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[GlobalISel] Take the result size into account when const folding icmp #134365

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Merged
merged 1 commit into from
May 5, 2025
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[GlobalISel] Take the result size into account when const folding icmp #134365

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1 change: 1 addition & 0 deletions llvm/include/llvm/CodeGen/GlobalISel/Utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -325,6 +325,7 @@ ConstantFoldCountZeros(Register Src, const MachineRegisterInfo &MRI,

std::optional<SmallVector<APInt>>
ConstantFoldICmp(unsigned Pred, const Register Op1, const Register Op2,
unsigned DstScalarSizeInBits, unsigned ExtOp,
const MachineRegisterInfo &MRI);

/// Test if the given value is known to have exactly one bit set. This differs
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8 changes: 5 additions & 3 deletions llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp
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Expand Up @@ -189,10 +189,12 @@ MachineInstrBuilder CSEMIRBuilder::buildInstr(unsigned Opc,
assert(SrcOps.size() == 3 && "Invalid sources");
assert(DstOps.size() == 1 && "Invalid dsts");
LLT SrcTy = SrcOps[1].getLLTTy(*getMRI());
LLT DstTy = DstOps[0].getLLTTy(*getMRI());
auto BoolExtOp = getBoolExtOp(SrcTy.isVector(), false);

if (std::optional<SmallVector<APInt>> Cst =
ConstantFoldICmp(SrcOps[0].getPredicate(), SrcOps[1].getReg(),
SrcOps[2].getReg(), *getMRI())) {
if (std::optional<SmallVector<APInt>> Cst = ConstantFoldICmp(
SrcOps[0].getPredicate(), SrcOps[1].getReg(), SrcOps[2].getReg(),
DstTy.getScalarSizeInBits(), BoolExtOp, *getMRI())) {
if (SrcTy.isVector())
return buildBuildVectorConstant(DstOps[0], *Cst);
return buildConstant(DstOps[0], Cst->front());
Expand Down
45 changes: 28 additions & 17 deletions llvm/lib/CodeGen/GlobalISel/Utils.cpp
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Expand Up @@ -1027,39 +1027,50 @@ llvm::ConstantFoldCountZeros(Register Src, const MachineRegisterInfo &MRI,

std::optional<SmallVector<APInt>>
llvm::ConstantFoldICmp(unsigned Pred, const Register Op1, const Register Op2,
unsigned DstScalarSizeInBits, unsigned ExtOp,
const MachineRegisterInfo &MRI) {
LLT Ty = MRI.getType(Op1);
if (Ty != MRI.getType(Op2))
return std::nullopt;
assert(ExtOp == TargetOpcode::G_SEXT || ExtOp == TargetOpcode::G_ZEXT ||
ExtOp == TargetOpcode::G_ANYEXT);

auto TryFoldScalar = [&MRI, Pred](Register LHS,
Register RHS) -> std::optional<APInt> {
auto LHSCst = getIConstantVRegVal(LHS, MRI);
const LLT Ty = MRI.getType(Op1);

auto GetICmpResultCst = [&](bool IsTrue) {
if (IsTrue)
return ExtOp == TargetOpcode::G_SEXT
? APInt::getAllOnes(DstScalarSizeInBits)
: APInt::getOneBitSet(DstScalarSizeInBits, 0);
return APInt::getZero(DstScalarSizeInBits);
};

auto TryFoldScalar = [&](Register LHS, Register RHS) -> std::optional<APInt> {
auto RHSCst = getIConstantVRegVal(RHS, MRI);
if (!LHSCst || !RHSCst)
if (!RHSCst)
return std::nullopt;
auto LHSCst = getIConstantVRegVal(LHS, MRI);
if (!LHSCst)
return std::nullopt;

switch (Pred) {
case CmpInst::Predicate::ICMP_EQ:
return APInt(/*numBits=*/1, LHSCst->eq(*RHSCst));
return GetICmpResultCst(LHSCst->eq(*RHSCst));
case CmpInst::Predicate::ICMP_NE:
return APInt(/*numBits=*/1, LHSCst->ne(*RHSCst));
return GetICmpResultCst(LHSCst->ne(*RHSCst));
case CmpInst::Predicate::ICMP_UGT:
return APInt(/*numBits=*/1, LHSCst->ugt(*RHSCst));
return GetICmpResultCst(LHSCst->ugt(*RHSCst));
case CmpInst::Predicate::ICMP_UGE:
return APInt(/*numBits=*/1, LHSCst->uge(*RHSCst));
return GetICmpResultCst(LHSCst->uge(*RHSCst));
case CmpInst::Predicate::ICMP_ULT:
return APInt(/*numBits=*/1, LHSCst->ult(*RHSCst));
return GetICmpResultCst(LHSCst->ult(*RHSCst));
case CmpInst::Predicate::ICMP_ULE:
return APInt(/*numBits=*/1, LHSCst->ule(*RHSCst));
return GetICmpResultCst(LHSCst->ule(*RHSCst));
case CmpInst::Predicate::ICMP_SGT:
return APInt(/*numBits=*/1, LHSCst->sgt(*RHSCst));
return GetICmpResultCst(LHSCst->sgt(*RHSCst));
case CmpInst::Predicate::ICMP_SGE:
return APInt(/*numBits=*/1, LHSCst->sge(*RHSCst));
return GetICmpResultCst(LHSCst->sge(*RHSCst));
case CmpInst::Predicate::ICMP_SLT:
return APInt(/*numBits=*/1, LHSCst->slt(*RHSCst));
return GetICmpResultCst(LHSCst->slt(*RHSCst));
case CmpInst::Predicate::ICMP_SLE:
return APInt(/*numBits=*/1, LHSCst->sle(*RHSCst));
return GetICmpResultCst(LHSCst->sle(*RHSCst));
default:
return std::nullopt;
}
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45 changes: 45 additions & 0 deletions llvm/unittests/CodeGen/GlobalISel/CSETest.cpp
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Expand Up @@ -500,6 +500,18 @@ TEST_F(AArch64GISelMITest, TestConstantFoldICMP) {
EXPECT_TRUE(I->getOperand(1).getCImm()->getZExtValue());
}

{
auto I = CSEB.buildICmp(CmpInst::Predicate::ICMP_EQ, s32, One, One);
EXPECT_TRUE(I->getOpcode() == TargetOpcode::G_CONSTANT);
EXPECT_EQ(I->getOperand(1).getCImm()->getZExtValue(), 1);
}

{
auto I = CSEB.buildICmp(CmpInst::Predicate::ICMP_EQ, s32, One, Two);
EXPECT_TRUE(I->getOpcode() == TargetOpcode::G_CONSTANT);
EXPECT_EQ(I->getOperand(1).getCImm()->getZExtValue(), 0);
}

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Check a vector case?

LLT VecTy = LLT::fixed_vector(2, s32);
LLT DstTy = LLT::fixed_vector(2, s1);
auto Three = CSEB.buildConstant(s32, 3);
Expand All @@ -508,6 +520,8 @@ TEST_F(AArch64GISelMITest, TestConstantFoldICMP) {
auto OneTwo = CSEB.buildBuildVector(VecTy, {One.getReg(0), Two.getReg(0)});
auto TwoThree =
CSEB.buildBuildVector(VecTy, {Two.getReg(0), Three.getReg(0)});
auto OneThree =
CSEB.buildBuildVector(VecTy, {One.getReg(0), Three.getReg(0)});
auto MinusOneOne =
CSEB.buildBuildVector(VecTy, {MinusOne.getReg(0), MinusOne.getReg(0)});
auto MinusOneTwo =
Expand Down Expand Up @@ -547,6 +561,36 @@ TEST_F(AArch64GISelMITest, TestConstantFoldICMP) {
// ICMP_SLE
CSEB.buildICmp(CmpInst::Predicate::ICMP_SLE, DstTy, MinusOneTwo, MinusOneOne);

{
auto I =
CSEB.buildICmp(CmpInst::Predicate::ICMP_EQ, VecTy, OneOne, TwoThree);
EXPECT_TRUE(I->getOpcode() == TargetOpcode::G_BUILD_VECTOR);
const APInt HiCst = *getIConstantVRegVal(I->getOperand(1).getReg(), *MRI);
const APInt LoCst = *getIConstantVRegVal(I->getOperand(2).getReg(), *MRI);
EXPECT_EQ(HiCst.getSExtValue(), 0);
EXPECT_EQ(LoCst.getSExtValue(), 0);
}

{
auto I =
CSEB.buildICmp(CmpInst::Predicate::ICMP_EQ, VecTy, OneThree, TwoThree);
EXPECT_TRUE(I->getOpcode() == TargetOpcode::G_BUILD_VECTOR);
const APInt HiCst = *getIConstantVRegVal(I->getOperand(1).getReg(), *MRI);
const APInt LoCst = *getIConstantVRegVal(I->getOperand(2).getReg(), *MRI);
EXPECT_EQ(HiCst.getSExtValue(), 0);
EXPECT_EQ(LoCst.getSExtValue(), -1);
}

{
auto I =
CSEB.buildICmp(CmpInst::Predicate::ICMP_EQ, VecTy, TwoThree, TwoThree);
EXPECT_TRUE(I->getOpcode() == TargetOpcode::G_BUILD_VECTOR);
const APInt HiCst = *getIConstantVRegVal(I->getOperand(1).getReg(), *MRI);
const APInt LoCst = *getIConstantVRegVal(I->getOperand(2).getReg(), *MRI);
EXPECT_EQ(HiCst.getSExtValue(), -1);
EXPECT_EQ(LoCst.getSExtValue(), -1);
}

auto CheckStr = R"(
; CHECK: [[One:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
; CHECK: [[Two:%[0-9]+]]:_(s32) = G_CONSTANT i32 2
Expand All @@ -558,6 +602,7 @@ TEST_F(AArch64GISelMITest, TestConstantFoldICMP) {
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[One]]:_(s32), [[One]]:_(s32)
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[One]]:_(s32), [[Two]]:_(s32)
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[Two]]:_(s32), [[Three]]:_(s32)
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[One]]:_(s32), [[Three]]:_(s32)
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[MinusOne]]:_(s32), [[MinusOne]]:_(s32)
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[MinusOne]]:_(s32), [[MinusTwo]]:_(s32)
; CHECK: {{%[0-9]+}}:_(<2 x s32>) = G_BUILD_VECTOR [[MinusTwo]]:_(s32), [[MinusThree]]:_(s32)
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