Re: [x86_64 PATCH] PR target/106231: Optimize (any_extend:DI (ctz:SI ...)).

[Uros Bizjak <ubizjak@gmail.com>]

On Sat, Jul 16, 2022 at 9:10 PM Roger Sayle <roger@nextmovesoftware.com> wrote:
>
>
> This patch resolves PR target/106231 by providing insns that recognize
> (zero_extend:DI (ctz:SI ...)) and (sign_extend:DI (ctz:SI ...)).  The
> result of ctz:SI is always between 0 and 32 (or undefined), so
> sign_extension is the same as zero_extension, and the result is already
> extended in the destination register.
>
> Things are a little complicated, because the existing implementation
> of *ctzsi2 handles multiple cases, including false dependencies, which
> we continue to support in this patch.
>
> This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> and make -k check with no new failures.  Ok for mainline?
>
> 2022-07-16  Roger Sayle  <roger@nextmovesoftware.com>
>
> gcc/ChangeLog
>         PR target/106231
>         * config/i386/i386.md (*ctzsidi2_<s>ext): New insn_and_split
>         to recognize any_extend:DI of ctz:SI which is implicitly extended.
>         (*ctzsidi2_<s>ext_falsedep): New define_insn to model a DImode
>         extended ctz:SI that has preceding xor to break false dependency.
>
> gcc/testsuite/ChangeLog
>         PR target/106231
>         * gcc.target/i386/pr106231-1.c: New test case.
>         * gcc.target/i386/pr106231-2.c: New test case.

OK.

Thanks,
Uros.

>
> Thanks in advance,
> Roger
> --
>