[backport from gcc-4.7/trunk <mikpe@it.uu.se>]

gcc/

2011-11-07  Sergey Ostanevich  <sergos.gnu@gmail.com>

	PR rtl-optimization/47698
	* ifcvt.c (noce_operand_ok): Return false for mems with side effects.

gcc/testsuite/

2011-11-07  Sergey Ostanevich  <sergos.gnu@gmail.com>

	PR rtl-optimization/47698
	* gcc.target/i386/47698.c: New test.

--- gcc-4.6.2/gcc/ifcvt.c.~1~	2010-12-14 01:23:40.000000000 +0100
+++ gcc-4.6.2/gcc/ifcvt.c	2011-11-19 15:32:00.000000000 +0100
@@ -2311,12 +2311,12 @@ noce_operand_ok (const_rtx op)
 {
   /* We special-case memories, so handle any of them with
      no address side effects.  */
-  if (MEM_P (op))
-    return ! side_effects_p (XEXP (op, 0));
-
   if (side_effects_p (op))
     return FALSE;
 
+  if (MEM_P (op))
+    return ! side_effects_p (XEXP (op, 0));
+
   return ! may_trap_p (op);
 }
 
--- gcc-4.6.2/gcc/testsuite/gcc.target/i386/47698.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.2/gcc/testsuite/gcc.target/i386/47698.c	2011-11-19 15:32:00.000000000 +0100
@@ -0,0 +1,10 @@
+/* { dg-options "-Os" } */
+/* { dg-final { scan-assembler-not "cmov" } } */
+
+extern volatile unsigned long mmio;
+unsigned long foo(int cond)
+{
+      if (cond)
+              return mmio;
+        return 0;
+}