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7ac2d3146a
llvm-6502/lib/CodeGen/LiveIntervalAnalysis.cpp
Chris Lattner 7ac2d3146a Big change to compute logical value numbers for each LiveRange added to an 
Interval.  This generalizes the isDefinedOnce mechanism that we used before
to help us coallesce ranges that overlap.  As part of this, every logical
range with a different value is assigned a different number in the interval.
For example, for code that looks like this:

0  X = ...
4  X += ...
  ...
N    = X

We now generate a live interval that contains two ranges: [2,6:0),[6,?:1)
reflecting the fact that there are two different values in the range at
different positions in the code.

Currently we are not using this information at all, so this just slows down
liveintervals.  In the future, this will change.

Note that this change also substantially refactors the joinIntervalsInMachineBB
method to merge the cases for virt-virt and phys-virt joining into a single
case, adds comments, and makes the code a bit easier to follow.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15154 91177308-0d34-0410-b5e6-96231b3b80d8
2004-07-24 02:59:07 +00:00

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//===-- LiveIntervalAnalysis.cpp - Live Interval Analysis -----------------===//
//
// 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 the LiveInterval analysis pass which is used
// by the Linear Scan Register allocator. This pass linearizes the
// basic blocks of the function in DFS order and uses the
// LiveVariables pass to conservatively compute live intervals for
// each virtual and physical register.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "liveintervals"
#include "LiveIntervalAnalysis.h"
#include "llvm/Value.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFrameInfo.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 "Support/CommandLine.h"
#include "Support/Debug.h"
#include "Support/Statistic.h"
#include "Support/STLExtras.h"
#include "VirtRegMap.h"
#include <cmath>
using namespace llvm;
namespace {
RegisterAnalysis<LiveIntervals> X("liveintervals",
"Live Interval Analysis");
Statistic<> numIntervals
("liveintervals", "Number of original intervals");
Statistic<> numIntervalsAfter
("liveintervals", "Number of intervals after coalescing");
Statistic<> numJoins
("liveintervals", "Number of interval joins performed");
Statistic<> numPeep
("liveintervals", "Number of identity moves eliminated after coalescing");
Statistic<> numFolded
("liveintervals", "Number of loads/stores folded into instructions");
cl::opt<bool>
EnableJoining("join-liveintervals",
cl::desc("Join compatible live intervals"),
cl::init(true));
};
void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const
{
AU.addPreserved<LiveVariables>();
AU.addRequired<LiveVariables>();
AU.addPreservedID(PHIEliminationID);
AU.addRequiredID(PHIEliminationID);
AU.addRequiredID(TwoAddressInstructionPassID);
AU.addRequired<LoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void LiveIntervals::releaseMemory()
{
mi2iMap_.clear();
i2miMap_.clear();
r2iMap_.clear();
r2rMap_.clear();
intervals_.clear();
}
/// runOnMachineFunction - Register allocate the whole function
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
lv_ = &getAnalysis<LiveVariables>();
// number MachineInstrs
unsigned miIndex = 0;
for (MachineFunction::iterator mbb = mf_->begin(), mbbEnd = mf_->end();
mbb != mbbEnd; ++mbb)
for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
mi != miEnd; ++mi) {
bool inserted = mi2iMap_.insert(std::make_pair(mi, miIndex)).second;
assert(inserted && "multiple MachineInstr -> index mappings");
i2miMap_.push_back(mi);
miIndex += InstrSlots::NUM;
}
computeIntervals();
numIntervals += intervals_.size();
#if 1
DEBUG(std::cerr << "********** INTERVALS **********\n");
DEBUG(std::copy(intervals_.begin(), intervals_.end(),
std::ostream_iterator<LiveInterval>(std::cerr, "\n")));
#endif
// join intervals if requested
if (EnableJoining) joinIntervals();
numIntervalsAfter += intervals_.size();
// perform a final pass over the instructions and compute spill
// weights, coalesce virtual registers and remove identity moves
const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
const TargetInstrInfo& tii = *tm_->getInstrInfo();
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
MachineBasicBlock* mbb = mbbi;
unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
mii != mie; ) {
// if the move will be an identity move delete it
unsigned srcReg, dstReg;
if (tii.isMoveInstr(*mii, srcReg, dstReg) &&
rep(srcReg) == rep(dstReg)) {
// remove from def list
LiveInterval& interval = getOrCreateInterval(rep(dstReg));
// remove index -> MachineInstr and
// MachineInstr -> index mappings
Mi2IndexMap::iterator mi2i = mi2iMap_.find(mii);
if (mi2i != mi2iMap_.end()) {
i2miMap_[mi2i->second/InstrSlots::NUM] = 0;
mi2iMap_.erase(mi2i);
}
mii = mbbi->erase(mii);
++numPeep;
}
else {
for (unsigned i = 0; i < mii->getNumOperands(); ++i) {
const MachineOperand& mop = mii->getOperand(i);
if (mop.isRegister() && mop.getReg() &&
MRegisterInfo::isVirtualRegister(mop.getReg())) {
// replace register with representative register
unsigned reg = rep(mop.getReg());
mii->SetMachineOperandReg(i, reg);
Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
assert(r2iit != r2iMap_.end());
r2iit->second->weight +=
(mop.isUse() + mop.isDef()) * pow(10.0F, loopDepth);
}
}
++mii;
}
}
}
DEBUG(std::cerr << "********** INTERVALS **********\n");
DEBUG(std::copy(intervals_.begin(), intervals_.end(),
std::ostream_iterator<LiveInterval>(std::cerr, "\n")));
DEBUG(std::cerr << "********** MACHINEINSTRS **********\n");
DEBUG(
for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
mbbi != mbbe; ++mbbi) {
std::cerr << ((Value*)mbbi->getBasicBlock())->getName() << ":\n";
for (MachineBasicBlock::iterator mii = mbbi->begin(),
mie = mbbi->end(); mii != mie; ++mii) {
std::cerr << getInstructionIndex(mii) << '\t';
mii->print(std::cerr, tm_);
}
});
return true;
}
std::vector<LiveInterval*> LiveIntervals::addIntervalsForSpills(
const LiveInterval& li,
VirtRegMap& vrm,
int slot)
{
std::vector<LiveInterval*> added;
assert(li.weight != HUGE_VAL &&
"attempt to spill already spilled interval!");
DEBUG(std::cerr << "\t\t\t\tadding intervals for spills for interval: "
<< li << '\n');
const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(li.reg);
for (LiveInterval::Ranges::const_iterator
i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
unsigned index = getBaseIndex(i->start);
unsigned end = getBaseIndex(i->end-1) + InstrSlots::NUM;
for (; index != end; index += InstrSlots::NUM) {
// skip deleted instructions
while (index != end && !getInstructionFromIndex(index))
index += InstrSlots::NUM;
if (index == end) break;
MachineBasicBlock::iterator mi = getInstructionFromIndex(index);
for_operand:
for (unsigned i = 0; i != mi->getNumOperands(); ++i) {
MachineOperand& mop = mi->getOperand(i);
if (mop.isRegister() && mop.getReg() == li.reg) {
if (MachineInstr* fmi =
mri_->foldMemoryOperand(mi, i, slot)) {
lv_->instructionChanged(mi, fmi);
vrm.virtFolded(li.reg, mi, fmi);
mi2iMap_.erase(mi);
i2miMap_[index/InstrSlots::NUM] = fmi;
mi2iMap_[fmi] = index;
MachineBasicBlock& mbb = *mi->getParent();
mi = mbb.insert(mbb.erase(mi), fmi);
++numFolded;
goto for_operand;
}
else {
// This is tricky. We need to add information in
// the interval about the spill code so we have to
// use our extra load/store slots.
//
// If we have a use we are going to have a load so
// we start the interval from the load slot
// onwards. Otherwise we start from the def slot.
unsigned start = (mop.isUse() ?
getLoadIndex(index) :
getDefIndex(index));
// If we have a def we are going to have a store
// right after it so we end the interval after the
// use of the next instruction. Otherwise we end
// after the use of this instruction.
unsigned end = 1 + (mop.isDef() ?
getStoreIndex(index) :
getUseIndex(index));
// create a new register for this spill
unsigned nReg =
mf_->getSSARegMap()->createVirtualRegister(rc);
mi->SetMachineOperandReg(i, nReg);
vrm.grow();
vrm.assignVirt2StackSlot(nReg, slot);
LiveInterval& nI = getOrCreateInterval(nReg);
assert(nI.empty());
// the spill weight is now infinity as it
// cannot be spilled again
nI.weight = HUGE_VAL;
LiveRange LR(start, end, nI.getNextValue());
DEBUG(std::cerr << " +" << LR);
nI.addRange(LR);
added.push_back(&nI);
// update live variables
lv_->addVirtualRegisterKilled(nReg, mi);
DEBUG(std::cerr << "\t\t\t\tadded new interval: "
<< nI << '\n');
}
}
}
}
}
return added;
}
void LiveIntervals::printRegName(unsigned reg) const
{
if (MRegisterInfo::isPhysicalRegister(reg))
std::cerr << mri_->getName(reg);
else
std::cerr << "%reg" << reg;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
MachineBasicBlock::iterator mi,
LiveInterval& interval)
{
DEBUG(std::cerr << "\t\tregister: "; printRegName(interval.reg));
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
// Virtual registers may be defined multiple times (due to phi
// elimination and 2-addr elimination). Much of what we do only has to be
// done once for the vreg. We use an empty interval to detect the first
// time we see a vreg.
if (interval.empty()) {
// Get the Idx of the defining instructions.
unsigned defIndex = getDefIndex(getInstructionIndex(mi));
unsigned ValNum = interval.getNextValue();
assert(ValNum == 0 && "First value in interval is not 0?");
ValNum = 0; // Clue in the optimizer.
// Loop over all of the blocks that the vreg is defined in. There are
// two cases we have to handle here. The most common case is a vreg
// whose lifetime is contained within a basic block. In this case there
// will be a single kill, in MBB, which comes after the definition.
if (vi.Kills.size() == 1 && vi.Kills[0]->getParent() == mbb) {
// FIXME: what about dead vars?
unsigned killIdx;
if (vi.Kills[0] != mi)
killIdx = getUseIndex(getInstructionIndex(vi.Kills[0]))+1;
else
killIdx = defIndex+1;
// If the kill happens after the definition, we have an intra-block
// live range.
if (killIdx > defIndex) {
assert(vi.AliveBlocks.empty() &&
"Shouldn't be alive across any blocks!");
LiveRange LR(defIndex, killIdx, ValNum);
interval.addRange(LR);
DEBUG(std::cerr << " +" << LR << "\n");
return;
}
}
// The other case we handle is when a virtual register lives to the end
// of the defining block, potentially live across some blocks, then is
// live into some number of blocks, but gets killed. Start by adding a
// range that goes from this definition to the end of the defining block.
LiveRange NewLR(defIndex, getInstructionIndex(&mbb->back()) +
InstrSlots::NUM, ValNum);
DEBUG(std::cerr << " +" << NewLR);
interval.addRange(NewLR);
// Iterate over all of the blocks that the variable is completely
// live in, adding [insrtIndex(begin), instrIndex(end)+4) to the
// live interval.
for (unsigned i = 0, e = vi.AliveBlocks.size(); i != e; ++i) {
if (vi.AliveBlocks[i]) {
MachineBasicBlock* mbb = mf_->getBlockNumbered(i);
if (!mbb->empty()) {
LiveRange LR(getInstructionIndex(&mbb->front()),
getInstructionIndex(&mbb->back())+InstrSlots::NUM,
ValNum);
interval.addRange(LR);
DEBUG(std::cerr << " +" << LR);
}
}
}
// Finally, this virtual register is live from the start of any killing
// block to the 'use' slot of the killing instruction.
for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
MachineInstr *Kill = vi.Kills[i];
LiveRange LR(getInstructionIndex(Kill->getParent()->begin()),
getUseIndex(getInstructionIndex(Kill))+1, ValNum);
interval.addRange(LR);
DEBUG(std::cerr << " +" << LR);
}
} else {
// If this is the second time we see a virtual register definition, it
// must be due to phi elimination or two addr elimination. If this is
// the result of two address elimination, then the vreg is the first
// operand, and is a def-and-use.
if (mi->getOperand(0).isRegister() &&
mi->getOperand(0).getReg() == interval.reg &&
mi->getOperand(0).isDef() && mi->getOperand(0).isUse()) {
// If this is a two-address definition, then we have already processed
// the live range. The only problem is that we didn't realize there
// are actually two values in the live interval. Because of this we
// need to take the LiveRegion that defines this register and split it
// into two values.
unsigned DefIndex = getDefIndex(getInstructionIndex(vi.DefInst));
unsigned RedefIndex = getDefIndex(getInstructionIndex(mi));
// Delete the initial value, which should be short and continuous,
// becuase the 2-addr copy must be in the same MBB as the redef.
interval.removeRange(DefIndex, RedefIndex);
LiveRange LR(DefIndex, RedefIndex, interval.getNextValue());
DEBUG(std::cerr << " replace range with " << LR);
interval.addRange(LR);
// If this redefinition is dead, we need to add a dummy unit live
// range covering the def slot.
for (LiveVariables::killed_iterator KI = lv_->dead_begin(mi),
E = lv_->dead_end(mi); KI != E; ++KI)
if (KI->second == interval.reg) {
interval.addRange(LiveRange(RedefIndex, RedefIndex+1, 0));
break;
}
DEBUG(std::cerr << "RESULT: " << interval);
} else {
// Otherwise, this must be because of phi elimination. In this case,
// the defined value will be live until the end of the basic block it
// is defined in.
unsigned defIndex = getDefIndex(getInstructionIndex(mi));
LiveRange LR(defIndex,
getInstructionIndex(&mbb->back()) + InstrSlots::NUM,
interval.getNextValue());
interval.addRange(LR);
DEBUG(std::cerr << " +" << LR);
}
}
DEBUG(std::cerr << '\n');
}
void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator mi,
LiveInterval& interval)
{
// A physical register cannot be live across basic block, so its
// lifetime must end somewhere in its defining basic block.
DEBUG(std::cerr << "\t\tregister: "; printRegName(interval.reg));
typedef LiveVariables::killed_iterator KillIter;
unsigned baseIndex = getInstructionIndex(mi);
unsigned start = getDefIndex(baseIndex);
unsigned end = start;
// If it is not used after definition, it is considered dead at
// the instruction defining it. Hence its interval is:
// [defSlot(def), defSlot(def)+1)
for (KillIter ki = lv_->dead_begin(mi), ke = lv_->dead_end(mi);
ki != ke; ++ki) {
if (interval.reg == ki->second) {
DEBUG(std::cerr << " dead");
end = getDefIndex(start) + 1;
goto exit;
}
}
// If it is not dead on definition, it must be killed by a
// subsequent instruction. Hence its interval is:
// [defSlot(def), useSlot(kill)+1)
while (true) {
++mi;
assert(mi != MBB->end() && "physreg was not killed in defining block!");
baseIndex += InstrSlots::NUM;
for (KillIter ki = lv_->killed_begin(mi), ke = lv_->killed_end(mi);
ki != ke; ++ki) {
if (interval.reg == ki->second) {
DEBUG(std::cerr << " killed");
end = getUseIndex(baseIndex) + 1;
goto exit;
}
}
}
exit:
assert(start < end && "did not find end of interval?");
LiveRange LR(start, end, interval.getNextValue());
interval.addRange(LR);
DEBUG(std::cerr << " +" << LR << '\n');
}
void LiveIntervals::handleRegisterDef(MachineBasicBlock *MBB,
MachineBasicBlock::iterator MI,
unsigned reg) {
if (MRegisterInfo::isVirtualRegister(reg))
handleVirtualRegisterDef(MBB, MI, getOrCreateInterval(reg));
else if (lv_->getAllocatablePhysicalRegisters()[reg]) {
handlePhysicalRegisterDef(MBB, MI, getOrCreateInterval(reg));
for (const unsigned* AS = mri_->getAliasSet(reg); *AS; ++AS)
handlePhysicalRegisterDef(MBB, MI, getOrCreateInterval(*AS));
}
}
/// computeIntervals - computes the live intervals for virtual
/// registers. for some ordering of the machine instructions [1,N] a
/// live interval is an interval [i, j) where 1 <= i <= j < N for
/// which a variable is live
void LiveIntervals::computeIntervals()
{
DEBUG(std::cerr << "********** COMPUTING LIVE INTERVALS **********\n");
DEBUG(std::cerr << "********** Function: "
<< ((Value*)mf_->getFunction())->getName() << '\n');
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
I != E; ++I) {
MachineBasicBlock* mbb = I;
DEBUG(std::cerr << ((Value*)mbb->getBasicBlock())->getName() << ":\n");
for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
mi != miEnd; ++mi) {
const TargetInstrDescriptor& tid =
tm_->getInstrInfo()->get(mi->getOpcode());
DEBUG(std::cerr << getInstructionIndex(mi) << "\t";
mi->print(std::cerr, tm_));
// handle implicit defs
for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
handleRegisterDef(mbb, mi, *id);
// handle explicit defs
for (int i = mi->getNumOperands() - 1; i >= 0; --i) {
MachineOperand& mop = mi->getOperand(i);
// handle register defs - build intervals
if (mop.isRegister() && mop.getReg() && mop.isDef())
handleRegisterDef(mbb, mi, mop.getReg());
}
}
}
}
void LiveIntervals::joinIntervalsInMachineBB(MachineBasicBlock *MBB) {
DEBUG(std::cerr << ((Value*)MBB->getBasicBlock())->getName() << ":\n");
const TargetInstrInfo &TII = *tm_->getInstrInfo();
for (MachineBasicBlock::iterator mi = MBB->begin(), mie = MBB->end();
mi != mie; ++mi) {
DEBUG(std::cerr << getInstructionIndex(mi) << '\t' << *mi);
// we only join virtual registers with allocatable
// physical registers since we do not have liveness information
// on not allocatable physical registers
unsigned regA, regB;
if (TII.isMoveInstr(*mi, regA, regB) &&
(MRegisterInfo::isVirtualRegister(regA) ||
lv_->getAllocatablePhysicalRegisters()[regA]) &&
(MRegisterInfo::isVirtualRegister(regB) ||
lv_->getAllocatablePhysicalRegisters()[regB])) {
// Get representative registers.
regA = rep(regA);
regB = rep(regB);
// If they are already joined we continue.
if (regA == regB)
continue;
// If they are both physical registers, we cannot join them.
if (MRegisterInfo::isPhysicalRegister(regA) &&
MRegisterInfo::isPhysicalRegister(regB))
continue;
// If they are not of the same register class, we cannot join them.
if (differingRegisterClasses(regA, regB))
continue;
LiveInterval &IntA = getInterval(regA);
LiveInterval &IntB = getInterval(regB);
assert(IntA.reg == regA && IntB.reg == regB &&
"Register mapping is horribly broken!");
bool TriviallyJoinable =
IntA.containsOneValue() && IntB.containsOneValue();
unsigned MIDefIdx = getDefIndex(getInstructionIndex(mi));
if ((TriviallyJoinable || !IntB.joinable(IntA, MIDefIdx)) &&
!overlapsAliases(&IntA, &IntB)) {
IntB.join(IntA, MIDefIdx);
// FIXME: Turn 'intervals_' into an ilist so we don't need to do these
// map lookups!
intervals_.erase(r2iMap_[regA]);
r2iMap_[regA] = r2iMap_[regB];
if (!MRegisterInfo::isPhysicalRegister(regA)) {
r2rMap_[regA] = regB;
} else {
// Otherwise merge the data structures the other way so we don't lose
// the physreg information.
r2rMap_[regB] = regA;
IntB.reg = regA;
}
DEBUG(std::cerr << "Joined. Result = " << IntB << "\n");
++numJoins;
} else {
DEBUG(std::cerr << "Interference!\n");
}
}
}
}
namespace {
// DepthMBBCompare - Comparison predicate that sort first based on the loop
// depth of the basic block (the unsigned), and then on the MBB number.
struct DepthMBBCompare {
typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
if (LHS.first > RHS.first) return true; // Deeper loops first
return LHS.first == RHS.first &&
LHS.second->getNumber() < RHS.second->getNumber();
}
};
}
void LiveIntervals::joinIntervals() {
DEBUG(std::cerr << "********** JOINING INTERVALS ***********\n");
const LoopInfo &LI = getAnalysis<LoopInfo>();
if (LI.begin() == LI.end()) {
// If there are no loops in the function, join intervals in function order.
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
I != E; ++I)
joinIntervalsInMachineBB(I);
} else {
// Otherwise, join intervals in inner loops before other intervals.
// Unfortunately we can't just iterate over loop hierarchy here because
// there may be more MBB's than BB's. Collect MBB's for sorting.
std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();
I != E; ++I)
MBBs.push_back(std::make_pair(LI.getLoopDepth(I->getBasicBlock()), I));
// Sort by loop depth.
std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
// Finally, join intervals in loop nest order.
for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
joinIntervalsInMachineBB(MBBs[i].second);
}
}
/// Return true if the two specified registers belong to different register
/// classes. The registers may be either phys or virt regs.
bool LiveIntervals::differingRegisterClasses(unsigned RegA,
unsigned RegB) const {
const TargetRegisterClass *RegClass;
// Get the register classes for the first reg.
if (MRegisterInfo::isVirtualRegister(RegA))
RegClass = mf_->getSSARegMap()->getRegClass(RegA);
else
RegClass = mri_->getRegClass(RegA);
// Compare against the regclass for the second reg.
if (MRegisterInfo::isVirtualRegister(RegB))
return RegClass != mf_->getSSARegMap()->getRegClass(RegB);
else
return RegClass != mri_->getRegClass(RegB);
}
bool LiveIntervals::overlapsAliases(const LiveInterval *LHS,
const LiveInterval *RHS) const {
if (!MRegisterInfo::isPhysicalRegister(LHS->reg)) {
if (!MRegisterInfo::isPhysicalRegister(RHS->reg))
return false; // vreg-vreg merge has no aliases!
std::swap(LHS, RHS);
}
assert(MRegisterInfo::isPhysicalRegister(LHS->reg) &&
MRegisterInfo::isVirtualRegister(RHS->reg) &&
"first interval must describe a physical register");
for (const unsigned *AS = mri_->getAliasSet(LHS->reg); *AS; ++AS) {
Reg2IntervalMap::const_iterator r2i = r2iMap_.find(*AS);
assert(r2i != r2iMap_.end() && "alias does not have interval?");
if (RHS->overlaps(*r2i->second))
return true;
}
return false;
}
LiveInterval& LiveIntervals::getOrCreateInterval(unsigned reg)
{
Reg2IntervalMap::iterator r2iit = r2iMap_.lower_bound(reg);
if (r2iit == r2iMap_.end() || r2iit->first != reg) {
float Weight = MRegisterInfo::isPhysicalRegister(reg) ? HUGE_VAL :0.0F;
intervals_.push_back(LiveInterval(reg, Weight));
r2iit = r2iMap_.insert(r2iit, std::make_pair(reg, --intervals_.end()));
}
return *r2iit->second;
}
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