llvm/lib/Target/WebAssembly/GISel/WebAssemblyInstructionSelector.cpp

//===- WebAssemblyInstructionSelector.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 InstructionSelector class for
/// WebAssembly.
/// \todo This should be generated by TableGen.
//===----------------------------------------------------------------------===//

#include "GISel/WebAssemblyRegisterBankInfo.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "Utils/WasmAddressSpaces.h"
#include "Utils/WebAssemblyTypeUtilities.h"
#include "WebAssemblyRegisterInfo.h"
#include "WebAssemblySubtarget.h"
#include "WebAssemblyTargetMachine.h"
#include "llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/IR/IntrinsicsWebAssembly.h"

#define DEBUG_TYPE "wasm-isel"

using namespace llvm;

namespace {

#define GET_GLOBALISEL_PREDICATE_BITSET
#include "WebAssemblyGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATE_BITSET

class WebAssemblyInstructionSelector : public InstructionSelector {
public:
  WebAssemblyInstructionSelector(const WebAssemblyTargetMachine &TM,
                                 const WebAssemblySubtarget &STI,
                                 const WebAssemblyRegisterBankInfo &RBI);

  bool select(MachineInstr &I) override;

  InstructionSelector::ComplexRendererFns
  selectAddrOperands32(MachineOperand &Root) const;
  InstructionSelector::ComplexRendererFns
  selectAddrOperands64(MachineOperand &Root) const;

  static const char *getName() { return DEBUG_TYPE; }

private:
  bool selectImpl(MachineInstr &I, CodeGenCoverage &CoverageInfo) const;
  bool selectCopy(MachineInstr &I, MachineRegisterInfo &MRI) const;

  InstructionSelector::ComplexRendererFns
  selectAddrOperands(LLT AddrType, unsigned int ConstOpc,
                     MachineOperand &Root) const;

  const WebAssemblyTargetMachine &TM;
  const WebAssemblySubtarget &STI;
  const WebAssemblyInstrInfo &TII;
  const WebAssemblyRegisterInfo &TRI;
  const WebAssemblyRegisterBankInfo &RBI;

#define GET_GLOBALISEL_PREDICATES_DECL
#include "WebAssemblyGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATES_DECL

#define GET_GLOBALISEL_TEMPORARIES_DECL
#include "WebAssemblyGenGlobalISel.inc"
#undef GET_GLOBALISEL_TEMPORARIES_DECL
};

} // end anonymous namespace

#define GET_GLOBALISEL_IMPL
#include "WebAssemblyGenGlobalISel.inc"
#undef GET_GLOBALISEL_IMPL

WebAssemblyInstructionSelector::WebAssemblyInstructionSelector(
    const WebAssemblyTargetMachine &TM, const WebAssemblySubtarget &STI,
    const WebAssemblyRegisterBankInfo &RBI)
    : TM(TM), STI(STI), TII(*STI.getInstrInfo()), TRI(*STI.getRegisterInfo()),
      RBI(RBI),

#define GET_GLOBALISEL_PREDICATES_INIT
#include "WebAssemblyGenGlobalISel.inc"
#undef GET_GLOBALISEL_PREDICATES_INIT
#define GET_GLOBALISEL_TEMPORARIES_INIT
#include "WebAssemblyGenGlobalISel.inc"
#undef GET_GLOBALISEL_TEMPORARIES_INIT
{
}

InstructionSelector::ComplexRendererFns
WebAssemblyInstructionSelector::selectAddrOperands(LLT AddrType,
                                                   unsigned int ConstOpc,
                                                   MachineOperand &Root) const {
  return {{
      [=](MachineInstrBuilder &MIB) { MIB.addImm(0); },
      [=](MachineInstrBuilder &MIB) { MIB.addReg(Root.getReg()); },
  }};
}

InstructionSelector::ComplexRendererFns
WebAssemblyInstructionSelector::selectAddrOperands32(
    MachineOperand &Root) const {
  return selectAddrOperands(LLT::integer(32), WebAssembly::CONST_I32, Root);
}

InstructionSelector::ComplexRendererFns
WebAssemblyInstructionSelector::selectAddrOperands64(
    MachineOperand &Root) const {
  return selectAddrOperands(LLT::integer(64), WebAssembly::CONST_I64, Root);
}

bool WebAssemblyInstructionSelector::selectCopy(
    MachineInstr &I, MachineRegisterInfo &MRI) const {
  const TargetRegisterClass *DstRC =
      TRI.getConstrainedRegClassForOperand(I.getOperand(0), MRI);
  if (!DstRC)
    return false;

  const TargetRegisterClass *SrcRC =
      TRI.getConstrainedRegClassForOperand(I.getOperand(1), MRI);
  if (!SrcRC)
    return false;

  Register DstReg = I.getOperand(0).getReg();
  Register SrcReg = I.getOperand(1).getReg();

  if (DstReg.isVirtual())
    RBI.constrainGenericRegister(DstReg, *DstRC, MRI);
  if (SrcReg.isVirtual())
    RBI.constrainGenericRegister(SrcReg, *SrcRC, MRI);

  if (DstRC != SrcRC) {
    if (DstReg.isPhysical() || SrcReg.isPhysical())
      llvm_unreachable("COPY to/from SP[32/64] or FP[32/64] with mismatching "
                       "classes not currently supported");

    if (DstRC == &WebAssembly::I32RegClass &&
        SrcRC == &WebAssembly::F32RegClass) {
      I.setDesc(TII.get(WebAssembly::I32_REINTERPRET_F32));
      return true;
    }
    if (DstRC == &WebAssembly::F32RegClass &&
        SrcRC == &WebAssembly::I32RegClass) {
      I.setDesc(TII.get(WebAssembly::F32_REINTERPRET_I32));
      return true;
    }
    if (DstRC == &WebAssembly::I64RegClass &&
        SrcRC == &WebAssembly::F64RegClass) {
      I.setDesc(TII.get(WebAssembly::I64_REINTERPRET_F64));
      return true;
    }
    if (DstRC == &WebAssembly::F64RegClass &&
        SrcRC == &WebAssembly::I64RegClass) {
      I.setDesc(TII.get(WebAssembly::F64_REINTERPRET_I64));
      return true;
    }

    llvm_unreachable("COPY between unsupported reg classes.");
  }

  return true;
}

bool WebAssemblyInstructionSelector::select(MachineInstr &I) {
  MachineBasicBlock &MBB = *I.getParent();
  MachineFunction &MF = *MBB.getParent();
  MachineRegisterInfo &MRI = MF.getRegInfo();
  const TargetLowering &TLI = *STI.getTargetLowering();

  if (!I.isPreISelOpcode()) {
    if (I.isCopy())
      return selectCopy(I, MRI);
    return true;
  }

  if (selectImpl(I, *CoverageInfo))
    return true;

  using namespace TargetOpcode;

  switch (I.getOpcode()) {
  case G_IMPLICIT_DEF: {
    const Register DefReg = I.getOperand(0).getReg();

    const TargetRegisterClass *DefRC =
        TRI.getConstrainedRegClassForOperand(I.getOperand(0), MRI);

    if (!DefRC)
      return false;

    I.setDesc(TII.get(TargetOpcode::IMPLICIT_DEF));
    return RBI.constrainGenericRegister(DefReg, *DefRC, MRI) != nullptr;
  }
  case G_PTRTOINT: {
    bool PtrIsI64 = MRI.getType(I.getOperand(1).getReg()).getSizeInBits() == 64;

    I.setDesc(
        TII.get(PtrIsI64 ? WebAssembly::COPY_I64 : WebAssembly::COPY_I32));
    constrainSelectedInstRegOperands(I, TII, TRI, RBI);
    return true;
  }
  case G_INTTOPTR: {
    bool PtrIsI64 = MRI.getType(I.getOperand(0).getReg()).getSizeInBits() == 64;

    I.setDesc(
        TII.get(PtrIsI64 ? WebAssembly::COPY_I64 : WebAssembly::COPY_I32));
    constrainSelectedInstRegOperands(I, TII, TRI, RBI);
    return true;
  }
  case G_PTRMASK: {
    bool PtrIsI64 = MRI.getType(I.getOperand(0).getReg()).getSizeInBits() == 64;

    I.setDesc(TII.get(PtrIsI64 ? WebAssembly::AND_I64 : WebAssembly::AND_I32));
    constrainSelectedInstRegOperands(I, TII, TRI, RBI);
    return true;
  }
  case G_GLOBAL_VALUE: {
    assert(I.getOperand(1).getTargetFlags() == 0 &&
           "Unexpected target flags on generic G_GLOBAL_VALUE instruction");

    unsigned OperandFlags = 0;
    const llvm::GlobalValue *GV = I.getOperand(1).getGlobal();
    LLT PtrTy = MRI.getType(I.getOperand(0).getReg());
    bool PtrIsI64 = PtrTy.getSizeInBits() == 64;

    if (TLI.isPositionIndependent()) {
      if (TM.shouldAssumeDSOLocal(GV)) {
        const char *BaseName;
        if (GV->getValueType()->isFunctionTy()) {
          BaseName = MF.createExternalSymbolName("__table_base");
          OperandFlags = WebAssemblyII::MO_TABLE_BASE_REL;
        } else {
          BaseName = MF.createExternalSymbolName("__memory_base");
          OperandFlags = WebAssemblyII::MO_MEMORY_BASE_REL;
        }
        MachineIRBuilder B(I);

        Register MemBase = MRI.createVirtualRegister(
            PtrIsI64 ? &WebAssembly::I64RegClass : &WebAssembly::I32RegClass);

        Register Offset = MRI.createVirtualRegister(
            PtrIsI64 ? &WebAssembly::I64RegClass : &WebAssembly::I32RegClass);

        B.buildInstr(PtrIsI64 ? WebAssembly::GLOBAL_GET_I64
                              : WebAssembly::GLOBAL_GET_I32)
            .addDef(MemBase)
            .addExternalSymbol(BaseName);

        B.buildInstr(PtrIsI64 ? WebAssembly::CONST_I64 : WebAssembly::CONST_I32)
            .addDef(Offset)
            .addGlobalAddress(GV, I.getOperand(1).getOffset(), OperandFlags);

        auto MIB =
            B.buildInstr(PtrIsI64 ? WebAssembly::ADD_I64 : WebAssembly::ADD_I32)
                .addDef(I.getOperand(0).getReg())
                .addReg(MemBase)
                .addReg(Offset);
        constrainSelectedInstRegOperands(*MIB, TII, TRI, RBI);

        I.eraseFromParent();
        return true;
      }
      OperandFlags = WebAssemblyII::MO_GOT;
    }

    unsigned NewOpc =
        PtrIsI64 ? WebAssembly::CONST_I64 : WebAssembly::CONST_I32;

    if (OperandFlags & WebAssemblyII::MO_GOT) {
      NewOpc =
          PtrIsI64 ? WebAssembly::GLOBAL_GET_I64 : WebAssembly::GLOBAL_GET_I32;
    }

    I.setDesc(TII.get(NewOpc));
    I.getOperand(1).setTargetFlags(OperandFlags);
    constrainSelectedInstRegOperands(I, TII, TRI, RBI);

    return true;
  }
  default:
    break;
  }

  return false;
}

namespace llvm {
InstructionSelector *
createWebAssemblyInstructionSelector(const WebAssemblyTargetMachine &TM,
                                     const WebAssemblySubtarget &Subtarget,
                                     const WebAssemblyRegisterBankInfo &RBI) {
  return new WebAssemblyInstructionSelector(TM, Subtarget, RBI);
}
} // namespace llvm