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Simplify demanded bits of select sources where the condition is a constant vector

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160835 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Pete Cooper 2012-07-26 23:10:24 +00:00
parent 3ba90d9c0e
commit 7971de4178
3 changed files with 53 additions and 0 deletions
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11
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -899,5 +899,16 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
return &SI;
}
if (VectorType* VecTy = dyn_cast<VectorType>(SI.getType())) {
unsigned VWidth = VecTy->getNumElements();
APInt UndefElts(VWidth, 0);
APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) {
if (V != &SI)
return ReplaceInstUsesWith(SI, V);
return &SI;
}
}
return 0;
}

23
lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
View File

@ -989,6 +989,29 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
}
break;
}
case Instruction::Select: {
APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts);
if (ConstantVector* CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
for (unsigned i = 0; i < VWidth; i++) {
if (CV->getAggregateElement(i)->isNullValue())
LeftDemanded.clearBit(i);
else
RightDemanded.clearBit(i);
}
}
TmpV = SimplifyDemandedVectorElts(I->getOperand(1), LeftDemanded,
UndefElts, Depth+1);
if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
TmpV = SimplifyDemandedVectorElts(I->getOperand(2), RightDemanded,
UndefElts2, Depth+1);
if (TmpV) { I->setOperand(2, TmpV); MadeChange = true; }
// Output elements are undefined if both are undefined.
UndefElts &= UndefElts2;
break;
}
case Instruction::BitCast: {
// Vector->vector casts only.
VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());

19
test/Transforms/InstCombine/vec_demanded_elts.ll
View File

@ -190,4 +190,23 @@ define <2 x double> @test_fpext(float %f) {
ret <2 x double> %ret
}
define <4 x float> @test_select(float %f, float %g) {
; CHECK: @test_select
; CHECK: %a0 = insertelement <4 x float> undef, float %f, i32 0
; CHECK-NOT: insertelement
; CHECK: %a3 = insertelement <4 x float> %a0, float 3.000000e+00, i32 3
; CHECK-NOT: insertelement
; CHECK: %ret = select <4 x i1> <i1 true, i1 false, i1 false, i1 true>, <4 x float> %a3, <4 x float> <float undef, float 4.000000e+00, float 5.000000e+00, float undef>
%a0 = insertelement <4 x float> undef, float %f, i32 0
%a1 = insertelement <4 x float> %a0, float 1.000000e+00, i32 1
%a2 = insertelement <4 x float> %a1, float 2.000000e+00, i32 2
%a3 = insertelement <4 x float> %a2, float 3.000000e+00, i32 3
%b0 = insertelement <4 x float> undef, float %g, i32 0
%b1 = insertelement <4 x float> %b0, float 4.000000e+00, i32 1
%b2 = insertelement <4 x float> %b1, float 5.000000e+00, i32 2
%b3 = insertelement <4 x float> %b2, float 6.000000e+00, i32 3
%ret = select <4 x i1> <i1 true, i1 false, i1 false, i1 true>, <4 x float> %a3, <4 x float> %b3
ret <4 x float> %ret
}