llvm-project/llvm/lib/Target/SPIRV/SPIRVLegalizerInfo.cpp

//===- SPIRVLegalizerInfo.cpp --- SPIR-V Legalization Rules ------*- C++ -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the targeting of the Machinelegalizer class for SPIR-V.
//
//===----------------------------------------------------------------------===//

#include "SPIRVLegalizerInfo.h"
#include "SPIRV.h"
#include "SPIRVGlobalRegistry.h"
#include "SPIRVSubtarget.h"
#include "llvm/CodeGen/GlobalISel/LegalizerHelper.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"

using namespace llvm;
using namespace llvm::LegalizeActions;
using namespace llvm::LegalityPredicates;

LegalityPredicate typeOfExtendedScalars(unsigned TypeIdx, bool IsExtendedInts) {
  return [IsExtendedInts, TypeIdx](const LegalityQuery &Query) {
    const LLT Ty = Query.Types[TypeIdx];
    return IsExtendedInts && Ty.isValid() && Ty.isScalar();
  };
}

SPIRVLegalizerInfo::SPIRVLegalizerInfo(const SPIRVSubtarget &ST) {
  using namespace TargetOpcode;

  this->ST = &ST;
  GR = ST.getSPIRVGlobalRegistry();

  const LLT s1 = LLT::scalar(1);
  const LLT s8 = LLT::scalar(8);
  const LLT s16 = LLT::scalar(16);
  const LLT s32 = LLT::scalar(32);
  const LLT s64 = LLT::scalar(64);

  const LLT v16s64 = LLT::fixed_vector(16, 64);
  const LLT v16s32 = LLT::fixed_vector(16, 32);
  const LLT v16s16 = LLT::fixed_vector(16, 16);
  const LLT v16s8 = LLT::fixed_vector(16, 8);
  const LLT v16s1 = LLT::fixed_vector(16, 1);

  const LLT v8s64 = LLT::fixed_vector(8, 64);
  const LLT v8s32 = LLT::fixed_vector(8, 32);
  const LLT v8s16 = LLT::fixed_vector(8, 16);
  const LLT v8s8 = LLT::fixed_vector(8, 8);
  const LLT v8s1 = LLT::fixed_vector(8, 1);

  const LLT v4s64 = LLT::fixed_vector(4, 64);
  const LLT v4s32 = LLT::fixed_vector(4, 32);
  const LLT v4s16 = LLT::fixed_vector(4, 16);
  const LLT v4s8 = LLT::fixed_vector(4, 8);
  const LLT v4s1 = LLT::fixed_vector(4, 1);

  const LLT v3s64 = LLT::fixed_vector(3, 64);
  const LLT v3s32 = LLT::fixed_vector(3, 32);
  const LLT v3s16 = LLT::fixed_vector(3, 16);
  const LLT v3s8 = LLT::fixed_vector(3, 8);
  const LLT v3s1 = LLT::fixed_vector(3, 1);

  const LLT v2s64 = LLT::fixed_vector(2, 64);
  const LLT v2s32 = LLT::fixed_vector(2, 32);
  const LLT v2s16 = LLT::fixed_vector(2, 16);
  const LLT v2s8 = LLT::fixed_vector(2, 8);
  const LLT v2s1 = LLT::fixed_vector(2, 1);

  const unsigned PSize = ST.getPointerSize();
  const LLT p0 = LLT::pointer(0, PSize); // Function
  const LLT p1 = LLT::pointer(1, PSize); // CrossWorkgroup
  const LLT p2 = LLT::pointer(2, PSize); // UniformConstant
  const LLT p3 = LLT::pointer(3, PSize); // Workgroup
  const LLT p4 = LLT::pointer(4, PSize); // Generic
  const LLT p5 =
      LLT::pointer(5, PSize); // Input, SPV_INTEL_usm_storage_classes (Device)
  const LLT p6 = LLT::pointer(6, PSize); // SPV_INTEL_usm_storage_classes (Host)
  const LLT p7 = LLT::pointer(7, PSize); // Input
  const LLT p8 = LLT::pointer(8, PSize); // Output
  const LLT p10 = LLT::pointer(10, PSize); // Private
  const LLT p11 = LLT::pointer(11, PSize); // StorageBuffer
  const LLT p12 = LLT::pointer(12, PSize); // Uniform

  // TODO: remove copy-pasting here by using concatenation in some way.
  auto allPtrsScalarsAndVectors = {
      p0,    p1,    p2,    p3,     p4,     p5,    p6,    p7,    p8,
      p10,   p11,   p12,   s1,     s8,     s16,   s32,   s64,   v2s1,
      v2s8,  v2s16, v2s32, v2s64,  v3s1,   v3s8,  v3s16, v3s32, v3s64,
      v4s1,  v4s8,  v4s16, v4s32,  v4s64,  v8s1,  v8s8,  v8s16, v8s32,
      v8s64, v16s1, v16s8, v16s16, v16s32, v16s64};

  auto allVectors = {v2s1,  v2s8,   v2s16,  v2s32, v2s64, v3s1,  v3s8,
                     v3s16, v3s32,  v3s64,  v4s1,  v4s8,  v4s16, v4s32,
                     v4s64, v8s1,   v8s8,   v8s16, v8s32, v8s64, v16s1,
                     v16s8, v16s16, v16s32, v16s64};

  auto allScalarsAndVectors = {
      s1,   s8,   s16,   s32,   s64,   v2s1,  v2s8,  v2s16,  v2s32,  v2s64,
      v3s1, v3s8, v3s16, v3s32, v3s64, v4s1,  v4s8,  v4s16,  v4s32,  v4s64,
      v8s1, v8s8, v8s16, v8s32, v8s64, v16s1, v16s8, v16s16, v16s32, v16s64};

  auto allIntScalarsAndVectors = {s8,    s16,   s32,   s64,    v2s8,   v2s16,
                                  v2s32, v2s64, v3s8,  v3s16,  v3s32,  v3s64,
                                  v4s8,  v4s16, v4s32, v4s64,  v8s8,   v8s16,
                                  v8s32, v8s64, v16s8, v16s16, v16s32, v16s64};

  auto allBoolScalarsAndVectors = {s1, v2s1, v3s1, v4s1, v8s1, v16s1};

  auto allIntScalars = {s8, s16, s32, s64};

  auto allFloatScalars = {s16, s32, s64};

  auto allFloatScalarsAndVectors = {
      s16,   s32,   s64,   v2s16, v2s32, v2s64, v3s16,  v3s32,  v3s64,
      v4s16, v4s32, v4s64, v8s16, v8s32, v8s64, v16s16, v16s32, v16s64};

  auto allFloatAndIntScalarsAndPtrs = {s8, s16, s32, s64, p0, p1,  p2,  p3,
                                       p4, p5,  p6,  p7,  p8, p10, p11, p12};

  auto allPtrs = {p0, p1, p2, p3, p4, p5, p6, p7, p8, p10, p11, p12};

  bool IsExtendedInts =
      ST.canUseExtension(
          SPIRV::Extension::SPV_INTEL_arbitrary_precision_integers) ||
      ST.canUseExtension(SPIRV::Extension::SPV_KHR_bit_instructions) ||
      ST.canUseExtension(SPIRV::Extension::SPV_INTEL_int4);
  auto extendedScalarsAndVectors =
      [IsExtendedInts](const LegalityQuery &Query) {
        const LLT Ty = Query.Types[0];
        return IsExtendedInts && Ty.isValid() && !Ty.isPointerOrPointerVector();
      };
  auto extendedScalarsAndVectorsProduct = [IsExtendedInts](
                                              const LegalityQuery &Query) {
    const LLT Ty1 = Query.Types[0], Ty2 = Query.Types[1];
    return IsExtendedInts && Ty1.isValid() && Ty2.isValid() &&
           !Ty1.isPointerOrPointerVector() && !Ty2.isPointerOrPointerVector();
  };
  auto extendedPtrsScalarsAndVectors =
      [IsExtendedInts](const LegalityQuery &Query) {
        const LLT Ty = Query.Types[0];
        return IsExtendedInts && Ty.isValid();
      };

  for (auto Opc : getTypeFoldingSupportedOpcodes())
    getActionDefinitionsBuilder(Opc).custom();

  getActionDefinitionsBuilder(G_GLOBAL_VALUE).alwaysLegal();

  // TODO: add proper rules for vectors legalization.
  getActionDefinitionsBuilder(
      {G_BUILD_VECTOR, G_SHUFFLE_VECTOR, G_SPLAT_VECTOR})
      .alwaysLegal();

  // Vector Reduction Operations
  getActionDefinitionsBuilder(
      {G_VECREDUCE_SMIN, G_VECREDUCE_SMAX, G_VECREDUCE_UMIN, G_VECREDUCE_UMAX,
       G_VECREDUCE_ADD, G_VECREDUCE_MUL, G_VECREDUCE_FMUL, G_VECREDUCE_FMIN,
       G_VECREDUCE_FMAX, G_VECREDUCE_FMINIMUM, G_VECREDUCE_FMAXIMUM,
       G_VECREDUCE_OR, G_VECREDUCE_AND, G_VECREDUCE_XOR})
      .legalFor(allVectors)
      .scalarize(1)
      .lower();

  getActionDefinitionsBuilder({G_VECREDUCE_SEQ_FADD, G_VECREDUCE_SEQ_FMUL})
      .scalarize(2)
      .lower();

  // Merge/Unmerge
  // TODO: add proper legalization rules.
  getActionDefinitionsBuilder(G_UNMERGE_VALUES).alwaysLegal();

  getActionDefinitionsBuilder({G_MEMCPY, G_MEMMOVE})
      .legalIf(all(typeInSet(0, allPtrs), typeInSet(1, allPtrs)));

  getActionDefinitionsBuilder(G_MEMSET).legalIf(
      all(typeInSet(0, allPtrs), typeInSet(1, allIntScalars)));

  getActionDefinitionsBuilder(G_ADDRSPACE_CAST)
      .legalForCartesianProduct(allPtrs, allPtrs);

  getActionDefinitionsBuilder({G_LOAD, G_STORE}).legalIf(typeInSet(1, allPtrs));

  getActionDefinitionsBuilder({G_SMIN, G_SMAX, G_UMIN, G_UMAX, G_ABS,
                               G_BITREVERSE, G_SADDSAT, G_UADDSAT, G_SSUBSAT,
                               G_USUBSAT, G_SCMP, G_UCMP})
      .legalFor(allIntScalarsAndVectors)
      .legalIf(extendedScalarsAndVectors);

  getActionDefinitionsBuilder({G_FMA, G_STRICT_FMA})
      .legalFor(allFloatScalarsAndVectors);

  getActionDefinitionsBuilder(G_STRICT_FLDEXP)
      .legalForCartesianProduct(allFloatScalarsAndVectors, allIntScalars);

  getActionDefinitionsBuilder({G_FPTOSI, G_FPTOUI})
      .legalForCartesianProduct(allIntScalarsAndVectors,
                                allFloatScalarsAndVectors);

  getActionDefinitionsBuilder({G_FPTOSI_SAT, G_FPTOUI_SAT})
      .legalForCartesianProduct(allIntScalarsAndVectors,
                                allFloatScalarsAndVectors);

  getActionDefinitionsBuilder({G_SITOFP, G_UITOFP})
      .legalForCartesianProduct(allFloatScalarsAndVectors,
                                allScalarsAndVectors);

  getActionDefinitionsBuilder(G_CTPOP)
      .legalForCartesianProduct(allIntScalarsAndVectors)
      .legalIf(extendedScalarsAndVectorsProduct);

  // Extensions.
  getActionDefinitionsBuilder({G_TRUNC, G_ZEXT, G_SEXT, G_ANYEXT})
      .legalForCartesianProduct(allScalarsAndVectors)
      .legalIf(extendedScalarsAndVectorsProduct);

  getActionDefinitionsBuilder(G_PHI)
      .legalFor(allPtrsScalarsAndVectors)
      .legalIf(extendedPtrsScalarsAndVectors);

  getActionDefinitionsBuilder(G_BITCAST).legalIf(
      all(typeInSet(0, allPtrsScalarsAndVectors),
          typeInSet(1, allPtrsScalarsAndVectors)));

  getActionDefinitionsBuilder({G_IMPLICIT_DEF, G_FREEZE}).alwaysLegal();

  getActionDefinitionsBuilder({G_STACKSAVE, G_STACKRESTORE}).alwaysLegal();

  getActionDefinitionsBuilder(G_INTTOPTR)
      .legalForCartesianProduct(allPtrs, allIntScalars)
      .legalIf(
          all(typeInSet(0, allPtrs), typeOfExtendedScalars(1, IsExtendedInts)));
  getActionDefinitionsBuilder(G_PTRTOINT)
      .legalForCartesianProduct(allIntScalars, allPtrs)
      .legalIf(
          all(typeOfExtendedScalars(0, IsExtendedInts), typeInSet(1, allPtrs)));
  getActionDefinitionsBuilder(G_PTR_ADD)
      .legalForCartesianProduct(allPtrs, allIntScalars)
      .legalIf(
          all(typeInSet(0, allPtrs), typeOfExtendedScalars(1, IsExtendedInts)));

  // ST.canDirectlyComparePointers() for pointer args is supported in
  // legalizeCustom().
  getActionDefinitionsBuilder(G_ICMP).customIf(
      all(typeInSet(0, allBoolScalarsAndVectors),
          typeInSet(1, allPtrsScalarsAndVectors)));

  getActionDefinitionsBuilder(G_FCMP).legalIf(
      all(typeInSet(0, allBoolScalarsAndVectors),
          typeInSet(1, allFloatScalarsAndVectors)));

  getActionDefinitionsBuilder({G_ATOMICRMW_OR, G_ATOMICRMW_ADD, G_ATOMICRMW_AND,
                               G_ATOMICRMW_MAX, G_ATOMICRMW_MIN,
                               G_ATOMICRMW_SUB, G_ATOMICRMW_XOR,
                               G_ATOMICRMW_UMAX, G_ATOMICRMW_UMIN})
      .legalForCartesianProduct(allIntScalars, allPtrs);

  getActionDefinitionsBuilder(
      {G_ATOMICRMW_FADD, G_ATOMICRMW_FSUB, G_ATOMICRMW_FMIN, G_ATOMICRMW_FMAX})
      .legalForCartesianProduct(allFloatScalars, allPtrs);

  getActionDefinitionsBuilder(G_ATOMICRMW_XCHG)
      .legalForCartesianProduct(allFloatAndIntScalarsAndPtrs, allPtrs);

  getActionDefinitionsBuilder(G_ATOMIC_CMPXCHG_WITH_SUCCESS).lower();
  // TODO: add proper legalization rules.
  getActionDefinitionsBuilder(G_ATOMIC_CMPXCHG).alwaysLegal();

  getActionDefinitionsBuilder(
      {G_UADDO, G_SADDO, G_USUBO, G_SSUBO, G_UMULO, G_SMULO})
      .alwaysLegal();

  // FP conversions.
  getActionDefinitionsBuilder({G_FPTRUNC, G_FPEXT})
      .legalForCartesianProduct(allFloatScalarsAndVectors);

  // Pointer-handling.
  getActionDefinitionsBuilder(G_FRAME_INDEX).legalFor({p0});

  // Control-flow. In some cases (e.g. constants) s1 may be promoted to s32.
  getActionDefinitionsBuilder(G_BRCOND).legalFor({s1, s32});

  // TODO: Review the target OpenCL and GLSL Extended Instruction Set specs to
  // tighten these requirements. Many of these math functions are only legal on
  // specific bitwidths, so they are not selectable for
  // allFloatScalarsAndVectors.
  getActionDefinitionsBuilder({G_STRICT_FSQRT,
                               G_FPOW,
                               G_FEXP,
                               G_FEXP2,
                               G_FLOG,
                               G_FLOG2,
                               G_FLOG10,
                               G_FABS,
                               G_FMINNUM,
                               G_FMAXNUM,
                               G_FCEIL,
                               G_FCOS,
                               G_FSIN,
                               G_FTAN,
                               G_FACOS,
                               G_FASIN,
                               G_FATAN,
                               G_FATAN2,
                               G_FCOSH,
                               G_FSINH,
                               G_FTANH,
                               G_FSQRT,
                               G_FFLOOR,
                               G_FRINT,
                               G_FNEARBYINT,
                               G_INTRINSIC_ROUND,
                               G_INTRINSIC_TRUNC,
                               G_FMINIMUM,
                               G_FMAXIMUM,
                               G_INTRINSIC_ROUNDEVEN})
      .legalFor(allFloatScalarsAndVectors);

  getActionDefinitionsBuilder(G_FCOPYSIGN)
      .legalForCartesianProduct(allFloatScalarsAndVectors,
                                allFloatScalarsAndVectors);

  getActionDefinitionsBuilder(G_FPOWI).legalForCartesianProduct(
      allFloatScalarsAndVectors, allIntScalarsAndVectors);

  if (ST.canUseExtInstSet(SPIRV::InstructionSet::OpenCL_std)) {
    getActionDefinitionsBuilder(
        {G_CTTZ, G_CTTZ_ZERO_UNDEF, G_CTLZ, G_CTLZ_ZERO_UNDEF})
        .legalForCartesianProduct(allIntScalarsAndVectors,
                                  allIntScalarsAndVectors);

    // Struct return types become a single scalar, so cannot easily legalize.
    getActionDefinitionsBuilder({G_SMULH, G_UMULH}).alwaysLegal();
  }

  getActionDefinitionsBuilder(G_IS_FPCLASS).custom();

  getLegacyLegalizerInfo().computeTables();
  verify(*ST.getInstrInfo());
}

static Register convertPtrToInt(Register Reg, LLT ConvTy, SPIRVType *SpvType,
                                LegalizerHelper &Helper,
                                MachineRegisterInfo &MRI,
                                SPIRVGlobalRegistry *GR) {
  Register ConvReg = MRI.createGenericVirtualRegister(ConvTy);
  MRI.setRegClass(ConvReg, GR->getRegClass(SpvType));
  GR->assignSPIRVTypeToVReg(SpvType, ConvReg, Helper.MIRBuilder.getMF());
  Helper.MIRBuilder.buildInstr(TargetOpcode::G_PTRTOINT)
      .addDef(ConvReg)
      .addUse(Reg);
  return ConvReg;
}

bool SPIRVLegalizerInfo::legalizeCustom(
    LegalizerHelper &Helper, MachineInstr &MI,
    LostDebugLocObserver &LocObserver) const {
  MachineRegisterInfo &MRI = MI.getMF()->getRegInfo();
  switch (MI.getOpcode()) {
  default:
    // TODO: implement legalization for other opcodes.
    return true;
  case TargetOpcode::G_IS_FPCLASS:
    return legalizeIsFPClass(Helper, MI, LocObserver);
  case TargetOpcode::G_ICMP: {
    assert(GR->getSPIRVTypeForVReg(MI.getOperand(0).getReg()));
    auto &Op0 = MI.getOperand(2);
    auto &Op1 = MI.getOperand(3);
    Register Reg0 = Op0.getReg();
    Register Reg1 = Op1.getReg();
    CmpInst::Predicate Cond =
        static_cast<CmpInst::Predicate>(MI.getOperand(1).getPredicate());
    if ((!ST->canDirectlyComparePointers() ||
         (Cond != CmpInst::ICMP_EQ && Cond != CmpInst::ICMP_NE)) &&
        MRI.getType(Reg0).isPointer() && MRI.getType(Reg1).isPointer()) {
      LLT ConvT = LLT::scalar(ST->getPointerSize());
      Type *LLVMTy = IntegerType::get(MI.getMF()->getFunction().getContext(),
                                      ST->getPointerSize());
      SPIRVType *SpirvTy = GR->getOrCreateSPIRVType(
          LLVMTy, Helper.MIRBuilder, SPIRV::AccessQualifier::ReadWrite, true);
      Op0.setReg(convertPtrToInt(Reg0, ConvT, SpirvTy, Helper, MRI, GR));
      Op1.setReg(convertPtrToInt(Reg1, ConvT, SpirvTy, Helper, MRI, GR));
    }
    return true;
  }
  }
}

// Note this code was copied from LegalizerHelper::lowerISFPCLASS and adjusted
// to ensure that all instructions created during the lowering have SPIR-V types
// assigned to them.
bool SPIRVLegalizerInfo::legalizeIsFPClass(
    LegalizerHelper &Helper, MachineInstr &MI,
    LostDebugLocObserver &LocObserver) const {
  auto [DstReg, DstTy, SrcReg, SrcTy] = MI.getFirst2RegLLTs();
  FPClassTest Mask = static_cast<FPClassTest>(MI.getOperand(2).getImm());

  auto &MIRBuilder = Helper.MIRBuilder;
  auto &MF = MIRBuilder.getMF();
  MachineRegisterInfo &MRI = MF.getRegInfo();

  Type *LLVMDstTy =
      IntegerType::get(MIRBuilder.getContext(), DstTy.getScalarSizeInBits());
  if (DstTy.isVector())
    LLVMDstTy = VectorType::get(LLVMDstTy, DstTy.getElementCount());
  SPIRVType *SPIRVDstTy = GR->getOrCreateSPIRVType(
      LLVMDstTy, MIRBuilder, SPIRV::AccessQualifier::ReadWrite,
      /*EmitIR*/ true);

  unsigned BitSize = SrcTy.getScalarSizeInBits();
  const fltSemantics &Semantics = getFltSemanticForLLT(SrcTy.getScalarType());

  LLT IntTy = LLT::scalar(BitSize);
  Type *LLVMIntTy = IntegerType::get(MIRBuilder.getContext(), BitSize);
  if (SrcTy.isVector()) {
    IntTy = LLT::vector(SrcTy.getElementCount(), IntTy);
    LLVMIntTy = VectorType::get(LLVMIntTy, SrcTy.getElementCount());
  }
  SPIRVType *SPIRVIntTy = GR->getOrCreateSPIRVType(
      LLVMIntTy, MIRBuilder, SPIRV::AccessQualifier::ReadWrite,
      /*EmitIR*/ true);

  // Clang doesn't support capture of structured bindings:
  LLT DstTyCopy = DstTy;
  const auto assignSPIRVTy = [&](MachineInstrBuilder &&MI) {
    // Assign this MI's (assumed only) destination to one of the two types we
    // expect: either the G_IS_FPCLASS's destination type, or the integer type
    // bitcast from the source type.
    LLT MITy = MRI.getType(MI.getReg(0));
    assert((MITy == IntTy || MITy == DstTyCopy) &&
           "Unexpected LLT type while lowering G_IS_FPCLASS");
    auto *SPVTy = MITy == IntTy ? SPIRVIntTy : SPIRVDstTy;
    GR->assignSPIRVTypeToVReg(SPVTy, MI.getReg(0), MF);
    return MI;
  };

  // Helper to build and assign a constant in one go
  const auto buildSPIRVConstant = [&](LLT Ty, auto &&C) -> MachineInstrBuilder {
    if (!Ty.isFixedVector())
      return assignSPIRVTy(MIRBuilder.buildConstant(Ty, C));
    auto ScalarC = MIRBuilder.buildConstant(Ty.getScalarType(), C);
    assert((Ty == IntTy || Ty == DstTyCopy) &&
           "Unexpected LLT type while lowering constant for G_IS_FPCLASS");
    SPIRVType *VecEltTy = GR->getOrCreateSPIRVType(
        (Ty == IntTy ? LLVMIntTy : LLVMDstTy)->getScalarType(), MIRBuilder,
        SPIRV::AccessQualifier::ReadWrite,
        /*EmitIR*/ true);
    GR->assignSPIRVTypeToVReg(VecEltTy, ScalarC.getReg(0), MF);
    return assignSPIRVTy(MIRBuilder.buildSplatBuildVector(Ty, ScalarC));
  };

  if (Mask == fcNone) {
    MIRBuilder.buildCopy(DstReg, buildSPIRVConstant(DstTy, 0));
    MI.eraseFromParent();
    return true;
  }
  if (Mask == fcAllFlags) {
    MIRBuilder.buildCopy(DstReg, buildSPIRVConstant(DstTy, 1));
    MI.eraseFromParent();
    return true;
  }

  // Note that rather than creating a COPY here (between a floating-point and
  // integer type of the same size) we create a SPIR-V bitcast immediately. We
  // can't create a G_BITCAST because the LLTs are the same, and we can't seem
  // to correctly lower COPYs to SPIR-V bitcasts at this moment.
  Register ResVReg = MRI.createGenericVirtualRegister(IntTy);
  MRI.setRegClass(ResVReg, GR->getRegClass(SPIRVIntTy));
  GR->assignSPIRVTypeToVReg(SPIRVIntTy, ResVReg, Helper.MIRBuilder.getMF());
  auto AsInt = MIRBuilder.buildInstr(SPIRV::OpBitcast)
                   .addDef(ResVReg)
                   .addUse(GR->getSPIRVTypeID(SPIRVIntTy))
                   .addUse(SrcReg);
  AsInt = assignSPIRVTy(std::move(AsInt));

  // Various masks.
  APInt SignBit = APInt::getSignMask(BitSize);
  APInt ValueMask = APInt::getSignedMaxValue(BitSize);     // All bits but sign.
  APInt Inf = APFloat::getInf(Semantics).bitcastToAPInt(); // Exp and int bit.
  APInt ExpMask = Inf;
  APInt AllOneMantissa = APFloat::getLargest(Semantics).bitcastToAPInt() & ~Inf;
  APInt QNaNBitMask =
      APInt::getOneBitSet(BitSize, AllOneMantissa.getActiveBits() - 1);
  APInt InversionMask = APInt::getAllOnes(DstTy.getScalarSizeInBits());

  auto SignBitC = buildSPIRVConstant(IntTy, SignBit);
  auto ValueMaskC = buildSPIRVConstant(IntTy, ValueMask);
  auto InfC = buildSPIRVConstant(IntTy, Inf);
  auto ExpMaskC = buildSPIRVConstant(IntTy, ExpMask);
  auto ZeroC = buildSPIRVConstant(IntTy, 0);

  auto Abs = assignSPIRVTy(MIRBuilder.buildAnd(IntTy, AsInt, ValueMaskC));
  auto Sign = assignSPIRVTy(
      MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_NE, DstTy, AsInt, Abs));

  auto Res = buildSPIRVConstant(DstTy, 0);

  const auto appendToRes = [&](MachineInstrBuilder &&ToAppend) {
    Res = assignSPIRVTy(
        MIRBuilder.buildOr(DstTyCopy, Res, assignSPIRVTy(std::move(ToAppend))));
  };

  // Tests that involve more than one class should be processed first.
  if ((Mask & fcFinite) == fcFinite) {
    // finite(V) ==> abs(V) u< exp_mask
    appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_ULT, DstTy, Abs,
                                     ExpMaskC));
    Mask &= ~fcFinite;
  } else if ((Mask & fcFinite) == fcPosFinite) {
    // finite(V) && V > 0 ==> V u< exp_mask
    appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_ULT, DstTy, AsInt,
                                     ExpMaskC));
    Mask &= ~fcPosFinite;
  } else if ((Mask & fcFinite) == fcNegFinite) {
    // finite(V) && V < 0 ==> abs(V) u< exp_mask && signbit == 1
    auto Cmp = assignSPIRVTy(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_ULT,
                                                  DstTy, Abs, ExpMaskC));
    appendToRes(MIRBuilder.buildAnd(DstTy, Cmp, Sign));
    Mask &= ~fcNegFinite;
  }

  if (FPClassTest PartialCheck = Mask & (fcZero | fcSubnormal)) {
    // fcZero | fcSubnormal => test all exponent bits are 0
    // TODO: Handle sign bit specific cases
    // TODO: Handle inverted case
    if (PartialCheck == (fcZero | fcSubnormal)) {
      auto ExpBits = assignSPIRVTy(MIRBuilder.buildAnd(IntTy, AsInt, ExpMaskC));
      appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy,
                                       ExpBits, ZeroC));
      Mask &= ~PartialCheck;
    }
  }

  // Check for individual classes.
  if (FPClassTest PartialCheck = Mask & fcZero) {
    if (PartialCheck == fcPosZero)
      appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy,
                                       AsInt, ZeroC));
    else if (PartialCheck == fcZero)
      appendToRes(
          MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy, Abs, ZeroC));
    else // fcNegZero
      appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy,
                                       AsInt, SignBitC));
  }

  if (FPClassTest PartialCheck = Mask & fcSubnormal) {
    // issubnormal(V) ==> unsigned(abs(V) - 1) u< (all mantissa bits set)
    // issubnormal(V) && V>0 ==> unsigned(V - 1) u< (all mantissa bits set)
    auto V = (PartialCheck == fcPosSubnormal) ? AsInt : Abs;
    auto OneC = buildSPIRVConstant(IntTy, 1);
    auto VMinusOne = MIRBuilder.buildSub(IntTy, V, OneC);
    auto SubnormalRes = assignSPIRVTy(
        MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_ULT, DstTy, VMinusOne,
                             buildSPIRVConstant(IntTy, AllOneMantissa)));
    if (PartialCheck == fcNegSubnormal)
      SubnormalRes = MIRBuilder.buildAnd(DstTy, SubnormalRes, Sign);
    appendToRes(std::move(SubnormalRes));
  }

  if (FPClassTest PartialCheck = Mask & fcInf) {
    if (PartialCheck == fcPosInf)
      appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy,
                                       AsInt, InfC));
    else if (PartialCheck == fcInf)
      appendToRes(
          MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy, Abs, InfC));
    else { // fcNegInf
      APInt NegInf = APFloat::getInf(Semantics, true).bitcastToAPInt();
      auto NegInfC = buildSPIRVConstant(IntTy, NegInf);
      appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_EQ, DstTy,
                                       AsInt, NegInfC));
    }
  }

  if (FPClassTest PartialCheck = Mask & fcNan) {
    auto InfWithQnanBitC = buildSPIRVConstant(IntTy, Inf | QNaNBitMask);
    if (PartialCheck == fcNan) {
      // isnan(V) ==> abs(V) u> int(inf)
      appendToRes(
          MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_UGT, DstTy, Abs, InfC));
    } else if (PartialCheck == fcQNan) {
      // isquiet(V) ==> abs(V) u>= (unsigned(Inf) | quiet_bit)
      appendToRes(MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_UGE, DstTy, Abs,
                                       InfWithQnanBitC));
    } else { // fcSNan
      // issignaling(V) ==> abs(V) u> unsigned(Inf) &&
      //                    abs(V) u< (unsigned(Inf) | quiet_bit)
      auto IsNan = assignSPIRVTy(
          MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_UGT, DstTy, Abs, InfC));
      auto IsNotQnan = assignSPIRVTy(MIRBuilder.buildICmp(
          CmpInst::Predicate::ICMP_ULT, DstTy, Abs, InfWithQnanBitC));
      appendToRes(MIRBuilder.buildAnd(DstTy, IsNan, IsNotQnan));
    }
  }

  if (FPClassTest PartialCheck = Mask & fcNormal) {
    // isnormal(V) ==> (0 u< exp u< max_exp) ==> (unsigned(exp-1) u<
    // (max_exp-1))
    APInt ExpLSB = ExpMask & ~(ExpMask.shl(1));
    auto ExpMinusOne = assignSPIRVTy(
        MIRBuilder.buildSub(IntTy, Abs, buildSPIRVConstant(IntTy, ExpLSB)));
    APInt MaxExpMinusOne = ExpMask - ExpLSB;
    auto NormalRes = assignSPIRVTy(
        MIRBuilder.buildICmp(CmpInst::Predicate::ICMP_ULT, DstTy, ExpMinusOne,
                             buildSPIRVConstant(IntTy, MaxExpMinusOne)));
    if (PartialCheck == fcNegNormal)
      NormalRes = MIRBuilder.buildAnd(DstTy, NormalRes, Sign);
    else if (PartialCheck == fcPosNormal) {
      auto PosSign = assignSPIRVTy(MIRBuilder.buildXor(
          DstTy, Sign, buildSPIRVConstant(DstTy, InversionMask)));
      NormalRes = MIRBuilder.buildAnd(DstTy, NormalRes, PosSign);
    }
    appendToRes(std::move(NormalRes));
  }

  MIRBuilder.buildCopy(DstReg, Res);
  MI.eraseFromParent();
  return true;
}