[backport from gcc-4.8/trunk r185971, fixes PR53700 <mikpe@it.uu.se>]

Date: Thu, 29 Mar 2012 13:28:36 -0400
From: Vladimir Makarov <vmakarov at redhat dot com>
Subject: patch to fix a bug in coloring in multi-register allocnos presence.
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>

Frederic Riss sent me IRA dump files for an in-house GCC back-end which 
helped to find a bug in coloring in presence of multi-register 
allocnos.  The bug resulted in making allocno colorable too earlier and 
as a consequence in worse code.  The problem was in preventing 
processing of all conflicting objects of an allocno although the impact 
of each object was taken as 1.  It was my mistake in merging code for 
IRA coloring without cover classes and Bernd's work on multi-object 
allocnos.

The following patch changes SPEC2000 code on x86 (32-bit mode) for vpr, 
gcc, crafty, parser, and vortex and improves scores (up to 0.7% for 
crafty) and decrease code size (up to 0.5% for crafty) for these 
benchmarks.   Frederic Riss also reported considerable improvements for 
his back-end.

The patch was successfully bootstrapped on x86/x86-64 and committed as 
rev. 185971.

gcc/

2012-03-29  Vladimir Makarov  <vmakarov@redhat.com>

	* ira-color.c (setup_left_conflict_sizes_p): Process all
	conflicting objects.

--- gcc-4.7.1/gcc/ira-color.c.~1~	2012-02-22 00:27:59.000000000 +0100
+++ gcc-4.7.1/gcc/ira-color.c	2012-06-17 14:02:46.000000000 +0200
@@ -821,7 +821,6 @@ setup_left_conflict_sizes_p (ira_allocno
   node_preorder_num = node->preorder_num;
   COPY_HARD_REG_SET (node_set, node->hard_regs->set);
   node_check_tick++;
-  curr_allocno_process++;
   for (k = 0; k < nobj; k++)
     {
       ira_object_t obj = ALLOCNO_OBJECT (a, k);
@@ -838,12 +837,10 @@ setup_left_conflict_sizes_p (ira_allocno
 
 	  conflict_data = ALLOCNO_COLOR_DATA (conflict_a);
 	  if (! ALLOCNO_COLOR_DATA (conflict_a)->in_graph_p
-	      || conflict_data->last_process == curr_allocno_process
 	      || ! hard_reg_set_intersect_p (profitable_hard_regs,
 					     conflict_data
 					     ->profitable_hard_regs))
 	    continue;
-	  conflict_data->last_process = curr_allocno_process;
 	  conflict_node = conflict_data->hard_regs_node;
 	  COPY_HARD_REG_SET (conflict_node_set, conflict_node->hard_regs->set);
 	  if (hard_reg_set_subset_p (node_set, conflict_node_set))