//
// 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 is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "PhysRegTracker.h"
+#include "VirtRegMap.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
-#include "llvm/CodeGen/SSARegMap.h"
-#include "llvm/Target/MRegisterInfo.h"
+#include "llvm/CodeGen/RegAllocRegistry.h"
+#include "llvm/CodeGen/RegisterCoalescer.h"
+#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetMachine.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
-#include "LiveIntervalAnalysis.h"
-#include "PhysRegTracker.h"
-#include "VirtRegMap.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Compiler.h"
#include <algorithm>
-#include <cmath>
#include <set>
#include <queue>
-
+#include <memory>
+#include <cmath>
using namespace llvm;
-namespace {
+STATISTIC(NumIters , "Number of iterations performed");
+STATISTIC(NumBacktracks, "Number of times we had to backtrack");
+STATISTIC(NumCoalesce, "Number of copies coalesced");
- Statistic<double> efficiency
- ("regalloc", "Ratio of intervals processed over total intervals");
+static RegisterRegAlloc
+linearscanRegAlloc("linearscan", " linear scan register allocator",
+ createLinearScanRegisterAllocator);
- static unsigned numIterations = 0;
- static unsigned numIntervals = 0;
+namespace {
+ struct VISIBILITY_HIDDEN RALinScan : public MachineFunctionPass {
+ static char ID;
+ RALinScan() : MachineFunctionPass((intptr_t)&ID) {}
- struct RA : public MachineFunctionPass {
typedef std::pair<LiveInterval*, LiveInterval::iterator> IntervalPtr;
typedef std::vector<IntervalPtr> IntervalPtrs;
private:
+ /// RelatedRegClasses - This structure is built the first time a function is
+ /// compiled, and keeps track of which register classes have registers that
+ /// belong to multiple classes or have aliases that are in other classes.
+ EquivalenceClasses<const TargetRegisterClass*> RelatedRegClasses;
+ std::map<unsigned, const TargetRegisterClass*> OneClassForEachPhysReg;
+
MachineFunction* mf_;
const TargetMachine* tm_;
- const MRegisterInfo* mri_;
+ const TargetRegisterInfo* tri_;
+ const TargetInstrInfo* tii_;
+ MachineRegisterInfo *reginfo_;
+ BitVector allocatableRegs_;
LiveIntervals* li_;
+ const MachineLoopInfo *loopInfo;
/// handled_ - Intervals are added to the handled_ set in the order of their
/// start value. This is uses for backtracking.
std::auto_ptr<VirtRegMap> vrm_;
std::auto_ptr<Spiller> spiller_;
- typedef std::vector<float> SpillWeights;
- SpillWeights spillWeights_;
-
public:
virtual const char* getPassName() const {
return "Linear Scan Register Allocator";
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveIntervals>();
+ // Make sure PassManager knows which analyses to make available
+ // to coalescing and which analyses coalescing invalidates.
+ AU.addRequiredTransitive<RegisterCoalescer>();
+ AU.addRequired<MachineLoopInfo>();
+ AU.addPreserved<MachineLoopInfo>();
+ AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
/// ones to the active list.
void processInactiveIntervals(unsigned CurPoint);
- /// 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(LiveInterval* cur);
+ /// attemptTrivialCoalescing - If a simple interval is defined by a copy,
+ /// try allocate the definition the same register as the source register
+ /// if the register is not defined during live time of the interval. This
+ /// eliminate a copy. This is used to coalesce copies which were not
+ /// coalesced away before allocation either due to dest and src being in
+ /// different register classes or because the coalescer was overly
+ /// conservative.
+ unsigned attemptTrivialCoalescing(LiveInterval &cur, unsigned Reg);
+
///
/// register handling helpers
///
/// stack slot. returns the stack slot
int assignVirt2StackSlot(unsigned virtReg);
+ void ComputeRelatedRegClasses();
+
template <typename ItTy>
void printIntervals(const char* const str, ItTy i, ItTy e) const {
- if (str) std::cerr << str << " intervals:\n";
+ if (str) DOUT << str << " intervals:\n";
for (; i != e; ++i) {
- std::cerr << "\t" << *i->first << " -> ";
+ DOUT << "\t" << *i->first << " -> ";
unsigned reg = i->first->reg;
- if (MRegisterInfo::isVirtualRegister(reg)) {
+ if (TargetRegisterInfo::isVirtualRegister(reg)) {
reg = vrm_->getPhys(reg);
}
- std::cerr << mri_->getName(reg) << '\n';
+ DOUT << tri_->getName(reg) << '\n';
}
}
};
+ char RALinScan::ID = 0;
+}
+
+void RALinScan::ComputeRelatedRegClasses() {
+ const TargetRegisterInfo &TRI = *tri_;
+
+ // First pass, add all reg classes to the union, and determine at least one
+ // reg class that each register is in.
+ bool HasAliases = false;
+ for (TargetRegisterInfo::regclass_iterator RCI = TRI.regclass_begin(),
+ E = TRI.regclass_end(); RCI != E; ++RCI) {
+ RelatedRegClasses.insert(*RCI);
+ for (TargetRegisterClass::iterator I = (*RCI)->begin(), E = (*RCI)->end();
+ I != E; ++I) {
+ HasAliases = HasAliases || *TRI.getAliasSet(*I) != 0;
+
+ const TargetRegisterClass *&PRC = OneClassForEachPhysReg[*I];
+ if (PRC) {
+ // Already processed this register. Just make sure we know that
+ // multiple register classes share a register.
+ RelatedRegClasses.unionSets(PRC, *RCI);
+ } else {
+ PRC = *RCI;
+ }
+ }
+ }
+
+ // Second pass, now that we know conservatively what register classes each reg
+ // belongs to, add info about aliases. We don't need to do this for targets
+ // without register aliases.
+ if (HasAliases)
+ for (std::map<unsigned, const TargetRegisterClass*>::iterator
+ I = OneClassForEachPhysReg.begin(), E = OneClassForEachPhysReg.end();
+ I != E; ++I)
+ for (const unsigned *AS = TRI.getAliasSet(I->first); *AS; ++AS)
+ RelatedRegClasses.unionSets(I->second, OneClassForEachPhysReg[*AS]);
}
-bool RA::runOnMachineFunction(MachineFunction &fn) {
+/// attemptTrivialCoalescing - If a simple interval is defined by a copy,
+/// try allocate the definition the same register as the source register
+/// if the register is not defined during live time of the interval. This
+/// eliminate a copy. This is used to coalesce copies which were not
+/// coalesced away before allocation either due to dest and src being in
+/// different register classes or because the coalescer was overly
+/// conservative.
+unsigned RALinScan::attemptTrivialCoalescing(LiveInterval &cur, unsigned Reg) {
+ if ((cur.preference && cur.preference == Reg) || !cur.containsOneValue())
+ return Reg;
+
+ VNInfo *vni = cur.getValNumInfo(0);
+ if (!vni->def || vni->def == ~1U || vni->def == ~0U)
+ return Reg;
+ MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def);
+ unsigned SrcReg, DstReg;
+ if (!CopyMI || !tii_->isMoveInstr(*CopyMI, SrcReg, DstReg))
+ return Reg;
+ if (TargetRegisterInfo::isVirtualRegister(SrcReg))
+ if (!vrm_->isAssignedReg(SrcReg))
+ return Reg;
+ else
+ SrcReg = vrm_->getPhys(SrcReg);
+ if (Reg == SrcReg)
+ return Reg;
+
+ const TargetRegisterClass *RC = reginfo_->getRegClass(cur.reg);
+ if (!RC->contains(SrcReg))
+ return Reg;
+
+ // Try to coalesce.
+ if (!li_->conflictsWithPhysRegDef(cur, *vrm_, SrcReg)) {
+ DOUT << "Coalescing: " << cur << " -> " << tri_->getName(SrcReg) << '\n';
+ vrm_->clearVirt(cur.reg);
+ vrm_->assignVirt2Phys(cur.reg, SrcReg);
+ ++NumCoalesce;
+ return SrcReg;
+ }
+
+ return Reg;
+}
+
+bool RALinScan::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
tm_ = &fn.getTarget();
- mri_ = tm_->getRegisterInfo();
+ tri_ = tm_->getRegisterInfo();
+ tii_ = tm_->getInstrInfo();
+ reginfo_ = &mf_->getRegInfo();
+ allocatableRegs_ = tri_->getAllocatableSet(fn);
li_ = &getAnalysis<LiveIntervals>();
- if (!prt_.get()) prt_.reset(new PhysRegTracker(*mri_));
+ loopInfo = &getAnalysis<MachineLoopInfo>();
+
+ // We don't run the coalescer here because we have no reason to
+ // interact with it. If the coalescer requires interaction, it
+ // won't do anything. If it doesn't require interaction, we assume
+ // it was run as a separate pass.
+
+ // If this is the first function compiled, compute the related reg classes.
+ if (RelatedRegClasses.empty())
+ ComputeRelatedRegClasses();
+
+ if (!prt_.get()) prt_.reset(new PhysRegTracker(*tri_));
vrm_.reset(new VirtRegMap(*mf_));
if (!spiller_.get()) spiller_.reset(createSpiller());
linearScan();
+ // Rewrite spill code and update the PhysRegsUsed set.
spiller_->runOnMachineFunction(*mf_, *vrm_);
-
vrm_.reset(); // Free the VirtRegMap
-
while (!unhandled_.empty()) unhandled_.pop();
fixed_.clear();
active_.clear();
return true;
}
-void RA::linearScan()
+/// initIntervalSets - initialize the interval sets.
+///
+void RALinScan::initIntervalSets()
+{
+ assert(unhandled_.empty() && fixed_.empty() &&
+ active_.empty() && inactive_.empty() &&
+ "interval sets should be empty on initialization");
+
+ for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i) {
+ if (TargetRegisterInfo::isPhysicalRegister(i->second.reg)) {
+ reginfo_->setPhysRegUsed(i->second.reg);
+ fixed_.push_back(std::make_pair(&i->second, i->second.begin()));
+ } else
+ unhandled_.push(&i->second);
+ }
+}
+
+void RALinScan::linearScan()
{
// linear scan algorithm
- DEBUG(std::cerr << "********** LINEAR SCAN **********\n");
- DEBUG(std::cerr << "********** Function: "
- << mf_->getFunction()->getName() << '\n');
+ DOUT << "********** LINEAR SCAN **********\n";
+ DOUT << "********** Function: " << mf_->getFunction()->getName() << '\n';
- // DEBUG(printIntervals("unhandled", unhandled_.begin(), unhandled_.end()));
DEBUG(printIntervals("fixed", fixed_.begin(), fixed_.end()));
- DEBUG(printIntervals("active", active_.begin(), active_.end()));
- DEBUG(printIntervals("inactive", inactive_.begin(), inactive_.end()));
while (!unhandled_.empty()) {
// pick the interval with the earliest start point
LiveInterval* cur = unhandled_.top();
unhandled_.pop();
- ++numIterations;
- DEBUG(std::cerr << "\n*** CURRENT ***: " << *cur << '\n');
+ ++NumIters;
+ DOUT << "\n*** CURRENT ***: " << *cur << '\n';
processActiveIntervals(cur->beginNumber());
processInactiveIntervals(cur->beginNumber());
- // if this register is fixed we are done
- if (MRegisterInfo::isPhysicalRegister(cur->reg)) {
- prt_->addRegUse(cur->reg);
- active_.push_back(std::make_pair(cur, cur->begin()));
- handled_.push_back(cur);
- } else {
- // 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).
- assignRegOrStackSlotAtInterval(cur);
- }
+ assert(TargetRegisterInfo::isVirtualRegister(cur->reg) &&
+ "Can only allocate virtual registers!");
+
+ // Allocating a virtual register. try to find a free
+ // physical register or spill an interval (possibly this one) in order to
+ // assign it one.
+ assignRegOrStackSlotAtInterval(cur);
DEBUG(printIntervals("active", active_.begin(), active_.end()));
DEBUG(printIntervals("inactive", inactive_.begin(), inactive_.end()));
}
- numIntervals += li_->getNumIntervals();
- efficiency = double(numIterations) / double(numIntervals);
// expire any remaining active intervals
- for (IntervalPtrs::reverse_iterator
- i = active_.rbegin(); i != active_.rend(); ) {
- unsigned reg = i->first->reg;
- DEBUG(std::cerr << "\tinterval " << *i->first << " expired\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
+ while (!active_.empty()) {
+ IntervalPtr &IP = active_.back();
+ unsigned reg = IP.first->reg;
+ DOUT << "\tinterval " << *IP.first << " expired\n";
+ assert(TargetRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->delRegUse(reg);
- i = IntervalPtrs::reverse_iterator(active_.erase(i.base()-1));
+ active_.pop_back();
}
// expire any remaining inactive intervals
- for (IntervalPtrs::reverse_iterator
- i = inactive_.rbegin(); i != inactive_.rend(); ) {
- DEBUG(std::cerr << "\tinterval " << *i->first << " expired\n");
- i = IntervalPtrs::reverse_iterator(inactive_.erase(i.base()-1));
- }
-
- DEBUG(std::cerr << *vrm_);
-}
-
-/// initIntervalSets - initialize the interval sets.
-///
-void RA::initIntervalSets()
-{
- assert(unhandled_.empty() && fixed_.empty() &&
- active_.empty() && inactive_.empty() &&
- "interval sets should be empty on initialization");
+ DEBUG(for (IntervalPtrs::reverse_iterator
+ i = inactive_.rbegin(); i != inactive_.rend(); ++i)
+ DOUT << "\tinterval " << *i->first << " expired\n");
+ inactive_.clear();
- for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i){
- unhandled_.push(&i->second);
- if (MRegisterInfo::isPhysicalRegister(i->second.reg))
- fixed_.push_back(std::make_pair(&i->second, i->second.begin()));
+ // Add live-ins to every BB except for entry. Also perform trivial coalescing.
+ MachineFunction::iterator EntryMBB = mf_->begin();
+ SmallVector<MachineBasicBlock*, 8> LiveInMBBs;
+ for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i) {
+ LiveInterval &cur = i->second;
+ unsigned Reg = 0;
+ bool isPhys = TargetRegisterInfo::isPhysicalRegister(cur.reg);
+ if (isPhys)
+ Reg = i->second.reg;
+ else if (vrm_->isAssignedReg(cur.reg))
+ Reg = attemptTrivialCoalescing(cur, vrm_->getPhys(cur.reg));
+ if (!Reg)
+ continue;
+ // Ignore splited live intervals.
+ if (!isPhys && vrm_->getPreSplitReg(cur.reg))
+ continue;
+ for (LiveInterval::Ranges::const_iterator I = cur.begin(), E = cur.end();
+ I != E; ++I) {
+ const LiveRange &LR = *I;
+ if (li_->findLiveInMBBs(LR, LiveInMBBs)) {
+ for (unsigned i = 0, e = LiveInMBBs.size(); i != e; ++i)
+ if (LiveInMBBs[i] != EntryMBB)
+ LiveInMBBs[i]->addLiveIn(Reg);
+ LiveInMBBs.clear();
+ }
+ }
}
+
+ DOUT << *vrm_;
}
/// processActiveIntervals - expire old intervals and move non-overlapping ones
/// to the inactive list.
-void RA::processActiveIntervals(unsigned CurPoint)
+void RALinScan::processActiveIntervals(unsigned CurPoint)
{
- DEBUG(std::cerr << "\tprocessing active intervals:\n");
+ DOUT << "\tprocessing active intervals:\n";
for (unsigned i = 0, e = active_.size(); i != e; ++i) {
LiveInterval *Interval = active_[i].first;
IntervalPos = Interval->advanceTo(IntervalPos, CurPoint);
if (IntervalPos == Interval->end()) { // Remove expired intervals.
- DEBUG(std::cerr << "\t\tinterval " << *Interval << " expired\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
+ DOUT << "\t\tinterval " << *Interval << " expired\n";
+ assert(TargetRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->delRegUse(reg);
// Pop off the end of the list.
active_[i] = active_.back();
active_.pop_back();
--i; --e;
-
+
} else if (IntervalPos->start > CurPoint) {
// Move inactive intervals to inactive list.
- DEBUG(std::cerr << "\t\tinterval " << *Interval << " inactive\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
+ DOUT << "\t\tinterval " << *Interval << " inactive\n";
+ assert(TargetRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->delRegUse(reg);
// add to inactive.
inactive_.push_back(std::make_pair(Interval, IntervalPos));
/// processInactiveIntervals - expire old intervals and move overlapping
/// ones to the active list.
-void RA::processInactiveIntervals(unsigned CurPoint)
+void RALinScan::processInactiveIntervals(unsigned CurPoint)
{
- DEBUG(std::cerr << "\tprocessing inactive intervals:\n");
+ DOUT << "\tprocessing inactive intervals:\n";
+
for (unsigned i = 0, e = inactive_.size(); i != e; ++i) {
LiveInterval *Interval = inactive_[i].first;
LiveInterval::iterator IntervalPos = inactive_[i].second;
unsigned reg = Interval->reg;
IntervalPos = Interval->advanceTo(IntervalPos, CurPoint);
-
+
if (IntervalPos == Interval->end()) { // remove expired intervals.
- DEBUG(std::cerr << "\t\tinterval " << *Interval << " expired\n");
+ DOUT << "\t\tinterval " << *Interval << " expired\n";
// Pop off the end of the list.
inactive_[i] = inactive_.back();
--i; --e;
} else if (IntervalPos->start <= CurPoint) {
// move re-activated intervals in active list
- DEBUG(std::cerr << "\t\tinterval " << *Interval << " active\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
+ DOUT << "\t\tinterval " << *Interval << " active\n";
+ assert(TargetRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->addRegUse(reg);
// add to active
active_.push_back(std::make_pair(Interval, IntervalPos));
/// updateSpillWeights - updates the spill weights of the specifed physical
/// register and its weight.
-void RA::updateSpillWeights(unsigned reg, SpillWeights::value_type weight)
-{
- spillWeights_[reg] += weight;
- for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
- spillWeights_[*as] += weight;
+static void updateSpillWeights(std::vector<float> &Weights,
+ unsigned reg, float weight,
+ const TargetRegisterInfo *TRI) {
+ Weights[reg] += weight;
+ for (const unsigned* as = TRI->getAliasSet(reg); *as; ++as)
+ Weights[*as] += weight;
}
-static RA::IntervalPtrs::iterator FindIntervalInVector(RA::IntervalPtrs &IP,
- LiveInterval *LI) {
- for (RA::IntervalPtrs::iterator I = IP.begin(), E = IP.end(); I != E; ++I)
+static
+RALinScan::IntervalPtrs::iterator
+FindIntervalInVector(RALinScan::IntervalPtrs &IP, LiveInterval *LI) {
+ for (RALinScan::IntervalPtrs::iterator I = IP.begin(), E = IP.end();
+ I != E; ++I)
if (I->first == LI) return I;
return IP.end();
}
-
+static void RevertVectorIteratorsTo(RALinScan::IntervalPtrs &V, unsigned Point){
+ for (unsigned i = 0, e = V.size(); i != e; ++i) {
+ RALinScan::IntervalPtr &IP = V[i];
+ LiveInterval::iterator I = std::upper_bound(IP.first->begin(),
+ IP.second, Point);
+ if (I != IP.first->begin()) --I;
+ IP.second = I;
+ }
+}
/// assignRegOrStackSlotAtInterval - assign a register if one is available, or
/// spill.
-void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
+void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur)
{
- DEBUG(std::cerr << "\tallocating current interval: ");
+ DOUT << "\tallocating current interval: ";
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->first->reg;
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- updateSpillWeights(reg, i->first->weight);
+ std::vector<std::pair<unsigned, float> > SpillWeightsToAdd;
+ unsigned StartPosition = cur->beginNumber();
+ const TargetRegisterClass *RC = reginfo_->getRegClass(cur->reg);
+ const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC);
+
+ // If this live interval is defined by a move instruction and its source is
+ // assigned a physical register that is compatible with the target register
+ // class, then we should try to assign it the same register.
+ // This can happen when the move is from a larger register class to a smaller
+ // one, e.g. X86::mov32to32_. These move instructions are not coalescable.
+ if (!cur->preference && cur->containsOneValue()) {
+ VNInfo *vni = cur->getValNumInfo(0);
+ if (vni->def && vni->def != ~1U && vni->def != ~0U) {
+ MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def);
+ unsigned SrcReg, DstReg;
+ if (tii_->isMoveInstr(*CopyMI, SrcReg, DstReg)) {
+ unsigned Reg = 0;
+ if (TargetRegisterInfo::isPhysicalRegister(SrcReg))
+ Reg = SrcReg;
+ else if (vrm_->isAssignedReg(SrcReg))
+ Reg = vrm_->getPhys(SrcReg);
+ if (Reg && allocatableRegs_[Reg] && RC->contains(Reg))
+ cur->preference = Reg;
+ }
+ }
}
// for every interval in inactive we overlap with, mark the
- // register as not free and update spill weights
+ // 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->first)) {
- unsigned reg = i->first->reg;
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- prt_->addRegUse(reg);
- updateSpillWeights(reg, i->first->weight);
+ unsigned Reg = i->first->reg;
+ assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
+ "Can only allocate virtual registers!");
+ const TargetRegisterClass *RegRC = reginfo_->getRegClass(Reg);
+ // If this is not in a related reg class to the register we're allocating,
+ // don't check it.
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader &&
+ cur->overlapsFrom(*i->first, i->second-1)) {
+ Reg = vrm_->getPhys(Reg);
+ prt_->addRegUse(Reg);
+ SpillWeightsToAdd.push_back(std::make_pair(Reg, i->first->weight));
}
}
+
+ // Speculatively check to see if we can get a register right now. If not,
+ // we know we won't be able to by adding more constraints. If so, we can
+ // check to see if it is valid. Doing an exhaustive search of the fixed_ list
+ // is very bad (it contains all callee clobbered registers for any functions
+ // with a call), so we want to avoid doing that if possible.
+ unsigned physReg = getFreePhysReg(cur);
+ if (physReg) {
+ // We got a register. However, if it's in the fixed_ list, we might
+ // conflict with it. Check to see if we conflict with it or any of its
+ // aliases.
+ SmallSet<unsigned, 8> RegAliases;
+ for (const unsigned *AS = tri_->getAliasSet(physReg); *AS; ++AS)
+ RegAliases.insert(*AS);
+
+ bool ConflictsWithFixed = false;
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ IntervalPtr &IP = fixed_[i];
+ if (physReg == IP.first->reg || RegAliases.count(IP.first->reg)) {
+ // Okay, this reg is on the fixed list. Check to see if we actually
+ // conflict.
+ LiveInterval *I = IP.first;
+ if (I->endNumber() > StartPosition) {
+ LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition);
+ IP.second = II;
+ if (II != I->begin() && II->start > StartPosition)
+ --II;
+ if (cur->overlapsFrom(*I, II)) {
+ ConflictsWithFixed = true;
+ break;
+ }
+ }
+ }
+ }
+
+ // Okay, the register picked by our speculative getFreePhysReg call turned
+ // out to be in use. Actually add all of the conflicting fixed registers to
+ // prt so we can do an accurate query.
+ if (ConflictsWithFixed) {
+ // For every interval in fixed we overlap with, mark the register as not
+ // free and update spill weights.
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ IntervalPtr &IP = fixed_[i];
+ LiveInterval *I = IP.first;
+
+ const TargetRegisterClass *RegRC = OneClassForEachPhysReg[I->reg];
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader &&
+ I->endNumber() > StartPosition) {
+ LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition);
+ IP.second = II;
+ if (II != I->begin() && II->start > StartPosition)
+ --II;
+ if (cur->overlapsFrom(*I, II)) {
+ unsigned reg = I->reg;
+ prt_->addRegUse(reg);
+ SpillWeightsToAdd.push_back(std::make_pair(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->first)) {
- unsigned reg = i->first->reg;
- prt_->addRegUse(reg);
- updateSpillWeights(reg, i->first->weight);
+ // Using the newly updated prt_ object, which includes conflicts in the
+ // future, see if there are any registers available.
+ physReg = getFreePhysReg(cur);
}
}
-
- unsigned physReg = getFreePhysReg(cur);
- // restore the physical register tracker
+
+ // Restore the physical register tracker, removing information about the
+ // future.
*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) {
- DEBUG(std::cerr << mri_->getName(physReg) << '\n');
+ DOUT << tri_->getName(physReg) << '\n';
vrm_->assignVirt2Phys(cur->reg, physReg);
prt_->addRegUse(physReg);
active_.push_back(std::make_pair(cur, cur->begin()));
handled_.push_back(cur);
return;
}
- DEBUG(std::cerr << "no free registers\n");
-
- DEBUG(std::cerr << "\tassigning stack slot at interval "<< *cur << ":\n");
-
- float minWeight = HUGE_VAL;
- 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;
+ DOUT << "no free registers\n";
+
+ // Compile the spill weights into an array that is better for scanning.
+ std::vector<float> SpillWeights(tri_->getNumRegs(), 0.0);
+ for (std::vector<std::pair<unsigned, float> >::iterator
+ I = SpillWeightsToAdd.begin(), E = SpillWeightsToAdd.end(); I != E; ++I)
+ updateSpillWeights(SpillWeights, I->first, I->second, tri_);
+
+ // for each interval in active, update spill weights.
+ for (IntervalPtrs::const_iterator i = active_.begin(), e = active_.end();
+ i != e; ++i) {
+ unsigned reg = i->first->reg;
+ assert(TargetRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
+ updateSpillWeights(SpillWeights, reg, i->first->weight, tri_);
+ }
+
+ DOUT << "\tassigning stack slot at interval "<< *cur << ":\n";
+
+ // Find a register to spill.
+ float minWeight = HUGE_VALF;
+ unsigned minReg = cur->preference; // Try the preferred register first.
+
+ if (!minReg || SpillWeights[minReg] == HUGE_VALF)
+ for (TargetRegisterClass::iterator i = RC->allocation_order_begin(*mf_),
+ e = RC->allocation_order_end(*mf_); i != e; ++i) {
+ unsigned reg = *i;
+ if (minWeight > SpillWeights[reg]) {
+ minWeight = SpillWeights[reg];
+ minReg = reg;
+ }
+ }
+
+ // If we didn't find a register that is spillable, try aliases?
+ if (!minReg) {
+ for (TargetRegisterClass::iterator i = RC->allocation_order_begin(*mf_),
+ e = RC->allocation_order_end(*mf_); i != e; ++i) {
+ unsigned reg = *i;
+ // No need to worry about if the alias register size < regsize of RC.
+ // We are going to spill all registers that alias it anyway.
+ for (const unsigned* as = tri_->getAliasSet(reg); *as; ++as) {
+ if (minWeight > SpillWeights[*as]) {
+ minWeight = SpillWeights[*as];
+ minReg = *as;
+ }
+ }
}
+
+ // All registers must have inf weight. Just grab one!
+ if (!minReg)
+ minReg = *RC->allocation_order_begin(*mf_);
}
- DEBUG(std::cerr << "\t\tregister with min weight: "
- << mri_->getName(minReg) << " (" << minWeight << ")\n");
+
+ DOUT << "\t\tregister with min weight: "
+ << tri_->getName(minReg) << " (" << minWeight << ")\n";
// if the current has the minimum weight, we need to spill it and
// add any added intervals back to unhandled, and restart
// linearscan.
- if (cur->weight <= minWeight) {
- DEBUG(std::cerr << "\t\t\tspilling(c): " << *cur << '\n';);
- int slot = vrm_->assignVirt2StackSlot(cur->reg);
+ if (cur->weight != HUGE_VALF && cur->weight <= minWeight) {
+ DOUT << "\t\t\tspilling(c): " << *cur << '\n';
std::vector<LiveInterval*> added =
- li_->addIntervalsForSpills(*cur, *vrm_, slot);
+ li_->addIntervalsForSpills(*cur, loopInfo, *vrm_);
if (added.empty())
return; // Early exit if all spills were folded.
return;
}
+ ++NumBacktracks;
+
// push the current interval back to unhandled since we are going
// to re-run at least this iteration. Since we didn't modify it it
// should go back right in the front of the list
// minimum weight, rollback to the interval with the earliest
// start point and let the linear scan algorithm run again
std::vector<LiveInterval*> added;
- assert(MRegisterInfo::isPhysicalRegister(minReg) &&
+ assert(TargetRegisterInfo::isPhysicalRegister(minReg) &&
"did not choose a register to spill?");
- std::vector<bool> toSpill(mri_->getNumRegs(), false);
- // we are going to spill minReg and all its aliases
+ BitVector toSpill(tri_->getNumRegs());
+
+ // We are going to spill minReg and all its aliases.
toSpill[minReg] = true;
- for (const unsigned* as = mri_->getAliasSet(minReg); *as; ++as)
+ for (const unsigned* as = tri_->getAliasSet(minReg); *as; ++as)
toSpill[*as] = true;
// the earliest start of a spilled interval indicates up to where
unsigned earliestStart = cur->beginNumber();
// set of spilled vregs (used later to rollback properly)
- std::set<unsigned> spilled;
-
- // spill live intervals of virtual regs mapped to the physical
- // register we want to clear (and its aliases). we only spill
- // those that overlap with the current interval as the rest do not
- // affect its allocation. we also keep track of the earliest start
- // of all spilled live intervals since this will mark our rollback
- // point
- for (IntervalPtrs::iterator
- i = active_.begin(); i != active_.end(); ++i) {
+ SmallSet<unsigned, 32> spilled;
+
+ // spill live intervals of virtual regs mapped to the physical register we
+ // want to clear (and its aliases). We only spill those that overlap with the
+ // current interval as the rest do not affect its allocation. we also keep
+ // track of the earliest start of all spilled live intervals since this will
+ // mark our rollback point.
+ for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ++i) {
unsigned reg = i->first->reg;
- if (MRegisterInfo::isVirtualRegister(reg) &&
+ if (//TargetRegisterInfo::isVirtualRegister(reg) &&
toSpill[vrm_->getPhys(reg)] &&
- cur->overlaps(*i->first)) {
- DEBUG(std::cerr << "\t\t\tspilling(a): " << *i->first << '\n');
+ cur->overlapsFrom(*i->first, i->second)) {
+ DOUT << "\t\t\tspilling(a): " << *i->first << '\n';
earliestStart = std::min(earliestStart, i->first->beginNumber());
- int slot = vrm_->assignVirt2StackSlot(i->first->reg);
std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(*i->first, *vrm_, slot);
+ li_->addIntervalsForSpills(*i->first, loopInfo, *vrm_);
std::copy(newIs.begin(), newIs.end(), std::back_inserter(added));
spilled.insert(reg);
}
}
- for (IntervalPtrs::iterator
- i = inactive_.begin(); i != inactive_.end(); ++i) {
+ for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end(); ++i){
unsigned reg = i->first->reg;
- if (MRegisterInfo::isVirtualRegister(reg) &&
+ if (//TargetRegisterInfo::isVirtualRegister(reg) &&
toSpill[vrm_->getPhys(reg)] &&
- cur->overlaps(*i->first)) {
- DEBUG(std::cerr << "\t\t\tspilling(i): " << *i->first << '\n');
+ cur->overlapsFrom(*i->first, i->second-1)) {
+ DOUT << "\t\t\tspilling(i): " << *i->first << '\n';
earliestStart = std::min(earliestStart, i->first->beginNumber());
- int slot = vrm_->assignVirt2StackSlot(reg);
std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(*i->first, *vrm_, slot);
+ li_->addIntervalsForSpills(*i->first, loopInfo, *vrm_);
std::copy(newIs.begin(), newIs.end(), std::back_inserter(added));
spilled.insert(reg);
}
}
- DEBUG(std::cerr << "\t\trolling back to: " << earliestStart << '\n');
+ DOUT << "\t\trolling back to: " << earliestStart << '\n';
// Scan handled in reverse order up to the earliest start of a
// spilled live interval and undo each one, restoring the state of
// If this interval starts before t we are done.
if (i->beginNumber() < earliestStart)
break;
- DEBUG(std::cerr << "\t\t\tundo changes for: " << *i << '\n');
+ DOUT << "\t\t\tundo changes for: " << *i << '\n';
handled_.pop_back();
// When undoing a live interval allocation we must know if it is active or
IntervalPtrs::iterator it;
if ((it = FindIntervalInVector(active_, i)) != active_.end()) {
active_.erase(it);
- if (MRegisterInfo::isPhysicalRegister(i->reg)) {
- prt_->delRegUse(i->reg);
+ assert(!TargetRegisterInfo::isPhysicalRegister(i->reg));
+ if (!spilled.count(i->reg))
unhandled_.push(i);
- } else {
- if (!spilled.count(i->reg))
- unhandled_.push(i);
- prt_->delRegUse(vrm_->getPhys(i->reg));
- vrm_->clearVirt(i->reg);
- }
+ prt_->delRegUse(vrm_->getPhys(i->reg));
+ vrm_->clearVirt(i->reg);
} else if ((it = FindIntervalInVector(inactive_, i)) != inactive_.end()) {
inactive_.erase(it);
- if (MRegisterInfo::isPhysicalRegister(i->reg))
+ assert(!TargetRegisterInfo::isPhysicalRegister(i->reg));
+ if (!spilled.count(i->reg))
unhandled_.push(i);
- else {
- if (!spilled.count(i->reg))
- unhandled_.push(i);
- vrm_->clearVirt(i->reg);
- }
- }
- else {
- if (MRegisterInfo::isVirtualRegister(i->reg))
- vrm_->clearVirt(i->reg);
+ vrm_->clearVirt(i->reg);
+ } else {
+ assert(TargetRegisterInfo::isVirtualRegister(i->reg) &&
+ "Can only allocate virtual registers!");
+ vrm_->clearVirt(i->reg);
unhandled_.push(i);
}
+
+ // It interval has a preference, it must be defined by a copy. Clear the
+ // preference now since the source interval allocation may have been undone
+ // as well.
+ i->preference = 0;
}
+ // Rewind the iterators in the active, inactive, and fixed lists back to the
+ // point we reverted to.
+ RevertVectorIteratorsTo(active_, earliestStart);
+ RevertVectorIteratorsTo(inactive_, earliestStart);
+ RevertVectorIteratorsTo(fixed_, earliestStart);
+
// 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)
LiveInterval *HI = handled_[i];
if (!HI->expiredAt(earliestStart) &&
HI->expiredAt(cur->beginNumber())) {
- DEBUG(std::cerr << "\t\t\tundo changes for: " << *HI << '\n');
+ DOUT << "\t\t\tundo changes for: " << *HI << '\n';
active_.push_back(std::make_pair(HI, HI->begin()));
- if (MRegisterInfo::isPhysicalRegister(HI->reg))
- prt_->addRegUse(HI->reg);
- else
- prt_->addRegUse(vrm_->getPhys(HI->reg));
+ assert(!TargetRegisterInfo::isPhysicalRegister(HI->reg));
+ prt_->addRegUse(vrm_->getPhys(HI->reg));
}
}
/// getFreePhysReg - return a free physical register for this virtual register
/// interval if we have one, otherwise return 0.
-unsigned RA::getFreePhysReg(LiveInterval* cur)
-{
- std::vector<unsigned> inactiveCounts(mri_->getNumRegs(), 0);
+unsigned RALinScan::getFreePhysReg(LiveInterval *cur) {
+ std::vector<unsigned> inactiveCounts(tri_->getNumRegs(), 0);
+ unsigned MaxInactiveCount = 0;
+
+ const TargetRegisterClass *RC = reginfo_->getRegClass(cur->reg);
+ const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC);
+
for (IntervalPtrs::iterator i = inactive_.begin(), e = inactive_.end();
i != e; ++i) {
unsigned reg = i->first->reg;
- if (MRegisterInfo::isVirtualRegister(reg))
+ assert(TargetRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+
+ // If this is not in a related reg class to the register we're allocating,
+ // don't check it.
+ const TargetRegisterClass *RegRC = reginfo_->getRegClass(reg);
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader) {
reg = vrm_->getPhys(reg);
- ++inactiveCounts[reg];
+ ++inactiveCounts[reg];
+ MaxInactiveCount = std::max(MaxInactiveCount, inactiveCounts[reg]);
+ }
}
- const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
-
- unsigned freeReg = 0;
- for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
- i != rc->allocation_order_end(*mf_); ++i) {
- unsigned reg = *i;
- if (prt_->isRegAvail(reg) &&
- (!freeReg || inactiveCounts[freeReg] < inactiveCounts[reg]))
- freeReg = reg;
+ unsigned FreeReg = 0;
+ unsigned FreeRegInactiveCount = 0;
+
+ // If copy coalescer has assigned a "preferred" register, check if it's
+ // available first.
+ if (cur->preference)
+ if (prt_->isRegAvail(cur->preference)) {
+ DOUT << "\t\tassigned the preferred register: "
+ << tri_->getName(cur->preference) << "\n";
+ return cur->preference;
+ } else
+ DOUT << "\t\tunable to assign the preferred register: "
+ << tri_->getName(cur->preference) << "\n";
+
+ // Scan for the first available register.
+ TargetRegisterClass::iterator I = RC->allocation_order_begin(*mf_);
+ TargetRegisterClass::iterator E = RC->allocation_order_end(*mf_);
+ for (; I != E; ++I)
+ if (prt_->isRegAvail(*I)) {
+ FreeReg = *I;
+ FreeRegInactiveCount = inactiveCounts[FreeReg];
+ break;
+ }
+
+ // If there are no free regs, or if this reg has the max inactive count,
+ // return this register.
+ if (FreeReg == 0 || FreeRegInactiveCount == MaxInactiveCount) return FreeReg;
+
+ // Continue scanning the registers, looking for the one with the highest
+ // inactive count. Alkis found that this reduced register pressure very
+ // slightly on X86 (in rev 1.94 of this file), though this should probably be
+ // reevaluated now.
+ for (; I != E; ++I) {
+ unsigned Reg = *I;
+ if (prt_->isRegAvail(Reg) && FreeRegInactiveCount < inactiveCounts[Reg]) {
+ FreeReg = Reg;
+ FreeRegInactiveCount = inactiveCounts[Reg];
+ if (FreeRegInactiveCount == MaxInactiveCount)
+ break; // We found the one with the max inactive count.
+ }
}
- return freeReg;
+
+ return FreeReg;
}
FunctionPass* llvm::createLinearScanRegisterAllocator() {
- return new RA();
+ return new RALinScan();
}