WIP: interrupt API

compiler/compiler.go

@@ -217,7 +217,7 @@ func (c *Compiler) Compile(mainPath string) []error {
 				path = path[len(tinygoPath+"/src/"):]
 			}
 			switch path {
-			case "machine", "os", "reflect", "runtime", "runtime/volatile", "sync", "testing", "internal/reflectlite":
+			case "machine", "os", "reflect", "runtime", "runtime/interrupt", "runtime/volatile", "sync", "testing", "internal/reflectlite":
 				return path
 			default:
 				if strings.HasPrefix(path, "device/") || strings.HasPrefix(path, "examples/") {
@@ -828,9 +828,6 @@ func (c *Compiler) parseFunc(frame *Frame) {
 		frame.fn.LLVMFn.SetLinkage(llvm.InternalLinkage)
 		frame.fn.LLVMFn.SetUnnamedAddr(true)
 	}
-	if frame.fn.IsInterrupt() && strings.HasPrefix(c.Triple(), "avr") {
-		frame.fn.LLVMFn.SetFunctionCallConv(85) // CallingConv::AVR_SIGNAL
-	}
 
 	// Some functions have a pragma controlling the inlining level.
 	switch frame.fn.Inline() {

compiler/optimizer.go

@@ -57,6 +57,12 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) []er
 		transform.OptimizeStringToBytes(c.mod)
 		transform.OptimizeAllocs(c.mod)
 		transform.LowerInterfaces(c.mod)
+
+		errs := transform.LowerInterruptRegistrations(c.mod)
+		if len(errs) > 0 {
+			return errs
+		}
+
 		if c.funcImplementation() == funcValueSwitch {
 			transform.LowerFuncValues(c.mod)
 		}
@@ -100,6 +106,10 @@ func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) []er
 		if err != nil {
 			return []error{err}
 		}
+		errs := transform.LowerInterruptRegistrations(c.mod)
+		if len(errs) > 0 {
+			return errs
+		}
 	}
 	if c.VerifyIR() {
 		if errs := c.checkModule(); errs != nil {

ir/ir.go

@@ -27,14 +27,13 @@ type Program struct {
 // Function or method.
 type Function struct {
 	*ssa.Function
-	LLVMFn    llvm.Value
-	module    string     // go:wasm-module
-	linkName  string     // go:linkname, go:export, go:interrupt
-	exported  bool       // go:export
-	nobounds  bool       // go:nobounds
-	flag      bool       // used by dead code elimination
-	interrupt bool       // go:interrupt
-	inline    InlineType // go:inline
+	LLVMFn   llvm.Value
+	module   string     // go:wasm-module
+	linkName string     // go:linkname, go:export
+	exported bool       // go:export
+	nobounds bool       // go:nobounds
+	flag     bool       // used by dead code elimination
+	inline   InlineType // go:inline
 }
 
 // Interface type that is at some point used in a type assert (to check whether
@@ -243,18 +242,6 @@ func (f *Function) parsePragmas() {
 				f.inline = InlineHint
 			case "//go:noinline":
 				f.inline = InlineNone
-			case "//go:interrupt":
-				if len(parts) != 2 {
-					continue
-				}
-				name := parts[1]
-				if strings.HasSuffix(name, "_vect") {
-					// AVR vector naming
-					name = "__vector_" + name[:len(name)-5]
-				}
-				f.linkName = name
-				f.exported = true
-				f.interrupt = true
 			case "//go:linkname":
 				if len(parts) != 3 || parts[1] != f.Name() {
 					continue
@@ -288,14 +275,6 @@ func (f *Function) IsExported() bool {
 	return f.exported || f.CName() != ""
 }
 
-// Return true for functions annotated with //go:interrupt. The function name is
-// already customized in LinkName() to hook up in the interrupt vector.
-//
-// On some platforms (like AVR), interrupts need a special compiler flag.
-func (f *Function) IsInterrupt() bool {
-	return f.interrupt
-}
-
 // Return the inline directive of this function.
 func (f *Function) Inline() InlineType {
 	return f.inline

src/machine/machine_atmega.go

@@ -4,6 +4,7 @@ package machine
 
 import (
 	"device/avr"
+	"runtime/interrupt"
 	"runtime/volatile"
 )
 
@@ -232,6 +233,18 @@ func (uart UART) Configure(config UARTConfig) {
 		config.BaudRate = 9600
 	}
 
+	// Register the UART interrupt.
+	interrupt.New(avr.IRQ_USART_RX, func(intr interrupt.Interrupt) {
+		// Read register to clear it.
+		data := avr.UDR0.Get()
+
+		// Ensure no error.
+		if !avr.UCSR0A.HasBits(avr.UCSR0A_FE0 | avr.UCSR0A_DOR0 | avr.UCSR0A_UPE0) {
+			// Put data from UDR register into buffer.
+			UART0.Receive(byte(data))
+		}
+	})
+
 	// Set baud rate based on prescale formula from
 	// https://www.microchip.com/webdoc/AVRLibcReferenceManual/FAQ_1faq_wrong_baud_rate.html
 	// ((F_CPU + UART_BAUD_RATE * 8L) / (UART_BAUD_RATE * 16L) - 1)
@@ -254,15 +267,3 @@ func (uart UART) WriteByte(c byte) error {
 	avr.UDR0.Set(c) // send char
 	return nil
 }
-
-//go:interrupt USART_RX_vect
-func handleUSART_RX() {
-	// Read register to clear it.
-	data := avr.UDR0.Get()
-
-	// Ensure no error.
-	if !avr.UCSR0A.HasBits(avr.UCSR0A_FE0 | avr.UCSR0A_DOR0 | avr.UCSR0A_UPE0) {
-		// Put data from UDR register into buffer.
-		UART0.Receive(byte(data))
-	}
-}

src/machine/machine_atsamd21.go

@@ -11,6 +11,7 @@ import (
 	"device/arm"
 	"device/sam"
 	"errors"
+	"runtime/interrupt"
 	"unsafe"
 )
 
@@ -1368,7 +1369,8 @@ func (usbcdc USBCDC) Configure(config UARTConfig) {
 	sam.USB_DEVICE.CTRLA.SetBits(sam.USB_DEVICE_CTRLA_ENABLE)
 
 	// enable IRQ
-	arm.EnableIRQ(sam.IRQ_USB)
+	intr := interrupt.New(sam.IRQ_USB, handleUSB)
+	intr.Enable()
 }
 
 func handlePadCalibration() {
@@ -1414,8 +1416,7 @@ func handlePadCalibration() {
 	sam.USB_DEVICE.PADCAL.SetBits(calibTrim << sam.USB_DEVICE_PADCAL_TRIM_Pos)
 }
 
-//go:export USB_IRQHandler
-func handleUSB() {
+func handleUSB(intr interrupt.Interrupt) {
 	// reset all interrupt flags
 	flags := sam.USB_DEVICE.INTFLAG.Get()
 	sam.USB_DEVICE.INTFLAG.Set(flags)

src/machine/machine_nrf.go

@@ -3,9 +3,9 @@
 package machine
 
 import (
-	"device/arm"
 	"device/nrf"
 	"errors"
+	"runtime/interrupt"
 )
 
 var (
@@ -88,8 +88,11 @@ func (uart UART) Configure(config UARTConfig) {
 	nrf.UART0.INTENSET.Set(nrf.UART_INTENSET_RXDRDY_Msk)
 
 	// Enable RX IRQ.
-	arm.SetPriority(nrf.IRQ_UART0, 0xc0) // low priority
-	arm.EnableIRQ(nrf.IRQ_UART0)
+	intr := interrupt.New(nrf.IRQ_UART0, func(intr interrupt.Interrupt) {
+		UART0.handleInterrupt()
+	})
+	intr.SetPriority(0xc0) // low priority
+	intr.Enable()
 }
 
 // SetBaudRate sets the communication speed for the UART.

src/machine/machine_nrf51.go

@@ -20,11 +20,6 @@ func (uart UART) setPins(tx, rx Pin) {
 	nrf.UART0.PSELRXD.Set(uint32(rx))
 }
 
-//go:export UART0_IRQHandler
-func handleUART0() {
-	UART0.handleInterrupt()
-}
-
 func (i2c I2C) setPins(scl, sda Pin) {
 	i2c.Bus.PSELSCL.Set(uint32(scl))
 	i2c.Bus.PSELSDA.Set(uint32(sda))

src/machine/machine_nrf52.go

@@ -21,11 +21,6 @@ func (uart UART) setPins(tx, rx Pin) {
 	nrf.UART0.PSELRXD.Set(uint32(rx))
 }
 
-//go:export UARTE0_UART0_IRQHandler
-func handleUART0() {
-	UART0.handleInterrupt()
-}
-
 func (i2c I2C) setPins(scl, sda Pin) {
 	i2c.Bus.PSELSCL.Set(uint32(scl))
 	i2c.Bus.PSELSDA.Set(uint32(sda))

src/machine/machine_nrf52840.go

@@ -25,11 +25,6 @@ func (uart UART) setPins(tx, rx Pin) {
 	nrf.UART0.PSEL.RXD.Set(uint32(rx))
 }
 
-//go:export UARTE0_UART0_IRQHandler
-func handleUART0() {
-	UART0.handleInterrupt()
-}
-
 func (i2c I2C) setPins(scl, sda Pin) {
 	i2c.Bus.PSEL.SCL.Set(uint32(scl))
 	i2c.Bus.PSEL.SDA.Set(uint32(sda))

src/runtime/interrupt/interrupt.go

@@ -0,0 +1,25 @@
+// Package interrupt provides access to hardware interrupts. It provides a way
+// to define interrupts and to enable/disable them.
+package interrupt
+
+// Interrupt provides direct access to hardware interrupts. You can configure
+// this interrupt through this interface.
+//
+// Do not use the zero value of an Interrupt object. Instead, call New to obtain
+// an interrupt handle.
+type Interrupt struct {
+	// Make this number unexported so it cannot be set directly. This provides
+	// some encapsulation.
+	num int
+}
+
+// New is a compiler intrinsic that creates a new Interrupt object. You may call
+// it only once, and must pass constant parameters to it. That means that the
+// interrupt ID must be a Go constant and that the handler must be a simple
+// function: closures are not supported.
+func New(id int, handler func(Interrupt)) Interrupt
+
+// Register is used to declare an interrupt. You should not normally call this
+// function: it is only for telling the compiler about the mapping between an
+// interrupt number and the interrupt handler name.
+func Register(id int, handlerName string) int

src/runtime/interrupt/interrupt_cortexm.go

@@ -0,0 +1,23 @@
+// +build cortexm
+
+package interrupt
+
+import (
+	"device/arm"
+)
+
+// Enable enables this interrupt. Right after calling this function, the
+// interrupt may be invoked if it was already pending.
+func (irq Interrupt) Enable() {
+	arm.EnableIRQ(uint32(irq.num))
+}
+
+// SetPriority sets the interrupt priority for this interrupt. A lower number
+// means a higher priority. Additionally, most hardware doesn't implement all
+// priority bits (only the uppoer bits).
+//
+// Examples: 0xff (lowest priority), 0xc0 (low priority), 0x00 (highest possible
+// priority).
+func (irq Interrupt) SetPriority(priority uint8) {
+	arm.SetPriority(uint32(irq.num), uint32(priority))
+}

src/runtime/runtime_atsamd21.go

@@ -6,6 +6,7 @@ import (
 	"device/arm"
 	"device/sam"
 	"machine"
+	"runtime/interrupt"
 	"runtime/volatile"
 	"unsafe"
 )
@@ -214,8 +215,14 @@ func initRTC() {
 	sam.RTC_MODE0.CTRL.SetBits(sam.RTC_MODE0_CTRL_ENABLE)
 	waitForSync()
 
-	arm.SetPriority(sam.IRQ_RTC, 0xc0)
-	arm.EnableIRQ(sam.IRQ_RTC)
+	intr := interrupt.New(sam.IRQ_RTC, func(intr interrupt.Interrupt) {
+		// disable IRQ for CMP0 compare
+		sam.RTC_MODE0.INTFLAG.Set(sam.RTC_MODE0_INTENSET_CMP0)
+
+		timerWakeup.Set(1)
+	})
+	intr.SetPriority(0xc0)
+	intr.Enable()
 }
 
 func waitForSync() {
@@ -286,14 +293,6 @@ func timerSleep(ticks uint32) {
 	}
 }
 
-//go:export RTC_IRQHandler
-func handleRTC() {
-	// disable IRQ for CMP0 compare
-	sam.RTC_MODE0.INTFLAG.Set(sam.RTC_MODE0_INTENSET_CMP0)
-
-	timerWakeup.Set(1)
-}
-
 func initUSBClock() {
 	// Turn on clock for USB
 	sam.PM.APBBMASK.SetBits(sam.PM_APBBMASK_USB_)

src/runtime/runtime_nrf.go

@@ -6,6 +6,7 @@ import (
 	"device/arm"
 	"device/nrf"
 	"machine"
+	"runtime/interrupt"
 	"runtime/volatile"
 )
 
@@ -43,8 +44,13 @@ func initLFCLK() {
 
 func initRTC() {
 	nrf.RTC1.TASKS_START.Set(1)
-	arm.SetPriority(nrf.IRQ_RTC1, 0xc0) // low priority
-	arm.EnableIRQ(nrf.IRQ_RTC1)
+	intr := interrupt.New(nrf.IRQ_RTC1, func(intr interrupt.Interrupt) {
+		nrf.RTC1.INTENCLR.Set(nrf.RTC_INTENSET_COMPARE0)
+		nrf.RTC1.EVENTS_COMPARE[0].Set(0)
+		rtc_wakeup.Set(1)
+	})
+	intr.SetPriority(0xc0) // low priority
+	intr.Enable()
 }
 
 func putchar(c byte) {
@@ -96,10 +102,3 @@ func rtc_sleep(ticks uint32) {
 		arm.Asm("wfi")
 	}
 }
-
-//go:export RTC1_IRQHandler
-func handleRTC1() {
-	nrf.RTC1.INTENCLR.Set(nrf.RTC_INTENSET_COMPARE0)
-	nrf.RTC1.EVENTS_COMPARE[0].Set(0)
-	rtc_wakeup.Set(1)
-}

tools/gen-device-avr/gen-device-avr.go

@@ -260,6 +260,7 @@ func writeGo(outdir string, device *Device) error {
 package {{.pkgName}}
 
 import (
+	"runtime/interrupt"
 	"runtime/volatile"
 	"unsafe"
 )
@@ -277,6 +278,12 @@ const ({{range .interrupts}}
 	IRQ_max = {{.interruptMax}} // Highest interrupt number on this device.
 )
 
+// Map interrupt numbers to function names.
+// These aren't real calls, they're removed by the compiler.
+var ({{range .interrupts}}
+	_ = interrupt.Register(IRQ_{{.Name}}, "__vector_{{.Name}}"){{end}}
+)
+
 // Peripherals.
 var ({{range .peripherals}}
 	// {{.Caption}}

tools/gen-device-svd/gen-device-svd.go

@@ -82,6 +82,7 @@ type Device struct {
 
 type interrupt struct {
 	Name            string
+	HandlerName     string
 	peripheralIndex int
 	Value           int // interrupt number
 	Description     string
@@ -171,12 +172,12 @@ func readSVD(path, sourceURL string) (*Device, error) {
 		groupName := cleanName(periphEl.GroupName)
 
 		for _, interrupt := range periphEl.Interrupts {
-			addInterrupt(interrupts, interrupt.Name, interrupt.Index, description)
+			addInterrupt(interrupts, interrupt.Name, interrupt.Name, interrupt.Index, description)
 			// As a convenience, also use the peripheral name as the interrupt
 			// name. Only do that for the nrf for now, as the stm32 .svd files
 			// don't always put interrupts in the correct peripheral...
 			if len(periphEl.Interrupts) == 1 && strings.HasPrefix(device.Name, "nrf") {
-				addInterrupt(interrupts, periphEl.Name, interrupt.Index, description)
+				addInterrupt(interrupts, periphEl.Name, interrupt.Name, interrupt.Index, description)
 			}
 		}
 
@@ -388,7 +389,7 @@ func readSVD(path, sourceURL string) (*Device, error) {
 	}, nil
 }
 
-func addInterrupt(interrupts map[string]*interrupt, name string, index int, description string) {
+func addInterrupt(interrupts map[string]*interrupt, name, interruptName string, index int, description string) {
 	if _, ok := interrupts[name]; ok {
 		if interrupts[name].Value != index {
 			// Note: some SVD files like the one for STM32H7x7 contain mistakes.
@@ -409,6 +410,7 @@ func addInterrupt(interrupts map[string]*interrupt, name string, index int, desc
 	} else {
 		interrupts[name] = &interrupt{
 			Name:            name,
+			HandlerName:     interruptName + "_IRQHandler",
 			peripheralIndex: len(interrupts),
 			Value:           index,
 			Description:     description,
@@ -619,6 +621,7 @@ func writeGo(outdir string, device *Device) error {
 package {{.pkgName}}
 
 import (
+	"runtime/interrupt"
 	"runtime/volatile"
 	"unsafe"
 )
@@ -628,12 +631,18 @@ const (
 	DEVICE	 = "{{.metadata.name}}"
 )
 
-// Interrupt numbers
+// Interrupt numbers.
 const ({{range .interrupts}}
 	IRQ_{{.Name}} = {{.Value}} // {{.Description}}{{end}}
 	IRQ_max = {{.interruptMax}} // Highest interrupt number on this device.
 )
 
+// Map interrupt numbers to function names.
+// These aren't real calls, they're removed by the compiler.
+var ({{range .interrupts}}
+	_ = interrupt.Register(IRQ_{{.Name}}, "{{.HandlerName}}"){{end}}
+)
+
 // Peripherals.
 var (
 {{range .peripherals}}	{{.Name}} = (*{{.GroupName}}_Type)(unsafe.Pointer(uintptr(0x{{printf "%x" .BaseAddress}}))) // {{.Description}}
@@ -879,7 +888,7 @@ Default_Handler:
 			num++
 		}
 		num++
-		fmt.Fprintf(w, "    .long %s_IRQHandler\n", intr.Name)
+		fmt.Fprintf(w, "    .long %s\n", intr.HandlerName)
 	}
 
 	w.WriteString(`

transform/errors.go

@@ -0,0 +1,48 @@
+package transform
+
+import (
+	"go/scanner"
+	"go/token"
+	"path/filepath"
+
+	"tinygo.org/x/go-llvm"
+)
+
+// errorAt returns an error value at the location of the value.
+// The location information may not be complete as it depends on debug
+// information in the IR.
+func errorAt(val llvm.Value, msg string) scanner.Error {
+	return scanner.Error{
+		Pos: getPosition(val),
+		Msg: msg,
+	}
+}
+
+// getPosition returns the position information for the given value, as far as
+// it is available.
+func getPosition(val llvm.Value) token.Position {
+	if !val.IsAInstruction().IsNil() {
+		loc := val.InstructionDebugLoc()
+		if loc.IsNil() {
+			return token.Position{}
+		}
+		file := loc.LocationScope().ScopeFile()
+		return token.Position{
+			Filename: filepath.Join(file.FileDirectory(), file.FileFilename()),
+			Line:     int(loc.LocationLine()),
+			Column:   int(loc.LocationColumn()),
+		}
+	} else if !val.IsAFunction().IsNil() {
+		loc := val.Subprogram()
+		if loc.IsNil() {
+			return token.Position{}
+		}
+		file := loc.ScopeFile()
+		return token.Position{
+			Filename: filepath.Join(file.FileDirectory(), file.FileFilename()),
+			Line:     int(loc.SubprogramLine()),
+		}
+	} else {
+		return token.Position{}
+	}
+}

transform/interrupt.go

@@ -0,0 +1,221 @@
+package transform
+
+import (
+	"fmt"
+	"strings"
+
+	"tinygo.org/x/go-llvm"
+)
+
+func LowerInterruptRegistrations(mod llvm.Module) []error {
+	var errs []error
+
+	// Discover interrupts. The runtime/interrupt.Register call is a compiler
+	// intrinsic that maps interrupt numbers to handler names.
+	handlerNames := map[int64]string{}
+	for _, call := range getUses(mod.NamedFunction("runtime/interrupt.Register")) {
+		if call.IsACallInst().IsNil() {
+			errs = append(errs, errorAt(call, "expected a call to runtime/interrupt.Register?"))
+			continue
+		}
+
+		num := call.Operand(0)
+		if num.IsAConstant().IsNil() {
+			errs = append(errs, errorAt(call, "non-constant interrupt number?"))
+			continue
+		}
+
+		// extract the interrupt name
+		nameStrGEP := call.Operand(1)
+		if nameStrGEP.IsAConstantExpr().IsNil() || nameStrGEP.Opcode() != llvm.GetElementPtr {
+			errs = append(errs, errorAt(call, "expected a string operand?"))
+			continue
+		}
+		nameStrPtr := nameStrGEP.Operand(0) // note: assuming it's a GEP to the first byte
+		nameStrLen := call.Operand(2)
+		if nameStrPtr.IsAGlobalValue().IsNil() || !nameStrPtr.IsGlobalConstant() || nameStrLen.IsAConstant().IsNil() {
+			errs = append(errs, errorAt(call, "non-constant interrupt name?"))
+			continue
+		}
+
+		// keep track of this name
+		name := string(getGlobalBytes(nameStrPtr)[:nameStrLen.SExtValue()])
+		handlerNames[num.SExtValue()] = name
+
+		// remove this pseudo-call
+		call.ReplaceAllUsesWith(llvm.ConstNull(call.Type()))
+		call.EraseFromParentAsInstruction()
+	}
+
+	create := mod.NamedFunction("runtime/interrupt.New")
+	if create.IsNil() {
+		// No interrupt handlers to create.
+		return nil
+	}
+
+	ctx := mod.Context()
+	nullptr := llvm.ConstNull(llvm.PointerType(ctx.Int8Type(), 0))
+	builder := ctx.NewBuilder()
+	defer builder.Dispose()
+
+	var dibuilder *llvm.DIBuilder
+
+	// Create a function type with the signature of an interrupt handler.
+	fnType := llvm.FunctionType(ctx.VoidType(), nil, false)
+
+	for _, call := range getUses(create) {
+		if call.IsACallInst().IsNil() {
+			errs = append(errs, errorAt(call, "expected a call to runtime/interrupt.New"))
+			continue
+		}
+		if call.OperandsCount() != 6 {
+			// 6 params:
+			// * 1 for the IRQ number
+			// * 2 for the function
+			// * 2 extra: context and parentHandle
+			// * one more for the called value?
+			errs = append(errs, errorAt(call, fmt.Sprintf("unexpected interrupt.New signature, expected 6 operands, got %d", call.OperandsCount())))
+			continue
+		}
+		num := call.Operand(0)
+		if num.IsAConstant().IsNil() {
+			errs = append(errs, errorAt(call, "non-constant interrupt number"))
+			continue
+		}
+		name := handlerNames[num.SExtValue()]
+		if name == "" {
+			errs = append(errs, errorAt(call, fmt.Sprintf("cannot find interrupt name for number %d", num.SExtValue())))
+			continue
+		}
+
+		// Create the func value.
+		handlerContext := call.Operand(1)
+		handlerFuncPtr := call.Operand(2)
+		if isFunctionLocal(handlerContext) || isFunctionLocal(handlerFuncPtr) {
+			errs = append(errs, errorAt(call, "func value must be constant"))
+			continue
+		}
+		if !handlerFuncPtr.IsAConstantExpr().IsNil() && handlerFuncPtr.Opcode() == llvm.PtrToInt {
+			// This is a ptrtoint: the IR was created for func lowering using a
+			// switch statement.
+			global := handlerFuncPtr.Operand(0)
+			if global.IsAGlobalValue().IsNil() {
+				errs = append(errs, errorAt(call, "internal error: expected a global for func lowering"))
+				continue
+			}
+			initializer := global.Initializer()
+			if initializer.Type() != mod.GetTypeByName("runtime.funcValueWithSignature") {
+				errs = append(errs, errorAt(call, "internal error: func lowering global has unexpected type"))
+				continue
+			}
+			ptrtoint := llvm.ConstExtractValue(initializer, []uint32{0})
+			if ptrtoint.IsAConstantExpr().IsNil() || ptrtoint.Opcode() != llvm.PtrToInt {
+				errs = append(errs, errorAt(call, "internal error: func lowering global has unexpected func ptr type"))
+				continue
+			}
+			handlerFuncPtr = ptrtoint.Operand(0)
+		}
+		if handlerFuncPtr.Type().TypeKind() != llvm.PointerTypeKind || handlerFuncPtr.Type().ElementType().TypeKind() != llvm.FunctionTypeKind {
+			errs = append(errs, errorAt(call, "internal error: unexpected LLVM types in func value"))
+			continue
+		}
+
+		// Check for an existing handler, and report it as an error if there is
+		// one.
+		fn := mod.NamedFunction(name)
+		if fn.IsNil() {
+			fn = llvm.AddFunction(mod, name, fnType)
+		} else if fn.Type().ElementType() != fnType {
+			// Don't bother with a precise error message (listing the
+			// previsous location) because this should not normally happen
+			// anyway.
+			errs = append(errs, errorAt(call, name+" redeclared with a different signature"))
+			continue
+		} else if fn.IsDeclaration() {
+			// Interrupt handler was already defined. Check the first
+			// instruction (which should be a call) whether this handler would
+			// be identical anyway.
+			firstInst := fn.FirstBasicBlock().FirstInstruction()
+			if !firstInst.IsACallInst().IsNil() && firstInst.OperandsCount() == 4 && firstInst.Operand(0) == num && firstInst.Operand(1) != handlerContext {
+				// Already defined and apparently identical, so assume this is
+				// fine.
+				continue
+			}
+
+			errValue := name + " redeclared in this program"
+			fnPos := getPosition(fn)
+			if fnPos.IsValid() {
+				errValue += "\n\tprevious declaration at " + fnPos.String()
+			}
+			errs = append(errs, errorAt(call, errValue))
+			continue
+		}
+
+		// Create the wrapper function.
+		fn.SetUnnamedAddr(true)
+		entryBlock := ctx.AddBasicBlock(fn, "entry")
+		builder.SetInsertPointAtEnd(entryBlock)
+
+		// Set the 'interrupt' flag if needed on this platform.
+		if strings.HasPrefix(mod.Target(), "avr") {
+			fn.SetFunctionCallConv(85) // CallingConv::AVR_SIGNAL
+		}
+
+		// Attach a proper debug location to this function.
+		// Use the location of the call instruction, because as far as the user
+		// is concerned that is where the interrupt is defined. This is
+		// especially relevant for multiple definition errors, where you'd
+		// really want the previous interrupt.New call location to be used for
+		// easy debugging.
+		loc := call.InstructionDebugLoc()
+		if !loc.IsNil() {
+			if dibuilder == nil {
+				dibuilder = llvm.NewDIBuilder(mod)
+				defer func() {
+					dibuilder.Finalize()
+					dibuilder.Destroy()
+				}()
+				// Must create a new compile unit for some reason.
+				dibuilder.CreateCompileUnit(llvm.DICompileUnit{
+					File:      "<interrupt-lowering>",
+					Language:  0xb, // DW_LANG_C99 (0xc, off-by-one?)
+					Producer:  "TinyGo",
+					Optimized: true,
+				})
+			}
+
+			// Attach debug info to the function.
+			file := loc.LocationScope().ScopeFile()
+			diFnType := dibuilder.CreateSubroutineType(llvm.DISubroutineType{
+				File: file,
+			})
+			difunc := dibuilder.CreateFunction(file, llvm.DIFunction{
+				Name:         name,
+				LinkageName:  name,
+				File:         file,
+				Line:         int(loc.LocationLine()),
+				Type:         diFnType,
+				LocalToUnit:  false,
+				IsDefinition: true,
+				ScopeLine:    0,
+				Flags:        llvm.FlagPrototyped,
+				Optimized:    true,
+			})
+			fn.SetSubprogram(difunc)
+
+			// Use the same location inside the thunk.
+			builder.SetCurrentDebugLocation(loc.LocationLine(), loc.LocationColumn(), difunc, llvm.Metadata{})
+
+		}
+
+		// Fill the function declaration with the forwarding call.
+		builder.CreateCall(handlerFuncPtr, []llvm.Value{num, handlerContext, nullptr}, "")
+		builder.CreateRetVoid()
+
+		// Replace the function call.
+		interruptValue := llvm.ConstNamedStruct(mod.GetTypeByName("runtime/interrupt.Interrupt"), []llvm.Value{num})
+		call.ReplaceAllUsesWith(interruptValue)
+		call.EraseFromParentAsInstruction()
+	}
+	return errs
+}

transform/llvm.go

@@ -89,3 +89,19 @@ func typeHasPointers(t llvm.Type) bool {
 		return false
 	}
 }
+
+// isFunctionLocal returns true if (and only if) this value is local to a
+// function. That is, it returns true for instructions and parameters, and false
+// for constants and globals.
+func isFunctionLocal(val llvm.Value) bool {
+	if !val.IsAConstant().IsNil() {
+		return false
+	}
+	if !val.IsAInstruction().IsNil() {
+		return true
+	}
+	if !val.IsAGlobalValue().IsNil() {
+		return false
+	}
+	panic("unknown value kind")
+}