xref: /freebsd-src/contrib/llvm-project/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)

//===-- RISCVLegalizerInfo.cpp ----------------------------------*- 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
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements the targeting of the Machinelegalizer class for RISC-V.
/// \todo This should be generated by TableGen.
//===----------------------------------------------------------------------===//

#include "RISCVLegalizerInfo.h"
#include "MCTargetDesc/RISCVMatInt.h"
#include "RISCVMachineFunctionInfo.h"
#include "RISCVSubtarget.h"
#include "llvm/CodeGen/GlobalISel/GIMatchTableExecutor.h"
#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
#include "llvm/CodeGen/GlobalISel/LegalizerHelper.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Type.h"

using namespace llvm;
using namespace LegalityPredicates;
using namespace LegalizeMutations;

// Is this type supported by scalar FP arithmetic operations given the current
// subtarget.
static LegalityPredicate typeIsScalarFPArith(unsigned TypeIdx,
                                             const RISCVSubtarget &ST) {
  return [=, &ST](const LegalityQuery &Query) {
    return Query.Types[TypeIdx].isScalar() &&
           ((ST.hasStdExtZfh() && Query.Types[TypeIdx].getSizeInBits() == 16) ||
            (ST.hasStdExtF() && Query.Types[TypeIdx].getSizeInBits() == 32) ||
            (ST.hasStdExtD() && Query.Types[TypeIdx].getSizeInBits() == 64));
  };
}

static LegalityPredicate
typeIsLegalIntOrFPVec(unsigned TypeIdx,
                      std::initializer_list<LLT> IntOrFPVecTys,
                      const RISCVSubtarget &ST) {
  LegalityPredicate P = [=, &ST](const LegalityQuery &Query) {
    return ST.hasVInstructions() &&
           (Query.Types[TypeIdx].getScalarSizeInBits() != 64 ||
            ST.hasVInstructionsI64()) &&
           (Query.Types[TypeIdx].getElementCount().getKnownMinValue() != 1 ||
            ST.getELen() == 64);
  };

  return all(typeInSet(TypeIdx, IntOrFPVecTys), P);
}

static LegalityPredicate
typeIsLegalBoolVec(unsigned TypeIdx, std::initializer_list<LLT> BoolVecTys,
                   const RISCVSubtarget &ST) {
  LegalityPredicate P = [=, &ST](const LegalityQuery &Query) {
    return ST.hasVInstructions() &&
           (Query.Types[TypeIdx].getElementCount().getKnownMinValue() != 1 ||
            ST.getELen() == 64);
  };
  return all(typeInSet(TypeIdx, BoolVecTys), P);
}

RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST)
    : STI(ST), XLen(STI.getXLen()), sXLen(LLT::scalar(XLen)) {
  const LLT sDoubleXLen = LLT::scalar(2 * XLen);
  const LLT p0 = LLT::pointer(0, XLen);
  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 nxv1s1 = LLT::scalable_vector(1, s1);
  const LLT nxv2s1 = LLT::scalable_vector(2, s1);
  const LLT nxv4s1 = LLT::scalable_vector(4, s1);
  const LLT nxv8s1 = LLT::scalable_vector(8, s1);
  const LLT nxv16s1 = LLT::scalable_vector(16, s1);
  const LLT nxv32s1 = LLT::scalable_vector(32, s1);
  const LLT nxv64s1 = LLT::scalable_vector(64, s1);

  const LLT nxv1s8 = LLT::scalable_vector(1, s8);
  const LLT nxv2s8 = LLT::scalable_vector(2, s8);
  const LLT nxv4s8 = LLT::scalable_vector(4, s8);
  const LLT nxv8s8 = LLT::scalable_vector(8, s8);
  const LLT nxv16s8 = LLT::scalable_vector(16, s8);
  const LLT nxv32s8 = LLT::scalable_vector(32, s8);
  const LLT nxv64s8 = LLT::scalable_vector(64, s8);

  const LLT nxv1s16 = LLT::scalable_vector(1, s16);
  const LLT nxv2s16 = LLT::scalable_vector(2, s16);
  const LLT nxv4s16 = LLT::scalable_vector(4, s16);
  const LLT nxv8s16 = LLT::scalable_vector(8, s16);
  const LLT nxv16s16 = LLT::scalable_vector(16, s16);
  const LLT nxv32s16 = LLT::scalable_vector(32, s16);

  const LLT nxv1s32 = LLT::scalable_vector(1, s32);
  const LLT nxv2s32 = LLT::scalable_vector(2, s32);
  const LLT nxv4s32 = LLT::scalable_vector(4, s32);
  const LLT nxv8s32 = LLT::scalable_vector(8, s32);
  const LLT nxv16s32 = LLT::scalable_vector(16, s32);

  const LLT nxv1s64 = LLT::scalable_vector(1, s64);
  const LLT nxv2s64 = LLT::scalable_vector(2, s64);
  const LLT nxv4s64 = LLT::scalable_vector(4, s64);
  const LLT nxv8s64 = LLT::scalable_vector(8, s64);

  using namespace TargetOpcode;

  auto BoolVecTys = {nxv1s1, nxv2s1, nxv4s1, nxv8s1, nxv16s1, nxv32s1, nxv64s1};

  auto IntOrFPVecTys = {nxv1s8,   nxv2s8,  nxv4s8,  nxv8s8,  nxv16s8, nxv32s8,
                        nxv64s8,  nxv1s16, nxv2s16, nxv4s16, nxv8s16, nxv16s16,
                        nxv32s16, nxv1s32, nxv2s32, nxv4s32, nxv8s32, nxv16s32,
                        nxv1s64,  nxv2s64, nxv4s64, nxv8s64};

  getActionDefinitionsBuilder({G_ADD, G_SUB, G_AND, G_OR, G_XOR})
      .legalFor({s32, sXLen})
      .legalIf(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST))
      .widenScalarToNextPow2(0)
      .clampScalar(0, s32, sXLen);

  getActionDefinitionsBuilder(
      {G_UADDE, G_UADDO, G_USUBE, G_USUBO}).lower();

  getActionDefinitionsBuilder({G_SADDO, G_SSUBO}).minScalar(0, sXLen).lower();

  // TODO: Use Vector Single-Width Saturating Instructions for vector types.
  getActionDefinitionsBuilder({G_UADDSAT, G_SADDSAT, G_USUBSAT, G_SSUBSAT})
      .lower();

  auto &ShiftActions = getActionDefinitionsBuilder({G_ASHR, G_LSHR, G_SHL});
  if (ST.is64Bit())
    ShiftActions.customFor({{s32, s32}});
  ShiftActions.legalFor({{s32, s32}, {s32, sXLen}, {sXLen, sXLen}})
      .widenScalarToNextPow2(0)
      .clampScalar(1, s32, sXLen)
      .clampScalar(0, s32, sXLen)
      .minScalarSameAs(1, 0)
      .widenScalarToNextPow2(1);

  auto &ExtActions =
      getActionDefinitionsBuilder({G_ZEXT, G_SEXT, G_ANYEXT})
          .legalIf(all(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST),
                       typeIsLegalIntOrFPVec(1, IntOrFPVecTys, ST)));
  if (ST.is64Bit()) {
    ExtActions.legalFor({{sXLen, s32}});
    getActionDefinitionsBuilder(G_SEXT_INREG)
        .customFor({sXLen})
        .maxScalar(0, sXLen)
        .lower();
  } else {
    getActionDefinitionsBuilder(G_SEXT_INREG).maxScalar(0, sXLen).lower();
  }
  ExtActions.customIf(typeIsLegalBoolVec(1, BoolVecTys, ST))
      .maxScalar(0, sXLen);

  // Merge/Unmerge
  for (unsigned Op : {G_MERGE_VALUES, G_UNMERGE_VALUES}) {
    auto &MergeUnmergeActions = getActionDefinitionsBuilder(Op);
    unsigned BigTyIdx = Op == G_MERGE_VALUES ? 0 : 1;
    unsigned LitTyIdx = Op == G_MERGE_VALUES ? 1 : 0;
    if (XLen == 32 && ST.hasStdExtD()) {
      MergeUnmergeActions.legalIf(
          all(typeIs(BigTyIdx, s64), typeIs(LitTyIdx, s32)));
    }
    MergeUnmergeActions.widenScalarToNextPow2(LitTyIdx, XLen)
        .widenScalarToNextPow2(BigTyIdx, XLen)
        .clampScalar(LitTyIdx, sXLen, sXLen)
        .clampScalar(BigTyIdx, sXLen, sXLen);
  }

  getActionDefinitionsBuilder({G_FSHL, G_FSHR}).lower();

  auto &RotateActions = getActionDefinitionsBuilder({G_ROTL, G_ROTR});
  if (ST.hasStdExtZbb() || ST.hasStdExtZbkb()) {
    RotateActions.legalFor({{s32, sXLen}, {sXLen, sXLen}});
    // Widen s32 rotate amount to s64 so SDAG patterns will match.
    if (ST.is64Bit())
      RotateActions.widenScalarIf(all(typeIs(0, s32), typeIs(1, s32)),
                                  changeTo(1, sXLen));
  }
  RotateActions.lower();

  getActionDefinitionsBuilder(G_BITREVERSE).maxScalar(0, sXLen).lower();

  getActionDefinitionsBuilder(G_BITCAST).legalIf(
      all(LegalityPredicates::any(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST),
                                  typeIsLegalBoolVec(0, BoolVecTys, ST)),
          LegalityPredicates::any(typeIsLegalIntOrFPVec(1, IntOrFPVecTys, ST),
                                  typeIsLegalBoolVec(1, BoolVecTys, ST))));

  auto &BSWAPActions = getActionDefinitionsBuilder(G_BSWAP);
  if (ST.hasStdExtZbb() || ST.hasStdExtZbkb())
    BSWAPActions.legalFor({sXLen}).clampScalar(0, sXLen, sXLen);
  else
    BSWAPActions.maxScalar(0, sXLen).lower();

  auto &CountZerosActions = getActionDefinitionsBuilder({G_CTLZ, G_CTTZ});
  auto &CountZerosUndefActions =
      getActionDefinitionsBuilder({G_CTLZ_ZERO_UNDEF, G_CTTZ_ZERO_UNDEF});
  if (ST.hasStdExtZbb()) {
    CountZerosActions.legalFor({{s32, s32}, {sXLen, sXLen}})
        .clampScalar(0, s32, sXLen)
        .widenScalarToNextPow2(0)
        .scalarSameSizeAs(1, 0);
  } else {
    CountZerosActions.maxScalar(0, sXLen).scalarSameSizeAs(1, 0).lower();
    CountZerosUndefActions.maxScalar(0, sXLen).scalarSameSizeAs(1, 0);
  }
  CountZerosUndefActions.lower();

  auto &CTPOPActions = getActionDefinitionsBuilder(G_CTPOP);
  if (ST.hasStdExtZbb()) {
    CTPOPActions.legalFor({{s32, s32}, {sXLen, sXLen}})
        .clampScalar(0, s32, sXLen)
        .widenScalarToNextPow2(0)
        .scalarSameSizeAs(1, 0);
  } else {
    CTPOPActions.maxScalar(0, sXLen).scalarSameSizeAs(1, 0).lower();
  }

  auto &ConstantActions = getActionDefinitionsBuilder(G_CONSTANT);
  ConstantActions.legalFor({s32, p0});
  if (ST.is64Bit())
    ConstantActions.customFor({s64});
  ConstantActions.widenScalarToNextPow2(0).clampScalar(0, s32, sXLen);

  // TODO: transform illegal vector types into legal vector type
  getActionDefinitionsBuilder(
      {G_IMPLICIT_DEF, G_CONSTANT_FOLD_BARRIER, G_FREEZE})
      .legalFor({s32, sXLen, p0})
      .legalIf(typeIsLegalBoolVec(0, BoolVecTys, ST))
      .legalIf(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST))
      .widenScalarToNextPow2(0)
      .clampScalar(0, s32, sXLen);

  getActionDefinitionsBuilder(G_ICMP)
      .legalFor({{sXLen, sXLen}, {sXLen, p0}})
      .legalIf(all(typeIsLegalBoolVec(0, BoolVecTys, ST),
                   typeIsLegalIntOrFPVec(1, IntOrFPVecTys, ST)))
      .widenScalarOrEltToNextPow2OrMinSize(1, 8)
      .clampScalar(1, sXLen, sXLen)
      .clampScalar(0, sXLen, sXLen);

  auto &SelectActions =
      getActionDefinitionsBuilder(G_SELECT)
          .legalFor({{s32, sXLen}, {p0, sXLen}})
          .legalIf(all(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST),
                       typeIsLegalBoolVec(1, BoolVecTys, ST)));
  if (XLen == 64 || ST.hasStdExtD())
    SelectActions.legalFor({{s64, sXLen}});
  SelectActions.widenScalarToNextPow2(0)
      .clampScalar(0, s32, (XLen == 64 || ST.hasStdExtD()) ? s64 : s32)
      .clampScalar(1, sXLen, sXLen);

  auto &LoadStoreActions =
      getActionDefinitionsBuilder({G_LOAD, G_STORE})
          .legalForTypesWithMemDesc({{s32, p0, s8, 8},
                                     {s32, p0, s16, 16},
                                     {s32, p0, s32, 32},
                                     {p0, p0, sXLen, XLen}});
  auto &ExtLoadActions =
      getActionDefinitionsBuilder({G_SEXTLOAD, G_ZEXTLOAD})
          .legalForTypesWithMemDesc({{s32, p0, s8, 8}, {s32, p0, s16, 16}});
  if (XLen == 64) {
    LoadStoreActions.legalForTypesWithMemDesc({{s64, p0, s8, 8},
                                               {s64, p0, s16, 16},
                                               {s64, p0, s32, 32},
                                               {s64, p0, s64, 64}});
    ExtLoadActions.legalForTypesWithMemDesc(
        {{s64, p0, s8, 8}, {s64, p0, s16, 16}, {s64, p0, s32, 32}});
  } else if (ST.hasStdExtD()) {
    LoadStoreActions.legalForTypesWithMemDesc({{s64, p0, s64, 64}});
  }
  LoadStoreActions.clampScalar(0, s32, sXLen).lower();
  ExtLoadActions.widenScalarToNextPow2(0).clampScalar(0, s32, sXLen).lower();

  getActionDefinitionsBuilder({G_PTR_ADD, G_PTRMASK}).legalFor({{p0, sXLen}});

  getActionDefinitionsBuilder(G_PTRTOINT)
      .legalFor({{sXLen, p0}})
      .clampScalar(0, sXLen, sXLen);

  getActionDefinitionsBuilder(G_INTTOPTR)
      .legalFor({{p0, sXLen}})
      .clampScalar(1, sXLen, sXLen);

  getActionDefinitionsBuilder(G_BRCOND).legalFor({sXLen}).minScalar(0, sXLen);

  getActionDefinitionsBuilder(G_BRJT).legalFor({{p0, sXLen}});

  getActionDefinitionsBuilder(G_BRINDIRECT).legalFor({p0});

  getActionDefinitionsBuilder(G_PHI)
      .legalFor({p0, sXLen})
      .widenScalarToNextPow2(0)
      .clampScalar(0, sXLen, sXLen);

  getActionDefinitionsBuilder({G_GLOBAL_VALUE, G_JUMP_TABLE, G_CONSTANT_POOL})
      .legalFor({p0});

  if (ST.hasStdExtZmmul()) {
    getActionDefinitionsBuilder(G_MUL)
        .legalFor({s32, sXLen})
        .widenScalarToNextPow2(0)
        .clampScalar(0, s32, sXLen);

    // clang-format off
    getActionDefinitionsBuilder({G_SMULH, G_UMULH})
        .legalFor({sXLen})
        .lower();
    // clang-format on

    getActionDefinitionsBuilder({G_SMULO, G_UMULO}).minScalar(0, sXLen).lower();
  } else {
    getActionDefinitionsBuilder(G_MUL)
        .libcallFor({sXLen, sDoubleXLen})
        .widenScalarToNextPow2(0)
        .clampScalar(0, sXLen, sDoubleXLen);

    getActionDefinitionsBuilder({G_SMULH, G_UMULH}).lowerFor({sXLen});

    getActionDefinitionsBuilder({G_SMULO, G_UMULO})
        .minScalar(0, sXLen)
        // Widen sXLen to sDoubleXLen so we can use a single libcall to get
        // the low bits for the mul result and high bits to do the overflow
        // check.
        .widenScalarIf(typeIs(0, sXLen),
                       LegalizeMutations::changeTo(0, sDoubleXLen))
        .lower();
  }

  if (ST.hasStdExtM()) {
    getActionDefinitionsBuilder({G_UDIV, G_SDIV, G_UREM, G_SREM})
        .legalFor({s32, sXLen})
        .libcallFor({sDoubleXLen})
        .clampScalar(0, s32, sDoubleXLen)
        .widenScalarToNextPow2(0);
  } else {
    getActionDefinitionsBuilder({G_UDIV, G_SDIV, G_UREM, G_SREM})
        .libcallFor({sXLen, sDoubleXLen})
        .clampScalar(0, sXLen, sDoubleXLen)
        .widenScalarToNextPow2(0);
  }

  // TODO: Use libcall for sDoubleXLen.
  getActionDefinitionsBuilder({G_UDIVREM, G_SDIVREM}).lower();

  auto &AbsActions = getActionDefinitionsBuilder(G_ABS);
  if (ST.hasStdExtZbb())
    AbsActions.customFor({s32, sXLen}).minScalar(0, sXLen);
  AbsActions.lower();

  auto &MinMaxActions =
      getActionDefinitionsBuilder({G_UMAX, G_UMIN, G_SMAX, G_SMIN});
  if (ST.hasStdExtZbb())
    MinMaxActions.legalFor({sXLen}).minScalar(0, sXLen);
  MinMaxActions.lower();

  getActionDefinitionsBuilder(G_FRAME_INDEX).legalFor({p0});

  getActionDefinitionsBuilder({G_MEMCPY, G_MEMMOVE, G_MEMSET}).libcall();

  getActionDefinitionsBuilder(G_DYN_STACKALLOC).lower();

  // FP Operations

  getActionDefinitionsBuilder({G_FADD, G_FSUB, G_FMUL, G_FDIV, G_FMA, G_FNEG,
                               G_FABS, G_FSQRT, G_FMAXNUM, G_FMINNUM})
      .legalIf(typeIsScalarFPArith(0, ST));

  getActionDefinitionsBuilder(G_FREM)
      .libcallFor({s32, s64})
      .minScalar(0, s32)
      .scalarize(0);

  getActionDefinitionsBuilder(G_FCOPYSIGN)
      .legalIf(all(typeIsScalarFPArith(0, ST), typeIsScalarFPArith(1, ST)));

  // FIXME: Use Zfhmin.
  getActionDefinitionsBuilder(G_FPTRUNC).legalIf(
      [=, &ST](const LegalityQuery &Query) -> bool {
        return (ST.hasStdExtD() && typeIs(0, s32)(Query) &&
                typeIs(1, s64)(Query)) ||
               (ST.hasStdExtZfh() && typeIs(0, s16)(Query) &&
                typeIs(1, s32)(Query)) ||
               (ST.hasStdExtZfh() && ST.hasStdExtD() && typeIs(0, s16)(Query) &&
                typeIs(1, s64)(Query));
      });
  getActionDefinitionsBuilder(G_FPEXT).legalIf(
      [=, &ST](const LegalityQuery &Query) -> bool {
        return (ST.hasStdExtD() && typeIs(0, s64)(Query) &&
                typeIs(1, s32)(Query)) ||
               (ST.hasStdExtZfh() && typeIs(0, s32)(Query) &&
                typeIs(1, s16)(Query)) ||
               (ST.hasStdExtZfh() && ST.hasStdExtD() && typeIs(0, s64)(Query) &&
                typeIs(1, s16)(Query));
      });

  getActionDefinitionsBuilder(G_FCMP)
      .legalIf(all(typeIs(0, sXLen), typeIsScalarFPArith(1, ST)))
      .clampScalar(0, sXLen, sXLen);

  // TODO: Support vector version of G_IS_FPCLASS.
  getActionDefinitionsBuilder(G_IS_FPCLASS)
      .customIf(all(typeIs(0, s1), typeIsScalarFPArith(1, ST)));

  getActionDefinitionsBuilder(G_FCONSTANT)
      .legalIf(typeIsScalarFPArith(0, ST))
      .lowerFor({s32, s64});

  getActionDefinitionsBuilder({G_FPTOSI, G_FPTOUI})
      .legalIf(all(typeInSet(0, {s32, sXLen}), typeIsScalarFPArith(1, ST)))
      .widenScalarToNextPow2(0)
      .clampScalar(0, s32, sXLen)
      .libcall();

  getActionDefinitionsBuilder({G_SITOFP, G_UITOFP})
      .legalIf(all(typeIsScalarFPArith(0, ST), typeInSet(1, {s32, sXLen})))
      .widenScalarToNextPow2(1)
      .clampScalar(1, s32, sXLen);

  // FIXME: We can do custom inline expansion like SelectionDAG.
  // FIXME: Legal with Zfa.
  getActionDefinitionsBuilder({G_FCEIL, G_FFLOOR})
      .libcallFor({s32, s64});

  getActionDefinitionsBuilder(G_VASTART).customFor({p0});

  // va_list must be a pointer, but most sized types are pretty easy to handle
  // as the destination.
  getActionDefinitionsBuilder(G_VAARG)
      // TODO: Implement narrowScalar and widenScalar for G_VAARG for types
      // outside the [s32, sXLen] range.
      .clampScalar(0, s32, sXLen)
      .lowerForCartesianProduct({s32, sXLen, p0}, {p0});

  getActionDefinitionsBuilder(G_VSCALE)
      .clampScalar(0, sXLen, sXLen)
      .customFor({sXLen});

  auto &SplatActions =
      getActionDefinitionsBuilder(G_SPLAT_VECTOR)
          .legalIf(all(typeIsLegalIntOrFPVec(0, IntOrFPVecTys, ST),
                       typeIs(1, sXLen)))
          .customIf(all(typeIsLegalBoolVec(0, BoolVecTys, ST), typeIs(1, s1)));
  // Handle case of s64 element vectors on RV32. If the subtarget does not have
  // f64, then try to lower it to G_SPLAT_VECTOR_SPLIT_64_VL. If the subtarget
  // does have f64, then we don't know whether the type is an f64 or an i64,
  // so mark the G_SPLAT_VECTOR as legal and decide later what to do with it,
  // depending on how the instructions it consumes are legalized. They are not
  // legalized yet since legalization is in reverse postorder, so we cannot
  // make the decision at this moment.
  if (XLen == 32) {
    if (ST.hasVInstructionsF64() && ST.hasStdExtD())
      SplatActions.legalIf(all(
          typeInSet(0, {nxv1s64, nxv2s64, nxv4s64, nxv8s64}), typeIs(1, s64)));
    else if (ST.hasVInstructionsI64())
      SplatActions.customIf(all(
          typeInSet(0, {nxv1s64, nxv2s64, nxv4s64, nxv8s64}), typeIs(1, s64)));
  }

  SplatActions.clampScalar(1, sXLen, sXLen);

  getLegacyLegalizerInfo().computeTables();
}

bool RISCVLegalizerInfo::legalizeIntrinsic(LegalizerHelper &Helper,
                                           MachineInstr &MI) const {
  Intrinsic::ID IntrinsicID = cast<GIntrinsic>(MI).getIntrinsicID();
  switch (IntrinsicID) {
  default:
    return false;
  case Intrinsic::vacopy: {
    // vacopy arguments must be legal because of the intrinsic signature.
    // No need to check here.

    MachineIRBuilder &MIRBuilder = Helper.MIRBuilder;
    MachineRegisterInfo &MRI = *MIRBuilder.getMRI();
    MachineFunction &MF = *MI.getMF();
    const DataLayout &DL = MIRBuilder.getDataLayout();
    LLVMContext &Ctx = MF.getFunction().getContext();

    Register DstLst = MI.getOperand(1).getReg();
    LLT PtrTy = MRI.getType(DstLst);

    // Load the source va_list
    Align Alignment = DL.getABITypeAlign(getTypeForLLT(PtrTy, Ctx));
    MachineMemOperand *LoadMMO = MF.getMachineMemOperand(
        MachinePointerInfo(), MachineMemOperand::MOLoad, PtrTy, Alignment);
    auto Tmp = MIRBuilder.buildLoad(PtrTy, MI.getOperand(2), *LoadMMO);

    // Store the result in the destination va_list
    MachineMemOperand *StoreMMO = MF.getMachineMemOperand(
        MachinePointerInfo(), MachineMemOperand::MOStore, PtrTy, Alignment);
    MIRBuilder.buildStore(Tmp, DstLst, *StoreMMO);

    MI.eraseFromParent();
    return true;
  }
  }
}

bool RISCVLegalizerInfo::legalizeShlAshrLshr(
    MachineInstr &MI, MachineIRBuilder &MIRBuilder,
    GISelChangeObserver &Observer) const {
  assert(MI.getOpcode() == TargetOpcode::G_ASHR ||
         MI.getOpcode() == TargetOpcode::G_LSHR ||
         MI.getOpcode() == TargetOpcode::G_SHL);
  MachineRegisterInfo &MRI = *MIRBuilder.getMRI();
  // If the shift amount is a G_CONSTANT, promote it to a 64 bit type so the
  // imported patterns can select it later. Either way, it will be legal.
  Register AmtReg = MI.getOperand(2).getReg();
  auto VRegAndVal = getIConstantVRegValWithLookThrough(AmtReg, MRI);
  if (!VRegAndVal)
    return true;
  // Check the shift amount is in range for an immediate form.
  uint64_t Amount = VRegAndVal->Value.getZExtValue();
  if (Amount > 31)
    return true; // This will have to remain a register variant.
  auto ExtCst = MIRBuilder.buildConstant(LLT::scalar(64), Amount);
  Observer.changingInstr(MI);
  MI.getOperand(2).setReg(ExtCst.getReg(0));
  Observer.changedInstr(MI);
  return true;
}

bool RISCVLegalizerInfo::legalizeVAStart(MachineInstr &MI,
                                         MachineIRBuilder &MIRBuilder) const {
  // Stores the address of the VarArgsFrameIndex slot into the memory location
  assert(MI.getOpcode() == TargetOpcode::G_VASTART);
  MachineFunction *MF = MI.getParent()->getParent();
  RISCVMachineFunctionInfo *FuncInfo = MF->getInfo<RISCVMachineFunctionInfo>();
  int FI = FuncInfo->getVarArgsFrameIndex();
  LLT AddrTy = MIRBuilder.getMRI()->getType(MI.getOperand(0).getReg());
  auto FINAddr = MIRBuilder.buildFrameIndex(AddrTy, FI);
  assert(MI.hasOneMemOperand());
  MIRBuilder.buildStore(FINAddr, MI.getOperand(0).getReg(),
                        *MI.memoperands()[0]);
  MI.eraseFromParent();
  return true;
}

bool RISCVLegalizerInfo::shouldBeInConstantPool(APInt APImm,
                                                bool ShouldOptForSize) const {
  assert(APImm.getBitWidth() == 32 || APImm.getBitWidth() == 64);
  int64_t Imm = APImm.getSExtValue();
  // All simm32 constants should be handled by isel.
  // NOTE: The getMaxBuildIntsCost call below should return a value >= 2 making
  // this check redundant, but small immediates are common so this check
  // should have better compile time.
  if (isInt<32>(Imm))
    return false;

  // We only need to cost the immediate, if constant pool lowering is enabled.
  if (!STI.useConstantPoolForLargeInts())
    return false;

  RISCVMatInt::InstSeq Seq = RISCVMatInt::generateInstSeq(Imm, STI);
  if (Seq.size() <= STI.getMaxBuildIntsCost())
    return false;

  // Optimizations below are disabled for opt size. If we're optimizing for
  // size, use a constant pool.
  if (ShouldOptForSize)
    return true;
  //
  // Special case. See if we can build the constant as (ADD (SLLI X, C), X) do
  // that if it will avoid a constant pool.
  // It will require an extra temporary register though.
  // If we have Zba we can use (ADD_UW X, (SLLI X, 32)) to handle cases where
  // low and high 32 bits are the same and bit 31 and 63 are set.
  unsigned ShiftAmt, AddOpc;
  RISCVMatInt::InstSeq SeqLo =
      RISCVMatInt::generateTwoRegInstSeq(Imm, STI, ShiftAmt, AddOpc);
  return !(!SeqLo.empty() && (SeqLo.size() + 2) <= STI.getMaxBuildIntsCost());
}

bool RISCVLegalizerInfo::legalizeVScale(MachineInstr &MI,
                                        MachineIRBuilder &MIB) const {
  const LLT XLenTy(STI.getXLenVT());
  Register Dst = MI.getOperand(0).getReg();

  // We define our scalable vector types for lmul=1 to use a 64 bit known
  // minimum size. e.g. <vscale x 2 x i32>. VLENB is in bytes so we calculate
  // vscale as VLENB / 8.
  static_assert(RISCV::RVVBitsPerBlock == 64, "Unexpected bits per block!");
  if (STI.getRealMinVLen() < RISCV::RVVBitsPerBlock)
    // Support for VLEN==32 is incomplete.
    return false;

  // We assume VLENB is a multiple of 8. We manually choose the best shift
  // here because SimplifyDemandedBits isn't always able to simplify it.
  uint64_t Val = MI.getOperand(1).getCImm()->getZExtValue();
  if (isPowerOf2_64(Val)) {
    uint64_t Log2 = Log2_64(Val);
    if (Log2 < 3) {
      auto VLENB = MIB.buildInstr(RISCV::G_READ_VLENB, {XLenTy}, {});
      MIB.buildLShr(Dst, VLENB, MIB.buildConstant(XLenTy, 3 - Log2));
    } else if (Log2 > 3) {
      auto VLENB = MIB.buildInstr(RISCV::G_READ_VLENB, {XLenTy}, {});
      MIB.buildShl(Dst, VLENB, MIB.buildConstant(XLenTy, Log2 - 3));
    } else {
      MIB.buildInstr(RISCV::G_READ_VLENB, {Dst}, {});
    }
  } else if ((Val % 8) == 0) {
    // If the multiplier is a multiple of 8, scale it down to avoid needing
    // to shift the VLENB value.
    auto VLENB = MIB.buildInstr(RISCV::G_READ_VLENB, {XLenTy}, {});
    MIB.buildMul(Dst, VLENB, MIB.buildConstant(XLenTy, Val / 8));
  } else {
    auto VLENB = MIB.buildInstr(RISCV::G_READ_VLENB, {XLenTy}, {});
    auto VScale = MIB.buildLShr(XLenTy, VLENB, MIB.buildConstant(XLenTy, 3));
    MIB.buildMul(Dst, VScale, MIB.buildConstant(XLenTy, Val));
  }
  MI.eraseFromParent();
  return true;
}

// Custom-lower extensions from mask vectors by using a vselect either with 1
// for zero/any-extension or -1 for sign-extension:
//   (vXiN = (s|z)ext vXi1:vmask) -> (vXiN = vselect vmask, (-1 or 1), 0)
// Note that any-extension is lowered identically to zero-extension.
bool RISCVLegalizerInfo::legalizeExt(MachineInstr &MI,
                                     MachineIRBuilder &MIB) const {

  unsigned Opc = MI.getOpcode();
  assert(Opc == TargetOpcode::G_ZEXT || Opc == TargetOpcode::G_SEXT ||
         Opc == TargetOpcode::G_ANYEXT);

  MachineRegisterInfo &MRI = *MIB.getMRI();
  Register Dst = MI.getOperand(0).getReg();
  Register Src = MI.getOperand(1).getReg();

  LLT DstTy = MRI.getType(Dst);
  int64_t ExtTrueVal = Opc == TargetOpcode::G_SEXT ? -1 : 1;
  LLT DstEltTy = DstTy.getElementType();
  auto SplatZero = MIB.buildSplatVector(DstTy, MIB.buildConstant(DstEltTy, 0));
  auto SplatTrue =
      MIB.buildSplatVector(DstTy, MIB.buildConstant(DstEltTy, ExtTrueVal));
  MIB.buildSelect(Dst, Src, SplatTrue, SplatZero);

  MI.eraseFromParent();
  return true;
}

/// Return the type of the mask type suitable for masking the provided
/// vector type.  This is simply an i1 element type vector of the same
/// (possibly scalable) length.
static LLT getMaskTypeFor(LLT VecTy) {
  assert(VecTy.isVector());
  ElementCount EC = VecTy.getElementCount();
  return LLT::vector(EC, LLT::scalar(1));
}

/// Creates an all ones mask suitable for masking a vector of type VecTy with
/// vector length VL.
static MachineInstrBuilder buildAllOnesMask(LLT VecTy, const SrcOp &VL,
                                            MachineIRBuilder &MIB,
                                            MachineRegisterInfo &MRI) {
  LLT MaskTy = getMaskTypeFor(VecTy);
  return MIB.buildInstr(RISCV::G_VMSET_VL, {MaskTy}, {VL});
}

/// Gets the two common "VL" operands: an all-ones mask and the vector length.
/// VecTy is a scalable vector type.
static std::pair<MachineInstrBuilder, Register>
buildDefaultVLOps(const DstOp &Dst, MachineIRBuilder &MIB,
                  MachineRegisterInfo &MRI) {
  LLT VecTy = Dst.getLLTTy(MRI);
  assert(VecTy.isScalableVector() && "Expecting scalable container type");
  Register VL(RISCV::X0);
  MachineInstrBuilder Mask = buildAllOnesMask(VecTy, VL, MIB, MRI);
  return {Mask, VL};
}

static MachineInstrBuilder
buildSplatPartsS64WithVL(const DstOp &Dst, const SrcOp &Passthru, Register Lo,
                         Register Hi, Register VL, MachineIRBuilder &MIB,
                         MachineRegisterInfo &MRI) {
  // TODO: If the Hi bits of the splat are undefined, then it's fine to just
  // splat Lo even if it might be sign extended. I don't think we have
  // introduced a case where we're build a s64 where the upper bits are undef
  // yet.

  // Fall back to a stack store and stride x0 vector load.
  // TODO: need to lower G_SPLAT_VECTOR_SPLIT_I64. This is done in
  // preprocessDAG in SDAG.
  return MIB.buildInstr(RISCV::G_SPLAT_VECTOR_SPLIT_I64_VL, {Dst},
                        {Passthru, Lo, Hi, VL});
}

static MachineInstrBuilder
buildSplatSplitS64WithVL(const DstOp &Dst, const SrcOp &Passthru,
                         const SrcOp &Scalar, Register VL,
                         MachineIRBuilder &MIB, MachineRegisterInfo &MRI) {
  assert(Scalar.getLLTTy(MRI) == LLT::scalar(64) && "Unexpected VecTy!");
  auto Unmerge = MIB.buildUnmerge(LLT::scalar(32), Scalar);
  return buildSplatPartsS64WithVL(Dst, Passthru, Unmerge.getReg(0),
                                  Unmerge.getReg(1), VL, MIB, MRI);
}

// Lower splats of s1 types to G_ICMP. For each mask vector type, we have a
// legal equivalently-sized i8 type, so we can use that as a go-between.
// Splats of s1 types that have constant value can be legalized as VMSET_VL or
// VMCLR_VL.
bool RISCVLegalizerInfo::legalizeSplatVector(MachineInstr &MI,
                                             MachineIRBuilder &MIB) const {
  assert(MI.getOpcode() == TargetOpcode::G_SPLAT_VECTOR);

  MachineRegisterInfo &MRI = *MIB.getMRI();

  Register Dst = MI.getOperand(0).getReg();
  Register SplatVal = MI.getOperand(1).getReg();

  LLT VecTy = MRI.getType(Dst);
  LLT XLenTy(STI.getXLenVT());

  // Handle case of s64 element vectors on rv32
  if (XLenTy.getSizeInBits() == 32 &&
      VecTy.getElementType().getSizeInBits() == 64) {
    auto [_, VL] = buildDefaultVLOps(Dst, MIB, MRI);
    buildSplatSplitS64WithVL(Dst, MIB.buildUndef(VecTy), SplatVal, VL, MIB,
                             MRI);
    MI.eraseFromParent();
    return true;
  }

  // All-zeros or all-ones splats are handled specially.
  MachineInstr &SplatValMI = *MRI.getVRegDef(SplatVal);
  if (isAllOnesOrAllOnesSplat(SplatValMI, MRI)) {
    auto VL = buildDefaultVLOps(VecTy, MIB, MRI).second;
    MIB.buildInstr(RISCV::G_VMSET_VL, {Dst}, {VL});
    MI.eraseFromParent();
    return true;
  }
  if (isNullOrNullSplat(SplatValMI, MRI)) {
    auto VL = buildDefaultVLOps(VecTy, MIB, MRI).second;
    MIB.buildInstr(RISCV::G_VMCLR_VL, {Dst}, {VL});
    MI.eraseFromParent();
    return true;
  }

  // Handle non-constant mask splat (i.e. not sure if it's all zeros or all
  // ones) by promoting it to an s8 splat.
  LLT InterEltTy = LLT::scalar(8);
  LLT InterTy = VecTy.changeElementType(InterEltTy);
  auto ZExtSplatVal = MIB.buildZExt(InterEltTy, SplatVal);
  auto And =
      MIB.buildAnd(InterEltTy, ZExtSplatVal, MIB.buildConstant(InterEltTy, 1));
  auto LHS = MIB.buildSplatVector(InterTy, And);
  auto ZeroSplat =
      MIB.buildSplatVector(InterTy, MIB.buildConstant(InterEltTy, 0));
  MIB.buildICmp(CmpInst::Predicate::ICMP_NE, Dst, LHS, ZeroSplat);
  MI.eraseFromParent();
  return true;
}

bool RISCVLegalizerInfo::legalizeCustom(
    LegalizerHelper &Helper, MachineInstr &MI,
    LostDebugLocObserver &LocObserver) const {
  MachineIRBuilder &MIRBuilder = Helper.MIRBuilder;
  GISelChangeObserver &Observer = Helper.Observer;
  MachineFunction &MF = *MI.getParent()->getParent();
  switch (MI.getOpcode()) {
  default:
    // No idea what to do.
    return false;
  case TargetOpcode::G_ABS:
    return Helper.lowerAbsToMaxNeg(MI);
  // TODO: G_FCONSTANT
  case TargetOpcode::G_CONSTANT: {
    const Function &F = MF.getFunction();
    // TODO: if PSI and BFI are present, add " ||
    // llvm::shouldOptForSize(*CurMBB, PSI, BFI)".
    bool ShouldOptForSize = F.hasOptSize() || F.hasMinSize();
    const ConstantInt *ConstVal = MI.getOperand(1).getCImm();
    if (!shouldBeInConstantPool(ConstVal->getValue(), ShouldOptForSize))
      return true;
    return Helper.lowerConstant(MI);
  }
  case TargetOpcode::G_SHL:
  case TargetOpcode::G_ASHR:
  case TargetOpcode::G_LSHR:
    return legalizeShlAshrLshr(MI, MIRBuilder, Observer);
  case TargetOpcode::G_SEXT_INREG: {
    // Source size of 32 is sext.w.
    int64_t SizeInBits = MI.getOperand(2).getImm();
    if (SizeInBits == 32)
      return true;

    return Helper.lower(MI, 0, /* Unused hint type */ LLT()) ==
           LegalizerHelper::Legalized;
  }
  case TargetOpcode::G_IS_FPCLASS: {
    Register GISFPCLASS = MI.getOperand(0).getReg();
    Register Src = MI.getOperand(1).getReg();
    const MachineOperand &ImmOp = MI.getOperand(2);
    MachineIRBuilder MIB(MI);

    // Turn LLVM IR's floating point classes to that in RISC-V,
    // by simply rotating the 10-bit immediate right by two bits.
    APInt GFpClassImm(10, static_cast<uint64_t>(ImmOp.getImm()));
    auto FClassMask = MIB.buildConstant(sXLen, GFpClassImm.rotr(2).zext(XLen));
    auto ConstZero = MIB.buildConstant(sXLen, 0);

    auto GFClass = MIB.buildInstr(RISCV::G_FCLASS, {sXLen}, {Src});
    auto And = MIB.buildAnd(sXLen, GFClass, FClassMask);
    MIB.buildICmp(CmpInst::ICMP_NE, GISFPCLASS, And, ConstZero);

    MI.eraseFromParent();
    return true;
  }
  case TargetOpcode::G_VASTART:
    return legalizeVAStart(MI, MIRBuilder);
  case TargetOpcode::G_VSCALE:
    return legalizeVScale(MI, MIRBuilder);
  case TargetOpcode::G_ZEXT:
  case TargetOpcode::G_SEXT:
  case TargetOpcode::G_ANYEXT:
    return legalizeExt(MI, MIRBuilder);
  case TargetOpcode::G_SPLAT_VECTOR:
    return legalizeSplatVector(MI, MIRBuilder);
  }

  llvm_unreachable("expected switch to return");
}