re PR go/67101 (mprof.goc:408:5: error: calling ‘__builtin_frame_address’ with a…

re PR go/67101 (mprof.goc:408:5: error: calling ‘__builtin_frame_address’ with a nonzero argument is unsafe [-Werror=frame-address])

	PR go/67101

    runtime: Remove call to __builtin_frame_address.
    
    __builtin_frame_address was only supposed to use nonzero arguments
    for debugging purposes.  Calling it with nonzero arguments can have
    unpredictable results and uses are now marked unsafe when
    -Wframe-address is enabled.
    
    Reviewed-on: https://go-review.googlesource.com/13063

From-SVN: r226525

gcc/go/gofrontend/MERGE

-2bf7c643a1d2f8503070c8e6cb87852026e32400
+d5aad2f400a0f21724e33e4ae48e1583ed8b1a87
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/runtime/mprof.goc

@@ -402,10 +402,9 @@ func ThreadCreateProfile(p Slice) (n int, ok bool) {
 }
 
 func Stack(b Slice, all bool) (n int) {
-	byte *pc, *sp;
+	byte *pc;
 	bool enablegc;
 	
-	sp = runtime_getcallersp(&b);
 	pc = (byte*)(uintptr)runtime_getcallerpc(&b);
 
 	if(all) {
@@ -423,7 +422,6 @@ func Stack(b Slice, all bool) (n int) {
 		g->writebuf = (byte*)b.__values;
 		g->writenbuf = b.__count;
 		USED(pc);
-		USED(sp);
 		runtime_goroutineheader(g);
 		runtime_traceback();
 		runtime_printcreatedby(g);