re PR tree-optimization/66423 (a % (1 << b) no longer gets folded to a & (1 << b) for unsigned a)

2015-06-09  Richard Biener  <rguenther@suse.de>

	PR middle-end/66423
	* match.pd: Handle A % (unsigned)(1 << B).

	* gcc.dg/fold-modpow2.c: New testcase.

From-SVN: r224279

gcc/ChangeLog

+2015-06-09  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/66423
+	* match.pd: Handle A % (unsigned)(1 << B).
+
 2015-06-09  Aldy Hernandez  <aldyh@redhat.com>
 
 	* varasm.c (output_object_block_htab): Remove.

gcc/match.pd

@@ -248,11 +248,12 @@ along with GCC; see the file COPYING3.  If not see
  (lshift INTEGER_CST@1 @2))
 (for mod (trunc_mod floor_mod)
  (simplify
-  (mod @0 (power_of_two_cand@1 @2))
+  (mod @0 (convert?@3 (power_of_two_cand@1 @2)))
   (if ((TYPE_UNSIGNED (type)
 	|| tree_expr_nonnegative_p (@0))
+	&& tree_nop_conversion_p (type, TREE_TYPE (@3))
 	&& integer_pow2p (@2) && tree_int_cst_sgn (@2) > 0)
-   (bit_and @0 (minus @1 { build_int_cst (TREE_TYPE (@1), 1); })))))
+   (bit_and @0 (convert (minus @1 { build_int_cst (TREE_TYPE (@1), 1); }))))))
 
 /* X % Y is smaller than Y.  */
 (for cmp (lt ge)

gcc/testsuite/ChangeLog

 2015-06-09  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/66423
+	* gcc.dg/fold-modpow2.c: New testcase.
+
+2015-06-09  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/66419
 	* gcc.dg/vect/bb-slp-37.c: New testcase.
 

gcc/testsuite/gcc.dg/fold-modpow2.c

+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+unsigned int
+my_mod (unsigned int a, unsigned int b)
+{
+  return a % (1 << b);
+}
+
+/* The above should be simplified to (unsigned int) ((1 << b) + -1) & a */
+/* { dg-final { scan-tree-dump "& a;" "original" } } */