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+//===- BlockFrequencyImplInfo.cpp - Block Frequency Info Implementation ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Loops should be simplified before this analysis.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/GraphTraits.h"
+#include "llvm/ADT/None.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Support/BlockFrequency.h"
+#include "llvm/Support/BranchProbability.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ScaledNumber.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+#include <list>
+#include <numeric>
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+using namespace llvm::bfi_detail;
+
+#define DEBUG_TYPE "block-freq"
+
+ScaledNumber<uint64_t> BlockMass::toScaled() const {
+ if (isFull())
+ return ScaledNumber<uint64_t>(1, 0);
+ return ScaledNumber<uint64_t>(getMass() + 1, -64);
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void BlockMass::dump() const { print(dbgs()); }
+#endif
+
+static char getHexDigit(int N) {
+ assert(N < 16);
+ if (N < 10)
+ return '0' + N;
+ return 'a' + N - 10;
+}
+
+raw_ostream &BlockMass::print(raw_ostream &OS) const {
+ for (int Digits = 0; Digits < 16; ++Digits)
+ OS << getHexDigit(Mass >> (60 - Digits * 4) & 0xf);
+ return OS;
+}
+
+namespace {
+
+using BlockNode = BlockFrequencyInfoImplBase::BlockNode;
+using Distribution = BlockFrequencyInfoImplBase::Distribution;
+using WeightList = BlockFrequencyInfoImplBase::Distribution::WeightList;
+using Scaled64 = BlockFrequencyInfoImplBase::Scaled64;
+using LoopData = BlockFrequencyInfoImplBase::LoopData;
+using Weight = BlockFrequencyInfoImplBase::Weight;
+using FrequencyData = BlockFrequencyInfoImplBase::FrequencyData;
+
+/// Dithering mass distributer.
+///
+/// This class splits up a single mass into portions by weight, dithering to
+/// spread out error. No mass is lost. The dithering precision depends on the
+/// precision of the product of \a BlockMass and \a BranchProbability.
+///
+/// The distribution algorithm follows.
+///
+/// 1. Initialize by saving the sum of the weights in \a RemWeight and the
+/// mass to distribute in \a RemMass.
+///
+/// 2. For each portion:
+///
+/// 1. Construct a branch probability, P, as the portion's weight divided
+/// by the current value of \a RemWeight.
+/// 2. Calculate the portion's mass as \a RemMass times P.
+/// 3. Update \a RemWeight and \a RemMass at each portion by subtracting
+/// the current portion's weight and mass.
+struct DitheringDistributer {
+ uint32_t RemWeight;
+ BlockMass RemMass;
+
+ DitheringDistributer(Distribution &Dist, const BlockMass &Mass);
+
+ BlockMass takeMass(uint32_t Weight);
+};
+
+} // end anonymous namespace
+
+DitheringDistributer::DitheringDistributer(Distribution &Dist,
+ const BlockMass &Mass) {
+ Dist.normalize();
+ RemWeight = Dist.Total;
+ RemMass = Mass;
+}
+
+BlockMass DitheringDistributer::takeMass(uint32_t Weight) {
+ assert(Weight && "invalid weight");
+ assert(Weight <= RemWeight);
+ BlockMass Mass = RemMass * BranchProbability(Weight, RemWeight);
+
+ // Decrement totals (dither).
+ RemWeight -= Weight;
+ RemMass -= Mass;
+ return Mass;
+}
+
+void Distribution::add(const BlockNode &Node, uint64_t Amount,
+ Weight::DistType Type) {
+ assert(Amount && "invalid weight of 0");
+ uint64_t NewTotal = Total + Amount;
+
+ // Check for overflow. It should be impossible to overflow twice.
+ bool IsOverflow = NewTotal < Total;
+ assert(!(DidOverflow && IsOverflow) && "unexpected repeated overflow");
+ DidOverflow |= IsOverflow;
+
+ // Update the total.
+ Total = NewTotal;
+
+ // Save the weight.
+ Weights.push_back(Weight(Type, Node, Amount));
+}
+
+static void combineWeight(Weight &W, const Weight &OtherW) {
+ assert(OtherW.TargetNode.isValid());
+ if (!W.Amount) {
+ W = OtherW;
+ return;
+ }
+ assert(W.Type == OtherW.Type);
+ assert(W.TargetNode == OtherW.TargetNode);
+ assert(OtherW.Amount && "Expected non-zero weight");
+ if (W.Amount > W.Amount + OtherW.Amount)
+ // Saturate on overflow.
+ W.Amount = UINT64_MAX;
+ else
+ W.Amount += OtherW.Amount;
+}
+
+static void combineWeightsBySorting(WeightList &Weights) {
+ // Sort so edges to the same node are adjacent.
+ llvm::sort(Weights, [](const Weight &L, const Weight &R) {
+ return L.TargetNode < R.TargetNode;
+ });
+
+ // Combine adjacent edges.
+ WeightList::iterator O = Weights.begin();
+ for (WeightList::const_iterator I = O, L = O, E = Weights.end(); I != E;
+ ++O, (I = L)) {
+ *O = *I;
+
+ // Find the adjacent weights to the same node.
+ for (++L; L != E && I->TargetNode == L->TargetNode; ++L)
+ combineWeight(*O, *L);
+ }
+
+ // Erase extra entries.
+ Weights.erase(O, Weights.end());
+}
+
+static void combineWeightsByHashing(WeightList &Weights) {
+ // Collect weights into a DenseMap.
+ using HashTable = DenseMap<BlockNode::IndexType, Weight>;
+
+ HashTable Combined(NextPowerOf2(2 * Weights.size()));
+ for (const Weight &W : Weights)
+ combineWeight(Combined[W.TargetNode.Index], W);
+
+ // Check whether anything changed.
+ if (Weights.size() == Combined.size())
+ return;
+
+ // Fill in the new weights.
+ Weights.clear();
+ Weights.reserve(Combined.size());
+ for (const auto &I : Combined)
+ Weights.push_back(I.second);
+}
+
+static void combineWeights(WeightList &Weights) {
+ // Use a hash table for many successors to keep this linear.
+ if (Weights.size() > 128) {
+ combineWeightsByHashing(Weights);
+ return;
+ }
+
+ combineWeightsBySorting(Weights);
+}
+
+static uint64_t shiftRightAndRound(uint64_t N, int Shift) {
+ assert(Shift >= 0);
+ assert(Shift < 64);
+ if (!Shift)
+ return N;
+ return (N >> Shift) + (UINT64_C(1) & N >> (Shift - 1));
+}
+
+void Distribution::normalize() {
+ // Early exit for termination nodes.
+ if (Weights.empty())
+ return;
+
+ // Only bother if there are multiple successors.
+ if (Weights.size() > 1)
+ combineWeights(Weights);
+
+ // Early exit when combined into a single successor.
+ if (Weights.size() == 1) {
+ Total = 1;
+ Weights.front().Amount = 1;
+ return;
+ }
+
+ // Determine how much to shift right so that the total fits into 32-bits.
+ //
+ // If we shift at all, shift by 1 extra. Otherwise, the lower limit of 1
+ // for each weight can cause a 32-bit overflow.
+ int Shift = 0;
+ if (DidOverflow)
+ Shift = 33;
+ else if (Total > UINT32_MAX)
+ Shift = 33 - countLeadingZeros(Total);
+
+ // Early exit if nothing needs to be scaled.
+ if (!Shift) {
+ // If we didn't overflow then combineWeights() shouldn't have changed the
+ // sum of the weights, but let's double-check.
+ assert(Total == std::accumulate(Weights.begin(), Weights.end(), UINT64_C(0),
+ [](uint64_t Sum, const Weight &W) {
+ return Sum + W.Amount;
+ }) &&
+ "Expected total to be correct");
+ return;
+ }
+
+ // Recompute the total through accumulation (rather than shifting it) so that
+ // it's accurate after shifting and any changes combineWeights() made above.
+ Total = 0;
+
+ // Sum the weights to each node and shift right if necessary.
+ for (Weight &W : Weights) {
+ // Scale down below UINT32_MAX. Since Shift is larger than necessary, we
+ // can round here without concern about overflow.
+ assert(W.TargetNode.isValid());
+ W.Amount = std::max(UINT64_C(1), shiftRightAndRound(W.Amount, Shift));
+ assert(W.Amount <= UINT32_MAX);
+
+ // Update the total.
+ Total += W.Amount;
+ }
+ assert(Total <= UINT32_MAX);
+}
+
+void BlockFrequencyInfoImplBase::clear() {
+ // Swap with a default-constructed std::vector, since std::vector<>::clear()
+ // does not actually clear heap storage.
+ std::vector<FrequencyData>().swap(Freqs);
+ IsIrrLoopHeader.clear();
+ std::vector<WorkingData>().swap(Working);
+ Loops.clear();
+}
+
+/// Clear all memory not needed downstream.
+///
+/// Releases all memory not used downstream. In particular, saves Freqs.
+static void cleanup(BlockFrequencyInfoImplBase &BFI) {
+ std::vector<FrequencyData> SavedFreqs(std::move(BFI.Freqs));
+ SparseBitVector<> SavedIsIrrLoopHeader(std::move(BFI.IsIrrLoopHeader));
+ BFI.clear();
+ BFI.Freqs = std::move(SavedFreqs);
+ BFI.IsIrrLoopHeader = std::move(SavedIsIrrLoopHeader);
+}
+
+bool BlockFrequencyInfoImplBase::addToDist(Distribution &Dist,
+ const LoopData *OuterLoop,
+ const BlockNode &Pred,
+ const BlockNode &Succ,
+ uint64_t Weight) {
+ if (!Weight)
+ Weight = 1;
+
+ auto isLoopHeader = [&OuterLoop](const BlockNode &Node) {
+ return OuterLoop && OuterLoop->isHeader(Node);
+ };
+
+ BlockNode Resolved = Working[Succ.Index].getResolvedNode();
+
+#ifndef NDEBUG
+ auto debugSuccessor = [&](const char *Type) {
+ dbgs() << " =>"
+ << " [" << Type << "] weight = " << Weight;
+ if (!isLoopHeader(Resolved))
+ dbgs() << ", succ = " << getBlockName(Succ);
+ if (Resolved != Succ)
+ dbgs() << ", resolved = " << getBlockName(Resolved);
+ dbgs() << "\n";
+ };
+ (void)debugSuccessor;
+#endif
+
+ if (isLoopHeader(Resolved)) {
+ LLVM_DEBUG(debugSuccessor("backedge"));
+ Dist.addBackedge(Resolved, Weight);
+ return true;
+ }
+
+ if (Working[Resolved.Index].getContainingLoop() != OuterLoop) {
+ LLVM_DEBUG(debugSuccessor(" exit "));
+ Dist.addExit(Resolved, Weight);
+ return true;
+ }
+
+ if (Resolved < Pred) {
+ if (!isLoopHeader(Pred)) {
+ // If OuterLoop is an irreducible loop, we can't actually handle this.
+ assert((!OuterLoop || !OuterLoop->isIrreducible()) &&
+ "unhandled irreducible control flow");
+
+ // Irreducible backedge. Abort.
+ LLVM_DEBUG(debugSuccessor("abort!!!"));
+ return false;
+ }
+
+ // If "Pred" is a loop header, then this isn't really a backedge; rather,
+ // OuterLoop must be irreducible. These false backedges can come only from
+ // secondary loop headers.
+ assert(OuterLoop && OuterLoop->isIrreducible() && !isLoopHeader(Resolved) &&
+ "unhandled irreducible control flow");
+ }
+
+ LLVM_DEBUG(debugSuccessor(" local "));
+ Dist.addLocal(Resolved, Weight);
+ return true;
+}
+
+bool BlockFrequencyInfoImplBase::addLoopSuccessorsToDist(
+ const LoopData *OuterLoop, LoopData &Loop, Distribution &Dist) {
+ // Copy the exit map into Dist.
+ for (const auto &I : Loop.Exits)
+ if (!addToDist(Dist, OuterLoop, Loop.getHeader(), I.first,
+ I.second.getMass()))
+ // Irreducible backedge.
+ return false;
+
+ return true;
+}
+
+/// Compute the loop scale for a loop.
+void BlockFrequencyInfoImplBase::computeLoopScale(LoopData &Loop) {
+ // Compute loop scale.
+ LLVM_DEBUG(dbgs() << "compute-loop-scale: " << getLoopName(Loop) << "\n");
+
+ // Infinite loops need special handling. If we give the back edge an infinite
+ // mass, they may saturate all the other scales in the function down to 1,
+ // making all the other region temperatures look exactly the same. Choose an
+ // arbitrary scale to avoid these issues.
+ //
+ // FIXME: An alternate way would be to select a symbolic scale which is later
+ // replaced to be the maximum of all computed scales plus 1. This would
+ // appropriately describe the loop as having a large scale, without skewing
+ // the final frequency computation.
+ const Scaled64 InfiniteLoopScale(1, 12);
+
+ // LoopScale == 1 / ExitMass
+ // ExitMass == HeadMass - BackedgeMass
+ BlockMass TotalBackedgeMass;
+ for (auto &Mass : Loop.BackedgeMass)
+ TotalBackedgeMass += Mass;
+ BlockMass ExitMass = BlockMass::getFull() - TotalBackedgeMass;
+
+ // Block scale stores the inverse of the scale. If this is an infinite loop,
+ // its exit mass will be zero. In this case, use an arbitrary scale for the
+ // loop scale.
+ Loop.Scale =
+ ExitMass.isEmpty() ? InfiniteLoopScale : ExitMass.toScaled().inverse();
+
+ LLVM_DEBUG(dbgs() << " - exit-mass = " << ExitMass << " ("
+ << BlockMass::getFull() << " - " << TotalBackedgeMass
+ << ")\n"
+ << " - scale = " << Loop.Scale << "\n");
+}
+
+/// Package up a loop.
+void BlockFrequencyInfoImplBase::packageLoop(LoopData &Loop) {
+ LLVM_DEBUG(dbgs() << "packaging-loop: " << getLoopName(Loop) << "\n");
+
+ // Clear the subloop exits to prevent quadratic memory usage.
+ for (const BlockNode &M : Loop.Nodes) {
+ if (auto *Loop = Working[M.Index].getPackagedLoop())
+ Loop->Exits.clear();
+ LLVM_DEBUG(dbgs() << " - node: " << getBlockName(M.Index) << "\n");
+ }
+ Loop.IsPackaged = true;
+}
+
+#ifndef NDEBUG
+static void debugAssign(const BlockFrequencyInfoImplBase &BFI,
+ const DitheringDistributer &D, const BlockNode &T,
+ const BlockMass &M, const char *Desc) {
+ dbgs() << " => assign " << M << " (" << D.RemMass << ")";
+ if (Desc)
+ dbgs() << " [" << Desc << "]";
+ if (T.isValid())
+ dbgs() << " to " << BFI.getBlockName(T);
+ dbgs() << "\n";
+}
+#endif
+
+void BlockFrequencyInfoImplBase::distributeMass(const BlockNode &Source,
+ LoopData *OuterLoop,
+ Distribution &Dist) {
+ BlockMass Mass = Working[Source.Index].getMass();
+ LLVM_DEBUG(dbgs() << " => mass: " << Mass << "\n");
+
+ // Distribute mass to successors as laid out in Dist.
+ DitheringDistributer D(Dist, Mass);
+
+ for (const Weight &W : Dist.Weights) {
+ // Check for a local edge (non-backedge and non-exit).
+ BlockMass Taken = D.takeMass(W.Amount);
+ if (W.Type == Weight::Local) {
+ Working[W.TargetNode.Index].getMass() += Taken;
+ LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, nullptr));
+ continue;
+ }
+
+ // Backedges and exits only make sense if we're processing a loop.
+ assert(OuterLoop && "backedge or exit outside of loop");
+
+ // Check for a backedge.
+ if (W.Type == Weight::Backedge) {
+ OuterLoop->BackedgeMass[OuterLoop->getHeaderIndex(W.TargetNode)] += Taken;
+ LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, "back"));
+ continue;
+ }
+
+ // This must be an exit.
+ assert(W.Type == Weight::Exit);
+ OuterLoop->Exits.push_back(std::make_pair(W.TargetNode, Taken));
+ LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, "exit"));
+ }
+}
+
+static void convertFloatingToInteger(BlockFrequencyInfoImplBase &BFI,
+ const Scaled64 &Min, const Scaled64 &Max) {
+ // Scale the Factor to a size that creates integers. Ideally, integers would
+ // be scaled so that Max == UINT64_MAX so that they can be best
+ // differentiated. However, in the presence of large frequency values, small
+ // frequencies are scaled down to 1, making it impossible to differentiate
+ // small, unequal numbers. When the spread between Min and Max frequencies
+ // fits well within MaxBits, we make the scale be at least 8.
+ const unsigned MaxBits = 64;
+ const unsigned SpreadBits = (Max / Min).lg();
+ Scaled64 ScalingFactor;
+ if (SpreadBits <= MaxBits - 3) {
+ // If the values are small enough, make the scaling factor at least 8 to
+ // allow distinguishing small values.
+ ScalingFactor = Min.inverse();
+ ScalingFactor <<= 3;
+ } else {
+ // If the values need more than MaxBits to be represented, saturate small
+ // frequency values down to 1 by using a scaling factor that benefits large
+ // frequency values.
+ ScalingFactor = Scaled64(1, MaxBits) / Max;
+ }
+
+ // Translate the floats to integers.
+ LLVM_DEBUG(dbgs() << "float-to-int: min = " << Min << ", max = " << Max
+ << ", factor = " << ScalingFactor << "\n");
+ for (size_t Index = 0; Index < BFI.Freqs.size(); ++Index) {
+ Scaled64 Scaled = BFI.Freqs[Index].Scaled * ScalingFactor;
+ BFI.Freqs[Index].Integer = std::max(UINT64_C(1), Scaled.toInt<uint64_t>());
+ LLVM_DEBUG(dbgs() << " - " << BFI.getBlockName(Index) << ": float = "
+ << BFI.Freqs[Index].Scaled << ", scaled = " << Scaled
+ << ", int = " << BFI.Freqs[Index].Integer << "\n");
+ }
+}
+
+/// Unwrap a loop package.
+///
+/// Visits all the members of a loop, adjusting their BlockData according to
+/// the loop's pseudo-node.
+static void unwrapLoop(BlockFrequencyInfoImplBase &BFI, LoopData &Loop) {
+ LLVM_DEBUG(dbgs() << "unwrap-loop-package: " << BFI.getLoopName(Loop)
+ << ": mass = " << Loop.Mass << ", scale = " << Loop.Scale
+ << "\n");
+ Loop.Scale *= Loop.Mass.toScaled();
+ Loop.IsPackaged = false;
+ LLVM_DEBUG(dbgs() << " => combined-scale = " << Loop.Scale << "\n");
+
+ // Propagate the head scale through the loop. Since members are visited in
+ // RPO, the head scale will be updated by the loop scale first, and then the
+ // final head scale will be used for updated the rest of the members.
+ for (const BlockNode &N : Loop.Nodes) {
+ const auto &Working = BFI.Working[N.Index];
+ Scaled64 &F = Working.isAPackage() ? Working.getPackagedLoop()->Scale
+ : BFI.Freqs[N.Index].Scaled;
+ Scaled64 New = Loop.Scale * F;
+ LLVM_DEBUG(dbgs() << " - " << BFI.getBlockName(N) << ": " << F << " => "
+ << New << "\n");
+ F = New;
+ }
+}
+
+void BlockFrequencyInfoImplBase::unwrapLoops() {
+ // Set initial frequencies from loop-local masses.
+ for (size_t Index = 0; Index < Working.size(); ++Index)
+ Freqs[Index].Scaled = Working[Index].Mass.toScaled();
+
+ for (LoopData &Loop : Loops)
+ unwrapLoop(*this, Loop);
+}
+
+void BlockFrequencyInfoImplBase::finalizeMetrics() {
+ // Unwrap loop packages in reverse post-order, tracking min and max
+ // frequencies.
+ auto Min = Scaled64::getLargest();
+ auto Max = Scaled64::getZero();
+ for (size_t Index = 0; Index < Working.size(); ++Index) {
+ // Update min/max scale.
+ Min = std::min(Min, Freqs[Index].Scaled);
+ Max = std::max(Max, Freqs[Index].Scaled);
+ }
+
+ // Convert to integers.
+ convertFloatingToInteger(*this, Min, Max);
+
+ // Clean up data structures.
+ cleanup(*this);
+
+ // Print out the final stats.
+ LLVM_DEBUG(dump());
+}
+
+BlockFrequency
+BlockFrequencyInfoImplBase::getBlockFreq(const BlockNode &Node) const {
+ if (!Node.isValid())
+ return 0;
+ return Freqs[Node.Index].Integer;
+}
+
+Optional<uint64_t>
+BlockFrequencyInfoImplBase::getBlockProfileCount(const Function &F,
+ const BlockNode &Node,
+ bool AllowSynthetic) const {
+ return getProfileCountFromFreq(F, getBlockFreq(Node).getFrequency(),
+ AllowSynthetic);
+}
+
+Optional<uint64_t>
+BlockFrequencyInfoImplBase::getProfileCountFromFreq(const Function &F,
+ uint64_t Freq,
+ bool AllowSynthetic) const {
+ auto EntryCount = F.getEntryCount(AllowSynthetic);
+ if (!EntryCount)
+ return None;
+ // Use 128 bit APInt to do the arithmetic to avoid overflow.
+ APInt BlockCount(128, EntryCount.getCount());
+ APInt BlockFreq(128, Freq);
+ APInt EntryFreq(128, getEntryFreq());
+ BlockCount *= BlockFreq;
+ // Rounded division of BlockCount by EntryFreq. Since EntryFreq is unsigned
+ // lshr by 1 gives EntryFreq/2.
+ BlockCount = (BlockCount + EntryFreq.lshr(1)).udiv(EntryFreq);
+ return BlockCount.getLimitedValue();
+}
+
+bool
+BlockFrequencyInfoImplBase::isIrrLoopHeader(const BlockNode &Node) {
+ if (!Node.isValid())
+ return false;
+ return IsIrrLoopHeader.test(Node.Index);
+}
+
+Scaled64
+BlockFrequencyInfoImplBase::getFloatingBlockFreq(const BlockNode &Node) const {
+ if (!Node.isValid())
+ return Scaled64::getZero();
+ return Freqs[Node.Index].Scaled;
+}
+
+void BlockFrequencyInfoImplBase::setBlockFreq(const BlockNode &Node,
+ uint64_t Freq) {
+ assert(Node.isValid() && "Expected valid node");
+ assert(Node.Index < Freqs.size() && "Expected legal index");
+ Freqs[Node.Index].Integer = Freq;
+}
+
+std::string
+BlockFrequencyInfoImplBase::getBlockName(const BlockNode &Node) const {
+ return {};
+}
+
+std::string
+BlockFrequencyInfoImplBase::getLoopName(const LoopData &Loop) const {
+ return getBlockName(Loop.getHeader()) + (Loop.isIrreducible() ? "**" : "*");
+}
+
+raw_ostream &
+BlockFrequencyInfoImplBase::printBlockFreq(raw_ostream &OS,
+ const BlockNode &Node) const {
+ return OS << getFloatingBlockFreq(Node);
+}
+
+raw_ostream &
+BlockFrequencyInfoImplBase::printBlockFreq(raw_ostream &OS,
+ const BlockFrequency &Freq) const {
+ Scaled64 Block(Freq.getFrequency(), 0);
+ Scaled64 Entry(getEntryFreq(), 0);
+
+ return OS << Block / Entry;
+}
+
+void IrreducibleGraph::addNodesInLoop(const BFIBase::LoopData &OuterLoop) {
+ Start = OuterLoop.getHeader();
+ Nodes.reserve(OuterLoop.Nodes.size());
+ for (auto N : OuterLoop.Nodes)
+ addNode(N);
+ indexNodes();
+}
+
+void IrreducibleGraph::addNodesInFunction() {
+ Start = 0;
+ for (uint32_t Index = 0; Index < BFI.Working.size(); ++Index)
+ if (!BFI.Working[Index].isPackaged())
+ addNode(Index);
+ indexNodes();
+}
+
+void IrreducibleGraph::indexNodes() {
+ for (auto &I : Nodes)
+ Lookup[I.Node.Index] = &I;
+}
+
+void IrreducibleGraph::addEdge(IrrNode &Irr, const BlockNode &Succ,
+ const BFIBase::LoopData *OuterLoop) {
+ if (OuterLoop && OuterLoop->isHeader(Succ))
+ return;
+ auto L = Lookup.find(Succ.Index);
+ if (L == Lookup.end())
+ return;
+ IrrNode &SuccIrr = *L->second;
+ Irr.Edges.push_back(&SuccIrr);
+ SuccIrr.Edges.push_front(&Irr);
+ ++SuccIrr.NumIn;
+}
+
+namespace llvm {
+
+template <> struct GraphTraits<IrreducibleGraph> {
+ using GraphT = bfi_detail::IrreducibleGraph;
+ using NodeRef = const GraphT::IrrNode *;
+ using ChildIteratorType = GraphT::IrrNode::iterator;
+
+ static NodeRef getEntryNode(const GraphT &G) { return G.StartIrr; }
+ static ChildIteratorType child_begin(NodeRef N) { return N->succ_begin(); }
+ static ChildIteratorType child_end(NodeRef N) { return N->succ_end(); }
+};
+
+} // end namespace llvm
+
+/// Find extra irreducible headers.
+///
+/// Find entry blocks and other blocks with backedges, which exist when \c G
+/// contains irreducible sub-SCCs.
+static void findIrreducibleHeaders(
+ const BlockFrequencyInfoImplBase &BFI,
+ const IrreducibleGraph &G,
+ const std::vector<const IrreducibleGraph::IrrNode *> &SCC,
+ LoopData::NodeList &Headers, LoopData::NodeList &Others) {
+ // Map from nodes in the SCC to whether it's an entry block.
+ SmallDenseMap<const IrreducibleGraph::IrrNode *, bool, 8> InSCC;
+
+ // InSCC also acts the set of nodes in the graph. Seed it.
+ for (const auto *I : SCC)
+ InSCC[I] = false;
+
+ for (auto I = InSCC.begin(), E = InSCC.end(); I != E; ++I) {
+ auto &Irr = *I->first;
+ for (const auto *P : make_range(Irr.pred_begin(), Irr.pred_end())) {
+ if (InSCC.count(P))
+ continue;
+
+ // This is an entry block.
+ I->second = true;
+ Headers.push_back(Irr.Node);
+ LLVM_DEBUG(dbgs() << " => entry = " << BFI.getBlockName(Irr.Node)
+ << "\n");
+ break;
+ }
+ }
+ assert(Headers.size() >= 2 &&
+ "Expected irreducible CFG; -loop-info is likely invalid");
+ if (Headers.size() == InSCC.size()) {
+ // Every block is a header.
+ llvm::sort(Headers);
+ return;
+ }
+
+ // Look for extra headers from irreducible sub-SCCs.
+ for (const auto &I : InSCC) {
+ // Entry blocks are already headers.
+ if (I.second)
+ continue;
+
+ auto &Irr = *I.first;
+ for (const auto *P : make_range(Irr.pred_begin(), Irr.pred_end())) {
+ // Skip forward edges.
+ if (P->Node < Irr.Node)
+ continue;
+
+ // Skip predecessors from entry blocks. These can have inverted
+ // ordering.
+ if (InSCC.lookup(P))
+ continue;
+
+ // Store the extra header.
+ Headers.push_back(Irr.Node);
+ LLVM_DEBUG(dbgs() << " => extra = " << BFI.getBlockName(Irr.Node)
+ << "\n");
+ break;
+ }
+ if (Headers.back() == Irr.Node)
+ // Added this as a header.
+ continue;
+
+ // This is not a header.
+ Others.push_back(Irr.Node);
+ LLVM_DEBUG(dbgs() << " => other = " << BFI.getBlockName(Irr.Node) << "\n");
+ }
+ llvm::sort(Headers);
+ llvm::sort(Others);
+}
+
+static void createIrreducibleLoop(
+ BlockFrequencyInfoImplBase &BFI, const IrreducibleGraph &G,
+ LoopData *OuterLoop, std::list<LoopData>::iterator Insert,
+ const std::vector<const IrreducibleGraph::IrrNode *> &SCC) {
+ // Translate the SCC into RPO.
+ LLVM_DEBUG(dbgs() << " - found-scc\n");
+
+ LoopData::NodeList Headers;
+ LoopData::NodeList Others;
+ findIrreducibleHeaders(BFI, G, SCC, Headers, Others);
+
+ auto Loop = BFI.Loops.emplace(Insert, OuterLoop, Headers.begin(),
+ Headers.end(), Others.begin(), Others.end());
+
+ // Update loop hierarchy.
+ for (const auto &N : Loop->Nodes)
+ if (BFI.Working[N.Index].isLoopHeader())
+ BFI.Working[N.Index].Loop->Parent = &*Loop;
+ else
+ BFI.Working[N.Index].Loop = &*Loop;
+}
+
+iterator_range<std::list<LoopData>::iterator>
+BlockFrequencyInfoImplBase::analyzeIrreducible(
+ const IrreducibleGraph &G, LoopData *OuterLoop,
+ std::list<LoopData>::iterator Insert) {
+ assert((OuterLoop == nullptr) == (Insert == Loops.begin()));
+ auto Prev = OuterLoop ? std::prev(Insert) : Loops.end();
+
+ for (auto I = scc_begin(G); !I.isAtEnd(); ++I) {
+ if (I->size() < 2)
+ continue;
+
+ // Translate the SCC into RPO.
+ createIrreducibleLoop(*this, G, OuterLoop, Insert, *I);
+ }
+
+ if (OuterLoop)
+ return make_range(std::next(Prev), Insert);
+ return make_range(Loops.begin(), Insert);
+}
+
+void
+BlockFrequencyInfoImplBase::updateLoopWithIrreducible(LoopData &OuterLoop) {
+ OuterLoop.Exits.clear();
+ for (auto &Mass : OuterLoop.BackedgeMass)
+ Mass = BlockMass::getEmpty();
+ auto O = OuterLoop.Nodes.begin() + 1;
+ for (auto I = O, E = OuterLoop.Nodes.end(); I != E; ++I)
+ if (!Working[I->Index].isPackaged())
+ *O++ = *I;
+ OuterLoop.Nodes.erase(O, OuterLoop.Nodes.end());
+}
+
+void BlockFrequencyInfoImplBase::adjustLoopHeaderMass(LoopData &Loop) {
+ assert(Loop.isIrreducible() && "this only makes sense on irreducible loops");
+
+ // Since the loop has more than one header block, the mass flowing back into
+ // each header will be different. Adjust the mass in each header loop to
+ // reflect the masses flowing through back edges.
+ //
+ // To do this, we distribute the initial mass using the backedge masses
+ // as weights for the distribution.
+ BlockMass LoopMass = BlockMass::getFull();
+ Distribution Dist;
+
+ LLVM_DEBUG(dbgs() << "adjust-loop-header-mass:\n");
+ for (uint32_t H = 0; H < Loop.NumHeaders; ++H) {
+ auto &HeaderNode = Loop.Nodes[H];
+ auto &BackedgeMass = Loop.BackedgeMass[Loop.getHeaderIndex(HeaderNode)];
+ LLVM_DEBUG(dbgs() << " - Add back edge mass for node "
+ << getBlockName(HeaderNode) << ": " << BackedgeMass
+ << "\n");
+ if (BackedgeMass.getMass() > 0)
+ Dist.addLocal(HeaderNode, BackedgeMass.getMass());
+ else
+ LLVM_DEBUG(dbgs() << " Nothing added. Back edge mass is zero\n");
+ }
+
+ DitheringDistributer D(Dist, LoopMass);
+
+ LLVM_DEBUG(dbgs() << " Distribute loop mass " << LoopMass
+ << " to headers using above weights\n");
+ for (const Weight &W : Dist.Weights) {
+ BlockMass Taken = D.takeMass(W.Amount);
+ assert(W.Type == Weight::Local && "all weights should be local");
+ Working[W.TargetNode.Index].getMass() = Taken;
+ LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, nullptr));
+ }
+}
+
+void BlockFrequencyInfoImplBase::distributeIrrLoopHeaderMass(Distribution &Dist) {
+ BlockMass LoopMass = BlockMass::getFull();
+ DitheringDistributer D(Dist, LoopMass);
+ for (const Weight &W : Dist.Weights) {
+ BlockMass Taken = D.takeMass(W.Amount);
+ assert(W.Type == Weight::Local && "all weights should be local");
+ Working[W.TargetNode.Index].getMass() = Taken;
+ LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, nullptr));
+ }
+}
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