From 3690e33a205b9cd961dffe95f6ab331a7a080e7f Mon Sep 17 00:00:00 2001
From: Julian Seward <jseward@acm.org>
Date: Fri, 27 Feb 2015 12:51:22 +0000
Subject: [PATCH] fold_Expr: add rules    Xor8/16/32/64(0,t) ==> t   
 Xor8/16/32/64(t,0) ==> t

git-svn-id: svn://svn.valgrind.org/vex/trunk@3094
---
 VEX/priv/ir_opt.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/VEX/priv/ir_opt.c b/VEX/priv/ir_opt.c
index ffd18f95be..f503bef181 100644
--- a/VEX/priv/ir_opt.c
+++ b/VEX/priv/ir_opt.c
@@ -2292,6 +2292,17 @@ static IRExpr* fold_Expr ( IRExpr** env, IRExpr* e )
                   //   e2 = e->Iex.Binop.arg2;
                   //   break;
                   //}
+               } else {
+                  /* Xor8/16/32/64(0,t) ==> t */
+                  if (isZeroU(e->Iex.Binop.arg1)) {
+                     e2 = e->Iex.Binop.arg2;
+                     break;
+                  }
+                  /* Xor8/16/32/64(t,0) ==> t */
+                  if (isZeroU(e->Iex.Binop.arg2)) {
+                     e2 = e->Iex.Binop.arg1;
+                     break;
+                  }
                }
                break;
 
-- 
2.47.2