Re: [PATCH] Optimize kmov + kmov + or to kortest.

[Hongtao Liu]

On Thu, Nov 13, 2025 at 2:22 PM liuhongt <hongtao....@intel.com> wrote:
>
> For instruction sequence like
>         kmovb   %k0, %edx
>         kmovb   %k1, %ecx
>         orb     %cl, %dl
>         je      .L5
>
> if only CCZ is cared, it can be optimized to
>
>         kortestb %k1, %k0
>         je      .L5
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32}.
> Ready push to trunk.
>
> gcc/ChangeLog:
>
>         * config/i386/i386.md (*ior<mode>_ccz_1): New define_insn.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/i386/kortest_ccz-1.c: New test.
> ---
>  gcc/config/i386/i386.md                       | 16 ++++++++++++++++
>  gcc/testsuite/gcc.target/i386/kortest_ccz-1.c | 13 +++++++++++++
>  2 files changed, 29 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.target/i386/kortest_ccz-1.c
>
> diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
> index 3ea2439526b..ae26ef02c22 100644
> --- a/gcc/config/i386/i386.md
> +++ b/gcc/config/i386/i386.md
> @@ -14203,6 +14203,22 @@ (define_insn "*<code>si_2_zext_imm"
>     (set_attr "isa" "*,apx_ndd")
>     (set_attr "mode" "SI")])
>
> +;; It must be put before *<code><mode>_3, the blow one.
> +(define_insn "*ior<mode>_ccz_1"
> +  [(set (reg:CCZ FLAGS_REG)
> +       (compare:CCZ
> +        (ior:SWI1248_AVX512BWDQ_64
> +         (match_operand:SWI1248_AVX512BWDQ_64 1 "nonimmediate_operand" 
> "%0,?k")
> +         (match_operand:SWI1248_AVX512BWDQ_64 2 "<general_operand>" "<g>, 
> k"))
> +        (const_int 0)))
> +   (clobber (match_scratch:SWI1248_AVX512BWDQ_64 0 "=<r>, k"))]
> +  "TARGET_AVX512F && !(MEM_P (operands[1]) && MEM_P (operands[2]))"
> +  "@
> +   or{<imodesuffix>}\t{%2, %0|%0, %2}
> +   kortest<mskmodesuffix>\t{%1, %2|%2, %1}"
> +  [(set_attr "type" "alu,msklog")
> +   (set_attr "mode" "<MODE>")])
> +
>  (define_insn "*<code><mode>_3"
>    [(set (reg FLAGS_REG)
>         (compare (any_or:SWI
> diff --git a/gcc/testsuite/gcc.target/i386/kortest_ccz-1.c 
> b/gcc/testsuite/gcc.target/i386/kortest_ccz-1.c
> new file mode 100644
> index 00000000000..0f8d4bf9f22
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/kortest_ccz-1.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=x86-64-v4 -O3" } */
> +/* { dg-final { scan-assembler-not "kmov" } } */
> +/* { dg-final { scan-assembler "kortest" } } */
> +
> +int
> +foo (int *__restrict a, int* __restrict d, int b, int c, int n)
> +{
> +  for (int i = 0; i != 10000; i++)
> +    if (a[i] > b || d[i] > c)
There's typo here, shou;d be | instead of ||.
> +      return 1;
> +  return 0;
> +}
> --
> 2.34.1
>


-- 
BR,
Hongtao