SmallPtrSet<MachineBasicBlock*, 16>& v);
void mergeLiveIntervals(unsigned primary, unsigned secondary, unsigned VN);
};
-
- char StrongPHIElimination::ID = 0;
- RegisterPass<StrongPHIElimination> X("strong-phi-node-elimination",
- "Eliminate PHI nodes for register allocation, intelligently");
}
+char StrongPHIElimination::ID = 0;
+static RegisterPass<StrongPHIElimination>
+X("strong-phi-node-elimination",
+ "Eliminate PHI nodes for register allocation, intelligently");
+
const PassInfo *llvm::StrongPHIEliminationID = X.getPassInfo();
/// computeDFS - Computes the DFS-in and DFS-out numbers of the dominator tree
}
bool inserted = false;
- for (MachineDomTreeNode::iterator I = node->begin(), E = node->end();
+ for (MachineDomTreeNode::iterator I = currNode->begin(), E = currNode->end();
I != E; ++I)
if (!frontier.count(*I) && !visited.count(*I)) {
worklist.push_back(*I);
}
}
+namespace {
+
/// PreorderSorter - a helper class that is used to sort registers
/// according to the preorder number of their defining blocks
class PreorderSorter {
}
};
+}
+
/// computeDomForest - compute the subforest of the DomTree corresponding
/// to the defining blocks of the registers in question
std::vector<StrongPHIElimination::DomForestNode*>
// before the current one.
std::set<unsigned> ProcessedNames;
- MachineBasicBlock::iterator FirstNonPHI = MBB->begin();
- while (FirstNonPHI->getOpcode() == TargetInstrInfo::PHI) FirstNonPHI++;
-
// Iterate over all the PHI nodes in this block
MachineBasicBlock::iterator P = MBB->begin();
- while (P != FirstNonPHI && P->getOpcode() == TargetInstrInfo::PHI) {
+ while (P != MBB->end() && P->getOpcode() == TargetInstrInfo::PHI) {
unsigned DestReg = P->getOperand(0).getReg();
+ // Don't both doing PHI elimination for dead PHI's.
+ if (P->registerDefIsDead(DestReg)) {
+ ++P;
+ continue;
+ }
+
LiveInterval& PI = LI.getOrCreateInterval(DestReg);
- unsigned pIdx = LI.getInstructionIndex(FirstNonPHI);
+ unsigned pIdx = LI.getDefIndex(LI.getInstructionIndex(P));
VNInfo* PVN = PI.getLiveRangeContaining(pIdx)->valno;
PhiValueNumber.insert(std::make_pair(DestReg, PVN->id));
std::vector<std::pair<unsigned, unsigned> > localInterferences;
processPHIUnion(P, PHIUnion, DF, localInterferences);
+ // If one of the inputs is defined in the same block as the current PHI
+ // then we need to check for a local interference between that input and
+ // the PHI.
+ for (std::map<unsigned, unsigned>::iterator I = PHIUnion.begin(),
+ E = PHIUnion.end(); I != E; ++I)
+ if (MRI.getVRegDef(I->first)->getParent() == P->getParent())
+ localInterferences.push_back(std::make_pair(I->first,
+ P->getOperand(0).getReg()));
+
// The dominator forest walk may have returned some register pairs whose
- // interference cannot be determines from dominator analysis. We now
+ // interference cannot be determined from dominator analysis. We now
// examine these pairs for local interferences.
for (std::vector<std::pair<unsigned, unsigned> >::iterator I =
localInterferences.begin(), E = localInterferences.end(); I != E; ++I) {
}
}
- // Add the renaming set for this PHI node to our overal renaming information
+ // Add the renaming set for this PHI node to our overall renaming information
RenameSets.insert(std::make_pair(P->getOperand(0).getReg(), PHIUnion));
// Remember which registers are already renamed, so that we don't try to
map.insert(std::make_pair(I->first, I->first));
map.insert(std::make_pair(I->second, I->second));
- if (!UsedByAnother.count(I->first)) {
+ if (!UsedByAnother.count(I->second)) {
worklist.insert(*I);
// Avoid iterator invalidation
// coalesced.
SmallVector<int, 16> LHSValNoAssignments;
SmallVector<int, 16> RHSValNoAssignments;
- DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS;
- DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS;
SmallVector<VNInfo*, 16> NewVNInfo;
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
unsigned VN = VNI->id;
if (LHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
continue;
- ComputeUltimateVN(VNI, NewVNInfo,
- LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
- LHSValNoAssignments, RHSValNoAssignments);
+
+ NewVNInfo.push_back(VNI);
+ LHSValNoAssignments[VN] = NewVNInfo.size()-1;
}
for (LiveInterval::vni_iterator I = RHS.vni_begin(), E = RHS.vni_end();
unsigned VN = VNI->id;
if (RHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
continue;
- // If this value number isn't a copy from the LHS, it's a new number.
- if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) {
- NewVNInfo.push_back(VNI);
- RHSValNoAssignments[VN] = NewVNInfo.size()-1;
- continue;
- }
-
- ComputeUltimateVN(VNI, NewVNInfo,
- RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
- RHSValNoAssignments, LHSValNoAssignments);
- }
-
- // Update kill info. Some live ranges are extended due to copy coalescing.
- for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(),
- E = LHSValsDefinedFromRHS.end(); I != E; ++I) {
- VNInfo *VNI = I->first;
- unsigned LHSValID = LHSValNoAssignments[VNI->id];
- LiveInterval::removeKill(NewVNInfo[LHSValID], VNI->def);
- NewVNInfo[LHSValID]->hasPHIKill |= VNI->hasPHIKill;
- RHS.addKills(NewVNInfo[LHSValID], VNI->kills);
- }
-
- // Update kill info. Some live ranges are extended due to copy coalescing.
- for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(),
- E = RHSValsDefinedFromLHS.end(); I != E; ++I) {
- VNInfo *VNI = I->first;
- unsigned RHSValID = RHSValNoAssignments[VNI->id];
- LiveInterval::removeKill(NewVNInfo[RHSValID], VNI->def);
- NewVNInfo[RHSValID]->hasPHIKill |= VNI->hasPHIKill;
- LHS.addKills(NewVNInfo[RHSValID], VNI->kills);
+
+ NewVNInfo.push_back(VNI);
+ RHSValNoAssignments[VN] = NewVNInfo.size()-1;
}
- // Use the VNInfo we collected earlier to ensure that the phi copy is
- // merged correctly.
- // FIXME: This is not working correctly yet.
- // RHSValNoAssignments[secondaryVN] = primaryVN;
-
// If we get here, we know that we can coalesce the live ranges. Ask the
// intervals to coalesce themselves now.
- if ((RHS.ranges.size() > LHS.ranges.size() &&
- TargetRegisterInfo::isVirtualRegister(LHS.reg)) ||
- TargetRegisterInfo::isPhysicalRegister(RHS.reg)) {
- RHS.join(LHS, &RHSValNoAssignments[0], &LHSValNoAssignments[0], NewVNInfo);
- LI.removeInterval(primary);
- } else {
- LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo);
- LI.removeInterval(secondary);
- }
+
+ LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo);
+ LI.removeInterval(secondary);
+
+ // The valno that was previously the input to the PHI node
+ // now has a PHIKill.
+ LHS.getValNumInfo(RHSValNoAssignments[secondaryVN])->hasPHIKill = true;
}
bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
+ LiveIntervals& LI = getAnalysis<LiveIntervals>();
+
// Compute DFS numbers of each block
computeDFS(Fn);
phis.push_back(BI);
}
- LiveIntervals& LI = getAnalysis<LiveIntervals>();
-
for (std::vector<MachineInstr*>::iterator I = phis.begin(), E = phis.end();
- I != E; ++I) {
- LI.RemoveMachineInstrFromMaps(*I);
- (*I)->eraseFromParent();
+ I != E; ) {
+ MachineInstr* PInstr = *(I++);
+
+ // If this is a dead PHI node, then remove it from LiveIntervals.
+ unsigned DestReg = PInstr->getOperand(0).getReg();
+ LiveInterval& PI = LI.getInterval(DestReg);
+ if (PInstr->registerDefIsDead(DestReg)) {
+ if (PI.containsOneValue()) {
+ LI.removeInterval(DestReg);
+ } else {
+ unsigned idx = LI.getDefIndex(LI.getInstructionIndex(PInstr));
+ PI.removeRange(*PI.getLiveRangeContaining(idx), true);
+ }
+ } else {
+ // If the PHI is not dead, then the valno defined by the PHI
+ // now has an unknown def.
+ unsigned idx = LI.getDefIndex(LI.getInstructionIndex(PInstr));
+ PI.getLiveRangeContaining(idx)->valno->def = ~0U;
+ }
+
+ LI.RemoveMachineInstrFromMaps(PInstr);
+ PInstr->eraseFromParent();
}
- return false;
+ return true;
}