compileopts: refactor defaultTarget function

Move triple calculation into defaultTarget. It was separate for historic
reasons that no longer apply. Merging the code makes future changes
easier (in particular, softfloat support).

The new code is actually shorter than the old code even though it has
more comments.

Author: aykevl

builder/builder_test.go

@@ -64,7 +64,6 @@ func TestClangAttributes(t *testing.T) {
 		{GOOS: "windows", GOARCH: "amd64"},
 		{GOOS: "windows", GOARCH: "arm64"},
 		{GOOS: "wasip1", GOARCH: "wasm"},
-		{GOOS: "wasip2", GOARCH: "wasm"},
 	} {
 		name := "GOOS=" + options.GOOS + ",GOARCH=" + options.GOARCH
 		if options.GOARCH == "arm" {

compileopts/target.go

@@ -172,63 +172,7 @@ func (spec *TargetSpec) resolveInherits() error {
 // Load a target specification.
 func LoadTarget(options *Options) (*TargetSpec, error) {
 	if options.Target == "" {
-		// Configure based on GOOS/GOARCH environment variables (falling back to
-		// runtime.GOOS/runtime.GOARCH), and generate a LLVM target based on it.
-		var llvmarch string
-		switch options.GOARCH {
-		case "386":
-			llvmarch = "i386"
-		case "amd64":
-			llvmarch = "x86_64"
-		case "arm64":
-			llvmarch = "aarch64"
-		case "arm":
-			switch options.GOARM {
-			case "5":
-				llvmarch = "armv5"
-			case "6":
-				llvmarch = "armv6"
-			case "7":
-				llvmarch = "armv7"
-			default:
-				return nil, fmt.Errorf("invalid GOARM=%s, must be 5, 6, or 7", options.GOARM)
-			}
-		case "mips":
-			llvmarch = "mips"
-		case "mipsle":
-			llvmarch = "mipsel"
-		case "wasm":
-			llvmarch = "wasm32"
-		default:
-			llvmarch = options.GOARCH
-		}
-		llvmvendor := "unknown"
-		llvmos := options.GOOS
-		switch llvmos {
-		case "darwin":
-			// Use macosx* instead of darwin, otherwise darwin/arm64 will refer
-			// to iOS!
-			llvmos = "macosx10.12.0"
-			if llvmarch == "aarch64" {
-				// Looks like Apple prefers to call this architecture ARM64
-				// instead of AArch64.
-				llvmarch = "arm64"
-				llvmos = "macosx11.0.0"
-			}
-			llvmvendor = "apple"
-		case "wasip1":
-			llvmos = "wasi"
-		}
-		// Target triples (which actually have four components, but are called
-		// triples for historical reasons) have the form:
-		//   arch-vendor-os-environment
-		target := llvmarch + "-" + llvmvendor + "-" + llvmos
-		if options.GOOS == "windows" {
-			target += "-gnu"
-		} else if options.GOARCH == "arm" {
-			target += "-gnueabihf"
-		}
-		return defaultTarget(options.GOOS, options.GOARCH, target)
+		return defaultTarget(options)
 	}
 
 	// See whether there is a target specification for this target (e.g.
@@ -289,44 +233,57 @@ func GetTargetSpecs() (map[string]*TargetSpec, error) {
 	return maps, nil
 }
 
-func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
-	// No target spec available. Use the default one, useful on most systems
-	// with a regular OS.
+// Load a target from environment variables (which default to
+// runtime.GOOS/runtime.GOARCH).
+func defaultTarget(options *Options) (*TargetSpec, error) {
 	spec := TargetSpec{
-		Triple:           triple,
-		GOOS:             goos,
-		GOARCH:           goarch,
-		BuildTags:        []string{goos, goarch},
+		GOOS:             options.GOOS,
+		GOARCH:           options.GOARCH,
+		BuildTags:        []string{options.GOOS, options.GOARCH},
 		GC:               "precise",
 		Scheduler:        "tasks",
 		Linker:           "cc",
 		DefaultStackSize: 1024 * 64, // 64kB
 		GDB:              []string{"gdb"},
 		PortReset:        "false",
 	}
-	switch goarch {
+
+	// Configure target based on GOARCH.
+	var llvmarch string
+	switch options.GOARCH {
 	case "386":
+		llvmarch = "i386"
 		spec.CPU = "pentium4"
 		spec.Features = "+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87"
 	case "amd64":
+		llvmarch = "x86_64"
 		spec.CPU = "x86-64"
 		spec.Features = "+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87"
 	case "arm":
 		spec.CPU = "generic"
 		spec.CFlags = append(spec.CFlags, "-fno-unwind-tables", "-fno-asynchronous-unwind-tables")
-		switch strings.Split(triple, "-")[0] {
-		case "armv5":
+		switch options.GOARM {
+		case "5":
+			llvmarch = "armv5"
 			spec.Features = "+armv5t,+strict-align,-aes,-bf16,-d32,-dotprod,-fp-armv8,-fp-armv8d16,-fp-armv8d16sp,-fp-armv8sp,-fp16,-fp16fml,-fp64,-fpregs,-fullfp16,-mve.fp,-neon,-sha2,-thumb-mode,-vfp2,-vfp2sp,-vfp3,-vfp3d16,-vfp3d16sp,-vfp3sp,-vfp4,-vfp4d16,-vfp4d16sp,-vfp4sp"
-		case "armv6":
+		case "6":
+			llvmarch = "armv6"
 			spec.Features = "+armv6,+dsp,+fp64,+strict-align,+vfp2,+vfp2sp,-aes,-d32,-fp-armv8,-fp-armv8d16,-fp-armv8d16sp,-fp-armv8sp,-fp16,-fp16fml,-fullfp16,-neon,-sha2,-thumb-mode,-vfp3,-vfp3d16,-vfp3d16sp,-vfp3sp,-vfp4,-vfp4d16,-vfp4d16sp,-vfp4sp"
-		case "armv7":
+		case "7":
+			llvmarch = "armv7"
 			spec.Features = "+armv7-a,+d32,+dsp,+fp64,+neon,+vfp2,+vfp2sp,+vfp3,+vfp3d16,+vfp3d16sp,+vfp3sp,-aes,-fp-armv8,-fp-armv8d16,-fp-armv8d16sp,-fp-armv8sp,-fp16,-fp16fml,-fullfp16,-sha2,-thumb-mode,-vfp4,-vfp4d16,-vfp4d16sp,-vfp4sp"
+		default:
+			return nil, fmt.Errorf("invalid GOARM=%s, must be 5, 6, or 7", options.GOARM)
 		}
 	case "arm64":
 		spec.CPU = "generic"
-		if goos == "darwin" {
+		llvmarch = "aarch64"
+		if options.GOOS == "darwin" {
 			spec.Features = "+fp-armv8,+neon"
-		} else if goos == "windows" {
+			// Looks like Apple prefers to call this architecture ARM64
+			// instead of AArch64.
+			llvmarch = "arm64"
+		} else if options.GOOS == "windows" {
 			spec.Features = "+fp-armv8,+neon,-fmv"
 		} else { // linux
 			spec.Features = "+fp-armv8,+neon,-fmv,-outline-atomics"
@@ -335,7 +292,13 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 		spec.CPU = "mips32r2"
 		spec.Features = "+fpxx,+mips32r2,+nooddspreg,-noabicalls"
 		spec.CFlags = append(spec.CFlags, "-fno-pic")
+		if options.GOOS == "mips" {
+			llvmarch = "mips" // big endian
+		} else {
+			llvmarch = "mipsel" // little endian
+		}
 	case "wasm":
+		llvmarch = "wasm32"
 		spec.CPU = "generic"
 		spec.Features = "+bulk-memory,+mutable-globals,+nontrapping-fptoint,+sign-ext"
 		spec.BuildTags = append(spec.BuildTags, "tinygo.wasm")
@@ -344,24 +307,37 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 			"-mnontrapping-fptoint",
 			"-msign-ext",
 		)
+	default:
+		return nil, fmt.Errorf("unknown GOARCH=%s", options.GOARCH)
 	}
-	if goos == "darwin" {
+
+	// Configure target based on GOOS.
+	llvmos := options.GOOS
+	llvmvendor := "unknown"
+	switch options.GOOS {
+	case "darwin":
+		platformVersion := "10.12.0"
+		if options.GOARCH == "arm64" {
+			platformVersion = "11.0.0" // first macosx platform with arm64 support
+		}
+		llvmvendor = "apple"
 		spec.Linker = "ld.lld"
 		spec.Libc = "darwin-libSystem"
-		arch := strings.Split(triple, "-")[0]
-		platformVersion := strings.TrimPrefix(strings.Split(triple, "-")[2], "macosx")
+		// Use macosx* instead of darwin, otherwise darwin/arm64 will refer to
+		// iOS!
+		llvmos = "macosx" + platformVersion
 		spec.LDFlags = append(spec.LDFlags,
 			"-flavor", "darwin",
 			"-dead_strip",
-			"-arch", arch,
+			"-arch", llvmarch,
 			"-platform_version", "macos", platformVersion, platformVersion,
 		)
-	} else if goos == "linux" {
+	case "linux":
 		spec.Linker = "ld.lld"
 		spec.RTLib = "compiler-rt"
 		spec.Libc = "musl"
 		spec.LDFlags = append(spec.LDFlags, "--gc-sections")
-		if goarch == "arm64" {
+		if options.GOARCH == "arm64" {
 			// Disable outline atomics. For details, see:
 			// https://cpufun.substack.com/p/atomics-in-aarch64
 			// A better way would be to fully support outline atomics, which
@@ -375,7 +351,7 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 			// proper threading.
 			spec.CFlags = append(spec.CFlags, "-mno-outline-atomics")
 		}
-	} else if goos == "windows" {
+	case "windows":
 		spec.Linker = "ld.lld"
 		spec.Libc = "mingw-w64"
 		// Note: using a medium code model, low image base and no ASLR
@@ -384,7 +360,7 @@ 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 {
+		switch options.GOARCH {
 		case "amd64":
 			spec.LDFlags = append(spec.LDFlags,
 				"-m", "i386pep",
@@ -401,7 +377,7 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 			"--no-insert-timestamp",
 			"--no-dynamicbase",
 		)
-	} else if goos == "wasip1" {
+	case "wasip1":
 		spec.GC = "" // use default GC
 		spec.Scheduler = "asyncify"
 		spec.Linker = "wasm-ld"
@@ -417,28 +393,43 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 			"src/runtime/asm_tinygowasm.S",
 			"src/internal/task/task_asyncify_wasm.S",
 		)
-	} else {
-		spec.LDFlags = append(spec.LDFlags, "-no-pie", "-Wl,--gc-sections") // WARNING: clang < 5.0 requires -nopie
+		llvmos = "wasi"
+	default:
+		return nil, fmt.Errorf("unknown GOOS=%s", options.GOOS)
 	}
-	if goarch != "wasm" {
+
+	// Target triples (which actually have four components, but are called
+	// triples for historical reasons) have the form:
+	//   arch-vendor-os-environment
+	spec.Triple = llvmarch + "-" + llvmvendor + "-" + llvmos
+	if options.GOOS == "windows" {
+		spec.Triple += "-gnu"
+	} else if options.GOARCH == "arm" {
+		spec.Triple += "-gnueabihf"
+	}
+
+	// Add extra assembly files (needed for the scheduler etc).
+	if options.GOARCH != "wasm" {
 		suffix := ""
-		if goos == "windows" && goarch == "amd64" {
+		if options.GOOS == "windows" && options.GOARCH == "amd64" {
 			// Windows uses a different calling convention on amd64 from other
 			// operating systems so we need separate assembly files.
 			suffix = "_windows"
 		}
-		asmGoarch := goarch
-		if goarch == "mips" || goarch == "mipsle" {
+		asmGoarch := options.GOARCH
+		if options.GOARCH == "mips" || options.GOARCH == "mipsle" {
 			asmGoarch = "mipsx"
 		}
 		spec.ExtraFiles = append(spec.ExtraFiles, "src/runtime/asm_"+asmGoarch+suffix+".S")
 		spec.ExtraFiles = append(spec.ExtraFiles, "src/internal/task/task_stack_"+asmGoarch+suffix+".S")
 	}
-	if goarch != runtime.GOARCH {
+
+	// Configure the emulator.
+	if options.GOARCH != runtime.GOARCH {
 		// Some educated guesses as to how to invoke helper programs.
 		spec.GDB = []string{"gdb-multiarch"}
-		if goos == "linux" {
-			switch goarch {
+		if options.GOOS == "linux" {
+			switch options.GOARCH {
 			case "386":
 				// amd64 can _usually_ run 32-bit programs, so skip the emulator in that case.
 				if runtime.GOARCH != "amd64" {
@@ -457,11 +448,12 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 			}
 		}
 	}
-	if goos != runtime.GOOS {
-		if goos == "windows" {
+	if options.GOOS != runtime.GOOS {
+		if options.GOOS == "windows" {
 			spec.Emulator = "wine {}"
 		}
 	}
+
 	return &spec, nil
 }