Hi,
this patch fixes PR50251, which was caused by r178353.
The patch was bootstrapped and reg-tested on i686 and x86_64.
On i686, the test-cases reported failing in PR50251 pass again.
The patch selects the DRAP type stack realignment method in case a stack_restore
is used. If that is not done, the presence of the stack_restore at reload leaves
FRAME_POINTER without an elimination rule for i386 port.
OK for trunk?
Thanks,
- Tom
2011-09-03 Tom de Vries <[email protected]>
* explow.c (emit_stack_restore): Set crtl->need_drap if
stack_restore is emitted.
Index: gcc/explow.c
===================================================================
--- gcc/explow.c (revision 178145)
+++ gcc/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)
{
