LLVM  7.0.0svn
NewGVN.cpp
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1 //===- NewGVN.cpp - Global Value Numbering Pass ---------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 /// \file
11 /// This file implements the new LLVM's Global Value Numbering pass.
12 /// GVN partitions values computed by a function into congruence classes.
13 /// Values ending up in the same congruence class are guaranteed to be the same
14 /// for every execution of the program. In that respect, congruency is a
15 /// compile-time approximation of equivalence of values at runtime.
16 /// The algorithm implemented here uses a sparse formulation and it's based
17 /// on the ideas described in the paper:
18 /// "A Sparse Algorithm for Predicated Global Value Numbering" from
19 /// Karthik Gargi.
20 ///
21 /// A brief overview of the algorithm: The algorithm is essentially the same as
22 /// the standard RPO value numbering algorithm (a good reference is the paper
23 /// "SCC based value numbering" by L. Taylor Simpson) with one major difference:
24 /// The RPO algorithm proceeds, on every iteration, to process every reachable
25 /// block and every instruction in that block. This is because the standard RPO
26 /// algorithm does not track what things have the same value number, it only
27 /// tracks what the value number of a given operation is (the mapping is
28 /// operation -> value number). Thus, when a value number of an operation
29 /// changes, it must reprocess everything to ensure all uses of a value number
30 /// get updated properly. In constrast, the sparse algorithm we use *also*
31 /// tracks what operations have a given value number (IE it also tracks the
32 /// reverse mapping from value number -> operations with that value number), so
33 /// that it only needs to reprocess the instructions that are affected when
34 /// something's value number changes. The vast majority of complexity and code
35 /// in this file is devoted to tracking what value numbers could change for what
36 /// instructions when various things happen. The rest of the algorithm is
37 /// devoted to performing symbolic evaluation, forward propagation, and
38 /// simplification of operations based on the value numbers deduced so far
39 ///
40 /// In order to make the GVN mostly-complete, we use a technique derived from
41 /// "Detection of Redundant Expressions: A Complete and Polynomial-time
42 /// Algorithm in SSA" by R.R. Pai. The source of incompleteness in most SSA
43 /// based GVN algorithms is related to their inability to detect equivalence
44 /// between phi of ops (IE phi(a+b, c+d)) and op of phis (phi(a,c) + phi(b, d)).
45 /// We resolve this issue by generating the equivalent "phi of ops" form for
46 /// each op of phis we see, in a way that only takes polynomial time to resolve.
47 ///
48 /// We also do not perform elimination by using any published algorithm. All
49 /// published algorithms are O(Instructions). Instead, we use a technique that
50 /// is O(number of operations with the same value number), enabling us to skip
51 /// trying to eliminate things that have unique value numbers.
52 //
53 //===----------------------------------------------------------------------===//
54 
56 #include "llvm/ADT/ArrayRef.h"
57 #include "llvm/ADT/BitVector.h"
58 #include "llvm/ADT/DenseMap.h"
59 #include "llvm/ADT/DenseMapInfo.h"
60 #include "llvm/ADT/DenseSet.h"
62 #include "llvm/ADT/GraphTraits.h"
63 #include "llvm/ADT/Hashing.h"
66 #include "llvm/ADT/SmallPtrSet.h"
67 #include "llvm/ADT/SmallVector.h"
69 #include "llvm/ADT/Statistic.h"
81 #include "llvm/IR/Argument.h"
82 #include "llvm/IR/BasicBlock.h"
83 #include "llvm/IR/Constant.h"
84 #include "llvm/IR/Constants.h"
85 #include "llvm/IR/Dominators.h"
86 #include "llvm/IR/Function.h"
87 #include "llvm/IR/InstrTypes.h"
88 #include "llvm/IR/Instruction.h"
89 #include "llvm/IR/Instructions.h"
90 #include "llvm/IR/IntrinsicInst.h"
91 #include "llvm/IR/Intrinsics.h"
92 #include "llvm/IR/LLVMContext.h"
93 #include "llvm/IR/Type.h"
94 #include "llvm/IR/Use.h"
95 #include "llvm/IR/User.h"
96 #include "llvm/IR/Value.h"
97 #include "llvm/Pass.h"
98 #include "llvm/Support/Allocator.h"
100 #include "llvm/Support/Casting.h"
102 #include "llvm/Support/Debug.h"
107 #include "llvm/Transforms/Scalar.h"
111 #include <algorithm>
112 #include <cassert>
113 #include <cstdint>
114 #include <iterator>
115 #include <map>
116 #include <memory>
117 #include <set>
118 #include <string>
119 #include <tuple>
120 #include <utility>
121 #include <vector>
122 
123 using namespace llvm;
124 using namespace llvm::GVNExpression;
125 using namespace llvm::VNCoercion;
126 
127 #define DEBUG_TYPE "newgvn"
128 
129 STATISTIC(NumGVNInstrDeleted, "Number of instructions deleted");
130 STATISTIC(NumGVNBlocksDeleted, "Number of blocks deleted");
131 STATISTIC(NumGVNOpsSimplified, "Number of Expressions simplified");
132 STATISTIC(NumGVNPhisAllSame, "Number of PHIs whos arguments are all the same");
133 STATISTIC(NumGVNMaxIterations,
134  "Maximum Number of iterations it took to converge GVN");
135 STATISTIC(NumGVNLeaderChanges, "Number of leader changes");
136 STATISTIC(NumGVNSortedLeaderChanges, "Number of sorted leader changes");
137 STATISTIC(NumGVNAvoidedSortedLeaderChanges,
138  "Number of avoided sorted leader changes");
139 STATISTIC(NumGVNDeadStores, "Number of redundant/dead stores eliminated");
140 STATISTIC(NumGVNPHIOfOpsCreated, "Number of PHI of ops created");
141 STATISTIC(NumGVNPHIOfOpsEliminations,
142  "Number of things eliminated using PHI of ops");
143 DEBUG_COUNTER(VNCounter, "newgvn-vn",
144  "Controls which instructions are value numbered");
145 DEBUG_COUNTER(PHIOfOpsCounter, "newgvn-phi",
146  "Controls which instructions we create phi of ops for");
147 // Currently store defining access refinement is too slow due to basicaa being
148 // egregiously slow. This flag lets us keep it working while we work on this
149 // issue.
150 static cl::opt<bool> EnableStoreRefinement("enable-store-refinement",
151  cl::init(false), cl::Hidden);
152 
153 /// Currently, the generation "phi of ops" can result in correctness issues.
154 static cl::opt<bool> EnablePhiOfOps("enable-phi-of-ops", cl::init(true),
155  cl::Hidden);
156 
157 //===----------------------------------------------------------------------===//
158 // GVN Pass
159 //===----------------------------------------------------------------------===//
160 
161 // Anchor methods.
162 namespace llvm {
163 namespace GVNExpression {
164 
165 Expression::~Expression() = default;
172 
173 } // end namespace GVNExpression
174 } // end namespace llvm
175 
176 namespace {
177 
178 // Tarjan's SCC finding algorithm with Nuutila's improvements
179 // SCCIterator is actually fairly complex for the simple thing we want.
180 // It also wants to hand us SCC's that are unrelated to the phi node we ask
181 // about, and have us process them there or risk redoing work.
182 // Graph traits over a filter iterator also doesn't work that well here.
183 // This SCC finder is specialized to walk use-def chains, and only follows
184 // instructions,
185 // not generic values (arguments, etc).
186 struct TarjanSCC {
187  TarjanSCC() : Components(1) {}
188 
189  void Start(const Instruction *Start) {
190  if (Root.lookup(Start) == 0)
191  FindSCC(Start);
192  }
193 
194  const SmallPtrSetImpl<const Value *> &getComponentFor(const Value *V) const {
195  unsigned ComponentID = ValueToComponent.lookup(V);
196 
197  assert(ComponentID > 0 &&
198  "Asking for a component for a value we never processed");
199  return Components[ComponentID];
200  }
201 
202 private:
203  void FindSCC(const Instruction *I) {
204  Root[I] = ++DFSNum;
205  // Store the DFS Number we had before it possibly gets incremented.
206  unsigned int OurDFS = DFSNum;
207  for (auto &Op : I->operands()) {
208  if (auto *InstOp = dyn_cast<Instruction>(Op)) {
209  if (Root.lookup(Op) == 0)
210  FindSCC(InstOp);
211  if (!InComponent.count(Op))
212  Root[I] = std::min(Root.lookup(I), Root.lookup(Op));
213  }
214  }
215  // See if we really were the root of a component, by seeing if we still have
216  // our DFSNumber. If we do, we are the root of the component, and we have
217  // completed a component. If we do not, we are not the root of a component,
218  // and belong on the component stack.
219  if (Root.lookup(I) == OurDFS) {
220  unsigned ComponentID = Components.size();
221  Components.resize(Components.size() + 1);
222  auto &Component = Components.back();
223  Component.insert(I);
224  LLVM_DEBUG(dbgs() << "Component root is " << *I << "\n");
225  InComponent.insert(I);
226  ValueToComponent[I] = ComponentID;
227  // Pop a component off the stack and label it.
228  while (!Stack.empty() && Root.lookup(Stack.back()) >= OurDFS) {
229  auto *Member = Stack.back();
230  LLVM_DEBUG(dbgs() << "Component member is " << *Member << "\n");
231  Component.insert(Member);
232  InComponent.insert(Member);
233  ValueToComponent[Member] = ComponentID;
234  Stack.pop_back();
235  }
236  } else {
237  // Part of a component, push to stack
238  Stack.push_back(I);
239  }
240  }
241 
242  unsigned int DFSNum = 1;
243  SmallPtrSet<const Value *, 8> InComponent;
246 
247  // Store the components as vector of ptr sets, because we need the topo order
248  // of SCC's, but not individual member order
250 
251  DenseMap<const Value *, unsigned> ValueToComponent;
252 };
253 
254 // Congruence classes represent the set of expressions/instructions
255 // that are all the same *during some scope in the function*.
256 // That is, because of the way we perform equality propagation, and
257 // because of memory value numbering, it is not correct to assume
258 // you can willy-nilly replace any member with any other at any
259 // point in the function.
260 //
261 // For any Value in the Member set, it is valid to replace any dominated member
262 // with that Value.
263 //
264 // Every congruence class has a leader, and the leader is used to symbolize
265 // instructions in a canonical way (IE every operand of an instruction that is a
266 // member of the same congruence class will always be replaced with leader
267 // during symbolization). To simplify symbolization, we keep the leader as a
268 // constant if class can be proved to be a constant value. Otherwise, the
269 // leader is the member of the value set with the smallest DFS number. Each
270 // congruence class also has a defining expression, though the expression may be
271 // null. If it exists, it can be used for forward propagation and reassociation
272 // of values.
273 
274 // For memory, we also track a representative MemoryAccess, and a set of memory
275 // members for MemoryPhis (which have no real instructions). Note that for
276 // memory, it seems tempting to try to split the memory members into a
277 // MemoryCongruenceClass or something. Unfortunately, this does not work
278 // easily. The value numbering of a given memory expression depends on the
279 // leader of the memory congruence class, and the leader of memory congruence
280 // class depends on the value numbering of a given memory expression. This
281 // leads to wasted propagation, and in some cases, missed optimization. For
282 // example: If we had value numbered two stores together before, but now do not,
283 // we move them to a new value congruence class. This in turn will move at one
284 // of the memorydefs to a new memory congruence class. Which in turn, affects
285 // the value numbering of the stores we just value numbered (because the memory
286 // congruence class is part of the value number). So while theoretically
287 // possible to split them up, it turns out to be *incredibly* complicated to get
288 // it to work right, because of the interdependency. While structurally
289 // slightly messier, it is algorithmically much simpler and faster to do what we
290 // do here, and track them both at once in the same class.
291 // Note: The default iterators for this class iterate over values
292 class CongruenceClass {
293 public:
294  using MemberType = Value;
295  using MemberSet = SmallPtrSet<MemberType *, 4>;
296  using MemoryMemberType = MemoryPhi;
297  using MemoryMemberSet = SmallPtrSet<const MemoryMemberType *, 2>;
298 
299  explicit CongruenceClass(unsigned ID) : ID(ID) {}
300  CongruenceClass(unsigned ID, Value *Leader, const Expression *E)
301  : ID(ID), RepLeader(Leader), DefiningExpr(E) {}
302 
303  unsigned getID() const { return ID; }
304 
305  // True if this class has no members left. This is mainly used for assertion
306  // purposes, and for skipping empty classes.
307  bool isDead() const {
308  // If it's both dead from a value perspective, and dead from a memory
309  // perspective, it's really dead.
310  return empty() && memory_empty();
311  }
312 
313  // Leader functions
314  Value *getLeader() const { return RepLeader; }
315  void setLeader(Value *Leader) { RepLeader = Leader; }
316  const std::pair<Value *, unsigned int> &getNextLeader() const {
317  return NextLeader;
318  }
319  void resetNextLeader() { NextLeader = {nullptr, ~0}; }
320  void addPossibleNextLeader(std::pair<Value *, unsigned int> LeaderPair) {
321  if (LeaderPair.second < NextLeader.second)
322  NextLeader = LeaderPair;
323  }
324 
325  Value *getStoredValue() const { return RepStoredValue; }
326  void setStoredValue(Value *Leader) { RepStoredValue = Leader; }
327  const MemoryAccess *getMemoryLeader() const { return RepMemoryAccess; }
328  void setMemoryLeader(const MemoryAccess *Leader) { RepMemoryAccess = Leader; }
329 
330  // Forward propagation info
331  const Expression *getDefiningExpr() const { return DefiningExpr; }
332 
333  // Value member set
334  bool empty() const { return Members.empty(); }
335  unsigned size() const { return Members.size(); }
336  MemberSet::const_iterator begin() const { return Members.begin(); }
337  MemberSet::const_iterator end() const { return Members.end(); }
338  void insert(MemberType *M) { Members.insert(M); }
339  void erase(MemberType *M) { Members.erase(M); }
340  void swap(MemberSet &Other) { Members.swap(Other); }
341 
342  // Memory member set
343  bool memory_empty() const { return MemoryMembers.empty(); }
344  unsigned memory_size() const { return MemoryMembers.size(); }
345  MemoryMemberSet::const_iterator memory_begin() const {
346  return MemoryMembers.begin();
347  }
348  MemoryMemberSet::const_iterator memory_end() const {
349  return MemoryMembers.end();
350  }
352  return make_range(memory_begin(), memory_end());
353  }
354 
355  void memory_insert(const MemoryMemberType *M) { MemoryMembers.insert(M); }
356  void memory_erase(const MemoryMemberType *M) { MemoryMembers.erase(M); }
357 
358  // Store count
359  unsigned getStoreCount() const { return StoreCount; }
360  void incStoreCount() { ++StoreCount; }
361  void decStoreCount() {
362  assert(StoreCount != 0 && "Store count went negative");
363  --StoreCount;
364  }
365 
366  // True if this class has no memory members.
367  bool definesNoMemory() const { return StoreCount == 0 && memory_empty(); }
368 
369  // Return true if two congruence classes are equivalent to each other. This
370  // means that every field but the ID number and the dead field are equivalent.
371  bool isEquivalentTo(const CongruenceClass *Other) const {
372  if (!Other)
373  return false;
374  if (this == Other)
375  return true;
376 
377  if (std::tie(StoreCount, RepLeader, RepStoredValue, RepMemoryAccess) !=
378  std::tie(Other->StoreCount, Other->RepLeader, Other->RepStoredValue,
379  Other->RepMemoryAccess))
380  return false;
381  if (DefiningExpr != Other->DefiningExpr)
382  if (!DefiningExpr || !Other->DefiningExpr ||
383  *DefiningExpr != *Other->DefiningExpr)
384  return false;
385 
386  if (Members.size() != Other->Members.size())
387  return false;
388 
389  return all_of(Members,
390  [&](const Value *V) { return Other->Members.count(V); });
391  }
392 
393 private:
394  unsigned ID;
395 
396  // Representative leader.
397  Value *RepLeader = nullptr;
398 
399  // The most dominating leader after our current leader, because the member set
400  // is not sorted and is expensive to keep sorted all the time.
401  std::pair<Value *, unsigned int> NextLeader = {nullptr, ~0U};
402 
403  // If this is represented by a store, the value of the store.
404  Value *RepStoredValue = nullptr;
405 
406  // If this class contains MemoryDefs or MemoryPhis, this is the leading memory
407  // access.
408  const MemoryAccess *RepMemoryAccess = nullptr;
409 
410  // Defining Expression.
411  const Expression *DefiningExpr = nullptr;
412 
413  // Actual members of this class.
414  MemberSet Members;
415 
416  // This is the set of MemoryPhis that exist in the class. MemoryDefs and
417  // MemoryUses have real instructions representing them, so we only need to
418  // track MemoryPhis here.
419  MemoryMemberSet MemoryMembers;
420 
421  // Number of stores in this congruence class.
422  // This is used so we can detect store equivalence changes properly.
423  int StoreCount = 0;
424 };
425 
426 } // end anonymous namespace
427 
428 namespace llvm {
429 
431  const Expression &E;
432 
433  explicit ExactEqualsExpression(const Expression &E) : E(E) {}
434 
435  hash_code getComputedHash() const { return E.getComputedHash(); }
436 
437  bool operator==(const Expression &Other) const {
438  return E.exactlyEquals(Other);
439  }
440 };
441 
442 template <> struct DenseMapInfo<const Expression *> {
443  static const Expression *getEmptyKey() {
444  auto Val = static_cast<uintptr_t>(-1);
445  Val <<= PointerLikeTypeTraits<const Expression *>::NumLowBitsAvailable;
446  return reinterpret_cast<const Expression *>(Val);
447  }
448 
449  static const Expression *getTombstoneKey() {
450  auto Val = static_cast<uintptr_t>(~1U);
451  Val <<= PointerLikeTypeTraits<const Expression *>::NumLowBitsAvailable;
452  return reinterpret_cast<const Expression *>(Val);
453  }
454 
455  static unsigned getHashValue(const Expression *E) {
456  return E->getComputedHash();
457  }
458 
459  static unsigned getHashValue(const ExactEqualsExpression &E) {
460  return E.getComputedHash();
461  }
462 
463  static bool isEqual(const ExactEqualsExpression &LHS, const Expression *RHS) {
464  if (RHS == getTombstoneKey() || RHS == getEmptyKey())
465  return false;
466  return LHS == *RHS;
467  }
468 
469  static bool isEqual(const Expression *LHS, const Expression *RHS) {
470  if (LHS == RHS)
471  return true;
472  if (LHS == getTombstoneKey() || RHS == getTombstoneKey() ||
473  LHS == getEmptyKey() || RHS == getEmptyKey())
474  return false;
475  // Compare hashes before equality. This is *not* what the hashtable does,
476  // since it is computing it modulo the number of buckets, whereas we are
477  // using the full hash keyspace. Since the hashes are precomputed, this
478  // check is *much* faster than equality.
479  if (LHS->getComputedHash() != RHS->getComputedHash())
480  return false;
481  return *LHS == *RHS;
482  }
483 };
484 
485 } // end namespace llvm
486 
487 namespace {
488 
489 class NewGVN {
490  Function &F;
491  DominatorTree *DT;
492  const TargetLibraryInfo *TLI;
493  AliasAnalysis *AA;
494  MemorySSA *MSSA;
495  MemorySSAWalker *MSSAWalker;
496  const DataLayout &DL;
497  std::unique_ptr<PredicateInfo> PredInfo;
498 
499  // These are the only two things the create* functions should have
500  // side-effects on due to allocating memory.
501  mutable BumpPtrAllocator ExpressionAllocator;
502  mutable ArrayRecycler<Value *> ArgRecycler;
503  mutable TarjanSCC SCCFinder;
504  const SimplifyQuery SQ;
505 
506  // Number of function arguments, used by ranking
507  unsigned int NumFuncArgs;
508 
509  // RPOOrdering of basic blocks
511 
512  // Congruence class info.
513 
514  // This class is called INITIAL in the paper. It is the class everything
515  // startsout in, and represents any value. Being an optimistic analysis,
516  // anything in the TOP class has the value TOP, which is indeterminate and
517  // equivalent to everything.
518  CongruenceClass *TOPClass;
519  std::vector<CongruenceClass *> CongruenceClasses;
520  unsigned NextCongruenceNum;
521 
522  // Value Mappings.
524  DenseMap<Value *, const Expression *> ValueToExpression;
525 
526  // Value PHI handling, used to make equivalence between phi(op, op) and
527  // op(phi, phi).
528  // These mappings just store various data that would normally be part of the
529  // IR.
531 
532  DenseMap<const Value *, bool> OpSafeForPHIOfOps;
533 
534  // Map a temporary instruction we created to a parent block.
536 
537  // Map between the already in-program instructions and the temporary phis we
538  // created that they are known equivalent to.
540 
541  // In order to know when we should re-process instructions that have
542  // phi-of-ops, we track the set of expressions that they needed as
543  // leaders. When we discover new leaders for those expressions, we process the
544  // associated phi-of-op instructions again in case they have changed. The
545  // other way they may change is if they had leaders, and those leaders
546  // disappear. However, at the point they have leaders, there are uses of the
547  // relevant operands in the created phi node, and so they will get reprocessed
548  // through the normal user marking we perform.
549  mutable DenseMap<const Value *, SmallPtrSet<Value *, 2>> AdditionalUsers;
551  ExpressionToPhiOfOps;
552 
553  // Map from temporary operation to MemoryAccess.
555 
556  // Set of all temporary instructions we created.
557  // Note: This will include instructions that were just created during value
558  // numbering. The way to test if something is using them is to check
559  // RealToTemp.
560  DenseSet<Instruction *> AllTempInstructions;
561 
562  // This is the set of instructions to revisit on a reachability change. At
563  // the end of the main iteration loop it will contain at least all the phi of
564  // ops instructions that will be changed to phis, as well as regular phis.
565  // During the iteration loop, it may contain other things, such as phi of ops
566  // instructions that used edge reachability to reach a result, and so need to
567  // be revisited when the edge changes, independent of whether the phi they
568  // depended on changes.
569  DenseMap<BasicBlock *, SparseBitVector<>> RevisitOnReachabilityChange;
570 
571  // Mapping from predicate info we used to the instructions we used it with.
572  // In order to correctly ensure propagation, we must keep track of what
573  // comparisons we used, so that when the values of the comparisons change, we
574  // propagate the information to the places we used the comparison.
576  PredicateToUsers;
577 
578  // the same reasoning as PredicateToUsers. When we skip MemoryAccesses for
579  // stores, we no longer can rely solely on the def-use chains of MemorySSA.
581  MemoryToUsers;
582 
583  // A table storing which memorydefs/phis represent a memory state provably
584  // equivalent to another memory state.
585  // We could use the congruence class machinery, but the MemoryAccess's are
586  // abstract memory states, so they can only ever be equivalent to each other,
587  // and not to constants, etc.
589 
590  // We could, if we wanted, build MemoryPhiExpressions and
591  // MemoryVariableExpressions, etc, and value number them the same way we value
592  // number phi expressions. For the moment, this seems like overkill. They
593  // can only exist in one of three states: they can be TOP (equal to
594  // everything), Equivalent to something else, or unique. Because we do not
595  // create expressions for them, we need to simulate leader change not just
596  // when they change class, but when they change state. Note: We can do the
597  // same thing for phis, and avoid having phi expressions if we wanted, We
598  // should eventually unify in one direction or the other, so this is a little
599  // bit of an experiment in which turns out easier to maintain.
600  enum MemoryPhiState { MPS_Invalid, MPS_TOP, MPS_Equivalent, MPS_Unique };
602 
603  enum InstCycleState { ICS_Unknown, ICS_CycleFree, ICS_Cycle };
604  mutable DenseMap<const Instruction *, InstCycleState> InstCycleState;
605 
606  // Expression to class mapping.
607  using ExpressionClassMap = DenseMap<const Expression *, CongruenceClass *>;
608  ExpressionClassMap ExpressionToClass;
609 
610  // We have a single expression that represents currently DeadExpressions.
611  // For dead expressions we can prove will stay dead, we mark them with
612  // DFS number zero. However, it's possible in the case of phi nodes
613  // for us to assume/prove all arguments are dead during fixpointing.
614  // We use DeadExpression for that case.
615  DeadExpression *SingletonDeadExpression = nullptr;
616 
617  // Which values have changed as a result of leader changes.
618  SmallPtrSet<Value *, 8> LeaderChanges;
619 
620  // Reachability info.
621  using BlockEdge = BasicBlockEdge;
622  DenseSet<BlockEdge> ReachableEdges;
623  SmallPtrSet<const BasicBlock *, 8> ReachableBlocks;
624 
625  // This is a bitvector because, on larger functions, we may have
626  // thousands of touched instructions at once (entire blocks,
627  // instructions with hundreds of uses, etc). Even with optimization
628  // for when we mark whole blocks as touched, when this was a
629  // SmallPtrSet or DenseSet, for some functions, we spent >20% of all
630  // the time in GVN just managing this list. The bitvector, on the
631  // other hand, efficiently supports test/set/clear of both
632  // individual and ranges, as well as "find next element" This
633  // enables us to use it as a worklist with essentially 0 cost.
634  BitVector TouchedInstructions;
635 
637 
638 #ifndef NDEBUG
639  // Debugging for how many times each block and instruction got processed.
640  DenseMap<const Value *, unsigned> ProcessedCount;
641 #endif
642 
643  // DFS info.
644  // This contains a mapping from Instructions to DFS numbers.
645  // The numbering starts at 1. An instruction with DFS number zero
646  // means that the instruction is dead.
648 
649  // This contains the mapping DFS numbers to instructions.
650  SmallVector<Value *, 32> DFSToInstr;
651 
652  // Deletion info.
653  SmallPtrSet<Instruction *, 8> InstructionsToErase;
654 
655 public:
656  NewGVN(Function &F, DominatorTree *DT, AssumptionCache *AC,
657  TargetLibraryInfo *TLI, AliasAnalysis *AA, MemorySSA *MSSA,
658  const DataLayout &DL)
659  : F(F), DT(DT), TLI(TLI), AA(AA), MSSA(MSSA), DL(DL),
660  PredInfo(make_unique<PredicateInfo>(F, *DT, *AC)), SQ(DL, TLI, DT, AC) {
661  }
662 
663  bool runGVN();
664 
665 private:
666  // Expression handling.
667  const Expression *createExpression(Instruction *) const;
668  const Expression *createBinaryExpression(unsigned, Type *, Value *, Value *,
669  Instruction *) const;
670 
671  // Our canonical form for phi arguments is a pair of incoming value, incoming
672  // basic block.
673  using ValPair = std::pair<Value *, BasicBlock *>;
674 
675  PHIExpression *createPHIExpression(ArrayRef<ValPair>, const Instruction *,
676  BasicBlock *, bool &HasBackEdge,
677  bool &OriginalOpsConstant) const;
678  const DeadExpression *createDeadExpression() const;
679  const VariableExpression *createVariableExpression(Value *) const;
680  const ConstantExpression *createConstantExpression(Constant *) const;
681  const Expression *createVariableOrConstant(Value *V) const;
682  const UnknownExpression *createUnknownExpression(Instruction *) const;
683  const StoreExpression *createStoreExpression(StoreInst *,
684  const MemoryAccess *) const;
685  LoadExpression *createLoadExpression(Type *, Value *, LoadInst *,
686  const MemoryAccess *) const;
687  const CallExpression *createCallExpression(CallInst *,
688  const MemoryAccess *) const;
690  createAggregateValueExpression(Instruction *) const;
691  bool setBasicExpressionInfo(Instruction *, BasicExpression *) const;
692 
693  // Congruence class handling.
694  CongruenceClass *createCongruenceClass(Value *Leader, const Expression *E) {
695  auto *result = new CongruenceClass(NextCongruenceNum++, Leader, E);
696  CongruenceClasses.emplace_back(result);
697  return result;
698  }
699 
700  CongruenceClass *createMemoryClass(MemoryAccess *MA) {
701  auto *CC = createCongruenceClass(nullptr, nullptr);
702  CC->setMemoryLeader(MA);
703  return CC;
704  }
705 
706  CongruenceClass *ensureLeaderOfMemoryClass(MemoryAccess *MA) {
707  auto *CC = getMemoryClass(MA);
708  if (CC->getMemoryLeader() != MA)
709  CC = createMemoryClass(MA);
710  return CC;
711  }
712 
713  CongruenceClass *createSingletonCongruenceClass(Value *Member) {
714  CongruenceClass *CClass = createCongruenceClass(Member, nullptr);
715  CClass->insert(Member);
716  ValueToClass[Member] = CClass;
717  return CClass;
718  }
719 
720  void initializeCongruenceClasses(Function &F);
721  const Expression *makePossiblePHIOfOps(Instruction *,
723  Value *findLeaderForInst(Instruction *ValueOp,
724  SmallPtrSetImpl<Value *> &Visited,
725  MemoryAccess *MemAccess, Instruction *OrigInst,
726  BasicBlock *PredBB);
727  bool OpIsSafeForPHIOfOpsHelper(Value *V, const BasicBlock *PHIBlock,
730  bool OpIsSafeForPHIOfOps(Value *Op, const BasicBlock *PHIBlock,
732  void addPhiOfOps(PHINode *Op, BasicBlock *BB, Instruction *ExistingValue);
733  void removePhiOfOps(Instruction *I, PHINode *PHITemp);
734 
735  // Value number an Instruction or MemoryPhi.
736  void valueNumberMemoryPhi(MemoryPhi *);
737  void valueNumberInstruction(Instruction *);
738 
739  // Symbolic evaluation.
740  const Expression *checkSimplificationResults(Expression *, Instruction *,
741  Value *) const;
742  const Expression *performSymbolicEvaluation(Value *,
743  SmallPtrSetImpl<Value *> &) const;
744  const Expression *performSymbolicLoadCoercion(Type *, Value *, LoadInst *,
745  Instruction *,
746  MemoryAccess *) const;
747  const Expression *performSymbolicLoadEvaluation(Instruction *) const;
748  const Expression *performSymbolicStoreEvaluation(Instruction *) const;
749  const Expression *performSymbolicCallEvaluation(Instruction *) const;
750  void sortPHIOps(MutableArrayRef<ValPair> Ops) const;
751  const Expression *performSymbolicPHIEvaluation(ArrayRef<ValPair>,
752  Instruction *I,
753  BasicBlock *PHIBlock) const;
754  const Expression *performSymbolicAggrValueEvaluation(Instruction *) const;
755  const Expression *performSymbolicCmpEvaluation(Instruction *) const;
756  const Expression *performSymbolicPredicateInfoEvaluation(Instruction *) const;
757 
758  // Congruence finding.
759  bool someEquivalentDominates(const Instruction *, const Instruction *) const;
760  Value *lookupOperandLeader(Value *) const;
761  CongruenceClass *getClassForExpression(const Expression *E) const;
762  void performCongruenceFinding(Instruction *, const Expression *);
763  void moveValueToNewCongruenceClass(Instruction *, const Expression *,
764  CongruenceClass *, CongruenceClass *);
765  void moveMemoryToNewCongruenceClass(Instruction *, MemoryAccess *,
766  CongruenceClass *, CongruenceClass *);
767  Value *getNextValueLeader(CongruenceClass *) const;
768  const MemoryAccess *getNextMemoryLeader(CongruenceClass *) const;
769  bool setMemoryClass(const MemoryAccess *From, CongruenceClass *To);
770  CongruenceClass *getMemoryClass(const MemoryAccess *MA) const;
771  const MemoryAccess *lookupMemoryLeader(const MemoryAccess *) const;
772  bool isMemoryAccessTOP(const MemoryAccess *) const;
773 
774  // Ranking
775  unsigned int getRank(const Value *) const;
776  bool shouldSwapOperands(const Value *, const Value *) const;
777 
778  // Reachability handling.
779  void updateReachableEdge(BasicBlock *, BasicBlock *);
780  void processOutgoingEdges(TerminatorInst *, BasicBlock *);
781  Value *findConditionEquivalence(Value *) const;
782 
783  // Elimination.
784  struct ValueDFS;
785  void convertClassToDFSOrdered(const CongruenceClass &,
789  void convertClassToLoadsAndStores(const CongruenceClass &,
790  SmallVectorImpl<ValueDFS> &) const;
791 
792  bool eliminateInstructions(Function &);
793  void replaceInstruction(Instruction *, Value *);
794  void markInstructionForDeletion(Instruction *);
795  void deleteInstructionsInBlock(BasicBlock *);
796  Value *findPHIOfOpsLeader(const Expression *, const Instruction *,
797  const BasicBlock *) const;
798 
799  // New instruction creation.
800  void handleNewInstruction(Instruction *) {}
801 
802  // Various instruction touch utilities
803  template <typename Map, typename KeyType, typename Func>
804  void for_each_found(Map &, const KeyType &, Func);
805  template <typename Map, typename KeyType>
806  void touchAndErase(Map &, const KeyType &);
807  void markUsersTouched(Value *);
808  void markMemoryUsersTouched(const MemoryAccess *);
809  void markMemoryDefTouched(const MemoryAccess *);
810  void markPredicateUsersTouched(Instruction *);
811  void markValueLeaderChangeTouched(CongruenceClass *CC);
812  void markMemoryLeaderChangeTouched(CongruenceClass *CC);
813  void markPhiOfOpsChanged(const Expression *E);
814  void addPredicateUsers(const PredicateBase *, Instruction *) const;
815  void addMemoryUsers(const MemoryAccess *To, MemoryAccess *U) const;
816  void addAdditionalUsers(Value *To, Value *User) const;
817 
818  // Main loop of value numbering
819  void iterateTouchedInstructions();
820 
821  // Utilities.
822  void cleanupTables();
823  std::pair<unsigned, unsigned> assignDFSNumbers(BasicBlock *, unsigned);
824  void updateProcessedCount(const Value *V);
825  void verifyMemoryCongruency() const;
826  void verifyIterationSettled(Function &F);
827  void verifyStoreExpressions() const;
828  bool singleReachablePHIPath(SmallPtrSet<const MemoryAccess *, 8> &,
829  const MemoryAccess *, const MemoryAccess *) const;
830  BasicBlock *getBlockForValue(Value *V) const;
831  void deleteExpression(const Expression *E) const;
832  MemoryUseOrDef *getMemoryAccess(const Instruction *) const;
833  MemoryAccess *getDefiningAccess(const MemoryAccess *) const;
834  MemoryPhi *getMemoryAccess(const BasicBlock *) const;
835  template <class T, class Range> T *getMinDFSOfRange(const Range &) const;
836 
837  unsigned InstrToDFSNum(const Value *V) const {
838  assert(isa<Instruction>(V) && "This should not be used for MemoryAccesses");
839  return InstrDFS.lookup(V);
840  }
841 
842  unsigned InstrToDFSNum(const MemoryAccess *MA) const {
843  return MemoryToDFSNum(MA);
844  }
845 
846  Value *InstrFromDFSNum(unsigned DFSNum) { return DFSToInstr[DFSNum]; }
847 
848  // Given a MemoryAccess, return the relevant instruction DFS number. Note:
849  // This deliberately takes a value so it can be used with Use's, which will
850  // auto-convert to Value's but not to MemoryAccess's.
851  unsigned MemoryToDFSNum(const Value *MA) const {
852  assert(isa<MemoryAccess>(MA) &&
853  "This should not be used with instructions");
854  return isa<MemoryUseOrDef>(MA)
855  ? InstrToDFSNum(cast<MemoryUseOrDef>(MA)->getMemoryInst())
856  : InstrDFS.lookup(MA);
857  }
858 
859  bool isCycleFree(const Instruction *) const;
860  bool isBackedge(BasicBlock *From, BasicBlock *To) const;
861 
862  // Debug counter info. When verifying, we have to reset the value numbering
863  // debug counter to the same state it started in to get the same results.
864  std::pair<int, int> StartingVNCounter;
865 };
866 
867 } // end anonymous namespace
868 
869 template <typename T>
870 static bool equalsLoadStoreHelper(const T &LHS, const Expression &RHS) {
871  if (!isa<LoadExpression>(RHS) && !isa<StoreExpression>(RHS))
872  return false;
873  return LHS.MemoryExpression::equals(RHS);
874 }
875 
876 bool LoadExpression::equals(const Expression &Other) const {
877  return equalsLoadStoreHelper(*this, Other);
878 }
879 
880 bool StoreExpression::equals(const Expression &Other) const {
881  if (!equalsLoadStoreHelper(*this, Other))
882  return false;
883  // Make sure that store vs store includes the value operand.
884  if (const auto *S = dyn_cast<StoreExpression>(&Other))
885  if (getStoredValue() != S->getStoredValue())
886  return false;
887  return true;
888 }
889 
890 // Determine if the edge From->To is a backedge
891 bool NewGVN::isBackedge(BasicBlock *From, BasicBlock *To) const {
892  return From == To ||
893  RPOOrdering.lookup(DT->getNode(From)) >=
894  RPOOrdering.lookup(DT->getNode(To));
895 }
896 
897 #ifndef NDEBUG
898 static std::string getBlockName(const BasicBlock *B) {
900 }
901 #endif
902 
903 // Get a MemoryAccess for an instruction, fake or real.
904 MemoryUseOrDef *NewGVN::getMemoryAccess(const Instruction *I) const {
905  auto *Result = MSSA->getMemoryAccess(I);
906  return Result ? Result : TempToMemory.lookup(I);
907 }
908 
909 // Get a MemoryPhi for a basic block. These are all real.
910 MemoryPhi *NewGVN::getMemoryAccess(const BasicBlock *BB) const {
911  return MSSA->getMemoryAccess(BB);
912 }
913 
914 // Get the basic block from an instruction/memory value.
915 BasicBlock *NewGVN::getBlockForValue(Value *V) const {
916  if (auto *I = dyn_cast<Instruction>(V)) {
917  auto *Parent = I->getParent();
918  if (Parent)
919  return Parent;
920  Parent = TempToBlock.lookup(V);
921  assert(Parent && "Every fake instruction should have a block");
922  return Parent;
923  }
924 
925  auto *MP = dyn_cast<MemoryPhi>(V);
926  assert(MP && "Should have been an instruction or a MemoryPhi");
927  return MP->getBlock();
928 }
929 
930 // Delete a definitely dead expression, so it can be reused by the expression
931 // allocator. Some of these are not in creation functions, so we have to accept
932 // const versions.
933 void NewGVN::deleteExpression(const Expression *E) const {
934  assert(isa<BasicExpression>(E));
935  auto *BE = cast<BasicExpression>(E);
936  const_cast<BasicExpression *>(BE)->deallocateOperands(ArgRecycler);
937  ExpressionAllocator.Deallocate(E);
938 }
939 
940 // If V is a predicateinfo copy, get the thing it is a copy of.
941 static Value *getCopyOf(const Value *V) {
942  if (auto *II = dyn_cast<IntrinsicInst>(V))
943  if (II->getIntrinsicID() == Intrinsic::ssa_copy)
944  return II->getOperand(0);
945  return nullptr;
946 }
947 
948 // Return true if V is really PN, even accounting for predicateinfo copies.
949 static bool isCopyOfPHI(const Value *V, const PHINode *PN) {
950  return V == PN || getCopyOf(V) == PN;
951 }
952 
953 static bool isCopyOfAPHI(const Value *V) {
954  auto *CO = getCopyOf(V);
955  return CO && isa<PHINode>(CO);
956 }
957 
958 // Sort PHI Operands into a canonical order. What we use here is an RPO
959 // order. The BlockInstRange numbers are generated in an RPO walk of the basic
960 // blocks.
961 void NewGVN::sortPHIOps(MutableArrayRef<ValPair> Ops) const {
962  llvm::sort(Ops.begin(), Ops.end(),
963  [&](const ValPair &P1, const ValPair &P2) {
964  return BlockInstRange.lookup(P1.second).first <
965  BlockInstRange.lookup(P2.second).first;
966  });
967 }
968 
969 // Return true if V is a value that will always be available (IE can
970 // be placed anywhere) in the function. We don't do globals here
971 // because they are often worse to put in place.
972 static bool alwaysAvailable(Value *V) {
973  return isa<Constant>(V) || isa<Argument>(V);
974 }
975 
976 // Create a PHIExpression from an array of {incoming edge, value} pairs. I is
977 // the original instruction we are creating a PHIExpression for (but may not be
978 // a phi node). We require, as an invariant, that all the PHIOperands in the
979 // same block are sorted the same way. sortPHIOps will sort them into a
980 // canonical order.
981 PHIExpression *NewGVN::createPHIExpression(ArrayRef<ValPair> PHIOperands,
982  const Instruction *I,
983  BasicBlock *PHIBlock,
984  bool &HasBackedge,
985  bool &OriginalOpsConstant) const {
986  unsigned NumOps = PHIOperands.size();
987  auto *E = new (ExpressionAllocator) PHIExpression(NumOps, PHIBlock);
988 
989  E->allocateOperands(ArgRecycler, ExpressionAllocator);
990  E->setType(PHIOperands.begin()->first->getType());
991  E->setOpcode(Instruction::PHI);
992 
993  // Filter out unreachable phi operands.
994  auto Filtered = make_filter_range(PHIOperands, [&](const ValPair &P) {
995  auto *BB = P.second;
996  if (auto *PHIOp = dyn_cast<PHINode>(I))
997  if (isCopyOfPHI(P.first, PHIOp))
998  return false;
999  if (!ReachableEdges.count({BB, PHIBlock}))
1000  return false;
1001  // Things in TOPClass are equivalent to everything.
1002  if (ValueToClass.lookup(P.first) == TOPClass)
1003  return false;
1004  OriginalOpsConstant = OriginalOpsConstant && isa<Constant>(P.first);
1005  HasBackedge = HasBackedge || isBackedge(BB, PHIBlock);
1006  return lookupOperandLeader(P.first) != I;
1007  });
1008  std::transform(Filtered.begin(), Filtered.end(), op_inserter(E),
1009  [&](const ValPair &P) -> Value * {
1010  return lookupOperandLeader(P.first);
1011  });
1012  return E;
1013 }
1014 
1015 // Set basic expression info (Arguments, type, opcode) for Expression
1016 // E from Instruction I in block B.
1017 bool NewGVN::setBasicExpressionInfo(Instruction *I, BasicExpression *E) const {
1018  bool AllConstant = true;
1019  if (auto *GEP = dyn_cast<GetElementPtrInst>(I))
1020  E->setType(GEP->getSourceElementType());
1021  else
1022  E->setType(I->getType());
1023  E->setOpcode(I->getOpcode());
1024  E->allocateOperands(ArgRecycler, ExpressionAllocator);
1025 
1026  // Transform the operand array into an operand leader array, and keep track of
1027  // whether all members are constant.
1028  std::transform(I->op_begin(), I->op_end(), op_inserter(E), [&](Value *O) {
1029  auto Operand = lookupOperandLeader(O);
1030  AllConstant = AllConstant && isa<Constant>(Operand);
1031  return Operand;
1032  });
1033 
1034  return AllConstant;
1035 }
1036 
1037 const Expression *NewGVN::createBinaryExpression(unsigned Opcode, Type *T,
1038  Value *Arg1, Value *Arg2,
1039  Instruction *I) const {
1040  auto *E = new (ExpressionAllocator) BasicExpression(2);
1041 
1042  E->setType(T);
1043  E->setOpcode(Opcode);
1044  E->allocateOperands(ArgRecycler, ExpressionAllocator);
1045  if (Instruction::isCommutative(Opcode)) {
1046  // Ensure that commutative instructions that only differ by a permutation
1047  // of their operands get the same value number by sorting the operand value
1048  // numbers. Since all commutative instructions have two operands it is more
1049  // efficient to sort by hand rather than using, say, std::sort.
1050  if (shouldSwapOperands(Arg1, Arg2))
1051  std::swap(Arg1, Arg2);
1052  }
1053  E->op_push_back(lookupOperandLeader(Arg1));
1054  E->op_push_back(lookupOperandLeader(Arg2));
1055 
1056  Value *V = SimplifyBinOp(Opcode, E->getOperand(0), E->getOperand(1), SQ);
1057  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1058  return SimplifiedE;
1059  return E;
1060 }
1061 
1062 // Take a Value returned by simplification of Expression E/Instruction
1063 // I, and see if it resulted in a simpler expression. If so, return
1064 // that expression.
1065 const Expression *NewGVN::checkSimplificationResults(Expression *E,
1066  Instruction *I,
1067  Value *V) const {
1068  if (!V)
1069  return nullptr;
1070  if (auto *C = dyn_cast<Constant>(V)) {
1071  if (I)
1072  LLVM_DEBUG(dbgs() << "Simplified " << *I << " to "
1073  << " constant " << *C << "\n");
1074  NumGVNOpsSimplified++;
1075  assert(isa<BasicExpression>(E) &&
1076  "We should always have had a basic expression here");
1077  deleteExpression(E);
1078  return createConstantExpression(C);
1079  } else if (isa<Argument>(V) || isa<GlobalVariable>(V)) {
1080  if (I)
1081  LLVM_DEBUG(dbgs() << "Simplified " << *I << " to "
1082  << " variable " << *V << "\n");
1083  deleteExpression(E);
1084  return createVariableExpression(V);
1085  }
1086 
1087  CongruenceClass *CC = ValueToClass.lookup(V);
1088  if (CC) {
1089  if (CC->getLeader() && CC->getLeader() != I) {
1090  // Don't add temporary instructions to the user lists.
1091  if (!AllTempInstructions.count(I))
1092  addAdditionalUsers(V, I);
1093  return createVariableOrConstant(CC->getLeader());
1094  }
1095  if (CC->getDefiningExpr()) {
1096  // If we simplified to something else, we need to communicate
1097  // that we're users of the value we simplified to.
1098  if (I != V) {
1099  // Don't add temporary instructions to the user lists.
1100  if (!AllTempInstructions.count(I))
1101  addAdditionalUsers(V, I);
1102  }
1103 
1104  if (I)
1105  LLVM_DEBUG(dbgs() << "Simplified " << *I << " to "
1106  << " expression " << *CC->getDefiningExpr() << "\n");
1107  NumGVNOpsSimplified++;
1108  deleteExpression(E);
1109  return CC->getDefiningExpr();
1110  }
1111  }
1112 
1113  return nullptr;
1114 }
1115 
1116 // Create a value expression from the instruction I, replacing operands with
1117 // their leaders.
1118 
1119 const Expression *NewGVN::createExpression(Instruction *I) const {
1120  auto *E = new (ExpressionAllocator) BasicExpression(I->getNumOperands());
1121 
1122  bool AllConstant = setBasicExpressionInfo(I, E);
1123 
1124  if (I->isCommutative()) {
1125  // Ensure that commutative instructions that only differ by a permutation
1126  // of their operands get the same value number by sorting the operand value
1127  // numbers. Since all commutative instructions have two operands it is more
1128  // efficient to sort by hand rather than using, say, std::sort.
1129  assert(I->getNumOperands() == 2 && "Unsupported commutative instruction!");
1130  if (shouldSwapOperands(E->getOperand(0), E->getOperand(1)))
1131  E->swapOperands(0, 1);
1132  }
1133  // Perform simplification.
1134  if (auto *CI = dyn_cast<CmpInst>(I)) {
1135  // Sort the operand value numbers so x<y and y>x get the same value
1136  // number.
1137  CmpInst::Predicate Predicate = CI->getPredicate();
1138  if (shouldSwapOperands(E->getOperand(0), E->getOperand(1))) {
1139  E->swapOperands(0, 1);
1140  Predicate = CmpInst::getSwappedPredicate(Predicate);
1141  }
1142  E->setOpcode((CI->getOpcode() << 8) | Predicate);
1143  // TODO: 25% of our time is spent in SimplifyCmpInst with pointer operands
1144  assert(I->getOperand(0)->getType() == I->getOperand(1)->getType() &&
1145  "Wrong types on cmp instruction");
1146  assert((E->getOperand(0)->getType() == I->getOperand(0)->getType() &&
1147  E->getOperand(1)->getType() == I->getOperand(1)->getType()));
1148  Value *V =
1149  SimplifyCmpInst(Predicate, E->getOperand(0), E->getOperand(1), SQ);
1150  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1151  return SimplifiedE;
1152  } else if (isa<SelectInst>(I)) {
1153  if (isa<Constant>(E->getOperand(0)) ||
1154  E->getOperand(1) == E->getOperand(2)) {
1155  assert(E->getOperand(1)->getType() == I->getOperand(1)->getType() &&
1156  E->getOperand(2)->getType() == I->getOperand(2)->getType());
1157  Value *V = SimplifySelectInst(E->getOperand(0), E->getOperand(1),
1158  E->getOperand(2), SQ);
1159  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1160  return SimplifiedE;
1161  }
1162  } else if (I->isBinaryOp()) {
1163  Value *V =
1164  SimplifyBinOp(E->getOpcode(), E->getOperand(0), E->getOperand(1), SQ);
1165  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1166  return SimplifiedE;
1167  } else if (auto *BI = dyn_cast<BitCastInst>(I)) {
1168  Value *V =
1169  SimplifyCastInst(BI->getOpcode(), BI->getOperand(0), BI->getType(), SQ);
1170  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1171  return SimplifiedE;
1172  } else if (isa<GetElementPtrInst>(I)) {
1173  Value *V = SimplifyGEPInst(
1174  E->getType(), ArrayRef<Value *>(E->op_begin(), E->op_end()), SQ);
1175  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1176  return SimplifiedE;
1177  } else if (AllConstant) {
1178  // We don't bother trying to simplify unless all of the operands
1179  // were constant.
1180  // TODO: There are a lot of Simplify*'s we could call here, if we
1181  // wanted to. The original motivating case for this code was a
1182  // zext i1 false to i8, which we don't have an interface to
1183  // simplify (IE there is no SimplifyZExt).
1184 
1186  for (Value *Arg : E->operands())
1187  C.emplace_back(cast<Constant>(Arg));
1188 
1189  if (Value *V = ConstantFoldInstOperands(I, C, DL, TLI))
1190  if (const Expression *SimplifiedE = checkSimplificationResults(E, I, V))
1191  return SimplifiedE;
1192  }
1193  return E;
1194 }
1195 
1197 NewGVN::createAggregateValueExpression(Instruction *I) const {
1198  if (auto *II = dyn_cast<InsertValueInst>(I)) {
1199  auto *E = new (ExpressionAllocator)
1200  AggregateValueExpression(I->getNumOperands(), II->getNumIndices());
1201  setBasicExpressionInfo(I, E);
1202  E->allocateIntOperands(ExpressionAllocator);
1203  std::copy(II->idx_begin(), II->idx_end(), int_op_inserter(E));
1204  return E;
1205  } else if (auto *EI = dyn_cast<ExtractValueInst>(I)) {
1206  auto *E = new (ExpressionAllocator)
1207  AggregateValueExpression(I->getNumOperands(), EI->getNumIndices());
1208  setBasicExpressionInfo(EI, E);
1209  E->allocateIntOperands(ExpressionAllocator);
1210  std::copy(EI->idx_begin(), EI->idx_end(), int_op_inserter(E));
1211  return E;
1212  }
1213  llvm_unreachable("Unhandled type of aggregate value operation");
1214 }
1215 
1216 const DeadExpression *NewGVN::createDeadExpression() const {
1217  // DeadExpression has no arguments and all DeadExpression's are the same,
1218  // so we only need one of them.
1219  return SingletonDeadExpression;
1220 }
1221 
1222 const VariableExpression *NewGVN::createVariableExpression(Value *V) const {
1223  auto *E = new (ExpressionAllocator) VariableExpression(V);
1224  E->setOpcode(V->getValueID());
1225  return E;
1226 }
1227 
1228 const Expression *NewGVN::createVariableOrConstant(Value *V) const {
1229  if (auto *C = dyn_cast<Constant>(V))
1230  return createConstantExpression(C);
1231  return createVariableExpression(V);
1232 }
1233 
1234 const ConstantExpression *NewGVN::createConstantExpression(Constant *C) const {
1235  auto *E = new (ExpressionAllocator) ConstantExpression(C);
1236  E->setOpcode(C->getValueID());
1237  return E;
1238 }
1239 
1240 const UnknownExpression *NewGVN::createUnknownExpression(Instruction *I) const {
1241  auto *E = new (ExpressionAllocator) UnknownExpression(I);
1242  E->setOpcode(I->getOpcode());
1243  return E;
1244 }
1245 
1246 const CallExpression *
1247 NewGVN::createCallExpression(CallInst *CI, const MemoryAccess *MA) const {
1248  // FIXME: Add operand bundles for calls.
1249  auto *E =
1250  new (ExpressionAllocator) CallExpression(CI->getNumOperands(), CI, MA);
1251  setBasicExpressionInfo(CI, E);
1252  return E;
1253 }
1254 
1255 // Return true if some equivalent of instruction Inst dominates instruction U.
1256 bool NewGVN::someEquivalentDominates(const Instruction *Inst,
1257  const Instruction *U) const {
1258  auto *CC = ValueToClass.lookup(Inst);
1259  // This must be an instruction because we are only called from phi nodes
1260  // in the case that the value it needs to check against is an instruction.
1261 
1262  // The most likely candidates for dominance are the leader and the next leader.
1263  // The leader or nextleader will dominate in all cases where there is an
1264  // equivalent that is higher up in the dom tree.
1265  // We can't *only* check them, however, because the
1266  // dominator tree could have an infinite number of non-dominating siblings
1267  // with instructions that are in the right congruence class.
1268  // A
1269  // B C D E F G
1270  // |
1271  // H
1272  // Instruction U could be in H, with equivalents in every other sibling.
1273  // Depending on the rpo order picked, the leader could be the equivalent in
1274  // any of these siblings.
1275  if (!CC)
1276  return false;
1277  if (alwaysAvailable(CC->getLeader()))
1278  return true;
1279  if (DT->dominates(cast<Instruction>(CC->getLeader()), U))
1280  return true;
1281  if (CC->getNextLeader().first &&
1282  DT->dominates(cast<Instruction>(CC->getNextLeader().first), U))
1283  return true;
1284  return llvm::any_of(*CC, [&](const Value *Member) {
1285  return Member != CC->getLeader() &&
1286  DT->dominates(cast<Instruction>(Member), U);
1287  });
1288 }
1289 
1290 // See if we have a congruence class and leader for this operand, and if so,
1291 // return it. Otherwise, return the operand itself.
1292 Value *NewGVN::lookupOperandLeader(Value *V) const {
1293  CongruenceClass *CC = ValueToClass.lookup(V);
1294  if (CC) {
1295  // Everything in TOP is represented by undef, as it can be any value.
1296  // We do have to make sure we get the type right though, so we can't set the
1297  // RepLeader to undef.
1298  if (CC == TOPClass)
1299  return UndefValue::get(V->getType());
1300  return CC->getStoredValue() ? CC->getStoredValue() : CC->getLeader();
1301  }
1302 
1303  return V;
1304 }
1305 
1306 const MemoryAccess *NewGVN::lookupMemoryLeader(const MemoryAccess *MA) const {
1307  auto *CC = getMemoryClass(MA);
1308  assert(CC->getMemoryLeader() &&
1309  "Every MemoryAccess should be mapped to a congruence class with a "
1310  "representative memory access");
1311  return CC->getMemoryLeader();
1312 }
1313 
1314 // Return true if the MemoryAccess is really equivalent to everything. This is
1315 // equivalent to the lattice value "TOP" in most lattices. This is the initial
1316 // state of all MemoryAccesses.
1317 bool NewGVN::isMemoryAccessTOP(const MemoryAccess *MA) const {
1318  return getMemoryClass(MA) == TOPClass;
1319 }
1320 
1321 LoadExpression *NewGVN::createLoadExpression(Type *LoadType, Value *PointerOp,
1322  LoadInst *LI,
1323  const MemoryAccess *MA) const {
1324  auto *E =
1325  new (ExpressionAllocator) LoadExpression(1, LI, lookupMemoryLeader(MA));
1326  E->allocateOperands(ArgRecycler, ExpressionAllocator);
1327  E->setType(LoadType);
1328 
1329  // Give store and loads same opcode so they value number together.
1330  E->setOpcode(0);
1331  E->op_push_back(PointerOp);
1332  if (LI)
1333  E->setAlignment(LI->getAlignment());
1334 
1335  // TODO: Value number heap versions. We may be able to discover
1336  // things alias analysis can't on it's own (IE that a store and a
1337  // load have the same value, and thus, it isn't clobbering the load).
1338  return E;
1339 }
1340 
1341 const StoreExpression *
1342 NewGVN::createStoreExpression(StoreInst *SI, const MemoryAccess *MA) const {
1343  auto *StoredValueLeader = lookupOperandLeader(SI->getValueOperand());
1344  auto *E = new (ExpressionAllocator)
1345  StoreExpression(SI->getNumOperands(), SI, StoredValueLeader, MA);
1346  E->allocateOperands(ArgRecycler, ExpressionAllocator);
1347  E->setType(SI->getValueOperand()->getType());
1348 
1349  // Give store and loads same opcode so they value number together.
1350  E->setOpcode(0);
1351  E->op_push_back(lookupOperandLeader(SI->getPointerOperand()));
1352 
1353  // TODO: Value number heap versions. We may be able to discover
1354  // things alias analysis can't on it's own (IE that a store and a
1355  // load have the same value, and thus, it isn't clobbering the load).
1356  return E;
1357 }
1358 
1359 const Expression *NewGVN::performSymbolicStoreEvaluation(Instruction *I) const {
1360  // Unlike loads, we never try to eliminate stores, so we do not check if they
1361  // are simple and avoid value numbering them.
1362  auto *SI = cast<StoreInst>(I);
1363  auto *StoreAccess = getMemoryAccess(SI);
1364  // Get the expression, if any, for the RHS of the MemoryDef.
1365  const MemoryAccess *StoreRHS = StoreAccess->getDefiningAccess();
1367  StoreRHS = MSSAWalker->getClobberingMemoryAccess(StoreAccess);
1368  // If we bypassed the use-def chains, make sure we add a use.
1369  StoreRHS = lookupMemoryLeader(StoreRHS);
1370  if (StoreRHS != StoreAccess->getDefiningAccess())
1371  addMemoryUsers(StoreRHS, StoreAccess);
1372  // If we are defined by ourselves, use the live on entry def.
1373  if (StoreRHS == StoreAccess)
1374  StoreRHS = MSSA->getLiveOnEntryDef();
1375 
1376  if (SI->isSimple()) {
1377  // See if we are defined by a previous store expression, it already has a
1378  // value, and it's the same value as our current store. FIXME: Right now, we
1379  // only do this for simple stores, we should expand to cover memcpys, etc.
1380  const auto *LastStore = createStoreExpression(SI, StoreRHS);
1381  const auto *LastCC = ExpressionToClass.lookup(LastStore);
1382  // We really want to check whether the expression we matched was a store. No
1383  // easy way to do that. However, we can check that the class we found has a
1384  // store, which, assuming the value numbering state is not corrupt, is
1385  // sufficient, because we must also be equivalent to that store's expression
1386  // for it to be in the same class as the load.
1387  if (LastCC && LastCC->getStoredValue() == LastStore->getStoredValue())
1388  return LastStore;
1389  // Also check if our value operand is defined by a load of the same memory
1390  // location, and the memory state is the same as it was then (otherwise, it
1391  // could have been overwritten later. See test32 in
1392  // transforms/DeadStoreElimination/simple.ll).
1393  if (auto *LI = dyn_cast<LoadInst>(LastStore->getStoredValue()))
1394  if ((lookupOperandLeader(LI->getPointerOperand()) ==
1395  LastStore->getOperand(0)) &&
1396  (lookupMemoryLeader(getMemoryAccess(LI)->getDefiningAccess()) ==
1397  StoreRHS))
1398  return LastStore;
1399  deleteExpression(LastStore);
1400  }
1401 
1402  // If the store is not equivalent to anything, value number it as a store that
1403  // produces a unique memory state (instead of using it's MemoryUse, we use
1404  // it's MemoryDef).
1405  return createStoreExpression(SI, StoreAccess);
1406 }
1407 
1408 // See if we can extract the value of a loaded pointer from a load, a store, or
1409 // a memory instruction.
1410 const Expression *
1411 NewGVN::performSymbolicLoadCoercion(Type *LoadType, Value *LoadPtr,
1412  LoadInst *LI, Instruction *DepInst,
1413  MemoryAccess *DefiningAccess) const {
1414  assert((!LI || LI->isSimple()) && "Not a simple load");
1415  if (auto *DepSI = dyn_cast<StoreInst>(DepInst)) {
1416  // Can't forward from non-atomic to atomic without violating memory model.
1417  // Also don't need to coerce if they are the same type, we will just
1418  // propagate.
1419  if (LI->isAtomic() > DepSI->isAtomic() ||
1420  LoadType == DepSI->getValueOperand()->getType())
1421  return nullptr;
1422  int Offset = analyzeLoadFromClobberingStore(LoadType, LoadPtr, DepSI, DL);
1423  if (Offset >= 0) {
1424  if (auto *C = dyn_cast<Constant>(
1425  lookupOperandLeader(DepSI->getValueOperand()))) {
1426  LLVM_DEBUG(dbgs() << "Coercing load from store " << *DepSI
1427  << " to constant " << *C << "\n");
1428  return createConstantExpression(
1429  getConstantStoreValueForLoad(C, Offset, LoadType, DL));
1430  }
1431  }
1432  } else if (auto *DepLI = dyn_cast<LoadInst>(DepInst)) {
1433  // Can't forward from non-atomic to atomic without violating memory model.
1434  if (LI->isAtomic() > DepLI->isAtomic())
1435  return nullptr;
1436  int Offset = analyzeLoadFromClobberingLoad(LoadType, LoadPtr, DepLI, DL);
1437  if (Offset >= 0) {
1438  // We can coerce a constant load into a load.
1439  if (auto *C = dyn_cast<Constant>(lookupOperandLeader(DepLI)))
1440  if (auto *PossibleConstant =
1441  getConstantLoadValueForLoad(C, Offset, LoadType, DL)) {
1442  LLVM_DEBUG(dbgs() << "Coercing load from load " << *LI
1443  << " to constant " << *PossibleConstant << "\n");
1444  return createConstantExpression(PossibleConstant);
1445  }
1446  }
1447  } else if (auto *DepMI = dyn_cast<MemIntrinsic>(DepInst)) {
1448  int Offset = analyzeLoadFromClobberingMemInst(LoadType, LoadPtr, DepMI, DL);
1449  if (Offset >= 0) {
1450  if (auto *PossibleConstant =
1451  getConstantMemInstValueForLoad(DepMI, Offset, LoadType, DL)) {
1452  LLVM_DEBUG(dbgs() << "Coercing load from meminst " << *DepMI
1453  << " to constant " << *PossibleConstant << "\n");
1454  return createConstantExpression(PossibleConstant);
1455  }
1456  }
1457  }
1458 
1459  // All of the below are only true if the loaded pointer is produced
1460  // by the dependent instruction.
1461  if (LoadPtr != lookupOperandLeader(DepInst) &&
1462  !AA->isMustAlias(LoadPtr, DepInst))
1463  return nullptr;
1464  // If this load really doesn't depend on anything, then we must be loading an
1465  // undef value. This can happen when loading for a fresh allocation with no
1466  // intervening stores, for example. Note that this is only true in the case
1467  // that the result of the allocation is pointer equal to the load ptr.
1468  if (isa<AllocaInst>(DepInst) || isMallocLikeFn(DepInst, TLI)) {
1469  return createConstantExpression(UndefValue::get(LoadType));
1470  }
1471  // If this load occurs either right after a lifetime begin,
1472  // then the loaded value is undefined.
1473  else if (auto *II = dyn_cast<IntrinsicInst>(DepInst)) {
1474  if (II->getIntrinsicID() == Intrinsic::lifetime_start)
1475  return createConstantExpression(UndefValue::get(LoadType));
1476  }
1477  // If this load follows a calloc (which zero initializes memory),
1478  // then the loaded value is zero
1479  else if (isCallocLikeFn(DepInst, TLI)) {
1480  return createConstantExpression(Constant::getNullValue(LoadType));
1481  }
1482 
1483  return nullptr;
1484 }
1485 
1486 const Expression *NewGVN::performSymbolicLoadEvaluation(Instruction *I) const {
1487  auto *LI = cast<LoadInst>(I);
1488 
1489  // We can eliminate in favor of non-simple loads, but we won't be able to
1490  // eliminate the loads themselves.
1491  if (!LI->isSimple())
1492  return nullptr;
1493 
1494  Value *LoadAddressLeader = lookupOperandLeader(LI->getPointerOperand());
1495  // Load of undef is undef.
1496  if (isa<UndefValue>(LoadAddressLeader))
1497  return createConstantExpression(UndefValue::get(LI->getType()));
1498  MemoryAccess *OriginalAccess = getMemoryAccess(I);
1499  MemoryAccess *DefiningAccess =
1500  MSSAWalker->getClobberingMemoryAccess(OriginalAccess);
1501 
1502  if (!MSSA->isLiveOnEntryDef(DefiningAccess)) {
1503  if (auto *MD = dyn_cast<MemoryDef>(DefiningAccess)) {
1504  Instruction *DefiningInst = MD->getMemoryInst();
1505  // If the defining instruction is not reachable, replace with undef.
1506  if (!ReachableBlocks.count(DefiningInst->getParent()))
1507  return createConstantExpression(UndefValue::get(LI->getType()));
1508  // This will handle stores and memory insts. We only do if it the
1509  // defining access has a different type, or it is a pointer produced by
1510  // certain memory operations that cause the memory to have a fixed value
1511  // (IE things like calloc).
1512  if (const auto *CoercionResult =
1513  performSymbolicLoadCoercion(LI->getType(), LoadAddressLeader, LI,
1514  DefiningInst, DefiningAccess))
1515  return CoercionResult;
1516  }
1517  }
1518 
1519  const auto *LE = createLoadExpression(LI->getType(), LoadAddressLeader, LI,
1520  DefiningAccess);
1521  // If our MemoryLeader is not our defining access, add a use to the
1522  // MemoryLeader, so that we get reprocessed when it changes.
1523  if (LE->getMemoryLeader() != DefiningAccess)
1524  addMemoryUsers(LE->getMemoryLeader(), OriginalAccess);
1525  return LE;
1526 }
1527 
1528 const Expression *
1529 NewGVN::performSymbolicPredicateInfoEvaluation(Instruction *I) const {
1530  auto *PI = PredInfo->getPredicateInfoFor(I);
1531  if (!PI)
1532  return nullptr;
1533 
1534  LLVM_DEBUG(dbgs() << "Found predicate info from instruction !\n");
1535 
1536  auto *PWC = dyn_cast<PredicateWithCondition>(PI);
1537  if (!PWC)
1538  return nullptr;
1539 
1540  auto *CopyOf = I->getOperand(0);
1541  auto *Cond = PWC->Condition;
1542 
1543  // If this a copy of the condition, it must be either true or false depending
1544  // on the predicate info type and edge.
1545  if (CopyOf == Cond) {
1546  // We should not need to add predicate users because the predicate info is
1547  // already a use of this operand.
1548  if (isa<PredicateAssume>(PI))
1549  return createConstantExpression(ConstantInt::getTrue(Cond->getType()));
1550  if (auto *PBranch = dyn_cast<PredicateBranch>(PI)) {
1551  if (PBranch->TrueEdge)
1552  return createConstantExpression(ConstantInt::getTrue(Cond->getType()));
1553  return createConstantExpression(ConstantInt::getFalse(Cond->getType()));
1554  }
1555  if (auto *PSwitch = dyn_cast<PredicateSwitch>(PI))
1556  return createConstantExpression(cast<Constant>(PSwitch->CaseValue));
1557  }
1558 
1559  // Not a copy of the condition, so see what the predicates tell us about this
1560  // value. First, though, we check to make sure the value is actually a copy
1561  // of one of the condition operands. It's possible, in certain cases, for it
1562  // to be a copy of a predicateinfo copy. In particular, if two branch
1563  // operations use the same condition, and one branch dominates the other, we
1564  // will end up with a copy of a copy. This is currently a small deficiency in
1565  // predicateinfo. What will end up happening here is that we will value
1566  // number both copies the same anyway.
1567 
1568  // Everything below relies on the condition being a comparison.
1569  auto *Cmp = dyn_cast<CmpInst>(Cond);
1570  if (!Cmp)
1571  return nullptr;
1572 
1573  if (CopyOf != Cmp->getOperand(0) && CopyOf != Cmp->getOperand(1)) {
1574  LLVM_DEBUG(dbgs() << "Copy is not of any condition operands!\n");
1575  return nullptr;
1576  }
1577  Value *FirstOp = lookupOperandLeader(Cmp->getOperand(0));
1578  Value *SecondOp = lookupOperandLeader(Cmp->getOperand(1));
1579  bool SwappedOps = false;
1580  // Sort the ops.
1581  if (shouldSwapOperands(FirstOp, SecondOp)) {
1582  std::swap(FirstOp, SecondOp);
1583  SwappedOps = true;
1584  }
1586  SwappedOps ? Cmp->getSwappedPredicate() : Cmp->getPredicate();
1587 
1588  if (isa<PredicateAssume>(PI)) {
1589  // If we assume the operands are equal, then they are equal.
1590  if (Predicate == CmpInst::ICMP_EQ) {
1591  addPredicateUsers(PI, I);
1592  addAdditionalUsers(SwappedOps ? Cmp->getOperand(1) : Cmp->getOperand(0),
1593  I);
1594  return createVariableOrConstant(FirstOp);
1595  }
1596  }
1597  if (const auto *PBranch = dyn_cast<PredicateBranch>(PI)) {
1598  // If we are *not* a copy of the comparison, we may equal to the other
1599  // operand when the predicate implies something about equality of
1600  // operations. In particular, if the comparison is true/false when the
1601  // operands are equal, and we are on the right edge, we know this operation
1602  // is equal to something.
1603  if ((PBranch->TrueEdge && Predicate == CmpInst::ICMP_EQ) ||
1604  (!PBranch->TrueEdge && Predicate == CmpInst::ICMP_NE)) {
1605  addPredicateUsers(PI, I);
1606  addAdditionalUsers(SwappedOps ? Cmp->getOperand(1) : Cmp->getOperand(0),
1607  I);
1608  return createVariableOrConstant(FirstOp);
1609  }
1610  // Handle the special case of floating point.
1611  if (((PBranch->TrueEdge && Predicate == CmpInst::FCMP_OEQ) ||
1612  (!PBranch->TrueEdge && Predicate == CmpInst::FCMP_UNE)) &&
1613  isa<ConstantFP>(FirstOp) && !cast<ConstantFP>(FirstOp)->isZero()) {
1614  addPredicateUsers(PI, I);
1615  addAdditionalUsers(SwappedOps ? Cmp->getOperand(1) : Cmp->getOperand(0),
1616  I);
1617  return createConstantExpression(cast<Constant>(FirstOp));
1618  }
1619  }
1620  return nullptr;
1621 }
1622 
1623 // Evaluate read only and pure calls, and create an expression result.
1624 const Expression *NewGVN::performSymbolicCallEvaluation(Instruction *I) const {
1625  auto *CI = cast<CallInst>(I);
1626  if (auto *II = dyn_cast<IntrinsicInst>(I)) {
1627  // Intrinsics with the returned attribute are copies of arguments.
1628  if (auto *ReturnedValue = II->getReturnedArgOperand()) {
1629  if (II->getIntrinsicID() == Intrinsic::ssa_copy)
1630  if (const auto *Result = performSymbolicPredicateInfoEvaluation(I))
1631  return Result;
1632  return createVariableOrConstant(ReturnedValue);
1633  }
1634  }
1635  if (AA->doesNotAccessMemory(CI)) {
1636  return createCallExpression(CI, TOPClass->getMemoryLeader());
1637  } else if (AA->onlyReadsMemory(CI)) {
1638  MemoryAccess *DefiningAccess = MSSAWalker->getClobberingMemoryAccess(CI);
1639  return createCallExpression(CI, DefiningAccess);
1640  }
1641  return nullptr;
1642 }
1643 
1644 // Retrieve the memory class for a given MemoryAccess.
1645 CongruenceClass *NewGVN::getMemoryClass(const MemoryAccess *MA) const {
1646  auto *Result = MemoryAccessToClass.lookup(MA);
1647  assert(Result && "Should have found memory class");
1648  return Result;
1649 }
1650 
1651 // Update the MemoryAccess equivalence table to say that From is equal to To,
1652 // and return true if this is different from what already existed in the table.
1653 bool NewGVN::setMemoryClass(const MemoryAccess *From,
1654  CongruenceClass *NewClass) {
1655  assert(NewClass &&
1656  "Every MemoryAccess should be getting mapped to a non-null class");
1657  LLVM_DEBUG(dbgs() << "Setting " << *From);
1658  LLVM_DEBUG(dbgs() << " equivalent to congruence class ");
1659  LLVM_DEBUG(dbgs() << NewClass->getID()
1660  << " with current MemoryAccess leader ");
1661  LLVM_DEBUG(dbgs() << *NewClass->getMemoryLeader() << "\n");
1662 
1663  auto LookupResult = MemoryAccessToClass.find(From);
1664  bool Changed = false;
1665  // If it's already in the table, see if the value changed.
1666  if (LookupResult != MemoryAccessToClass.end()) {
1667  auto *OldClass = LookupResult->second;
1668  if (OldClass != NewClass) {
1669  // If this is a phi, we have to handle memory member updates.
1670  if (auto *MP = dyn_cast<MemoryPhi>(From)) {
1671  OldClass->memory_erase(MP);
1672  NewClass->memory_insert(MP);
1673  // This may have killed the class if it had no non-memory members
1674  if (OldClass->getMemoryLeader() == From) {
1675  if (OldClass->definesNoMemory()) {
1676  OldClass->setMemoryLeader(nullptr);
1677  } else {
1678  OldClass->setMemoryLeader(getNextMemoryLeader(OldClass));
1679  LLVM_DEBUG(dbgs() << "Memory class leader change for class "
1680  << OldClass->getID() << " to "
1681  << *OldClass->getMemoryLeader()
1682  << " due to removal of a memory member " << *From
1683  << "\n");
1684  markMemoryLeaderChangeTouched(OldClass);
1685  }
1686  }
1687  }
1688  // It wasn't equivalent before, and now it is.
1689  LookupResult->second = NewClass;
1690  Changed = true;
1691  }
1692  }
1693 
1694  return Changed;
1695 }
1696 
1697 // Determine if a instruction is cycle-free. That means the values in the
1698 // instruction don't depend on any expressions that can change value as a result
1699 // of the instruction. For example, a non-cycle free instruction would be v =
1700 // phi(0, v+1).
1701 bool NewGVN::isCycleFree(const Instruction *I) const {
1702  // In order to compute cycle-freeness, we do SCC finding on the instruction,
1703  // and see what kind of SCC it ends up in. If it is a singleton, it is
1704  // cycle-free. If it is not in a singleton, it is only cycle free if the
1705  // other members are all phi nodes (as they do not compute anything, they are
1706  // copies).
1707  auto ICS = InstCycleState.lookup(I);
1708  if (ICS == ICS_Unknown) {
1709  SCCFinder.Start(I);
1710  auto &SCC = SCCFinder.getComponentFor(I);
1711  // It's cycle free if it's size 1 or the SCC is *only* phi nodes.
1712  if (SCC.size() == 1)
1713  InstCycleState.insert({I, ICS_CycleFree});
1714  else {
1715  bool AllPhis = llvm::all_of(SCC, [](const Value *V) {
1716  return isa<PHINode>(V) || isCopyOfAPHI(V);
1717  });
1718  ICS = AllPhis ? ICS_CycleFree : ICS_Cycle;
1719  for (auto *Member : SCC)
1720  if (auto *MemberPhi = dyn_cast<PHINode>(Member))
1721  InstCycleState.insert({MemberPhi, ICS});
1722  }
1723  }
1724  if (ICS == ICS_Cycle)
1725  return false;
1726  return true;
1727 }
1728 
1729 // Evaluate PHI nodes symbolically and create an expression result.
1730 const Expression *
1731 NewGVN::performSymbolicPHIEvaluation(ArrayRef<ValPair> PHIOps,
1732  Instruction *I,
1733  BasicBlock *PHIBlock) const {
1734  // True if one of the incoming phi edges is a backedge.
1735  bool HasBackedge = false;
1736  // All constant tracks the state of whether all the *original* phi operands
1737  // This is really shorthand for "this phi cannot cycle due to forward
1738  // change in value of the phi is guaranteed not to later change the value of
1739  // the phi. IE it can't be v = phi(undef, v+1)
1740  bool OriginalOpsConstant = true;
1741  auto *E = cast<PHIExpression>(createPHIExpression(
1742  PHIOps, I, PHIBlock, HasBackedge, OriginalOpsConstant));
1743  // We match the semantics of SimplifyPhiNode from InstructionSimplify here.
1744  // See if all arguments are the same.
1745  // We track if any were undef because they need special handling.
1746  bool HasUndef = false;
1747  auto Filtered = make_filter_range(E->operands(), [&](Value *Arg) {
1748  if (isa<UndefValue>(Arg)) {
1749  HasUndef = true;
1750  return false;
1751  }
1752  return true;
1753  });
1754  // If we are left with no operands, it's dead.
1755  if (Filtered.begin() == Filtered.end()) {
1756  // If it has undef at this point, it means there are no-non-undef arguments,
1757  // and thus, the value of the phi node must be undef.
1758  if (HasUndef) {
1759  LLVM_DEBUG(
1760  dbgs() << "PHI Node " << *I
1761  << " has no non-undef arguments, valuing it as undef\n");
1762  return createConstantExpression(UndefValue::get(I->getType()));
1763  }
1764 
1765  LLVM_DEBUG(dbgs() << "No arguments of PHI node " << *I << " are live\n");
1766  deleteExpression(E);
1767  return createDeadExpression();
1768  }
1769  Value *AllSameValue = *(Filtered.begin());
1770  ++Filtered.begin();
1771  // Can't use std::equal here, sadly, because filter.begin moves.
1772  if (llvm::all_of(Filtered, [&](Value *Arg) { return Arg == AllSameValue; })) {
1773  // In LLVM's non-standard representation of phi nodes, it's possible to have
1774  // phi nodes with cycles (IE dependent on other phis that are .... dependent
1775  // on the original phi node), especially in weird CFG's where some arguments
1776  // are unreachable, or uninitialized along certain paths. This can cause
1777  // infinite loops during evaluation. We work around this by not trying to
1778  // really evaluate them independently, but instead using a variable
1779  // expression to say if one is equivalent to the other.
1780  // We also special case undef, so that if we have an undef, we can't use the
1781  // common value unless it dominates the phi block.
1782  if (HasUndef) {
1783  // If we have undef and at least one other value, this is really a
1784  // multivalued phi, and we need to know if it's cycle free in order to
1785  // evaluate whether we can ignore the undef. The other parts of this are
1786  // just shortcuts. If there is no backedge, or all operands are
1787  // constants, it also must be cycle free.
1788  if (HasBackedge && !OriginalOpsConstant &&
1789  !isa<UndefValue>(AllSameValue) && !isCycleFree(I))
1790  return E;
1791 
1792  // Only have to check for instructions
1793  if (auto *AllSameInst = dyn_cast<Instruction>(AllSameValue))
1794  if (!someEquivalentDominates(AllSameInst, I))
1795  return E;
1796  }
1797  // Can't simplify to something that comes later in the iteration.
1798  // Otherwise, when and if it changes congruence class, we will never catch
1799  // up. We will always be a class behind it.
1800  if (isa<Instruction>(AllSameValue) &&
1801  InstrToDFSNum(AllSameValue) > InstrToDFSNum(I))
1802  return E;
1803  NumGVNPhisAllSame++;
1804  LLVM_DEBUG(dbgs() << "Simplified PHI node " << *I << " to " << *AllSameValue
1805  << "\n");
1806  deleteExpression(E);
1807  return createVariableOrConstant(AllSameValue);
1808  }
1809  return E;
1810 }
1811 
1812 const Expression *
1813 NewGVN::performSymbolicAggrValueEvaluation(Instruction *I) const {
1814  if (auto *EI = dyn_cast<ExtractValueInst>(I)) {
1815  auto *II = dyn_cast<IntrinsicInst>(EI->getAggregateOperand());
1816  if (II && EI->getNumIndices() == 1 && *EI->idx_begin() == 0) {
1817  unsigned Opcode = 0;
1818  // EI might be an extract from one of our recognised intrinsics. If it
1819  // is we'll synthesize a semantically equivalent expression instead on
1820  // an extract value expression.
1821  switch (II->getIntrinsicID()) {
1822  case Intrinsic::sadd_with_overflow:
1823  case Intrinsic::uadd_with_overflow:
1824  Opcode = Instruction::Add;
1825  break;
1826  case Intrinsic::ssub_with_overflow:
1827  case Intrinsic::usub_with_overflow:
1828  Opcode = Instruction::Sub;
1829  break;
1830  case Intrinsic::smul_with_overflow:
1831  case Intrinsic::umul_with_overflow:
1832  Opcode = Instruction::Mul;
1833  break;
1834  default:
1835  break;
1836  }
1837 
1838  if (Opcode != 0) {
1839  // Intrinsic recognized. Grab its args to finish building the
1840  // expression.
1841  assert(II->getNumArgOperands() == 2 &&
1842  "Expect two args for recognised intrinsics.");
1843  return createBinaryExpression(Opcode, EI->getType(),
1844  II->getArgOperand(0),
1845  II->getArgOperand(1), I);
1846  }
1847  }
1848  }
1849 
1850  return createAggregateValueExpression(I);
1851 }
1852 
1853 const Expression *NewGVN::performSymbolicCmpEvaluation(Instruction *I) const {
1854  assert(isa<CmpInst>(I) && "Expected a cmp instruction.");
1855 
1856  auto *CI = cast<CmpInst>(I);
1857  // See if our operands are equal to those of a previous predicate, and if so,
1858  // if it implies true or false.
1859  auto Op0 = lookupOperandLeader(CI->getOperand(0));
1860  auto Op1 = lookupOperandLeader(CI->getOperand(1));
1861  auto OurPredicate = CI->getPredicate();
1862  if (shouldSwapOperands(Op0, Op1)) {
1863  std::swap(Op0, Op1);
1864  OurPredicate = CI->getSwappedPredicate();
1865  }
1866 
1867  // Avoid processing the same info twice.
1868  const PredicateBase *LastPredInfo = nullptr;
1869  // See if we know something about the comparison itself, like it is the target
1870  // of an assume.
1871  auto *CmpPI = PredInfo->getPredicateInfoFor(I);
1872  if (dyn_cast_or_null<PredicateAssume>(CmpPI))
1873  return createConstantExpression(ConstantInt::getTrue(CI->getType()));
1874 
1875  if (Op0 == Op1) {
1876  // This condition does not depend on predicates, no need to add users
1877  if (CI->isTrueWhenEqual())
1878  return createConstantExpression(ConstantInt::getTrue(CI->getType()));
1879  else if (CI->isFalseWhenEqual())
1880  return createConstantExpression(ConstantInt::getFalse(CI->getType()));
1881  }
1882 
1883  // NOTE: Because we are comparing both operands here and below, and using
1884  // previous comparisons, we rely on fact that predicateinfo knows to mark
1885  // comparisons that use renamed operands as users of the earlier comparisons.
1886  // It is *not* enough to just mark predicateinfo renamed operands as users of
1887  // the earlier comparisons, because the *other* operand may have changed in a
1888  // previous iteration.
1889  // Example:
1890  // icmp slt %a, %b
1891  // %b.0 = ssa.copy(%b)
1892  // false branch:
1893  // icmp slt %c, %b.0
1894 
1895  // %c and %a may start out equal, and thus, the code below will say the second
1896  // %icmp is false. c may become equal to something else, and in that case the
1897  // %second icmp *must* be reexamined, but would not if only the renamed
1898  // %operands are considered users of the icmp.
1899 
1900  // *Currently* we only check one level of comparisons back, and only mark one
1901  // level back as touched when changes happen. If you modify this code to look
1902  // back farther through comparisons, you *must* mark the appropriate
1903  // comparisons as users in PredicateInfo.cpp, or you will cause bugs. See if
1904  // we know something just from the operands themselves
1905 
1906  // See if our operands have predicate info, so that we may be able to derive
1907  // something from a previous comparison.
1908  for (const auto &Op : CI->operands()) {
1909  auto *PI = PredInfo->getPredicateInfoFor(Op);
1910  if (const auto *PBranch = dyn_cast_or_null<PredicateBranch>(PI)) {
1911  if (PI == LastPredInfo)
1912  continue;
1913  LastPredInfo = PI;
1914  // In phi of ops cases, we may have predicate info that we are evaluating
1915  // in a different context.
1916  if (!DT->dominates(PBranch->To, getBlockForValue(I)))
1917  continue;
1918  // TODO: Along the false edge, we may know more things too, like
1919  // icmp of
1920  // same operands is false.
1921  // TODO: We only handle actual comparison conditions below, not
1922  // and/or.
1923  auto *BranchCond = dyn_cast<CmpInst>(PBranch->Condition);
1924  if (!BranchCond)
1925  continue;
1926  auto *BranchOp0 = lookupOperandLeader(BranchCond->getOperand(0));
1927  auto *BranchOp1 = lookupOperandLeader(BranchCond->getOperand(1));
1928  auto BranchPredicate = BranchCond->getPredicate();
1929  if (shouldSwapOperands(BranchOp0, BranchOp1)) {
1930  std::swap(BranchOp0, BranchOp1);
1931  BranchPredicate = BranchCond->getSwappedPredicate();
1932  }
1933  if (BranchOp0 == Op0 && BranchOp1 == Op1) {
1934  if (PBranch->TrueEdge) {
1935  // If we know the previous predicate is true and we are in the true
1936  // edge then we may be implied true or false.
1937  if (CmpInst::isImpliedTrueByMatchingCmp(BranchPredicate,
1938  OurPredicate)) {
1939  addPredicateUsers(PI, I);
1940  return createConstantExpression(
1941  ConstantInt::getTrue(CI->getType()));
1942  }
1943 
1944  if (CmpInst::isImpliedFalseByMatchingCmp(BranchPredicate,
1945  OurPredicate)) {
1946  addPredicateUsers(PI, I);
1947  return createConstantExpression(
1949  }
1950  } else {
1951  // Just handle the ne and eq cases, where if we have the same
1952  // operands, we may know something.
1953  if (BranchPredicate == OurPredicate) {
1954  addPredicateUsers(PI, I);
1955  // Same predicate, same ops,we know it was false, so this is false.
1956  return createConstantExpression(
1958  } else if (BranchPredicate ==
1959  CmpInst::getInversePredicate(OurPredicate)) {
1960  addPredicateUsers(PI, I);
1961  // Inverse predicate, we know the other was false, so this is true.
1962  return createConstantExpression(
1963  ConstantInt::getTrue(CI->getType()));
1964  }
1965  }
1966  }
1967  }
1968  }
1969  // Create expression will take care of simplifyCmpInst
1970  return createExpression(I);
1971 }
1972 
1973 // Substitute and symbolize the value before value numbering.
1974 const Expression *
1975 NewGVN::performSymbolicEvaluation(Value *V,
1976  SmallPtrSetImpl<Value *> &Visited) const {
1977  const Expression *E = nullptr;
1978  if (auto *C = dyn_cast<Constant>(V))
1979  E = createConstantExpression(C);
1980  else if (isa<Argument>(V) || isa<GlobalVariable>(V)) {
1981  E = createVariableExpression(V);
1982  } else {
1983  // TODO: memory intrinsics.
1984  // TODO: Some day, we should do the forward propagation and reassociation
1985  // parts of the algorithm.
1986  auto *I = cast<Instruction>(V);
1987  switch (I->getOpcode()) {
1988  case Instruction::ExtractValue:
1989  case Instruction::InsertValue:
1990  E = performSymbolicAggrValueEvaluation(I);
1991  break;
1992  case Instruction::PHI: {
1994  auto *PN = cast<PHINode>(I);
1995  for (unsigned i = 0; i < PN->getNumOperands(); ++i)
1996  Ops.push_back({PN->getIncomingValue(i), PN->getIncomingBlock(i)});
1997  // Sort to ensure the invariant createPHIExpression requires is met.
1998  sortPHIOps(Ops);
1999  E = performSymbolicPHIEvaluation(Ops, I, getBlockForValue(I));
2000  } break;
2001  case Instruction::Call:
2002  E = performSymbolicCallEvaluation(I);
2003  break;
2004  case Instruction::Store:
2005  E = performSymbolicStoreEvaluation(I);
2006  break;
2007  case Instruction::Load:
2008  E = performSymbolicLoadEvaluation(I);
2009  break;
2010  case Instruction::BitCast:
2011  E = createExpression(I);
2012  break;
2013  case Instruction::ICmp:
2014  case Instruction::FCmp:
2015  E = performSymbolicCmpEvaluation(I);
2016  break;
2017  case Instruction::Add:
2018  case Instruction::FAdd:
2019  case Instruction::Sub:
2020  case Instruction::FSub:
2021  case Instruction::Mul:
2022  case Instruction::FMul:
2023  case Instruction::UDiv:
2024  case Instruction::SDiv:
2025  case Instruction::FDiv:
2026  case Instruction::URem:
2027  case Instruction::SRem:
2028  case Instruction::FRem:
2029  case Instruction::Shl:
2030  case Instruction::LShr:
2031  case Instruction::AShr:
2032  case Instruction::And:
2033  case Instruction::Or:
2034  case Instruction::Xor:
2035  case Instruction::Trunc:
2036  case Instruction::ZExt:
2037  case Instruction::SExt:
2038  case Instruction::FPToUI:
2039  case Instruction::FPToSI:
2040  case Instruction::UIToFP:
2041  case Instruction::SIToFP:
2042  case Instruction::FPTrunc:
2043  case Instruction::FPExt:
2044  case Instruction::PtrToInt:
2045  case Instruction::IntToPtr:
2046  case Instruction::Select:
2047  case Instruction::ExtractElement:
2048  case Instruction::InsertElement:
2049  case Instruction::ShuffleVector:
2050  case Instruction::GetElementPtr:
2051  E = createExpression(I);
2052  break;
2053  default:
2054  return nullptr;
2055  }
2056  }
2057  return E;
2058 }
2059 
2060 // Look up a container in a map, and then call a function for each thing in the
2061 // found container.
2062 template <typename Map, typename KeyType, typename Func>
2063 void NewGVN::for_each_found(Map &M, const KeyType &Key, Func F) {
2064  const auto Result = M.find_as(Key);
2065  if (Result != M.end())
2066  for (typename Map::mapped_type::value_type Mapped : Result->second)
2067  F(Mapped);
2068 }
2069 
2070 // Look up a container of values/instructions in a map, and touch all the
2071 // instructions in the container. Then erase value from the map.
2072 template <typename Map, typename KeyType>
2073 void NewGVN::touchAndErase(Map &M, const KeyType &Key) {
2074  const auto Result = M.find_as(Key);
2075  if (Result != M.end()) {
2076  for (const typename Map::mapped_type::value_type Mapped : Result->second)
2077  TouchedInstructions.set(InstrToDFSNum(Mapped));
2078  M.erase(Result);
2079  }
2080 }
2081 
2082 void NewGVN::addAdditionalUsers(Value *To, Value *User) const {
2083  assert(User && To != User);
2084  if (isa<Instruction>(To))
2085  AdditionalUsers[To].insert(User);
2086 }
2087 
2088 void NewGVN::markUsersTouched(Value *V) {
2089  // Now mark the users as touched.
2090  for (auto *User : V->users()) {
2091  assert(isa<Instruction>(User) && "Use of value not within an instruction?");
2092  TouchedInstructions.set(InstrToDFSNum(User));
2093  }
2094  touchAndErase(AdditionalUsers, V);
2095 }
2096 
2097 void NewGVN::addMemoryUsers(const MemoryAccess *To, MemoryAccess *U) const {
2098  LLVM_DEBUG(dbgs() << "Adding memory user " << *U << " to " << *To << "\n");
2099  MemoryToUsers[To].insert(U);
2100 }
2101 
2102 void NewGVN::markMemoryDefTouched(const MemoryAccess *MA) {
2103  TouchedInstructions.set(MemoryToDFSNum(MA));
2104 }
2105 
2106 void NewGVN::markMemoryUsersTouched(const MemoryAccess *MA) {
2107  if (isa<MemoryUse>(MA))
2108  return;
2109  for (auto U : MA->users())
2110  TouchedInstructions.set(MemoryToDFSNum(U));
2111  touchAndErase(MemoryToUsers, MA);
2112 }
2113 
2114 // Add I to the set of users of a given predicate.
2115 void NewGVN::addPredicateUsers(const PredicateBase *PB, Instruction *I) const {
2116  // Don't add temporary instructions to the user lists.
2117  if (AllTempInstructions.count(I))
2118  return;
2119 
2120  if (auto *PBranch = dyn_cast<PredicateBranch>(PB))
2121  PredicateToUsers[PBranch->Condition].insert(I);
2122  else if (auto *PAssume = dyn_cast<PredicateBranch>(PB))
2123  PredicateToUsers[PAssume->Condition].insert(I);
2124 }
2125 
2126 // Touch all the predicates that depend on this instruction.
2127 void NewGVN::markPredicateUsersTouched(Instruction *I) {
2128  touchAndErase(PredicateToUsers, I);
2129 }
2130 
2131 // Mark users affected by a memory leader change.
2132 void NewGVN::markMemoryLeaderChangeTouched(CongruenceClass *CC) {
2133  for (auto M : CC->memory())
2134  markMemoryDefTouched(M);
2135 }
2136 
2137 // Touch the instructions that need to be updated after a congruence class has a
2138 // leader change, and mark changed values.
2139 void NewGVN::markValueLeaderChangeTouched(CongruenceClass *CC) {
2140  for (auto M : *CC) {
2141  if (auto *I = dyn_cast<Instruction>(M))
2142  TouchedInstructions.set(InstrToDFSNum(I));
2143  LeaderChanges.insert(M);
2144  }
2145 }
2146 
2147 // Give a range of things that have instruction DFS numbers, this will return
2148 // the member of the range with the smallest dfs number.
2149 template <class T, class Range>
2150 T *NewGVN::getMinDFSOfRange(const Range &R) const {
2151  std::pair<T *, unsigned> MinDFS = {nullptr, ~0U};
2152  for (const auto X : R) {
2153  auto DFSNum = InstrToDFSNum(X);
2154  if (DFSNum < MinDFS.second)
2155  MinDFS = {X, DFSNum};
2156  }
2157  return MinDFS.first;
2158 }
2159 
2160 // This function returns the MemoryAccess that should be the next leader of
2161 // congruence class CC, under the assumption that the current leader is going to
2162 // disappear.
2163 const MemoryAccess *NewGVN::getNextMemoryLeader(CongruenceClass *CC) const {
2164  // TODO: If this ends up to slow, we can maintain a next memory leader like we
2165  // do for regular leaders.
2166  // Make sure there will be a leader to find.
2167  assert(!CC->definesNoMemory() && "Can't get next leader if there is none");
2168  if (CC->getStoreCount() > 0) {
2169  if (auto *NL = dyn_cast_or_null<StoreInst>(CC->getNextLeader().first))
2170  return getMemoryAccess(NL);
2171  // Find the store with the minimum DFS number.
2172  auto *V = getMinDFSOfRange<Value>(make_filter_range(
2173  *CC, [&](const Value *V) { return isa<StoreInst>(V); }));
2174  return getMemoryAccess(cast<StoreInst>(V));
2175  }
2176  assert(CC->getStoreCount() == 0);
2177 
2178  // Given our assertion, hitting this part must mean
2179  // !OldClass->memory_empty()
2180  if (CC->memory_size() == 1)
2181  return *CC->memory_begin();
2182  return getMinDFSOfRange<const MemoryPhi>(CC->memory());
2183 }
2184 
2185 // This function returns the next value leader of a congruence class, under the
2186 // assumption that the current leader is going away. This should end up being
2187 // the next most dominating member.
2188 Value *NewGVN::getNextValueLeader(CongruenceClass *CC) const {
2189  // We don't need to sort members if there is only 1, and we don't care about
2190  // sorting the TOP class because everything either gets out of it or is
2191  // unreachable.
2192 
2193  if (CC->size() == 1 || CC == TOPClass) {
2194  return *(CC->begin());
2195  } else if (CC->getNextLeader().first) {
2196  ++NumGVNAvoidedSortedLeaderChanges;
2197  return CC->getNextLeader().first;
2198  } else {
2199  ++NumGVNSortedLeaderChanges;
2200  // NOTE: If this ends up to slow, we can maintain a dual structure for
2201  // member testing/insertion, or keep things mostly sorted, and sort only
2202  // here, or use SparseBitVector or ....
2203  return getMinDFSOfRange<Value>(*CC);
2204  }
2205 }
2206 
2207 // Move a MemoryAccess, currently in OldClass, to NewClass, including updates to
2208 // the memory members, etc for the move.
2209 //
2210 // The invariants of this function are:
2211 //
2212 // - I must be moving to NewClass from OldClass
2213 // - The StoreCount of OldClass and NewClass is expected to have been updated
2214 // for I already if it is a store.
2215 // - The OldClass memory leader has not been updated yet if I was the leader.
2216 void NewGVN::moveMemoryToNewCongruenceClass(Instruction *I,
2217  MemoryAccess *InstMA,
2218  CongruenceClass *OldClass,
2219  CongruenceClass *NewClass) {
2220  // If the leader is I, and we had a representative MemoryAccess, it should
2221  // be the MemoryAccess of OldClass.
2222  assert((!InstMA || !OldClass->getMemoryLeader() ||
2223  OldClass->getLeader() != I ||
2224  MemoryAccessToClass.lookup(OldClass->getMemoryLeader()) ==
2225  MemoryAccessToClass.lookup(InstMA)) &&
2226  "Representative MemoryAccess mismatch");
2227  // First, see what happens to the new class
2228  if (!NewClass->getMemoryLeader()) {
2229  // Should be a new class, or a store becoming a leader of a new class.
2230  assert(NewClass->size() == 1 ||
2231  (isa<StoreInst>(I) && NewClass->getStoreCount() == 1));
2232  NewClass->setMemoryLeader(InstMA);
2233  // Mark it touched if we didn't just create a singleton
2234  LLVM_DEBUG(dbgs() << "Memory class leader change for class "
2235  << NewClass->getID()
2236  << " due to new memory instruction becoming leader\n");
2237  markMemoryLeaderChangeTouched(NewClass);
2238  }
2239  setMemoryClass(InstMA, NewClass);
2240  // Now, fixup the old class if necessary
2241  if (OldClass->getMemoryLeader() == InstMA) {
2242  if (!OldClass->definesNoMemory()) {
2243  OldClass->setMemoryLeader(getNextMemoryLeader(OldClass));
2244  LLVM_DEBUG(dbgs() << "Memory class leader change for class "
2245  << OldClass->getID() << " to "
2246  << *OldClass->getMemoryLeader()
2247  << " due to removal of old leader " << *InstMA << "\n");
2248  markMemoryLeaderChangeTouched(OldClass);
2249  } else
2250  OldClass->setMemoryLeader(nullptr);
2251  }
2252 }
2253 
2254 // Move a value, currently in OldClass, to be part of NewClass
2255 // Update OldClass and NewClass for the move (including changing leaders, etc).
2256 void NewGVN::moveValueToNewCongruenceClass(Instruction *I, const Expression *E,
2257  CongruenceClass *OldClass,
2258  CongruenceClass *NewClass) {
2259  if (I == OldClass->getNextLeader().first)
2260  OldClass->resetNextLeader();
2261 
2262  OldClass->erase(I);
2263  NewClass->insert(I);
2264 
2265  if (NewClass->getLeader() != I)
2266  NewClass->addPossibleNextLeader({I, InstrToDFSNum(I)});
2267  // Handle our special casing of stores.
2268  if (auto *SI = dyn_cast<StoreInst>(I)) {
2269  OldClass->decStoreCount();
2270  // Okay, so when do we want to make a store a leader of a class?
2271  // If we have a store defined by an earlier load, we want the earlier load
2272  // to lead the class.
2273  // If we have a store defined by something else, we want the store to lead
2274  // the class so everything else gets the "something else" as a value.
2275  // If we have a store as the single member of the class, we want the store
2276  // as the leader
2277  if (NewClass->getStoreCount() == 0 && !NewClass->getStoredValue()) {
2278  // If it's a store expression we are using, it means we are not equivalent
2279  // to something earlier.
2280  if (auto *SE = dyn_cast<StoreExpression>(E)) {
2281  NewClass->setStoredValue(SE->getStoredValue());
2282  markValueLeaderChangeTouched(NewClass);
2283  // Shift the new class leader to be the store
2284  LLVM_DEBUG(dbgs() << "Changing leader of congruence class "
2285  << NewClass->getID() << " from "
2286  << *NewClass->getLeader() << " to " << *SI
2287  << " because store joined class\n");
2288  // If we changed the leader, we have to mark it changed because we don't
2289  // know what it will do to symbolic evaluation.
2290  NewClass->setLeader(SI);
2291  }
2292  // We rely on the code below handling the MemoryAccess change.
2293  }
2294  NewClass->incStoreCount();
2295  }
2296  // True if there is no memory instructions left in a class that had memory
2297  // instructions before.
2298 
2299  // If it's not a memory use, set the MemoryAccess equivalence
2300  auto *InstMA = dyn_cast_or_null<MemoryDef>(getMemoryAccess(I));
2301  if (InstMA)
2302  moveMemoryToNewCongruenceClass(I, InstMA, OldClass, NewClass);
2303  ValueToClass[I] = NewClass;
2304  // See if we destroyed the class or need to swap leaders.
2305  if (OldClass->empty() && OldClass != TOPClass) {
2306  if (OldClass->getDefiningExpr()) {
2307  LLVM_DEBUG(dbgs() << "Erasing expression " << *OldClass->getDefiningExpr()
2308  << " from table\n");
2309  // We erase it as an exact expression to make sure we don't just erase an
2310  // equivalent one.
2311  auto Iter = ExpressionToClass.find_as(
2312  ExactEqualsExpression(*OldClass->getDefiningExpr()));
2313  if (Iter != ExpressionToClass.end())
2314  ExpressionToClass.erase(Iter);
2315 #ifdef EXPENSIVE_CHECKS
2316  assert(
2317  (*OldClass->getDefiningExpr() != *E || ExpressionToClass.lookup(E)) &&
2318  "We erased the expression we just inserted, which should not happen");
2319 #endif
2320  }
2321  } else if (OldClass->getLeader() == I) {
2322  // When the leader changes, the value numbering of
2323  // everything may change due to symbolization changes, so we need to
2324  // reprocess.
2325  LLVM_DEBUG(dbgs() << "Value class leader change for class "
2326  << OldClass->getID() << "\n");
2327  ++NumGVNLeaderChanges;
2328  // Destroy the stored value if there are no more stores to represent it.
2329  // Note that this is basically clean up for the expression removal that
2330  // happens below. If we remove stores from a class, we may leave it as a
2331  // class of equivalent memory phis.
2332  if (OldClass->getStoreCount() == 0) {
2333  if (OldClass->getStoredValue())
2334  OldClass->setStoredValue(nullptr);
2335  }
2336  OldClass->setLeader(getNextValueLeader(OldClass));
2337  OldClass->resetNextLeader();
2338  markValueLeaderChangeTouched(OldClass);
2339  }
2340 }
2341 
2342 // For a given expression, mark the phi of ops instructions that could have
2343 // changed as a result.
2344 void NewGVN::markPhiOfOpsChanged(const Expression *E) {
2345  touchAndErase(ExpressionToPhiOfOps, E);
2346 }
2347 
2348 // Perform congruence finding on a given value numbering expression.
2349 void NewGVN::performCongruenceFinding(Instruction *I, const Expression *E) {
2350  // This is guaranteed to return something, since it will at least find
2351  // TOP.
2352 
2353  CongruenceClass *IClass = ValueToClass.lookup(I);
2354  assert(IClass && "Should have found a IClass");
2355  // Dead classes should have been eliminated from the mapping.
2356  assert(!IClass->isDead() && "Found a dead class");
2357 
2358  CongruenceClass *EClass = nullptr;
2359  if (const auto *VE = dyn_cast<VariableExpression>(E)) {
2360  EClass = ValueToClass.lookup(VE->getVariableValue());
2361  } else if (isa<DeadExpression>(E)) {
2362  EClass = TOPClass;
2363  }
2364  if (!EClass) {
2365  auto lookupResult = ExpressionToClass.insert({E, nullptr});
2366 
2367  // If it's not in the value table, create a new congruence class.
2368  if (lookupResult.second) {
2369  CongruenceClass *NewClass = createCongruenceClass(nullptr, E);
2370  auto place = lookupResult.first;
2371  place->second = NewClass;
2372 
2373  // Constants and variables should always be made the leader.
2374  if (const auto *CE = dyn_cast<ConstantExpression>(E)) {
2375  NewClass->setLeader(CE->getConstantValue());
2376  } else if (const auto *SE = dyn_cast<StoreExpression>(E)) {
2377  StoreInst *SI = SE->getStoreInst();
2378  NewClass->setLeader(SI);
2379  NewClass->setStoredValue(SE->getStoredValue());
2380  // The RepMemoryAccess field will be filled in properly by the
2381  // moveValueToNewCongruenceClass call.
2382  } else {
2383  NewClass->setLeader(I);
2384  }
2385  assert(!isa<VariableExpression>(E) &&
2386  "VariableExpression should have been handled already");
2387 
2388  EClass = NewClass;
2389  LLVM_DEBUG(dbgs() << "Created new congruence class for " << *I
2390  << " using expression " << *E << " at "
2391  << NewClass->getID() << " and leader "
2392  << *(NewClass->getLeader()));
2393  if (NewClass->getStoredValue())
2394  LLVM_DEBUG(dbgs() << " and stored value "
2395  << *(NewClass->getStoredValue()));
2396  LLVM_DEBUG(dbgs() << "\n");
2397  } else {
2398  EClass = lookupResult.first->second;
2399  if (isa<ConstantExpression>(E))
2400  assert((isa<Constant>(EClass->getLeader()) ||
2401  (EClass->getStoredValue() &&
2402  isa<Constant>(EClass->getStoredValue()))) &&
2403  "Any class with a constant expression should have a "
2404  "constant leader");
2405 
2406  assert(EClass && "Somehow don't have an eclass");
2407 
2408  assert(!EClass->isDead() && "We accidentally looked up a dead class");
2409  }
2410  }
2411  bool ClassChanged = IClass != EClass;
2412  bool LeaderChanged = LeaderChanges.erase(I);
2413  if (ClassChanged || LeaderChanged) {
2414  LLVM_DEBUG(dbgs() << "New class " << EClass->getID() << " for expression "
2415  << *E << "\n");
2416  if (ClassChanged) {
2417  moveValueToNewCongruenceClass(I, E, IClass, EClass);
2418  markPhiOfOpsChanged(E);
2419  }
2420 
2421  markUsersTouched(I);
2422  if (MemoryAccess *MA = getMemoryAccess(I))
2423  markMemoryUsersTouched(MA);
2424  if (auto *CI = dyn_cast<CmpInst>(I))
2425  markPredicateUsersTouched(CI);
2426  }
2427  // If we changed the class of the store, we want to ensure nothing finds the
2428  // old store expression. In particular, loads do not compare against stored
2429  // value, so they will find old store expressions (and associated class
2430  // mappings) if we leave them in the table.
2431  if (ClassChanged && isa<StoreInst>(I)) {
2432  auto *OldE = ValueToExpression.lookup(I);
2433  // It could just be that the old class died. We don't want to erase it if we
2434  // just moved classes.
2435  if (OldE && isa<StoreExpression>(OldE) && *E != *OldE) {
2436  // Erase this as an exact expression to ensure we don't erase expressions
2437  // equivalent to it.
2438  auto Iter = ExpressionToClass.find_as(ExactEqualsExpression(*OldE));
2439  if (Iter != ExpressionToClass.end())
2440  ExpressionToClass.erase(Iter);
2441  }
2442  }
2443  ValueToExpression[I] = E;
2444 }
2445 
2446 // Process the fact that Edge (from, to) is reachable, including marking
2447 // any newly reachable blocks and instructions for processing.
2448 void NewGVN::updateReachableEdge(BasicBlock *From, BasicBlock *To) {
2449  // Check if the Edge was reachable before.
2450  if (ReachableEdges.insert({From, To}).second) {
2451  // If this block wasn't reachable before, all instructions are touched.
2452  if (ReachableBlocks.insert(To).second) {
2453  LLVM_DEBUG(dbgs() << "Block " << getBlockName(To)
2454  << " marked reachable\n");
2455  const auto &InstRange = BlockInstRange.lookup(To);
2456  TouchedInstructions.set(InstRange.first, InstRange.second);
2457  } else {
2458  LLVM_DEBUG(dbgs() << "Block " << getBlockName(To)
2459  << " was reachable, but new edge {"
2460  << getBlockName(From) << "," << getBlockName(To)
2461  << "} to it found\n");
2462 
2463  // We've made an edge reachable to an existing block, which may
2464  // impact predicates. Otherwise, only mark the phi nodes as touched, as
2465  // they are the only thing that depend on new edges. Anything using their
2466  // values will get propagated to if necessary.
2467  if (MemoryAccess *MemPhi = getMemoryAccess(To))
2468  TouchedInstructions.set(InstrToDFSNum(MemPhi));
2469 
2470  // FIXME: We should just add a union op on a Bitvector and
2471  // SparseBitVector. We can do it word by word faster than we are doing it
2472  // here.
2473  for (auto InstNum : RevisitOnReachabilityChange[To])
2474  TouchedInstructions.set(InstNum);
2475  }
2476  }
2477 }
2478 
2479 // Given a predicate condition (from a switch, cmp, or whatever) and a block,
2480 // see if we know some constant value for it already.
2481 Value *NewGVN::findConditionEquivalence(Value *Cond) const {
2482  auto Result = lookupOperandLeader(Cond);
2483  return isa<Constant>(Result) ? Result : nullptr;
2484 }
2485 
2486 // Process the outgoing edges of a block for reachability.
2487 void NewGVN::processOutgoingEdges(TerminatorInst *TI, BasicBlock *B) {
2488  // Evaluate reachability of terminator instruction.
2489  BranchInst *BR;
2490  if ((BR = dyn_cast<BranchInst>(TI)) && BR->isConditional()) {
2491  Value *Cond = BR->getCondition();
2492  Value *CondEvaluated = findConditionEquivalence(Cond);
2493  if (!CondEvaluated) {
2494  if (auto *I = dyn_cast<Instruction>(Cond)) {
2495  const Expression *E = createExpression(I);
2496  if (const auto *CE = dyn_cast<ConstantExpression>(E)) {
2497  CondEvaluated = CE->getConstantValue();
2498  }
2499  } else if (isa<ConstantInt>(Cond)) {
2500  CondEvaluated = Cond;
2501  }
2502  }
2503  ConstantInt *CI;
2504  BasicBlock *TrueSucc = BR->getSuccessor(0);
2505  BasicBlock *FalseSucc = BR->getSuccessor(1);
2506  if (CondEvaluated && (CI = dyn_cast<ConstantInt>(CondEvaluated))) {
2507  if (CI->isOne()) {
2508  LLVM_DEBUG(dbgs() << "Condition for Terminator " << *TI
2509  << " evaluated to true\n");
2510  updateReachableEdge(B, TrueSucc);
2511  } else if (CI->isZero()) {
2512  LLVM_DEBUG(dbgs() << "Condition for Terminator " << *TI
2513  << " evaluated to false\n");
2514  updateReachableEdge(B, FalseSucc);
2515  }
2516  } else {
2517  updateReachableEdge(B, TrueSucc);
2518  updateReachableEdge(B, FalseSucc);
2519  }
2520  } else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
2521  // For switches, propagate the case values into the case
2522  // destinations.
2523 
2524  // Remember how many outgoing edges there are to every successor.
2526 
2527  Value *SwitchCond = SI->getCondition();
2528  Value *CondEvaluated = findConditionEquivalence(SwitchCond);
2529  // See if we were able to turn this switch statement into a constant.
2530  if (CondEvaluated && isa<ConstantInt>(CondEvaluated)) {
2531  auto *CondVal = cast<ConstantInt>(CondEvaluated);
2532  // We should be able to get case value for this.
2533  auto Case = *SI->findCaseValue(CondVal);
2534  if (Case.getCaseSuccessor() == SI->getDefaultDest()) {
2535  // We proved the value is outside of the range of the case.
2536  // We can't do anything other than mark the default dest as reachable,
2537  // and go home.
2538  updateReachableEdge(B, SI->getDefaultDest());
2539  return;
2540  }
2541  // Now get where it goes and mark it reachable.
2542  BasicBlock *TargetBlock = Case.getCaseSuccessor();
2543  updateReachableEdge(B, TargetBlock);
2544  } else {
2545  for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
2546  BasicBlock *TargetBlock = SI->getSuccessor(i);
2547  ++SwitchEdges[TargetBlock];
2548  updateReachableEdge(B, TargetBlock);
2549  }
2550  }
2551  } else {
2552  // Otherwise this is either unconditional, or a type we have no
2553  // idea about. Just mark successors as reachable.
2554  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
2555  BasicBlock *TargetBlock = TI->getSuccessor(i);
2556  updateReachableEdge(B, TargetBlock);
2557  }
2558 
2559  // This also may be a memory defining terminator, in which case, set it
2560  // equivalent only to itself.
2561  //
2562  auto *MA = getMemoryAccess(TI);
2563  if (MA && !isa<MemoryUse>(MA)) {
2564  auto *CC = ensureLeaderOfMemoryClass(MA);
2565  if (setMemoryClass(MA, CC))
2566  markMemoryUsersTouched(MA);
2567  }
2568  }
2569 }
2570 
2571 // Remove the PHI of Ops PHI for I
2572 void NewGVN::removePhiOfOps(Instruction *I, PHINode *PHITemp) {
2573  InstrDFS.erase(PHITemp);
2574  // It's still a temp instruction. We keep it in the array so it gets erased.
2575  // However, it's no longer used by I, or in the block
2576  TempToBlock.erase(PHITemp);
2577  RealToTemp.erase(I);
2578  // We don't remove the users from the phi node uses. This wastes a little
2579  // time, but such is life. We could use two sets to track which were there
2580  // are the start of NewGVN, and which were added, but right nowt he cost of
2581  // tracking is more than the cost of checking for more phi of ops.
2582 }
2583 
2584 // Add PHI Op in BB as a PHI of operations version of ExistingValue.
2585 void NewGVN::addPhiOfOps(PHINode *Op, BasicBlock *BB,
2586  Instruction *ExistingValue) {
2587  InstrDFS[Op] = InstrToDFSNum(ExistingValue);
2588  AllTempInstructions.insert(Op);
2589  TempToBlock[Op] = BB;
2590  RealToTemp[ExistingValue] = Op;
2591  // Add all users to phi node use, as they are now uses of the phi of ops phis
2592  // and may themselves be phi of ops.
2593  for (auto *U : ExistingValue->users())
2594  if (auto *UI = dyn_cast<Instruction>(U))
2595  PHINodeUses.insert(UI);
2596 }
2597 
2598 static bool okayForPHIOfOps(const Instruction *I) {
2599  if (!EnablePhiOfOps)
2600  return false;
2601  return isa<BinaryOperator>(I) || isa<SelectInst>(I) || isa<CmpInst>(I) ||
2602  isa<LoadInst>(I);
2603 }
2604 
2605 bool NewGVN::OpIsSafeForPHIOfOpsHelper(
2606  Value *V, const BasicBlock *PHIBlock,
2608  SmallVectorImpl<Instruction *> &Worklist) {
2609 
2610  if (!isa<Instruction>(V))
2611  return true;
2612  auto OISIt = OpSafeForPHIOfOps.find(V);
2613  if (OISIt != OpSafeForPHIOfOps.end())
2614  return OISIt->second;
2615 
2616  // Keep walking until we either dominate the phi block, or hit a phi, or run
2617  // out of things to check.
2618  if (DT->properlyDominates(getBlockForValue(V), PHIBlock)) {
2619  OpSafeForPHIOfOps.insert({V, true});
2620  return true;
2621  }
2622  // PHI in the same block.
2623  if (isa<PHINode>(V) && getBlockForValue(V) == PHIBlock) {
2624  OpSafeForPHIOfOps.insert({V, false});
2625  return false;
2626  }
2627 
2628  auto *OrigI = cast<Instruction>(V);
2629  for (auto *Op : OrigI->operand_values()) {
2630  if (!isa<Instruction>(Op))
2631  continue;
2632  // Stop now if we find an unsafe operand.
2633  auto OISIt = OpSafeForPHIOfOps.find(OrigI);
2634  if (OISIt != OpSafeForPHIOfOps.end()) {
2635  if (!OISIt->second) {
2636  OpSafeForPHIOfOps.insert({V, false});
2637  return false;
2638  }
2639  continue;
2640  }
2641  if (!Visited.insert(Op).second)
2642  continue;
2643  Worklist.push_back(cast<Instruction>(Op));
2644  }
2645  return true;
2646 }
2647 
2648 // Return true if this operand will be safe to use for phi of ops.
2649 //
2650 // The reason some operands are unsafe is that we are not trying to recursively
2651 // translate everything back through phi nodes. We actually expect some lookups
2652 // of expressions to fail. In particular, a lookup where the expression cannot
2653 // exist in the predecessor. This is true even if the expression, as shown, can
2654 // be determined to be constant.
2655 bool NewGVN::OpIsSafeForPHIOfOps(Value *V, const BasicBlock *PHIBlock,
2656  SmallPtrSetImpl<const Value *> &Visited) {
2658  if (!OpIsSafeForPHIOfOpsHelper(V, PHIBlock, Visited, Worklist))
2659  return false;
2660  while (!Worklist.empty()) {
2661  auto *I = Worklist.pop_back_val();
2662  if (!OpIsSafeForPHIOfOpsHelper(I, PHIBlock, Visited, Worklist))
2663  return false;
2664  }
2665  OpSafeForPHIOfOps.insert({V, true});
2666  return true;
2667 }
2668 
2669 // Try to find a leader for instruction TransInst, which is a phi translated
2670 // version of something in our original program. Visited is used to ensure we
2671 // don't infinite loop during translations of cycles. OrigInst is the
2672 // instruction in the original program, and PredBB is the predecessor we
2673 // translated it through.
2674 Value *NewGVN::findLeaderForInst(Instruction *TransInst,
2675  SmallPtrSetImpl<Value *> &Visited,
2676  MemoryAccess *MemAccess, Instruction *OrigInst,
2677  BasicBlock *PredBB) {
2678  unsigned IDFSNum = InstrToDFSNum(OrigInst);
2679  // Make sure it's marked as a temporary instruction.
2680  AllTempInstructions.insert(TransInst);
2681  // and make sure anything that tries to add it's DFS number is
2682  // redirected to the instruction we are making a phi of ops
2683  // for.
2684  TempToBlock.insert({TransInst, PredBB});
2685  InstrDFS.insert({TransInst, IDFSNum});
2686 
2687  const Expression *E = performSymbolicEvaluation(TransInst, Visited);
2688  InstrDFS.erase(TransInst);
2689  AllTempInstructions.erase(TransInst);
2690  TempToBlock.erase(TransInst);
2691  if (MemAccess)
2692  TempToMemory.erase(TransInst);
2693  if (!E)
2694  return nullptr;
2695  auto *FoundVal = findPHIOfOpsLeader(E, OrigInst, PredBB);
2696  if (!FoundVal) {
2697  ExpressionToPhiOfOps[E].insert(OrigInst);
2698  LLVM_DEBUG(dbgs() << "Cannot find phi of ops operand for " << *TransInst
2699  << " in block " << getBlockName(PredBB) << "\n");
2700  return nullptr;
2701  }
2702  if (auto *SI = dyn_cast<StoreInst>(FoundVal))
2703  FoundVal = SI->getValueOperand();
2704  return FoundVal;
2705 }
2706 
2707 // When we see an instruction that is an op of phis, generate the equivalent phi
2708 // of ops form.
2709 const Expression *
2710 NewGVN::makePossiblePHIOfOps(Instruction *I,
2711  SmallPtrSetImpl<Value *> &Visited) {
2712  if (!okayForPHIOfOps(I))
2713  return nullptr;
2714 
2715  if (!Visited.insert(I).second)
2716  return nullptr;
2717  // For now, we require the instruction be cycle free because we don't
2718  // *always* create a phi of ops for instructions that could be done as phi
2719  // of ops, we only do it if we think it is useful. If we did do it all the
2720  // time, we could remove the cycle free check.
2721  if (!isCycleFree(I))
2722  return nullptr;
2723 
2724  SmallPtrSet<const Value *, 8> ProcessedPHIs;
2725  // TODO: We don't do phi translation on memory accesses because it's
2726  // complicated. For a load, we'd need to be able to simulate a new memoryuse,
2727  // which we don't have a good way of doing ATM.
2728  auto *MemAccess = getMemoryAccess(I);
2729  // If the memory operation is defined by a memory operation this block that
2730  // isn't a MemoryPhi, transforming the pointer backwards through a scalar phi
2731  // can't help, as it would still be killed by that memory operation.
2732  if (MemAccess && !isa<MemoryPhi>(MemAccess->getDefiningAccess()) &&
2733  MemAccess->getDefiningAccess()->getBlock() == I->getParent())
2734  return nullptr;
2735 
2736  // Convert op of phis to phi of ops
2737  SmallPtrSet<const Value *, 10> VisitedOps;
2739  BasicBlock *SamePHIBlock = nullptr;
2740  PHINode *OpPHI = nullptr;
2741  if (!DebugCounter::shouldExecute(PHIOfOpsCounter))
2742  return nullptr;
2743  for (auto *Op : Ops) {
2744  if (!isa<PHINode>(Op)) {
2745  auto *ValuePHI = RealToTemp.lookup(Op);
2746  if (!ValuePHI)
2747  continue;
2748  LLVM_DEBUG(dbgs() << "Found possible dependent phi of ops\n");
2749  Op = ValuePHI;
2750  }
2751  OpPHI = cast<PHINode>(Op);
2752  if (!SamePHIBlock) {
2753  SamePHIBlock = getBlockForValue(OpPHI);
2754  } else if (SamePHIBlock != getBlockForValue(OpPHI)) {
2755  LLVM_DEBUG(
2756  dbgs()
2757  << "PHIs for operands are not all in the same block, aborting\n");
2758  return nullptr;
2759  }
2760  // No point in doing this for one-operand phis.
2761  if (OpPHI->getNumOperands() == 1) {
2762  OpPHI = nullptr;
2763  continue;
2764  }
2765  }
2766 
2767  if (!OpPHI)
2768  return nullptr;
2769 
2770  SmallVector<ValPair, 4> PHIOps;
2772  auto *PHIBlock = getBlockForValue(OpPHI);
2773  RevisitOnReachabilityChange[PHIBlock].reset(InstrToDFSNum(I));
2774  for (unsigned PredNum = 0; PredNum < OpPHI->getNumOperands(); ++PredNum) {
2775  auto *PredBB = OpPHI->getIncomingBlock(PredNum);
2776  Value *FoundVal = nullptr;
2777  SmallPtrSet<Value *, 4> CurrentDeps;
2778  // We could just skip unreachable edges entirely but it's tricky to do
2779  // with rewriting existing phi nodes.
2780  if (ReachableEdges.count({PredBB, PHIBlock})) {
2781  // Clone the instruction, create an expression from it that is
2782  // translated back into the predecessor, and see if we have a leader.
2783  Instruction *ValueOp = I->clone();
2784  if (MemAccess)
2785  TempToMemory.insert({ValueOp, MemAccess});
2786  bool SafeForPHIOfOps = true;
2787  VisitedOps.clear();
2788  for (auto &Op : ValueOp->operands()) {
2789  auto *OrigOp = &*Op;
2790  // When these operand changes, it could change whether there is a
2791  // leader for us or not, so we have to add additional users.
2792  if (isa<PHINode>(Op)) {
2793  Op = Op->DoPHITranslation(PHIBlock, PredBB);
2794  if (Op != OrigOp && Op != I)
2795  CurrentDeps.insert(Op);
2796  } else if (auto *ValuePHI = RealToTemp.lookup(Op)) {
2797  if (getBlockForValue(ValuePHI) == PHIBlock)
2798  Op = ValuePHI->getIncomingValueForBlock(PredBB);
2799  }
2800  // If we phi-translated the op, it must be safe.
2801  SafeForPHIOfOps =
2802  SafeForPHIOfOps &&
2803  (Op != OrigOp || OpIsSafeForPHIOfOps(Op, PHIBlock, VisitedOps));
2804  }
2805  // FIXME: For those things that are not safe we could generate
2806  // expressions all the way down, and see if this comes out to a
2807  // constant. For anything where that is true, and unsafe, we should
2808  // have made a phi-of-ops (or value numbered it equivalent to something)
2809  // for the pieces already.
2810  FoundVal = !SafeForPHIOfOps ? nullptr
2811  : findLeaderForInst(ValueOp, Visited,
2812  MemAccess, I, PredBB);
2813  ValueOp->deleteValue();
2814  if (!FoundVal) {
2815  // We failed to find a leader for the current ValueOp, but this might
2816  // change in case of the translated operands change.
2817  if (SafeForPHIOfOps)
2818  for (auto Dep : CurrentDeps)
2819  addAdditionalUsers(Dep, I);
2820 
2821  return nullptr;
2822  }
2823  Deps.insert(CurrentDeps.begin(), CurrentDeps.end());
2824  } else {
2825  LLVM_DEBUG(dbgs() << "Skipping phi of ops operand for incoming block "
2826  << getBlockName(PredBB)
2827  << " because the block is unreachable\n");
2828  FoundVal = UndefValue::get(I->getType());
2829  RevisitOnReachabilityChange[PHIBlock].set(InstrToDFSNum(I));
2830  }
2831 
2832  PHIOps.push_back({FoundVal, PredBB});
2833  LLVM_DEBUG(dbgs() << "Found phi of ops operand " << *FoundVal << " in "
2834  << getBlockName(PredBB) << "\n");
2835  }
2836  for (auto Dep : Deps)
2837  addAdditionalUsers(Dep, I);
2838  sortPHIOps(PHIOps);
2839  auto *E = performSymbolicPHIEvaluation(PHIOps, I, PHIBlock);
2840  if (isa<ConstantExpression>(E) || isa<VariableExpression>(E)) {
2841  LLVM_DEBUG(
2842  dbgs()
2843  << "Not creating real PHI of ops because it simplified to existing "
2844  "value or constant\n");
2845  return E;
2846  }
2847  auto *ValuePHI = RealToTemp.lookup(I);
2848  bool NewPHI = false;
2849  if (!ValuePHI) {
2850  ValuePHI =
2851  PHINode::Create(I->getType(), OpPHI->getNumOperands(), "phiofops");
2852  addPhiOfOps(ValuePHI, PHIBlock, I);
2853  NewPHI = true;
2854  NumGVNPHIOfOpsCreated++;
2855  }
2856  if (NewPHI) {
2857  for (auto PHIOp : PHIOps)
2858  ValuePHI->addIncoming(PHIOp.first, PHIOp.second);
2859  } else {
2860  TempToBlock[ValuePHI] = PHIBlock;
2861  unsigned int i = 0;
2862  for (auto PHIOp : PHIOps) {
2863  ValuePHI->setIncomingValue(i, PHIOp.first);
2864  ValuePHI->setIncomingBlock(i, PHIOp.second);
2865  ++i;
2866  }
2867  }
2868  RevisitOnReachabilityChange[PHIBlock].set(InstrToDFSNum(I));
2869  LLVM_DEBUG(dbgs() << "Created phi of ops " << *ValuePHI << " for " << *I
2870  << "\n");
2871 
2872  return E;
2873 }
2874 
2875 // The algorithm initially places the values of the routine in the TOP
2876 // congruence class. The leader of TOP is the undetermined value `undef`.
2877 // When the algorithm has finished, values still in TOP are unreachable.
2878 void NewGVN::initializeCongruenceClasses(Function &F) {
2879  NextCongruenceNum = 0;
2880 
2881  // Note that even though we use the live on entry def as a representative
2882  // MemoryAccess, it is *not* the same as the actual live on entry def. We
2883  // have no real equivalemnt to undef for MemoryAccesses, and so we really
2884  // should be checking whether the MemoryAccess is top if we want to know if it
2885  // is equivalent to everything. Otherwise, what this really signifies is that
2886  // the access "it reaches all the way back to the beginning of the function"
2887 
2888  // Initialize all other instructions to be in TOP class.
2889  TOPClass = createCongruenceClass(nullptr, nullptr);
2890  TOPClass->setMemoryLeader(MSSA->getLiveOnEntryDef());
2891  // The live on entry def gets put into it's own class
2892  MemoryAccessToClass[MSSA->getLiveOnEntryDef()] =
2893  createMemoryClass(MSSA->getLiveOnEntryDef());
2894 
2895  for (auto DTN : nodes(DT)) {
2896  BasicBlock *BB = DTN->getBlock();
2897  // All MemoryAccesses are equivalent to live on entry to start. They must
2898  // be initialized to something so that initial changes are noticed. For
2899  // the maximal answer, we initialize them all to be the same as
2900  // liveOnEntry.
2901  auto *MemoryBlockDefs = MSSA->getBlockDefs(BB);
2902  if (MemoryBlockDefs)
2903  for (const auto &Def : *MemoryBlockDefs) {
2904  MemoryAccessToClass[&Def] = TOPClass;
2905  auto *MD = dyn_cast<MemoryDef>(&Def);
2906  // Insert the memory phis into the member list.
2907  if (!MD) {
2908  const MemoryPhi *MP = cast<MemoryPhi>(&Def);
2909  TOPClass->memory_insert(MP);
2910  MemoryPhiState.insert({MP, MPS_TOP});
2911  }
2912 
2913  if (MD && isa<StoreInst>(MD->getMemoryInst()))
2914  TOPClass->incStoreCount();
2915  }
2916 
2917  // FIXME: This is trying to discover which instructions are uses of phi
2918  // nodes. We should move this into one of the myriad of places that walk
2919  // all the operands already.
2920  for (auto &I : *BB) {
2921  if (isa<PHINode>(&I))
2922  for (auto *U : I.users())
2923  if (auto *UInst = dyn_cast<Instruction>(U))
2924  if (InstrToDFSNum(UInst) != 0 && okayForPHIOfOps(UInst))
2925  PHINodeUses.insert(UInst);
2926  // Don't insert void terminators into the class. We don't value number
2927  // them, and they just end up sitting in TOP.
2928  if (isa<TerminatorInst>(I) && I.getType()->isVoidTy())
2929  continue;
2930  TOPClass->insert(&I);
2931  ValueToClass[&I] = TOPClass;
2932  }
2933  }
2934 
2935  // Initialize arguments to be in their own unique congruence classes
2936  for (auto &FA : F.args())
2937  createSingletonCongruenceClass(&FA);
2938 }
2939 
2940 void NewGVN::cleanupTables() {
2941  for (unsigned i = 0, e = CongruenceClasses.size(); i != e; ++i) {
2942  LLVM_DEBUG(dbgs() << "Congruence class " << CongruenceClasses[i]->getID()
2943  << " has " << CongruenceClasses[i]->size()
2944  << " members\n");
2945  // Make sure we delete the congruence class (probably worth switching to
2946  // a unique_ptr at some point.
2947  delete CongruenceClasses[i];
2948  CongruenceClasses[i] = nullptr;
2949  }
2950 
2951  // Destroy the value expressions
2952  SmallVector<Instruction *, 8> TempInst(AllTempInstructions.begin(),
2953  AllTempInstructions.end());
2954  AllTempInstructions.clear();
2955 
2956  // We have to drop all references for everything first, so there are no uses
2957  // left as we delete them.
2958  for (auto *I : TempInst) {
2959  I->dropAllReferences();
2960  }
2961 
2962  while (!TempInst.empty()) {
2963  auto *I = TempInst.back();
2964  TempInst.pop_back();
2965  I->deleteValue();
2966  }
2967 
2968  ValueToClass.clear();
2969  ArgRecycler.clear(ExpressionAllocator);
2970  ExpressionAllocator.Reset();
2971  CongruenceClasses.clear();
2972  ExpressionToClass.clear();
2973  ValueToExpression.clear();
2974  RealToTemp.clear();
2975  AdditionalUsers.clear();
2976  ExpressionToPhiOfOps.clear();
2977  TempToBlock.clear();
2978  TempToMemory.clear();
2979  PHINodeUses.clear();
2980  OpSafeForPHIOfOps.clear();
2981  ReachableBlocks.clear();
2982  ReachableEdges.clear();
2983 #ifndef NDEBUG
2984  ProcessedCount.clear();
2985 #endif
2986  InstrDFS.clear();
2987  InstructionsToErase.clear();
2988  DFSToInstr.clear();
2989  BlockInstRange.clear();
2990  TouchedInstructions.clear();
2991  MemoryAccessToClass.clear();
2992  PredicateToUsers.clear();
2993  MemoryToUsers.clear();
2994  RevisitOnReachabilityChange.clear();
2995 }
2996 
2997 // Assign local DFS number mapping to instructions, and leave space for Value
2998 // PHI's.
2999 std::pair<unsigned, unsigned> NewGVN::assignDFSNumbers(BasicBlock *B,
3000  unsigned Start) {
3001  unsigned End = Start;
3002  if (MemoryAccess *MemPhi = getMemoryAccess(B)) {
3003  InstrDFS[MemPhi] = End++;
3004  DFSToInstr.emplace_back(MemPhi);
3005  }
3006 
3007  // Then the real block goes next.
3008  for (auto &I : *B) {
3009  // There's no need to call isInstructionTriviallyDead more than once on
3010  // an instruction. Therefore, once we know that an instruction is dead
3011  // we change its DFS number so that it doesn't get value numbered.
3012  if (isInstructionTriviallyDead(&I, TLI)) {
3013  InstrDFS[&I] = 0;
3014  LLVM_DEBUG(dbgs() << "Skipping trivially dead instruction " << I << "\n");
3015  markInstructionForDeletion(&I);
3016  continue;
3017  }
3018  if (isa<PHINode>(&I))
3019  RevisitOnReachabilityChange[B].set(End);
3020  InstrDFS[&I] = End++;
3021  DFSToInstr.emplace_back(&I);
3022  }
3023 
3024  // All of the range functions taken half-open ranges (open on the end side).
3025  // So we do not subtract one from count, because at this point it is one
3026  // greater than the last instruction.
3027  return std::make_pair(Start, End);
3028 }
3029 
3030 void NewGVN::updateProcessedCount(const Value *V) {
3031 #ifndef NDEBUG
3032  if (ProcessedCount.count(V) == 0) {
3033  ProcessedCount.insert({V, 1});
3034  } else {
3035  ++ProcessedCount[V];
3036  assert(ProcessedCount[V] < 100 &&
3037  "Seem to have processed the same Value a lot");
3038  }
3039 #endif
3040 }
3041 
3042 // Evaluate MemoryPhi nodes symbolically, just like PHI nodes
3043 void NewGVN::valueNumberMemoryPhi(MemoryPhi *MP) {
3044  // If all the arguments are the same, the MemoryPhi has the same value as the
3045  // argument. Filter out unreachable blocks and self phis from our operands.
3046  // TODO: We could do cycle-checking on the memory phis to allow valueizing for
3047  // self-phi checking.
3048  const BasicBlock *PHIBlock = MP->getBlock();
3049  auto Filtered = make_filter_range(MP->operands(), [&](const Use &U) {
3050  return cast<MemoryAccess>(U) != MP &&
3051  !isMemoryAccessTOP(cast<MemoryAccess>(U)) &&
3052  ReachableEdges.count({MP->getIncomingBlock(U), PHIBlock});
3053  });
3054  // If all that is left is nothing, our memoryphi is undef. We keep it as
3055  // InitialClass. Note: The only case this should happen is if we have at
3056  // least one self-argument.
3057  if (Filtered.begin() == Filtered.end()) {
3058  if (setMemoryClass(MP, TOPClass))
3059  markMemoryUsersTouched(MP);
3060  return;
3061  }
3062 
3063  // Transform the remaining operands into operand leaders.
3064  // FIXME: mapped_iterator should have a range version.
3065  auto LookupFunc = [&](const Use &U) {
3066  return lookupMemoryLeader(cast<MemoryAccess>(U));
3067  };
3068  auto MappedBegin = map_iterator(Filtered.begin(), LookupFunc);
3069  auto MappedEnd = map_iterator(Filtered.end(), LookupFunc);
3070 
3071  // and now check if all the elements are equal.
3072  // Sadly, we can't use std::equals since these are random access iterators.
3073  const auto *AllSameValue = *MappedBegin;
3074  ++MappedBegin;
3075  bool AllEqual = std::all_of(
3076  MappedBegin, MappedEnd,
3077  [&AllSameValue](const MemoryAccess *V) { return V == AllSameValue; });
3078 
3079  if (AllEqual)
3080  LLVM_DEBUG(dbgs() << "Memory Phi value numbered to " << *AllSameValue
3081  << "\n");
3082  else
3083  LLVM_DEBUG(dbgs() << "Memory Phi value numbered to itself\n");
3084  // If it's equal to something, it's in that class. Otherwise, it has to be in
3085  // a class where it is the leader (other things may be equivalent to it, but
3086  // it needs to start off in its own class, which means it must have been the
3087  // leader, and it can't have stopped being the leader because it was never
3088  // removed).
3089  CongruenceClass *CC =
3090  AllEqual ? getMemoryClass(AllSameValue) : ensureLeaderOfMemoryClass(MP);
3091  auto OldState = MemoryPhiState.lookup(MP);
3092  assert(OldState != MPS_Invalid && "Invalid memory phi state");
3093  auto NewState = AllEqual ? MPS_Equivalent : MPS_Unique;
3094  MemoryPhiState[MP] = NewState;
3095  if (setMemoryClass(MP, CC) || OldState != NewState)
3096  markMemoryUsersTouched(MP);
3097 }
3098 
3099 // Value number a single instruction, symbolically evaluating, performing
3100 // congruence finding, and updating mappings.
3101 void NewGVN::valueNumberInstruction(Instruction *I) {
3102  LLVM_DEBUG(dbgs() << "Processing instruction " << *I << "\n");
3103  if (!I->isTerminator()) {
3104  const Expression *Symbolized = nullptr;
3105  SmallPtrSet<Value *, 2> Visited;
3106  if (DebugCounter::shouldExecute(VNCounter)) {
3107  Symbolized = performSymbolicEvaluation(I, Visited);
3108  // Make a phi of ops if necessary
3109  if (Symbolized && !isa<ConstantExpression>(Symbolized) &&
3110  !isa<VariableExpression>(Symbolized) && PHINodeUses.count(I)) {
3111  auto *PHIE = makePossiblePHIOfOps(I, Visited);
3112  // If we created a phi of ops, use it.
3113  // If we couldn't create one, make sure we don't leave one lying around
3114  if (PHIE) {
3115  Symbolized = PHIE;
3116  } else if (auto *Op = RealToTemp.lookup(I)) {
3117  removePhiOfOps(I, Op);
3118  }
3119  }
3120  } else {
3121  // Mark the instruction as unused so we don't value number it again.
3122  InstrDFS[I] = 0;
3123  }
3124  // If we couldn't come up with a symbolic expression, use the unknown
3125  // expression
3126  if (Symbolized == nullptr)
3127  Symbolized = createUnknownExpression(I);
3128  performCongruenceFinding(I, Symbolized);
3129  } else {
3130  // Handle terminators that return values. All of them produce values we
3131  // don't currently understand. We don't place non-value producing
3132  // terminators in a class.
3133  if (!I->getType()->isVoidTy()) {
3134  auto *Symbolized = createUnknownExpression(I);
3135  performCongruenceFinding(I, Symbolized);
3136  }
3137  processOutgoingEdges(dyn_cast<TerminatorInst>(I), I->getParent());
3138  }
3139 }
3140 
3141 // Check if there is a path, using single or equal argument phi nodes, from
3142 // First to Second.
3143 bool NewGVN::singleReachablePHIPath(
3144  SmallPtrSet<const MemoryAccess *, 8> &Visited, const MemoryAccess *First,
3145  const MemoryAccess *Second) const {
3146  if (First == Second)
3147  return true;
3148  if (MSSA->isLiveOnEntryDef(First))
3149  return false;
3150 
3151  // This is not perfect, but as we're just verifying here, we can live with
3152  // the loss of precision. The real solution would be that of doing strongly
3153  // connected component finding in this routine, and it's probably not worth
3154  // the complexity for the time being. So, we just keep a set of visited
3155  // MemoryAccess and return true when we hit a cycle.
3156  if (Visited.count(First))
3157  return true;
3158  Visited.insert(First);
3159 
3160  const auto *EndDef = First;
3161  for (auto *ChainDef : optimized_def_chain(First)) {
3162  if (ChainDef == Second)
3163  return true;
3164  if (MSSA->isLiveOnEntryDef(ChainDef))
3165  return false;
3166  EndDef = ChainDef;
3167  }
3168  auto *MP = cast<MemoryPhi>(EndDef);
3169  auto ReachableOperandPred = [&](const Use &U) {
3170  return ReachableEdges.count({MP->getIncomingBlock(U), MP->getBlock()});
3171  };
3172  auto FilteredPhiArgs =
3173  make_filter_range(MP->operands(), ReachableOperandPred);
3174  SmallVector<const Value *, 32> OperandList;
3175  std::copy(FilteredPhiArgs.begin(), FilteredPhiArgs.end(),
3176  std::back_inserter(OperandList));
3177  bool Okay = OperandList.size() == 1;
3178  if (!Okay)
3179  Okay =
3180  std::equal(OperandList.begin(), OperandList.end(), OperandList.begin());
3181  if (Okay)
3182  return singleReachablePHIPath(Visited, cast<MemoryAccess>(OperandList[0]),
3183  Second);
3184  return false;
3185 }
3186 
3187 // Verify the that the memory equivalence table makes sense relative to the
3188 // congruence classes. Note that this checking is not perfect, and is currently
3189 // subject to very rare false negatives. It is only useful for
3190 // testing/debugging.
3191 void NewGVN::verifyMemoryCongruency() const {
3192 #ifndef NDEBUG
3193  // Verify that the memory table equivalence and memory member set match
3194  for (const auto *CC : CongruenceClasses) {
3195  if (CC == TOPClass || CC->isDead())
3196  continue;
3197  if (CC->getStoreCount() != 0) {
3198  assert((CC->getStoredValue() || !isa<StoreInst>(CC->getLeader())) &&
3199  "Any class with a store as a leader should have a "
3200  "representative stored value");
3201  assert(CC->getMemoryLeader() &&
3202  "Any congruence class with a store should have a "
3203  "representative access");
3204  }
3205 
3206  if (CC->getMemoryLeader())
3207  assert(MemoryAccessToClass.lookup(CC->getMemoryLeader()) == CC &&
3208  "Representative MemoryAccess does not appear to be reverse "
3209  "mapped properly");
3210  for (auto M : CC->memory())
3211  assert(MemoryAccessToClass.lookup(M) == CC &&
3212  "Memory member does not appear to be reverse mapped properly");
3213  }
3214 
3215  // Anything equivalent in the MemoryAccess table should be in the same
3216  // congruence class.
3217 
3218  // Filter out the unreachable and trivially dead entries, because they may
3219  // never have been updated if the instructions were not processed.
3220  auto ReachableAccessPred =
3221  [&](const std::pair<const MemoryAccess *, CongruenceClass *> Pair) {
3222  bool Result = ReachableBlocks.count(Pair.first->getBlock());
3223  if (!Result || MSSA->isLiveOnEntryDef(Pair.first) ||
3224  MemoryToDFSNum(Pair.first) == 0)
3225  return false;
3226  if (auto *MemDef = dyn_cast<MemoryDef>(Pair.first))
3227  return !isInstructionTriviallyDead(MemDef->getMemoryInst());
3228 
3229  // We could have phi nodes which operands are all trivially dead,
3230  // so we don't process them.
3231  if (auto *MemPHI = dyn_cast<MemoryPhi>(Pair.first)) {
3232  for (auto &U : MemPHI->incoming_values()) {
3233  if (auto *I = dyn_cast<Instruction>(&*U)) {
3235  return true;
3236  }
3237  }
3238  return false;
3239  }
3240 
3241  return true;
3242  };
3243 
3244  auto Filtered = make_filter_range(MemoryAccessToClass, ReachableAccessPred);
3245  for (auto KV : Filtered) {
3246  if (auto *FirstMUD = dyn_cast<MemoryUseOrDef>(KV.first)) {
3247  auto *SecondMUD = dyn_cast<MemoryUseOrDef>(KV.second->getMemoryLeader());
3248  if (FirstMUD && SecondMUD) {
3250  assert((singleReachablePHIPath(VisitedMAS, FirstMUD, SecondMUD) ||
3251  ValueToClass.lookup(FirstMUD->getMemoryInst()) ==
3252  ValueToClass.lookup(SecondMUD->getMemoryInst())) &&
3253  "The instructions for these memory operations should have "
3254  "been in the same congruence class or reachable through"
3255  "a single argument phi");
3256  }
3257  } else if (auto *FirstMP = dyn_cast<MemoryPhi>(KV.first)) {
3258  // We can only sanely verify that MemoryDefs in the operand list all have
3259  // the same class.
3260  auto ReachableOperandPred = [&](const Use &U) {
3261  return ReachableEdges.count(
3262  {FirstMP->getIncomingBlock(U), FirstMP->getBlock()}) &&
3263  isa<MemoryDef>(U);
3264 
3265  };
3266  // All arguments should in the same class, ignoring unreachable arguments
3267  auto FilteredPhiArgs =
3268  make_filter_range(FirstMP->operands(), ReachableOperandPred);
3270  std::transform(FilteredPhiArgs.begin(), FilteredPhiArgs.end(),
3271  std::back_inserter(PhiOpClasses), [&](const Use &U) {
3272  const MemoryDef *MD = cast<MemoryDef>(U);
3273  return ValueToClass.lookup(MD->getMemoryInst());
3274  });
3275  assert(std::equal(PhiOpClasses.begin(), PhiOpClasses.end(),
3276  PhiOpClasses.begin()) &&
3277  "All MemoryPhi arguments should be in the same class");
3278  }
3279  }
3280 #endif
3281 }
3282 
3283 // Verify that the sparse propagation we did actually found the maximal fixpoint
3284 // We do this by storing the value to class mapping, touching all instructions,
3285 // and redoing the iteration to see if anything changed.
3286 void NewGVN::verifyIterationSettled(Function &F) {
3287 #ifndef NDEBUG
3288  LLVM_DEBUG(dbgs() << "Beginning iteration verification\n");
3289  if (DebugCounter::isCounterSet(VNCounter))
3290  DebugCounter::setCounterValue(VNCounter, StartingVNCounter);
3291 
3292  // Note that we have to store the actual classes, as we may change existing
3293  // classes during iteration. This is because our memory iteration propagation
3294  // is not perfect, and so may waste a little work. But it should generate
3295  // exactly the same congruence classes we have now, with different IDs.
3296  std::map<const Value *, CongruenceClass> BeforeIteration;
3297 
3298  for (auto &KV : ValueToClass) {
3299  if (auto *I = dyn_cast<Instruction>(KV.first))
3300  // Skip unused/dead instructions.
3301  if (InstrToDFSNum(I) == 0)
3302  continue;
3303  BeforeIteration.insert({KV.first, *KV.second});
3304  }
3305 
3306  TouchedInstructions.set();
3307  TouchedInstructions.reset(0);
3308  iterateTouchedInstructions();
3310  EqualClasses;
3311  for (const auto &KV : ValueToClass) {
3312  if (auto *I = dyn_cast<Instruction>(KV.first))
3313  // Skip unused/dead instructions.
3314  if (InstrToDFSNum(I) == 0)
3315  continue;
3316  // We could sink these uses, but i think this adds a bit of clarity here as
3317  // to what we are comparing.
3318  auto *BeforeCC = &BeforeIteration.find(KV.first)->second;
3319  auto *AfterCC = KV.second;
3320  // Note that the classes can't change at this point, so we memoize the set
3321  // that are equal.
3322  if (!EqualClasses.count({BeforeCC, AfterCC})) {
3323  assert(BeforeCC->isEquivalentTo(AfterCC) &&
3324  "Value number changed after main loop completed!");
3325  EqualClasses.insert({BeforeCC, AfterCC});
3326  }
3327  }
3328 #endif
3329 }
3330 
3331 // Verify that for each store expression in the expression to class mapping,
3332 // only the latest appears, and multiple ones do not appear.
3333 // Because loads do not use the stored value when doing equality with stores,
3334 // if we don't erase the old store expressions from the table, a load can find
3335 // a no-longer valid StoreExpression.
3336 void NewGVN::verifyStoreExpressions() const {
3337 #ifndef NDEBUG
3338  // This is the only use of this, and it's not worth defining a complicated
3339  // densemapinfo hash/equality function for it.
3340  std::set<
3341  std::pair<const Value *,
3342  std::tuple<const Value *, const CongruenceClass *, Value *>>>
3343  StoreExpressionSet;
3344  for (const auto &KV : ExpressionToClass) {
3345  if (auto *SE = dyn_cast<StoreExpression>(KV.first)) {
3346  // Make sure a version that will conflict with loads is not already there
3347  auto Res = StoreExpressionSet.insert(
3348  {SE->getOperand(0), std::make_tuple(SE->getMemoryLeader(), KV.second,
3349  SE->getStoredValue())});
3350  bool Okay = Res.second;
3351  // It's okay to have the same expression already in there if it is
3352  // identical in nature.
3353  // This can happen when the leader of the stored value changes over time.
3354  if (!Okay)
3355  Okay = (std::get<1>(Res.first->second) == KV.second) &&
3356  (lookupOperandLeader(std::get<2>(Res.first->second)) ==
3357  lookupOperandLeader(SE->getStoredValue()));
3358  assert(Okay && "Stored expression conflict exists in expression table");
3359  auto *ValueExpr = ValueToExpression.lookup(SE->getStoreInst());
3360  assert(ValueExpr && ValueExpr->equals(*SE) &&
3361  "StoreExpression in ExpressionToClass is not latest "
3362  "StoreExpression for value");
3363  }
3364  }
3365 #endif
3366 }
3367 
3368 // This is the main value numbering loop, it iterates over the initial touched
3369 // instruction set, propagating value numbers, marking things touched, etc,
3370 // until the set of touched instructions is completely empty.
3371 void NewGVN::iterateTouchedInstructions() {
3372  unsigned int Iterations = 0;
3373  // Figure out where touchedinstructions starts
3374  int FirstInstr = TouchedInstructions.find_first();
3375  // Nothing set, nothing to iterate, just return.
3376  if (FirstInstr == -1)
3377  return;
3378  const BasicBlock *LastBlock = getBlockForValue(InstrFromDFSNum(FirstInstr));
3379  while (TouchedInstructions.any()) {
3380  ++Iterations;
3381  // Walk through all the instructions in all the blocks in RPO.
3382  // TODO: As we hit a new block, we should push and pop equalities into a
3383  // table lookupOperandLeader can use, to catch things PredicateInfo
3384  // might miss, like edge-only equivalences.
3385  for (unsigned InstrNum : TouchedInstructions.set_bits()) {
3386 
3387  // This instruction was found to be dead. We don't bother looking
3388  // at it again.
3389  if (InstrNum == 0) {
3390  TouchedInstructions.reset(InstrNum);
3391  continue;
3392  }
3393 
3394  Value *V = InstrFromDFSNum(InstrNum);
3395  const BasicBlock *CurrBlock = getBlockForValue(V);
3396 
3397  // If we hit a new block, do reachability processing.
3398  if (CurrBlock != LastBlock) {
3399  LastBlock = CurrBlock;
3400  bool BlockReachable = ReachableBlocks.count(CurrBlock);
3401  const auto &CurrInstRange = BlockInstRange.lookup(CurrBlock);
3402 
3403  // If it's not reachable, erase any touched instructions and move on.
3404  if (!BlockReachable) {
3405  TouchedInstructions.reset(CurrInstRange.first, CurrInstRange.second);
3406  LLVM_DEBUG(dbgs() << "Skipping instructions in block "
3407  << getBlockName(CurrBlock)
3408  << " because it is unreachable\n");
3409  continue;
3410  }
3411  updateProcessedCount(CurrBlock);
3412  }
3413  // Reset after processing (because we may mark ourselves as touched when
3414  // we propagate equalities).
3415  TouchedInstructions.reset(InstrNum);
3416 
3417  if (auto *MP = dyn_cast<MemoryPhi>(V)) {
3418  LLVM_DEBUG(dbgs() << "Processing MemoryPhi " << *MP << "\n");
3419  valueNumberMemoryPhi(MP);
3420  } else if (auto *I = dyn_cast<Instruction>(V)) {
3421  valueNumberInstruction(I);
3422  } else {
3423  llvm_unreachable("Should have been a MemoryPhi or Instruction");
3424  }
3425  updateProcessedCount(V);
3426  }
3427  }
3428  NumGVNMaxIterations = std::max(NumGVNMaxIterations.getValue(), Iterations);
3429 }
3430 
3431 // This is the main transformation entry point.
3432 bool NewGVN::runGVN() {
3433  if (DebugCounter::isCounterSet(VNCounter))
3434  StartingVNCounter = DebugCounter::getCounterValue(VNCounter);
3435  bool Changed = false;
3436  NumFuncArgs = F.arg_size();
3437  MSSAWalker = MSSA->getWalker();
3438  SingletonDeadExpression = new (ExpressionAllocator) DeadExpression();
3439 
3440  // Count number of instructions for sizing of hash tables, and come
3441  // up with a global dfs numbering for instructions.
3442  unsigned ICount = 1;
3443  // Add an empty instruction to account for the fact that we start at 1
3444  DFSToInstr.emplace_back(nullptr);
3445  // Note: We want ideal RPO traversal of the blocks, which is not quite the
3446  // same as dominator tree order, particularly with regard whether backedges
3447  // get visited first or second, given a block with multiple successors.
3448  // If we visit in the wrong order, we will end up performing N times as many
3449  // iterations.
3450  // The dominator tree does guarantee that, for a given dom tree node, it's
3451  // parent must occur before it in the RPO ordering. Thus, we only need to sort
3452  // the siblings.
3454  unsigned Counter = 0;
3455  for (auto &B : RPOT) {
3456  auto *Node = DT->getNode(B);
3457  assert(Node && "RPO and Dominator tree should have same reachability");
3458  RPOOrdering[Node] = ++Counter;
3459  }
3460  // Sort dominator tree children arrays into RPO.
3461  for (auto &B : RPOT) {
3462  auto *Node = DT->getNode(B);
3463  if (Node->getChildren().size() > 1)
3464  llvm::sort(Node->begin(), Node->end(),
3465  [&](const DomTreeNode *A, const DomTreeNode *B) {
3466  return RPOOrdering[A] < RPOOrdering[B];
3467  });
3468  }
3469 
3470  // Now a standard depth first ordering of the domtree is equivalent to RPO.
3471  for (auto DTN : depth_first(DT->getRootNode())) {
3472  BasicBlock *B = DTN->getBlock();
3473  const auto &BlockRange = assignDFSNumbers(B, ICount);
3474  BlockInstRange.insert({B, BlockRange});
3475  ICount += BlockRange.second - BlockRange.first;
3476  }
3477  initializeCongruenceClasses(F);
3478 
3479  TouchedInstructions.resize(ICount);
3480  // Ensure we don't end up resizing the expressionToClass map, as
3481  // that can be quite expensive. At most, we have one expression per
3482  // instruction.
3483  ExpressionToClass.reserve(ICount);
3484 
3485  // Initialize the touched instructions to include the entry block.
3486  const auto &InstRange = BlockInstRange.lookup(&F.getEntryBlock());
3487  TouchedInstructions.set(InstRange.first, InstRange.second);
3488  LLVM_DEBUG(dbgs() << "Block " << getBlockName(&F.getEntryBlock())
3489  << " marked reachable\n");
3490  ReachableBlocks.insert(&F.getEntryBlock());
3491 
3492  iterateTouchedInstructions();
3493  verifyMemoryCongruency();
3494  verifyIterationSettled(F);
3495  verifyStoreExpressions();
3496 
3497  Changed |= eliminateInstructions(F);
3498 
3499  // Delete all instructions marked for deletion.
3500  for (Instruction *ToErase : InstructionsToErase) {
3501  if (!ToErase->use_empty())
3502  ToErase->replaceAllUsesWith(UndefValue::get(ToErase->getType()));
3503 
3504  if (ToErase->getParent())
3505  ToErase->eraseFromParent();
3506  }
3507 
3508  // Delete all unreachable blocks.
3509  auto UnreachableBlockPred = [&](const BasicBlock &BB) {
3510  return !ReachableBlocks.count(&BB);
3511  };
3512 
3513  for (auto &BB : make_filter_range(F, UnreachableBlockPred)) {
3514  LLVM_DEBUG(dbgs() << "We believe block " << getBlockName(&BB)
3515  << " is unreachable\n");
3516  deleteInstructionsInBlock(&BB);
3517  Changed = true;
3518  }
3519 
3520  cleanupTables();
3521  return Changed;
3522 }
3523 
3525  int DFSIn = 0;
3526  int DFSOut = 0;
3527  int LocalNum = 0;
3528 
3529  // Only one of Def and U will be set.
3530  // The bool in the Def tells us whether the Def is the stored value of a
3531  // store.
3533  Use *U = nullptr;
3534 
3535  bool operator<(const ValueDFS &Other) const {
3536  // It's not enough that any given field be less than - we have sets
3537  // of fields that need to be evaluated together to give a proper ordering.
3538  // For example, if you have;
3539  // DFS (1, 3)
3540  // Val 0
3541  // DFS (1, 2)
3542  // Val 50
3543  // We want the second to be less than the first, but if we just go field
3544  // by field, we will get to Val 0 < Val 50 and say the first is less than
3545  // the second. We only want it to be less than if the DFS orders are equal.
3546  //
3547  // Each LLVM instruction only produces one value, and thus the lowest-level
3548  // differentiator that really matters for the stack (and what we use as as a
3549  // replacement) is the local dfs number.
3550  // Everything else in the structure is instruction level, and only affects
3551  // the order in which we will replace operands of a given instruction.
3552  //
3553  // For a given instruction (IE things with equal dfsin, dfsout, localnum),
3554  // the order of replacement of uses does not matter.
3555  // IE given,
3556  // a = 5
3557  // b = a + a
3558  // When you hit b, you will have two valuedfs with the same dfsin, out, and
3559  // localnum.
3560  // The .val will be the same as well.
3561  // The .u's will be different.
3562  // You will replace both, and it does not matter what order you replace them
3563  // in (IE whether you replace operand 2, then operand 1, or operand 1, then
3564  // operand 2).
3565  // Similarly for the case of same dfsin, dfsout, localnum, but different
3566  // .val's
3567  // a = 5
3568  // b = 6
3569  // c = a + b
3570  // in c, we will a valuedfs for a, and one for b,with everything the same
3571  // but .val and .u.
3572  // It does not matter what order we replace these operands in.
3573  // You will always end up with the same IR, and this is guaranteed.
3574  return std::tie(DFSIn, DFSOut, LocalNum, Def, U) <
3575  std::tie(Other.DFSIn, Other.DFSOut, Other.LocalNum, Other.Def,
3576  Other.U);
3577  }
3578 };
3579 
3580 // This function converts the set of members for a congruence class from values,
3581 // to sets of defs and uses with associated DFS info. The total number of
3582 // reachable uses for each value is stored in UseCount, and instructions that
3583 // seem
3584 // dead (have no non-dead uses) are stored in ProbablyDead.
3585 void NewGVN::convertClassToDFSOrdered(
3586  const CongruenceClass &Dense, SmallVectorImpl<ValueDFS> &DFSOrderedSet,
3588  SmallPtrSetImpl<Instruction *> &ProbablyDead) const {
3589  for (auto D : Dense) {
3590  // First add the value.
3591  BasicBlock *BB = getBlockForValue(D);
3592  // Constants are handled prior to ever calling this function, so
3593  // we should only be left with instructions as members.
3594  assert(BB && "Should have figured out a basic block for value");
3595  ValueDFS VDDef;
3596  DomTreeNode *DomNode = DT->getNode(BB);
3597  VDDef.DFSIn = DomNode->getDFSNumIn();
3598  VDDef.DFSOut = DomNode->getDFSNumOut();
3599  // If it's a store, use the leader of the value operand, if it's always
3600  // available, or the value operand. TODO: We could do dominance checks to
3601  // find a dominating leader, but not worth it ATM.
3602  if (auto *SI = dyn_cast<StoreInst>(D)) {
3603  auto Leader = lookupOperandLeader(SI->getValueOperand());
3604  if (alwaysAvailable(Leader)) {
3605  VDDef.Def.setPointer(Leader);
3606  } else {
3607  VDDef.Def.setPointer(SI->getValueOperand());
3608  VDDef.Def.setInt(true);
3609  }
3610  } else {
3611  VDDef.Def.setPointer(D);
3612  }
3613  assert(isa<Instruction>(D) &&
3614  "The dense set member should always be an instruction");
3615  Instruction *Def = cast<Instruction>(D);
3616  VDDef.LocalNum = InstrToDFSNum(D);
3617  DFSOrderedSet.push_back(VDDef);
3618  // If there is a phi node equivalent, add it
3619  if (auto *PN = RealToTemp.lookup(Def)) {
3620  auto *PHIE =
3621  dyn_cast_or_null<PHIExpression>(ValueToExpression.lookup(Def));
3622  if (PHIE) {
3623  VDDef.Def.setInt(false);
3624  VDDef.Def.setPointer(PN);
3625  VDDef.LocalNum = 0;
3626  DFSOrderedSet.push_back(VDDef);
3627  }
3628  }
3629 
3630  unsigned int UseCount = 0;
3631  // Now add the uses.
3632  for (auto &U : Def->uses()) {
3633  if (auto *I = dyn_cast<Instruction>(U.getUser())) {
3634  // Don't try to replace into dead uses
3635  if (InstructionsToErase.count(I))
3636  continue;
3637  ValueDFS VDUse;
3638  // Put the phi node uses in the incoming block.
3639  BasicBlock *IBlock;
3640  if (auto *P = dyn_cast<PHINode>(I)) {
3641  IBlock = P->getIncomingBlock(U);
3642  // Make phi node users appear last in the incoming block
3643  // they are from.
3644  VDUse.LocalNum = InstrDFS.size() + 1;
3645  } else {
3646  IBlock = getBlockForValue(I);
3647  VDUse.LocalNum = InstrToDFSNum(I);
3648  }
3649 
3650  // Skip uses in unreachable blocks, as we're going
3651  // to delete them.
3652  if (ReachableBlocks.count(IBlock) == 0)
3653  continue;
3654 
3655  DomTreeNode *DomNode = DT->getNode(IBlock);
3656  VDUse.DFSIn = DomNode->getDFSNumIn();
3657  VDUse.DFSOut = DomNode->getDFSNumOut();
3658  VDUse.U = &U;
3659  ++UseCount;
3660  DFSOrderedSet.emplace_back(VDUse);
3661  }
3662  }
3663 
3664  // If there are no uses, it's probably dead (but it may have side-effects,
3665  // so not definitely dead. Otherwise, store the number of uses so we can
3666  // track if it becomes dead later).
3667  if (UseCount == 0)
3668  ProbablyDead.insert(Def);
3669  else
3670  UseCounts[Def] = UseCount;
3671  }
3672 }
3673 
3674 // This function converts the set of members for a congruence class from values,
3675 // to the set of defs for loads and stores, with associated DFS info.
3676 void NewGVN::convertClassToLoadsAndStores(
3677  const CongruenceClass &Dense,
3678  SmallVectorImpl<ValueDFS> &LoadsAndStores) const {
3679  for (auto D : Dense) {
3680  if (!isa<LoadInst>(D) && !isa<StoreInst>(D))
3681  continue;
3682 
3683  BasicBlock *BB = getBlockForValue(D);
3684  ValueDFS VD;
3685  DomTreeNode *DomNode = DT->getNode(BB);
3686  VD.DFSIn = DomNode->getDFSNumIn();
3687  VD.DFSOut = DomNode->getDFSNumOut();
3688  VD.Def.setPointer(D);
3689 
3690  // If it's an instruction, use the real local dfs number.
3691  if (auto *I = dyn_cast<Instruction>(D))
3692  VD.LocalNum = InstrToDFSNum(I);
3693  else
3694  llvm_unreachable("Should have been an instruction");
3695 
3696  LoadsAndStores.emplace_back(VD);
3697  }
3698 }
3699 
3701  auto *ReplInst = dyn_cast<Instruction>(Repl);
3702  if (!ReplInst)
3703  return;
3704 
3705  // Patch the replacement so that it is not more restrictive than the value
3706  // being replaced.
3707  // Note that if 'I' is a load being replaced by some operation,
3708  // for example, by an arithmetic operation, then andIRFlags()
3709  // would just erase all math flags from the original arithmetic
3710  // operation, which is clearly not wanted and not needed.
3711  if (!isa<LoadInst>(I))
3712  ReplInst->andIRFlags(I);
3713 
3714  // FIXME: If both the original and replacement value are part of the
3715  // same control-flow region (meaning that the execution of one
3716  // guarantees the execution of the other), then we can combine the
3717  // noalias scopes here and do better than the general conservative
3718  // answer used in combineMetadata().
3719 
3720  // In general, GVN unifies expressions over different control-flow
3721  // regions, and so we need a conservative combination of the noalias
3722  // scopes.
3723  static const unsigned KnownIDs[] = {
3728  combineMetadata(ReplInst, I, KnownIDs);
3729 }
3730 
3732  patchReplacementInstruction(I, Repl);
3733  I->replaceAllUsesWith(Repl);
3734 }
3735 
3736 void NewGVN::deleteInstructionsInBlock(BasicBlock *BB) {
3737  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
3738  ++NumGVNBlocksDeleted;
3739 
3740  // Delete the instructions backwards, as it has a reduced likelihood of having
3741  // to update as many def-use and use-def chains. Start after the terminator.
3742  auto StartPoint = BB->rbegin();
3743  ++StartPoint;
3744  // Note that we explicitly recalculate BB->rend() on each iteration,
3745  // as it may change when we remove the first instruction.
3746  for (BasicBlock::reverse_iterator I(StartPoint); I != BB->rend();) {
3747  Instruction &Inst = *I++;
3748  if (!Inst.use_empty())
3750  if (isa<LandingPadInst>(Inst))
3751  continue;
3752 
3753  Inst.eraseFromParent();
3754  ++NumGVNInstrDeleted;
3755  }
3756  // Now insert something that simplifycfg will turn into an unreachable.
3757  Type *Int8Ty = Type::getInt8Ty(BB->getContext());
3758  new StoreInst(UndefValue::get(Int8Ty),
3760  BB->getTerminator());
3761 }
3762 
3763 void NewGVN::markInstructionForDeletion(Instruction *I) {
3764  LLVM_DEBUG(dbgs() << "Marking " << *I << " for deletion\n");
3765  InstructionsToErase.insert(I);
3766 }
3767 
3768 void NewGVN::replaceInstruction(Instruction *I, Value *V) {
3769  LLVM_DEBUG(dbgs() << "Replacing " << *I << " with " << *V << "\n");
3771  // We save the actual erasing to avoid invalidating memory
3772  // dependencies until we are done with everything.
3773  markInstructionForDeletion(I);
3774 }
3775 
3776 namespace {
3777 
3778 // This is a stack that contains both the value and dfs info of where
3779 // that value is valid.
3780 class ValueDFSStack {
3781 public:
3782  Value *back() const { return ValueStack.back(); }
3783  std::pair<int, int> dfs_back() const { return DFSStack.back(); }
3784 
3785  void push_back(Value *V, int DFSIn, int DFSOut) {
3786  ValueStack.emplace_back(V);
3787  DFSStack.emplace_back(DFSIn, DFSOut);
3788  }
3789 
3790  bool empty() const { return DFSStack.empty(); }
3791 
3792  bool isInScope(int DFSIn, int DFSOut) const {
3793  if (empty())
3794  return false;
3795  return DFSIn >= DFSStack.back().first && DFSOut <= DFSStack.back().second;
3796  }
3797 
3798  void popUntilDFSScope(int DFSIn, int DFSOut) {
3799 
3800  // These two should always be in sync at this point.
3801  assert(ValueStack.size() == DFSStack.size() &&
3802  "Mismatch between ValueStack and DFSStack");
3803  while (
3804  !DFSStack.empty() &&
3805  !(DFSIn >= DFSStack.back().first && DFSOut <= DFSStack.back().second)) {
3806  DFSStack.pop_back();
3807  ValueStack.pop_back();
3808  }
3809  }
3810 
3811 private:
3812  SmallVector<Value *, 8> ValueStack;
3813  SmallVector<std::pair<int, int>, 8> DFSStack;
3814 };
3815 
3816 } // end anonymous namespace
3817 
3818 // Given an expression, get the congruence class for it.
3819 CongruenceClass *NewGVN::getClassForExpression(const Expression *E) const {
3820  if (auto *VE = dyn_cast<VariableExpression>(E))
3821  return ValueToClass.lookup(VE->getVariableValue());
3822  else if (isa<DeadExpression>(E))
3823  return TOPClass;
3824  return ExpressionToClass.lookup(E);
3825 }
3826 
3827 // Given a value and a basic block we are trying to see if it is available in,
3828 // see if the value has a leader available in that block.
3829 Value *NewGVN::findPHIOfOpsLeader(const Expression *E,
3830  const Instruction *OrigInst,
3831  const BasicBlock *BB) const {
3832  // It would already be constant if we could make it constant
3833  if (auto *CE = dyn_cast<ConstantExpression>(E))
3834  return CE->getConstantValue();
3835  if (auto *VE = dyn_cast<VariableExpression>(E)) {
3836  auto *V = VE->getVariableValue();
3837  if (alwaysAvailable(V) || DT->dominates(getBlockForValue(V), BB))
3838  return VE->getVariableValue();
3839  }
3840 
3841  auto *CC = getClassForExpression(E);
3842  if (!CC)
3843  return nullptr;
3844  if (alwaysAvailable(CC->getLeader()))
3845  return CC->getLeader();
3846 
3847  for (auto Member : *CC) {
3848  auto *MemberInst = dyn_cast<Instruction>(Member);
3849  if (MemberInst == OrigInst)
3850  continue;
3851  // Anything that isn't an instruction is always available.
3852  if (!MemberInst)
3853  return Member;
3854  if (DT->dominates(getBlockForValue(MemberInst), BB))
3855  return Member;
3856  }
3857  return nullptr;
3858 }
3859 
3860 bool NewGVN::eliminateInstructions(Function &F) {
3861  // This is a non-standard eliminator. The normal way to eliminate is
3862  // to walk the dominator tree in order, keeping track of available
3863  // values, and eliminating them. However, this is mildly
3864  // pointless. It requires doing lookups on every instruction,
3865  // regardless of whether we will ever eliminate it. For
3866  // instructions part of most singleton congruence classes, we know we
3867  // will never eliminate them.
3868 
3869  // Instead, this eliminator looks at the congruence classes directly, sorts
3870  // them into a DFS ordering of the dominator tree, and then we just
3871  // perform elimination straight on the sets by walking the congruence
3872  // class member uses in order, and eliminate the ones dominated by the
3873  // last member. This is worst case O(E log E) where E = number of
3874  // instructions in a single congruence class. In theory, this is all
3875  // instructions. In practice, it is much faster, as most instructions are
3876  // either in singleton congruence classes or can't possibly be eliminated
3877  // anyway (if there are no overlapping DFS ranges in class).
3878  // When we find something not dominated, it becomes the new leader
3879  // for elimination purposes.
3880  // TODO: If we wanted to be faster, We could remove any members with no
3881  // overlapping ranges while sorting, as we will never eliminate anything
3882  // with those members, as they don't dominate anything else in our set.
3883 
3884  bool AnythingReplaced = false;
3885 
3886  // Since we are going to walk the domtree anyway, and we can't guarantee the
3887  // DFS numbers are updated, we compute some ourselves.
3888  DT->updateDFSNumbers();
3889 
3890  // Go through all of our phi nodes, and kill the arguments associated with
3891  // unreachable edges.
3892  auto ReplaceUnreachablePHIArgs = [&](PHINode *PHI, BasicBlock *BB) {
3893  for (auto &Operand : PHI->incoming_values())
3894  if (!ReachableEdges.count({PHI->getIncomingBlock(Operand), BB})) {
3895  LLVM_DEBUG(dbgs() << "Replacing incoming value of " << PHI
3896  << " for block "
3897  << getBlockName(PHI->getIncomingBlock(Operand))
3898  << " with undef due to it being unreachable\n");
3899  Operand.set(UndefValue::get(PHI->getType()));
3900  }
3901  };
3902  // Replace unreachable phi arguments.
3903  // At this point, RevisitOnReachabilityChange only contains:
3904  //
3905  // 1. PHIs
3906  // 2. Temporaries that will convert to PHIs
3907  // 3. Operations that are affected by an unreachable edge but do not fit into
3908  // 1 or 2 (rare).
3909  // So it is a slight overshoot of what we want. We could make it exact by
3910  // using two SparseBitVectors per block.
3911  DenseMap<const BasicBlock *, unsigned> ReachablePredCount;
3912  for (auto &KV : ReachableEdges)
3913  ReachablePredCount[KV.getEnd()]++;
3914  for (auto &BBPair : RevisitOnReachabilityChange) {
3915  for (auto InstNum : BBPair.second) {
3916  auto *Inst = InstrFromDFSNum(InstNum);
3917  auto *PHI = dyn_cast<PHINode>(Inst);
3918  PHI = PHI ? PHI : dyn_cast_or_null<PHINode>(RealToTemp.lookup(Inst));
3919  if (!PHI)
3920  continue;
3921  auto *BB = BBPair.first;
3922  if (ReachablePredCount.lookup(BB) != PHI->getNumIncomingValues())
3923  ReplaceUnreachablePHIArgs(PHI, BB);
3924  }
3925  }
3926 
3927  // Map to store the use counts
3929  for (auto *CC : reverse(CongruenceClasses)) {
3930  LLVM_DEBUG(dbgs() << "Eliminating in congruence class " << CC->getID()
3931  << "\n");
3932  // Track the equivalent store info so we can decide whether to try
3933  // dead store elimination.
3934  SmallVector<ValueDFS, 8> PossibleDeadStores;
3935  SmallPtrSet<Instruction *, 8> ProbablyDead;
3936  if (CC->isDead() || CC->empty())
3937  continue;
3938  // Everything still in the TOP class is unreachable or dead.
3939  if (CC == TOPClass) {
3940  for (auto M : *CC) {
3941  auto *VTE = ValueToExpression.lookup(M);
3942  if (VTE && isa<DeadExpression>(VTE))
3943  markInstructionForDeletion(cast<Instruction>(M));
3944  assert((!ReachableBlocks.count(cast<Instruction>(M)->getParent()) ||
3945  InstructionsToErase.count(cast<Instruction>(M))) &&
3946  "Everything in TOP should be unreachable or dead at this "
3947  "point");
3948  }
3949  continue;
3950  }
3951 
3952  assert(CC->getLeader() && "We should have had a leader");
3953  // If this is a leader that is always available, and it's a
3954  // constant or has no equivalences, just replace everything with
3955  // it. We then update the congruence class with whatever members
3956  // are left.
3957  Value *Leader =
3958  CC->getStoredValue() ? CC->getStoredValue() : CC->getLeader();
3959  if (alwaysAvailable(Leader)) {
3960  CongruenceClass::MemberSet MembersLeft;
3961  for (auto M : *CC) {
3962  Value *Member = M;
3963  // Void things have no uses we can replace.
3964  if (Member == Leader || !isa<Instruction>(Member) ||
3965  Member->getType()->isVoidTy()) {
3966  MembersLeft.insert(Member);
3967  continue;
3968  }
3969  LLVM_DEBUG(dbgs() << "Found replacement " << *(Leader) << " for "
3970  << *Member << "\n");
3971  auto *I = cast<Instruction>(Member);
3972  assert(Leader != I && "About to accidentally remove our leader");
3973  replaceInstruction(I, Leader);
3974  AnythingReplaced = true;
3975  }
3976  CC->swap(MembersLeft);
3977  } else {
3978  // If this is a singleton, we can skip it.
3979  if (CC->size() != 1 || RealToTemp.count(Leader)) {
3980  // This is a stack because equality replacement/etc may place
3981  // constants in the middle of the member list, and we want to use
3982  // those constant values in preference to the current leader, over
3983  // the scope of those constants.
3984  ValueDFSStack EliminationStack;
3985 
3986  // Convert the members to DFS ordered sets and then merge them.
3987  SmallVector<ValueDFS, 8> DFSOrderedSet;
3988  convertClassToDFSOrdered(*CC, DFSOrderedSet, UseCounts, ProbablyDead);
3989 
3990  // Sort the whole thing.
3991  llvm::sort(DFSOrderedSet.begin(), DFSOrderedSet.end());
3992  for (auto &VD : DFSOrderedSet) {
3993  int MemberDFSIn = VD.DFSIn;
3994  int MemberDFSOut = VD.DFSOut;
3995  Value *Def = VD.Def.getPointer();
3996  bool FromStore = VD.Def.getInt();
3997  Use *U = VD.U;
3998  // We ignore void things because we can't get a value from them.
3999  if (Def && Def->getType()->isVoidTy())
4000  continue;
4001  auto *DefInst = dyn_cast_or_null<Instruction>(Def);
4002  if (DefInst && AllTempInstructions.count(DefInst)) {
4003  auto *PN = cast<PHINode>(DefInst);
4004 
4005  // If this is a value phi and that's the expression we used, insert
4006  // it into the program
4007  // remove from temp instruction list.
4008  AllTempInstructions.erase(PN);
4009  auto *DefBlock = getBlockForValue(Def);
4010  LLVM_DEBUG(dbgs() << "Inserting fully real phi of ops" << *Def
4011  << " into block "
4012  << getBlockName(getBlockForValue(Def)) << "\n");
4013  PN->insertBefore(&DefBlock->front());
4014  Def = PN;
4015  NumGVNPHIOfOpsEliminations++;
4016  }
4017 
4018  if (EliminationStack.empty()) {
4019  LLVM_DEBUG(dbgs() << "Elimination Stack is empty\n");
4020  } else {
4021  LLVM_DEBUG(dbgs() << "Elimination Stack Top DFS numbers are ("
4022  << EliminationStack.dfs_back().first << ","
4023  << EliminationStack.dfs_back().second << ")\n");
4024  }
4025 
4026  LLVM_DEBUG(dbgs() << "Current DFS numbers are (" << MemberDFSIn << ","
4027  << MemberDFSOut << ")\n");
4028  // First, we see if we are out of scope or empty. If so,
4029  // and there equivalences, we try to replace the top of
4030  // stack with equivalences (if it's on the stack, it must
4031  // not have been eliminated yet).
4032  // Then we synchronize to our current scope, by
4033  // popping until we are back within a DFS scope that
4034  // dominates the current member.
4035  // Then, what happens depends on a few factors
4036  // If the stack is now empty, we need to push
4037  // If we have a constant or a local equivalence we want to
4038  // start using, we also push.
4039  // Otherwise, we walk along, processing members who are
4040  // dominated by this scope, and eliminate them.
4041  bool ShouldPush = Def && EliminationStack.empty();
4042  bool OutOfScope =
4043  !EliminationStack.isInScope(MemberDFSIn, MemberDFSOut);
4044 
4045  if (OutOfScope || ShouldPush) {
4046  // Sync to our current scope.
4047  EliminationStack.popUntilDFSScope(MemberDFSIn, MemberDFSOut);
4048  bool ShouldPush = Def && EliminationStack.empty();
4049  if (ShouldPush) {
4050  EliminationStack.push_back(Def, MemberDFSIn, MemberDFSOut);
4051  }
4052  }
4053 
4054  // Skip the Def's, we only want to eliminate on their uses. But mark
4055  // dominated defs as dead.
4056  if (Def) {
4057  // For anything in this case, what and how we value number
4058  // guarantees that any side-effets that would have occurred (ie
4059  // throwing, etc) can be proven to either still occur (because it's
4060  // dominated by something that has the same side-effects), or never
4061  // occur. Otherwise, we would not have been able to prove it value
4062  // equivalent to something else. For these things, we can just mark
4063  // it all dead. Note that this is different from the "ProbablyDead"
4064  // set, which may not be dominated by anything, and thus, are only
4065  // easy to prove dead if they are also side-effect free. Note that
4066  // because stores are put in terms of the stored value, we skip
4067  // stored values here. If the stored value is really dead, it will
4068  // still be marked for deletion when we process it in its own class.
4069  if (!EliminationStack.empty() && Def != EliminationStack.back() &&
4070  isa<Instruction>(Def) && !FromStore)
4071  markInstructionForDeletion(cast<Instruction>(Def));
4072  continue;
4073  }
4074  // At this point, we know it is a Use we are trying to possibly
4075  // replace.
4076 
4077  assert(isa<Instruction>(U->get()) &&
4078  "Current def should have been an instruction");
4079  assert(isa<Instruction>(U->getUser()) &&
4080  "Current user should have been an instruction");
4081 
4082  // If the thing we are replacing into is already marked to be dead,
4083  // this use is dead. Note that this is true regardless of whether
4084  // we have anything dominating the use or not. We do this here
4085  // because we are already walking all the uses anyway.
4086  Instruction *InstUse = cast<Instruction>(U->getUser());
4087  if (InstructionsToErase.count(InstUse)) {
4088  auto &UseCount = UseCounts[U->get()];
4089  if (--UseCount == 0) {
4090  ProbablyDead.insert(cast<Instruction>(U->get()));
4091  }
4092  }
4093 
4094  // If we get to this point, and the stack is empty we must have a use
4095  // with nothing we can use to eliminate this use, so just skip it.
4096  if (EliminationStack.empty())
4097  continue;
4098 
4099  Value *DominatingLeader = EliminationStack.back();
4100 
4101  auto *II = dyn_cast<IntrinsicInst>(DominatingLeader);
4102  bool isSSACopy = II && II->getIntrinsicID() == Intrinsic::ssa_copy;
4103  if (isSSACopy)
4104  DominatingLeader = II->getOperand(0);
4105 
4106  // Don't replace our existing users with ourselves.
4107  if (U->get() == DominatingLeader)
4108  continue;
4109  LLVM_DEBUG(dbgs()
4110  << "Found replacement " << *DominatingLeader << " for "
4111  << *U->get() << " in " << *(U->getUser()) << "\n");
4112 
4113  // If we replaced something in an instruction, handle the patching of
4114  // metadata. Skip this if we are replacing predicateinfo with its
4115  // original operand, as we already know we can just drop it.
4116  auto *ReplacedInst = cast<Instruction>(U->get());
4117  auto *PI = PredInfo->getPredicateInfoFor(ReplacedInst);
4118  if (!PI || DominatingLeader != PI->OriginalOp)
4119  patchReplacementInstruction(ReplacedInst, DominatingLeader);
4120  U->set(DominatingLeader);
4121  // This is now a use of the dominating leader, which means if the
4122  // dominating leader was dead, it's now live!
4123  auto &LeaderUseCount = UseCounts[DominatingLeader];
4124  // It's about to be alive again.
4125  if (LeaderUseCount == 0 && isa<Instruction>(DominatingLeader))
4126  ProbablyDead.erase(cast<Instruction>(DominatingLeader));
4127  // Copy instructions, however, are still dead because we use their
4128  // operand as the leader.
4129  if (LeaderUseCount == 0 && isSSACopy)
4130  ProbablyDead.insert(II);
4131  ++LeaderUseCount;
4132  AnythingReplaced = true;
4133  }
4134  }
4135  }
4136 
4137  // At this point, anything still in the ProbablyDead set is actually dead if
4138  // would be trivially dead.
4139  for (auto *I : ProbablyDead)
4141  markInstructionForDeletion(I);
4142 
4143  // Cleanup the congruence class.
4144  CongruenceClass::MemberSet MembersLeft;
4145  for (auto *Member : *CC)
4146  if (!isa<Instruction>(Member) ||
4147  !InstructionsToErase.count(cast<Instruction>(Member)))
4148  MembersLeft.insert(Member);
4149  CC->swap(MembersLeft);
4150 
4151  // If we have possible dead stores to look at, try to eliminate them.
4152  if (CC->getStoreCount() > 0) {
4153  convertClassToLoadsAndStores(*CC, PossibleDeadStores);
4154  llvm::sort(PossibleDeadStores.begin(), PossibleDeadStores.end());
4155  ValueDFSStack EliminationStack;
4156  for (auto &VD : PossibleDeadStores) {
4157  int MemberDFSIn = VD.DFSIn;
4158  int MemberDFSOut = VD.DFSOut;
4159  Instruction *Member = cast<Instruction>(VD.Def.getPointer());
4160  if (EliminationStack.empty() ||
4161  !EliminationStack.isInScope(MemberDFSIn, MemberDFSOut)) {
4162  // Sync to our current scope.
4163  EliminationStack.popUntilDFSScope(MemberDFSIn, MemberDFSOut);
4164  if (EliminationStack.empty()) {
4165  EliminationStack.push_back(Member, MemberDFSIn, MemberDFSOut);
4166  continue;
4167  }
4168  }
4169  // We already did load elimination, so nothing to do here.
4170  if (isa<LoadInst>(Member))
4171  continue;
4172  assert(!EliminationStack.empty());
4173  Instruction *Leader = cast<Instruction>(EliminationStack.back());
4174  (void)Leader;
4175  assert(DT->dominates(Leader->getParent(), Member->getParent()));
4176  // Member is dominater by Leader, and thus dead
4177  LLVM_DEBUG(dbgs() << "Marking dead store " << *Member
4178  << " that is dominated by " << *Leader << "\n");
4179  markInstructionForDeletion(Member);
4180  CC->erase(Member);
4181  ++NumGVNDeadStores;
4182  }
4183  }
4184  }
4185  return AnythingReplaced;
4186 }
4187 
4188 // This function provides global ranking of operations so that we can place them
4189 // in a canonical order. Note that rank alone is not necessarily enough for a
4190 // complete ordering, as constants all have the same rank. However, generally,
4191 // we will simplify an operation with all constants so that it doesn't matter
4192 // what order they appear in.
4193 unsigned int NewGVN::getRank(const Value *V) const {
4194  // Prefer constants to undef to anything else
4195  // Undef is a constant, have to check it first.
4196  // Prefer smaller constants to constantexprs
4197  if (isa<ConstantExpr>(V))
4198  return 2;
4199  if (isa<UndefValue>(V))
4200  return 1;
4201  if (isa<Constant>(V))
4202  return 0;
4203  else if (auto *A = dyn_cast<Argument>(V))
4204  return 3 + A->getArgNo();
4205 
4206  // Need to shift the instruction DFS by number of arguments + 3 to account for
4207  // the constant and argument ranking above.
4208  unsigned Result = InstrToDFSNum(V);
4209  if (Result > 0)
4210  return 4 + NumFuncArgs + Result;
4211  // Unreachable or something else, just return a really large number.
4212  return ~0;
4213 }
4214 
4215 // This is a function that says whether two commutative operations should
4216 // have their order swapped when canonicalizing.
4217 bool NewGVN::shouldSwapOperands(const Value *A, const Value *B) const {
4218  // Because we only care about a total ordering, and don't rewrite expressions
4219  // in this order, we order by rank, which will give a strict weak ordering to
4220  // everything but constants, and then we order by pointer address.
4221  return std::make_pair(getRank(A), A) > std::make_pair(getRank(B), B);
4222 }
4223 
4224 namespace {
4225 
4226 class NewGVNLegacyPass : public FunctionPass {
4227 public:
4228  // Pass identification, replacement for typeid.
4229  static char ID;
4230 
4231  NewGVNLegacyPass() : FunctionPass(ID) {
4233  }
4234 
4235  bool runOnFunction(Function &F) override;
4236 
4237 private:
4238  void getAnalysisUsage(AnalysisUsage &AU) const override {
4246  }
4247 };
4248 
4249 } // end anonymous namespace
4250 
4252  if (skipFunction(F))
4253  return false;
4254  return NewGVN(F, &getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
4255  &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
4256  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
4257  &getAnalysis<AAResultsWrapperPass>().getAAResults(),
4258  &getAnalysis<MemorySSAWrapperPass>().getMSSA(),
4259  F.getParent()->getDataLayout())
4260  .runGVN();
4261 }
4262 
4263 char NewGVNLegacyPass::ID = 0;
4264 
4265 INITIALIZE_PASS_BEGIN(NewGVNLegacyPass, "newgvn", "Global Value Numbering",
4266  false, false)
4273 INITIALIZE_PASS_END(NewGVNLegacyPass, "newgvn", "Global Value Numbering", false,
4274  false)
4275 
4276 // createGVNPass - The public interface to this file.
4277 FunctionPass *llvm::createNewGVNPass() { return new NewGVNLegacyPass(); }
4278 
4280  // Apparently the order in which we get these results matter for
4281  // the old GVN (see Chandler's comment in GVN.cpp). I'll keep
4282  // the same order here, just in case.
4283  auto &AC = AM.getResult<AssumptionAnalysis>(F);
4284  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
4285  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
4286  auto &AA = AM.getResult<AAManager>(F);
4287  auto &MSSA = AM.getResult<MemorySSAAnalysis>(F).getMSSA();
4288  bool Changed =
4289  NewGVN(F, &DT, &AC, &TLI, &AA, &MSSA, F.getParent()->getDataLayout())
4290  .runGVN();
4291  if (!Changed)
4292  return PreservedAnalyses::all();
4293  PreservedAnalyses PA;
4295  PA.preserve<GlobalsAA>();
4296  return PA;
4297 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Global Value Numbering
Definition: NewGVN.cpp:4273
void initializeNewGVNLegacyPassPass(PassRegistry &)
uint64_t CallInst * C
Value * getValueOperand()
Definition: Instructions.h:395
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:250
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:574
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:875
void setInt(IntType IntVal)
bool isSimple() const
Definition: Instructions.h:262
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
iterator_range< use_iterator > uses()
Definition: Value.h:354
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
int analyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr, LoadInst *DepLI, const DataLayout &DL)
This function determines whether a value for the pointer LoadPtr can be extracted from the load at De...
Definition: VNCoercion.cpp:219
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
GCNRegPressure max(const GCNRegPressure &P1, const GCNRegPressure &P2)
unsigned getValueID() const
Return an ID for the concrete type of this object.
Definition: Value.h:463
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:241
void dropAllReferences()
Drop all references to operands.
Definition: User.h:295
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:687
static bool equalsLoadStoreHelper(const T &LHS, const Expression &RHS)
Definition: NewGVN.cpp:870
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
bool isAtomic() const
Return true if this instruction has an AtomicOrdering of unordered or higher.
static bool isEqual(const ExactEqualsExpression &LHS, const Expression *RHS)
Definition: NewGVN.cpp:463
This is the interface for a simple mod/ref and alias analysis over globals.
BasicBlock * getSuccessor(unsigned idx) const
Return the specified successor.
iterator begin() const
Definition: ArrayRef.h:137
static bool okayForPHIOfOps(const Instruction *I)
Definition: NewGVN.cpp:2598
Implements a dense probed hash-table based set.
Definition: DenseSet.h:221
This provides a very simple, boring adaptor for a begin and end iterator into a range type...
This class represents a function call, abstracting a target machine&#39;s calling convention.
An immutable pass that tracks lazily created AssumptionCache objects.
A cache of @llvm.assume calls within a function.
Represents a read-write access to memory, whether it is a must-alias, or a may-alias.
Definition: MemorySSA.h:376
bool isTerminator() const
Definition: Instruction.h:129
1 1 1 0 True if unordered or not equal
Definition: InstrTypes.h:901
Recycle small arrays allocated from a BumpPtrAllocator.
Definition: ArrayRecycler.h:29
void deleteValue()
Delete a pointer to a generic Value.
Definition: Value.cpp:99
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:908
BasicBlock * getSuccessor(unsigned i) const
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:225
F(f)
reverse_iterator rend()
Definition: BasicBlock.h:271
An instruction for reading from memory.
Definition: Instructions.h:164
reverse_iterator rbegin()
Definition: BasicBlock.h:269
Hexagon Common GEP
Value * getCondition() const
This defines the Use class.
Constant * getConstantMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset, Type *LoadTy, const DataLayout &DL)
Definition: VNCoercion.cpp:483
const Value * DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB) const
Translate PHI node to its predecessor from the given basic block.
Definition: Value.cpp:705
ExactEqualsExpression(const Expression &E)
Definition: NewGVN.cpp:433
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:33
op_iterator op_begin()
Definition: User.h:230
This file defines the MallocAllocator and BumpPtrAllocator interfaces.
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:258
static bool isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2)
Determine if Pred1 implies Pred2 is false when two compares have matching operands.
hash_code getComputedHash() const
Definition: GVNExpression.h:92
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
Legacy analysis pass which computes MemorySSA.
Definition: MemorySSA.h:877
void setPointer(PointerTy PtrVal)
static cl::opt< bool > EnablePhiOfOps("enable-phi-of-ops", cl::init(true), cl::Hidden)
Currently, the generation "phi of ops" can result in correctness issues.
Predicate getInversePredicate() const
For example, EQ -> NE, UGT -> ULE, SLT -> SGE, OEQ -> UNE, UGT -> OLE, OLT -> UGE, etc.
Definition: InstrTypes.h:983
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
Value * SimplifyGEPInst(Type *SrcTy, ArrayRef< Value *> Ops, const SimplifyQuery &Q)
Given operands for a GetElementPtrInst, fold the result or return null.
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
PointerType * getPointerTo(unsigned AddrSpace=0) const
Return a pointer to the current type.
Definition: Type.cpp:639
hash_code getComputedHash() const
Definition: NewGVN.cpp:435
int analyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr, MemIntrinsic *DepMI, const DataLayout &DL)
This function determines whether a value for the pointer LoadPtr can be extracted from the memory int...
Definition: VNCoercion.cpp:251
Constant * getConstantStoreValueForLoad(Constant *SrcVal, unsigned Offset, Type *LoadTy, const DataLayout &DL)
Definition: VNCoercion.cpp:351
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:42
Encapsulates MemorySSA, including all data associated with memory accesses.
Definition: MemorySSA.h:640
static bool isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2)
Determine if Pred1 implies Pred2 is true when two compares have matching operands.
PointerIntPair< Value *, 1, bool > Def
Definition: NewGVN.cpp:3532
friend const_iterator begin(StringRef path, Style style)
Get begin iterator over path.
Definition: Path.cpp:241
bool equals(const Expression &Other) const override
Definition: NewGVN.cpp:876
This file provides an implementation of debug counters.
static unsigned getHashValue(const ExactEqualsExpression &E)
Definition: NewGVN.cpp:459
auto reverse(ContainerTy &&C, typename std::enable_if< has_rbegin< ContainerTy >::value >::type *=nullptr) -> decltype(make_range(C.rbegin(), C.rend()))
Definition: STLExtras.h:237
bool isOne() const
This is just a convenience method to make client code smaller for a common case.
Definition: Constants.h:201
Instruction * clone() const
Create a copy of &#39;this&#39; instruction that is identical in all ways except the following: ...
Key
PAL metadata keys.
Value * SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, const SimplifyQuery &Q)
Given operands for a CmpInst, fold the result or return null.
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
static int getID(struct InternalInstruction *insn, const void *miiArg)
void andIRFlags(const Value *V)
Logical &#39;and&#39; of any supported wrapping, exact, and fast-math flags of V and this instruction...
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
static bool isCounterSet(unsigned ID)
Definition: DebugCounter.h:106
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:126
An instruction for storing to memory.
Definition: Instructions.h:306
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:439
This is the generic walker interface for walkers of MemorySSA.
Definition: MemorySSA.h:908
const Expression & E
Definition: NewGVN.cpp:431
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:142
static const Expression * getEmptyKey()
Definition: NewGVN.cpp:443
Value * getOperand(unsigned i) const
Definition: User.h:170
int analyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr, StoreInst *DepSI, const DataLayout &DL)
This function determines whether a value for the pointer LoadPtr can be extracted from the store at D...
Definition: VNCoercion.cpp:202
Value * getOperand(unsigned i_nocapture) const
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:141
const BasicBlock & getEntryBlock() const
Definition: Function.h:626
unsigned getDFSNumIn() const
getDFSNumIn/getDFSNumOut - These return the DFS visitation order for nodes in the dominator tree...
static bool runOnFunction(Function &F, bool PostInlining)
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:410
unsigned getNumOperands() const
friend const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:250
Value * SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, const SimplifyQuery &Q)
Given operands for a SelectInst, fold the result or return null.
Control flow instructions. These all have token chains.
Definition: ISDOpcodes.h:590
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
Subclasses of this class are all able to terminate a basic block.
Definition: InstrTypes.h:55
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
* if(!EatIfPresent(lltok::kw_thread_local)) return false
ParseOptionalThreadLocal := /*empty.
MutableArrayRef - Represent a mutable reference to an array (0 or more elements consecutively in memo...
Definition: ArrayRef.h:291
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
Allocate memory in an ever growing pool, as if by bump-pointer.
Definition: Allocator.h:140
Conditional or Unconditional Branch instruction.
size_t size() const
size - Get the array size.
Definition: ArrayRef.h:149
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:117
Value * getIncomingValueForBlock(const BasicBlock *BB) const
Constant * getConstantLoadValueForLoad(Constant *SrcVal, unsigned Offset, Type *LoadTy, const DataLayout &DL)
Definition: VNCoercion.cpp:409
This file contains the declarations for the subclasses of Constant, which represent the different fla...
mapped_iterator< ItTy, FuncTy > map_iterator(ItTy I, FuncTy F)
Definition: STLExtras.h:210
A manager for alias analyses.
static void patchAndReplaceAllUsesWith(Instruction *I, Value *Repl)
Definition: NewGVN.cpp:3731
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
static void setCounterValue(unsigned ID, const std::pair< int, int > &Val)
Definition: DebugCounter.h:119
Value * SimplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty, const SimplifyQuery &Q)
Given operands for a CastInst, fold the result or return null.
Represent the analysis usage information of a pass.
op_iterator op_end()
Definition: User.h:232
iterator_range< def_chain_iterator< T, true > > optimized_def_chain(T MA)
Definition: MemorySSA.h:1222
bool any_of(R &&Range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:915
Analysis pass providing a never-invalidated alias analysis result.
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:885
bool isBinaryOp() const
Definition: Instruction.h:130
static const unsigned End
This file provides the interface for LLVM&#39;s Global Value Numbering pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
size_t arg_size() const
Definition: Function.h:684
op_range operands()
Definition: User.h:238
Value * getPointerOperand()
Definition: Instructions.h:270
unsigned getDFSNumOut() const
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
static bool shouldExecute(unsigned CounterName)
Definition: DebugCounter.h:72
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1382
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
static const Expression * getTombstoneKey()
Definition: NewGVN.cpp:449
This file implements the PredicateInfo analysis, which creates an Extended SSA form for operations us...
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
static bool isCopyOfAPHI(const Value *V)
Definition: NewGVN.cpp:953
static std::pair< int, int > getCounterValue(unsigned ID)
Definition: DebugCounter.h:111
void sort(IteratorTy Start, IteratorTy End)
Definition: STLExtras.h:859
Intrinsic::ID getIntrinsicID() const
Return the intrinsic ID of this intrinsic.
Definition: IntrinsicInst.h:51
DOTGraphTraits - Template class that can be specialized to customize how graphs are converted to &#39;dot...
A function analysis which provides an AssumptionCache.
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:192
This is the shared class of boolean and integer constants.
Definition: Constants.h:84
auto size(R &&Range, typename std::enable_if< std::is_same< typename std::iterator_traits< decltype(Range.begin())>::iterator_category, std::random_access_iterator_tag >::value, void >::type *=nullptr) -> decltype(std::distance(Range.begin(), Range.end()))
Get the size of a range.
Definition: STLExtras.h:1032
void setOpcode(unsigned opcode)
bool erase(PtrType Ptr)
erase - If the set contains the specified pointer, remove it and return true, otherwise return false...
Definition: SmallPtrSet.h:378
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
Provides information about what library functions are available for the current target.
An analysis that produces MemorySSA for a function.
Definition: MemorySSA.h:841
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:382
PreservedAnalyses run(Function &F, AnalysisManager< Function > &AM)
Run the pass over the function.
Definition: NewGVN.cpp:4279
BasicBlock * getBlock() const
Definition: MemorySSA.h:157
static GCRegistry::Add< StatepointGC > D("statepoint-example", "an example strategy for statepoint")
bool isConditional() const
static PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
static ConstantInt * getTrue(LLVMContext &Context)
Definition: Constants.cpp:567
bool isCommutative() const
Return true if the instruction is commutative:
Definition: Instruction.h:457
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:924
A range adaptor for a pair of iterators.
static bool alwaysAvailable(Value *V)
Definition: NewGVN.cpp:972
Class that has the common methods + fields of memory uses/defs.
Definition: MemorySSA.h:245
iterator_range< user_iterator > users()
Definition: Value.h:399
BasicBlock * getIncomingBlock(unsigned I) const
Return incoming basic block number i.
Definition: MemorySSA.h:521
iterator begin() const
Definition: ArrayRef.h:331
An opaque object representing a hash code.
Definition: Hashing.h:72
bool isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, bool LookThroughBitCast=false)
Tests if a value is a call or invoke to a library function that allocates uninitialized memory (such ...
Instruction * getMemoryInst() const
Get the instruction that this MemoryUse represents.
Definition: MemorySSA.h:252
bool operator<(const ValueDFS &Other) const
Definition: NewGVN.cpp:3535
amdgpu Simplify well known AMD library false Value Value * Arg
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:959
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:121
iterator_range< typename GraphTraits< GraphType >::nodes_iterator > nodes(const GraphType &G)
Definition: GraphTraits.h:102
static Value * getCopyOf(const Value *V)
Definition: NewGVN.cpp:941
iterator begin() const
Definition: SmallPtrSet.h:397
unsigned getAlignment() const
Return the alignment of the access that is being performed.
Definition: Instructions.h:226
void emplace_back(ArgTypes &&... Args)
Definition: SmallVector.h:653
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:62
BasicBlock * getIncomingBlock(unsigned i) const
Return incoming basic block number i.
bool isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, bool LookThroughBitCast=false)
Tests if a value is a call or invoke to a library function that allocates zero-filled memory (such as...
#define I(x, y, z)
Definition: MD5.cpp:58
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
iterator find(const_arg_type_t< ValueT > V)
Definition: DenseSet.h:165
bool isZero() const
This is just a convenience method to make client code smaller for a common code.
Definition: Constants.h:193
iterator_range< value_op_iterator > operand_values()
Definition: User.h:262
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
Constant * ConstantFoldInstOperands(Instruction *I, ArrayRef< Constant *> Ops, const DataLayout &DL, const TargetLibraryInfo *TLI=nullptr)
ConstantFoldInstOperands - Attempt to constant fold an instruction with the specified operands...
void preserve()
Mark an analysis as preserved.
Definition: PassManager.h:174
size_type count(const_arg_type_t< ValueT > V) const
Return 1 if the specified key is in the set, 0 otherwise.
Definition: DenseSet.h:91
iterator_range< filter_iterator< detail::IterOfRange< RangeT >, PredicateT > > make_filter_range(RangeT &&Range, PredicateT Pred)
Convenience function that takes a range of elements and a predicate, and return a new filter_iterator...
Definition: STLExtras.h:398
static std::string getBlockName(const BasicBlock *B)
Definition: NewGVN.cpp:898
iterator end() const
Definition: SmallPtrSet.h:402
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:181
OutputIt transform(R &&Range, OutputIt d_first, UnaryPredicate P)
Wrapper function around std::transform to apply a function to a range and store the result elsewhere...
Definition: STLExtras.h:990
Analysis pass providing the TargetLibraryInfo.
iterator_range< df_iterator< T > > depth_first(const T &G)
Value * SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, const SimplifyQuery &Q)
Given operands for a BinaryOperator, fold the result or return null.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
unsigned getNumSuccessors() const
Return the number of successors that this terminator has.
bool equals(const Expression &Other) const override
Definition: NewGVN.cpp:880
static bool isEqual(const Expression *LHS, const Expression *RHS)
Definition: NewGVN.cpp:469
static bool isCopyOfPHI(const Value *V, const PHINode *PN)
Definition: NewGVN.cpp:949
aarch64 promote const
0 0 0 1 True if ordered and equal
Definition: InstrTypes.h:888
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:565
bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
Return true if the result produced by the instruction is not used, and the instruction has no side ef...
Definition: Local.cpp:346
LLVM Value Representation.
Definition: Value.h:73
Value * getOperand(unsigned N) const
The header file for the GVN pass that contains expression handling classes.
iterator end() const
Definition: ArrayRef.h:332
bool wouldInstructionBeTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
Return true if the result produced by the instruction would have no side effects if it was not used...
Definition: Local.cpp:353
static cl::opt< bool > EnableStoreRefinement("enable-store-refinement", cl::init(false), cl::Hidden)
This file exposes an interface to building/using memory SSA to walk memory instructions using a use/d...
FunctionPass * createNewGVNPass()
Definition: NewGVN.cpp:4277
Predicate getSwappedPredicate() const
For example, EQ->EQ, SLE->SGE, ULT->UGT, OEQ->OEQ, ULE->UGE, OLT->OGT, etc.
Definition: InstrTypes.h:999
A container for analyses that lazily runs them and caches their results.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:254
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object...
bool isSimple() const
Definition: Instructions.h:387
Represents phi nodes for memory accesses.
Definition: MemorySSA.h:459
const TerminatorInst * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:138
static unsigned getHashValue(const Expression *E)
Definition: NewGVN.cpp:455
virtual bool exactlyEquals(const Expression &Other) const
#define LLVM_DEBUG(X)
Definition: Debug.h:119
op_range incoming_values()
OutputIt copy(R &&Range, OutputIt Out)
Definition: STLExtras.h:960
Value * getPointerOperand()
Definition: Instructions.h:398
DEBUG_COUNTER(VNCounter, "newgvn-vn", "Controls which instructions are value numbered")
static IntegerType * getInt8Ty(LLVMContext &C)
Definition: Type.cpp:174
void combineMetadata(Instruction *K, const Instruction *J, ArrayRef< unsigned > KnownIDs)
Combine the metadata of two instructions so that K can replace J.
Definition: Local.cpp:2061
INITIALIZE_PASS_BEGIN(NewGVNLegacyPass, "newgvn", "Global Value Numbering", false, false) INITIALIZE_PASS_END(NewGVNLegacyPass
static void patchReplacementInstruction(Instruction *I, Value *Repl)
Definition: NewGVN.cpp:3700
bool use_empty() const
Definition: Value.h:322
void allocateOperands(RecyclerType &Recycler, BumpPtrAllocator &Allocator)
iterator_range< arg_iterator > args()
Definition: Function.h:675
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:44
const BasicBlock * getParent() const
Definition: Instruction.h:67
newgvn
Definition: NewGVN.cpp:4273
bool operator==(const Expression &Other) const
Definition: NewGVN.cpp:437