Handle GIMPLE_ASSIGNs with different vuse in gimple_equal_p

2013-11-14  Tom de Vries  <tom@codesourcery.com>

	* tree-ssa-tail-merge.c (gimple_equal_p): Add test for structural
	equality for GIMPLE_ASSIGN.

	* gcc.dg/tail-merge-store.c: New test.

From-SVN: r204767

gcc/ChangeLog

 2013-11-14  Tom de Vries  <tom@codesourcery.com>
 
+	* tree-ssa-tail-merge.c (gimple_equal_p): Add test for structural
+	equality for GIMPLE_ASSIGN.
+
+2013-11-14  Tom de Vries  <tom@codesourcery.com>
+
 	* tree-ssa-tail-merge.c (gimple_operand_equal_value_p): Factor new
 	function out of ...
 	(gimple_equal_p): ... here.

gcc/testsuite/ChangeLog

+2013-11-14  Tom de Vries  <tom@codesourcery.com>
+
+	* gcc.dg/tail-merge-store.c: New test.
+
 2013-11-13  Andrew MacLeod  <amacleod@redhat.com>
 
 	* testsuite/g++.dg/plugin/selfassign.c: Include gimple-iterator.h.

gcc/testsuite/gcc.dg/tail-merge-store.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-tail-merge -fdump-tree-pre" } */
+
+int z;
+int x;
+
+void
+f (int c, int d)
+{
+  if (c)
+    z = 5;
+  else
+    {
+      if (d)
+	x = 4;
+      z = 5;
+    }
+}
+
+/* { dg-final { scan-tree-dump-times "duplicate of" 1 "pre"} } */
+/* { dg-final { scan-tree-dump-times "z = 5" 1 "pre"} } */
+/* { dg-final { cleanup-tree-dump "pre" } } */

gcc/tree-ssa-tail-merge.c

@@ -1142,8 +1142,17 @@ gimple_equal_p (same_succ same_succ, gimple s1, gimple s2)
       lhs2 = gimple_get_lhs (s2);
       if (TREE_CODE (lhs1) != SSA_NAME
 	  && TREE_CODE (lhs2) != SSA_NAME)
-	return (vn_valueize (gimple_vdef (s1))
-		== vn_valueize (gimple_vdef (s2)));
+	{
+	  /* If the vdef is the same, it's the same statement.  */
+	  if (vn_valueize (gimple_vdef (s1))
+	      == vn_valueize (gimple_vdef (s2)))
+	    return true;
+
+	  /* Test for structural equality.  */
+	  return (operand_equal_p (lhs1, lhs2, 0)
+		  && gimple_operand_equal_value_p (gimple_assign_rhs1 (s1),
+						   gimple_assign_rhs1 (s2)));
+	}
       else if (TREE_CODE (lhs1) == SSA_NAME
 	       && TREE_CODE (lhs2) == SSA_NAME)
 	return vn_valueize (lhs1) == vn_valueize (lhs2);