main: include prebuilt compiler-rt libraries in release tarball

This avoids depending on clang-7 to build compiler-rt for the most
common ARM microcontrollers.

Makefile

@@ -117,6 +117,9 @@ release: static gen-device
 	@mkdir -p build/release/tinygo/lib/CMSIS/CMSIS
 	@mkdir -p build/release/tinygo/lib/compiler-rt/lib
 	@mkdir -p build/release/tinygo/lib/nrfx
+	@mkdir -p build/release/tinygo/pkg/armv6m-none-eabi
+	@mkdir -p build/release/tinygo/pkg/armv7m-none-eabi
+	@mkdir -p build/release/tinygo/pkg/armv7em-none-eabi
 	@cp -p  build/tinygo                 build/release/tinygo/bin
 	@cp -rp lib/CMSIS/CMSIS/Include      build/release/tinygo/lib/CMSIS/CMSIS
 	@cp -rp lib/CMSIS/README.md          build/release/tinygo/lib/CMSIS
@@ -126,6 +129,9 @@ release: static gen-device
 	@cp -rp lib/nrfx/*                   build/release/tinygo/lib/nrfx
 	@cp -rp src                          build/release/tinygo/src
 	@cp -rp targets                      build/release/tinygo/targets
+	./build/tinygo build-builtins -target=armv6m-none-eabi  -o build/release/tinygo/pkg/armv6m-none-eabi/compiler-rt.a
+	./build/tinygo build-builtins -target=armv7m-none-eabi  -o build/release/tinygo/pkg/armv7m-none-eabi/compiler-rt.a
+	./build/tinygo build-builtins -target=armv7em-none-eabi -o build/release/tinygo/pkg/armv7em-none-eabi/compiler-rt.a
 	tar -czf build/release.tar.gz -C build/release tinygo
 
 # Binary that can run on the host.

buildcache.go

@@ -80,29 +80,45 @@ func cacheStore(tmppath, name, configKey string, sourceFiles []string) (string,
 		return "", err
 	}
 	cachepath := filepath.Join(dir, name)
-	err = os.Rename(tmppath, cachepath)
+	err = moveFile(tmppath, cachepath)
 	if err != nil {
-		inf, err := os.Open(tmppath)
+		return "", err
-		if err != nil {
-			return "", err
-		}
-		defer inf.Close()
-		outf, err := os.Create(cachepath + ".tmp")
-		if err != nil {
-			return "", err
-		}
-
-		_, err = io.Copy(outf, inf)
-		if err != nil {
-			return "", err
-		}
-
-		err = os.Rename(cachepath+".tmp", cachepath)
-		if err != nil {
-			return "", err
-		}
-
-		return cachepath, outf.Close()
 	}
 	return cachepath, nil
 }
+
+// moveFile renames the file from src to dst. If renaming doesn't work (for
+// example, the rename crosses a filesystem boundary), the file is copied and
+// the old file is removed.
+func moveFile(src, dst string) error {
+	err := os.Rename(src, dst)
+	if err == nil {
+		// Success!
+		return nil
+	}
+	// Failed to move, probably a different filesystem.
+	// Do a copy + remove.
+	inf, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer inf.Close()
+	outpath := dst + ".tmp"
+	outf, err := os.Create(outpath)
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(outf, inf)
+	if err != nil {
+		os.Remove(outpath)
+		return err
+	}
+
+	err = os.Rename(dst+".tmp", dst)
+	if err != nil {
+		return err
+	}
+
+	return outf.Close()
+}

builtins.go

@@ -157,16 +157,29 @@ var aeabiBuiltins = []string{
 
 func builtinFiles(target string) []string {
 	builtins := append([]string{}, genericBuiltins...) // copy genericBuiltins
-	if target[:3] == "arm" {
+	if strings.HasPrefix(target, "arm") {
 		builtins = append(builtins, aeabiBuiltins...)
 	}
 	return builtins
 }
 
+// builtinsDir returns the directory where the sources for compiler-rt are kept.
+func builtinsDir() string {
+	return filepath.Join(sourceDir(), "lib", "compiler-rt", "lib", "builtins")
+}
+
 // Get the builtins archive, possibly generating it as needed.
 func loadBuiltins(target string) (path string, err error) {
+	// Try to load a precompiled compiler-rt library.
+	precompiledPath := filepath.Join(sourceDir(), "pkg", target, "compiler-rt.a")
+	if _, err := os.Stat(precompiledPath); err == nil {
+		// Found a precompiled compiler-rt for this OS/architecture. Return the
+		// path directly.
+		return precompiledPath, nil
+	}
+
 	outfile := "librt-" + target + ".a"
-	builtinsDir := filepath.Join(sourceDir(), "lib", "compiler-rt", "lib", "builtins")
+	builtinsDir := builtinsDir()
 
 	builtins := builtinFiles(target)
 	srcs := make([]string, len(builtins))
@@ -178,9 +191,33 @@ func loadBuiltins(target string) (path string, err error) {
 		return path, err
 	}
 
-	dir, err := ioutil.TempDir("", "tinygo-builtins")
+	var cachepath string
+	err = compileBuiltins(target, func(path string) error {
+		path, err := cacheStore(path, outfile, commands["clang"], srcs)
+		cachepath = path
+		return err
+	})
+	return cachepath, err
+}
+
+// compileBuiltins compiles builtins from compiler-rt into a static library.
+// When it succeeds, it will call the callback with the resulting path. The path
+// will be removed after callback returns. If callback returns an error, this is
+// passed through to the return value of this function.
+func compileBuiltins(target string, callback func(path string) error) error {
+	builtinsDir := builtinsDir()
+
+	builtins := builtinFiles(target)
+	srcs := make([]string, len(builtins))
+	for i, name := range builtins {
+		srcs[i] = filepath.Join(builtinsDir, name)
+	}
+
+	dirPrefix := "tinygo-builtins"
+	remapDir := filepath.Join(os.TempDir(), dirPrefix)
+	dir, err := ioutil.TempDir(os.TempDir(), dirPrefix)
 	if err != nil {
-		return "", err
+		return err
 	}
 	defer os.RemoveAll(dir)
 
@@ -195,13 +232,16 @@ func loadBuiltins(target string) (path string, err error) {
 		objpath := filepath.Join(dir, objname+".o")
 		objs = append(objs, objpath)
 		srcpath := filepath.Join(builtinsDir, name)
-		cmd := exec.Command(commands["clang"], "-c", "-Oz", "-g", "-Werror", "-Wall", "-std=c11", "-fshort-enums", "-nostdlibinc", "-ffunction-sections", "-fdata-sections", "--target="+target, "-o", objpath, srcpath)
+		// Note: -fdebug-prefix-map is necessary to make the output archive
+		// reproducible. Otherwise the temporary directory is stored in the
+		// archive itself, which varies each run.
+		cmd := exec.Command(commands["clang"], "-c", "-Oz", "-g", "-Werror", "-Wall", "-std=c11", "-fshort-enums", "-nostdlibinc", "-ffunction-sections", "-fdata-sections", "--target="+target, "-fdebug-prefix-map="+dir+"="+remapDir, "-o", objpath, srcpath)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 		cmd.Dir = dir
 		err = cmd.Run()
 		if err != nil {
-			return "", &commandError{"failed to build", srcpath, err}
+			return &commandError{"failed to build", srcpath, err}
 		}
 	}
 
@@ -213,8 +253,10 @@ func loadBuiltins(target string) (path string, err error) {
 	cmd.Dir = dir
 	err = cmd.Run()
 	if err != nil {
-		return "", &commandError{"failed to make static library", arpath, err}
+		return &commandError{"failed to make static library", arpath, err}
 	}
 
-	return cacheStore(arpath, outfile, commands["clang"], srcs)
+	// Give the caller the resulting file. The callback must copy the file,
+	// because after it returns the temporary directory will be removed.
+	return callback(arpath)
 }

main.go

@@ -186,13 +186,12 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 
 		// Load builtins library from the cache, possibly compiling it on the
 		// fly.
-		var cachePath string
+		var librt string
 		if spec.RTLib == "compiler-rt" {
-			librt, err := loadBuiltins(spec.Triple)
+			librt, err = loadBuiltins(spec.Triple)
 			if err != nil {
 				return err
 			}
-			cachePath, _ = filepath.Split(librt)
 		}
 
 		// Prepare link command.
@@ -200,7 +199,7 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		tmppath := executable // final file
 		ldflags := append(spec.LDFlags, "-o", executable, objfile)
 		if spec.RTLib == "compiler-rt" {
-			ldflags = append(ldflags, "-L", cachePath, "-lrt-"+spec.Triple)
+			ldflags = append(ldflags, librt)
 		}
 
 		// Compile extra files.
@@ -554,6 +553,20 @@ func main() {
 		}
 		err := Build(flag.Arg(0), *outpath, target, config)
 		handleCompilerError(err)
+	case "build-builtins":
+		// Note: this command is only meant to be used while making a release!
+		if *outpath == "" {
+			fmt.Fprintln(os.Stderr, "No output filename supplied (-o).")
+			usage()
+			os.Exit(1)
+		}
+		if *target == "" {
+			fmt.Fprintln(os.Stderr, "No target (-target).")
+		}
+		err := compileBuiltins(*target, func(path string) error {
+			return moveFile(path, *outpath)
+		})
+		handleCompilerError(err)
 	case "flash", "gdb":
 		if *outpath != "" {
 			fmt.Fprintln(os.Stderr, "Output cannot be specified with the flash command.")