From patchwork Wed Nov  7 22:11:58 2012
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Subject: patch to fix PR55122
Date: Wed, 07 Nov 2012 12:11:58 -0000
From: Vladimir Makarov <vmakarov@redhat.com>
X-Patchwork-Id: 197733
Message-Id: <509ADCAE.4060907@redhat.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>

The following patch fixes

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55122

   The problem was in generation of reload pseudo for matching operands 
with uniq value which prevented to assign the same hard register for the 
reload pseudo and the original input pseudo when the choice of hard regs 
was quite small (AD regs).

   The patch was successfully bootstrapped and tested on x86/x86-64.

   Committed as rev. 193310.

2012-11-07  Vladimir Makarov  <vmakarov@redhat.com>

         PR rtl-optimization/55122
         * lra-constraints.c (match_reload): Sync values for dead input
         pseudos.

2012-11-07  Vladimir Makarov  <vmakarov@redhat.com>

         PR rtl-optimization/55122
         * gcc.dg/pr55122.c: New test.


Index: lra-constraints.c
===================================================================
--- lra-constraints.c	(revision 193303)
+++ lra-constraints.c	(working copy)
@@ -682,6 +682,11 @@ match_reload (signed char out, signed ch
 	    new_out_reg = gen_lowpart_SUBREG (outmode, reg);
 	  else
 	    new_out_reg = gen_rtx_SUBREG (outmode, reg, 0);
+	  /* If the input reg is dying here, we can use the same hard
+	     register for REG and IN_RTX.  */
+	  if (REG_P (in_rtx)
+	      && find_regno_note (curr_insn, REG_DEAD, REGNO (in_rtx)))
+	    lra_reg_info[REGNO (reg)].val = lra_reg_info[REGNO (in_rtx)].val;
 	}
       else
 	{
@@ -698,6 +703,19 @@ match_reload (signed char out, signed ch
 	     it at the end of LRA work.  */
 	  clobber = emit_clobber (new_out_reg);
 	  LRA_TEMP_CLOBBER_P (PATTERN (clobber)) = 1;
+	  if (GET_CODE (in_rtx) == SUBREG)
+	    {
+	      rtx subreg_reg = SUBREG_REG (in_rtx);
+	      
+	      /* If SUBREG_REG is dying here and sub-registers IN_RTX
+		 and NEW_IN_REG are similar, we can use the same hard
+		 register for REG and SUBREG_REG.  */
+	      if (REG_P (subreg_reg) && GET_MODE (subreg_reg) == outmode
+		  && SUBREG_BYTE (in_rtx) == SUBREG_BYTE (new_in_reg)
+		  && find_regno_note (curr_insn, REG_DEAD, REGNO (subreg_reg)))
+		lra_reg_info[REGNO (reg)].val
+		  = lra_reg_info[REGNO (subreg_reg)].val;
+	    }
 	}
     }
   else
Index: testsuite/gcc.dg/pr55122.c
===================================================================
--- testsuite/gcc.dg/pr55122.c	(revision 0)
+++ testsuite/gcc.dg/pr55122.c	(working copy)
@@ -0,0 +1,14 @@
+/* PR rtl-optimization/55122 */
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+int i, a;
+unsigned long long b;
+
+void f(void)
+{
+    for(i = 0; i < 15; i++)
+        b *= b;
+
+    b *= a ? 0 : b;
+}