From 4cce27a3fa0cc1f13afa6ffa358efa07144e00ec Mon Sep 17 00:00:00 2001
From: Michael Munday <munday@ca.ibm.com>
Date: Fri, 20 Jan 2017 22:03:13 -0500
Subject: [PATCH] cmd/compile: fix constant propagation through s390x MOVDNE
 instructions

The constant propagation rules selected the wrong operand to
propagate. So MOVDNE (move if not equal) propagated operands as if
it were a MOVDEQ (move if equal).

Fixes #18735.

Change-Id: I87ac469172f9df7d5aabaf7106e2936ce54ae202
Reviewed-on: https://go-review.googlesource.com/35498
Run-TryBot: Michael Munday <munday@ca.ibm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/cmd/compile/internal/ssa/gen/S390X.rules |  6 +++---
 src/cmd/compile/internal/ssa/rewriteS390X.go | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/cmd/compile/internal/ssa/gen/S390X.rules b/src/cmd/compile/internal/ssa/gen/S390X.rules
index 3e0533a951..be0d581fe0 100644
--- a/src/cmd/compile/internal/ssa/gen/S390X.rules
+++ b/src/cmd/compile/internal/ssa/gen/S390X.rules
@@ -885,9 +885,9 @@
 (MOVDEQ y _ (FlagLT)) -> y
 (MOVDEQ y _ (FlagGT)) -> y
 
-(MOVDNE _ y (FlagEQ)) -> y
-(MOVDNE x _ (FlagLT)) -> x
-(MOVDNE x _ (FlagGT)) -> x
+(MOVDNE y _ (FlagEQ)) -> y
+(MOVDNE _ x (FlagLT)) -> x
+(MOVDNE _ x (FlagGT)) -> x
 
 (MOVDLT y _ (FlagEQ)) -> y
 (MOVDLT _ x (FlagLT)) -> x
diff --git a/src/cmd/compile/internal/ssa/rewriteS390X.go b/src/cmd/compile/internal/ssa/rewriteS390X.go
index 7d023bcf8b..5acaf2dbdc 100644
--- a/src/cmd/compile/internal/ssa/rewriteS390X.go
+++ b/src/cmd/compile/internal/ssa/rewriteS390X.go
@@ -9847,11 +9847,11 @@ func rewriteValueS390X_OpS390XMOVDNE(v *Value, config *Config) bool {
 		v.AddArg(cmp)
 		return true
 	}
-	// match: (MOVDNE _ y (FlagEQ))
+	// match: (MOVDNE y _ (FlagEQ))
 	// cond:
 	// result: y
 	for {
-		y := v.Args[1]
+		y := v.Args[0]
 		v_2 := v.Args[2]
 		if v_2.Op != OpS390XFlagEQ {
 			break
@@ -9861,11 +9861,11 @@ func rewriteValueS390X_OpS390XMOVDNE(v *Value, config *Config) bool {
 		v.AddArg(y)
 		return true
 	}
-	// match: (MOVDNE x _ (FlagLT))
+	// match: (MOVDNE _ x (FlagLT))
 	// cond:
 	// result: x
 	for {
-		x := v.Args[0]
+		x := v.Args[1]
 		v_2 := v.Args[2]
 		if v_2.Op != OpS390XFlagLT {
 			break
@@ -9875,11 +9875,11 @@ func rewriteValueS390X_OpS390XMOVDNE(v *Value, config *Config) bool {
 		v.AddArg(x)
 		return true
 	}
-	// match: (MOVDNE x _ (FlagGT))
+	// match: (MOVDNE _ x (FlagGT))
 	// cond:
 	// result: x
 	for {
-		x := v.Args[0]
+		x := v.Args[1]
 		v_2 := v.Args[2]
 		if v_2.Op != OpS390XFlagGT {
 			break