[llvm-bugs] [Bug 37549] New: SSE4.1 blend formation logic is not flexible

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37549

            Bug ID: 37549
           Summary: SSE4.1 blend formation logic is not flexible
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: llvm-bugs at lists.llvm.org

https://godbolt.org/g/iHXjfc

#include <smmintrin.h>

void scalar(float* in, float thr, float* replace) {
    if(in[0] >= thr || in[1] >= thr || in[2] >= thr || in[3] >= thr)
    {
      for(int c = 0; c < 4; c++)
      {
        in[c] = replace[c];
      }
    } else {
      for(int c = 0; c < 4; c++)
      {
        in[c] = in[c];
      }
    }
}

__m128 notblend(__m128 in, __m128 thr, __m128 replace) {
    __m128 isoe = _mm_cmpge_ps(in, thr);
    isoe = _mm_or_ps(_mm_unpacklo_ps(isoe, isoe), _mm_unpackhi_ps(isoe, isoe));
    isoe = _mm_or_ps(_mm_unpacklo_ps(isoe, isoe), _mm_unpackhi_ps(isoe, isoe));
    __m128 result = _mm_or_ps(_mm_andnot_ps(isoe, in), _mm_and_ps(isoe,
replace));
    return result;
}

__m128 almostblend(__m128 in, __m128 thr, __m128 replace) {
    __m128 isoe = _mm_cmpge_ps(in, thr);
    __m128 result = _mm_or_ps(_mm_andnot_ps(isoe, in), _mm_and_ps(isoe,
replace));
    return result;
}

__m128 blend(__m128 in, __m128 thr, __m128 replace) {
    __m128 isoe = _mm_cmpge_ps(in, thr);
    __m128 result = _mm_blendv_ps(in, replace, isoe);
    return result;
}



Last two are codegen'ed as vblendvps, the first two aren't.
The first one is likely a vectorizer failure.

The second example, notblend(), is of the most interest here.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180522/a4d433eb/attachment.html>