On Tue, Jul 21, 2015 at 11:16 AM, Hurugalawadi, Naveen
<[email protected]> wrote:
> Hi,
>
>>> For signed types with TYPE_OVERFLOW_UNDEFINED
>>> you can simply cancel the operation (even for non-power-of-two multipliers).
>
> Thanks for the review and comments.
>
> Please find attached the modified patch as per your comments.
>
> Please review the same and let me know if any further modifications are
> required.
>
> Regression Tested on X86_64.
@@ -280,6 +280,20 @@ 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 (unsigned t * 2)/2 -> unsigned t & 0x7FFFFFFF. */
+(simplify
+ (exact_div (mult @0 INTEGER_CST@1) @1)
+ (if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
+ @0))
The comment applies to the pattern below and the pattern above lacks a comment
+(simplify
+ (trunc_div (mult @0 integer_pow2p@1) @1)
+ (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
+ (with { tree n2 = build_int_cst (TREE_TYPE (@0),
+ wi::exact_log2 (@1)); }
+ (bit_and @0 (rshift (lshift { build_minus_one_cst (TREE_TYPE (@0)); }
+ { n2; }) { n2; })))))
please use
(with
{
int n2 = wi::exact_log2 (@1);
tree mask = wide_int_to_tree (type, wi::rshift (wi::lshift (-1, n2), n2));
}
(bit_and @0 { mask; }))))
in fact, the -1 << log2 >> log2 looks like it does wi::mask
(TYPE_PRECISION (type) - wi::exact_log2 (@1), false, TYPE_PRECISION
(type));
so using wi::mask is prefered here.
Thanks,
Richard.
> Thanks,
> Naveen
>
> gcc/testsuite/ChangeLog:
>
> 2015-07-21 Naveen H.S <[email protected]>
>
> PR middle-end/25529
> * gcc.dg/pr25529.c: New test.
>
> gcc/ChangeLog:
>
> 2015-07-21 Naveen H.S <[email protected]>
>
> 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.
