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[X86] Remove zext from vXi32 to vXi64 on indices of gather/scatter instructions if we can prove the pre-extended value is positive. 

Gather/scatter can implicitly sign extend from i32->i64 on indices. So if we know the sign bit of the input to a zext is 0 we can use the implicit extension.

llvm-svn: 321209
This commit is contained in:
Craig Topper 2017-12-20 19:25:33 +00:00
parent d60951f469
commit 07820f2fe4
2 changed files with 62 additions and 0 deletions
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17
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -36273,6 +36273,23 @@ static SDValue combineGatherScatter(SDNode *N, SelectionDAG &DAG,
DCI.AddToWorklist(N);
return SDValue(N, 0);
}
// Try to remove zero extends from 32->64 if we know the sign bit of
// the input is zero.
if (Index.getOpcode() == ISD::ZERO_EXTEND &&
Index.getScalarValueSizeInBits() == 64 &&
Index.getOperand(0).getScalarValueSizeInBits() == 32) {
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);
}
}
}
// Gather and Scatter instructions use k-registers for masks. The type of

45
llvm/test/CodeGen/X86/masked_gather_scatter.ll
View File

@ -2742,3 +2742,48 @@ define void @test_scatter_2i32_index(<2 x double> %a1, double* %base, <2 x i32>
}
declare void @llvm.masked.scatter.v2f64.v2p0f64(<2 x double>, <2 x double*>, i32, <2 x i1>)
define <16 x float> @zext_index(float* %base, <16 x i32> %ind) {
; KNL_64-LABEL: zext_index:
; KNL_64: # %bb.0:
; KNL_64-NEXT: vpandd {{.*}}(%rip){1to16}, %zmm0, %zmm1
; KNL_64-NEXT: kxnorw %k0, %k0, %k1
; KNL_64-NEXT: vgatherdps (%rdi,%zmm1,4), %zmm0 {%k1}
; KNL_64-NEXT: retq
;
; KNL_32-LABEL: zext_index:
; KNL_32: # %bb.0:
; KNL_32-NEXT: movl {{[0-9]+}}(%esp), %eax
; KNL_32-NEXT: vpandd {{\.LCPI.*}}{1to16}, %zmm0, %zmm1
; KNL_32-NEXT: kxnorw %k0, %k0, %k1
; KNL_32-NEXT: vgatherdps (%eax,%zmm1,4), %zmm0 {%k1}
; KNL_32-NEXT: retl
;
; SKX_SMALL-LABEL: zext_index:
; SKX_SMALL: # %bb.0:
; SKX_SMALL-NEXT: vandps {{.*}}(%rip){1to16}, %zmm0, %zmm1
; SKX_SMALL-NEXT: kxnorw %k0, %k0, %k1
; SKX_SMALL-NEXT: vgatherdps (%rdi,%zmm1,4), %zmm0 {%k1}
; SKX_SMALL-NEXT: retq
;
; SKX_LARGE-LABEL: zext_index:
; SKX_LARGE: # %bb.0:
; SKX_LARGE-NEXT: movabsq ${{\.LCPI.*}}, %rax
; SKX_LARGE-NEXT: vandps (%rax){1to16}, %zmm0, %zmm1
; SKX_LARGE-NEXT: kxnorw %k0, %k0, %k1
; SKX_LARGE-NEXT: vgatherdps (%rdi,%zmm1,4), %zmm0 {%k1}
; SKX_LARGE-NEXT: retq
;
; SKX_32-LABEL: zext_index:
; SKX_32: # %bb.0:
; SKX_32-NEXT: movl {{[0-9]+}}(%esp), %eax
; SKX_32-NEXT: vandps {{\.LCPI.*}}{1to16}, %zmm0, %zmm1
; SKX_32-NEXT: kxnorw %k0, %k0, %k1
; SKX_32-NEXT: vgatherdps (%eax,%zmm1,4), %zmm0 {%k1}
; SKX_32-NEXT: retl
%ind_masked = and <16 x i32> %ind, <i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15, i32 15>
%sext_ind = zext <16 x i32> %ind_masked to <16 x i64>
%gep.random = getelementptr float, float *%base, <16 x i64> %sext_ind
%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)
ret <16 x float>%res
}