[backport from gcc-4.7/trunk, PR43513 fix part 6, PR50251 regression fix part 1 <mikpe@it.uu.se>]

gcc/

2011-09-14  Tom de Vries  <tom@codesourcery.com>

	PR middle-end/50251
	* explow.c (emit_stack_restore): Set crtl->need_drap if
	stack_restore is emitted.

--- gcc-4.6.1/gcc/explow.c.~1~	2011-03-03 22:56:58.000000000 +0100
+++ gcc-4.6.1/gcc/explow.c	2011-09-23 12:49:50.000000000 +0200
@@ -1025,6 +1025,20 @@ emit_stack_restore (enum save_level save
   /* The default is that we use a move insn.  */
   rtx (*fcn) (rtx, rtx) = gen_move_insn;
 
+  /* If stack_realign_drap, the x86 backend emits a prologue that aligns both
+     STACK_POINTER and HARD_FRAME_POINTER.
+     If stack_realign_fp, the x86 backend emits a prologue that aligns only
+     STACK_POINTER. This renders the HARD_FRAME_POINTER unusable for accessing
+     aligned variables, which is reflected in ix86_can_eliminate.
+     We normally still have the realigned STACK_POINTER that we can use.
+     But if there is a stack restore still present at reload, it can trigger 
+     mark_not_eliminable for the STACK_POINTER, leaving no way to eliminate
+     FRAME_POINTER into a hard reg.
+     To prevent this situation, we force need_drap if we emit a stack
+     restore.  */
+  if (SUPPORTS_STACK_ALIGNMENT)
+    crtl->need_drap = true;
+
   /* See if this machine has anything special to do for this kind of save.  */
   switch (save_level)
     {