On Wed, 6 May 2020, Jakub Jelinek wrote:
> Hi!
>
> According to my verification proglet, this transformation for signed types
> with undefined overflow doesn't introduce nor remove any UB cases, so should
> be valid even for signed integral types.
> Not using a for because of the :c on plus which can't be there on minus.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2020-05-06 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/94921
> * match.pd (~(~X - Y) -> X + Y, ~(~X + Y) -> X - Y): New
> simplifications.
>
> * gcc.dg/tree-ssa/pr94921.c: New test.
>
> --- gcc/match.pd.jj 2020-05-05 11:36:17.510911674 +0200
> +++ gcc/match.pd 2020-05-05 16:48:59.496883197 +0200
> @@ -1010,6 +1010,14 @@ (define_operator_list COND_TERNARY
> @0))
> #endif
>
> +/* ~(~X - Y) -> X + Y and ~(~X + Y) -> X - Y. */
> +(simplify
> + (bit_not (minus (bit_not @0) @1))
> + (plus @0 @1))
> +(simplify
> + (bit_not (plus:c (bit_not @0) @1))
> + (minus @0 @1))
> +
> /* x + (x & 1) -> (x + 1) & ~1 */
> (simplify
> (plus:c @0 (bit_and:s @0 integer_onep@1))
> --- gcc/testsuite/gcc.dg/tree-ssa/pr94921.c.jj 2020-05-05
> 16:58:32.913192128 +0200
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr94921.c 2020-05-05 16:59:26.231384053
> +0200
> @@ -0,0 +1,18 @@
> +/* PR tree-optimization/94921 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +/* { dg-final { scan-tree-dump " \[ab]_\[0-9]+\\\(D\\\) \\+
> \[ab]_\[0-9]+\\\(D\\\);" "optimized" } } */
> +/* { dg-final { scan-tree-dump " c_\[0-9]+\\\(D\\\) - d_\[0-9]+\\\(D\\\);"
> "optimized" } } */
> +/* { dg-final { scan-tree-dump-not " ~\[abcd]\?_\[0-9]\+" "optimized" } } */
> +
> +int
> +foo (int a, int b)
> +{
> + return ~(~a - b);
> +}
> +
> +int
> +bar (int c, int d)
> +{
> + return ~(~c + d);
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
