svn commit: r260530 - stable/8/contrib/gcc

[Pedro F. Giffuni]

Author: pfg
Date: Sat Jan 11 01:50:45 2014
New Revision: 260530
URL: http://svnweb.freebsd.org/changeset/base/260530

Log:
  MFC	r260361:
  
  gcc: Fix optimization bug.
  
  GCC-PR rtl-optimization/34628
  	* combine.c (try_combine): Stop and undo after the first combination
  	if an autoincrement side-effect on the first insn has effectively
  	been lost.

Modified:
  stable/8/contrib/gcc/combine.c
Directory Properties:
  stable/8/   (props changed)
  stable/8/contrib/   (props changed)
  stable/8/contrib/gcc/   (props changed)

Modified: stable/8/contrib/gcc/combine.c
==============================================================================
--- stable/8/contrib/gcc/combine.c	Sat Jan 11 01:45:20 2014	(r260529)
+++ stable/8/contrib/gcc/combine.c	Sat Jan 11 01:50:45 2014	(r260530)
@@ -2370,12 +2370,17 @@ try_combine (rtx i3, rtx i2, rtx i1, int
 
   if (i1 && GET_CODE (newpat) != CLOBBER)
     {
-      /* Before we can do this substitution, we must redo the test done
-	 above (see detailed comments there) that ensures  that I1DEST
-	 isn't mentioned in any SETs in NEWPAT that are field assignments.  */
-
-      if (! combinable_i3pat (NULL_RTX, &newpat, i1dest, NULL_RTX,
-			      0, (rtx*) 0))
+      /* Check that an autoincrement side-effect on I1 has not been lost.
+	 This happens if I1DEST is mentioned in I2 and dies there, and
+	 has disappeared from the new pattern.  */
+      if ((FIND_REG_INC_NOTE (i1, NULL_RTX) != 0
+	   && !i1_feeds_i3
+	   && dead_or_set_p (i2, i1dest)
+	   && !reg_overlap_mentioned_p (i1dest, newpat))
+	  /* Before we can do this substitution, we must redo the test done
+	     above (see detailed comments there) that ensures  that I1DEST
+	     isn't mentioned in any SETs in NEWPAT that are field assignments.  */
+          || !combinable_i3pat (NULL_RTX, &newpat, i1dest, NULL_RTX, 0, 0))
 	{
 	  undo_all ();
 	  return 0;