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[X86] When removing sign extends from gather/scatter indices, make sure we handle UpdateNodeOperands finding an existing node to CSE with.

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If this happens the operands aren't updated and the existing node is returned. Make sure we pass this existing node up to the DAG combiner so that a proper replacement happens. Otherwise we get stuck in an infinite loop with an unoptimized node.

llvm-svn: 338090
This commit is contained in:
Craig Topper 2018-07-27 00:00:30 +00:00
parent 136b0d96f0
commit 2ad9a263b5
2 changed files with 71 additions and 15 deletions
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35
lib/Target/X86/X86ISelLowering.cpp
View File

@ -38100,12 +38100,14 @@ static SDValue combineGatherScatter(SDNode *N, SelectionDAG &DAG,
Index.getOperand(0).getScalarValueSizeInBits() <= 32) {
SmallVector<SDValue, 5> NewOps(N->op_begin(), N->op_end());
NewOps[4] = Index.getOperand(0);
DAG.UpdateNodeOperands(N, NewOps);
// The original sign extend has less users, add back to worklist in case
// it needs to be removed
DCI.AddToWorklist(Index.getNode());
DCI.AddToWorklist(N);
return SDValue(N, 0);
SDNode *Res = DAG.UpdateNodeOperands(N, NewOps);
if (Res == N) {
// The original sign extend has less users, add back to worklist in
// case it needs to be removed
DCI.AddToWorklist(Index.getNode());
DCI.AddToWorklist(N);
}
return SDValue(Res, 0);
}
}
@ -38118,9 +38120,10 @@ static SDValue combineGatherScatter(SDNode *N, SelectionDAG &DAG,
Index = DAG.getSExtOrTrunc(Index, DL, IndexVT);
SmallVector<SDValue, 5> NewOps(N->op_begin(), N->op_end());
NewOps[4] = Index;
DAG.UpdateNodeOperands(N, NewOps);
DCI.AddToWorklist(N);
return SDValue(N, 0);
SDNode *Res = DAG.UpdateNodeOperands(N, NewOps);
if (Res == N)
DCI.AddToWorklist(N);
return SDValue(Res, 0);
}
// Try to remove zero extends from 32->64 if we know the sign bit of
@ -38131,12 +38134,14 @@ static SDValue combineGatherScatter(SDNode *N, SelectionDAG &DAG,
if (DAG.SignBitIsZero(Index.getOperand(0))) {
SmallVector<SDValue, 5> NewOps(N->op_begin(), N->op_end());
NewOps[4] = Index.getOperand(0);
DAG.UpdateNodeOperands(N, NewOps);
// The original zero extend has less users, add back to worklist in case
// it needs to be removed
DCI.AddToWorklist(Index.getNode());
DCI.AddToWorklist(N);
return SDValue(N, 0);
SDNode *Res = DAG.UpdateNodeOperands(N, NewOps);
if (Res == N) {
// The original sign extend has less users, add back to worklist in
// case it needs to be removed
DCI.AddToWorklist(Index.getNode());
DCI.AddToWorklist(N);
}
return SDValue(Res, 0);
}
}
}

51
test/CodeGen/X86/masked_gather_scatter.ll
View File

@ -2928,3 +2928,54 @@ define void @test_scatter_setcc_split(double* %base, <16 x i32> %ind, <16 x i32>
call void @llvm.masked.scatter.v16f64.v16p0f64(<16 x double> %src0, <16 x double*> %gep.random, i32 4, <16 x i1> %mask)
ret void
}
; This test case previously triggered an infinite loop when the two gathers became identical after DAG combine removed the sign extend.
define <16 x float> @test_sext_cse(float* %base, <16 x i32> %ind, <16 x i32>* %foo) {
; KNL_64-LABEL: test_sext_cse:
; KNL_64: # %bb.0:
; KNL_64-NEXT: vmovaps %zmm0, (%rsi)
; KNL_64-NEXT: kxnorw %k0, %k0, %k1
; KNL_64-NEXT: vgatherdps (%rdi,%zmm0,4), %zmm1 {%k1}
; KNL_64-NEXT: vaddps %zmm1, %zmm1, %zmm0
; KNL_64-NEXT: retq
;
; KNL_32-LABEL: test_sext_cse:
; KNL_32: # %bb.0:
; KNL_32-NEXT: movl {{[0-9]+}}(%esp), %eax
; KNL_32-NEXT: movl {{[0-9]+}}(%esp), %ecx
; KNL_32-NEXT: vmovaps %zmm0, (%ecx)
; KNL_32-NEXT: kxnorw %k0, %k0, %k1
; KNL_32-NEXT: vgatherdps (%eax,%zmm0,4), %zmm1 {%k1}
; KNL_32-NEXT: vaddps %zmm1, %zmm1, %zmm0
; KNL_32-NEXT: retl
;
; SKX-LABEL: test_sext_cse:
; SKX: # %bb.0:
; SKX-NEXT: vmovaps %zmm0, (%rsi)
; SKX-NEXT: kxnorw %k0, %k0, %k1
; SKX-NEXT: vgatherdps (%rdi,%zmm0,4), %zmm1 {%k1}
; SKX-NEXT: vaddps %zmm1, %zmm1, %zmm0
; SKX-NEXT: retq
;
; SKX_32-LABEL: test_sext_cse:
; SKX_32: # %bb.0:
; SKX_32-NEXT: movl {{[0-9]+}}(%esp), %eax
; SKX_32-NEXT: movl {{[0-9]+}}(%esp), %ecx
; SKX_32-NEXT: vmovaps %zmm0, (%ecx)
; SKX_32-NEXT: kxnorw %k0, %k0, %k1
; SKX_32-NEXT: vgatherdps (%eax,%zmm0,4), %zmm1 {%k1}
; SKX_32-NEXT: vaddps %zmm1, %zmm1, %zmm0
; SKX_32-NEXT: retl
%broadcast.splatinsert = insertelement <16 x float*> undef, float* %base, i32 0
%broadcast.splat = shufflevector <16 x float*> %broadcast.splatinsert, <16 x float*> undef, <16 x i32> zeroinitializer
%sext_ind = sext <16 x i32> %ind to <16 x i64>
%gep.random = getelementptr float, <16 x float*> %broadcast.splat, <16 x i64> %sext_ind
store <16 x i32> %ind, <16 x i32>* %foo
%res = call <16 x float> @llvm.masked.gather.v16f32.v16p0f32(<16 x float*> %gep.random, i32 4, <16 x i1> <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>, <16 x float> undef)
%gep.random2 = getelementptr float, <16 x float*> %broadcast.splat, <16 x i32> %ind
%res2 = call <16 x float> @llvm.masked.gather.v16f32.v16p0f32(<16 x float*> %gep.random2, i32 4, <16 x i1> <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>, <16 x float> undef)
%res3 = fadd <16 x float> %res2, %res
ret <16 x float>%res3
}