re PR middle-end/58742 (pointer arithmetic simplification)

2013-10-21  Richard Biener  <rguenther@suse.de>

	PR middle-end/58742
	* fold-const.c (fold_binary_loc): Fold ((T) (X /[ex] C)) * C
	to (T) X for sign-changing conversions (or no conversion).

	* c-c++-common/fold-divmul-1.c: New testcase.

From-SVN: r203890

gcc/ChangeLog

+2013-10-21  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/58742
+	* fold-const.c (fold_binary_loc): Fold ((T) (X /[ex] C)) * C
+	to (T) X for sign-changing conversions (or no conversion).
+
 2013-10-20  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.md (kxnor<mode>): Add FLAGS_REG clobber.

gcc/fold-const.c

@@ -11002,6 +11002,13 @@ fold_binary_loc (location_t loc,
 				fold_build2_loc (loc, MULT_EXPR, type,
 					     build_int_cst (type, 2) , arg1));
 
+	  /* ((T) (X /[ex] C)) * C cancels out if the conversion is
+	     sign-changing only.  */
+	  if (TREE_CODE (arg1) == INTEGER_CST
+	      && TREE_CODE (arg0) == EXACT_DIV_EXPR
+	      && operand_equal_p (arg1, TREE_OPERAND (arg0, 1), 0))
+	    return fold_convert_loc (loc, type, TREE_OPERAND (arg0, 0));
+
 	  strict_overflow_p = false;
 	  if (TREE_CODE (arg1) == INTEGER_CST
 	      && 0 != (tem = extract_muldiv (op0, arg1, code, NULL_TREE,

gcc/testsuite/ChangeLog

+2013-10-21  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/58742
+	* c-c++-common/fold-divmul-1.c: New testcase.
+
 2013-10-21  Michael Zolotukhin  <michael.v.zolotukhin@gmail.com>
 
 	* gcc.target/i386/memset-vector_loop-1.c: New test.

gcc/testsuite/c-c++-common/fold-divmul-1.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+int *
+fx (int *b, int *e)
+{
+  return b + (e - b);
+}
+
+/* { dg-final { scan-tree-dump-not "/\\\[ex\\\]" "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */