LLVM  9.0.0svn
SCCP.cpp
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1 //===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements sparse conditional constant propagation and merging:
10 //
11 // Specifically, this:
12 // * Assumes values are constant unless proven otherwise
13 // * Assumes BasicBlocks are dead unless proven otherwise
14 // * Proves values to be constant, and replaces them with constants
15 // * Proves conditional branches to be unconditional
16 //
17 //===----------------------------------------------------------------------===//
18 
20 #include "llvm/ADT/ArrayRef.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/DenseSet.h"
23 #include "llvm/ADT/MapVector.h"
25 #include "llvm/ADT/STLExtras.h"
26 #include "llvm/ADT/SmallPtrSet.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/ADT/Statistic.h"
35 #include "llvm/IR/BasicBlock.h"
36 #include "llvm/IR/CallSite.h"
37 #include "llvm/IR/Constant.h"
38 #include "llvm/IR/Constants.h"
39 #include "llvm/IR/DataLayout.h"
40 #include "llvm/IR/DerivedTypes.h"
41 #include "llvm/IR/Function.h"
42 #include "llvm/IR/GlobalVariable.h"
43 #include "llvm/IR/InstVisitor.h"
44 #include "llvm/IR/InstrTypes.h"
45 #include "llvm/IR/Instruction.h"
46 #include "llvm/IR/Instructions.h"
47 #include "llvm/IR/Module.h"
48 #include "llvm/IR/PassManager.h"
49 #include "llvm/IR/Type.h"
50 #include "llvm/IR/User.h"
51 #include "llvm/IR/Value.h"
52 #include "llvm/Pass.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/Debug.h"
57 #include "llvm/Transforms/Scalar.h"
59 #include <cassert>
60 #include <utility>
61 #include <vector>
62 
63 using namespace llvm;
64 
65 #define DEBUG_TYPE "sccp"
66 
67 STATISTIC(NumInstRemoved, "Number of instructions removed");
68 STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
69 
70 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
71 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
72 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
73 
74 namespace {
75 
76 /// LatticeVal class - This class represents the different lattice values that
77 /// an LLVM value may occupy. It is a simple class with value semantics.
78 ///
79 class LatticeVal {
80  enum LatticeValueTy {
81  /// unknown - This LLVM Value has no known value yet.
82  unknown,
83 
84  /// constant - This LLVM Value has a specific constant value.
85  constant,
86 
87  /// forcedconstant - This LLVM Value was thought to be undef until
88  /// ResolvedUndefsIn. This is treated just like 'constant', but if merged
89  /// with another (different) constant, it goes to overdefined, instead of
90  /// asserting.
91  forcedconstant,
92 
93  /// overdefined - This instruction is not known to be constant, and we know
94  /// it has a value.
95  overdefined
96  };
97 
98  /// Val: This stores the current lattice value along with the Constant* for
99  /// the constant if this is a 'constant' or 'forcedconstant' value.
101 
102  LatticeValueTy getLatticeValue() const {
103  return Val.getInt();
104  }
105 
106 public:
107  LatticeVal() : Val(nullptr, unknown) {}
108 
109  bool isUnknown() const { return getLatticeValue() == unknown; }
110 
111  bool isConstant() const {
112  return getLatticeValue() == constant || getLatticeValue() == forcedconstant;
113  }
114 
115  bool isOverdefined() const { return getLatticeValue() == overdefined; }
116 
117  Constant *getConstant() const {
118  assert(isConstant() && "Cannot get the constant of a non-constant!");
119  return Val.getPointer();
120  }
121 
122  /// markOverdefined - Return true if this is a change in status.
123  bool markOverdefined() {
124  if (isOverdefined())
125  return false;
126 
127  Val.setInt(overdefined);
128  return true;
129  }
130 
131  /// markConstant - Return true if this is a change in status.
132  bool markConstant(Constant *V) {
133  if (getLatticeValue() == constant) { // Constant but not forcedconstant.
134  assert(getConstant() == V && "Marking constant with different value");
135  return false;
136  }
137 
138  if (isUnknown()) {
139  Val.setInt(constant);
140  assert(V && "Marking constant with NULL");
141  Val.setPointer(V);
142  } else {
143  assert(getLatticeValue() == forcedconstant &&
144  "Cannot move from overdefined to constant!");
145  // Stay at forcedconstant if the constant is the same.
146  if (V == getConstant()) return false;
147 
148  // Otherwise, we go to overdefined. Assumptions made based on the
149  // forced value are possibly wrong. Assuming this is another constant
150  // could expose a contradiction.
151  Val.setInt(overdefined);
152  }
153  return true;
154  }
155 
156  /// getConstantInt - If this is a constant with a ConstantInt value, return it
157  /// otherwise return null.
158  ConstantInt *getConstantInt() const {
159  if (isConstant())
160  return dyn_cast<ConstantInt>(getConstant());
161  return nullptr;
162  }
163 
164  /// getBlockAddress - If this is a constant with a BlockAddress value, return
165  /// it, otherwise return null.
166  BlockAddress *getBlockAddress() const {
167  if (isConstant())
168  return dyn_cast<BlockAddress>(getConstant());
169  return nullptr;
170  }
171 
172  void markForcedConstant(Constant *V) {
173  assert(isUnknown() && "Can't force a defined value!");
174  Val.setInt(forcedconstant);
175  Val.setPointer(V);
176  }
177 
178  ValueLatticeElement toValueLattice() const {
179  if (isOverdefined())
181  if (isConstant())
183  return ValueLatticeElement();
184  }
185 };
186 
187 //===----------------------------------------------------------------------===//
188 //
189 /// SCCPSolver - This class is a general purpose solver for Sparse Conditional
190 /// Constant Propagation.
191 ///
192 class SCCPSolver : public InstVisitor<SCCPSolver> {
193  const DataLayout &DL;
194  const TargetLibraryInfo *TLI;
195  SmallPtrSet<BasicBlock *, 8> BBExecutable; // The BBs that are executable.
196  DenseMap<Value *, LatticeVal> ValueState; // The state each value is in.
197  // The state each parameter is in.
199 
200  /// StructValueState - This maintains ValueState for values that have
201  /// StructType, for example for formal arguments, calls, insertelement, etc.
202  DenseMap<std::pair<Value *, unsigned>, LatticeVal> StructValueState;
203 
204  /// GlobalValue - If we are tracking any values for the contents of a global
205  /// variable, we keep a mapping from the constant accessor to the element of
206  /// the global, to the currently known value. If the value becomes
207  /// overdefined, it's entry is simply removed from this map.
209 
210  /// TrackedRetVals - If we are tracking arguments into and the return
211  /// value out of a function, it will have an entry in this map, indicating
212  /// what the known return value for the function is.
213  MapVector<Function *, LatticeVal> TrackedRetVals;
214 
215  /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
216  /// that return multiple values.
217  MapVector<std::pair<Function *, unsigned>, LatticeVal> TrackedMultipleRetVals;
218 
219  /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
220  /// represented here for efficient lookup.
221  SmallPtrSet<Function *, 16> MRVFunctionsTracked;
222 
223  /// MustTailFunctions - Each function here is a callee of non-removable
224  /// musttail call site.
225  SmallPtrSet<Function *, 16> MustTailCallees;
226 
227  /// TrackingIncomingArguments - This is the set of functions for whose
228  /// arguments we make optimistic assumptions about and try to prove as
229  /// constants.
230  SmallPtrSet<Function *, 16> TrackingIncomingArguments;
231 
232  /// The reason for two worklists is that overdefined is the lowest state
233  /// on the lattice, and moving things to overdefined as fast as possible
234  /// makes SCCP converge much faster.
235  ///
236  /// By having a separate worklist, we accomplish this because everything
237  /// possibly overdefined will become overdefined at the soonest possible
238  /// point.
239  SmallVector<Value *, 64> OverdefinedInstWorkList;
240  SmallVector<Value *, 64> InstWorkList;
241 
242  // The BasicBlock work list
244 
245  /// KnownFeasibleEdges - Entries in this set are edges which have already had
246  /// PHI nodes retriggered.
247  using Edge = std::pair<BasicBlock *, BasicBlock *>;
248  DenseSet<Edge> KnownFeasibleEdges;
249 
252 
253 public:
254  void addAnalysis(Function &F, AnalysisResultsForFn A) {
255  AnalysisResults.insert({&F, std::move(A)});
256  }
257 
258  const PredicateBase *getPredicateInfoFor(Instruction *I) {
259  auto A = AnalysisResults.find(I->getParent()->getParent());
260  if (A == AnalysisResults.end())
261  return nullptr;
262  return A->second.PredInfo->getPredicateInfoFor(I);
263  }
264 
265  DomTreeUpdater getDTU(Function &F) {
266  auto A = AnalysisResults.find(&F);
267  assert(A != AnalysisResults.end() && "Need analysis results for function.");
268  return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy};
269  }
270 
271  SCCPSolver(const DataLayout &DL, const TargetLibraryInfo *tli)
272  : DL(DL), TLI(tli) {}
273 
274  /// MarkBlockExecutable - This method can be used by clients to mark all of
275  /// the blocks that are known to be intrinsically live in the processed unit.
276  ///
277  /// This returns true if the block was not considered live before.
278  bool MarkBlockExecutable(BasicBlock *BB) {
279  if (!BBExecutable.insert(BB).second)
280  return false;
281  LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n');
282  BBWorkList.push_back(BB); // Add the block to the work list!
283  return true;
284  }
285 
286  /// TrackValueOfGlobalVariable - Clients can use this method to
287  /// inform the SCCPSolver that it should track loads and stores to the
288  /// specified global variable if it can. This is only legal to call if
289  /// performing Interprocedural SCCP.
290  void TrackValueOfGlobalVariable(GlobalVariable *GV) {
291  // We only track the contents of scalar globals.
292  if (GV->getValueType()->isSingleValueType()) {
293  LatticeVal &IV = TrackedGlobals[GV];
294  if (!isa<UndefValue>(GV->getInitializer()))
295  IV.markConstant(GV->getInitializer());
296  }
297  }
298 
299  /// AddTrackedFunction - If the SCCP solver is supposed to track calls into
300  /// and out of the specified function (which cannot have its address taken),
301  /// this method must be called.
302  void AddTrackedFunction(Function *F) {
303  // Add an entry, F -> undef.
304  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
305  MRVFunctionsTracked.insert(F);
306  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
307  TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
308  LatticeVal()));
309  } else
310  TrackedRetVals.insert(std::make_pair(F, LatticeVal()));
311  }
312 
313  /// AddMustTailCallee - If the SCCP solver finds that this function is called
314  /// from non-removable musttail call site.
315  void AddMustTailCallee(Function *F) {
316  MustTailCallees.insert(F);
317  }
318 
319  /// Returns true if the given function is called from non-removable musttail
320  /// call site.
321  bool isMustTailCallee(Function *F) {
322  return MustTailCallees.count(F);
323  }
324 
325  void AddArgumentTrackedFunction(Function *F) {
326  TrackingIncomingArguments.insert(F);
327  }
328 
329  /// Returns true if the given function is in the solver's set of
330  /// argument-tracked functions.
331  bool isArgumentTrackedFunction(Function *F) {
332  return TrackingIncomingArguments.count(F);
333  }
334 
335  /// Solve - Solve for constants and executable blocks.
336  void Solve();
337 
338  /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
339  /// that branches on undef values cannot reach any of their successors.
340  /// However, this is not a safe assumption. After we solve dataflow, this
341  /// method should be use to handle this. If this returns true, the solver
342  /// should be rerun.
343  bool ResolvedUndefsIn(Function &F);
344 
345  bool isBlockExecutable(BasicBlock *BB) const {
346  return BBExecutable.count(BB);
347  }
348 
349  // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
350  // block to the 'To' basic block is currently feasible.
351  bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
352 
353  std::vector<LatticeVal> getStructLatticeValueFor(Value *V) const {
354  std::vector<LatticeVal> StructValues;
355  auto *STy = dyn_cast<StructType>(V->getType());
356  assert(STy && "getStructLatticeValueFor() can be called only on structs");
357  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
358  auto I = StructValueState.find(std::make_pair(V, i));
359  assert(I != StructValueState.end() && "Value not in valuemap!");
360  StructValues.push_back(I->second);
361  }
362  return StructValues;
363  }
364 
365  const LatticeVal &getLatticeValueFor(Value *V) const {
366  assert(!V->getType()->isStructTy() &&
367  "Should use getStructLatticeValueFor");
369  assert(I != ValueState.end() &&
370  "V not found in ValueState nor Paramstate map!");
371  return I->second;
372  }
373 
374  /// getTrackedRetVals - Get the inferred return value map.
375  const MapVector<Function*, LatticeVal> &getTrackedRetVals() {
376  return TrackedRetVals;
377  }
378 
379  /// getTrackedGlobals - Get and return the set of inferred initializers for
380  /// global variables.
381  const DenseMap<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
382  return TrackedGlobals;
383  }
384 
385  /// getMRVFunctionsTracked - Get the set of functions which return multiple
386  /// values tracked by the pass.
387  const SmallPtrSet<Function *, 16> getMRVFunctionsTracked() {
388  return MRVFunctionsTracked;
389  }
390 
391  /// getMustTailCallees - Get the set of functions which are called
392  /// from non-removable musttail call sites.
393  const SmallPtrSet<Function *, 16> getMustTailCallees() {
394  return MustTailCallees;
395  }
396 
397  /// markOverdefined - Mark the specified value overdefined. This
398  /// works with both scalars and structs.
399  void markOverdefined(Value *V) {
400  if (auto *STy = dyn_cast<StructType>(V->getType()))
401  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
402  markOverdefined(getStructValueState(V, i), V);
403  else
404  markOverdefined(ValueState[V], V);
405  }
406 
407  // isStructLatticeConstant - Return true if all the lattice values
408  // corresponding to elements of the structure are not overdefined,
409  // false otherwise.
410  bool isStructLatticeConstant(Function *F, StructType *STy) {
411  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
412  const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i));
413  assert(It != TrackedMultipleRetVals.end());
414  LatticeVal LV = It->second;
415  if (LV.isOverdefined())
416  return false;
417  }
418  return true;
419  }
420 
421 private:
422  // pushToWorkList - Helper for markConstant/markForcedConstant/markOverdefined
423  void pushToWorkList(LatticeVal &IV, Value *V) {
424  if (IV.isOverdefined())
425  return OverdefinedInstWorkList.push_back(V);
426  InstWorkList.push_back(V);
427  }
428 
429  // markConstant - Make a value be marked as "constant". If the value
430  // is not already a constant, add it to the instruction work list so that
431  // the users of the instruction are updated later.
432  bool markConstant(LatticeVal &IV, Value *V, Constant *C) {
433  if (!IV.markConstant(C)) return false;
434  LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
435  pushToWorkList(IV, V);
436  return true;
437  }
438 
439  bool markConstant(Value *V, Constant *C) {
440  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
441  return markConstant(ValueState[V], V, C);
442  }
443 
444  void markForcedConstant(Value *V, Constant *C) {
445  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
446  LatticeVal &IV = ValueState[V];
447  IV.markForcedConstant(C);
448  LLVM_DEBUG(dbgs() << "markForcedConstant: " << *C << ": " << *V << '\n');
449  pushToWorkList(IV, V);
450  }
451 
452  // markOverdefined - Make a value be marked as "overdefined". If the
453  // value is not already overdefined, add it to the overdefined instruction
454  // work list so that the users of the instruction are updated later.
455  bool markOverdefined(LatticeVal &IV, Value *V) {
456  if (!IV.markOverdefined()) return false;
457 
458  LLVM_DEBUG(dbgs() << "markOverdefined: ";
459  if (auto *F = dyn_cast<Function>(V)) dbgs()
460  << "Function '" << F->getName() << "'\n";
461  else dbgs() << *V << '\n');
462  // Only instructions go on the work list
463  pushToWorkList(IV, V);
464  return true;
465  }
466 
467  bool mergeInValue(LatticeVal &IV, Value *V, LatticeVal MergeWithV) {
468  if (IV.isOverdefined() || MergeWithV.isUnknown())
469  return false; // Noop.
470  if (MergeWithV.isOverdefined())
471  return markOverdefined(IV, V);
472  if (IV.isUnknown())
473  return markConstant(IV, V, MergeWithV.getConstant());
474  if (IV.getConstant() != MergeWithV.getConstant())
475  return markOverdefined(IV, V);
476  return false;
477  }
478 
479  bool mergeInValue(Value *V, LatticeVal MergeWithV) {
480  assert(!V->getType()->isStructTy() &&
481  "non-structs should use markConstant");
482  return mergeInValue(ValueState[V], V, MergeWithV);
483  }
484 
485  /// getValueState - Return the LatticeVal object that corresponds to the
486  /// value. This function handles the case when the value hasn't been seen yet
487  /// by properly seeding constants etc.
488  LatticeVal &getValueState(Value *V) {
489  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
490 
491  std::pair<DenseMap<Value*, LatticeVal>::iterator, bool> I =
492  ValueState.insert(std::make_pair(V, LatticeVal()));
493  LatticeVal &LV = I.first->second;
494 
495  if (!I.second)
496  return LV; // Common case, already in the map.
497 
498  if (auto *C = dyn_cast<Constant>(V)) {
499  // Undef values remain unknown.
500  if (!isa<UndefValue>(V))
501  LV.markConstant(C); // Constants are constant
502  }
503 
504  // All others are underdefined by default.
505  return LV;
506  }
507 
508  ValueLatticeElement &getParamState(Value *V) {
509  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
510 
511  std::pair<DenseMap<Value*, ValueLatticeElement>::iterator, bool>
512  PI = ParamState.insert(std::make_pair(V, ValueLatticeElement()));
513  ValueLatticeElement &LV = PI.first->second;
514  if (PI.second)
515  LV = getValueState(V).toValueLattice();
516 
517  return LV;
518  }
519 
520  /// getStructValueState - Return the LatticeVal object that corresponds to the
521  /// value/field pair. This function handles the case when the value hasn't
522  /// been seen yet by properly seeding constants etc.
523  LatticeVal &getStructValueState(Value *V, unsigned i) {
524  assert(V->getType()->isStructTy() && "Should use getValueState");
525  assert(i < cast<StructType>(V->getType())->getNumElements() &&
526  "Invalid element #");
527 
528  std::pair<DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator,
529  bool> I = StructValueState.insert(
530  std::make_pair(std::make_pair(V, i), LatticeVal()));
531  LatticeVal &LV = I.first->second;
532 
533  if (!I.second)
534  return LV; // Common case, already in the map.
535 
536  if (auto *C = dyn_cast<Constant>(V)) {
537  Constant *Elt = C->getAggregateElement(i);
538 
539  if (!Elt)
540  LV.markOverdefined(); // Unknown sort of constant.
541  else if (isa<UndefValue>(Elt))
542  ; // Undef values remain unknown.
543  else
544  LV.markConstant(Elt); // Constants are constant.
545  }
546 
547  // All others are underdefined by default.
548  return LV;
549  }
550 
551  /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
552  /// work list if it is not already executable.
553  bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
554  if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
555  return false; // This edge is already known to be executable!
556 
557  if (!MarkBlockExecutable(Dest)) {
558  // If the destination is already executable, we just made an *edge*
559  // feasible that wasn't before. Revisit the PHI nodes in the block
560  // because they have potentially new operands.
561  LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
562  << " -> " << Dest->getName() << '\n');
563 
564  for (PHINode &PN : Dest->phis())
565  visitPHINode(PN);
566  }
567  return true;
568  }
569 
570  // getFeasibleSuccessors - Return a vector of booleans to indicate which
571  // successors are reachable from a given terminator instruction.
572  void getFeasibleSuccessors(Instruction &TI, SmallVectorImpl<bool> &Succs);
573 
574  // OperandChangedState - This method is invoked on all of the users of an
575  // instruction that was just changed state somehow. Based on this
576  // information, we need to update the specified user of this instruction.
577  void OperandChangedState(Instruction *I) {
578  if (BBExecutable.count(I->getParent())) // Inst is executable?
579  visit(*I);
580  }
581 
582  // Add U as additional user of V.
583  void addAdditionalUser(Value *V, User *U) {
584  auto Iter = AdditionalUsers.insert({V, {}});
585  Iter.first->second.insert(U);
586  }
587 
588  // Mark I's users as changed, including AdditionalUsers.
589  void markUsersAsChanged(Value *I) {
590  for (User *U : I->users())
591  if (auto *UI = dyn_cast<Instruction>(U))
592  OperandChangedState(UI);
593 
594  auto Iter = AdditionalUsers.find(I);
595  if (Iter != AdditionalUsers.end()) {
596  for (User *U : Iter->second)
597  if (auto *UI = dyn_cast<Instruction>(U))
598  OperandChangedState(UI);
599  }
600  }
601 
602 private:
603  friend class InstVisitor<SCCPSolver>;
604 
605  // visit implementations - Something changed in this instruction. Either an
606  // operand made a transition, or the instruction is newly executable. Change
607  // the value type of I to reflect these changes if appropriate.
608  void visitPHINode(PHINode &I);
609 
610  // Terminators
611 
612  void visitReturnInst(ReturnInst &I);
613  void visitTerminator(Instruction &TI);
614 
615  void visitCastInst(CastInst &I);
616  void visitSelectInst(SelectInst &I);
617  void visitUnaryOperator(Instruction &I);
618  void visitBinaryOperator(Instruction &I);
619  void visitCmpInst(CmpInst &I);
620  void visitExtractValueInst(ExtractValueInst &EVI);
621  void visitInsertValueInst(InsertValueInst &IVI);
622 
623  void visitCatchSwitchInst(CatchSwitchInst &CPI) {
624  markOverdefined(&CPI);
625  visitTerminator(CPI);
626  }
627 
628  // Instructions that cannot be folded away.
629 
630  void visitStoreInst (StoreInst &I);
631  void visitLoadInst (LoadInst &I);
632  void visitGetElementPtrInst(GetElementPtrInst &I);
633 
634  void visitCallInst (CallInst &I) {
635  visitCallSite(&I);
636  }
637 
638  void visitInvokeInst (InvokeInst &II) {
639  visitCallSite(&II);
640  visitTerminator(II);
641  }
642 
643  void visitCallBrInst (CallBrInst &CBI) {
644  visitCallSite(&CBI);
645  visitTerminator(CBI);
646  }
647 
648  void visitCallSite (CallSite CS);
649  void visitResumeInst (ResumeInst &I) { /*returns void*/ }
650  void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ }
651  void visitFenceInst (FenceInst &I) { /*returns void*/ }
652 
653  void visitInstruction(Instruction &I) {
654  // All the instructions we don't do any special handling for just
655  // go to overdefined.
656  LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n');
657  markOverdefined(&I);
658  }
659 };
660 
661 } // end anonymous namespace
662 
663 // getFeasibleSuccessors - Return a vector of booleans to indicate which
664 // successors are reachable from a given terminator instruction.
665 void SCCPSolver::getFeasibleSuccessors(Instruction &TI,
666  SmallVectorImpl<bool> &Succs) {
667  Succs.resize(TI.getNumSuccessors());
668  if (auto *BI = dyn_cast<BranchInst>(&TI)) {
669  if (BI->isUnconditional()) {
670  Succs[0] = true;
671  return;
672  }
673 
674  LatticeVal BCValue = getValueState(BI->getCondition());
675  ConstantInt *CI = BCValue.getConstantInt();
676  if (!CI) {
677  // Overdefined condition variables, and branches on unfoldable constant
678  // conditions, mean the branch could go either way.
679  if (!BCValue.isUnknown())
680  Succs[0] = Succs[1] = true;
681  return;
682  }
683 
684  // Constant condition variables mean the branch can only go a single way.
685  Succs[CI->isZero()] = true;
686  return;
687  }
688 
689  // Unwinding instructions successors are always executable.
690  if (TI.isExceptionalTerminator()) {
691  Succs.assign(TI.getNumSuccessors(), true);
692  return;
693  }
694 
695  if (auto *SI = dyn_cast<SwitchInst>(&TI)) {
696  if (!SI->getNumCases()) {
697  Succs[0] = true;
698  return;
699  }
700  LatticeVal SCValue = getValueState(SI->getCondition());
701  ConstantInt *CI = SCValue.getConstantInt();
702 
703  if (!CI) { // Overdefined or unknown condition?
704  // All destinations are executable!
705  if (!SCValue.isUnknown())
706  Succs.assign(TI.getNumSuccessors(), true);
707  return;
708  }
709 
710  Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
711  return;
712  }
713 
714  // In case of indirect branch and its address is a blockaddress, we mark
715  // the target as executable.
716  if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) {
717  // Casts are folded by visitCastInst.
718  LatticeVal IBRValue = getValueState(IBR->getAddress());
719  BlockAddress *Addr = IBRValue.getBlockAddress();
720  if (!Addr) { // Overdefined or unknown condition?
721  // All destinations are executable!
722  if (!IBRValue.isUnknown())
723  Succs.assign(TI.getNumSuccessors(), true);
724  return;
725  }
726 
727  BasicBlock* T = Addr->getBasicBlock();
728  assert(Addr->getFunction() == T->getParent() &&
729  "Block address of a different function ?");
730  for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) {
731  // This is the target.
732  if (IBR->getDestination(i) == T) {
733  Succs[i] = true;
734  return;
735  }
736  }
737 
738  // If we didn't find our destination in the IBR successor list, then we
739  // have undefined behavior. Its ok to assume no successor is executable.
740  return;
741  }
742 
743  // In case of callbr, we pessimistically assume that all successors are
744  // feasible.
745  if (isa<CallBrInst>(&TI)) {
746  Succs.assign(TI.getNumSuccessors(), true);
747  return;
748  }
749 
750  LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n');
751  llvm_unreachable("SCCP: Don't know how to handle this terminator!");
752 }
753 
754 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
755 // block to the 'To' basic block is currently feasible.
756 bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
757  // Check if we've called markEdgeExecutable on the edge yet. (We could
758  // be more aggressive and try to consider edges which haven't been marked
759  // yet, but there isn't any need.)
760  return KnownFeasibleEdges.count(Edge(From, To));
761 }
762 
763 // visit Implementations - Something changed in this instruction, either an
764 // operand made a transition, or the instruction is newly executable. Change
765 // the value type of I to reflect these changes if appropriate. This method
766 // makes sure to do the following actions:
767 //
768 // 1. If a phi node merges two constants in, and has conflicting value coming
769 // from different branches, or if the PHI node merges in an overdefined
770 // value, then the PHI node becomes overdefined.
771 // 2. If a phi node merges only constants in, and they all agree on value, the
772 // PHI node becomes a constant value equal to that.
773 // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant
774 // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined
775 // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined
776 // 6. If a conditional branch has a value that is constant, make the selected
777 // destination executable
778 // 7. If a conditional branch has a value that is overdefined, make all
779 // successors executable.
780 void SCCPSolver::visitPHINode(PHINode &PN) {
781  // If this PN returns a struct, just mark the result overdefined.
782  // TODO: We could do a lot better than this if code actually uses this.
783  if (PN.getType()->isStructTy())
784  return (void)markOverdefined(&PN);
785 
786  if (getValueState(&PN).isOverdefined())
787  return; // Quick exit
788 
789  // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
790  // and slow us down a lot. Just mark them overdefined.
791  if (PN.getNumIncomingValues() > 64)
792  return (void)markOverdefined(&PN);
793 
794  // Look at all of the executable operands of the PHI node. If any of them
795  // are overdefined, the PHI becomes overdefined as well. If they are all
796  // constant, and they agree with each other, the PHI becomes the identical
797  // constant. If they are constant and don't agree, the PHI is overdefined.
798  // If there are no executable operands, the PHI remains unknown.
799  Constant *OperandVal = nullptr;
800  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
801  LatticeVal IV = getValueState(PN.getIncomingValue(i));
802  if (IV.isUnknown()) continue; // Doesn't influence PHI node.
803 
804  if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
805  continue;
806 
807  if (IV.isOverdefined()) // PHI node becomes overdefined!
808  return (void)markOverdefined(&PN);
809 
810  if (!OperandVal) { // Grab the first value.
811  OperandVal = IV.getConstant();
812  continue;
813  }
814 
815  // There is already a reachable operand. If we conflict with it,
816  // then the PHI node becomes overdefined. If we agree with it, we
817  // can continue on.
818 
819  // Check to see if there are two different constants merging, if so, the PHI
820  // node is overdefined.
821  if (IV.getConstant() != OperandVal)
822  return (void)markOverdefined(&PN);
823  }
824 
825  // If we exited the loop, this means that the PHI node only has constant
826  // arguments that agree with each other(and OperandVal is the constant) or
827  // OperandVal is null because there are no defined incoming arguments. If
828  // this is the case, the PHI remains unknown.
829  if (OperandVal)
830  markConstant(&PN, OperandVal); // Acquire operand value
831 }
832 
833 void SCCPSolver::visitReturnInst(ReturnInst &I) {
834  if (I.getNumOperands() == 0) return; // ret void
835 
836  Function *F = I.getParent()->getParent();
837  Value *ResultOp = I.getOperand(0);
838 
839  // If we are tracking the return value of this function, merge it in.
840  if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
842  TrackedRetVals.find(F);
843  if (TFRVI != TrackedRetVals.end()) {
844  mergeInValue(TFRVI->second, F, getValueState(ResultOp));
845  return;
846  }
847  }
848 
849  // Handle functions that return multiple values.
850  if (!TrackedMultipleRetVals.empty()) {
851  if (auto *STy = dyn_cast<StructType>(ResultOp->getType()))
852  if (MRVFunctionsTracked.count(F))
853  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
854  mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
855  getStructValueState(ResultOp, i));
856  }
857 }
858 
859 void SCCPSolver::visitTerminator(Instruction &TI) {
860  SmallVector<bool, 16> SuccFeasible;
861  getFeasibleSuccessors(TI, SuccFeasible);
862 
863  BasicBlock *BB = TI.getParent();
864 
865  // Mark all feasible successors executable.
866  for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
867  if (SuccFeasible[i])
868  markEdgeExecutable(BB, TI.getSuccessor(i));
869 }
870 
871 void SCCPSolver::visitCastInst(CastInst &I) {
872  LatticeVal OpSt = getValueState(I.getOperand(0));
873  if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
874  markOverdefined(&I);
875  else if (OpSt.isConstant()) {
876  // Fold the constant as we build.
877  Constant *C = ConstantFoldCastOperand(I.getOpcode(), OpSt.getConstant(),
878  I.getType(), DL);
879  if (isa<UndefValue>(C))
880  return;
881  // Propagate constant value
882  markConstant(&I, C);
883  }
884 }
885 
886 void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
887  // If this returns a struct, mark all elements over defined, we don't track
888  // structs in structs.
889  if (EVI.getType()->isStructTy())
890  return (void)markOverdefined(&EVI);
891 
892  // If this is extracting from more than one level of struct, we don't know.
893  if (EVI.getNumIndices() != 1)
894  return (void)markOverdefined(&EVI);
895 
896  Value *AggVal = EVI.getAggregateOperand();
897  if (AggVal->getType()->isStructTy()) {
898  unsigned i = *EVI.idx_begin();
899  LatticeVal EltVal = getStructValueState(AggVal, i);
900  mergeInValue(getValueState(&EVI), &EVI, EltVal);
901  } else {
902  // Otherwise, must be extracting from an array.
903  return (void)markOverdefined(&EVI);
904  }
905 }
906 
907 void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
908  auto *STy = dyn_cast<StructType>(IVI.getType());
909  if (!STy)
910  return (void)markOverdefined(&IVI);
911 
912  // If this has more than one index, we can't handle it, drive all results to
913  // undef.
914  if (IVI.getNumIndices() != 1)
915  return (void)markOverdefined(&IVI);
916 
917  Value *Aggr = IVI.getAggregateOperand();
918  unsigned Idx = *IVI.idx_begin();
919 
920  // Compute the result based on what we're inserting.
921  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
922  // This passes through all values that aren't the inserted element.
923  if (i != Idx) {
924  LatticeVal EltVal = getStructValueState(Aggr, i);
925  mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
926  continue;
927  }
928 
929  Value *Val = IVI.getInsertedValueOperand();
930  if (Val->getType()->isStructTy())
931  // We don't track structs in structs.
932  markOverdefined(getStructValueState(&IVI, i), &IVI);
933  else {
934  LatticeVal InVal = getValueState(Val);
935  mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
936  }
937  }
938 }
939 
940 void SCCPSolver::visitSelectInst(SelectInst &I) {
941  // If this select returns a struct, just mark the result overdefined.
942  // TODO: We could do a lot better than this if code actually uses this.
943  if (I.getType()->isStructTy())
944  return (void)markOverdefined(&I);
945 
946  LatticeVal CondValue = getValueState(I.getCondition());
947  if (CondValue.isUnknown())
948  return;
949 
950  if (ConstantInt *CondCB = CondValue.getConstantInt()) {
951  Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
952  mergeInValue(&I, getValueState(OpVal));
953  return;
954  }
955 
956  // Otherwise, the condition is overdefined or a constant we can't evaluate.
957  // See if we can produce something better than overdefined based on the T/F
958  // value.
959  LatticeVal TVal = getValueState(I.getTrueValue());
960  LatticeVal FVal = getValueState(I.getFalseValue());
961 
962  // select ?, C, C -> C.
963  if (TVal.isConstant() && FVal.isConstant() &&
964  TVal.getConstant() == FVal.getConstant())
965  return (void)markConstant(&I, FVal.getConstant());
966 
967  if (TVal.isUnknown()) // select ?, undef, X -> X.
968  return (void)mergeInValue(&I, FVal);
969  if (FVal.isUnknown()) // select ?, X, undef -> X.
970  return (void)mergeInValue(&I, TVal);
971  markOverdefined(&I);
972 }
973 
974 // Handle Unary Operators.
975 void SCCPSolver::visitUnaryOperator(Instruction &I) {
976  LatticeVal V0State = getValueState(I.getOperand(0));
977 
978  LatticeVal &IV = ValueState[&I];
979  if (IV.isOverdefined()) return;
980 
981  if (V0State.isConstant()) {
982  Constant *C = ConstantExpr::get(I.getOpcode(), V0State.getConstant());
983 
984  // op Y -> undef.
985  if (isa<UndefValue>(C))
986  return;
987  return (void)markConstant(IV, &I, C);
988  }
989 
990  // If something is undef, wait for it to resolve.
991  if (!V0State.isOverdefined())
992  return;
993 
994  markOverdefined(&I);
995 }
996 
997 // Handle Binary Operators.
998 void SCCPSolver::visitBinaryOperator(Instruction &I) {
999  LatticeVal V1State = getValueState(I.getOperand(0));
1000  LatticeVal V2State = getValueState(I.getOperand(1));
1001 
1002  LatticeVal &IV = ValueState[&I];
1003  if (IV.isOverdefined()) return;
1004 
1005  if (V1State.isConstant() && V2State.isConstant()) {
1006  Constant *C = ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
1007  V2State.getConstant());
1008  // X op Y -> undef.
1009  if (isa<UndefValue>(C))
1010  return;
1011  return (void)markConstant(IV, &I, C);
1012  }
1013 
1014  // If something is undef, wait for it to resolve.
1015  if (!V1State.isOverdefined() && !V2State.isOverdefined())
1016  return;
1017 
1018  // Otherwise, one of our operands is overdefined. Try to produce something
1019  // better than overdefined with some tricks.
1020  // If this is 0 / Y, it doesn't matter that the second operand is
1021  // overdefined, and we can replace it with zero.
1022  if (I.getOpcode() == Instruction::UDiv || I.getOpcode() == Instruction::SDiv)
1023  if (V1State.isConstant() && V1State.getConstant()->isNullValue())
1024  return (void)markConstant(IV, &I, V1State.getConstant());
1025 
1026  // If this is:
1027  // -> AND/MUL with 0
1028  // -> OR with -1
1029  // it doesn't matter that the other operand is overdefined.
1030  if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Mul ||
1031  I.getOpcode() == Instruction::Or) {
1032  LatticeVal *NonOverdefVal = nullptr;
1033  if (!V1State.isOverdefined())
1034  NonOverdefVal = &V1State;
1035  else if (!V2State.isOverdefined())
1036  NonOverdefVal = &V2State;
1037 
1038  if (NonOverdefVal) {
1039  if (NonOverdefVal->isUnknown())
1040  return;
1041 
1042  if (I.getOpcode() == Instruction::And ||
1043  I.getOpcode() == Instruction::Mul) {
1044  // X and 0 = 0
1045  // X * 0 = 0
1046  if (NonOverdefVal->getConstant()->isNullValue())
1047  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1048  } else {
1049  // X or -1 = -1
1050  if (ConstantInt *CI = NonOverdefVal->getConstantInt())
1051  if (CI->isMinusOne())
1052  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1053  }
1054  }
1055  }
1056 
1057  markOverdefined(&I);
1058 }
1059 
1060 // Handle ICmpInst instruction.
1061 void SCCPSolver::visitCmpInst(CmpInst &I) {
1062  // Do not cache this lookup, getValueState calls later in the function might
1063  // invalidate the reference.
1064  if (ValueState[&I].isOverdefined()) return;
1065 
1066  Value *Op1 = I.getOperand(0);
1067  Value *Op2 = I.getOperand(1);
1068 
1069  // For parameters, use ParamState which includes constant range info if
1070  // available.
1071  auto V1Param = ParamState.find(Op1);
1072  ValueLatticeElement V1State = (V1Param != ParamState.end())
1073  ? V1Param->second
1074  : getValueState(Op1).toValueLattice();
1075 
1076  auto V2Param = ParamState.find(Op2);
1077  ValueLatticeElement V2State = V2Param != ParamState.end()
1078  ? V2Param->second
1079  : getValueState(Op2).toValueLattice();
1080 
1081  Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
1082  if (C) {
1083  if (isa<UndefValue>(C))
1084  return;
1085  LatticeVal CV;
1086  CV.markConstant(C);
1087  mergeInValue(&I, CV);
1088  return;
1089  }
1090 
1091  // If operands are still unknown, wait for it to resolve.
1092  if (!V1State.isOverdefined() && !V2State.isOverdefined() &&
1093  !ValueState[&I].isConstant())
1094  return;
1095 
1096  markOverdefined(&I);
1097 }
1098 
1099 // Handle getelementptr instructions. If all operands are constants then we
1100 // can turn this into a getelementptr ConstantExpr.
1101 void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
1102  if (ValueState[&I].isOverdefined()) return;
1103 
1104  SmallVector<Constant*, 8> Operands;
1105  Operands.reserve(I.getNumOperands());
1106 
1107  for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
1108  LatticeVal State = getValueState(I.getOperand(i));
1109  if (State.isUnknown())
1110  return; // Operands are not resolved yet.
1111 
1112  if (State.isOverdefined())
1113  return (void)markOverdefined(&I);
1114 
1115  assert(State.isConstant() && "Unknown state!");
1116  Operands.push_back(State.getConstant());
1117  }
1118 
1119  Constant *Ptr = Operands[0];
1120  auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end());
1121  Constant *C =
1123  if (isa<UndefValue>(C))
1124  return;
1125  markConstant(&I, C);
1126 }
1127 
1128 void SCCPSolver::visitStoreInst(StoreInst &SI) {
1129  // If this store is of a struct, ignore it.
1130  if (SI.getOperand(0)->getType()->isStructTy())
1131  return;
1132 
1133  if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
1134  return;
1135 
1136  GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
1138  if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
1139 
1140  // Get the value we are storing into the global, then merge it.
1141  mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
1142  if (I->second.isOverdefined())
1143  TrackedGlobals.erase(I); // No need to keep tracking this!
1144 }
1145 
1146 // Handle load instructions. If the operand is a constant pointer to a constant
1147 // global, we can replace the load with the loaded constant value!
1148 void SCCPSolver::visitLoadInst(LoadInst &I) {
1149  // If this load is of a struct, just mark the result overdefined.
1150  if (I.getType()->isStructTy())
1151  return (void)markOverdefined(&I);
1152 
1153  LatticeVal PtrVal = getValueState(I.getOperand(0));
1154  if (PtrVal.isUnknown()) return; // The pointer is not resolved yet!
1155 
1156  LatticeVal &IV = ValueState[&I];
1157  if (IV.isOverdefined()) return;
1158 
1159  if (!PtrVal.isConstant() || I.isVolatile())
1160  return (void)markOverdefined(IV, &I);
1161 
1162  Constant *Ptr = PtrVal.getConstant();
1163 
1164  // load null is undefined.
1165  if (isa<ConstantPointerNull>(Ptr)) {
1167  return (void)markOverdefined(IV, &I);
1168  else
1169  return;
1170  }
1171 
1172  // Transform load (constant global) into the value loaded.
1173  if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) {
1174  if (!TrackedGlobals.empty()) {
1175  // If we are tracking this global, merge in the known value for it.
1177  TrackedGlobals.find(GV);
1178  if (It != TrackedGlobals.end()) {
1179  mergeInValue(IV, &I, It->second);
1180  return;
1181  }
1182  }
1183  }
1184 
1185  // Transform load from a constant into a constant if possible.
1186  if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) {
1187  if (isa<UndefValue>(C))
1188  return;
1189  return (void)markConstant(IV, &I, C);
1190  }
1191 
1192  // Otherwise we cannot say for certain what value this load will produce.
1193  // Bail out.
1194  markOverdefined(IV, &I);
1195 }
1196 
1197 void SCCPSolver::visitCallSite(CallSite CS) {
1198  Function *F = CS.getCalledFunction();
1199  Instruction *I = CS.getInstruction();
1200 
1201  if (auto *II = dyn_cast<IntrinsicInst>(I)) {
1202  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
1203  if (ValueState[I].isOverdefined())
1204  return;
1205 
1206  auto *PI = getPredicateInfoFor(I);
1207  if (!PI)
1208  return;
1209 
1210  Value *CopyOf = I->getOperand(0);
1211  auto *PBranch = dyn_cast<PredicateBranch>(PI);
1212  if (!PBranch) {
1213  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1214  return;
1215  }
1216 
1217  Value *Cond = PBranch->Condition;
1218 
1219  // Everything below relies on the condition being a comparison.
1220  auto *Cmp = dyn_cast<CmpInst>(Cond);
1221  if (!Cmp) {
1222  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1223  return;
1224  }
1225 
1226  Value *CmpOp0 = Cmp->getOperand(0);
1227  Value *CmpOp1 = Cmp->getOperand(1);
1228  if (CopyOf != CmpOp0 && CopyOf != CmpOp1) {
1229  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1230  return;
1231  }
1232 
1233  if (CmpOp0 != CopyOf)
1234  std::swap(CmpOp0, CmpOp1);
1235 
1236  LatticeVal OriginalVal = getValueState(CopyOf);
1237  LatticeVal EqVal = getValueState(CmpOp1);
1238  LatticeVal &IV = ValueState[I];
1239  if (PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_EQ) {
1240  addAdditionalUser(CmpOp1, I);
1241  if (OriginalVal.isConstant())
1242  mergeInValue(IV, I, OriginalVal);
1243  else
1244  mergeInValue(IV, I, EqVal);
1245  return;
1246  }
1247  if (!PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_NE) {
1248  addAdditionalUser(CmpOp1, I);
1249  if (OriginalVal.isConstant())
1250  mergeInValue(IV, I, OriginalVal);
1251  else
1252  mergeInValue(IV, I, EqVal);
1253  return;
1254  }
1255 
1256  return (void)mergeInValue(IV, I, getValueState(CopyOf));
1257  }
1258  }
1259 
1260  // The common case is that we aren't tracking the callee, either because we
1261  // are not doing interprocedural analysis or the callee is indirect, or is
1262  // external. Handle these cases first.
1263  if (!F || F->isDeclaration()) {
1264 CallOverdefined:
1265  // Void return and not tracking callee, just bail.
1266  if (I->getType()->isVoidTy()) return;
1267 
1268  // Otherwise, if we have a single return value case, and if the function is
1269  // a declaration, maybe we can constant fold it.
1270  if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
1271  canConstantFoldCallTo(cast<CallBase>(CS.getInstruction()), F)) {
1272  SmallVector<Constant*, 8> Operands;
1273  for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
1274  AI != E; ++AI) {
1275  if (AI->get()->getType()->isStructTy())
1276  return markOverdefined(I); // Can't handle struct args.
1277  LatticeVal State = getValueState(*AI);
1278 
1279  if (State.isUnknown())
1280  return; // Operands are not resolved yet.
1281  if (State.isOverdefined())
1282  return (void)markOverdefined(I);
1283  assert(State.isConstant() && "Unknown state!");
1284  Operands.push_back(State.getConstant());
1285  }
1286 
1287  if (getValueState(I).isOverdefined())
1288  return;
1289 
1290  // If we can constant fold this, mark the result of the call as a
1291  // constant.
1292  if (Constant *C = ConstantFoldCall(cast<CallBase>(CS.getInstruction()), F,
1293  Operands, TLI)) {
1294  // call -> undef.
1295  if (isa<UndefValue>(C))
1296  return;
1297  return (void)markConstant(I, C);
1298  }
1299  }
1300 
1301  // Otherwise, we don't know anything about this call, mark it overdefined.
1302  return (void)markOverdefined(I);
1303  }
1304 
1305  // If this is a local function that doesn't have its address taken, mark its
1306  // entry block executable and merge in the actual arguments to the call into
1307  // the formal arguments of the function.
1308  if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
1309  MarkBlockExecutable(&F->front());
1310 
1311  // Propagate information from this call site into the callee.
1312  CallSite::arg_iterator CAI = CS.arg_begin();
1313  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
1314  AI != E; ++AI, ++CAI) {
1315  // If this argument is byval, and if the function is not readonly, there
1316  // will be an implicit copy formed of the input aggregate.
1317  if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
1318  markOverdefined(&*AI);
1319  continue;
1320  }
1321 
1322  if (auto *STy = dyn_cast<StructType>(AI->getType())) {
1323  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1324  LatticeVal CallArg = getStructValueState(*CAI, i);
1325  mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
1326  }
1327  } else {
1328  // Most other parts of the Solver still only use the simpler value
1329  // lattice, so we propagate changes for parameters to both lattices.
1330  LatticeVal ConcreteArgument = getValueState(*CAI);
1331  bool ParamChanged =
1332  getParamState(&*AI).mergeIn(ConcreteArgument.toValueLattice(), DL);
1333  bool ValueChanged = mergeInValue(&*AI, ConcreteArgument);
1334  // Add argument to work list, if the state of a parameter changes but
1335  // ValueState does not change (because it is already overdefined there),
1336  // We have to take changes in ParamState into account, as it is used
1337  // when evaluating Cmp instructions.
1338  if (!ValueChanged && ParamChanged)
1339  pushToWorkList(ValueState[&*AI], &*AI);
1340  }
1341  }
1342  }
1343 
1344  // If this is a single/zero retval case, see if we're tracking the function.
1345  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
1346  if (!MRVFunctionsTracked.count(F))
1347  goto CallOverdefined; // Not tracking this callee.
1348 
1349  // If we are tracking this callee, propagate the result of the function
1350  // into this call site.
1351  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1352  mergeInValue(getStructValueState(I, i), I,
1353  TrackedMultipleRetVals[std::make_pair(F, i)]);
1354  } else {
1355  MapVector<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
1356  if (TFRVI == TrackedRetVals.end())
1357  goto CallOverdefined; // Not tracking this callee.
1358 
1359  // If so, propagate the return value of the callee into this call result.
1360  mergeInValue(I, TFRVI->second);
1361  }
1362 }
1363 
1364 void SCCPSolver::Solve() {
1365  // Process the work lists until they are empty!
1366  while (!BBWorkList.empty() || !InstWorkList.empty() ||
1367  !OverdefinedInstWorkList.empty()) {
1368  // Process the overdefined instruction's work list first, which drives other
1369  // things to overdefined more quickly.
1370  while (!OverdefinedInstWorkList.empty()) {
1371  Value *I = OverdefinedInstWorkList.pop_back_val();
1372 
1373  LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
1374 
1375  // "I" got into the work list because it either made the transition from
1376  // bottom to constant, or to overdefined.
1377  //
1378  // Anything on this worklist that is overdefined need not be visited
1379  // since all of its users will have already been marked as overdefined
1380  // Update all of the users of this instruction's value.
1381  //
1382  markUsersAsChanged(I);
1383  }
1384 
1385  // Process the instruction work list.
1386  while (!InstWorkList.empty()) {
1387  Value *I = InstWorkList.pop_back_val();
1388 
1389  LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
1390 
1391  // "I" got into the work list because it made the transition from undef to
1392  // constant.
1393  //
1394  // Anything on this worklist that is overdefined need not be visited
1395  // since all of its users will have already been marked as overdefined.
1396  // Update all of the users of this instruction's value.
1397  //
1398  if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
1399  markUsersAsChanged(I);
1400  }
1401 
1402  // Process the basic block work list.
1403  while (!BBWorkList.empty()) {
1404  BasicBlock *BB = BBWorkList.back();
1405  BBWorkList.pop_back();
1406 
1407  LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
1408 
1409  // Notify all instructions in this basic block that they are newly
1410  // executable.
1411  visit(BB);
1412  }
1413  }
1414 }
1415 
1416 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
1417 /// that branches on undef values cannot reach any of their successors.
1418 /// However, this is not a safe assumption. After we solve dataflow, this
1419 /// method should be use to handle this. If this returns true, the solver
1420 /// should be rerun.
1421 ///
1422 /// This method handles this by finding an unresolved branch and marking it one
1423 /// of the edges from the block as being feasible, even though the condition
1424 /// doesn't say it would otherwise be. This allows SCCP to find the rest of the
1425 /// CFG and only slightly pessimizes the analysis results (by marking one,
1426 /// potentially infeasible, edge feasible). This cannot usefully modify the
1427 /// constraints on the condition of the branch, as that would impact other users
1428 /// of the value.
1429 ///
1430 /// This scan also checks for values that use undefs, whose results are actually
1431 /// defined. For example, 'zext i8 undef to i32' should produce all zeros
1432 /// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
1433 /// even if X isn't defined.
1434 bool SCCPSolver::ResolvedUndefsIn(Function &F) {
1435  for (BasicBlock &BB : F) {
1436  if (!BBExecutable.count(&BB))
1437  continue;
1438 
1439  for (Instruction &I : BB) {
1440  // Look for instructions which produce undef values.
1441  if (I.getType()->isVoidTy()) continue;
1442 
1443  if (auto *STy = dyn_cast<StructType>(I.getType())) {
1444  // Only a few things that can be structs matter for undef.
1445 
1446  // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
1447  if (CallSite CS = CallSite(&I))
1448  if (Function *F = CS.getCalledFunction())
1449  if (MRVFunctionsTracked.count(F))
1450  continue;
1451 
1452  // extractvalue and insertvalue don't need to be marked; they are
1453  // tracked as precisely as their operands.
1454  if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
1455  continue;
1456 
1457  // Send the results of everything else to overdefined. We could be
1458  // more precise than this but it isn't worth bothering.
1459  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1460  LatticeVal &LV = getStructValueState(&I, i);
1461  if (LV.isUnknown())
1462  markOverdefined(LV, &I);
1463  }
1464  continue;
1465  }
1466 
1467  LatticeVal &LV = getValueState(&I);
1468  if (!LV.isUnknown()) continue;
1469 
1470  // extractvalue is safe; check here because the argument is a struct.
1471  if (isa<ExtractValueInst>(I))
1472  continue;
1473 
1474  // Compute the operand LatticeVals, for convenience below.
1475  // Anything taking a struct is conservatively assumed to require
1476  // overdefined markings.
1477  if (I.getOperand(0)->getType()->isStructTy()) {
1478  markOverdefined(&I);
1479  return true;
1480  }
1481  LatticeVal Op0LV = getValueState(I.getOperand(0));
1482  LatticeVal Op1LV;
1483  if (I.getNumOperands() == 2) {
1484  if (I.getOperand(1)->getType()->isStructTy()) {
1485  markOverdefined(&I);
1486  return true;
1487  }
1488 
1489  Op1LV = getValueState(I.getOperand(1));
1490  }
1491  // If this is an instructions whose result is defined even if the input is
1492  // not fully defined, propagate the information.
1493  Type *ITy = I.getType();
1494  switch (I.getOpcode()) {
1495  case Instruction::Add:
1496  case Instruction::Sub:
1497  case Instruction::Trunc:
1498  case Instruction::FPTrunc:
1499  case Instruction::BitCast:
1500  break; // Any undef -> undef
1501  case Instruction::FSub:
1502  case Instruction::FAdd:
1503  case Instruction::FMul:
1504  case Instruction::FDiv:
1505  case Instruction::FRem:
1506  // Floating-point binary operation: be conservative.
1507  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1508  markForcedConstant(&I, Constant::getNullValue(ITy));
1509  else
1510  markOverdefined(&I);
1511  return true;
1512  case Instruction::FNeg:
1513  break; // fneg undef -> undef
1514  case Instruction::ZExt:
1515  case Instruction::SExt:
1516  case Instruction::FPToUI:
1517  case Instruction::FPToSI:
1518  case Instruction::FPExt:
1519  case Instruction::PtrToInt:
1520  case Instruction::IntToPtr:
1521  case Instruction::SIToFP:
1522  case Instruction::UIToFP:
1523  // undef -> 0; some outputs are impossible
1524  markForcedConstant(&I, Constant::getNullValue(ITy));
1525  return true;
1526  case Instruction::Mul:
1527  case Instruction::And:
1528  // Both operands undef -> undef
1529  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1530  break;
1531  // undef * X -> 0. X could be zero.
1532  // undef & X -> 0. X could be zero.
1533  markForcedConstant(&I, Constant::getNullValue(ITy));
1534  return true;
1535  case Instruction::Or:
1536  // Both operands undef -> undef
1537  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1538  break;
1539  // undef | X -> -1. X could be -1.
1540  markForcedConstant(&I, Constant::getAllOnesValue(ITy));
1541  return true;
1542  case Instruction::Xor:
1543  // undef ^ undef -> 0; strictly speaking, this is not strictly
1544  // necessary, but we try to be nice to people who expect this
1545  // behavior in simple cases
1546  if (Op0LV.isUnknown() && Op1LV.isUnknown()) {
1547  markForcedConstant(&I, Constant::getNullValue(ITy));
1548  return true;
1549  }
1550  // undef ^ X -> undef
1551  break;
1552  case Instruction::SDiv:
1553  case Instruction::UDiv:
1554  case Instruction::SRem:
1555  case Instruction::URem:
1556  // X / undef -> undef. No change.
1557  // X % undef -> undef. No change.
1558  if (Op1LV.isUnknown()) break;
1559 
1560  // X / 0 -> undef. No change.
1561  // X % 0 -> undef. No change.
1562  if (Op1LV.isConstant() && Op1LV.getConstant()->isZeroValue())
1563  break;
1564 
1565  // undef / X -> 0. X could be maxint.
1566  // undef % X -> 0. X could be 1.
1567  markForcedConstant(&I, Constant::getNullValue(ITy));
1568  return true;
1569  case Instruction::AShr:
1570  // X >>a undef -> undef.
1571  if (Op1LV.isUnknown()) break;
1572 
1573  // Shifting by the bitwidth or more is undefined.
1574  if (Op1LV.isConstant()) {
1575  if (auto *ShiftAmt = Op1LV.getConstantInt())
1576  if (ShiftAmt->getLimitedValue() >=
1577  ShiftAmt->getType()->getScalarSizeInBits())
1578  break;
1579  }
1580 
1581  // undef >>a X -> 0
1582  markForcedConstant(&I, Constant::getNullValue(ITy));
1583  return true;
1584  case Instruction::LShr:
1585  case Instruction::Shl:
1586  // X << undef -> undef.
1587  // X >> undef -> undef.
1588  if (Op1LV.isUnknown()) break;
1589 
1590  // Shifting by the bitwidth or more is undefined.
1591  if (Op1LV.isConstant()) {
1592  if (auto *ShiftAmt = Op1LV.getConstantInt())
1593  if (ShiftAmt->getLimitedValue() >=
1594  ShiftAmt->getType()->getScalarSizeInBits())
1595  break;
1596  }
1597 
1598  // undef << X -> 0
1599  // undef >> X -> 0
1600  markForcedConstant(&I, Constant::getNullValue(ITy));
1601  return true;
1602  case Instruction::Select:
1603  Op1LV = getValueState(I.getOperand(1));
1604  // undef ? X : Y -> X or Y. There could be commonality between X/Y.
1605  if (Op0LV.isUnknown()) {
1606  if (!Op1LV.isConstant()) // Pick the constant one if there is any.
1607  Op1LV = getValueState(I.getOperand(2));
1608  } else if (Op1LV.isUnknown()) {
1609  // c ? undef : undef -> undef. No change.
1610  Op1LV = getValueState(I.getOperand(2));
1611  if (Op1LV.isUnknown())
1612  break;
1613  // Otherwise, c ? undef : x -> x.
1614  } else {
1615  // Leave Op1LV as Operand(1)'s LatticeValue.
1616  }
1617 
1618  if (Op1LV.isConstant())
1619  markForcedConstant(&I, Op1LV.getConstant());
1620  else
1621  markOverdefined(&I);
1622  return true;
1623  case Instruction::Load:
1624  // A load here means one of two things: a load of undef from a global,
1625  // a load from an unknown pointer. Either way, having it return undef
1626  // is okay.
1627  break;
1628  case Instruction::ICmp:
1629  // X == undef -> undef. Other comparisons get more complicated.
1630  Op0LV = getValueState(I.getOperand(0));
1631  Op1LV = getValueState(I.getOperand(1));
1632 
1633  if ((Op0LV.isUnknown() || Op1LV.isUnknown()) &&
1634  cast<ICmpInst>(&I)->isEquality())
1635  break;
1636  markOverdefined(&I);
1637  return true;
1638  case Instruction::Call:
1639  case Instruction::Invoke:
1640  case Instruction::CallBr:
1641  // There are two reasons a call can have an undef result
1642  // 1. It could be tracked.
1643  // 2. It could be constant-foldable.
1644  // Because of the way we solve return values, tracked calls must
1645  // never be marked overdefined in ResolvedUndefsIn.
1646  if (Function *F = CallSite(&I).getCalledFunction())
1647  if (TrackedRetVals.count(F))
1648  break;
1649 
1650  // If the call is constant-foldable, we mark it overdefined because
1651  // we do not know what return values are valid.
1652  markOverdefined(&I);
1653  return true;
1654  default:
1655  // If we don't know what should happen here, conservatively mark it
1656  // overdefined.
1657  markOverdefined(&I);
1658  return true;
1659  }
1660  }
1661 
1662  // Check to see if we have a branch or switch on an undefined value. If so
1663  // we force the branch to go one way or the other to make the successor
1664  // values live. It doesn't really matter which way we force it.
1665  Instruction *TI = BB.getTerminator();
1666  if (auto *BI = dyn_cast<BranchInst>(TI)) {
1667  if (!BI->isConditional()) continue;
1668  if (!getValueState(BI->getCondition()).isUnknown())
1669  continue;
1670 
1671  // If the input to SCCP is actually branch on undef, fix the undef to
1672  // false.
1673  if (isa<UndefValue>(BI->getCondition())) {
1674  BI->setCondition(ConstantInt::getFalse(BI->getContext()));
1675  markEdgeExecutable(&BB, TI->getSuccessor(1));
1676  return true;
1677  }
1678 
1679  // Otherwise, it is a branch on a symbolic value which is currently
1680  // considered to be undef. Make sure some edge is executable, so a
1681  // branch on "undef" always flows somewhere.
1682  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1683  BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
1684  if (markEdgeExecutable(&BB, DefaultSuccessor))
1685  return true;
1686 
1687  continue;
1688  }
1689 
1690  if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
1691  // Indirect branch with no successor ?. Its ok to assume it branches
1692  // to no target.
1693  if (IBR->getNumSuccessors() < 1)
1694  continue;
1695 
1696  if (!getValueState(IBR->getAddress()).isUnknown())
1697  continue;
1698 
1699  // If the input to SCCP is actually branch on undef, fix the undef to
1700  // the first successor of the indirect branch.
1701  if (isa<UndefValue>(IBR->getAddress())) {
1702  IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
1703  markEdgeExecutable(&BB, IBR->getSuccessor(0));
1704  return true;
1705  }
1706 
1707  // Otherwise, it is a branch on a symbolic value which is currently
1708  // considered to be undef. Make sure some edge is executable, so a
1709  // branch on "undef" always flows somewhere.
1710  // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
1711  // we can assume the branch has undefined behavior instead.
1712  BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
1713  if (markEdgeExecutable(&BB, DefaultSuccessor))
1714  return true;
1715 
1716  continue;
1717  }
1718 
1719  if (auto *SI = dyn_cast<SwitchInst>(TI)) {
1720  if (!SI->getNumCases() || !getValueState(SI->getCondition()).isUnknown())
1721  continue;
1722 
1723  // If the input to SCCP is actually switch on undef, fix the undef to
1724  // the first constant.
1725  if (isa<UndefValue>(SI->getCondition())) {
1726  SI->setCondition(SI->case_begin()->getCaseValue());
1727  markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
1728  return true;
1729  }
1730 
1731  // Otherwise, it is a branch on a symbolic value which is currently
1732  // considered to be undef. Make sure some edge is executable, so a
1733  // branch on "undef" always flows somewhere.
1734  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1735  BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
1736  if (markEdgeExecutable(&BB, DefaultSuccessor))
1737  return true;
1738 
1739  continue;
1740  }
1741  }
1742 
1743  return false;
1744 }
1745 
1746 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
1747  Constant *Const = nullptr;
1748  if (V->getType()->isStructTy()) {
1749  std::vector<LatticeVal> IVs = Solver.getStructLatticeValueFor(V);
1750  if (llvm::any_of(IVs,
1751  [](const LatticeVal &LV) { return LV.isOverdefined(); }))
1752  return false;
1753  std::vector<Constant *> ConstVals;
1754  auto *ST = dyn_cast<StructType>(V->getType());
1755  for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1756  LatticeVal V = IVs[i];
1757  ConstVals.push_back(V.isConstant()
1758  ? V.getConstant()
1759  : UndefValue::get(ST->getElementType(i)));
1760  }
1761  Const = ConstantStruct::get(ST, ConstVals);
1762  } else {
1763  const LatticeVal &IV = Solver.getLatticeValueFor(V);
1764  if (IV.isOverdefined())
1765  return false;
1766 
1767  Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
1768  }
1769  assert(Const && "Constant is nullptr here!");
1770 
1771  // Replacing `musttail` instructions with constant breaks `musttail` invariant
1772  // unless the call itself can be removed
1773  CallInst *CI = dyn_cast<CallInst>(V);
1774  if (CI && CI->isMustTailCall() && !CI->isSafeToRemove()) {
1775  CallSite CS(CI);
1776  Function *F = CS.getCalledFunction();
1777 
1778  // Don't zap returns of the callee
1779  if (F)
1780  Solver.AddMustTailCallee(F);
1781 
1782  LLVM_DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI
1783  << " as a constant\n");
1784  return false;
1785  }
1786 
1787  LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
1788 
1789  // Replaces all of the uses of a variable with uses of the constant.
1790  V->replaceAllUsesWith(Const);
1791  return true;
1792 }
1793 
1794 // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
1795 // and return true if the function was modified.
1796 static bool runSCCP(Function &F, const DataLayout &DL,
1797  const TargetLibraryInfo *TLI) {
1798  LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
1799  SCCPSolver Solver(DL, TLI);
1800 
1801  // Mark the first block of the function as being executable.
1802  Solver.MarkBlockExecutable(&F.front());
1803 
1804  // Mark all arguments to the function as being overdefined.
1805  for (Argument &AI : F.args())
1806  Solver.markOverdefined(&AI);
1807 
1808  // Solve for constants.
1809  bool ResolvedUndefs = true;
1810  while (ResolvedUndefs) {
1811  Solver.Solve();
1812  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n");
1813  ResolvedUndefs = Solver.ResolvedUndefsIn(F);
1814  }
1815 
1816  bool MadeChanges = false;
1817 
1818  // If we decided that there are basic blocks that are dead in this function,
1819  // delete their contents now. Note that we cannot actually delete the blocks,
1820  // as we cannot modify the CFG of the function.
1821 
1822  for (BasicBlock &BB : F) {
1823  if (!Solver.isBlockExecutable(&BB)) {
1824  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1825 
1826  ++NumDeadBlocks;
1827  NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB);
1828 
1829  MadeChanges = true;
1830  continue;
1831  }
1832 
1833  // Iterate over all of the instructions in a function, replacing them with
1834  // constants if we have found them to be of constant values.
1835  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
1836  Instruction *Inst = &*BI++;
1837  if (Inst->getType()->isVoidTy() || Inst->isTerminator())
1838  continue;
1839 
1840  if (tryToReplaceWithConstant(Solver, Inst)) {
1841  if (isInstructionTriviallyDead(Inst))
1842  Inst->eraseFromParent();
1843  // Hey, we just changed something!
1844  MadeChanges = true;
1845  ++NumInstRemoved;
1846  }
1847  }
1848  }
1849 
1850  return MadeChanges;
1851 }
1852 
1854  const DataLayout &DL = F.getParent()->getDataLayout();
1855  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
1856  if (!runSCCP(F, DL, &TLI))
1857  return PreservedAnalyses::all();
1858 
1859  auto PA = PreservedAnalyses();
1860  PA.preserve<GlobalsAA>();
1861  PA.preserveSet<CFGAnalyses>();
1862  return PA;
1863 }
1864 
1865 namespace {
1866 
1867 //===--------------------------------------------------------------------===//
1868 //
1869 /// SCCP Class - This class uses the SCCPSolver to implement a per-function
1870 /// Sparse Conditional Constant Propagator.
1871 ///
1872 class SCCPLegacyPass : public FunctionPass {
1873 public:
1874  // Pass identification, replacement for typeid
1875  static char ID;
1876 
1877  SCCPLegacyPass() : FunctionPass(ID) {
1879  }
1880 
1881  void getAnalysisUsage(AnalysisUsage &AU) const override {
1884  AU.setPreservesCFG();
1885  }
1886 
1887  // runOnFunction - Run the Sparse Conditional Constant Propagation
1888  // algorithm, and return true if the function was modified.
1889  bool runOnFunction(Function &F) override {
1890  if (skipFunction(F))
1891  return false;
1892  const DataLayout &DL = F.getParent()->getDataLayout();
1893  const TargetLibraryInfo *TLI =
1894  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1895  return runSCCP(F, DL, TLI);
1896  }
1897 };
1898 
1899 } // end anonymous namespace
1900 
1901 char SCCPLegacyPass::ID = 0;
1902 
1903 INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp",
1904  "Sparse Conditional Constant Propagation", false, false)
1906 INITIALIZE_PASS_END(SCCPLegacyPass, "sccp",
1907  "Sparse Conditional Constant Propagation", false, false)
1908 
1909 // createSCCPPass - This is the public interface to this file.
1910 FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); }
1911 
1913  SmallVector<ReturnInst *, 8> &ReturnsToZap,
1914  SCCPSolver &Solver) {
1915  // We can only do this if we know that nothing else can call the function.
1916  if (!Solver.isArgumentTrackedFunction(&F))
1917  return;
1918 
1919  // There is a non-removable musttail call site of this function. Zapping
1920  // returns is not allowed.
1921  if (Solver.isMustTailCallee(&F)) {
1922  LLVM_DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName()
1923  << " due to present musttail call of it\n");
1924  return;
1925  }
1926 
1927  for (BasicBlock &BB : F) {
1928  if (CallInst *CI = BB.getTerminatingMustTailCall()) {
1929  LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "
1930  << "musttail call : " << *CI << "\n");
1931  (void)CI;
1932  return;
1933  }
1934 
1935  if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1936  if (!isa<UndefValue>(RI->getOperand(0)))
1937  ReturnsToZap.push_back(RI);
1938  }
1939 }
1940 
1941 // Update the condition for terminators that are branching on indeterminate
1942 // values, forcing them to use a specific edge.
1943 static void forceIndeterminateEdge(Instruction* I, SCCPSolver &Solver) {
1944  BasicBlock *Dest = nullptr;
1945  Constant *C = nullptr;
1946  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
1947  if (!isa<ConstantInt>(SI->getCondition())) {
1948  // Indeterminate switch; use first case value.
1949  Dest = SI->case_begin()->getCaseSuccessor();
1950  C = SI->case_begin()->getCaseValue();
1951  }
1952  } else if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
1953  if (!isa<ConstantInt>(BI->getCondition())) {
1954  // Indeterminate branch; use false.
1955  Dest = BI->getSuccessor(1);
1956  C = ConstantInt::getFalse(BI->getContext());
1957  }
1958  } else if (IndirectBrInst *IBR = dyn_cast<IndirectBrInst>(I)) {
1959  if (!isa<BlockAddress>(IBR->getAddress()->stripPointerCasts())) {
1960  // Indeterminate indirectbr; use successor 0.
1961  Dest = IBR->getSuccessor(0);
1962  C = BlockAddress::get(IBR->getSuccessor(0));
1963  }
1964  } else {
1965  llvm_unreachable("Unexpected terminator instruction");
1966  }
1967  if (C) {
1968  assert(Solver.isEdgeFeasible(I->getParent(), Dest) &&
1969  "Didn't find feasible edge?");
1970  (void)Dest;
1971 
1972  I->setOperand(0, C);
1973  }
1974 }
1975 
1977  Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI,
1978  function_ref<AnalysisResultsForFn(Function &)> getAnalysis) {
1979  SCCPSolver Solver(DL, TLI);
1980 
1981  // Loop over all functions, marking arguments to those with their addresses
1982  // taken or that are external as overdefined.
1983  for (Function &F : M) {
1984  if (F.isDeclaration())
1985  continue;
1986 
1987  Solver.addAnalysis(F, getAnalysis(F));
1988 
1989  // Determine if we can track the function's return values. If so, add the
1990  // function to the solver's set of return-tracked functions.
1992  Solver.AddTrackedFunction(&F);
1993 
1994  // Determine if we can track the function's arguments. If so, add the
1995  // function to the solver's set of argument-tracked functions.
1997  Solver.AddArgumentTrackedFunction(&F);
1998  continue;
1999  }
2000 
2001  // Assume the function is called.
2002  Solver.MarkBlockExecutable(&F.front());
2003 
2004  // Assume nothing about the incoming arguments.
2005  for (Argument &AI : F.args())
2006  Solver.markOverdefined(&AI);
2007  }
2008 
2009  // Determine if we can track any of the module's global variables. If so, add
2010  // the global variables we can track to the solver's set of tracked global
2011  // variables.
2012  for (GlobalVariable &G : M.globals()) {
2013  G.removeDeadConstantUsers();
2015  Solver.TrackValueOfGlobalVariable(&G);
2016  }
2017 
2018  // Solve for constants.
2019  bool ResolvedUndefs = true;
2020  Solver.Solve();
2021  while (ResolvedUndefs) {
2022  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n");
2023  ResolvedUndefs = false;
2024  for (Function &F : M)
2025  if (Solver.ResolvedUndefsIn(F)) {
2026  // We run Solve() after we resolved an undef in a function, because
2027  // we might deduce a fact that eliminates an undef in another function.
2028  Solver.Solve();
2029  ResolvedUndefs = true;
2030  }
2031  }
2032 
2033  bool MadeChanges = false;
2034 
2035  // Iterate over all of the instructions in the module, replacing them with
2036  // constants if we have found them to be of constant values.
2037 
2038  for (Function &F : M) {
2039  if (F.isDeclaration())
2040  continue;
2041 
2042  SmallVector<BasicBlock *, 512> BlocksToErase;
2043 
2044  if (Solver.isBlockExecutable(&F.front()))
2045  for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
2046  ++AI) {
2047  if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
2048  ++IPNumArgsElimed;
2049  continue;
2050  }
2051  }
2052 
2053  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
2054  if (!Solver.isBlockExecutable(&*BB)) {
2055  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
2056  ++NumDeadBlocks;
2057 
2058  MadeChanges = true;
2059 
2060  if (&*BB != &F.front())
2061  BlocksToErase.push_back(&*BB);
2062  continue;
2063  }
2064 
2065  for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
2066  Instruction *Inst = &*BI++;
2067  if (Inst->getType()->isVoidTy())
2068  continue;
2069  if (tryToReplaceWithConstant(Solver, Inst)) {
2070  if (Inst->isSafeToRemove())
2071  Inst->eraseFromParent();
2072  // Hey, we just changed something!
2073  MadeChanges = true;
2074  ++IPNumInstRemoved;
2075  }
2076  }
2077  }
2078 
2079  DomTreeUpdater DTU = Solver.getDTU(F);
2080  // Change dead blocks to unreachable. We do it after replacing constants
2081  // in all executable blocks, because changeToUnreachable may remove PHI
2082  // nodes in executable blocks we found values for. The function's entry
2083  // block is not part of BlocksToErase, so we have to handle it separately.
2084  for (BasicBlock *BB : BlocksToErase) {
2085  NumInstRemoved +=
2086  changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false,
2087  /*PreserveLCSSA=*/false, &DTU);
2088  }
2089  if (!Solver.isBlockExecutable(&F.front()))
2090  NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
2091  /*UseLLVMTrap=*/false,
2092  /*PreserveLCSSA=*/false, &DTU);
2093 
2094  // Now that all instructions in the function are constant folded,
2095  // use ConstantFoldTerminator to get rid of in-edges, record DT updates and
2096  // delete dead BBs.
2097  for (BasicBlock *DeadBB : BlocksToErase) {
2098  // If there are any PHI nodes in this successor, drop entries for BB now.
2099  for (Value::user_iterator UI = DeadBB->user_begin(),
2100  UE = DeadBB->user_end();
2101  UI != UE;) {
2102  // Grab the user and then increment the iterator early, as the user
2103  // will be deleted. Step past all adjacent uses from the same user.
2104  auto *I = dyn_cast<Instruction>(*UI);
2105  do { ++UI; } while (UI != UE && *UI == I);
2106 
2107  // Ignore blockaddress users; BasicBlock's dtor will handle them.
2108  if (!I) continue;
2109 
2110  // If we have forced an edge for an indeterminate value, then force the
2111  // terminator to fold to that edge.
2112  forceIndeterminateEdge(I, Solver);
2113  BasicBlock *InstBB = I->getParent();
2114  bool Folded = ConstantFoldTerminator(InstBB,
2115  /*DeleteDeadConditions=*/false,
2116  /*TLI=*/nullptr, &DTU);
2117  assert(Folded &&
2118  "Expect TermInst on constantint or blockaddress to be folded");
2119  (void) Folded;
2120  // If we folded the terminator to an unconditional branch to another
2121  // dead block, replace it with Unreachable, to avoid trying to fold that
2122  // branch again.
2123  BranchInst *BI = cast<BranchInst>(InstBB->getTerminator());
2124  if (BI && BI->isUnconditional() &&
2125  !Solver.isBlockExecutable(BI->getSuccessor(0))) {
2126  InstBB->getTerminator()->eraseFromParent();
2127  new UnreachableInst(InstBB->getContext(), InstBB);
2128  }
2129  }
2130  // Mark dead BB for deletion.
2131  DTU.deleteBB(DeadBB);
2132  }
2133 
2134  for (BasicBlock &BB : F) {
2135  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
2136  Instruction *Inst = &*BI++;
2137  if (Solver.getPredicateInfoFor(Inst)) {
2138  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
2139  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
2140  Value *Op = II->getOperand(0);
2141  Inst->replaceAllUsesWith(Op);
2142  Inst->eraseFromParent();
2143  }
2144  }
2145  }
2146  }
2147  }
2148  }
2149 
2150  // If we inferred constant or undef return values for a function, we replaced
2151  // all call uses with the inferred value. This means we don't need to bother
2152  // actually returning anything from the function. Replace all return
2153  // instructions with return undef.
2154  //
2155  // Do this in two stages: first identify the functions we should process, then
2156  // actually zap their returns. This is important because we can only do this
2157  // if the address of the function isn't taken. In cases where a return is the
2158  // last use of a function, the order of processing functions would affect
2159  // whether other functions are optimizable.
2160  SmallVector<ReturnInst*, 8> ReturnsToZap;
2161 
2162  const MapVector<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
2163  for (const auto &I : RV) {
2164  Function *F = I.first;
2165  if (I.second.isOverdefined() || F->getReturnType()->isVoidTy())
2166  continue;
2167  findReturnsToZap(*F, ReturnsToZap, Solver);
2168  }
2169 
2170  for (const auto &F : Solver.getMRVFunctionsTracked()) {
2171  assert(F->getReturnType()->isStructTy() &&
2172  "The return type should be a struct");
2173  StructType *STy = cast<StructType>(F->getReturnType());
2174  if (Solver.isStructLatticeConstant(F, STy))
2175  findReturnsToZap(*F, ReturnsToZap, Solver);
2176  }
2177 
2178  // Zap all returns which we've identified as zap to change.
2179  for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
2180  Function *F = ReturnsToZap[i]->getParent()->getParent();
2181  ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
2182  }
2183 
2184  // If we inferred constant or undef values for globals variables, we can
2185  // delete the global and any stores that remain to it.
2186  const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
2188  E = TG.end(); I != E; ++I) {
2189  GlobalVariable *GV = I->first;
2190  assert(!I->second.isOverdefined() &&
2191  "Overdefined values should have been taken out of the map!");
2192  LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName()
2193  << "' is constant!\n");
2194  while (!GV->use_empty()) {
2195  StoreInst *SI = cast<StoreInst>(GV->user_back());
2196  SI->eraseFromParent();
2197  }
2198  M.getGlobalList().erase(GV);
2199  ++IPNumGlobalConst;
2200  }
2201 
2202  return MadeChanges;
2203 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Constant * ConstantFoldCastOperand(unsigned Opcode, Constant *C, Type *DestTy, const DataLayout &DL)
Attempt to constant fold a cast with the specified operand.
bool onlyReadsMemory() const
Determine if the function does not access or only reads memory.
Definition: Function.h:481
IterTy arg_end() const
Definition: CallSite.h:588
uint64_t CallInst * C
Return a value (possibly void), from a function.
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:67
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:110
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:594
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:722
void setInt(IntType IntVal)
static bool isConstant(const MachineInstr &MI)
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
This instruction extracts a struct member or array element value from an aggregate value...
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents an incoming formal argument to a Function.
Definition: Argument.h:29
Base class for instruction visitors.
Definition: InstVisitor.h:80
Value * getAggregateOperand()
Interprocedural Sparse Conditional Constant Propagation
Definition: SCCP.cpp:85
sccp
Definition: SCCP.cpp:1906
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:776
iterator erase(iterator where)
Definition: ilist.h:265
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
IterTy arg_begin() const
Definition: CallSite.h:584
This class represents lattice values for constants.
Definition: AllocatorList.h:23
PointerTy getPointer() const
This is the interface for a simple mod/ref and alias analysis over globals.
unsigned getNumIndices() const
bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions=false, const TargetLibraryInfo *TLI=nullptr, DomTreeUpdater *DTU=nullptr)
If a terminator instruction is predicated on a constant value, convert it into an unconditional branc...
Definition: Local.cpp:109
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:65
static Constant * getGetElementPtr(Type *Ty, Constant *C, ArrayRef< Constant *> IdxList, bool InBounds=false, Optional< unsigned > InRangeIndex=None, Type *OnlyIfReducedTy=nullptr)
Getelementptr form.
Definition: Constants.h:1153
BasicBlock * getSuccessor(unsigned Idx) const
Return the specified successor. This instruction must be a terminator.
An instruction for ordering other memory operations.
Definition: Instructions.h:454
bool canTrackArgumentsInterprocedurally(Function *F)
Determine if the values of the given function&#39;s arguments can be tracked interprocedurally.
Constant * ConstantFoldCall(const CallBase *Call, Function *F, ArrayRef< Constant *> Operands, const TargetLibraryInfo *TLI=nullptr)
ConstantFoldCall - Attempt to constant fold a call to the specified function with the specified argum...
Implements a dense probed hash-table based set.
Definition: DenseSet.h:249
unsigned getNumElements() const
Random access to the elements.
Definition: DerivedTypes.h:345
bool isSafeToRemove() const
Return true if the instruction can be removed if the result is unused.
static ValueLatticeElement get(Constant *C)
Definition: ValueLattice.h:119
This class represents a function call, abstracting a target machine&#39;s calling convention.
const Value * getTrueValue() const
An efficient, type-erasing, non-owning reference to a callable.
Definition: STLExtras.h:116
bool isTerminator() const
Definition: Instruction.h:128
This class implements a map that also provides access to all stored values in a deterministic order...
Definition: MapVector.h:37
BasicBlock * getSuccessor(unsigned i) const
arg_iterator arg_end()
Definition: Function.h:704
STATISTIC(NumFunctions, "Total number of functions")
F(f)
An instruction for reading from memory.
Definition: Instructions.h:167
FunTy * getCalledFunction() const
Return the function being called if this is a direct call, otherwise return null (if it&#39;s an indirect...
Definition: CallSite.h:111
const Instruction * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:137
void reserve(size_type N)
Definition: SmallVector.h:369
bool isMustTailCall() const
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:32
static void findReturnsToZap(Function &F, SmallVector< ReturnInst *, 8 > &ReturnsToZap, SCCPSolver &Solver)
Definition: SCCP.cpp:1912
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:274
std::unique_ptr< PredicateInfo > PredInfo
Definition: SCCP.h:43
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:221
The address of a basic block.
Definition: Constants.h:839
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
void setPointer(PointerTy PtrVal)
bool isVolatile() const
Return true if this is a load from a volatile memory location.
Definition: Instructions.h:231
This class represents the LLVM &#39;select&#39; instruction.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:369
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:439
ArrayRef< T > makeArrayRef(const T &OneElt)
Construct an ArrayRef from a single element.
Definition: ArrayRef.h:450
Class to represent struct types.
Definition: DerivedTypes.h:233
void initializeSCCPLegacyPassPass(PassRegistry &)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: SCCP.cpp:1853
static void forceIndeterminateEdge(Instruction *I, SCCPSolver &Solver)
Definition: SCCP.cpp:1943
bool empty() const
Definition: MapVector.h:79
FunctionPass * createSCCPPass()
Definition: SCCP.cpp:1910
Type * getSourceElementType() const
Definition: Instructions.h:972
Helper struct for bundling up the analysis results per function for IPSCCP.
Definition: SCCP.h:42
static int64_t getConstant(const MachineInstr *MI)
void assign(size_type NumElts, const T &Elt)
Definition: SmallVector.h:412
InstrTy * getInstruction() const
Definition: CallSite.h:96
Instruction::CastOps getOpcode() const
Return the opcode of this CastInst.
Definition: InstrTypes.h:692
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
IntType getInt() const
Value * getInsertedValueOperand()
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:125
PostDominatorTree * PDT
Definition: SCCP.h:45
An instruction for storing to memory.
Definition: Instructions.h:320
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
iterator find(const KeyT &Key)
Definition: MapVector.h:147
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
Value * getOperand(unsigned i) const
Definition: User.h:169
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:344
bool canTrackReturnsInterprocedurally(Function *F)
Determine if the values of the given function&#39;s returns can be tracked interprocedurally.
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:140
an instruction for type-safe pointer arithmetic to access elements of arrays and structs ...
Definition: Instructions.h:875
static bool runOnFunction(Function &F, bool PostInlining)
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:168
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
PointerIntPair - This class implements a pair of a pointer and small integer.
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
void deleteBB(BasicBlock *DelBB)
Delete DelBB.
Conditional or Unconditional Branch instruction.
static BlockAddress * get(Function *F, BasicBlock *BB)
Return a BlockAddress for the specified function and basic block.
Definition: Constants.cpp:1443
This function has undefined behavior.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:41
LLVM_NODISCARD bool empty() const
Definition: SmallPtrSet.h:91
Resume the propagation of an exception.
This file contains the declarations for the subclasses of Constant, which represent the different fla...
Indirect Branch Instruction.
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:370
unsigned getNumIndices() const
Represent the analysis usage information of a pass.
bool any_of(R &&range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1199
Analysis pass providing a never-invalidated alias analysis result.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
static Constant * get(StructType *T, ArrayRef< Constant *> V)
Definition: Constants.cpp:1053
arg_iterator arg_begin()
Definition: Function.h:695
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:381
const Function * getFunction() const
Return the function this instruction belongs to.
Definition: Instruction.cpp:59
static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V)
Definition: SCCP.cpp:1746
Constant * ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL)
ConstantFoldLoadFromConstPtr - Return the value that a load from C would produce if it is constant an...
const Value * getCondition() const
static Constant * getAllOnesValue(Type *Ty)
Definition: Constants.cpp:328
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1424
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
bool isExceptionalTerminator() const
Definition: Instruction.h:135
size_t size() const
Definition: SmallVector.h:52
Value * getIncomingValue(unsigned i) const
Return incoming value number x.
This file implements the PredicateInfo analysis, which creates an Extended SSA form for operations us...
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
CallBr instruction, tracking function calls that may not return control but instead transfer it to a ...
bool canConstantFoldCallTo(const CallBase *Call, const Function *F)
canConstantFoldCallTo - Return true if its even possible to fold a call to the specified function...
idx_iterator idx_begin() const
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: MapVector.h:117
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:191
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:417
This is the shared class of boolean and integer constants.
Definition: Constants.h:83
BlockVerifier::State From
INITIALIZE_PASS_BEGIN(IPSCCPLegacyPass, "ipsccp", "Interprocedural Sparse Conditional Constant Propagation", false, false) INITIALIZE_PASS_END(IPSCCPLegacyPass
Constant * getCompare(CmpInst::Predicate Pred, Type *Ty, const ValueLatticeElement &Other) const
Compares this symbolic value with Other using Pred and returns either true, false or undef constants...
Definition: ValueLattice.h:293
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
Module.h This file contains the declarations for the Module class.
Provides information about what library functions are available for the current target.
bool canTrackGlobalVariableInterprocedurally(GlobalVariable *GV)
Determine if the value maintained in the given global variable can be tracked interprocedurally.
size_type count(const KeyT &Key) const
Definition: MapVector.h:142
const DataFlowGraph & G
Definition: RDFGraph.cpp:202
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:374
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
unsigned removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB)
Remove all instructions from a basic block other than it&#39;s terminator and any present EH pad instruct...
Definition: Local.cpp:1896
typename VectorType::iterator iterator
Definition: MapVector.h:49
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:220
unsigned getNumIncomingValues() const
Return the number of incoming edges.
static const Function * getCalledFunction(const Value *V, bool LookThroughBitCast, bool &IsNoBuiltin)
bool NullPointerIsDefined(const Function *F, unsigned AS=0)
Check whether null pointer dereferencing is considered undefined behavior for a given function or an ...
Definition: Function.cpp:1523
void setOperand(unsigned i, Value *Val)
Definition: User.h:174
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:940
iterator_range< user_iterator > users()
Definition: Value.h:399
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
const Value * getFalseValue() const
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:807
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
BasicBlock * getIncomingBlock(unsigned i) const
Return incoming basic block number i.
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:106
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:368
DominatorTree * DT
Definition: SCCP.h:44
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:332
idx_iterator idx_begin() const
Type * getValueType() const
Definition: GlobalValue.h:279
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:324
size_type count(const_arg_type_t< ValueT > V) const
Return 1 if the specified key is in the set, 0 otherwise.
Definition: DenseSet.h:91
bool isUnconditional() const
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:227
Analysis pass providing the TargetLibraryInfo.
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:290
Multiway switch.
iterator end()
Definition: MapVector.h:71
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const BasicBlock & front() const
Definition: Function.h:687
bool isSingleValueType() const
Return true if the type is a valid type for a register in codegen.
Definition: Type.h:249
bool runIPSCCP(Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI, function_ref< AnalysisResultsForFn(Function &)> getAnalysis)
Definition: SCCP.cpp:1976
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:575
bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
Return true if the result produced by the instruction is not used, and the instruction has no side ef...
Definition: Local.cpp:353
LLVM Value Representation.
Definition: Value.h:72
Invoke instruction.
static ValueLatticeElement getOverdefined()
Definition: ValueLattice.h:136
A container for analyses that lazily runs them and caches their results.
This header defines various interfaces for pass management in LLVM.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap, bool PreserveLCSSA=false, DomTreeUpdater *DTU=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Insert an unreachable instruction before the specified instruction, making it and the rest of the cod...
Definition: Local.cpp:1917
bool use_empty() const
Definition: Value.h:322
static bool runSCCP(Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI)
Definition: SCCP.cpp:1796
iterator_range< arg_iterator > args()
Definition: Function.h:713
bool isStructTy() const
True if this is an instance of StructType.
Definition: Type.h:217
User * user_back()
Definition: Value.h:385
const BasicBlock * getParent() const
Definition: Instruction.h:66
This instruction inserts a struct field of array element value into an aggregate value.
void resize(size_type N)
Definition: SmallVector.h:344
static Constant * get(unsigned Opcode, Constant *C1, unsigned Flags=0, Type *OnlyIfReducedTy=nullptr)
get - Return a unary operator constant expression, folding if possible.
Definition: Constants.cpp:1815