re PR tree-optimization/15255 ([tree-ssa] a * 2 + a * 2 is not converted to a * 4)

2008-04-29  Richard Guenther  <rguenther@suse.de>

	PR middle-end/15255
	* fold-const.c (fold_binary): Fold (A + A) * C to A * 2*C.

	* gcc.dg/fold-plusmult.c: New testcase.

From-SVN: r134798

gcc/ChangeLog

 2008-04-29  Richard Guenther  <rguenther@suse.de>
 
+	PR middle-end/15255
+	* fold-const.c (fold_binary): Fold (A + A) * C to A * 2*C.
+
+2008-04-29  Richard Guenther  <rguenther@suse.de>
+
 	* tree-ssa-alias.c (finalize_ref_all_pointers): Remove.
 	(compute_may_aliases): Do not call finalize_ref_all_pointers.
 	(compute_flow_insensitive_aliasing): Do not treat

gcc/fold-const.c

@@ -10154,6 +10154,17 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	    return fold_build2 (LSHIFT_EXPR, type, op1,
 				TREE_OPERAND (arg0, 1));
 
+	  /* (A + A) * C -> A * 2 * C  */
+	  if (TREE_CODE (arg0) == PLUS_EXPR
+	      && TREE_CODE (arg1) == INTEGER_CST
+	      && operand_equal_p (TREE_OPERAND (arg0, 0),
+			          TREE_OPERAND (arg0, 1), 0))
+	    return fold_build2 (MULT_EXPR, type,
+				omit_one_operand (type, TREE_OPERAND (arg0, 0),
+						  TREE_OPERAND (arg0, 1)),
+				fold_build2 (MULT_EXPR, type,
+					     build_int_cst (type, 2) , arg1));
+
 	  strict_overflow_p = false;
 	  if (TREE_CODE (arg1) == INTEGER_CST
 	      && 0 != (tem = extract_muldiv (op0, arg1, code, NULL_TREE,

gcc/testsuite/ChangeLog

 2008-04-29  Richard Guenther  <rguenther@suse.de>
 
+	PR middle-end/15255
+	* gcc.dg/fold-plusmult.c: New testcase.
+
+2008-04-29  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/36077
 	* gcc.c-torture/execute/pr36077.c: New testcase.
 

gcc/testsuite/gcc.dg/fold-plusmult.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+int test1 (int a)
+{
+  return 2*a + 2*a;
+}
+
+int test2 (int a)
+{
+  return (a + a)*2;
+}
+
+/* { dg-final { scan-tree-dump-times "<a> \\\* 4" 2 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */