go.tools/cmd/ssadump: move ssa/ssadump.go command to its own package.

(Its former location was based on a misunderstanding of 'go build'.)

Also: set GOMAXPROCS to NumCPU by default.

R=crawshaw
CC=golang-dev
https://golang.org/cl/13354043

cmd/ssadump/main.go

@@ -2,17 +2,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build ignore
-
-package main
-
 // ssadump: a tool for displaying and interpreting the SSA form of Go programs.
+package main
 
 import (
 	"flag"
 	"fmt"
 	"log"
 	"os"
+	"runtime"
 	"runtime/pprof"
 
 	"code.google.com/p/go.tools/importer"
@@ -52,6 +50,18 @@ Examples:
 
 var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
 
+func init() {
+	// If $GOMAXPROCS isn't set, use the full capacity of the machine.
+	// For small machines, use at least 4 threads.
+	if os.Getenv("GOMAXPROCS") == "" {
+		n := runtime.NumCPU()
+		if n < 4 {
+			n = 4
+		}
+		runtime.GOMAXPROCS(n)
+	}
+}
+
 func main() {
 	flag.Parse()
 	args := flag.Args()

ssa/interp/interp_test.go

@@ -185,7 +185,7 @@ func run(t *testing.T, dir, input string) bool {
 		}
 	}()
 
-	hint = fmt.Sprintf("To dump SSA representation, run:\n%% go run src/code.google.com/p/go.tools/ssa/ssadump.go -build=CFP %s\n", input)
+	hint = fmt.Sprintf("To dump SSA representation, run:\n%% go build code.google.com/p/go.tools/cmd/ssadump; ./ssadump -build=CFP %s\n", input)
 	info := imp.CreateSourcePackage("main", files)
 	if info.Err != nil {
 		t.Errorf("importer.CreateSourcePackage(%s) failed: %s", inputs, info.Err.Error())
@@ -201,7 +201,7 @@ func run(t *testing.T, dir, input string) bool {
 	mainPkg := prog.Package(info.Pkg)
 	mainPkg.CreateTestMainFunction() // (no-op if main already exists)
 
-	hint = fmt.Sprintf("To trace execution, run:\n%% go run src/code.google.com/p/go.tools/ssa/ssadump.go -build=C -run --interp=T %s\n", input)
+	hint = fmt.Sprintf("To trace execution, run:\n%% go build code.google.com/p/go.tools/cmd/ssadump; ./ssadump -build=C -run --interp=T %s\n", input)
 	if exitCode := interp.Interpret(mainPkg, 0, inputs[0], []string{}); exitCode != 0 {
 		t.Errorf("interp.Interpret(%s) exited with code %d, want zero", inputs, exitCode)
 		return false