[backport from gcc-4.7/trunk r179188, fixes PR45771 <mikpe@it.uu.se>]

gcc/

2011-09-26  Eric Botcazou  <ebotcazou@adacore.com>

	* ifcvt.c (noce_try_cmove_arith): Use may_trap_or_fault_p in lieu of
	may_trap_p to detect loads that may trap of fault.

gcc/testsuite/

2011-09-26  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/opt21.adb: New test.
	* gnat.dg/opt21_pkg.ad[sb]: New helper.

--- gcc-4.6.2/gcc/ifcvt.c.~1~	2010-12-14 01:23:40.000000000 +0100
+++ gcc-4.6.2/gcc/ifcvt.c	2012-02-05 22:36:16.000000000 +0100
@@ -1512,9 +1512,9 @@ noce_try_cmove_arith (struct noce_if_inf
     }
 
   /* ??? We could handle this if we knew that a load from A or B could
-     not fault.  This is also true if we've already loaded
+     not trap or fault.  This is also true if we've already loaded
      from the address along the path from ENTRY.  */
-  else if (may_trap_p (a) || may_trap_p (b))
+  else if (may_trap_or_fault_p (a) || may_trap_or_fault_p (b))
     return FALSE;
 
   /* if (test) x = a + b; else x = c - d;
--- gcc-4.6.2/gcc/testsuite/gnat.dg/opt21.adb.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.2/gcc/testsuite/gnat.dg/opt21.adb	2012-02-05 22:36:16.000000000 +0100
@@ -0,0 +1,11 @@
+-- { dg-do run }
+-- { dg-options "-O2" }
+
+with System;
+with Opt21_Pkg; use Opt21_Pkg;
+
+procedure Opt21 is
+   V : System.Address := Convert (null);
+begin
+   null;
+end;
--- gcc-4.6.2/gcc/testsuite/gnat.dg/opt21_pkg.adb.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.2/gcc/testsuite/gnat.dg/opt21_pkg.adb	2012-02-05 22:36:16.000000000 +0100
@@ -0,0 +1,17 @@
+package body Opt21_Pkg is
+
+   function Get_Object (Object : not null access R) return System.Address is
+   begin
+      return Object.Ptr;
+   end;
+
+   function Convert (W : Obj) return System.Address is
+   begin
+      if W = null then
+         return System.Null_Address;
+      else
+         return Get_Object (W);
+      end if;
+   end;
+
+end Opt21_Pkg;
--- gcc-4.6.2/gcc/testsuite/gnat.dg/opt21_pkg.ads.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.2/gcc/testsuite/gnat.dg/opt21_pkg.ads	2012-02-05 22:36:16.000000000 +0100
@@ -0,0 +1,15 @@
+with System;
+
+package Opt21_Pkg is
+
+   type R is record
+      Ptr : System.Address := System.Null_Address;
+   end record;
+
+   type Obj is access all R;
+
+   function Get_Object (Object : not null access R) return System.Address;
+
+   function Convert (W : Obj) return System.Address;
+
+end Opt21_Pkg;