windows: add ARM64 support

This was actually surprising once I got TinyGo to build on Windows 11
ARM64. All the changes are exactly what you'd expect for a new
architecture, there was no special weirdness just for arm64.

Actually getting TinyGo to build was kind of involved though. The very
short summary is: install arm64 versions of some pieces of software
(like golang, cmake) instead of installing them though choco. In
particular, use the llvm-mingw[1] toolchain instead of using standard
mingw.

[1]: https://github.com/mstorsjo/llvm-mingw/releases

Makefile

@@ -738,6 +738,7 @@ endif
 	@$(MD5SUM) test.hex
 	GOOS=linux GOARCH=arm $(TINYGO) build -size short -o test.elf       ./testdata/cgo
 	GOOS=windows GOARCH=amd64 $(TINYGO) build -size short -o test.exe   ./testdata/cgo
+	GOOS=windows GOARCH=arm64 $(TINYGO) build -size short -o test.exe   ./testdata/cgo
 	GOOS=darwin GOARCH=amd64 $(TINYGO) build  -size short -o test       ./testdata/cgo
 	GOOS=darwin GOARCH=arm64 $(TINYGO) build  -size short -o test       ./testdata/cgo
 ifneq ($(OS),Windows_NT)

builder/build.go

@@ -151,7 +151,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 			return BuildResult{}, err
 		}
 		unlock()
-		libcDependencies = append(libcDependencies, makeMinGWExtraLibs(tmpdir)...)
+		libcDependencies = append(libcDependencies, makeMinGWExtraLibs(tmpdir, config.GOARCH())...)
 	case "":
 		// no library specified, so nothing to do
 	default:

builder/builder_test.go

@@ -59,6 +59,7 @@ func TestClangAttributes(t *testing.T) {
 		{GOOS: "darwin", GOARCH: "amd64"},
 		{GOOS: "darwin", GOARCH: "arm64"},
 		{GOOS: "windows", GOARCH: "amd64"},
+		{GOOS: "windows", GOARCH: "arm64"},
 	} {
 		name := "GOOS=" + options.GOOS + ",GOARCH=" + options.GOARCH
 		if options.GOARCH == "arm" {

builder/mingw-w64.go

@@ -1,6 +1,7 @@
 package builder
 
 import (
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
@@ -43,7 +44,7 @@ var MinGW = Library{
 //
 // TODO: cache the result. At the moment, it costs a few hundred milliseconds to
 // compile these files.
-func makeMinGWExtraLibs(tmpdir string) []*compileJob {
+func makeMinGWExtraLibs(tmpdir, goarch string) []*compileJob {
 	var jobs []*compileJob
 	root := goenv.Get("TINYGOROOT")
 	// Normally all the api-ms-win-crt-*.def files are all compiled to a single
@@ -74,16 +75,27 @@ func makeMinGWExtraLibs(tmpdir string) []*compileJob {
 			result:      outpath,
 			run: func(job *compileJob) error {
 				defpath := inpath
+				var archDef, emulation string
+				switch goarch {
+				case "amd64":
+					archDef = "-DDEF_X64"
+					emulation = "i386pep"
+				case "arm64":
+					archDef = "-DDEF_ARM64"
+					emulation = "arm64pe"
+				default:
+					return fmt.Errorf("unsupported architecture for mingw-w64: %s", goarch)
+				}
 				if strings.HasSuffix(inpath, ".in") {
 					// .in files need to be preprocessed by a preprocessor (-E)
 					// first.
 					defpath = outpath + ".def"
-					err := runCCompiler("-E", "-x", "c", "-Wp,-w", "-P", "-DDEF_X64", "-DDATA", "-o", defpath, inpath, "-I"+goenv.Get("TINYGOROOT")+"/lib/mingw-w64/mingw-w64-crt/def-include/")
+					err := runCCompiler("-E", "-x", "c", "-Wp,-w", "-P", archDef, "-DDATA", "-o", defpath, inpath, "-I"+goenv.Get("TINYGOROOT")+"/lib/mingw-w64/mingw-w64-crt/def-include/")
 					if err != nil {
 						return err
 					}
 				}
-				return link("ld.lld", "-m", "i386pep", "-o", outpath, defpath)
+				return link("ld.lld", "-m", emulation, "-o", outpath, defpath)
 			},
 		}
 		jobs = append(jobs, job)

builder/tools-builtin.go

@@ -28,7 +28,7 @@ const hasBuiltinTools = true
 func RunTool(tool string, args ...string) error {
 	linker := "elf"
 	if tool == "ld.lld" && len(args) >= 2 {
-		if args[0] == "-m" && args[1] == "i386pep" {
+		if args[0] == "-m" && (args[1] == "i386pep" || args[1] == "arm64pe") {
 			linker = "mingw"
 		} else if args[0] == "-flavor" {
 			linker = args[1]

compileopts/target.go

@@ -304,10 +304,19 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 		// normally present in Go (without explicitly opting in).
 		// For more discussion:
 		// https://groups.google.com/g/Golang-nuts/c/Jd9tlNc6jUE/m/Zo-7zIP_m3MJ?pli=1
+		switch goarch {
+		case "amd64":
+			spec.LDFlags = append(spec.LDFlags,
+				"-m", "i386pep",
+				"--image-base", "0x400000",
+			)
+		case "arm64":
+			spec.LDFlags = append(spec.LDFlags,
+				"-m", "arm64pe",
+			)
+		}
 		spec.LDFlags = append(spec.LDFlags,
-			"-m", "i386pep",
 			"-Bdynamic",
-			"--image-base", "0x400000",
 			"--gc-sections",
 			"--no-insert-timestamp",
 			"--no-dynamicbase",

compiler/defer.go

@@ -162,9 +162,9 @@ mov x0, #0
 1:
 `
 		constraints = "={x0},{x1},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x13},~{x14},~{x15},~{x16},~{x17},~{x19},~{x20},~{x21},~{x22},~{x23},~{x24},~{x25},~{x26},~{x27},~{x28},~{lr},~{q0},~{q1},~{q2},~{q3},~{q4},~{q5},~{q6},~{q7},~{q8},~{q9},~{q10},~{q11},~{q12},~{q13},~{q14},~{q15},~{q16},~{q17},~{q18},~{q19},~{q20},~{q21},~{q22},~{q23},~{q24},~{q25},~{q26},~{q27},~{q28},~{q29},~{q30},~{nzcv},~{ffr},~{vg},~{memory}"
-		if b.GOOS != "darwin" {
+		if b.GOOS != "darwin" && b.GOOS != "windows" {
 			// These registers cause the following warning when compiling for
-			// MacOS:
+			// MacOS and Windows:
 			//     warning: inline asm clobber list contains reserved registers:
 			//     X18, FP
 			//     Reserved registers on the clobber list may not be preserved

src/internal/task/task_stack_arm64.go

@@ -1,4 +1,4 @@
-//go:build scheduler.tasks && arm64
+//go:build scheduler.tasks && arm64 && !windows
 
 package task
 

src/internal/task/task_stack_arm64_windows.S

@@ -0,0 +1,65 @@
+.section .text.tinygo_startTask,"ax"
+.global  tinygo_startTask
+tinygo_startTask:
+    .cfi_startproc
+    // Small assembly stub for starting a goroutine. This is already run on the
+    // new stack, with the callee-saved registers already loaded.
+    // Most importantly, x19 contains the pc of the to-be-started function and
+    // x20 contains the only argument it is given. Multiple arguments are packed
+    // into one by storing them in a new allocation.
+
+    // Indicate to the unwinder that there is nothing to unwind, this is the
+    // root frame. It avoids the following (bogus) error message in GDB:
+    //     Backtrace stopped: previous frame identical to this frame (corrupt stack?)
+    .cfi_undefined lr
+
+    // Set the first argument of the goroutine start wrapper, which contains all
+    // the arguments.
+    mov   x0, x20
+
+    // Branch to the "goroutine start" function. By using blx instead of bx,
+    // we'll return here instead of tail calling.
+    blr   x19
+
+    // After return, exit this goroutine. This is a tail call.
+    b     tinygo_pause
+    .cfi_endproc
+
+
+.global tinygo_swapTask
+tinygo_swapTask:
+    // This function gets the following parameters:
+    // x0 = newStack uintptr
+    // x1 = oldStack *uintptr
+
+    // Save all callee-saved registers:
+    stp     x19, x20, [sp, #-160]!
+    stp     x21, x22, [sp, #16]
+    stp     x23, x24, [sp, #32]
+    stp     x25, x26, [sp, #48]
+    stp     x27, x28, [sp, #64]
+    stp     x29, x30, [sp, #80]
+    stp     d8,  d9,  [sp, #96]
+    stp     d10, d11, [sp, #112]
+    stp     d12, d13, [sp, #128]
+    stp     d14, d15, [sp, #144]
+
+    // Save the current stack pointer in oldStack.
+    mov x8, sp
+    str x8, [x1]
+
+    // Switch to the new stack pointer.
+    mov sp, x0
+
+    // Restore stack state and return.
+    ldp     d14, d15, [sp, #144]
+    ldp     d12, d13, [sp, #128]
+    ldp     d10, d11, [sp, #112]
+    ldp     d8, d9, [sp, #96]
+    ldp     x29, x30, [sp, #80]
+    ldp     x27, x28, [sp, #64]
+    ldp     x25, x26, [sp, #48]
+    ldp     x23, x24, [sp, #32]
+    ldp     x21, x22, [sp, #16]
+    ldp     x19, x20, [sp], #160
+    ret

src/internal/task/task_stack_arm64_windows.go

@@ -0,0 +1,72 @@
+//go:build scheduler.tasks && arm64 && windows
+
+package task
+
+import "unsafe"
+
+var systemStack uintptr
+
+// calleeSavedRegs is the list of registers that must be saved and restored
+// when switching between tasks. Also see task_stack_arm64_windows.S that
+// relies on the exact layout of this struct.
+type calleeSavedRegs struct {
+	x19 uintptr
+	x20 uintptr
+	x21 uintptr
+	x22 uintptr
+	x23 uintptr
+	x24 uintptr
+	x25 uintptr
+	x26 uintptr
+	x27 uintptr
+	x28 uintptr
+	x29 uintptr
+	pc  uintptr // aka x30 aka LR
+
+	d8  uintptr
+	d9  uintptr
+	d10 uintptr
+	d11 uintptr
+	d12 uintptr
+	d13 uintptr
+	d14 uintptr
+	d15 uintptr
+}
+
+// archInit runs architecture-specific setup for the goroutine startup.
+func (s *state) archInit(r *calleeSavedRegs, fn uintptr, args unsafe.Pointer) {
+	// Store the initial sp for the startTask function (implemented in assembly).
+	s.sp = uintptr(unsafe.Pointer(r))
+
+	// Initialize the registers.
+	// These will be popped off of the stack on the first resume of the goroutine.
+
+	// Start the function at tinygo_startTask (defined in src/internal/task/task_stack_arm64_windows.S).
+	// This assembly code calls a function (passed in x19) with a single argument
+	// (passed in x20). After the function returns, it calls Pause().
+	r.pc = uintptr(unsafe.Pointer(&startTask))
+
+	// Pass the function to call in x19.
+	// This function is a compiler-generated wrapper which loads arguments out of a struct pointer.
+	// See createGoroutineStartWrapper (defined in compiler/goroutine.go) for more information.
+	r.x19 = fn
+
+	// Pass the pointer to the arguments struct in x20.
+	r.x20 = uintptr(args)
+}
+
+func (s *state) resume() {
+	swapTask(s.sp, &systemStack)
+}
+
+func (s *state) pause() {
+	newStack := systemStack
+	systemStack = 0
+	swapTask(newStack, &s.sp)
+}
+
+// SystemStack returns the system stack pointer when called from a task stack.
+// When called from the system stack, it returns 0.
+func SystemStack() uintptr {
+	return systemStack
+}

src/runtime/asm_arm64_windows.S

@@ -0,0 +1,36 @@
+.section .text.tinygo_scanCurrentStack,"ax"
+.global tinygo_scanCurrentStack
+tinygo_scanCurrentStack:
+    // Sources:
+    //   * https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170
+    //   * https://godbolt.org/z/foc1xncvb
+
+    // Save callee-saved registers.
+    stp     x29, x30, [sp, #-160]!
+    stp     x28, x27, [sp, #16]
+    stp     x26, x25, [sp, #32]
+    stp     x24, x23, [sp, #48]
+    stp     x22, x21, [sp, #64]
+    stp     x20, x19, [sp, #80]
+    stp     d8,  d9,  [sp, #96]
+    stp     d10, d11, [sp, #112]
+    stp     d12, d13, [sp, #128]
+    stp     d14, d15, [sp, #144]
+
+    // Scan the stack.
+    mov     x0, sp
+    bl      tinygo_scanstack
+
+    // Restore stack state and return.
+    ldp     x29, x30, [sp], #160
+    ret
+
+
+.section .text.tinygo_longjmp,"ax"
+.global tinygo_longjmp
+tinygo_longjmp:
+    // Note: the code we jump to assumes x0 is set to a non-zero value if we
+    // jump from here (which is conveniently already the case).
+    ldp x1, x2, [x0] // jumpSP, jumpPC
+    mov sp, x1
+    br  x2