From 5f9a9433ea5f3e933d9950994edaf45c36a92ffb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Oudompheng?= <oudomphe@phare.normalesup.org>
Date: Tue, 26 Mar 2013 23:35:42 +0100
Subject: [PATCH] cmd/gc: enable racewalk of HMUL nodes.

A HMUL node appears in some constant divisions, but
to observe a false negative in race detector the divisor must be
suitably chosen to make sure the only memory access is
done for HMUL.

R=dvyukov
CC=golang-dev
https://golang.org/cl/7935045
---
 src/cmd/gc/racewalk.c                     | 18 +++++++++---------
 src/pkg/runtime/race/testdata/mop_test.go |  4 ++--
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/cmd/gc/racewalk.c b/src/cmd/gc/racewalk.c
index 80257985dd..fee5cf4226 100644
--- a/src/cmd/gc/racewalk.c
+++ b/src/cmd/gc/racewalk.c
@@ -241,6 +241,7 @@ racewalknode(Node **np, NodeList **init, int wr, int skip)
 	case OXOR:
 	case OSUB:
 	case OMUL:
+	case OHMUL:
 	case OEQ:
 	case ONE:
 	case OLT:
@@ -379,19 +380,18 @@ racewalknode(Node **np, NodeList **init, int wr, int skip)
 	case OPARAM:     // it appears only in fn->exit to copy heap params back
 	case OCLOSUREVAR:// immutable pointer to captured variable
 	case ODOTMETH:   // either part of CALLMETH or CALLPART (lowered to PTRLIT)
+	case OINDREG:    // at this stage, only n(SP) nodes from nodarg
+	case ODCL:       // declarations (without value) cannot be races
+	case ODCLCONST:
+	case ODCLTYPE:
+	case OTYPE:
+	case ONONAME:
+	case OLITERAL:
+	case OSLICESTR:  // always preceded by bounds checking, avoid double instrumentation.
 		goto ret;
 
 	// unimplemented
-	case OSLICESTR:
 	case OAPPEND:
-	case ODCL:
-	case ODCLCONST:
-	case ODCLTYPE:
-	case OLITERAL:
-	case OTYPE:
-	case ONONAME:
-	case OINDREG:
-	case OHMUL:
 		goto ret;
 	}
 
diff --git a/src/pkg/runtime/race/testdata/mop_test.go b/src/pkg/runtime/race/testdata/mop_test.go
index f0fe868ccb..1a7ed96249 100644
--- a/src/pkg/runtime/race/testdata/mop_test.go
+++ b/src/pkg/runtime/race/testdata/mop_test.go
@@ -339,11 +339,11 @@ func TestRaceDiv(t *testing.T) {
 }
 
 func TestRaceDivConst(t *testing.T) {
-	var x, y, z int
+	var x, y, z uint32
 	ch := make(chan int, 2)
 
 	go func() {
-		x = y / 3
+		x = y / 3 // involves only a HMUL node
 		ch <- 1
 	}()
 	go func() {