Re: [PR25529] Convert (unsigned t * 2)/2 into unsigned (t & 0x7FFFFFFF)

[Hurugalawadi, Naveen]

>> so using wi::mask is prefered here.

Thanks for your review and comments.

Please find attached the modified patch as per your comments.

Please let me know if this version is okay?

Thanks,
Naveen

2015-07-22  Naveen H.S  <naveen.hurugalaw...@caviumnetworks.com>

gcc/testsuite/ChangeLog:
         PR middle-end/25529
         * gcc.dg/pr25529.c: New test.

gcc/ChangeLog:
         PR middle-end/25529
         * match.pd (exact_div (mult @0 INTEGER_CST@1) @1) :     New simplifier.
         (trunc_div (mult @0 integer_pow2p@1) @1) : New simplifier.

diff --git a/gcc/match.pd b/gcc/match.pd
index 9a66f52..9c8080f 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -29,7 +29,8 @@ along with GCC; see the file COPYING3.  If not see
    integer_each_onep integer_truep
    real_zerop real_onep real_minus_onep
    CONSTANT_CLASS_P
-   tree_expr_nonnegative_p)
+   tree_expr_nonnegative_p
+   integer_pow2p)
 
 /* Operator lists.  */
 (define_operator_list tcc_comparison
@@ -280,6 +281,20 @@ along with GCC; see the file COPYING3.  If not see
 	&& integer_pow2p (@2) && tree_int_cst_sgn (@2) > 0)
    (bit_and @0 (convert (minus @1 { build_int_cst (TREE_TYPE (@1), 1); }))))))
 
+/* Simplify (t * 2)/2 ->  t.  */
+(simplify
+ (exact_div (mult @0 INTEGER_CST@1) @1)
+ (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
+  @0))
+
+/* Simplify (unsigned t * 2)/2 -> unsigned t & 0x7FFFFFFF.  */
+(simplify
+ (trunc_div (mult @0 integer_pow2p@1) @1)
+ (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
+  (bit_and @0 { wide_int_to_tree
+		(type, wi::mask (TYPE_PRECISION (type) - wi::exact_log2 (@1),
+				 false, TYPE_PRECISION (type))); })))
+
 /* X % Y is smaller than Y.  */
 (for cmp (lt ge)
  (simplify
diff --git a/gcc/testsuite/gcc.dg/pr25529.c b/gcc/testsuite/gcc.dg/pr25529.c
new file mode 100644
index 0000000..4d9fe9e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr25529.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+f (unsigned t)
+{
+  return (t * 2) / 2;
+}
+
+/* { dg-final { scan-tree-dump "\& 2147483647" "optimized" } } */