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Add option to join live intervals. Two intervals are joined if there

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is a move between two registers, at least one of the registers is
virtual and the two live intervals do not overlap.

This results in about 40% reduction in intervals, 30% decrease in the
register allocators running time and a 20% increase in peephole
optimizations (mainly move eliminations).

The option can be enabled by passing -join-liveintervals where
appropriate.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10965 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Alkis Evlogimenos
2004-01-22 23:08:45 +00:00
parent 8abff7945a
commit e88280a422
5 changed files with 300 additions and 64 deletions
Download Patch File Download Diff File Expand all files Collapse all files

67
lib/CodeGen/RegAllocLinearScan.cpp
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@ -32,12 +32,15 @@ using namespace llvm;
namespace {
Statistic<> numSpilled ("ra-linearscan", "Number of registers spilled");
Statistic<> numReloaded("ra-linearscan", "Number of registers reloaded");
Statistic<> numPeep ("ra-linearscan",
"Number of identity moves eliminated");
class RA : public MachineFunctionPass {
private:
MachineFunction* mf_;
const TargetMachine* tm_;
const MRegisterInfo* mri_;
LiveIntervals* li_;
MachineFunction::iterator currentMbb_;
MachineBasicBlock::iterator currentInstr_;
typedef std::vector<const LiveIntervals::Interval*> IntervalPtrs;
@ -203,8 +206,8 @@ bool RA::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
initIntervalSets(getAnalysis<LiveIntervals>().getIntervals());
li_ = &getAnalysis<LiveIntervals>();
initIntervalSets(li_->getIntervals());
v2pMap_.clear();
v2ssMap_.clear();
@ -231,6 +234,7 @@ bool RA::runOnMachineFunction(MachineFunction &fn) {
reserved_[29] = true; /* FP6 */
// linear scan algorithm
DEBUG(std::cerr << "Machine Function\n");
DEBUG(printIntervals("\tunhandled", unhandled_.begin(), unhandled_.end()));
DEBUG(printIntervals("\tfixed", fixed_.begin(), fixed_.end()));
@ -324,15 +328,54 @@ bool RA::runOnMachineFunction(MachineFunction &fn) {
active_.clear();
inactive_.clear();
DEBUG(std::cerr << "finished register allocation\n");
typedef LiveIntervals::Reg2RegMap Reg2RegMap;
const Reg2RegMap& r2rMap = li_->getJoinedRegMap();
DEBUG(printVirtRegAssignment());
DEBUG(std::cerr << "Performing coalescing on joined intervals\n");
// perform coalescing if we were passed joined intervals
for(Reg2RegMap::const_iterator i = r2rMap.begin(), e = r2rMap.end();
i != e; ++i) {
unsigned reg = i->first;
unsigned rep = li_->rep(reg);
assert((rep < MRegisterInfo::FirstVirtualRegister ||
v2pMap_.find(rep) != v2pMap_.end() ||
v2ssMap_.find(rep) != v2ssMap_.end()) &&
"representative register is not allocated!");
assert(reg >= MRegisterInfo::FirstVirtualRegister &&
v2pMap_.find(reg) == v2pMap_.end() &&
v2ssMap_.find(reg) == v2ssMap_.end() &&
"coalesced register is already allocated!");
if (rep < MRegisterInfo::FirstVirtualRegister) {
v2pMap_.insert(std::make_pair(reg, rep));
}
else {
Virt2PhysMap::const_iterator pr = v2pMap_.find(rep);
if (pr != v2pMap_.end()) {
v2pMap_.insert(std::make_pair(reg, pr->second));
}
else {
Virt2StackSlotMap::const_iterator ss = v2ssMap_.find(rep);
assert(ss != v2ssMap_.end());
v2ssMap_.insert(std::make_pair(reg, ss->second));
}
}
}
DEBUG(printVirtRegAssignment());
DEBUG(std::cerr << "finished register allocation\n");
const TargetInstrInfo& tii = tm_->getInstrInfo();
DEBUG(std::cerr << "Rewrite machine code:\n");
for (currentMbb_ = mf_->begin(); currentMbb_ != mf_->end(); ++currentMbb_) {
instrAdded_ = 0;
for (currentInstr_ = currentMbb_->begin();
currentInstr_ != currentMbb_->end(); ++currentInstr_) {
currentInstr_ != currentMbb_->end(); ) {
DEBUG(std::cerr << "\tinstruction: ";
(*currentInstr_)->print(std::cerr, *tm_););
@ -355,6 +398,21 @@ bool RA::runOnMachineFunction(MachineFunction &fn) {
}
}
unsigned srcReg, dstReg;
if (tii.isMoveInstr(**currentInstr_, srcReg, dstReg) &&
((srcReg < MRegisterInfo::FirstVirtualRegister &&
dstReg < MRegisterInfo::FirstVirtualRegister &&
srcReg == dstReg) ||
(srcReg >= MRegisterInfo::FirstVirtualRegister &&
dstReg >= MRegisterInfo::FirstVirtualRegister &&
v2ssMap_[srcReg] == v2ssMap_[dstReg]))) {
delete *currentInstr_;
currentInstr_ = currentMbb_->erase(currentInstr_);
++numPeep;
DEBUG(std::cerr << "\t\tdeleting instruction\n");
continue;
}
DEBUG(std::cerr << "\t\tloading temporarily used operands to "
"registers:\n");
for (unsigned i = 0, e = (*currentInstr_)->getNumOperands();
@ -416,6 +474,7 @@ bool RA::runOnMachineFunction(MachineFunction &fn) {
}
--currentInstr_; // restore currentInstr_ iterator
tempDefOperands_.clear();
++currentInstr_;
}
}