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[X86] Add a combine to recognize when we have two insert subvectors that together write the whole vector, but the starting vector isn't undef.

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In this case we should replace the starting vector with undef.

llvm-svn: 312462
This commit is contained in:
Craig Topper 2017-09-04 01:13:36 +00:00
parent 86c2b6cc78
commit a18221589e
3 changed files with 12 additions and 3 deletions
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12
lib/Target/X86/X86ISelLowering.cpp
View File

@ -35750,6 +35750,18 @@ static SDValue combineInsertSubvector(SDNode *N, SelectionDAG &DAG,
return DAG.getNode(ISD::INSERT_SUBVECTOR, dl, OpVT,
getZeroVector(OpVT, Subtarget, DAG, dl), SubVec2,
Vec.getOperand(2));
// If we are inserting into both halves of the vector, the starting
// vector should be undef. If it isn't, make it so. Only do this if the
// the early insert has no other uses.
// TODO: Should this be a generic DAG combine?
if (!Vec.getOperand(0).isUndef() && Vec.hasOneUse()) {
Vec = DAG.getNode(ISD::INSERT_SUBVECTOR, dl, OpVT, DAG.getUNDEF(OpVT),
SubVec2, Vec.getOperand(2));
DCI.AddToWorklist(Vec.getNode());
return DAG.getNode(ISD::INSERT_SUBVECTOR, dl, OpVT, Vec, SubVec, Idx);
}
}
}

1
test/CodeGen/X86/clear_upper_vector_element_bits.ll
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@ -758,7 +758,6 @@ define <16 x i16> @_clearupper16xi16b(<16 x i16>) nounwind {
; AVX: # BB#0:
; AVX-NEXT: vmovaps {{.*#+}} xmm1 = [255,0,255,0,255,0,255,0,255,0,255,0,255,0,255,0]
; AVX-NEXT: vandps %xmm1, %xmm0, %xmm2
; AVX-NEXT: vblendps {{.*#+}} ymm2 = ymm2[0,1,2,3],ymm0[4,5,6,7]
; AVX-NEXT: vextractf128 $1, %ymm0, %xmm0
; AVX-NEXT: vandps %xmm1, %xmm0, %xmm0
; AVX-NEXT: vinsertf128 $1, %xmm0, %ymm2, %ymm0

2
test/CodeGen/X86/insertelement-zero.ll
View File

@ -473,7 +473,6 @@ define <32 x i8> @insert_v32i8_z123456789ABCDEzGHIJKLMNOPQRSTzz(<32 x i8> %a) {
; AVX1-NEXT: xorl %eax, %eax
; AVX1-NEXT: vpinsrb $0, %eax, %xmm0, %xmm1
; AVX1-NEXT: vpinsrb $15, %eax, %xmm1, %xmm1
; AVX1-NEXT: vblendps {{.*#+}} ymm1 = ymm1[0,1,2,3],ymm0[4,5,6,7]
; AVX1-NEXT: vextractf128 $1, %ymm0, %xmm0
; AVX1-NEXT: vpxor %xmm2, %xmm2, %xmm2
; AVX1-NEXT: vpblendw {{.*#+}} xmm0 = xmm0[0,1,2,3,4,5,6],xmm2[7]
@ -485,7 +484,6 @@ define <32 x i8> @insert_v32i8_z123456789ABCDEzGHIJKLMNOPQRSTzz(<32 x i8> %a) {
; AVX2-NEXT: xorl %eax, %eax
; AVX2-NEXT: vpinsrb $0, %eax, %xmm0, %xmm1
; AVX2-NEXT: vpinsrb $15, %eax, %xmm1, %xmm1
; AVX2-NEXT: vpblendd {{.*#+}} ymm1 = ymm1[0,1,2,3],ymm0[4,5,6,7]
; AVX2-NEXT: vextracti128 $1, %ymm0, %xmm0
; AVX2-NEXT: vpxor %xmm2, %xmm2, %xmm2
; AVX2-NEXT: vpblendw {{.*#+}} xmm0 = xmm0[0,1,2,3,4,5,6],xmm2[7]