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[RISCV][GISel] Use libcalls for f32/f64 G_FCMP without F/D extensions. #117660

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Merged
merged 3 commits into from
Nov 26, 2024
Merged

[RISCV][GISel] Use libcalls for f32/f64 G_FCMP without F/D extensions. #117660

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4a6235b
[RISCV][GISel] Use libcalls for f32/f64 G_FCMP without F/D extensions.
topperc Nov 26, 2024
673e4be
fixup! Add FIXMEs to test.
topperc Nov 26, 2024
6684db7
fixup! remove -verify-machineinstrs
topperc Nov 26, 2024
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64 changes: 42 additions & 22 deletions llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1001,23 +1001,36 @@ LegalizerHelper::createSetStateLibcall(MachineIRBuilder &MIRBuilder,
/// the ICMP predicate that should be generated to compare with #0
/// after the libcall.
static std::pair<RTLIB::Libcall, CmpInst::Predicate>
getFCMPLibcallDesc(const CmpInst::Predicate Pred) {
getFCMPLibcallDesc(const CmpInst::Predicate Pred, unsigned Size) {
#define RTLIBCASE_CMP(LibcallPrefix, ICmpPred) \
do { \
switch (Size) { \
case 32: \
return {RTLIB::LibcallPrefix##32, ICmpPred}; \
case 64: \
return {RTLIB::LibcallPrefix##64, ICmpPred}; \
case 128: \
return {RTLIB::LibcallPrefix##128, ICmpPred}; \
default: \
llvm_unreachable("unexpected size"); \
} \
} while (0)

switch (Pred) {
case CmpInst::FCMP_OEQ:
return {RTLIB::OEQ_F128, CmpInst::ICMP_EQ};
RTLIBCASE_CMP(OEQ_F, CmpInst::ICMP_EQ);
case CmpInst::FCMP_UNE:
return {RTLIB::UNE_F128, CmpInst::ICMP_NE};
RTLIBCASE_CMP(UNE_F, CmpInst::ICMP_NE);
case CmpInst::FCMP_OGE:
return {RTLIB::OGE_F128, CmpInst::ICMP_SGE};
RTLIBCASE_CMP(OGE_F, CmpInst::ICMP_SGE);
case CmpInst::FCMP_OLT:
return {RTLIB::OLT_F128, CmpInst::ICMP_SLT};
RTLIBCASE_CMP(OLT_F, CmpInst::ICMP_SLT);
case CmpInst::FCMP_OLE:
return {RTLIB::OLE_F128, CmpInst::ICMP_SLE};
RTLIBCASE_CMP(OLE_F, CmpInst::ICMP_SLE);
case CmpInst::FCMP_OGT:
return {RTLIB::OGT_F128, CmpInst::ICMP_SGT};
RTLIBCASE_CMP(OGT_F, CmpInst::ICMP_SGT);
case CmpInst::FCMP_UNO:
return {RTLIB::UO_F128, CmpInst::ICMP_NE};
RTLIBCASE_CMP(UO_F, CmpInst::ICMP_NE);
default:
return {RTLIB::UNKNOWN_LIBCALL, CmpInst::BAD_ICMP_PREDICATE};
}
Expand All @@ -1032,21 +1045,24 @@ LegalizerHelper::createFCMPLibcall(MachineIRBuilder &MIRBuilder,
const GFCmp *Cmp = cast<GFCmp>(&MI);

LLT OpLLT = MRI.getType(Cmp->getLHSReg());
if (OpLLT != LLT::scalar(128) || OpLLT != MRI.getType(Cmp->getRHSReg()))
unsigned Size = OpLLT.getSizeInBits();
if ((Size != 32 && Size != 64 && Size != 128) ||
OpLLT != MRI.getType(Cmp->getRHSReg()))
return UnableToLegalize;

Type *OpType = getFloatTypeForLLT(Ctx, OpLLT);

// DstReg type is s32
const Register DstReg = Cmp->getReg(0);
LLT DstTy = MRI.getType(DstReg);
const auto Cond = Cmp->getCond();

// Reference:
// https://gcc.gnu.org/onlinedocs/gccint/Soft-float-library-routines.html#Comparison-functions-1
// Generates a libcall followed by ICMP.
const auto BuildLibcall =
[&](const RTLIB::Libcall Libcall, const CmpInst::Predicate ICmpPred,
const DstOp &Res = LLT::scalar(32)) -> Register {
const auto BuildLibcall = [&](const RTLIB::Libcall Libcall,
const CmpInst::Predicate ICmpPred,
const DstOp &Res) -> Register {
// FCMP libcall always returns an i32, and needs an ICMP with #0.
constexpr LLT TempLLT = LLT::scalar(32);
Register Temp = MRI.createGenericVirtualRegister(TempLLT);
Expand All @@ -1065,7 +1081,7 @@ LegalizerHelper::createFCMPLibcall(MachineIRBuilder &MIRBuilder,
};

// Simple case if we have a direct mapping from predicate to libcall
if (const auto [Libcall, ICmpPred] = getFCMPLibcallDesc(Cond);
if (const auto [Libcall, ICmpPred] = getFCMPLibcallDesc(Cond, Size);
Libcall != RTLIB::UNKNOWN_LIBCALL &&
ICmpPred != CmpInst::BAD_ICMP_PREDICATE) {
if (BuildLibcall(Libcall, ICmpPred, DstReg)) {
Expand All @@ -1081,11 +1097,13 @@ LegalizerHelper::createFCMPLibcall(MachineIRBuilder &MIRBuilder,
// FCMP_UEQ: unordered or equal
// Convert into (FCMP_OEQ || FCMP_UNO).

const auto [OeqLibcall, OeqPred] = getFCMPLibcallDesc(CmpInst::FCMP_OEQ);
const auto Oeq = BuildLibcall(OeqLibcall, OeqPred);
const auto [OeqLibcall, OeqPred] =
getFCMPLibcallDesc(CmpInst::FCMP_OEQ, Size);
const auto Oeq = BuildLibcall(OeqLibcall, OeqPred, DstTy);

const auto [UnoLibcall, UnoPred] = getFCMPLibcallDesc(CmpInst::FCMP_UNO);
const auto Uno = BuildLibcall(UnoLibcall, UnoPred);
const auto [UnoLibcall, UnoPred] =
getFCMPLibcallDesc(CmpInst::FCMP_UNO, Size);
const auto Uno = BuildLibcall(UnoLibcall, UnoPred, DstTy);
if (Oeq && Uno)
MIRBuilder.buildOr(DstReg, Oeq, Uno);
else
Expand All @@ -1100,13 +1118,15 @@ LegalizerHelper::createFCMPLibcall(MachineIRBuilder &MIRBuilder,
// We inverse the predicate instead of generating a NOT
// to save one instruction.
// On AArch64 isel can even select two cmp into a single ccmp.
const auto [OeqLibcall, OeqPred] = getFCMPLibcallDesc(CmpInst::FCMP_OEQ);
const auto [OeqLibcall, OeqPred] =
getFCMPLibcallDesc(CmpInst::FCMP_OEQ, Size);
const auto NotOeq =
BuildLibcall(OeqLibcall, CmpInst::getInversePredicate(OeqPred));
BuildLibcall(OeqLibcall, CmpInst::getInversePredicate(OeqPred), DstTy);

const auto [UnoLibcall, UnoPred] = getFCMPLibcallDesc(CmpInst::FCMP_UNO);
const auto [UnoLibcall, UnoPred] =
getFCMPLibcallDesc(CmpInst::FCMP_UNO, Size);
const auto NotUno =
BuildLibcall(UnoLibcall, CmpInst::getInversePredicate(UnoPred));
BuildLibcall(UnoLibcall, CmpInst::getInversePredicate(UnoPred), DstTy);

if (NotOeq && NotUno)
MIRBuilder.buildAnd(DstReg, NotOeq, NotUno);
Expand All @@ -1128,7 +1148,7 @@ LegalizerHelper::createFCMPLibcall(MachineIRBuilder &MIRBuilder,
// MIRBuilder.buildFCmp(CmpInst::getInversePredicate(Pred), PredTy,
// Op1, Op2));
const auto [InversedLibcall, InversedPred] =
getFCMPLibcallDesc(CmpInst::getInversePredicate(Cond));
getFCMPLibcallDesc(CmpInst::getInversePredicate(Cond), Size);
if (!BuildLibcall(InversedLibcall,
CmpInst::getInversePredicate(InversedPred), DstReg))
return UnableToLegalize;
Expand Down
3 changes: 2 additions & 1 deletion llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -530,7 +530,8 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST)
.legalFor(ST.hasStdExtF(), {{sXLen, s32}})
.legalFor(ST.hasStdExtD(), {{sXLen, s64}})
.legalFor(ST.hasStdExtZfh(), {{sXLen, s16}})
.clampScalar(ST.hasStdExtF(), 0, sXLen, sXLen);
.clampScalar(0, sXLen, sXLen)
.libcallFor({{sXLen, s32}, {sXLen, s64}});

// TODO: Support vector version of G_IS_FPCLASS.
getActionDefinitionsBuilder(G_IS_FPCLASS)
Expand Down
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