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[InstCombine] Reuse common code between foldSelectICmpAndBinOp and foldSelectICmpAnd. #131902

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Mar 19, 2025
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[InstCombine] Reuse common code between foldSelectICmpAndBinOp and foldSelectICmpAnd. #131902

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184 changes: 81 additions & 103 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -119,63 +119,15 @@ static Instruction *foldSelectBinOpIdentity(SelectInst &Sel,
/// (shl (and (X, C1)), (log2(TC-FC) - log2(C1))) + FC
/// With some variations depending if FC is larger than TC, or the shift
/// isn't needed, or the bit widths don't match.
static Value *foldSelectICmpAnd(SelectInst &Sel, Value *CondVal,
InstCombiner::BuilderTy &Builder,
const SimplifyQuery &SQ) {
static Value *foldSelectICmpAnd(SelectInst &Sel, Value *CondVal, Value *TrueVal,
Value *FalseVal, Value *V, const APInt &AndMask,
bool CreateAnd,
InstCombiner::BuilderTy &Builder) {
const APInt *SelTC, *SelFC;
if (!match(Sel.getTrueValue(), m_APInt(SelTC)) ||
!match(Sel.getFalseValue(), m_APInt(SelFC)))
if (!match(TrueVal, m_APInt(SelTC)) || !match(FalseVal, m_APInt(SelFC)))
return nullptr;

// If this is a vector select, we need a vector compare.
Type *SelType = Sel.getType();
if (SelType->isVectorTy() != CondVal->getType()->isVectorTy())
return nullptr;

Value *V;
APInt AndMask;
bool CreateAnd = false;
CmpPredicate Pred;
Value *CmpLHS, *CmpRHS;

if (match(CondVal, m_ICmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS)))) {
if (ICmpInst::isEquality(Pred)) {
if (!match(CmpRHS, m_Zero()))
return nullptr;

V = CmpLHS;
const APInt *AndRHS;
if (!match(V, m_And(m_Value(), m_Power2(AndRHS))))
return nullptr;

AndMask = *AndRHS;
} else if (auto Res = decomposeBitTestICmp(CmpLHS, CmpRHS, Pred)) {
assert(ICmpInst::isEquality(Res->Pred) && "Not equality test?");
AndMask = Res->Mask;
V = Res->X;
KnownBits Known =
computeKnownBits(V, /*Depth=*/0, SQ.getWithInstruction(&Sel));
AndMask &= Known.getMaxValue();
if (!AndMask.isPowerOf2())
return nullptr;

Pred = Res->Pred;
CreateAnd = true;
} else {
return nullptr;
}

} else if (auto *Trunc = dyn_cast<TruncInst>(CondVal)) {
V = Trunc->getOperand(0);
AndMask = APInt(V->getType()->getScalarSizeInBits(), 1);
Pred = ICmpInst::ICMP_NE;
CreateAnd = !Trunc->hasNoUnsignedWrap();
} else {
return nullptr;
}
if (Pred == ICmpInst::ICMP_NE)
std::swap(SelTC, SelFC);

// In general, when both constants are non-zero, we would need an offset to
// replace the select. This would require more instructions than we started
// with. But there's one special-case that we handle here because it can
Expand Down Expand Up @@ -762,60 +714,26 @@ static Value *foldSelectICmpLshrAshr(const ICmpInst *IC, Value *TrueVal,
/// 2. The select operands are reversed
/// 3. The magnitude of C2 and C1 are flipped
static Value *foldSelectICmpAndBinOp(Value *CondVal, Value *TrueVal,
Value *FalseVal,
Value *FalseVal, Value *V,
const APInt &AndMask, bool CreateAnd,
InstCombiner::BuilderTy &Builder) {
// Only handle integer compares. Also, if this is a vector select, we need a
// vector compare.
if (!TrueVal->getType()->isIntOrIntVectorTy() ||
TrueVal->getType()->isVectorTy() != CondVal->getType()->isVectorTy())
return nullptr;

unsigned C1Log;
bool NeedAnd = false;
CmpPredicate Pred;
Value *CmpLHS, *CmpRHS;

if (match(CondVal, m_ICmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS)))) {
if (ICmpInst::isEquality(Pred)) {
if (!match(CmpRHS, m_Zero()))
return nullptr;

const APInt *C1;
if (!match(CmpLHS, m_And(m_Value(), m_Power2(C1))))
return nullptr;

C1Log = C1->logBase2();
} else {
auto Res = decomposeBitTestICmp(CmpLHS, CmpRHS, Pred);
if (!Res || !Res->Mask.isPowerOf2())
return nullptr;

CmpLHS = Res->X;
Pred = Res->Pred;
C1Log = Res->Mask.logBase2();
NeedAnd = true;
}
} else if (auto *Trunc = dyn_cast<TruncInst>(CondVal)) {
CmpLHS = Trunc->getOperand(0);
C1Log = 0;
Pred = ICmpInst::ICMP_NE;
NeedAnd = !Trunc->hasNoUnsignedWrap();
} else {
// Only handle integer compares.
if (!TrueVal->getType()->isIntOrIntVectorTy())
return nullptr;
}

Value *Y, *V = CmpLHS;
unsigned C1Log = AndMask.logBase2();
Value *Y;
BinaryOperator *BinOp;
const APInt *C2;
bool NeedXor;
if (match(FalseVal, m_BinOp(m_Specific(TrueVal), m_Power2(C2)))) {
Y = TrueVal;
BinOp = cast<BinaryOperator>(FalseVal);
NeedXor = Pred == ICmpInst::ICMP_NE;
NeedXor = false;
} else if (match(TrueVal, m_BinOp(m_Specific(FalseVal), m_Power2(C2)))) {
Y = FalseVal;
BinOp = cast<BinaryOperator>(TrueVal);
NeedXor = Pred == ICmpInst::ICMP_EQ;
NeedXor = true;
} else {
return nullptr;
}
Expand All @@ -834,14 +752,13 @@ static Value *foldSelectICmpAndBinOp(Value *CondVal, Value *TrueVal,
V->getType()->getScalarSizeInBits();

// Make sure we don't create more instructions than we save.
if ((NeedShift + NeedXor + NeedZExtTrunc + NeedAnd) >
if ((NeedShift + NeedXor + NeedZExtTrunc + CreateAnd) >
(CondVal->hasOneUse() + BinOp->hasOneUse()))
return nullptr;

if (NeedAnd) {
if (CreateAnd) {
// Insert the AND instruction on the input to the truncate.
APInt C1 = APInt::getOneBitSet(V->getType()->getScalarSizeInBits(), C1Log);
V = Builder.CreateAnd(V, ConstantInt::get(V->getType(), C1));
V = Builder.CreateAnd(V, ConstantInt::get(V->getType(), AndMask));
}

if (C2Log > C1Log) {
Expand Down Expand Up @@ -3797,6 +3714,70 @@ static Value *foldSelectIntoAddConstant(SelectInst &SI,
return nullptr;
}

static Value *foldSelectBitTest(SelectInst &Sel, Value *CondVal, Value *TrueVal,
Value *FalseVal,
InstCombiner::BuilderTy &Builder,
const SimplifyQuery &SQ) {
// If this is a vector select, we need a vector compare.
Type *SelType = Sel.getType();
if (SelType->isVectorTy() != CondVal->getType()->isVectorTy())
return nullptr;

Value *V;
APInt AndMask;
bool CreateAnd = false;
CmpPredicate Pred;
Value *CmpLHS, *CmpRHS;

if (match(CondVal, m_ICmp(Pred, m_Value(CmpLHS), m_Value(CmpRHS)))) {
if (ICmpInst::isEquality(Pred)) {
if (!match(CmpRHS, m_Zero()))
return nullptr;

V = CmpLHS;
const APInt *AndRHS;
if (!match(CmpLHS, m_And(m_Value(), m_Power2(AndRHS))))
return nullptr;

AndMask = *AndRHS;
} else if (auto Res = decomposeBitTestICmp(CmpLHS, CmpRHS, Pred)) {
assert(ICmpInst::isEquality(Res->Pred) && "Not equality test?");
AndMask = Res->Mask;
V = Res->X;
KnownBits Known =
computeKnownBits(V, /*Depth=*/0, SQ.getWithInstruction(&Sel));
AndMask &= Known.getMaxValue();
if (!AndMask.isPowerOf2())
return nullptr;

Pred = Res->Pred;
CreateAnd = true;
} else {
return nullptr;
}
} else if (auto *Trunc = dyn_cast<TruncInst>(CondVal)) {
V = Trunc->getOperand(0);
AndMask = APInt(V->getType()->getScalarSizeInBits(), 1);
Pred = ICmpInst::ICMP_NE;
CreateAnd = !Trunc->hasNoUnsignedWrap();
} else {
return nullptr;
}

if (Pred == ICmpInst::ICMP_NE)
std::swap(TrueVal, FalseVal);

if (Value *X = foldSelectICmpAnd(Sel, CondVal, TrueVal, FalseVal, V, AndMask,
CreateAnd, Builder))
return X;

if (Value *X = foldSelectICmpAndBinOp(CondVal, TrueVal, FalseVal, V, AndMask,
CreateAnd, Builder))
return X;

return nullptr;
}

Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
Expand Down Expand Up @@ -3969,10 +3950,7 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
if (Instruction *Result = foldSelectInstWithICmp(SI, ICI))
return Result;

if (Value *V = foldSelectICmpAnd(SI, CondVal, Builder, SQ))
return replaceInstUsesWith(SI, V);

if (Value *V = foldSelectICmpAndBinOp(CondVal, TrueVal, FalseVal, Builder))
if (Value *V = foldSelectBitTest(SI, CondVal, TrueVal, FalseVal, Builder, SQ))
return replaceInstUsesWith(SI, V);

if (Instruction *Add = foldAddSubSelect(SI, Builder))
Expand Down
6 changes: 3 additions & 3 deletions llvm/test/Transforms/InstCombine/select-with-bitwise-ops.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -1832,9 +1832,9 @@ define i8 @neg_select_trunc_or_2(i8 %x, i8 %y) {

define i8 @select_icmp_bittest_range(i8 range(i8 0, 64) %a, i8 %y) {
; CHECK-LABEL: @select_icmp_bittest_range(
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign ult i8 [[A:%.*]], 32
; CHECK-NEXT: [[OR:%.*]] = or i8 [[Y:%.*]], 2
; CHECK-NEXT: [[RES:%.*]] = select i1 [[CMP]], i8 [[Y]], i8 [[OR]]
; CHECK-NEXT: [[TMP1:%.*]] = lshr i8 [[A:%.*]], 4
; CHECK-NEXT: [[TMP2:%.*]] = and i8 [[TMP1]], 2
; CHECK-NEXT: [[RES:%.*]] = or i8 [[Y:%.*]], [[TMP2]]
; CHECK-NEXT: ret i8 [[RES]]
;
%cmp = icmp ult i8 %a, 32
Expand Down