PR35542 Fix fwprop only propagates one operand

[hutchinsonandy@aim.com]

Can this be approved and commiited please or inform me in the errors of 
my ways?


Andy



-----Original Message-----
From: Andy H <hutchinsonandy@aim.com>
To: gcc-patches@gcc.gnu.org; Paolo Bonzini <bonzini@gnu.org>; 
aoliva@redhat.com
Sent: Thu, 20 Mar 2008 5:23 pm
Subject: PR35542 Fix fwprop only propagates one operand


This patch fixes problem where incorrect comparison of RTL causes 
fwprop to omit propagating registers if one propagation has already 
modified the instruction. 
I believe this is a regression as it seemed to have originated from DF 
changes. 
 
Further details are shown in 
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35542 
 
The attached copy is the same change listed in the PR updated against 
todays HEAD. 
 
The fix uses reg_mentioned_p which does not rely on exact equality of 
LOC - as this will get changed by an earlier propagation. 
 
This patch has been regression tested courtesy of Mike Stein: 
 
the patch "http://gcc.gnu.org/bugzilla/attachment.cgi?id=15300" caused 
0 regressions when applied against trunk, svn revision 133362 for the 
target x86_64. 
 
configure flags used for this regression test: 
--enable-languages=all \ 
--disable-nls \ 
--enable-checking=yes,rtl,df,fold 
 
A short test with linux-2.6.24 (make allmodconfig;make) showed no new 
ICEs. 
 
I have also tested this on AVR target under Cygwin with no regressions. 
 
Please consider this for approval. My paperwork in on file with FSF. 
 
Andy Hutchinson <hutchinsonamdy@aim.com> 
 
  * fwprop.c (forward_propagate_and_simplify): Replace 
  loc_reg_mentioned_in_p with reg_mentioned_p so that   modified RTL 
can be matched. 
 
 



Index: fwprop.c
===================================================================
--- fwprop.c    (revision 133399)
+++ fwprop.c    (working copy)
@@ -932,7 +932,7 @@
   else
     parent = PATTERN (use_insn);

-  if (!loc_mentioned_in_p (DF_REF_LOC (use), parent))
+  if (!reg_mentioned_p (DF_REF_REG (use), parent))
     return;

   def_insn = DF_REF_INSN (def);