C++ CodeMetrics类代码示例

/// ApproximateLoopSize - Approximate the size of the loop.
static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
                                    bool &NotDuplicatable,
                                    const TargetTransformInfo &TTI,
                                    AssumptionCache *AC) {
  SmallPtrSet<const Value *, 32> EphValues;
  CodeMetrics::collectEphemeralValues(L, AC, EphValues);

  CodeMetrics Metrics;
  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
       I != E; ++I)
    Metrics.analyzeBasicBlock(*I, TTI, EphValues);
  NumCalls = Metrics.NumInlineCandidates;
  NotDuplicatable = Metrics.notDuplicatable;

  unsigned LoopSize = Metrics.NumInsts;

  // Don't allow an estimate of size zero.  This would allows unrolling of loops
  // with huge iteration counts, which is a compile time problem even if it's
  // not a problem for code quality. Also, the code using this size may assume
  // that each loop has at least three instructions (likely a conditional
  // branch, a comparison feeding that branch, and some kind of loop increment
  // feeding that comparison instruction).
  LoopSize = std::max(LoopSize, 3u);

  return LoopSize;
}

// Analyze loop. Check its size, calculate is it possible to unswitch
// it. Returns true if we can unswitch this loop.
bool LUAnalysisCache::countLoop(const Loop *L, const TargetTransformInfo &TTI,
                                AssumptionCache *AC) {

  LoopPropsMapIt PropsIt;
  bool Inserted;
  std::tie(PropsIt, Inserted) =
      LoopsProperties.insert(std::make_pair(L, LoopProperties()));

  LoopProperties &Props = PropsIt->second;

  if (Inserted) {
    // New loop.

    // Limit the number of instructions to avoid causing significant code
    // expansion, and the number of basic blocks, to avoid loops with
    // large numbers of branches which cause loop unswitching to go crazy.
    // This is a very ad-hoc heuristic.

    SmallPtrSet<const Value *, 32> EphValues;
    CodeMetrics::collectEphemeralValues(L, AC, EphValues);

    // FIXME: This is overly conservative because it does not take into
    // consideration code simplification opportunities and code that can
    // be shared by the resultant unswitched loops.
    CodeMetrics Metrics;
    for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
         I != E; ++I)
      Metrics.analyzeBasicBlock(*I, TTI, EphValues);

    Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
    Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
    MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;

    if (Metrics.notDuplicatable) {
      DEBUG(dbgs() << "NOT unswitching loop %"
                   << L->getHeader()->getName() << ", contents cannot be "
                   << "duplicated!\n");
      return false;
    }
  }

  if (!Props.CanBeUnswitchedCount) {
    DEBUG(dbgs() << "NOT unswitching loop %"
                 << L->getHeader()->getName() << ", cost too high: "
                 << L->getBlocks().size() << "\n");
    return false;
  }

  // Be careful. This links are good only before new loop addition.
  CurrentLoopProperties = &Props;
  CurLoopInstructions = &Props.UnswitchedVals;

  return true;
}

/// UnswitchIfProfitable - We have found that we can unswitch currentLoop when
/// LoopCond == Val to simplify the loop.  If we decide that this is profitable,
/// unswitch the loop, reprocess the pieces, then return true.
bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val) {

  initLoopData();

  // If LoopSimplify was unable to form a preheader, don't do any unswitching.
  if (!loopPreheader)
    return false;

  Function *F = loopHeader->getParent();

  Constant *CondVal = 0;
  BasicBlock *ExitBlock = 0;
  if (IsTrivialUnswitchCondition(LoopCond, &CondVal, &ExitBlock)) {
    // If the condition is trivial, always unswitch. There is no code growth
    // for this case.
    UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, ExitBlock);
    return true;
  }

  // Check to see if it would be profitable to unswitch current loop.

  // Do not do non-trivial unswitch while optimizing for size.
  if (OptimizeForSize || F->hasFnAttr(Attribute::OptimizeForSize))
    return false;

  // FIXME: This is overly conservative because it does not take into
  // consideration code simplification opportunities and code that can
  // be shared by the resultant unswitched loops.
  CodeMetrics Metrics;
  for (Loop::block_iterator I = currentLoop->block_begin(), 
         E = currentLoop->block_end();
       I != E; ++I)
    Metrics.analyzeBasicBlock(*I);

  // Limit the number of instructions to avoid causing significant code
  // expansion, and the number of basic blocks, to avoid loops with
  // large numbers of branches which cause loop unswitching to go crazy.
  // This is a very ad-hoc heuristic.
  if (Metrics.NumInsts > Threshold ||
      Metrics.NumBlocks * 5 > Threshold ||
      Metrics.containsIndirectBr || Metrics.isRecursive) {
    DEBUG(dbgs() << "NOT unswitching loop %"
          << currentLoop->getHeader()->getName() << ", cost too high: "
          << currentLoop->getBlocks().size() << "\n");
    return false;
  }

  UnswitchNontrivialCondition(LoopCond, Val, currentLoop);
  return true;
}

/// Rotate loop LP. Return true if the loop is rotated.
///
/// \param SimplifiedLatch is true if the latch was just folded into the final
/// loop exit. In this case we may want to rotate even though the new latch is
/// now an exiting branch. This rotation would have happened had the latch not
/// been simplified. However, if SimplifiedLatch is false, then we avoid
/// rotating loops in which the latch exits to avoid excessive or endless
/// rotation. LoopRotate should be repeatable and converge to a canonical
/// form. This property is satisfied because simplifying the loop latch can only
/// happen once across multiple invocations of the LoopRotate pass.
bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
  // If the loop has only one block then there is not much to rotate.
  if (L->getBlocks().size() == 1)
    return false;

  BasicBlock *OrigHeader = L->getHeader();
  BasicBlock *OrigLatch = L->getLoopLatch();

  BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
  if (!BI || BI->isUnconditional())
    return false;

  // If the loop header is not one of the loop exiting blocks then
  // either this loop is already rotated or it is not
  // suitable for loop rotation transformations.
  if (!L->isLoopExiting(OrigHeader))
    return false;

  // If the loop latch already contains a branch that leaves the loop then the
  // loop is already rotated.
  if (!OrigLatch)
    return false;

  // Rotate if either the loop latch does *not* exit the loop, or if the loop
  // latch was just simplified. Or if we think it will be profitable.
  if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch && IsUtilMode == false &&
      !shouldRotateLoopExitingLatch(L))
    return false;

  // Check size of original header and reject loop if it is very big or we can't
  // duplicate blocks inside it.
  {
    SmallPtrSet<const Value *, 32> EphValues;
    CodeMetrics::collectEphemeralValues(L, AC, EphValues);

    CodeMetrics Metrics;
    Metrics.analyzeBasicBlock(OrigHeader, *TTI, EphValues);
    if (Metrics.notDuplicatable) {
      LLVM_DEBUG(
          dbgs() << "LoopRotation: NOT rotating - contains non-duplicatable"
                 << " instructions: ";
          L->dump());
      return false;
    }
    if (Metrics.convergent) {
      LLVM_DEBUG(dbgs() << "LoopRotation: NOT rotating - contains convergent "
                           "instructions: ";
                 L->dump());
      return false;
    }

/// ApproximateLoopSize - Approximate the size of the loop.
static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls) {
  CodeMetrics Metrics;
  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
       I != E; ++I)
    Metrics.analyzeBasicBlock(*I);
  NumCalls = Metrics.NumInlineCandidates;

  unsigned LoopSize = Metrics.NumInsts;

  // Don't allow an estimate of size zero.  This would allows unrolling of loops
  // with huge iteration counts, which is a compile time problem even if it's
  // not a problem for code quality.
  if (LoopSize == 0) LoopSize = 1;

  return LoopSize;
}

// Analyze loop. Check its size, calculate is it possible to unswitch
// it. Returns true if we can unswitch this loop.
bool LUAnalysisCache::countLoop(const Loop* L) {

  std::pair<LoopPropsMapIt, bool> InsertRes =
      LoopsProperties.insert(std::make_pair(L, LoopProperties()));

  LoopProperties& Props = InsertRes.first->second;

  if (InsertRes.second) {
    // New loop.

    // Limit the number of instructions to avoid causing significant code
    // expansion, and the number of basic blocks, to avoid loops with
    // large numbers of branches which cause loop unswitching to go crazy.
    // This is a very ad-hoc heuristic.

    // FIXME: This is overly conservative because it does not take into
    // consideration code simplification opportunities and code that can
    // be shared by the resultant unswitched loops.
    CodeMetrics Metrics;
    for (Loop::block_iterator I = L->block_begin(),
           E = L->block_end();
         I != E; ++I)
      Metrics.analyzeBasicBlock(*I);

    Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
    Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
    MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
  }

  if (!Props.CanBeUnswitchedCount) {
    DEBUG(dbgs() << "NOT unswitching loop %"
          << L->getHeader()->getName() << ", cost too high: "
          << L->getBlocks().size() << "\n");

    return false;
  }

  // Be careful. This links are good only before new loop addition.
  CurrentLoopProperties = &Props;
  CurLoopInstructions = &Props.UnswitchedVals;

  return true;
}

/// Rotate loop LP. Return true if the loop is rotated.
///
/// \param SimplifiedLatch is true if the latch was just folded into the final
/// loop exit. In this case we may want to rotate even though the new latch is
/// now an exiting branch. This rotation would have happened had the latch not
/// been simplified. However, if SimplifiedLatch is false, then we avoid
/// rotating loops in which the latch exits to avoid excessive or endless
/// rotation. LoopRotate should be repeatable and converge to a canonical
/// form. This property is satisfied because simplifying the loop latch can only
/// happen once across multiple invocations of the LoopRotate pass.
bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
  // If the loop has only one block then there is not much to rotate.
  if (L->getBlocks().size() == 1)
    return false;

  BasicBlock *OrigHeader = L->getHeader();
  BasicBlock *OrigLatch = L->getLoopLatch();

  BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
  if (BI == 0 || BI->isUnconditional())
    return false;

  // If the loop header is not one of the loop exiting blocks then
  // either this loop is already rotated or it is not
  // suitable for loop rotation transformations.
  if (!L->isLoopExiting(OrigHeader))
    return false;

  // If the loop latch already contains a branch that leaves the loop then the
  // loop is already rotated.
  if (OrigLatch == 0)
    return false;

  // Rotate if either the loop latch does *not* exit the loop, or if the loop
  // latch was just simplified.
  if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch)
    return false;

  // Check size of original header and reject loop if it is very big or we can't
  // duplicate blocks inside it.
  {
    CodeMetrics Metrics;
    Metrics.analyzeBasicBlock(OrigHeader, *TTI);
    if (Metrics.notDuplicatable) {
      DEBUG(dbgs() << "LoopRotation: NOT rotating - contains non duplicatable"
            << " instructions: "; L->dump());
      return false;
    }
    if (Metrics.NumInsts > MAX_HEADER_SIZE)
      return false;
  }

/// ApproximateLoopSize - Approximate the size of the loop.
static unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
                                    bool &NotDuplicatable,
                                    const TargetTransformInfo &TTI,
                                    AssumptionTracker *AT) {
  SmallPtrSet<const Value *, 32> EphValues;
  CodeMetrics::collectEphemeralValues(L, AT, EphValues);

  CodeMetrics Metrics;
  for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
       I != E; ++I)
    Metrics.analyzeBasicBlock(*I, TTI, EphValues);
  NumCalls = Metrics.NumInlineCandidates;
  NotDuplicatable = Metrics.notDuplicatable;

  unsigned LoopSize = Metrics.NumInsts;

  // Don't allow an estimate of size zero.  This would allows unrolling of loops
  // with huge iteration counts, which is a compile time problem even if it's
  // not a problem for code quality.
  if (LoopSize == 0) LoopSize = 1;

  return LoopSize;
}

bool PPCLoopDataPrefetch::runOnLoop(Loop *L) {
  bool MadeChange = false;

  // Only prefetch in the inner-most loop
  if (!L->empty())
    return MadeChange;

  SmallPtrSet<const Value *, 32> EphValues;
  CodeMetrics::collectEphemeralValues(L, AC, EphValues);

  // Calculate the number of iterations ahead to prefetch
  CodeMetrics Metrics;
  for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
       I != IE; ++I) {

    // If the loop already has prefetches, then assume that the user knows
    // what he or she is doing and don't add any more.
    for (BasicBlock::iterator J = (*I)->begin(), JE = (*I)->end();
         J != JE; ++J)
      if (CallInst *CI = dyn_cast<CallInst>(J))
        if (Function *F = CI->getCalledFunction())
          if (F->getIntrinsicID() == Intrinsic::prefetch)
            return MadeChange;

    Metrics.analyzeBasicBlock(*I, *TTI, EphValues);
  }
  unsigned LoopSize = Metrics.NumInsts;
  if (!LoopSize)
    LoopSize = 1;

  unsigned ItersAhead = PrefDist/LoopSize;
  if (!ItersAhead)
    ItersAhead = 1;

  SmallVector<std::pair<Instruction *, const SCEVAddRecExpr *>, 16> PrefLoads;
  for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
       I != IE; ++I) {
    for (BasicBlock::iterator J = (*I)->begin(), JE = (*I)->end();
        J != JE; ++J) {
      Value *PtrValue;
      Instruction *MemI;

      if (LoadInst *LMemI = dyn_cast<LoadInst>(J)) {
        MemI = LMemI;
        PtrValue = LMemI->getPointerOperand();
      } else if (StoreInst *SMemI = dyn_cast<StoreInst>(J)) {
        if (!PrefetchWrites) continue;
        MemI = SMemI;
        PtrValue = SMemI->getPointerOperand();
      } else continue;

      unsigned PtrAddrSpace = PtrValue->getType()->getPointerAddressSpace();
      if (PtrAddrSpace)
        continue;

      if (L->isLoopInvariant(PtrValue))
        continue;

      const SCEV *LSCEV = SE->getSCEV(PtrValue);
      const SCEVAddRecExpr *LSCEVAddRec = dyn_cast<SCEVAddRecExpr>(LSCEV);
      if (!LSCEVAddRec)
        continue;

      // We don't want to double prefetch individual cache lines. If this load
      // is known to be within one cache line of some other load that has
      // already been prefetched, then don't prefetch this one as well.
      bool DupPref = false;
      for (SmallVector<std::pair<Instruction *, const SCEVAddRecExpr *>,
             16>::iterator K = PrefLoads.begin(), KE = PrefLoads.end();
           K != KE; ++K) {
        const SCEV *PtrDiff = SE->getMinusSCEV(LSCEVAddRec, K->second);
        if (const SCEVConstant *ConstPtrDiff =
            dyn_cast<SCEVConstant>(PtrDiff)) {
          int64_t PD = std::abs(ConstPtrDiff->getValue()->getSExtValue());
          if (PD < (int64_t) CacheLineSize) {
            DupPref = true;
            break;
          }
        }
      }
      if (DupPref)
        continue;

      const SCEV *NextLSCEV = SE->getAddExpr(LSCEVAddRec, SE->getMulExpr(
        SE->getConstant(LSCEVAddRec->getType(), ItersAhead),
        LSCEVAddRec->getStepRecurrence(*SE)));
      if (!isSafeToExpand(NextLSCEV, *SE))
        continue;

      PrefLoads.push_back(std::make_pair(MemI, LSCEVAddRec));

      Type *I8Ptr = Type::getInt8PtrTy((*I)->getContext(), PtrAddrSpace);
      SCEVExpander SCEVE(*SE, J->getModule()->getDataLayout(), "prefaddr");
      Value *PrefPtrValue = SCEVE.expandCodeFor(NextLSCEV, I8Ptr, MemI);

      IRBuilder<> Builder(MemI);
      Module *M = (*I)->getParent()->getParent();
      Type *I32 = Type::getInt32Ty((*I)->getContext());
      Value *PrefetchFunc = Intrinsic::getDeclaration(M, Intrinsic::prefetch);
      Builder.CreateCall4(PrefetchFunc, PrefPtrValue,
//.........这里部分代码省略.........

bool PPCCTRLoops::convertToCTRLoop(Loop *L) {
  bool MadeChange = false;

  // Do not convert small short loops to CTR loop.
  unsigned ConstTripCount = SE->getSmallConstantTripCount(L);
  if (ConstTripCount && ConstTripCount < SmallCTRLoopThreshold) {
    SmallPtrSet<const Value *, 32> EphValues;
    auto AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
        *L->getHeader()->getParent());
    CodeMetrics::collectEphemeralValues(L, &AC, EphValues);
    CodeMetrics Metrics;
    for (BasicBlock *BB : L->blocks())
      Metrics.analyzeBasicBlock(BB, *TTI, EphValues);
    // 6 is an approximate latency for the mtctr instruction.
    if (Metrics.NumInsts <= (6 * SchedModel.getIssueWidth()))
      return false;
  }

  // Process nested loops first.
  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) {
    MadeChange |= convertToCTRLoop(*I);
    LLVM_DEBUG(dbgs() << "Nested loop converted\n");
  }

  // If a nested loop has been converted, then we can't convert this loop.
  if (MadeChange)
    return MadeChange;

  // Bail out if the loop has irreducible control flow.
  LoopBlocksRPO RPOT(L);
  RPOT.perform(LI);
  if (containsIrreducibleCFG<const BasicBlock *>(RPOT, *LI))
    return false;

#ifndef NDEBUG
  // Stop trying after reaching the limit (if any).
  int Limit = CTRLoopLimit;
  if (Limit >= 0) {
    if (Counter >= CTRLoopLimit)
      return false;
    Counter++;
  }
#endif

  // We don't want to spill/restore the counter register, and so we don't
  // want to use the counter register if the loop contains calls.
  for (Loop::block_iterator I = L->block_begin(), IE = L->block_end();
       I != IE; ++I)
    if (mightUseCTR(*I))
      return MadeChange;

  SmallVector<BasicBlock*, 4> ExitingBlocks;
  L->getExitingBlocks(ExitingBlocks);

  // If there is an exit edge known to be frequently taken,
  // we should not transform this loop.
  for (auto &BB : ExitingBlocks) {
    Instruction *TI = BB->getTerminator();
    if (!TI) continue;

    if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
      uint64_t TrueWeight = 0, FalseWeight = 0;
      if (!BI->isConditional() ||
          !BI->extractProfMetadata(TrueWeight, FalseWeight))
        continue;

      // If the exit path is more frequent than the loop path,
      // we return here without further analysis for this loop.
      bool TrueIsExit = !L->contains(BI->getSuccessor(0));
      if (( TrueIsExit && FalseWeight < TrueWeight) ||
          (!TrueIsExit && FalseWeight > TrueWeight))
        return MadeChange;
    }
  }

  BasicBlock *CountedExitBlock = nullptr;
  const SCEV *ExitCount = nullptr;
  BranchInst *CountedExitBranch = nullptr;
  for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(),
       IE = ExitingBlocks.end(); I != IE; ++I) {
    const SCEV *EC = SE->getExitCount(L, *I);
    LLVM_DEBUG(dbgs() << "Exit Count for " << *L << " from block "
                      << (*I)->getName() << ": " << *EC << "\n");
    if (isa<SCEVCouldNotCompute>(EC))
      continue;
    if (const SCEVConstant *ConstEC = dyn_cast<SCEVConstant>(EC)) {
      if (ConstEC->getValue()->isZero())
        continue;
    } else if (!SE->isLoopInvariant(EC, L))
      continue;

    if (SE->getTypeSizeInBits(EC->getType()) > (TM->isPPC64() ? 64 : 32))
      continue;

    // If this exiting block is contained in a nested loop, it is not eligible
    // for insertion of the branch-and-decrement since the inner loop would
    // end up messing up the value in the CTR.
    if (LI->getLoopFor(*I) != L)
      continue;

//.........这里部分代码省略.........