[backport from gcc-4.7.0 r177658, fixes IA64 ICE PR53701 <mikpe@it.uu.se>]

From: Alexander Monakov <amonakov at ispras dot ru>
Subject: [PATCH 8/8] Only merge deps status for true dependencies
Date: Wed,  3 Aug 2011 19:30:38 +0400
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>

From: Sergey Grechanik <mouseentity@condor.intra.ispras.ru>

This patch avoids changing speculative bits of a register use when it is moved
up above a speculation check where that register is used as the address
register.  We should only call ds_full_merge when the producer (speculation
check) writes to a register.

(A similar check was in place when selective scheduler was in active
development, but was dropped before it was merged, probably by accident)

gcc/

2011-08-11  Sergey Grechanik  <mouseentity@ispras.ru>

	* sel-sched-ir.c (has_dependence_note_reg_use): Call ds_full_merge
	only if producer writes to the register given by regno.

--- gcc-4.6.3/gcc/sel-sched-ir.c.~1~	2011-06-28 14:19:18.000000000 +0200
+++ gcc-4.6.3/gcc/sel-sched-ir.c	2012-06-17 16:11:06.000000000 +0200
@@ -3157,7 +3157,8 @@ has_dependence_note_reg_use (int regno)
 	  pro_spec_checked_ds = INSN_SPEC_CHECKED_DS (has_dependence_data.pro);
 	  pro_spec_checked_ds = ds_get_max_dep_weak (pro_spec_checked_ds);
 
-	  if (pro_spec_checked_ds != 0)
+	  if (pro_spec_checked_ds != 0
+	      && bitmap_bit_p (INSN_REG_SETS (has_dependence_data.pro), regno))
 	    /* Merge BE_IN_SPEC bits into *DSP.  */
 	    *dsp = ds_full_merge (*dsp, pro_spec_checked_ds,
 				  NULL_RTX, NULL_RTX);