Add option to join live intervals. Two intervals are joined if there
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
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index 5f1290d2..d25dc34 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -32,12 +32,15 @@
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 @@
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 @@
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 @@
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 @@
}
}
+ 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 @@
}
--currentInstr_; // restore currentInstr_ iterator
tempDefOperands_.clear();
+ ++currentInstr_;
}
}