//===----------------------------------------------------------------------===//
#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/SSARegMap.h"
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Target/TargetMachine.h"
-#include "llvm/Support/Debug.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 <algorithm>
#include <cmath>
+#include <iostream>
#include <set>
#include <queue>
+#include <memory>
using namespace llvm;
namespace {
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_;
LiveIntervals* li_;
+ bool *PhysRegsUsed;
/// handled_ - Intervals are added to the handled_ set in the order of their
/// start value. This is uses for backtracking.
/// 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";
};
}
+void RA::ComputeRelatedRegClasses() {
+ const MRegisterInfo &MRI = *mri_;
+
+ // 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 (MRegisterInfo::regclass_iterator RCI = MRI.regclass_begin(),
+ E = MRI.regclass_end(); RCI != E; ++RCI) {
+ RelatedRegClasses.insert(*RCI);
+ for (TargetRegisterClass::iterator I = (*RCI)->begin(), E = (*RCI)->end();
+ I != E; ++I) {
+ HasAliases = HasAliases || *MRI.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 = MRI.getAliasSet(I->first); *AS; ++AS)
+ RelatedRegClasses.unionSets(I->second, OneClassForEachPhysReg[*AS]);
+}
+
bool RA::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
li_ = &getAnalysis<LiveIntervals>();
+ // If this is the first function compiled, compute the related reg classes.
+ if (RelatedRegClasses.empty())
+ ComputeRelatedRegClasses();
+
+ PhysRegsUsed = new bool[mri_->getNumRegs()];
+ std::fill(PhysRegsUsed, PhysRegsUsed+mri_->getNumRegs(), false);
+ fn.setUsedPhysRegs(PhysRegsUsed);
+
if (!prt_.get()) prt_.reset(new PhysRegTracker(*mri_));
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
"interval sets should be empty on initialization");
for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i) {
- if (MRegisterInfo::isPhysicalRegister(i->second.reg))
+ if (MRegisterInfo::isPhysicalRegister(i->second.reg)) {
+ PhysRegsUsed[i->second.reg] = true;
fixed_.push_back(std::make_pair(&i->second, i->second.begin()));
- else
+ } else
unhandled_.push(&i->second);
}
}
assert(MRegisterInfo::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.
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");
unsigned reg = Interval->reg;
IntervalPos = Interval->advanceTo(IntervalPos, CurPoint);
-
+
if (IntervalPos == Interval->end()) { // remove expired intervals.
DEBUG(std::cerr << "\t\tinterval " << *Interval << " expired\n");
/// updateSpillWeights - updates the spill weights of the specifed physical
/// register and its weight.
-static void updateSpillWeights(std::vector<float> &Weights,
+static void updateSpillWeights(std::vector<float> &Weights,
unsigned reg, float weight,
const MRegisterInfo *MRI) {
Weights[reg] += weight;
PhysRegTracker backupPrt = *prt_;
- std::vector<float> SpillWeights;
- SpillWeights.assign(mri_->getNumRegs(), 0.0);
-
+ std::vector<std::pair<unsigned, float> > SpillWeightsToAdd;
unsigned StartPosition = cur->beginNumber();
-
- // 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(MRegisterInfo::isVirtualRegister(reg) &&
- "Can only allocate virtual registers!");
- reg = vrm_->getPhys(reg);
- updateSpillWeights(SpillWeights, reg, i->first->weight, mri_);
- }
-
+ const TargetRegisterClass *RC = mf_->getSSARegMap()->getRegClass(cur->reg);
+ const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC);
+
// 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->overlapsFrom(*i->first, i->second-1)) {
- unsigned reg = i->first->reg;
- assert(MRegisterInfo::isVirtualRegister(reg) &&
- "Can only allocate virtual registers!");
- reg = vrm_->getPhys(reg);
- prt_->addRegUse(reg);
- updateSpillWeights(SpillWeights, reg, i->first->weight, mri_);
+ unsigned Reg = i->first->reg;
+ assert(MRegisterInfo::isVirtualRegister(Reg) &&
+ "Can only allocate virtual registers!");
+ const TargetRegisterClass *RegRC = mf_->getSSARegMap()->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));
}
}
-
- // 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;
- 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)) {
- unsigned reg = I->reg;
- prt_->addRegUse(reg);
- updateSpillWeights(SpillWeights, reg, I->weight, mri_);
+
+ // 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.
+ std::set<unsigned> RegAliases;
+ for (const unsigned *AS = mri_->getAliasSet(physReg); *AS; ++AS)
+ RegAliases.insert(*AS);
+
+ bool ConflictsWithFixed = false;
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ if (physReg == fixed_[i].first->reg ||
+ RegAliases.count(fixed_[i].first->reg)) {
+ // Okay, this reg is on the fixed list. Check to see if we actually
+ // conflict.
+ IntervalPtr &IP = fixed_[i];
+ 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));
+ }
+ }
+ }
- unsigned physReg = getFreePhysReg(cur);
- // restore the physical register tracker
+ // Using the newly updated prt_ object, which includes conflicts in the
+ // future, see if there are any registers available.
+ physReg = getFreePhysReg(cur);
+ }
+ }
+
+ // 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.
}
DEBUG(std::cerr << "no free registers\n");
+ // Compile the spill weights into an array that is better for scanning.
+ std::vector<float> SpillWeights(mri_->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, mri_);
+
+ // 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(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
+ updateSpillWeights(SpillWeights, reg, i->first->weight, mri_);
+ }
+
DEBUG(std::cerr << "\tassigning stack slot at interval "<< *cur << ":\n");
float minWeight = float(HUGE_VAL);
unsigned minReg = 0;
- const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
- for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_),
- e = rc->allocation_order_end(*mf_); i != e; ++i) {
+ 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;
}
}
+// FIXME: assert(minReg && "Didn't find any reg!");
DEBUG(std::cerr << "\t\tregister with min weight: "
<< mri_->getName(minReg) << " (" << minWeight << ")\n");
IntervalPtrs::iterator it;
if ((it = FindIntervalInVector(active_, i)) != active_.end()) {
active_.erase(it);
- if (MRegisterInfo::isPhysicalRegister(i->reg)) {
- assert(0 && "daksjlfd");
- prt_->delRegUse(i->reg);
+ assert(!MRegisterInfo::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(0 && "daksjlfd");
+ assert(!MRegisterInfo::isPhysicalRegister(i->reg));
+ if (!spilled.count(i->reg))
unhandled_.push(i);
- } else {
- if (!spilled.count(i->reg))
- unhandled_.push(i);
- vrm_->clearVirt(i->reg);
- }
+ vrm_->clearVirt(i->reg);
} else {
assert(MRegisterInfo::isVirtualRegister(i->reg) &&
"Can only allocate virtual registers!");
HI->expiredAt(cur->beginNumber())) {
DEBUG(std::cerr << "\t\t\tundo changes for: " << *HI << '\n');
active_.push_back(std::make_pair(HI, HI->begin()));
- if (MRegisterInfo::isPhysicalRegister(HI->reg)) {
- assert(0 &&"sdflkajsdf");
- prt_->addRegUse(HI->reg);
- } else
- prt_->addRegUse(vrm_->getPhys(HI->reg));
+ assert(!MRegisterInfo::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)
-{
+unsigned RA::getFreePhysReg(LiveInterval *cur) {
std::vector<unsigned> inactiveCounts(mri_->getNumRegs(), 0);
+ unsigned MaxInactiveCount = 0;
+
+ const TargetRegisterClass *RC = mf_->getSSARegMap()->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;
assert(MRegisterInfo::isVirtualRegister(reg) &&
"Can only allocate virtual registers!");
- reg = vrm_->getPhys(reg);
- ++inactiveCounts[reg];
+
+ // If this is not in a related reg class to the register we're allocating,
+ // don't check it.
+ const TargetRegisterClass *RegRC = mf_->getSSARegMap()->getRegClass(reg);
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader) {
+ reg = vrm_->getPhys(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_),
- e = rc->allocation_order_end(*mf_); i != e; ++i) {
- unsigned reg = *i;
- if (prt_->isRegAvail(reg) &&
- (!freeReg || inactiveCounts[freeReg] < inactiveCounts[reg]))
- freeReg = reg;
+ unsigned FreeReg = 0;
+ unsigned FreeRegInactiveCount = 0;
+
+ // 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() {
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