VirtRegMap.cpp

//===-- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the VirtRegMap class.
//
// It also contains implementations of the the Spiller interface, which, given a
// virtual register map and a machine function, eliminates all virtual
// references by replacing them with physical register references - adding spill
// code as necessary.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "spiller"
#include "VirtRegMap.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include <algorithm>
using namespace llvm;

STATISTIC(NumSpills  , "Number of register spills");
STATISTIC(NumPSpills ,"Number of physical register spills");
STATISTIC(NumReMats  , "Number of re-materialization");
STATISTIC(NumDRM     , "Number of re-materializable defs elided");
STATISTIC(NumStores  , "Number of stores added");
STATISTIC(NumLoads   , "Number of loads added");
STATISTIC(NumReused  , "Number of values reused");
STATISTIC(NumDSE     , "Number of dead stores elided");
STATISTIC(NumDCE     , "Number of copies elided");
STATISTIC(NumDSS     , "Number of dead spill slots removed");
STATISTIC(NumCommutes, "Number of instructions commuted");

namespace {
  enum SpillerName { simple, local };
}

static cl::opt<SpillerName>
SpillerOpt("spiller",
           cl::desc("Spiller to use: (default: local)"),
           cl::Prefix,
           cl::values(clEnumVal(simple, "  simple spiller"),
                      clEnumVal(local,  "  local spiller"),
                      clEnumValEnd),
           cl::init(local));

//===----------------------------------------------------------------------===//
//  VirtRegMap implementation
//===----------------------------------------------------------------------===//

VirtRegMap::VirtRegMap(MachineFunction &mf)
  : TII(*mf.getTarget().getInstrInfo()), MF(mf), 
    Virt2PhysMap(NO_PHYS_REG), Virt2StackSlotMap(NO_STACK_SLOT),
    Virt2ReMatIdMap(NO_STACK_SLOT), Virt2SplitMap(0),
    Virt2SplitKillMap(0), ReMatMap(NULL), ReMatId(MAX_STACK_SLOT+1),
    LowSpillSlot(NO_STACK_SLOT), HighSpillSlot(NO_STACK_SLOT) {
  SpillSlotToUsesMap.resize(8);
  ImplicitDefed.resize(MF.getRegInfo().getLastVirtReg()+1-
                       TargetRegisterInfo::FirstVirtualRegister);
  grow();
}

void VirtRegMap::grow() {
  unsigned LastVirtReg = MF.getRegInfo().getLastVirtReg();
  Virt2PhysMap.grow(LastVirtReg);
  Virt2StackSlotMap.grow(LastVirtReg);
  Virt2ReMatIdMap.grow(LastVirtReg);
  Virt2SplitMap.grow(LastVirtReg);
  Virt2SplitKillMap.grow(LastVirtReg);
  ReMatMap.grow(LastVirtReg);
  ImplicitDefed.resize(LastVirtReg-TargetRegisterInfo::FirstVirtualRegister+1);
}

int VirtRegMap::assignVirt2StackSlot(unsigned virtReg) {
  assert(TargetRegisterInfo::isVirtualRegister(virtReg));
  assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
         "attempt to assign stack slot to already spilled register");
  const TargetRegisterClass* RC = MF.getRegInfo().getRegClass(virtReg);
  int SS = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
                                                RC->getAlignment());
  if (LowSpillSlot == NO_STACK_SLOT)
    LowSpillSlot = SS;
  if (HighSpillSlot == NO_STACK_SLOT || SS > HighSpillSlot)
    HighSpillSlot = SS;
  unsigned Idx = SS-LowSpillSlot;
  while (Idx >= SpillSlotToUsesMap.size())
    SpillSlotToUsesMap.resize(SpillSlotToUsesMap.size()*2);
  Virt2StackSlotMap[virtReg] = SS;
  ++NumSpills;
  return SS;
}

void VirtRegMap::assignVirt2StackSlot(unsigned virtReg, int SS) {
  assert(TargetRegisterInfo::isVirtualRegister(virtReg));
  assert(Virt2StackSlotMap[virtReg] == NO_STACK_SLOT &&
         "attempt to assign stack slot to already spilled register");
  assert((SS >= 0 ||
          (SS >= MF.getFrameInfo()->getObjectIndexBegin())) &&
         "illegal fixed frame index");
  Virt2StackSlotMap[virtReg] = SS;
}

int VirtRegMap::assignVirtReMatId(unsigned virtReg) {
  assert(TargetRegisterInfo::isVirtualRegister(virtReg));
  assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
         "attempt to assign re-mat id to already spilled register");
  Virt2ReMatIdMap[virtReg] = ReMatId;
  return ReMatId++;
}

void VirtRegMap::assignVirtReMatId(unsigned virtReg, int id) {
  assert(TargetRegisterInfo::isVirtualRegister(virtReg));
  assert(Virt2ReMatIdMap[virtReg] == NO_STACK_SLOT &&
         "attempt to assign re-mat id to already spilled register");
  Virt2ReMatIdMap[virtReg] = id;
}

int VirtRegMap::getEmergencySpillSlot(const TargetRegisterClass *RC) {
  std::map<const TargetRegisterClass*, int>::iterator I =
    EmergencySpillSlots.find(RC);
  if (I != EmergencySpillSlots.end())
    return I->second;
  int SS = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
                                                RC->getAlignment());
  if (LowSpillSlot == NO_STACK_SLOT)
    LowSpillSlot = SS;
  if (HighSpillSlot == NO_STACK_SLOT || SS > HighSpillSlot)
    HighSpillSlot = SS;
  I->second = SS;
  return SS;
}

void VirtRegMap::addSpillSlotUse(int FI, MachineInstr *MI) {
  if (!MF.getFrameInfo()->isFixedObjectIndex(FI)) {
    // If FI < LowSpillSlot, this stack reference was produced by
    // instruction selection and is not a spill
    if (FI >= LowSpillSlot) {
      assert(FI >= 0 && "Spill slot index should not be negative!");
      assert((unsigned)FI-LowSpillSlot < SpillSlotToUsesMap.size()
             && "Invalid spill slot");
      SpillSlotToUsesMap[FI-LowSpillSlot].insert(MI);
    }
  }
}

void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *OldMI,
                            MachineInstr *NewMI, ModRef MRInfo) {
  // Move previous memory references folded to new instruction.
  MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(NewMI);
  for (MI2VirtMapTy::iterator I = MI2VirtMap.lower_bound(OldMI),
         E = MI2VirtMap.end(); I != E && I->first == OldMI; ) {
    MI2VirtMap.insert(IP, std::make_pair(NewMI, I->second));
    MI2VirtMap.erase(I++);
  }

  // add new memory reference
  MI2VirtMap.insert(IP, std::make_pair(NewMI, std::make_pair(VirtReg, MRInfo)));
}

void VirtRegMap::virtFolded(unsigned VirtReg, MachineInstr *MI, ModRef MRInfo) {
  MI2VirtMapTy::iterator IP = MI2VirtMap.lower_bound(MI);
  MI2VirtMap.insert(IP, std::make_pair(MI, std::make_pair(VirtReg, MRInfo)));
}

void VirtRegMap::RemoveMachineInstrFromMaps(MachineInstr *MI) {
  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
    MachineOperand &MO = MI->getOperand(i);
    if (!MO.isFrameIndex())
      continue;
    int FI = MO.getIndex();
    if (MF.getFrameInfo()->isFixedObjectIndex(FI))
      continue;
    // This stack reference was produced by instruction selection and
    // is not a spill
    if (FI < LowSpillSlot)
      continue;
    assert((unsigned)FI-LowSpillSlot < SpillSlotToUsesMap.size()
           && "Invalid spill slot");
    SpillSlotToUsesMap[FI-LowSpillSlot].erase(MI);
  }
  MI2VirtMap.erase(MI);
  SpillPt2VirtMap.erase(MI);
  RestorePt2VirtMap.erase(MI);