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Diffstat (limited to 'contrib/llvm/lib/CodeGen/MachineTraceMetrics.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/MachineTraceMetrics.cpp | 1153 |
1 files changed, 1153 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/MachineTraceMetrics.cpp b/contrib/llvm/lib/CodeGen/MachineTraceMetrics.cpp new file mode 100644 index 000000000000..1a3aa6091825 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/MachineTraceMetrics.cpp @@ -0,0 +1,1153 @@ +//===- lib/CodeGen/MachineTraceMetrics.cpp ----------------------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "machine-trace-metrics" +#include "MachineTraceMetrics.h" +#include "llvm/CodeGen/MachineBasicBlock.h" +#include "llvm/CodeGen/MachineBranchProbabilityInfo.h" +#include "llvm/CodeGen/MachineLoopInfo.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/Passes.h" +#include "llvm/MC/MCInstrItineraries.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/ADT/PostOrderIterator.h" +#include "llvm/ADT/SparseSet.h" + +using namespace llvm; + +char MachineTraceMetrics::ID = 0; +char &llvm::MachineTraceMetricsID = MachineTraceMetrics::ID; + +INITIALIZE_PASS_BEGIN(MachineTraceMetrics, + "machine-trace-metrics", "Machine Trace Metrics", false, true) +INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo) +INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) +INITIALIZE_PASS_END(MachineTraceMetrics, + "machine-trace-metrics", "Machine Trace Metrics", false, true) + +MachineTraceMetrics::MachineTraceMetrics() + : MachineFunctionPass(ID), MF(0), TII(0), TRI(0), MRI(0), Loops(0) { + std::fill(Ensembles, array_endof(Ensembles), (Ensemble*)0); +} + +void MachineTraceMetrics::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesAll(); + AU.addRequired<MachineBranchProbabilityInfo>(); + AU.addRequired<MachineLoopInfo>(); + MachineFunctionPass::getAnalysisUsage(AU); +} + +bool MachineTraceMetrics::runOnMachineFunction(MachineFunction &Func) { + MF = &Func; + TII = MF->getTarget().getInstrInfo(); + TRI = MF->getTarget().getRegisterInfo(); + ItinData = MF->getTarget().getInstrItineraryData(); + MRI = &MF->getRegInfo(); + Loops = &getAnalysis<MachineLoopInfo>(); + BlockInfo.resize(MF->getNumBlockIDs()); + return false; +} + +void MachineTraceMetrics::releaseMemory() { + MF = 0; + BlockInfo.clear(); + for (unsigned i = 0; i != TS_NumStrategies; ++i) { + delete Ensembles[i]; + Ensembles[i] = 0; + } +} + +//===----------------------------------------------------------------------===// +// Fixed block information +//===----------------------------------------------------------------------===// +// +// The number of instructions in a basic block and the CPU resources used by +// those instructions don't depend on any given trace strategy. + +/// Compute the resource usage in basic block MBB. +const MachineTraceMetrics::FixedBlockInfo* +MachineTraceMetrics::getResources(const MachineBasicBlock *MBB) { + assert(MBB && "No basic block"); + FixedBlockInfo *FBI = &BlockInfo[MBB->getNumber()]; + if (FBI->hasResources()) + return FBI; + + // Compute resource usage in the block. + // FIXME: Compute per-functional unit counts. + FBI->HasCalls = false; + unsigned InstrCount = 0; + for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end(); + I != E; ++I) { + const MachineInstr *MI = I; + if (MI->isTransient()) + continue; + ++InstrCount; + if (MI->isCall()) + FBI->HasCalls = true; + } + FBI->InstrCount = InstrCount; + return FBI; +} + +//===----------------------------------------------------------------------===// +// Ensemble utility functions +//===----------------------------------------------------------------------===// + +MachineTraceMetrics::Ensemble::Ensemble(MachineTraceMetrics *ct) + : MTM(*ct) { + BlockInfo.resize(MTM.BlockInfo.size()); +} + +// Virtual destructor serves as an anchor. +MachineTraceMetrics::Ensemble::~Ensemble() {} + +const MachineLoop* +MachineTraceMetrics::Ensemble::getLoopFor(const MachineBasicBlock *MBB) const { + return MTM.Loops->getLoopFor(MBB); +} + +// Update resource-related information in the TraceBlockInfo for MBB. +// Only update resources related to the trace above MBB. +void MachineTraceMetrics::Ensemble:: +computeDepthResources(const MachineBasicBlock *MBB) { + TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()]; + + // Compute resources from trace above. The top block is simple. + if (!TBI->Pred) { + TBI->InstrDepth = 0; + TBI->Head = MBB->getNumber(); + return; + } + + // Compute from the block above. A post-order traversal ensures the + // predecessor is always computed first. + TraceBlockInfo *PredTBI = &BlockInfo[TBI->Pred->getNumber()]; + assert(PredTBI->hasValidDepth() && "Trace above has not been computed yet"); + const FixedBlockInfo *PredFBI = MTM.getResources(TBI->Pred); + TBI->InstrDepth = PredTBI->InstrDepth + PredFBI->InstrCount; + TBI->Head = PredTBI->Head; +} + +// Update resource-related information in the TraceBlockInfo for MBB. +// Only update resources related to the trace below MBB. +void MachineTraceMetrics::Ensemble:: +computeHeightResources(const MachineBasicBlock *MBB) { + TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()]; + + // Compute resources for the current block. + TBI->InstrHeight = MTM.getResources(MBB)->InstrCount; + + // The trace tail is done. + if (!TBI->Succ) { + TBI->Tail = MBB->getNumber(); + return; + } + + // Compute from the block below. A post-order traversal ensures the + // predecessor is always computed first. + TraceBlockInfo *SuccTBI = &BlockInfo[TBI->Succ->getNumber()]; + assert(SuccTBI->hasValidHeight() && "Trace below has not been computed yet"); + TBI->InstrHeight += SuccTBI->InstrHeight; + TBI->Tail = SuccTBI->Tail; +} + +// Check if depth resources for MBB are valid and return the TBI. +// Return NULL if the resources have been invalidated. +const MachineTraceMetrics::TraceBlockInfo* +MachineTraceMetrics::Ensemble:: +getDepthResources(const MachineBasicBlock *MBB) const { + const TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()]; + return TBI->hasValidDepth() ? TBI : 0; +} + +// Check if height resources for MBB are valid and return the TBI. +// Return NULL if the resources have been invalidated. +const MachineTraceMetrics::TraceBlockInfo* +MachineTraceMetrics::Ensemble:: +getHeightResources(const MachineBasicBlock *MBB) const { + const TraceBlockInfo *TBI = &BlockInfo[MBB->getNumber()]; + return TBI->hasValidHeight() ? TBI : 0; +} + +//===----------------------------------------------------------------------===// +// Trace Selection Strategies +//===----------------------------------------------------------------------===// +// +// A trace selection strategy is implemented as a sub-class of Ensemble. The +// trace through a block B is computed by two DFS traversals of the CFG +// starting from B. One upwards, and one downwards. During the upwards DFS, +// pickTracePred() is called on the post-ordered blocks. During the downwards +// DFS, pickTraceSucc() is called in a post-order. +// + +// We never allow traces that leave loops, but we do allow traces to enter +// nested loops. We also never allow traces to contain back-edges. +// +// This means that a loop header can never appear above the center block of a +// trace, except as the trace head. Below the center block, loop exiting edges +// are banned. +// +// Return true if an edge from the From loop to the To loop is leaving a loop. +// Either of To and From can be null. +static bool isExitingLoop(const MachineLoop *From, const MachineLoop *To) { + return From && !From->contains(To); +} + +// MinInstrCountEnsemble - Pick the trace that executes the least number of +// instructions. +namespace { +class MinInstrCountEnsemble : public MachineTraceMetrics::Ensemble { + const char *getName() const { return "MinInstr"; } + const MachineBasicBlock *pickTracePred(const MachineBasicBlock*); + const MachineBasicBlock *pickTraceSucc(const MachineBasicBlock*); + +public: + MinInstrCountEnsemble(MachineTraceMetrics *mtm) + : MachineTraceMetrics::Ensemble(mtm) {} +}; +} + +// Select the preferred predecessor for MBB. +const MachineBasicBlock* +MinInstrCountEnsemble::pickTracePred(const MachineBasicBlock *MBB) { + if (MBB->pred_empty()) + return 0; + const MachineLoop *CurLoop = getLoopFor(MBB); + // Don't leave loops, and never follow back-edges. + if (CurLoop && MBB == CurLoop->getHeader()) + return 0; + unsigned CurCount = MTM.getResources(MBB)->InstrCount; + const MachineBasicBlock *Best = 0; + unsigned BestDepth = 0; + for (MachineBasicBlock::const_pred_iterator + I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) { + const MachineBasicBlock *Pred = *I; + const MachineTraceMetrics::TraceBlockInfo *PredTBI = + getDepthResources(Pred); + // Ignore cycles that aren't natural loops. + if (!PredTBI) + continue; + // Pick the predecessor that would give this block the smallest InstrDepth. + unsigned Depth = PredTBI->InstrDepth + CurCount; + if (!Best || Depth < BestDepth) + Best = Pred, BestDepth = Depth; + } + return Best; +} + +// Select the preferred successor for MBB. +const MachineBasicBlock* +MinInstrCountEnsemble::pickTraceSucc(const MachineBasicBlock *MBB) { + if (MBB->pred_empty()) + return 0; + const MachineLoop *CurLoop = getLoopFor(MBB); + const MachineBasicBlock *Best = 0; + unsigned BestHeight = 0; + for (MachineBasicBlock::const_succ_iterator + I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) { + const MachineBasicBlock *Succ = *I; + // Don't consider back-edges. + if (CurLoop && Succ == CurLoop->getHeader()) + continue; + // Don't consider successors exiting CurLoop. + if (isExitingLoop(CurLoop, getLoopFor(Succ))) + continue; + const MachineTraceMetrics::TraceBlockInfo *SuccTBI = + getHeightResources(Succ); + // Ignore cycles that aren't natural loops. + if (!SuccTBI) + continue; + // Pick the successor that would give this block the smallest InstrHeight. + unsigned Height = SuccTBI->InstrHeight; + if (!Best || Height < BestHeight) + Best = Succ, BestHeight = Height; + } + return Best; +} + +// Get an Ensemble sub-class for the requested trace strategy. +MachineTraceMetrics::Ensemble * +MachineTraceMetrics::getEnsemble(MachineTraceMetrics::Strategy strategy) { + assert(strategy < TS_NumStrategies && "Invalid trace strategy enum"); + Ensemble *&E = Ensembles[strategy]; + if (E) + return E; + + // Allocate new Ensemble on demand. + switch (strategy) { + case TS_MinInstrCount: return (E = new MinInstrCountEnsemble(this)); + default: llvm_unreachable("Invalid trace strategy enum"); + } +} + +void MachineTraceMetrics::invalidate(const MachineBasicBlock *MBB) { + DEBUG(dbgs() << "Invalidate traces through BB#" << MBB->getNumber() << '\n'); + BlockInfo[MBB->getNumber()].invalidate(); + for (unsigned i = 0; i != TS_NumStrategies; ++i) + if (Ensembles[i]) + Ensembles[i]->invalidate(MBB); +} + +void MachineTraceMetrics::verifyAnalysis() const { + if (!MF) + return; +#ifndef NDEBUG + assert(BlockInfo.size() == MF->getNumBlockIDs() && "Outdated BlockInfo size"); + for (unsigned i = 0; i != TS_NumStrategies; ++i) + if (Ensembles[i]) + Ensembles[i]->verify(); +#endif +} + +//===----------------------------------------------------------------------===// +// Trace building +//===----------------------------------------------------------------------===// +// +// Traces are built by two CFG traversals. To avoid recomputing too much, use a +// set abstraction that confines the search to the current loop, and doesn't +// revisit blocks. + +namespace { +struct LoopBounds { + MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> Blocks; + SmallPtrSet<const MachineBasicBlock*, 8> Visited; + const MachineLoopInfo *Loops; + bool Downward; + LoopBounds(MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> blocks, + const MachineLoopInfo *loops) + : Blocks(blocks), Loops(loops), Downward(false) {} +}; +} + +// Specialize po_iterator_storage in order to prune the post-order traversal so +// it is limited to the current loop and doesn't traverse the loop back edges. +namespace llvm { +template<> +class po_iterator_storage<LoopBounds, true> { + LoopBounds &LB; +public: + po_iterator_storage(LoopBounds &lb) : LB(lb) {} + void finishPostorder(const MachineBasicBlock*) {} + + bool insertEdge(const MachineBasicBlock *From, const MachineBasicBlock *To) { + // Skip already visited To blocks. + MachineTraceMetrics::TraceBlockInfo &TBI = LB.Blocks[To->getNumber()]; + if (LB.Downward ? TBI.hasValidHeight() : TBI.hasValidDepth()) + return false; + // From is null once when To is the trace center block. + if (From) { + if (const MachineLoop *FromLoop = LB.Loops->getLoopFor(From)) { + // Don't follow backedges, don't leave FromLoop when going upwards. + if ((LB.Downward ? To : From) == FromLoop->getHeader()) + return false; + // Don't leave FromLoop. + if (isExitingLoop(FromLoop, LB.Loops->getLoopFor(To))) + return false; + } + } + // To is a new block. Mark the block as visited in case the CFG has cycles + // that MachineLoopInfo didn't recognize as a natural loop. + return LB.Visited.insert(To); + } +}; +} + +/// Compute the trace through MBB. +void MachineTraceMetrics::Ensemble::computeTrace(const MachineBasicBlock *MBB) { + DEBUG(dbgs() << "Computing " << getName() << " trace through BB#" + << MBB->getNumber() << '\n'); + // Set up loop bounds for the backwards post-order traversal. + LoopBounds Bounds(BlockInfo, MTM.Loops); + + // Run an upwards post-order search for the trace start. + Bounds.Downward = false; + Bounds.Visited.clear(); + typedef ipo_ext_iterator<const MachineBasicBlock*, LoopBounds> UpwardPO; + for (UpwardPO I = ipo_ext_begin(MBB, Bounds), E = ipo_ext_end(MBB, Bounds); + I != E; ++I) { + DEBUG(dbgs() << " pred for BB#" << I->getNumber() << ": "); + TraceBlockInfo &TBI = BlockInfo[I->getNumber()]; + // All the predecessors have been visited, pick the preferred one. + TBI.Pred = pickTracePred(*I); + DEBUG({ + if (TBI.Pred) + dbgs() << "BB#" << TBI.Pred->getNumber() << '\n'; + else + dbgs() << "null\n"; + }); + // The trace leading to I is now known, compute the depth resources. + computeDepthResources(*I); + } + + // Run a downwards post-order search for the trace end. + Bounds.Downward = true; + Bounds.Visited.clear(); + typedef po_ext_iterator<const MachineBasicBlock*, LoopBounds> DownwardPO; + for (DownwardPO I = po_ext_begin(MBB, Bounds), E = po_ext_end(MBB, Bounds); + I != E; ++I) { + DEBUG(dbgs() << " succ for BB#" << I->getNumber() << ": "); + TraceBlockInfo &TBI = BlockInfo[I->getNumber()]; + // All the successors have been visited, pick the preferred one. + TBI.Succ = pickTraceSucc(*I); + DEBUG({ + if (TBI.Succ) + dbgs() << "BB#" << TBI.Succ->getNumber() << '\n'; + else + dbgs() << "null\n"; + }); + // The trace leaving I is now known, compute the height resources. + computeHeightResources(*I); + } +} + +/// Invalidate traces through BadMBB. +void +MachineTraceMetrics::Ensemble::invalidate(const MachineBasicBlock *BadMBB) { + SmallVector<const MachineBasicBlock*, 16> WorkList; + TraceBlockInfo &BadTBI = BlockInfo[BadMBB->getNumber()]; + + // Invalidate height resources of blocks above MBB. + if (BadTBI.hasValidHeight()) { + BadTBI.invalidateHeight(); + WorkList.push_back(BadMBB); + do { + const MachineBasicBlock *MBB = WorkList.pop_back_val(); + DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName() + << " height.\n"); + // Find any MBB predecessors that have MBB as their preferred successor. + // They are the only ones that need to be invalidated. + for (MachineBasicBlock::const_pred_iterator + I = MBB->pred_begin(), E = MBB->pred_end(); I != E; ++I) { + TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()]; + if (!TBI.hasValidHeight()) + continue; + if (TBI.Succ == MBB) { + TBI.invalidateHeight(); + WorkList.push_back(*I); + continue; + } + // Verify that TBI.Succ is actually a *I successor. + assert((!TBI.Succ || (*I)->isSuccessor(TBI.Succ)) && "CFG changed"); + } + } while (!WorkList.empty()); + } + + // Invalidate depth resources of blocks below MBB. + if (BadTBI.hasValidDepth()) { + BadTBI.invalidateDepth(); + WorkList.push_back(BadMBB); + do { + const MachineBasicBlock *MBB = WorkList.pop_back_val(); + DEBUG(dbgs() << "Invalidate BB#" << MBB->getNumber() << ' ' << getName() + << " depth.\n"); + // Find any MBB successors that have MBB as their preferred predecessor. + // They are the only ones that need to be invalidated. + for (MachineBasicBlock::const_succ_iterator + I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) { + TraceBlockInfo &TBI = BlockInfo[(*I)->getNumber()]; + if (!TBI.hasValidDepth()) + continue; + if (TBI.Pred == MBB) { + TBI.invalidateDepth(); + WorkList.push_back(*I); + continue; + } + // Verify that TBI.Pred is actually a *I predecessor. + assert((!TBI.Pred || (*I)->isPredecessor(TBI.Pred)) && "CFG changed"); + } + } while (!WorkList.empty()); + } + + // Clear any per-instruction data. We only have to do this for BadMBB itself + // because the instructions in that block may change. Other blocks may be + // invalidated, but their instructions will stay the same, so there is no + // need to erase the Cycle entries. They will be overwritten when we + // recompute. + for (MachineBasicBlock::const_iterator I = BadMBB->begin(), E = BadMBB->end(); + I != E; ++I) + Cycles.erase(I); +} + +void MachineTraceMetrics::Ensemble::verify() const { +#ifndef NDEBUG + assert(BlockInfo.size() == MTM.MF->getNumBlockIDs() && + "Outdated BlockInfo size"); + for (unsigned Num = 0, e = BlockInfo.size(); Num != e; ++Num) { + const TraceBlockInfo &TBI = BlockInfo[Num]; + if (TBI.hasValidDepth() && TBI.Pred) { + const MachineBasicBlock *MBB = MTM.MF->getBlockNumbered(Num); + assert(MBB->isPredecessor(TBI.Pred) && "CFG doesn't match trace"); + assert(BlockInfo[TBI.Pred->getNumber()].hasValidDepth() && + "Trace is broken, depth should have been invalidated."); + const MachineLoop *Loop = getLoopFor(MBB); + assert(!(Loop && MBB == Loop->getHeader()) && "Trace contains backedge"); + } + if (TBI.hasValidHeight() && TBI.Succ) { + const MachineBasicBlock *MBB = MTM.MF->getBlockNumbered(Num); + assert(MBB->isSuccessor(TBI.Succ) && "CFG doesn't match trace"); + assert(BlockInfo[TBI.Succ->getNumber()].hasValidHeight() && + "Trace is broken, height should have been invalidated."); + const MachineLoop *Loop = getLoopFor(MBB); + const MachineLoop *SuccLoop = getLoopFor(TBI.Succ); + assert(!(Loop && Loop == SuccLoop && TBI.Succ == Loop->getHeader()) && + "Trace contains backedge"); + } + } +#endif +} + +//===----------------------------------------------------------------------===// +// Data Dependencies +//===----------------------------------------------------------------------===// +// +// Compute the depth and height of each instruction based on data dependencies +// and instruction latencies. These cycle numbers assume that the CPU can issue +// an infinite number of instructions per cycle as long as their dependencies +// are ready. + +// A data dependency is represented as a defining MI and operand numbers on the +// defining and using MI. +namespace { +struct DataDep { + const MachineInstr *DefMI; + unsigned DefOp; + unsigned UseOp; + + DataDep(const MachineInstr *DefMI, unsigned DefOp, unsigned UseOp) + : DefMI(DefMI), DefOp(DefOp), UseOp(UseOp) {} + + /// Create a DataDep from an SSA form virtual register. + DataDep(const MachineRegisterInfo *MRI, unsigned VirtReg, unsigned UseOp) + : UseOp(UseOp) { + assert(TargetRegisterInfo::isVirtualRegister(VirtReg)); + MachineRegisterInfo::def_iterator DefI = MRI->def_begin(VirtReg); + assert(!DefI.atEnd() && "Register has no defs"); + DefMI = &*DefI; + DefOp = DefI.getOperandNo(); + assert((++DefI).atEnd() && "Register has multiple defs"); + } +}; +} + +// Get the input data dependencies that must be ready before UseMI can issue. +// Return true if UseMI has any physreg operands. +static bool getDataDeps(const MachineInstr *UseMI, + SmallVectorImpl<DataDep> &Deps, + const MachineRegisterInfo *MRI) { + bool HasPhysRegs = false; + for (ConstMIOperands MO(UseMI); MO.isValid(); ++MO) { + if (!MO->isReg()) + continue; + unsigned Reg = MO->getReg(); + if (!Reg) + continue; + if (TargetRegisterInfo::isPhysicalRegister(Reg)) { + HasPhysRegs = true; + continue; + } + // Collect virtual register reads. + if (MO->readsReg()) + Deps.push_back(DataDep(MRI, Reg, MO.getOperandNo())); + } + return HasPhysRegs; +} + +// Get the input data dependencies of a PHI instruction, using Pred as the +// preferred predecessor. +// This will add at most one dependency to Deps. +static void getPHIDeps(const MachineInstr *UseMI, + SmallVectorImpl<DataDep> &Deps, + const MachineBasicBlock *Pred, + const MachineRegisterInfo *MRI) { + // No predecessor at the beginning of a trace. Ignore dependencies. + if (!Pred) + return; + assert(UseMI->isPHI() && UseMI->getNumOperands() % 2 && "Bad PHI"); + for (unsigned i = 1; i != UseMI->getNumOperands(); i += 2) { + if (UseMI->getOperand(i + 1).getMBB() == Pred) { + unsigned Reg = UseMI->getOperand(i).getReg(); + Deps.push_back(DataDep(MRI, Reg, i)); + return; + } + } +} + +// Keep track of physreg data dependencies by recording each live register unit. +// Associate each regunit with an instruction operand. Depending on the +// direction instructions are scanned, it could be the operand that defined the +// regunit, or the highest operand to read the regunit. +namespace { +struct LiveRegUnit { + unsigned RegUnit; + unsigned Cycle; + const MachineInstr *MI; + unsigned Op; + + unsigned getSparseSetIndex() const { return RegUnit; } + + LiveRegUnit(unsigned RU) : RegUnit(RU), Cycle(0), MI(0), Op(0) {} +}; +} + +// Identify physreg dependencies for UseMI, and update the live regunit +// tracking set when scanning instructions downwards. +static void updatePhysDepsDownwards(const MachineInstr *UseMI, + SmallVectorImpl<DataDep> &Deps, + SparseSet<LiveRegUnit> &RegUnits, + const TargetRegisterInfo *TRI) { + SmallVector<unsigned, 8> Kills; + SmallVector<unsigned, 8> LiveDefOps; + + for (ConstMIOperands MO(UseMI); MO.isValid(); ++MO) { + if (!MO->isReg()) + continue; + unsigned Reg = MO->getReg(); + if (!TargetRegisterInfo::isPhysicalRegister(Reg)) + continue; + // Track live defs and kills for updating RegUnits. + if (MO->isDef()) { + if (MO->isDead()) + Kills.push_back(Reg); + else + LiveDefOps.push_back(MO.getOperandNo()); + } else if (MO->isKill()) + Kills.push_back(Reg); + // Identify dependencies. + if (!MO->readsReg()) + continue; + for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) { + SparseSet<LiveRegUnit>::iterator I = RegUnits.find(*Units); + if (I == RegUnits.end()) + continue; + Deps.push_back(DataDep(I->MI, I->Op, MO.getOperandNo())); + break; + } + } + + // Update RegUnits to reflect live registers after UseMI. + // First kills. + for (unsigned i = 0, e = Kills.size(); i != e; ++i) + for (MCRegUnitIterator Units(Kills[i], TRI); Units.isValid(); ++Units) + RegUnits.erase(*Units); + + // Second, live defs. + for (unsigned i = 0, e = LiveDefOps.size(); i != e; ++i) { + unsigned DefOp = LiveDefOps[i]; + for (MCRegUnitIterator Units(UseMI->getOperand(DefOp).getReg(), TRI); + Units.isValid(); ++Units) { + LiveRegUnit &LRU = RegUnits[*Units]; + LRU.MI = UseMI; + LRU.Op = DefOp; + } + } +} + +/// The length of the critical path through a trace is the maximum of two path +/// lengths: +/// +/// 1. The maximum height+depth over all instructions in the trace center block. +/// +/// 2. The longest cross-block dependency chain. For small blocks, it is +/// possible that the critical path through the trace doesn't include any +/// instructions in the block. +/// +/// This function computes the second number from the live-in list of the +/// center block. +unsigned MachineTraceMetrics::Ensemble:: +computeCrossBlockCriticalPath(const TraceBlockInfo &TBI) { + assert(TBI.HasValidInstrDepths && "Missing depth info"); + assert(TBI.HasValidInstrHeights && "Missing height info"); + unsigned MaxLen = 0; + for (unsigned i = 0, e = TBI.LiveIns.size(); i != e; ++i) { + const LiveInReg &LIR = TBI.LiveIns[i]; + if (!TargetRegisterInfo::isVirtualRegister(LIR.Reg)) + continue; + const MachineInstr *DefMI = MTM.MRI->getVRegDef(LIR.Reg); + // Ignore dependencies outside the current trace. + const TraceBlockInfo &DefTBI = BlockInfo[DefMI->getParent()->getNumber()]; + if (!DefTBI.hasValidDepth() || DefTBI.Head != TBI.Head) + continue; + unsigned Len = LIR.Height + Cycles[DefMI].Depth; + MaxLen = std::max(MaxLen, Len); + } + return MaxLen; +} + +/// Compute instruction depths for all instructions above or in MBB in its +/// trace. This assumes that the trace through MBB has already been computed. +void MachineTraceMetrics::Ensemble:: +computeInstrDepths(const MachineBasicBlock *MBB) { + // The top of the trace may already be computed, and HasValidInstrDepths + // implies Head->HasValidInstrDepths, so we only need to start from the first + // block in the trace that needs to be recomputed. + SmallVector<const MachineBasicBlock*, 8> Stack; + do { + TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()]; + assert(TBI.hasValidDepth() && "Incomplete trace"); + if (TBI.HasValidInstrDepths) + break; + Stack.push_back(MBB); + MBB = TBI.Pred; + } while (MBB); + + // FIXME: If MBB is non-null at this point, it is the last pre-computed block + // in the trace. We should track any live-out physregs that were defined in + // the trace. This is quite rare in SSA form, typically created by CSE + // hoisting a compare. + SparseSet<LiveRegUnit> RegUnits; + RegUnits.setUniverse(MTM.TRI->getNumRegUnits()); + + // Go through trace blocks in top-down order, stopping after the center block. + SmallVector<DataDep, 8> Deps; + while (!Stack.empty()) { + MBB = Stack.pop_back_val(); + DEBUG(dbgs() << "Depths for BB#" << MBB->getNumber() << ":\n"); + TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()]; + TBI.HasValidInstrDepths = true; + TBI.CriticalPath = 0; + + // Also compute the critical path length through MBB when possible. + if (TBI.HasValidInstrHeights) + TBI.CriticalPath = computeCrossBlockCriticalPath(TBI); + + for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end(); + I != E; ++I) { + const MachineInstr *UseMI = I; + + // Collect all data dependencies. + Deps.clear(); + if (UseMI->isPHI()) + getPHIDeps(UseMI, Deps, TBI.Pred, MTM.MRI); + else if (getDataDeps(UseMI, Deps, MTM.MRI)) + updatePhysDepsDownwards(UseMI, Deps, RegUnits, MTM.TRI); + + // Filter and process dependencies, computing the earliest issue cycle. + unsigned Cycle = 0; + for (unsigned i = 0, e = Deps.size(); i != e; ++i) { + const DataDep &Dep = Deps[i]; + const TraceBlockInfo&DepTBI = + BlockInfo[Dep.DefMI->getParent()->getNumber()]; + // Ignore dependencies from outside the current trace. + if (!DepTBI.hasValidDepth() || DepTBI.Head != TBI.Head) + continue; + assert(DepTBI.HasValidInstrDepths && "Inconsistent dependency"); + unsigned DepCycle = Cycles.lookup(Dep.DefMI).Depth; + // Add latency if DefMI is a real instruction. Transients get latency 0. + if (!Dep.DefMI->isTransient()) + DepCycle += MTM.TII->computeOperandLatency(MTM.ItinData, + Dep.DefMI, Dep.DefOp, + UseMI, Dep.UseOp, + /* FindMin = */ false); + Cycle = std::max(Cycle, DepCycle); + } + // Remember the instruction depth. + InstrCycles &MICycles = Cycles[UseMI]; + MICycles.Depth = Cycle; + + if (!TBI.HasValidInstrHeights) { + DEBUG(dbgs() << Cycle << '\t' << *UseMI); + continue; + } + // Update critical path length. + TBI.CriticalPath = std::max(TBI.CriticalPath, Cycle + MICycles.Height); + DEBUG(dbgs() << TBI.CriticalPath << '\t' << Cycle << '\t' << *UseMI); + } + } +} + +// Identify physreg dependencies for MI when scanning instructions upwards. +// Return the issue height of MI after considering any live regunits. +// Height is the issue height computed from virtual register dependencies alone. +static unsigned updatePhysDepsUpwards(const MachineInstr *MI, unsigned Height, + SparseSet<LiveRegUnit> &RegUnits, + const InstrItineraryData *ItinData, + const TargetInstrInfo *TII, + const TargetRegisterInfo *TRI) { + SmallVector<unsigned, 8> ReadOps; + for (ConstMIOperands MO(MI); MO.isValid(); ++MO) { + if (!MO->isReg()) + continue; + unsigned Reg = MO->getReg(); + if (!TargetRegisterInfo::isPhysicalRegister(Reg)) + continue; + if (MO->readsReg()) + ReadOps.push_back(MO.getOperandNo()); + if (!MO->isDef()) + continue; + // This is a def of Reg. Remove corresponding entries from RegUnits, and + // update MI Height to consider the physreg dependencies. + for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) { + SparseSet<LiveRegUnit>::iterator I = RegUnits.find(*Units); + if (I == RegUnits.end()) + continue; + unsigned DepHeight = I->Cycle; + if (!MI->isTransient()) { + // We may not know the UseMI of this dependency, if it came from the + // live-in list. + if (I->MI) + DepHeight += TII->computeOperandLatency(ItinData, + MI, MO.getOperandNo(), + I->MI, I->Op); + else + // No UseMI. Just use the MI latency instead. + DepHeight += TII->getInstrLatency(ItinData, MI); + } + Height = std::max(Height, DepHeight); + // This regunit is dead above MI. + RegUnits.erase(I); + } + } + + // Now we know the height of MI. Update any regunits read. + for (unsigned i = 0, e = ReadOps.size(); i != e; ++i) { + unsigned Reg = MI->getOperand(ReadOps[i]).getReg(); + for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) { + LiveRegUnit &LRU = RegUnits[*Units]; + // Set the height to the highest reader of the unit. + if (LRU.Cycle <= Height && LRU.MI != MI) { + LRU.Cycle = Height; + LRU.MI = MI; + LRU.Op = ReadOps[i]; + } + } + } + + return Height; +} + + +typedef DenseMap<const MachineInstr *, unsigned> MIHeightMap; + +// Push the height of DefMI upwards if required to match UseMI. +// Return true if this is the first time DefMI was seen. +static bool pushDepHeight(const DataDep &Dep, + const MachineInstr *UseMI, unsigned UseHeight, + MIHeightMap &Heights, + const InstrItineraryData *ItinData, + const TargetInstrInfo *TII) { + // Adjust height by Dep.DefMI latency. + if (!Dep.DefMI->isTransient()) + UseHeight += TII->computeOperandLatency(ItinData, Dep.DefMI, Dep.DefOp, + UseMI, Dep.UseOp); + + // Update Heights[DefMI] to be the maximum height seen. + MIHeightMap::iterator I; + bool New; + tie(I, New) = Heights.insert(std::make_pair(Dep.DefMI, UseHeight)); + if (New) + return true; + + // DefMI has been pushed before. Give it the max height. + if (I->second < UseHeight) + I->second = UseHeight; + return false; +} + +/// Assuming that DefMI was used by Trace.back(), add it to the live-in lists +/// of all the blocks in Trace. Stop when reaching the block that contains +/// DefMI. +void MachineTraceMetrics::Ensemble:: +addLiveIns(const MachineInstr *DefMI, + ArrayRef<const MachineBasicBlock*> Trace) { + assert(!Trace.empty() && "Trace should contain at least one block"); + unsigned Reg = DefMI->getOperand(0).getReg(); + assert(TargetRegisterInfo::isVirtualRegister(Reg)); + const MachineBasicBlock *DefMBB = DefMI->getParent(); + + // Reg is live-in to all blocks in Trace that follow DefMBB. + for (unsigned i = Trace.size(); i; --i) { + const MachineBasicBlock *MBB = Trace[i-1]; + if (MBB == DefMBB) + return; + TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()]; + // Just add the register. The height will be updated later. + TBI.LiveIns.push_back(Reg); + } +} + +/// Compute instruction heights in the trace through MBB. This updates MBB and +/// the blocks below it in the trace. It is assumed that the trace has already +/// been computed. +void MachineTraceMetrics::Ensemble:: +computeInstrHeights(const MachineBasicBlock *MBB) { + // The bottom of the trace may already be computed. + // Find the blocks that need updating. + SmallVector<const MachineBasicBlock*, 8> Stack; + do { + TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()]; + assert(TBI.hasValidHeight() && "Incomplete trace"); + if (TBI.HasValidInstrHeights) + break; + Stack.push_back(MBB); + TBI.LiveIns.clear(); + MBB = TBI.Succ; + } while (MBB); + + // As we move upwards in the trace, keep track of instructions that are + // required by deeper trace instructions. Map MI -> height required so far. + MIHeightMap Heights; + + // For physregs, the def isn't known when we see the use. + // Instead, keep track of the highest use of each regunit. + SparseSet<LiveRegUnit> RegUnits; + RegUnits.setUniverse(MTM.TRI->getNumRegUnits()); + + // If the bottom of the trace was already precomputed, initialize heights + // from its live-in list. + // MBB is the highest precomputed block in the trace. + if (MBB) { + TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()]; + for (unsigned i = 0, e = TBI.LiveIns.size(); i != e; ++i) { + LiveInReg LI = TBI.LiveIns[i]; + if (TargetRegisterInfo::isVirtualRegister(LI.Reg)) { + // For virtual registers, the def latency is included. + unsigned &Height = Heights[MTM.MRI->getVRegDef(LI.Reg)]; + if (Height < LI.Height) + Height = LI.Height; + } else { + // For register units, the def latency is not included because we don't + // know the def yet. + RegUnits[LI.Reg].Cycle = LI.Height; + } + } + } + + // Go through the trace blocks in bottom-up order. + SmallVector<DataDep, 8> Deps; + for (;!Stack.empty(); Stack.pop_back()) { + MBB = Stack.back(); + DEBUG(dbgs() << "Heights for BB#" << MBB->getNumber() << ":\n"); + TraceBlockInfo &TBI = BlockInfo[MBB->getNumber()]; + TBI.HasValidInstrHeights = true; + TBI.CriticalPath = 0; + + // Get dependencies from PHIs in the trace successor. + const MachineBasicBlock *Succ = TBI.Succ; + // If MBB is the last block in the trace, and it has a back-edge to the + // loop header, get loop-carried dependencies from PHIs in the header. For + // that purpose, pretend that all the loop header PHIs have height 0. + if (!Succ) + if (const MachineLoop *Loop = getLoopFor(MBB)) + if (MBB->isSuccessor(Loop->getHeader())) + Succ = Loop->getHeader(); + + if (Succ) { + for (MachineBasicBlock::const_iterator I = Succ->begin(), E = Succ->end(); + I != E && I->isPHI(); ++I) { + const MachineInstr *PHI = I; + Deps.clear(); + getPHIDeps(PHI, Deps, MBB, MTM.MRI); + if (!Deps.empty()) { + // Loop header PHI heights are all 0. + unsigned Height = TBI.Succ ? Cycles.lookup(PHI).Height : 0; + DEBUG(dbgs() << "pred\t" << Height << '\t' << *PHI); + if (pushDepHeight(Deps.front(), PHI, Height, + Heights, MTM.ItinData, MTM.TII)) + addLiveIns(Deps.front().DefMI, Stack); + } + } + } + + // Go through the block backwards. + for (MachineBasicBlock::const_iterator BI = MBB->end(), BB = MBB->begin(); + BI != BB;) { + const MachineInstr *MI = --BI; + + // Find the MI height as determined by virtual register uses in the + // trace below. + unsigned Cycle = 0; + MIHeightMap::iterator HeightI = Heights.find(MI); + if (HeightI != Heights.end()) { + Cycle = HeightI->second; + // We won't be seeing any more MI uses. + Heights.erase(HeightI); + } + + // Don't process PHI deps. They depend on the specific predecessor, and + // we'll get them when visiting the predecessor. + Deps.clear(); + bool HasPhysRegs = !MI->isPHI() && getDataDeps(MI, Deps, MTM.MRI); + + // There may also be regunit dependencies to include in the height. + if (HasPhysRegs) + Cycle = updatePhysDepsUpwards(MI, Cycle, RegUnits, + MTM.ItinData, MTM.TII, MTM.TRI); + + // Update the required height of any virtual registers read by MI. + for (unsigned i = 0, e = Deps.size(); i != e; ++i) + if (pushDepHeight(Deps[i], MI, Cycle, Heights, MTM.ItinData, MTM.TII)) + addLiveIns(Deps[i].DefMI, Stack); + + InstrCycles &MICycles = Cycles[MI]; + MICycles.Height = Cycle; + if (!TBI.HasValidInstrDepths) { + DEBUG(dbgs() << Cycle << '\t' << *MI); + continue; + } + // Update critical path length. + TBI.CriticalPath = std::max(TBI.CriticalPath, Cycle + MICycles.Depth); + DEBUG(dbgs() << TBI.CriticalPath << '\t' << Cycle << '\t' << *MI); + } + + // Update virtual live-in heights. They were added by addLiveIns() with a 0 + // height because the final height isn't known until now. + DEBUG(dbgs() << "BB#" << MBB->getNumber() << " Live-ins:"); + for (unsigned i = 0, e = TBI.LiveIns.size(); i != e; ++i) { + LiveInReg &LIR = TBI.LiveIns[i]; + const MachineInstr *DefMI = MTM.MRI->getVRegDef(LIR.Reg); + LIR.Height = Heights.lookup(DefMI); + DEBUG(dbgs() << ' ' << PrintReg(LIR.Reg) << '@' << LIR.Height); + } + + // Transfer the live regunits to the live-in list. + for (SparseSet<LiveRegUnit>::const_iterator + RI = RegUnits.begin(), RE = RegUnits.end(); RI != RE; ++RI) { + TBI.LiveIns.push_back(LiveInReg(RI->RegUnit, RI->Cycle)); + DEBUG(dbgs() << ' ' << PrintRegUnit(RI->RegUnit, MTM.TRI) + << '@' << RI->Cycle); + } + DEBUG(dbgs() << '\n'); + + if (!TBI.HasValidInstrDepths) + continue; + // Add live-ins to the critical path length. + TBI.CriticalPath = std::max(TBI.CriticalPath, + computeCrossBlockCriticalPath(TBI)); + DEBUG(dbgs() << "Critical path: " << TBI.CriticalPath << '\n'); + } +} + +MachineTraceMetrics::Trace +MachineTraceMetrics::Ensemble::getTrace(const MachineBasicBlock *MBB) { + // FIXME: Check cache tags, recompute as needed. + computeTrace(MBB); + computeInstrDepths(MBB); + computeInstrHeights(MBB); + return Trace(*this, BlockInfo[MBB->getNumber()]); +} + +unsigned +MachineTraceMetrics::Trace::getInstrSlack(const MachineInstr *MI) const { + assert(MI && "Not an instruction."); + assert(getBlockNum() == unsigned(MI->getParent()->getNumber()) && + "MI must be in the trace center block"); + InstrCycles Cyc = getInstrCycles(MI); + return getCriticalPath() - (Cyc.Depth + Cyc.Height); +} + +unsigned +MachineTraceMetrics::Trace::getPHIDepth(const MachineInstr *PHI) const { + const MachineBasicBlock *MBB = TE.MTM.MF->getBlockNumbered(getBlockNum()); + SmallVector<DataDep, 1> Deps; + getPHIDeps(PHI, Deps, MBB, TE.MTM.MRI); + assert(Deps.size() == 1 && "PHI doesn't have MBB as a predecessor"); + DataDep &Dep = Deps.front(); + unsigned DepCycle = getInstrCycles(Dep.DefMI).Depth; + // Add latency if DefMI is a real instruction. Transients get latency 0. + if (!Dep.DefMI->isTransient()) + DepCycle += TE.MTM.TII->computeOperandLatency(TE.MTM.ItinData, + Dep.DefMI, Dep.DefOp, + PHI, Dep.UseOp, + /* FindMin = */ false); + return DepCycle; +} + +unsigned MachineTraceMetrics::Trace::getResourceDepth(bool Bottom) const { + // For now, we compute the resource depth from instruction count / issue + // width. Eventually, we should compute resource depth per functional unit + // and return the max. + unsigned Instrs = TBI.InstrDepth; + if (Bottom) + Instrs += TE.MTM.BlockInfo[getBlockNum()].InstrCount; + if (const MCSchedModel *Model = TE.MTM.ItinData->SchedModel) + if (Model->IssueWidth != 0) + return Instrs / Model->IssueWidth; + // Assume issue width 1 without a schedule model. + return Instrs; +} + +unsigned MachineTraceMetrics::Trace:: +getResourceLength(ArrayRef<const MachineBasicBlock*> Extrablocks) const { + unsigned Instrs = TBI.InstrDepth + TBI.InstrHeight; + for (unsigned i = 0, e = Extrablocks.size(); i != e; ++i) + Instrs += TE.MTM.getResources(Extrablocks[i])->InstrCount; + if (const MCSchedModel *Model = TE.MTM.ItinData->SchedModel) + if (Model->IssueWidth != 0) + return Instrs / Model->IssueWidth; + // Assume issue width 1 without a schedule model. + return Instrs; +} + +void MachineTraceMetrics::Ensemble::print(raw_ostream &OS) const { + OS << getName() << " ensemble:\n"; + for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) { + OS << " BB#" << i << '\t'; + BlockInfo[i].print(OS); + OS << '\n'; + } +} + +void MachineTraceMetrics::TraceBlockInfo::print(raw_ostream &OS) const { + if (hasValidDepth()) { + OS << "depth=" << InstrDepth; + if (Pred) + OS << " pred=BB#" << Pred->getNumber(); + else + OS << " pred=null"; + OS << " head=BB#" << Head; + if (HasValidInstrDepths) + OS << " +instrs"; + } else + OS << "depth invalid"; + OS << ", "; + if (hasValidHeight()) { + OS << "height=" << InstrHeight; + if (Succ) + OS << " succ=BB#" << Succ->getNumber(); + else + OS << " succ=null"; + OS << " tail=BB#" << Tail; + if (HasValidInstrHeights) + OS << " +instrs"; + } else + OS << "height invalid"; + if (HasValidInstrDepths && HasValidInstrHeights) + OS << ", crit=" << CriticalPath; +} + +void MachineTraceMetrics::Trace::print(raw_ostream &OS) const { + unsigned MBBNum = &TBI - &TE.BlockInfo[0]; + + OS << TE.getName() << " trace BB#" << TBI.Head << " --> BB#" << MBBNum + << " --> BB#" << TBI.Tail << ':'; + if (TBI.hasValidHeight() && TBI.hasValidDepth()) + OS << ' ' << getInstrCount() << " instrs."; + if (TBI.HasValidInstrDepths && TBI.HasValidInstrHeights) + OS << ' ' << TBI.CriticalPath << " cycles."; + + const MachineTraceMetrics::TraceBlockInfo *Block = &TBI; + OS << "\nBB#" << MBBNum; + while (Block->hasValidDepth() && Block->Pred) { + unsigned Num = Block->Pred->getNumber(); + OS << " <- BB#" << Num; + Block = &TE.BlockInfo[Num]; + } + + Block = &TBI; + OS << "\n "; + while (Block->hasValidHeight() && Block->Succ) { + unsigned Num = Block->Succ->getNumber(); + OS << " -> BB#" << Num; + Block = &TE.BlockInfo[Num]; + } + OS << '\n'; +} |