windows: add windows/386 support

builder/builder_test.go

@@ -66,6 +66,7 @@ func TestClangAttributes(t *testing.T) {
 		{GOOS: "linux", GOARCH: "mipsle", GOMIPS: "softfloat"},
 		{GOOS: "darwin", GOARCH: "amd64"},
 		{GOOS: "darwin", GOARCH: "arm64"},
+		{GOOS: "windows", GOARCH: "386"},
 		{GOOS: "windows", GOARCH: "amd64"},
 		{GOOS: "windows", GOARCH: "arm64"},
 		{GOOS: "wasip1", GOARCH: "wasm"},

builder/mingw-w64.go

@@ -93,6 +93,9 @@ func makeMinGWExtraLibs(tmpdir, goarch string) []*compileJob {
 				defpath := inpath
 				var archDef, emulation string
 				switch goarch {
+				case "386":
+					archDef = "-DDEF_I386"
+					emulation = "i386pe"
 				case "amd64":
 					archDef = "-DDEF_X64"
 					emulation = "i386pep"

compileopts/target.go

@@ -420,14 +420,20 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 	case "windows":
 		spec.Linker = "ld.lld"
 		spec.Libc = "mingw-w64"
-		// Note: using a medium code model, low image base and no ASLR
-		// because Go doesn't really need those features. ASLR patches
-		// around issues for unsafe languages like C/C++ that are not
-		// 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 options.GOARCH {
+		case "386":
+			spec.LDFlags = append(spec.LDFlags,
+				"-m", "i386pe",
+			)
+			// __udivdi3 is not present in ucrt it seems.
+			spec.RTLib = "compiler-rt"
 		case "amd64":
+			// Note: using a medium code model, low image base and no ASLR
+			// because Go doesn't really need those features. ASLR patches
+			// around issues for unsafe languages like C/C++ that are not
+			// 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
 			spec.LDFlags = append(spec.LDFlags,
 				"-m", "i386pep",
 				"--image-base", "0x400000",

main_test.go

@@ -203,6 +203,13 @@ func TestBuild(t *testing.T) {
 			t.Parallel()
 			runPlatTests(optionsFromTarget("wasip2", sema), tests, t)
 		})
+	} else if runtime.GOOS == "windows" {
+		if runtime.GOARCH != "386" {
+			t.Run("Windows386", func(t *testing.T) {
+				t.Parallel()
+				runPlatTests(optionsFromOSARCH("windows/386", sema), tests, t)
+			})
+		}
 	}
 }
 

src/internal/task/task_stack_386.S

@@ -1,7 +1,12 @@
+#ifdef _WIN32
+.global  _tinygo_startTask
+_tinygo_startTask:
+#else // Linux etc
 .section .text.tinygo_startTask
 .global  tinygo_startTask
 .type    tinygo_startTask, %function
 tinygo_startTask:
+#endif
     .cfi_startproc
     // Small assembly stub for starting a goroutine. This is already run on the
     // new stack, with the callee-saved registers already loaded.
@@ -24,12 +29,21 @@ tinygo_startTask:
     addl $4, %esp
 
     // After return, exit this goroutine. This is a tail call.
+    #ifdef _WIN32
+    jmp _tinygo_pause
+    #else
     jmp tinygo_pause
+    #endif
     .cfi_endproc
 
+#ifdef _WIN32
+.global _tinygo_swapTask
+_tinygo_swapTask:
+#else
 .global tinygo_swapTask
 .type tinygo_swapTask, %function
 tinygo_swapTask:
+#endif
     // This function gets the following parameters:
     movl 4(%esp), %eax // newStack uintptr
     movl 8(%esp), %ecx // oldStack *uintptr

src/runtime/asm_386.S

@@ -1,7 +1,12 @@
+#ifdef _WIN32
+.global _tinygo_scanCurrentStack
+_tinygo_scanCurrentStack:
+#else
 .section .text.tinygo_scanCurrentStack
 .global tinygo_scanCurrentStack
 .type tinygo_scanCurrentStack, %function
 tinygo_scanCurrentStack:
+#endif
     // Sources:
     //   * https://stackoverflow.com/questions/18024672/what-registers-are-preserved-through-a-linux-x86-64-function-call
     //   * https://godbolt.org/z/q7e8dn
@@ -15,17 +20,26 @@ tinygo_scanCurrentStack:
     // Scan the stack.
     subl $8, %esp // adjust the stack before the call to maintain 16-byte alignment
     pushl %esp
+    #ifdef _WIN32
+    calll _tinygo_scanstack
+    #else
     calll tinygo_scanstack
+    #endif
 
     // Restore the stack pointer. Registers do not need to be restored as they
     // were only pushed to be discoverable by the GC.
     addl $28, %esp
     retl
 
 
+#ifdef _WIN32
+.global _tinygo_longjmp
+_tinygo_longjmp:
+#else
 .section .text.tinygo_longjmp
 .global tinygo_longjmp
 tinygo_longjmp:
+#endif
     // Note: the code we jump to assumes eax is set to a non-zero value if we
     // jump from here.
     movl 4(%esp), %eax