RISCVPostRAExpandPseudoInsts.cpp

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//===-- RISCVPostRAExpandPseudoInsts.cpp - Expand pseudo instrs ----===//
//
// 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 the pseudo instruction pseudolisimm32
// into target instructions. This pass should be run during the post-regalloc
// passes, before post RA scheduling.
//
//===----------------------------------------------------------------------===//
 
#include "MCTargetDesc/RISCVMatInt.h"
#include "RISCV.h"
#include "RISCVInstrInfo.h"
#include "RISCVTargetMachine.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
 
using namespace llvm;
 
#define RISCV_POST_RA_EXPAND_PSEUDO_NAME                                       \
  "RISC-V post-regalloc pseudo instruction expansion pass"
 
namespace {
 
class RISCVPostRAExpandPseudo : public MachineFunctionPass {
public:
  const RISCVInstrInfo *TII;
  static char ID;
 
  RISCVPostRAExpandPseudo() : MachineFunctionPass(ID) {}
 
  bool runOnMachineFunction(MachineFunction &MF) override;
 
  StringRef getPassName() const override {
    return RISCV_POST_RA_EXPAND_PSEUDO_NAME;
  }
 
private:
  bool expandMBB(MachineBasicBlock &MBB);
  bool expandMI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                MachineBasicBlock::iterator &NextMBBI);
  bool expandMovImm(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI);
};
 
char RISCVPostRAExpandPseudo::ID = 0;
 
bool RISCVPostRAExpandPseudo::runOnMachineFunction(MachineFunction &MF) {
  TII = static_cast<const RISCVInstrInfo *>(MF.getSubtarget().getInstrInfo());
  bool Modified = false;
  for (auto &MBB : MF)
    Modified |= expandMBB(MBB);
  return Modified;
}
 
bool RISCVPostRAExpandPseudo::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 RISCVPostRAExpandPseudo::expandMI(MachineBasicBlock &MBB,
                                       MachineBasicBlock::iterator MBBI,
                                       MachineBasicBlock::iterator &NextMBBI) {
  switch (MBBI->getOpcode()) {
  case RISCV::PseudoMovImm:
    return expandMovImm(MBB, MBBI);
  default:
    return false;
  }
}
 
bool RISCVPostRAExpandPseudo::expandMovImm(MachineBasicBlock &MBB,
                                           MachineBasicBlock::iterator MBBI) {
  DebugLoc DL = MBBI->getDebugLoc();
 
  int64_t Val = MBBI->getOperand(1).getImm();
 
  RISCVMatInt::InstSeq Seq =
      RISCVMatInt::generateInstSeq(Val, MBB.getParent()->getSubtarget());
  assert(!Seq.empty());
 
  Register DstReg = MBBI->getOperand(0).getReg();
  bool DstIsDead = MBBI->getOperand(0).isDead();
  bool Renamable = MBBI->getOperand(0).isRenamable();
 
  TII->movImm(MBB, MBBI, DL, DstReg, Val, MachineInstr::NoFlags, Renamable,
              DstIsDead);
 
  MBBI->eraseFromParent();
  return true;
}
 
} // end of anonymous namespace
 
INITIALIZE_PASS(RISCVPostRAExpandPseudo, "riscv-expand-pseudolisimm32",
                RISCV_POST_RA_EXPAND_PSEUDO_NAME, false, false)
namespace llvm {
 
FunctionPass *createRISCVPostRAExpandPseudoPass() {
  return new RISCVPostRAExpandPseudo();
}
 
} // end of namespace llvm