 3, 4, 5:
+		// The top value is the number of PWM ticks a PWM period takes. It is
+		// initially picked assuming an unlimited counter top and no PWM
+		// prescaler.
+		var top uint64
+		if config.Period == 0 {
+			// Use a top appropriate for LEDs. Picking a relatively low period
+			// here (0xff) for consistency with the other timers.
+			top = 0xff
+		} else {
+			// The formula below calculates the following formula, optimized:
+			//     top = period * (CPUFrequency() / 1e9)
+			// By dividing the CPU frequency first (an operation that is easily
+			// optimized away) the period has less chance of overflowing.
+			top = config.Period * (uint64(CPUFrequency()) / 1000000) / 1000
+		}
+
+		// The ideal PWM period may be larger than would fit in the PWM counter,
+		// which is 16 bits (see maxTop). Therefore, try to make the PWM clock
+		// speed lower with a prescaler to make the top value fit the maximum
+		// top value.
+
+		const maxTop = 0x10000
+		var prescalingTop uint8
+		switch {
+		case top <= maxTop:
+			prescalingTop = 3<<3 | 1 // no prescaling
+		case top/8 <= maxTop:
+			prescalingTop = 3<<3 | 2 // divide by 8
+			top /= 8
+		case top/64 <= maxTop:
+			prescalingTop = 3<<3 | 3 // divide by 64
+			top /= 64
+		case top/256 <= maxTop:
+			prescalingTop = 3<<3 | 4 // divide by 256
+			top /= 256
+		case top/1024 <= maxTop:
+			prescalingTop = 3<<3 | 5 // divide by 1024
+			top /= 1024
+		default:
+			return ErrPWMPeriodTooLong
+		}
+
+		// A top of 0x10000 is at 100% duty cycle. Subtract one because the
+		// counter counts from 0, not 1 (avoiding an off-by-one).
+		top -= 1
+
+		switch pwm.num {
+		case 1:
+			avr.TCCR1A.Set(avr.TCCR1A_WGM11)
+			avr.TCCR1B.Set(prescalingTop)
+			avr.ICR1H.Set(uint8(top >> 8))
+			avr.ICR1L.Set(uint8(top))
+		case 3:
+			avr.TCCR3A.Set(avr.TCCR3A_WGM31)
+			avr.TCCR3B.Set(prescalingTop)
+			avr.ICR3H.Set(uint8(top >> 8))
+			avr.ICR3L.Set(uint8(top))
+		case 4:
+			avr.TCCR4A.Set(avr.TCCR4A_WGM41)
+			avr.TCCR4B.Set(prescalingTop)
+			avr.ICR4H.Set(uint8(top >> 8))
+			avr.ICR4L.Set(uint8(top))
+		case 5:
+			avr.TCCR5A.Set(avr.TCCR5A_WGM51)
+			avr.TCCR5B.Set(prescalingTop)
+			avr.ICR5H.Set(uint8(top >> 8))
+			avr.ICR5L.Set(uint8(top))
+		}
+	}
+	return nil
+}
+
+// SetPeriod updates the period of this PWM peripheral.
+// To set a particular frequency, use the following formula:
+//
+//     period = 1e9 / frequency
+//
+// If you use a period of 0, a period that works well for LEDs will be picked.
+//
+// SetPeriod will not change the prescaler, but also won't change the current
+// value in any of the channels. This means that you may need to update the
+// value for the particular channel.
+//
+// Note that you cannot pick any arbitrary period after the PWM peripheral has
+// been configured. If you want to switch between frequencies, pick the lowest
+// frequency (longest period) once when calling Configure and adjust the
+// frequency here as needed.
+func (pwm PWM) SetPeriod(period uint64) error {
+	if pwm.num == 0 || pwm.num == 2 {
+		return ErrPWMPeriodTooLong // TODO better error message
+	}
+
+	// The top value is the number of PWM ticks a PWM period takes. It is
+	// initially picked assuming an unlimited counter top and no PWM
+	// prescaler.
+	var top uint64
+	if period == 0 {
+		// Use a top appropriate for LEDs. Picking a relatively low period
+		// here (0xff) for consistency with the other timers.
+		top = 0xff
+	} else {
+		// The formula below calculates the following formula, optimized:
+		//     top = period * (CPUFrequency() / 1e9)
+		// By dividing the CPU frequency first (an operation that is easily
+		// optimized away) the period has less chance of overflowing.
+		top = period * (uint64(CPUFrequency()) / 1000000) / 1000
+	}
+
+	var prescaler uint8
+
+	switch pwm.num {
+	case 1:
+		prescaler = avr.TCCR1B.Get() & 0x7
+	case 3:
+		prescaler = avr.TCCR3B.Get() & 0x7
+	case 4:
+		prescaler = avr.TCCR4B.Get() & 0x7
+	case 5:
+		prescaler = avr.TCCR5B.Get() & 0x7
+	}
+
+	switch prescaler {
+	case 1:
+		top /= 1
+	case 2:
+		top /= 8
+	case 3:
+		top /= 64
+	case 4:
+		top /= 256
+	case 5:
+		top /= 1024
+	}
+
+	// A top of 0x10000 is at 100% duty cycle. Subtract one because the counter
+	// counts from 0, not 1 (avoiding an off-by-one).
+	top -= 1
+
+	if top > 0xffff {
+		return ErrPWMPeriodTooLong
+	}
+
+	switch pwm.num {
+	case 1:
+		// Warning: this change is not atomic!
+		avr.ICR1H.Set(uint8(top >> 8))
+		avr.ICR1L.Set(uint8(top))
+
+		// ... and because of that, set the counter back to zero to avoid most of
+		// the effects of this non-atomicity.
+		avr.TCNT1H.Set(0)
+		avr.TCNT1L.Set(0)
+	case 3:
+		// Warning: this change is not atomic!
+		avr.ICR3H.Set(uint8(top >> 8))
+		avr.ICR3L.Set(uint8(top))
+
+		// ... and because of that, set the counter back to zero to avoid most of
+		// the effects of this non-atomicity.
+		avr.TCNT3H.Set(0)
+		avr.TCNT3L.Set(0)
+	case 4:
+		// Warning: this change is not atomic!
+		avr.ICR4H.Set(uint8(top >> 8))
+		avr.ICR4L.Set(uint8(top))
+
+		// ... and because of that, set the counter back to zero to avoid most of
+		// the effects of this non-atomicity.
+		avr.TCNT4H.Set(0)
+		avr.TCNT4L.Set(0)
+	case 5:
+		// Warning: this change is not atomic!
+		avr.ICR5H.Set(uint8(top >> 8))
+		avr.ICR5L.Set(uint8(top))
+
+		// ... and because of that, set the counter back to zero to avoid most of
+		// the effects of this non-atomicity.
+		avr.TCNT5H.Set(0)
+		avr.TCNT5L.Set(0)
+	}
+
+	return nil
+}
+
+// Top returns the current counter top, for use in duty cycle calculation. It
+// will only change with a call to Configure or SetPeriod, otherwise it is
+// constant.
+//
+// The value returned here is hardware dependent. In general, it's best to treat
+// it as an opaque value that can be divided by some number and passed to Set
+// (see Set documentation for more information).
+func (pwm PWM) Top() uint32 {
+	switch pwm.num {
+	case 1:
+		// Timer 1 has a configurable top value.
+		low := avr.ICR1L.Get()
+		high := avr.ICR1H.Get()
+		return uint32(high)<<8 | uint32(low) + 1
+	case 3:
+		// Timer 3 has a configurable top value.
+		low := avr.ICR3L.Get()
+		high := avr.ICR3H.Get()
+		return uint32(high)<<8 | uint32(low) + 1
+	case 4:
+		// Timer 4 has a configurable top value.
+		low := avr.ICR4L.Get()
+		high := avr.ICR4H.Get()
+		return uint32(high)<<8 | uint32(low) + 1
+	case 5:
+		// Timer 5 has a configurable top value.
+		low := avr.ICR5L.Get()
+		high := avr.ICR5H.Get()
+		return uint32(high)<<8 | uint32(low) + 1
+	}
+
+	// Other timers go from 0 to 0xff (0x100 or 256 in total).
+	return 256
+}
+
+// Counter returns the current counter value of the timer in this PWM
+// peripheral. It may be useful for debugging.
+func (pwm PWM) Counter() uint32 {
+	switch pwm.num {
+	case 0:
+		return uint32(avr.TCNT0.Get())
+	case 1:
+		mask := interrupt.Disable()
+		low := avr.TCNT1L.Get()
+		high := avr.TCNT1H.Get()
+		interrupt.Restore(mask)
+		return uint32(high)<<8 | uint32(low)
+	case 2:
+		return uint32(avr.TCNT2.Get())
+	case 3:
+		mask := interrupt.Disable()
+		low := avr.TCNT3L.Get()
+		high := avr.TCNT3H.Get()
+		interrupt.Restore(mask)
+		return uint32(high)<<8 | uint32(low)
+	case 4:
+		mask := interrupt.Disable()
+		low := avr.TCNT4L.Get()
+		high := avr.TCNT4H.Get()
+		interrupt.Restore(mask)
+		return uint32(high)<<8 | uint32(low)
+	case 5:
+		mask := interrupt.Disable()
+		low := avr.TCNT5L.Get()
+		high := avr.TCNT5H.Get()
+		interrupt.Restore(mask)
+		return uint32(high)<<8 | uint32(low)
+	}
+
+	// Unknown PWM.
+	return 0
+}
+
+// Period returns the used PWM period in nanoseconds. It might deviate slightly
+// from the configured period due to rounding.
+func (pwm PWM) Period() uint64 {
+	var prescaler uint8
+	switch pwm.num {
+	case 0:
+		prescaler = avr.TCCR0B.Get() & 0x7
+	case 1:
+		prescaler = avr.TCCR1B.Get() & 0x7
+	case 2:
+		prescaler = avr.TCCR2B.Get() & 0x7
+	case 3:
+		prescaler = avr.TCCR3B.Get() & 0x7
+	case 4:
+		prescaler = avr.TCCR4B.Get() & 0x7
+	case 5:
+		prescaler = avr.TCCR5B.Get() & 0x7
+	}
+	top := uint64(pwm.Top())
+	switch prescaler {
+	case 1: // prescaler 1
+		return 1 * top * 1000 / uint64(CPUFrequency()/1e6)
+	case 2: // prescaler 8
+		return 8 * top * 1000 / uint64(CPUFrequency()/1e6)
+	case 3: // prescaler 64
+		return 64 * top * 1000 / uint64(CPUFrequency()/1e6)
+	case 4: // prescaler 256
+		return 256 * top * 1000 / uint64(CPUFrequency()/1e6)
+	case 5: // prescaler 1024
+		return 1024 * top * 1000 / uint64(CPUFrequency()/1e6)
+	default: // unknown clock source
+		return 0
+	}
+}
+
+// Channel returns a PWM channel for the given pin.
+func (pwm PWM) Channel(pin Pin) (uint8, error) {
+	pin.Configure(PinConfig{Mode: PinOutput})
+	pin.Low()
+	switch pwm.num {
+	case 0:
+		switch pin {
+		case PB7: // channel A
+			avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
+			return 0, nil
+		case PG5: // channel B
+			avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
+			return 1, nil
+		}
+	case 1:
+		switch pin {
+		case PB5: // channel A
+			avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
+			return 0, nil
+		case PB6: // channel B
+			avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
+			return 1, nil
+		}
+	case 2:
+		switch pin {
+		case PB4: // channel A
+			avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
+			return 0, nil
+		case PH6: // channel B
+			avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
+			return 1, nil
+		}
+	case 3:
+		switch pin {
+		case PE3: // channel A
+			avr.TCCR3A.SetBits(avr.TCCR3A_COM3A1)
+			return 0, nil
+		case PE4: //channel B
+			avr.TCCR3A.SetBits(avr.TCCR3A_COM3B1)
+			return 1, nil
+		case PE5: //channel C
+			avr.TCCR3A.SetBits(avr.TCCR3A_COM3C1)
+			return 2, nil
+		}
+	case 4:
+		switch pin {
+		case PH3: // channel A
+			avr.TCCR4A.SetBits(avr.TCCR4A_COM4A1)
+			return 0, nil
+		case PH4: //channel B
+			avr.TCCR4A.SetBits(avr.TCCR4A_COM4B1)
+			return 1, nil
+		case PH5: //channel C
+			avr.TCCR4A.SetBits(avr.TCCR4A_COM4C1)
+			return 2, nil
+		}
+	case 5:
+		switch pin {
+		case PL3: // channel A
+			avr.TCCR5A.SetBits(avr.TCCR5A_COM5A1)
+			return 0, nil
+		case PL4: //channel B
+			avr.TCCR5A.SetBits(avr.TCCR5A_COM5B1)
+			return 1, nil
+		case PL5: //channel C
+			avr.TCCR5A.SetBits(avr.TCCR5A_COM5C1)
+			return 2, nil
+		}
+	}
+	return 0, ErrInvalidOutputPin
+}
+
+// SetInverting sets whether to invert the output of this channel.
+// Without inverting, a 25% duty cycle would mean the output is high for 25% of
+// the time and low for the rest. Inverting flips the output as if a NOT gate
+// was placed at the output, meaning that the output would be 25% low and 75%
+// high with a duty cycle of 25%.
+//
+// Note: the invert state may not be applied on the AVR until the next call to
+// ch.Set().
+func (pwm PWM) SetInverting(channel uint8, inverting bool) {
+	switch pwm.num {
+	case 0:
+		switch channel {
+		case 0: // channel A, PB7
+			if inverting {
+				avr.PORTB.SetBits(1 << 7) // PB7 high
+				avr.TCCR0A.SetBits(avr.TCCR0A_COM0A0)
+			} else {
+				avr.PORTB.ClearBits(1 << 7) // PB7 low
+				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A0)
+			}
+		case 1: // channel B, PG5
+			if inverting {
+				avr.PORTG.SetBits(1 << 5) // PG5 high
+				avr.TCCR0A.SetBits(avr.TCCR0A_COM0B0)
+			} else {
+				avr.PORTG.ClearBits(1 << 5) // PG5 low
+				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B0)
+			}
+		}
+	case 1:
+		// Note: the COM1A0/COM1B0 bit is not set with the configuration below.
+		// It will be set the following call to Set(), however.
+		switch channel {
+		case 0: // channel A, PB5
+			if inverting {
+				avr.PORTB.SetBits(1 << 5) // PB5 high
+			} else {
+				avr.PORTB.ClearBits(1 << 5) // PB5 low
+			}
+		case 1: // channel B, PB6
+			if inverting {
+				avr.PORTB.SetBits(1 << 6) // PB6 high
+			} else {
+				avr.PORTB.ClearBits(1 << 6) // PB6 low
+			}
+		}
+	case 2:
+		switch channel {
+		case 0: // channel A, PB4
+			if inverting {
+				avr.PORTB.SetBits(1 << 4) // PB4 high
+				avr.TCCR2A.SetBits(avr.TCCR2A_COM2A0)
+			} else {
+				avr.PORTB.ClearBits(1 << 4) // PB4 low
+				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A0)
+			}
+		case 1: // channel B, PH6
+			if inverting {
+				avr.PORTH.SetBits(1 << 6) // PH6 high
+				avr.TCCR2A.SetBits(avr.TCCR2A_COM2B0)
+			} else {
+				avr.PORTH.ClearBits(1 << 6) // PH6 low
+				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B0)
+			}
+		}
+	case 3:
+		// Note: the COM3A0/COM3B0 bit is not set with the configuration below.
+		// It will be set the following call to Set(), however.
+		switch channel {
+		case 0: // channel A, PE3
+			if inverting {
+				avr.PORTE.SetBits(1 << 3) // PE3 high
+			} else {
+				avr.PORTE.ClearBits(1 << 3) // PE3 low
+			}
+		case 1: // channel B, PE4
+			if inverting {
+				avr.PORTE.SetBits(1 << 4) // PE4 high
+			} else {
+				avr.PORTE.ClearBits(1 << 4) // PE4 low
+			}
+		case 2: // channel C, PE5
+			if inverting {
+				avr.PORTE.SetBits(1 << 5) // PE4 high
+			} else {
+				avr.PORTE.ClearBits(1 << 5) // PE4 low
+			}
+		}
+	case 4:
+		// Note: the COM3A0/COM3B0 bit is not set with the configuration below.
+		// It will be set the following call to Set(), however.
+		switch channel {
+		case 0: // channel A, PH3
+			if inverting {
+				avr.PORTH.SetBits(1 << 3) // PH3 high
+			} else {
+				avr.PORTH.ClearBits(1 << 3) // PH3 low
+			}
+		case 1: // channel B, PH4
+			if inverting {
+				avr.PORTH.SetBits(1 << 4) // PH4 high
+			} else {
+				avr.PORTH.ClearBits(1 << 4) // PH4 low
+			}
+		case 2: // channel C, PH5
+			if inverting {
+				avr.PORTH.SetBits(1 << 5) // PH4 high
+			} else {
+				avr.PORTH.ClearBits(1 << 5) // PH4 low
+			}
+		}
+	case 5:
+		// Note: the COM3A0/COM3B0 bit is not set with the configuration below.
+		// It will be set the following call to Set(), however.
+		switch channel {
+		case 0: // channel A, PL3
+			if inverting {
+				avr.PORTL.SetBits(1 << 3) // PL3 high
+			} else {
+				avr.PORTL.ClearBits(1 << 3) // PL3 low
+			}
+		case 1: // channel B, PL4
+			if inverting {
+				avr.PORTL.SetBits(1 << 4) // PL4 high
+			} else {
+				avr.PORTL.ClearBits(1 << 4) // PL4 low
+			}
+		case 2: // channel C, PH5
+			if inverting {
+				avr.PORTL.SetBits(1 << 5) // PL4 high
+			} else {
+				avr.PORTL.ClearBits(1 << 5) // PL4 low
+			}
+		}
+	}
+}
+
+// Set updates the channel value. This is used to control the channel duty
+// cycle, in other words the fraction of time the channel output is high (or low
+// when inverted). For example, to set it to a 25% duty cycle, use:
+//
+//     pwm.Set(channel, pwm.Top() / 4)
+//
+// pwm.Set(channel, 0) will set the output to low and pwm.Set(channel,
+// pwm.Top()) will set the output to high, assuming the output isn't inverted.
+func (pwm PWM) Set(channel uint8, value uint32) {
+	switch pwm.num {
+	case 0:
+		value := uint16(value)
+		switch channel {
+		case 0: // channel A
+			if value == 0 {
+				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0A1)
+			} else {
+				avr.OCR0A.Set(uint8(value - 1))
+				avr.TCCR0A.SetBits(avr.TCCR0A_COM0A1)
+			}
+		case 1: // channel B
+			if value == 0 {
+				avr.TCCR0A.ClearBits(avr.TCCR0A_COM0B1)
+			} else {
+				avr.OCR0B.Set(uint8(value) - 1)
+				avr.TCCR0A.SetBits(avr.TCCR0A_COM0B1)
+			}
+		}
+	case 1:
+		mask := interrupt.Disable()
+		switch channel {
+		case 0: // channel A, PB5
+			if value == 0 {
+				avr.TCCR1A.ClearBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR1AH.Set(uint8(value >> 8))
+				avr.OCR1AL.Set(uint8(value))
+				if avr.PORTB.HasBits(1 << 5) { // is PB1 high?
+					// Yes, set the inverting bit.
+					avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1 | avr.TCCR1A_COM1A0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR1A.SetBits(avr.TCCR1A_COM1A1)
+				}
+			}
+		case 1: // channel B, PB6
+			if value == 0 {
+				avr.TCCR1A.ClearBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR1BH.Set(uint8(value >> 8))
+				avr.OCR1BL.Set(uint8(value))
+				if avr.PORTB.HasBits(1 << 6) { // is PB6 high?
+					// Yes, set the inverting bit.
+					avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1 | avr.TCCR1A_COM1B0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR1A.SetBits(avr.TCCR1A_COM1B1)
+				}
+			}
+		}
+		interrupt.Restore(mask)
+	case 2:
+		value := uint16(value)
+		switch channel {
+		case 0: // channel A
+			if value == 0 {
+				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2A1)
+			} else {
+				avr.OCR2A.Set(uint8(value - 1))
+				avr.TCCR2A.SetBits(avr.TCCR2A_COM2A1)
+			}
+		case 1: // channel B
+			if value == 0 {
+				avr.TCCR2A.ClearBits(avr.TCCR2A_COM2B1)
+			} else {
+				avr.OCR2B.Set(uint8(value - 1))
+				avr.TCCR2A.SetBits(avr.TCCR2A_COM2B1)
+			}
+		}
+	case 3:
+		mask := interrupt.Disable()
+		switch channel {
+		case 0: // channel A, PE3
+			if value == 0 {
+				avr.TCCR3A.ClearBits(avr.TCCR3A_COM3A1 | avr.TCCR3A_COM3A0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR3AH.Set(uint8(value >> 8))
+				avr.OCR3AL.Set(uint8(value))
+				if avr.PORTE.HasBits(1 << 3) { // is PE3 high?
+					// Yes, set the inverting bit.
+					avr.TCCR3A.SetBits(avr.TCCR3A_COM3A1 | avr.TCCR3A_COM3A0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR3A.SetBits(avr.TCCR3A_COM3A1)
+				}
+			}
+		case 1: // channel B, PE4
+			if value == 0 {
+				avr.TCCR3A.ClearBits(avr.TCCR3A_COM3B1 | avr.TCCR3A_COM3B0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR3BH.Set(uint8(value >> 8))
+				avr.OCR3BL.Set(uint8(value))
+				if avr.PORTE.HasBits(1 << 4) { // is PE4 high?
+					// Yes, set the inverting bit.
+					avr.TCCR3A.SetBits(avr.TCCR3A_COM3B1 | avr.TCCR3A_COM3B0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR3A.SetBits(avr.TCCR3A_COM3B1)
+				}
+			}
+		case 2: // channel C, PE5
+			if value == 0 {
+				avr.TCCR3A.ClearBits(avr.TCCR3A_COM3C1 | avr.TCCR3A_COM3C0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR3CH.Set(uint8(value >> 8))
+				avr.OCR3CL.Set(uint8(value))
+				if avr.PORTE.HasBits(1 << 5) { // is PE5 high?
+					// Yes, set the inverting bit.
+					avr.TCCR3A.SetBits(avr.TCCR3A_COM3C1 | avr.TCCR3A_COM3C0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR3A.SetBits(avr.TCCR3A_COM3C1)
+				}
+			}
+		}
+		interrupt.Restore(mask)
+	case 4:
+		mask := interrupt.Disable()
+		switch channel {
+		case 0: // channel A, PH3
+			if value == 0 {
+				avr.TCCR4A.ClearBits(avr.TCCR4A_COM4A1 | avr.TCCR4A_COM4A0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR4AH.Set(uint8(value >> 8))
+				avr.OCR4AL.Set(uint8(value))
+				if avr.PORTH.HasBits(1 << 3) { // is PH3 high?
+					// Yes, set the inverting bit.
+					avr.TCCR4A.SetBits(avr.TCCR4A_COM4A1 | avr.TCCR4A_COM4A0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR4A.SetBits(avr.TCCR4A_COM4A1)
+				}
+			}
+		case 1: // channel B, PH4
+			if value == 0 {
+				avr.TCCR4A.ClearBits(avr.TCCR4A_COM4B1 | avr.TCCR4A_COM4B0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR4BH.Set(uint8(value >> 8))
+				avr.OCR4BL.Set(uint8(value))
+				if avr.PORTH.HasBits(1 << 4) { // is PH4 high?
+					// Yes, set the inverting bit.
+					avr.TCCR4A.SetBits(avr.TCCR4A_COM4B1 | avr.TCCR4A_COM4B0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR4A.SetBits(avr.TCCR4A_COM4B1)
+				}
+			}
+		case 2: // channel C, PH5
+			if value == 0 {
+				avr.TCCR4A.ClearBits(avr.TCCR4A_COM4C1 | avr.TCCR4A_COM4C0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR4CH.Set(uint8(value >> 8))
+				avr.OCR4CL.Set(uint8(value))
+				if avr.PORTH.HasBits(1 << 5) { // is PH5 high?
+					// Yes, set the inverting bit.
+					avr.TCCR4A.SetBits(avr.TCCR4A_COM4C1 | avr.TCCR4A_COM4C0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR4A.SetBits(avr.TCCR4A_COM4C1)
+				}
+			}
+		}
+		interrupt.Restore(mask)
+	case 5:
+		mask := interrupt.Disable()
+		switch channel {
+		case 0: // channel A, PL3
+			if value == 0 {
+				avr.TCCR5A.ClearBits(avr.TCCR5A_COM5A1 | avr.TCCR5A_COM5A0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR5AH.Set(uint8(value >> 8))
+				avr.OCR5AL.Set(uint8(value))
+				if avr.PORTL.HasBits(1 << 3) { // is PL3 high?
+					// Yes, set the inverting bit.
+					avr.TCCR5A.SetBits(avr.TCCR5A_COM5A1 | avr.TCCR5A_COM5A0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR5A.SetBits(avr.TCCR5A_COM5A1)
+				}
+			}
+		case 1: // channel B, PL4
+			if value == 0 {
+				avr.TCCR5A.ClearBits(avr.TCCR5A_COM5B1 | avr.TCCR5A_COM5B0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR5BH.Set(uint8(value >> 8))
+				avr.OCR5BL.Set(uint8(value))
+				if avr.PORTL.HasBits(1 << 4) { // is PL4 high?
+					// Yes, set the inverting bit.
+					avr.TCCR5A.SetBits(avr.TCCR5A_COM5B1 | avr.TCCR5A_COM5B0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR5A.SetBits(avr.TCCR5A_COM5B1)
+				}
+			}
+		case 2: // channel C, PL5
+			if value == 0 {
+				avr.TCCR5A.ClearBits(avr.TCCR5A_COM5C1 | avr.TCCR5A_COM5C0)
+			} else {
+				value := uint16(value) - 1 // yes, this is safe (it relies on underflow)
+				avr.OCR5CH.Set(uint8(value >> 8))
+				avr.OCR5CL.Set(uint8(value))
+				if avr.PORTL.HasBits(1 << 5) { // is PL5 high?
+					// Yes, set the inverting bit.
+					avr.TCCR5A.SetBits(avr.TCCR5A_COM5C1 | avr.TCCR5A_COM5C0)
+				} else {
+					// No, output is non-inverting.
+					avr.TCCR5A.SetBits(avr.TCCR5A_COM5C1)
+				}
+			}
+		}
+		interrupt.Restore(mask)
+	}
+}
+
+// SPI configuration
+var SPI0 = SPI{
+	spcr: avr.SPCR,
+	spdr: avr.SPDR,
+	spsr: avr.SPSR,
+	sck:  PB1,
+	sdo:  PB2,
+	sdi:  PB3,
+	cs:   PB0}

src/machine/machine_atsamd21.go

@@ -2298,7 +2298,7 @@ func handleStandardSetup(setup usbSetup) bool {
 func cdcSetup(setup usbSetup) bool {
 	if setup.bmRequestType == usb_REQUEST_DEVICETOHOST_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_GET_LINE_CODING {
-			b := make([]byte, 7)
+			var b [cdcLineInfoSize]byte
 			b[0] = byte(usbLineInfo.dwDTERate)
 			b[1] = byte(usbLineInfo.dwDTERate >> 8)
 			b[2] = byte(usbLineInfo.dwDTERate >> 16)
@@ -2307,14 +2307,18 @@ func cdcSetup(setup usbSetup) bool {
 			b[5] = byte(usbLineInfo.bParityType)
 			b[6] = byte(usbLineInfo.bDataBits)
 
-			sendUSBPacket(0, b)
+			sendUSBPacket(0, b[:])
 			return true
 		}
 	}
 
 	if setup.bmRequestType == usb_REQUEST_HOSTTODEVICE_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_SET_LINE_CODING {
-			b := receiveUSBControlPacket()
+			b, err := receiveUSBControlPacket()
+			if err != nil {
+				return false
+			}
+
 			usbLineInfo.dwDTERate = uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
 			usbLineInfo.bCharFormat = b[4]
 			usbLineInfo.bParityType = b[5]
@@ -2361,7 +2365,9 @@ func sendUSBPacket(ep uint32, data []byte) {
 	usbEndpointDescriptors[ep].DeviceDescBank[1].PCKSIZE.SetBits(uint32((len(data) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask) << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos))
 }
 
-func receiveUSBControlPacket() []byte {
+func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
+	var b [cdcLineInfoSize]byte
+
 	// address
 	usbEndpointDescriptors[0].DeviceDescBank[0].ADDR.Set(uint32(uintptr(unsafe.Pointer(&udd_ep_out_cache_buffer[0]))))
 
@@ -2376,7 +2382,7 @@ func receiveUSBControlPacket() []byte {
 	for (getEPSTATUS(0) & sam.USB_DEVICE_EPSTATUS_BK0RDY) == 0 {
 		timeout--
 		if timeout == 0 {
-			return []byte{}
+			return b, errUSBCDCReadTimeout
 		}
 	}
 
@@ -2385,7 +2391,7 @@ func receiveUSBControlPacket() []byte {
 	for (getEPINTFLAG(0) & sam.USB_DEVICE_EPINTFLAG_TRCPT0) == 0 {
 		timeout--
 		if timeout == 0 {
-			return []byte{}
+			return b, errUSBCDCReadTimeout
 		}
 	}
 
@@ -2393,10 +2399,13 @@ func receiveUSBControlPacket() []byte {
 	bytesread := uint32((usbEndpointDescriptors[0].DeviceDescBank[0].PCKSIZE.Get() >>
 		usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask)
 
-	data := make([]byte, bytesread)
-	copy(data, udd_ep_out_cache_buffer[0][:])
+	if bytesread != cdcLineInfoSize {
+		return b, errUSBCDCBytesRead
+	}
 
-	return data
+	copy(b[:7], udd_ep_out_cache_buffer[0][:7])
+
+	return b, nil
 }
 
 func handleEndpoint(ep uint32) {

src/machine/machine_atsamd51.go

@@ -2426,7 +2426,7 @@ func handleStandardSetup(setup usbSetup) bool {
 func cdcSetup(setup usbSetup) bool {
 	if setup.bmRequestType == usb_REQUEST_DEVICETOHOST_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_GET_LINE_CODING {
-			b := make([]byte, 7)
+			var b [cdcLineInfoSize]byte
 			b[0] = byte(usbLineInfo.dwDTERate)
 			b[1] = byte(usbLineInfo.dwDTERate >> 8)
 			b[2] = byte(usbLineInfo.dwDTERate >> 16)
@@ -2435,14 +2435,18 @@ func cdcSetup(setup usbSetup) bool {
 			b[5] = byte(usbLineInfo.bParityType)
 			b[6] = byte(usbLineInfo.bDataBits)
 
-			sendUSBPacket(0, b)
+			sendUSBPacket(0, b[:])
 			return true
 		}
 	}
 
 	if setup.bmRequestType == usb_REQUEST_HOSTTODEVICE_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_SET_LINE_CODING {
-			b := receiveUSBControlPacket()
+			b, err := receiveUSBControlPacket()
+			if err != nil {
+				return false
+			}
+
 			usbLineInfo.dwDTERate = uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
 			usbLineInfo.bCharFormat = b[4]
 			usbLineInfo.bParityType = b[5]
@@ -2489,7 +2493,9 @@ func sendUSBPacket(ep uint32, data []byte) {
 	usbEndpointDescriptors[ep].DeviceDescBank[1].PCKSIZE.SetBits(uint32((len(data) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask) << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos))
 }
 
-func receiveUSBControlPacket() []byte {
+func receiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
+	var b [cdcLineInfoSize]byte
+
 	// address
 	usbEndpointDescriptors[0].DeviceDescBank[0].ADDR.Set(uint32(uintptr(unsafe.Pointer(&udd_ep_out_cache_buffer[0]))))
 
@@ -2504,7 +2510,7 @@ func receiveUSBControlPacket() []byte {
 	for (getEPSTATUS(0) & sam.USB_DEVICE_ENDPOINT_EPSTATUS_BK0RDY) == 0 {
 		timeout--
 		if timeout == 0 {
-			return []byte{}
+			return b, errUSBCDCReadTimeout
 		}
 	}
 
@@ -2513,7 +2519,7 @@ func receiveUSBControlPacket() []byte {
 	for (getEPINTFLAG(0) & sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1) == 0 {
 		timeout--
 		if timeout == 0 {
-			return []byte{}
+			return b, errUSBCDCReadTimeout
 		}
 	}
 
@@ -2521,10 +2527,13 @@ func receiveUSBControlPacket() []byte {
 	bytesread := uint32((usbEndpointDescriptors[0].DeviceDescBank[0].PCKSIZE.Get() >>
 		usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask)
 
-	data := make([]byte, bytesread)
-	copy(data, udd_ep_out_cache_buffer[0][:])
+	if bytesread != cdcLineInfoSize {
+		return b, errUSBCDCBytesRead
+	}
 
-	return data
+	copy(b[:7], udd_ep_out_cache_buffer[0][:7])
+
+	return b, nil
 }
 
 func handleEndpoint(ep uint32) {

src/machine/machine_atsamd51p20.go

@@ -11,60 +11,49 @@ import "device/sam"
 
 const HSRAM_SIZE = 0x00040000
 
-// InitPWM initializes the PWM interface.
-func InitPWM() {
-	// turn on timer clocks used for PWM
-	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_ | sam.MCLK_APBBMASK_TCC1_)
-	sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_ | sam.MCLK_APBCMASK_TCC3_)
-	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
+// This chip has five TCC peripherals, which have PWM as one feature.
+var (
+	TCC0 = (*TCC)(sam.TCC0)
+	TCC1 = (*TCC)(sam.TCC1)
+	TCC2 = (*TCC)(sam.TCC2)
+	TCC3 = (*TCC)(sam.TCC3)
+	TCC4 = (*TCC)(sam.TCC4)
+)
 
-	//use clock generator 0
-	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
-		sam.GCLK_PCHCTRL_CHEN)
-	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
-		sam.GCLK_PCHCTRL_CHEN)
-	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) |
-		sam.GCLK_PCHCTRL_CHEN)
-}
-
-// getTimer returns the timer to be used for PWM on this pin
-func (pwm PWM) getTimer() *sam.TCC_Type {
-	switch pwm.Pin {
-	case PC18:
-		return sam.TCC0
-	case PC19:
-		return sam.TCC0
-	case PC20:
-		return sam.TCC0
-	case PC21:
-		return sam.TCC0
-	case PD20:
-		return sam.TCC1
-	case PD21:
-		return sam.TCC1
-	case PB18:
-		return sam.TCC1
-	case PB12:
-		return sam.TCC3
-	case PB13:
-		return sam.TCC3
-	case PA15:
-		return sam.TCC2
-	case PC17:
-		return sam.TCC0
-	case PC16:
-		return sam.TCC0
-	case PA14:
-		return sam.TCC2
-	case PB15:
-		return sam.TCC4
-	case PB14:
-		return sam.TCC4
-	case PB20:
-		return sam.TCC1
-	case PB21:
-		return sam.TCC1
-	default:
-		return nil // not supported on this pin
+func (tcc *TCC) configureClock() {
+	// Turn on timer clocks used for TCC and use generic clock generator 0.
+	switch tcc.timer() {
+	case sam.TCC0:
+		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC1:
+		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC2:
+		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC3:
+		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC4:
+		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	}
+}
+
+func (tcc *TCC) timerNum() uint8 {
+	switch tcc.timer() {
+	case sam.TCC0:
+		return 0
+	case sam.TCC1:
+		return 1
+	case sam.TCC2:
+		return 2
+	case sam.TCC3:
+		return 3
+	case sam.TCC4:
+		return 4
+	default:
+		return 0x0f // should not happen
 	}
 }

src/machine/machine_atsame51j19.go

@@ -0,0 +1,59 @@
+// +build sam,atsame51,atsame51j19
+
+// Peripheral abstraction layer for the atsame51.
+//
+// Datasheet:
+// http://ww1.microchip.com/downloads/en/DeviceDoc/SAM_D5xE5x_Family_Data_Sheet_DS60001507F.pdf
+//
+package machine
+
+import "device/sam"
+
+const HSRAM_SIZE = 0x00030000
+
+// This chip has five TCC peripherals, which have PWM as one feature.
+var (
+	TCC0 = (*TCC)(sam.TCC0)
+	TCC1 = (*TCC)(sam.TCC1)
+	TCC2 = (*TCC)(sam.TCC2)
+	TCC3 = (*TCC)(sam.TCC3)
+	TCC4 = (*TCC)(sam.TCC4)
+)
+
+func (tcc *TCC) configureClock() {
+	// Turn on timer clocks used for the TCC and use generic clock generator 0.
+	switch tcc.timer() {
+	case sam.TCC0:
+		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC1:
+		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC2:
+		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC3:
+		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC4:
+		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	}
+}
+
+func (tcc *TCC) timerNum() uint8 {
+	switch tcc.timer() {
+	case sam.TCC0:
+		return 0
+	case sam.TCC1:
+		return 1
+	case sam.TCC2:
+		return 2
+	case sam.TCC3:
+		return 3
+	case sam.TCC4:
+		return 4
+	default:
+		return 0x0f // should not happen
+	}
+}

src/machine/machine_atsame54p20.go

@@ -0,0 +1,59 @@
+// +build sam,atsame5x,atsame54p20
+
+// Peripheral abstraction layer for the atsame54.
+//
+// Datasheet:
+// http://ww1.microchip.com/downloads/en/DeviceDoc/60001507C.pdf
+//
+package machine
+
+import "device/sam"
+
+const HSRAM_SIZE = 0x00040000
+
+// This chip has five TCC peripherals, which have PWM as one feature.
+var (
+	TCC0 = (*TCC)(sam.TCC0)
+	TCC1 = (*TCC)(sam.TCC1)
+	TCC2 = (*TCC)(sam.TCC2)
+	TCC3 = (*TCC)(sam.TCC3)
+	TCC4 = (*TCC)(sam.TCC4)
+)
+
+func (tcc *TCC) configureClock() {
+	// Turn on timer clocks used for TCC and use generic clock generator 0.
+	switch tcc.timer() {
+	case sam.TCC0:
+		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC0_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC1:
+		sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_TCC1_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC2:
+		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC2_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC2].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC3:
+		sam.MCLK.APBCMASK.SetBits(sam.MCLK_APBCMASK_TCC3_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC3].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	case sam.TCC4:
+		sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_TCC4_)
+		sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_TCC4].Set((sam.GCLK_PCHCTRL_GEN_GCLK0 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	}
+}
+
+func (tcc *TCC) timerNum() uint8 {
+	switch tcc.timer() {
+	case sam.TCC0:
+		return 0
+	case sam.TCC1:
+		return 1
+	case sam.TCC2:
+		return 2
+	case sam.TCC3:
+		return 3
+	case sam.TCC4:
+		return 4
+	default:
+		return 0x0f // should not happen
+	}
+}

src/machine/machine_gameboyadvance.go

@@ -54,7 +54,7 @@ func (d FramebufDisplay) Size() (x, y int16) {
 }
 
 func (d FramebufDisplay) SetPixel(x, y int16, c color.RGBA) {
-	d.port[y][x].Set(uint16(c.R)&0x1f | uint16(c.G)&0x1f<<5 | uint16(c.B)&0x1f<<10)
+	d.port[y][x].Set((uint16(c.R) >> 3) | ((uint16(c.G) >> 3) << 5) | ((uint16(c.B) >> 3) << 10))
 }
 
 func (d FramebufDisplay) Display() error {

src/machine/machine_nrf52833.go

@@ -83,7 +83,8 @@ func (i2c *I2C) setPins(scl, sda Pin) {
 
 // PWM
 var (
-	pwmChannelPins     = [4]uint32{0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF}
-	pwms               = [4]*nrf.PWM_Type{nrf.PWM0, nrf.PWM1, nrf.PWM2, nrf.PWM3}
-	pwmChannelSequence [4]uint16
+	PWM0 = &PWM{PWM: nrf.PWM0}
+	PWM1 = &PWM{PWM: nrf.PWM1}
+	PWM2 = &PWM{PWM: nrf.PWM2}
+	PWM3 = &PWM{PWM: nrf.PWM3}
 )

src/machine/machine_nrf52840_usb.go

@@ -445,7 +445,7 @@ func handleStandardSetup(setup usbSetup) bool {
 func cdcSetup(setup usbSetup) bool {
 	if setup.bmRequestType == usb_REQUEST_DEVICETOHOST_CLASS_INTERFACE {
 		if setup.bRequest == usb_CDC_GET_LINE_CODING {
-			b := make([]byte, 7)
+			var b [cdcLineInfoSize]byte
 			b[0] = byte(usbLineInfo.dwDTERate)
 			b[1] = byte(usbLineInfo.dwDTERate >> 8)
 			b[2] = byte(usbLineInfo.dwDTERate >> 16)
@@ -454,7 +454,7 @@ func cdcSetup(setup usbSetup) bool {
 			b[5] = byte(usbLineInfo.bParityType)
 			b[6] = byte(usbLineInfo.bDataBits)
 
-			sendUSBPacket(0, b)
+			sendUSBPacket(0, b[:])
 			return true
 		}
 	}

src/machine/machine_stm32_moder_gpio.go

@@ -55,9 +55,11 @@ const (
 	gpioPullMask     = 0x3
 
 	// OSPEED bitfields.
-	gpioOutputSpeedHigh = 2
-	gpioOutputSpeedLow  = 0
-	gpioOutputSpeedMask = 0x3
+	gpioOutputSpeedVeryHigh = 3
+	gpioOutputSpeedHigh     = 2
+	gpioOutputSpeedMedium   = 1
+	gpioOutputSpeedLow      = 0
+	gpioOutputSpeedMask     = 0x3
 )
 
 // Configure this pin with the given configuration
@@ -120,7 +122,7 @@ func (p Pin) ConfigureAltFunc(config PinConfig, altFunc uint8) {
 	// SPI
 	case PinModeSPICLK:
 		port.MODER.ReplaceBits(gpioModeAlternate, gpioModeMask, pos)
-		port.OSPEEDR.ReplaceBits(gpioOutputSpeedLow, gpioOutputSpeedMask, pos)
+		port.OSPEEDR.ReplaceBits(gpioOutputSpeedHigh, gpioOutputSpeedMask, pos)
 		port.PUPDR.ReplaceBits(gpioPullFloating, gpioPullMask, pos)
 		p.SetAltFunc(altFunc)
 	case PinModeSPISDO:

src/machine/machine_stm32_spi.go

@@ -1,4 +1,4 @@
-// +build stm32,!stm32f7x2,!stm32l5x2,!stm32l4x2
+// +build stm32,!stm32f7x2,!stm32l5x2
 
 package machine
 
@@ -6,6 +6,7 @@ package machine
 
 import (
 	"device/stm32"
+	"runtime/volatile"
 	"unsafe"
 )
 
@@ -86,7 +87,12 @@ func (spi SPI) Configure(config SPIConfig) {
 
 	// now set the configuration
 	spi.Bus.CR1.Set(conf)
-	spi.Bus.CR2.SetBits((conf & stm32.SPI_CR1_SSM_Msk) >> 16)
+
+	// Series-specific configuration to set 8-bit transfer mode
+	spi.config8Bits()
+
+	// enable SPI
+	spi.Bus.CR1.SetBits(stm32.SPI_CR1_SPE)
 }
 
 // Transfer writes/reads a single byte using the SPI interface.
@@ -103,8 +109,10 @@ func (spi SPI) Transfer(w byte) (byte, error) {
 	// 5. Wait until TXE=1 and then wait until BSY=0 before disabling the SPI.
 
 	// put output word (8-bit) in data register (DR), which is parallel-loaded
-	// into shift register, and shifted out on MOSI.
-	spi.Bus.DR.Set(uint32(w))
+	// into shift register, and shifted out on MOSI.  Some series have 16-bit
+	// register but writes must be strictly 8-bit to output a byte.  Writing
+	// 16-bits indicates a packed transfer (2 bytes).
+	(*volatile.Register8)(unsafe.Pointer(&spi.Bus.DR.Reg)).Set(w)
 
 	// wait for SPI bus receive buffer not empty bit (RXNE) to be set.
 	// warning: blocks forever until this condition is met.

src/machine/machine_stm32f103.go

@@ -161,6 +161,10 @@ var (
 	SPI0 = SPI1
 )
 
+func (spi SPI) config8Bits() {
+	// no-op on this series
+}
+
 // Set baud rate for SPI
 func (spi SPI) getBaudRate(config SPIConfig) uint32 {
 	var conf uint32

src/machine/machine_stm32f405.go

@@ -67,6 +67,10 @@ type SPI struct {
 	AltFuncSelector uint8
 }
 
+func (spi SPI) config8Bits() {
+	// no-op on this series
+}
+
 func (spi SPI) configurePins(config SPIConfig) {
 	config.SCK.ConfigureAltFunc(PinConfig{Mode: PinModeSPICLK}, spi.AltFuncSelector)
 	config.SDO.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDO}, spi.AltFuncSelector)

src/machine/machine_stm32f407.go

@@ -70,6 +70,10 @@ type SPI struct {
 	AltFuncSelector uint8
 }
 
+func (spi SPI) config8Bits() {
+	// no-op on this series
+}
+
 // Set baud rate for SPI
 func (spi SPI) getBaudRate(config SPIConfig) uint32 {
 	var conf uint32

src/machine/machine_stm32l0.go

@@ -184,6 +184,10 @@ type SPI struct {
 	AltFuncSelector uint8
 }
 
+func (spi SPI) config8Bits() {
+	// no-op on this series
+}
+
 // Set baud rate for SPI
 func (spi SPI) getBaudRate(config SPIConfig) uint32 {
 	var conf uint32

src/machine/machine_stm32l4.go

@@ -182,3 +182,67 @@ func enableAltFuncClock(bus unsafe.Pointer) {
 		stm32.RCC.APB2ENR.SetBits(stm32.RCC_APB2ENR_TIM1EN)
 	}
 }
+
+//---------- SPI related types and code
+
+// SPI on the STM32Fxxx using MODER / alternate function pins
+type SPI struct {
+	Bus             *stm32.SPI_Type
+	AltFuncSelector uint8
+}
+
+func (spi SPI) config8Bits() {
+	// Set rx threshold to 8-bits, so RXNE flag is set for 1 byte
+	// (common STM32 SPI implementation does 8-bit transfers only)
+	spi.Bus.CR2.SetBits(stm32.SPI_CR2_FRXTH)
+}
+
+// Set baud rate for SPI
+func (spi SPI) getBaudRate(config SPIConfig) uint32 {
+	var conf uint32
+
+	// Default
+	if config.Frequency == 0 {
+		config.Frequency = 4e6
+	}
+
+	localFrequency := config.Frequency
+
+	// set frequency dependent on PCLK prescaler. Since these are rather weird
+	// speeds due to the CPU freqency, pick a range up to that frquency for
+	// clients to use more human-understandable numbers, e.g. nearest 100KHz
+
+	// These are based on 80MHz peripheral clock frquency
+	switch {
+	case localFrequency < 312500:
+		conf = stm32.SPI_CR1_BR_Div256
+	case localFrequency < 625000:
+		conf = stm32.SPI_CR1_BR_Div128
+	case localFrequency < 1250000:
+		conf = stm32.SPI_CR1_BR_Div64
+	case localFrequency < 2500000:
+		conf = stm32.SPI_CR1_BR_Div32
+	case localFrequency < 5000000:
+		conf = stm32.SPI_CR1_BR_Div16
+	case localFrequency < 10000000:
+		conf = stm32.SPI_CR1_BR_Div8
+		// NOTE: many SPI components won't operate reliably (or at all) above 10MHz
+		// Check the datasheet of the part
+	case localFrequency < 20000000:
+		conf = stm32.SPI_CR1_BR_Div4
+	case localFrequency < 40000000:
+		conf = stm32.SPI_CR1_BR_Div2
+	default:
+		// None of the specific baudrates were selected; choose the lowest speed
+		conf = stm32.SPI_CR1_BR_Div256
+	}
+
+	return conf << stm32.SPI_CR1_BR_Pos
+}
+
+// Configure SPI pins for input output and clock
+func (spi SPI) configurePins(config SPIConfig) {
+	config.SCK.ConfigureAltFunc(PinConfig{Mode: PinModeSPICLK}, spi.AltFuncSelector)
+	config.SDO.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDO}, spi.AltFuncSelector)
+	config.SDI.ConfigureAltFunc(PinConfig{Mode: PinModeSPISDI}, spi.AltFuncSelector)
+}

src/machine/spi.go

@@ -1,4 +1,4 @@
-// +build !baremetal stm32,!stm32f7x2,!stm32l5x2,!stm32l4x2 fe310 k210 atmega
+// +build !baremetal stm32,!stm32f7x2,!stm32l5x2 fe310 k210 atmega
 
 package machine
 

src/machine/usb.go

@@ -12,6 +12,8 @@ const deviceDescriptorSize = 18
 var (
 	errUSBCDCBufferEmpty      = errors.New("USB-CDC buffer empty")
 	errUSBCDCWriteByteTimeout = errors.New("USB-CDC write byte timeout")
+	errUSBCDCReadTimeout      = errors.New("USB-CDC read timeout")
+	errUSBCDCBytesRead        = errors.New("USB-CDC invalid number of bytes read")
 )
 
 // DeviceDescriptor implements the USB standard device descriptor.
@@ -43,8 +45,8 @@ func NewDeviceDescriptor(class, subClass, proto, packetSize0 uint8, vid, pid, ve
 }
 
 // Bytes returns DeviceDescriptor data
-func (d DeviceDescriptor) Bytes() []byte {
-	b := make([]byte, deviceDescriptorSize)
+func (d DeviceDescriptor) Bytes() [deviceDescriptorSize]byte {
+	var b [deviceDescriptorSize]byte
 	b[0] = byte(d.bLength)
 	b[1] = byte(d.bDescriptorType)
 	b[2] = byte(d.bcdUSB)
@@ -91,8 +93,8 @@ func NewConfigDescriptor(totalLength uint16, interfaces uint8) ConfigDescriptor
 }
 
 // Bytes returns ConfigDescriptor data.
-func (d ConfigDescriptor) Bytes() []byte {
-	b := make([]byte, configDescriptorSize)
+func (d ConfigDescriptor) Bytes() [configDescriptorSize]byte {
+	var b [configDescriptorSize]byte
 	b[0] = byte(d.bLength)
 	b[1] = byte(d.bDescriptorType)
 	b[2] = byte(d.wTotalLength)
@@ -131,8 +133,8 @@ func NewInterfaceDescriptor(n, numEndpoints, class, subClass, protocol uint8) In
 }
 
 // Bytes returns InterfaceDescriptor data.
-func (d InterfaceDescriptor) Bytes() []byte {
-	b := make([]byte, interfaceDescriptorSize)
+func (d InterfaceDescriptor) Bytes() [interfaceDescriptorSize]byte {
+	var b [interfaceDescriptorSize]byte
 	b[0] = byte(d.bLength)
 	b[1] = byte(d.bDescriptorType)
 	b[2] = byte(d.bInterfaceNumber)
@@ -167,8 +169,8 @@ func NewEndpointDescriptor(addr, attr uint8, packetSize uint16, interval uint8)
 }
 
 // Bytes returns EndpointDescriptor data.
-func (d EndpointDescriptor) Bytes() []byte {
-	b := make([]byte, endpointDescriptorSize)
+func (d EndpointDescriptor) Bytes() [endpointDescriptorSize]byte {
+	var b [endpointDescriptorSize]byte
 	b[0] = byte(d.bLength)
 	b[1] = byte(d.bDescriptorType)
 	b[2] = byte(d.bEndpointAddress)
@@ -205,8 +207,8 @@ func NewIADDescriptor(firstInterface, count, class, subClass, protocol uint8) IA
 }
 
 // Bytes returns IADDescriptor data.
-func (d IADDescriptor) Bytes() []byte {
-	b := make([]byte, iadDescriptorSize)
+func (d IADDescriptor) Bytes() [iadDescriptorSize]byte {
+	var b [iadDescriptorSize]byte
 	b[0] = byte(d.bLength)
 	b[1] = byte(d.bDescriptorType)
 	b[2] = byte(d.bFirstInterface)
@@ -235,8 +237,8 @@ func NewCDCCSInterfaceDescriptor(subtype, d0, d1 uint8) CDCCSInterfaceDescriptor
 }
 
 // Bytes returns CDCCSInterfaceDescriptor data.
-func (d CDCCSInterfaceDescriptor) Bytes() []byte {
-	b := make([]byte, cdcCSInterfaceDescriptorSize)
+func (d CDCCSInterfaceDescriptor) Bytes() [cdcCSInterfaceDescriptorSize]byte {
+	var b [cdcCSInterfaceDescriptorSize]byte
 	b[0] = byte(d.len)
 	b[1] = byte(d.dtype)
 	b[2] = byte(d.subtype)
@@ -262,8 +264,8 @@ func NewCMFunctionalDescriptor(subtype, d0, d1 uint8) CMFunctionalDescriptor {
 }
 
 // Bytes returns the CMFunctionalDescriptor data.
-func (d CMFunctionalDescriptor) Bytes() []byte {
-	b := make([]byte, cmFunctionalDescriptorSize)
+func (d CMFunctionalDescriptor) Bytes() [cmFunctionalDescriptorSize]byte {
+	var b [cmFunctionalDescriptorSize]byte
 	b[0] = byte(d.bFunctionLength)
 	b[1] = byte(d.bDescriptorType)
 	b[2] = byte(d.bDescriptorSubtype)
@@ -288,8 +290,8 @@ func NewACMFunctionalDescriptor(subtype, d0 uint8) ACMFunctionalDescriptor {
 }
 
 // Bytes returns the ACMFunctionalDescriptor data.
-func (d ACMFunctionalDescriptor) Bytes() []byte {
-	b := make([]byte, acmFunctionalDescriptorSize)
+func (d ACMFunctionalDescriptor) Bytes() [acmFunctionalDescriptorSize]byte {
+	var b [acmFunctionalDescriptorSize]byte
 	b[0] = byte(d.len)
 	b[1] = byte(d.dtype)
 	b[2] = byte(d.subtype)
@@ -351,19 +353,51 @@ const cdcSize = iadDescriptorSize +
 	endpointDescriptorSize
 
 // Bytes returns CDCDescriptor data.
-func (d CDCDescriptor) Bytes() []byte {
-	var buf []byte
-	buf = append(buf, d.iad.Bytes()...)
-	buf = append(buf, d.cif.Bytes()...)
-	buf = append(buf, d.header.Bytes()...)
-	buf = append(buf, d.controlManagement.Bytes()...)
-	buf = append(buf, d.functionalDescriptor.Bytes()...)
-	buf = append(buf, d.callManagement.Bytes()...)
-	buf = append(buf, d.cifin.Bytes()...)
-	buf = append(buf, d.dif.Bytes()...)
-	buf = append(buf, d.out.Bytes()...)
-	buf = append(buf, d.in.Bytes()...)
-	return buf
+func (d CDCDescriptor) Bytes() [cdcSize]byte {
+	var b [cdcSize]byte
+	offset := 0
+
+	iad := d.iad.Bytes()
+	copy(b[offset:], iad[:])
+	offset += len(iad)
+
+	cif := d.cif.Bytes()
+	copy(b[offset:], cif[:])
+	offset += len(cif)
+
+	header := d.header.Bytes()
+	copy(b[offset:], header[:])
+	offset += len(header)
+
+	controlManagement := d.controlManagement.Bytes()
+	copy(b[offset:], controlManagement[:])
+	offset += len(controlManagement)
+
+	functionalDescriptor := d.functionalDescriptor.Bytes()
+	copy(b[offset:], functionalDescriptor[:])
+	offset += len(functionalDescriptor)
+
+	callManagement := d.callManagement.Bytes()
+	copy(b[offset:], callManagement[:])
+	offset += len(callManagement)
+
+	cifin := d.cifin.Bytes()
+	copy(b[offset:], cifin[:])
+	offset += len(cifin)
+
+	dif := d.dif.Bytes()
+	copy(b[offset:], dif[:])
+	offset += len(dif)
+
+	out := d.out.Bytes()
+	copy(b[offset:], out[:])
+	offset += len(out)
+
+	in := d.in.Bytes()
+	copy(b[offset:], in[:])
+	offset += len(in)
+
+	return b
 }
 
 // MSCDescriptor is not used yet.
@@ -373,6 +407,8 @@ type MSCDescriptor struct {
 	out EndpointDescriptor
 }
 
+const cdcLineInfoSize = 7
+
 type cdcLineInfo struct {
 	dwDTERate   uint32
 	bCharFormat uint8
@@ -633,7 +669,8 @@ func sendDescriptor(setup usbSetup) {
 		if setup.wLength < deviceDescriptorSize {
 			l = int(setup.wLength)
 		}
-		sendUSBPacket(0, dd.Bytes()[:l])
+		buf := dd.Bytes()
+		sendUSBPacket(0, buf[:l])
 		return
 
 	case usb_STRING_DESCRIPTOR_TYPE:
@@ -669,7 +706,8 @@ func sendConfiguration(setup usbSetup) {
 	if setup.wLength == 9 {
 		sz := uint16(configDescriptorSize + cdcSize)
 		config := NewConfigDescriptor(sz, 2)
-		sendUSBPacket(0, config.Bytes())
+		configBuf := config.Bytes()
+		sendUSBPacket(0, configBuf[:])
 	} else {
 		iad := NewIADDescriptor(0, 2, usb_CDC_COMMUNICATION_INTERFACE_CLASS, usb_CDC_ABSTRACT_CONTROL_MODEL, 0)
 
@@ -705,10 +743,12 @@ func sendConfiguration(setup usbSetup) {
 		sz := uint16(configDescriptorSize + cdcSize)
 		config := NewConfigDescriptor(sz, 2)
 
-		buf := make([]byte, 0, sz)
-		buf = append(buf, config.Bytes()...)
-		buf = append(buf, cdc.Bytes()...)
+		configBuf := config.Bytes()
+		cdcBuf := cdc.Bytes()
+		var buf [configDescriptorSize + cdcSize]byte
+		copy(buf[0:], configBuf[:])
+		copy(buf[configDescriptorSize:], cdcBuf[:])
 
-		sendUSBPacket(0, buf)
+		sendUSBPacket(0, buf[:])
 	}
 }

src/reflect/type.go

@@ -322,6 +322,9 @@ func TypeOf(i interface{}) Type {
 }
 
 func PtrTo(t Type) Type {
+	if t.Kind() == Ptr {
+		panic("reflect: cannot make **T type")
+	}
 	ptrType := t.(rawType)<<5 | 5 // 0b0101 == 5
 	if ptrType>>5 != t {
 		panic("reflect: PtrTo type does not fit")

src/reflect/value.go

@@ -724,8 +724,14 @@ func Zero(typ Type) Value {
 	panic("unimplemented: reflect.Zero()")
 }
 
+// New is the reflect equivalent of the new(T) keyword, returning a pointer to a
+// new value of the given type.
 func New(typ Type) Value {
-	panic("unimplemented: reflect.New()")
+	return Value{
+		typecode: PtrTo(typ).(rawType),
+		value:    alloc(typ.Size()),
+		flags:    valueFlagExported,
+	}
 }
 
 type funcHeader struct {
@@ -756,6 +762,9 @@ func (e *ValueError) Error() string {
 // llvm.memcpy.p0i8.p0i8.i32().
 func memcpy(dst, src unsafe.Pointer, size uintptr)
 
+//go:linkname alloc runtime.alloc
+func alloc(size uintptr) unsafe.Pointer
+
 // Copy copies the contents of src into dst until either
 // dst has been filled or src has been exhausted.
 func Copy(dst, src Value) int {

src/runtime/func.go

@@ -16,13 +16,13 @@ type funcValue struct {
 
 // funcValueWithSignature is used before the func lowering pass.
 type funcValueWithSignature struct {
-	funcPtr   uintptr     // ptrtoint of the actual function pointer
-	signature *typecodeID // pointer to identify this signature (the value is undef)
+	funcPtr   uintptr // ptrtoint of the actual function pointer
+	signature *uint8  // external *i8 with a name identifying the function signature
 }
 
 // getFuncPtr is a dummy function that may be used if the func lowering pass is
 // not used. It is generally too slow but may be a useful fallback to debug the
 // func lowering pass.
-func getFuncPtr(val funcValue, signature *typecodeID) uintptr {
+func getFuncPtr(val funcValue, signature *uint8) uintptr {
 	return (*funcValueWithSignature)(unsafe.Pointer(val.id)).funcPtr
 }

src/runtime/interface.go

@@ -112,6 +112,11 @@ type typecodeID struct {
 	length uintptr
 
 	methodSet *interfaceMethodInfo // nil or a GEP of an array
+
+	// The type that's a pointer to this type, nil if it is already a pointer.
+	// Keeping the type struct alive here is important so that values from
+	// reflect.New (which uses reflect.PtrTo) can be used in type asserts etc.
+	ptrTo *typecodeID
 }
 
 // structField is used by the compiler to pass information to the interface

src/runtime/runtime.go

@@ -23,7 +23,9 @@ func GOROOT() string {
 	return "/usr/local/go"
 }
 
-// TODO: fill with real args.
+// This is the default set of arguments, if nothing else has been set.
+// This may be overriden by modifying this global at runtime init (for example,
+// on Linux where there are real command line arguments).
 var args = []string{"/proc/self/exe"}
 
 //go:linkname os_runtime_args os.runtime_args
@@ -47,6 +49,9 @@ func memmove(dst, src unsafe.Pointer, size uintptr)
 // llvm.memset.p0i8.i32(ptr, 0, size, false).
 func memzero(ptr unsafe.Pointer, size uintptr)
 
+//export strlen
+func strlen(ptr unsafe.Pointer) uintptr
+
 // Compare two same-size buffers for equality.
 func memequal(x, y unsafe.Pointer, n uintptr) bool {
 	for i := uintptr(0); i < n; i++ {
@@ -89,8 +94,3 @@ func AdjustTimeOffset(offset int64) {
 func os_sigpipe() {
 	runtimePanic("too many writes on closed pipe")
 }
-
-//go:linkname syscall_runtime_envs syscall.runtime_envs
-func syscall_runtime_envs() []string {
-	return nil
-}

src/runtime/runtime_atsame51j19.go

@@ -0,0 +1,43 @@
+// +build sam,atsame51,atsame51j19
+
+package runtime
+
+import (
+	"device/sam"
+)
+
+func initSERCOMClocks() {
+	// Turn on clock to SERCOM0 for UART0
+	sam.MCLK.APBAMASK.SetBits(sam.MCLK_APBAMASK_SERCOM0_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM0_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// sets the "slow" clock shared by all SERCOM
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOMX_SLOW].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM1
+	sam.MCLK.APBAMASK.SetBits(sam.MCLK_APBAMASK_SERCOM1_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM1_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM2
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_SERCOM2_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM2_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM3
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_SERCOM3_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM3_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM4
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_SERCOM4_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM4_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM5
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_SERCOM5_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM5_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+}

src/runtime/runtime_atsame54p20.go

@@ -0,0 +1,53 @@
+// +build sam,atsame5x,atsame54p20
+
+package runtime
+
+import (
+	"device/sam"
+)
+
+func initSERCOMClocks() {
+	// Turn on clock to SERCOM0 for UART0
+	sam.MCLK.APBAMASK.SetBits(sam.MCLK_APBAMASK_SERCOM0_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM0_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// sets the "slow" clock shared by all SERCOM
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOMX_SLOW].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM1
+	sam.MCLK.APBAMASK.SetBits(sam.MCLK_APBAMASK_SERCOM1_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM1_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM2
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_SERCOM2_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM2_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM3
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_SERCOM3_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM3_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM4
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_SERCOM4_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM4_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM5
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_SERCOM5_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM5_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM6
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_SERCOM6_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM6_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+
+	// Turn on clock to SERCOM7
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_SERCOM7_)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_SERCOM7_CORE].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+}

src/runtime/runtime_atsame5x.go

@@ -0,0 +1,338 @@
+// +build sam,atsame5x
+
+package runtime
+
+import (
+	"device/arm"
+	"device/sam"
+	"machine"
+	"runtime/interrupt"
+	"runtime/volatile"
+)
+
+type timeUnit int64
+
+func postinit() {}
+
+//export Reset_Handler
+func main() {
+	preinit()
+	run()
+	abort()
+}
+
+func init() {
+	initClocks()
+	initRTC()
+	initSERCOMClocks()
+	initUSBClock()
+	initADCClock()
+
+	// connect to USB CDC interface
+	machine.UART0.Configure(machine.UARTConfig{})
+}
+
+func putchar(c byte) {
+	machine.UART0.WriteByte(c)
+}
+
+func initClocks() {
+	// set flash wait state
+	sam.NVMCTRL.CTRLA.SetBits(0 << sam.NVMCTRL_CTRLA_RWS_Pos)
+
+	// software reset
+	sam.GCLK.CTRLA.SetBits(sam.GCLK_CTRLA_SWRST)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_SWRST) {
+	}
+
+	// Set OSCULP32K as source of Generic Clock Generator 3
+	// GCLK->GENCTRL[GENERIC_CLOCK_GENERATOR_XOSC32K].reg = GCLK_GENCTRL_SRC(GCLK_GENCTRL_SRC_OSCULP32K) | GCLK_GENCTRL_GENEN; //generic clock gen 3
+	sam.GCLK.GENCTRL[3].Set((sam.GCLK_GENCTRL_SRC_OSCULP32K << sam.GCLK_GENCTRL_SRC_Pos) |
+		sam.GCLK_GENCTRL_GENEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK3) {
+	}
+
+	// Set OSCULP32K as source of Generic Clock Generator 0
+	sam.GCLK.GENCTRL[0].Set((sam.GCLK_GENCTRL_SRC_OSCULP32K << sam.GCLK_GENCTRL_SRC_Pos) |
+		sam.GCLK_GENCTRL_GENEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK0) {
+	}
+
+	// Enable DFLL48M clock
+	sam.OSCCTRL.DFLLCTRLA.Set(0)
+	sam.OSCCTRL.DFLLMUL.Set((0x1 << sam.OSCCTRL_DFLLMUL_CSTEP_Pos) |
+		(0x1 << sam.OSCCTRL_DFLLMUL_FSTEP_Pos) |
+		(0x0 << sam.OSCCTRL_DFLLMUL_MUL_Pos))
+	for sam.OSCCTRL.DFLLSYNC.HasBits(sam.OSCCTRL_DFLLSYNC_DFLLMUL) {
+	}
+
+	sam.OSCCTRL.DFLLCTRLB.Set(0)
+	for sam.OSCCTRL.DFLLSYNC.HasBits(sam.OSCCTRL_DFLLSYNC_DFLLCTRLB) {
+	}
+
+	sam.OSCCTRL.DFLLCTRLA.SetBits(sam.OSCCTRL_DFLLCTRLA_ENABLE)
+	for sam.OSCCTRL.DFLLSYNC.HasBits(sam.OSCCTRL_DFLLSYNC_ENABLE) {
+	}
+
+	sam.OSCCTRL.DFLLVAL.Set(sam.OSCCTRL.DFLLVAL.Get())
+	for sam.OSCCTRL.DFLLSYNC.HasBits(sam.OSCCTRL_DFLLSYNC_DFLLVAL) {
+	}
+
+	sam.OSCCTRL.DFLLCTRLB.Set(sam.OSCCTRL_DFLLCTRLB_WAITLOCK |
+		sam.OSCCTRL_DFLLCTRLB_CCDIS |
+		sam.OSCCTRL_DFLLCTRLB_USBCRM)
+	for !sam.OSCCTRL.STATUS.HasBits(sam.OSCCTRL_STATUS_DFLLRDY) {
+	}
+
+	// set GCLK7 to run at 2MHz, using DFLL48M as clock source
+	// GCLK7 = 48MHz / 24 = 2MHz
+	sam.GCLK.GENCTRL[7].Set((sam.GCLK_GENCTRL_SRC_DFLL << sam.GCLK_GENCTRL_SRC_Pos) |
+		(24 << sam.GCLK_GENCTRL_DIV_Pos) |
+		sam.GCLK_GENCTRL_GENEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK7) {
+	}
+
+	// Set up the PLLs
+
+	// Set PLL0 to run at 120MHz, using GCLK7 as clock source
+	sam.GCLK.PCHCTRL[1].Set(sam.GCLK_PCHCTRL_CHEN |
+		(sam.GCLK_PCHCTRL_GEN_GCLK7 << sam.GCLK_PCHCTRL_GEN_Pos))
+
+	// multiplier = 59 + 1 + (0/32) = 60
+	// PLL0 = 2MHz * 60 = 120MHz
+	sam.OSCCTRL.DPLL[0].DPLLRATIO.Set((0x0 << sam.OSCCTRL_DPLL_DPLLRATIO_LDRFRAC_Pos) |
+		(59 << sam.OSCCTRL_DPLL_DPLLRATIO_LDR_Pos))
+	for sam.OSCCTRL.DPLL[0].DPLLSYNCBUSY.HasBits(sam.OSCCTRL_DPLL_DPLLSYNCBUSY_DPLLRATIO) {
+	}
+
+	// MUST USE LBYPASS DUE TO BUG IN REV A OF SAMD51, via Adafruit lib.
+	sam.OSCCTRL.DPLL[0].DPLLCTRLB.Set((sam.OSCCTRL_DPLL_DPLLCTRLB_REFCLK_GCLK << sam.OSCCTRL_DPLL_DPLLCTRLB_REFCLK_Pos) |
+		sam.OSCCTRL_DPLL_DPLLCTRLB_LBYPASS)
+
+	sam.OSCCTRL.DPLL[0].DPLLCTRLA.Set(sam.OSCCTRL_DPLL_DPLLCTRLA_ENABLE)
+	for !sam.OSCCTRL.DPLL[0].DPLLSTATUS.HasBits(sam.OSCCTRL_DPLL_DPLLSTATUS_CLKRDY) ||
+		!sam.OSCCTRL.DPLL[0].DPLLSTATUS.HasBits(sam.OSCCTRL_DPLL_DPLLSTATUS_LOCK) {
+	}
+
+	// Set PLL1 to run at 100MHz, using GCLK7 as clock source
+	sam.GCLK.PCHCTRL[2].Set(sam.GCLK_PCHCTRL_CHEN |
+		(sam.GCLK_PCHCTRL_GEN_GCLK7 << sam.GCLK_PCHCTRL_GEN_Pos))
+
+	// multiplier = 49 + 1 + (0/32) = 50
+	// PLL1 = 2MHz * 50 = 100MHz
+	sam.OSCCTRL.DPLL[1].DPLLRATIO.Set((0x0 << sam.OSCCTRL_DPLL_DPLLRATIO_LDRFRAC_Pos) |
+		(49 << sam.OSCCTRL_DPLL_DPLLRATIO_LDR_Pos))
+	for sam.OSCCTRL.DPLL[1].DPLLSYNCBUSY.HasBits(sam.OSCCTRL_DPLL_DPLLSYNCBUSY_DPLLRATIO) {
+	}
+
+	// // MUST USE LBYPASS DUE TO BUG IN REV A OF SAMD51
+	sam.OSCCTRL.DPLL[1].DPLLCTRLB.Set((sam.OSCCTRL_DPLL_DPLLCTRLB_REFCLK_GCLK << sam.OSCCTRL_DPLL_DPLLCTRLB_REFCLK_Pos) |
+		sam.OSCCTRL_DPLL_DPLLCTRLB_LBYPASS)
+
+	sam.OSCCTRL.DPLL[1].DPLLCTRLA.Set(sam.OSCCTRL_DPLL_DPLLCTRLA_ENABLE)
+	// for !sam.OSCCTRL.DPLLSTATUS1.HasBits(sam.OSCCTRL_DPLLSTATUS_CLKRDY) ||
+	// 	!sam.OSCCTRL.DPLLSTATUS1.HasBits(sam.OSCCTRL_DPLLSTATUS_LOCK) {
+	// }
+
+	// Set up the peripheral clocks
+	// Set 48MHZ CLOCK FOR USB
+	sam.GCLK.GENCTRL[1].Set((sam.GCLK_GENCTRL_SRC_DFLL << sam.GCLK_GENCTRL_SRC_Pos) |
+		sam.GCLK_GENCTRL_IDC |
+		sam.GCLK_GENCTRL_GENEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK1) {
+	}
+
+	// // Set 100MHZ CLOCK FOR OTHER PERIPHERALS
+	// sam.GCLK.GENCTRL2.Set((sam.GCLK_GENCTRL_SRC_DPLL1 << sam.GCLK_GENCTRL_SRC_Pos) |
+	// 	sam.GCLK_GENCTRL_IDC |
+	// 	sam.GCLK_GENCTRL_GENEN)
+	// for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL2) {
+	// }
+
+	// // Set 12MHZ CLOCK FOR DAC
+	sam.GCLK.GENCTRL[4].Set((sam.GCLK_GENCTRL_SRC_DFLL << sam.GCLK_GENCTRL_SRC_Pos) |
+		sam.GCLK_GENCTRL_IDC |
+		(4 << sam.GCLK_GENCTRL_DIVSEL_Pos) |
+		sam.GCLK_GENCTRL_GENEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK4) {
+	}
+
+	// // Set up main clock
+	sam.GCLK.GENCTRL[0].Set((sam.GCLK_GENCTRL_SRC_DPLL0 << sam.GCLK_GENCTRL_SRC_Pos) |
+		sam.GCLK_GENCTRL_IDC |
+		sam.GCLK_GENCTRL_GENEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK0) {
+	}
+
+	sam.MCLK.CPUDIV.Set(sam.MCLK_CPUDIV_DIV_DIV1)
+
+	// Use the LDO regulator by default
+	sam.SUPC.VREG.ClearBits(sam.SUPC_VREG_SEL)
+
+	// Start up the "Debug Watchpoint and Trace" unit, so that we can use
+	// it's 32bit cycle counter for timing.
+	//CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
+	//DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
+}
+
+func initRTC() {
+	// turn on digital interface clock
+	sam.MCLK.APBAMASK.SetBits(sam.MCLK_APBAMASK_RTC_)
+
+	// disable RTC
+	sam.RTC_MODE0.CTRLA.ClearBits(sam.RTC_MODE0_CTRLA_ENABLE)
+	//sam.RTC_MODE0.CTRLA.Set(0)
+	for sam.RTC_MODE0.SYNCBUSY.HasBits(sam.RTC_MODE0_SYNCBUSY_ENABLE) {
+	}
+
+	// reset RTC
+	sam.RTC_MODE0.CTRLA.SetBits(sam.RTC_MODE0_CTRLA_SWRST)
+	for sam.RTC_MODE0.SYNCBUSY.HasBits(sam.RTC_MODE0_SYNCBUSY_SWRST) {
+	}
+
+	// set to use ulp 32k oscillator
+	sam.OSC32KCTRL.OSCULP32K.SetBits(sam.OSC32KCTRL_OSCULP32K_EN32K)
+	sam.OSC32KCTRL.RTCCTRL.Set(sam.OSC32KCTRL_RTCCTRL_RTCSEL_ULP32K)
+
+	// set Mode0 to 32-bit counter (mode 0) with prescaler 1 and GCLK2 is 32KHz/1
+	sam.RTC_MODE0.CTRLA.Set((sam.RTC_MODE0_CTRLA_MODE_COUNT32 << sam.RTC_MODE0_CTRLA_MODE_Pos) |
+		(sam.RTC_MODE0_CTRLA_PRESCALER_DIV1 << sam.RTC_MODE0_CTRLA_PRESCALER_Pos) |
+		(sam.RTC_MODE0_CTRLA_COUNTSYNC))
+
+	// re-enable RTC
+	sam.RTC_MODE0.CTRLA.SetBits(sam.RTC_MODE0_CTRLA_ENABLE)
+	for sam.RTC_MODE0.SYNCBUSY.HasBits(sam.RTC_MODE0_SYNCBUSY_ENABLE) {
+	}
+
+	irq := interrupt.New(sam.IRQ_RTC, func(interrupt.Interrupt) {
+		// disable IRQ for CMP0 compare
+		sam.RTC_MODE0.INTFLAG.SetBits(sam.RTC_MODE0_INTENSET_CMP0)
+
+		timerWakeup.Set(1)
+	})
+	irq.SetPriority(0xc0)
+	irq.Enable()
+}
+
+func waitForSync() {
+	for sam.RTC_MODE0.SYNCBUSY.HasBits(sam.RTC_MODE0_SYNCBUSY_COUNT) {
+	}
+}
+
+var (
+	timestamp        timeUnit // ticks since boottime
+	timerLastCounter uint64
+)
+
+var timerWakeup volatile.Register8
+
+const asyncScheduler = false
+
+// ticksToNanoseconds converts RTC ticks (at 32768Hz) to nanoseconds.
+func ticksToNanoseconds(ticks timeUnit) int64 {
+	// The following calculation is actually the following, but with both sides
+	// reduced to reduce the risk of overflow:
+	//     ticks * 1e9 / 32768
+	return int64(ticks) * 1953125 / 64
+}
+
+// nanosecondsToTicks converts nanoseconds to RTC ticks (running at 32768Hz).
+func nanosecondsToTicks(ns int64) timeUnit {
+	// The following calculation is actually the following, but with both sides
+	// reduced to reduce the risk of overflow:
+	//     ns * 32768 / 1e9
+	return timeUnit(ns * 64 / 1953125)
+}
+
+// sleepTicks should sleep for d number of microseconds.
+func sleepTicks(d timeUnit) {
+	for d != 0 {
+		ticks() // update timestamp
+		ticks := uint32(d)
+		if !timerSleep(ticks) {
+			return
+		}
+		d -= timeUnit(ticks)
+	}
+}
+
+// ticks returns number of microseconds since start.
+func ticks() timeUnit {
+	waitForSync()
+
+	rtcCounter := uint64(sam.RTC_MODE0.COUNT.Get())
+	offset := (rtcCounter - timerLastCounter) // change since last measurement
+	timerLastCounter = rtcCounter
+	timestamp += timeUnit(offset)
+	return timestamp
+}
+
+// ticks are in microseconds
+// Returns true if the timer completed.
+// Returns false if another interrupt occured which requires an early return to scheduler.
+func timerSleep(ticks uint32) bool {
+	timerWakeup.Set(0)
+	if ticks < 8 {
+		// due to delay waiting for the register value to sync, the minimum sleep value
+		// for the SAMD51 is 260us.
+		// For related info for SAMD21, see:
+		// https://community.atmel.com/comment/2507091#comment-2507091
+		ticks = 8
+	}
+
+	// request read of count
+	waitForSync()
+
+	// set compare value
+	cnt := sam.RTC_MODE0.COUNT.Get()
+
+	sam.RTC_MODE0.COMP[0].Set(uint32(cnt) + ticks)
+
+	// enable IRQ for CMP0 compare
+	sam.RTC_MODE0.INTENSET.SetBits(sam.RTC_MODE0_INTENSET_CMP0)
+
+wait:
+	waitForEvents()
+	if timerWakeup.Get() != 0 {
+		return true
+	}
+	if hasScheduler {
+		// The interurpt may have awoken a goroutine, so bail out early.
+		// Disable IRQ for CMP0 compare.
+		sam.RTC_MODE0.INTENCLR.SetBits(sam.RTC_MODE0_INTENSET_CMP0)
+		return false
+	} else {
+		// This is running without a scheduler.
+		// The application expects this to sleep the whole time.
+		goto wait
+	}
+}
+
+func initUSBClock() {
+	// Turn on clock(s) for USB
+	//MCLK->APBBMASK.reg |= MCLK_APBBMASK_USB;
+	//MCLK->AHBMASK.reg |= MCLK_AHBMASK_USB;
+	sam.MCLK.APBBMASK.SetBits(sam.MCLK_APBBMASK_USB_)
+	sam.MCLK.AHBMASK.SetBits(sam.MCLK_AHBMASK_USB_)
+
+	// Put Generic Clock Generator 1 as source for USB
+	//GCLK->PCHCTRL[USB_GCLK_ID].reg = GCLK_PCHCTRL_GEN_GCLK1_Val | (1 << GCLK_PCHCTRL_CHEN_Pos);
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_USB].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+}
+
+func initADCClock() {
+	// Turn on clocks for ADC0/ADC1.
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_ADC0_)
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_ADC1_)
+
+	// Put Generic Clock Generator 1 as source for ADC0 and ADC1.
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_ADC0].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+	sam.GCLK.PCHCTRL[sam.PCHCTRL_GCLK_ADC1].Set((sam.GCLK_PCHCTRL_GEN_GCLK1 << sam.GCLK_PCHCTRL_GEN_Pos) |
+		sam.GCLK_PCHCTRL_CHEN)
+}
+
+func waitForEvents() {
+	arm.Asm("wfe")
+}

src/runtime/runtime_nrf_softdevice.go

@@ -27,7 +27,7 @@ func waitForEvents() {
 		if nrf.DEVICE == "nrf51" {
 			// sd_app_evt_wait: SOC_SVC_BASE_NOT_AVAILABLE + 29
 			arm.SVCall0(0x2B + 29)
-		} else if nrf.DEVICE == "nrf52" || nrf.DEVICE == "nrf52840" {
+		} else if nrf.DEVICE == "nrf52" || nrf.DEVICE == "nrf52840" || nrf.DEVICE == "nrf52833" {
 			// sd_app_evt_wait: SOC_SVC_BASE_NOT_AVAILABLE + 21
 			arm.SVCall0(0x2C + 21)
 		} else {

src/runtime/runtime_unix.go

@@ -43,9 +43,34 @@ func postinit() {}
 
 // Entry point for Go. Initialize all packages and call main.main().
 //export main
-func main() int {
+func main(argc int32, argv *unsafe.Pointer) int {
 	preinit()
 
+	// Make args global big enough so that it can store all command line
+	// arguments. Unfortunately this has to be done with some magic as the heap
+	// is not yet initialized.
+	argsSlice := (*struct {
+		ptr unsafe.Pointer
+		len uintptr
+		cap uintptr
+	})(unsafe.Pointer(&args))
+	argsSlice.ptr = malloc(uintptr(argc) * (unsafe.Sizeof(uintptr(0))) * 3)
+	argsSlice.len = 0
+	argsSlice.cap = uintptr(argc)
+
+	// Initialize command line parameters.
+	for *argv != nil {
+		// Convert the C string to a Go string.
+		length := strlen(*argv)
+		argString := _string{
+			length: length,
+			ptr:    (*byte)(*argv),
+		}
+		args = append(args, *(*string)(unsafe.Pointer(&argString)))
+		// This is the Go equivalent of "argc++" in C.
+		argv = (*unsafe.Pointer)(unsafe.Pointer(uintptr(unsafe.Pointer(argv)) + unsafe.Sizeof(argv)))
+	}
+
 	// Obtain the initial stack pointer right before calling the run() function.
 	// The run function has been moved to a separate (non-inlined) function so
 	// that the correct stack pointer is read.
@@ -62,6 +87,37 @@ func runMain() {
 	run()
 }
 
+//go:extern environ
+var environ *unsafe.Pointer
+
+//go:linkname syscall_runtime_envs syscall.runtime_envs
+func syscall_runtime_envs() []string {
+	// Count how many environment variables there are.
+	env := environ
+	numEnvs := 0
+	for *env != nil {
+		numEnvs++
+		env = (*unsafe.Pointer)(unsafe.Pointer(uintptr(unsafe.Pointer(env)) + unsafe.Sizeof(environ)))
+	}
+
+	// Create a string slice of all environment variables.
+	// This requires just a single heap allocation.
+	env = environ
+	envs := make([]string, 0, numEnvs)
+	for *env != nil {
+		ptr := *env
+		length := strlen(ptr)
+		s := _string{
+			ptr:    (*byte)(ptr),
+			length: length,
+		}
+		envs = append(envs, *(*string)(unsafe.Pointer(&s)))
+		env = (*unsafe.Pointer)(unsafe.Pointer(uintptr(unsafe.Pointer(env)) + unsafe.Sizeof(environ)))
+	}
+
+	return envs
+}
+
 func putchar(c byte) {
 	_putchar(int(c))
 }

src/runtime/runtime_wasm.go

@@ -16,6 +16,12 @@ type __wasi_iovec_t struct {
 //export fd_write
 func fd_write(id uint32, iovs *__wasi_iovec_t, iovs_len uint, nwritten *uint) (errno uint)
 
+// See:
+// https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#-proc_exitrval-exitcode
+//go:wasm-module wasi_snapshot_preview1
+//export proc_exit
+func proc_exit(exitcode uint32)
+
 func postinit() {}
 
 const (
@@ -49,6 +55,11 @@ func abort() {
 	trap()
 }
 
+//go:linkname syscall_Exit syscall.Exit
+func syscall_Exit(code int) {
+	proc_exit(uint32(code))
+}
+
 // TinyGo does not yet support any form of parallelism on WebAssembly, so these
 // can be left empty.
 

src/runtime/runtime_wasm_js.go

@@ -15,6 +15,11 @@ func _start() {
 	run()
 }
 
+//go:linkname syscall_runtime_envs syscall.runtime_envs
+func syscall_runtime_envs() []string {
+	return nil
+}
+
 var handleEvent func()
 
 //go:linkname setEventHandler syscall/js.setEventHandler

src/runtime/runtime_wasm_wasi.go

@@ -21,6 +21,33 @@ func _start() {
 	run()
 }
 
+// Read the command line arguments from WASI.
+// For example, they can be passed to a program with wasmtime like this:
+//
+//     wasmtime ./program.wasm arg1 arg2
+func init() {
+	// Read the number of args (argc) and the buffer size required to store all
+	// these args (argv).
+	var argc, argv_buf_size uint32
+	args_sizes_get(&argc, &argv_buf_size)
+
+	// Obtain the command line arguments
+	argsSlice := make([]unsafe.Pointer, argc)
+	buf := make([]byte, argv_buf_size)
+	args_get(&argsSlice[0], unsafe.Pointer(&buf[0]))
+
+	// Convert the array of C strings to an array of Go strings.
+	args = make([]string, argc)
+	for i, cstr := range argsSlice {
+		length := strlen(cstr)
+		argString := _string{
+			length: length,
+			ptr:    (*byte)(cstr),
+		}
+		args[i] = *(*string)(unsafe.Pointer(&argString))
+	}
+}
+
 func ticksToNanoseconds(ticks timeUnit) int64 {
 	return int64(ticks)
 }
@@ -62,7 +89,15 @@ func ticks() timeUnit {
 	return timeUnit(nano)
 }
 
-// Implementations of wasi_unstable APIs
+// Implementations of WASI APIs
+
+//go:wasm-module wasi_snapshot_preview1
+//export args_get
+func args_get(argv *unsafe.Pointer, argv_buf unsafe.Pointer) (errno uint16)
+
+//go:wasm-module wasi_snapshot_preview1
+//export args_sizes_get
+func args_sizes_get(argc *uint32, argv_buf_size *uint32) (errno uint16)
 
 //go:wasm-module wasi_snapshot_preview1
 //export clock_time_get

targets/arduino-mega1280.json

@@ -0,0 +1,8 @@
+{
+    "inherits": ["atmega1280"],
+    "build-tags": ["arduino_mega1280"],
+    "ldflags": [
+        "-Wl,--defsym=_bootloader_size=4096"
+    ],
+    "flash-command":"avrdude -c arduino -b 57600 -p atmega1280 -P {port} -U flash:w:{hex}:i -v -D"
+}

targets/atmega1280.json

@@ -0,0 +1,17 @@
+{
+    "inherits": ["avr"],
+    "cpu": "atmega1280",
+    "build-tags": ["atmega1280", "atmega"],
+    "cflags": [
+        "-mmcu=atmega1280"
+    ],
+    "ldflags": [
+        "-mmcu=avr51",
+        "-Wl,--defsym=_stack_size=512"
+    ],
+    "linkerscript": "src/device/avr/atmega1280.ld",
+    "extra-files": [
+        "targets/avr.S",
+        "src/device/avr/atmega1280.s"
+    ]
+}

targets/atsamd21e18a.json

@@ -1,11 +1,6 @@
 {
-	"inherits": ["cortex-m"],
-	"llvm-target": "armv6m-none-eabi",
+	"inherits": ["cortex-m0plus"],
 	"build-tags": ["atsamd21e18a", "atsamd21e18", "atsamd21", "sam"],
-	"cflags": [
-		"--target=armv6m-none-eabi",
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd21.ld",
 	"extra-files": [
 		"src/device/sam/atsamd21e18a.s"

targets/atsamd21g18a.json

@@ -1,11 +1,6 @@
 {
-	"inherits": ["cortex-m"],
-	"llvm-target": "armv6m-none-eabi",
+	"inherits": ["cortex-m0plus"],
 	"build-tags": ["atsamd21g18a", "atsamd21g18", "atsamd21", "sam"],
-	"cflags": [
-		"--target=armv6m-none-eabi",
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd21.ld",
 	"extra-files": [
 		"src/device/sam/atsamd21g18a.s"

targets/atsamd51g19a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["atsamd51g19a", "atsamd51g19", "atsamd51", "sam"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51g19a.s"

targets/atsamd51j19a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["atsamd51j19a", "atsamd51j19", "atsamd51", "sam"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51j19a.s"

targets/atsamd51j20a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["sam", "atsamd51", "atsamd51j20", "atsamd51j20a"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51j20a.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51j20a.s"

targets/atsamd51p19a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["atsamd51p19a", "atsamd51p19", "atsamd51", "sam"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51p19a.s"

targets/atsamd51p20a.json

@@ -1,9 +1,6 @@
 {
 	"inherits": ["cortex-m4"],
 	"build-tags": ["sam", "atsamd51", "atsamd51p20", "atsamd51p20a"],
-	"cflags": [
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/atsamd51p20a.ld",
 	"extra-files": [
 		"src/device/sam/atsamd51p20a.s"

targets/atsame51j19a.json

@@ -0,0 +1,10 @@
+{
+	"inherits": ["cortex-m4"],
+	"build-tags": ["atsame51j19a", "atsame51j19", "atsame51", "atsame5x", "sam"],
+	"linkerscript": "targets/atsame5xx19.ld",
+	"extra-files": [
+		"src/device/sam/atsame51j19a.s"
+	],
+	"openocd-transport": "swd",
+	"openocd-target": "atsame5x"
+}

targets/atsame54-xpro.json

@@ -0,0 +1,6 @@
+{
+    "inherits": ["atsame54p20a"],
+    "build-tags": ["atsame54_xpro"],
+    "flash-method": "openocd",
+    "openocd-interface": "cmsis-dap"
+}

targets/atsame54p20a.json

@@ -0,0 +1,10 @@
+{
+	"inherits": ["cortex-m4"],
+	"build-tags": ["sam", "atsame5x", "atsame54p20", "atsame54p20a"],
+	"linkerscript": "targets/atsame5xx20-no-bootloader.ld",
+	"extra-files": [
+		"src/device/sam/atsame54p20a.s"
+	],
+	"openocd-transport": "swd",
+	"openocd-target": "atsame5x"
+}

targets/atsame5xx19.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x00000000+0x4000, LENGTH = 0x00080000-0x4000  /* First 16KB used by bootloader */
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x00030000
+}
+
+_stack_size = 4K;
+
+INCLUDE "targets/arm.ld"

targets/atsame5xx20-no-bootloader.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x00000000+0x0000, LENGTH = 0x00100000-0x0000
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x00040000
+}
+
+_stack_size = 4K;
+
+INCLUDE "targets/arm.ld"

targets/attiny85.json

@@ -4,8 +4,7 @@
 	"build-tags": ["attiny85", "attiny", "avr2", "avr25"],
 	"cflags": [
 		"-mmcu=attiny85",
-		"-D__AVR_ARCH__=25",
-		"-Qunused-arguments"
+		"-D__AVR_ARCH__=25"
 	],
 	"ldflags": [
 		"-mmcu=avr25"

targets/avr.json

@@ -3,13 +3,13 @@
 	"build-tags": ["avr", "baremetal", "linux", "arm"],
 	"goos": "linux",
 	"goarch": "arm",
-	"compiler": "clang",
 	"gc": "conservative",
 	"linker": "avr-gcc",
 	"scheduler": "none",
 	"default-stack-size": 256,
 	"cflags": [
-		"--target=avr-unknown-unknown"
+		"--target=avr-unknown-unknown",
+		"-Werror"
 	],
 	"ldflags": [
 		"-T", "targets/avr.ld",

targets/bluepill.json

@@ -1,11 +1,6 @@
 {
-	"inherits": ["cortex-m"],
-	"llvm-target": "armv7m-none-eabi",
+	"inherits": ["cortex-m3"],
 	"build-tags": ["bluepill", "stm32f103", "stm32f1", "stm32"],
-	"cflags": [
-		"--target=armv7m-none-eabi",
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/stm32.ld",
 	"extra-files": [
 		"src/device/stm32/stm32f103.s"

targets/cortex-m-qemu.json

@@ -1,11 +1,6 @@
 {
-	"inherits": ["cortex-m"],
-	"llvm-target": "armv7m-none-eabi",
+	"inherits": ["cortex-m3"],
 	"build-tags": ["qemu", "lm3s6965"],
-	"cflags": [
-		"--target=armv7m-none-eabi",
-		"-Qunused-arguments"
-	],
 	"linkerscript": "targets/lm3s6965.ld",
 	"extra-files": [
 		"targets/cortex-m-qemu.s"

targets/cortex-m.json

@@ -2,7 +2,6 @@
 	"build-tags": ["cortexm", "baremetal", "linux", "arm"],
 	"goos": "linux",
 	"goarch": "arm",
-	"compiler": "clang",
 	"gc": "conservative",
 	"scheduler": "tasks",
 	"linker": "ld.lld",

targets/cortex-m0.json

@@ -2,7 +2,6 @@
 	"inherits": ["cortex-m"],
 	"llvm-target": "armv6m-none-eabi",
 	"cflags": [
-		"--target=armv6m-none-eabi",
-		"-Qunused-arguments"
+		"--target=armv6m-none-eabi"
 	]
 }

targets/cortex-m0plus.json

@@ -0,0 +1,7 @@
+{
+	"inherits": ["cortex-m"],
+	"llvm-target": "armv6m-none-eabi",
+	"cflags": [
+		"--target=armv6m-none-eabi"
+	]
+}

targets/cortex-m3.json

@@ -0,0 +1,7 @@
+{
+	"inherits": ["cortex-m"],
+	"llvm-target": "armv7m-none-eabi",
+	"cflags": [
+		"--target=armv7m-none-eabi"
+	]
+}

targets/cortex-m33.json

@@ -3,7 +3,6 @@
     "llvm-target": "armv7m-none-eabi",
     "cflags": [
         "--target=armv7m-none-eabi",
-        "-mfloat-abi=soft",
-        "-Qunused-arguments"
+        "-mfloat-abi=soft"
     ]
 }

targets/cortex-m4.json

@@ -3,7 +3,6 @@
 	"llvm-target": "armv7em-none-eabi",
 	"cflags": [
 		"--target=armv7em-none-eabi",
-		"-mfloat-abi=soft",
-		"-Qunused-arguments"
+		"-mfloat-abi=soft"
 	]
 }