From patchwork Mon Aug 16 22:35:53 2010
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Subject: fix PR/45292,
 miscompilation of sync_bool_compare_and_swap due to deferred pop
Date: Mon, 16 Aug 2010 12:35:53 -0000
From: Paolo Bonzini <bonzini@gnu.org>
X-Patchwork-Id: 61845
Message-Id: <4C69BD49.9040209@gnu.org>
To: GCC Patches <gcc-patches@gcc.gnu.org>

This fixes a bug in expansion of sync_bool_compare_and_swap, where we 
were relying on the CC value from the sync_compare_and_swap optab but 
clobbering it before reading it.  This is due to a 
do_pending_stack_adjust in emit_store_flag_1.  Fixed by doing the stack 
adjust before everything else.

This is a regression from 4.4.  The testcase is libgomp; 
bootstrapped/regtested x86_64-pc-linux-gnu, checked the problematic file 
using -march=i486 -mtune=i586.  Ok for 4.5 and trunk?

Paolo
2010-08-17  Paolo Bonzini  <bonzini@gnu.org>

        * optabs.c (expand_bool_compare_and_swap): Expand pending
        pops before trying the optab.


Index: optabs.c
===================================================================
--- optabs.c	(revision 162940)
+++ optabs.c	(working copy)
@@ -6909,6 +6909,7 @@ expand_bool_compare_and_swap (rtx mem, r
   if (icode == CODE_FOR_nothing)
     return NULL_RTX;
 
+  do_pending_stack_adjust ();
   do
     {
       start_sequence ();