RISCVExpandPseudoInsts.cpp

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//===-- RISCVExpandPseudoInsts.cpp - Expand pseudo instructions -----------===//
//
// 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 contains a pass that expands pseudo instructions into target
// instructions. This pass should be run after register allocation but before
// the post-regalloc scheduling pass.
//
//===----------------------------------------------------------------------===//
 
#include "RISCV.h"
#include "RISCVInstrInfo.h"
#include "RISCVTargetMachine.h"
 
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/MC/MCContext.h"
 
using namespace llvm;
 
#define RISCV_EXPAND_PSEUDO_NAME "RISCV pseudo instruction expansion pass"
#define RISCV_PRERA_EXPAND_PSEUDO_NAME "RISCV Pre-RA pseudo instruction expansion pass"
 
namespace {
 
class RISCVExpandPseudo : public MachineFunctionPass {
public:
  const RISCVInstrInfo *TII;
  static char ID;
 
  RISCVExpandPseudo() : MachineFunctionPass(ID) {
    initializeRISCVExpandPseudoPass(*PassRegistry::getPassRegistry());
  }
 
  bool runOnMachineFunction(MachineFunction &MF) override;
 
  StringRef getPassName() const override { return RISCV_EXPAND_PSEUDO_NAME; }
 
private:
  bool expandMBB(MachineBasicBlock &MBB);
  bool expandMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                MachineBasicBlock::iterator &NextMBBI);
  bool expandCCOp(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                  MachineBasicBlock::iterator &NextMBBI);
  bool expandVSetVL(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI);
  bool expandVMSET_VMCLR(MachineBasicBlock &MBB,
                         MachineBasicBlock::iterator MBBI, unsigned Opcode);
#ifndef NDEBUG
  unsigned getInstSizeInBytes(const MachineFunction &MF) const {
    unsigned Size = 0;
    for (auto &MBB : MF)
      for (auto &MI : MBB)
        Size += TII->getInstSizeInBytes(MI);
    return Size;
  }
#endif
};
 
char RISCVExpandPseudo::ID = 0;
 
bool RISCVExpandPseudo::runOnMachineFunction(MachineFunction &MF) {
  TII = static_cast<const RISCVInstrInfo *>(MF.getSubtarget().getInstrInfo());
 
#ifndef NDEBUG
  const unsigned OldSize = getInstSizeInBytes(MF);
#endif
 
  bool Modified = false;
  for (auto &MBB : MF)
    Modified |= expandMBB(MBB);
 
#ifndef NDEBUG
  const unsigned NewSize = getInstSizeInBytes(MF);
  assert(OldSize >= NewSize);
#endif
  return Modified;
}
 
bool RISCVExpandPseudo::expandMBB(MachineBasicBlock &MBB) {
  bool Modified = false;
 
  MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
  while (MBBI != E) {
    MachineBasicBlock::iterator NMBBI = std::next(MBBI);
    Modified |= expandMI(MBB, MBBI, NMBBI);
    MBBI = NMBBI;
  }
 
  return Modified;
}
 
bool RISCVExpandPseudo::expandMI(MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator MBBI,
                                 MachineBasicBlock::iterator &NextMBBI) {
  // RISCVInstrInfo::getInstSizeInBytes expects that the total size of the
  // expanded instructions for each pseudo is correct in the Size field of the
  // tablegen definition for the pseudo.
  switch (MBBI->getOpcode()) {
  case RISCV::PseudoCCMOVGPR:
  case RISCV::PseudoCCADD:
  case RISCV::PseudoCCSUB:
  case RISCV::PseudoCCAND:
  case RISCV::PseudoCCOR:
  case RISCV::PseudoCCXOR:
  case RISCV::PseudoCCADDW:
  case RISCV::PseudoCCSUBW:
    return expandCCOp(MBB, MBBI, NextMBBI);
  case RISCV::PseudoVSETVLI:
  case RISCV::PseudoVSETVLIX0:
  case RISCV::PseudoVSETIVLI:
    return expandVSetVL(MBB, MBBI);
  case RISCV::PseudoVMCLR_M_B1:
  case RISCV::PseudoVMCLR_M_B2:
  case RISCV::PseudoVMCLR_M_B4:
  case RISCV::PseudoVMCLR_M_B8:
  case RISCV::PseudoVMCLR_M_B16:
  case RISCV::PseudoVMCLR_M_B32:
  case RISCV::PseudoVMCLR_M_B64:
    // vmclr.m vd => vmxor.mm vd, vd, vd
    return expandVMSET_VMCLR(MBB, MBBI, RISCV::VMXOR_MM);
  case RISCV::PseudoVMSET_M_B1:
  case RISCV::PseudoVMSET_M_B2:
  case RISCV::PseudoVMSET_M_B4:
  case RISCV::PseudoVMSET_M_B8:
  case RISCV::PseudoVMSET_M_B16:
  case RISCV::PseudoVMSET_M_B32:
  case RISCV::PseudoVMSET_M_B64:
    // vmset.m vd => vmxnor.mm vd, vd, vd
    return expandVMSET_VMCLR(MBB, MBBI, RISCV::VMXNOR_MM);
  }
 
  return false;
}
 
bool RISCVExpandPseudo::expandCCOp(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator MBBI,
                                   MachineBasicBlock::iterator &NextMBBI) {
 
  MachineFunction *MF = MBB.getParent();
  MachineInstr &MI = *MBBI;
  DebugLoc DL = MI.getDebugLoc();
 
  MachineBasicBlock *TrueBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());
  MachineBasicBlock *MergeBB = MF->CreateMachineBasicBlock(MBB.getBasicBlock());
 
  MF->insert(++MBB.getIterator(), TrueBB);
  MF->insert(++TrueBB->getIterator(), MergeBB);
 
  // We want to copy the "true" value when the condition is true which means
  // we need to invert the branch condition to jump over TrueBB when the
  // condition is false.
  auto CC = static_cast<RISCVCC::CondCode>(MI.getOperand(3).getImm());
  CC = RISCVCC::getOppositeBranchCondition(CC);
 
  // Insert branch instruction.
  BuildMI(MBB, MBBI, DL, TII->getBrCond(CC))
      .addReg(MI.getOperand(1).getReg())
      .addReg(MI.getOperand(2).getReg())
      .addMBB(MergeBB);
 
  Register DestReg = MI.getOperand(0).getReg();
  assert(MI.getOperand(4).getReg() == DestReg);
 
  if (MI.getOpcode() == RISCV::PseudoCCMOVGPR) {
    // Add MV.
    BuildMI(TrueBB, DL, TII->get(RISCV::ADDI), DestReg)
        .add(MI.getOperand(5))
        .addImm(0);
  } else {
    unsigned NewOpc;
    switch (MI.getOpcode()) {
    default:
      llvm_unreachable("Unexpected opcode!");
    case RISCV::PseudoCCADD:   NewOpc = RISCV::ADD;   break;
    case RISCV::PseudoCCSUB:   NewOpc = RISCV::SUB;   break;
    case RISCV::PseudoCCAND:   NewOpc = RISCV::AND;   break;
    case RISCV::PseudoCCOR:    NewOpc = RISCV::OR;    break;
    case RISCV::PseudoCCXOR:   NewOpc = RISCV::XOR;   break;
    case RISCV::PseudoCCADDW:  NewOpc = RISCV::ADDW;  break;
    case RISCV::PseudoCCSUBW:  NewOpc = RISCV::SUBW;  break;
    }
    BuildMI(TrueBB, DL, TII->get(NewOpc), DestReg)
        .add(MI.getOperand(5))
        .add(MI.getOperand(6));
  }
 
  TrueBB->addSuccessor(MergeBB);
 
  MergeBB->splice(MergeBB->end(), &MBB, MI, MBB.end());
  MergeBB->transferSuccessors(&MBB);
 
  MBB.addSuccessor(TrueBB);
  MBB.addSuccessor(MergeBB);
 
  NextMBBI = MBB.end();
  MI.eraseFromParent();
 
  // Make sure live-ins are correctly attached to this new basic block.
  LivePhysRegs LiveRegs;
  computeAndAddLiveIns(LiveRegs, *TrueBB);
  computeAndAddLiveIns(LiveRegs, *MergeBB);
 
  return true;
}
 
bool RISCVExpandPseudo::expandVSetVL(MachineBasicBlock &MBB,
                                     MachineBasicBlock::iterator MBBI) {
  assert(MBBI->getNumExplicitOperands() == 3 && MBBI->getNumOperands() >= 5 &&
         "Unexpected instruction format");
 
  DebugLoc DL = MBBI->getDebugLoc();
 
  assert((MBBI->getOpcode() == RISCV::PseudoVSETVLI ||
          MBBI->getOpcode() == RISCV::PseudoVSETVLIX0 ||
          MBBI->getOpcode() == RISCV::PseudoVSETIVLI) &&
         "Unexpected pseudo instruction");
  unsigned Opcode;
  if (MBBI->getOpcode() == RISCV::PseudoVSETIVLI)
    Opcode = RISCV::VSETIVLI;
  else
    Opcode = RISCV::VSETVLI;
  const MCInstrDesc &Desc = TII->get(Opcode);
  assert(Desc.getNumOperands() == 3 && "Unexpected instruction format");
 
  Register DstReg = MBBI->getOperand(0).getReg();
  bool DstIsDead = MBBI->getOperand(0).isDead();
  BuildMI(MBB, MBBI, DL, Desc)
      .addReg(DstReg, RegState::Define | getDeadRegState(DstIsDead))
      .add(MBBI->getOperand(1))  // VL
      .add(MBBI->getOperand(2)); // VType
 
  MBBI->eraseFromParent(); // The pseudo instruction is gone now.
  return true;
}
 
bool RISCVExpandPseudo::expandVMSET_VMCLR(MachineBasicBlock &MBB,
                                          MachineBasicBlock::iterator MBBI,
                                          unsigned Opcode) {
  DebugLoc DL = MBBI->getDebugLoc();
  Register DstReg = MBBI->getOperand(0).getReg();
  const MCInstrDesc &Desc = TII->get(Opcode);
  BuildMI(MBB, MBBI, DL, Desc, DstReg)
      .addReg(DstReg, RegState::Undef)
      .addReg(DstReg, RegState::Undef);
  MBBI->eraseFromParent(); // The pseudo instruction is gone now.
  return true;
}
 
class RISCVPreRAExpandPseudo : public MachineFunctionPass {
public:
  const RISCVInstrInfo *TII;
  static char ID;
 
  RISCVPreRAExpandPseudo() : MachineFunctionPass(ID) {
    initializeRISCVPreRAExpandPseudoPass(*PassRegistry::getPassRegistry());
  }
 
  bool runOnMachineFunction(MachineFunction &MF) override;
 
  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.setPreservesCFG();
    MachineFunctionPass::getAnalysisUsage(AU);
  }
  StringRef getPassName() const override {
    return RISCV_PRERA_EXPAND_PSEUDO_NAME;
  }
 
private:
  bool expandMBB(MachineBasicBlock &MBB);
  bool expandMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                MachineBasicBlock::iterator &NextMBBI);
  bool expandAuipcInstPair(MachineBasicBlock &MBB,
                           MachineBasicBlock::iterator MBBI,
                           MachineBasicBlock::iterator &NextMBBI,
                           unsigned FlagsHi, unsigned SecondOpcode);
  bool expandLoadLocalAddress(MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator MBBI,
                              MachineBasicBlock::iterator &NextMBBI);
  bool expandLoadAddress(MachineBasicBlock &MBB,
                         MachineBasicBlock::iterator MBBI,
                         MachineBasicBlock::iterator &NextMBBI);
  bool expandLoadTLSIEAddress(MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator MBBI,
                              MachineBasicBlock::iterator &NextMBBI);
  bool expandLoadTLSGDAddress(MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator MBBI,
                              MachineBasicBlock::iterator &NextMBBI);
#ifndef NDEBUG
  unsigned getInstSizeInBytes(const MachineFunction &MF) const {
    unsigned Size = 0;
    for (auto &MBB : MF)
      for (auto &MI : MBB)
        Size += TII->getInstSizeInBytes(MI);
    return Size;
  }
#endif
};
 
char RISCVPreRAExpandPseudo::ID = 0;
 
bool RISCVPreRAExpandPseudo::runOnMachineFunction(MachineFunction &MF) {
  TII = static_cast<const RISCVInstrInfo *>(MF.getSubtarget().getInstrInfo());
 
#ifndef NDEBUG
  const unsigned OldSize = getInstSizeInBytes(MF);
#endif
 
  bool Modified = false;
  for (auto &MBB : MF)
    Modified |= expandMBB(MBB);
 
#ifndef NDEBUG
  const unsigned NewSize = getInstSizeInBytes(MF);
  assert(OldSize >= NewSize);
#endif
  return Modified;
}
 
bool RISCVPreRAExpandPseudo::expandMBB(MachineBasicBlock &MBB) {
  bool Modified = false;
 
  MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
  while (MBBI != E) {
    MachineBasicBlock::iterator NMBBI = std::next(MBBI);
    Modified |= expandMI(MBB, MBBI, NMBBI);
    MBBI = NMBBI;
  }
 
  return Modified;
}
 
bool RISCVPreRAExpandPseudo::expandMI(MachineBasicBlock &MBB,
                                      MachineBasicBlock::iterator MBBI,
                                      MachineBasicBlock::iterator &NextMBBI) {
 
  switch (MBBI->getOpcode()) {
  case RISCV::PseudoLLA:
    return expandLoadLocalAddress(MBB, MBBI, NextMBBI);
  case RISCV::PseudoLA:
    return expandLoadAddress(MBB, MBBI, NextMBBI);
  case RISCV::PseudoLA_TLS_IE:
    return expandLoadTLSIEAddress(MBB, MBBI, NextMBBI);
  case RISCV::PseudoLA_TLS_GD:
    return expandLoadTLSGDAddress(MBB, MBBI, NextMBBI);
  }
  return false;
}
 
bool RISCVPreRAExpandPseudo::expandAuipcInstPair(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    MachineBasicBlock::iterator &NextMBBI, unsigned FlagsHi,
    unsigned SecondOpcode) {
  MachineFunction *MF = MBB.getParent();
  MachineInstr &MI = *MBBI;
  DebugLoc DL = MI.getDebugLoc();
 
  Register DestReg = MI.getOperand(0).getReg();
  Register ScratchReg =
      MF->getRegInfo().createVirtualRegister(&RISCV::GPRRegClass);
 
  MachineOperand &Symbol = MI.getOperand(1);
  Symbol.setTargetFlags(FlagsHi);
  MCSymbol *AUIPCSymbol = MF->getContext().createNamedTempSymbol("pcrel_hi");
 
  MachineInstr *MIAUIPC =
      BuildMI(MBB, MBBI, DL, TII->get(RISCV::AUIPC), ScratchReg).add(Symbol);
  MIAUIPC->setPreInstrSymbol(*MF, AUIPCSymbol);
 
  MachineInstr *SecondMI =
      BuildMI(MBB, MBBI, DL, TII->get(SecondOpcode), DestReg)
          .addReg(ScratchReg)
          .addSym(AUIPCSymbol, RISCVII::MO_PCREL_LO);
 
  if (MI.hasOneMemOperand())
    SecondMI->addMemOperand(*MF, *MI.memoperands_begin());
 
  MI.eraseFromParent();
  return true;
}
 
bool RISCVPreRAExpandPseudo::expandLoadLocalAddress(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    MachineBasicBlock::iterator &NextMBBI) {
  return expandAuipcInstPair(MBB, MBBI, NextMBBI, RISCVII::MO_PCREL_HI,
                             RISCV::ADDI);
}
 
bool RISCVPreRAExpandPseudo::expandLoadAddress(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    MachineBasicBlock::iterator &NextMBBI) {
  MachineFunction *MF = MBB.getParent();
 
  const auto &STI = MF->getSubtarget<RISCVSubtarget>();
  // When HWASAN is used and tagging of global variables is enabled
  // they should be accessed via the GOT, since the tagged address of a global
  // is incompatible with existing code models. This also applies to non-pic
  // mode.
  assert(MF->getTarget().isPositionIndependent() || STI.allowTaggedGlobals());
  unsigned SecondOpcode = STI.is64Bit() ? RISCV::LD : RISCV::LW;
  return expandAuipcInstPair(MBB, MBBI, NextMBBI, RISCVII::MO_GOT_HI,
                             SecondOpcode);
}
 
bool RISCVPreRAExpandPseudo::expandLoadTLSIEAddress(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    MachineBasicBlock::iterator &NextMBBI) {
  MachineFunction *MF = MBB.getParent();
 
  const auto &STI = MF->getSubtarget<RISCVSubtarget>();
  unsigned SecondOpcode = STI.is64Bit() ? RISCV::LD : RISCV::LW;
  return expandAuipcInstPair(MBB, MBBI, NextMBBI, RISCVII::MO_TLS_GOT_HI,
                             SecondOpcode);
}
 
bool RISCVPreRAExpandPseudo::expandLoadTLSGDAddress(
    MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
    MachineBasicBlock::iterator &NextMBBI) {
  return expandAuipcInstPair(MBB, MBBI, NextMBBI, RISCVII::MO_TLS_GD_HI,
                             RISCV::ADDI);
}
 
} // end of anonymous namespace
 
INITIALIZE_PASS(RISCVExpandPseudo, "riscv-expand-pseudo",
                RISCV_EXPAND_PSEUDO_NAME, false, false)
 
INITIALIZE_PASS(RISCVPreRAExpandPseudo, "riscv-prera-expand-pseudo",
                RISCV_PRERA_EXPAND_PSEUDO_NAME, false, false)
 
namespace llvm {
 
FunctionPass *createRISCVExpandPseudoPass() { return new RISCVExpandPseudo(); }
FunctionPass *createRISCVPreRAExpandPseudoPass() { return new RISCVPreRAExpandPseudo(); }
 
} // end of namespace llvm