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BlockFrequencyInfoImpl.h
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1 //==- BlockFrequencyInfoImpl.h - Block Frequency Implementation --*- C++ -*-==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // Shared implementation of BlockFrequency for IR and Machine Instructions.
10 // See the documentation below for BlockFrequencyInfoImpl for details.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ANALYSIS_BLOCKFREQUENCYINFOIMPL_H
15 #define LLVM_ANALYSIS_BLOCKFREQUENCYINFOIMPL_H
16 
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/DenseSet.h"
19 #include "llvm/ADT/GraphTraits.h"
20 #include "llvm/ADT/Optional.h"
22 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/Twine.h"
26 #include "llvm/IR/BasicBlock.h"
30 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/Format.h"
35 #include <algorithm>
36 #include <cassert>
37 #include <cstddef>
38 #include <cstdint>
39 #include <deque>
40 #include <iterator>
41 #include <limits>
42 #include <list>
43 #include <string>
44 #include <utility>
45 #include <vector>
46 
47 #define DEBUG_TYPE "block-freq"
48 
49 namespace llvm {
50 
51 class BranchProbabilityInfo;
52 class Function;
53 class Loop;
54 class LoopInfo;
55 class MachineBasicBlock;
56 class MachineBranchProbabilityInfo;
57 class MachineFunction;
58 class MachineLoop;
59 class MachineLoopInfo;
60 
61 namespace bfi_detail {
62 
63 struct IrreducibleGraph;
64 
65 // This is part of a workaround for a GCC 4.7 crash on lambdas.
66 template <class BT> struct BlockEdgesAdder;
67 
68 /// Mass of a block.
69 ///
70 /// This class implements a sort of fixed-point fraction always between 0.0 and
71 /// 1.0. getMass() == std::numeric_limits<uint64_t>::max() indicates a value of
72 /// 1.0.
73 ///
74 /// Masses can be added and subtracted. Simple saturation arithmetic is used,
75 /// so arithmetic operations never overflow or underflow.
76 ///
77 /// Masses can be multiplied. Multiplication treats full mass as 1.0 and uses
78 /// an inexpensive floating-point algorithm that's off-by-one (almost, but not
79 /// quite, maximum precision).
80 ///
81 /// Masses can be scaled by \a BranchProbability at maximum precision.
82 class BlockMass {
83  uint64_t Mass = 0;
84 
85 public:
86  BlockMass() = default;
87  explicit BlockMass(uint64_t Mass) : Mass(Mass) {}
88 
89  static BlockMass getEmpty() { return BlockMass(); }
90 
91  static BlockMass getFull() {
93  }
94 
95  uint64_t getMass() const { return Mass; }
96 
97  bool isFull() const { return Mass == std::numeric_limits<uint64_t>::max(); }
98  bool isEmpty() const { return !Mass; }
99 
100  bool operator!() const { return isEmpty(); }
101 
102  /// Add another mass.
103  ///
104  /// Adds another mass, saturating at \a isFull() rather than overflowing.
106  uint64_t Sum = Mass + X.Mass;
108  return *this;
109  }
110 
111  /// Subtract another mass.
112  ///
113  /// Subtracts another mass, saturating at \a isEmpty() rather than
114  /// undeflowing.
116  uint64_t Diff = Mass - X.Mass;
117  Mass = Diff > Mass ? 0 : Diff;
118  return *this;
119  }
120 
122  Mass = P.scale(Mass);
123  return *this;
124  }
125 
126  bool operator==(BlockMass X) const { return Mass == X.Mass; }
127  bool operator!=(BlockMass X) const { return Mass != X.Mass; }
128  bool operator<=(BlockMass X) const { return Mass <= X.Mass; }
129  bool operator>=(BlockMass X) const { return Mass >= X.Mass; }
130  bool operator<(BlockMass X) const { return Mass < X.Mass; }
131  bool operator>(BlockMass X) const { return Mass > X.Mass; }
132 
133  /// Convert to scaled number.
134  ///
135  /// Convert to \a ScaledNumber. \a isFull() gives 1.0, while \a isEmpty()
136  /// gives slightly above 0.0.
138 
139  void dump() const;
140  raw_ostream &print(raw_ostream &OS) const;
141 };
142 
144  return BlockMass(L) += R;
145 }
147  return BlockMass(L) -= R;
148 }
150  return BlockMass(L) *= R;
151 }
153  return BlockMass(R) *= L;
154 }
155 
157  return X.print(OS);
158 }
159 
160 } // end namespace bfi_detail
161 
162 /// Base class for BlockFrequencyInfoImpl
163 ///
164 /// BlockFrequencyInfoImplBase has supporting data structures and some
165 /// algorithms for BlockFrequencyInfoImplBase. Only algorithms that depend on
166 /// the block type (or that call such algorithms) are skipped here.
167 ///
168 /// Nevertheless, the majority of the overall algorithm documention lives with
169 /// BlockFrequencyInfoImpl. See there for details.
171 public:
174 
175  /// Representative of a block.
176  ///
177  /// This is a simple wrapper around an index into the reverse-post-order
178  /// traversal of the blocks.
179  ///
180  /// Unlike a block pointer, its order has meaning (location in the
181  /// topological sort) and it's class is the same regardless of block type.
182  struct BlockNode {
184 
186 
187  BlockNode() : Index(std::numeric_limits<uint32_t>::max()) {}
188  BlockNode(IndexType Index) : Index(Index) {}
189 
190  bool operator==(const BlockNode &X) const { return Index == X.Index; }
191  bool operator!=(const BlockNode &X) const { return Index != X.Index; }
192  bool operator<=(const BlockNode &X) const { return Index <= X.Index; }
193  bool operator>=(const BlockNode &X) const { return Index >= X.Index; }
194  bool operator<(const BlockNode &X) const { return Index < X.Index; }
195  bool operator>(const BlockNode &X) const { return Index > X.Index; }
196 
197  bool isValid() const { return Index <= getMaxIndex(); }
198 
199  static size_t getMaxIndex() {
201  }
202  };
203 
204  /// Stats about a block itself.
205  struct FrequencyData {
207  uint64_t Integer;
208  };
209 
210  /// Data about a loop.
211  ///
212  /// Contains the data necessary to represent a loop as a pseudo-node once it's
213  /// packaged.
214  struct LoopData {
218 
219  LoopData *Parent; ///< The parent loop.
220  bool IsPackaged = false; ///< Whether this has been packaged.
221  uint32_t NumHeaders = 1; ///< Number of headers.
222  ExitMap Exits; ///< Successor edges (and weights).
223  NodeList Nodes; ///< Header and the members of the loop.
224  HeaderMassList BackedgeMass; ///< Mass returned to each loop header.
227 
228  LoopData(LoopData *Parent, const BlockNode &Header)
229  : Parent(Parent), Nodes(1, Header), BackedgeMass(1) {}
230 
231  template <class It1, class It2>
232  LoopData(LoopData *Parent, It1 FirstHeader, It1 LastHeader, It2 FirstOther,
233  It2 LastOther)
234  : Parent(Parent), Nodes(FirstHeader, LastHeader) {
235  NumHeaders = Nodes.size();
236  Nodes.insert(Nodes.end(), FirstOther, LastOther);
237  BackedgeMass.resize(NumHeaders);
238  }
239 
240  bool isHeader(const BlockNode &Node) const {
241  if (isIrreducible())
242  return std::binary_search(Nodes.begin(), Nodes.begin() + NumHeaders,
243  Node);
244  return Node == Nodes[0];
245  }
246 
247  BlockNode getHeader() const { return Nodes[0]; }
248  bool isIrreducible() const { return NumHeaders > 1; }
249 
251  assert(isHeader(B) && "this is only valid on loop header blocks");
252  if (isIrreducible())
253  return std::lower_bound(Nodes.begin(), Nodes.begin() + NumHeaders, B) -
254  Nodes.begin();
255  return 0;
256  }
257 
259  return Nodes.begin() + NumHeaders;
260  }
261 
262  NodeList::const_iterator members_end() const { return Nodes.end(); }
264  return make_range(members_begin(), members_end());
265  }
266  };
267 
268  /// Index of loop information.
269  struct WorkingData {
270  BlockNode Node; ///< This node.
271  LoopData *Loop = nullptr; ///< The loop this block is inside.
272  BlockMass Mass; ///< Mass distribution from the entry block.
273 
274  WorkingData(const BlockNode &Node) : Node(Node) {}
275 
276  bool isLoopHeader() const { return Loop && Loop->isHeader(Node); }
277 
278  bool isDoubleLoopHeader() const {
279  return isLoopHeader() && Loop->Parent && Loop->Parent->isIrreducible() &&
280  Loop->Parent->isHeader(Node);
281  }
282 
284  if (!isLoopHeader())
285  return Loop;
286  if (!isDoubleLoopHeader())
287  return Loop->Parent;
288  return Loop->Parent->Parent;
289  }
290 
291  /// Resolve a node to its representative.
292  ///
293  /// Get the node currently representing Node, which could be a containing
294  /// loop.
295  ///
296  /// This function should only be called when distributing mass. As long as
297  /// there are no irreducible edges to Node, then it will have complexity
298  /// O(1) in this context.
299  ///
300  /// In general, the complexity is O(L), where L is the number of loop
301  /// headers Node has been packaged into. Since this method is called in
302  /// the context of distributing mass, L will be the number of loop headers
303  /// an early exit edge jumps out of.
305  auto L = getPackagedLoop();
306  return L ? L->getHeader() : Node;
307  }
308 
310  if (!Loop || !Loop->IsPackaged)
311  return nullptr;
312  auto L = Loop;
313  while (L->Parent && L->Parent->IsPackaged)
314  L = L->Parent;
315  return L;
316  }
317 
318  /// Get the appropriate mass for a node.
319  ///
320  /// Get appropriate mass for Node. If Node is a loop-header (whose loop
321  /// has been packaged), returns the mass of its pseudo-node. If it's a
322  /// node inside a packaged loop, it returns the loop's mass.
324  if (!isAPackage())
325  return Mass;
326  if (!isADoublePackage())
327  return Loop->Mass;
328  return Loop->Parent->Mass;
329  }
330 
331  /// Has ContainingLoop been packaged up?
332  bool isPackaged() const { return getResolvedNode() != Node; }
333 
334  /// Has Loop been packaged up?
335  bool isAPackage() const { return isLoopHeader() && Loop->IsPackaged; }
336 
337  /// Has Loop been packaged up twice?
338  bool isADoublePackage() const {
339  return isDoubleLoopHeader() && Loop->Parent->IsPackaged;
340  }
341  };
342 
343  /// Unscaled probability weight.
344  ///
345  /// Probability weight for an edge in the graph (including the
346  /// successor/target node).
347  ///
348  /// All edges in the original function are 32-bit. However, exit edges from
349  /// loop packages are taken from 64-bit exit masses, so we need 64-bits of
350  /// space in general.
351  ///
352  /// In addition to the raw weight amount, Weight stores the type of the edge
353  /// in the current context (i.e., the context of the loop being processed).
354  /// Is this a local edge within the loop, an exit from the loop, or a
355  /// backedge to the loop header?
356  struct Weight {
357  enum DistType { Local, Exit, Backedge };
358  DistType Type = Local;
360  uint64_t Amount = 0;
361 
362  Weight() = default;
363  Weight(DistType Type, BlockNode TargetNode, uint64_t Amount)
364  : Type(Type), TargetNode(TargetNode), Amount(Amount) {}
365  };
366 
367  /// Distribution of unscaled probability weight.
368  ///
369  /// Distribution of unscaled probability weight to a set of successors.
370  ///
371  /// This class collates the successor edge weights for later processing.
372  ///
373  /// \a DidOverflow indicates whether \a Total did overflow while adding to
374  /// the distribution. It should never overflow twice.
375  struct Distribution {
377 
378  WeightList Weights; ///< Individual successor weights.
379  uint64_t Total = 0; ///< Sum of all weights.
380  bool DidOverflow = false; ///< Whether \a Total did overflow.
381 
382  Distribution() = default;
383 
384  void addLocal(const BlockNode &Node, uint64_t Amount) {
385  add(Node, Amount, Weight::Local);
386  }
387 
388  void addExit(const BlockNode &Node, uint64_t Amount) {
389  add(Node, Amount, Weight::Exit);
390  }
391 
392  void addBackedge(const BlockNode &Node, uint64_t Amount) {
393  add(Node, Amount, Weight::Backedge);
394  }
395 
396  /// Normalize the distribution.
397  ///
398  /// Combines multiple edges to the same \a Weight::TargetNode and scales
399  /// down so that \a Total fits into 32-bits.
400  ///
401  /// This is linear in the size of \a Weights. For the vast majority of
402  /// cases, adjacent edge weights are combined by sorting WeightList and
403  /// combining adjacent weights. However, for very large edge lists an
404  /// auxiliary hash table is used.
405  void normalize();
406 
407  private:
408  void add(const BlockNode &Node, uint64_t Amount, Weight::DistType Type);
409  };
410 
411  /// Data about each block. This is used downstream.
412  std::vector<FrequencyData> Freqs;
413 
414  /// Whether each block is an irreducible loop header.
415  /// This is used downstream.
417 
418  /// Loop data: see initializeLoops().
419  std::vector<WorkingData> Working;
420 
421  /// Indexed information about loops.
422  std::list<LoopData> Loops;
423 
424  /// Virtual destructor.
425  ///
426  /// Need a virtual destructor to mask the compiler warning about
427  /// getBlockName().
428  virtual ~BlockFrequencyInfoImplBase() = default;
429 
430  /// Add all edges out of a packaged loop to the distribution.
431  ///
432  /// Adds all edges from LocalLoopHead to Dist. Calls addToDist() to add each
433  /// successor edge.
434  ///
435  /// \return \c true unless there's an irreducible backedge.
436  bool addLoopSuccessorsToDist(const LoopData *OuterLoop, LoopData &Loop,
437  Distribution &Dist);
438 
439  /// Add an edge to the distribution.
440  ///
441  /// Adds an edge to Succ to Dist. If \c LoopHead.isValid(), then whether the
442  /// edge is local/exit/backedge is in the context of LoopHead. Otherwise,
443  /// every edge should be a local edge (since all the loops are packaged up).
444  ///
445  /// \return \c true unless aborted due to an irreducible backedge.
446  bool addToDist(Distribution &Dist, const LoopData *OuterLoop,
447  const BlockNode &Pred, const BlockNode &Succ, uint64_t Weight);
448 
450  assert(Head.Index < Working.size());
451  assert(Working[Head.Index].isLoopHeader());
452  return *Working[Head.Index].Loop;
453  }
454 
455  /// Analyze irreducible SCCs.
456  ///
457  /// Separate irreducible SCCs from \c G, which is an explict graph of \c
458  /// OuterLoop (or the top-level function, if \c OuterLoop is \c nullptr).
459  /// Insert them into \a Loops before \c Insert.
460  ///
461  /// \return the \c LoopData nodes representing the irreducible SCCs.
463  analyzeIrreducible(const bfi_detail::IrreducibleGraph &G, LoopData *OuterLoop,
464  std::list<LoopData>::iterator Insert);
465 
466  /// Update a loop after packaging irreducible SCCs inside of it.
467  ///
468  /// Update \c OuterLoop. Before finding irreducible control flow, it was
469  /// partway through \a computeMassInLoop(), so \a LoopData::Exits and \a
470  /// LoopData::BackedgeMass need to be reset. Also, nodes that were packaged
471  /// up need to be removed from \a OuterLoop::Nodes.
472  void updateLoopWithIrreducible(LoopData &OuterLoop);
473 
474  /// Distribute mass according to a distribution.
475  ///
476  /// Distributes the mass in Source according to Dist. If LoopHead.isValid(),
477  /// backedges and exits are stored in its entry in Loops.
478  ///
479  /// Mass is distributed in parallel from two copies of the source mass.
480  void distributeMass(const BlockNode &Source, LoopData *OuterLoop,
481  Distribution &Dist);
482 
483  /// Compute the loop scale for a loop.
484  void computeLoopScale(LoopData &Loop);
485 
486  /// Adjust the mass of all headers in an irreducible loop.
487  ///
488  /// Initially, irreducible loops are assumed to distribute their mass
489  /// equally among its headers. This can lead to wrong frequency estimates
490  /// since some headers may be executed more frequently than others.
491  ///
492  /// This adjusts header mass distribution so it matches the weights of
493  /// the backedges going into each of the loop headers.
494  void adjustLoopHeaderMass(LoopData &Loop);
495 
496  void distributeIrrLoopHeaderMass(Distribution &Dist);
497 
498  /// Package up a loop.
499  void packageLoop(LoopData &Loop);
500 
501  /// Unwrap loops.
502  void unwrapLoops();
503 
504  /// Finalize frequency metrics.
505  ///
506  /// Calculates final frequencies and cleans up no-longer-needed data
507  /// structures.
508  void finalizeMetrics();
509 
510  /// Clear all memory.
511  void clear();
512 
513  virtual std::string getBlockName(const BlockNode &Node) const;
514  std::string getLoopName(const LoopData &Loop) const;
515 
516  virtual raw_ostream &print(raw_ostream &OS) const { return OS; }
517  void dump() const { print(dbgs()); }
518 
519  Scaled64 getFloatingBlockFreq(const BlockNode &Node) const;
520 
521  BlockFrequency getBlockFreq(const BlockNode &Node) const;
522  Optional<uint64_t> getBlockProfileCount(const Function &F,
523  const BlockNode &Node,
524  bool AllowSynthetic = false) const;
525  Optional<uint64_t> getProfileCountFromFreq(const Function &F,
526  uint64_t Freq,
527  bool AllowSynthetic = false) const;
528  bool isIrrLoopHeader(const BlockNode &Node);
529 
530  void setBlockFreq(const BlockNode &Node, uint64_t Freq);
531 
532  raw_ostream &printBlockFreq(raw_ostream &OS, const BlockNode &Node) const;
533  raw_ostream &printBlockFreq(raw_ostream &OS,
534  const BlockFrequency &Freq) const;
535 
536  uint64_t getEntryFreq() const {
537  assert(!Freqs.empty());
538  return Freqs[0].Integer;
539  }
540 };
541 
542 namespace bfi_detail {
543 
544 template <class BlockT> struct TypeMap {};
545 template <> struct TypeMap<BasicBlock> {
549  using LoopT = Loop;
551 };
552 template <> struct TypeMap<MachineBasicBlock> {
558 };
559 
560 /// Get the name of a MachineBasicBlock.
561 ///
562 /// Get the name of a MachineBasicBlock. It's templated so that including from
563 /// CodeGen is unnecessary (that would be a layering issue).
564 ///
565 /// This is used mainly for debug output. The name is similar to
566 /// MachineBasicBlock::getFullName(), but skips the name of the function.
567 template <class BlockT> std::string getBlockName(const BlockT *BB) {
568  assert(BB && "Unexpected nullptr");
569  auto MachineName = "BB" + Twine(BB->getNumber());
570  if (BB->getBasicBlock())
571  return (MachineName + "[" + BB->getName() + "]").str();
572  return MachineName.str();
573 }
574 /// Get the name of a BasicBlock.
575 template <> inline std::string getBlockName(const BasicBlock *BB) {
576  assert(BB && "Unexpected nullptr");
577  return BB->getName().str();
578 }
579 
580 /// Graph of irreducible control flow.
581 ///
582 /// This graph is used for determining the SCCs in a loop (or top-level
583 /// function) that has irreducible control flow.
584 ///
585 /// During the block frequency algorithm, the local graphs are defined in a
586 /// light-weight way, deferring to the \a BasicBlock or \a MachineBasicBlock
587 /// graphs for most edges, but getting others from \a LoopData::ExitMap. The
588 /// latter only has successor information.
589 ///
590 /// \a IrreducibleGraph makes this graph explicit. It's in a form that can use
591 /// \a GraphTraits (so that \a analyzeIrreducible() can use \a scc_iterator),
592 /// and it explicitly lists predecessors and successors. The initialization
593 /// that relies on \c MachineBasicBlock is defined in the header.
596 
598 
600  struct IrrNode {
602  unsigned NumIn = 0;
603  std::deque<const IrrNode *> Edges;
604 
605  IrrNode(const BlockNode &Node) : Node(Node) {}
606 
607  using iterator = std::deque<const IrrNode *>::const_iterator;
608 
609  iterator pred_begin() const { return Edges.begin(); }
610  iterator succ_begin() const { return Edges.begin() + NumIn; }
611  iterator pred_end() const { return succ_begin(); }
612  iterator succ_end() const { return Edges.end(); }
613  };
615  const IrrNode *StartIrr = nullptr;
616  std::vector<IrrNode> Nodes;
618 
619  /// Construct an explicit graph containing irreducible control flow.
620  ///
621  /// Construct an explicit graph of the control flow in \c OuterLoop (or the
622  /// top-level function, if \c OuterLoop is \c nullptr). Uses \c
623  /// addBlockEdges to add block successors that have not been packaged into
624  /// loops.
625  ///
626  /// \a BlockFrequencyInfoImpl::computeIrreducibleMass() is the only expected
627  /// user of this.
628  template <class BlockEdgesAdder>
630  BlockEdgesAdder addBlockEdges) : BFI(BFI) {
631  initialize(OuterLoop, addBlockEdges);
632  }
633 
634  template <class BlockEdgesAdder>
635  void initialize(const BFIBase::LoopData *OuterLoop,
636  BlockEdgesAdder addBlockEdges);
637  void addNodesInLoop(const BFIBase::LoopData &OuterLoop);
638  void addNodesInFunction();
639 
640  void addNode(const BlockNode &Node) {
641  Nodes.emplace_back(Node);
642  BFI.Working[Node.Index].getMass() = BlockMass::getEmpty();
643  }
644 
645  void indexNodes();
646  template <class BlockEdgesAdder>
647  void addEdges(const BlockNode &Node, const BFIBase::LoopData *OuterLoop,
648  BlockEdgesAdder addBlockEdges);
649  void addEdge(IrrNode &Irr, const BlockNode &Succ,
650  const BFIBase::LoopData *OuterLoop);
651 };
652 
653 template <class BlockEdgesAdder>
655  BlockEdgesAdder addBlockEdges) {
656  if (OuterLoop) {
657  addNodesInLoop(*OuterLoop);
658  for (auto N : OuterLoop->Nodes)
659  addEdges(N, OuterLoop, addBlockEdges);
660  } else {
661  addNodesInFunction();
662  for (uint32_t Index = 0; Index < BFI.Working.size(); ++Index)
663  addEdges(Index, OuterLoop, addBlockEdges);
664  }
665  StartIrr = Lookup[Start.Index];
666 }
667 
668 template <class BlockEdgesAdder>
670  const BFIBase::LoopData *OuterLoop,
671  BlockEdgesAdder addBlockEdges) {
672  auto L = Lookup.find(Node.Index);
673  if (L == Lookup.end())
674  return;
675  IrrNode &Irr = *L->second;
676  const auto &Working = BFI.Working[Node.Index];
677 
678  if (Working.isAPackage())
679  for (const auto &I : Working.Loop->Exits)
680  addEdge(Irr, I.first, OuterLoop);
681  else
682  addBlockEdges(*this, Irr, OuterLoop);
683 }
684 
685 } // end namespace bfi_detail
686 
687 /// Shared implementation for block frequency analysis.
688 ///
689 /// This is a shared implementation of BlockFrequencyInfo and
690 /// MachineBlockFrequencyInfo, and calculates the relative frequencies of
691 /// blocks.
692 ///
693 /// LoopInfo defines a loop as a "non-trivial" SCC dominated by a single block,
694 /// which is called the header. A given loop, L, can have sub-loops, which are
695 /// loops within the subgraph of L that exclude its header. (A "trivial" SCC
696 /// consists of a single block that does not have a self-edge.)
697 ///
698 /// In addition to loops, this algorithm has limited support for irreducible
699 /// SCCs, which are SCCs with multiple entry blocks. Irreducible SCCs are
700 /// discovered on they fly, and modelled as loops with multiple headers.
701 ///
702 /// The headers of irreducible sub-SCCs consist of its entry blocks and all
703 /// nodes that are targets of a backedge within it (excluding backedges within
704 /// true sub-loops). Block frequency calculations act as if a block is
705 /// inserted that intercepts all the edges to the headers. All backedges and
706 /// entries point to this block. Its successors are the headers, which split
707 /// the frequency evenly.
708 ///
709 /// This algorithm leverages BlockMass and ScaledNumber to maintain precision,
710 /// separates mass distribution from loop scaling, and dithers to eliminate
711 /// probability mass loss.
712 ///
713 /// The implementation is split between BlockFrequencyInfoImpl, which knows the
714 /// type of graph being modelled (BasicBlock vs. MachineBasicBlock), and
715 /// BlockFrequencyInfoImplBase, which doesn't. The base class uses \a
716 /// BlockNode, a wrapper around a uint32_t. BlockNode is numbered from 0 in
717 /// reverse-post order. This gives two advantages: it's easy to compare the
718 /// relative ordering of two nodes, and maps keyed on BlockT can be represented
719 /// by vectors.
720 ///
721 /// This algorithm is O(V+E), unless there is irreducible control flow, in
722 /// which case it's O(V*E) in the worst case.
723 ///
724 /// These are the main stages:
725 ///
726 /// 0. Reverse post-order traversal (\a initializeRPOT()).
727 ///
728 /// Run a single post-order traversal and save it (in reverse) in RPOT.
729 /// All other stages make use of this ordering. Save a lookup from BlockT
730 /// to BlockNode (the index into RPOT) in Nodes.
731 ///
732 /// 1. Loop initialization (\a initializeLoops()).
733 ///
734 /// Translate LoopInfo/MachineLoopInfo into a form suitable for the rest of
735 /// the algorithm. In particular, store the immediate members of each loop
736 /// in reverse post-order.
737 ///
738 /// 2. Calculate mass and scale in loops (\a computeMassInLoops()).
739 ///
740 /// For each loop (bottom-up), distribute mass through the DAG resulting
741 /// from ignoring backedges and treating sub-loops as a single pseudo-node.
742 /// Track the backedge mass distributed to the loop header, and use it to
743 /// calculate the loop scale (number of loop iterations). Immediate
744 /// members that represent sub-loops will already have been visited and
745 /// packaged into a pseudo-node.
746 ///
747 /// Distributing mass in a loop is a reverse-post-order traversal through
748 /// the loop. Start by assigning full mass to the Loop header. For each
749 /// node in the loop:
750 ///
751 /// - Fetch and categorize the weight distribution for its successors.
752 /// If this is a packaged-subloop, the weight distribution is stored
753 /// in \a LoopData::Exits. Otherwise, fetch it from
754 /// BranchProbabilityInfo.
755 ///
756 /// - Each successor is categorized as \a Weight::Local, a local edge
757 /// within the current loop, \a Weight::Backedge, a backedge to the
758 /// loop header, or \a Weight::Exit, any successor outside the loop.
759 /// The weight, the successor, and its category are stored in \a
760 /// Distribution. There can be multiple edges to each successor.
761 ///
762 /// - If there's a backedge to a non-header, there's an irreducible SCC.
763 /// The usual flow is temporarily aborted. \a
764 /// computeIrreducibleMass() finds the irreducible SCCs within the
765 /// loop, packages them up, and restarts the flow.
766 ///
767 /// - Normalize the distribution: scale weights down so that their sum
768 /// is 32-bits, and coalesce multiple edges to the same node.
769 ///
770 /// - Distribute the mass accordingly, dithering to minimize mass loss,
771 /// as described in \a distributeMass().
772 ///
773 /// In the case of irreducible loops, instead of a single loop header,
774 /// there will be several. The computation of backedge masses is similar
775 /// but instead of having a single backedge mass, there will be one
776 /// backedge per loop header. In these cases, each backedge will carry
777 /// a mass proportional to the edge weights along the corresponding
778 /// path.
779 ///
780 /// At the end of propagation, the full mass assigned to the loop will be
781 /// distributed among the loop headers proportionally according to the
782 /// mass flowing through their backedges.
783 ///
784 /// Finally, calculate the loop scale from the accumulated backedge mass.
785 ///
786 /// 3. Distribute mass in the function (\a computeMassInFunction()).
787 ///
788 /// Finally, distribute mass through the DAG resulting from packaging all
789 /// loops in the function. This uses the same algorithm as distributing
790 /// mass in a loop, except that there are no exit or backedge edges.
791 ///
792 /// 4. Unpackage loops (\a unwrapLoops()).
793 ///
794 /// Initialize each block's frequency to a floating point representation of
795 /// its mass.
796 ///
797 /// Visit loops top-down, scaling the frequencies of its immediate members
798 /// by the loop's pseudo-node's frequency.
799 ///
800 /// 5. Convert frequencies to a 64-bit range (\a finalizeMetrics()).
801 ///
802 /// Using the min and max frequencies as a guide, translate floating point
803 /// frequencies to an appropriate range in uint64_t.
804 ///
805 /// It has some known flaws.
806 ///
807 /// - The model of irreducible control flow is a rough approximation.
808 ///
809 /// Modelling irreducible control flow exactly involves setting up and
810 /// solving a group of infinite geometric series. Such precision is
811 /// unlikely to be worthwhile, since most of our algorithms give up on
812 /// irreducible control flow anyway.
813 ///
814 /// Nevertheless, we might find that we need to get closer. Here's a sort
815 /// of TODO list for the model with diminishing returns, to be completed as
816 /// necessary.
817 ///
818 /// - The headers for the \a LoopData representing an irreducible SCC
819 /// include non-entry blocks. When these extra blocks exist, they
820 /// indicate a self-contained irreducible sub-SCC. We could treat them
821 /// as sub-loops, rather than arbitrarily shoving the problematic
822 /// blocks into the headers of the main irreducible SCC.
823 ///
824 /// - Entry frequencies are assumed to be evenly split between the
825 /// headers of a given irreducible SCC, which is the only option if we
826 /// need to compute mass in the SCC before its parent loop. Instead,
827 /// we could partially compute mass in the parent loop, and stop when
828 /// we get to the SCC. Here, we have the correct ratio of entry
829 /// masses, which we can use to adjust their relative frequencies.
830 /// Compute mass in the SCC, and then continue propagation in the
831 /// parent.
832 ///
833 /// - We can propagate mass iteratively through the SCC, for some fixed
834 /// number of iterations. Each iteration starts by assigning the entry
835 /// blocks their backedge mass from the prior iteration. The final
836 /// mass for each block (and each exit, and the total backedge mass
837 /// used for computing loop scale) is the sum of all iterations.
838 /// (Running this until fixed point would "solve" the geometric
839 /// series by simulation.)
840 template <class BT> class BlockFrequencyInfoImpl : BlockFrequencyInfoImplBase {
841  // This is part of a workaround for a GCC 4.7 crash on lambdas.
843 
844  using BlockT = typename bfi_detail::TypeMap<BT>::BlockT;
845  using FunctionT = typename bfi_detail::TypeMap<BT>::FunctionT;
846  using BranchProbabilityInfoT =
848  using LoopT = typename bfi_detail::TypeMap<BT>::LoopT;
849  using LoopInfoT = typename bfi_detail::TypeMap<BT>::LoopInfoT;
852 
853  const BranchProbabilityInfoT *BPI = nullptr;
854  const LoopInfoT *LI = nullptr;
855  const FunctionT *F = nullptr;
856 
857  // All blocks in reverse postorder.
858  std::vector<const BlockT *> RPOT;
860 
861  using rpot_iterator = typename std::vector<const BlockT *>::const_iterator;
862 
863  rpot_iterator rpot_begin() const { return RPOT.begin(); }
864  rpot_iterator rpot_end() const { return RPOT.end(); }
865 
866  size_t getIndex(const rpot_iterator &I) const { return I - rpot_begin(); }
867 
868  BlockNode getNode(const rpot_iterator &I) const {
869  return BlockNode(getIndex(I));
870  }
871  BlockNode getNode(const BlockT *BB) const { return Nodes.lookup(BB); }
872 
873  const BlockT *getBlock(const BlockNode &Node) const {
874  assert(Node.Index < RPOT.size());
875  return RPOT[Node.Index];
876  }
877 
878  /// Run (and save) a post-order traversal.
879  ///
880  /// Saves a reverse post-order traversal of all the nodes in \a F.
881  void initializeRPOT();
882 
883  /// Initialize loop data.
884  ///
885  /// Build up \a Loops using \a LoopInfo. \a LoopInfo gives us a mapping from
886  /// each block to the deepest loop it's in, but we need the inverse. For each
887  /// loop, we store in reverse post-order its "immediate" members, defined as
888  /// the header, the headers of immediate sub-loops, and all other blocks in
889  /// the loop that are not in sub-loops.
890  void initializeLoops();
891 
892  /// Propagate to a block's successors.
893  ///
894  /// In the context of distributing mass through \c OuterLoop, divide the mass
895  /// currently assigned to \c Node between its successors.
896  ///
897  /// \return \c true unless there's an irreducible backedge.
898  bool propagateMassToSuccessors(LoopData *OuterLoop, const BlockNode &Node);
899 
900  /// Compute mass in a particular loop.
901  ///
902  /// Assign mass to \c Loop's header, and then for each block in \c Loop in
903  /// reverse post-order, distribute mass to its successors. Only visits nodes
904  /// that have not been packaged into sub-loops.
905  ///
906  /// \pre \a computeMassInLoop() has been called for each subloop of \c Loop.
907  /// \return \c true unless there's an irreducible backedge.
908  bool computeMassInLoop(LoopData &Loop);
909 
910  /// Try to compute mass in the top-level function.
911  ///
912  /// Assign mass to the entry block, and then for each block in reverse
913  /// post-order, distribute mass to its successors. Skips nodes that have
914  /// been packaged into loops.
915  ///
916  /// \pre \a computeMassInLoops() has been called.
917  /// \return \c true unless there's an irreducible backedge.
918  bool tryToComputeMassInFunction();
919 
920  /// Compute mass in (and package up) irreducible SCCs.
921  ///
922  /// Find the irreducible SCCs in \c OuterLoop, add them to \a Loops (in front
923  /// of \c Insert), and call \a computeMassInLoop() on each of them.
924  ///
925  /// If \c OuterLoop is \c nullptr, it refers to the top-level function.
926  ///
927  /// \pre \a computeMassInLoop() has been called for each subloop of \c
928  /// OuterLoop.
929  /// \pre \c Insert points at the last loop successfully processed by \a
930  /// computeMassInLoop().
931  /// \pre \c OuterLoop has irreducible SCCs.
932  void computeIrreducibleMass(LoopData *OuterLoop,
933  std::list<LoopData>::iterator Insert);
934 
935  /// Compute mass in all loops.
936  ///
937  /// For each loop bottom-up, call \a computeMassInLoop().
938  ///
939  /// \a computeMassInLoop() aborts (and returns \c false) on loops that
940  /// contain a irreducible sub-SCCs. Use \a computeIrreducibleMass() and then
941  /// re-enter \a computeMassInLoop().
942  ///
943  /// \post \a computeMassInLoop() has returned \c true for every loop.
944  void computeMassInLoops();
945 
946  /// Compute mass in the top-level function.
947  ///
948  /// Uses \a tryToComputeMassInFunction() and \a computeIrreducibleMass() to
949  /// compute mass in the top-level function.
950  ///
951  /// \post \a tryToComputeMassInFunction() has returned \c true.
952  void computeMassInFunction();
953 
954  std::string getBlockName(const BlockNode &Node) const override {
955  return bfi_detail::getBlockName(getBlock(Node));
956  }
957 
958 public:
959  BlockFrequencyInfoImpl() = default;
960 
961  const FunctionT *getFunction() const { return F; }
962 
963  void calculate(const FunctionT &F, const BranchProbabilityInfoT &BPI,
964  const LoopInfoT &LI);
965 
967 
968  BlockFrequency getBlockFreq(const BlockT *BB) const {
969  return BlockFrequencyInfoImplBase::getBlockFreq(getNode(BB));
970  }
971 
973  const BlockT *BB,
974  bool AllowSynthetic = false) const {
976  AllowSynthetic);
977  }
978 
980  uint64_t Freq,
981  bool AllowSynthetic = false) const {
983  AllowSynthetic);
984  }
985 
986  bool isIrrLoopHeader(const BlockT *BB) {
988  }
989 
990  void setBlockFreq(const BlockT *BB, uint64_t Freq);
991 
992  Scaled64 getFloatingBlockFreq(const BlockT *BB) const {
994  }
995 
996  const BranchProbabilityInfoT &getBPI() const { return *BPI; }
997 
998  /// Print the frequencies for the current function.
999  ///
1000  /// Prints the frequencies for the blocks in the current function.
1001  ///
1002  /// Blocks are printed in the natural iteration order of the function, rather
1003  /// than reverse post-order. This provides two advantages: writing -analyze
1004  /// tests is easier (since blocks come out in source order), and even
1005  /// unreachable blocks are printed.
1006  ///
1007  /// \a BlockFrequencyInfoImplBase::print() only knows reverse post-order, so
1008  /// we need to override it here.
1009  raw_ostream &print(raw_ostream &OS) const override;
1010 
1013 
1014  raw_ostream &printBlockFreq(raw_ostream &OS, const BlockT *BB) const {
1015  return BlockFrequencyInfoImplBase::printBlockFreq(OS, getNode(BB));
1016  }
1017 };
1018 
1019 template <class BT>
1021  const BranchProbabilityInfoT &BPI,
1022  const LoopInfoT &LI) {
1023  // Save the parameters.
1024  this->BPI = &BPI;
1025  this->LI = &LI;
1026  this->F = &F;
1027 
1028  // Clean up left-over data structures.
1030  RPOT.clear();
1031  Nodes.clear();
1032 
1033  // Initialize.
1034  LLVM_DEBUG(dbgs() << "\nblock-frequency: " << F.getName()
1035  << "\n================="
1036  << std::string(F.getName().size(), '=') << "\n");
1037  initializeRPOT();
1038  initializeLoops();
1039 
1040  // Visit loops in post-order to find the local mass distribution, and then do
1041  // the full function.
1042  computeMassInLoops();
1043  computeMassInFunction();
1044  unwrapLoops();
1045  finalizeMetrics();
1046 }
1047 
1048 template <class BT>
1049 void BlockFrequencyInfoImpl<BT>::setBlockFreq(const BlockT *BB, uint64_t Freq) {
1050  if (Nodes.count(BB))
1051  BlockFrequencyInfoImplBase::setBlockFreq(getNode(BB), Freq);
1052  else {
1053  // If BB is a newly added block after BFI is done, we need to create a new
1054  // BlockNode for it assigned with a new index. The index can be determined
1055  // by the size of Freqs.
1056  BlockNode NewNode(Freqs.size());
1057  Nodes[BB] = NewNode;
1058  Freqs.emplace_back();
1060  }
1061 }
1062 
1063 template <class BT> void BlockFrequencyInfoImpl<BT>::initializeRPOT() {
1064  const BlockT *Entry = &F->front();
1065  RPOT.reserve(F->size());
1066  std::copy(po_begin(Entry), po_end(Entry), std::back_inserter(RPOT));
1067  std::reverse(RPOT.begin(), RPOT.end());
1068 
1069  assert(RPOT.size() - 1 <= BlockNode::getMaxIndex() &&
1070  "More nodes in function than Block Frequency Info supports");
1071 
1072  LLVM_DEBUG(dbgs() << "reverse-post-order-traversal\n");
1073  for (rpot_iterator I = rpot_begin(), E = rpot_end(); I != E; ++I) {
1074  BlockNode Node = getNode(I);
1075  LLVM_DEBUG(dbgs() << " - " << getIndex(I) << ": " << getBlockName(Node)
1076  << "\n");
1077  Nodes[*I] = Node;
1078  }
1079 
1080  Working.reserve(RPOT.size());
1081  for (size_t Index = 0; Index < RPOT.size(); ++Index)
1082  Working.emplace_back(Index);
1083  Freqs.resize(RPOT.size());
1084 }
1085 
1086 template <class BT> void BlockFrequencyInfoImpl<BT>::initializeLoops() {
1087  LLVM_DEBUG(dbgs() << "loop-detection\n");
1088  if (LI->empty())
1089  return;
1090 
1091  // Visit loops top down and assign them an index.
1092  std::deque<std::pair<const LoopT *, LoopData *>> Q;
1093  for (const LoopT *L : *LI)
1094  Q.emplace_back(L, nullptr);
1095  while (!Q.empty()) {
1096  const LoopT *Loop = Q.front().first;
1097  LoopData *Parent = Q.front().second;
1098  Q.pop_front();
1099 
1100  BlockNode Header = getNode(Loop->getHeader());
1101  assert(Header.isValid());
1102 
1103  Loops.emplace_back(Parent, Header);
1104  Working[Header.Index].Loop = &Loops.back();
1105  LLVM_DEBUG(dbgs() << " - loop = " << getBlockName(Header) << "\n");
1106 
1107  for (const LoopT *L : *Loop)
1108  Q.emplace_back(L, &Loops.back());
1109  }
1110 
1111  // Visit nodes in reverse post-order and add them to their deepest containing
1112  // loop.
1113  for (size_t Index = 0; Index < RPOT.size(); ++Index) {
1114  // Loop headers have already been mostly mapped.
1115  if (Working[Index].isLoopHeader()) {
1116  LoopData *ContainingLoop = Working[Index].getContainingLoop();
1117  if (ContainingLoop)
1118  ContainingLoop->Nodes.push_back(Index);
1119  continue;
1120  }
1121 
1122  const LoopT *Loop = LI->getLoopFor(RPOT[Index]);
1123  if (!Loop)
1124  continue;
1125 
1126  // Add this node to its containing loop's member list.
1127  BlockNode Header = getNode(Loop->getHeader());
1128  assert(Header.isValid());
1129  const auto &HeaderData = Working[Header.Index];
1130  assert(HeaderData.isLoopHeader());
1131 
1132  Working[Index].Loop = HeaderData.Loop;
1133  HeaderData.Loop->Nodes.push_back(Index);
1134  LLVM_DEBUG(dbgs() << " - loop = " << getBlockName(Header)
1135  << ": member = " << getBlockName(Index) << "\n");
1136  }
1137 }
1138 
1139 template <class BT> void BlockFrequencyInfoImpl<BT>::computeMassInLoops() {
1140  // Visit loops with the deepest first, and the top-level loops last.
1141  for (auto L = Loops.rbegin(), E = Loops.rend(); L != E; ++L) {
1142  if (computeMassInLoop(*L))
1143  continue;
1144  auto Next = std::next(L);
1145  computeIrreducibleMass(&*L, L.base());
1146  L = std::prev(Next);
1147  if (computeMassInLoop(*L))
1148  continue;
1149  llvm_unreachable("unhandled irreducible control flow");
1150  }
1151 }
1152 
1153 template <class BT>
1155  // Compute mass in loop.
1156  LLVM_DEBUG(dbgs() << "compute-mass-in-loop: " << getLoopName(Loop) << "\n");
1157 
1158  if (Loop.isIrreducible()) {
1159  LLVM_DEBUG(dbgs() << "isIrreducible = true\n");
1160  Distribution Dist;
1161  unsigned NumHeadersWithWeight = 0;
1162  Optional<uint64_t> MinHeaderWeight;
1163  DenseSet<uint32_t> HeadersWithoutWeight;
1164  HeadersWithoutWeight.reserve(Loop.NumHeaders);
1165  for (uint32_t H = 0; H < Loop.NumHeaders; ++H) {
1166  auto &HeaderNode = Loop.Nodes[H];
1167  const BlockT *Block = getBlock(HeaderNode);
1168  IsIrrLoopHeader.set(Loop.Nodes[H].Index);
1169  Optional<uint64_t> HeaderWeight = Block->getIrrLoopHeaderWeight();
1170  if (!HeaderWeight) {
1171  LLVM_DEBUG(dbgs() << "Missing irr loop header metadata on "
1172  << getBlockName(HeaderNode) << "\n");
1173  HeadersWithoutWeight.insert(H);
1174  continue;
1175  }
1176  LLVM_DEBUG(dbgs() << getBlockName(HeaderNode)
1177  << " has irr loop header weight "
1178  << HeaderWeight.getValue() << "\n");
1179  NumHeadersWithWeight++;
1180  uint64_t HeaderWeightValue = HeaderWeight.getValue();
1181  if (!MinHeaderWeight || HeaderWeightValue < MinHeaderWeight)
1182  MinHeaderWeight = HeaderWeightValue;
1183  if (HeaderWeightValue) {
1184  Dist.addLocal(HeaderNode, HeaderWeightValue);
1185  }
1186  }
1187  // As a heuristic, if some headers don't have a weight, give them the
1188  // minimium weight seen (not to disrupt the existing trends too much by
1189  // using a weight that's in the general range of the other headers' weights,
1190  // and the minimum seems to perform better than the average.)
1191  // FIXME: better update in the passes that drop the header weight.
1192  // If no headers have a weight, give them even weight (use weight 1).
1193  if (!MinHeaderWeight)
1194  MinHeaderWeight = 1;
1195  for (uint32_t H : HeadersWithoutWeight) {
1196  auto &HeaderNode = Loop.Nodes[H];
1197  assert(!getBlock(HeaderNode)->getIrrLoopHeaderWeight() &&
1198  "Shouldn't have a weight metadata");
1199  uint64_t MinWeight = MinHeaderWeight.getValue();
1200  LLVM_DEBUG(dbgs() << "Giving weight " << MinWeight << " to "
1201  << getBlockName(HeaderNode) << "\n");
1202  if (MinWeight)
1203  Dist.addLocal(HeaderNode, MinWeight);
1204  }
1205  distributeIrrLoopHeaderMass(Dist);
1206  for (const BlockNode &M : Loop.Nodes)
1207  if (!propagateMassToSuccessors(&Loop, M))
1208  llvm_unreachable("unhandled irreducible control flow");
1209  if (NumHeadersWithWeight == 0)
1210  // No headers have a metadata. Adjust header mass.
1211  adjustLoopHeaderMass(Loop);
1212  } else {
1213  Working[Loop.getHeader().Index].getMass() = BlockMass::getFull();
1214  if (!propagateMassToSuccessors(&Loop, Loop.getHeader()))
1215  llvm_unreachable("irreducible control flow to loop header!?");
1216  for (const BlockNode &M : Loop.members())
1217  if (!propagateMassToSuccessors(&Loop, M))
1218  // Irreducible backedge.
1219  return false;
1220  }
1221 
1222  computeLoopScale(Loop);
1223  packageLoop(Loop);
1224  return true;
1225 }
1226 
1227 template <class BT>
1229  // Compute mass in function.
1230  LLVM_DEBUG(dbgs() << "compute-mass-in-function\n");
1231  assert(!Working.empty() && "no blocks in function");
1232  assert(!Working[0].isLoopHeader() && "entry block is a loop header");
1233 
1234  Working[0].getMass() = BlockMass::getFull();
1235  for (rpot_iterator I = rpot_begin(), IE = rpot_end(); I != IE; ++I) {
1236  // Check for nodes that have been packaged.
1237  BlockNode Node = getNode(I);
1238  if (Working[Node.Index].isPackaged())
1239  continue;
1240 
1241  if (!propagateMassToSuccessors(nullptr, Node))
1242  return false;
1243  }
1244  return true;
1245 }
1246 
1247 template <class BT> void BlockFrequencyInfoImpl<BT>::computeMassInFunction() {
1248  if (tryToComputeMassInFunction())
1249  return;
1250  computeIrreducibleMass(nullptr, Loops.begin());
1251  if (tryToComputeMassInFunction())
1252  return;
1253  llvm_unreachable("unhandled irreducible control flow");
1254 }
1255 
1256 /// \note This should be a lambda, but that crashes GCC 4.7.
1257 namespace bfi_detail {
1258 
1259 template <class BT> struct BlockEdgesAdder {
1260  using BlockT = BT;
1263 
1265 
1267  : BFI(BFI) {}
1268 
1270  const LoopData *OuterLoop) {
1271  const BlockT *BB = BFI.RPOT[Irr.Node.Index];
1272  for (const auto Succ : children<const BlockT *>(BB))
1273  G.addEdge(Irr, BFI.getNode(Succ), OuterLoop);
1274  }
1275 };
1276 
1277 } // end namespace bfi_detail
1278 
1279 template <class BT>
1281  LoopData *OuterLoop, std::list<LoopData>::iterator Insert) {
1282  LLVM_DEBUG(dbgs() << "analyze-irreducible-in-";
1283  if (OuterLoop) dbgs()
1284  << "loop: " << getLoopName(*OuterLoop) << "\n";
1285  else dbgs() << "function\n");
1286 
1287  using namespace bfi_detail;
1288 
1289  // Ideally, addBlockEdges() would be declared here as a lambda, but that
1290  // crashes GCC 4.7.
1291  BlockEdgesAdder<BT> addBlockEdges(*this);
1292  IrreducibleGraph G(*this, OuterLoop, addBlockEdges);
1293 
1294  for (auto &L : analyzeIrreducible(G, OuterLoop, Insert))
1295  computeMassInLoop(L);
1296 
1297  if (!OuterLoop)
1298  return;
1299  updateLoopWithIrreducible(*OuterLoop);
1300 }
1301 
1302 // A helper function that converts a branch probability into weight.
1304  return Prob.getNumerator();
1305 }
1306 
1307 template <class BT>
1308 bool
1310  const BlockNode &Node) {
1311  LLVM_DEBUG(dbgs() << " - node: " << getBlockName(Node) << "\n");
1312  // Calculate probability for successors.
1313  Distribution Dist;
1314  if (auto *Loop = Working[Node.Index].getPackagedLoop()) {
1315  assert(Loop != OuterLoop && "Cannot propagate mass in a packaged loop");
1316  if (!addLoopSuccessorsToDist(OuterLoop, *Loop, Dist))
1317  // Irreducible backedge.
1318  return false;
1319  } else {
1320  const BlockT *BB = getBlock(Node);
1323  SI != SE; ++SI)
1324  if (!addToDist(
1325  Dist, OuterLoop, Node, getNode(*SI),
1326  getWeightFromBranchProb(BPI->getEdgeProbability(BB, SI))))
1327  // Irreducible backedge.
1328  return false;
1329  }
1330 
1331  // Distribute mass to successors, saving exit and backedge data in the
1332  // loop header.
1333  distributeMass(Node, OuterLoop, Dist);
1334  return true;
1335 }
1336 
1337 template <class BT>
1339  if (!F)
1340  return OS;
1341  OS << "block-frequency-info: " << F->getName() << "\n";
1342  for (const BlockT &BB : *F) {
1343  OS << " - " << bfi_detail::getBlockName(&BB) << ": float = ";
1344  getFloatingBlockFreq(&BB).print(OS, 5)
1345  << ", int = " << getBlockFreq(&BB).getFrequency();
1348  F->getFunction(), getNode(&BB)))
1349  OS << ", count = " << ProfileCount.getValue();
1350  if (Optional<uint64_t> IrrLoopHeaderWeight =
1351  BB.getIrrLoopHeaderWeight())
1352  OS << ", irr_loop_header_weight = " << IrrLoopHeaderWeight.getValue();
1353  OS << "\n";
1354  }
1355 
1356  // Add an extra newline for readability.
1357  OS << "\n";
1358  return OS;
1359 }
1360 
1361 // Graph trait base class for block frequency information graph
1362 // viewer.
1363 
1365 
1366 template <class BlockFrequencyInfoT, class BranchProbabilityInfoT>
1369  using NodeRef = typename GTraits::NodeRef;
1370  using EdgeIter = typename GTraits::ChildIteratorType;
1371  using NodeIter = typename GTraits::nodes_iterator;
1372 
1373  uint64_t MaxFrequency = 0;
1374 
1375  explicit BFIDOTGraphTraitsBase(bool isSimple = false)
1377 
1378  static std::string getGraphName(const BlockFrequencyInfoT *G) {
1379  return G->getFunction()->getName();
1380  }
1381 
1382  std::string getNodeAttributes(NodeRef Node, const BlockFrequencyInfoT *Graph,
1383  unsigned HotPercentThreshold = 0) {
1384  std::string Result;
1385  if (!HotPercentThreshold)
1386  return Result;
1387 
1388  // Compute MaxFrequency on the fly:
1389  if (!MaxFrequency) {
1390  for (NodeIter I = GTraits::nodes_begin(Graph),
1391  E = GTraits::nodes_end(Graph);
1392  I != E; ++I) {
1393  NodeRef N = *I;
1394  MaxFrequency =
1395  std::max(MaxFrequency, Graph->getBlockFreq(N).getFrequency());
1396  }
1397  }
1398  BlockFrequency Freq = Graph->getBlockFreq(Node);
1399  BlockFrequency HotFreq =
1400  (BlockFrequency(MaxFrequency) *
1401  BranchProbability::getBranchProbability(HotPercentThreshold, 100));
1402 
1403  if (Freq < HotFreq)
1404  return Result;
1405 
1406  raw_string_ostream OS(Result);
1407  OS << "color=\"red\"";
1408  OS.flush();
1409  return Result;
1410  }
1411 
1412  std::string getNodeLabel(NodeRef Node, const BlockFrequencyInfoT *Graph,
1413  GVDAGType GType, int layout_order = -1) {
1414  std::string Result;
1415  raw_string_ostream OS(Result);
1416 
1417  if (layout_order != -1)
1418  OS << Node->getName() << "[" << layout_order << "] : ";
1419  else
1420  OS << Node->getName() << " : ";
1421  switch (GType) {
1422  case GVDT_Fraction:
1423  Graph->printBlockFreq(OS, Node);
1424  break;
1425  case GVDT_Integer:
1426  OS << Graph->getBlockFreq(Node).getFrequency();
1427  break;
1428  case GVDT_Count: {
1429  auto Count = Graph->getBlockProfileCount(Node);
1430  if (Count)
1431  OS << Count.getValue();
1432  else
1433  OS << "Unknown";
1434  break;
1435  }
1436  case GVDT_None:
1437  llvm_unreachable("If we are not supposed to render a graph we should "
1438  "never reach this point.");
1439  }
1440  return Result;
1441  }
1442 
1443  std::string getEdgeAttributes(NodeRef Node, EdgeIter EI,
1444  const BlockFrequencyInfoT *BFI,
1445  const BranchProbabilityInfoT *BPI,
1446  unsigned HotPercentThreshold = 0) {
1447  std::string Str;
1448  if (!BPI)
1449  return Str;
1450 
1451  BranchProbability BP = BPI->getEdgeProbability(Node, EI);
1452  uint32_t N = BP.getNumerator();
1453  uint32_t D = BP.getDenominator();
1454  double Percent = 100.0 * N / D;
1455  raw_string_ostream OS(Str);
1456  OS << format("label=\"%.1f%%\"", Percent);
1457 
1458  if (HotPercentThreshold) {
1459  BlockFrequency EFreq = BFI->getBlockFreq(Node) * BP;
1460  BlockFrequency HotFreq = BlockFrequency(MaxFrequency) *
1461  BranchProbability(HotPercentThreshold, 100);
1462 
1463  if (EFreq >= HotFreq) {
1464  OS << ",color=\"red\"";
1465  }
1466  }
1467 
1468  OS.flush();
1469  return Str;
1470  }
1471 };
1472 
1473 } // end namespace llvm
1474 
1475 #undef DEBUG_TYPE
1476 
1477 #endif // LLVM_ANALYSIS_BLOCKFREQUENCYINFOIMPL_H
auto lower_bound(R &&Range, T &&Value) -> decltype(adl_begin(Range))
Provide wrappers to std::lower_bound which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1261
BlockMass operator+(BlockMass L, BlockMass R)
void setBlockFreq(const BlockT *BB, uint64_t Freq)
Optional< uint64_t > getBlockProfileCount(const Function &F, const BlockT *BB, bool AllowSynthetic=false) const
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
bool IsPackaged
Whether this has been packaged.
LLVM_NODISCARD std::string str() const
str - Get the contents as an std::string.
Definition: StringRef.h:232
bool operator<=(BlockMass X) const
typename SuperClass::const_iterator const_iterator
Definition: SmallVector.h:320
This class represents lattice values for constants.
Definition: AllocatorList.h:23
Scaled64 getFloatingBlockFreq(const BlockT *BB) const
bool isIrrLoopHeader(const BlockT *BB)
Various leaf nodes.
Definition: ISDOpcodes.h:59
LoopData(LoopData *Parent, It1 FirstHeader, It1 LastHeader, It2 FirstOther, It2 LastOther)
void push_back(const T &Elt)
Definition: SmallVector.h:211
NodeList::const_iterator members_begin() const
This provides a very simple, boring adaptor for a begin and end iterator into a range type...
raw_ostream & printBlockFreq(raw_ostream &OS, const BlockNode &Node) const
format_object< Ts... > format(const char *Fmt, const Ts &... Vals)
These are helper functions used to produce formatted output.
Definition: Format.h:124
static std::string getGraphName(const BlockFrequencyInfoT *G)
BlockFrequency getBlockFreq(const BlockT *BB) const
raw_ostream & print(raw_ostream &OS) const
const BranchProbabilityInfoT & getBPI() const
void addLocal(const BlockNode &Node, uint64_t Amount)
F(f)
SmallDenseMap< uint32_t, IrrNode *, 4 > Lookup
IrreducibleGraph(BFIBase &BFI, const BFIBase::LoopData *OuterLoop, BlockEdgesAdder addBlockEdges)
Construct an explicit graph containing irreducible control flow.
const BlockFrequencyInfoImpl< BT > & BFI
void setBlockFreq(const BlockNode &Node, uint64_t Freq)
BFIDOTGraphTraitsBase(bool isSimple=false)
SparseBitVector IsIrrLoopHeader
Whether each block is an irreducible loop header.
void operator()(IrreducibleGraph &G, IrreducibleGraph::IrrNode &Irr, const LoopData *OuterLoop)
Weight(DistType Type, BlockNode TargetNode, uint64_t Amount)
NodeList::const_iterator members_end() const
Hexagon Hardware Loops
uint32_t getWeightFromBranchProb(const BranchProbability Prob)
Definition: BitVector.h:937
BlockMass & getMass()
Get the appropriate mass for a node.
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:80
Scaled64 getFloatingBlockFreq(const BlockNode &Node) const
static int Lookup(ArrayRef< TableEntry > Table, unsigned Opcode)
bool isAPackage() const
Has Loop been packaged up?
virtual raw_ostream & print(raw_ostream &OS) const
std::string getNodeLabel(NodeRef Node, const BlockFrequencyInfoT *Graph, GVDAGType GType, int layout_order=-1)
void addEdge(IrrNode &Irr, const BlockNode &Succ, const BFIBase::LoopData *OuterLoop)
BlockMass & operator*=(BranchProbability P)
bool operator>=(BlockMass X) const
Interval::succ_iterator succ_begin(Interval *I)
succ_begin/succ_end - define methods so that Intervals may be used just like BasicBlocks can with the...
Definition: Interval.h:102
static bool isSimple(Instruction *I)
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:261
bool operator==(BlockMass X) const
Graph of irreducible control flow.
const T & getValue() const LLVM_LVALUE_FUNCTION
Definition: Optional.h:255
std::deque< const IrrNode * >::const_iterator iterator
static void initialize(TargetLibraryInfoImpl &TLI, const Triple &T, ArrayRef< StringLiteral > StandardNames)
Initialize the set of available library functions based on the specified target triple.
void calculate(const FunctionT &F, const BranchProbabilityInfoT &BPI, const LoopInfoT &LI)
static void addEdge(SmallVectorImpl< LazyCallGraph::Edge > &Edges, DenseMap< LazyCallGraph::Node *, int > &EdgeIndexMap, LazyCallGraph::Node &N, LazyCallGraph::Edge::Kind EK)
raw_ostream & print(raw_ostream &OS) const override
Print the frequencies for the current function.
void addBackedge(const BlockNode &Node, uint64_t Amount)
void initialize(const BFIBase::LoopData *OuterLoop, BlockEdgesAdder addBlockEdges)
bool isHeader(const BlockNode &Node) const
bool isIrrLoopHeader(const BlockNode &Node)
Optional< uint64_t > getBlockProfileCount(const Function &F, const BlockNode &Node, bool AllowSynthetic=false) const
#define P(N)
std::vector< FrequencyData > Freqs
Data about each block. This is used downstream.
typename GraphType::UnknownGraphTypeError NodeRef
Definition: GraphTraits.h:78
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
BlockMass & operator-=(BlockMass X)
Subtract another mass.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
BlockMass & operator+=(BlockMass X)
Add another mass.
#define H(x, y, z)
Definition: MD5.cpp:57
Distribution of unscaled probability weight.
std::pair< iterator, bool > insert(const ValueT &V)
Definition: DenseSet.h:187
po_iterator< T > po_end(const T &G)
BlockNode getResolvedNode() const
Resolve a node to its representative.
BlockMass Mass
Mass distribution from the entry block.
typename GTraits::NodeRef NodeRef
BlockEdgesAdder(const BlockFrequencyInfoImpl< BT > &BFI)
BlockMass operator*(BlockMass L, BranchProbability R)
Class to represent profile counts.
Definition: Function.h:260
size_t size() const
Definition: SmallVector.h:52
std::string getEdgeAttributes(NodeRef Node, EdgeIter EI, const BlockFrequencyInfoT *BFI, const BranchProbabilityInfoT *BPI, unsigned HotPercentThreshold=0)
raw_ostream & operator<<(raw_ostream &OS, BlockMass X)
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
void addExit(const BlockNode &Node, uint64_t Amount)
std::string getNodeAttributes(NodeRef Node, const BlockFrequencyInfoT *Graph, unsigned HotPercentThreshold=0)
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
static uint32_t getDenominator()
bool isADoublePackage() const
Has Loop been packaged up twice?
Align max(MaybeAlign Lhs, Align Rhs)
Definition: Alignment.h:390
ExitMap Exits
Successor edges (and weights).
static uint64_t add(uint64_t LeftOp, uint64_t RightOp)
Definition: FileCheck.cpp:215
static BranchProbability getBranchProbability(uint64_t Numerator, uint64_t Denominator)
const DataFlowGraph & G
Definition: RDFGraph.cpp:202
BlockMass operator-(BlockMass L, BlockMass R)
uint64_t scale(uint64_t Num) const
Scale a large integer.
static GCRegistry::Add< StatepointGC > D("statepoint-example", "an example strategy for statepoint")
ScaledNumber< uint64_t > toScaled() const
Convert to scaled number.
std::list< LoopData > Loops
Indexed information about loops.
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
A range adaptor for a pair of iterators.
std::string getBlockName(const BlockT *BB)
Get the name of a MachineBasicBlock.
LoopData(LoopData *Parent, const BlockNode &Header)
static void clear(coro::Shape &Shape)
Definition: Coroutines.cpp:225
iterator insert(iterator I, T &&Elt)
Definition: SmallVector.h:467
Optional< uint64_t > getProfileCountFromFreq(const Function &F, uint64_t Freq, bool AllowSynthetic=false) const
Analysis providing branch probability information.
bool operator>(BlockMass X) const
void addEdges(const BlockNode &Node, const BFIBase::LoopData *OuterLoop, BlockEdgesAdder addBlockEdges)
iterator begin()
Definition: DenseMap.h:73
BitTracker BT
Definition: BitTracker.cpp:73
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:509
raw_ostream & printBlockFreq(raw_ostream &OS, const BlockT *BB) const
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
void reserve(size_t Size)
Grow the DenseSet so that it can contain at least NumEntries items before resizing again...
Definition: DenseSet.h:84
typename GTraits::ChildIteratorType EdgeIter
typename GTraits::nodes_iterator NodeIter
size_type count(const_arg_type_t< KeyT > Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:145
std::string str() const
Return the twine contents as a std::string.
Definition: Twine.cpp:17
ValueT lookup(const_arg_type_t< KeyT > Val) const
lookup - Return the entry for the specified key, or a default constructed value if no such entry exis...
Definition: DenseMap.h:185
iterator_range< NodeList::const_iterator > members() const
bool operator!=(BlockMass X) const
NodeList Nodes
Header and the members of the loop.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
A raw_ostream that writes to an std::string.
Definition: raw_ostream.h:503
bool operator<(BlockMass X) const
std::vector< WorkingData > Working
Loop data: see initializeLoops().
HeaderMassList BackedgeMass
Mass returned to each loop header.
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
DefaultDOTGraphTraits - This class provides the default implementations of all of the DOTGraphTraits ...
const FunctionT * getFunction() const
Shared implementation for block frequency analysis.
BlockFrequency getBlockFreq(const BlockNode &Node) const
Optional< uint64_t > getProfileCountFromFreq(const Function &F, uint64_t Freq, bool AllowSynthetic=false) const
Base class for BlockFrequencyInfoImpl.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
OutputIt copy(R &&Range, OutputIt Out)
Definition: STLExtras.h:1217
HeaderMassList::difference_type getHeaderIndex(const BlockNode &B)
LoopData & getLoopPackage(const BlockNode &Head)
uint32_t getNumerator() const
bool isPackaged() const
Has ContainingLoop been packaged up?
po_iterator< T > po_begin(const T &G)
WeightList Weights
Individual successor weights.
void resize(size_type N)
Definition: SmallVector.h:344