X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FMachineSSAUpdater.cpp;h=71a6ebaba243117aec7b2c54190ba144083f0f30;hb=273cdae7e91c1b11ae9f55c6a78b1e9d820b9ea9;hp=bca3ffad583dcf2a8a8d5d5968ca40e5019b14bd;hpb=229694f0ee630ceabe96a8bd48952f6740f928b2;p=oota-llvm.git diff --git a/lib/CodeGen/MachineSSAUpdater.cpp b/lib/CodeGen/MachineSSAUpdater.cpp index bca3ffad583..71a6ebaba24 100644 --- a/lib/CodeGen/MachineSSAUpdater.cpp +++ b/lib/CodeGen/MachineSSAUpdater.cpp @@ -13,56 +13,48 @@ //===----------------------------------------------------------------------===// #include "llvm/CodeGen/MachineSSAUpdater.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallVector.h" #include "llvm/CodeGen/MachineInstr.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineRegisterInfo.h" -#include "llvm/Target/TargetInstrInfo.h" -#include "llvm/Target/TargetMachine.h" -#include "llvm/Target/TargetRegisterInfo.h" -#include "llvm/ADT/DenseMap.h" +#include "llvm/Support/AlignOf.h" +#include "llvm/Support/Allocator.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Target/TargetSubtargetInfo.h" +#include "llvm/Transforms/Utils/SSAUpdaterImpl.h" using namespace llvm; -typedef DenseMap AvailableValsTy; -typedef std::vector > - IncomingPredInfoTy; +#define DEBUG_TYPE "machine-ssaupdater" +typedef DenseMap AvailableValsTy; static AvailableValsTy &getAvailableVals(void *AV) { return *static_cast(AV); } -static IncomingPredInfoTy &getIncomingPredInfo(void *IPI) { - return *static_cast(IPI); -} - - MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF, SmallVectorImpl *NewPHI) - : AV(0), IPI(0), InsertedPHIs(NewPHI) { - TII = MF.getTarget().getInstrInfo(); + : AV(nullptr), InsertedPHIs(NewPHI) { + TII = MF.getSubtarget().getInstrInfo(); MRI = &MF.getRegInfo(); } MachineSSAUpdater::~MachineSSAUpdater() { - delete &getAvailableVals(AV); - delete &getIncomingPredInfo(IPI); + delete static_cast(AV); } /// Initialize - Reset this object to get ready for a new set of SSA /// updates. ProtoValue is the value used to name PHI nodes. void MachineSSAUpdater::Initialize(unsigned V) { - if (AV == 0) + if (!AV) AV = new AvailableValsTy(); else getAvailableVals(AV).clear(); - if (IPI == 0) - IPI = new IncomingPredInfoTy(); - else - getIncomingPredInfo(IPI).clear(); - VR = V; VRC = MRI->getRegClass(VR); } @@ -85,17 +77,48 @@ unsigned MachineSSAUpdater::GetValueAtEndOfBlock(MachineBasicBlock *BB) { return GetValueAtEndOfBlockInternal(BB); } -/// InsertNewPHI - Insert an empty PHI instruction which define a value of the -/// given register class at the start of the specified basic block. It returns -/// the virtual register defined by the PHI instruction. static -MachineInstr *InsertNewPHI(MachineBasicBlock *BB, const TargetRegisterClass *RC, - MachineRegisterInfo *MRI, const TargetInstrInfo *TII) { +unsigned LookForIdenticalPHI(MachineBasicBlock *BB, + SmallVectorImpl > &PredValues) { + if (BB->empty()) + return 0; + + MachineBasicBlock::iterator I = BB->begin(); + if (!I->isPHI()) + return 0; + + AvailableValsTy AVals; + for (unsigned i = 0, e = PredValues.size(); i != e; ++i) + AVals[PredValues[i].first] = PredValues[i].second; + while (I != BB->end() && I->isPHI()) { + bool Same = true; + for (unsigned i = 1, e = I->getNumOperands(); i != e; i += 2) { + unsigned SrcReg = I->getOperand(i).getReg(); + MachineBasicBlock *SrcBB = I->getOperand(i+1).getMBB(); + if (AVals[SrcBB] != SrcReg) { + Same = false; + break; + } + } + if (Same) + return I->getOperand(0).getReg(); + ++I; + } + return 0; +} + +/// InsertNewDef - Insert an empty PHI or IMPLICIT_DEF instruction which define +/// a value of the given register class at the start of the specified basic +/// block. It returns the virtual register defined by the instruction. +static +MachineInstrBuilder InsertNewDef(unsigned Opcode, + MachineBasicBlock *BB, MachineBasicBlock::iterator I, + const TargetRegisterClass *RC, + MachineRegisterInfo *MRI, + const TargetInstrInfo *TII) { unsigned NewVR = MRI->createVirtualRegister(RC); - return BuildMI(*BB, BB->front(), BB->front().getDebugLoc(), - TII->get(TargetInstrInfo::PHI), NewVR); + return BuildMI(*BB, I, DebugLoc(), TII->get(Opcode), NewVR); } - /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that /// is live in the middle of the specified block. @@ -119,11 +142,17 @@ MachineInstr *InsertNewPHI(MachineBasicBlock *BB, const TargetRegisterClass *RC, unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) { // If there is no definition of the renamed variable in this block, just use // GetValueAtEndOfBlock to do our work. - if (!getAvailableVals(AV).count(BB)) - return GetValueAtEndOfBlock(BB); - - if (BB->pred_empty()) - llvm_unreachable("Unreachable block!"); + if (!HasValueForBlock(BB)) + return GetValueAtEndOfBlockInternal(BB); + + // If there are no predecessors, just return undef. + if (BB->pred_empty()) { + // Insert an implicit_def to represent an undef value. + MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF, + BB, BB->getFirstTerminator(), + VRC, MRI, TII); + return NewDef->getOperand(0).getReg(); + } // Otherwise, we have the hard case. Get the live-in values for each // predecessor. @@ -149,13 +178,19 @@ unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) { if (SingularValue != 0) return SingularValue; + // If an identical PHI is already in BB, just reuse it. + unsigned DupPHI = LookForIdenticalPHI(BB, PredValues); + if (DupPHI) + return DupPHI; + // Otherwise, we do need a PHI: insert one now. - MachineInstr *InsertedPHI = InsertNewPHI(BB, VRC, MRI, TII); + MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->begin(); + MachineInstrBuilder InsertedPHI = InsertNewDef(TargetOpcode::PHI, BB, + Loc, VRC, MRI, TII); // Fill in all the predecessors of the PHI. - MachineInstrBuilder MIB(InsertedPHI); for (unsigned i = 0, e = PredValues.size(); i != e; ++i) - MIB.addReg(PredValues[i].second).addMBB(PredValues[i].first); + InsertedPHI.addReg(PredValues[i].second).addMBB(PredValues[i].first); // See if the PHI node can be merged to a single value. This can happen in // loop cases when we get a PHI of itself and one other value. @@ -167,7 +202,7 @@ unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) { // If the client wants to know about all new instructions, tell it. if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI); - DEBUG(errs() << " Inserted PHI: " << *InsertedPHI << "\n"); + DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n"); return InsertedPHI->getOperand(0).getReg(); } @@ -180,7 +215,6 @@ MachineBasicBlock *findCorrespondingPred(const MachineInstr *MI, } llvm_unreachable("MachineOperand::getParent() failure?"); - return 0; } /// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes, @@ -188,9 +222,9 @@ MachineBasicBlock *findCorrespondingPred(const MachineInstr *MI, void MachineSSAUpdater::RewriteUse(MachineOperand &U) { MachineInstr *UseMI = U.getParent(); unsigned NewVR = 0; - if (UseMI->getOpcode() == TargetInstrInfo::PHI) { + if (UseMI->isPHI()) { MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U); - NewVR = GetValueAtEndOfBlock(SourceBB); + NewVR = GetValueAtEndOfBlockInternal(SourceBB); } else { NewVR = GetValueInMiddleOfBlock(UseMI->getParent()); } @@ -198,132 +232,125 @@ void MachineSSAUpdater::RewriteUse(MachineOperand &U) { U.setReg(NewVR); } -/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry -/// for the specified BB and if so, return it. If not, construct SSA form by -/// walking predecessors inserting PHI nodes as needed until we get to a block -/// where the value is available. -/// -unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){ - AvailableValsTy &AvailableVals = getAvailableVals(AV); - - // Query AvailableVals by doing an insertion of null. - std::pair InsertRes = - AvailableVals.insert(std::make_pair(BB, 0)); - - // Handle the case when the insertion fails because we have already seen BB. - if (!InsertRes.second) { - // If the insertion failed, there are two cases. The first case is that the - // value is already available for the specified block. If we get this, just - // return the value. - if (InsertRes.first->second != 0) - return InsertRes.first->second; - - // Otherwise, if the value we find is null, then this is the value is not - // known but it is being computed elsewhere in our recursion. This means - // that we have a cycle. Handle this by inserting a PHI node and returning - // it. When we get back to the first instance of the recursion we will fill - // in the PHI node. - MachineInstr *NewPHI = InsertNewPHI(BB, VRC, MRI, TII); - unsigned NewVR = NewPHI->getOperand(0).getReg(); - InsertRes.first->second = NewVR; - return NewVR; +/// SSAUpdaterTraits - Traits for the SSAUpdaterImpl +/// template, specialized for MachineSSAUpdater. +namespace llvm { +template<> +class SSAUpdaterTraits { +public: + typedef MachineBasicBlock BlkT; + typedef unsigned ValT; + typedef MachineInstr PhiT; + + typedef MachineBasicBlock::succ_iterator BlkSucc_iterator; + static BlkSucc_iterator BlkSucc_begin(BlkT *BB) { return BB->succ_begin(); } + static BlkSucc_iterator BlkSucc_end(BlkT *BB) { return BB->succ_end(); } + + /// Iterator for PHI operands. + class PHI_iterator { + private: + MachineInstr *PHI; + unsigned idx; + + public: + explicit PHI_iterator(MachineInstr *P) // begin iterator + : PHI(P), idx(1) {} + PHI_iterator(MachineInstr *P, bool) // end iterator + : PHI(P), idx(PHI->getNumOperands()) {} + + PHI_iterator &operator++() { idx += 2; return *this; } + bool operator==(const PHI_iterator& x) const { return idx == x.idx; } + bool operator!=(const PHI_iterator& x) const { return !operator==(x); } + unsigned getIncomingValue() { return PHI->getOperand(idx).getReg(); } + MachineBasicBlock *getIncomingBlock() { + return PHI->getOperand(idx+1).getMBB(); + } + }; + static inline PHI_iterator PHI_begin(PhiT *PHI) { return PHI_iterator(PHI); } + static inline PHI_iterator PHI_end(PhiT *PHI) { + return PHI_iterator(PHI, true); } - if (BB->pred_empty()) - llvm_unreachable("Unreachable block!"); - - // Okay, the value isn't in the map and we just inserted a null in the entry - // to indicate that we're processing the block. Since we have no idea what - // value is in this block, we have to recurse through our predecessors. - // - // While we're walking our predecessors, we keep track of them in a vector, - // then insert a PHI node in the end if we actually need one. We could use a - // smallvector here, but that would take a lot of stack space for every level - // of the recursion, just use IncomingPredInfo as an explicit stack. - IncomingPredInfoTy &IncomingPredInfo = getIncomingPredInfo(IPI); - unsigned FirstPredInfoEntry = IncomingPredInfo.size(); - - // As we're walking the predecessors, keep track of whether they are all - // producing the same value. If so, this value will capture it, if not, it - // will get reset to null. We distinguish the no-predecessor case explicitly - // below. - unsigned SingularValue = 0; - bool isFirstPred = true; - for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(), - E = BB->pred_end(); PI != E; ++PI) { - MachineBasicBlock *PredBB = *PI; - unsigned PredVal = GetValueAtEndOfBlockInternal(PredBB); - IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal)); - - // Compute SingularValue. - if (isFirstPred) { - SingularValue = PredVal; - isFirstPred = false; - } else if (PredVal != SingularValue) - SingularValue = 0; + /// FindPredecessorBlocks - Put the predecessors of BB into the Preds + /// vector. + static void FindPredecessorBlocks(MachineBasicBlock *BB, + SmallVectorImpl *Preds){ + for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(), + E = BB->pred_end(); PI != E; ++PI) + Preds->push_back(*PI); } - /// Look up BB's entry in AvailableVals. 'InsertRes' may be invalidated. If - /// this block is involved in a loop, a no-entry PHI node will have been - /// inserted as InsertedVal. Otherwise, we'll still have the null we inserted - /// above. - unsigned InsertedVal = AvailableVals[BB]; - - // If all the predecessor values are the same then we don't need to insert a - // PHI. This is the simple and common case. - if (SingularValue) { - // If a PHI node got inserted, replace it with the singlar value and delete - // it. - if (InsertedVal) { - MachineInstr *OldVal = MRI->getVRegDef(InsertedVal); - // Be careful about dead loops. These RAUW's also update InsertedVal. - assert(InsertedVal != SingularValue && "Dead loop?"); - MRI->replaceRegWith(InsertedVal, SingularValue); - OldVal->eraseFromParent(); - } else { - InsertedVal = SingularValue; - } - - // Drop the entries we added in IncomingPredInfo to restore the stack. - IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry, - IncomingPredInfo.end()); - return InsertedVal; + /// GetUndefVal - Create an IMPLICIT_DEF instruction with a new register. + /// Add it into the specified block and return the register. + static unsigned GetUndefVal(MachineBasicBlock *BB, + MachineSSAUpdater *Updater) { + // Insert an implicit_def to represent an undef value. + MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF, + BB, BB->getFirstTerminator(), + Updater->VRC, Updater->MRI, + Updater->TII); + return NewDef->getOperand(0).getReg(); } + /// CreateEmptyPHI - Create a PHI instruction that defines a new register. + /// Add it into the specified block and return the register. + static unsigned CreateEmptyPHI(MachineBasicBlock *BB, unsigned NumPreds, + MachineSSAUpdater *Updater) { + MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->begin(); + MachineInstr *PHI = InsertNewDef(TargetOpcode::PHI, BB, Loc, + Updater->VRC, Updater->MRI, + Updater->TII); + return PHI->getOperand(0).getReg(); + } - // Otherwise, we do need a PHI: insert one now if we don't already have one. - MachineInstr *InsertedPHI; - if (InsertedVal == 0) { - InsertedPHI = InsertNewPHI(BB, VRC, MRI, TII); - InsertedVal = InsertedPHI->getOperand(0).getReg(); - } else { - InsertedPHI = MRI->getVRegDef(InsertedVal); + /// AddPHIOperand - Add the specified value as an operand of the PHI for + /// the specified predecessor block. + static void AddPHIOperand(MachineInstr *PHI, unsigned Val, + MachineBasicBlock *Pred) { + MachineInstrBuilder(*Pred->getParent(), PHI).addReg(Val).addMBB(Pred); } - // Fill in all the predecessors of the PHI. - MachineInstrBuilder MIB(InsertedPHI); - for (IncomingPredInfoTy::iterator I = - IncomingPredInfo.begin()+FirstPredInfoEntry, - E = IncomingPredInfo.end(); I != E; ++I) - MIB.addReg(I->second).addMBB(I->first); + /// InstrIsPHI - Check if an instruction is a PHI. + /// + static MachineInstr *InstrIsPHI(MachineInstr *I) { + if (I && I->isPHI()) + return I; + return nullptr; + } - // Drop the entries we added in IncomingPredInfo to restore the stack. - IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry, - IncomingPredInfo.end()); + /// ValueIsPHI - Check if the instruction that defines the specified register + /// is a PHI instruction. + static MachineInstr *ValueIsPHI(unsigned Val, MachineSSAUpdater *Updater) { + return InstrIsPHI(Updater->MRI->getVRegDef(Val)); + } - // See if the PHI node can be merged to a single value. This can happen in - // loop cases when we get a PHI of itself and one other value. - if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) { - MRI->replaceRegWith(InsertedVal, ConstVal); - InsertedPHI->eraseFromParent(); - InsertedVal = ConstVal; - } else { - DEBUG(errs() << " Inserted PHI: " << *InsertedPHI << "\n"); + /// ValueIsNewPHI - Like ValueIsPHI but also check if the PHI has no source + /// operands, i.e., it was just added. + static MachineInstr *ValueIsNewPHI(unsigned Val, MachineSSAUpdater *Updater) { + MachineInstr *PHI = ValueIsPHI(Val, Updater); + if (PHI && PHI->getNumOperands() <= 1) + return PHI; + return nullptr; + } - // If the client wants to know about all new instructions, tell it. - if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI); + /// GetPHIValue - For the specified PHI instruction, return the register + /// that it defines. + static unsigned GetPHIValue(MachineInstr *PHI) { + return PHI->getOperand(0).getReg(); } +}; + +} // End llvm namespace - return InsertedVal; +/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry +/// for the specified BB and if so, return it. If not, construct SSA form by +/// first calculating the required placement of PHIs and then inserting new +/// PHIs where needed. +unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){ + AvailableValsTy &AvailableVals = getAvailableVals(AV); + if (unsigned V = AvailableVals[BB]) + return V; + SSAUpdaterImpl Impl(this, &AvailableVals, InsertedPHIs); + return Impl.GetValue(BB); }