loop.c (express_from): Try harder to unify (* c N) and (* c M) where N and M are constant and N is an...

        * loop.c (express_from): Try harder to unify (* c N) and (* c M)
        where N and M are constant and N is an integer multiple of M.

From-SVN: r28868

1 files changed, 24 insertions, 0 deletions

diff --git a/gcc/loop.c b/gcc/loop.c
index 810f3a2..eb99eca 100644
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -6843,6 +6843,30 @@ express_from (g1, g2)
 
   add = express_from_1 (g1->add_val, g2->add_val, mult);
   if (add == NULL_RTX)
+    {
+      /* Failed.  If we've got a multiplication factor between G1 and G2,
+	 scale G1's addend and try again.  */
+      if (INTVAL (mult) > 1)
+	{
+	  rtx g1_add_val = g1->add_val;
+	  if (GET_CODE (g1_add_val) == MULT
+	      && GET_CODE (XEXP (g1_add_val, 1)) == CONST_INT)
+	    {
+	      HOST_WIDE_INT m;
+	      m = INTVAL (mult) * INTVAL (XEXP (g1_add_val, 1));
+	      g1_add_val = gen_rtx_MULT (GET_MODE (g1_add_val),
+					 XEXP (g1_add_val, 0), GEN_INT (m));
+	    }
+	  else
+	    {
+	      g1_add_val = gen_rtx_MULT (GET_MODE (g1_add_val), g1_add_val,
+					 mult);
+	    }
+
+	  add = express_from_1 (g1_add_val, g2->add_val, const1_rtx);
+	}
+    }
+  if (add == NULL_RTX)
     return NULL_RTX;
 
   /* Form simplified final result.  */