[Bug target/114429] New: [x86] (neg a) ashifrt>> 31 can be optimized to a > 0.

[liuhongt at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114429

            Bug ID: 114429
           Summary: [x86] (neg a) ashifrt>> 31 can be optimized to a > 0.
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: liuhongt at gcc dot gnu.org
  Target Milestone: ---

typedef unsigned char uint8_t;
uint8_t x264_clip_uint8( int x )
{
    return x&(~255) ? (-x)>>31 : x;
}

void
foo (int* a, int* __restrict b, int n)
{
    for (int i = 0; i != 8; i++)
      b[i] = x264_clip_uint8 (a[i]);
}

gcc -O2 -march=x86-64-v3 -S


foo(int*, int*, int):
        ..
        mov     eax, 255
        vpxor   xmm0, xmm0, xmm0
        vmovd   xmm1, eax
        vpbroadcastd    ymm1, xmm1
        vmovdqu ymm2, YMMWORD PTR [rdi]
        vpminud ymm3, ymm2, ymm1
        vpsubd  ymm0, ymm0, ymm2
        vmovdqa YMMWORD PTR [rsp-32], ymm3
        vpsrad  ymm0, ymm0, 31
        vpcmpeqd        ymm3, ymm2, YMMWORD PTR [rsp-32]
        vpblendvb       ymm0, ymm0, ymm2, ymm3
        vpand   ymm1, ymm1, ymm0
        vmovdqu YMMWORD PTR [rsi], ymm1


It can be better with

        mov     eax, 255
        vmovd   xmm1, eax
        vpxor xmm0, xmm0, xmm0. 
        vpbroadcastd    ymm1, xmm1
        vmovdqu ymm2, YMMWORD PTR [rdi]
        vpminud ymm3, ymm2, ymm1
        vmovdqa YMMWORD PTR [rsp-32], ymm3
        vcmpgtps  ymm0, ymm2, ymm0
        vpcmpeqd        ymm3, ymm2, YMMWORD PTR [rsp-32]
        vpblendvb       ymm0, ymm0, ymm2, ymm3
        vpand   ymm1, ymm1, ymm0
        vmovdqu YMMWORD PTR [rsi], ymm1