SystemZCopyPhysRegs.cpp

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//===---------- SystemZPhysRegCopy.cpp - Handle phys reg copies -----------===//
//
// 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 pass makes sure that a COPY of a physical register will be
// implementable after register allocation in copyPhysReg() (this could be
// done in EmitInstrWithCustomInserter() instead if COPY instructions would
// be passed to it).
//
//===----------------------------------------------------------------------===//
 
#include "SystemZ.h"
#include "SystemZTargetMachine.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionAnalysisManager.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachinePassManager.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/IR/Analysis.h"
 
using namespace llvm;
 
namespace {
 
class SystemZCopyPhysRegsLegacy : public MachineFunctionPass {
public:
  static char ID;
  SystemZCopyPhysRegsLegacy() : MachineFunctionPass(ID) {}
 
  bool runOnMachineFunction(MachineFunction &MF) override;
  void getAnalysisUsage(AnalysisUsage &AU) const override;
};
 
char SystemZCopyPhysRegsLegacy::ID = 0;
 
} // end anonymous namespace
 
INITIALIZE_PASS(SystemZCopyPhysRegsLegacy, "systemz-copy-physregs",
                "SystemZ Copy Physregs", false, false)
 
FunctionPass *
llvm::createSystemZCopyPhysRegsLegacyPass(SystemZTargetMachine &TM) {
  return new SystemZCopyPhysRegsLegacy();
}
 
void SystemZCopyPhysRegsLegacy::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.setPreservesCFG();
  MachineFunctionPass::getAnalysisUsage(AU);
}
 
static bool visitMBB(MachineBasicBlock &MBB, MachineRegisterInfo *MRI,
                     const TargetInstrInfo *TII) {
  bool Modified = false;
 
  // Certain special registers can only be copied from a subset of the
  // default register class of the type. It is therefore necessary to create
  // the target copy instructions before regalloc instead of in copyPhysReg().
  for (MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
       MBBI != E; ) {
    MachineInstr *MI = &*MBBI++;
    if (!MI->isCopy())
      continue;
 
    DebugLoc DL = MI->getDebugLoc();
    Register SrcReg = MI->getOperand(1).getReg();
    Register DstReg = MI->getOperand(0).getReg();
 
    if (DstReg.isVirtual() &&
        (SrcReg == SystemZ::CC || SystemZ::AR32BitRegClass.contains(SrcReg))) {
      Register Tmp = MRI->createVirtualRegister(&SystemZ::GR32BitRegClass);
      if (SrcReg == SystemZ::CC)
        BuildMI(MBB, MI, DL, TII->get(SystemZ::IPM), Tmp);
      else
        BuildMI(MBB, MI, DL, TII->get(SystemZ::EAR), Tmp).addReg(SrcReg);
      MI->getOperand(1).setReg(Tmp);
      Modified = true;
    }
    else if (SrcReg.isVirtual() &&
             SystemZ::AR32BitRegClass.contains(DstReg)) {
      Register Tmp = MRI->createVirtualRegister(&SystemZ::GR32BitRegClass);
      MI->getOperand(0).setReg(Tmp);
      MachineInstr *NMI =
          BuildMI(MBB, MBBI, DL, TII->get(SystemZ::SAR), DstReg).addReg(Tmp);
      // SAR now writes the final value to DstReg, so update debug values.
      MBB.getParent()->substituteDebugValuesForInst(*MI, *NMI);
      Modified = true;
    }
  }
 
  return Modified;
}
 
static bool runCopyPhysRegsOnMF(MachineFunction &F) {
  const TargetInstrInfo *TII =
      F.getSubtarget<SystemZSubtarget>().getInstrInfo();
  MachineRegisterInfo *MRI = &F.getRegInfo();
 
  bool Modified = false;
  for (auto &MBB : F)
    Modified |= visitMBB(MBB, MRI, TII);
 
  return Modified;
}
 
bool SystemZCopyPhysRegsLegacy::runOnMachineFunction(MachineFunction &MF) {
  return runCopyPhysRegsOnMF(MF);
}
 
PreservedAnalyses
SystemZCopyPhysRegsPass::run(MachineFunction &MF,
                             MachineFunctionAnalysisManager &MFAM) {
  return runCopyPhysRegsOnMF(MF) ? getMachineFunctionPassPreservedAnalyses()
                                       .preserveSet<CFGAnalyses>()
                                 : PreservedAnalyses::all();
}