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[Bug middle-end/50251] [4.7 Regression] Revision 178353 caused many test failures


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50251

--- Comment #16 from vries at gcc dot gnu.org 2011-09-02 22:47:42 UTC ---
Started testing patch from comment 9, augmented with comments:
...
Index: explow.c
===================================================================
--- explow.c (revision 178145)
+++ explow.c (working copy)
@@ -1062,6 +1062,20 @@ 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)
     {
...


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