cmd/compile: add processor level selection support to ppc64{,le}

ppc64{,le} processor level selection allows the compiler to generate instructions
targeting newer processors and processor-specific optimizations without breaking
compatibility with our current baseline. This feature introduces a new environment
variable, GOPPC64.

GOPPC64 is a GOARCH=ppc64{,le} specific option, for a choice between different
processor levels (i.e. Instruction Set Architecture versions) for which the
compiler will target. The default is 'power8'.

Change-Id: Ic152e283ae1c47084ece4346fa002a3eabb3bb9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/163758
Run-TryBot: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

doc/install-source.html

@@ -627,6 +627,17 @@ contains further details regarding Go's ARM support.
 </p>
 </li>
 
+<li><code>$GOPPC64</code> (for <code>ppc64</code> and <code>ppc64le</code> only)
+<p>
+This variable sets the processor level (i.e. Instruction Set Architecture version)
+for which the compiler will target. The default is <code>power8</code>.
+</p>
+<ul>
+	<li><code>GOPPC64=power8</code>: generate ISA v2.07 instructions</li>
+	<li><code>GOPPC64=power9</code>: generate ISA v3.00 instructions</li>
+</ul>
+</li>
+
 </ul>
 
 <p>

src/cmd/dist/build.go

@@ -33,6 +33,7 @@ var (
 	go386            string
 	gomips           string
 	gomips64         string
+	goppc64          string
 	goroot           string
 	goroot_final     string
 	goextlinkenabled string
@@ -159,6 +160,12 @@ func xinit() {
 	}
 	gomips64 = b
 
+	b = os.Getenv("GOPPC64")
+	if b == "" {
+		b = "power8"
+	}
+	goppc64 = b
+
 	if p := pathf("%s/src/all.bash", goroot); !isfile(p) {
 		fatalf("$GOROOT is not set correctly or not exported\n"+
 			"\tGOROOT=%s\n"+
@@ -219,6 +226,7 @@ func xinit() {
 	os.Setenv("GOOS", goos)
 	os.Setenv("GOMIPS", gomips)
 	os.Setenv("GOMIPS64", gomips64)
+	os.Setenv("GOPPC64", goppc64)
 	os.Setenv("GOROOT", goroot)
 	os.Setenv("GOROOT_FINAL", goroot_final)
 
@@ -1117,6 +1125,9 @@ func cmdenv() {
 	if goarch == "mips64" || goarch == "mips64le" {
 		xprintf(format, "GOMIPS64", gomips64)
 	}
+	if goarch == "ppc64" || goarch == "ppc64le" {
+		xprintf(format, "GOPPC64", goppc64)
+	}
 
 	if *path {
 		sep := ":"

src/cmd/dist/buildruntime.go

@@ -45,6 +45,7 @@ func mkzversion(dir, file string) {
 //	const defaultGOARM = <goarm>
 //	const defaultGOMIPS = <gomips>
 //	const defaultGOMIPS64 = <gomips64>
+//	const defaultGOPPC64 = <goppc64>
 //	const defaultGOOS = runtime.GOOS
 //	const defaultGOARCH = runtime.GOARCH
 //	const defaultGO_EXTLINK_ENABLED = <goextlinkenabled>
@@ -73,6 +74,7 @@ func mkzbootstrap(file string) {
 	fmt.Fprintf(&buf, "const defaultGOARM = `%s`\n", goarm)
 	fmt.Fprintf(&buf, "const defaultGOMIPS = `%s`\n", gomips)
 	fmt.Fprintf(&buf, "const defaultGOMIPS64 = `%s`\n", gomips64)
+	fmt.Fprintf(&buf, "const defaultGOPPC64 = `%s`\n", goppc64)
 	fmt.Fprintf(&buf, "const defaultGOOS = runtime.GOOS\n")
 	fmt.Fprintf(&buf, "const defaultGOARCH = runtime.GOARCH\n")
 	fmt.Fprintf(&buf, "const defaultGO_EXTLINK_ENABLED = `%s`\n", goextlinkenabled)

src/cmd/go/internal/cfg/cfg.go

@@ -104,6 +104,7 @@ var (
 	GO386    = objabi.GO386
 	GOMIPS   = objabi.GOMIPS
 	GOMIPS64 = objabi.GOMIPS64
+	GOPPC64  = fmt.Sprintf("%s%d", "power", objabi.GOPPC64)
 )
 
 // Update build context to use our computed GOROOT.

src/cmd/go/internal/envcmd/env.go

@@ -81,6 +81,8 @@ func MkEnv() []cfg.EnvVar {
 		env = append(env, cfg.EnvVar{Name: "GOMIPS", Value: cfg.GOMIPS})
 	case "mips64", "mips64le":
 		env = append(env, cfg.EnvVar{Name: "GOMIPS64", Value: cfg.GOMIPS64})
+	case "ppc64", "ppc64le":
+		env = append(env, cfg.EnvVar{Name: "GOPPC64", Value: cfg.GOPPC64})
 	}
 
 	cc := cfg.DefaultCC(cfg.Goos, cfg.Goarch)

src/cmd/internal/objabi/util.go

@@ -28,6 +28,7 @@ var (
 	GOARM    = goarm()
 	GOMIPS   = gomips()
 	GOMIPS64 = gomips64()
+	GOPPC64  = goppc64()
 	GO_LDSO  = defaultGO_LDSO
 	Version  = version
 )
@@ -64,6 +65,17 @@ func gomips64() string {
 	panic("unreachable")
 }
 
+func goppc64() int {
+	switch v := envOr("GOPPC64", defaultGOPPC64); v {
+	case "power8":
+		return 8
+	case "power9":
+		return 9
+	}
+	log.Fatalf("Invalid GOPPC64 value. Must be power8 or power9.")
+	panic("unreachable")
+}
+
 func Getgoextlinkenabled() string {
 	return envOr("GO_EXTLINK_ENABLED", defaultGO_EXTLINK_ENABLED)
 }

test/run.go

@@ -1382,8 +1382,8 @@ var (
 		"arm64":   {},
 		"mips":    {"GOMIPS", "hardfloat", "softfloat"},
 		"mips64":  {"GOMIPS64", "hardfloat", "softfloat"},
-		"ppc64":   {},
-		"ppc64le": {},
+		"ppc64":   {"GOPPC64", "power8", "power9"},
+		"ppc64le": {"GOPPC64", "power8", "power9"},
 		"s390x":   {},
 	}
 )