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4191b96f41
llvm-6502/lib/CodeGen/VirtRegMap.cpp
Evan Cheng 4191b96f41 Minor debug output bug. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48261 91177308-0d34-0410-b5e6-96231b3b80d8
2008-03-12 00:02:46 +00:00

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//===-- 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/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/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");
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);
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);
}
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)) {
assert(FI >= 0 && "Spill slot index should not be negative!");
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;
SpillSlotToUsesMap[FI-LowSpillSlot].erase(MI);
}
MI2VirtMap.erase(MI);
SpillPt2VirtMap.erase(MI);
RestorePt2VirtMap.erase(MI);
EmergencySpillMap.erase(MI);
}
void VirtRegMap::print(std::ostream &OS) const {
const TargetRegisterInfo* TRI = MF.getTarget().getRegisterInfo();
OS << "********** REGISTER MAP **********\n";
for (unsigned i = TargetRegisterInfo::FirstVirtualRegister,
e = MF.getRegInfo().getLastVirtReg(); i <= e; ++i) {
if (Virt2PhysMap[i] != (unsigned)VirtRegMap::NO_PHYS_REG)
OS << "[reg" << i << " -> " << TRI->getName(Virt2PhysMap[i])
<< "]\n";
}
for (unsigned i = TargetRegisterInfo::FirstVirtualRegister,
e = MF.getRegInfo().getLastVirtReg(); i <= e; ++i)
if (Virt2StackSlotMap[i] != VirtRegMap::NO_STACK_SLOT)
OS << "[reg" << i << " -> fi#" << Virt2StackSlotMap[i] << "]\n";
OS << '\n';
}
void VirtRegMap::dump() const {
print(DOUT);
}
//===----------------------------------------------------------------------===//
// Simple Spiller Implementation
//===----------------------------------------------------------------------===//
Spiller::~Spiller() {}
namespace {
struct VISIBILITY_HIDDEN SimpleSpiller : public Spiller {
bool runOnMachineFunction(MachineFunction& mf, VirtRegMap &VRM);
};
}
bool SimpleSpiller::runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
DOUT << "********** REWRITE MACHINE CODE **********\n";
DOUT << "********** Function: " << MF.getFunction()->getName() << '\n';
const TargetMachine &TM = MF.getTarget();
const TargetInstrInfo &TII = *TM.getInstrInfo();
// LoadedRegs - Keep track of which vregs are loaded, so that we only load
// each vreg once (in the case where a spilled vreg is used by multiple
// operands). This is always smaller than the number of operands to the
// current machine instr, so it should be small.
std::vector<unsigned> LoadedRegs;
for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
MBBI != E; ++MBBI) {
DOUT << MBBI->getBasicBlock()->getName() << ":\n";
MachineBasicBlock &MBB = *MBBI;
for (MachineBasicBlock::iterator MII = MBB.begin(),
E = MBB.end(); MII != E; ++MII) {
MachineInstr &MI = *MII;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (MO.isRegister() && MO.getReg()) {
if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
unsigned VirtReg = MO.getReg();
unsigned PhysReg = VRM.getPhys(VirtReg);
if (!VRM.isAssignedReg(VirtReg)) {
int StackSlot = VRM.getStackSlot(VirtReg);
const TargetRegisterClass* RC =
MF.getRegInfo().getRegClass(VirtReg);
if (MO.isUse() &&
std::find(LoadedRegs.begin(), LoadedRegs.end(), VirtReg)
== LoadedRegs.end()) {
TII.loadRegFromStackSlot(MBB, &MI, PhysReg, StackSlot, RC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(StackSlot, LoadMI);
LoadedRegs.push_back(VirtReg);
++NumLoads;
DOUT << '\t' << *LoadMI;
}
if (MO.isDef()) {
TII.storeRegToStackSlot(MBB, next(MII), PhysReg, true,
StackSlot, RC);
MachineInstr *StoreMI = next(MII);
VRM.addSpillSlotUse(StackSlot, StoreMI);
++NumStores;
}
}
MF.getRegInfo().setPhysRegUsed(PhysReg);
MI.getOperand(i).setReg(PhysReg);
} else {
MF.getRegInfo().setPhysRegUsed(MO.getReg());
}
}
}
DOUT << '\t' << MI;
LoadedRegs.clear();
}
}
return true;
}
//===----------------------------------------------------------------------===//
// Local Spiller Implementation
//===----------------------------------------------------------------------===//
namespace {
class AvailableSpills;
/// LocalSpiller - This spiller does a simple pass over the machine basic
/// block to attempt to keep spills in registers as much as possible for
/// blocks that have low register pressure (the vreg may be spilled due to
/// register pressure in other blocks).
class VISIBILITY_HIDDEN LocalSpiller : public Spiller {
MachineRegisterInfo *RegInfo;
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
public:
bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM) {
RegInfo = &MF.getRegInfo();
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
DOUT << "\n**** Local spiller rewriting function '"
<< MF.getFunction()->getName() << "':\n";
DOUT << "**** Machine Instrs (NOTE! Does not include spills and reloads!)"
" ****\n";
DEBUG(MF.dump());
for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
MBB != E; ++MBB)
RewriteMBB(*MBB, VRM);
// Mark unused spill slots.
MachineFrameInfo *MFI = MF.getFrameInfo();
int SS = VRM.getLowSpillSlot();
if (SS != VirtRegMap::NO_STACK_SLOT)
for (int e = VRM.getHighSpillSlot(); SS <= e; ++SS)
if (!VRM.isSpillSlotUsed(SS)) {
MFI->RemoveStackObject(SS);
++NumDSS;
}
DOUT << "**** Post Machine Instrs ****\n";
DEBUG(MF.dump());
return true;
}
private:
bool PrepForUnfoldOpti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
std::vector<MachineInstr*> &MaybeDeadStores,
AvailableSpills &Spills, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM);
void SpillRegToStackSlot(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
int Idx, unsigned PhysReg, int StackSlot,
const TargetRegisterClass *RC,
bool isAvailable, MachineInstr *&LastStore,
AvailableSpills &Spills,
SmallSet<MachineInstr*, 4> &ReMatDefs,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM);
void RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM);
};
}
/// AvailableSpills - As the local spiller is scanning and rewriting an MBB from
/// top down, keep track of which spills slots or remat are available in each
/// register.
///
/// Note that not all physregs are created equal here. In particular, some
/// physregs are reloads that we are allowed to clobber or ignore at any time.
/// Other physregs are values that the register allocated program is using that
/// we cannot CHANGE, but we can read if we like. We keep track of this on a
/// per-stack-slot / remat id basis as the low bit in the value of the
/// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks
/// this bit and addAvailable sets it if.
namespace {
class VISIBILITY_HIDDEN AvailableSpills {
const TargetRegisterInfo *TRI;
const TargetInstrInfo *TII;
// SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled
// or remat'ed virtual register values that are still available, due to being
// loaded or stored to, but not invalidated yet.
std::map<int, unsigned> SpillSlotsOrReMatsAvailable;
// PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable,
// indicating which stack slot values are currently held by a physreg. This
// is used to invalidate entries in SpillSlotsOrReMatsAvailable when a
// physreg is modified.
std::multimap<unsigned, int> PhysRegsAvailable;
void disallowClobberPhysRegOnly(unsigned PhysReg);
void ClobberPhysRegOnly(unsigned PhysReg);
public:
AvailableSpills(const TargetRegisterInfo *tri, const TargetInstrInfo *tii)
: TRI(tri), TII(tii) {
}
const TargetRegisterInfo *getRegInfo() const { return TRI; }
/// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is
/// available in a physical register, return that PhysReg, otherwise
/// return 0.
unsigned getSpillSlotOrReMatPhysReg(int Slot) const {
std::map<int, unsigned>::const_iterator I =
SpillSlotsOrReMatsAvailable.find(Slot);
if (I != SpillSlotsOrReMatsAvailable.end()) {
return I->second >> 1; // Remove the CanClobber bit.
}
return 0;
}
/// addAvailable - Mark that the specified stack slot / remat is available in
/// the specified physreg. If CanClobber is true, the physreg can be modified
/// at any time without changing the semantics of the program.
void addAvailable(int SlotOrReMat, MachineInstr *MI, unsigned Reg,
bool CanClobber = true) {
// If this stack slot is thought to be available in some other physreg,
// remove its record.
ModifyStackSlotOrReMat(SlotOrReMat);
PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat));
SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | (unsigned)CanClobber;
if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
DOUT << "Remembering RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Remembering SS#" << SlotOrReMat;
DOUT << " in physreg " << TRI->getName(Reg) << "\n";
}
/// canClobberPhysReg - Return true if the spiller is allowed to change the
/// value of the specified stackslot register if it desires. The specified
/// stack slot must be available in a physreg for this query to make sense.
bool canClobberPhysReg(int SlotOrReMat) const {
assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) &&
"Value not available!");
return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1;
}
/// disallowClobberPhysReg - Unset the CanClobber bit of the specified
/// stackslot register. The register is still available but is no longer
/// allowed to be modifed.
void disallowClobberPhysReg(unsigned PhysReg);
/// ClobberPhysReg - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff that lives in
/// it and any of its aliases.
void ClobberPhysReg(unsigned PhysReg);
/// ModifyStackSlotOrReMat - This method is called when the value in a stack
/// slot changes. This removes information about which register the previous
/// value for this slot lives in (as the previous value is dead now).
void ModifyStackSlotOrReMat(int SlotOrReMat);
};
}
/// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified
/// stackslot register. The register is still available but is no longer
/// allowed to be modifed.
void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) {
std::multimap<unsigned, int>::iterator I =
PhysRegsAvailable.lower_bound(PhysReg);
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int SlotOrReMat = I->second;
I++;
assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
"Bidirectional map mismatch!");
SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1;
DOUT << "PhysReg " << TRI->getName(PhysReg)
<< " copied, it is available for use but can no longer be modified\n";
}
}
/// disallowClobberPhysReg - Unset the CanClobber bit of the specified
/// stackslot register and its aliases. The register and its aliases may
/// still available but is no longer allowed to be modifed.
void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) {
for (const unsigned *AS = TRI->getAliasSet(PhysReg); *AS; ++AS)
disallowClobberPhysRegOnly(*AS);
disallowClobberPhysRegOnly(PhysReg);
}
/// ClobberPhysRegOnly - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff we thing lives in it.
void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) {
std::multimap<unsigned, int>::iterator I =
PhysRegsAvailable.lower_bound(PhysReg);
while (I != PhysRegsAvailable.end() && I->first == PhysReg) {
int SlotOrReMat = I->second;
PhysRegsAvailable.erase(I++);
assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg &&
"Bidirectional map mismatch!");
SpillSlotsOrReMatsAvailable.erase(SlotOrReMat);
DOUT << "PhysReg " << TRI->getName(PhysReg)
<< " clobbered, invalidating ";
if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT)
DOUT << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 << "\n";
else
DOUT << "SS#" << SlotOrReMat << "\n";
}
}
/// ClobberPhysReg - This is called when the specified physreg changes
/// value. We use this to invalidate any info about stuff we thing lives in
/// it and any of its aliases.
void AvailableSpills::ClobberPhysReg(unsigned PhysReg) {
for (const unsigned *AS = TRI->getAliasSet(PhysReg); *AS; ++AS)
ClobberPhysRegOnly(*AS);
ClobberPhysRegOnly(PhysReg);
}
/// ModifyStackSlotOrReMat - This method is called when the value in a stack
/// slot changes. This removes information about which register the previous
/// value for this slot lives in (as the previous value is dead now).
void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) {
std::map<int, unsigned>::iterator It =
SpillSlotsOrReMatsAvailable.find(SlotOrReMat);
if (It == SpillSlotsOrReMatsAvailable.end()) return;
unsigned Reg = It->second >> 1;
SpillSlotsOrReMatsAvailable.erase(It);
// This register may hold the value of multiple stack slots, only remove this
// stack slot from the set of values the register contains.
std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg);
for (; ; ++I) {
assert(I != PhysRegsAvailable.end() && I->first == Reg &&
"Map inverse broken!");
if (I->second == SlotOrReMat) break;
}
PhysRegsAvailable.erase(I);
}
/// InvalidateKills - MI is going to be deleted. If any of its operands are
/// marked kill, then invalidate the information.
static void InvalidateKills(MachineInstr &MI, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
SmallVector<unsigned, 2> *KillRegs = NULL) {
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isRegister() || !MO.isUse() || !MO.isKill())
continue;
unsigned Reg = MO.getReg();
if (KillRegs)
KillRegs->push_back(Reg);
if (KillOps[Reg] == &MO) {
RegKills.reset(Reg);
KillOps[Reg] = NULL;
}
}
}
/// InvalidateKill - A MI that defines the specified register is being deleted,
/// invalidate the register kill information.
static void InvalidateKill(unsigned Reg, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
if (RegKills[Reg]) {
KillOps[Reg]->setIsKill(false);
KillOps[Reg] = NULL;
RegKills.reset(Reg);
}
}
/// InvalidateRegDef - If the def operand of the specified def MI is now dead
/// (since it's spill instruction is removed), mark it isDead. Also checks if
/// the def MI has other definition operands that are not dead. Returns it by
/// reference.
static bool InvalidateRegDef(MachineBasicBlock::iterator I,
MachineInstr &NewDef, unsigned Reg,
bool &HasLiveDef) {
// Due to remat, it's possible this reg isn't being reused. That is,
// the def of this reg (by prev MI) is now dead.
MachineInstr *DefMI = I;
MachineOperand *DefOp = NULL;
for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = DefMI->getOperand(i);
if (MO.isRegister() && MO.isDef()) {
if (MO.getReg() == Reg)
DefOp = &MO;
else if (!MO.isDead())
HasLiveDef = true;
}
}
if (!DefOp)
return false;
bool FoundUse = false, Done = false;
MachineBasicBlock::iterator E = NewDef;
++I; ++E;
for (; !Done && I != E; ++I) {
MachineInstr *NMI = I;
for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) {
MachineOperand &MO = NMI->getOperand(j);
if (!MO.isRegister() || MO.getReg() != Reg)
continue;
if (MO.isUse())
FoundUse = true;
Done = true; // Stop after scanning all the operands of this MI.
}
}
if (!FoundUse) {
// Def is dead!
DefOp->setIsDead();
return true;
}
return false;
}
/// UpdateKills - Track and update kill info. If a MI reads a register that is
/// marked kill, then it must be due to register reuse. Transfer the kill info
/// over.
static void UpdateKills(MachineInstr &MI, BitVector &RegKills,
std::vector<MachineOperand*> &KillOps) {
const TargetInstrDesc &TID = MI.getDesc();
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isRegister() || !MO.isUse())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (RegKills[Reg]) {
// That can't be right. Register is killed but not re-defined and it's
// being reused. Let's fix that.
KillOps[Reg]->setIsKill(false);
KillOps[Reg] = NULL;
RegKills.reset(Reg);
if (i < TID.getNumOperands() &&
TID.getOperandConstraint(i, TOI::TIED_TO) == -1)
// Unless it's a two-address operand, this is the new kill.
MO.setIsKill();
}
if (MO.isKill()) {
RegKills.set(Reg);
KillOps[Reg] = &MO;
}
}
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI.getOperand(i);
if (!MO.isRegister() || !MO.isDef())
continue;
unsigned Reg = MO.getReg();
RegKills.reset(Reg);
KillOps[Reg] = NULL;
}
}
/// ReMaterialize - Re-materialize definition for Reg targetting DestReg.
///
static void ReMaterialize(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
unsigned DestReg, unsigned Reg,
const TargetRegisterInfo *TRI,
VirtRegMap &VRM) {
TRI->reMaterialize(MBB, MII, DestReg, VRM.getReMaterializedMI(Reg));
MachineInstr *NewMI = prior(MII);
for (unsigned i = 0, e = NewMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = NewMI->getOperand(i);
if (!MO.isRegister() || MO.getReg() == 0)
continue;
unsigned VirtReg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(VirtReg))
continue;
assert(MO.isUse());
unsigned SubIdx = MO.getSubReg();
unsigned Phys = VRM.getPhys(VirtReg);
assert(Phys);
unsigned RReg = SubIdx ? TRI->getSubReg(Phys, SubIdx) : Phys;
MO.setReg(RReg);
}
++NumReMats;
}
// ReusedOp - For each reused operand, we keep track of a bit of information, in
// case we need to rollback upon processing a new operand. See comments below.
namespace {
struct ReusedOp {
// The MachineInstr operand that reused an available value.
unsigned Operand;
// StackSlotOrReMat - The spill slot or remat id of the value being reused.
unsigned StackSlotOrReMat;
// PhysRegReused - The physical register the value was available in.
unsigned PhysRegReused;
// AssignedPhysReg - The physreg that was assigned for use by the reload.
unsigned AssignedPhysReg;
// VirtReg - The virtual register itself.
unsigned VirtReg;
ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr,
unsigned vreg)
: Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr),
AssignedPhysReg(apr), VirtReg(vreg) {}
};
/// ReuseInfo - This maintains a collection of ReuseOp's for each operand that
/// is reused instead of reloaded.
class VISIBILITY_HIDDEN ReuseInfo {
MachineInstr &MI;
std::vector<ReusedOp> Reuses;
BitVector PhysRegsClobbered;
public:
ReuseInfo(MachineInstr &mi, const TargetRegisterInfo *tri) : MI(mi) {
PhysRegsClobbered.resize(tri->getNumRegs());
}
bool hasReuses() const {
return !Reuses.empty();
}
/// addReuse - If we choose to reuse a virtual register that is already
/// available instead of reloading it, remember that we did so.
void addReuse(unsigned OpNo, unsigned StackSlotOrReMat,
unsigned PhysRegReused, unsigned AssignedPhysReg,
unsigned VirtReg) {
// If the reload is to the assigned register anyway, no undo will be
// required.
if (PhysRegReused == AssignedPhysReg) return;
// Otherwise, remember this.
Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused,
AssignedPhysReg, VirtReg));
}
void markClobbered(unsigned PhysReg) {
PhysRegsClobbered.set(PhysReg);
}
bool isClobbered(unsigned PhysReg) const {
return PhysRegsClobbered.test(PhysReg);
}
/// GetRegForReload - We are about to emit a reload into PhysReg. If there
/// is some other operand that is using the specified register, either pick
/// a new register to use, or evict the previous reload and use this reg.
unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
AvailableSpills &Spills,
std::vector<MachineInstr*> &MaybeDeadStores,
SmallSet<unsigned, 8> &Rejected,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
const TargetInstrInfo* TII = MI->getParent()->getParent()->getTarget()
.getInstrInfo();
if (Reuses.empty()) return PhysReg; // This is most often empty.
for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) {
ReusedOp &Op = Reuses[ro];
// If we find some other reuse that was supposed to use this register
// exactly for its reload, we can change this reload to use ITS reload
// register. That is, unless its reload register has already been
// considered and subsequently rejected because it has also been reused
// by another operand.
if (Op.PhysRegReused == PhysReg &&
Rejected.count(Op.AssignedPhysReg) == 0) {
// Yup, use the reload register that we didn't use before.
unsigned NewReg = Op.AssignedPhysReg;
Rejected.insert(PhysReg);
return GetRegForReload(NewReg, MI, Spills, MaybeDeadStores, Rejected,
RegKills, KillOps, VRM);
} else {
// Otherwise, we might also have a problem if a previously reused
// value aliases the new register. If so, codegen the previous reload
// and use this one.
unsigned PRRU = Op.PhysRegReused;
const TargetRegisterInfo *TRI = Spills.getRegInfo();
if (TRI->areAliases(PRRU, PhysReg)) {
// Okay, we found out that an alias of a reused register
// was used. This isn't good because it means we have
// to undo a previous reuse.
MachineBasicBlock *MBB = MI->getParent();
const TargetRegisterClass *AliasRC =
MBB->getParent()->getRegInfo().getRegClass(Op.VirtReg);
// Copy Op out of the vector and remove it, we're going to insert an
// explicit load for it.
ReusedOp NewOp = Op;
Reuses.erase(Reuses.begin()+ro);
// Ok, we're going to try to reload the assigned physreg into the
// slot that we were supposed to in the first place. However, that
// register could hold a reuse. Check to see if it conflicts or
// would prefer us to use a different register.
unsigned NewPhysReg = GetRegForReload(NewOp.AssignedPhysReg,
MI, Spills, MaybeDeadStores,
Rejected, RegKills, KillOps, VRM);
MachineBasicBlock::iterator MII = MI;
if (NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT) {
ReMaterialize(*MBB, MII, NewPhysReg, NewOp.VirtReg, TRI, VRM);
} else {
TII->loadRegFromStackSlot(*MBB, MII, NewPhysReg,
NewOp.StackSlotOrReMat, AliasRC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(NewOp.StackSlotOrReMat, LoadMI);
// Any stores to this stack slot are not dead anymore.
MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL;
++NumLoads;
}
Spills.ClobberPhysReg(NewPhysReg);
Spills.ClobberPhysReg(NewOp.PhysRegReused);
MI->getOperand(NewOp.Operand).setReg(NewPhysReg);
Spills.addAvailable(NewOp.StackSlotOrReMat, MI, NewPhysReg);
--MII;
UpdateKills(*MII, RegKills, KillOps);
DOUT << '\t' << *MII;
DOUT << "Reuse undone!\n";
--NumReused;
// Finally, PhysReg is now available, go ahead and use it.
return PhysReg;
}
}
}
return PhysReg;
}
/// GetRegForReload - Helper for the above GetRegForReload(). Add a
/// 'Rejected' set to remember which registers have been considered and
/// rejected for the reload. This avoids infinite looping in case like
/// this:
/// t1 := op t2, t3
/// t2 <- assigned r0 for use by the reload but ended up reuse r1
/// t3 <- assigned r1 for use by the reload but ended up reuse r0
/// t1 <- desires r1
/// sees r1 is taken by t2, tries t2's reload register r0
/// sees r0 is taken by t3, tries t3's reload register r1
/// sees r1 is taken by t2, tries t2's reload register r0 ...
unsigned GetRegForReload(unsigned PhysReg, MachineInstr *MI,
AvailableSpills &Spills,
std::vector<MachineInstr*> &MaybeDeadStores,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
SmallSet<unsigned, 8> Rejected;
return GetRegForReload(PhysReg, MI, Spills, MaybeDeadStores, Rejected,
RegKills, KillOps, VRM);
}
};
}
/// PrepForUnfoldOpti - Turn a store folding instruction into a load folding
/// instruction. e.g.
/// xorl %edi, %eax
/// movl %eax, -32(%ebp)
/// movl -36(%ebp), %eax
/// orl %eax, -32(%ebp)
/// ==>
/// xorl %edi, %eax
/// orl -36(%ebp), %eax
/// mov %eax, -32(%ebp)
/// This enables unfolding optimization for a subsequent instruction which will
/// also eliminate the newly introduced store instruction.
bool LocalSpiller::PrepForUnfoldOpti(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
std::vector<MachineInstr*> &MaybeDeadStores,
AvailableSpills &Spills,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
MachineFunction &MF = *MBB.getParent();
MachineInstr &MI = *MII;
unsigned UnfoldedOpc = 0;
unsigned UnfoldPR = 0;
unsigned UnfoldVR = 0;
int FoldedSS = VirtRegMap::NO_STACK_SLOT;
VirtRegMap::MI2VirtMapTy::const_iterator I, End;
for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
// Only transform a MI that folds a single register.
if (UnfoldedOpc)
return false;
UnfoldVR = I->second.first;
VirtRegMap::ModRef MR = I->second.second;
if (VRM.isAssignedReg(UnfoldVR))
continue;
// If this reference is not a use, any previous store is now dead.
// Otherwise, the store to this stack slot is not dead anymore.
FoldedSS = VRM.getStackSlot(UnfoldVR);
MachineInstr* DeadStore = MaybeDeadStores[FoldedSS];
if (DeadStore && (MR & VirtRegMap::isModRef)) {
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(FoldedSS);
if (!PhysReg || !DeadStore->readsRegister(PhysReg))
continue;
UnfoldPR = PhysReg;
UnfoldedOpc = TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(),
false, true);
}
}
if (!UnfoldedOpc)
return false;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isRegister() || MO.getReg() == 0 || !MO.isUse())
continue;
unsigned VirtReg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(VirtReg) || MO.getSubReg())
continue;
if (VRM.isAssignedReg(VirtReg)) {
unsigned PhysReg = VRM.getPhys(VirtReg);
if (PhysReg && TRI->regsOverlap(PhysReg, UnfoldPR))
return false;
} else if (VRM.isReMaterialized(VirtReg))
continue;
int SS = VRM.getStackSlot(VirtReg);
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
if (PhysReg) {
if (TRI->regsOverlap(PhysReg, UnfoldPR))
return false;
continue;
}
PhysReg = VRM.getPhys(VirtReg);
if (!TRI->regsOverlap(PhysReg, UnfoldPR))
continue;
// Ok, we'll need to reload the value into a register which makes
// it impossible to perform the store unfolding optimization later.
// Let's see if it is possible to fold the load if the store is
// unfolded. This allows us to perform the store unfolding
// optimization.
SmallVector<MachineInstr*, 4> NewMIs;
if (TII->unfoldMemoryOperand(MF, &MI, UnfoldVR, false, false, NewMIs)) {
assert(NewMIs.size() == 1);
MachineInstr *NewMI = NewMIs.back();
NewMIs.clear();
int Idx = NewMI->findRegisterUseOperandIdx(VirtReg, false);
assert(Idx != -1);
SmallVector<unsigned, 2> Ops;
Ops.push_back(Idx);
MachineInstr *FoldedMI = TII->foldMemoryOperand(MF, NewMI, Ops, SS);
if (FoldedMI) {
VRM.addSpillSlotUse(SS, FoldedMI);
if (!VRM.hasPhys(UnfoldVR))
VRM.assignVirt2Phys(UnfoldVR, UnfoldPR);
VRM.virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef);
MII = MBB.insert(MII, FoldedMI);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
return true;
}
delete NewMI;
}
}
return false;
}
/// findSuperReg - Find the SubReg's super-register of given register class
/// where its SubIdx sub-register is SubReg.
static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg,
unsigned SubIdx, const TargetRegisterInfo *TRI) {
for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end();
I != E; ++I) {
unsigned Reg = *I;
if (TRI->getSubReg(Reg, SubIdx) == SubReg)
return Reg;
}
return 0;
}
/// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if
/// the last store to the same slot is now dead. If so, remove the last store.
void LocalSpiller::SpillRegToStackSlot(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MII,
int Idx, unsigned PhysReg, int StackSlot,
const TargetRegisterClass *RC,
bool isAvailable, MachineInstr *&LastStore,
AvailableSpills &Spills,
SmallSet<MachineInstr*, 4> &ReMatDefs,
BitVector &RegKills,
std::vector<MachineOperand*> &KillOps,
VirtRegMap &VRM) {
TII->storeRegToStackSlot(MBB, next(MII), PhysReg, true, StackSlot, RC);
MachineInstr *StoreMI = next(MII);
VRM.addSpillSlotUse(StackSlot, StoreMI);
DOUT << "Store:\t" << *StoreMI;
// If there is a dead store to this stack slot, nuke it now.
if (LastStore) {
DOUT << "Removed dead store:\t" << *LastStore;
++NumDSE;
SmallVector<unsigned, 2> KillRegs;
InvalidateKills(*LastStore, RegKills, KillOps, &KillRegs);
MachineBasicBlock::iterator PrevMII = LastStore;
bool CheckDef = PrevMII != MBB.begin();
if (CheckDef)
--PrevMII;
VRM.RemoveMachineInstrFromMaps(LastStore);
MBB.erase(LastStore);
if (CheckDef) {
// Look at defs of killed registers on the store. Mark the defs
// as dead since the store has been deleted and they aren't
// being reused.
for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) {
bool HasOtherDef = false;
if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef)) {
MachineInstr *DeadDef = PrevMII;
if (ReMatDefs.count(DeadDef) && !HasOtherDef) {
// FIXME: This assumes a remat def does not have side
// effects.
VRM.RemoveMachineInstrFromMaps(DeadDef);
MBB.erase(DeadDef);
++NumDRM;
}
}
}
}
}
LastStore = next(MII);
// If the stack slot value was previously available in some other
// register, change it now. Otherwise, make the register available,
// in PhysReg.
Spills.ModifyStackSlotOrReMat(StackSlot);
Spills.ClobberPhysReg(PhysReg);
Spills.addAvailable(StackSlot, LastStore, PhysReg, isAvailable);
++NumStores;
}
/// rewriteMBB - Keep track of which spills are available even after the
/// register allocator is done with them. If possible, avid reloading vregs.
void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
DOUT << MBB.getBasicBlock()->getName() << ":\n";
MachineFunction &MF = *MBB.getParent();
// Spills - Keep track of which spilled values are available in physregs so
// that we can choose to reuse the physregs instead of emitting reloads.
AvailableSpills Spills(TRI, TII);
// MaybeDeadStores - When we need to write a value back into a stack slot,
// keep track of the inserted store. If the stack slot value is never read
// (because the value was used from some available register, for example), and
// subsequently stored to, the original store is dead. This map keeps track
// of inserted stores that are not used. If we see a subsequent store to the
// same stack slot, the original store is deleted.
std::vector<MachineInstr*> MaybeDeadStores;
MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL);
// ReMatDefs - These are rematerializable def MIs which are not deleted.
SmallSet<MachineInstr*, 4> ReMatDefs;
// Keep track of kill information.
BitVector RegKills(TRI->getNumRegs());
std::vector<MachineOperand*> KillOps;
KillOps.resize(TRI->getNumRegs(), NULL);
for (MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end();
MII != E; ) {
MachineBasicBlock::iterator NextMII = MII; ++NextMII;
VirtRegMap::MI2VirtMapTy::const_iterator I, End;
bool Erased = false;
bool BackTracked = false;
if (PrepForUnfoldOpti(MBB, MII,
MaybeDeadStores, Spills, RegKills, KillOps, VRM))
NextMII = next(MII);
MachineInstr &MI = *MII;
const TargetInstrDesc &TID = MI.getDesc();
if (VRM.hasEmergencySpills(&MI)) {
// Spill physical register(s) in the rare case the allocator has run out
// of registers to allocate.
SmallSet<int, 4> UsedSS;
std::vector<unsigned> &EmSpills = VRM.getEmergencySpills(&MI);
for (unsigned i = 0, e = EmSpills.size(); i != e; ++i) {
unsigned PhysReg = EmSpills[i];
const TargetRegisterClass *RC =
TRI->getPhysicalRegisterRegClass(PhysReg);
assert(RC && "Unable to determine register class!");
int SS = VRM.getEmergencySpillSlot(RC);
if (UsedSS.count(SS))
assert(0 && "Need to spill more than one physical registers!");
UsedSS.insert(SS);
TII->storeRegToStackSlot(MBB, MII, PhysReg, true, SS, RC);
MachineInstr *StoreMI = prior(MII);
VRM.addSpillSlotUse(SS, StoreMI);
TII->loadRegFromStackSlot(MBB, next(MII), PhysReg, SS, RC);
MachineInstr *LoadMI = next(MII);
VRM.addSpillSlotUse(SS, LoadMI);
++NumPSpills;
}
}
// Insert restores here if asked to.
if (VRM.isRestorePt(&MI)) {
std::vector<unsigned> &RestoreRegs = VRM.getRestorePtRestores(&MI);
for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) {
unsigned VirtReg = RestoreRegs[e-i-1]; // Reverse order.
if (!VRM.getPreSplitReg(VirtReg))
continue; // Split interval spilled again.
unsigned Phys = VRM.getPhys(VirtReg);
RegInfo->setPhysRegUsed(Phys);
if (VRM.isReMaterialized(VirtReg)) {
ReMaterialize(MBB, MII, Phys, VirtReg, TRI, VRM);
} else {
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
int SS = VRM.getStackSlot(VirtReg);
TII->loadRegFromStackSlot(MBB, &MI, Phys, SS, RC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(SS, LoadMI);
++NumLoads;
}
// This invalidates Phys.
Spills.ClobberPhysReg(Phys);
UpdateKills(*prior(MII), RegKills, KillOps);
DOUT << '\t' << *prior(MII);
}
}
// Insert spills here if asked to.
if (VRM.isSpillPt(&MI)) {
std::vector<std::pair<unsigned,bool> > &SpillRegs =
VRM.getSpillPtSpills(&MI);
for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) {
unsigned VirtReg = SpillRegs[i].first;
bool isKill = SpillRegs[i].second;
if (!VRM.getPreSplitReg(VirtReg))
continue; // Split interval spilled again.
const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
unsigned Phys = VRM.getPhys(VirtReg);
int StackSlot = VRM.getStackSlot(VirtReg);
TII->storeRegToStackSlot(MBB, next(MII), Phys, isKill, StackSlot, RC);
MachineInstr *StoreMI = next(MII);
VRM.addSpillSlotUse(StackSlot, StoreMI);
DOUT << "Store:\t" << *StoreMI;
VRM.virtFolded(VirtReg, StoreMI, VirtRegMap::isMod);
}
NextMII = next(MII);
}
/// ReusedOperands - Keep track of operand reuse in case we need to undo
/// reuse.
ReuseInfo ReusedOperands(MI, TRI);
SmallVector<unsigned, 4> VirtUseOps;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isRegister() || MO.getReg() == 0)
continue; // Ignore non-register operands.
unsigned VirtReg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(VirtReg)) {
// Ignore physregs for spilling, but remember that it is used by this
// function.
RegInfo->setPhysRegUsed(VirtReg);
continue;
}
// We want to process implicit virtual register uses first.
if (MO.isImplicit())
VirtUseOps.insert(VirtUseOps.begin(), i);
else
VirtUseOps.push_back(i);
}
// Process all of the spilled uses and all non spilled reg references.
for (unsigned j = 0, e = VirtUseOps.size(); j != e; ++j) {
unsigned i = VirtUseOps[j];
MachineOperand &MO = MI.getOperand(i);
unsigned VirtReg = MO.getReg();
assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
"Not a virtual register?");
unsigned SubIdx = MO.getSubReg();
if (VRM.isAssignedReg(VirtReg)) {
// This virtual register was assigned a physreg!
unsigned Phys = VRM.getPhys(VirtReg);
RegInfo->setPhysRegUsed(Phys);
if (MO.isDef())
ReusedOperands.markClobbered(Phys);
unsigned RReg = SubIdx ? TRI->getSubReg(Phys, SubIdx) : Phys;
MI.getOperand(i).setReg(RReg);
continue;
}
// This virtual register is now known to be a spilled value.
if (!MO.isUse())
continue; // Handle defs in the loop below (handle use&def here though)
bool DoReMat = VRM.isReMaterialized(VirtReg);
int SSorRMId = DoReMat
? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
int ReuseSlot = SSorRMId;
// Check to see if this stack slot is available.
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
// If this is a sub-register use, make sure the reuse register is in the
// right register class. For example, for x86 not all of the 32-bit
// registers have accessible sub-registers.
// Similarly so for EXTRACT_SUBREG. Consider this:
// EDI = op
// MOV32_mr fi#1, EDI
// ...
// = EXTRACT_SUBREG fi#1
// fi#1 is available in EDI, but it cannot be reused because it's not in
// the right register file.
if (PhysReg &&
(SubIdx || MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)) {
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
if (!RC->contains(PhysReg))
PhysReg = 0;
}
if (PhysReg) {
// This spilled operand might be part of a two-address operand. If this
// is the case, then changing it will necessarily require changing the
// def part of the instruction as well. However, in some cases, we
// aren't allowed to modify the reused register. If none of these cases
// apply, reuse it.
bool CanReuse = true;
int ti = TID.getOperandConstraint(i, TOI::TIED_TO);
if (ti != -1 &&
MI.getOperand(ti).isRegister() &&
MI.getOperand(ti).getReg() == VirtReg) {
// Okay, we have a two address operand. We can reuse this physreg as
// long as we are allowed to clobber the value and there isn't an
// earlier def that has already clobbered the physreg.
CanReuse = Spills.canClobberPhysReg(ReuseSlot) &&
!ReusedOperands.isClobbered(PhysReg);
}
if (CanReuse) {
// If this stack slot value is already available, reuse it!
if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Reusing SS#" << ReuseSlot;
DOUT << " from physreg "
<< TRI->getName(PhysReg) << " for vreg"
<< VirtReg <<" instead of reloading into physreg "
<< TRI->getName(VRM.getPhys(VirtReg)) << "\n";
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
MI.getOperand(i).setReg(RReg);
// The only technical detail we have is that we don't know that
// PhysReg won't be clobbered by a reloaded stack slot that occurs
// later in the instruction. In particular, consider 'op V1, V2'.
// If V1 is available in physreg R0, we would choose to reuse it
// here, instead of reloading it into the register the allocator
// indicated (say R1). However, V2 might have to be reloaded
// later, and it might indicate that it needs to live in R0. When
// this occurs, we need to have information available that
// indicates it is safe to use R1 for the reload instead of R0.
//
// To further complicate matters, we might conflict with an alias,
// or R0 and R1 might not be compatible with each other. In this
// case, we actually insert a reload for V1 in R1, ensuring that
// we can get at R0 or its alias.
ReusedOperands.addReuse(i, ReuseSlot, PhysReg,
VRM.getPhys(VirtReg), VirtReg);
if (ti != -1)
// Only mark it clobbered if this is a use&def operand.
ReusedOperands.markClobbered(PhysReg);
++NumReused;
if (MI.getOperand(i).isKill() &&
ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) {
// This was the last use and the spilled value is still available
// for reuse. That means the spill was unnecessary!
MachineInstr* DeadStore = MaybeDeadStores[ReuseSlot];
if (DeadStore) {
DOUT << "Removed dead store:\t" << *DeadStore;
InvalidateKills(*DeadStore, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DeadStore);
MBB.erase(DeadStore);
MaybeDeadStores[ReuseSlot] = NULL;
++NumDSE;
}
}
continue;
} // CanReuse
// Otherwise we have a situation where we have a two-address instruction
// whose mod/ref operand needs to be reloaded. This reload is already
// available in some register "PhysReg", but if we used PhysReg as the
// operand to our 2-addr instruction, the instruction would modify
// PhysReg. This isn't cool if something later uses PhysReg and expects
// to get its initial value.
//
// To avoid this problem, and to avoid doing a load right after a store,
// we emit a copy from PhysReg into the designated register for this
// operand.
unsigned DesignatedReg = VRM.getPhys(VirtReg);
assert(DesignatedReg && "Must map virtreg to physreg!");
// Note that, if we reused a register for a previous operand, the
// register we want to reload into might not actually be
// available. If this occurs, use the register indicated by the
// reuser.
if (ReusedOperands.hasReuses())
DesignatedReg = ReusedOperands.GetRegForReload(DesignatedReg, &MI,
Spills, MaybeDeadStores, RegKills, KillOps, VRM);
// If the mapped designated register is actually the physreg we have
// incoming, we don't need to inserted a dead copy.
if (DesignatedReg == PhysReg) {
// If this stack slot value is already available, reuse it!
if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT)
DOUT << "Reusing RM#" << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1;
else
DOUT << "Reusing SS#" << ReuseSlot;
DOUT << " from physreg " << TRI->getName(PhysReg)
<< " for vreg" << VirtReg
<< " instead of reloading into same physreg.\n";
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
MI.getOperand(i).setReg(RReg);
ReusedOperands.markClobbered(RReg);
++NumReused;
continue;
}
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
RegInfo->setPhysRegUsed(DesignatedReg);
ReusedOperands.markClobbered(DesignatedReg);
TII->copyRegToReg(MBB, &MI, DesignatedReg, PhysReg, RC, RC);
MachineInstr *CopyMI = prior(MII);
UpdateKills(*CopyMI, RegKills, KillOps);
// This invalidates DesignatedReg.
Spills.ClobberPhysReg(DesignatedReg);
Spills.addAvailable(ReuseSlot, &MI, DesignatedReg);
unsigned RReg =
SubIdx ? TRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg;
MI.getOperand(i).setReg(RReg);
DOUT << '\t' << *prior(MII);
++NumReused;
continue;
} // if (PhysReg)
// Otherwise, reload it and remember that we have it.
PhysReg = VRM.getPhys(VirtReg);
assert(PhysReg && "Must map virtreg to physreg!");
// Note that, if we reused a register for a previous operand, the
// register we want to reload into might not actually be
// available. If this occurs, use the register indicated by the
// reuser.
if (ReusedOperands.hasReuses())
PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
Spills, MaybeDeadStores, RegKills, KillOps, VRM);
RegInfo->setPhysRegUsed(PhysReg);
ReusedOperands.markClobbered(PhysReg);
if (DoReMat) {
ReMaterialize(MBB, MII, PhysReg, VirtReg, TRI, VRM);
} else {
const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
TII->loadRegFromStackSlot(MBB, &MI, PhysReg, SSorRMId, RC);
MachineInstr *LoadMI = prior(MII);
VRM.addSpillSlotUse(SSorRMId, LoadMI);
++NumLoads;
}
// This invalidates PhysReg.
Spills.ClobberPhysReg(PhysReg);
// Any stores to this stack slot are not dead anymore.
if (!DoReMat)
MaybeDeadStores[SSorRMId] = NULL;
Spills.addAvailable(SSorRMId, &MI, PhysReg);
// Assumes this is the last use. IsKill will be unset if reg is reused
// unless it's a two-address operand.
if (TID.getOperandConstraint(i, TOI::TIED_TO) == -1)
MI.getOperand(i).setIsKill();
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
MI.getOperand(i).setReg(RReg);
UpdateKills(*prior(MII), RegKills, KillOps);
DOUT << '\t' << *prior(MII);
}
DOUT << '\t' << MI;
// If we have folded references to memory operands, make sure we clear all
// physical registers that may contain the value of the spilled virtual
// register
SmallSet<int, 2> FoldedSS;
for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) {
unsigned VirtReg = I->second.first;
VirtRegMap::ModRef MR = I->second.second;
DOUT << "Folded vreg: " << VirtReg << " MR: " << MR;
int SS = VRM.getStackSlot(VirtReg);
if (SS == VirtRegMap::NO_STACK_SLOT)
continue;
FoldedSS.insert(SS);
DOUT << " - StackSlot: " << SS << "\n";
// If this folded instruction is just a use, check to see if it's a
// straight load from the virt reg slot.
if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) {
int FrameIdx;
unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx);
if (DestReg && FrameIdx == SS) {
// If this spill slot is available, turn it into a copy (or nothing)
// instead of leaving it as a load!
if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) {
DOUT << "Promoted Load To Copy: " << MI;
if (DestReg != InReg) {
const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
TII->copyRegToReg(MBB, &MI, DestReg, InReg, RC, RC);
// Revisit the copy so we make sure to notice the effects of the
// operation on the destreg (either needing to RA it if it's
// virtual or needing to clobber any values if it's physical).
NextMII = &MI;
--NextMII; // backtrack to the copy.
BackTracked = true;
} else {
DOUT << "Removing now-noop copy: " << MI;
// Unset last kill since it's being reused.
InvalidateKill(InReg, RegKills, KillOps);
}
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
goto ProcessNextInst;
}
} else {
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
SmallVector<MachineInstr*, 4> NewMIs;
if (PhysReg &&
TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) {
MBB.insert(MII, NewMIs[0]);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
--NextMII; // backtrack to the unfolded instruction.
BackTracked = true;
goto ProcessNextInst;
}
}
}
// If this reference is not a use, any previous store is now dead.
// Otherwise, the store to this stack slot is not dead anymore.
MachineInstr* DeadStore = MaybeDeadStores[SS];
if (DeadStore) {
bool isDead = !(MR & VirtRegMap::isRef);
MachineInstr *NewStore = NULL;
if (MR & VirtRegMap::isModRef) {
unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS);
SmallVector<MachineInstr*, 4> NewMIs;
// We can reuse this physreg as long as we are allowed to clobber
// the value and there isn't an earlier def that has already clobbered
// the physreg.
if (PhysReg &&
!TII->isStoreToStackSlot(&MI, SS) && // Not profitable!
DeadStore->killsRegister(PhysReg) &&
TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, true, NewMIs)) {
MBB.insert(MII, NewMIs[0]);
NewStore = NewMIs[1];
MBB.insert(MII, NewStore);
VRM.addSpillSlotUse(SS, NewStore);
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
--NextMII;
--NextMII; // backtrack to the unfolded instruction.
BackTracked = true;
isDead = true;
}
}
if (isDead) { // Previous store is dead.
// If we get here, the store is dead, nuke it now.
DOUT << "Removed dead store:\t" << *DeadStore;
InvalidateKills(*DeadStore, RegKills, KillOps);
VRM.RemoveMachineInstrFromMaps(DeadStore);
MBB.erase(DeadStore);
if (!NewStore)
++NumDSE;
}
MaybeDeadStores[SS] = NULL;
if (NewStore) {
// Treat this store as a spill merged into a copy. That makes the
// stack slot value available.
VRM.virtFolded(VirtReg, NewStore, VirtRegMap::isMod);
goto ProcessNextInst;
}
}
// If the spill slot value is available, and this is a new definition of
// the value, the value is not available anymore.
if (MR & VirtRegMap::isMod) {
// Notice that the value in this stack slot has been modified.
Spills.ModifyStackSlotOrReMat(SS);
// If this is *just* a mod of the value, check to see if this is just a
// store to the spill slot (i.e. the spill got merged into the copy). If
// so, realize that the vreg is available now, and add the store to the
// MaybeDeadStore info.
int StackSlot;
if (!(MR & VirtRegMap::isRef)) {
if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) {
assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
"Src hasn't been allocated yet?");
// Okay, this is certainly a store of SrcReg to [StackSlot]. Mark
// this as a potentially dead store in case there is a subsequent
// store into the stack slot without a read from it.
MaybeDeadStores[StackSlot] = &MI;
// If the stack slot value was previously available in some other
// register, change it now. Otherwise, make the register available,
// in PhysReg.
Spills.addAvailable(StackSlot, &MI, SrcReg, false/*don't clobber*/);
}
}
}
}
// Process all of the spilled defs.
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!(MO.isRegister() && MO.getReg() && MO.isDef()))
continue;
unsigned VirtReg = MO.getReg();
if (!TargetRegisterInfo::isVirtualRegister(VirtReg)) {
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
unsigned Src, Dst;
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
Spills.disallowClobberPhysReg(VirtReg);
goto ProcessNextInst;
}
// If it's not a no-op copy, it clobbers the value in the destreg.
Spills.ClobberPhysReg(VirtReg);
ReusedOperands.markClobbered(VirtReg);
// Check to see if this instruction is a load from a stack slot into
// a register. If so, this provides the stack slot value in the reg.
int FrameIdx;
if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) {
assert(DestReg == VirtReg && "Unknown load situation!");
// If it is a folded reference, then it's not safe to clobber.
bool Folded = FoldedSS.count(FrameIdx);
// Otherwise, if it wasn't available, remember that it is now!
Spills.addAvailable(FrameIdx, &MI, DestReg, !Folded);
goto ProcessNextInst;
}
continue;
}
unsigned SubIdx = MO.getSubReg();
bool DoReMat = VRM.isReMaterialized(VirtReg);
if (DoReMat)
ReMatDefs.insert(&MI);
// The only vregs left are stack slot definitions.
int StackSlot = VRM.getStackSlot(VirtReg);
const TargetRegisterClass *RC = RegInfo->getRegClass(VirtReg);
// If this def is part of a two-address operand, make sure to execute
// the store from the correct physical register.
unsigned PhysReg;
int TiedOp = MI.getDesc().findTiedToSrcOperand(i);
if (TiedOp != -1) {
PhysReg = MI.getOperand(TiedOp).getReg();
if (SubIdx) {
unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, TRI);
assert(SuperReg && TRI->getSubReg(SuperReg, SubIdx) == PhysReg &&
"Can't find corresponding super-register!");
PhysReg = SuperReg;
}
} else {
PhysReg = VRM.getPhys(VirtReg);
if (ReusedOperands.isClobbered(PhysReg)) {
// Another def has taken the assigned physreg. It must have been a
// use&def which got it due to reuse. Undo the reuse!
PhysReg = ReusedOperands.GetRegForReload(PhysReg, &MI,
Spills, MaybeDeadStores, RegKills, KillOps, VRM);
}
}
RegInfo->setPhysRegUsed(PhysReg);
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
ReusedOperands.markClobbered(RReg);
MI.getOperand(i).setReg(RReg);
if (!MO.isDead()) {
MachineInstr *&LastStore = MaybeDeadStores[StackSlot];
SpillRegToStackSlot(MBB, MII, -1, PhysReg, StackSlot, RC, true,
LastStore, Spills, ReMatDefs, RegKills, KillOps, VRM);
NextMII = next(MII);
// Check to see if this is a noop copy. If so, eliminate the
// instruction before considering the dest reg to be changed.
{
unsigned Src, Dst;
if (TII->isMoveInstr(MI, Src, Dst) && Src == Dst) {
++NumDCE;
DOUT << "Removing now-noop copy: " << MI;
VRM.RemoveMachineInstrFromMaps(&MI);
MBB.erase(&MI);
Erased = true;
UpdateKills(*LastStore, RegKills, KillOps);
goto ProcessNextInst;
}
}
}
}
ProcessNextInst:
if (!Erased && !BackTracked) {
for (MachineBasicBlock::iterator II = MI; II != NextMII; ++II)
UpdateKills(*II, RegKills, KillOps);
}
MII = NextMII;
}
}
llvm::Spiller* llvm::createSpiller() {
switch (SpillerOpt) {
default: assert(0 && "Unreachable!");
case local:
return new LocalSpiller();
case simple:
return new SimpleSpiller();
}
}
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