LLVM  3.7.0
GVN.cpp
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1 //===- GVN.cpp - Eliminate redundant values and loads ---------------------===//
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 // This pass performs global value numbering to eliminate fully redundant
11 // instructions. It also performs simple dead load elimination.
12 //
13 // Note that this pass does the value numbering itself; it does not use the
14 // ValueNumbering analysis passes.
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #include "llvm/Transforms/Scalar.h"
19 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/Hashing.h"
22 #include "llvm/ADT/MapVector.h"
24 #include "llvm/ADT/SetVector.h"
25 #include "llvm/ADT/SmallPtrSet.h"
26 #include "llvm/ADT/Statistic.h"
29 #include "llvm/Analysis/CFG.h"
32 #include "llvm/Analysis/Loads.h"
38 #include "llvm/IR/DataLayout.h"
39 #include "llvm/IR/Dominators.h"
40 #include "llvm/IR/GlobalVariable.h"
41 #include "llvm/IR/IRBuilder.h"
42 #include "llvm/IR/IntrinsicInst.h"
43 #include "llvm/IR/LLVMContext.h"
44 #include "llvm/IR/Metadata.h"
45 #include "llvm/IR/PatternMatch.h"
46 #include "llvm/Support/Allocator.h"
48 #include "llvm/Support/Debug.h"
53 #include <vector>
54 using namespace llvm;
55 using namespace PatternMatch;
56 
57 #define DEBUG_TYPE "gvn"
58 
59 STATISTIC(NumGVNInstr, "Number of instructions deleted");
60 STATISTIC(NumGVNLoad, "Number of loads deleted");
61 STATISTIC(NumGVNPRE, "Number of instructions PRE'd");
62 STATISTIC(NumGVNBlocks, "Number of blocks merged");
63 STATISTIC(NumGVNSimpl, "Number of instructions simplified");
64 STATISTIC(NumGVNEqProp, "Number of equalities propagated");
65 STATISTIC(NumPRELoad, "Number of loads PRE'd");
66 
67 static cl::opt<bool> EnablePRE("enable-pre",
68  cl::init(true), cl::Hidden);
69 static cl::opt<bool> EnableLoadPRE("enable-load-pre", cl::init(true));
70 
71 // Maximum allowed recursion depth.
72 static cl::opt<uint32_t>
73 MaxRecurseDepth("max-recurse-depth", cl::Hidden, cl::init(1000), cl::ZeroOrMore,
74  cl::desc("Max recurse depth (default = 1000)"));
75 
76 //===----------------------------------------------------------------------===//
77 // ValueTable Class
78 //===----------------------------------------------------------------------===//
79 
80 /// This class holds the mapping between values and value numbers. It is used
81 /// as an efficient mechanism to determine the expression-wise equivalence of
82 /// two values.
83 namespace {
84  struct Expression {
85  uint32_t opcode;
86  Type *type;
88 
89  Expression(uint32_t o = ~2U) : opcode(o) { }
90 
91  bool operator==(const Expression &other) const {
92  if (opcode != other.opcode)
93  return false;
94  if (opcode == ~0U || opcode == ~1U)
95  return true;
96  if (type != other.type)
97  return false;
98  if (varargs != other.varargs)
99  return false;
100  return true;
101  }
102 
103  friend hash_code hash_value(const Expression &Value) {
104  return hash_combine(Value.opcode, Value.type,
105  hash_combine_range(Value.varargs.begin(),
106  Value.varargs.end()));
107  }
108  };
109 
110  class ValueTable {
111  DenseMap<Value*, uint32_t> valueNumbering;
112  DenseMap<Expression, uint32_t> expressionNumbering;
113  AliasAnalysis *AA;
115  DominatorTree *DT;
116 
117  uint32_t nextValueNumber;
118 
119  Expression create_expression(Instruction* I);
120  Expression create_cmp_expression(unsigned Opcode,
122  Value *LHS, Value *RHS);
123  Expression create_extractvalue_expression(ExtractValueInst* EI);
124  uint32_t lookup_or_add_call(CallInst* C);
125  public:
126  ValueTable() : nextValueNumber(1) { }
127  uint32_t lookup_or_add(Value *V);
128  uint32_t lookup(Value *V) const;
129  uint32_t lookup_or_add_cmp(unsigned Opcode, CmpInst::Predicate Pred,
130  Value *LHS, Value *RHS);
131  void add(Value *V, uint32_t num);
132  void clear();
133  void erase(Value *v);
134  void setAliasAnalysis(AliasAnalysis* A) { AA = A; }
135  AliasAnalysis *getAliasAnalysis() const { return AA; }
136  void setMemDep(MemoryDependenceAnalysis* M) { MD = M; }
137  void setDomTree(DominatorTree* D) { DT = D; }
138  uint32_t getNextUnusedValueNumber() { return nextValueNumber; }
139  void verifyRemoved(const Value *) const;
140  };
141 }
142 
143 namespace llvm {
144 template <> struct DenseMapInfo<Expression> {
145  static inline Expression getEmptyKey() {
146  return ~0U;
147  }
148 
149  static inline Expression getTombstoneKey() {
150  return ~1U;
151  }
152 
153  static unsigned getHashValue(const Expression e) {
154  using llvm::hash_value;
155  return static_cast<unsigned>(hash_value(e));
156  }
157  static bool isEqual(const Expression &LHS, const Expression &RHS) {
158  return LHS == RHS;
159  }
160 };
161 
162 }
163 
164 //===----------------------------------------------------------------------===//
165 // ValueTable Internal Functions
166 //===----------------------------------------------------------------------===//
167 
168 Expression ValueTable::create_expression(Instruction *I) {
169  Expression e;
170  e.type = I->getType();
171  e.opcode = I->getOpcode();
172  for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
173  OI != OE; ++OI)
174  e.varargs.push_back(lookup_or_add(*OI));
175  if (I->isCommutative()) {
176  // Ensure that commutative instructions that only differ by a permutation
177  // of their operands get the same value number by sorting the operand value
178  // numbers. Since all commutative instructions have two operands it is more
179  // efficient to sort by hand rather than using, say, std::sort.
180  assert(I->getNumOperands() == 2 && "Unsupported commutative instruction!");
181  if (e.varargs[0] > e.varargs[1])
182  std::swap(e.varargs[0], e.varargs[1]);
183  }
184 
185  if (CmpInst *C = dyn_cast<CmpInst>(I)) {
186  // Sort the operand value numbers so x<y and y>x get the same value number.
187  CmpInst::Predicate Predicate = C->getPredicate();
188  if (e.varargs[0] > e.varargs[1]) {
189  std::swap(e.varargs[0], e.varargs[1]);
190  Predicate = CmpInst::getSwappedPredicate(Predicate);
191  }
192  e.opcode = (C->getOpcode() << 8) | Predicate;
193  } else if (InsertValueInst *E = dyn_cast<InsertValueInst>(I)) {
194  for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
195  II != IE; ++II)
196  e.varargs.push_back(*II);
197  }
198 
199  return e;
200 }
201 
202 Expression ValueTable::create_cmp_expression(unsigned Opcode,
203  CmpInst::Predicate Predicate,
204  Value *LHS, Value *RHS) {
205  assert((Opcode == Instruction::ICmp || Opcode == Instruction::FCmp) &&
206  "Not a comparison!");
207  Expression e;
208  e.type = CmpInst::makeCmpResultType(LHS->getType());
209  e.varargs.push_back(lookup_or_add(LHS));
210  e.varargs.push_back(lookup_or_add(RHS));
211 
212  // Sort the operand value numbers so x<y and y>x get the same value number.
213  if (e.varargs[0] > e.varargs[1]) {
214  std::swap(e.varargs[0], e.varargs[1]);
215  Predicate = CmpInst::getSwappedPredicate(Predicate);
216  }
217  e.opcode = (Opcode << 8) | Predicate;
218  return e;
219 }
220 
221 Expression ValueTable::create_extractvalue_expression(ExtractValueInst *EI) {
222  assert(EI && "Not an ExtractValueInst?");
223  Expression e;
224  e.type = EI->getType();
225  e.opcode = 0;
226 
228  if (I != nullptr && EI->getNumIndices() == 1 && *EI->idx_begin() == 0 ) {
229  // EI might be an extract from one of our recognised intrinsics. If it
230  // is we'll synthesize a semantically equivalent expression instead on
231  // an extract value expression.
232  switch (I->getIntrinsicID()) {
233  case Intrinsic::sadd_with_overflow:
234  case Intrinsic::uadd_with_overflow:
235  e.opcode = Instruction::Add;
236  break;
237  case Intrinsic::ssub_with_overflow:
238  case Intrinsic::usub_with_overflow:
239  e.opcode = Instruction::Sub;
240  break;
241  case Intrinsic::smul_with_overflow:
242  case Intrinsic::umul_with_overflow:
243  e.opcode = Instruction::Mul;
244  break;
245  default:
246  break;
247  }
248 
249  if (e.opcode != 0) {
250  // Intrinsic recognized. Grab its args to finish building the expression.
251  assert(I->getNumArgOperands() == 2 &&
252  "Expect two args for recognised intrinsics.");
253  e.varargs.push_back(lookup_or_add(I->getArgOperand(0)));
254  e.varargs.push_back(lookup_or_add(I->getArgOperand(1)));
255  return e;
256  }
257  }
258 
259  // Not a recognised intrinsic. Fall back to producing an extract value
260  // expression.
261  e.opcode = EI->getOpcode();
262  for (Instruction::op_iterator OI = EI->op_begin(), OE = EI->op_end();
263  OI != OE; ++OI)
264  e.varargs.push_back(lookup_or_add(*OI));
265 
266  for (ExtractValueInst::idx_iterator II = EI->idx_begin(), IE = EI->idx_end();
267  II != IE; ++II)
268  e.varargs.push_back(*II);
269 
270  return e;
271 }
272 
273 //===----------------------------------------------------------------------===//
274 // ValueTable External Functions
275 //===----------------------------------------------------------------------===//
276 
277 /// add - Insert a value into the table with a specified value number.
278 void ValueTable::add(Value *V, uint32_t num) {
279  valueNumbering.insert(std::make_pair(V, num));
280 }
281 
282 uint32_t ValueTable::lookup_or_add_call(CallInst *C) {
283  if (AA->doesNotAccessMemory(C)) {
284  Expression exp = create_expression(C);
285  uint32_t &e = expressionNumbering[exp];
286  if (!e) e = nextValueNumber++;
287  valueNumbering[C] = e;
288  return e;
289  } else if (AA->onlyReadsMemory(C)) {
290  Expression exp = create_expression(C);
291  uint32_t &e = expressionNumbering[exp];
292  if (!e) {
293  e = nextValueNumber++;
294  valueNumbering[C] = e;
295  return e;
296  }
297  if (!MD) {
298  e = nextValueNumber++;
299  valueNumbering[C] = e;
300  return e;
301  }
302 
303  MemDepResult local_dep = MD->getDependency(C);
304 
305  if (!local_dep.isDef() && !local_dep.isNonLocal()) {
306  valueNumbering[C] = nextValueNumber;
307  return nextValueNumber++;
308  }
309 
310  if (local_dep.isDef()) {
311  CallInst* local_cdep = cast<CallInst>(local_dep.getInst());
312 
313  if (local_cdep->getNumArgOperands() != C->getNumArgOperands()) {
314  valueNumbering[C] = nextValueNumber;
315  return nextValueNumber++;
316  }
317 
318  for (unsigned i = 0, e = C->getNumArgOperands(); i < e; ++i) {
319  uint32_t c_vn = lookup_or_add(C->getArgOperand(i));
320  uint32_t cd_vn = lookup_or_add(local_cdep->getArgOperand(i));
321  if (c_vn != cd_vn) {
322  valueNumbering[C] = nextValueNumber;
323  return nextValueNumber++;
324  }
325  }
326 
327  uint32_t v = lookup_or_add(local_cdep);
328  valueNumbering[C] = v;
329  return v;
330  }
331 
332  // Non-local case.
334  MD->getNonLocalCallDependency(CallSite(C));
335  // FIXME: Move the checking logic to MemDep!
336  CallInst* cdep = nullptr;
337 
338  // Check to see if we have a single dominating call instruction that is
339  // identical to C.
340  for (unsigned i = 0, e = deps.size(); i != e; ++i) {
341  const NonLocalDepEntry *I = &deps[i];
342  if (I->getResult().isNonLocal())
343  continue;
344 
345  // We don't handle non-definitions. If we already have a call, reject
346  // instruction dependencies.
347  if (!I->getResult().isDef() || cdep != nullptr) {
348  cdep = nullptr;
349  break;
350  }
351 
352  CallInst *NonLocalDepCall = dyn_cast<CallInst>(I->getResult().getInst());
353  // FIXME: All duplicated with non-local case.
354  if (NonLocalDepCall && DT->properlyDominates(I->getBB(), C->getParent())){
355  cdep = NonLocalDepCall;
356  continue;
357  }
358 
359  cdep = nullptr;
360  break;
361  }
362 
363  if (!cdep) {
364  valueNumbering[C] = nextValueNumber;
365  return nextValueNumber++;
366  }
367 
368  if (cdep->getNumArgOperands() != C->getNumArgOperands()) {
369  valueNumbering[C] = nextValueNumber;
370  return nextValueNumber++;
371  }
372  for (unsigned i = 0, e = C->getNumArgOperands(); i < e; ++i) {
373  uint32_t c_vn = lookup_or_add(C->getArgOperand(i));
374  uint32_t cd_vn = lookup_or_add(cdep->getArgOperand(i));
375  if (c_vn != cd_vn) {
376  valueNumbering[C] = nextValueNumber;
377  return nextValueNumber++;
378  }
379  }
380 
381  uint32_t v = lookup_or_add(cdep);
382  valueNumbering[C] = v;
383  return v;
384 
385  } else {
386  valueNumbering[C] = nextValueNumber;
387  return nextValueNumber++;
388  }
389 }
390 
391 /// lookup_or_add - Returns the value number for the specified value, assigning
392 /// it a new number if it did not have one before.
393 uint32_t ValueTable::lookup_or_add(Value *V) {
394  DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
395  if (VI != valueNumbering.end())
396  return VI->second;
397 
398  if (!isa<Instruction>(V)) {
399  valueNumbering[V] = nextValueNumber;
400  return nextValueNumber++;
401  }
402 
403  Instruction* I = cast<Instruction>(V);
404  Expression exp;
405  switch (I->getOpcode()) {
406  case Instruction::Call:
407  return lookup_or_add_call(cast<CallInst>(I));
408  case Instruction::Add:
409  case Instruction::FAdd:
410  case Instruction::Sub:
411  case Instruction::FSub:
412  case Instruction::Mul:
413  case Instruction::FMul:
414  case Instruction::UDiv:
415  case Instruction::SDiv:
416  case Instruction::FDiv:
417  case Instruction::URem:
418  case Instruction::SRem:
419  case Instruction::FRem:
420  case Instruction::Shl:
421  case Instruction::LShr:
422  case Instruction::AShr:
423  case Instruction::And:
424  case Instruction::Or:
425  case Instruction::Xor:
426  case Instruction::ICmp:
427  case Instruction::FCmp:
428  case Instruction::Trunc:
429  case Instruction::ZExt:
430  case Instruction::SExt:
431  case Instruction::FPToUI:
432  case Instruction::FPToSI:
433  case Instruction::UIToFP:
434  case Instruction::SIToFP:
435  case Instruction::FPTrunc:
436  case Instruction::FPExt:
437  case Instruction::PtrToInt:
438  case Instruction::IntToPtr:
439  case Instruction::BitCast:
440  case Instruction::Select:
442  case Instruction::InsertElement:
443  case Instruction::ShuffleVector:
444  case Instruction::InsertValue:
445  case Instruction::GetElementPtr:
446  exp = create_expression(I);
447  break;
448  case Instruction::ExtractValue:
449  exp = create_extractvalue_expression(cast<ExtractValueInst>(I));
450  break;
451  default:
452  valueNumbering[V] = nextValueNumber;
453  return nextValueNumber++;
454  }
455 
456  uint32_t& e = expressionNumbering[exp];
457  if (!e) e = nextValueNumber++;
458  valueNumbering[V] = e;
459  return e;
460 }
461 
462 /// Returns the value number of the specified value. Fails if
463 /// the value has not yet been numbered.
464 uint32_t ValueTable::lookup(Value *V) const {
465  DenseMap<Value*, uint32_t>::const_iterator VI = valueNumbering.find(V);
466  assert(VI != valueNumbering.end() && "Value not numbered?");
467  return VI->second;
468 }
469 
470 /// Returns the value number of the given comparison,
471 /// assigning it a new number if it did not have one before. Useful when
472 /// we deduced the result of a comparison, but don't immediately have an
473 /// instruction realizing that comparison to hand.
474 uint32_t ValueTable::lookup_or_add_cmp(unsigned Opcode,
475  CmpInst::Predicate Predicate,
476  Value *LHS, Value *RHS) {
477  Expression exp = create_cmp_expression(Opcode, Predicate, LHS, RHS);
478  uint32_t& e = expressionNumbering[exp];
479  if (!e) e = nextValueNumber++;
480  return e;
481 }
482 
483 /// Remove all entries from the ValueTable.
484 void ValueTable::clear() {
485  valueNumbering.clear();
486  expressionNumbering.clear();
487  nextValueNumber = 1;
488 }
489 
490 /// Remove a value from the value numbering.
491 void ValueTable::erase(Value *V) {
492  valueNumbering.erase(V);
493 }
494 
495 /// verifyRemoved - Verify that the value is removed from all internal data
496 /// structures.
497 void ValueTable::verifyRemoved(const Value *V) const {
499  I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) {
500  assert(I->first != V && "Inst still occurs in value numbering map!");
501  }
502 }
503 
504 //===----------------------------------------------------------------------===//
505 // GVN Pass
506 //===----------------------------------------------------------------------===//
507 
508 namespace {
509  class GVN;
510  struct AvailableValueInBlock {
511  /// BB - The basic block in question.
512  BasicBlock *BB;
513  enum ValType {
514  SimpleVal, // A simple offsetted value that is accessed.
515  LoadVal, // A value produced by a load.
516  MemIntrin, // A memory intrinsic which is loaded from.
517  UndefVal // A UndefValue representing a value from dead block (which
518  // is not yet physically removed from the CFG).
519  };
520 
521  /// V - The value that is live out of the block.
523 
524  /// Offset - The byte offset in Val that is interesting for the load query.
525  unsigned Offset;
526 
527  static AvailableValueInBlock get(BasicBlock *BB, Value *V,
528  unsigned Offset = 0) {
529  AvailableValueInBlock Res;
530  Res.BB = BB;
531  Res.Val.setPointer(V);
532  Res.Val.setInt(SimpleVal);
533  Res.Offset = Offset;
534  return Res;
535  }
536 
537  static AvailableValueInBlock getMI(BasicBlock *BB, MemIntrinsic *MI,
538  unsigned Offset = 0) {
539  AvailableValueInBlock Res;
540  Res.BB = BB;
541  Res.Val.setPointer(MI);
542  Res.Val.setInt(MemIntrin);
543  Res.Offset = Offset;
544  return Res;
545  }
546 
547  static AvailableValueInBlock getLoad(BasicBlock *BB, LoadInst *LI,
548  unsigned Offset = 0) {
549  AvailableValueInBlock Res;
550  Res.BB = BB;
551  Res.Val.setPointer(LI);
552  Res.Val.setInt(LoadVal);
553  Res.Offset = Offset;
554  return Res;
555  }
556 
557  static AvailableValueInBlock getUndef(BasicBlock *BB) {
558  AvailableValueInBlock Res;
559  Res.BB = BB;
560  Res.Val.setPointer(nullptr);
561  Res.Val.setInt(UndefVal);
562  Res.Offset = 0;
563  return Res;
564  }
565 
566  bool isSimpleValue() const { return Val.getInt() == SimpleVal; }
567  bool isCoercedLoadValue() const { return Val.getInt() == LoadVal; }
568  bool isMemIntrinValue() const { return Val.getInt() == MemIntrin; }
569  bool isUndefValue() const { return Val.getInt() == UndefVal; }
570 
571  Value *getSimpleValue() const {
572  assert(isSimpleValue() && "Wrong accessor");
573  return Val.getPointer();
574  }
575 
576  LoadInst *getCoercedLoadValue() const {
577  assert(isCoercedLoadValue() && "Wrong accessor");
578  return cast<LoadInst>(Val.getPointer());
579  }
580 
581  MemIntrinsic *getMemIntrinValue() const {
582  assert(isMemIntrinValue() && "Wrong accessor");
583  return cast<MemIntrinsic>(Val.getPointer());
584  }
585 
586  /// Emit code into this block to adjust the value defined here to the
587  /// specified type. This handles various coercion cases.
588  Value *MaterializeAdjustedValue(LoadInst *LI, GVN &gvn) const;
589  };
590 
591  class GVN : public FunctionPass {
592  bool NoLoads;
594  DominatorTree *DT;
595  const TargetLibraryInfo *TLI;
596  AssumptionCache *AC;
597  SetVector<BasicBlock *> DeadBlocks;
598 
599  ValueTable VN;
600 
601  /// A mapping from value numbers to lists of Value*'s that
602  /// have that value number. Use findLeader to query it.
603  struct LeaderTableEntry {
604  Value *Val;
605  const BasicBlock *BB;
606  LeaderTableEntry *Next;
607  };
609  BumpPtrAllocator TableAllocator;
610 
611  SmallVector<Instruction*, 8> InstrsToErase;
612 
613  typedef SmallVector<NonLocalDepResult, 64> LoadDepVect;
614  typedef SmallVector<AvailableValueInBlock, 64> AvailValInBlkVect;
615  typedef SmallVector<BasicBlock*, 64> UnavailBlkVect;
616 
617  public:
618  static char ID; // Pass identification, replacement for typeid
619  explicit GVN(bool noloads = false)
620  : FunctionPass(ID), NoLoads(noloads), MD(nullptr) {
622  }
623 
624  bool runOnFunction(Function &F) override;
625 
626  /// This removes the specified instruction from
627  /// our various maps and marks it for deletion.
628  void markInstructionForDeletion(Instruction *I) {
629  VN.erase(I);
630  InstrsToErase.push_back(I);
631  }
632 
633  DominatorTree &getDominatorTree() const { return *DT; }
634  AliasAnalysis *getAliasAnalysis() const { return VN.getAliasAnalysis(); }
635  MemoryDependenceAnalysis &getMemDep() const { return *MD; }
636  private:
637  /// Push a new Value to the LeaderTable onto the list for its value number.
638  void addToLeaderTable(uint32_t N, Value *V, const BasicBlock *BB) {
639  LeaderTableEntry &Curr = LeaderTable[N];
640  if (!Curr.Val) {
641  Curr.Val = V;
642  Curr.BB = BB;
643  return;
644  }
645 
646  LeaderTableEntry *Node = TableAllocator.Allocate<LeaderTableEntry>();
647  Node->Val = V;
648  Node->BB = BB;
649  Node->Next = Curr.Next;
650  Curr.Next = Node;
651  }
652 
653  /// Scan the list of values corresponding to a given
654  /// value number, and remove the given instruction if encountered.
655  void removeFromLeaderTable(uint32_t N, Instruction *I, BasicBlock *BB) {
656  LeaderTableEntry* Prev = nullptr;
657  LeaderTableEntry* Curr = &LeaderTable[N];
658 
659  while (Curr && (Curr->Val != I || Curr->BB != BB)) {
660  Prev = Curr;
661  Curr = Curr->Next;
662  }
663 
664  if (!Curr)
665  return;
666 
667  if (Prev) {
668  Prev->Next = Curr->Next;
669  } else {
670  if (!Curr->Next) {
671  Curr->Val = nullptr;
672  Curr->BB = nullptr;
673  } else {
674  LeaderTableEntry* Next = Curr->Next;
675  Curr->Val = Next->Val;
676  Curr->BB = Next->BB;
677  Curr->Next = Next->Next;
678  }
679  }
680  }
681 
682  // List of critical edges to be split between iterations.
684 
685  // This transformation requires dominator postdominator info
686  void getAnalysisUsage(AnalysisUsage &AU) const override {
690  if (!NoLoads)
693 
696  }
697 
698 
699  // Helper fuctions of redundant load elimination
700  bool processLoad(LoadInst *L);
701  bool processNonLocalLoad(LoadInst *L);
702  void AnalyzeLoadAvailability(LoadInst *LI, LoadDepVect &Deps,
703  AvailValInBlkVect &ValuesPerBlock,
704  UnavailBlkVect &UnavailableBlocks);
705  bool PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
706  UnavailBlkVect &UnavailableBlocks);
707 
708  // Other helper routines
710  bool processBlock(BasicBlock *BB);
712  bool iterateOnFunction(Function &F);
713  bool performPRE(Function &F);
714  bool performScalarPRE(Instruction *I);
715  bool performScalarPREInsertion(Instruction *Instr, BasicBlock *Pred,
716  unsigned int ValNo);
717  Value *findLeader(const BasicBlock *BB, uint32_t num);
718  void cleanupGlobalSets();
719  void verifyRemoved(const Instruction *I) const;
720  bool splitCriticalEdges();
721  BasicBlock *splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ);
722  bool propagateEquality(Value *LHS, Value *RHS, const BasicBlockEdge &Root);
723  bool processFoldableCondBr(BranchInst *BI);
724  void addDeadBlock(BasicBlock *BB);
725  void assignValNumForDeadCode();
726  };
727 
728  char GVN::ID = 0;
729 }
730 
731 // The public interface to this file...
733  return new GVN(NoLoads);
734 }
735 
736 INITIALIZE_PASS_BEGIN(GVN, "gvn", "Global Value Numbering", false, false)
742 INITIALIZE_PASS_END(GVN, "gvn", "Global Value Numbering", false, false)
743 
744 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
746  errs() << "{\n";
748  E = d.end(); I != E; ++I) {
749  errs() << I->first << "\n";
750  I->second->dump();
751  }
752  errs() << "}\n";
753 }
754 #endif
755 
756 /// Return true if we can prove that the value
757 /// we're analyzing is fully available in the specified block. As we go, keep
758 /// track of which blocks we know are fully alive in FullyAvailableBlocks. This
759 /// map is actually a tri-state map with the following values:
760 /// 0) we know the block *is not* fully available.
761 /// 1) we know the block *is* fully available.
762 /// 2) we do not know whether the block is fully available or not, but we are
763 /// currently speculating that it will be.
764 /// 3) we are speculating for this block and have used that to speculate for
765 /// other blocks.
767  DenseMap<BasicBlock*, char> &FullyAvailableBlocks,
768  uint32_t RecurseDepth) {
769  if (RecurseDepth > MaxRecurseDepth)
770  return false;
771 
772  // Optimistically assume that the block is fully available and check to see
773  // if we already know about this block in one lookup.
774  std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV =
775  FullyAvailableBlocks.insert(std::make_pair(BB, 2));
776 
777  // If the entry already existed for this block, return the precomputed value.
778  if (!IV.second) {
779  // If this is a speculative "available" value, mark it as being used for
780  // speculation of other blocks.
781  if (IV.first->second == 2)
782  IV.first->second = 3;
783  return IV.first->second != 0;
784  }
785 
786  // Otherwise, see if it is fully available in all predecessors.
787  pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
788 
789  // If this block has no predecessors, it isn't live-in here.
790  if (PI == PE)
791  goto SpeculationFailure;
792 
793  for (; PI != PE; ++PI)
794  // If the value isn't fully available in one of our predecessors, then it
795  // isn't fully available in this block either. Undo our previous
796  // optimistic assumption and bail out.
797  if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks,RecurseDepth+1))
798  goto SpeculationFailure;
799 
800  return true;
801 
802 // If we get here, we found out that this is not, after
803 // all, a fully-available block. We have a problem if we speculated on this and
804 // used the speculation to mark other blocks as available.
805 SpeculationFailure:
806  char &BBVal = FullyAvailableBlocks[BB];
807 
808  // If we didn't speculate on this, just return with it set to false.
809  if (BBVal == 2) {
810  BBVal = 0;
811  return false;
812  }
813 
814  // If we did speculate on this value, we could have blocks set to 1 that are
815  // incorrect. Walk the (transitive) successors of this block and mark them as
816  // 0 if set to one.
817  SmallVector<BasicBlock*, 32> BBWorklist;
818  BBWorklist.push_back(BB);
819 
820  do {
821  BasicBlock *Entry = BBWorklist.pop_back_val();
822  // Note that this sets blocks to 0 (unavailable) if they happen to not
823  // already be in FullyAvailableBlocks. This is safe.
824  char &EntryVal = FullyAvailableBlocks[Entry];
825  if (EntryVal == 0) continue; // Already unavailable.
826 
827  // Mark as unavailable.
828  EntryVal = 0;
829 
830  BBWorklist.append(succ_begin(Entry), succ_end(Entry));
831  } while (!BBWorklist.empty());
832 
833  return false;
834 }
835 
836 
837 /// Return true if CoerceAvailableValueToLoadType will succeed.
838 static bool CanCoerceMustAliasedValueToLoad(Value *StoredVal,
839  Type *LoadTy,
840  const DataLayout &DL) {
841  // If the loaded or stored value is an first class array or struct, don't try
842  // to transform them. We need to be able to bitcast to integer.
843  if (LoadTy->isStructTy() || LoadTy->isArrayTy() ||
844  StoredVal->getType()->isStructTy() ||
845  StoredVal->getType()->isArrayTy())
846  return false;
847 
848  // The store has to be at least as big as the load.
849  if (DL.getTypeSizeInBits(StoredVal->getType()) <
850  DL.getTypeSizeInBits(LoadTy))
851  return false;
852 
853  return true;
854 }
855 
856 /// If we saw a store of a value to memory, and
857 /// then a load from a must-aliased pointer of a different type, try to coerce
858 /// the stored value. LoadedTy is the type of the load we want to replace.
859 /// IRB is IRBuilder used to insert new instructions.
860 ///
861 /// If we can't do it, return null.
862 static Value *CoerceAvailableValueToLoadType(Value *StoredVal, Type *LoadedTy,
863  IRBuilder<> &IRB,
864  const DataLayout &DL) {
865  if (!CanCoerceMustAliasedValueToLoad(StoredVal, LoadedTy, DL))
866  return nullptr;
867 
868  // If this is already the right type, just return it.
869  Type *StoredValTy = StoredVal->getType();
870 
871  uint64_t StoreSize = DL.getTypeSizeInBits(StoredValTy);
872  uint64_t LoadSize = DL.getTypeSizeInBits(LoadedTy);
873 
874  // If the store and reload are the same size, we can always reuse it.
875  if (StoreSize == LoadSize) {
876  // Pointer to Pointer -> use bitcast.
877  if (StoredValTy->getScalarType()->isPointerTy() &&
878  LoadedTy->getScalarType()->isPointerTy())
879  return IRB.CreateBitCast(StoredVal, LoadedTy);
880 
881  // Convert source pointers to integers, which can be bitcast.
882  if (StoredValTy->getScalarType()->isPointerTy()) {
883  StoredValTy = DL.getIntPtrType(StoredValTy);
884  StoredVal = IRB.CreatePtrToInt(StoredVal, StoredValTy);
885  }
886 
887  Type *TypeToCastTo = LoadedTy;
888  if (TypeToCastTo->getScalarType()->isPointerTy())
889  TypeToCastTo = DL.getIntPtrType(TypeToCastTo);
890 
891  if (StoredValTy != TypeToCastTo)
892  StoredVal = IRB.CreateBitCast(StoredVal, TypeToCastTo);
893 
894  // Cast to pointer if the load needs a pointer type.
895  if (LoadedTy->getScalarType()->isPointerTy())
896  StoredVal = IRB.CreateIntToPtr(StoredVal, LoadedTy);
897 
898  return StoredVal;
899  }
900 
901  // If the loaded value is smaller than the available value, then we can
902  // extract out a piece from it. If the available value is too small, then we
903  // can't do anything.
904  assert(StoreSize >= LoadSize && "CanCoerceMustAliasedValueToLoad fail");
905 
906  // Convert source pointers to integers, which can be manipulated.
907  if (StoredValTy->getScalarType()->isPointerTy()) {
908  StoredValTy = DL.getIntPtrType(StoredValTy);
909  StoredVal = IRB.CreatePtrToInt(StoredVal, StoredValTy);
910  }
911 
912  // Convert vectors and fp to integer, which can be manipulated.
913  if (!StoredValTy->isIntegerTy()) {
914  StoredValTy = IntegerType::get(StoredValTy->getContext(), StoreSize);
915  StoredVal = IRB.CreateBitCast(StoredVal, StoredValTy);
916  }
917 
918  // If this is a big-endian system, we need to shift the value down to the low
919  // bits so that a truncate will work.
920  if (DL.isBigEndian()) {
921  StoredVal = IRB.CreateLShr(StoredVal, StoreSize - LoadSize, "tmp");
922  }
923 
924  // Truncate the integer to the right size now.
925  Type *NewIntTy = IntegerType::get(StoredValTy->getContext(), LoadSize);
926  StoredVal = IRB.CreateTrunc(StoredVal, NewIntTy, "trunc");
927 
928  if (LoadedTy == NewIntTy)
929  return StoredVal;
930 
931  // If the result is a pointer, inttoptr.
932  if (LoadedTy->getScalarType()->isPointerTy())
933  return IRB.CreateIntToPtr(StoredVal, LoadedTy, "inttoptr");
934 
935  // Otherwise, bitcast.
936  return IRB.CreateBitCast(StoredVal, LoadedTy, "bitcast");
937 }
938 
939 /// This function is called when we have a
940 /// memdep query of a load that ends up being a clobbering memory write (store,
941 /// memset, memcpy, memmove). This means that the write *may* provide bits used
942 /// by the load but we can't be sure because the pointers don't mustalias.
943 ///
944 /// Check this case to see if there is anything more we can do before we give
945 /// up. This returns -1 if we have to give up, or a byte number in the stored
946 /// value of the piece that feeds the load.
947 static int AnalyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr,
948  Value *WritePtr,
949  uint64_t WriteSizeInBits,
950  const DataLayout &DL) {
951  // If the loaded or stored value is a first class array or struct, don't try
952  // to transform them. We need to be able to bitcast to integer.
953  if (LoadTy->isStructTy() || LoadTy->isArrayTy())
954  return -1;
955 
956  int64_t StoreOffset = 0, LoadOffset = 0;
957  Value *StoreBase =
958  GetPointerBaseWithConstantOffset(WritePtr, StoreOffset, DL);
959  Value *LoadBase = GetPointerBaseWithConstantOffset(LoadPtr, LoadOffset, DL);
960  if (StoreBase != LoadBase)
961  return -1;
962 
963  // If the load and store are to the exact same address, they should have been
964  // a must alias. AA must have gotten confused.
965  // FIXME: Study to see if/when this happens. One case is forwarding a memset
966  // to a load from the base of the memset.
967 #if 0
968  if (LoadOffset == StoreOffset) {
969  dbgs() << "STORE/LOAD DEP WITH COMMON POINTER MISSED:\n"
970  << "Base = " << *StoreBase << "\n"
971  << "Store Ptr = " << *WritePtr << "\n"
972  << "Store Offs = " << StoreOffset << "\n"
973  << "Load Ptr = " << *LoadPtr << "\n";
974  abort();
975  }
976 #endif
977 
978  // If the load and store don't overlap at all, the store doesn't provide
979  // anything to the load. In this case, they really don't alias at all, AA
980  // must have gotten confused.
981  uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy);
982 
983  if ((WriteSizeInBits & 7) | (LoadSize & 7))
984  return -1;
985  uint64_t StoreSize = WriteSizeInBits >> 3; // Convert to bytes.
986  LoadSize >>= 3;
987 
988 
989  bool isAAFailure = false;
990  if (StoreOffset < LoadOffset)
991  isAAFailure = StoreOffset+int64_t(StoreSize) <= LoadOffset;
992  else
993  isAAFailure = LoadOffset+int64_t(LoadSize) <= StoreOffset;
994 
995  if (isAAFailure) {
996 #if 0
997  dbgs() << "STORE LOAD DEP WITH COMMON BASE:\n"
998  << "Base = " << *StoreBase << "\n"
999  << "Store Ptr = " << *WritePtr << "\n"
1000  << "Store Offs = " << StoreOffset << "\n"
1001  << "Load Ptr = " << *LoadPtr << "\n";
1002  abort();
1003 #endif
1004  return -1;
1005  }
1006 
1007  // If the Load isn't completely contained within the stored bits, we don't
1008  // have all the bits to feed it. We could do something crazy in the future
1009  // (issue a smaller load then merge the bits in) but this seems unlikely to be
1010  // valuable.
1011  if (StoreOffset > LoadOffset ||
1012  StoreOffset+StoreSize < LoadOffset+LoadSize)
1013  return -1;
1014 
1015  // Okay, we can do this transformation. Return the number of bytes into the
1016  // store that the load is.
1017  return LoadOffset-StoreOffset;
1018 }
1019 
1020 /// This function is called when we have a
1021 /// memdep query of a load that ends up being a clobbering store.
1022 static int AnalyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr,
1023  StoreInst *DepSI) {
1024  // Cannot handle reading from store of first-class aggregate yet.
1025  if (DepSI->getValueOperand()->getType()->isStructTy() ||
1026  DepSI->getValueOperand()->getType()->isArrayTy())
1027  return -1;
1028 
1029  const DataLayout &DL = DepSI->getModule()->getDataLayout();
1030  Value *StorePtr = DepSI->getPointerOperand();
1031  uint64_t StoreSize =DL.getTypeSizeInBits(DepSI->getValueOperand()->getType());
1032  return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr,
1033  StorePtr, StoreSize, DL);
1034 }
1035 
1036 /// This function is called when we have a
1037 /// memdep query of a load that ends up being clobbered by another load. See if
1038 /// the other load can feed into the second load.
1039 static int AnalyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr,
1040  LoadInst *DepLI, const DataLayout &DL){
1041  // Cannot handle reading from store of first-class aggregate yet.
1042  if (DepLI->getType()->isStructTy() || DepLI->getType()->isArrayTy())
1043  return -1;
1044 
1045  Value *DepPtr = DepLI->getPointerOperand();
1046  uint64_t DepSize = DL.getTypeSizeInBits(DepLI->getType());
1047  int R = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, DepSize, DL);
1048  if (R != -1) return R;
1049 
1050  // If we have a load/load clobber an DepLI can be widened to cover this load,
1051  // then we should widen it!
1052  int64_t LoadOffs = 0;
1053  const Value *LoadBase =
1054  GetPointerBaseWithConstantOffset(LoadPtr, LoadOffs, DL);
1055  unsigned LoadSize = DL.getTypeStoreSize(LoadTy);
1056 
1058  LoadBase, LoadOffs, LoadSize, DepLI);
1059  if (Size == 0) return -1;
1060 
1061  return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, Size*8, DL);
1062 }
1063 
1064 
1065 
1066 static int AnalyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr,
1067  MemIntrinsic *MI,
1068  const DataLayout &DL) {
1069  // If the mem operation is a non-constant size, we can't handle it.
1070  ConstantInt *SizeCst = dyn_cast<ConstantInt>(MI->getLength());
1071  if (!SizeCst) return -1;
1072  uint64_t MemSizeInBits = SizeCst->getZExtValue()*8;
1073 
1074  // If this is memset, we just need to see if the offset is valid in the size
1075  // of the memset..
1076  if (MI->getIntrinsicID() == Intrinsic::memset)
1077  return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, MI->getDest(),
1078  MemSizeInBits, DL);
1079 
1080  // If we have a memcpy/memmove, the only case we can handle is if this is a
1081  // copy from constant memory. In that case, we can read directly from the
1082  // constant memory.
1083  MemTransferInst *MTI = cast<MemTransferInst>(MI);
1084 
1085  Constant *Src = dyn_cast<Constant>(MTI->getSource());
1086  if (!Src) return -1;
1087 
1089  if (!GV || !GV->isConstant()) return -1;
1090 
1091  // See if the access is within the bounds of the transfer.
1092  int Offset = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr,
1093  MI->getDest(), MemSizeInBits, DL);
1094  if (Offset == -1)
1095  return Offset;
1096 
1097  unsigned AS = Src->getType()->getPointerAddressSpace();
1098  // Otherwise, see if we can constant fold a load from the constant with the
1099  // offset applied as appropriate.
1100  Src = ConstantExpr::getBitCast(Src,
1101  Type::getInt8PtrTy(Src->getContext(), AS));
1102  Constant *OffsetCst =
1103  ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
1104  Src = ConstantExpr::getGetElementPtr(Type::getInt8Ty(Src->getContext()), Src,
1105  OffsetCst);
1106  Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
1107  if (ConstantFoldLoadFromConstPtr(Src, DL))
1108  return Offset;
1109  return -1;
1110 }
1111 
1112 
1113 /// This function is called when we have a
1114 /// memdep query of a load that ends up being a clobbering store. This means
1115 /// that the store provides bits used by the load but we the pointers don't
1116 /// mustalias. Check this case to see if there is anything more we can do
1117 /// before we give up.
1118 static Value *GetStoreValueForLoad(Value *SrcVal, unsigned Offset,
1119  Type *LoadTy,
1120  Instruction *InsertPt, const DataLayout &DL){
1121  LLVMContext &Ctx = SrcVal->getType()->getContext();
1122 
1123  uint64_t StoreSize = (DL.getTypeSizeInBits(SrcVal->getType()) + 7) / 8;
1124  uint64_t LoadSize = (DL.getTypeSizeInBits(LoadTy) + 7) / 8;
1125 
1126  IRBuilder<> Builder(InsertPt);
1127 
1128  // Compute which bits of the stored value are being used by the load. Convert
1129  // to an integer type to start with.
1130  if (SrcVal->getType()->getScalarType()->isPointerTy())
1131  SrcVal = Builder.CreatePtrToInt(SrcVal,
1132  DL.getIntPtrType(SrcVal->getType()));
1133  if (!SrcVal->getType()->isIntegerTy())
1134  SrcVal = Builder.CreateBitCast(SrcVal, IntegerType::get(Ctx, StoreSize*8));
1135 
1136  // Shift the bits to the least significant depending on endianness.
1137  unsigned ShiftAmt;
1138  if (DL.isLittleEndian())
1139  ShiftAmt = Offset*8;
1140  else
1141  ShiftAmt = (StoreSize-LoadSize-Offset)*8;
1142 
1143  if (ShiftAmt)
1144  SrcVal = Builder.CreateLShr(SrcVal, ShiftAmt);
1145 
1146  if (LoadSize != StoreSize)
1147  SrcVal = Builder.CreateTrunc(SrcVal, IntegerType::get(Ctx, LoadSize*8));
1148 
1149  return CoerceAvailableValueToLoadType(SrcVal, LoadTy, Builder, DL);
1150 }
1151 
1152 /// This function is called when we have a
1153 /// memdep query of a load that ends up being a clobbering load. This means
1154 /// that the load *may* provide bits used by the load but we can't be sure
1155 /// because the pointers don't mustalias. Check this case to see if there is
1156 /// anything more we can do before we give up.
1157 static Value *GetLoadValueForLoad(LoadInst *SrcVal, unsigned Offset,
1158  Type *LoadTy, Instruction *InsertPt,
1159  GVN &gvn) {
1160  const DataLayout &DL = SrcVal->getModule()->getDataLayout();
1161  // If Offset+LoadTy exceeds the size of SrcVal, then we must be wanting to
1162  // widen SrcVal out to a larger load.
1163  unsigned SrcValSize = DL.getTypeStoreSize(SrcVal->getType());
1164  unsigned LoadSize = DL.getTypeStoreSize(LoadTy);
1165  if (Offset+LoadSize > SrcValSize) {
1166  assert(SrcVal->isSimple() && "Cannot widen volatile/atomic load!");
1167  assert(SrcVal->getType()->isIntegerTy() && "Can't widen non-integer load");
1168  // If we have a load/load clobber an DepLI can be widened to cover this
1169  // load, then we should widen it to the next power of 2 size big enough!
1170  unsigned NewLoadSize = Offset+LoadSize;
1171  if (!isPowerOf2_32(NewLoadSize))
1172  NewLoadSize = NextPowerOf2(NewLoadSize);
1173 
1174  Value *PtrVal = SrcVal->getPointerOperand();
1175 
1176  // Insert the new load after the old load. This ensures that subsequent
1177  // memdep queries will find the new load. We can't easily remove the old
1178  // load completely because it is already in the value numbering table.
1179  IRBuilder<> Builder(SrcVal->getParent(), ++BasicBlock::iterator(SrcVal));
1180  Type *DestPTy =
1181  IntegerType::get(LoadTy->getContext(), NewLoadSize*8);
1182  DestPTy = PointerType::get(DestPTy,
1183  PtrVal->getType()->getPointerAddressSpace());
1184  Builder.SetCurrentDebugLocation(SrcVal->getDebugLoc());
1185  PtrVal = Builder.CreateBitCast(PtrVal, DestPTy);
1186  LoadInst *NewLoad = Builder.CreateLoad(PtrVal);
1187  NewLoad->takeName(SrcVal);
1188  NewLoad->setAlignment(SrcVal->getAlignment());
1189 
1190  DEBUG(dbgs() << "GVN WIDENED LOAD: " << *SrcVal << "\n");
1191  DEBUG(dbgs() << "TO: " << *NewLoad << "\n");
1192 
1193  // Replace uses of the original load with the wider load. On a big endian
1194  // system, we need to shift down to get the relevant bits.
1195  Value *RV = NewLoad;
1196  if (DL.isBigEndian())
1197  RV = Builder.CreateLShr(RV,
1198  NewLoadSize*8-SrcVal->getType()->getPrimitiveSizeInBits());
1199  RV = Builder.CreateTrunc(RV, SrcVal->getType());
1200  SrcVal->replaceAllUsesWith(RV);
1201 
1202  // We would like to use gvn.markInstructionForDeletion here, but we can't
1203  // because the load is already memoized into the leader map table that GVN
1204  // tracks. It is potentially possible to remove the load from the table,
1205  // but then there all of the operations based on it would need to be
1206  // rehashed. Just leave the dead load around.
1207  gvn.getMemDep().removeInstruction(SrcVal);
1208  SrcVal = NewLoad;
1209  }
1210 
1211  return GetStoreValueForLoad(SrcVal, Offset, LoadTy, InsertPt, DL);
1212 }
1213 
1214 
1215 /// This function is called when we have a
1216 /// memdep query of a load that ends up being a clobbering mem intrinsic.
1217 static Value *GetMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset,
1218  Type *LoadTy, Instruction *InsertPt,
1219  const DataLayout &DL){
1220  LLVMContext &Ctx = LoadTy->getContext();
1221  uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy)/8;
1222 
1223  IRBuilder<> Builder(InsertPt);
1224 
1225  // We know that this method is only called when the mem transfer fully
1226  // provides the bits for the load.
1227  if (MemSetInst *MSI = dyn_cast<MemSetInst>(SrcInst)) {
1228  // memset(P, 'x', 1234) -> splat('x'), even if x is a variable, and
1229  // independently of what the offset is.
1230  Value *Val = MSI->getValue();
1231  if (LoadSize != 1)
1232  Val = Builder.CreateZExt(Val, IntegerType::get(Ctx, LoadSize*8));
1233 
1234  Value *OneElt = Val;
1235 
1236  // Splat the value out to the right number of bits.
1237  for (unsigned NumBytesSet = 1; NumBytesSet != LoadSize; ) {
1238  // If we can double the number of bytes set, do it.
1239  if (NumBytesSet*2 <= LoadSize) {
1240  Value *ShVal = Builder.CreateShl(Val, NumBytesSet*8);
1241  Val = Builder.CreateOr(Val, ShVal);
1242  NumBytesSet <<= 1;
1243  continue;
1244  }
1245 
1246  // Otherwise insert one byte at a time.
1247  Value *ShVal = Builder.CreateShl(Val, 1*8);
1248  Val = Builder.CreateOr(OneElt, ShVal);
1249  ++NumBytesSet;
1250  }
1251 
1252  return CoerceAvailableValueToLoadType(Val, LoadTy, Builder, DL);
1253  }
1254 
1255  // Otherwise, this is a memcpy/memmove from a constant global.
1256  MemTransferInst *MTI = cast<MemTransferInst>(SrcInst);
1257  Constant *Src = cast<Constant>(MTI->getSource());
1258  unsigned AS = Src->getType()->getPointerAddressSpace();
1259 
1260  // Otherwise, see if we can constant fold a load from the constant with the
1261  // offset applied as appropriate.
1262  Src = ConstantExpr::getBitCast(Src,
1263  Type::getInt8PtrTy(Src->getContext(), AS));
1264  Constant *OffsetCst =
1265  ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
1266  Src = ConstantExpr::getGetElementPtr(Type::getInt8Ty(Src->getContext()), Src,
1267  OffsetCst);
1268  Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
1269  return ConstantFoldLoadFromConstPtr(Src, DL);
1270 }
1271 
1272 
1273 /// Given a set of loads specified by ValuesPerBlock,
1274 /// construct SSA form, allowing us to eliminate LI. This returns the value
1275 /// that should be used at LI's definition site.
1278  GVN &gvn) {
1279  // Check for the fully redundant, dominating load case. In this case, we can
1280  // just use the dominating value directly.
1281  if (ValuesPerBlock.size() == 1 &&
1282  gvn.getDominatorTree().properlyDominates(ValuesPerBlock[0].BB,
1283  LI->getParent())) {
1284  assert(!ValuesPerBlock[0].isUndefValue() && "Dead BB dominate this block");
1285  return ValuesPerBlock[0].MaterializeAdjustedValue(LI, gvn);
1286  }
1287 
1288  // Otherwise, we have to construct SSA form.
1289  SmallVector<PHINode*, 8> NewPHIs;
1290  SSAUpdater SSAUpdate(&NewPHIs);
1291  SSAUpdate.Initialize(LI->getType(), LI->getName());
1292 
1293  for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) {
1294  const AvailableValueInBlock &AV = ValuesPerBlock[i];
1295  BasicBlock *BB = AV.BB;
1296 
1297  if (SSAUpdate.HasValueForBlock(BB))
1298  continue;
1299 
1300  SSAUpdate.AddAvailableValue(BB, AV.MaterializeAdjustedValue(LI, gvn));
1301  }
1302 
1303  // Perform PHI construction.
1304  Value *V = SSAUpdate.GetValueInMiddleOfBlock(LI->getParent());
1305 
1306  // If new PHI nodes were created, notify alias analysis.
1307  if (V->getType()->getScalarType()->isPointerTy()) {
1308  AliasAnalysis *AA = gvn.getAliasAnalysis();
1309 
1310  // Scan the new PHIs and inform alias analysis that we've added potentially
1311  // escaping uses to any values that are operands to these PHIs.
1312  for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) {
1313  PHINode *P = NewPHIs[i];
1314  for (unsigned ii = 0, ee = P->getNumIncomingValues(); ii != ee; ++ii) {
1315  unsigned jj = PHINode::getOperandNumForIncomingValue(ii);
1316  AA->addEscapingUse(P->getOperandUse(jj));
1317  }
1318  }
1319  }
1320 
1321  return V;
1322 }
1323 
1324 Value *AvailableValueInBlock::MaterializeAdjustedValue(LoadInst *LI,
1325  GVN &gvn) const {
1326  Value *Res;
1327  Type *LoadTy = LI->getType();
1328  const DataLayout &DL = LI->getModule()->getDataLayout();
1329  if (isSimpleValue()) {
1330  Res = getSimpleValue();
1331  if (Res->getType() != LoadTy) {
1332  Res = GetStoreValueForLoad(Res, Offset, LoadTy, BB->getTerminator(), DL);
1333 
1334  DEBUG(dbgs() << "GVN COERCED NONLOCAL VAL:\nOffset: " << Offset << " "
1335  << *getSimpleValue() << '\n'
1336  << *Res << '\n' << "\n\n\n");
1337  }
1338  } else if (isCoercedLoadValue()) {
1339  LoadInst *Load = getCoercedLoadValue();
1340  if (Load->getType() == LoadTy && Offset == 0) {
1341  Res = Load;
1342  } else {
1343  Res = GetLoadValueForLoad(Load, Offset, LoadTy, BB->getTerminator(),
1344  gvn);
1345 
1346  DEBUG(dbgs() << "GVN COERCED NONLOCAL LOAD:\nOffset: " << Offset << " "
1347  << *getCoercedLoadValue() << '\n'
1348  << *Res << '\n' << "\n\n\n");
1349  }
1350  } else if (isMemIntrinValue()) {
1351  Res = GetMemInstValueForLoad(getMemIntrinValue(), Offset, LoadTy,
1352  BB->getTerminator(), DL);
1353  DEBUG(dbgs() << "GVN COERCED NONLOCAL MEM INTRIN:\nOffset: " << Offset
1354  << " " << *getMemIntrinValue() << '\n'
1355  << *Res << '\n' << "\n\n\n");
1356  } else {
1357  assert(isUndefValue() && "Should be UndefVal");
1358  DEBUG(dbgs() << "GVN COERCED NONLOCAL Undef:\n";);
1359  return UndefValue::get(LoadTy);
1360  }
1361  return Res;
1362 }
1363 
1364 static bool isLifetimeStart(const Instruction *Inst) {
1365  if (const IntrinsicInst* II = dyn_cast<IntrinsicInst>(Inst))
1366  return II->getIntrinsicID() == Intrinsic::lifetime_start;
1367  return false;
1368 }
1369 
1370 void GVN::AnalyzeLoadAvailability(LoadInst *LI, LoadDepVect &Deps,
1371  AvailValInBlkVect &ValuesPerBlock,
1372  UnavailBlkVect &UnavailableBlocks) {
1373 
1374  // Filter out useless results (non-locals, etc). Keep track of the blocks
1375  // where we have a value available in repl, also keep track of whether we see
1376  // dependencies that produce an unknown value for the load (such as a call
1377  // that could potentially clobber the load).
1378  unsigned NumDeps = Deps.size();
1379  const DataLayout &DL = LI->getModule()->getDataLayout();
1380  for (unsigned i = 0, e = NumDeps; i != e; ++i) {
1381  BasicBlock *DepBB = Deps[i].getBB();
1382  MemDepResult DepInfo = Deps[i].getResult();
1383 
1384  if (DeadBlocks.count(DepBB)) {
1385  // Dead dependent mem-op disguise as a load evaluating the same value
1386  // as the load in question.
1387  ValuesPerBlock.push_back(AvailableValueInBlock::getUndef(DepBB));
1388  continue;
1389  }
1390 
1391  if (!DepInfo.isDef() && !DepInfo.isClobber()) {
1392  UnavailableBlocks.push_back(DepBB);
1393  continue;
1394  }
1395 
1396  if (DepInfo.isClobber()) {
1397  // The address being loaded in this non-local block may not be the same as
1398  // the pointer operand of the load if PHI translation occurs. Make sure
1399  // to consider the right address.
1400  Value *Address = Deps[i].getAddress();
1401 
1402  // If the dependence is to a store that writes to a superset of the bits
1403  // read by the load, we can extract the bits we need for the load from the
1404  // stored value.
1405  if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInfo.getInst())) {
1406  if (Address) {
1407  int Offset =
1409  if (Offset != -1) {
1410  ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
1411  DepSI->getValueOperand(),
1412  Offset));
1413  continue;
1414  }
1415  }
1416  }
1417 
1418  // Check to see if we have something like this:
1419  // load i32* P
1420  // load i8* (P+1)
1421  // if we have this, replace the later with an extraction from the former.
1422  if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInfo.getInst())) {
1423  // If this is a clobber and L is the first instruction in its block, then
1424  // we have the first instruction in the entry block.
1425  if (DepLI != LI && Address) {
1426  int Offset =
1427  AnalyzeLoadFromClobberingLoad(LI->getType(), Address, DepLI, DL);
1428 
1429  if (Offset != -1) {
1430  ValuesPerBlock.push_back(AvailableValueInBlock::getLoad(DepBB,DepLI,
1431  Offset));
1432  continue;
1433  }
1434  }
1435  }
1436 
1437  // If the clobbering value is a memset/memcpy/memmove, see if we can
1438  // forward a value on from it.
1439  if (MemIntrinsic *DepMI = dyn_cast<MemIntrinsic>(DepInfo.getInst())) {
1440  if (Address) {
1441  int Offset = AnalyzeLoadFromClobberingMemInst(LI->getType(), Address,
1442  DepMI, DL);
1443  if (Offset != -1) {
1444  ValuesPerBlock.push_back(AvailableValueInBlock::getMI(DepBB, DepMI,
1445  Offset));
1446  continue;
1447  }
1448  }
1449  }
1450 
1451  UnavailableBlocks.push_back(DepBB);
1452  continue;
1453  }
1454 
1455  // DepInfo.isDef() here
1456 
1457  Instruction *DepInst = DepInfo.getInst();
1458 
1459  // Loading the allocation -> undef.
1460  if (isa<AllocaInst>(DepInst) || isMallocLikeFn(DepInst, TLI) ||
1461  // Loading immediately after lifetime begin -> undef.
1462  isLifetimeStart(DepInst)) {
1463  ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
1464  UndefValue::get(LI->getType())));
1465  continue;
1466  }
1467 
1468  // Loading from calloc (which zero initializes memory) -> zero
1469  if (isCallocLikeFn(DepInst, TLI)) {
1470  ValuesPerBlock.push_back(AvailableValueInBlock::get(
1471  DepBB, Constant::getNullValue(LI->getType())));
1472  continue;
1473  }
1474 
1475  if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
1476  // Reject loads and stores that are to the same address but are of
1477  // different types if we have to.
1478  if (S->getValueOperand()->getType() != LI->getType()) {
1479  // If the stored value is larger or equal to the loaded value, we can
1480  // reuse it.
1481  if (!CanCoerceMustAliasedValueToLoad(S->getValueOperand(),
1482  LI->getType(), DL)) {
1483  UnavailableBlocks.push_back(DepBB);
1484  continue;
1485  }
1486  }
1487 
1488  ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
1489  S->getValueOperand()));
1490  continue;
1491  }
1492 
1493  if (LoadInst *LD = dyn_cast<LoadInst>(DepInst)) {
1494  // If the types mismatch and we can't handle it, reject reuse of the load.
1495  if (LD->getType() != LI->getType()) {
1496  // If the stored value is larger or equal to the loaded value, we can
1497  // reuse it.
1498  if (!CanCoerceMustAliasedValueToLoad(LD, LI->getType(), DL)) {
1499  UnavailableBlocks.push_back(DepBB);
1500  continue;
1501  }
1502  }
1503  ValuesPerBlock.push_back(AvailableValueInBlock::getLoad(DepBB, LD));
1504  continue;
1505  }
1506 
1507  UnavailableBlocks.push_back(DepBB);
1508  }
1509 }
1510 
1511 bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
1512  UnavailBlkVect &UnavailableBlocks) {
1513  // Okay, we have *some* definitions of the value. This means that the value
1514  // is available in some of our (transitive) predecessors. Lets think about
1515  // doing PRE of this load. This will involve inserting a new load into the
1516  // predecessor when it's not available. We could do this in general, but
1517  // prefer to not increase code size. As such, we only do this when we know
1518  // that we only have to insert *one* load (which means we're basically moving
1519  // the load, not inserting a new one).
1520 
1522  for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
1523  Blockers.insert(UnavailableBlocks[i]);
1524 
1525  // Let's find the first basic block with more than one predecessor. Walk
1526  // backwards through predecessors if needed.
1527  BasicBlock *LoadBB = LI->getParent();
1528  BasicBlock *TmpBB = LoadBB;
1529 
1530  while (TmpBB->getSinglePredecessor()) {
1531  TmpBB = TmpBB->getSinglePredecessor();
1532  if (TmpBB == LoadBB) // Infinite (unreachable) loop.
1533  return false;
1534  if (Blockers.count(TmpBB))
1535  return false;
1536 
1537  // If any of these blocks has more than one successor (i.e. if the edge we
1538  // just traversed was critical), then there are other paths through this
1539  // block along which the load may not be anticipated. Hoisting the load
1540  // above this block would be adding the load to execution paths along
1541  // which it was not previously executed.
1542  if (TmpBB->getTerminator()->getNumSuccessors() != 1)
1543  return false;
1544  }
1545 
1546  assert(TmpBB);
1547  LoadBB = TmpBB;
1548 
1549  // Check to see how many predecessors have the loaded value fully
1550  // available.
1552  DenseMap<BasicBlock*, char> FullyAvailableBlocks;
1553  for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
1554  FullyAvailableBlocks[ValuesPerBlock[i].BB] = true;
1555  for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
1556  FullyAvailableBlocks[UnavailableBlocks[i]] = false;
1557 
1558  SmallVector<BasicBlock *, 4> CriticalEdgePred;
1559  for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
1560  PI != E; ++PI) {
1561  BasicBlock *Pred = *PI;
1562  if (IsValueFullyAvailableInBlock(Pred, FullyAvailableBlocks, 0)) {
1563  continue;
1564  }
1565 
1566  if (Pred->getTerminator()->getNumSuccessors() != 1) {
1567  if (isa<IndirectBrInst>(Pred->getTerminator())) {
1568  DEBUG(dbgs() << "COULD NOT PRE LOAD BECAUSE OF INDBR CRITICAL EDGE '"
1569  << Pred->getName() << "': " << *LI << '\n');
1570  return false;
1571  }
1572 
1573  if (LoadBB->isLandingPad()) {
1574  DEBUG(dbgs()
1575  << "COULD NOT PRE LOAD BECAUSE OF LANDING PAD CRITICAL EDGE '"
1576  << Pred->getName() << "': " << *LI << '\n');
1577  return false;
1578  }
1579 
1580  CriticalEdgePred.push_back(Pred);
1581  } else {
1582  // Only add the predecessors that will not be split for now.
1583  PredLoads[Pred] = nullptr;
1584  }
1585  }
1586 
1587  // Decide whether PRE is profitable for this load.
1588  unsigned NumUnavailablePreds = PredLoads.size() + CriticalEdgePred.size();
1589  assert(NumUnavailablePreds != 0 &&
1590  "Fully available value should already be eliminated!");
1591 
1592  // If this load is unavailable in multiple predecessors, reject it.
1593  // FIXME: If we could restructure the CFG, we could make a common pred with
1594  // all the preds that don't have an available LI and insert a new load into
1595  // that one block.
1596  if (NumUnavailablePreds != 1)
1597  return false;
1598 
1599  // Split critical edges, and update the unavailable predecessors accordingly.
1600  for (BasicBlock *OrigPred : CriticalEdgePred) {
1601  BasicBlock *NewPred = splitCriticalEdges(OrigPred, LoadBB);
1602  assert(!PredLoads.count(OrigPred) && "Split edges shouldn't be in map!");
1603  PredLoads[NewPred] = nullptr;
1604  DEBUG(dbgs() << "Split critical edge " << OrigPred->getName() << "->"
1605  << LoadBB->getName() << '\n');
1606  }
1607 
1608  // Check if the load can safely be moved to all the unavailable predecessors.
1609  bool CanDoPRE = true;
1610  const DataLayout &DL = LI->getModule()->getDataLayout();
1612  for (auto &PredLoad : PredLoads) {
1613  BasicBlock *UnavailablePred = PredLoad.first;
1614 
1615  // Do PHI translation to get its value in the predecessor if necessary. The
1616  // returned pointer (if non-null) is guaranteed to dominate UnavailablePred.
1617 
1618  // If all preds have a single successor, then we know it is safe to insert
1619  // the load on the pred (?!?), so we can insert code to materialize the
1620  // pointer if it is not available.
1621  PHITransAddr Address(LI->getPointerOperand(), DL, AC);
1622  Value *LoadPtr = nullptr;
1623  LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
1624  *DT, NewInsts);
1625 
1626  // If we couldn't find or insert a computation of this phi translated value,
1627  // we fail PRE.
1628  if (!LoadPtr) {
1629  DEBUG(dbgs() << "COULDN'T INSERT PHI TRANSLATED VALUE OF: "
1630  << *LI->getPointerOperand() << "\n");
1631  CanDoPRE = false;
1632  break;
1633  }
1634 
1635  PredLoad.second = LoadPtr;
1636  }
1637 
1638  if (!CanDoPRE) {
1639  while (!NewInsts.empty()) {
1640  Instruction *I = NewInsts.pop_back_val();
1641  if (MD) MD->removeInstruction(I);
1642  I->eraseFromParent();
1643  }
1644  // HINT: Don't revert the edge-splitting as following transformation may
1645  // also need to split these critical edges.
1646  return !CriticalEdgePred.empty();
1647  }
1648 
1649  // Okay, we can eliminate this load by inserting a reload in the predecessor
1650  // and using PHI construction to get the value in the other predecessors, do
1651  // it.
1652  DEBUG(dbgs() << "GVN REMOVING PRE LOAD: " << *LI << '\n');
1653  DEBUG(if (!NewInsts.empty())
1654  dbgs() << "INSERTED " << NewInsts.size() << " INSTS: "
1655  << *NewInsts.back() << '\n');
1656 
1657  // Assign value numbers to the new instructions.
1658  for (unsigned i = 0, e = NewInsts.size(); i != e; ++i) {
1659  // FIXME: We really _ought_ to insert these value numbers into their
1660  // parent's availability map. However, in doing so, we risk getting into
1661  // ordering issues. If a block hasn't been processed yet, we would be
1662  // marking a value as AVAIL-IN, which isn't what we intend.
1663  VN.lookup_or_add(NewInsts[i]);
1664  }
1665 
1666  for (const auto &PredLoad : PredLoads) {
1667  BasicBlock *UnavailablePred = PredLoad.first;
1668  Value *LoadPtr = PredLoad.second;
1669 
1670  Instruction *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
1671  LI->getAlignment(),
1672  UnavailablePred->getTerminator());
1673 
1674  // Transfer the old load's AA tags to the new load.
1675  AAMDNodes Tags;
1676  LI->getAAMetadata(Tags);
1677  if (Tags)
1678  NewLoad->setAAMetadata(Tags);
1679 
1680  // Transfer DebugLoc.
1681  NewLoad->setDebugLoc(LI->getDebugLoc());
1682 
1683  // Add the newly created load.
1684  ValuesPerBlock.push_back(AvailableValueInBlock::get(UnavailablePred,
1685  NewLoad));
1686  MD->invalidateCachedPointerInfo(LoadPtr);
1687  DEBUG(dbgs() << "GVN INSERTED " << *NewLoad << '\n');
1688  }
1689 
1690  // Perform PHI construction.
1691  Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, *this);
1692  LI->replaceAllUsesWith(V);
1693  if (isa<PHINode>(V))
1694  V->takeName(LI);
1695  if (Instruction *I = dyn_cast<Instruction>(V))
1696  I->setDebugLoc(LI->getDebugLoc());
1697  if (V->getType()->getScalarType()->isPointerTy())
1698  MD->invalidateCachedPointerInfo(V);
1699  markInstructionForDeletion(LI);
1700  ++NumPRELoad;
1701  return true;
1702 }
1703 
1704 /// Attempt to eliminate a load whose dependencies are
1705 /// non-local by performing PHI construction.
1706 bool GVN::processNonLocalLoad(LoadInst *LI) {
1707  // Step 1: Find the non-local dependencies of the load.
1708  LoadDepVect Deps;
1709  MD->getNonLocalPointerDependency(LI, Deps);
1710 
1711  // If we had to process more than one hundred blocks to find the
1712  // dependencies, this load isn't worth worrying about. Optimizing
1713  // it will be too expensive.
1714  unsigned NumDeps = Deps.size();
1715  if (NumDeps > 100)
1716  return false;
1717 
1718  // If we had a phi translation failure, we'll have a single entry which is a
1719  // clobber in the current block. Reject this early.
1720  if (NumDeps == 1 &&
1721  !Deps[0].getResult().isDef() && !Deps[0].getResult().isClobber()) {
1722  DEBUG(
1723  dbgs() << "GVN: non-local load ";
1724  LI->printAsOperand(dbgs());
1725  dbgs() << " has unknown dependencies\n";
1726  );
1727  return false;
1728  }
1729 
1730  // If this load follows a GEP, see if we can PRE the indices before analyzing.
1731  if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0))) {
1732  for (GetElementPtrInst::op_iterator OI = GEP->idx_begin(),
1733  OE = GEP->idx_end();
1734  OI != OE; ++OI)
1735  if (Instruction *I = dyn_cast<Instruction>(OI->get()))
1736  performScalarPRE(I);
1737  }
1738 
1739  // Step 2: Analyze the availability of the load
1740  AvailValInBlkVect ValuesPerBlock;
1741  UnavailBlkVect UnavailableBlocks;
1742  AnalyzeLoadAvailability(LI, Deps, ValuesPerBlock, UnavailableBlocks);
1743 
1744  // If we have no predecessors that produce a known value for this load, exit
1745  // early.
1746  if (ValuesPerBlock.empty())
1747  return false;
1748 
1749  // Step 3: Eliminate fully redundancy.
1750  //
1751  // If all of the instructions we depend on produce a known value for this
1752  // load, then it is fully redundant and we can use PHI insertion to compute
1753  // its value. Insert PHIs and remove the fully redundant value now.
1754  if (UnavailableBlocks.empty()) {
1755  DEBUG(dbgs() << "GVN REMOVING NONLOCAL LOAD: " << *LI << '\n');
1756 
1757  // Perform PHI construction.
1758  Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, *this);
1759  LI->replaceAllUsesWith(V);
1760 
1761  if (isa<PHINode>(V))
1762  V->takeName(LI);
1763  if (Instruction *I = dyn_cast<Instruction>(V))
1764  I->setDebugLoc(LI->getDebugLoc());
1765  if (V->getType()->getScalarType()->isPointerTy())
1766  MD->invalidateCachedPointerInfo(V);
1767  markInstructionForDeletion(LI);
1768  ++NumGVNLoad;
1769  return true;
1770  }
1771 
1772  // Step 4: Eliminate partial redundancy.
1773  if (!EnablePRE || !EnableLoadPRE)
1774  return false;
1775 
1776  return PerformLoadPRE(LI, ValuesPerBlock, UnavailableBlocks);
1777 }
1778 
1779 
1781  // Patch the replacement so that it is not more restrictive than the value
1782  // being replaced.
1784  BinaryOperator *ReplOp = dyn_cast<BinaryOperator>(Repl);
1785  if (Op && ReplOp)
1786  ReplOp->andIRFlags(Op);
1787 
1788  if (Instruction *ReplInst = dyn_cast<Instruction>(Repl)) {
1789  // FIXME: If both the original and replacement value are part of the
1790  // same control-flow region (meaning that the execution of one
1791  // guarentees the executation of the other), then we can combine the
1792  // noalias scopes here and do better than the general conservative
1793  // answer used in combineMetadata().
1794 
1795  // In general, GVN unifies expressions over different control-flow
1796  // regions, and so we need a conservative combination of the noalias
1797  // scopes.
1798  static const unsigned KnownIDs[] = {
1805  };
1806  combineMetadata(ReplInst, I, KnownIDs);
1807  }
1808 }
1809 
1811  patchReplacementInstruction(I, Repl);
1812  I->replaceAllUsesWith(Repl);
1813 }
1814 
1815 /// Attempt to eliminate a load, first by eliminating it
1816 /// locally, and then attempting non-local elimination if that fails.
1817 bool GVN::processLoad(LoadInst *L) {
1818  if (!MD)
1819  return false;
1820 
1821  if (!L->isSimple())
1822  return false;
1823 
1824  if (L->use_empty()) {
1825  markInstructionForDeletion(L);
1826  return true;
1827  }
1828 
1829  // ... to a pointer that has been loaded from before...
1830  MemDepResult Dep = MD->getDependency(L);
1831  const DataLayout &DL = L->getModule()->getDataLayout();
1832 
1833  // If we have a clobber and target data is around, see if this is a clobber
1834  // that we can fix up through code synthesis.
1835  if (Dep.isClobber()) {
1836  // Check to see if we have something like this:
1837  // store i32 123, i32* %P
1838  // %A = bitcast i32* %P to i8*
1839  // %B = gep i8* %A, i32 1
1840  // %C = load i8* %B
1841  //
1842  // We could do that by recognizing if the clobber instructions are obviously
1843  // a common base + constant offset, and if the previous store (or memset)
1844  // completely covers this load. This sort of thing can happen in bitfield
1845  // access code.
1846  Value *AvailVal = nullptr;
1847  if (StoreInst *DepSI = dyn_cast<StoreInst>(Dep.getInst())) {
1848  int Offset = AnalyzeLoadFromClobberingStore(
1849  L->getType(), L->getPointerOperand(), DepSI);
1850  if (Offset != -1)
1851  AvailVal = GetStoreValueForLoad(DepSI->getValueOperand(), Offset,
1852  L->getType(), L, DL);
1853  }
1854 
1855  // Check to see if we have something like this:
1856  // load i32* P
1857  // load i8* (P+1)
1858  // if we have this, replace the later with an extraction from the former.
1859  if (LoadInst *DepLI = dyn_cast<LoadInst>(Dep.getInst())) {
1860  // If this is a clobber and L is the first instruction in its block, then
1861  // we have the first instruction in the entry block.
1862  if (DepLI == L)
1863  return false;
1864 
1865  int Offset = AnalyzeLoadFromClobberingLoad(
1866  L->getType(), L->getPointerOperand(), DepLI, DL);
1867  if (Offset != -1)
1868  AvailVal = GetLoadValueForLoad(DepLI, Offset, L->getType(), L, *this);
1869  }
1870 
1871  // If the clobbering value is a memset/memcpy/memmove, see if we can forward
1872  // a value on from it.
1873  if (MemIntrinsic *DepMI = dyn_cast<MemIntrinsic>(Dep.getInst())) {
1874  int Offset = AnalyzeLoadFromClobberingMemInst(
1875  L->getType(), L->getPointerOperand(), DepMI, DL);
1876  if (Offset != -1)
1877  AvailVal = GetMemInstValueForLoad(DepMI, Offset, L->getType(), L, DL);
1878  }
1879 
1880  if (AvailVal) {
1881  DEBUG(dbgs() << "GVN COERCED INST:\n" << *Dep.getInst() << '\n'
1882  << *AvailVal << '\n' << *L << "\n\n\n");
1883 
1884  // Replace the load!
1885  L->replaceAllUsesWith(AvailVal);
1886  if (AvailVal->getType()->getScalarType()->isPointerTy())
1887  MD->invalidateCachedPointerInfo(AvailVal);
1888  markInstructionForDeletion(L);
1889  ++NumGVNLoad;
1890  return true;
1891  }
1892  }
1893 
1894  // If the value isn't available, don't do anything!
1895  if (Dep.isClobber()) {
1896  DEBUG(
1897  // fast print dep, using operator<< on instruction is too slow.
1898  dbgs() << "GVN: load ";
1899  L->printAsOperand(dbgs());
1900  Instruction *I = Dep.getInst();
1901  dbgs() << " is clobbered by " << *I << '\n';
1902  );
1903  return false;
1904  }
1905 
1906  // If it is defined in another block, try harder.
1907  if (Dep.isNonLocal())
1908  return processNonLocalLoad(L);
1909 
1910  if (!Dep.isDef()) {
1911  DEBUG(
1912  // fast print dep, using operator<< on instruction is too slow.
1913  dbgs() << "GVN: load ";
1914  L->printAsOperand(dbgs());
1915  dbgs() << " has unknown dependence\n";
1916  );
1917  return false;
1918  }
1919 
1920  Instruction *DepInst = Dep.getInst();
1921  if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInst)) {
1922  Value *StoredVal = DepSI->getValueOperand();
1923 
1924  // The store and load are to a must-aliased pointer, but they may not
1925  // actually have the same type. See if we know how to reuse the stored
1926  // value (depending on its type).
1927  if (StoredVal->getType() != L->getType()) {
1928  IRBuilder<> Builder(L);
1929  StoredVal =
1930  CoerceAvailableValueToLoadType(StoredVal, L->getType(), Builder, DL);
1931  if (!StoredVal)
1932  return false;
1933 
1934  DEBUG(dbgs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
1935  << '\n' << *L << "\n\n\n");
1936  }
1937 
1938  // Remove it!
1939  L->replaceAllUsesWith(StoredVal);
1940  if (StoredVal->getType()->getScalarType()->isPointerTy())
1941  MD->invalidateCachedPointerInfo(StoredVal);
1942  markInstructionForDeletion(L);
1943  ++NumGVNLoad;
1944  return true;
1945  }
1946 
1947  if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInst)) {
1948  Value *AvailableVal = DepLI;
1949 
1950  // The loads are of a must-aliased pointer, but they may not actually have
1951  // the same type. See if we know how to reuse the previously loaded value
1952  // (depending on its type).
1953  if (DepLI->getType() != L->getType()) {
1954  IRBuilder<> Builder(L);
1955  AvailableVal =
1956  CoerceAvailableValueToLoadType(DepLI, L->getType(), Builder, DL);
1957  if (!AvailableVal)
1958  return false;
1959 
1960  DEBUG(dbgs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
1961  << "\n" << *L << "\n\n\n");
1962  }
1963 
1964  // Remove it!
1965  patchAndReplaceAllUsesWith(L, AvailableVal);
1966  if (DepLI->getType()->getScalarType()->isPointerTy())
1967  MD->invalidateCachedPointerInfo(DepLI);
1968  markInstructionForDeletion(L);
1969  ++NumGVNLoad;
1970  return true;
1971  }
1972 
1973  // If this load really doesn't depend on anything, then we must be loading an
1974  // undef value. This can happen when loading for a fresh allocation with no
1975  // intervening stores, for example.
1976  if (isa<AllocaInst>(DepInst) || isMallocLikeFn(DepInst, TLI)) {
1978  markInstructionForDeletion(L);
1979  ++NumGVNLoad;
1980  return true;
1981  }
1982 
1983  // If this load occurs either right after a lifetime begin,
1984  // then the loaded value is undefined.
1985  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(DepInst)) {
1986  if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
1988  markInstructionForDeletion(L);
1989  ++NumGVNLoad;
1990  return true;
1991  }
1992  }
1993 
1994  // If this load follows a calloc (which zero initializes memory),
1995  // then the loaded value is zero
1996  if (isCallocLikeFn(DepInst, TLI)) {
1998  markInstructionForDeletion(L);
1999  ++NumGVNLoad;
2000  return true;
2001  }
2002 
2003  return false;
2004 }
2005 
2006 // In order to find a leader for a given value number at a
2007 // specific basic block, we first obtain the list of all Values for that number,
2008 // and then scan the list to find one whose block dominates the block in
2009 // question. This is fast because dominator tree queries consist of only
2010 // a few comparisons of DFS numbers.
2011 Value *GVN::findLeader(const BasicBlock *BB, uint32_t num) {
2012  LeaderTableEntry Vals = LeaderTable[num];
2013  if (!Vals.Val) return nullptr;
2014 
2015  Value *Val = nullptr;
2016  if (DT->dominates(Vals.BB, BB)) {
2017  Val = Vals.Val;
2018  if (isa<Constant>(Val)) return Val;
2019  }
2020 
2021  LeaderTableEntry* Next = Vals.Next;
2022  while (Next) {
2023  if (DT->dominates(Next->BB, BB)) {
2024  if (isa<Constant>(Next->Val)) return Next->Val;
2025  if (!Val) Val = Next->Val;
2026  }
2027 
2028  Next = Next->Next;
2029  }
2030 
2031  return Val;
2032 }
2033 
2034 /// There is an edge from 'Src' to 'Dst'. Return
2035 /// true if every path from the entry block to 'Dst' passes via this edge. In
2036 /// particular 'Dst' must not be reachable via another edge from 'Src'.
2038  DominatorTree *DT) {
2039  // While in theory it is interesting to consider the case in which Dst has
2040  // more than one predecessor, because Dst might be part of a loop which is
2041  // only reachable from Src, in practice it is pointless since at the time
2042  // GVN runs all such loops have preheaders, which means that Dst will have
2043  // been changed to have only one predecessor, namely Src.
2044  const BasicBlock *Pred = E.getEnd()->getSinglePredecessor();
2045  const BasicBlock *Src = E.getStart();
2046  assert((!Pred || Pred == Src) && "No edge between these basic blocks!");
2047  (void)Src;
2048  return Pred != nullptr;
2049 }
2050 
2051 /// The given values are known to be equal in every block
2052 /// dominated by 'Root'. Exploit this, for example by replacing 'LHS' with
2053 /// 'RHS' everywhere in the scope. Returns whether a change was made.
2054 bool GVN::propagateEquality(Value *LHS, Value *RHS,
2055  const BasicBlockEdge &Root) {
2057  Worklist.push_back(std::make_pair(LHS, RHS));
2058  bool Changed = false;
2059  // For speed, compute a conservative fast approximation to
2060  // DT->dominates(Root, Root.getEnd());
2061  bool RootDominatesEnd = isOnlyReachableViaThisEdge(Root, DT);
2062 
2063  while (!Worklist.empty()) {
2064  std::pair<Value*, Value*> Item = Worklist.pop_back_val();
2065  LHS = Item.first; RHS = Item.second;
2066 
2067  if (LHS == RHS) continue;
2068  assert(LHS->getType() == RHS->getType() && "Equality but unequal types!");
2069 
2070  // Don't try to propagate equalities between constants.
2071  if (isa<Constant>(LHS) && isa<Constant>(RHS)) continue;
2072 
2073  // Prefer a constant on the right-hand side, or an Argument if no constants.
2074  if (isa<Constant>(LHS) || (isa<Argument>(LHS) && !isa<Constant>(RHS)))
2075  std::swap(LHS, RHS);
2076  assert((isa<Argument>(LHS) || isa<Instruction>(LHS)) && "Unexpected value!");
2077 
2078  // If there is no obvious reason to prefer the left-hand side over the
2079  // right-hand side, ensure the longest lived term is on the right-hand side,
2080  // so the shortest lived term will be replaced by the longest lived.
2081  // This tends to expose more simplifications.
2082  uint32_t LVN = VN.lookup_or_add(LHS);
2083  if ((isa<Argument>(LHS) && isa<Argument>(RHS)) ||
2084  (isa<Instruction>(LHS) && isa<Instruction>(RHS))) {
2085  // Move the 'oldest' value to the right-hand side, using the value number
2086  // as a proxy for age.
2087  uint32_t RVN = VN.lookup_or_add(RHS);
2088  if (LVN < RVN) {
2089  std::swap(LHS, RHS);
2090  LVN = RVN;
2091  }
2092  }
2093 
2094  // If value numbering later sees that an instruction in the scope is equal
2095  // to 'LHS' then ensure it will be turned into 'RHS'. In order to preserve
2096  // the invariant that instructions only occur in the leader table for their
2097  // own value number (this is used by removeFromLeaderTable), do not do this
2098  // if RHS is an instruction (if an instruction in the scope is morphed into
2099  // LHS then it will be turned into RHS by the next GVN iteration anyway, so
2100  // using the leader table is about compiling faster, not optimizing better).
2101  // The leader table only tracks basic blocks, not edges. Only add to if we
2102  // have the simple case where the edge dominates the end.
2103  if (RootDominatesEnd && !isa<Instruction>(RHS))
2104  addToLeaderTable(LVN, RHS, Root.getEnd());
2105 
2106  // Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope. As
2107  // LHS always has at least one use that is not dominated by Root, this will
2108  // never do anything if LHS has only one use.
2109  if (!LHS->hasOneUse()) {
2110  unsigned NumReplacements = replaceDominatedUsesWith(LHS, RHS, *DT, Root);
2111  Changed |= NumReplacements > 0;
2112  NumGVNEqProp += NumReplacements;
2113  }
2114 
2115  // Now try to deduce additional equalities from this one. For example, if
2116  // the known equality was "(A != B)" == "false" then it follows that A and B
2117  // are equal in the scope. Only boolean equalities with an explicit true or
2118  // false RHS are currently supported.
2119  if (!RHS->getType()->isIntegerTy(1))
2120  // Not a boolean equality - bail out.
2121  continue;
2122  ConstantInt *CI = dyn_cast<ConstantInt>(RHS);
2123  if (!CI)
2124  // RHS neither 'true' nor 'false' - bail out.
2125  continue;
2126  // Whether RHS equals 'true'. Otherwise it equals 'false'.
2127  bool isKnownTrue = CI->isAllOnesValue();
2128  bool isKnownFalse = !isKnownTrue;
2129 
2130  // If "A && B" is known true then both A and B are known true. If "A || B"
2131  // is known false then both A and B are known false.
2132  Value *A, *B;
2133  if ((isKnownTrue && match(LHS, m_And(m_Value(A), m_Value(B)))) ||
2134  (isKnownFalse && match(LHS, m_Or(m_Value(A), m_Value(B))))) {
2135  Worklist.push_back(std::make_pair(A, RHS));
2136  Worklist.push_back(std::make_pair(B, RHS));
2137  continue;
2138  }
2139 
2140  // If we are propagating an equality like "(A == B)" == "true" then also
2141  // propagate the equality A == B. When propagating a comparison such as
2142  // "(A >= B)" == "true", replace all instances of "A < B" with "false".
2143  if (CmpInst *Cmp = dyn_cast<CmpInst>(LHS)) {
2144  Value *Op0 = Cmp->getOperand(0), *Op1 = Cmp->getOperand(1);
2145 
2146  // If "A == B" is known true, or "A != B" is known false, then replace
2147  // A with B everywhere in the scope.
2148  if ((isKnownTrue && Cmp->getPredicate() == CmpInst::ICMP_EQ) ||
2149  (isKnownFalse && Cmp->getPredicate() == CmpInst::ICMP_NE))
2150  Worklist.push_back(std::make_pair(Op0, Op1));
2151 
2152  // Handle the floating point versions of equality comparisons too.
2153  if ((isKnownTrue && Cmp->getPredicate() == CmpInst::FCMP_OEQ) ||
2154  (isKnownFalse && Cmp->getPredicate() == CmpInst::FCMP_UNE)) {
2155 
2156  // Floating point -0.0 and 0.0 compare equal, so we can only
2157  // propagate values if we know that we have a constant and that
2158  // its value is non-zero.
2159 
2160  // FIXME: We should do this optimization if 'no signed zeros' is
2161  // applicable via an instruction-level fast-math-flag or some other
2162  // indicator that relaxed FP semantics are being used.
2163 
2164  if (isa<ConstantFP>(Op1) && !cast<ConstantFP>(Op1)->isZero())
2165  Worklist.push_back(std::make_pair(Op0, Op1));
2166  }
2167 
2168  // If "A >= B" is known true, replace "A < B" with false everywhere.
2169  CmpInst::Predicate NotPred = Cmp->getInversePredicate();
2170  Constant *NotVal = ConstantInt::get(Cmp->getType(), isKnownFalse);
2171  // Since we don't have the instruction "A < B" immediately to hand, work
2172  // out the value number that it would have and use that to find an
2173  // appropriate instruction (if any).
2174  uint32_t NextNum = VN.getNextUnusedValueNumber();
2175  uint32_t Num = VN.lookup_or_add_cmp(Cmp->getOpcode(), NotPred, Op0, Op1);
2176  // If the number we were assigned was brand new then there is no point in
2177  // looking for an instruction realizing it: there cannot be one!
2178  if (Num < NextNum) {
2179  Value *NotCmp = findLeader(Root.getEnd(), Num);
2180  if (NotCmp && isa<Instruction>(NotCmp)) {
2181  unsigned NumReplacements =
2182  replaceDominatedUsesWith(NotCmp, NotVal, *DT, Root);
2183  Changed |= NumReplacements > 0;
2184  NumGVNEqProp += NumReplacements;
2185  }
2186  }
2187  // Ensure that any instruction in scope that gets the "A < B" value number
2188  // is replaced with false.
2189  // The leader table only tracks basic blocks, not edges. Only add to if we
2190  // have the simple case where the edge dominates the end.
2191  if (RootDominatesEnd)
2192  addToLeaderTable(Num, NotVal, Root.getEnd());
2193 
2194  continue;
2195  }
2196  }
2197 
2198  return Changed;
2199 }
2200 
2201 /// When calculating availability, handle an instruction
2202 /// by inserting it into the appropriate sets
2204  // Ignore dbg info intrinsics.
2205  if (isa<DbgInfoIntrinsic>(I))
2206  return false;
2207 
2208  // If the instruction can be easily simplified then do so now in preference
2209  // to value numbering it. Value numbering often exposes redundancies, for
2210  // example if it determines that %y is equal to %x then the instruction
2211  // "%z = and i32 %x, %y" becomes "%z = and i32 %x, %x" which we now simplify.
2212  const DataLayout &DL = I->getModule()->getDataLayout();
2213  if (Value *V = SimplifyInstruction(I, DL, TLI, DT, AC)) {
2214  I->replaceAllUsesWith(V);
2215  if (MD && V->getType()->getScalarType()->isPointerTy())
2216  MD->invalidateCachedPointerInfo(V);
2217  markInstructionForDeletion(I);
2218  ++NumGVNSimpl;
2219  return true;
2220  }
2221 
2222  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
2223  if (processLoad(LI))
2224  return true;
2225 
2226  unsigned Num = VN.lookup_or_add(LI);
2227  addToLeaderTable(Num, LI, LI->getParent());
2228  return false;
2229  }
2230 
2231  // For conditional branches, we can perform simple conditional propagation on
2232  // the condition value itself.
2233  if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
2234  if (!BI->isConditional())
2235  return false;
2236 
2237  if (isa<Constant>(BI->getCondition()))
2238  return processFoldableCondBr(BI);
2239 
2240  Value *BranchCond = BI->getCondition();
2241  BasicBlock *TrueSucc = BI->getSuccessor(0);
2242  BasicBlock *FalseSucc = BI->getSuccessor(1);
2243  // Avoid multiple edges early.
2244  if (TrueSucc == FalseSucc)
2245  return false;
2246 
2247  BasicBlock *Parent = BI->getParent();
2248  bool Changed = false;
2249 
2250  Value *TrueVal = ConstantInt::getTrue(TrueSucc->getContext());
2251  BasicBlockEdge TrueE(Parent, TrueSucc);
2252  Changed |= propagateEquality(BranchCond, TrueVal, TrueE);
2253 
2254  Value *FalseVal = ConstantInt::getFalse(FalseSucc->getContext());
2255  BasicBlockEdge FalseE(Parent, FalseSucc);
2256  Changed |= propagateEquality(BranchCond, FalseVal, FalseE);
2257 
2258  return Changed;
2259  }
2260 
2261  // For switches, propagate the case values into the case destinations.
2262  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
2263  Value *SwitchCond = SI->getCondition();
2264  BasicBlock *Parent = SI->getParent();
2265  bool Changed = false;
2266 
2267  // Remember how many outgoing edges there are to every successor.
2269  for (unsigned i = 0, n = SI->getNumSuccessors(); i != n; ++i)
2270  ++SwitchEdges[SI->getSuccessor(i)];
2271 
2272  for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
2273  i != e; ++i) {
2274  BasicBlock *Dst = i.getCaseSuccessor();
2275  // If there is only a single edge, propagate the case value into it.
2276  if (SwitchEdges.lookup(Dst) == 1) {
2277  BasicBlockEdge E(Parent, Dst);
2278  Changed |= propagateEquality(SwitchCond, i.getCaseValue(), E);
2279  }
2280  }
2281  return Changed;
2282  }
2283 
2284  // Instructions with void type don't return a value, so there's
2285  // no point in trying to find redundancies in them.
2286  if (I->getType()->isVoidTy()) return false;
2287 
2288  uint32_t NextNum = VN.getNextUnusedValueNumber();
2289  unsigned Num = VN.lookup_or_add(I);
2290 
2291  // Allocations are always uniquely numbered, so we can save time and memory
2292  // by fast failing them.
2293  if (isa<AllocaInst>(I) || isa<TerminatorInst>(I) || isa<PHINode>(I)) {
2294  addToLeaderTable(Num, I, I->getParent());
2295  return false;
2296  }
2297 
2298  // If the number we were assigned was a brand new VN, then we don't
2299  // need to do a lookup to see if the number already exists
2300  // somewhere in the domtree: it can't!
2301  if (Num >= NextNum) {
2302  addToLeaderTable(Num, I, I->getParent());
2303  return false;
2304  }
2305 
2306  // Perform fast-path value-number based elimination of values inherited from
2307  // dominators.
2308  Value *repl = findLeader(I->getParent(), Num);
2309  if (!repl) {
2310  // Failure, just remember this instance for future use.
2311  addToLeaderTable(Num, I, I->getParent());
2312  return false;
2313  }
2314 
2315  // Remove it!
2316  patchAndReplaceAllUsesWith(I, repl);
2317  if (MD && repl->getType()->getScalarType()->isPointerTy())
2318  MD->invalidateCachedPointerInfo(repl);
2319  markInstructionForDeletion(I);
2320  return true;
2321 }
2322 
2323 /// runOnFunction - This is the main transformation entry point for a function.
2324 bool GVN::runOnFunction(Function& F) {
2325  if (skipOptnoneFunction(F))
2326  return false;
2327 
2328  if (!NoLoads)
2329  MD = &getAnalysis<MemoryDependenceAnalysis>();
2330  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
2331  AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
2332  TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
2333  VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
2334  VN.setMemDep(MD);
2335  VN.setDomTree(DT);
2336 
2337  bool Changed = false;
2338  bool ShouldContinue = true;
2339 
2340  // Merge unconditional branches, allowing PRE to catch more
2341  // optimization opportunities.
2342  for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) {
2343  BasicBlock *BB = FI++;
2344 
2345  bool removedBlock = MergeBlockIntoPredecessor(
2346  BB, DT, /* LoopInfo */ nullptr, VN.getAliasAnalysis(), MD);
2347  if (removedBlock) ++NumGVNBlocks;
2348 
2349  Changed |= removedBlock;
2350  }
2351 
2352  unsigned Iteration = 0;
2353  while (ShouldContinue) {
2354  DEBUG(dbgs() << "GVN iteration: " << Iteration << "\n");
2355  ShouldContinue = iterateOnFunction(F);
2356  Changed |= ShouldContinue;
2357  ++Iteration;
2358  }
2359 
2360  if (EnablePRE) {
2361  // Fabricate val-num for dead-code in order to suppress assertion in
2362  // performPRE().
2363  assignValNumForDeadCode();
2364  bool PREChanged = true;
2365  while (PREChanged) {
2366  PREChanged = performPRE(F);
2367  Changed |= PREChanged;
2368  }
2369  }
2370 
2371  // FIXME: Should perform GVN again after PRE does something. PRE can move
2372  // computations into blocks where they become fully redundant. Note that
2373  // we can't do this until PRE's critical edge splitting updates memdep.
2374  // Actually, when this happens, we should just fully integrate PRE into GVN.
2375 
2376  cleanupGlobalSets();
2377  // Do not cleanup DeadBlocks in cleanupGlobalSets() as it's called for each
2378  // iteration.
2379  DeadBlocks.clear();
2380 
2381  return Changed;
2382 }
2383 
2384 
2385 bool GVN::processBlock(BasicBlock *BB) {
2386  // FIXME: Kill off InstrsToErase by doing erasing eagerly in a helper function
2387  // (and incrementing BI before processing an instruction).
2388  assert(InstrsToErase.empty() &&
2389  "We expect InstrsToErase to be empty across iterations");
2390  if (DeadBlocks.count(BB))
2391  return false;
2392 
2393  bool ChangedFunction = false;
2394 
2395  for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
2396  BI != BE;) {
2397  ChangedFunction |= processInstruction(BI);
2398  if (InstrsToErase.empty()) {
2399  ++BI;
2400  continue;
2401  }
2402 
2403  // If we need some instructions deleted, do it now.
2404  NumGVNInstr += InstrsToErase.size();
2405 
2406  // Avoid iterator invalidation.
2407  bool AtStart = BI == BB->begin();
2408  if (!AtStart)
2409  --BI;
2410 
2411  for (SmallVectorImpl<Instruction *>::iterator I = InstrsToErase.begin(),
2412  E = InstrsToErase.end(); I != E; ++I) {
2413  DEBUG(dbgs() << "GVN removed: " << **I << '\n');
2414  if (MD) MD->removeInstruction(*I);
2415  DEBUG(verifyRemoved(*I));
2416  (*I)->eraseFromParent();
2417  }
2418  InstrsToErase.clear();
2419 
2420  if (AtStart)
2421  BI = BB->begin();
2422  else
2423  ++BI;
2424  }
2425 
2426  return ChangedFunction;
2427 }
2428 
2429 // Instantiate an expression in a predecessor that lacked it.
2430 bool GVN::performScalarPREInsertion(Instruction *Instr, BasicBlock *Pred,
2431  unsigned int ValNo) {
2432  // Because we are going top-down through the block, all value numbers
2433  // will be available in the predecessor by the time we need them. Any
2434  // that weren't originally present will have been instantiated earlier
2435  // in this loop.
2436  bool success = true;
2437  for (unsigned i = 0, e = Instr->getNumOperands(); i != e; ++i) {
2438  Value *Op = Instr->getOperand(i);
2439  if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
2440  continue;
2441 
2442  if (Value *V = findLeader(Pred, VN.lookup(Op))) {
2443  Instr->setOperand(i, V);
2444  } else {
2445  success = false;
2446  break;
2447  }
2448  }
2449 
2450  // Fail out if we encounter an operand that is not available in
2451  // the PRE predecessor. This is typically because of loads which
2452  // are not value numbered precisely.
2453  if (!success)
2454  return false;
2455 
2456  Instr->insertBefore(Pred->getTerminator());
2457  Instr->setName(Instr->getName() + ".pre");
2458  Instr->setDebugLoc(Instr->getDebugLoc());
2459  VN.add(Instr, ValNo);
2460 
2461  // Update the availability map to include the new instruction.
2462  addToLeaderTable(ValNo, Instr, Pred);
2463  return true;
2464 }
2465 
2466 bool GVN::performScalarPRE(Instruction *CurInst) {
2468 
2469  if (isa<AllocaInst>(CurInst) || isa<TerminatorInst>(CurInst) ||
2470  isa<PHINode>(CurInst) || CurInst->getType()->isVoidTy() ||
2471  CurInst->mayReadFromMemory() || CurInst->mayHaveSideEffects() ||
2472  isa<DbgInfoIntrinsic>(CurInst))
2473  return false;
2474 
2475  // Don't do PRE on compares. The PHI would prevent CodeGenPrepare from
2476  // sinking the compare again, and it would force the code generator to
2477  // move the i1 from processor flags or predicate registers into a general
2478  // purpose register.
2479  if (isa<CmpInst>(CurInst))
2480  return false;
2481 
2482  // We don't currently value number ANY inline asm calls.
2483  if (CallInst *CallI = dyn_cast<CallInst>(CurInst))
2484  if (CallI->isInlineAsm())
2485  return false;
2486 
2487  uint32_t ValNo = VN.lookup(CurInst);
2488 
2489  // Look for the predecessors for PRE opportunities. We're
2490  // only trying to solve the basic diamond case, where
2491  // a value is computed in the successor and one predecessor,
2492  // but not the other. We also explicitly disallow cases
2493  // where the successor is its own predecessor, because they're
2494  // more complicated to get right.
2495  unsigned NumWith = 0;
2496  unsigned NumWithout = 0;
2497  BasicBlock *PREPred = nullptr;
2498  BasicBlock *CurrentBlock = CurInst->getParent();
2499  predMap.clear();
2500 
2501  for (pred_iterator PI = pred_begin(CurrentBlock), PE = pred_end(CurrentBlock);
2502  PI != PE; ++PI) {
2503  BasicBlock *P = *PI;
2504  // We're not interested in PRE where the block is its
2505  // own predecessor, or in blocks with predecessors
2506  // that are not reachable.
2507  if (P == CurrentBlock) {
2508  NumWithout = 2;
2509  break;
2510  } else if (!DT->isReachableFromEntry(P)) {
2511  NumWithout = 2;
2512  break;
2513  }
2514 
2515  Value *predV = findLeader(P, ValNo);
2516  if (!predV) {
2517  predMap.push_back(std::make_pair(static_cast<Value *>(nullptr), P));
2518  PREPred = P;
2519  ++NumWithout;
2520  } else if (predV == CurInst) {
2521  /* CurInst dominates this predecessor. */
2522  NumWithout = 2;
2523  break;
2524  } else {
2525  predMap.push_back(std::make_pair(predV, P));
2526  ++NumWith;
2527  }
2528  }
2529 
2530  // Don't do PRE when it might increase code size, i.e. when
2531  // we would need to insert instructions in more than one pred.
2532  if (NumWithout > 1 || NumWith == 0)
2533  return false;
2534 
2535  // We may have a case where all predecessors have the instruction,
2536  // and we just need to insert a phi node. Otherwise, perform
2537  // insertion.
2538  Instruction *PREInstr = nullptr;
2539 
2540  if (NumWithout != 0) {
2541  // Don't do PRE across indirect branch.
2542  if (isa<IndirectBrInst>(PREPred->getTerminator()))
2543  return false;
2544 
2545  // We can't do PRE safely on a critical edge, so instead we schedule
2546  // the edge to be split and perform the PRE the next time we iterate
2547  // on the function.
2548  unsigned SuccNum = GetSuccessorNumber(PREPred, CurrentBlock);
2549  if (isCriticalEdge(PREPred->getTerminator(), SuccNum)) {
2550  toSplit.push_back(std::make_pair(PREPred->getTerminator(), SuccNum));
2551  return false;
2552  }
2553  // We need to insert somewhere, so let's give it a shot
2554  PREInstr = CurInst->clone();
2555  if (!performScalarPREInsertion(PREInstr, PREPred, ValNo)) {
2556  // If we failed insertion, make sure we remove the instruction.
2557  DEBUG(verifyRemoved(PREInstr));
2558  delete PREInstr;
2559  return false;
2560  }
2561  }
2562 
2563  // Either we should have filled in the PRE instruction, or we should
2564  // not have needed insertions.
2565  assert (PREInstr != nullptr || NumWithout == 0);
2566 
2567  ++NumGVNPRE;
2568 
2569  // Create a PHI to make the value available in this block.
2570  PHINode *Phi =
2571  PHINode::Create(CurInst->getType(), predMap.size(),
2572  CurInst->getName() + ".pre-phi", CurrentBlock->begin());
2573  for (unsigned i = 0, e = predMap.size(); i != e; ++i) {
2574  if (Value *V = predMap[i].first)
2575  Phi->addIncoming(V, predMap[i].second);
2576  else
2577  Phi->addIncoming(PREInstr, PREPred);
2578  }
2579 
2580  VN.add(Phi, ValNo);
2581  addToLeaderTable(ValNo, Phi, CurrentBlock);
2582  Phi->setDebugLoc(CurInst->getDebugLoc());
2583  CurInst->replaceAllUsesWith(Phi);
2584  if (Phi->getType()->getScalarType()->isPointerTy()) {
2585  // Because we have added a PHI-use of the pointer value, it has now
2586  // "escaped" from alias analysis' perspective. We need to inform
2587  // AA of this.
2588  for (unsigned ii = 0, ee = Phi->getNumIncomingValues(); ii != ee; ++ii) {
2589  unsigned jj = PHINode::getOperandNumForIncomingValue(ii);
2590  VN.getAliasAnalysis()->addEscapingUse(Phi->getOperandUse(jj));
2591  }
2592 
2593  if (MD)
2594  MD->invalidateCachedPointerInfo(Phi);
2595  }
2596  VN.erase(CurInst);
2597  removeFromLeaderTable(ValNo, CurInst, CurrentBlock);
2598 
2599  DEBUG(dbgs() << "GVN PRE removed: " << *CurInst << '\n');
2600  if (MD)
2601  MD->removeInstruction(CurInst);
2602  DEBUG(verifyRemoved(CurInst));
2603  CurInst->eraseFromParent();
2604  ++NumGVNInstr;
2605 
2606  return true;
2607 }
2608 
2609 /// Perform a purely local form of PRE that looks for diamond
2610 /// control flow patterns and attempts to perform simple PRE at the join point.
2611 bool GVN::performPRE(Function &F) {
2612  bool Changed = false;
2613  for (BasicBlock *CurrentBlock : depth_first(&F.getEntryBlock())) {
2614  // Nothing to PRE in the entry block.
2615  if (CurrentBlock == &F.getEntryBlock())
2616  continue;
2617 
2618  // Don't perform PRE on a landing pad.
2619  if (CurrentBlock->isLandingPad())
2620  continue;
2621 
2622  for (BasicBlock::iterator BI = CurrentBlock->begin(),
2623  BE = CurrentBlock->end();
2624  BI != BE;) {
2625  Instruction *CurInst = BI++;
2626  Changed = performScalarPRE(CurInst);
2627  }
2628  }
2629 
2630  if (splitCriticalEdges())
2631  Changed = true;
2632 
2633  return Changed;
2634 }
2635 
2636 /// Split the critical edge connecting the given two blocks, and return
2637 /// the block inserted to the critical edge.
2638 BasicBlock *GVN::splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ) {
2640  Pred, Succ, CriticalEdgeSplittingOptions(getAliasAnalysis(), DT));
2641  if (MD)
2642  MD->invalidateCachedPredecessors();
2643  return BB;
2644 }
2645 
2646 /// Split critical edges found during the previous
2647 /// iteration that may enable further optimization.
2648 bool GVN::splitCriticalEdges() {
2649  if (toSplit.empty())
2650  return false;
2651  do {
2652  std::pair<TerminatorInst*, unsigned> Edge = toSplit.pop_back_val();
2653  SplitCriticalEdge(Edge.first, Edge.second,
2654  CriticalEdgeSplittingOptions(getAliasAnalysis(), DT));
2655  } while (!toSplit.empty());
2656  if (MD) MD->invalidateCachedPredecessors();
2657  return true;
2658 }
2659 
2660 /// Executes one iteration of GVN
2661 bool GVN::iterateOnFunction(Function &F) {
2662  cleanupGlobalSets();
2663 
2664  // Top-down walk of the dominator tree
2665  bool Changed = false;
2666  // Save the blocks this function have before transformation begins. GVN may
2667  // split critical edge, and hence may invalidate the RPO/DT iterator.
2668  //
2669  std::vector<BasicBlock *> BBVect;
2670  BBVect.reserve(256);
2671  // Needed for value numbering with phi construction to work.
2674  RE = RPOT.end();
2675  RI != RE; ++RI)
2676  BBVect.push_back(*RI);
2677 
2678  for (std::vector<BasicBlock *>::iterator I = BBVect.begin(), E = BBVect.end();
2679  I != E; I++)
2680  Changed |= processBlock(*I);
2681 
2682  return Changed;
2683 }
2684 
2685 void GVN::cleanupGlobalSets() {
2686  VN.clear();
2687  LeaderTable.clear();
2688  TableAllocator.Reset();
2689 }
2690 
2691 /// Verify that the specified instruction does not occur in our
2692 /// internal data structures.
2693 void GVN::verifyRemoved(const Instruction *Inst) const {
2694  VN.verifyRemoved(Inst);
2695 
2696  // Walk through the value number scope to make sure the instruction isn't
2697  // ferreted away in it.
2699  I = LeaderTable.begin(), E = LeaderTable.end(); I != E; ++I) {
2700  const LeaderTableEntry *Node = &I->second;
2701  assert(Node->Val != Inst && "Inst still in value numbering scope!");
2702 
2703  while (Node->Next) {
2704  Node = Node->Next;
2705  assert(Node->Val != Inst && "Inst still in value numbering scope!");
2706  }
2707  }
2708 }
2709 
2710 /// BB is declared dead, which implied other blocks become dead as well. This
2711 /// function is to add all these blocks to "DeadBlocks". For the dead blocks'
2712 /// live successors, update their phi nodes by replacing the operands
2713 /// corresponding to dead blocks with UndefVal.
2714 void GVN::addDeadBlock(BasicBlock *BB) {
2717 
2718  NewDead.push_back(BB);
2719  while (!NewDead.empty()) {
2720  BasicBlock *D = NewDead.pop_back_val();
2721  if (DeadBlocks.count(D))
2722  continue;
2723 
2724  // All blocks dominated by D are dead.
2726  DT->getDescendants(D, Dom);
2727  DeadBlocks.insert(Dom.begin(), Dom.end());
2728 
2729  // Figure out the dominance-frontier(D).
2731  E = Dom.end(); I != E; I++) {
2732  BasicBlock *B = *I;
2733  for (succ_iterator SI = succ_begin(B), SE = succ_end(B); SI != SE; SI++) {
2734  BasicBlock *S = *SI;
2735  if (DeadBlocks.count(S))
2736  continue;
2737 
2738  bool AllPredDead = true;
2739  for (pred_iterator PI = pred_begin(S), PE = pred_end(S); PI != PE; PI++)
2740  if (!DeadBlocks.count(*PI)) {
2741  AllPredDead = false;
2742  break;
2743  }
2744 
2745  if (!AllPredDead) {
2746  // S could be proved dead later on. That is why we don't update phi
2747  // operands at this moment.
2748  DF.insert(S);
2749  } else {
2750  // While S is not dominated by D, it is dead by now. This could take
2751  // place if S already have a dead predecessor before D is declared
2752  // dead.
2753  NewDead.push_back(S);
2754  }
2755  }
2756  }
2757  }
2758 
2759  // For the dead blocks' live successors, update their phi nodes by replacing
2760  // the operands corresponding to dead blocks with UndefVal.
2761  for(SmallSetVector<BasicBlock *, 4>::iterator I = DF.begin(), E = DF.end();
2762  I != E; I++) {
2763  BasicBlock *B = *I;
2764  if (DeadBlocks.count(B))
2765  continue;
2766 
2768  for (SmallVectorImpl<BasicBlock *>::iterator PI = Preds.begin(),
2769  PE = Preds.end(); PI != PE; PI++) {
2770  BasicBlock *P = *PI;
2771 
2772  if (!DeadBlocks.count(P))
2773  continue;
2774 
2775  if (isCriticalEdge(P->getTerminator(), GetSuccessorNumber(P, B))) {
2776  if (BasicBlock *S = splitCriticalEdges(P, B))
2777  DeadBlocks.insert(P = S);
2778  }
2779 
2780  for (BasicBlock::iterator II = B->begin(); isa<PHINode>(II); ++II) {
2781  PHINode &Phi = cast<PHINode>(*II);
2783  UndefValue::get(Phi.getType()));
2784  }
2785  }
2786  }
2787 }
2788 
2789 // If the given branch is recognized as a foldable branch (i.e. conditional
2790 // branch with constant condition), it will perform following analyses and
2791 // transformation.
2792 // 1) If the dead out-coming edge is a critical-edge, split it. Let
2793 // R be the target of the dead out-coming edge.
2794 // 1) Identify the set of dead blocks implied by the branch's dead outcoming
2795 // edge. The result of this step will be {X| X is dominated by R}
2796 // 2) Identify those blocks which haves at least one dead prodecessor. The
2797 // result of this step will be dominance-frontier(R).
2798 // 3) Update the PHIs in DF(R) by replacing the operands corresponding to
2799 // dead blocks with "UndefVal" in an hope these PHIs will optimized away.
2800 //
2801 // Return true iff *NEW* dead code are found.
2802 bool GVN::processFoldableCondBr(BranchInst *BI) {
2803  if (!BI || BI->isUnconditional())
2804  return false;
2805 
2806  // If a branch has two identical successors, we cannot declare either dead.
2807  if (BI->getSuccessor(0) == BI->getSuccessor(1))
2808  return false;
2809 
2810  ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
2811  if (!Cond)
2812  return false;
2813 
2814  BasicBlock *DeadRoot = Cond->getZExtValue() ?
2815  BI->getSuccessor(1) : BI->getSuccessor(0);
2816  if (DeadBlocks.count(DeadRoot))
2817  return false;
2818 
2819  if (!DeadRoot->getSinglePredecessor())
2820  DeadRoot = splitCriticalEdges(BI->getParent(), DeadRoot);
2821 
2822  addDeadBlock(DeadRoot);
2823  return true;
2824 }
2825 
2826 // performPRE() will trigger assert if it comes across an instruction without
2827 // associated val-num. As it normally has far more live instructions than dead
2828 // instructions, it makes more sense just to "fabricate" a val-number for the
2829 // dead code than checking if instruction involved is dead or not.
2830 void GVN::assignValNumForDeadCode() {
2831  for (SetVector<BasicBlock *>::iterator I = DeadBlocks.begin(),
2832  E = DeadBlocks.end(); I != E; I++) {
2833  BasicBlock *BB = *I;
2834  for (BasicBlock::iterator II = BB->begin(), EE = BB->end();
2835  II != EE; II++) {
2836  Instruction *Inst = &*II;
2837  unsigned ValNum = VN.lookup_or_add(Inst);
2838  addToLeaderTable(ValNum, Inst, BB);
2839  }
2840  }
2841 }
Value * CreateLShr(Value *LHS, Value *RHS, const Twine &Name="", bool isExact=false)
Definition: IRBuilder.h:842
const Use & getOperandUse(unsigned i) const
Definition: User.h:129
BinaryOp_match< LHS, RHS, Instruction::And > m_And(const LHS &L, const RHS &R)
Definition: PatternMatch.h:506
Value * getValueOperand()
Definition: Instructions.h:406
iplist< Instruction >::iterator eraseFromParent()
eraseFromParent - This method unlinks 'this' from the containing basic block and deletes it...
Definition: Instruction.cpp:70
FunctionPass * createGVNPass(bool NoLoads=false)
Definition: GVN.cpp:732
static cl::opt< bool > EnableLoadPRE("enable-load-pre", cl::init(true))
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:104
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:537
class_match< Value > m_Value()
Match an arbitrary value and ignore it.
Definition: PatternMatch.h:64
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:679
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
Helper class for SSA formation on a set of values defined in multiple blocks.
Definition: SSAUpdater.h:38
void addIncoming(Value *V, BasicBlock *BB)
addIncoming - Add an incoming value to the end of the PHI list
ExtractValueInst - This instruction extracts a struct member or array element value from an aggregate...
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
bool isDef() const
isDef - Return true if this MemDepResult represents a query that is an instruction definition depende...
static Type * makeCmpResultType(Type *opnd_type)
Create a result type for fcmp/icmp.
Definition: InstrTypes.h:878
static int AnalyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr, MemIntrinsic *MI, const DataLayout &DL)
Definition: GVN.cpp:1066
STATISTIC(NumFunctions,"Total number of functions")
ValueT lookup(const KeyT &Val) const
lookup - Return the entry for the specified key, or a default constructed value if no such entry exis...
Definition: DenseMap.h:159
void Initialize(Type *Ty, StringRef Name)
Reset this object to get ready for a new set of SSA updates with type 'Ty'.
Definition: SSAUpdater.cpp:45
iterator end()
Definition: Function.h:459
Intrinsic::ID getIntrinsicID() const
getIntrinsicID - Return the intrinsic ID of this intrinsic.
Definition: IntrinsicInst.h:44
const BasicBlock * getStart() const
Definition: Dominators.h:56
unsigned getNumOperands() const
Definition: User.h:138
void AddAvailableValue(BasicBlock *BB, Value *V)
Indicate that a rewritten value is available in the specified block with the specified value...
Definition: SSAUpdater.cpp:58
static bool isEqual(const Expression &LHS, const Expression &RHS)
Definition: GVN.cpp:157
CallInst - This class represents a function call, abstracting a target machine's calling convention...
This file contains the declarations for metadata subclasses.
size_type count(PtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:276
An immutable pass that tracks lazily created AssumptionCache objects.
static PointerType * get(Type *ElementType, unsigned AddressSpace)
PointerType::get - This constructs a pointer to an object of the specified type in a numbered address...
Definition: Type.cpp:738
bool mayHaveSideEffects() const
mayHaveSideEffects - Return true if the instruction may have side effects.
Definition: Instruction.h:387
static Constant * getGetElementPtr(Type *Ty, Constant *C, ArrayRef< Constant * > IdxList, bool InBounds=false, Type *OnlyIfReducedTy=nullptr)
Getelementptr form.
Definition: Constants.h:1092
A cache of .assume calls within a function.
1 1 1 0 True if unordered or not equal
Definition: InstrTypes.h:713
static int AnalyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr, Value *WritePtr, uint64_t WriteSizeInBits, const DataLayout &DL)
This function is called when we have a memdep query of a load that ends up being a clobbering memory ...
Definition: GVN.cpp:947
MemSetInst - This class wraps the llvm.memset intrinsic.
This class implements a map that also provides access to all stored values in a deterministic order...
Definition: MapVector.h:32
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:111
F(f)
unsigned GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ)
Search for the specified successor of basic block BB and return its position in the terminator instru...
Definition: CFG.cpp:72
LoadInst - an instruction for reading from memory.
Definition: Instructions.h:177
static IntegerType * getInt64Ty(LLVMContext &C)
Definition: Type.cpp:240
Hexagon Common GEP
unsigned getPointerAddressSpace() const
Get the address space of this pointer or pointer vector type.
Definition: Type.cpp:216
static Expression getEmptyKey()
Definition: GVN.cpp:145
unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT, const BasicBlockEdge &Edge)
Replace each use of 'From' with 'To' if that use is dominated by the given edge.
Definition: Local.cpp:1328
bool isSimple() const
Definition: Instructions.h:279
iterator end()
Get an iterator to the end of the SetVector.
Definition: SetVector.h:79
op_iterator op_begin()
Definition: User.h:183
bool isClobber() const
isClobber - Return true if this MemDepResult represents a query that is an instruction clobber depend...
This file defines the MallocAllocator and BumpPtrAllocator interfaces.
static Constant * getNullValue(Type *Ty)
Definition: Constants.cpp:178
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:188
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:231
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:169
static unsigned getHashValue(const Expression e)
Definition: GVN.cpp:153
static unsigned getOperandNumForIncomingValue(unsigned i)
bool match(Val *V, const Pattern &P)
Definition: PatternMatch.h:41
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:70
bool isUnconditional() const
static cl::opt< uint32_t > MaxRecurseDepth("max-recurse-depth", cl::Hidden, cl::init(1000), cl::ZeroOrMore, cl::desc("Max recurse depth (default = 1000)"))
static cl::opt< bool > EnablePRE("enable-pre", cl::init(true), cl::Hidden)
Option class for critical edge splitting.
T LLVM_ATTRIBUTE_UNUSED_RESULT pop_back_val()
Definition: SmallVector.h:406
Value * CreateIntToPtr(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:1249
Constant * ConstantFoldLoadFromConstPtr(Constant *C, const DataLayout &DL)
ConstantFoldLoadFromConstPtr - Return the value that a load from C would produce if it is constant an...
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APInt.h:33
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:75
unsigned getNumArgOperands() const
getNumArgOperands - Return the number of call arguments.
static int AnalyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr, LoadInst *DepLI, const DataLayout &DL)
This function is called when we have a memdep query of a load that ends up being clobbered by another...
Definition: GVN.cpp:1039
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:517
unsigned getNumIndices() const
MemoryDependenceAnalysis - This is an analysis that determines, for a given memory operation...
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:250
static ConstantInt * ExtractElement(Constant *V, Constant *Idx)
Instruction * clone() const
clone() - Create a copy of 'this' instruction that is identical in all ways except the following: ...
#define false
Definition: ConvertUTF.c:65
Interval::succ_iterator succ_begin(Interval *I)
succ_begin/succ_end - define methods so that Intervals may be used just like BasicBlocks can with the...
Definition: Interval.h:104
uint64_t getZExtValue() const
Return the constant as a 64-bit unsigned integer value after it has been zero extended as appropriate...
Definition: Constants.h:117
static void patchReplacementInstruction(Instruction *I, Value *Repl)
Definition: GVN.cpp:1780
bool insert(const value_type &X)
Insert a new element into the SetVector.
Definition: SetVector.h:102
bool mayReadFromMemory() const
mayReadFromMemory - Return true if this instruction may read memory.
LLVMContext & getContext() const
getContext - Return the LLVMContext in which this type was uniqued.
Definition: Type.h:125
Value * CreateOr(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:894
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const
Definition: SmallVector.h:57
void printAsOperand(raw_ostream &O, bool PrintType=true, const Module *M=nullptr) const
Print the name of this Value out to the specified raw_ostream.
Definition: AsmWriter.cpp:3287
Value * GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset, const DataLayout &DL)
GetPointerBaseWithConstantOffset - Analyze the specified pointer to see if it can be expressed as a b...
static bool processInstruction(Loop &L, Instruction &Inst, DominatorTree &DT, const SmallVectorImpl< BasicBlock * > &ExitBlocks, PredIteratorCache &PredCache, LoopInfo *LI)
Given an instruction in the loop, check to see if it has any uses that are outside the current loop...
Definition: LCSSA.cpp:62
bool MergeBlockIntoPredecessor(BasicBlock *BB, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr, AliasAnalysis *AA=nullptr, MemoryDependenceAnalysis *MemDep=nullptr)
MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, if possible.
static bool add(uint64_t *dest, const uint64_t *x, const uint64_t *y, unsigned len)
This function adds the integer array x to the integer array Y and places the result in dest...
Definition: APInt.cpp:238
BasicBlock * getSuccessor(unsigned i) const
iterator begin()
Get an iterator to the beginning of the SetVector.
Definition: SetVector.h:69
virtual void addEscapingUse(Use &U)
addEscapingUse - This method should be used whenever an escaping use is added to a pointer value...
hash_code hash_value(const APFloat &Arg)
See friend declarations above.
Definition: APFloat.cpp:2848
static Value * GetMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset, Type *LoadTy, Instruction *InsertPt, const DataLayout &DL)
This function is called when we have a memdep query of a load that ends up being a clobbering mem int...
Definition: GVN.cpp:1217
bool isLittleEndian() const
Layout endianness...
Definition: DataLayout.h:217
StoreInst - an instruction for storing to memory.
Definition: Instructions.h:316
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:351
bool isArrayTy() const
isArrayTy - True if this is an instance of ArrayType.
Definition: Type.h:213
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:256
iterator begin()
Definition: Function.h:457
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:67
static Value * GetLoadValueForLoad(LoadInst *SrcVal, unsigned Offset, Type *LoadTy, Instruction *InsertPt, GVN &gvn)
This function is called when we have a memdep query of a load that ends up being a clobbering load...
Definition: GVN.cpp:1157
unsigned getNumIncomingValues() const
getNumIncomingValues - Return the number of incoming edges
Interval::succ_iterator succ_end(Interval *I)
Definition: Interval.h:107
static Constant * getBitCast(Constant *C, Type *Ty, bool OnlyIfReduced=false)
Definition: Constants.cpp:1835
unsigned getNumSuccessors() const
Return the number of successors that this terminator has.
Definition: InstrTypes.h:57
GetElementPtrInst - an instruction for type-safe pointer arithmetic to access elements of arrays and ...
Definition: Instructions.h:830
BasicBlock * SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, const CriticalEdgeSplittingOptions &Options=CriticalEdgeSplittingOptions())
SplitCriticalEdge - If this edge is a critical edge, insert a new node to split the critical edge...
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:325
Value * GetValueInMiddleOfBlock(BasicBlock *BB)
Construct SSA form, materializing a value that is live in the middle of the specified block...
Definition: SSAUpdater.cpp:86
static Value * GetStoreValueForLoad(Value *SrcVal, unsigned Offset, Type *LoadTy, Instruction *InsertPt, const DataLayout &DL)
This function is called when we have a memdep query of a load that ends up being a clobbering store...
Definition: GVN.cpp:1118
void dump(const SparseBitVector< ElementSize > &LHS, raw_ostream &out)
* if(!EatIfPresent(lltok::kw_thread_local)) return false
ParseOptionalThreadLocal := /*empty.
void setDebugLoc(DebugLoc Loc)
setDebugLoc - Set the debug location information for this instruction.
Definition: Instruction.h:227
void insertBefore(Instruction *InsertPos)
Insert an unlinked instruction into a basic block immediately before the specified instruction...
Definition: Instruction.cpp:76
void setAAMetadata(const AAMDNodes &N)
setAAMetadata - Sets the metadata on this instruction from the AAMDNodes structure.
Definition: Metadata.cpp:1122
LLVM Basic Block Representation.
Definition: BasicBlock.h:65
PointerIntPair - This class implements a pair of a pointer and small integer.
PHITransAddr - An address value which tracks and handles phi translation.
Definition: PHITransAddr.h:36
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
BinaryOp_match< LHS, RHS, Instruction::Or > m_Or(const LHS &L, const RHS &R)
Definition: PatternMatch.h:512
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:41
Allocate memory in an ever growing pool, as if by bump-pointer.
Definition: Allocator.h:135
BranchInst - Conditional or Unconditional Branch instruction.
static Value * ConstructSSAForLoadSet(LoadInst *LI, SmallVectorImpl< AvailableValueInBlock > &ValuesPerBlock, GVN &gvn)
Given a set of loads specified by ValuesPerBlock, construct SSA form, allowing us to eliminate LI...
Definition: GVN.cpp:1276
Value * CreatePtrToInt(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:1245
This is an important base class in LLVM.
Definition: Constant.h:41
APInt Or(const APInt &LHS, const APInt &RHS)
Bitwise OR function for APInt.
Definition: APInt.h:1895
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:264
APInt Xor(const APInt &LHS, const APInt &RHS)
Bitwise XOR function for APInt.
Definition: APInt.h:1900
Interval::pred_iterator pred_begin(Interval *I)
pred_begin/pred_end - define methods so that Intervals may be used just like BasicBlocks can with the...
Definition: Interval.h:114
const DebugLoc & getDebugLoc() const
getDebugLoc - Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:230
Represent the analysis usage information of a pass.
op_iterator op_end()
Definition: User.h:185
size_type size() const
Definition: MapVector.h:44
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:697
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:294
Value * getOperand(unsigned i) const
Definition: User.h:118
Interval::pred_iterator pred_end(Interval *I)
Definition: Interval.h:117
Value * getPointerOperand()
Definition: Instructions.h:284
bool isCommutative() const
isCommutative - Return true if the instruction is commutative:
Definition: Instruction.h:327
const MemDepResult & getResult() const
bool HasValueForBlock(BasicBlock *BB) const
Return true if the SSAUpdater already has a value for the specified block.
Definition: SSAUpdater.cpp:54
void setAlignment(unsigned Align)
#define INITIALIZE_AG_DEPENDENCY(depName)
Definition: PassSupport.h:72
void append(in_iter in_start, in_iter in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:416
bool isPointerTy() const
isPointerTy - True if this is an instance of PointerType.
Definition: Type.h:217
static UndefValue * get(Type *T)
get() - Static factory methods - Return an 'undef' object of the specified type.
Definition: Constants.cpp:1473
uint64_t NextPowerOf2(uint64_t A)
NextPowerOf2 - Returns the next power of two (in 64-bits) that is strictly greater than A...
Definition: MathExtras.h:582
void andIRFlags(const Value *V)
Logical 'and' of any supported wrapping, exact, and fast-math flags of V and this instruction...
static PointerType * getInt8PtrTy(LLVMContext &C, unsigned AS=0)
Definition: Type.cpp:283
Value * GetUnderlyingObject(Value *V, const DataLayout &DL, unsigned MaxLookup=6)
GetUnderlyingObject - This method strips off any GEP address adjustments and pointer casts from the s...
std::vector< NodeType * >::reverse_iterator rpo_iterator
MemDepResult - A memory dependence query can return one of three different answers, described below.
const BasicBlock * getEnd() const
Definition: Dominators.h:59
void dump() const
Support for debugging, callable in GDB: V->dump()
Definition: AsmWriter.cpp:3353
IntegerType * getIntPtrType(LLVMContext &C, unsigned AddressSpace=0) const
Returns an integer type with size at least as big as that of a pointer in the given address space...
Definition: DataLayout.cpp:694
static IntegerType * get(LLVMContext &C, unsigned NumBits)
This static method is the primary way of constructing an IntegerType.
Definition: Type.cpp:304
A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:217
MemIntrinsic - This is the common base class for memset/memcpy/memmove.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:299
This is the shared class of boolean and integer constants.
Definition: Constants.h:47
Value * CreateZExt(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:1192
static bool CanCoerceMustAliasedValueToLoad(Value *StoredVal, Type *LoadTy, const DataLayout &DL)
Return true if CoerceAvailableValueToLoadType will succeed.
Definition: GVN.cpp:838
Value * getDest() const
getDest - This is just like getRawDest, but it strips off any cast instructions that feed it...
iterator end()
Definition: BasicBlock.h:233
const Module * getModule() const
Return the module owning the function this instruction belongs to or nullptr it the function does not...
Definition: Instruction.cpp:57
Value * CreateBitCast(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:1253
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:861
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:222
Provides information about what library functions are available for the current target.
#define INITIALIZE_PASS_BEGIN(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:67
A collection of metadata nodes that might be associated with a memory access used by the alias-analys...
Definition: Metadata.h:548
Value * getLength() const
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const
Definition: ilist.h:385
bool isNonLocal() const
isNonLocal - Return true if this MemDepResult represents a query that is transparent to the start of ...
std::vector< NonLocalDepEntry > NonLocalDepInfo
Predicate getSwappedPredicate() const
For example, EQ->EQ, SLE->SGE, ULT->UGT, OEQ->OEQ, ULE->UGE, OLT->OGT, etc.
Definition: InstrTypes.h:799
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:582
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...
const BasicBlock & getEntryBlock() const
Definition: Function.h:442
static ConstantInt * getTrue(LLVMContext &Context)
Definition: Constants.cpp:530
void setOperand(unsigned i, Value *Val)
Definition: User.h:122
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:123
bool isAllOnesValue() const
isAllOnesValue - Return true if this is the value that would be returned by getAllOnesValue.
Definition: Constants.cpp:88
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:576
Value * getArgOperand(unsigned i) const
getArgOperand/setArgOperand - Return/set the i-th call argument.
size_type count(const KeyT &Key) const
Definition: MapVector.h:103
hash_code hash_combine(const Ts &...args)
Combine values into a single hash_code.
Definition: Hashing.h:603
bool isConstant() const
If the value is a global constant, its value is immutable throughout the runtime execution of the pro...
bool isIntegerTy() const
isIntegerTy - True if this is an instance of IntegerType.
Definition: Type.h:193
BasicBlock * getSinglePredecessor()
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:211
LLVM_ATTRIBUTE_UNUSED_RESULT 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:285
hash_code hash_combine_range(InputIteratorT first, InputIteratorT last)
Compute a hash_code for a sequence of values.
Definition: Hashing.h:481
idx_iterator idx_end() const
An opaque object representing a hash code.
Definition: Hashing.h:73
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 ...
iterator insert(iterator I, T &&Elt)
Definition: SmallVector.h:481
const Type * getScalarType() const LLVM_READONLY
getScalarType - If this is a vector type, return the element type, otherwise return 'this'...
Definition: Type.cpp:51
APInt And(const APInt &LHS, const APInt &RHS)
Bitwise AND function for APInt.
Definition: APInt.h:1890
bool isStructTy() const
isStructTy - True if this is an instance of StructType.
Definition: Type.h:209
Value * CreateShl(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:823
Value * getSource() const
getSource - This is just like getRawSource, but it strips off any cast instructions that feed it...
static bool isLifetimeStart(const Instruction *Inst)
Definition: GVN.cpp:1364
static const uint16_t * lookup(unsigned opcode, unsigned domain)
static bool isZero(Value *V, const DataLayout &DL, DominatorTree *DT, AssumptionCache *AC)
Definition: Lint.cpp:697
MemTransferInst - This class wraps the llvm.memcpy/memmove intrinsics.
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:372
Instruction * getInst() const
getInst() - If this is a normal dependency, return the instruction that is depended on...
Value * getCondition() const
unsigned getAlignment() const
getAlignment - Return the alignment of the access that is being performed
Definition: Instructions.h:243
void getAAMetadata(AAMDNodes &N, bool Merge=false) const
getAAMetadata - Fills the AAMDNodes structure with AA metadata from this instruction.
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:54
#define N
TerminatorInst * getTerminator()
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:124
bool isLandingPad() const
Return true if this basic block is a landing pad.
Definition: BasicBlock.cpp:413
bool hasOneUse() const
Return true if there is exactly one user of this value.
Definition: Value.h:311
uint64_t getTypeStoreSize(Type *Ty) const
Returns the maximum number of bytes that may be overwritten by storing the specified type...
Definition: DataLayout.h:371
iterator_range< df_iterator< T > > depth_first(const T &G)
static Expression getTombstoneKey()
Definition: GVN.cpp:149
SwitchInst - Multiway switch.
bool use_empty() const
Definition: Value.h:275
static int AnalyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr, StoreInst *DepSI)
This function is called when we have a memdep query of a load that ends up being a clobbering store...
Definition: GVN.cpp:1022
Use * op_iterator
Definition: User.h:178
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:32
unsigned getPrimitiveSizeInBits() const LLVM_READONLY
getPrimitiveSizeInBits - Return the basic size of this type if it is a primitive type.
Definition: Type.cpp:121
static bool IsValueFullyAvailableInBlock(BasicBlock *BB, DenseMap< BasicBlock *, char > &FullyAvailableBlocks, uint32_t RecurseDepth)
Return true if we can prove that the value we're analyzing is fully available in the specified block...
Definition: GVN.cpp:766
0 0 0 1 True if ordered and equal
Definition: InstrTypes.h:700
Value * CreateTrunc(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:1189
LLVM Value Representation.
Definition: Value.h:69
vector_type::const_iterator iterator
Definition: SetVector.h:45
unsigned getOpcode() const
getOpcode() returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:112
A vector that has set insertion semantics.
Definition: SetVector.h:37
uint64_t getTypeSizeInBits(Type *Ty) const
Size examples:
Definition: DataLayout.h:507
#define DEBUG(X)
Definition: Debug.h:92
static Value * CoerceAvailableValueToLoadType(Value *StoredVal, Type *LoadedTy, IRBuilder<> &IRB, const DataLayout &DL)
If we saw a store of a value to memory, and then a load from a must-aliased pointer of a different ty...
Definition: GVN.cpp:862
C - The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
bool isPowerOf2_32(uint32_t Value)
isPowerOf2_32 - This function returns true if the argument is a power of two > 0. ...
Definition: MathExtras.h:354
NonLocalDepEntry - This is an entry in the NonLocalDepInfo cache.
Value * SimplifyInstruction(Instruction *I, const DataLayout &DL, const TargetLibraryInfo *TLI=nullptr, const DominatorTree *DT=nullptr, AssumptionCache *AC=nullptr)
SimplifyInstruction - See if we can compute a simplified version of this instruction.
static void patchAndReplaceAllUsesWith(Instruction *I, Value *Repl)
Definition: GVN.cpp:1810
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:203
idx_iterator idx_begin() const
bool operator==(uint64_t V1, const APInt &V2)
Definition: APInt.h:1734
void setIncomingValue(unsigned i, Value *V)
bool isBigEndian() const
Definition: DataLayout.h:218
static unsigned getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs, unsigned MemLocSize, const LoadInst *LI)
getLoadLoadClobberFullWidthSize - This is a little bit of analysis that looks at a memory location fo...
Value * getPointerOperand()
Definition: Instructions.h:409
int getBasicBlockIndex(const BasicBlock *BB) const
getBasicBlockIndex - Return the first index of the specified basic block in the value list for this P...
static IntegerType * getInt8Ty(LLVMContext &C)
Definition: Type.cpp:237
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:1286
const BasicBlock * getParent() const
Definition: Instruction.h:72
InstListType::iterator iterator
Instruction iterators...
Definition: BasicBlock.h:93
static bool isOnlyReachableViaThisEdge(const BasicBlockEdge &E, DominatorTree *DT)
There is an edge from 'Src' to 'Dst'.
Definition: GVN.cpp:2037
IntrinsicInst - A useful wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:37
bool isVoidTy() const
isVoidTy - Return true if this is 'void'.
Definition: Type.h:137
InsertValueInst - This instruction inserts a struct field of array element value into an aggregate va...
bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum, bool AllowIdenticalEdges=false)
Return true if the specified edge is a critical edge.
Definition: CFG.cpp:87
void initializeGVNPass(PassRegistry &)