cmd/compile/internal/gc: add runtime/trace support

This change adds runtime/trace support to go tool compile.

Change-Id: I6c496b9b063796123f75eba6af511c53a57c0196
Reviewed-on: https://go-review.googlesource.com/25354
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/cmd/compile/internal/gc/main.go

@@ -208,6 +208,7 @@ func Main() {
 	flag.StringVar(&cpuprofile, "cpuprofile", "", "write cpu profile to `file`")
 	flag.StringVar(&memprofile, "memprofile", "", "write memory profile to `file`")
 	flag.Int64Var(&memprofilerate, "memprofilerate", 0, "set runtime.MemProfileRate to `rate`")
+	flag.StringVar(&traceprofile, "traceprofile", "", "write an execution trace to `file`")
 	flag.StringVar(&benchfile, "bench", "", "append benchmark times to `file`")
 	obj.Flagparse(usage)
 

src/cmd/compile/internal/gc/trace.go

@@ -0,0 +1,27 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.7
+
+package gc
+
+import (
+	"os"
+	tracepkg "runtime/trace"
+)
+
+func init() {
+	traceHandler = traceHandlerGo17
+}
+
+func traceHandlerGo17(traceprofile string) {
+	f, err := os.Create(traceprofile)
+	if err != nil {
+		Fatalf("%v", err)
+	}
+	if err := tracepkg.Start(f); err != nil {
+		Fatalf("%v", err)
+	}
+	atExit(tracepkg.Stop)
+}

src/cmd/compile/internal/gc/util.go

@@ -33,6 +33,8 @@ var (
 	cpuprofile     string
 	memprofile     string
 	memprofilerate int64
+	traceprofile   string
+	traceHandler   func(string)
 )
 
 func startProfile() {
@@ -61,4 +63,7 @@ func startProfile() {
 			}
 		})
 	}
+	if traceprofile != "" && traceHandler != nil {
+		traceHandler(traceprofile)
+	}
 }