go/build, go/types, cmd/dist: add js/wasm architecture

This is the first commit of a series that will add WebAssembly
as an architecture target. The design document can be found at
https://docs.google.com/document/d/131vjr4DH6JFnb-blm_uRdaC0_Nv3OUwjEY5qVCxCup4.

The GOARCH name "wasm" is the official abbreviation of WebAssembly.
The GOOS name "js" got chosen because initially the host environment
that executes WebAssembly bytecode will be web browsers and Node.js,
which both use JavaScript to embed WebAssembly. Other GOOS values
may be possible later, see:
https://github.com/WebAssembly/design/blob/master/NonWeb.md

Updates #18892

Change-Id: Ia25b4fa26bba8029c25923f48ad009fd3681933a
Reviewed-on: https://go-review.googlesource.com/102835
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: neelance

src/cmd/dist/build.go

@@ -1380,6 +1380,7 @@ var cgoEnabled = map[string]bool{
 	"android/amd64":   true,
 	"android/arm":     true,
 	"android/arm64":   true,
+	"js/wasm":         false,
 	"nacl/386":        false,
 	"nacl/amd64p32":   false,
 	"nacl/arm":        false,

src/cmd/vet/all/main.go

@@ -192,6 +192,12 @@ func vetPlatforms(pp []platform) {
 }
 
 func (p platform) vet() {
+	if p.os == "js" && p.arch == "wasm" {
+		// TODO(neelance): enable as soon as js/wasm has fully landed
+		fmt.Println("skipping js/wasm")
+		return
+	}
+
 	var buf bytes.Buffer
 	fmt.Fprintf(&buf, "go run main.go -p %s\n", p)
 

src/go/build/syslist.go

@@ -4,5 +4,5 @@
 
 package build
 
-const goosList = "android darwin dragonfly freebsd linux nacl netbsd openbsd plan9 solaris windows zos "
-const goarchList = "386 amd64 amd64p32 arm armbe arm64 arm64be ppc64 ppc64le mips mipsle mips64 mips64le mips64p32 mips64p32le ppc s390 s390x sparc sparc64 "
+const goosList = "android darwin dragonfly freebsd js linux nacl netbsd openbsd plan9 solaris windows zos "
+const goarchList = "386 amd64 amd64p32 arm armbe arm64 arm64be ppc64 ppc64le mips mipsle mips64 mips64le mips64p32 mips64p32le ppc s390 s390x sparc sparc64 wasm "

src/go/types/sizes.go

@@ -168,6 +168,7 @@ var gcArchSizes = map[string]*StdSizes{
 	"ppc64":    {8, 8},
 	"ppc64le":  {8, 8},
 	"s390x":    {8, 8},
+	"wasm":     {8, 8},
 	// When adding more architectures here,
 	// update the doc string of SizesFor below.
 }
@@ -177,7 +178,7 @@ var gcArchSizes = map[string]*StdSizes{
 //
 // Supported architectures for compiler "gc":
 // "386", "arm", "arm64", "amd64", "amd64p32", "mips", "mipsle",
-// "mips64", "mips64le", "ppc64", "ppc64le", "s390x".
+// "mips64", "mips64le", "ppc64", "ppc64le", "s390x", "wasm".
 func SizesFor(compiler, arch string) Sizes {
 	if compiler != "gc" {
 		return nil