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Diffstat (limited to 'contrib/llvm/lib/CodeGen/SplitKit.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/SplitKit.cpp | 1097 |
1 files changed, 1097 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/SplitKit.cpp b/contrib/llvm/lib/CodeGen/SplitKit.cpp new file mode 100644 index 0000000..29474f0 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/SplitKit.cpp @@ -0,0 +1,1097 @@ +//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains the SplitAnalysis class as well as mutator functions for +// live range splitting. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "splitter" +#include "SplitKit.h" +#include "VirtRegMap.h" +#include "llvm/CodeGen/CalcSpillWeights.h" +#include "llvm/CodeGen/LiveIntervalAnalysis.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineLoopInfo.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetMachine.h" + +using namespace llvm; + +static cl::opt<bool> +AllowSplit("spiller-splits-edges", + cl::desc("Allow critical edge splitting during spilling")); + +//===----------------------------------------------------------------------===// +// Split Analysis +//===----------------------------------------------------------------------===// + +SplitAnalysis::SplitAnalysis(const MachineFunction &mf, + const LiveIntervals &lis, + const MachineLoopInfo &mli) + : mf_(mf), + lis_(lis), + loops_(mli), + tii_(*mf.getTarget().getInstrInfo()), + curli_(0) {} + +void SplitAnalysis::clear() { + usingInstrs_.clear(); + usingBlocks_.clear(); + usingLoops_.clear(); + curli_ = 0; +} + +bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) { + MachineBasicBlock *T, *F; + SmallVector<MachineOperand, 4> Cond; + return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond); +} + +/// analyzeUses - Count instructions, basic blocks, and loops using curli. +void SplitAnalysis::analyzeUses() { + const MachineRegisterInfo &MRI = mf_.getRegInfo(); + for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg); + MachineInstr *MI = I.skipInstruction();) { + if (MI->isDebugValue() || !usingInstrs_.insert(MI)) + continue; + MachineBasicBlock *MBB = MI->getParent(); + if (usingBlocks_[MBB]++) + continue; + if (MachineLoop *Loop = loops_.getLoopFor(MBB)) + usingLoops_[Loop]++; + } + DEBUG(dbgs() << " counted " + << usingInstrs_.size() << " instrs, " + << usingBlocks_.size() << " blocks, " + << usingLoops_.size() << " loops.\n"); +} + +/// removeUse - Update statistics by noting that MI no longer uses curli. +void SplitAnalysis::removeUse(const MachineInstr *MI) { + if (!usingInstrs_.erase(MI)) + return; + + // Decrement MBB count. + const MachineBasicBlock *MBB = MI->getParent(); + BlockCountMap::iterator bi = usingBlocks_.find(MBB); + assert(bi != usingBlocks_.end() && "MBB missing"); + assert(bi->second && "0 count in map"); + if (--bi->second) + return; + // No more uses in MBB. + usingBlocks_.erase(bi); + + // Decrement loop count. + MachineLoop *Loop = loops_.getLoopFor(MBB); + if (!Loop) + return; + LoopCountMap::iterator li = usingLoops_.find(Loop); + assert(li != usingLoops_.end() && "Loop missing"); + assert(li->second && "0 count in map"); + if (--li->second) + return; + // No more blocks in Loop. + usingLoops_.erase(li); +} + +// Get three sets of basic blocks surrounding a loop: Blocks inside the loop, +// predecessor blocks, and exit blocks. +void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) { + Blocks.clear(); + + // Blocks in the loop. + Blocks.Loop.insert(Loop->block_begin(), Loop->block_end()); + + // Predecessor blocks. + const MachineBasicBlock *Header = Loop->getHeader(); + for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(), + E = Header->pred_end(); I != E; ++I) + if (!Blocks.Loop.count(*I)) + Blocks.Preds.insert(*I); + + // Exit blocks. + for (MachineLoop::block_iterator I = Loop->block_begin(), + E = Loop->block_end(); I != E; ++I) { + const MachineBasicBlock *MBB = *I; + for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(), + SE = MBB->succ_end(); SI != SE; ++SI) + if (!Blocks.Loop.count(*SI)) + Blocks.Exits.insert(*SI); + } +} + +/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in +/// and around the Loop. +SplitAnalysis::LoopPeripheralUse SplitAnalysis:: +analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) { + LoopPeripheralUse use = ContainedInLoop; + for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end(); + I != E; ++I) { + const MachineBasicBlock *MBB = I->first; + // Is this a peripheral block? + if (use < MultiPeripheral && + (Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) { + if (I->second > 1) use = MultiPeripheral; + else use = SinglePeripheral; + continue; + } + // Is it a loop block? + if (Blocks.Loop.count(MBB)) + continue; + // It must be an unrelated block. + return OutsideLoop; + } + return use; +} + +/// getCriticalExits - It may be necessary to partially break critical edges +/// leaving the loop if an exit block has phi uses of curli. Collect the exit +/// blocks that need special treatment into CriticalExits. +void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks, + BlockPtrSet &CriticalExits) { + CriticalExits.clear(); + + // A critical exit block contains a phi def of curli, and has a predecessor + // that is not in the loop nor a loop predecessor. + // For such an exit block, the edges carrying the new variable must be moved + // to a new pre-exit block. + for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end(); + I != E; ++I) { + const MachineBasicBlock *Succ = *I; + SlotIndex SuccIdx = lis_.getMBBStartIdx(Succ); + VNInfo *SuccVNI = curli_->getVNInfoAt(SuccIdx); + // This exit may not have curli live in at all. No need to split. + if (!SuccVNI) + continue; + // If this is not a PHI def, it is either using a value from before the + // loop, or a value defined inside the loop. Both are safe. + if (!SuccVNI->isPHIDef() || SuccVNI->def.getBaseIndex() != SuccIdx) + continue; + // This exit block does have a PHI. Does it also have a predecessor that is + // not a loop block or loop predecessor? + for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(), + PE = Succ->pred_end(); PI != PE; ++PI) { + const MachineBasicBlock *Pred = *PI; + if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred)) + continue; + // This is a critical exit block, and we need to split the exit edge. + CriticalExits.insert(Succ); + break; + } + } +} + +/// canSplitCriticalExits - Return true if it is possible to insert new exit +/// blocks before the blocks in CriticalExits. +bool +SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks, + BlockPtrSet &CriticalExits) { + // If we don't allow critical edge splitting, require no critical exits. + if (!AllowSplit) + return CriticalExits.empty(); + + for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end(); + I != E; ++I) { + const MachineBasicBlock *Succ = *I; + // We want to insert a new pre-exit MBB before Succ, and change all the + // in-loop blocks to branch to the pre-exit instead of Succ. + // Check that all the in-loop predecessors can be changed. + for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(), + PE = Succ->pred_end(); PI != PE; ++PI) { + const MachineBasicBlock *Pred = *PI; + // The external predecessors won't be altered. + if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred)) + continue; + if (!canAnalyzeBranch(Pred)) + return false; + } + + // If Succ's layout predecessor falls through, that too must be analyzable. + // We need to insert the pre-exit block in the gap. + MachineFunction::const_iterator MFI = Succ; + if (MFI == mf_.begin()) + continue; + if (!canAnalyzeBranch(--MFI)) + return false; + } + // No problems found. + return true; +} + +void SplitAnalysis::analyze(const LiveInterval *li) { + clear(); + curli_ = li; + analyzeUses(); +} + +const MachineLoop *SplitAnalysis::getBestSplitLoop() { + assert(curli_ && "Call analyze() before getBestSplitLoop"); + if (usingLoops_.empty()) + return 0; + + LoopPtrSet Loops, SecondLoops; + LoopBlocks Blocks; + BlockPtrSet CriticalExits; + + // Find first-class and second class candidate loops. + // We prefer to split around loops where curli is used outside the periphery. + for (LoopCountMap::const_iterator I = usingLoops_.begin(), + E = usingLoops_.end(); I != E; ++I) { + const MachineLoop *Loop = I->first; + getLoopBlocks(Loop, Blocks); + + // FIXME: We need an SSA updater to properly handle multiple exit blocks. + if (Blocks.Exits.size() > 1) { + DEBUG(dbgs() << " multiple exits from " << *Loop); + continue; + } + + LoopPtrSet *LPS = 0; + switch(analyzeLoopPeripheralUse(Blocks)) { + case OutsideLoop: + LPS = &Loops; + break; + case MultiPeripheral: + LPS = &SecondLoops; + break; + case ContainedInLoop: + DEBUG(dbgs() << " contained in " << *Loop); + continue; + case SinglePeripheral: + DEBUG(dbgs() << " single peripheral use in " << *Loop); + continue; + } + // Will it be possible to split around this loop? + getCriticalExits(Blocks, CriticalExits); + DEBUG(dbgs() << " " << CriticalExits.size() << " critical exits from " + << *Loop); + if (!canSplitCriticalExits(Blocks, CriticalExits)) + continue; + // This is a possible split. + assert(LPS); + LPS->insert(Loop); + } + + DEBUG(dbgs() << " getBestSplitLoop found " << Loops.size() << " + " + << SecondLoops.size() << " candidate loops.\n"); + + // If there are no first class loops available, look at second class loops. + if (Loops.empty()) + Loops = SecondLoops; + + if (Loops.empty()) + return 0; + + // Pick the earliest loop. + // FIXME: Are there other heuristics to consider? + const MachineLoop *Best = 0; + SlotIndex BestIdx; + for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E; + ++I) { + SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader()); + if (!Best || Idx < BestIdx) + Best = *I, BestIdx = Idx; + } + DEBUG(dbgs() << " getBestSplitLoop found " << *Best); + return Best; +} + +/// getMultiUseBlocks - if curli has more than one use in a basic block, it +/// may be an advantage to split curli for the duration of the block. +bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) { + // If curli is local to one block, there is no point to splitting it. + if (usingBlocks_.size() <= 1) + return false; + // Add blocks with multiple uses. + for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end(); + I != E; ++I) + switch (I->second) { + case 0: + case 1: + continue; + case 2: { + // It doesn't pay to split a 2-instr block if it redefines curli. + VNInfo *VN1 = curli_->getVNInfoAt(lis_.getMBBStartIdx(I->first)); + VNInfo *VN2 = + curli_->getVNInfoAt(lis_.getMBBEndIdx(I->first).getPrevIndex()); + // live-in and live-out with a different value. + if (VN1 && VN2 && VN1 != VN2) + continue; + } // Fall through. + default: + Blocks.insert(I->first); + } + return !Blocks.empty(); +} + +//===----------------------------------------------------------------------===// +// LiveIntervalMap +//===----------------------------------------------------------------------===// + +// defValue - Introduce a li_ def for ParentVNI that could be later than +// ParentVNI->def. +VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) { + assert(ParentVNI && "Mapping NULL value"); + assert(Idx.isValid() && "Invalid SlotIndex"); + assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI"); + + // Is this a simple 1-1 mapping? Not likely. + if (Idx == ParentVNI->def) + return mapValue(ParentVNI, Idx); + + // This is a complex def. Mark with a NULL in valueMap. + VNInfo *OldVNI = + valueMap_.insert( + ValueMap::value_type(ParentVNI, static_cast<VNInfo *>(0))).first->second; + // The static_cast<VNInfo *> is only needed to work around a bug in an + // old version of the C++0x standard which the following compilers + // implemented and have yet to fix: + // + // Microsoft Visual Studio 2010 Version 10.0.30319.1 RTMRel + // Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01 + // + // If/When we move to C++0x, this can be replaced by nullptr. + (void)OldVNI; + assert(OldVNI == 0 && "Simple/Complex values mixed"); + + // Should we insert a minimal snippet of VNI LiveRange, or can we count on + // callers to do that? We need it for lookups of complex values. + VNInfo *VNI = li_.getNextValue(Idx, 0, true, lis_.getVNInfoAllocator()); + return VNI; +} + +// mapValue - Find the mapped value for ParentVNI at Idx. +// Potentially create phi-def values. +VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx) { + assert(ParentVNI && "Mapping NULL value"); + assert(Idx.isValid() && "Invalid SlotIndex"); + assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI"); + + // Use insert for lookup, so we can add missing values with a second lookup. + std::pair<ValueMap::iterator,bool> InsP = + valueMap_.insert(ValueMap::value_type(ParentVNI, static_cast<VNInfo *>(0))); + // The static_cast<VNInfo *> is only needed to work around a bug in an + // old version of the C++0x standard which the following compilers + // implemented and have yet to fix: + // + // Microsoft Visual Studio 2010 Version 10.0.30319.1 RTMRel + // Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01 + // + // If/When we move to C++0x, this can be replaced by nullptr. + + // This was an unknown value. Create a simple mapping. + if (InsP.second) + return InsP.first->second = li_.createValueCopy(ParentVNI, + lis_.getVNInfoAllocator()); + // This was a simple mapped value. + if (InsP.first->second) + return InsP.first->second; + + // This is a complex mapped value. There may be multiple defs, and we may need + // to create phi-defs. + MachineBasicBlock *IdxMBB = lis_.getMBBFromIndex(Idx); + assert(IdxMBB && "No MBB at Idx"); + + // Is there a def in the same MBB we can extend? + if (VNInfo *VNI = extendTo(IdxMBB, Idx)) + return VNI; + + // Now for the fun part. We know that ParentVNI potentially has multiple defs, + // and we may need to create even more phi-defs to preserve VNInfo SSA form. + // Perform a depth-first search for predecessor blocks where we know the + // dominating VNInfo. Insert phi-def VNInfos along the path back to IdxMBB. + + // Track MBBs where we have created or learned the dominating value. + // This may change during the DFS as we create new phi-defs. + typedef DenseMap<MachineBasicBlock*, VNInfo*> MBBValueMap; + MBBValueMap DomValue; + + for (idf_iterator<MachineBasicBlock*> + IDFI = idf_begin(IdxMBB), + IDFE = idf_end(IdxMBB); IDFI != IDFE;) { + MachineBasicBlock *MBB = *IDFI; + SlotIndex End = lis_.getMBBEndIdx(MBB); + + // We are operating on the restricted CFG where ParentVNI is live. + if (parentli_.getVNInfoAt(End.getPrevSlot()) != ParentVNI) { + IDFI.skipChildren(); + continue; + } + + // Do we have a dominating value in this block? + VNInfo *VNI = extendTo(MBB, End); + if (!VNI) { + ++IDFI; + continue; + } + + // Yes, VNI dominates MBB. Track the path back to IdxMBB, creating phi-defs + // as needed along the way. + for (unsigned PI = IDFI.getPathLength()-1; PI != 0; --PI) { + // Start from MBB's immediate successor. End at IdxMBB. + MachineBasicBlock *Succ = IDFI.getPath(PI-1); + std::pair<MBBValueMap::iterator, bool> InsP = + DomValue.insert(MBBValueMap::value_type(Succ, VNI)); + + // This is the first time we backtrack to Succ. + if (InsP.second) + continue; + + // We reached Succ again with the same VNI. Nothing is going to change. + VNInfo *OVNI = InsP.first->second; + if (OVNI == VNI) + break; + + // Succ already has a phi-def. No need to continue. + SlotIndex Start = lis_.getMBBStartIdx(Succ); + if (OVNI->def == Start) + break; + + // We have a collision between the old and new VNI at Succ. That means + // neither dominates and we need a new phi-def. + VNI = li_.getNextValue(Start, 0, true, lis_.getVNInfoAllocator()); + VNI->setIsPHIDef(true); + InsP.first->second = VNI; + + // Replace OVNI with VNI in the remaining path. + for (; PI > 1 ; --PI) { + MBBValueMap::iterator I = DomValue.find(IDFI.getPath(PI-2)); + if (I == DomValue.end() || I->second != OVNI) + break; + I->second = VNI; + } + } + + // No need to search the children, we found a dominating value. + IDFI.skipChildren(); + } + + // The search should at least find a dominating value for IdxMBB. + assert(!DomValue.empty() && "Couldn't find a reaching definition"); + + // Since we went through the trouble of a full DFS visiting all reaching defs, + // the values in DomValue are now accurate. No more phi-defs are needed for + // these blocks, so we can color the live ranges. + // This makes the next mapValue call much faster. + VNInfo *IdxVNI = 0; + for (MBBValueMap::iterator I = DomValue.begin(), E = DomValue.end(); I != E; + ++I) { + MachineBasicBlock *MBB = I->first; + VNInfo *VNI = I->second; + SlotIndex Start = lis_.getMBBStartIdx(MBB); + if (MBB == IdxMBB) { + // Don't add full liveness to IdxMBB, stop at Idx. + if (Start != Idx) + li_.addRange(LiveRange(Start, Idx, VNI)); + // The caller had better add some liveness to IdxVNI, or it leaks. + IdxVNI = VNI; + } else + li_.addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); + } + + assert(IdxVNI && "Didn't find value for Idx"); + return IdxVNI; +} + +// extendTo - Find the last li_ value defined in MBB at or before Idx. The +// parentli_ is assumed to be live at Idx. Extend the live range to Idx. +// Return the found VNInfo, or NULL. +VNInfo *LiveIntervalMap::extendTo(MachineBasicBlock *MBB, SlotIndex Idx) { + LiveInterval::iterator I = std::upper_bound(li_.begin(), li_.end(), Idx); + if (I == li_.begin()) + return 0; + --I; + if (I->start < lis_.getMBBStartIdx(MBB)) + return 0; + if (I->end < Idx) + I->end = Idx; + return I->valno; +} + +// addSimpleRange - Add a simple range from parentli_ to li_. +// ParentVNI must be live in the [Start;End) interval. +void LiveIntervalMap::addSimpleRange(SlotIndex Start, SlotIndex End, + const VNInfo *ParentVNI) { + VNInfo *VNI = mapValue(ParentVNI, Start); + // A simple mappoing is easy. + if (VNI->def == ParentVNI->def) { + li_.addRange(LiveRange(Start, End, VNI)); + return; + } + + // ParentVNI is a complex value. We must map per MBB. + MachineFunction::iterator MBB = lis_.getMBBFromIndex(Start); + MachineFunction::iterator MBBE = lis_.getMBBFromIndex(End); + + if (MBB == MBBE) { + li_.addRange(LiveRange(Start, End, VNI)); + return; + } + + // First block. + li_.addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI)); + + // Run sequence of full blocks. + for (++MBB; MBB != MBBE; ++MBB) { + Start = lis_.getMBBStartIdx(MBB); + li_.addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), + mapValue(ParentVNI, Start))); + } + + // Final block. + Start = lis_.getMBBStartIdx(MBB); + if (Start != End) + li_.addRange(LiveRange(Start, End, mapValue(ParentVNI, Start))); +} + +/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_. +/// All needed values whose def is not inside [Start;End) must be defined +/// beforehand so mapValue will work. +void LiveIntervalMap::addRange(SlotIndex Start, SlotIndex End) { + LiveInterval::const_iterator B = parentli_.begin(), E = parentli_.end(); + LiveInterval::const_iterator I = std::lower_bound(B, E, Start); + + // Check if --I begins before Start and overlaps. + if (I != B) { + --I; + if (I->end > Start) + addSimpleRange(Start, std::min(End, I->end), I->valno); + ++I; + } + + // The remaining ranges begin after Start. + for (;I != E && I->start < End; ++I) + addSimpleRange(I->start, std::min(End, I->end), I->valno); +} + +//===----------------------------------------------------------------------===// +// Split Editor +//===----------------------------------------------------------------------===// + +/// Create a new SplitEditor for editing the LiveInterval analyzed by SA. +SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm, + SmallVectorImpl<LiveInterval*> &intervals) + : sa_(sa), lis_(lis), vrm_(vrm), + mri_(vrm.getMachineFunction().getRegInfo()), + tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()), + curli_(sa_.getCurLI()), + dupli_(0), openli_(0), + intervals_(intervals), + firstInterval(intervals_.size()) +{ + assert(curli_ && "SplitEditor created from empty SplitAnalysis"); + + // Make sure curli_ is assigned a stack slot, so all our intervals get the + // same slot as curli_. + if (vrm_.getStackSlot(curli_->reg) == VirtRegMap::NO_STACK_SLOT) + vrm_.assignVirt2StackSlot(curli_->reg); + +} + +LiveInterval *SplitEditor::createInterval() { + unsigned curli = sa_.getCurLI()->reg; + unsigned Reg = mri_.createVirtualRegister(mri_.getRegClass(curli)); + LiveInterval &Intv = lis_.getOrCreateInterval(Reg); + vrm_.grow(); + vrm_.assignVirt2StackSlot(Reg, vrm_.getStackSlot(curli)); + return &Intv; +} + +LiveInterval *SplitEditor::getDupLI() { + if (!dupli_) { + // Create an interval for dupli that is a copy of curli. + dupli_ = createInterval(); + dupli_->Copy(*curli_, &mri_, lis_.getVNInfoAllocator()); + } + return dupli_; +} + +VNInfo *SplitEditor::mapValue(const VNInfo *curliVNI) { + VNInfo *&VNI = valueMap_[curliVNI]; + if (!VNI) + VNI = openli_->createValueCopy(curliVNI, lis_.getVNInfoAllocator()); + return VNI; +} + +/// Insert a COPY instruction curli -> li. Allocate a new value from li +/// defined by the COPY. Note that rewrite() will deal with the curli +/// register, so this function can be used to copy from any interval - openli, +/// curli, or dupli. +VNInfo *SplitEditor::insertCopy(LiveInterval &LI, + MachineBasicBlock &MBB, + MachineBasicBlock::iterator I) { + MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY), + LI.reg).addReg(curli_->reg); + SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex(); + return LI.getNextValue(DefIdx, MI, true, lis_.getVNInfoAllocator()); +} + +/// Create a new virtual register and live interval. +void SplitEditor::openIntv() { + assert(!openli_ && "Previous LI not closed before openIntv"); + openli_ = createInterval(); + intervals_.push_back(openli_); + liveThrough_ = false; +} + +/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is +/// not live before Idx, a COPY is not inserted. +void SplitEditor::enterIntvBefore(SlotIndex Idx) { + assert(openli_ && "openIntv not called before enterIntvBefore"); + + // Copy from curli_ if it is live. + if (VNInfo *CurVNI = curli_->getVNInfoAt(Idx.getUseIndex())) { + MachineInstr *MI = lis_.getInstructionFromIndex(Idx); + assert(MI && "enterIntvBefore called with invalid index"); + VNInfo *VNI = insertCopy(*openli_, *MI->getParent(), MI); + openli_->addRange(LiveRange(VNI->def, Idx.getDefIndex(), VNI)); + + // Make sure CurVNI is properly mapped. + VNInfo *&mapVNI = valueMap_[CurVNI]; + // We dont have SSA update yet, so only one entry per value is allowed. + assert(!mapVNI && "enterIntvBefore called more than once for the same value"); + mapVNI = VNI; + } + DEBUG(dbgs() << " enterIntvBefore " << Idx << ": " << *openli_ << '\n'); +} + +/// enterIntvAtEnd - Enter openli at the end of MBB. +/// PhiMBB is a successor inside openli where a PHI value is created. +/// Currently, all entries must share the same PhiMBB. +void SplitEditor::enterIntvAtEnd(MachineBasicBlock &A, MachineBasicBlock &B) { + assert(openli_ && "openIntv not called before enterIntvAtEnd"); + + SlotIndex EndA = lis_.getMBBEndIdx(&A); + VNInfo *CurVNIA = curli_->getVNInfoAt(EndA.getPrevIndex()); + if (!CurVNIA) { + DEBUG(dbgs() << " enterIntvAtEnd, curli not live out of BB#" + << A.getNumber() << ".\n"); + return; + } + + // Add a phi kill value and live range out of A. + VNInfo *VNIA = insertCopy(*openli_, A, A.getFirstTerminator()); + openli_->addRange(LiveRange(VNIA->def, EndA, VNIA)); + + // FIXME: If this is the only entry edge, we don't need the extra PHI value. + // FIXME: If there are multiple entry blocks (so not a loop), we need proper + // SSA update. + + // Now look at the start of B. + SlotIndex StartB = lis_.getMBBStartIdx(&B); + SlotIndex EndB = lis_.getMBBEndIdx(&B); + const LiveRange *CurB = curli_->getLiveRangeContaining(StartB); + if (!CurB) { + DEBUG(dbgs() << " enterIntvAtEnd: curli not live in to BB#" + << B.getNumber() << ".\n"); + return; + } + + VNInfo *VNIB = openli_->getVNInfoAt(StartB); + if (!VNIB) { + // Create a phi value. + VNIB = openli_->getNextValue(SlotIndex(StartB, true), 0, false, + lis_.getVNInfoAllocator()); + VNIB->setIsPHIDef(true); + VNInfo *&mapVNI = valueMap_[CurB->valno]; + if (mapVNI) { + // Multiple copies - must create PHI value. + abort(); + } else { + // This is the first copy of dupLR. Mark the mapping. + mapVNI = VNIB; + } + + } + + DEBUG(dbgs() << " enterIntvAtEnd: " << *openli_ << '\n'); +} + +/// useIntv - indicate that all instructions in MBB should use openli. +void SplitEditor::useIntv(const MachineBasicBlock &MBB) { + useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB)); +} + +void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) { + assert(openli_ && "openIntv not called before useIntv"); + + // Map the curli values from the interval into openli_ + LiveInterval::const_iterator B = curli_->begin(), E = curli_->end(); + LiveInterval::const_iterator I = std::lower_bound(B, E, Start); + + if (I != B) { + --I; + // I begins before Start, but overlaps. + if (I->end > Start) + openli_->addRange(LiveRange(Start, std::min(End, I->end), + mapValue(I->valno))); + ++I; + } + + // The remaining ranges begin after Start. + for (;I != E && I->start < End; ++I) + openli_->addRange(LiveRange(I->start, std::min(End, I->end), + mapValue(I->valno))); + DEBUG(dbgs() << " use [" << Start << ';' << End << "): " << *openli_ + << '\n'); +} + +/// leaveIntvAfter - Leave openli after the instruction at Idx. +void SplitEditor::leaveIntvAfter(SlotIndex Idx) { + assert(openli_ && "openIntv not called before leaveIntvAfter"); + + const LiveRange *CurLR = curli_->getLiveRangeContaining(Idx.getDefIndex()); + if (!CurLR || CurLR->end <= Idx.getBoundaryIndex()) { + DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": not live\n"); + return; + } + + // Was this value of curli live through openli? + if (!openli_->liveAt(CurLR->valno->def)) { + DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": using external value\n"); + liveThrough_ = true; + return; + } + + // We are going to insert a back copy, so we must have a dupli_. + LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Idx.getDefIndex()); + assert(DupLR && "dupli not live into black, but curli is?"); + + // Insert the COPY instruction. + MachineBasicBlock::iterator I = lis_.getInstructionFromIndex(Idx); + MachineInstr *MI = BuildMI(*I->getParent(), llvm::next(I), I->getDebugLoc(), + tii_.get(TargetOpcode::COPY), dupli_->reg) + .addReg(openli_->reg); + SlotIndex CopyIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex(); + openli_->addRange(LiveRange(Idx.getDefIndex(), CopyIdx, + mapValue(CurLR->valno))); + DupLR->valno->def = CopyIdx; + DEBUG(dbgs() << " leaveIntvAfter " << Idx << ": " << *openli_ << '\n'); +} + +/// leaveIntvAtTop - Leave the interval at the top of MBB. +/// Currently, only one value can leave the interval. +void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) { + assert(openli_ && "openIntv not called before leaveIntvAtTop"); + + SlotIndex Start = lis_.getMBBStartIdx(&MBB); + const LiveRange *CurLR = curli_->getLiveRangeContaining(Start); + + // Is curli even live-in to MBB? + if (!CurLR) { + DEBUG(dbgs() << " leaveIntvAtTop at " << Start << ": not live\n"); + return; + } + + // Is curli defined by PHI at the beginning of MBB? + bool isPHIDef = CurLR->valno->isPHIDef() && + CurLR->valno->def.getBaseIndex() == Start; + + // If MBB is using a value of curli that was defined outside the openli range, + // we don't want to copy it back here. + if (!isPHIDef && !openli_->liveAt(CurLR->valno->def)) { + DEBUG(dbgs() << " leaveIntvAtTop at " << Start + << ": using external value\n"); + liveThrough_ = true; + return; + } + + // We are going to insert a back copy, so we must have a dupli_. + LiveRange *DupLR = getDupLI()->getLiveRangeContaining(Start); + assert(DupLR && "dupli not live into black, but curli is?"); + + // Insert the COPY instruction. + MachineInstr *MI = BuildMI(MBB, MBB.begin(), DebugLoc(), + tii_.get(TargetOpcode::COPY), dupli_->reg) + .addReg(openli_->reg); + SlotIndex Idx = lis_.InsertMachineInstrInMaps(MI).getDefIndex(); + + // Adjust dupli and openli values. + if (isPHIDef) { + // dupli was already a PHI on entry to MBB. Simply insert an openli PHI, + // and shift the dupli def down to the COPY. + VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false, + lis_.getVNInfoAllocator()); + VNI->setIsPHIDef(true); + openli_->addRange(LiveRange(VNI->def, Idx, VNI)); + + dupli_->removeRange(Start, Idx); + DupLR->valno->def = Idx; + DupLR->valno->setIsPHIDef(false); + } else { + // The dupli value was defined somewhere inside the openli range. + DEBUG(dbgs() << " leaveIntvAtTop source value defined at " + << DupLR->valno->def << "\n"); + // FIXME: We may not need a PHI here if all predecessors have the same + // value. + VNInfo *VNI = openli_->getNextValue(SlotIndex(Start, true), 0, false, + lis_.getVNInfoAllocator()); + VNI->setIsPHIDef(true); + openli_->addRange(LiveRange(VNI->def, Idx, VNI)); + + // FIXME: What if DupLR->valno is used by multiple exits? SSA Update. + + // closeIntv is going to remove the superfluous live ranges. + DupLR->valno->def = Idx; + DupLR->valno->setIsPHIDef(false); + } + + DEBUG(dbgs() << " leaveIntvAtTop at " << Idx << ": " << *openli_ << '\n'); +} + +/// closeIntv - Indicate that we are done editing the currently open +/// LiveInterval, and ranges can be trimmed. +void SplitEditor::closeIntv() { + assert(openli_ && "openIntv not called before closeIntv"); + + DEBUG(dbgs() << " closeIntv cleaning up\n"); + DEBUG(dbgs() << " open " << *openli_ << '\n'); + + if (liveThrough_) { + DEBUG(dbgs() << " value live through region, leaving dupli as is.\n"); + } else { + // live out with copies inserted, or killed by region. Either way we need to + // remove the overlapping region from dupli. + getDupLI(); + for (LiveInterval::iterator I = openli_->begin(), E = openli_->end(); + I != E; ++I) { + dupli_->removeRange(I->start, I->end); + } + // FIXME: A block branching to the entry block may also branch elsewhere + // curli is live. We need both openli and curli to be live in that case. + DEBUG(dbgs() << " dup2 " << *dupli_ << '\n'); + } + openli_ = 0; + valueMap_.clear(); +} + +/// rewrite - after all the new live ranges have been created, rewrite +/// instructions using curli to use the new intervals. +void SplitEditor::rewrite() { + assert(!openli_ && "Previous LI not closed before rewrite"); + const LiveInterval *curli = sa_.getCurLI(); + for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(curli->reg), + RE = mri_.reg_end(); RI != RE;) { + MachineOperand &MO = RI.getOperand(); + MachineInstr *MI = MO.getParent(); + ++RI; + if (MI->isDebugValue()) { + DEBUG(dbgs() << "Zapping " << *MI); + // FIXME: We can do much better with debug values. + MO.setReg(0); + continue; + } + SlotIndex Idx = lis_.getInstructionIndex(MI); + Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex(); + LiveInterval *LI = dupli_; + for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) { + LiveInterval *testli = intervals_[i]; + if (testli->liveAt(Idx)) { + LI = testli; + break; + } + } + if (LI) { + MO.setReg(LI->reg); + sa_.removeUse(MI); + DEBUG(dbgs() << " rewrite " << Idx << '\t' << *MI); + } + } + + // dupli_ goes in last, after rewriting. + if (dupli_) { + if (dupli_->empty()) { + DEBUG(dbgs() << " dupli became empty?\n"); + lis_.removeInterval(dupli_->reg); + dupli_ = 0; + } else { + dupli_->RenumberValues(lis_); + intervals_.push_back(dupli_); + } + } + + // Calculate spill weight and allocation hints for new intervals. + VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_); + for (unsigned i = firstInterval, e = intervals_.size(); i != e; ++i) { + LiveInterval &li = *intervals_[i]; + vrai.CalculateRegClass(li.reg); + vrai.CalculateWeightAndHint(li); + DEBUG(dbgs() << " new interval " << mri_.getRegClass(li.reg)->getName() + << ":" << li << '\n'); + } +} + + +//===----------------------------------------------------------------------===// +// Loop Splitting +//===----------------------------------------------------------------------===// + +bool SplitEditor::splitAroundLoop(const MachineLoop *Loop) { + SplitAnalysis::LoopBlocks Blocks; + sa_.getLoopBlocks(Loop, Blocks); + + // Break critical edges as needed. + SplitAnalysis::BlockPtrSet CriticalExits; + sa_.getCriticalExits(Blocks, CriticalExits); + assert(CriticalExits.empty() && "Cannot break critical exits yet"); + + // Create new live interval for the loop. + openIntv(); + + // Insert copies in the predecessors. + for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(), + E = Blocks.Preds.end(); I != E; ++I) { + MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I); + enterIntvAtEnd(MBB, *Loop->getHeader()); + } + + // Switch all loop blocks. + for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(), + E = Blocks.Loop.end(); I != E; ++I) + useIntv(**I); + + // Insert back copies in the exit blocks. + for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(), + E = Blocks.Exits.end(); I != E; ++I) { + MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I); + leaveIntvAtTop(MBB); + } + + // Done. + closeIntv(); + rewrite(); + return dupli_; +} + + +//===----------------------------------------------------------------------===// +// Single Block Splitting +//===----------------------------------------------------------------------===// + +/// splitSingleBlocks - Split curli into a separate live interval inside each +/// basic block in Blocks. Return true if curli has been completely replaced, +/// false if curli is still intact, and needs to be spilled or split further. +bool SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) { + DEBUG(dbgs() << " splitSingleBlocks for " << Blocks.size() << " blocks.\n"); + // Determine the first and last instruction using curli in each block. + typedef std::pair<SlotIndex,SlotIndex> IndexPair; + typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap; + IndexPairMap MBBRange; + for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(), + E = sa_.usingInstrs_.end(); I != E; ++I) { + const MachineBasicBlock *MBB = (*I)->getParent(); + if (!Blocks.count(MBB)) + continue; + SlotIndex Idx = lis_.getInstructionIndex(*I); + DEBUG(dbgs() << " BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I); + IndexPair &IP = MBBRange[MBB]; + if (!IP.first.isValid() || Idx < IP.first) + IP.first = Idx; + if (!IP.second.isValid() || Idx > IP.second) + IP.second = Idx; + } + + // Create a new interval for each block. + for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(), + E = Blocks.end(); I != E; ++I) { + IndexPair &IP = MBBRange[*I]; + DEBUG(dbgs() << " splitting for BB#" << (*I)->getNumber() << ": [" + << IP.first << ';' << IP.second << ")\n"); + assert(IP.first.isValid() && IP.second.isValid()); + + openIntv(); + enterIntvBefore(IP.first); + useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex()); + leaveIntvAfter(IP.second); + closeIntv(); + } + rewrite(); + return dupli_; +} + + +//===----------------------------------------------------------------------===// +// Sub Block Splitting +//===----------------------------------------------------------------------===// + +/// getBlockForInsideSplit - If curli is contained inside a single basic block, +/// and it wou pay to subdivide the interval inside that block, return it. +/// Otherwise return NULL. The returned block can be passed to +/// SplitEditor::splitInsideBlock. +const MachineBasicBlock *SplitAnalysis::getBlockForInsideSplit() { + // The interval must be exclusive to one block. + if (usingBlocks_.size() != 1) + return 0; + // Don't to this for less than 4 instructions. We want to be sure that + // splitting actually reduces the instruction count per interval. + if (usingInstrs_.size() < 4) + return 0; + return usingBlocks_.begin()->first; +} + +/// splitInsideBlock - Split curli into multiple intervals inside MBB. Return +/// true if curli has been completely replaced, false if curli is still +/// intact, and needs to be spilled or split further. +bool SplitEditor::splitInsideBlock(const MachineBasicBlock *MBB) { + SmallVector<SlotIndex, 32> Uses; + Uses.reserve(sa_.usingInstrs_.size()); + for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(), + E = sa_.usingInstrs_.end(); I != E; ++I) + if ((*I)->getParent() == MBB) + Uses.push_back(lis_.getInstructionIndex(*I)); + DEBUG(dbgs() << " splitInsideBlock BB#" << MBB->getNumber() << " for " + << Uses.size() << " instructions.\n"); + assert(Uses.size() >= 3 && "Need at least 3 instructions"); + array_pod_sort(Uses.begin(), Uses.end()); + + // Simple algorithm: Find the largest gap between uses as determined by slot + // indices. Create new intervals for instructions before the gap and after the + // gap. + unsigned bestPos = 0; + int bestGap = 0; + DEBUG(dbgs() << " dist (" << Uses[0]); + for (unsigned i = 1, e = Uses.size(); i != e; ++i) { + int g = Uses[i-1].distance(Uses[i]); + DEBUG(dbgs() << ") -" << g << "- (" << Uses[i]); + if (g > bestGap) + bestPos = i, bestGap = g; + } + DEBUG(dbgs() << "), best: -" << bestGap << "-\n"); + + // bestPos points to the first use after the best gap. + assert(bestPos > 0 && "Invalid gap"); + + // FIXME: Don't create intervals for low densities. + + // First interval before the gap. Don't create single-instr intervals. + if (bestPos > 1) { + openIntv(); + enterIntvBefore(Uses.front()); + useIntv(Uses.front().getBaseIndex(), Uses[bestPos-1].getBoundaryIndex()); + leaveIntvAfter(Uses[bestPos-1]); + closeIntv(); + } + + // Second interval after the gap. + if (bestPos < Uses.size()-1) { + openIntv(); + enterIntvBefore(Uses[bestPos]); + useIntv(Uses[bestPos].getBaseIndex(), Uses.back().getBoundaryIndex()); + leaveIntvAfter(Uses.back()); + closeIntv(); + } + + rewrite(); + return dupli_; +} |
