[PATCH] Fix PR56605

[Bill Schmidt]

This patch (suggested by Steven B) removes some redundant loop
assertions that are currently being missed, resulting in redundant
branches appearing prior to many loops on powerpc64.  Bootstrapped and
tested with no new regressions on powerpc64-unknown-linux-gnu.  Ok for
trunk?

Thanks,
Bill


gcc:

2013-03-13  Bill Schmidt  <wschm...@linux.vnet.ibm.com>
            Steven Bosscher <ste...@gcc.gnu.org>

        PR rtl-optimization/56605
        * loop-iv.c (implies_p): Handle equal RTXs and subregs.

gcc/testsuite:

2013-03-13  Bill Schmidt  wschm...@linux.vnet.ibm.com>

        PR rtl-optimization/56605
        * gcc.target/powerpc/pr56605.c: New.



Index: gcc/testsuite/gcc.target/powerpc/pr56605.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/pr56605.c  (revision 0)
+++ gcc/testsuite/gcc.target/powerpc/pr56605.c  (revision 0)
@@ -0,0 +1,13 @@
+/* PR rtl-optimization/56605 */
+/* { dg-do compile { target { powerpc64-*-* && lp64 } } } */
+/* { dg-options "-O3 -mvsx -mcpu=power7 -fno-unroll-loops 
-fdump-rtl-loop2_doloop" } */
+
+void foo (short* __restrict sb, int* __restrict ia)
+{
+  int i;
+  for (i = 0; i < 4000; i++)
+    ia[i] = (int) sb[i];
+}
+
+/* { dg-final { scan-rtl-dump-times "\\\(compare:CC \\\(subreg:SI \\\(reg:DI" 
1 "loop2_doloop" } } */
+/* { dg-final { cleanup-rtl-dump "loop2_doloop" } } */
Index: gcc/loop-iv.c
===================================================================
--- gcc/loop-iv.c       (revision 196633)
+++ gcc/loop-iv.c       (working copy)
@@ -1496,19 +1496,26 @@ implies_p (rtx a, rtx b)
   rtx op0, op1, opb0, opb1, r;
   enum machine_mode mode;
 
+  if (rtx_equal_p (a, b))
+    return true;
+
   if (GET_CODE (a) == EQ)
     {
       op0 = XEXP (a, 0);
       op1 = XEXP (a, 1);
 
-      if (REG_P (op0))
+      if (REG_P (op0)
+         || (GET_CODE (op0) == SUBREG
+             && REG_P (SUBREG_REG (op0))))
        {
          r = simplify_replace_rtx (b, op0, op1);
          if (r == const_true_rtx)
            return true;
        }
 
-      if (REG_P (op1))
+      if (REG_P (op1)
+         || (GET_CODE (op1) == SUBREG
+             && REG_P (SUBREG_REG (op1))))
        {
          r = simplify_replace_rtx (b, op1, op0);
          if (r == const_true_rtx)