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llvm/lib/CodeGen/RegAllocLinearScan.cpp
Alkis Evlogimenos 843b160a20 Eliminate the use of spill (reserved) registers. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11476 91177308-0d34-0410-b5e6-96231b3b80d8
2004-02-15 10:24:21 +00:00

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//===-- RegAllocLinearScan.cpp - Linear Scan register allocator -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a linear scan register allocator.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "llvm/Function.h"
#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/CFG.h"
#include "Support/Debug.h"
#include "Support/DepthFirstIterator.h"
#include "Support/Statistic.h"
#include "Support/STLExtras.h"
#include <algorithm>
using namespace llvm;
namespace {
Statistic<> numSpilled ("ra-linearscan", "Number of registers spilled");
Statistic<> numReloaded("ra-linearscan", "Number of registers reloaded");
class PhysRegTracker {
private:
const MRegisterInfo* mri_;
std::vector<unsigned> regUse_;
public:
PhysRegTracker(MachineFunction* mf)
: mri_(mf ? mf->getTarget().getRegisterInfo() : NULL) {
if (mri_) {
regUse_.assign(mri_->getNumRegs(), 0);
}
}
PhysRegTracker(const PhysRegTracker& rhs)
: mri_(rhs.mri_),
regUse_(rhs.regUse_) {
}
const PhysRegTracker& operator=(const PhysRegTracker& rhs) {
mri_ = rhs.mri_;
regUse_ = rhs.regUse_;
return *this;
}
void addPhysRegUse(unsigned physReg) {
++regUse_[physReg];
for (const unsigned* as = mri_->getAliasSet(physReg); *as; ++as) {
physReg = *as;
++regUse_[physReg];
}
}
void delPhysRegUse(unsigned physReg) {
assert(regUse_[physReg] != 0);
--regUse_[physReg];
for (const unsigned* as = mri_->getAliasSet(physReg); *as; ++as) {
physReg = *as;
assert(regUse_[physReg] != 0);
--regUse_[physReg];
}
}
bool isPhysRegAvail(unsigned physReg) const {
return regUse_[physReg] == 0;
}
};
class RA : public MachineFunctionPass {
private:
MachineFunction* mf_;
const TargetMachine* tm_;
const MRegisterInfo* mri_;
LiveIntervals* li_;
typedef std::list<LiveIntervals::Interval*> IntervalPtrs;
IntervalPtrs unhandled_, fixed_, active_, inactive_, handled_;
PhysRegTracker prt_;
typedef std::map<unsigned, unsigned> Virt2PhysMap;
Virt2PhysMap v2pMap_;
typedef std::map<unsigned, int> Virt2StackSlotMap;
Virt2StackSlotMap v2ssMap_;
int instrAdded_;
typedef std::vector<float> SpillWeights;
SpillWeights spillWeights_;
public:
RA()
: prt_(NULL) {
}
virtual const char* getPassName() const {
return "Linear Scan Register Allocator";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveVariables>();
AU.addRequired<LiveIntervals>();
MachineFunctionPass::getAnalysisUsage(AU);
}
/// runOnMachineFunction - register allocate the whole function
bool runOnMachineFunction(MachineFunction&);
void releaseMemory();
private:
/// initIntervalSets - initializa the four interval sets:
/// unhandled, fixed, active and inactive
void initIntervalSets(LiveIntervals::Intervals& li);
/// processActiveIntervals - expire old intervals and move
/// non-overlapping ones to the incative list
void processActiveIntervals(IntervalPtrs::value_type cur);
/// processInactiveIntervals - expire old intervals and move
/// overlapping ones to the active list
void processInactiveIntervals(IntervalPtrs::value_type cur);
/// updateSpillWeights - updates the spill weights of the
/// specifed physical register and its weight
void updateSpillWeights(unsigned reg, SpillWeights::value_type weight);
/// assignRegOrStackSlotAtInterval - assign a register if one
/// is available, or spill.
void assignRegOrStackSlotAtInterval(IntervalPtrs::value_type cur);
/// addSpillCode - adds spill code for interval. The interval
/// must be modified by LiveIntervals::updateIntervalForSpill.
void addSpillCode(IntervalPtrs::value_type li, int slot);
///
/// register handling helpers
///
/// getFreePhysReg - return a free physical register for this
/// virtual register interval if we have one, otherwise return
/// 0
unsigned getFreePhysReg(IntervalPtrs::value_type cur);
/// assignVirt2PhysReg - assigns the free physical register to
/// the virtual register passed as arguments
Virt2PhysMap::iterator
assignVirt2PhysReg(unsigned virtReg, unsigned physReg);
/// clearVirtReg - free the physical register associated with this
/// virtual register and disassociate virtual->physical and
/// physical->virtual mappings
void clearVirtReg(Virt2PhysMap::iterator it);
/// assignVirt2StackSlot - assigns this virtual register to a
/// stack slot. returns the stack slot
int assignVirt2StackSlot(unsigned virtReg);
/// getStackSlot - returns the offset of the specified
/// register on the stack
int getStackSlot(unsigned virtReg);
void printVirtRegAssignment() const {
std::cerr << "register assignment:\n";
for (Virt2PhysMap::const_iterator
i = v2pMap_.begin(), e = v2pMap_.end(); i != e; ++i) {
assert(i->second != 0);
std::cerr << '[' << i->first << ','
<< mri_->getName(i->second) << "]\n";
}
for (Virt2StackSlotMap::const_iterator
i = v2ssMap_.begin(), e = v2ssMap_.end(); i != e; ++i) {
std::cerr << '[' << i->first << ",ss#" << i->second << "]\n";
}
std::cerr << '\n';
}
void printIntervals(const char* const str,
RA::IntervalPtrs::const_iterator i,
RA::IntervalPtrs::const_iterator e) const {
if (str) std::cerr << str << " intervals:\n";
for (; i != e; ++i) {
std::cerr << "\t\t" << **i << " -> ";
unsigned reg = (*i)->reg;
if (MRegisterInfo::isVirtualRegister(reg)) {
Virt2PhysMap::const_iterator it = v2pMap_.find(reg);
reg = (it == v2pMap_.end() ? 0 : it->second);
}
std::cerr << mri_->getName(reg) << '\n';
}
}
};
}
void RA::releaseMemory()
{
v2pMap_.clear();
v2ssMap_.clear();
unhandled_.clear();
active_.clear();
inactive_.clear();
fixed_.clear();
handled_.clear();
}
bool RA::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
li_ = &getAnalysis<LiveIntervals>();
prt_ = PhysRegTracker(mf_);
initIntervalSets(li_->getIntervals());
// linear scan algorithm
DEBUG(std::cerr << "Machine Function\n");
DEBUG(printIntervals("\tunhandled", unhandled_.begin(), unhandled_.end()));
DEBUG(printIntervals("\tfixed", fixed_.begin(), fixed_.end()));
DEBUG(printIntervals("\tactive", active_.begin(), active_.end()));
DEBUG(printIntervals("\tinactive", inactive_.begin(), inactive_.end()));
while (!unhandled_.empty() || !fixed_.empty()) {
// pick the interval with the earliest start point
IntervalPtrs::value_type cur;
if (fixed_.empty()) {
cur = unhandled_.front();
unhandled_.pop_front();
}
else if (unhandled_.empty()) {
cur = fixed_.front();
fixed_.pop_front();
}
else if (unhandled_.front()->start() < fixed_.front()->start()) {
cur = unhandled_.front();
unhandled_.pop_front();
}
else {
cur = fixed_.front();
fixed_.pop_front();
}
DEBUG(std::cerr << *cur << '\n');
processActiveIntervals(cur);
processInactiveIntervals(cur);
// if this register is fixed we are done
if (MRegisterInfo::isPhysicalRegister(cur->reg)) {
prt_.addPhysRegUse(cur->reg);
active_.push_back(cur);
handled_.push_back(cur);
}
// otherwise we are allocating a virtual register. try to find
// a free physical register or spill an interval in order to
// assign it one (we could spill the current though).
else {
assignRegOrStackSlotAtInterval(cur);
}
DEBUG(printIntervals("\tactive", active_.begin(), active_.end()));
DEBUG(printIntervals("\tinactive", inactive_.begin(), inactive_.end())); }
// expire any remaining active intervals
for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ++i) {
unsigned reg = (*i)->reg;
DEBUG(std::cerr << "\t\tinterval " << **i << " expired\n");
if (MRegisterInfo::isVirtualRegister(reg)) {
reg = v2pMap_[reg];
}
prt_.delPhysRegUse(reg);
}
DEBUG(printVirtRegAssignment());
DEBUG(std::cerr << "finished register allocation\n");
const TargetInstrInfo& tii = tm_->getInstrInfo();
DEBUG(std::cerr << "Rewrite machine code:\n");
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
instrAdded_ = 0;
for (MachineBasicBlock::iterator mii = mbbi->begin(), mie = mbbi->end();
mii != mie; ++mii) {
DEBUG(std::cerr << '\t'; mii->print(std::cerr, *tm_));
// use our current mapping and actually replace every
// virtual register with its allocated physical registers
DEBUG(std::cerr << "\t\treplacing virtual registers with mapped "
"physical registers:\n");
for (unsigned i = 0, e = mii->getNumOperands();
i != e; ++i) {
MachineOperand& op = mii->getOperand(i);
if (op.isRegister() &&
MRegisterInfo::isVirtualRegister(op.getReg())) {
unsigned virtReg = op.getReg();
Virt2PhysMap::iterator it = v2pMap_.find(virtReg);
assert(it != v2pMap_.end() &&
"all virtual registers must be allocated");
unsigned physReg = it->second;
assert(MRegisterInfo::isPhysicalRegister(physReg));
DEBUG(std::cerr << "\t\t\t%reg" << virtReg
<< " -> " << mri_->getName(physReg) << '\n');
mii->SetMachineOperandReg(i, physReg);
}
}
}
}
return true;
}
void RA::initIntervalSets(LiveIntervals::Intervals& li)
{
assert(unhandled_.empty() && fixed_.empty() &&
active_.empty() && inactive_.empty() &&
"interval sets should be empty on initialization");
for (LiveIntervals::Intervals::iterator i = li.begin(), e = li.end();
i != e; ++i) {
if (MRegisterInfo::isPhysicalRegister(i->reg))
fixed_.push_back(&*i);
else
unhandled_.push_back(&*i);
}
}
void RA::processActiveIntervals(IntervalPtrs::value_type cur)
{
DEBUG(std::cerr << "\tprocessing active intervals:\n");
for (IntervalPtrs::iterator i = active_.begin(); i != active_.end();) {
unsigned reg = (*i)->reg;
// remove expired intervals
if ((*i)->expiredAt(cur->start())) {
DEBUG(std::cerr << "\t\tinterval " << **i << " expired\n");
if (MRegisterInfo::isVirtualRegister(reg)) {
reg = v2pMap_[reg];
}
prt_.delPhysRegUse(reg);
// remove from active
i = active_.erase(i);
}
// move inactive intervals to inactive list
else if (!(*i)->liveAt(cur->start())) {
DEBUG(std::cerr << "\t\t\tinterval " << **i << " inactive\n");
if (MRegisterInfo::isVirtualRegister(reg)) {
reg = v2pMap_[reg];
}
prt_.delPhysRegUse(reg);
// add to inactive
inactive_.push_back(*i);
// remove from active
i = active_.erase(i);
}
else {
++i;
}
}
}
void RA::processInactiveIntervals(IntervalPtrs::value_type cur)
{
DEBUG(std::cerr << "\tprocessing inactive intervals:\n");
for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end();) {
unsigned reg = (*i)->reg;
// remove expired intervals
if ((*i)->expiredAt(cur->start())) {
DEBUG(std::cerr << "\t\t\tinterval " << **i << " expired\n");
// remove from inactive
i = inactive_.erase(i);
}
// move re-activated intervals in active list
else if ((*i)->liveAt(cur->start())) {
DEBUG(std::cerr << "\t\t\tinterval " << **i << " active\n");
if (MRegisterInfo::isVirtualRegister(reg)) {
reg = v2pMap_[reg];
}
prt_.addPhysRegUse(reg);
// add to active
active_.push_back(*i);
// remove from inactive
i = inactive_.erase(i);
}
else {
++i;
}
}
}
void RA::updateSpillWeights(unsigned reg, SpillWeights::value_type weight)
{
spillWeights_[reg] += weight;
for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
spillWeights_[*as] += weight;
}
void RA::assignRegOrStackSlotAtInterval(IntervalPtrs::value_type cur)
{
DEBUG(std::cerr << "\tallocating current interval:\n");
PhysRegTracker backupPrt = prt_;
spillWeights_.assign(mri_->getNumRegs(), 0.0);
// for each interval in active update spill weights
for (IntervalPtrs::const_iterator i = active_.begin(), e = active_.end();
i != e; ++i) {
unsigned reg = (*i)->reg;
if (MRegisterInfo::isVirtualRegister(reg))
reg = v2pMap_[reg];
updateSpillWeights(reg, (*i)->weight);
}
// for every interval in inactive we overlap with, mark the
// register as not free and update spill weights
for (IntervalPtrs::const_iterator i = inactive_.begin(),
e = inactive_.end(); i != e; ++i) {
if (cur->overlaps(**i)) {
unsigned reg = (*i)->reg;
if (MRegisterInfo::isVirtualRegister(reg))
reg = v2pMap_[reg];
prt_.addPhysRegUse(reg);
updateSpillWeights(reg, (*i)->weight);
}
}
// for every interval in fixed we overlap with,
// mark the register as not free and update spill weights
for (IntervalPtrs::const_iterator i = fixed_.begin(),
e = fixed_.end(); i != e; ++i) {
if (cur->overlaps(**i)) {
unsigned reg = (*i)->reg;
prt_.addPhysRegUse(reg);
updateSpillWeights(reg, (*i)->weight);
}
}
unsigned physReg = getFreePhysReg(cur);
// restore the physical register tracker
prt_ = backupPrt;
// if we find a free register, we are done: assign this virtual to
// the free physical register and add this interval to the active
// list.
if (physReg) {
assignVirt2PhysReg(cur->reg, physReg);
active_.push_back(cur);
handled_.push_back(cur);
return;
}
DEBUG(std::cerr << "\t\tassigning stack slot at interval "<< *cur << ":\n");
// push the current interval back to unhandled since we are going
// to re-run at least this iteration
unhandled_.push_front(cur);
float minWeight = std::numeric_limits<float>::infinity();
unsigned minReg = 0;
const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
i != rc->allocation_order_end(*mf_); ++i) {
unsigned reg = *i;
if (minWeight > spillWeights_[reg]) {
minWeight = spillWeights_[reg];
minReg = reg;
}
}
DEBUG(std::cerr << "\t\t\tregister with min weight: "
<< mri_->getName(minReg) << " (" << minWeight << ")\n");
// if the current has the minimum weight, we need to modify it,
// push it back in unhandled and let the linear scan algorithm run
// again
if (cur->weight < minWeight) {
DEBUG(std::cerr << "\t\t\t\tspilling(c): " << *cur;);
int slot = assignVirt2StackSlot(cur->reg);
li_->updateSpilledInterval(*cur);
addSpillCode(cur, slot);
DEBUG(std::cerr << "[ " << *cur << " ]\n");
return;
}
// otherwise we spill all intervals aliasing the register with
// minimum weight, rollback to the interval with the earliest
// start point and let the linear scan algorithm run again
std::vector<bool> toSpill(mri_->getNumRegs(), false);
toSpill[minReg] = true;
for (const unsigned* as = mri_->getAliasSet(minReg); *as; ++as)
toSpill[*as] = true;
unsigned earliestStart = cur->start();
for (IntervalPtrs::iterator i = active_.begin();
i != active_.end(); ++i) {
unsigned reg = (*i)->reg;
if (MRegisterInfo::isVirtualRegister(reg) &&
toSpill[v2pMap_[reg]] &&
cur->overlaps(**i)) {
DEBUG(std::cerr << "\t\t\t\tspilling(a): " << **i);
int slot = assignVirt2StackSlot((*i)->reg);
li_->updateSpilledInterval(**i);
addSpillCode(*i, slot);
DEBUG(std::cerr << "[ " << **i << " ]\n");
earliestStart = std::min(earliestStart, (*i)->start());
}
}
for (IntervalPtrs::iterator i = inactive_.begin();
i != inactive_.end(); ++i) {
unsigned reg = (*i)->reg;
if (MRegisterInfo::isVirtualRegister(reg) &&
toSpill[v2pMap_[reg]] &&
cur->overlaps(**i)) {
DEBUG(std::cerr << "\t\t\t\tspilling(i): " << **i << '\n');
int slot = assignVirt2StackSlot((*i)->reg);
li_->updateSpilledInterval(**i);
addSpillCode(*i, slot);
DEBUG(std::cerr << "[ " << **i << " ]\n");
earliestStart = std::min(earliestStart, (*i)->start());
}
}
DEBUG(std::cerr << "\t\t\t\trolling back to: " << earliestStart << '\n');
// scan handled in reverse order and undo each one, restoring the
// state of unhandled and fixed
while (!handled_.empty()) {
IntervalPtrs::value_type i = handled_.back();
// if this interval starts before t we are done
if (i->start() < earliestStart)
break;
DEBUG(std::cerr << "\t\t\t\t\tundo changes for: " << *i << '\n');
handled_.pop_back();
IntervalPtrs::iterator it;
if ((it = find(active_.begin(), active_.end(), i)) != active_.end()) {
active_.erase(it);
if (MRegisterInfo::isPhysicalRegister(i->reg)) {
fixed_.push_front(i);
prt_.delPhysRegUse(i->reg);
}
else {
Virt2PhysMap::iterator v2pIt = v2pMap_.find(i->reg);
clearVirtReg(v2pIt);
unhandled_.push_front(i);
prt_.delPhysRegUse(v2pIt->second);
}
}
else if ((it = find(inactive_.begin(), inactive_.end(), i)) != inactive_.end()) {
inactive_.erase(it);
if (MRegisterInfo::isPhysicalRegister(i->reg))
fixed_.push_front(i);
else {
Virt2PhysMap::iterator v2pIt = v2pMap_.find(i->reg);
clearVirtReg(v2pIt);
unhandled_.push_front(i);
}
}
else {
if (MRegisterInfo::isPhysicalRegister(i->reg))
fixed_.push_front(i);
else {
Virt2PhysMap::iterator v2pIt = v2pMap_.find(i->reg);
clearVirtReg(v2pIt);
unhandled_.push_front(i);
}
}
}
// scan the rest and undo each interval that expired after t and
// insert it in active (the next iteration of the algorithm will
// put it in inactive if required)
IntervalPtrs::iterator i = handled_.begin(), e = handled_.end();
for (; i != e; ++i) {
if (!(*i)->expiredAt(earliestStart) && (*i)->expiredAt(cur->start())) {
DEBUG(std::cerr << "\t\t\t\t\tundo changes for: " << **i << '\n');
active_.push_back(*i);
if (MRegisterInfo::isPhysicalRegister((*i)->reg))
prt_.addPhysRegUse((*i)->reg);
else {
assert(v2pMap_.count((*i)->reg));
prt_.addPhysRegUse(v2pMap_.find((*i)->reg)->second);
}
}
}
}
void RA::addSpillCode(IntervalPtrs::value_type li, int slot)
{
// We scan the instructions corresponding to each range. We load
// when we have a use and spill at end of basic blocks or end of
// ranges only if the register was modified.
const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(li->reg);
for (LiveIntervals::Interval::Ranges::iterator i = li->ranges.begin(),
e = li->ranges.end(); i != e; ++i) {
unsigned index = i->first & ~1;
unsigned end = i->second;
entry:
bool dirty = false, loaded = false;
// skip deleted instructions. getInstructionFromIndex returns
// null if the instruction was deleted (because of coalescing
// for example)
while (!li_->getInstructionFromIndex(index)) index += 2;
MachineBasicBlock::iterator mi = li_->getInstructionFromIndex(index);
MachineBasicBlock* mbb = mi->getParent();
for (; index < end; index += 2) {
// ignore deleted instructions
while (!li_->getInstructionFromIndex(index)) index += 2;
// if we changed basic block we need to start over
mi = li_->getInstructionFromIndex(index);
if (mbb != mi->getParent()) {
if (dirty) {
mi = li_->getInstructionFromIndex(index-2);
assert(mbb == mi->getParent() &&
"rewound to wrong instruction?");
DEBUG(std::cerr << "add store for reg" << li->reg << " to "
"stack slot " << slot << " after: ";
mi->print(std::cerr, *tm_));
++numSpilled;
mri_->storeRegToStackSlot(*mi->getParent(),
next(mi), li->reg, slot, rc);
}
goto entry;
}
// if it is used in this instruction load it
for (unsigned i = 0; i < mi->getNumOperands(); ++i) {
MachineOperand& mop = mi->getOperand(i);
if (mop.isRegister() && mop.getReg() == li->reg &&
mop.isUse() && !loaded) {
loaded = true;
DEBUG(std::cerr << "add load for reg" << li->reg
<< " from stack slot " << slot << " before: ";
mi->print(std::cerr, *tm_));
++numReloaded;
mri_->loadRegFromStackSlot(*mi->getParent(),
mi, li->reg, slot, rc);
}
}
// if it is defined in this instruction mark as dirty
for (unsigned i = 0; i < mi->getNumOperands(); ++i) {
MachineOperand& mop = mi->getOperand(i);
if (mop.isRegister() && mop.getReg() == li->reg &&
mop.isDef())
dirty = loaded = true;
}
}
if (dirty) {
mi = li_->getInstructionFromIndex(index-2);
assert(mbb == mi->getParent() &&
"rewound to wrong instruction?");
DEBUG(std::cerr << "add store for reg" << li->reg << " to "
"stack slot " << slot << " after: ";
mi->print(std::cerr, *tm_));
++numSpilled;
mri_->storeRegToStackSlot(*mi->getParent(),
next(mi), li->reg, slot, rc);
}
}
}
unsigned RA::getFreePhysReg(IntervalPtrs::value_type cur)
{
DEBUG(std::cerr << "\t\tgetting free physical register: ");
const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
i != rc->allocation_order_end(*mf_); ++i) {
unsigned reg = *i;
if (prt_.isPhysRegAvail(reg)) {
DEBUG(std::cerr << mri_->getName(reg) << '\n');
return reg;
}
}
DEBUG(std::cerr << "no free register\n");
return 0;
}
RA::Virt2PhysMap::iterator
RA::assignVirt2PhysReg(unsigned virtReg, unsigned physReg)
{
bool inserted;
Virt2PhysMap::iterator it;
tie(it, inserted) = v2pMap_.insert(std::make_pair(virtReg, physReg));
assert(inserted && "attempting to assign a virt->phys mapping to an "
"already mapped register");
prt_.addPhysRegUse(physReg);
return it;
}
void RA::clearVirtReg(Virt2PhysMap::iterator it)
{
assert(it != v2pMap_.end() &&
"attempting to clear a not allocated virtual register");
unsigned physReg = it->second;
v2pMap_.erase(it);
DEBUG(std::cerr << "\t\t\tcleared register " << mri_->getName(physReg)
<< "\n");
}
int RA::assignVirt2StackSlot(unsigned virtReg)
{
const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(virtReg);
int frameIndex = mf_->getFrameInfo()->CreateStackObject(rc);
bool inserted = v2ssMap_.insert(std::make_pair(virtReg, frameIndex)).second;
assert(inserted && "attempt to assign stack slot to spilled register!");
return frameIndex;
}
int RA::getStackSlot(unsigned virtReg)
{
assert(v2ssMap_.count(virtReg) &&
"attempt to get stack slot for a non spilled register");
return v2ssMap_.find(virtReg)->second;
}
FunctionPass* llvm::createLinearScanRegisterAllocator() {
return new RA();
}
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