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-rw-r--r--llvm/lib/Transforms/InstCombine/InstCombineInternal.h3
-rw-r--r--llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp71
-rw-r--r--llvm/test/Transforms/InstCombine/select-bitext.ll8
3 files changed, 38 insertions, 44 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 7fb0659a79e..dca24d2eb91 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -590,8 +590,7 @@ private:
Instruction *foldICmpIntrinsicWithConstant(ICmpInst &ICI, const APInt *C);
// Helpers of visitSelectInst().
- Instruction *foldSelectExtConst(SelectInst &Sel, Instruction *ExtInst,
- const APInt &C);
+ Instruction *foldSelectExtConst(SelectInst &Sel);
Instruction *foldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI);
Instruction *foldSelectIntoOp(SelectInst &SI, Value *, Value *);
Instruction *foldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index c62598d4f2d..b8213426a63 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -916,32 +916,42 @@ static Instruction *foldAddSubSelect(SelectInst &SI,
return nullptr;
}
-/// If one of the operands is a sext/zext from i1 and the other is a constant,
-/// we may be able to create an i1 select which can be further folded to
-/// logical ops.
-Instruction *InstCombiner::foldSelectExtConst(SelectInst &Sel,
- Instruction *ExtInst,
- const APInt &C) {
+Instruction *InstCombiner::foldSelectExtConst(SelectInst &Sel) {
+ Instruction *ExtInst;
+ if (!match(Sel.getTrueValue(), m_Instruction(ExtInst)) &&
+ !match(Sel.getFalseValue(), m_Instruction(ExtInst)))
+ return nullptr;
+
+ auto ExtOpcode = ExtInst->getOpcode();
+ if (ExtOpcode != Instruction::ZExt && ExtOpcode != Instruction::SExt)
+ return nullptr;
+
// TODO: Handle larger types? That requires adjusting FoldOpIntoSelect too.
- Value *SmallVal = ExtInst->getOperand(0);
- Type *SmallType = SmallVal->getType();
+ Value *X = ExtInst->getOperand(0);
+ Type *SmallType = X->getType();
if (!SmallType->getScalarType()->isIntegerTy(1))
return nullptr;
- Value *Cond = Sel.getCondition();
- bool IsExtTrueVal = Sel.getTrueValue() == ExtInst;
- bool IsSext = ExtInst->getOpcode() == Instruction::SExt;
- if (C == 0 || (!IsSext && C == 1) || (IsSext && C.isAllOnesValue())) {
- Value *SmallConst = ConstantInt::get(SmallType, C.trunc(1));
- Value *TrueVal = IsExtTrueVal ? SmallVal : SmallConst;
- Value *FalseVal = IsExtTrueVal ? SmallConst : SmallVal;
- Value *NewSel = Builder->CreateSelect(Cond, TrueVal, FalseVal,
- "fold." + Sel.getName(), &Sel);
-
- if (IsSext)
- return new SExtInst(NewSel, Sel.getType());
+ Constant *C;
+ if (!match(Sel.getTrueValue(), m_Constant(C)) &&
+ !match(Sel.getFalseValue(), m_Constant(C)))
+ return nullptr;
- return new ZExtInst(NewSel, Sel.getType());
+ // If the constant is the same after truncation to the smaller type and
+ // extension to the original type, we can narrow the select.
+ Type *SelType = Sel.getType();
+ Constant *TruncC = ConstantExpr::getTrunc(C, SmallType);
+ Constant *ExtC = ConstantExpr::getCast(ExtOpcode, TruncC, SelType);
+ if (ExtC == C) {
+ Value *Cond = Sel.getCondition();
+ Value *TruncCVal = cast<Value>(TruncC);
+ if (ExtInst == Sel.getFalseValue())
+ std::swap(X, TruncCVal);
+
+ // select Cond, (ext X), C --> ext(select Cond, X, C')
+ // select Cond, C, (ext X) --> ext(select Cond, C', X)
+ Value *NewSel = Builder->CreateSelect(Cond, X, TruncCVal, "narrow", &Sel);
+ return CastInst::Create(Instruction::CastOps(ExtOpcode), NewSel, SelType);
}
return nullptr;
@@ -1172,23 +1182,8 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
if (Instruction *IV = foldSelectOpOp(SI, TI, FI))
return IV;
- // (select C, (ext X), const) -> (ext (select C, X, const')) and variations
- // thereof when extending from i1, as that allows further folding into logic
- // ops. When the sext is from a larger type, prefer to have it as an operand.
- if (TI && (TI->getOpcode() == Instruction::ZExt ||
- TI->getOpcode() == Instruction::SExt)) {
- const APInt *C;
- if (match(FalseVal, m_APInt(C)))
- if (auto *I = foldSelectExtConst(SI, TI, *C))
- return I;
- }
- if (FI && (FI->getOpcode() == Instruction::ZExt ||
- FI->getOpcode() == Instruction::SExt)) {
- const APInt *C;
- if (match(TrueVal, m_APInt(C)))
- if (auto *I = foldSelectExtConst(SI, FI, *C))
- return I;
- }
+ if (Instruction *I = foldSelectExtConst(SI))
+ return I;
// See if we can fold the select into one of our operands.
if (SelType->isIntOrIntVectorTy() || SelType->isFPOrFPVectorTy()) {
diff --git a/llvm/test/Transforms/InstCombine/select-bitext.ll b/llvm/test/Transforms/InstCombine/select-bitext.ll
index f259981f0f2..3fdba41ad29 100644
--- a/llvm/test/Transforms/InstCombine/select-bitext.ll
+++ b/llvm/test/Transforms/InstCombine/select-bitext.ll
@@ -168,8 +168,8 @@ define <2 x i32> @test_vectors_sext(<2 x i1> %cca, <2 x i1> %ccb) {
define <2 x i32> @test_vectors_sext_nonsplat(<2 x i1> %cca, <2 x i1> %ccb) {
; CHECK-LABEL: @test_vectors_sext_nonsplat(
-; CHECK-NEXT: [[CCAX:%.*]] = sext <2 x i1> %cca to <2 x i32>
-; CHECK-NEXT: [[R:%.*]] = select <2 x i1> %ccb, <2 x i32> [[CCAX]], <2 x i32> <i32 0, i32 -1>
+; CHECK-NEXT: [[NARROW:%.*]] = select <2 x i1> %ccb, <2 x i1> %cca, <2 x i1> <i1 false, i1 true>
+; CHECK-NEXT: [[R:%.*]] = sext <2 x i1> [[NARROW]] to <2 x i32>
; CHECK-NEXT: ret <2 x i32> [[R]]
;
%ccax = sext <2 x i1> %cca to <2 x i32>
@@ -190,8 +190,8 @@ define <2 x i32> @test_vectors_zext(<2 x i1> %cca, <2 x i1> %ccb) {
define <2 x i32> @test_vectors_zext_nonsplat(<2 x i1> %cca, <2 x i1> %ccb) {
; CHECK-LABEL: @test_vectors_zext_nonsplat(
-; CHECK-NEXT: [[CCAX:%.*]] = zext <2 x i1> %cca to <2 x i32>
-; CHECK-NEXT: [[R:%.*]] = select <2 x i1> %ccb, <2 x i32> [[CCAX]], <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT: [[NARROW:%.*]] = select <2 x i1> %ccb, <2 x i1> %cca, <2 x i1> <i1 true, i1 false>
+; CHECK-NEXT: [[R:%.*]] = zext <2 x i1> [[NARROW]] to <2 x i32>
; CHECK-NEXT: ret <2 x i32> [[R]]
;
%ccax = zext <2 x i1> %cca to <2 x i32>
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