[backport gcc-4.9/trunk r199049 <mikpe@it.uu.se>]

List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>
Date: Fri, 3 May 2013 14:10:19 +0100
From: Julian Brown <julian at codesourcery dot com>
Subject: [PATCH] Fix latent bug in RTL GCSE/PRE (PR57159)

Hi,

This is a patch which fixes a latent bug in RTL GCSE/PRE, described
more fully in:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57159

I haven't been able to reproduce the problem on mainline (nor on a
supported target). Maybe someone more familiar with the code in question
than I am can tell if the patch is correct nonetheless?

Thanks,

Julian

gcc/

2013-05-17  Julian Brown  <julian@codesourcery.com>

	* gcse.c (compute_ld_motion_mems): If a non-simple MEM is
	found in a REG_EQUAL note, invalidate it.

--- gcc-4.7.3/gcc/gcse.c.~1~	2012-11-27 21:26:57.000000000 +0100
+++ gcc-4.7.3/gcc/gcse.c	2013-05-18 11:52:19.121141687 +0200
@@ -3482,6 +3482,8 @@ compute_ld_motion_mems (void)
 		{
 		  rtx src = SET_SRC (PATTERN (insn));
 		  rtx dest = SET_DEST (PATTERN (insn));
+		  rtx note = find_reg_equal_equiv_note (insn);
+		  rtx src_eq;
 
 		  /* Check for a simple LOAD...  */
 		  if (MEM_P (src) && simple_mem (src))
@@ -3498,6 +3500,15 @@ compute_ld_motion_mems (void)
 		      invalidate_any_buried_refs (src);
 		    }
 
+		  if (note != 0 && REG_NOTE_KIND (note) == REG_EQUAL)
+		    src_eq = XEXP (note, 0);
+		  else
+		    src_eq = NULL_RTX;
+
+		  if (src_eq != NULL_RTX
+		      && !(MEM_P (src_eq) && simple_mem (src_eq)))
+		    invalidate_any_buried_refs (src_eq);
+
 		  /* Check for stores. Don't worry about aliased ones, they
 		     will block any movement we might do later. We only care
 		     about this exact pattern since those are the only