+//===- 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 "early-ifcvt"
+#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/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/PostOrderIterator.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), 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 &MF) {
+ TII = MF.getTarget().getInstrInfo();
+ TRI = MF.getTarget().getRegisterInfo();
+ MRI = &MF.getRegInfo();
+ Loops = &getAnalysis<MachineLoopInfo>();
+ unsigned NumBlocks = MF.getNumBlockIDs();
+ BlockInfo.resize(NumBlocks);
+ return false;
+}
+
+void MachineTraceMetrics::releaseMemory() {
+ 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.
+
+/// Is MI an instruction that should be considered free because it will likely
+/// be eliminated by later passes?
+static bool isFree(const MachineInstr *MI) {
+ switch(MI->getOpcode()) {
+ default: return false;
+ case TargetOpcode::PHI:
+ case TargetOpcode::PROLOG_LABEL:
+ case TargetOpcode::EH_LABEL:
+ case TargetOpcode::GC_LABEL:
+ case TargetOpcode::KILL:
+ case TargetOpcode::EXTRACT_SUBREG:
+ case TargetOpcode::INSERT_SUBREG:
+ case TargetOpcode::IMPLICIT_DEF:
+ case TargetOpcode::SUBREG_TO_REG:
+ case TargetOpcode::COPY_TO_REGCLASS:
+ case TargetOpcode::DBG_VALUE:
+ case TargetOpcode::REG_SEQUENCE:
+ case TargetOpcode::COPY:
+ return true;
+ }
+}
+
+/// 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 (isFree(MI))
+ continue;
+ ++InstrCount;
+ if (MI->isCall())
+ FBI->HasCalls = true;
+ }
+ FBI->InstrCount = InstrCount;
+ return FBI;
+}
+
+//===----------------------------------------------------------------------===//
+// Ensemble utility functions
+//===----------------------------------------------------------------------===//
+
+MachineTraceMetrics::Ensemble::Ensemble(MachineTraceMetrics *ct)
+ : CT(*ct) {
+ BlockInfo.resize(CT.BlockInfo.size());
+}
+
+// Virtual destructor serves as an anchor.
+MachineTraceMetrics::Ensemble::~Ensemble() {}
+
+MachineLoop*
+MachineTraceMetrics::Ensemble::getLoopFor(const MachineBasicBlock *MBB) {
+ return CT.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;
+ 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 = CT.getResources(TBI->Pred);
+ TBI->InstrDepth = PredTBI->InstrDepth + PredFBI->InstrCount;
+}
+
+// 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 = CT.getResources(MBB)->InstrCount;
+
+ // The trace tail is done.
+ if (!TBI->Succ)
+ 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;
+}
+
+// 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.
+//
+
+// MinInstrCountEnsemble - Pick the trace that executes the least number of
+// instructions.
+namespace {
+class MinInstrCountEnsemble : public MachineTraceMetrics::Ensemble {
+ const char *getName() { return "MinInstr"; }
+ const MachineBasicBlock *pickTracePred(const MachineBasicBlock*);
+ const MachineBasicBlock *pickTraceSucc(const MachineBasicBlock*);
+
+public:
+ MinInstrCountEnsemble(MachineTraceMetrics *ct)
+ : MachineTraceMetrics::Ensemble(ct) {}
+};
+}
+
+// Select the preferred predecessor for MBB.
+const MachineBasicBlock*
+MinInstrCountEnsemble::pickTracePred(const MachineBasicBlock *MBB) {
+ if (MBB->pred_empty())
+ return 0;
+ MachineLoop *CurLoop = getLoopFor(MBB);
+ // Don't leave loops, and never follow back-edges.
+ if (CurLoop && MBB == CurLoop->getHeader())
+ return 0;
+ unsigned CurCount = CT.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 invalidated predecessors. This never happens on the first scan,
+ // but if we rejected this predecessor earlier, it won't be revalidated.
+ if (!PredTBI)
+ continue;
+ // Don't consider predecessors in other loops.
+ if (getLoopFor(Pred) != CurLoop)
+ 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;
+ 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;
+ const MachineTraceMetrics::TraceBlockInfo *SuccTBI =
+ getHeightResources(Succ);
+ // Ignore invalidated successors.
+ if (!SuccTBI)
+ continue;
+ // Don't consider back-edges.
+ if (CurLoop && Succ == CurLoop->getHeader())
+ continue;
+ // Don't consider successors in other loops.
+ if (getLoopFor(Succ) != CurLoop)
+ 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);
+}
+
+//===----------------------------------------------------------------------===//
+// 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;
+ const MachineLoopInfo *Loops;
+ const MachineLoop *CurLoop;
+ bool Downward;
+ LoopBounds(MutableArrayRef<MachineTraceMetrics::TraceBlockInfo> blocks,
+ const MachineLoopInfo *loops, const MachineLoop *curloop)
+ : Blocks(blocks), Loops(loops), CurLoop(curloop), 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;
+ // Don't follow CurLoop backedges.
+ if (LB.CurLoop && (LB.Downward ? To : From) == LB.CurLoop->getHeader())
+ return false;
+ // Don't leave CurLoop.
+ if (LB.Loops->getLoopFor(To) != LB.CurLoop)
+ return false;
+ // This is a new block. The PO traversal will compute height/depth
+ // resources, causing us to reject new edges to To. This only works because
+ // we reject back-edges, so the CFG is cycle-free.
+ return true;
+ }
+};
+}
+
+/// 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, CT.Loops, getLoopFor(MBB));
+
+ // Run an upwards post-order search for the trace start.
+ Bounds.Downward = false;
+ 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;
+ 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.
+ BlockInfo[I->getNumber()].Succ = pickTraceSucc(*I);
+ DEBUG({
+ if (TBI.Pred)
+ 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() && TBI.Succ == MBB) {
+ TBI.invalidateHeight();
+ WorkList.push_back(*I);
+ }
+ }
+ } 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() && TBI.Pred == MBB) {
+ TBI.invalidateDepth();
+ WorkList.push_back(*I);
+ }
+ }
+ } while (!WorkList.empty());
+ }
+}
+
+
+MachineTraceMetrics::Trace
+MachineTraceMetrics::Ensemble::getTrace(const MachineBasicBlock *MBB) {
+ // FIXME: Check cache tags, recompute as needed.
+ computeTrace(MBB);
+ return Trace(*this, BlockInfo[MBB->getNumber()]);
+}
+
+void MachineTraceMetrics::Trace::print(raw_ostream &OS) const {
+ OS << TE.getName() << " trace:";
+ if (TBI.hasValidHeight() && TBI.hasValidDepth())
+ OS << ' ' << getInstrCount() << " instrs.";
+
+ const MachineTraceMetrics::TraceBlockInfo *Block = &TBI;
+ OS << "\n *";
+ 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';
+}
projects / oota-llvm.git / commitdiff