[backport from gcc-4.6.4 r191315, for expedited testing <mikpe@it.uu.se>]

gcc/

2012-09-14  Wei Guozhi  <carrot@google.com>

	Backport from 2012-02-13 mainline r184169.

	* cselib.c (expand_loc): Return sp, fp, hfp or cfa base reg right
	away if seen.

--- gcc-4.6.3/gcc/cselib.c.~1~	2012-02-15 00:33:23.000000000 +0100
+++ gcc-4.6.3/gcc/cselib.c	2012-09-15 14:16:12.000000000 +0200
@@ -1237,8 +1237,18 @@ expand_loc (struct elt_loc_list *p, stru
   unsigned int regno = UINT_MAX;
   struct elt_loc_list *p_in = p;
 
-  for (; p; p = p -> next)
+  for (; p; p = p->next)
     {
+      /* Return these right away to avoid returning stack pointer based
+	 expressions for frame pointer and vice versa, which is something
+	 that would confuse DSE.  See the comment in cselib_expand_value_rtx_1
+	 for more details.  */
+      if (REG_P (p->loc)
+	  && (REGNO (p->loc) == STACK_POINTER_REGNUM
+	      || REGNO (p->loc) == FRAME_POINTER_REGNUM
+	      || REGNO (p->loc) == HARD_FRAME_POINTER_REGNUM
+	      || REGNO (p->loc) == cfa_base_preserved_regno))
+	return p->loc;
       /* Avoid infinite recursion trying to expand a reg into a
 	 the same reg.  */
       if ((REG_P (p->loc))