gc: better loopdepth analysis for labels

This avoids degraded performance caused by extra labels
emitted by inlining (breaking strconv ftoa alloc count unittest) and is better in any case.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5483071

1 files changed, 21 insertions, 0 deletions

diff --git a/test/escape2.go b/test/escape2.go
index 13ebe271d..e4d5084c7 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1011,3 +1011,24 @@ func foo121b() {
 		go fmt.Printf("%d", i)    // ERROR "[.][.][.] argument escapes to heap"
 	}
 }
+
+// a harmless forward jump
+func foo122() {
+	var i *int
+
+	goto L1
+L1:
+	i = new(int)	// ERROR "does not escape"
+	_ = i
+}
+
+// a backward jump, increases loopdepth
+func foo123() {
+	var i *int
+
+L1:
+	i = new(int)  // ERROR "escapes"
+
+	goto L1
+	_ = i
+}
\ No newline at end of file