[llvm-bugs] [Bug 45015] New: [X86][AVX] Failure to generate vaddsubps for pattern after 19b62b79

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45015

            Bug ID: 45015
           Summary: [X86][AVX] Failure to generate vaddsubps for pattern
                    after 19b62b79
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: douglas_yung at playstation.sony.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

Consider the following code:

#include <x86intrin.h>
__m128 haddsub0ps(__m128 a, __m128 b) {
  return (__m128){ a[0] - b[0], a[1] + b[1], a[2] - b[2], a[3] + b[3] };
}

Prior to commit 19b62b79db1bb154b40e8baba9a28ab8aa935b6b, when compiled with
optimizations and avx (-O2 -mavx), the compiler would generate the following
assembly:

vaddsubps       %xmm1, %xmm0, %xmm0

But now the compiler is instead generating the following assembly:

vsubss          %xmm1, %xmm0, %xmm2
vaddps          %xmm1, %xmm0, %xmm3
vblendps        $1, %xmm2, %xmm3, %xmm2 # xmm2 = xmm2[0],xmm3[1,2,3]
vsubps          %xmm1, %xmm0, %xmm0
vblendps        $3, %xmm2, %xmm0, %xmm0 # xmm0 = xmm2[0,1],xmm0[2,3]
vblendps        $8, %xmm3, %xmm0, %xmm0 # xmm0 = xmm0[0,1,2],xmm3[3]

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