On Tue, 7 Jul 2015, Richard Biener wrote:
On Tue, Jul 7, 2015 at 8:06 AM, Marc Glisse <marc.gli...@inria.fr> wrote:
On Tue, 7 Jul 2015, Hurugalawadi, Naveen wrote:
Please find attached the patch "PR25529.patch" that converts the pattern:-
(unsigned * 2)/2 is into unsigned &0x7FFFFFFF
+/* Simplify (unsigned t * 2)/2 -> unsigned t & 0x7FFFFFFF. */
+(for div (trunc_div ceil_div floor_div round_div exact_div)
+ (simplify
+ (div (mult @0 INTEGER_CST@1) INTEGER_CST@1)
You don't need to repeat INTEGER_CST, the second time @1 is enough.
+ (with { tree n2 = build_int_cst (TREE_TYPE (@0),
+ wi::exact_log2 (@1)); }
+ (if (TYPE_UNSIGNED (TREE_TYPE (@0)))
+ (bit_and @0 (rshift (lshift { build_minus_one_cst (TREE_TYPE (@0)); }
+ { n2; }) { n2; }))))))
What happens if you write t*3/3?
Huh, and you posted this patch twice? See my reply to the other copy
for the correctness issues and better handling of exact_div
They are not the same, one is for left shifts and the other one for right
shifts. And that makes a big difference: in t*c/c, the division is always
exact, so all divisions are equivalent. This is not the case for t/c*c.
--
Marc Glisse
