LLVM  9.0.0svn
SCCP.cpp
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1 //===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements sparse conditional constant propagation and merging:
11 //
12 // Specifically, this:
13 // * Assumes values are constant unless proven otherwise
14 // * Assumes BasicBlocks are dead unless proven otherwise
15 // * Proves values to be constant, and replaces them with constants
16 // * Proves conditional branches to be unconditional
17 //
18 //===----------------------------------------------------------------------===//
19 
21 #include "llvm/ADT/ArrayRef.h"
22 #include "llvm/ADT/DenseMap.h"
23 #include "llvm/ADT/DenseSet.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  DenseMap<Function *, LatticeVal> TrackedRetVals;
214 
215  /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
216  /// that return multiple values.
217  DenseMap<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 DenseMap<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 visitBinaryOperator(Instruction &I);
618  void visitCmpInst(CmpInst &I);
619  void visitExtractValueInst(ExtractValueInst &EVI);
620  void visitInsertValueInst(InsertValueInst &IVI);
621 
622  void visitCatchSwitchInst(CatchSwitchInst &CPI) {
623  markOverdefined(&CPI);
624  visitTerminator(CPI);
625  }
626 
627  // Instructions that cannot be folded away.
628 
629  void visitStoreInst (StoreInst &I);
630  void visitLoadInst (LoadInst &I);
631  void visitGetElementPtrInst(GetElementPtrInst &I);
632 
633  void visitCallInst (CallInst &I) {
634  visitCallSite(&I);
635  }
636 
637  void visitInvokeInst (InvokeInst &II) {
638  visitCallSite(&II);
639  visitTerminator(II);
640  }
641 
642  void visitCallSite (CallSite CS);
643  void visitResumeInst (ResumeInst &I) { /*returns void*/ }
644  void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ }
645  void visitFenceInst (FenceInst &I) { /*returns void*/ }
646 
647  void visitInstruction(Instruction &I) {
648  // All the instructions we don't do any special handling for just
649  // go to overdefined.
650  LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n');
651  markOverdefined(&I);
652  }
653 };
654 
655 } // end anonymous namespace
656 
657 // getFeasibleSuccessors - Return a vector of booleans to indicate which
658 // successors are reachable from a given terminator instruction.
659 void SCCPSolver::getFeasibleSuccessors(Instruction &TI,
660  SmallVectorImpl<bool> &Succs) {
661  Succs.resize(TI.getNumSuccessors());
662  if (auto *BI = dyn_cast<BranchInst>(&TI)) {
663  if (BI->isUnconditional()) {
664  Succs[0] = true;
665  return;
666  }
667 
668  LatticeVal BCValue = getValueState(BI->getCondition());
669  ConstantInt *CI = BCValue.getConstantInt();
670  if (!CI) {
671  // Overdefined condition variables, and branches on unfoldable constant
672  // conditions, mean the branch could go either way.
673  if (!BCValue.isUnknown())
674  Succs[0] = Succs[1] = true;
675  return;
676  }
677 
678  // Constant condition variables mean the branch can only go a single way.
679  Succs[CI->isZero()] = true;
680  return;
681  }
682 
683  // Unwinding instructions successors are always executable.
684  if (TI.isExceptionalTerminator()) {
685  Succs.assign(TI.getNumSuccessors(), true);
686  return;
687  }
688 
689  if (auto *SI = dyn_cast<SwitchInst>(&TI)) {
690  if (!SI->getNumCases()) {
691  Succs[0] = true;
692  return;
693  }
694  LatticeVal SCValue = getValueState(SI->getCondition());
695  ConstantInt *CI = SCValue.getConstantInt();
696 
697  if (!CI) { // Overdefined or unknown condition?
698  // All destinations are executable!
699  if (!SCValue.isUnknown())
700  Succs.assign(TI.getNumSuccessors(), true);
701  return;
702  }
703 
704  Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
705  return;
706  }
707 
708  // In case of indirect branch and its address is a blockaddress, we mark
709  // the target as executable.
710  if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) {
711  // Casts are folded by visitCastInst.
712  LatticeVal IBRValue = getValueState(IBR->getAddress());
713  BlockAddress *Addr = IBRValue.getBlockAddress();
714  if (!Addr) { // Overdefined or unknown condition?
715  // All destinations are executable!
716  if (!IBRValue.isUnknown())
717  Succs.assign(TI.getNumSuccessors(), true);
718  return;
719  }
720 
721  BasicBlock* T = Addr->getBasicBlock();
722  assert(Addr->getFunction() == T->getParent() &&
723  "Block address of a different function ?");
724  for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) {
725  // This is the target.
726  if (IBR->getDestination(i) == T) {
727  Succs[i] = true;
728  return;
729  }
730  }
731 
732  // If we didn't find our destination in the IBR successor list, then we
733  // have undefined behavior. Its ok to assume no successor is executable.
734  return;
735  }
736 
737  LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n');
738  llvm_unreachable("SCCP: Don't know how to handle this terminator!");
739 }
740 
741 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
742 // block to the 'To' basic block is currently feasible.
743 bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
744  // Check if we've called markEdgeExecutable on the edge yet. (We could
745  // be more aggressive and try to consider edges which haven't been marked
746  // yet, but there isn't any need.)
747  return KnownFeasibleEdges.count(Edge(From, To));
748 }
749 
750 // visit Implementations - Something changed in this instruction, either an
751 // operand made a transition, or the instruction is newly executable. Change
752 // the value type of I to reflect these changes if appropriate. This method
753 // makes sure to do the following actions:
754 //
755 // 1. If a phi node merges two constants in, and has conflicting value coming
756 // from different branches, or if the PHI node merges in an overdefined
757 // value, then the PHI node becomes overdefined.
758 // 2. If a phi node merges only constants in, and they all agree on value, the
759 // PHI node becomes a constant value equal to that.
760 // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant
761 // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined
762 // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined
763 // 6. If a conditional branch has a value that is constant, make the selected
764 // destination executable
765 // 7. If a conditional branch has a value that is overdefined, make all
766 // successors executable.
767 void SCCPSolver::visitPHINode(PHINode &PN) {
768  // If this PN returns a struct, just mark the result overdefined.
769  // TODO: We could do a lot better than this if code actually uses this.
770  if (PN.getType()->isStructTy())
771  return (void)markOverdefined(&PN);
772 
773  if (getValueState(&PN).isOverdefined())
774  return; // Quick exit
775 
776  // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
777  // and slow us down a lot. Just mark them overdefined.
778  if (PN.getNumIncomingValues() > 64)
779  return (void)markOverdefined(&PN);
780 
781  // Look at all of the executable operands of the PHI node. If any of them
782  // are overdefined, the PHI becomes overdefined as well. If they are all
783  // constant, and they agree with each other, the PHI becomes the identical
784  // constant. If they are constant and don't agree, the PHI is overdefined.
785  // If there are no executable operands, the PHI remains unknown.
786  Constant *OperandVal = nullptr;
787  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
788  LatticeVal IV = getValueState(PN.getIncomingValue(i));
789  if (IV.isUnknown()) continue; // Doesn't influence PHI node.
790 
791  if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
792  continue;
793 
794  if (IV.isOverdefined()) // PHI node becomes overdefined!
795  return (void)markOverdefined(&PN);
796 
797  if (!OperandVal) { // Grab the first value.
798  OperandVal = IV.getConstant();
799  continue;
800  }
801 
802  // There is already a reachable operand. If we conflict with it,
803  // then the PHI node becomes overdefined. If we agree with it, we
804  // can continue on.
805 
806  // Check to see if there are two different constants merging, if so, the PHI
807  // node is overdefined.
808  if (IV.getConstant() != OperandVal)
809  return (void)markOverdefined(&PN);
810  }
811 
812  // If we exited the loop, this means that the PHI node only has constant
813  // arguments that agree with each other(and OperandVal is the constant) or
814  // OperandVal is null because there are no defined incoming arguments. If
815  // this is the case, the PHI remains unknown.
816  if (OperandVal)
817  markConstant(&PN, OperandVal); // Acquire operand value
818 }
819 
820 void SCCPSolver::visitReturnInst(ReturnInst &I) {
821  if (I.getNumOperands() == 0) return; // ret void
822 
823  Function *F = I.getParent()->getParent();
824  Value *ResultOp = I.getOperand(0);
825 
826  // If we are tracking the return value of this function, merge it in.
827  if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
829  TrackedRetVals.find(F);
830  if (TFRVI != TrackedRetVals.end()) {
831  mergeInValue(TFRVI->second, F, getValueState(ResultOp));
832  return;
833  }
834  }
835 
836  // Handle functions that return multiple values.
837  if (!TrackedMultipleRetVals.empty()) {
838  if (auto *STy = dyn_cast<StructType>(ResultOp->getType()))
839  if (MRVFunctionsTracked.count(F))
840  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
841  mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
842  getStructValueState(ResultOp, i));
843  }
844 }
845 
846 void SCCPSolver::visitTerminator(Instruction &TI) {
847  SmallVector<bool, 16> SuccFeasible;
848  getFeasibleSuccessors(TI, SuccFeasible);
849 
850  BasicBlock *BB = TI.getParent();
851 
852  // Mark all feasible successors executable.
853  for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
854  if (SuccFeasible[i])
855  markEdgeExecutable(BB, TI.getSuccessor(i));
856 }
857 
858 void SCCPSolver::visitCastInst(CastInst &I) {
859  LatticeVal OpSt = getValueState(I.getOperand(0));
860  if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
861  markOverdefined(&I);
862  else if (OpSt.isConstant()) {
863  // Fold the constant as we build.
864  Constant *C = ConstantFoldCastOperand(I.getOpcode(), OpSt.getConstant(),
865  I.getType(), DL);
866  if (isa<UndefValue>(C))
867  return;
868  // Propagate constant value
869  markConstant(&I, C);
870  }
871 }
872 
873 void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
874  // If this returns a struct, mark all elements over defined, we don't track
875  // structs in structs.
876  if (EVI.getType()->isStructTy())
877  return (void)markOverdefined(&EVI);
878 
879  // If this is extracting from more than one level of struct, we don't know.
880  if (EVI.getNumIndices() != 1)
881  return (void)markOverdefined(&EVI);
882 
883  Value *AggVal = EVI.getAggregateOperand();
884  if (AggVal->getType()->isStructTy()) {
885  unsigned i = *EVI.idx_begin();
886  LatticeVal EltVal = getStructValueState(AggVal, i);
887  mergeInValue(getValueState(&EVI), &EVI, EltVal);
888  } else {
889  // Otherwise, must be extracting from an array.
890  return (void)markOverdefined(&EVI);
891  }
892 }
893 
894 void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
895  auto *STy = dyn_cast<StructType>(IVI.getType());
896  if (!STy)
897  return (void)markOverdefined(&IVI);
898 
899  // If this has more than one index, we can't handle it, drive all results to
900  // undef.
901  if (IVI.getNumIndices() != 1)
902  return (void)markOverdefined(&IVI);
903 
904  Value *Aggr = IVI.getAggregateOperand();
905  unsigned Idx = *IVI.idx_begin();
906 
907  // Compute the result based on what we're inserting.
908  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
909  // This passes through all values that aren't the inserted element.
910  if (i != Idx) {
911  LatticeVal EltVal = getStructValueState(Aggr, i);
912  mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
913  continue;
914  }
915 
916  Value *Val = IVI.getInsertedValueOperand();
917  if (Val->getType()->isStructTy())
918  // We don't track structs in structs.
919  markOverdefined(getStructValueState(&IVI, i), &IVI);
920  else {
921  LatticeVal InVal = getValueState(Val);
922  mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
923  }
924  }
925 }
926 
927 void SCCPSolver::visitSelectInst(SelectInst &I) {
928  // If this select returns a struct, just mark the result overdefined.
929  // TODO: We could do a lot better than this if code actually uses this.
930  if (I.getType()->isStructTy())
931  return (void)markOverdefined(&I);
932 
933  LatticeVal CondValue = getValueState(I.getCondition());
934  if (CondValue.isUnknown())
935  return;
936 
937  if (ConstantInt *CondCB = CondValue.getConstantInt()) {
938  Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
939  mergeInValue(&I, getValueState(OpVal));
940  return;
941  }
942 
943  // Otherwise, the condition is overdefined or a constant we can't evaluate.
944  // See if we can produce something better than overdefined based on the T/F
945  // value.
946  LatticeVal TVal = getValueState(I.getTrueValue());
947  LatticeVal FVal = getValueState(I.getFalseValue());
948 
949  // select ?, C, C -> C.
950  if (TVal.isConstant() && FVal.isConstant() &&
951  TVal.getConstant() == FVal.getConstant())
952  return (void)markConstant(&I, FVal.getConstant());
953 
954  if (TVal.isUnknown()) // select ?, undef, X -> X.
955  return (void)mergeInValue(&I, FVal);
956  if (FVal.isUnknown()) // select ?, X, undef -> X.
957  return (void)mergeInValue(&I, TVal);
958  markOverdefined(&I);
959 }
960 
961 // Handle Binary Operators.
962 void SCCPSolver::visitBinaryOperator(Instruction &I) {
963  LatticeVal V1State = getValueState(I.getOperand(0));
964  LatticeVal V2State = getValueState(I.getOperand(1));
965 
966  LatticeVal &IV = ValueState[&I];
967  if (IV.isOverdefined()) return;
968 
969  if (V1State.isConstant() && V2State.isConstant()) {
970  Constant *C = ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
971  V2State.getConstant());
972  // X op Y -> undef.
973  if (isa<UndefValue>(C))
974  return;
975  return (void)markConstant(IV, &I, C);
976  }
977 
978  // If something is undef, wait for it to resolve.
979  if (!V1State.isOverdefined() && !V2State.isOverdefined())
980  return;
981 
982  // Otherwise, one of our operands is overdefined. Try to produce something
983  // better than overdefined with some tricks.
984  // If this is 0 / Y, it doesn't matter that the second operand is
985  // overdefined, and we can replace it with zero.
986  if (I.getOpcode() == Instruction::UDiv || I.getOpcode() == Instruction::SDiv)
987  if (V1State.isConstant() && V1State.getConstant()->isNullValue())
988  return (void)markConstant(IV, &I, V1State.getConstant());
989 
990  // If this is:
991  // -> AND/MUL with 0
992  // -> OR with -1
993  // it doesn't matter that the other operand is overdefined.
994  if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Mul ||
995  I.getOpcode() == Instruction::Or) {
996  LatticeVal *NonOverdefVal = nullptr;
997  if (!V1State.isOverdefined())
998  NonOverdefVal = &V1State;
999  else if (!V2State.isOverdefined())
1000  NonOverdefVal = &V2State;
1001 
1002  if (NonOverdefVal) {
1003  if (NonOverdefVal->isUnknown())
1004  return;
1005 
1006  if (I.getOpcode() == Instruction::And ||
1007  I.getOpcode() == Instruction::Mul) {
1008  // X and 0 = 0
1009  // X * 0 = 0
1010  if (NonOverdefVal->getConstant()->isNullValue())
1011  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1012  } else {
1013  // X or -1 = -1
1014  if (ConstantInt *CI = NonOverdefVal->getConstantInt())
1015  if (CI->isMinusOne())
1016  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1017  }
1018  }
1019  }
1020 
1021  markOverdefined(&I);
1022 }
1023 
1024 // Handle ICmpInst instruction.
1025 void SCCPSolver::visitCmpInst(CmpInst &I) {
1026  // Do not cache this lookup, getValueState calls later in the function might
1027  // invalidate the reference.
1028  if (ValueState[&I].isOverdefined()) return;
1029 
1030  Value *Op1 = I.getOperand(0);
1031  Value *Op2 = I.getOperand(1);
1032 
1033  // For parameters, use ParamState which includes constant range info if
1034  // available.
1035  auto V1Param = ParamState.find(Op1);
1036  ValueLatticeElement V1State = (V1Param != ParamState.end())
1037  ? V1Param->second
1038  : getValueState(Op1).toValueLattice();
1039 
1040  auto V2Param = ParamState.find(Op2);
1041  ValueLatticeElement V2State = V2Param != ParamState.end()
1042  ? V2Param->second
1043  : getValueState(Op2).toValueLattice();
1044 
1045  Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
1046  if (C) {
1047  if (isa<UndefValue>(C))
1048  return;
1049  LatticeVal CV;
1050  CV.markConstant(C);
1051  mergeInValue(&I, CV);
1052  return;
1053  }
1054 
1055  // If operands are still unknown, wait for it to resolve.
1056  if (!V1State.isOverdefined() && !V2State.isOverdefined() &&
1057  !ValueState[&I].isConstant())
1058  return;
1059 
1060  markOverdefined(&I);
1061 }
1062 
1063 // Handle getelementptr instructions. If all operands are constants then we
1064 // can turn this into a getelementptr ConstantExpr.
1065 void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
1066  if (ValueState[&I].isOverdefined()) return;
1067 
1068  SmallVector<Constant*, 8> Operands;
1069  Operands.reserve(I.getNumOperands());
1070 
1071  for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
1072  LatticeVal State = getValueState(I.getOperand(i));
1073  if (State.isUnknown())
1074  return; // Operands are not resolved yet.
1075 
1076  if (State.isOverdefined())
1077  return (void)markOverdefined(&I);
1078 
1079  assert(State.isConstant() && "Unknown state!");
1080  Operands.push_back(State.getConstant());
1081  }
1082 
1083  Constant *Ptr = Operands[0];
1084  auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end());
1085  Constant *C =
1087  if (isa<UndefValue>(C))
1088  return;
1089  markConstant(&I, C);
1090 }
1091 
1092 void SCCPSolver::visitStoreInst(StoreInst &SI) {
1093  // If this store is of a struct, ignore it.
1094  if (SI.getOperand(0)->getType()->isStructTy())
1095  return;
1096 
1097  if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
1098  return;
1099 
1100  GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
1102  if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
1103 
1104  // Get the value we are storing into the global, then merge it.
1105  mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
1106  if (I->second.isOverdefined())
1107  TrackedGlobals.erase(I); // No need to keep tracking this!
1108 }
1109 
1110 // Handle load instructions. If the operand is a constant pointer to a constant
1111 // global, we can replace the load with the loaded constant value!
1112 void SCCPSolver::visitLoadInst(LoadInst &I) {
1113  // If this load is of a struct, just mark the result overdefined.
1114  if (I.getType()->isStructTy())
1115  return (void)markOverdefined(&I);
1116 
1117  LatticeVal PtrVal = getValueState(I.getOperand(0));
1118  if (PtrVal.isUnknown()) return; // The pointer is not resolved yet!
1119 
1120  LatticeVal &IV = ValueState[&I];
1121  if (IV.isOverdefined()) return;
1122 
1123  if (!PtrVal.isConstant() || I.isVolatile())
1124  return (void)markOverdefined(IV, &I);
1125 
1126  Constant *Ptr = PtrVal.getConstant();
1127 
1128  // load null is undefined.
1129  if (isa<ConstantPointerNull>(Ptr)) {
1131  return (void)markOverdefined(IV, &I);
1132  else
1133  return;
1134  }
1135 
1136  // Transform load (constant global) into the value loaded.
1137  if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) {
1138  if (!TrackedGlobals.empty()) {
1139  // If we are tracking this global, merge in the known value for it.
1141  TrackedGlobals.find(GV);
1142  if (It != TrackedGlobals.end()) {
1143  mergeInValue(IV, &I, It->second);
1144  return;
1145  }
1146  }
1147  }
1148 
1149  // Transform load from a constant into a constant if possible.
1150  if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) {
1151  if (isa<UndefValue>(C))
1152  return;
1153  return (void)markConstant(IV, &I, C);
1154  }
1155 
1156  // Otherwise we cannot say for certain what value this load will produce.
1157  // Bail out.
1158  markOverdefined(IV, &I);
1159 }
1160 
1161 void SCCPSolver::visitCallSite(CallSite CS) {
1162  Function *F = CS.getCalledFunction();
1163  Instruction *I = CS.getInstruction();
1164 
1165  if (auto *II = dyn_cast<IntrinsicInst>(I)) {
1166  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
1167  if (ValueState[I].isOverdefined())
1168  return;
1169 
1170  auto *PI = getPredicateInfoFor(I);
1171  if (!PI)
1172  return;
1173 
1174  Value *CopyOf = I->getOperand(0);
1175  auto *PBranch = dyn_cast<PredicateBranch>(PI);
1176  if (!PBranch) {
1177  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1178  return;
1179  }
1180 
1181  Value *Cond = PBranch->Condition;
1182 
1183  // Everything below relies on the condition being a comparison.
1184  auto *Cmp = dyn_cast<CmpInst>(Cond);
1185  if (!Cmp) {
1186  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1187  return;
1188  }
1189 
1190  Value *CmpOp0 = Cmp->getOperand(0);
1191  Value *CmpOp1 = Cmp->getOperand(1);
1192  if (CopyOf != CmpOp0 && CopyOf != CmpOp1) {
1193  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1194  return;
1195  }
1196 
1197  if (CmpOp0 != CopyOf)
1198  std::swap(CmpOp0, CmpOp1);
1199 
1200  LatticeVal OriginalVal = getValueState(CopyOf);
1201  LatticeVal EqVal = getValueState(CmpOp1);
1202  LatticeVal &IV = ValueState[I];
1203  if (PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_EQ) {
1204  addAdditionalUser(CmpOp1, I);
1205  if (OriginalVal.isConstant())
1206  mergeInValue(IV, I, OriginalVal);
1207  else
1208  mergeInValue(IV, I, EqVal);
1209  return;
1210  }
1211  if (!PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_NE) {
1212  addAdditionalUser(CmpOp1, I);
1213  if (OriginalVal.isConstant())
1214  mergeInValue(IV, I, OriginalVal);
1215  else
1216  mergeInValue(IV, I, EqVal);
1217  return;
1218  }
1219 
1220  return (void)mergeInValue(IV, I, getValueState(CopyOf));
1221  }
1222  }
1223 
1224  // The common case is that we aren't tracking the callee, either because we
1225  // are not doing interprocedural analysis or the callee is indirect, or is
1226  // external. Handle these cases first.
1227  if (!F || F->isDeclaration()) {
1228 CallOverdefined:
1229  // Void return and not tracking callee, just bail.
1230  if (I->getType()->isVoidTy()) return;
1231 
1232  // Otherwise, if we have a single return value case, and if the function is
1233  // a declaration, maybe we can constant fold it.
1234  if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
1235  canConstantFoldCallTo(CS, F)) {
1236  SmallVector<Constant*, 8> Operands;
1237  for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
1238  AI != E; ++AI) {
1239  if (AI->get()->getType()->isStructTy())
1240  return markOverdefined(I); // Can't handle struct args.
1241  LatticeVal State = getValueState(*AI);
1242 
1243  if (State.isUnknown())
1244  return; // Operands are not resolved yet.
1245  if (State.isOverdefined())
1246  return (void)markOverdefined(I);
1247  assert(State.isConstant() && "Unknown state!");
1248  Operands.push_back(State.getConstant());
1249  }
1250 
1251  if (getValueState(I).isOverdefined())
1252  return;
1253 
1254  // If we can constant fold this, mark the result of the call as a
1255  // constant.
1256  if (Constant *C = ConstantFoldCall(CS, F, Operands, TLI)) {
1257  // call -> undef.
1258  if (isa<UndefValue>(C))
1259  return;
1260  return (void)markConstant(I, C);
1261  }
1262  }
1263 
1264  // Otherwise, we don't know anything about this call, mark it overdefined.
1265  return (void)markOverdefined(I);
1266  }
1267 
1268  // If this is a local function that doesn't have its address taken, mark its
1269  // entry block executable and merge in the actual arguments to the call into
1270  // the formal arguments of the function.
1271  if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
1272  MarkBlockExecutable(&F->front());
1273 
1274  // Propagate information from this call site into the callee.
1275  CallSite::arg_iterator CAI = CS.arg_begin();
1276  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
1277  AI != E; ++AI, ++CAI) {
1278  // If this argument is byval, and if the function is not readonly, there
1279  // will be an implicit copy formed of the input aggregate.
1280  if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
1281  markOverdefined(&*AI);
1282  continue;
1283  }
1284 
1285  if (auto *STy = dyn_cast<StructType>(AI->getType())) {
1286  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1287  LatticeVal CallArg = getStructValueState(*CAI, i);
1288  mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
1289  }
1290  } else {
1291  // Most other parts of the Solver still only use the simpler value
1292  // lattice, so we propagate changes for parameters to both lattices.
1293  LatticeVal ConcreteArgument = getValueState(*CAI);
1294  bool ParamChanged =
1295  getParamState(&*AI).mergeIn(ConcreteArgument.toValueLattice(), DL);
1296  bool ValueChanged = mergeInValue(&*AI, ConcreteArgument);
1297  // Add argument to work list, if the state of a parameter changes but
1298  // ValueState does not change (because it is already overdefined there),
1299  // We have to take changes in ParamState into account, as it is used
1300  // when evaluating Cmp instructions.
1301  if (!ValueChanged && ParamChanged)
1302  pushToWorkList(ValueState[&*AI], &*AI);
1303  }
1304  }
1305  }
1306 
1307  // If this is a single/zero retval case, see if we're tracking the function.
1308  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
1309  if (!MRVFunctionsTracked.count(F))
1310  goto CallOverdefined; // Not tracking this callee.
1311 
1312  // If we are tracking this callee, propagate the result of the function
1313  // into this call site.
1314  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1315  mergeInValue(getStructValueState(I, i), I,
1316  TrackedMultipleRetVals[std::make_pair(F, i)]);
1317  } else {
1318  DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
1319  if (TFRVI == TrackedRetVals.end())
1320  goto CallOverdefined; // Not tracking this callee.
1321 
1322  // If so, propagate the return value of the callee into this call result.
1323  mergeInValue(I, TFRVI->second);
1324  }
1325 }
1326 
1327 void SCCPSolver::Solve() {
1328  // Process the work lists until they are empty!
1329  while (!BBWorkList.empty() || !InstWorkList.empty() ||
1330  !OverdefinedInstWorkList.empty()) {
1331  // Process the overdefined instruction's work list first, which drives other
1332  // things to overdefined more quickly.
1333  while (!OverdefinedInstWorkList.empty()) {
1334  Value *I = OverdefinedInstWorkList.pop_back_val();
1335 
1336  LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
1337 
1338  // "I" got into the work list because it either made the transition from
1339  // bottom to constant, or to overdefined.
1340  //
1341  // Anything on this worklist that is overdefined need not be visited
1342  // since all of its users will have already been marked as overdefined
1343  // Update all of the users of this instruction's value.
1344  //
1345  markUsersAsChanged(I);
1346  }
1347 
1348  // Process the instruction work list.
1349  while (!InstWorkList.empty()) {
1350  Value *I = InstWorkList.pop_back_val();
1351 
1352  LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
1353 
1354  // "I" got into the work list because it made the transition from undef to
1355  // constant.
1356  //
1357  // Anything on this worklist that is overdefined need not be visited
1358  // since all of its users will have already been marked as overdefined.
1359  // Update all of the users of this instruction's value.
1360  //
1361  if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
1362  markUsersAsChanged(I);
1363  }
1364 
1365  // Process the basic block work list.
1366  while (!BBWorkList.empty()) {
1367  BasicBlock *BB = BBWorkList.back();
1368  BBWorkList.pop_back();
1369 
1370  LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
1371 
1372  // Notify all instructions in this basic block that they are newly
1373  // executable.
1374  visit(BB);
1375  }
1376  }
1377 }
1378 
1379 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
1380 /// that branches on undef values cannot reach any of their successors.
1381 /// However, this is not a safe assumption. After we solve dataflow, this
1382 /// method should be use to handle this. If this returns true, the solver
1383 /// should be rerun.
1384 ///
1385 /// This method handles this by finding an unresolved branch and marking it one
1386 /// of the edges from the block as being feasible, even though the condition
1387 /// doesn't say it would otherwise be. This allows SCCP to find the rest of the
1388 /// CFG and only slightly pessimizes the analysis results (by marking one,
1389 /// potentially infeasible, edge feasible). This cannot usefully modify the
1390 /// constraints on the condition of the branch, as that would impact other users
1391 /// of the value.
1392 ///
1393 /// This scan also checks for values that use undefs, whose results are actually
1394 /// defined. For example, 'zext i8 undef to i32' should produce all zeros
1395 /// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
1396 /// even if X isn't defined.
1397 bool SCCPSolver::ResolvedUndefsIn(Function &F) {
1398  for (BasicBlock &BB : F) {
1399  if (!BBExecutable.count(&BB))
1400  continue;
1401 
1402  for (Instruction &I : BB) {
1403  // Look for instructions which produce undef values.
1404  if (I.getType()->isVoidTy()) continue;
1405 
1406  if (auto *STy = dyn_cast<StructType>(I.getType())) {
1407  // Only a few things that can be structs matter for undef.
1408 
1409  // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
1410  if (CallSite CS = CallSite(&I))
1411  if (Function *F = CS.getCalledFunction())
1412  if (MRVFunctionsTracked.count(F))
1413  continue;
1414 
1415  // extractvalue and insertvalue don't need to be marked; they are
1416  // tracked as precisely as their operands.
1417  if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
1418  continue;
1419 
1420  // Send the results of everything else to overdefined. We could be
1421  // more precise than this but it isn't worth bothering.
1422  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1423  LatticeVal &LV = getStructValueState(&I, i);
1424  if (LV.isUnknown())
1425  markOverdefined(LV, &I);
1426  }
1427  continue;
1428  }
1429 
1430  LatticeVal &LV = getValueState(&I);
1431  if (!LV.isUnknown()) continue;
1432 
1433  // extractvalue is safe; check here because the argument is a struct.
1434  if (isa<ExtractValueInst>(I))
1435  continue;
1436 
1437  // Compute the operand LatticeVals, for convenience below.
1438  // Anything taking a struct is conservatively assumed to require
1439  // overdefined markings.
1440  if (I.getOperand(0)->getType()->isStructTy()) {
1441  markOverdefined(&I);
1442  return true;
1443  }
1444  LatticeVal Op0LV = getValueState(I.getOperand(0));
1445  LatticeVal Op1LV;
1446  if (I.getNumOperands() == 2) {
1447  if (I.getOperand(1)->getType()->isStructTy()) {
1448  markOverdefined(&I);
1449  return true;
1450  }
1451 
1452  Op1LV = getValueState(I.getOperand(1));
1453  }
1454  // If this is an instructions whose result is defined even if the input is
1455  // not fully defined, propagate the information.
1456  Type *ITy = I.getType();
1457  switch (I.getOpcode()) {
1458  case Instruction::Add:
1459  case Instruction::Sub:
1460  case Instruction::Trunc:
1461  case Instruction::FPTrunc:
1462  case Instruction::BitCast:
1463  break; // Any undef -> undef
1464  case Instruction::FSub:
1465  case Instruction::FAdd:
1466  case Instruction::FMul:
1467  case Instruction::FDiv:
1468  case Instruction::FRem:
1469  // Floating-point binary operation: be conservative.
1470  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1471  markForcedConstant(&I, Constant::getNullValue(ITy));
1472  else
1473  markOverdefined(&I);
1474  return true;
1475  case Instruction::ZExt:
1476  case Instruction::SExt:
1477  case Instruction::FPToUI:
1478  case Instruction::FPToSI:
1479  case Instruction::FPExt:
1480  case Instruction::PtrToInt:
1481  case Instruction::IntToPtr:
1482  case Instruction::SIToFP:
1483  case Instruction::UIToFP:
1484  // undef -> 0; some outputs are impossible
1485  markForcedConstant(&I, Constant::getNullValue(ITy));
1486  return true;
1487  case Instruction::Mul:
1488  case Instruction::And:
1489  // Both operands undef -> undef
1490  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1491  break;
1492  // undef * X -> 0. X could be zero.
1493  // undef & X -> 0. X could be zero.
1494  markForcedConstant(&I, Constant::getNullValue(ITy));
1495  return true;
1496  case Instruction::Or:
1497  // Both operands undef -> undef
1498  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1499  break;
1500  // undef | X -> -1. X could be -1.
1501  markForcedConstant(&I, Constant::getAllOnesValue(ITy));
1502  return true;
1503  case Instruction::Xor:
1504  // undef ^ undef -> 0; strictly speaking, this is not strictly
1505  // necessary, but we try to be nice to people who expect this
1506  // behavior in simple cases
1507  if (Op0LV.isUnknown() && Op1LV.isUnknown()) {
1508  markForcedConstant(&I, Constant::getNullValue(ITy));
1509  return true;
1510  }
1511  // undef ^ X -> undef
1512  break;
1513  case Instruction::SDiv:
1514  case Instruction::UDiv:
1515  case Instruction::SRem:
1516  case Instruction::URem:
1517  // X / undef -> undef. No change.
1518  // X % undef -> undef. No change.
1519  if (Op1LV.isUnknown()) break;
1520 
1521  // X / 0 -> undef. No change.
1522  // X % 0 -> undef. No change.
1523  if (Op1LV.isConstant() && Op1LV.getConstant()->isZeroValue())
1524  break;
1525 
1526  // undef / X -> 0. X could be maxint.
1527  // undef % X -> 0. X could be 1.
1528  markForcedConstant(&I, Constant::getNullValue(ITy));
1529  return true;
1530  case Instruction::AShr:
1531  // X >>a undef -> undef.
1532  if (Op1LV.isUnknown()) break;
1533 
1534  // Shifting by the bitwidth or more is undefined.
1535  if (Op1LV.isConstant()) {
1536  if (auto *ShiftAmt = Op1LV.getConstantInt())
1537  if (ShiftAmt->getLimitedValue() >=
1538  ShiftAmt->getType()->getScalarSizeInBits())
1539  break;
1540  }
1541 
1542  // undef >>a X -> 0
1543  markForcedConstant(&I, Constant::getNullValue(ITy));
1544  return true;
1545  case Instruction::LShr:
1546  case Instruction::Shl:
1547  // X << undef -> undef.
1548  // X >> undef -> undef.
1549  if (Op1LV.isUnknown()) break;
1550 
1551  // Shifting by the bitwidth or more is undefined.
1552  if (Op1LV.isConstant()) {
1553  if (auto *ShiftAmt = Op1LV.getConstantInt())
1554  if (ShiftAmt->getLimitedValue() >=
1555  ShiftAmt->getType()->getScalarSizeInBits())
1556  break;
1557  }
1558 
1559  // undef << X -> 0
1560  // undef >> X -> 0
1561  markForcedConstant(&I, Constant::getNullValue(ITy));
1562  return true;
1563  case Instruction::Select:
1564  Op1LV = getValueState(I.getOperand(1));
1565  // undef ? X : Y -> X or Y. There could be commonality between X/Y.
1566  if (Op0LV.isUnknown()) {
1567  if (!Op1LV.isConstant()) // Pick the constant one if there is any.
1568  Op1LV = getValueState(I.getOperand(2));
1569  } else if (Op1LV.isUnknown()) {
1570  // c ? undef : undef -> undef. No change.
1571  Op1LV = getValueState(I.getOperand(2));
1572  if (Op1LV.isUnknown())
1573  break;
1574  // Otherwise, c ? undef : x -> x.
1575  } else {
1576  // Leave Op1LV as Operand(1)'s LatticeValue.
1577  }
1578 
1579  if (Op1LV.isConstant())
1580  markForcedConstant(&I, Op1LV.getConstant());
1581  else
1582  markOverdefined(&I);
1583  return true;
1584  case Instruction::Load:
1585  // A load here means one of two things: a load of undef from a global,
1586  // a load from an unknown pointer. Either way, having it return undef
1587  // is okay.
1588  break;
1589  case Instruction::ICmp:
1590  // X == undef -> undef. Other comparisons get more complicated.
1591  Op0LV = getValueState(I.getOperand(0));
1592  Op1LV = getValueState(I.getOperand(1));
1593 
1594  if ((Op0LV.isUnknown() || Op1LV.isUnknown()) &&
1595  cast<ICmpInst>(&I)->isEquality())
1596  break;
1597  markOverdefined(&I);
1598  return true;
1599  case Instruction::Call:
1600  case Instruction::Invoke:
1601  // There are two reasons a call can have an undef result
1602  // 1. It could be tracked.
1603  // 2. It could be constant-foldable.
1604  // Because of the way we solve return values, tracked calls must
1605  // never be marked overdefined in ResolvedUndefsIn.
1606  if (Function *F = CallSite(&I).getCalledFunction())
1607  if (TrackedRetVals.count(F))
1608  break;
1609 
1610  // If the call is constant-foldable, we mark it overdefined because
1611  // we do not know what return values are valid.
1612  markOverdefined(&I);
1613  return true;
1614  default:
1615  // If we don't know what should happen here, conservatively mark it
1616  // overdefined.
1617  markOverdefined(&I);
1618  return true;
1619  }
1620  }
1621 
1622  // Check to see if we have a branch or switch on an undefined value. If so
1623  // we force the branch to go one way or the other to make the successor
1624  // values live. It doesn't really matter which way we force it.
1625  Instruction *TI = BB.getTerminator();
1626  if (auto *BI = dyn_cast<BranchInst>(TI)) {
1627  if (!BI->isConditional()) continue;
1628  if (!getValueState(BI->getCondition()).isUnknown())
1629  continue;
1630 
1631  // If the input to SCCP is actually branch on undef, fix the undef to
1632  // false.
1633  if (isa<UndefValue>(BI->getCondition())) {
1634  BI->setCondition(ConstantInt::getFalse(BI->getContext()));
1635  markEdgeExecutable(&BB, TI->getSuccessor(1));
1636  return true;
1637  }
1638 
1639  // Otherwise, it is a branch on a symbolic value which is currently
1640  // considered to be undef. Make sure some edge is executable, so a
1641  // branch on "undef" always flows somewhere.
1642  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1643  BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
1644  if (markEdgeExecutable(&BB, DefaultSuccessor))
1645  return true;
1646 
1647  continue;
1648  }
1649 
1650  if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
1651  // Indirect branch with no successor ?. Its ok to assume it branches
1652  // to no target.
1653  if (IBR->getNumSuccessors() < 1)
1654  continue;
1655 
1656  if (!getValueState(IBR->getAddress()).isUnknown())
1657  continue;
1658 
1659  // If the input to SCCP is actually branch on undef, fix the undef to
1660  // the first successor of the indirect branch.
1661  if (isa<UndefValue>(IBR->getAddress())) {
1662  IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
1663  markEdgeExecutable(&BB, IBR->getSuccessor(0));
1664  return true;
1665  }
1666 
1667  // Otherwise, it is a branch on a symbolic value which is currently
1668  // considered to be undef. Make sure some edge is executable, so a
1669  // branch on "undef" always flows somewhere.
1670  // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
1671  // we can assume the branch has undefined behavior instead.
1672  BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
1673  if (markEdgeExecutable(&BB, DefaultSuccessor))
1674  return true;
1675 
1676  continue;
1677  }
1678 
1679  if (auto *SI = dyn_cast<SwitchInst>(TI)) {
1680  if (!SI->getNumCases() || !getValueState(SI->getCondition()).isUnknown())
1681  continue;
1682 
1683  // If the input to SCCP is actually switch on undef, fix the undef to
1684  // the first constant.
1685  if (isa<UndefValue>(SI->getCondition())) {
1686  SI->setCondition(SI->case_begin()->getCaseValue());
1687  markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
1688  return true;
1689  }
1690 
1691  // Otherwise, it is a branch on a symbolic value which is currently
1692  // considered to be undef. Make sure some edge is executable, so a
1693  // branch on "undef" always flows somewhere.
1694  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1695  BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
1696  if (markEdgeExecutable(&BB, DefaultSuccessor))
1697  return true;
1698 
1699  continue;
1700  }
1701  }
1702 
1703  return false;
1704 }
1705 
1706 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
1707  Constant *Const = nullptr;
1708  if (V->getType()->isStructTy()) {
1709  std::vector<LatticeVal> IVs = Solver.getStructLatticeValueFor(V);
1710  if (llvm::any_of(IVs,
1711  [](const LatticeVal &LV) { return LV.isOverdefined(); }))
1712  return false;
1713  std::vector<Constant *> ConstVals;
1714  auto *ST = dyn_cast<StructType>(V->getType());
1715  for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1716  LatticeVal V = IVs[i];
1717  ConstVals.push_back(V.isConstant()
1718  ? V.getConstant()
1719  : UndefValue::get(ST->getElementType(i)));
1720  }
1721  Const = ConstantStruct::get(ST, ConstVals);
1722  } else {
1723  const LatticeVal &IV = Solver.getLatticeValueFor(V);
1724  if (IV.isOverdefined())
1725  return false;
1726 
1727  Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
1728  }
1729  assert(Const && "Constant is nullptr here!");
1730 
1731  // Replacing `musttail` instructions with constant breaks `musttail` invariant
1732  // unless the call itself can be removed
1733  CallInst *CI = dyn_cast<CallInst>(V);
1734  if (CI && CI->isMustTailCall() && !CI->isSafeToRemove()) {
1735  CallSite CS(CI);
1736  Function *F = CS.getCalledFunction();
1737 
1738  // Don't zap returns of the callee
1739  if (F)
1740  Solver.AddMustTailCallee(F);
1741 
1742  LLVM_DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI
1743  << " as a constant\n");
1744  return false;
1745  }
1746 
1747  LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
1748 
1749  // Replaces all of the uses of a variable with uses of the constant.
1750  V->replaceAllUsesWith(Const);
1751  return true;
1752 }
1753 
1754 // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
1755 // and return true if the function was modified.
1756 static bool runSCCP(Function &F, const DataLayout &DL,
1757  const TargetLibraryInfo *TLI) {
1758  LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
1759  SCCPSolver Solver(DL, TLI);
1760 
1761  // Mark the first block of the function as being executable.
1762  Solver.MarkBlockExecutable(&F.front());
1763 
1764  // Mark all arguments to the function as being overdefined.
1765  for (Argument &AI : F.args())
1766  Solver.markOverdefined(&AI);
1767 
1768  // Solve for constants.
1769  bool ResolvedUndefs = true;
1770  while (ResolvedUndefs) {
1771  Solver.Solve();
1772  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n");
1773  ResolvedUndefs = Solver.ResolvedUndefsIn(F);
1774  }
1775 
1776  bool MadeChanges = false;
1777 
1778  // If we decided that there are basic blocks that are dead in this function,
1779  // delete their contents now. Note that we cannot actually delete the blocks,
1780  // as we cannot modify the CFG of the function.
1781 
1782  for (BasicBlock &BB : F) {
1783  if (!Solver.isBlockExecutable(&BB)) {
1784  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1785 
1786  ++NumDeadBlocks;
1787  NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB);
1788 
1789  MadeChanges = true;
1790  continue;
1791  }
1792 
1793  // Iterate over all of the instructions in a function, replacing them with
1794  // constants if we have found them to be of constant values.
1795  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
1796  Instruction *Inst = &*BI++;
1797  if (Inst->getType()->isVoidTy() || Inst->isTerminator())
1798  continue;
1799 
1800  if (tryToReplaceWithConstant(Solver, Inst)) {
1801  if (isInstructionTriviallyDead(Inst))
1802  Inst->eraseFromParent();
1803  // Hey, we just changed something!
1804  MadeChanges = true;
1805  ++NumInstRemoved;
1806  }
1807  }
1808  }
1809 
1810  return MadeChanges;
1811 }
1812 
1814  const DataLayout &DL = F.getParent()->getDataLayout();
1815  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
1816  if (!runSCCP(F, DL, &TLI))
1817  return PreservedAnalyses::all();
1818 
1819  auto PA = PreservedAnalyses();
1820  PA.preserve<GlobalsAA>();
1821  PA.preserveSet<CFGAnalyses>();
1822  return PA;
1823 }
1824 
1825 namespace {
1826 
1827 //===--------------------------------------------------------------------===//
1828 //
1829 /// SCCP Class - This class uses the SCCPSolver to implement a per-function
1830 /// Sparse Conditional Constant Propagator.
1831 ///
1832 class SCCPLegacyPass : public FunctionPass {
1833 public:
1834  // Pass identification, replacement for typeid
1835  static char ID;
1836 
1837  SCCPLegacyPass() : FunctionPass(ID) {
1839  }
1840 
1841  void getAnalysisUsage(AnalysisUsage &AU) const override {
1844  AU.setPreservesCFG();
1845  }
1846 
1847  // runOnFunction - Run the Sparse Conditional Constant Propagation
1848  // algorithm, and return true if the function was modified.
1849  bool runOnFunction(Function &F) override {
1850  if (skipFunction(F))
1851  return false;
1852  const DataLayout &DL = F.getParent()->getDataLayout();
1853  const TargetLibraryInfo *TLI =
1854  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1855  return runSCCP(F, DL, TLI);
1856  }
1857 };
1858 
1859 } // end anonymous namespace
1860 
1861 char SCCPLegacyPass::ID = 0;
1862 
1863 INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp",
1864  "Sparse Conditional Constant Propagation", false, false)
1866 INITIALIZE_PASS_END(SCCPLegacyPass, "sccp",
1867  "Sparse Conditional Constant Propagation", false, false)
1868 
1869 // createSCCPPass - This is the public interface to this file.
1870 FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); }
1871 
1873  SmallVector<ReturnInst *, 8> &ReturnsToZap,
1874  SCCPSolver &Solver) {
1875  // We can only do this if we know that nothing else can call the function.
1876  if (!Solver.isArgumentTrackedFunction(&F))
1877  return;
1878 
1879  // There is a non-removable musttail call site of this function. Zapping
1880  // returns is not allowed.
1881  if (Solver.isMustTailCallee(&F)) {
1882  LLVM_DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName()
1883  << " due to present musttail call of it\n");
1884  return;
1885  }
1886 
1887  for (BasicBlock &BB : F) {
1888  if (CallInst *CI = BB.getTerminatingMustTailCall()) {
1889  LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "
1890  << "musttail call : " << *CI << "\n");
1891  (void)CI;
1892  return;
1893  }
1894 
1895  if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1896  if (!isa<UndefValue>(RI->getOperand(0)))
1897  ReturnsToZap.push_back(RI);
1898  }
1899 }
1900 
1901 // Update the condition for terminators that are branching on indeterminate
1902 // values, forcing them to use a specific edge.
1903 static void forceIndeterminateEdge(Instruction* I, SCCPSolver &Solver) {
1904  BasicBlock *Dest = nullptr;
1905  Constant *C = nullptr;
1906  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
1907  if (!isa<ConstantInt>(SI->getCondition())) {
1908  // Indeterminate switch; use first case value.
1909  Dest = SI->case_begin()->getCaseSuccessor();
1910  C = SI->case_begin()->getCaseValue();
1911  }
1912  } else if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
1913  if (!isa<ConstantInt>(BI->getCondition())) {
1914  // Indeterminate branch; use false.
1915  Dest = BI->getSuccessor(1);
1916  C = ConstantInt::getFalse(BI->getContext());
1917  }
1918  } else if (IndirectBrInst *IBR = dyn_cast<IndirectBrInst>(I)) {
1919  if (!isa<BlockAddress>(IBR->getAddress()->stripPointerCasts())) {
1920  // Indeterminate indirectbr; use successor 0.
1921  Dest = IBR->getSuccessor(0);
1922  C = BlockAddress::get(IBR->getSuccessor(0));
1923  }
1924  } else {
1925  llvm_unreachable("Unexpected terminator instruction");
1926  }
1927  if (C) {
1928  assert(Solver.isEdgeFeasible(I->getParent(), Dest) &&
1929  "Didn't find feasible edge?");
1930  (void)Dest;
1931 
1932  I->setOperand(0, C);
1933  }
1934 }
1935 
1937  Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI,
1938  function_ref<AnalysisResultsForFn(Function &)> getAnalysis) {
1939  SCCPSolver Solver(DL, TLI);
1940 
1941  // Loop over all functions, marking arguments to those with their addresses
1942  // taken or that are external as overdefined.
1943  for (Function &F : M) {
1944  if (F.isDeclaration())
1945  continue;
1946 
1947  Solver.addAnalysis(F, getAnalysis(F));
1948 
1949  // Determine if we can track the function's return values. If so, add the
1950  // function to the solver's set of return-tracked functions.
1952  Solver.AddTrackedFunction(&F);
1953 
1954  // Determine if we can track the function's arguments. If so, add the
1955  // function to the solver's set of argument-tracked functions.
1957  Solver.AddArgumentTrackedFunction(&F);
1958  continue;
1959  }
1960 
1961  // Assume the function is called.
1962  Solver.MarkBlockExecutable(&F.front());
1963 
1964  // Assume nothing about the incoming arguments.
1965  for (Argument &AI : F.args())
1966  Solver.markOverdefined(&AI);
1967  }
1968 
1969  // Determine if we can track any of the module's global variables. If so, add
1970  // the global variables we can track to the solver's set of tracked global
1971  // variables.
1972  for (GlobalVariable &G : M.globals()) {
1973  G.removeDeadConstantUsers();
1975  Solver.TrackValueOfGlobalVariable(&G);
1976  }
1977 
1978  // Solve for constants.
1979  bool ResolvedUndefs = true;
1980  Solver.Solve();
1981  while (ResolvedUndefs) {
1982  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n");
1983  ResolvedUndefs = false;
1984  for (Function &F : M)
1985  if (Solver.ResolvedUndefsIn(F)) {
1986  // We run Solve() after we resolved an undef in a function, because
1987  // we might deduce a fact that eliminates an undef in another function.
1988  Solver.Solve();
1989  ResolvedUndefs = true;
1990  }
1991  }
1992 
1993  bool MadeChanges = false;
1994 
1995  // Iterate over all of the instructions in the module, replacing them with
1996  // constants if we have found them to be of constant values.
1997 
1998  for (Function &F : M) {
1999  if (F.isDeclaration())
2000  continue;
2001 
2002  SmallVector<BasicBlock *, 512> BlocksToErase;
2003 
2004  if (Solver.isBlockExecutable(&F.front()))
2005  for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
2006  ++AI) {
2007  if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
2008  ++IPNumArgsElimed;
2009  continue;
2010  }
2011  }
2012 
2013  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
2014  if (!Solver.isBlockExecutable(&*BB)) {
2015  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
2016  ++NumDeadBlocks;
2017 
2018  MadeChanges = true;
2019 
2020  if (&*BB != &F.front())
2021  BlocksToErase.push_back(&*BB);
2022  continue;
2023  }
2024 
2025  for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
2026  Instruction *Inst = &*BI++;
2027  if (Inst->getType()->isVoidTy())
2028  continue;
2029  if (tryToReplaceWithConstant(Solver, Inst)) {
2030  if (Inst->isSafeToRemove())
2031  Inst->eraseFromParent();
2032  // Hey, we just changed something!
2033  MadeChanges = true;
2034  ++IPNumInstRemoved;
2035  }
2036  }
2037  }
2038 
2039  DomTreeUpdater DTU = Solver.getDTU(F);
2040  // Change dead blocks to unreachable. We do it after replacing constants
2041  // in all executable blocks, because changeToUnreachable may remove PHI
2042  // nodes in executable blocks we found values for. The function's entry
2043  // block is not part of BlocksToErase, so we have to handle it separately.
2044  for (BasicBlock *BB : BlocksToErase) {
2045  NumInstRemoved +=
2046  changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false,
2047  /*PreserveLCSSA=*/false, &DTU);
2048  }
2049  if (!Solver.isBlockExecutable(&F.front()))
2050  NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
2051  /*UseLLVMTrap=*/false,
2052  /*PreserveLCSSA=*/false, &DTU);
2053 
2054  // Now that all instructions in the function are constant folded,
2055  // use ConstantFoldTerminator to get rid of in-edges, record DT updates and
2056  // delete dead BBs.
2057  for (BasicBlock *DeadBB : BlocksToErase) {
2058  // If there are any PHI nodes in this successor, drop entries for BB now.
2059  for (Value::user_iterator UI = DeadBB->user_begin(),
2060  UE = DeadBB->user_end();
2061  UI != UE;) {
2062  // Grab the user and then increment the iterator early, as the user
2063  // will be deleted. Step past all adjacent uses from the same user.
2064  auto *I = dyn_cast<Instruction>(*UI);
2065  do { ++UI; } while (UI != UE && *UI == I);
2066 
2067  // Ignore blockaddress users; BasicBlock's dtor will handle them.
2068  if (!I) continue;
2069 
2070  // If we have forced an edge for an indeterminate value, then force the
2071  // terminator to fold to that edge.
2072  forceIndeterminateEdge(I, Solver);
2073  bool Folded = ConstantFoldTerminator(I->getParent(),
2074  /*DeleteDeadConditions=*/false,
2075  /*TLI=*/nullptr, &DTU);
2076  assert(Folded &&
2077  "Expect TermInst on constantint or blockaddress to be folded");
2078  (void) Folded;
2079  }
2080  // Mark dead BB for deletion.
2081  DTU.deleteBB(DeadBB);
2082  }
2083 
2084  for (BasicBlock &BB : F) {
2085  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
2086  Instruction *Inst = &*BI++;
2087  if (Solver.getPredicateInfoFor(Inst)) {
2088  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
2089  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
2090  Value *Op = II->getOperand(0);
2091  Inst->replaceAllUsesWith(Op);
2092  Inst->eraseFromParent();
2093  }
2094  }
2095  }
2096  }
2097  }
2098  }
2099 
2100  // If we inferred constant or undef return values for a function, we replaced
2101  // all call uses with the inferred value. This means we don't need to bother
2102  // actually returning anything from the function. Replace all return
2103  // instructions with return undef.
2104  //
2105  // Do this in two stages: first identify the functions we should process, then
2106  // actually zap their returns. This is important because we can only do this
2107  // if the address of the function isn't taken. In cases where a return is the
2108  // last use of a function, the order of processing functions would affect
2109  // whether other functions are optimizable.
2110  SmallVector<ReturnInst*, 8> ReturnsToZap;
2111 
2112  const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
2113  for (const auto &I : RV) {
2114  Function *F = I.first;
2115  if (I.second.isOverdefined() || F->getReturnType()->isVoidTy())
2116  continue;
2117  findReturnsToZap(*F, ReturnsToZap, Solver);
2118  }
2119 
2120  for (const auto &F : Solver.getMRVFunctionsTracked()) {
2121  assert(F->getReturnType()->isStructTy() &&
2122  "The return type should be a struct");
2123  StructType *STy = cast<StructType>(F->getReturnType());
2124  if (Solver.isStructLatticeConstant(F, STy))
2125  findReturnsToZap(*F, ReturnsToZap, Solver);
2126  }
2127 
2128  // Zap all returns which we've identified as zap to change.
2129  for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
2130  Function *F = ReturnsToZap[i]->getParent()->getParent();
2131  ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
2132  }
2133 
2134  // If we inferred constant or undef values for globals variables, we can
2135  // delete the global and any stores that remain to it.
2136  const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
2138  E = TG.end(); I != E; ++I) {
2139  GlobalVariable *GV = I->first;
2140  assert(!I->second.isOverdefined() &&
2141  "Overdefined values should have been taken out of the map!");
2142  LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName()
2143  << "' is constant!\n");
2144  while (!GV->use_empty()) {
2145  StoreInst *SI = cast<StoreInst>(GV->user_back());
2146  SI->eraseFromParent();
2147  }
2148  M.getGlobalList().erase(GV);
2149  ++IPNumGlobalConst;
2150  }
2151 
2152  return MadeChanges;
2153 }
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:468
uint64_t CallInst * C
Return a value (possibly void), from a function.
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:213
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:68
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:111
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:585
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:636
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:30
Base class for instruction visitors.
Definition: InstVisitor.h:81
Value * getAggregateOperand()
Interprocedural Sparse Conditional Constant Propagation
Definition: SCCP.cpp:84
sccp
Definition: SCCP.cpp:1866
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:770
iterator erase(iterator where)
Definition: ilist.h:267
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
This class represents lattice values for constants.
Definition: AllocatorList.h:24
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:106
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:1154
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:455
bool canTrackArgumentsInterprocedurally(Function *F)
Determine if the values of the given function&#39;s arguments can be tracked interprocedurally.
Implements a dense probed hash-table based set.
Definition: DenseSet.h:250
unsigned getNumElements() const
Random access to the elements.
Definition: DerivedTypes.h:313
bool isSafeToRemove() const
Return true if the instruction can be removed if the result is unused.
static ValueLatticeElement get(Constant *C)
Definition: ValueLattice.h:120
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:117
bool isTerminator() const
Definition: Instruction.h:129
arg_iterator arg_end()
Definition: Function.h:680
STATISTIC(NumFunctions, "Total number of functions")
F(f)
An instruction for reading from memory.
Definition: Instructions.h:168
void reserve(size_type N)
Definition: SmallVector.h:376
bool isMustTailCall() const
static void findReturnsToZap(Function &F, SmallVector< ReturnInst *, 8 > &ReturnsToZap, SCCPSolver &Solver)
Definition: SCCP.cpp:1872
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:265
std::unique_ptr< PredicateInfo > PredInfo
Definition: SCCP.h:44
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:221
The address of a basic block.
Definition: Constants.h:840
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
void setPointer(PointerTy PtrVal)
bool isVolatile() const
Return true if this is a load from a volatile memory location.
Definition: Instructions.h:232
This class represents the LLVM &#39;select&#39; instruction.
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap, bool PreserveLCSSA=false, DomTreeUpdater *DTU=nullptr)
Insert an unreachable instruction before the specified instruction, making it and the rest of the cod...
Definition: Local.cpp:1896
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:371
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:353
ArrayRef< T > makeArrayRef(const T &OneElt)
Construct an ArrayRef from a single element.
Definition: ArrayRef.h:451
Class to represent struct types.
Definition: DerivedTypes.h:201
void initializeSCCPLegacyPassPass(PassRegistry &)
IterTy arg_end() const
Definition: CallSite.h:575
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: SCCP.cpp:1813
InstrTy * getInstruction() const
Definition: CallSite.h:92
static void forceIndeterminateEdge(Instruction *I, SCCPSolver &Solver)
Definition: SCCP.cpp:1903
FunctionPass * createSCCPPass()
Definition: SCCP.cpp:1870
Type * getSourceElementType() const
Definition: Instructions.h:951
Helper struct for bundling up the analysis results per function for IPSCCP.
Definition: SCCP.h:43
static int64_t getConstant(const MachineInstr *MI)
void assign(size_type NumElts, const T &Elt)
Definition: SmallVector.h:423
Instruction::CastOps getOpcode() const
Return the opcode of this CastInst.
Definition: InstrTypes.h:606
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
IntType getInt() const
#define T
Value * getInsertedValueOperand()
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:126
PostDominatorTree * PDT
Definition: SCCP.h:46
An instruction for storing to memory.
Definition: Instructions.h:321
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
Value * getOperand(unsigned i) const
Definition: User.h:170
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:335
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:141
an instruction for type-safe pointer arithmetic to access elements of arrays and structs ...
Definition: Instructions.h:854
static bool runOnFunction(Function &F, bool PostInlining)
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:169
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:154
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
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:46
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:1434
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:42
LLVM_NODISCARD bool empty() const
Definition: SmallPtrSet.h:92
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:129
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:371
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:1193
Analysis pass providing a never-invalidated alias analysis result.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
static Constant * get(StructType *T, ArrayRef< Constant *> V)
Definition: Constants.cpp:1044
arg_iterator arg_begin()
Definition: Function.h:671
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
const Function * getFunction() const
Return the function this instruction belongs to.
Definition: Instruction.cpp:60
static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V)
Definition: SCCP.cpp:1706
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:319
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1415
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
bool isExceptionalTerminator() const
Definition: Instruction.h:136
size_t size() const
Definition: SmallVector.h:53
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.
idx_iterator idx_begin() const
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:192
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
This is the shared class of boolean and integer constants.
Definition: Constants.h:84
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:294
IterTy arg_begin() const
Definition: CallSite.h:571
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
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.
const DataFlowGraph & G
Definition: RDFGraph.cpp:211
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:381
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:286
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:1875
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:1437
void setOperand(unsigned i, Value *Val)
Definition: User.h:175
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:133
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:941
iterator_range< user_iterator > users()
Definition: Value.h:400
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:115
const Value * getFalseValue() const
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:721
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:133
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:56
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:107
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:369
DominatorTree * DT
Definition: SCCP.h:45
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
idx_iterator idx_begin() const
Type * getValueType() const
Definition: GlobalValue.h:276
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:325
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:92
size_type count(const_arg_type_t< KeyT > Val) const
Return 1 if the specified key is in the map, 0 otherwise.
Definition: DenseMap.h:171
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:206
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:107
Analysis pass providing the TargetLibraryInfo.
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:291
Multiway switch.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const BasicBlock & front() const
Definition: Function.h:663
bool isSingleValueType() const
Return true if the type is a valid type for a register in codegen.
Definition: Type.h:250
bool runIPSCCP(Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI, function_ref< AnalysisResultsForFn(Function &)> getAnalysis)
Definition: SCCP.cpp:1936
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:566
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:349
LLVM Value Representation.
Definition: Value.h:73
bool canConstantFoldCallTo(ImmutableCallSite CS, const Function *F)
canConstantFoldCallTo - Return true if its even possible to fold a call to the specified function...
Invoke instruction.
static ValueLatticeElement getOverdefined()
Definition: ValueLattice.h:137
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:123
Constant * ConstantFoldCall(ImmutableCallSite CS, Function *F, ArrayRef< Constant *> Operands, const TargetLibraryInfo *TLI=nullptr)
ConstantFoldCall - Attempt to constant fold a call to the specified function with the specified argum...
bool use_empty() const
Definition: Value.h:323
static bool runSCCP(Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI)
Definition: SCCP.cpp:1756
iterator_range< arg_iterator > args()
Definition: Function.h:689
bool isStructTy() const
True if this is an instance of StructType.
Definition: Type.h:218
User * user_back()
Definition: Value.h:386
const BasicBlock * getParent() const
Definition: Instruction.h:67
This instruction inserts a struct field of array element value into an aggregate value.
void resize(size_type N)
Definition: SmallVector.h:351
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:1806