diff options
Diffstat (limited to 'contrib/llvm/lib/CodeGen/PHIElimination.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/PHIElimination.cpp | 143 |
1 files changed, 79 insertions, 64 deletions
diff --git a/contrib/llvm/lib/CodeGen/PHIElimination.cpp b/contrib/llvm/lib/CodeGen/PHIElimination.cpp index d4df4c5..5f7cf58 100644 --- a/contrib/llvm/lib/CodeGen/PHIElimination.cpp +++ b/contrib/llvm/lib/CodeGen/PHIElimination.cpp @@ -14,7 +14,7 @@ //===----------------------------------------------------------------------===// #define DEBUG_TYPE "phielim" -#include "PHIElimination.h" +#include "PHIEliminationUtils.h" #include "llvm/CodeGen/LiveVariables.h" #include "llvm/CodeGen/Passes.h" #include "llvm/CodeGen/MachineDominators.h" @@ -34,23 +34,72 @@ #include <map> using namespace llvm; +namespace { + class PHIElimination : public MachineFunctionPass { + MachineRegisterInfo *MRI; // Machine register information + + public: + static char ID; // Pass identification, replacement for typeid + PHIElimination() : MachineFunctionPass(ID) { + initializePHIEliminationPass(*PassRegistry::getPassRegistry()); + } + + virtual bool runOnMachineFunction(MachineFunction &Fn); + virtual void getAnalysisUsage(AnalysisUsage &AU) const; + + private: + /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions + /// in predecessor basic blocks. + /// + bool EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB); + void LowerAtomicPHINode(MachineBasicBlock &MBB, + MachineBasicBlock::iterator AfterPHIsIt); + + /// analyzePHINodes - Gather information about the PHI nodes in + /// here. In particular, we want to map the number of uses of a virtual + /// register which is used in a PHI node. We map that to the BB the + /// vreg is coming from. This is used later to determine when the vreg + /// is killed in the BB. + /// + void analyzePHINodes(const MachineFunction& Fn); + + /// Split critical edges where necessary for good coalescer performance. + bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB, + LiveVariables &LV, MachineLoopInfo *MLI); + + typedef std::pair<unsigned, unsigned> BBVRegPair; + typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse; + + VRegPHIUse VRegPHIUseCount; + + // Defs of PHI sources which are implicit_def. + SmallPtrSet<MachineInstr*, 4> ImpDefs; + + // Map reusable lowered PHI node -> incoming join register. + typedef DenseMap<MachineInstr*, unsigned, + MachineInstrExpressionTrait> LoweredPHIMap; + LoweredPHIMap LoweredPHIs; + }; +} + STATISTIC(NumAtomic, "Number of atomic phis lowered"); +STATISTIC(NumCriticalEdgesSplit, "Number of critical edges split"); STATISTIC(NumReused, "Number of reused lowered phis"); char PHIElimination::ID = 0; INITIALIZE_PASS(PHIElimination, "phi-node-elimination", - "Eliminate PHI nodes for register allocation", false, false); + "Eliminate PHI nodes for register allocation", false, false) -char &llvm::PHIEliminationID = PHIElimination::ID; +char& llvm::PHIEliminationID = PHIElimination::ID; -void llvm::PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const { +void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const { AU.addPreserved<LiveVariables>(); AU.addPreserved<MachineDominatorTree>(); AU.addPreserved<MachineLoopInfo>(); MachineFunctionPass::getAnalysisUsage(AU); } -bool llvm::PHIElimination::runOnMachineFunction(MachineFunction &MF) { +bool PHIElimination::runOnMachineFunction(MachineFunction &MF) { MRI = &MF.getRegInfo(); bool Changed = false; @@ -93,14 +142,14 @@ bool llvm::PHIElimination::runOnMachineFunction(MachineFunction &MF) { /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in /// predecessor basic blocks. /// -bool llvm::PHIElimination::EliminatePHINodes(MachineFunction &MF, +bool PHIElimination::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) { if (MBB.empty() || !MBB.front().isPHI()) return false; // Quick exit for basic blocks without PHIs. // Get an iterator to the first instruction after the last PHI node (this may // also be the end of the basic block). - MachineBasicBlock::iterator AfterPHIsIt = SkipPHIsAndLabels(MBB, MBB.begin()); + MachineBasicBlock::iterator AfterPHIsIt = MBB.SkipPHIsAndLabels(MBB.begin()); while (MBB.front().isPHI()) LowerAtomicPHINode(MBB, AfterPHIsIt); @@ -121,58 +170,14 @@ static bool isSourceDefinedByImplicitDef(const MachineInstr *MPhi, return true; } -// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from SrcReg -// when following the CFG edge to SuccMBB. This needs to be after any def of -// SrcReg, but before any subsequent point where control flow might jump out of -// the basic block. -MachineBasicBlock::iterator -llvm::PHIElimination::FindCopyInsertPoint(MachineBasicBlock &MBB, - MachineBasicBlock &SuccMBB, - unsigned SrcReg) { - // Handle the trivial case trivially. - if (MBB.empty()) - return MBB.begin(); - - // Usually, we just want to insert the copy before the first terminator - // instruction. However, for the edge going to a landing pad, we must insert - // the copy before the call/invoke instruction. - if (!SuccMBB.isLandingPad()) - return MBB.getFirstTerminator(); - - // Discover any defs/uses in this basic block. - SmallPtrSet<MachineInstr*, 8> DefUsesInMBB; - for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg), - RE = MRI->reg_end(); RI != RE; ++RI) { - MachineInstr *DefUseMI = &*RI; - if (DefUseMI->getParent() == &MBB) - DefUsesInMBB.insert(DefUseMI); - } - MachineBasicBlock::iterator InsertPoint; - if (DefUsesInMBB.empty()) { - // No defs. Insert the copy at the start of the basic block. - InsertPoint = MBB.begin(); - } else if (DefUsesInMBB.size() == 1) { - // Insert the copy immediately after the def/use. - InsertPoint = *DefUsesInMBB.begin(); - ++InsertPoint; - } else { - // Insert the copy immediately after the last def/use. - InsertPoint = MBB.end(); - while (!DefUsesInMBB.count(&*--InsertPoint)) {} - ++InsertPoint; - } - - // Make sure the copy goes after any phi nodes however. - return SkipPHIsAndLabels(MBB, InsertPoint); -} /// LowerAtomicPHINode - Lower the PHI node at the top of the specified block, /// under the assuption that it needs to be lowered in a way that supports /// atomic execution of PHIs. This lowering method is always correct all of the /// time. /// -void llvm::PHIElimination::LowerAtomicPHINode( +void PHIElimination::LowerAtomicPHINode( MachineBasicBlock &MBB, MachineBasicBlock::iterator AfterPHIsIt) { ++NumAtomic; @@ -207,7 +212,7 @@ void llvm::PHIElimination::LowerAtomicPHINode( IncomingReg = entry; reusedIncoming = true; ++NumReused; - DEBUG(dbgs() << "Reusing %reg" << IncomingReg << " for " << *MPhi); + DEBUG(dbgs() << "Reusing " << PrintReg(IncomingReg) << " for " << *MPhi); } else { const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(DestReg); entry = IncomingReg = MF.getRegInfo().createVirtualRegister(RC); @@ -294,7 +299,7 @@ void llvm::PHIElimination::LowerAtomicPHINode( // Find a safe location to insert the copy, this may be the first terminator // in the block (or end()). MachineBasicBlock::iterator InsertPos = - FindCopyInsertPoint(opBlock, MBB, SrcReg); + findPHICopyInsertPoint(&opBlock, &MBB, SrcReg); // Insert the copy. if (!reusedIncoming && IncomingReg) @@ -335,6 +340,8 @@ void llvm::PHIElimination::LowerAtomicPHINode( #ifndef NDEBUG for (MachineBasicBlock::iterator TI = llvm::next(Term); TI != opBlock.end(); ++TI) { + if (TI->isDebugValue()) + continue; assert(!TI->readsRegister(SrcReg) && "Terminator instructions cannot use virtual registers unless" "they are the first terminator in a block!"); @@ -343,9 +350,13 @@ void llvm::PHIElimination::LowerAtomicPHINode( } else if (reusedIncoming || !IncomingReg) { // We may have to rewind a bit if we didn't insert a copy this time. KillInst = Term; - while (KillInst != opBlock.begin()) - if ((--KillInst)->readsRegister(SrcReg)) + while (KillInst != opBlock.begin()) { + --KillInst; + if (KillInst->isDebugValue()) + continue; + if (KillInst->readsRegister(SrcReg)) break; + } } else { // We just inserted this copy. KillInst = prior(InsertPos); @@ -371,7 +382,7 @@ void llvm::PHIElimination::LowerAtomicPHINode( /// used in a PHI node. We map that to the BB the vreg is coming from. This is /// used later to determine when the vreg is killed in the BB. /// -void llvm::PHIElimination::analyzePHINodes(const MachineFunction& MF) { +void PHIElimination::analyzePHINodes(const MachineFunction& MF) { for (MachineFunction::const_iterator I = MF.begin(), E = MF.end(); I != E; ++I) for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end(); @@ -381,10 +392,10 @@ void llvm::PHIElimination::analyzePHINodes(const MachineFunction& MF) { BBI->getOperand(i).getReg())]; } -bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF, - MachineBasicBlock &MBB, - LiveVariables &LV, - MachineLoopInfo *MLI) { +bool PHIElimination::SplitPHIEdges(MachineFunction &MF, + MachineBasicBlock &MBB, + LiveVariables &LV, + MachineLoopInfo *MLI) { if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad()) return false; // Quick exit for basic blocks without PHIs. @@ -403,10 +414,14 @@ bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF, !LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB)) { if (!MLI || !(MLI->getLoopFor(PreMBB) == MLI->getLoopFor(&MBB) && - MLI->isLoopHeader(&MBB))) - Changed |= PreMBB->SplitCriticalEdge(&MBB, this) != 0; + MLI->isLoopHeader(&MBB))) { + if (PreMBB->SplitCriticalEdge(&MBB, this)) { + Changed = true; + ++NumCriticalEdgesSplit; + } + } } } } - return true; + return Changed; } |
