On Fri, May 15, 2015 at 7:22 PM, Marc Glisse <marc.gli...@inria.fr> wrote:
> Hello,
>
> we already have the more complicated: x & ~(x & y) -> x & ~y (which I am
> reindenting by the way) and the simpler: (~x | y) & x -> x & y, so I am
> proposing this one for completeness. Regtested on ppc64le-redhat-linux.
Ok (doesn't seem to be in fold-const.c).
Btw, there are quite some (simple) ones only in fold-const.c which are eligible
for moving to match.pd (thus remove them from fold-const.c and implement in
match.pd). Mostly canonicalization ones though.
Richard.
> 2015-05-15 Marc Glisse <marc.gli...@inria.fr>
>
> gcc/
> * match.pd ((x | y) & ~x -> y & ~x, (x & y) | ~x -> y | ~x): New
> simplifications.
> gcc/testsuite/
> * gcc.dg/nand.c: New testcase.
>
> --
> Marc Glisse
> Index: match.pd
> ===================================================================
> --- match.pd (revision 223217)
> +++ match.pd (working copy)
> @@ -257,24 +257,32 @@ along with GCC; see the file COPYING3.
>
> /* x + (x & 1) -> (x + 1) & ~1 */
> (simplify
> (plus:c @0 (bit_and@2 @0 integer_onep@1))
> (if (TREE_CODE (@2) != SSA_NAME || has_single_use (@2))
> (bit_and (plus @0 @1) (bit_not @1))))
>
> /* x & ~(x & y) -> x & ~y */
> /* x | ~(x | y) -> x | ~y */
> (for bitop (bit_and bit_ior)
> - (simplify
> - (bitop:c @0 (bit_not (bitop:c@2 @0 @1)))
> - (if (TREE_CODE (@2) != SSA_NAME || has_single_use (@2))
> - (bitop @0 (bit_not @1)))))
> + (simplify
> + (bitop:c @0 (bit_not (bitop:c@2 @0 @1)))
> + (if (TREE_CODE (@2) != SSA_NAME || has_single_use (@2))
> + (bitop @0 (bit_not @1)))))
> +
> +/* (x | y) & ~x -> y & ~x */
> +/* (x & y) | ~x -> y | ~x */
> +(for bitop (bit_and bit_ior)
> + rbitop (bit_ior bit_and)
> + (simplify
> + (bitop:c (rbitop:c @0 @1) (bit_not@2 @0))
> + (bitop @1 @2)))
>
> (simplify
> (abs (negate @0))
> (abs @0))
> (simplify
> (abs tree_expr_nonnegative_p@0)
> @0)
>
>
> /* Try to fold (type) X op CST -> (type) (X op ((type-x) CST))
> Index: testsuite/gcc.dg/nand.c
> ===================================================================
> --- testsuite/gcc.dg/nand.c (revision 0)
> +++ testsuite/gcc.dg/nand.c (working copy)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-original" } */
> +
> +unsigned f(unsigned x, unsigned y){
> + return (x | y) & ~x;
> +}
> +unsigned g(unsigned x, unsigned y){
> + return ~x & (y | x);
> +}
> +
> +/* { dg-final { scan-tree-dump-times "return ~x & y;" 2 "original" } } */
> +/* { dg-final { cleanup-tree-dump "original" } } */
>
