#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/Support/Compiler.h"
using namespace llvm;
-
namespace {
struct VISIBILITY_HIDDEN StrongPHIElimination : public MachineFunctionPass {
static char ID; // Pass identification, replacement for typeid
// used as operands to another another PHI node
std::set<unsigned> UsedByAnother;
- // RenameSets are the sets of operands (and their VNInfo IDs) to a PHI
- // (the defining instruction of the key) that can be renamed without copies.
+ // RenameSets are the is a map from a PHI-defined register
+ // to the input registers to be coalesced along with the index
+ // of the input registers.
std::map<unsigned, std::map<unsigned, unsigned> > RenameSets;
// PhiValueNumber holds the ID numbers of the VNs for each phi that we're
// TODO: Actually make this true.
AU.addPreserved<LiveIntervals>();
+ AU.addPreserved<RegisterCoalescer>();
MachineFunctionPass::getAnalysisUsage(AU);
}
std::vector<StrongPHIElimination::DomForestNode*>& DF,
std::vector<std::pair<unsigned, unsigned> >& locals);
void ScheduleCopies(MachineBasicBlock* MBB, std::set<unsigned>& pushed);
- void InsertCopies(MachineBasicBlock* MBB, std::set<MachineBasicBlock*>& v);
+ void InsertCopies(MachineBasicBlock* MBB,
+ 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");
}
-const PassInfo *llvm::StrongPHIEliminationID = X.getPassInfo();
+char StrongPHIElimination::ID = 0;
+static RegisterPass<StrongPHIElimination>
+X("strong-phi-node-elimination",
+ "Eliminate PHI nodes for register allocation, intelligently");
+
+const PassInfo *const llvm::StrongPHIEliminationID = &X;
/// computeDFS - Computes the DFS-in and DFS-out numbers of the dominator tree
/// of the given MachineFunction. These numbers are then used in other parts
}
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));
// is refinded over the course of this function. UnionedBlocks is the set
// of corresponding MBBs.
std::map<unsigned, unsigned> PHIUnion;
- std::set<MachineBasicBlock*> UnionedBlocks;
+ SmallPtrSet<MachineBasicBlock*, 8> UnionedBlocks;
// Iterate over the operands of the PHI node
for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
UsedByAnother.insert(SrcReg);
} else {
// Otherwise, add it to the renaming set
- LiveInterval& I = LI.getOrCreateInterval(SrcReg);
- unsigned idx = LI.getMBBEndIdx(P->getOperand(i).getMBB());
- VNInfo* VN = I.getLiveRangeContaining(idx)->valno;
+ // We need to subtract one from the index because live ranges are open
+ // at the end.
+ unsigned idx = LI.getMBBEndIdx(P->getOperand(i).getMBB()) - 1;
- assert(VN && "No VNInfo for register?");
-
- PHIUnion.insert(std::make_pair(SrcReg, VN->id));
+ PHIUnion.insert(std::make_pair(SrcReg, idx));
UnionedBlocks.insert(MRI.getVRegDef(SrcReg)->getParent());
}
}
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
/// of Static Single Assignment Form" by Briggs, et al.
void StrongPHIElimination::ScheduleCopies(MachineBasicBlock* MBB,
std::set<unsigned>& pushed) {
- // FIXME: This function needs to update LiveVariables
+ // FIXME: This function needs to update LiveIntervals
std::map<unsigned, unsigned>& copy_set= Waiting[MBB];
std::map<unsigned, unsigned> worklist;
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
MachineRegisterInfo& MRI = MF->getRegInfo();
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
+ SmallVector<std::pair<unsigned, MachineInstr*>, 4> InsertedPHIDests;
+
// Iterate over the worklist, inserting copies
while (!worklist.empty() || !copy_set.empty()) {
while (!worklist.empty()) {
map[curr.first], RC, RC);
map[curr.first] = curr.second;
+ // Push this copy onto InsertedPHICopies so we can
+ // update LiveIntervals with it.
+ MachineBasicBlock::iterator MI = MBB->getFirstTerminator();
+ InsertedPHIDests.push_back(std::make_pair(curr.second, --MI));
+
// If curr.first is a destination in copy_set...
for (std::map<unsigned, unsigned>::iterator I = copy_set.begin(),
E = copy_set.end(); I != E; )
worklist.insert(curr);
}
}
+
+ // Renumber the instructions so that we can perform the index computations
+ // needed to create new live intervals.
+ LI.computeNumbering();
+
+ // For copies that we inserted at the ends of predecessors, we construct
+ // live intervals. This is pretty easy, since we know that the destination
+ // register cannot have be in live at that point previously. We just have
+ // to make sure that, for registers that serve as inputs to more than one
+ // PHI, we don't create multiple overlapping live intervals.
+ std::set<unsigned> RegHandled;
+ for (SmallVector<std::pair<unsigned, MachineInstr*>, 4>::iterator I =
+ InsertedPHIDests.begin(), E = InsertedPHIDests.end(); I != E; ++I)
+ if (!RegHandled.count(I->first))
+ LI.addLiveRangeToEndOfBlock(I->first, I->second);
}
/// InsertCopies - insert copies into MBB and all of its successors
void StrongPHIElimination::InsertCopies(MachineBasicBlock* MBB,
- std::set<MachineBasicBlock*>& visited) {
+ SmallPtrSet<MachineBasicBlock*, 16>& visited) {
visited.insert(MBB);
std::set<unsigned> pushed;
Stacks[*I].pop_back();
}
-/// ComputeUltimateVN - Assuming we are going to join two live intervals,
-/// compute what the resultant value numbers for each value in the input two
-/// ranges will be. This is complicated by copies between the two which can
-/// and will commonly cause multiple value numbers to be merged into one.
-///
-/// VN is the value number that we're trying to resolve. InstDefiningValue
-/// keeps track of the new InstDefiningValue assignment for the result
-/// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
-/// whether a value in this or other is a copy from the opposite set.
-/// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
-/// already been assigned.
-///
-/// ThisFromOther[x] - If x is defined as a copy from the other interval, this
-/// contains the value number the copy is from.
-///
-static unsigned ComputeUltimateVN(VNInfo *VNI,
- SmallVector<VNInfo*, 16> &NewVNInfo,
- DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
- DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
- SmallVector<int, 16> &ThisValNoAssignments,
- SmallVector<int, 16> &OtherValNoAssignments) {
- unsigned VN = VNI->id;
-
- // If the VN has already been computed, just return it.
- if (ThisValNoAssignments[VN] >= 0)
- return ThisValNoAssignments[VN];
-// assert(ThisValNoAssignments[VN] != -2 && "Cyclic case?");
-
- // If this val is not a copy from the other val, then it must be a new value
- // number in the destination.
- DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
- if (I == ThisFromOther.end()) {
- NewVNInfo.push_back(VNI);
- return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
- }
- VNInfo *OtherValNo = I->second;
-
- // Otherwise, this *is* a copy from the RHS. If the other side has already
- // been computed, return it.
- if (OtherValNoAssignments[OtherValNo->id] >= 0)
- return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
-
- // Mark this value number as currently being computed, then ask what the
- // ultimate value # of the other value is.
- ThisValNoAssignments[VN] = -2;
- unsigned UltimateVN =
- ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
- OtherValNoAssignments, ThisValNoAssignments);
- return ThisValNoAssignments[VN] = UltimateVN;
-}
-
void StrongPHIElimination::mergeLiveIntervals(unsigned primary,
- unsigned secondary, unsigned secondaryVN) {
- unsigned primaryVN = PhiValueNumber[primary];
+ unsigned secondary,
+ unsigned secondaryIdx) {
LiveIntervals& LI = getAnalysis<LiveIntervals>();
LiveInterval& LHS = LI.getOrCreateInterval(primary);
LiveInterval& RHS = LI.getOrCreateInterval(secondary);
- // Compute the final value assignment, assuming that the live ranges can be
- // 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);
- RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
- NewVNInfo.resize(LHS.getNumValNums(), NULL);
-
- // Loop over the value numbers of the LHS, seeing if any are defined from
- // the RHS.
- for (LiveInterval::vni_iterator I = LHS.vni_begin(), E = LHS.vni_end();
- I != E; ++E) {
- VNInfo *VNI = *I;
- if (VNI->def == ~1U || VNI->copy == 0) // Src not defined by a copy?
- continue;
-
- // DstReg is known to be a register in the LHS interval. If the src is
- // from the RHS interval, we can use its value #.
- if (LI.getVNInfoSourceReg(VNI) != RHS.reg)
- continue;
-
- // Figure out the value # from the RHS.
- LHSValsDefinedFromRHS[VNI]=RHS.getLiveRangeContaining(VNI->def-1)->valno;
- }
+ LI.computeNumbering();
- // Loop over the value numbers of the RHS, seeing if any are defined from
- // the LHS.
- for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
- i != e; ++i) {
- VNInfo *VNI = *i;
- if (VNI->def == ~1U || VNI->copy == 0) // Src not defined by a copy?
- continue;
-
- // DstReg is known to be a register in the RHS interval. If the src is
- // from the LHS interval, we can use its value #.
- if (LI.getVNInfoSourceReg(VNI) != LHS.reg)
- continue;
-
- // Figure out the value # from the LHS.
- RHSValsDefinedFromLHS[VNI]=LHS.getLiveRangeContaining(VNI->def-1)->valno;
- }
-
- LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
- RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
- NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
-
- for (LiveInterval::vni_iterator I = LHS.vni_begin(), E = LHS.vni_end();
- I != E; ++I) {
- VNInfo *VNI = *I;
- unsigned VN = VNI->id;
- if (LHSValNoAssignments[VN] >= 0 || VNI->def == ~1U)
- continue;
- ComputeUltimateVN(VNI, NewVNInfo,
- LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
- LHSValNoAssignments, RHSValNoAssignments);
- }
-
- for (LiveInterval::vni_iterator I = RHS.vni_begin(), E = RHS.vni_end();
- I != E; ++I) {
- VNInfo *VNI = *I;
- 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);
- }
-
- // Use the VNInfo we collected earlier to ensure that the phi copy is
- // merged correctly.
- 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);
- } else {
- LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo);
- }
+ const LiveRange* RangeMergingIn = RHS.getLiveRangeContaining(secondaryIdx);
+ VNInfo* NewVN = LHS.getNextValue(secondaryIdx, RangeMergingIn->valno->copy,
+ LI.getVNInfoAllocator());
+ NewVN->hasPHIKill = true;
+ LiveRange NewRange(RangeMergingIn->start, RangeMergingIn->end, NewVN);
+ LHS.addRange(NewRange);
+ RHS.removeRange(RangeMergingIn->start, RangeMergingIn->end, true);
}
bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
+ LiveIntervals& LI = getAnalysis<LiveIntervals>();
+
// Compute DFS numbers of each block
computeDFS(Fn);
processBlock(I);
// Insert copies
- // FIXME: This process should probably preserve LiveVariables
- std::set<MachineBasicBlock*> visited;
+ // FIXME: This process should probably preserve LiveIntervals
+ SmallPtrSet<MachineBasicBlock*, 16> visited;
InsertCopies(Fn.begin(), visited);
// Perform renaming
}
for (std::vector<MachineInstr*>::iterator I = phis.begin(), E = phis.end();
- I != E; ++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;
+ LI.computeNumbering();
+
+ return true;
}
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