On Thu, 14 Jan 2021, Jakub Jelinek wrote:
> Hi!
>
> This patch optimizes two GIMPLE operations into just one.
> As mentioned in the PR, there is some risk this might create more expensive
> constants, but sometimes it will make them on the other side less expensive,
> it really depends on the exact value.
> And if it is an important issue, we should do it in md or during expansion.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2021-01-13 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/96688
> * match.pd (~(X >> Y) -> ~X >> Y): New simplification if
> ~X can be simplified.
>
> * gcc.dg/tree-ssa/pr96688.c: New test.
> * gcc.dg/tree-ssa/reassoc-37.c: Adjust scan-tree-dump regex.
> * gcc.target/i386/pr66821.c: Likewise.
>
> --- gcc/match.pd.jj 2021-01-13 15:27:13.843788907 +0100
> +++ gcc/match.pd 2021-01-13 18:01:09.706568135 +0100
> @@ -1109,6 +1109,18 @@ (define_operator_list COND_TERNARY
> && wi::to_wide (@1) != wi::min_value (TYPE_PRECISION (type),
> SIGNED))
> (minus (plus @1 { build_minus_one_cst (type); }) @0))))
> +
> +/* ~(X >> Y) -> ~X >> Y if ~X can be simplified. */
> +(simplify
> + (bit_not (rshift:s @0 @1))
> + (if (!TYPE_UNSIGNED (TREE_TYPE (@0)))
> + (rshift (bit_not! @0) @1)
> + /* For logical right shifts, this is possible only if @0 doesn't
> + have MSB set and the logical right shift is changed into
> + arithmetic shift. */
> + (if (!wi::neg_p (tree_nonzero_bits (@0)))
> + (with { tree stype = signed_type_for (TREE_TYPE (@0)); }
> + (convert (rshift (bit_not! (convert:stype @0)) @1))))))
> #endif
>
> /* x + (x & 1) -> (x + 1) & ~1 */
> --- gcc/testsuite/gcc.dg/tree-ssa/pr96688.c.jj 2021-01-13
> 19:12:26.396363212 +0100
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr96688.c 2021-01-13 19:13:32.146628538
> +0100
> @@ -0,0 +1,24 @@
> +/* PR tree-optimization/96688 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +/* { dg-final { scan-tree-dump-times " = -124 >> " 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " >> " 3 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " = ~" 1 "optimized" } } */
> +
> +int
> +foo (int x)
> +{
> + return ~(123 >> x);
> +}
> +
> +unsigned
> +bar (int x)
> +{
> + return ~(123U >> x);
> +}
> +
> +unsigned
> +baz (int x)
> +{
> + return ~(~123U >> x);
> +}
> --- gcc/testsuite/gcc.dg/tree-ssa/reassoc-37.c.jj 2020-01-12
> 11:54:37.609395365 +0100
> +++ gcc/testsuite/gcc.dg/tree-ssa/reassoc-37.c 2021-01-14
> 10:04:03.100243196 +0100
> @@ -12,5 +12,5 @@ foo (int x)
> }
>
> /* Check if the tests have been folded into a bit test. */
> -/* { dg-final { scan-tree-dump "(8784908|0x0*860c0c)" "optimized" { target
> i?86-*-* x86_64-*-* } } } */
> +/* { dg-final { scan-tree-dump "(8784908|-8784909|0x0*860c0c)" "optimized" {
> target i?86-*-* x86_64-*-* } } } */
> /* { dg-final { scan-tree-dump "(<<|>>)" "optimized" { target i?86-*-*
> x86_64-*-* } } } */
> --- gcc/testsuite/gcc.target/i386/pr66821.c.jj 2020-01-12
> 11:54:37.969389933 +0100
> +++ gcc/testsuite/gcc.target/i386/pr66821.c 2021-01-14 10:04:41.210807013
> +0100
> @@ -11,5 +11,5 @@ foo (int x)
> }
>
> /* Check if the tests have been folded into a bit test. */
> -/* { dg-final { scan-tree-dump "(8784908|0x0*860c0c)" "optimized" } } */
> +/* { dg-final { scan-tree-dump "(8784908|-8784909|0x0*860c0c)" "optimized" }
> } */
> /* { dg-final { scan-tree-dump "(<<|>>)" "optimized" } } */
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
