[llvm-bugs] [Bug 28678] New: [X86][AVX] Repeated subvector insertions during insertion of elements into upper subvectors

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28678

            Bug ID: 28678
           Summary: [X86][AVX] Repeated subvector insertions during
                    insertion of elements into upper subvectors
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: llvm-bugs at lists.llvm.org, spatel+llvm at rotateright.com
    Classification: Unclassified

Insertion of elements into an upper subvector results in duplicated insertions
of the subvector.

This might be fixable generally in DAGCombiner and might not be X86 specific.

test/CodeGen/X86/insertelement-zero.ll 

define <32 x i8> @insert_v32i8_z123456789ABCDEzGHIJKLMNOPQRSTzz(<32 x i8> %a) {
; AVX1-LABEL: insert_v32i8_z123456789ABCDEzGHIJKLMNOPQRSTzz:
; AVX1:       # BB#0:
; AVX1-NEXT:    xorl %eax, %eax
; AVX1-NEXT:    vpinsrb $0, %eax, %xmm0, %xmm1
; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0,1,2,3],ymm0[4,5,6,7]
; AVX1-NEXT:    vpinsrb $15, %eax, %xmm0, %xmm1
; AVX1-NEXT:    vblendps {{.*#+}} ymm0 = ymm1[0,1,2,3],ymm0[4,5,6,7]
; AVX1-NEXT:    vextractf128 $1, %ymm0, %xmm1
; AVX1-NEXT:    vpinsrb $14, %eax, %xmm1, %xmm1
; AVX1-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
; AVX1-NEXT:    vpinsrb $15, %eax, %xmm1, %xmm1
; AVX1-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
; AVX1-NEXT:    retq
; 
; AVX2-LABEL: insert_v32i8_z123456789ABCDEzGHIJKLMNOPQRSTzz:
; AVX2:       # BB#0:
; AVX2-NEXT:    xorl %eax, %eax
; AVX2-NEXT:    vpinsrb $0, %eax, %xmm0, %xmm1
; AVX2-NEXT:    vpblendd {{.*#+}} ymm0 = ymm1[0,1,2,3],ymm0[4,5,6,7]
; AVX2-NEXT:    vpinsrb $15, %eax, %xmm0, %xmm1
; AVX2-NEXT:    vpblendd {{.*#+}} ymm0 = ymm1[0,1,2,3],ymm0[4,5,6,7]
; AVX2-NEXT:    vextracti128 $1, %ymm0, %xmm1
; AVX2-NEXT:    vpinsrb $14, %eax, %xmm1, %xmm1
; AVX2-NEXT:    vinserti128 $1, %xmm1, %ymm0, %ymm0
; AVX2-NEXT:    vpinsrb $15, %eax, %xmm1, %xmm1
; AVX2-NEXT:    vinserti128 $1, %xmm1, %ymm0, %ymm0
; AVX2-NEXT:    retq
  %1 = insertelement <32 x i8> %a, i8 0, i32 0
  %2 = insertelement <32 x i8> %1, i8 0, i32 15
  %3 = insertelement <32 x i8> %2, i8 0, i32 30
  %4 = insertelement <32 x i8> %3, i8 0, i32 31
  ret <32 x i8> %4
}

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