[PATCH]i386: Optimize pmovskb on zero_extend of subreg HI of the result [PR98461]

[Uros Bizjak]

On Tue, Jan 5, 2021 at 7:30 AM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Mon, Jan 4, 2021 at 4:59 PM Hongtao Liu <crazylht@gmail.com> wrote:
> >
> > On Mon, Jan 4, 2021 at 4:49 PM Jakub Jelinek <jakub@redhat.com> wrote:
> > >
> > > On Mon, Jan 04, 2021 at 01:56:44PM +0800, Hongtao Liu via Gcc-patches wrote:
> > > > +(define_insn_and_split "*sse2_pmovskb_zexthisi"
> > > > +  [(set (match_operand:SI 0 "register_operand")
> > > > +       (zero_extend:SI (subreg:HI (unspec:SI
> > > > +         [(match_operand:V16QI 1 "register_operand")]
> > > > +          UNSPEC_MOVMSK) 0)))]
> > >
> > > Also, please fix up formatting.  Should be:
> > >         (zero_extend:SI
> > >           (subreg:HI
> > >             (unspec:SI
> > >               [(match_operand:V16QI 1 "register_operand")]
> > >               UNSPEC_MOVMSK) 0)))]
> > > I think.
> > >
> > >         Jakub
> > >
> >
> > Yes, thanks for the review both, and happy new year!
> >
> > --
> > BR,
> > Hongtao
>
> Sorry for the bother, this is an incremental patch to split
> (zero_extend:SI (not:HI (subreg:HI (pmovmskb result:SI)))) to
>
>         pmovmskb        %xmm0, %eax
> -       notl    %eax
> -       movzwl  %ax, %eax
> +       xorl    $65535, %eax
>
>
> The patch is below, regtestes and bootstrapped on x86_64-linux-gnu{-m32,}.
>   Ok for trunk?
>
> The following patch adds define_insn_and_split to optimize
>
>        vpmovmskb       %xmm0, %eax
> -       movzwl  %ax, %eax
>         notl    %eax
>
> and combine splitter to optimize
>
>         pmovmskb        %xmm0, %eax
> -       notl    %eax
> -       movzwl  %ax, %eax
> +       xorl    $65535, %eax
>
> gcc/ChangeLog
>         PR target/98461
>         * config/i386/sse.md (*sse2_pmovskb_zexthisi): New
>         define_insn_and_split for zero_extend of subreg HI of pmovskb
>         result.
>         (*sse2_pmovskb_zexthisi): Add new combine splitters for
>         zero_extend of not of subreg HI of pmovskb result.
>
> gcc/testsuite/ChangeLog
>         * gcc.target/i386/sse-pr98461-2.c: New test.
> ---
>  gcc/config/i386/sse.md                        | 32 +++++++++++++++++++
>  .../gcc.target/i386/sse2-pr98461-2.c          | 25 +++++++++++++++
>  2 files changed, 57 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.target/i386/sse2-pr98461-2.c
>
> diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md
> index d84103807ff..4fcff0800c0 100644
> --- a/gcc/config/i386/sse.md
> +++ b/gcc/config/i386/sse.md
> @@ -16099,6 +16099,38 @@ (define_insn "*sse2_pmovmskb_ext"
>     (set_attr "prefix" "maybe_vex")
>     (set_attr "mode" "SI")])
>
> +(define_insn_and_split "*sse2_pmovskb_zexthisi"
> +  [(set (match_operand:SI 0 "register_operand")
> +        (zero_extend:SI
> +          (subreg:HI
> +            (unspec:SI
> +              [(match_operand:V16QI 1 "register_operand")]
> +              UNSPEC_MOVMSK) 0)))]
> +  "TARGET_SSE2 && ix86_pre_reload_split ()"
> +  "#"
> +  "&& 1"
> +  [(set (match_dup 0)
> +        (unspec:SI [(match_dup 1)] UNSPEC_MOVMSK))])
> +
> +(define_split
> +  [(set (match_operand:SI 0 "register_operand")
> +        (zero_extend:SI
> +          (not:HI
> +            (subreg:HI
> +              (unspec:SI
> +                [(match_operand:V16QI 1 "register_operand")]
> +                UNSPEC_MOVMSK) 0))))]
> +  "TARGET_SSE2"
> +  [(set (match_dup 2)
> +        (unspec:SI [(match_dup 1)] UNSPEC_MOVMSK))
> +   (set (match_dup 0)
> +        (match_dup 3))]

Just write:

(set (match_dup 0)
    (xor:SI (match_dup 2)(const_int 65535))

Uros.

>
> +{
> +  operands[2] = gen_reg_rtx (SImode);
> +  operands[3] = gen_int_mode ((HOST_WIDE_INT_1 << 16) - 1, SImode);
> +  operands[3] = gen_rtx_XOR (SImode, operands[2], operands[3]);
> +})
> +
>  (define_split
>    [(set (match_operand:SI 0 "register_operand")
>          (unspec:SI
> diff --git a/gcc/testsuite/gcc.target/i386/sse2-pr98461-2.c
> b/gcc/testsuite/gcc.target/i386/sse2-pr98461-2.c
> new file mode 100644
> index 00000000000..330272c69bc
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/sse2-pr98461-2.c
> @@ -0,0 +1,25 @@
> +/* PR target/98461 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -msse2 -mno-sse3 -masm=att" } */
> +/* { dg-final { scan-assembler-times "\tpmovmskb\t" 3 } } */
> +/* { dg-final { scan-assembler-not "\tmovzwl" } } */
> +/* { dg-final { scan-assembler-times "\tnotl" 1 } } *
> +/* { dg-final { scan-assembler-times "\txorl" 1 } } */
> +
> +#include <immintrin.h>
> +
> +unsigned int movemask_not1(__m128i logical) {
> +  unsigned short res = (unsigned short)(_mm_movemask_epi8(logical));
> +  return ~res;
> +}
> +
> +unsigned int movemask_not2(__m128i logical) {
> +  unsigned short res = (unsigned short)(_mm_movemask_epi8(logical));
> +  res = ~res;
> +  return res;
> +}
> +
> +unsigned int movemask_zero_extend(__m128i logical) {
> +  unsigned int res = _mm_movemask_epi8(logical);
> +  return res & 0xffff;
> +}
> --
> 2.18.1
>
>
> --
> BR,
> Hongtao