main: remove -no-debug flag

The -no-debug flag controls whether to emit DWARF debug information.
However, instead of limiting debug information altogether, I think it's
better to strip it off at the end if it isn't needed. For several
reasons:

  * Some parts of the compiler now rely on the presence of debug
    information for proper diagnostics.
  * It works better with the cache: there is no distinction between
    debug and no-debug builds.
  * It makes it easier (or possible at all) to enable debug information
    in the wasi-libc library without big downsides.

I'm doing this in a separate commit so this can be reverted if needed.

builder/build.go

@@ -100,7 +100,6 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 		AutomaticStackSize: config.AutomaticStackSize(),
 		DefaultStackSize:   config.Target.DefaultStackSize,
 		NeedsStackObjects:  config.NeedsStackObjects(),
-		Debug:              config.EmitDWARF(),
 		LLVMFeatures:       config.LLVMFeatures(),
 	}
 

compileopts/config.go

@@ -209,9 +209,8 @@ func (c *Config) CFlags() []string {
 		cflags = append(cflags, "-nostdlibinc", "-Xclang", "-internal-isystem", "-Xclang", filepath.Join(root, "lib", "picolibc", "newlib", "libc", "include"))
 		cflags = append(cflags, "-I"+filepath.Join(root, "lib/picolibc-include"))
 	}
-	if c.EmitDWARF() {
+	// Always emit debug information. It is optionally stripped at link time.
 	cflags = append(cflags, "-g")
-	}
 	return cflags
 }
 
@@ -250,12 +249,6 @@ func (c *Config) VerifyIR() bool {
 	return c.Options.VerifyIR
 }
 
-// EmitDWARF returns whether to add debug symbols to the IR, for debugging with
-// GDB and similar.
-func (c *Config) EmitDWARF() bool {
-	return c.Options.EmitDWARF
-}
-
 // Debug returns whether debug (DWARF) information should be retained by the
 // linker. The default varies by target but can be controlled with the -debug
 // command line flag.

compileopts/options.go

@@ -29,7 +29,6 @@ type Options struct {
 	DumpSSA         bool
 	VerifyIR        bool
 	PrintCommands   func(cmd string, args ...string)
-	EmitDWARF       bool
 	Debug           string
 	PrintSizes      string
 	PrintAllocs     *regexp.Regexp // regexp string

compiler/compiler.go

@@ -58,7 +58,6 @@ type Config struct {
 	AutomaticStackSize bool
 	DefaultStackSize   uint64
 	NeedsStackObjects  bool
-	Debug              bool // Whether to emit debug information in the LLVM module.
 	LLVMFeatures       string
 }
 
@@ -103,9 +102,7 @@ func newCompilerContext(moduleName string, machine llvm.TargetMachine, config *C
 	c.mod = c.ctx.NewModule(moduleName)
 	c.mod.SetTarget(config.Triple)
 	c.mod.SetDataLayout(c.targetData.String())
-	if c.Debug {
 	c.dibuilder = llvm.NewDIBuilder(c.mod)
-	}
 
 	c.uintptrType = c.ctx.IntType(c.targetData.PointerSize() * 8)
 	if c.targetData.PointerSize() <= 4 {
@@ -263,7 +260,6 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 	ssaPkg.Build()
 
 	// Initialize debug information.
-	if c.Debug {
 	c.cu = c.dibuilder.CreateCompileUnit(llvm.DICompileUnit{
 		Language:  0xb, // DW_LANG_C99 (0xc, off-by-one?)
 		File:      "<unknown>",
@@ -271,7 +267,6 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 		Producer:  "TinyGo",
 		Optimized: true,
 	})
-	}
 
 	// Load comments such as //go:extern on globals.
 	c.loadASTComments(pkg)
@@ -286,7 +281,6 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 	c.createPackage(irbuilder, ssaPkg)
 
 	// see: https://reviews.llvm.org/D18355
-	if c.Debug {
 	c.mod.AddNamedMetadataOperand("llvm.module.flags",
 		c.ctx.MDNode([]llvm.Metadata{
 			llvm.ConstInt(c.ctx.Int32Type(), 1, false).ConstantAsMetadata(), // Error on mismatch
@@ -302,7 +296,6 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 		}),
 	)
 	c.dibuilder.Finalize()
-	}
 
 	return c.mod, c.diagnostics
 }
@@ -812,8 +805,7 @@ func (b *builder) createFunction() {
 		b.llvmFn.AddFunctionAttr(noinline)
 	}
 
-	// Add debug info, if needed.
+	// Add debug info.
-	if b.Debug {
 	if b.fn.Synthetic == "package initializer" {
 		// Package initializers have no debug info. Create some fake debug
 		// info to at least have *something*.
@@ -825,7 +817,6 @@ func (b *builder) createFunction() {
 	}
 	pos := b.program.Fset.Position(b.fn.Pos())
 	b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), b.difunc, llvm.Metadata{})
-	}
 
 	// Pre-create all basic blocks in the function.
 	for _, block := range b.fn.DomPreorder() {
@@ -850,7 +841,7 @@ func (b *builder) createFunction() {
 		b.locals[param] = b.collapseFormalParam(llvmType, fields)
 
 		// Add debug information to this parameter (if available)
-		if b.Debug && b.fn.Syntax() != nil {
+		if b.fn.Syntax() != nil {
 			dbgParam := b.getLocalVariable(param.Object().(*types.Var))
 			loc := b.GetCurrentDebugLocation()
 			if len(fields) == 1 {
@@ -910,9 +901,6 @@ func (b *builder) createFunction() {
 		b.currentBlock = block
 		for _, instr := range block.Instrs {
 			if instr, ok := instr.(*ssa.DebugRef); ok {
-				if !b.Debug {
-					continue
-				}
 				object := instr.Object()
 				variable, ok := object.(*types.Var)
 				if !ok {
@@ -1029,10 +1017,8 @@ func getPos(val posser) token.Pos {
 // createInstruction builds the LLVM IR equivalent instructions for the
 // particular Go SSA instruction.
 func (b *builder) createInstruction(instr ssa.Instruction) {
-	if b.Debug {
 	pos := b.program.Fset.Position(getPos(instr))
 	b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), b.difunc, llvm.Metadata{})
-	}
 
 	switch instr := instr.(type) {
 	case ssa.Value:

compiler/goroutine.go

@@ -182,7 +182,7 @@ func (c *compilerContext) createGoroutineStartWrapper(fn llvm.Value, prefix stri
 		entry := c.ctx.AddBasicBlock(wrapper, "entry")
 		builder.SetInsertPointAtEnd(entry)
 
-		if c.Debug {
+		// Add debug information.
 		pos := c.program.Fset.Position(pos)
 		diFuncType := c.dibuilder.CreateSubroutineType(llvm.DISubroutineType{
 			File:       c.getDIFile(pos.Filename),
@@ -202,7 +202,6 @@ func (c *compilerContext) createGoroutineStartWrapper(fn llvm.Value, prefix stri
 		})
 		wrapper.SetSubprogram(difunc)
 		builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
-		}
 
 		// Create the list of params for the call.
 		paramTypes := fn.Type().ElementType().ParamTypes()
@@ -246,7 +245,7 @@ func (c *compilerContext) createGoroutineStartWrapper(fn llvm.Value, prefix stri
 		entry := c.ctx.AddBasicBlock(wrapper, "entry")
 		builder.SetInsertPointAtEnd(entry)
 
-		if c.Debug {
+		// Add debug information.
 		pos := c.program.Fset.Position(pos)
 		diFuncType := c.dibuilder.CreateSubroutineType(llvm.DISubroutineType{
 			File:       c.getDIFile(pos.Filename),
@@ -266,7 +265,6 @@ func (c *compilerContext) createGoroutineStartWrapper(fn llvm.Value, prefix stri
 		})
 		wrapper.SetSubprogram(difunc)
 		builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
-		}
 
 		// Get the list of parameters, with the extra parameters at the end.
 		paramTypes := fn.Type().ElementType().ParamTypes()

compiler/interface.go

@@ -501,12 +501,10 @@ func (c *compilerContext) getInterfaceInvokeWrapper(fn *ssa.Function, llvmFn llv
 	}
 	defer b.Builder.Dispose()
 
-	// add debug info if needed
+	// add debug info
-	if c.Debug {
 	pos := c.program.Fset.Position(fn.Pos())
 	difunc := c.attachDebugInfoRaw(fn, wrapper, "$invoke", pos.Filename, pos.Line)
 	b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
-	}
 
 	// set up IR builder
 	block := b.ctx.AddBasicBlock(wrapper, "entry")

compiler/interrupt.go

@@ -52,7 +52,6 @@ func (b *builder) createInterruptGlobal(instr *ssa.CallCommon) (llvm.Value, erro
 	global.SetInitializer(initializer)
 
 	// Add debug info to the interrupt global.
-	if b.Debug {
 	pos := b.program.Fset.Position(instr.Pos())
 	diglobal := b.dibuilder.CreateGlobalVariableExpression(b.getDIFile(pos.Filename), llvm.DIGlobalVariableExpression{
 		Name:        "interrupt" + strconv.FormatInt(id.Int64(), 10),
@@ -64,7 +63,6 @@ func (b *builder) createInterruptGlobal(instr *ssa.CallCommon) (llvm.Value, erro
 		LocalToUnit: false,
 	})
 	global.AddMetadata(0, diglobal)
-	}
 
 	// Create the runtime/interrupt.Interrupt type. It is a struct with a single
 	// member of type int.

compiler/symbol.go

@@ -386,7 +386,7 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
 			llvmGlobal.SetAlignment(alignment)
 		}
 
-		if c.Debug && !info.extern {
+		if !info.extern {
 			// Add debug info.
 			pos := c.program.Fset.Position(g.Pos())
 			diglobal := c.dibuilder.CreateGlobalVariableExpression(c.difiles[pos.Filename], llvm.DIGlobalVariableExpression{

main.go

@@ -1020,7 +1020,6 @@ func main() {
 	printAllocsString := flag.String("print-allocs", "", "regular expression of functions for which heap allocations should be printed")
 	printCommands := flag.Bool("x", false, "Print commands")
 	debug := flag.String("debug", "auto", "remove debug information (auto, true, false)")
-	nodebug := flag.Bool("no-debug", false, "disable DWARF debug symbol generation")
 	ocdCommandsString := flag.String("ocd-commands", "", "OpenOCD commands, overriding target spec (can specify multiple separated by commas)")
 	ocdOutput := flag.Bool("ocd-output", false, "print OCD daemon output during debug")
 	port := flag.String("port", "", "flash port (can specify multiple candidates separated by commas)")
@@ -1087,7 +1086,6 @@ func main() {
 		PrintIR:         *printIR,
 		DumpSSA:         *dumpSSA,
 		VerifyIR:        *verifyIR,
-		EmitDWARF:       !*nodebug,
 		Debug:           *debug,
 		PrintSizes:      *printSize,
 		PrintStacks:     *printStacks,
@@ -1175,11 +1173,6 @@ func main() {
 			err := Flash(pkgName, *port, options)
 			handleCompilerError(err)
 		} else {
-			if !options.EmitDWARF {
-				fmt.Fprintln(os.Stderr, "Debug disabled while running gdb?")
-				usage()
-				os.Exit(1)
-			}
 			err := FlashGDB(pkgName, *ocdOutput, options)
 			handleCompilerError(err)
 		}