[llvm-bugs] [Bug 36036] New: [DAGCombine] Failure to recognise alternative ISD::ABS pattern

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36036

            Bug ID: 36036
           Summary: [DAGCombine] Failure to recognise alternative ISD::ABS
                    pattern
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: llvm-bugs at lists.llvm.org, spatel+llvm at rotateright.com

__v4si abs(__v4si v) {
    __m128i sign = _mm_srai_epi32( v, 31 );
    return _mm_xor_si128( _mm_add_epi32( v, sign ), sign );
}
__v4si abs_alt(__v4si v) {
    __m128i sign = _mm_srai_epi32( v, 31 );
    return _mm_sub_epi32( _mm_xor_si128( v, sign ), sign );
}

define <4 x i32> @abs(<4 x i32>) {
  %2 = icmp slt <4 x i32> %0, zeroinitializer
  %3 = sub <4 x i32> zeroinitializer, %0
  %4 = select <4 x i1> %2, <4 x i32> %3, <4 x i32> %0
  ret <4 x i32> %4
}

define <4 x i32> @abs_alt(<4 x i32>) {
  %2 = ashr <4 x i32> %0, <i32 31, i32 31, i32 31, i32 31>
  %3 = xor <4 x i32> %2, %0
  %4 = sub <4 x i32> %3, %2
  ret <4 x i32> %4
}

llc -mcpu=btver2

abs:
  vpabsd %xmm0, %xmm0
  retq

abs_alt:
  vpsrad $31, %xmm0, %xmm1
  vpxor %xmm0, %xmm1, %xmm0
  vpsubd %xmm1, %xmm0, %xmm0
  retq

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