From patchwork Thu Jul  1 11:05:39 2010
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Subject: 0008-Don-t-kill-generated-expressions-in-hoist_expr_reach
Date: Thu, 01 Jul 2010 01:05:39 -0000
From: Maxim Kuvyrkov <maxim@codesourcery.com>
X-Patchwork-Id: 57533
Message-Id: <4C2C7683.4070302@codesourcery.com>
To: Jeff Law <law@redhat.com>, gcc-patches <gcc-patches@gcc.gnu.org>
Cc: Steven Bosscher <stevenb.gcc@gmail.com>

This patch fixes a quirk in hoist_expr_reaches_here_p that makes it to 
avoid moving an expression across its computation in another block.

Bootstrapped and regtested on x86[_64]-linux-gnu and regtested on 
arm-linux-gnu.  This change reduces PIC code size on ARM by 0.3% and 
doesn't increase non-PIC code size.

OK to check in?


diff --git a/gcc/gcse.c b/gcc/gcse.c
index 47d0dba..f37e486 100644
--- a/gcc/gcse.c
+++ b/gcc/gcse.c
@@ -4478,9 +4478,6 @@ hoist_expr_reaches_here_p (basic_block expr_bb, int expr_index, basic_block bb,
 	break;
       else if (pred_bb == expr_bb)
 	continue;
-      /* Does this predecessor generate this expression?  */
-      else if (TEST_BIT (comp[pred_bb->index], expr_index))
-	break;
       else if (! TEST_BIT (transp[pred_bb->index], expr_index))
 	break;