1 //===-- LiveIntervals.cpp - Live Interval Analysis ------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the LiveInterval analysis pass which is used
11 // by the Linear Scan Register allocator. This pass linearizes the
12 // basic blocks of the function in DFS order and uses the
13 // LiveVariables pass to conservatively compute live intervals for
14 // each virtual and physical register.
16 //===----------------------------------------------------------------------===//
18 #define DEBUG_TYPE "liveintervals"
19 #include "llvm/CodeGen/LiveIntervals.h"
20 #include "llvm/Function.h"
21 #include "llvm/Analysis/LoopInfo.h"
22 #include "llvm/CodeGen/LiveVariables.h"
23 #include "llvm/CodeGen/MachineFrameInfo.h"
24 #include "llvm/CodeGen/MachineFunctionPass.h"
25 #include "llvm/CodeGen/MachineInstr.h"
26 #include "llvm/CodeGen/Passes.h"
27 #include "llvm/CodeGen/SSARegMap.h"
28 #include "llvm/Target/MRegisterInfo.h"
29 #include "llvm/Target/TargetInstrInfo.h"
30 #include "llvm/Target/TargetMachine.h"
31 #include "llvm/Target/TargetRegInfo.h"
32 #include "llvm/Support/CFG.h"
33 #include "Support/Debug.h"
34 #include "Support/DepthFirstIterator.h"
35 #include "Support/Statistic.h"
43 RegisterAnalysis<LiveIntervals> X("liveintervals",
44 "Live Interval Analysis");
46 Statistic<> numIntervals("liveintervals", "Number of intervals");
49 void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const
51 AU.addPreserved<LiveVariables>();
52 AU.addRequired<LiveVariables>();
53 AU.addPreservedID(PHIEliminationID);
54 AU.addRequiredID(PHIEliminationID);
55 AU.addRequiredID(TwoAddressInstructionPassID);
56 AU.addRequired<LoopInfo>();
57 MachineFunctionPass::getAnalysisUsage(AU);
60 /// runOnMachineFunction - Register allocate the whole function
62 bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
63 DEBUG(std::cerr << "Machine Function\n");
65 tm_ = &fn.getTarget();
66 mri_ = tm_->getRegisterInfo();
67 lv_ = &getAnalysis<LiveVariables>();
74 // number MachineInstrs
76 for (MachineFunction::iterator mbb = mf_->begin(), mbbEnd = mf_->end();
77 mbb != mbbEnd; ++mbb) {
78 const std::pair<MachineBasicBlock*, unsigned>& entry =
79 lv_->getMachineBasicBlockInfo(&*mbb);
80 bool inserted = mbbi2mbbMap_.insert(std::make_pair(entry.second,
82 assert(inserted && "multiple index -> MachineBasicBlock");
84 for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
86 inserted = mi2iMap_.insert(std::make_pair(*mi, miIndex)).second;
87 assert(inserted && "multiple MachineInstr -> index mappings");
94 // compute spill weights
95 const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
96 const TargetInstrInfo& tii = tm_->getInstrInfo();
98 for (MbbIndex2MbbMap::iterator
99 it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
101 MachineBasicBlock* mbb = it->second;
103 unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
105 for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
107 MachineInstr* instr = *mi;
108 for (int i = instr->getNumOperands() - 1; i >= 0; --i) {
109 MachineOperand& mop = instr->getOperand(i);
111 if (!mop.isVirtualRegister())
114 unsigned reg = mop.getAllocatedRegNum();
115 Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
116 assert(r2iit != r2iMap_.end());
117 intervals_[r2iit->second].weight += pow(10.0F, loopDepth);
122 numIntervals += intervals_.size();
127 void LiveIntervals::printRegName(unsigned reg) const
129 if (reg < MRegisterInfo::FirstVirtualRegister)
130 std::cerr << mri_->getName(reg);
132 std::cerr << '%' << reg;
135 void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
136 MachineBasicBlock::iterator mi,
139 DEBUG(std::cerr << "\t\tregister: ";printRegName(reg); std::cerr << '\n');
141 unsigned instrIndex = getInstructionIndex(*mi);
143 LiveVariables::VarInfo& vi = lv_->getVarInfo(reg);
145 Interval* interval = 0;
146 Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
147 if (r2iit == r2iMap_.end()) {
149 intervals_.push_back(Interval(reg));
150 // update interval index for this register
151 r2iMap_[reg] = intervals_.size() - 1;
152 interval = &intervals_.back();
155 interval = &intervals_[r2iit->second];
158 for (MbbIndex2MbbMap::iterator
159 it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
161 unsigned liveBlockIndex = it->first;
162 MachineBasicBlock* liveBlock = it->second;
163 if (liveBlockIndex < vi.AliveBlocks.size() &&
164 vi.AliveBlocks[liveBlockIndex] &&
165 !liveBlock->empty()) {
166 unsigned start = getInstructionIndex(liveBlock->front());
167 unsigned end = getInstructionIndex(liveBlock->back()) + 1;
168 interval->addRange(start, end);
172 bool killedInDefiningBasicBlock = false;
173 for (int i = 0, e = vi.Kills.size(); i != e; ++i) {
174 MachineBasicBlock* killerBlock = vi.Kills[i].first;
175 MachineInstr* killerInstr = vi.Kills[i].second;
176 unsigned start = (mbb == killerBlock ?
178 getInstructionIndex(killerBlock->front()));
179 unsigned end = getInstructionIndex(killerInstr) + 1;
181 killedInDefiningBasicBlock |= mbb == killerBlock;
182 interval->addRange(start, end);
186 if (!killedInDefiningBasicBlock) {
187 unsigned end = getInstructionIndex(mbb->back()) + 1;
188 interval->addRange(instrIndex, end);
192 void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock* mbb,
193 MachineBasicBlock::iterator mi,
196 DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
198 unsigned start = getInstructionIndex(*mi);
199 unsigned end = start;
201 // register can be dead by the instruction defining it but it can
202 // only be killed by subsequent instructions
204 for (LiveVariables::killed_iterator
205 ki = lv_->dead_begin(*mi),
206 ke = lv_->dead_end(*mi);
208 if (reg == ki->second) {
209 end = getInstructionIndex(ki->first) + 1;
210 DEBUG(std::cerr << " dead\n");
216 for (MachineBasicBlock::iterator e = mbb->end(); mi != e; ++mi) {
217 for (LiveVariables::killed_iterator
218 ki = lv_->dead_begin(*mi),
219 ke = lv_->dead_end(*mi);
221 if (reg == ki->second) {
222 end = getInstructionIndex(ki->first) + 1;
223 DEBUG(std::cerr << " dead\n");
228 for (LiveVariables::killed_iterator
229 ki = lv_->killed_begin(*mi),
230 ke = lv_->killed_end(*mi);
232 if (reg == ki->second) {
233 end = getInstructionIndex(ki->first) + 1;
234 DEBUG(std::cerr << " killed\n");
240 assert(start < end && "did not find end of interval?");
242 Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
243 if (r2iit != r2iMap_.end()) {
244 unsigned ii = r2iit->second;
245 Interval& interval = intervals_[ii];
246 interval.addRange(start, end);
249 intervals_.push_back(Interval(reg));
250 Interval& interval = intervals_.back();
251 // update interval index for this register
252 r2iMap_[reg] = intervals_.size() - 1;
253 interval.addRange(start, end);
257 void LiveIntervals::handleRegisterDef(MachineBasicBlock* mbb,
258 MachineBasicBlock::iterator mi,
261 if (reg < MRegisterInfo::FirstVirtualRegister) {
262 if (lv_->getAllocatablePhysicalRegisters()[reg]) {
263 handlePhysicalRegisterDef(mbb, mi, reg);
264 for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
265 handlePhysicalRegisterDef(mbb, mi, *as);
269 handleVirtualRegisterDef(mbb, mi, reg);
273 unsigned LiveIntervals::getInstructionIndex(MachineInstr* instr) const
275 assert(mi2iMap_.find(instr) != mi2iMap_.end() &&
276 "instruction not assigned a number");
277 return mi2iMap_.find(instr)->second;
280 /// computeIntervals - computes the live intervals for virtual
281 /// registers. for some ordering of the machine instructions [1,N] a
282 /// live interval is an interval [i, j] where 1 <= i <= j <= N for
283 /// which a variable is live
284 void LiveIntervals::computeIntervals()
286 DEBUG(std::cerr << "computing live intervals:\n");
288 for (MbbIndex2MbbMap::iterator
289 it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
291 MachineBasicBlock* mbb = it->second;
292 DEBUG(std::cerr << "machine basic block: "
293 << mbb->getBasicBlock()->getName() << "\n");
295 for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
297 MachineInstr* instr = *mi;
298 const TargetInstrDescriptor& tid =
299 tm_->getInstrInfo().get(instr->getOpcode());
300 DEBUG(std::cerr << "\t[" << getInstructionIndex(instr) << "] ";
301 instr->print(std::cerr, *tm_););
303 // handle implicit defs
304 for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
305 handleRegisterDef(mbb, mi, *id);
307 // handle explicit defs
308 for (int i = instr->getNumOperands() - 1; i >= 0; --i) {
309 MachineOperand& mop = instr->getOperand(i);
311 if (!mop.isRegister())
314 // handle defs - build intervals
316 handleRegisterDef(mbb, mi, mop.getAllocatedRegNum());
321 std::sort(intervals_.begin(), intervals_.end(), StartPointComp());
322 DEBUG(std::copy(intervals_.begin(), intervals_.end(),
323 std::ostream_iterator<Interval>(std::cerr, "\n")));
326 LiveIntervals::Interval::Interval(unsigned r)
328 weight((r < MRegisterInfo::FirstVirtualRegister ?
329 std::numeric_limits<float>::max() : 0.0F))
334 void LiveIntervals::Interval::addRange(unsigned start, unsigned end)
336 DEBUG(std::cerr << "\t\t\tadding range: [" << start <<','<< end << ") -> ");
337 //assert(start < end && "invalid range?");
338 Range range = std::make_pair(start, end);
339 Ranges::iterator it =
340 ranges.insert(std::upper_bound(ranges.begin(), ranges.end(), range),
343 mergeRangesForward(it);
344 mergeRangesBackward(it);
345 DEBUG(std::cerr << *this << '\n');
348 void LiveIntervals::Interval::mergeRangesForward(Ranges::iterator it)
350 for (Ranges::iterator next = it + 1;
351 next != ranges.end() && it->second >= next->first; ) {
352 it->second = std::max(it->second, next->second);
353 next = ranges.erase(next);
357 void LiveIntervals::Interval::mergeRangesBackward(Ranges::iterator it)
359 for (Ranges::iterator prev = it - 1;
360 it != ranges.begin() && it->first <= prev->second; ) {
361 it->first = std::min(it->first, prev->first);
362 it->second = std::max(it->second, prev->second);
363 it = ranges.erase(prev);
368 bool LiveIntervals::Interval::liveAt(unsigned index) const
370 Ranges::const_iterator r = ranges.begin();
371 while (r != ranges.end() && index < (r->second - 1)) {
372 if (index >= r->first)
379 bool LiveIntervals::Interval::overlaps(const Interval& other) const
381 Ranges::const_iterator i = ranges.begin();
382 Ranges::const_iterator j = other.ranges.begin();
384 while (i != ranges.end() && j != other.ranges.end()) {
385 if (i->first < j->first) {
386 if ((i->second - 1) > j->first) {
393 else if (j->first < i->first) {
394 if ((j->second - 1) > i->first) {
409 std::ostream& llvm::operator<<(std::ostream& os,
410 const LiveIntervals::Interval& li)
412 os << "%reg" << li.reg << ',' << li.weight << " = ";
413 for (LiveIntervals::Interval::Ranges::const_iterator
414 i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
415 os << "[" << i->first << "," << i->second << ")";