LLVM  9.0.0svn
SCCP.cpp
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1 //===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements sparse conditional constant propagation and merging:
10 //
11 // Specifically, this:
12 // * Assumes values are constant unless proven otherwise
13 // * Assumes BasicBlocks are dead unless proven otherwise
14 // * Proves values to be constant, and replaces them with constants
15 // * Proves conditional branches to be unconditional
16 //
17 //===----------------------------------------------------------------------===//
18 
20 #include "llvm/ADT/ArrayRef.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/DenseSet.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/ADT/SmallPtrSet.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include "llvm/ADT/Statistic.h"
34 #include "llvm/IR/BasicBlock.h"
35 #include "llvm/IR/CallSite.h"
36 #include "llvm/IR/Constant.h"
37 #include "llvm/IR/Constants.h"
38 #include "llvm/IR/DataLayout.h"
39 #include "llvm/IR/DerivedTypes.h"
40 #include "llvm/IR/Function.h"
41 #include "llvm/IR/GlobalVariable.h"
42 #include "llvm/IR/InstVisitor.h"
43 #include "llvm/IR/InstrTypes.h"
44 #include "llvm/IR/Instruction.h"
45 #include "llvm/IR/Instructions.h"
46 #include "llvm/IR/Module.h"
47 #include "llvm/IR/PassManager.h"
48 #include "llvm/IR/Type.h"
49 #include "llvm/IR/User.h"
50 #include "llvm/IR/Value.h"
51 #include "llvm/Pass.h"
52 #include "llvm/Support/Casting.h"
53 #include "llvm/Support/Debug.h"
56 #include "llvm/Transforms/Scalar.h"
58 #include <cassert>
59 #include <utility>
60 #include <vector>
61 
62 using namespace llvm;
63 
64 #define DEBUG_TYPE "sccp"
65 
66 STATISTIC(NumInstRemoved, "Number of instructions removed");
67 STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
68 
69 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
70 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
71 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
72 
73 namespace {
74 
75 /// LatticeVal class - This class represents the different lattice values that
76 /// an LLVM value may occupy. It is a simple class with value semantics.
77 ///
78 class LatticeVal {
79  enum LatticeValueTy {
80  /// unknown - This LLVM Value has no known value yet.
81  unknown,
82 
83  /// constant - This LLVM Value has a specific constant value.
84  constant,
85 
86  /// forcedconstant - This LLVM Value was thought to be undef until
87  /// ResolvedUndefsIn. This is treated just like 'constant', but if merged
88  /// with another (different) constant, it goes to overdefined, instead of
89  /// asserting.
90  forcedconstant,
91 
92  /// overdefined - This instruction is not known to be constant, and we know
93  /// it has a value.
94  overdefined
95  };
96 
97  /// Val: This stores the current lattice value along with the Constant* for
98  /// the constant if this is a 'constant' or 'forcedconstant' value.
100 
101  LatticeValueTy getLatticeValue() const {
102  return Val.getInt();
103  }
104 
105 public:
106  LatticeVal() : Val(nullptr, unknown) {}
107 
108  bool isUnknown() const { return getLatticeValue() == unknown; }
109 
110  bool isConstant() const {
111  return getLatticeValue() == constant || getLatticeValue() == forcedconstant;
112  }
113 
114  bool isOverdefined() const { return getLatticeValue() == overdefined; }
115 
116  Constant *getConstant() const {
117  assert(isConstant() && "Cannot get the constant of a non-constant!");
118  return Val.getPointer();
119  }
120 
121  /// markOverdefined - Return true if this is a change in status.
122  bool markOverdefined() {
123  if (isOverdefined())
124  return false;
125 
126  Val.setInt(overdefined);
127  return true;
128  }
129 
130  /// markConstant - Return true if this is a change in status.
131  bool markConstant(Constant *V) {
132  if (getLatticeValue() == constant) { // Constant but not forcedconstant.
133  assert(getConstant() == V && "Marking constant with different value");
134  return false;
135  }
136 
137  if (isUnknown()) {
138  Val.setInt(constant);
139  assert(V && "Marking constant with NULL");
140  Val.setPointer(V);
141  } else {
142  assert(getLatticeValue() == forcedconstant &&
143  "Cannot move from overdefined to constant!");
144  // Stay at forcedconstant if the constant is the same.
145  if (V == getConstant()) return false;
146 
147  // Otherwise, we go to overdefined. Assumptions made based on the
148  // forced value are possibly wrong. Assuming this is another constant
149  // could expose a contradiction.
150  Val.setInt(overdefined);
151  }
152  return true;
153  }
154 
155  /// getConstantInt - If this is a constant with a ConstantInt value, return it
156  /// otherwise return null.
157  ConstantInt *getConstantInt() const {
158  if (isConstant())
159  return dyn_cast<ConstantInt>(getConstant());
160  return nullptr;
161  }
162 
163  /// getBlockAddress - If this is a constant with a BlockAddress value, return
164  /// it, otherwise return null.
165  BlockAddress *getBlockAddress() const {
166  if (isConstant())
167  return dyn_cast<BlockAddress>(getConstant());
168  return nullptr;
169  }
170 
171  void markForcedConstant(Constant *V) {
172  assert(isUnknown() && "Can't force a defined value!");
173  Val.setInt(forcedconstant);
174  Val.setPointer(V);
175  }
176 
177  ValueLatticeElement toValueLattice() const {
178  if (isOverdefined())
180  if (isConstant())
182  return ValueLatticeElement();
183  }
184 };
185 
186 //===----------------------------------------------------------------------===//
187 //
188 /// SCCPSolver - This class is a general purpose solver for Sparse Conditional
189 /// Constant Propagation.
190 ///
191 class SCCPSolver : public InstVisitor<SCCPSolver> {
192  const DataLayout &DL;
193  const TargetLibraryInfo *TLI;
194  SmallPtrSet<BasicBlock *, 8> BBExecutable; // The BBs that are executable.
195  DenseMap<Value *, LatticeVal> ValueState; // The state each value is in.
196  // The state each parameter is in.
198 
199  /// StructValueState - This maintains ValueState for values that have
200  /// StructType, for example for formal arguments, calls, insertelement, etc.
201  DenseMap<std::pair<Value *, unsigned>, LatticeVal> StructValueState;
202 
203  /// GlobalValue - If we are tracking any values for the contents of a global
204  /// variable, we keep a mapping from the constant accessor to the element of
205  /// the global, to the currently known value. If the value becomes
206  /// overdefined, it's entry is simply removed from this map.
208 
209  /// TrackedRetVals - If we are tracking arguments into and the return
210  /// value out of a function, it will have an entry in this map, indicating
211  /// what the known return value for the function is.
212  DenseMap<Function *, LatticeVal> TrackedRetVals;
213 
214  /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
215  /// that return multiple values.
216  DenseMap<std::pair<Function *, unsigned>, LatticeVal> TrackedMultipleRetVals;
217 
218  /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
219  /// represented here for efficient lookup.
220  SmallPtrSet<Function *, 16> MRVFunctionsTracked;
221 
222  /// MustTailFunctions - Each function here is a callee of non-removable
223  /// musttail call site.
224  SmallPtrSet<Function *, 16> MustTailCallees;
225 
226  /// TrackingIncomingArguments - This is the set of functions for whose
227  /// arguments we make optimistic assumptions about and try to prove as
228  /// constants.
229  SmallPtrSet<Function *, 16> TrackingIncomingArguments;
230 
231  /// The reason for two worklists is that overdefined is the lowest state
232  /// on the lattice, and moving things to overdefined as fast as possible
233  /// makes SCCP converge much faster.
234  ///
235  /// By having a separate worklist, we accomplish this because everything
236  /// possibly overdefined will become overdefined at the soonest possible
237  /// point.
238  SmallVector<Value *, 64> OverdefinedInstWorkList;
239  SmallVector<Value *, 64> InstWorkList;
240 
241  // The BasicBlock work list
243 
244  /// KnownFeasibleEdges - Entries in this set are edges which have already had
245  /// PHI nodes retriggered.
246  using Edge = std::pair<BasicBlock *, BasicBlock *>;
247  DenseSet<Edge> KnownFeasibleEdges;
248 
251 
252 public:
253  void addAnalysis(Function &F, AnalysisResultsForFn A) {
254  AnalysisResults.insert({&F, std::move(A)});
255  }
256 
257  const PredicateBase *getPredicateInfoFor(Instruction *I) {
258  auto A = AnalysisResults.find(I->getParent()->getParent());
259  if (A == AnalysisResults.end())
260  return nullptr;
261  return A->second.PredInfo->getPredicateInfoFor(I);
262  }
263 
264  DomTreeUpdater getDTU(Function &F) {
265  auto A = AnalysisResults.find(&F);
266  assert(A != AnalysisResults.end() && "Need analysis results for function.");
267  return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy};
268  }
269 
270  SCCPSolver(const DataLayout &DL, const TargetLibraryInfo *tli)
271  : DL(DL), TLI(tli) {}
272 
273  /// MarkBlockExecutable - This method can be used by clients to mark all of
274  /// the blocks that are known to be intrinsically live in the processed unit.
275  ///
276  /// This returns true if the block was not considered live before.
277  bool MarkBlockExecutable(BasicBlock *BB) {
278  if (!BBExecutable.insert(BB).second)
279  return false;
280  LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n');
281  BBWorkList.push_back(BB); // Add the block to the work list!
282  return true;
283  }
284 
285  /// TrackValueOfGlobalVariable - Clients can use this method to
286  /// inform the SCCPSolver that it should track loads and stores to the
287  /// specified global variable if it can. This is only legal to call if
288  /// performing Interprocedural SCCP.
289  void TrackValueOfGlobalVariable(GlobalVariable *GV) {
290  // We only track the contents of scalar globals.
291  if (GV->getValueType()->isSingleValueType()) {
292  LatticeVal &IV = TrackedGlobals[GV];
293  if (!isa<UndefValue>(GV->getInitializer()))
294  IV.markConstant(GV->getInitializer());
295  }
296  }
297 
298  /// AddTrackedFunction - If the SCCP solver is supposed to track calls into
299  /// and out of the specified function (which cannot have its address taken),
300  /// this method must be called.
301  void AddTrackedFunction(Function *F) {
302  // Add an entry, F -> undef.
303  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
304  MRVFunctionsTracked.insert(F);
305  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
306  TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
307  LatticeVal()));
308  } else
309  TrackedRetVals.insert(std::make_pair(F, LatticeVal()));
310  }
311 
312  /// AddMustTailCallee - If the SCCP solver finds that this function is called
313  /// from non-removable musttail call site.
314  void AddMustTailCallee(Function *F) {
315  MustTailCallees.insert(F);
316  }
317 
318  /// Returns true if the given function is called from non-removable musttail
319  /// call site.
320  bool isMustTailCallee(Function *F) {
321  return MustTailCallees.count(F);
322  }
323 
324  void AddArgumentTrackedFunction(Function *F) {
325  TrackingIncomingArguments.insert(F);
326  }
327 
328  /// Returns true if the given function is in the solver's set of
329  /// argument-tracked functions.
330  bool isArgumentTrackedFunction(Function *F) {
331  return TrackingIncomingArguments.count(F);
332  }
333 
334  /// Solve - Solve for constants and executable blocks.
335  void Solve();
336 
337  /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
338  /// that branches on undef values cannot reach any of their successors.
339  /// However, this is not a safe assumption. After we solve dataflow, this
340  /// method should be use to handle this. If this returns true, the solver
341  /// should be rerun.
342  bool ResolvedUndefsIn(Function &F);
343 
344  bool isBlockExecutable(BasicBlock *BB) const {
345  return BBExecutable.count(BB);
346  }
347 
348  // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
349  // block to the 'To' basic block is currently feasible.
350  bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
351 
352  std::vector<LatticeVal> getStructLatticeValueFor(Value *V) const {
353  std::vector<LatticeVal> StructValues;
354  auto *STy = dyn_cast<StructType>(V->getType());
355  assert(STy && "getStructLatticeValueFor() can be called only on structs");
356  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
357  auto I = StructValueState.find(std::make_pair(V, i));
358  assert(I != StructValueState.end() && "Value not in valuemap!");
359  StructValues.push_back(I->second);
360  }
361  return StructValues;
362  }
363 
364  const LatticeVal &getLatticeValueFor(Value *V) const {
365  assert(!V->getType()->isStructTy() &&
366  "Should use getStructLatticeValueFor");
368  assert(I != ValueState.end() &&
369  "V not found in ValueState nor Paramstate map!");
370  return I->second;
371  }
372 
373  /// getTrackedRetVals - Get the inferred return value map.
374  const DenseMap<Function*, LatticeVal> &getTrackedRetVals() {
375  return TrackedRetVals;
376  }
377 
378  /// getTrackedGlobals - Get and return the set of inferred initializers for
379  /// global variables.
380  const DenseMap<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
381  return TrackedGlobals;
382  }
383 
384  /// getMRVFunctionsTracked - Get the set of functions which return multiple
385  /// values tracked by the pass.
386  const SmallPtrSet<Function *, 16> getMRVFunctionsTracked() {
387  return MRVFunctionsTracked;
388  }
389 
390  /// getMustTailCallees - Get the set of functions which are called
391  /// from non-removable musttail call sites.
392  const SmallPtrSet<Function *, 16> getMustTailCallees() {
393  return MustTailCallees;
394  }
395 
396  /// markOverdefined - Mark the specified value overdefined. This
397  /// works with both scalars and structs.
398  void markOverdefined(Value *V) {
399  if (auto *STy = dyn_cast<StructType>(V->getType()))
400  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
401  markOverdefined(getStructValueState(V, i), V);
402  else
403  markOverdefined(ValueState[V], V);
404  }
405 
406  // isStructLatticeConstant - Return true if all the lattice values
407  // corresponding to elements of the structure are not overdefined,
408  // false otherwise.
409  bool isStructLatticeConstant(Function *F, StructType *STy) {
410  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
411  const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i));
412  assert(It != TrackedMultipleRetVals.end());
413  LatticeVal LV = It->second;
414  if (LV.isOverdefined())
415  return false;
416  }
417  return true;
418  }
419 
420 private:
421  // pushToWorkList - Helper for markConstant/markForcedConstant/markOverdefined
422  void pushToWorkList(LatticeVal &IV, Value *V) {
423  if (IV.isOverdefined())
424  return OverdefinedInstWorkList.push_back(V);
425  InstWorkList.push_back(V);
426  }
427 
428  // markConstant - Make a value be marked as "constant". If the value
429  // is not already a constant, add it to the instruction work list so that
430  // the users of the instruction are updated later.
431  bool markConstant(LatticeVal &IV, Value *V, Constant *C) {
432  if (!IV.markConstant(C)) return false;
433  LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
434  pushToWorkList(IV, V);
435  return true;
436  }
437 
438  bool markConstant(Value *V, Constant *C) {
439  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
440  return markConstant(ValueState[V], V, C);
441  }
442 
443  void markForcedConstant(Value *V, Constant *C) {
444  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
445  LatticeVal &IV = ValueState[V];
446  IV.markForcedConstant(C);
447  LLVM_DEBUG(dbgs() << "markForcedConstant: " << *C << ": " << *V << '\n');
448  pushToWorkList(IV, V);
449  }
450 
451  // markOverdefined - Make a value be marked as "overdefined". If the
452  // value is not already overdefined, add it to the overdefined instruction
453  // work list so that the users of the instruction are updated later.
454  bool markOverdefined(LatticeVal &IV, Value *V) {
455  if (!IV.markOverdefined()) return false;
456 
457  LLVM_DEBUG(dbgs() << "markOverdefined: ";
458  if (auto *F = dyn_cast<Function>(V)) dbgs()
459  << "Function '" << F->getName() << "'\n";
460  else dbgs() << *V << '\n');
461  // Only instructions go on the work list
462  pushToWorkList(IV, V);
463  return true;
464  }
465 
466  bool mergeInValue(LatticeVal &IV, Value *V, LatticeVal MergeWithV) {
467  if (IV.isOverdefined() || MergeWithV.isUnknown())
468  return false; // Noop.
469  if (MergeWithV.isOverdefined())
470  return markOverdefined(IV, V);
471  if (IV.isUnknown())
472  return markConstant(IV, V, MergeWithV.getConstant());
473  if (IV.getConstant() != MergeWithV.getConstant())
474  return markOverdefined(IV, V);
475  return false;
476  }
477 
478  bool mergeInValue(Value *V, LatticeVal MergeWithV) {
479  assert(!V->getType()->isStructTy() &&
480  "non-structs should use markConstant");
481  return mergeInValue(ValueState[V], V, MergeWithV);
482  }
483 
484  /// getValueState - Return the LatticeVal object that corresponds to the
485  /// value. This function handles the case when the value hasn't been seen yet
486  /// by properly seeding constants etc.
487  LatticeVal &getValueState(Value *V) {
488  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
489 
490  std::pair<DenseMap<Value*, LatticeVal>::iterator, bool> I =
491  ValueState.insert(std::make_pair(V, LatticeVal()));
492  LatticeVal &LV = I.first->second;
493 
494  if (!I.second)
495  return LV; // Common case, already in the map.
496 
497  if (auto *C = dyn_cast<Constant>(V)) {
498  // Undef values remain unknown.
499  if (!isa<UndefValue>(V))
500  LV.markConstant(C); // Constants are constant
501  }
502 
503  // All others are underdefined by default.
504  return LV;
505  }
506 
507  ValueLatticeElement &getParamState(Value *V) {
508  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
509 
510  std::pair<DenseMap<Value*, ValueLatticeElement>::iterator, bool>
511  PI = ParamState.insert(std::make_pair(V, ValueLatticeElement()));
512  ValueLatticeElement &LV = PI.first->second;
513  if (PI.second)
514  LV = getValueState(V).toValueLattice();
515 
516  return LV;
517  }
518 
519  /// getStructValueState - Return the LatticeVal object that corresponds to the
520  /// value/field pair. This function handles the case when the value hasn't
521  /// been seen yet by properly seeding constants etc.
522  LatticeVal &getStructValueState(Value *V, unsigned i) {
523  assert(V->getType()->isStructTy() && "Should use getValueState");
524  assert(i < cast<StructType>(V->getType())->getNumElements() &&
525  "Invalid element #");
526 
527  std::pair<DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator,
528  bool> I = StructValueState.insert(
529  std::make_pair(std::make_pair(V, i), LatticeVal()));
530  LatticeVal &LV = I.first->second;
531 
532  if (!I.second)
533  return LV; // Common case, already in the map.
534 
535  if (auto *C = dyn_cast<Constant>(V)) {
536  Constant *Elt = C->getAggregateElement(i);
537 
538  if (!Elt)
539  LV.markOverdefined(); // Unknown sort of constant.
540  else if (isa<UndefValue>(Elt))
541  ; // Undef values remain unknown.
542  else
543  LV.markConstant(Elt); // Constants are constant.
544  }
545 
546  // All others are underdefined by default.
547  return LV;
548  }
549 
550  /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
551  /// work list if it is not already executable.
552  bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
553  if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
554  return false; // This edge is already known to be executable!
555 
556  if (!MarkBlockExecutable(Dest)) {
557  // If the destination is already executable, we just made an *edge*
558  // feasible that wasn't before. Revisit the PHI nodes in the block
559  // because they have potentially new operands.
560  LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
561  << " -> " << Dest->getName() << '\n');
562 
563  for (PHINode &PN : Dest->phis())
564  visitPHINode(PN);
565  }
566  return true;
567  }
568 
569  // getFeasibleSuccessors - Return a vector of booleans to indicate which
570  // successors are reachable from a given terminator instruction.
571  void getFeasibleSuccessors(Instruction &TI, SmallVectorImpl<bool> &Succs);
572 
573  // OperandChangedState - This method is invoked on all of the users of an
574  // instruction that was just changed state somehow. Based on this
575  // information, we need to update the specified user of this instruction.
576  void OperandChangedState(Instruction *I) {
577  if (BBExecutable.count(I->getParent())) // Inst is executable?
578  visit(*I);
579  }
580 
581  // Add U as additional user of V.
582  void addAdditionalUser(Value *V, User *U) {
583  auto Iter = AdditionalUsers.insert({V, {}});
584  Iter.first->second.insert(U);
585  }
586 
587  // Mark I's users as changed, including AdditionalUsers.
588  void markUsersAsChanged(Value *I) {
589  for (User *U : I->users())
590  if (auto *UI = dyn_cast<Instruction>(U))
591  OperandChangedState(UI);
592 
593  auto Iter = AdditionalUsers.find(I);
594  if (Iter != AdditionalUsers.end()) {
595  for (User *U : Iter->second)
596  if (auto *UI = dyn_cast<Instruction>(U))
597  OperandChangedState(UI);
598  }
599  }
600 
601 private:
602  friend class InstVisitor<SCCPSolver>;
603 
604  // visit implementations - Something changed in this instruction. Either an
605  // operand made a transition, or the instruction is newly executable. Change
606  // the value type of I to reflect these changes if appropriate.
607  void visitPHINode(PHINode &I);
608 
609  // Terminators
610 
611  void visitReturnInst(ReturnInst &I);
612  void visitTerminator(Instruction &TI);
613 
614  void visitCastInst(CastInst &I);
615  void visitSelectInst(SelectInst &I);
616  void visitUnaryOperator(Instruction &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 visitCallBrInst (CallBrInst &CBI) {
643  visitCallSite(&CBI);
644  visitTerminator(CBI);
645  }
646 
647  void visitCallSite (CallSite CS);
648  void visitResumeInst (ResumeInst &I) { /*returns void*/ }
649  void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ }
650  void visitFenceInst (FenceInst &I) { /*returns void*/ }
651 
652  void visitInstruction(Instruction &I) {
653  // All the instructions we don't do any special handling for just
654  // go to overdefined.
655  LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n');
656  markOverdefined(&I);
657  }
658 };
659 
660 } // end anonymous namespace
661 
662 // getFeasibleSuccessors - Return a vector of booleans to indicate which
663 // successors are reachable from a given terminator instruction.
664 void SCCPSolver::getFeasibleSuccessors(Instruction &TI,
665  SmallVectorImpl<bool> &Succs) {
666  Succs.resize(TI.getNumSuccessors());
667  if (auto *BI = dyn_cast<BranchInst>(&TI)) {
668  if (BI->isUnconditional()) {
669  Succs[0] = true;
670  return;
671  }
672 
673  LatticeVal BCValue = getValueState(BI->getCondition());
674  ConstantInt *CI = BCValue.getConstantInt();
675  if (!CI) {
676  // Overdefined condition variables, and branches on unfoldable constant
677  // conditions, mean the branch could go either way.
678  if (!BCValue.isUnknown())
679  Succs[0] = Succs[1] = true;
680  return;
681  }
682 
683  // Constant condition variables mean the branch can only go a single way.
684  Succs[CI->isZero()] = true;
685  return;
686  }
687 
688  // Unwinding instructions successors are always executable.
689  if (TI.isExceptionalTerminator()) {
690  Succs.assign(TI.getNumSuccessors(), true);
691  return;
692  }
693 
694  if (auto *SI = dyn_cast<SwitchInst>(&TI)) {
695  if (!SI->getNumCases()) {
696  Succs[0] = true;
697  return;
698  }
699  LatticeVal SCValue = getValueState(SI->getCondition());
700  ConstantInt *CI = SCValue.getConstantInt();
701 
702  if (!CI) { // Overdefined or unknown condition?
703  // All destinations are executable!
704  if (!SCValue.isUnknown())
705  Succs.assign(TI.getNumSuccessors(), true);
706  return;
707  }
708 
709  Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
710  return;
711  }
712 
713  // In case of indirect branch and its address is a blockaddress, we mark
714  // the target as executable.
715  if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) {
716  // Casts are folded by visitCastInst.
717  LatticeVal IBRValue = getValueState(IBR->getAddress());
718  BlockAddress *Addr = IBRValue.getBlockAddress();
719  if (!Addr) { // Overdefined or unknown condition?
720  // All destinations are executable!
721  if (!IBRValue.isUnknown())
722  Succs.assign(TI.getNumSuccessors(), true);
723  return;
724  }
725 
726  BasicBlock* T = Addr->getBasicBlock();
727  assert(Addr->getFunction() == T->getParent() &&
728  "Block address of a different function ?");
729  for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) {
730  // This is the target.
731  if (IBR->getDestination(i) == T) {
732  Succs[i] = true;
733  return;
734  }
735  }
736 
737  // If we didn't find our destination in the IBR successor list, then we
738  // have undefined behavior. Its ok to assume no successor is executable.
739  return;
740  }
741 
742  // In case of callbr, we pessimistically assume that all successors are
743  // feasible.
744  if (isa<CallBrInst>(&TI)) {
745  Succs.assign(TI.getNumSuccessors(), true);
746  return;
747  }
748 
749  LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n');
750  llvm_unreachable("SCCP: Don't know how to handle this terminator!");
751 }
752 
753 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
754 // block to the 'To' basic block is currently feasible.
755 bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
756  // Check if we've called markEdgeExecutable on the edge yet. (We could
757  // be more aggressive and try to consider edges which haven't been marked
758  // yet, but there isn't any need.)
759  return KnownFeasibleEdges.count(Edge(From, To));
760 }
761 
762 // visit Implementations - Something changed in this instruction, either an
763 // operand made a transition, or the instruction is newly executable. Change
764 // the value type of I to reflect these changes if appropriate. This method
765 // makes sure to do the following actions:
766 //
767 // 1. If a phi node merges two constants in, and has conflicting value coming
768 // from different branches, or if the PHI node merges in an overdefined
769 // value, then the PHI node becomes overdefined.
770 // 2. If a phi node merges only constants in, and they all agree on value, the
771 // PHI node becomes a constant value equal to that.
772 // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant
773 // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined
774 // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined
775 // 6. If a conditional branch has a value that is constant, make the selected
776 // destination executable
777 // 7. If a conditional branch has a value that is overdefined, make all
778 // successors executable.
779 void SCCPSolver::visitPHINode(PHINode &PN) {
780  // If this PN returns a struct, just mark the result overdefined.
781  // TODO: We could do a lot better than this if code actually uses this.
782  if (PN.getType()->isStructTy())
783  return (void)markOverdefined(&PN);
784 
785  if (getValueState(&PN).isOverdefined())
786  return; // Quick exit
787 
788  // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
789  // and slow us down a lot. Just mark them overdefined.
790  if (PN.getNumIncomingValues() > 64)
791  return (void)markOverdefined(&PN);
792 
793  // Look at all of the executable operands of the PHI node. If any of them
794  // are overdefined, the PHI becomes overdefined as well. If they are all
795  // constant, and they agree with each other, the PHI becomes the identical
796  // constant. If they are constant and don't agree, the PHI is overdefined.
797  // If there are no executable operands, the PHI remains unknown.
798  Constant *OperandVal = nullptr;
799  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
800  LatticeVal IV = getValueState(PN.getIncomingValue(i));
801  if (IV.isUnknown()) continue; // Doesn't influence PHI node.
802 
803  if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
804  continue;
805 
806  if (IV.isOverdefined()) // PHI node becomes overdefined!
807  return (void)markOverdefined(&PN);
808 
809  if (!OperandVal) { // Grab the first value.
810  OperandVal = IV.getConstant();
811  continue;
812  }
813 
814  // There is already a reachable operand. If we conflict with it,
815  // then the PHI node becomes overdefined. If we agree with it, we
816  // can continue on.
817 
818  // Check to see if there are two different constants merging, if so, the PHI
819  // node is overdefined.
820  if (IV.getConstant() != OperandVal)
821  return (void)markOverdefined(&PN);
822  }
823 
824  // If we exited the loop, this means that the PHI node only has constant
825  // arguments that agree with each other(and OperandVal is the constant) or
826  // OperandVal is null because there are no defined incoming arguments. If
827  // this is the case, the PHI remains unknown.
828  if (OperandVal)
829  markConstant(&PN, OperandVal); // Acquire operand value
830 }
831 
832 void SCCPSolver::visitReturnInst(ReturnInst &I) {
833  if (I.getNumOperands() == 0) return; // ret void
834 
835  Function *F = I.getParent()->getParent();
836  Value *ResultOp = I.getOperand(0);
837 
838  // If we are tracking the return value of this function, merge it in.
839  if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
841  TrackedRetVals.find(F);
842  if (TFRVI != TrackedRetVals.end()) {
843  mergeInValue(TFRVI->second, F, getValueState(ResultOp));
844  return;
845  }
846  }
847 
848  // Handle functions that return multiple values.
849  if (!TrackedMultipleRetVals.empty()) {
850  if (auto *STy = dyn_cast<StructType>(ResultOp->getType()))
851  if (MRVFunctionsTracked.count(F))
852  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
853  mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
854  getStructValueState(ResultOp, i));
855  }
856 }
857 
858 void SCCPSolver::visitTerminator(Instruction &TI) {
859  SmallVector<bool, 16> SuccFeasible;
860  getFeasibleSuccessors(TI, SuccFeasible);
861 
862  BasicBlock *BB = TI.getParent();
863 
864  // Mark all feasible successors executable.
865  for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
866  if (SuccFeasible[i])
867  markEdgeExecutable(BB, TI.getSuccessor(i));
868 }
869 
870 void SCCPSolver::visitCastInst(CastInst &I) {
871  LatticeVal OpSt = getValueState(I.getOperand(0));
872  if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
873  markOverdefined(&I);
874  else if (OpSt.isConstant()) {
875  // Fold the constant as we build.
876  Constant *C = ConstantFoldCastOperand(I.getOpcode(), OpSt.getConstant(),
877  I.getType(), DL);
878  if (isa<UndefValue>(C))
879  return;
880  // Propagate constant value
881  markConstant(&I, C);
882  }
883 }
884 
885 void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
886  // If this returns a struct, mark all elements over defined, we don't track
887  // structs in structs.
888  if (EVI.getType()->isStructTy())
889  return (void)markOverdefined(&EVI);
890 
891  // If this is extracting from more than one level of struct, we don't know.
892  if (EVI.getNumIndices() != 1)
893  return (void)markOverdefined(&EVI);
894 
895  Value *AggVal = EVI.getAggregateOperand();
896  if (AggVal->getType()->isStructTy()) {
897  unsigned i = *EVI.idx_begin();
898  LatticeVal EltVal = getStructValueState(AggVal, i);
899  mergeInValue(getValueState(&EVI), &EVI, EltVal);
900  } else {
901  // Otherwise, must be extracting from an array.
902  return (void)markOverdefined(&EVI);
903  }
904 }
905 
906 void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
907  auto *STy = dyn_cast<StructType>(IVI.getType());
908  if (!STy)
909  return (void)markOverdefined(&IVI);
910 
911  // If this has more than one index, we can't handle it, drive all results to
912  // undef.
913  if (IVI.getNumIndices() != 1)
914  return (void)markOverdefined(&IVI);
915 
916  Value *Aggr = IVI.getAggregateOperand();
917  unsigned Idx = *IVI.idx_begin();
918 
919  // Compute the result based on what we're inserting.
920  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
921  // This passes through all values that aren't the inserted element.
922  if (i != Idx) {
923  LatticeVal EltVal = getStructValueState(Aggr, i);
924  mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
925  continue;
926  }
927 
928  Value *Val = IVI.getInsertedValueOperand();
929  if (Val->getType()->isStructTy())
930  // We don't track structs in structs.
931  markOverdefined(getStructValueState(&IVI, i), &IVI);
932  else {
933  LatticeVal InVal = getValueState(Val);
934  mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
935  }
936  }
937 }
938 
939 void SCCPSolver::visitSelectInst(SelectInst &I) {
940  // If this select returns a struct, just mark the result overdefined.
941  // TODO: We could do a lot better than this if code actually uses this.
942  if (I.getType()->isStructTy())
943  return (void)markOverdefined(&I);
944 
945  LatticeVal CondValue = getValueState(I.getCondition());
946  if (CondValue.isUnknown())
947  return;
948 
949  if (ConstantInt *CondCB = CondValue.getConstantInt()) {
950  Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
951  mergeInValue(&I, getValueState(OpVal));
952  return;
953  }
954 
955  // Otherwise, the condition is overdefined or a constant we can't evaluate.
956  // See if we can produce something better than overdefined based on the T/F
957  // value.
958  LatticeVal TVal = getValueState(I.getTrueValue());
959  LatticeVal FVal = getValueState(I.getFalseValue());
960 
961  // select ?, C, C -> C.
962  if (TVal.isConstant() && FVal.isConstant() &&
963  TVal.getConstant() == FVal.getConstant())
964  return (void)markConstant(&I, FVal.getConstant());
965 
966  if (TVal.isUnknown()) // select ?, undef, X -> X.
967  return (void)mergeInValue(&I, FVal);
968  if (FVal.isUnknown()) // select ?, X, undef -> X.
969  return (void)mergeInValue(&I, TVal);
970  markOverdefined(&I);
971 }
972 
973 // Handle Unary Operators.
974 void SCCPSolver::visitUnaryOperator(Instruction &I) {
975  LatticeVal V0State = getValueState(I.getOperand(0));
976 
977  LatticeVal &IV = ValueState[&I];
978  if (IV.isOverdefined()) return;
979 
980  if (V0State.isConstant()) {
981  Constant *C = ConstantExpr::get(I.getOpcode(), V0State.getConstant());
982 
983  // op Y -> undef.
984  if (isa<UndefValue>(C))
985  return;
986  return (void)markConstant(IV, &I, C);
987  }
988 
989  // If something is undef, wait for it to resolve.
990  if (!V0State.isOverdefined())
991  return;
992 
993  markOverdefined(&I);
994 }
995 
996 // Handle Binary Operators.
997 void SCCPSolver::visitBinaryOperator(Instruction &I) {
998  LatticeVal V1State = getValueState(I.getOperand(0));
999  LatticeVal V2State = getValueState(I.getOperand(1));
1000 
1001  LatticeVal &IV = ValueState[&I];
1002  if (IV.isOverdefined()) return;
1003 
1004  if (V1State.isConstant() && V2State.isConstant()) {
1005  Constant *C = ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
1006  V2State.getConstant());
1007  // X op Y -> undef.
1008  if (isa<UndefValue>(C))
1009  return;
1010  return (void)markConstant(IV, &I, C);
1011  }
1012 
1013  // If something is undef, wait for it to resolve.
1014  if (!V1State.isOverdefined() && !V2State.isOverdefined())
1015  return;
1016 
1017  // Otherwise, one of our operands is overdefined. Try to produce something
1018  // better than overdefined with some tricks.
1019  // If this is 0 / Y, it doesn't matter that the second operand is
1020  // overdefined, and we can replace it with zero.
1021  if (I.getOpcode() == Instruction::UDiv || I.getOpcode() == Instruction::SDiv)
1022  if (V1State.isConstant() && V1State.getConstant()->isNullValue())
1023  return (void)markConstant(IV, &I, V1State.getConstant());
1024 
1025  // If this is:
1026  // -> AND/MUL with 0
1027  // -> OR with -1
1028  // it doesn't matter that the other operand is overdefined.
1029  if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Mul ||
1030  I.getOpcode() == Instruction::Or) {
1031  LatticeVal *NonOverdefVal = nullptr;
1032  if (!V1State.isOverdefined())
1033  NonOverdefVal = &V1State;
1034  else if (!V2State.isOverdefined())
1035  NonOverdefVal = &V2State;
1036 
1037  if (NonOverdefVal) {
1038  if (NonOverdefVal->isUnknown())
1039  return;
1040 
1041  if (I.getOpcode() == Instruction::And ||
1042  I.getOpcode() == Instruction::Mul) {
1043  // X and 0 = 0
1044  // X * 0 = 0
1045  if (NonOverdefVal->getConstant()->isNullValue())
1046  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1047  } else {
1048  // X or -1 = -1
1049  if (ConstantInt *CI = NonOverdefVal->getConstantInt())
1050  if (CI->isMinusOne())
1051  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1052  }
1053  }
1054  }
1055 
1056  markOverdefined(&I);
1057 }
1058 
1059 // Handle ICmpInst instruction.
1060 void SCCPSolver::visitCmpInst(CmpInst &I) {
1061  // Do not cache this lookup, getValueState calls later in the function might
1062  // invalidate the reference.
1063  if (ValueState[&I].isOverdefined()) return;
1064 
1065  Value *Op1 = I.getOperand(0);
1066  Value *Op2 = I.getOperand(1);
1067 
1068  // For parameters, use ParamState which includes constant range info if
1069  // available.
1070  auto V1Param = ParamState.find(Op1);
1071  ValueLatticeElement V1State = (V1Param != ParamState.end())
1072  ? V1Param->second
1073  : getValueState(Op1).toValueLattice();
1074 
1075  auto V2Param = ParamState.find(Op2);
1076  ValueLatticeElement V2State = V2Param != ParamState.end()
1077  ? V2Param->second
1078  : getValueState(Op2).toValueLattice();
1079 
1080  Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
1081  if (C) {
1082  if (isa<UndefValue>(C))
1083  return;
1084  LatticeVal CV;
1085  CV.markConstant(C);
1086  mergeInValue(&I, CV);
1087  return;
1088  }
1089 
1090  // If operands are still unknown, wait for it to resolve.
1091  if (!V1State.isOverdefined() && !V2State.isOverdefined() &&
1092  !ValueState[&I].isConstant())
1093  return;
1094 
1095  markOverdefined(&I);
1096 }
1097 
1098 // Handle getelementptr instructions. If all operands are constants then we
1099 // can turn this into a getelementptr ConstantExpr.
1100 void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
1101  if (ValueState[&I].isOverdefined()) return;
1102 
1103  SmallVector<Constant*, 8> Operands;
1104  Operands.reserve(I.getNumOperands());
1105 
1106  for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
1107  LatticeVal State = getValueState(I.getOperand(i));
1108  if (State.isUnknown())
1109  return; // Operands are not resolved yet.
1110 
1111  if (State.isOverdefined())
1112  return (void)markOverdefined(&I);
1113 
1114  assert(State.isConstant() && "Unknown state!");
1115  Operands.push_back(State.getConstant());
1116  }
1117 
1118  Constant *Ptr = Operands[0];
1119  auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end());
1120  Constant *C =
1122  if (isa<UndefValue>(C))
1123  return;
1124  markConstant(&I, C);
1125 }
1126 
1127 void SCCPSolver::visitStoreInst(StoreInst &SI) {
1128  // If this store is of a struct, ignore it.
1129  if (SI.getOperand(0)->getType()->isStructTy())
1130  return;
1131 
1132  if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
1133  return;
1134 
1135  GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
1137  if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
1138 
1139  // Get the value we are storing into the global, then merge it.
1140  mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
1141  if (I->second.isOverdefined())
1142  TrackedGlobals.erase(I); // No need to keep tracking this!
1143 }
1144 
1145 // Handle load instructions. If the operand is a constant pointer to a constant
1146 // global, we can replace the load with the loaded constant value!
1147 void SCCPSolver::visitLoadInst(LoadInst &I) {
1148  // If this load is of a struct, just mark the result overdefined.
1149  if (I.getType()->isStructTy())
1150  return (void)markOverdefined(&I);
1151 
1152  LatticeVal PtrVal = getValueState(I.getOperand(0));
1153  if (PtrVal.isUnknown()) return; // The pointer is not resolved yet!
1154 
1155  LatticeVal &IV = ValueState[&I];
1156  if (IV.isOverdefined()) return;
1157 
1158  if (!PtrVal.isConstant() || I.isVolatile())
1159  return (void)markOverdefined(IV, &I);
1160 
1161  Constant *Ptr = PtrVal.getConstant();
1162 
1163  // load null is undefined.
1164  if (isa<ConstantPointerNull>(Ptr)) {
1166  return (void)markOverdefined(IV, &I);
1167  else
1168  return;
1169  }
1170 
1171  // Transform load (constant global) into the value loaded.
1172  if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) {
1173  if (!TrackedGlobals.empty()) {
1174  // If we are tracking this global, merge in the known value for it.
1176  TrackedGlobals.find(GV);
1177  if (It != TrackedGlobals.end()) {
1178  mergeInValue(IV, &I, It->second);
1179  return;
1180  }
1181  }
1182  }
1183 
1184  // Transform load from a constant into a constant if possible.
1185  if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) {
1186  if (isa<UndefValue>(C))
1187  return;
1188  return (void)markConstant(IV, &I, C);
1189  }
1190 
1191  // Otherwise we cannot say for certain what value this load will produce.
1192  // Bail out.
1193  markOverdefined(IV, &I);
1194 }
1195 
1196 void SCCPSolver::visitCallSite(CallSite CS) {
1197  Function *F = CS.getCalledFunction();
1198  Instruction *I = CS.getInstruction();
1199 
1200  if (auto *II = dyn_cast<IntrinsicInst>(I)) {
1201  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
1202  if (ValueState[I].isOverdefined())
1203  return;
1204 
1205  auto *PI = getPredicateInfoFor(I);
1206  if (!PI)
1207  return;
1208 
1209  Value *CopyOf = I->getOperand(0);
1210  auto *PBranch = dyn_cast<PredicateBranch>(PI);
1211  if (!PBranch) {
1212  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1213  return;
1214  }
1215 
1216  Value *Cond = PBranch->Condition;
1217 
1218  // Everything below relies on the condition being a comparison.
1219  auto *Cmp = dyn_cast<CmpInst>(Cond);
1220  if (!Cmp) {
1221  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1222  return;
1223  }
1224 
1225  Value *CmpOp0 = Cmp->getOperand(0);
1226  Value *CmpOp1 = Cmp->getOperand(1);
1227  if (CopyOf != CmpOp0 && CopyOf != CmpOp1) {
1228  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1229  return;
1230  }
1231 
1232  if (CmpOp0 != CopyOf)
1233  std::swap(CmpOp0, CmpOp1);
1234 
1235  LatticeVal OriginalVal = getValueState(CopyOf);
1236  LatticeVal EqVal = getValueState(CmpOp1);
1237  LatticeVal &IV = ValueState[I];
1238  if (PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_EQ) {
1239  addAdditionalUser(CmpOp1, I);
1240  if (OriginalVal.isConstant())
1241  mergeInValue(IV, I, OriginalVal);
1242  else
1243  mergeInValue(IV, I, EqVal);
1244  return;
1245  }
1246  if (!PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_NE) {
1247  addAdditionalUser(CmpOp1, I);
1248  if (OriginalVal.isConstant())
1249  mergeInValue(IV, I, OriginalVal);
1250  else
1251  mergeInValue(IV, I, EqVal);
1252  return;
1253  }
1254 
1255  return (void)mergeInValue(IV, I, getValueState(CopyOf));
1256  }
1257  }
1258 
1259  // The common case is that we aren't tracking the callee, either because we
1260  // are not doing interprocedural analysis or the callee is indirect, or is
1261  // external. Handle these cases first.
1262  if (!F || F->isDeclaration()) {
1263 CallOverdefined:
1264  // Void return and not tracking callee, just bail.
1265  if (I->getType()->isVoidTy()) return;
1266 
1267  // Otherwise, if we have a single return value case, and if the function is
1268  // a declaration, maybe we can constant fold it.
1269  if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
1270  canConstantFoldCallTo(cast<CallBase>(CS.getInstruction()), F)) {
1271  SmallVector<Constant*, 8> Operands;
1272  for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
1273  AI != E; ++AI) {
1274  if (AI->get()->getType()->isStructTy())
1275  return markOverdefined(I); // Can't handle struct args.
1276  LatticeVal State = getValueState(*AI);
1277 
1278  if (State.isUnknown())
1279  return; // Operands are not resolved yet.
1280  if (State.isOverdefined())
1281  return (void)markOverdefined(I);
1282  assert(State.isConstant() && "Unknown state!");
1283  Operands.push_back(State.getConstant());
1284  }
1285 
1286  if (getValueState(I).isOverdefined())
1287  return;
1288 
1289  // If we can constant fold this, mark the result of the call as a
1290  // constant.
1291  if (Constant *C = ConstantFoldCall(cast<CallBase>(CS.getInstruction()), F,
1292  Operands, TLI)) {
1293  // call -> undef.
1294  if (isa<UndefValue>(C))
1295  return;
1296  return (void)markConstant(I, C);
1297  }
1298  }
1299 
1300  // Otherwise, we don't know anything about this call, mark it overdefined.
1301  return (void)markOverdefined(I);
1302  }
1303 
1304  // If this is a local function that doesn't have its address taken, mark its
1305  // entry block executable and merge in the actual arguments to the call into
1306  // the formal arguments of the function.
1307  if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
1308  MarkBlockExecutable(&F->front());
1309 
1310  // Propagate information from this call site into the callee.
1311  CallSite::arg_iterator CAI = CS.arg_begin();
1312  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
1313  AI != E; ++AI, ++CAI) {
1314  // If this argument is byval, and if the function is not readonly, there
1315  // will be an implicit copy formed of the input aggregate.
1316  if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
1317  markOverdefined(&*AI);
1318  continue;
1319  }
1320 
1321  if (auto *STy = dyn_cast<StructType>(AI->getType())) {
1322  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1323  LatticeVal CallArg = getStructValueState(*CAI, i);
1324  mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
1325  }
1326  } else {
1327  // Most other parts of the Solver still only use the simpler value
1328  // lattice, so we propagate changes for parameters to both lattices.
1329  LatticeVal ConcreteArgument = getValueState(*CAI);
1330  bool ParamChanged =
1331  getParamState(&*AI).mergeIn(ConcreteArgument.toValueLattice(), DL);
1332  bool ValueChanged = mergeInValue(&*AI, ConcreteArgument);
1333  // Add argument to work list, if the state of a parameter changes but
1334  // ValueState does not change (because it is already overdefined there),
1335  // We have to take changes in ParamState into account, as it is used
1336  // when evaluating Cmp instructions.
1337  if (!ValueChanged && ParamChanged)
1338  pushToWorkList(ValueState[&*AI], &*AI);
1339  }
1340  }
1341  }
1342 
1343  // If this is a single/zero retval case, see if we're tracking the function.
1344  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
1345  if (!MRVFunctionsTracked.count(F))
1346  goto CallOverdefined; // Not tracking this callee.
1347 
1348  // If we are tracking this callee, propagate the result of the function
1349  // into this call site.
1350  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1351  mergeInValue(getStructValueState(I, i), I,
1352  TrackedMultipleRetVals[std::make_pair(F, i)]);
1353  } else {
1354  DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
1355  if (TFRVI == TrackedRetVals.end())
1356  goto CallOverdefined; // Not tracking this callee.
1357 
1358  // If so, propagate the return value of the callee into this call result.
1359  mergeInValue(I, TFRVI->second);
1360  }
1361 }
1362 
1363 void SCCPSolver::Solve() {
1364  // Process the work lists until they are empty!
1365  while (!BBWorkList.empty() || !InstWorkList.empty() ||
1366  !OverdefinedInstWorkList.empty()) {
1367  // Process the overdefined instruction's work list first, which drives other
1368  // things to overdefined more quickly.
1369  while (!OverdefinedInstWorkList.empty()) {
1370  Value *I = OverdefinedInstWorkList.pop_back_val();
1371 
1372  LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
1373 
1374  // "I" got into the work list because it either made the transition from
1375  // bottom to constant, or to overdefined.
1376  //
1377  // Anything on this worklist that is overdefined need not be visited
1378  // since all of its users will have already been marked as overdefined
1379  // Update all of the users of this instruction's value.
1380  //
1381  markUsersAsChanged(I);
1382  }
1383 
1384  // Process the instruction work list.
1385  while (!InstWorkList.empty()) {
1386  Value *I = InstWorkList.pop_back_val();
1387 
1388  LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
1389 
1390  // "I" got into the work list because it made the transition from undef to
1391  // constant.
1392  //
1393  // Anything on this worklist that is overdefined need not be visited
1394  // since all of its users will have already been marked as overdefined.
1395  // Update all of the users of this instruction's value.
1396  //
1397  if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
1398  markUsersAsChanged(I);
1399  }
1400 
1401  // Process the basic block work list.
1402  while (!BBWorkList.empty()) {
1403  BasicBlock *BB = BBWorkList.back();
1404  BBWorkList.pop_back();
1405 
1406  LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
1407 
1408  // Notify all instructions in this basic block that they are newly
1409  // executable.
1410  visit(BB);
1411  }
1412  }
1413 }
1414 
1415 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
1416 /// that branches on undef values cannot reach any of their successors.
1417 /// However, this is not a safe assumption. After we solve dataflow, this
1418 /// method should be use to handle this. If this returns true, the solver
1419 /// should be rerun.
1420 ///
1421 /// This method handles this by finding an unresolved branch and marking it one
1422 /// of the edges from the block as being feasible, even though the condition
1423 /// doesn't say it would otherwise be. This allows SCCP to find the rest of the
1424 /// CFG and only slightly pessimizes the analysis results (by marking one,
1425 /// potentially infeasible, edge feasible). This cannot usefully modify the
1426 /// constraints on the condition of the branch, as that would impact other users
1427 /// of the value.
1428 ///
1429 /// This scan also checks for values that use undefs, whose results are actually
1430 /// defined. For example, 'zext i8 undef to i32' should produce all zeros
1431 /// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
1432 /// even if X isn't defined.
1433 bool SCCPSolver::ResolvedUndefsIn(Function &F) {
1434  for (BasicBlock &BB : F) {
1435  if (!BBExecutable.count(&BB))
1436  continue;
1437 
1438  for (Instruction &I : BB) {
1439  // Look for instructions which produce undef values.
1440  if (I.getType()->isVoidTy()) continue;
1441 
1442  if (auto *STy = dyn_cast<StructType>(I.getType())) {
1443  // Only a few things that can be structs matter for undef.
1444 
1445  // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
1446  if (CallSite CS = CallSite(&I))
1447  if (Function *F = CS.getCalledFunction())
1448  if (MRVFunctionsTracked.count(F))
1449  continue;
1450 
1451  // extractvalue and insertvalue don't need to be marked; they are
1452  // tracked as precisely as their operands.
1453  if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
1454  continue;
1455 
1456  // Send the results of everything else to overdefined. We could be
1457  // more precise than this but it isn't worth bothering.
1458  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1459  LatticeVal &LV = getStructValueState(&I, i);
1460  if (LV.isUnknown())
1461  markOverdefined(LV, &I);
1462  }
1463  continue;
1464  }
1465 
1466  LatticeVal &LV = getValueState(&I);
1467  if (!LV.isUnknown()) continue;
1468 
1469  // extractvalue is safe; check here because the argument is a struct.
1470  if (isa<ExtractValueInst>(I))
1471  continue;
1472 
1473  // Compute the operand LatticeVals, for convenience below.
1474  // Anything taking a struct is conservatively assumed to require
1475  // overdefined markings.
1476  if (I.getOperand(0)->getType()->isStructTy()) {
1477  markOverdefined(&I);
1478  return true;
1479  }
1480  LatticeVal Op0LV = getValueState(I.getOperand(0));
1481  LatticeVal Op1LV;
1482  if (I.getNumOperands() == 2) {
1483  if (I.getOperand(1)->getType()->isStructTy()) {
1484  markOverdefined(&I);
1485  return true;
1486  }
1487 
1488  Op1LV = getValueState(I.getOperand(1));
1489  }
1490  // If this is an instructions whose result is defined even if the input is
1491  // not fully defined, propagate the information.
1492  Type *ITy = I.getType();
1493  switch (I.getOpcode()) {
1494  case Instruction::Add:
1495  case Instruction::Sub:
1496  case Instruction::Trunc:
1497  case Instruction::FPTrunc:
1498  case Instruction::BitCast:
1499  break; // Any undef -> undef
1500  case Instruction::FSub:
1501  case Instruction::FAdd:
1502  case Instruction::FMul:
1503  case Instruction::FDiv:
1504  case Instruction::FRem:
1505  // Floating-point binary operation: be conservative.
1506  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1507  markForcedConstant(&I, Constant::getNullValue(ITy));
1508  else
1509  markOverdefined(&I);
1510  return true;
1511  case Instruction::FNeg:
1512  break; // fneg undef -> undef
1513  case Instruction::ZExt:
1514  case Instruction::SExt:
1515  case Instruction::FPToUI:
1516  case Instruction::FPToSI:
1517  case Instruction::FPExt:
1518  case Instruction::PtrToInt:
1519  case Instruction::IntToPtr:
1520  case Instruction::SIToFP:
1521  case Instruction::UIToFP:
1522  // undef -> 0; some outputs are impossible
1523  markForcedConstant(&I, Constant::getNullValue(ITy));
1524  return true;
1525  case Instruction::Mul:
1526  case Instruction::And:
1527  // Both operands undef -> undef
1528  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1529  break;
1530  // undef * X -> 0. X could be zero.
1531  // undef & X -> 0. X could be zero.
1532  markForcedConstant(&I, Constant::getNullValue(ITy));
1533  return true;
1534  case Instruction::Or:
1535  // Both operands undef -> undef
1536  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1537  break;
1538  // undef | X -> -1. X could be -1.
1539  markForcedConstant(&I, Constant::getAllOnesValue(ITy));
1540  return true;
1541  case Instruction::Xor:
1542  // undef ^ undef -> 0; strictly speaking, this is not strictly
1543  // necessary, but we try to be nice to people who expect this
1544  // behavior in simple cases
1545  if (Op0LV.isUnknown() && Op1LV.isUnknown()) {
1546  markForcedConstant(&I, Constant::getNullValue(ITy));
1547  return true;
1548  }
1549  // undef ^ X -> undef
1550  break;
1551  case Instruction::SDiv:
1552  case Instruction::UDiv:
1553  case Instruction::SRem:
1554  case Instruction::URem:
1555  // X / undef -> undef. No change.
1556  // X % undef -> undef. No change.
1557  if (Op1LV.isUnknown()) break;
1558 
1559  // X / 0 -> undef. No change.
1560  // X % 0 -> undef. No change.
1561  if (Op1LV.isConstant() && Op1LV.getConstant()->isZeroValue())
1562  break;
1563 
1564  // undef / X -> 0. X could be maxint.
1565  // undef % X -> 0. X could be 1.
1566  markForcedConstant(&I, Constant::getNullValue(ITy));
1567  return true;
1568  case Instruction::AShr:
1569  // X >>a undef -> undef.
1570  if (Op1LV.isUnknown()) break;
1571 
1572  // Shifting by the bitwidth or more is undefined.
1573  if (Op1LV.isConstant()) {
1574  if (auto *ShiftAmt = Op1LV.getConstantInt())
1575  if (ShiftAmt->getLimitedValue() >=
1576  ShiftAmt->getType()->getScalarSizeInBits())
1577  break;
1578  }
1579 
1580  // undef >>a X -> 0
1581  markForcedConstant(&I, Constant::getNullValue(ITy));
1582  return true;
1583  case Instruction::LShr:
1584  case Instruction::Shl:
1585  // X << undef -> undef.
1586  // X >> undef -> undef.
1587  if (Op1LV.isUnknown()) break;
1588 
1589  // Shifting by the bitwidth or more is undefined.
1590  if (Op1LV.isConstant()) {
1591  if (auto *ShiftAmt = Op1LV.getConstantInt())
1592  if (ShiftAmt->getLimitedValue() >=
1593  ShiftAmt->getType()->getScalarSizeInBits())
1594  break;
1595  }
1596 
1597  // undef << X -> 0
1598  // undef >> X -> 0
1599  markForcedConstant(&I, Constant::getNullValue(ITy));
1600  return true;
1601  case Instruction::Select:
1602  Op1LV = getValueState(I.getOperand(1));
1603  // undef ? X : Y -> X or Y. There could be commonality between X/Y.
1604  if (Op0LV.isUnknown()) {
1605  if (!Op1LV.isConstant()) // Pick the constant one if there is any.
1606  Op1LV = getValueState(I.getOperand(2));
1607  } else if (Op1LV.isUnknown()) {
1608  // c ? undef : undef -> undef. No change.
1609  Op1LV = getValueState(I.getOperand(2));
1610  if (Op1LV.isUnknown())
1611  break;
1612  // Otherwise, c ? undef : x -> x.
1613  } else {
1614  // Leave Op1LV as Operand(1)'s LatticeValue.
1615  }
1616 
1617  if (Op1LV.isConstant())
1618  markForcedConstant(&I, Op1LV.getConstant());
1619  else
1620  markOverdefined(&I);
1621  return true;
1622  case Instruction::Load:
1623  // A load here means one of two things: a load of undef from a global,
1624  // a load from an unknown pointer. Either way, having it return undef
1625  // is okay.
1626  break;
1627  case Instruction::ICmp:
1628  // X == undef -> undef. Other comparisons get more complicated.
1629  Op0LV = getValueState(I.getOperand(0));
1630  Op1LV = getValueState(I.getOperand(1));
1631 
1632  if ((Op0LV.isUnknown() || Op1LV.isUnknown()) &&
1633  cast<ICmpInst>(&I)->isEquality())
1634  break;
1635  markOverdefined(&I);
1636  return true;
1637  case Instruction::Call:
1638  case Instruction::Invoke:
1639  case Instruction::CallBr:
1640  // There are two reasons a call can have an undef result
1641  // 1. It could be tracked.
1642  // 2. It could be constant-foldable.
1643  // Because of the way we solve return values, tracked calls must
1644  // never be marked overdefined in ResolvedUndefsIn.
1645  if (Function *F = CallSite(&I).getCalledFunction())
1646  if (TrackedRetVals.count(F))
1647  break;
1648 
1649  // If the call is constant-foldable, we mark it overdefined because
1650  // we do not know what return values are valid.
1651  markOverdefined(&I);
1652  return true;
1653  default:
1654  // If we don't know what should happen here, conservatively mark it
1655  // overdefined.
1656  markOverdefined(&I);
1657  return true;
1658  }
1659  }
1660 
1661  // Check to see if we have a branch or switch on an undefined value. If so
1662  // we force the branch to go one way or the other to make the successor
1663  // values live. It doesn't really matter which way we force it.
1664  Instruction *TI = BB.getTerminator();
1665  if (auto *BI = dyn_cast<BranchInst>(TI)) {
1666  if (!BI->isConditional()) continue;
1667  if (!getValueState(BI->getCondition()).isUnknown())
1668  continue;
1669 
1670  // If the input to SCCP is actually branch on undef, fix the undef to
1671  // false.
1672  if (isa<UndefValue>(BI->getCondition())) {
1673  BI->setCondition(ConstantInt::getFalse(BI->getContext()));
1674  markEdgeExecutable(&BB, TI->getSuccessor(1));
1675  return true;
1676  }
1677 
1678  // Otherwise, it is a branch on a symbolic value which is currently
1679  // considered to be undef. Make sure some edge is executable, so a
1680  // branch on "undef" always flows somewhere.
1681  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1682  BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
1683  if (markEdgeExecutable(&BB, DefaultSuccessor))
1684  return true;
1685 
1686  continue;
1687  }
1688 
1689  if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
1690  // Indirect branch with no successor ?. Its ok to assume it branches
1691  // to no target.
1692  if (IBR->getNumSuccessors() < 1)
1693  continue;
1694 
1695  if (!getValueState(IBR->getAddress()).isUnknown())
1696  continue;
1697 
1698  // If the input to SCCP is actually branch on undef, fix the undef to
1699  // the first successor of the indirect branch.
1700  if (isa<UndefValue>(IBR->getAddress())) {
1701  IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
1702  markEdgeExecutable(&BB, IBR->getSuccessor(0));
1703  return true;
1704  }
1705 
1706  // Otherwise, it is a branch on a symbolic value which is currently
1707  // considered to be undef. Make sure some edge is executable, so a
1708  // branch on "undef" always flows somewhere.
1709  // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
1710  // we can assume the branch has undefined behavior instead.
1711  BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
1712  if (markEdgeExecutable(&BB, DefaultSuccessor))
1713  return true;
1714 
1715  continue;
1716  }
1717 
1718  if (auto *SI = dyn_cast<SwitchInst>(TI)) {
1719  if (!SI->getNumCases() || !getValueState(SI->getCondition()).isUnknown())
1720  continue;
1721 
1722  // If the input to SCCP is actually switch on undef, fix the undef to
1723  // the first constant.
1724  if (isa<UndefValue>(SI->getCondition())) {
1725  SI->setCondition(SI->case_begin()->getCaseValue());
1726  markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
1727  return true;
1728  }
1729 
1730  // Otherwise, it is a branch on a symbolic value which is currently
1731  // considered to be undef. Make sure some edge is executable, so a
1732  // branch on "undef" always flows somewhere.
1733  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1734  BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
1735  if (markEdgeExecutable(&BB, DefaultSuccessor))
1736  return true;
1737 
1738  continue;
1739  }
1740  }
1741 
1742  return false;
1743 }
1744 
1745 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
1746  Constant *Const = nullptr;
1747  if (V->getType()->isStructTy()) {
1748  std::vector<LatticeVal> IVs = Solver.getStructLatticeValueFor(V);
1749  if (llvm::any_of(IVs,
1750  [](const LatticeVal &LV) { return LV.isOverdefined(); }))
1751  return false;
1752  std::vector<Constant *> ConstVals;
1753  auto *ST = dyn_cast<StructType>(V->getType());
1754  for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1755  LatticeVal V = IVs[i];
1756  ConstVals.push_back(V.isConstant()
1757  ? V.getConstant()
1758  : UndefValue::get(ST->getElementType(i)));
1759  }
1760  Const = ConstantStruct::get(ST, ConstVals);
1761  } else {
1762  const LatticeVal &IV = Solver.getLatticeValueFor(V);
1763  if (IV.isOverdefined())
1764  return false;
1765 
1766  Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
1767  }
1768  assert(Const && "Constant is nullptr here!");
1769 
1770  // Replacing `musttail` instructions with constant breaks `musttail` invariant
1771  // unless the call itself can be removed
1772  CallInst *CI = dyn_cast<CallInst>(V);
1773  if (CI && CI->isMustTailCall() && !CI->isSafeToRemove()) {
1774  CallSite CS(CI);
1775  Function *F = CS.getCalledFunction();
1776 
1777  // Don't zap returns of the callee
1778  if (F)
1779  Solver.AddMustTailCallee(F);
1780 
1781  LLVM_DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI
1782  << " as a constant\n");
1783  return false;
1784  }
1785 
1786  LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
1787 
1788  // Replaces all of the uses of a variable with uses of the constant.
1789  V->replaceAllUsesWith(Const);
1790  return true;
1791 }
1792 
1793 // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
1794 // and return true if the function was modified.
1795 static bool runSCCP(Function &F, const DataLayout &DL,
1796  const TargetLibraryInfo *TLI) {
1797  LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
1798  SCCPSolver Solver(DL, TLI);
1799 
1800  // Mark the first block of the function as being executable.
1801  Solver.MarkBlockExecutable(&F.front());
1802 
1803  // Mark all arguments to the function as being overdefined.
1804  for (Argument &AI : F.args())
1805  Solver.markOverdefined(&AI);
1806 
1807  // Solve for constants.
1808  bool ResolvedUndefs = true;
1809  while (ResolvedUndefs) {
1810  Solver.Solve();
1811  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n");
1812  ResolvedUndefs = Solver.ResolvedUndefsIn(F);
1813  }
1814 
1815  bool MadeChanges = false;
1816 
1817  // If we decided that there are basic blocks that are dead in this function,
1818  // delete their contents now. Note that we cannot actually delete the blocks,
1819  // as we cannot modify the CFG of the function.
1820 
1821  for (BasicBlock &BB : F) {
1822  if (!Solver.isBlockExecutable(&BB)) {
1823  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1824 
1825  ++NumDeadBlocks;
1826  NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB);
1827 
1828  MadeChanges = true;
1829  continue;
1830  }
1831 
1832  // Iterate over all of the instructions in a function, replacing them with
1833  // constants if we have found them to be of constant values.
1834  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
1835  Instruction *Inst = &*BI++;
1836  if (Inst->getType()->isVoidTy() || Inst->isTerminator())
1837  continue;
1838 
1839  if (tryToReplaceWithConstant(Solver, Inst)) {
1840  if (isInstructionTriviallyDead(Inst))
1841  Inst->eraseFromParent();
1842  // Hey, we just changed something!
1843  MadeChanges = true;
1844  ++NumInstRemoved;
1845  }
1846  }
1847  }
1848 
1849  return MadeChanges;
1850 }
1851 
1853  const DataLayout &DL = F.getParent()->getDataLayout();
1854  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
1855  if (!runSCCP(F, DL, &TLI))
1856  return PreservedAnalyses::all();
1857 
1858  auto PA = PreservedAnalyses();
1859  PA.preserve<GlobalsAA>();
1860  PA.preserveSet<CFGAnalyses>();
1861  return PA;
1862 }
1863 
1864 namespace {
1865 
1866 //===--------------------------------------------------------------------===//
1867 //
1868 /// SCCP Class - This class uses the SCCPSolver to implement a per-function
1869 /// Sparse Conditional Constant Propagator.
1870 ///
1871 class SCCPLegacyPass : public FunctionPass {
1872 public:
1873  // Pass identification, replacement for typeid
1874  static char ID;
1875 
1876  SCCPLegacyPass() : FunctionPass(ID) {
1878  }
1879 
1880  void getAnalysisUsage(AnalysisUsage &AU) const override {
1883  AU.setPreservesCFG();
1884  }
1885 
1886  // runOnFunction - Run the Sparse Conditional Constant Propagation
1887  // algorithm, and return true if the function was modified.
1888  bool runOnFunction(Function &F) override {
1889  if (skipFunction(F))
1890  return false;
1891  const DataLayout &DL = F.getParent()->getDataLayout();
1892  const TargetLibraryInfo *TLI =
1893  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1894  return runSCCP(F, DL, TLI);
1895  }
1896 };
1897 
1898 } // end anonymous namespace
1899 
1900 char SCCPLegacyPass::ID = 0;
1901 
1902 INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp",
1903  "Sparse Conditional Constant Propagation", false, false)
1905 INITIALIZE_PASS_END(SCCPLegacyPass, "sccp",
1906  "Sparse Conditional Constant Propagation", false, false)
1907 
1908 // createSCCPPass - This is the public interface to this file.
1909 FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); }
1910 
1912  SmallVector<ReturnInst *, 8> &ReturnsToZap,
1913  SCCPSolver &Solver) {
1914  // We can only do this if we know that nothing else can call the function.
1915  if (!Solver.isArgumentTrackedFunction(&F))
1916  return;
1917 
1918  // There is a non-removable musttail call site of this function. Zapping
1919  // returns is not allowed.
1920  if (Solver.isMustTailCallee(&F)) {
1921  LLVM_DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName()
1922  << " due to present musttail call of it\n");
1923  return;
1924  }
1925 
1926  for (BasicBlock &BB : F) {
1927  if (CallInst *CI = BB.getTerminatingMustTailCall()) {
1928  LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "
1929  << "musttail call : " << *CI << "\n");
1930  (void)CI;
1931  return;
1932  }
1933 
1934  if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1935  if (!isa<UndefValue>(RI->getOperand(0)))
1936  ReturnsToZap.push_back(RI);
1937  }
1938 }
1939 
1940 // Update the condition for terminators that are branching on indeterminate
1941 // values, forcing them to use a specific edge.
1942 static void forceIndeterminateEdge(Instruction* I, SCCPSolver &Solver) {
1943  BasicBlock *Dest = nullptr;
1944  Constant *C = nullptr;
1945  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
1946  if (!isa<ConstantInt>(SI->getCondition())) {
1947  // Indeterminate switch; use first case value.
1948  Dest = SI->case_begin()->getCaseSuccessor();
1949  C = SI->case_begin()->getCaseValue();
1950  }
1951  } else if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
1952  if (!isa<ConstantInt>(BI->getCondition())) {
1953  // Indeterminate branch; use false.
1954  Dest = BI->getSuccessor(1);
1955  C = ConstantInt::getFalse(BI->getContext());
1956  }
1957  } else if (IndirectBrInst *IBR = dyn_cast<IndirectBrInst>(I)) {
1958  if (!isa<BlockAddress>(IBR->getAddress()->stripPointerCasts())) {
1959  // Indeterminate indirectbr; use successor 0.
1960  Dest = IBR->getSuccessor(0);
1961  C = BlockAddress::get(IBR->getSuccessor(0));
1962  }
1963  } else {
1964  llvm_unreachable("Unexpected terminator instruction");
1965  }
1966  if (C) {
1967  assert(Solver.isEdgeFeasible(I->getParent(), Dest) &&
1968  "Didn't find feasible edge?");
1969  (void)Dest;
1970 
1971  I->setOperand(0, C);
1972  }
1973 }
1974 
1976  Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI,
1977  function_ref<AnalysisResultsForFn(Function &)> getAnalysis) {
1978  SCCPSolver Solver(DL, TLI);
1979 
1980  // Loop over all functions, marking arguments to those with their addresses
1981  // taken or that are external as overdefined.
1982  for (Function &F : M) {
1983  if (F.isDeclaration())
1984  continue;
1985 
1986  Solver.addAnalysis(F, getAnalysis(F));
1987 
1988  // Determine if we can track the function's return values. If so, add the
1989  // function to the solver's set of return-tracked functions.
1991  Solver.AddTrackedFunction(&F);
1992 
1993  // Determine if we can track the function's arguments. If so, add the
1994  // function to the solver's set of argument-tracked functions.
1996  Solver.AddArgumentTrackedFunction(&F);
1997  continue;
1998  }
1999 
2000  // Assume the function is called.
2001  Solver.MarkBlockExecutable(&F.front());
2002 
2003  // Assume nothing about the incoming arguments.
2004  for (Argument &AI : F.args())
2005  Solver.markOverdefined(&AI);
2006  }
2007 
2008  // Determine if we can track any of the module's global variables. If so, add
2009  // the global variables we can track to the solver's set of tracked global
2010  // variables.
2011  for (GlobalVariable &G : M.globals()) {
2012  G.removeDeadConstantUsers();
2014  Solver.TrackValueOfGlobalVariable(&G);
2015  }
2016 
2017  // Solve for constants.
2018  bool ResolvedUndefs = true;
2019  Solver.Solve();
2020  while (ResolvedUndefs) {
2021  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n");
2022  ResolvedUndefs = false;
2023  for (Function &F : M)
2024  if (Solver.ResolvedUndefsIn(F)) {
2025  // We run Solve() after we resolved an undef in a function, because
2026  // we might deduce a fact that eliminates an undef in another function.
2027  Solver.Solve();
2028  ResolvedUndefs = true;
2029  }
2030  }
2031 
2032  bool MadeChanges = false;
2033 
2034  // Iterate over all of the instructions in the module, replacing them with
2035  // constants if we have found them to be of constant values.
2036 
2037  for (Function &F : M) {
2038  if (F.isDeclaration())
2039  continue;
2040 
2041  SmallVector<BasicBlock *, 512> BlocksToErase;
2042 
2043  if (Solver.isBlockExecutable(&F.front()))
2044  for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
2045  ++AI) {
2046  if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
2047  ++IPNumArgsElimed;
2048  continue;
2049  }
2050  }
2051 
2052  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
2053  if (!Solver.isBlockExecutable(&*BB)) {
2054  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
2055  ++NumDeadBlocks;
2056 
2057  MadeChanges = true;
2058 
2059  if (&*BB != &F.front())
2060  BlocksToErase.push_back(&*BB);
2061  continue;
2062  }
2063 
2064  for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
2065  Instruction *Inst = &*BI++;
2066  if (Inst->getType()->isVoidTy())
2067  continue;
2068  if (tryToReplaceWithConstant(Solver, Inst)) {
2069  if (Inst->isSafeToRemove())
2070  Inst->eraseFromParent();
2071  // Hey, we just changed something!
2072  MadeChanges = true;
2073  ++IPNumInstRemoved;
2074  }
2075  }
2076  }
2077 
2078  DomTreeUpdater DTU = Solver.getDTU(F);
2079  // Change dead blocks to unreachable. We do it after replacing constants
2080  // in all executable blocks, because changeToUnreachable may remove PHI
2081  // nodes in executable blocks we found values for. The function's entry
2082  // block is not part of BlocksToErase, so we have to handle it separately.
2083  for (BasicBlock *BB : BlocksToErase) {
2084  NumInstRemoved +=
2085  changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false,
2086  /*PreserveLCSSA=*/false, &DTU);
2087  }
2088  if (!Solver.isBlockExecutable(&F.front()))
2089  NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
2090  /*UseLLVMTrap=*/false,
2091  /*PreserveLCSSA=*/false, &DTU);
2092 
2093  // Now that all instructions in the function are constant folded,
2094  // use ConstantFoldTerminator to get rid of in-edges, record DT updates and
2095  // delete dead BBs.
2096  for (BasicBlock *DeadBB : BlocksToErase) {
2097  // If there are any PHI nodes in this successor, drop entries for BB now.
2098  for (Value::user_iterator UI = DeadBB->user_begin(),
2099  UE = DeadBB->user_end();
2100  UI != UE;) {
2101  // Grab the user and then increment the iterator early, as the user
2102  // will be deleted. Step past all adjacent uses from the same user.
2103  auto *I = dyn_cast<Instruction>(*UI);
2104  do { ++UI; } while (UI != UE && *UI == I);
2105 
2106  // Ignore blockaddress users; BasicBlock's dtor will handle them.
2107  if (!I) continue;
2108 
2109  // If we have forced an edge for an indeterminate value, then force the
2110  // terminator to fold to that edge.
2111  forceIndeterminateEdge(I, Solver);
2112  BasicBlock *InstBB = I->getParent();
2113  bool Folded = ConstantFoldTerminator(InstBB,
2114  /*DeleteDeadConditions=*/false,
2115  /*TLI=*/nullptr, &DTU);
2116  assert(Folded &&
2117  "Expect TermInst on constantint or blockaddress to be folded");
2118  (void) Folded;
2119  // If we folded the terminator to an unconditional branch to another
2120  // dead block, replace it with Unreachable, to avoid trying to fold that
2121  // branch again.
2122  BranchInst *BI = cast<BranchInst>(InstBB->getTerminator());
2123  if (BI && BI->isUnconditional() &&
2124  !Solver.isBlockExecutable(BI->getSuccessor(0))) {
2125  InstBB->getTerminator()->eraseFromParent();
2126  new UnreachableInst(InstBB->getContext(), InstBB);
2127  }
2128  }
2129  // Mark dead BB for deletion.
2130  DTU.deleteBB(DeadBB);
2131  }
2132 
2133  for (BasicBlock &BB : F) {
2134  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
2135  Instruction *Inst = &*BI++;
2136  if (Solver.getPredicateInfoFor(Inst)) {
2137  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
2138  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
2139  Value *Op = II->getOperand(0);
2140  Inst->replaceAllUsesWith(Op);
2141  Inst->eraseFromParent();
2142  }
2143  }
2144  }
2145  }
2146  }
2147  }
2148 
2149  // If we inferred constant or undef return values for a function, we replaced
2150  // all call uses with the inferred value. This means we don't need to bother
2151  // actually returning anything from the function. Replace all return
2152  // instructions with return undef.
2153  //
2154  // Do this in two stages: first identify the functions we should process, then
2155  // actually zap their returns. This is important because we can only do this
2156  // if the address of the function isn't taken. In cases where a return is the
2157  // last use of a function, the order of processing functions would affect
2158  // whether other functions are optimizable.
2159  SmallVector<ReturnInst*, 8> ReturnsToZap;
2160 
2161  const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
2162  for (const auto &I : RV) {
2163  Function *F = I.first;
2164  if (I.second.isOverdefined() || F->getReturnType()->isVoidTy())
2165  continue;
2166  findReturnsToZap(*F, ReturnsToZap, Solver);
2167  }
2168 
2169  for (const auto &F : Solver.getMRVFunctionsTracked()) {
2170  assert(F->getReturnType()->isStructTy() &&
2171  "The return type should be a struct");
2172  StructType *STy = cast<StructType>(F->getReturnType());
2173  if (Solver.isStructLatticeConstant(F, STy))
2174  findReturnsToZap(*F, ReturnsToZap, Solver);
2175  }
2176 
2177  // Zap all returns which we've identified as zap to change.
2178  for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
2179  Function *F = ReturnsToZap[i]->getParent()->getParent();
2180  ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
2181  }
2182 
2183  // If we inferred constant or undef values for globals variables, we can
2184  // delete the global and any stores that remain to it.
2185  const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
2187  E = TG.end(); I != E; ++I) {
2188  GlobalVariable *GV = I->first;
2189  assert(!I->second.isOverdefined() &&
2190  "Overdefined values should have been taken out of the map!");
2191  LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName()
2192  << "' is constant!\n");
2193  while (!GV->use_empty()) {
2194  StoreInst *SI = cast<StoreInst>(GV->user_back());
2195  SI->eraseFromParent();
2196  }
2197  M.getGlobalList().erase(GV);
2198  ++IPNumGlobalConst;
2199  }
2200 
2201  return MadeChanges;
2202 }
Legacy wrapper pass to provide the GlobalsAAResult object.
Constant * ConstantFoldCastOperand(unsigned Opcode, Constant *C, Type *DestTy, const DataLayout &DL)
Attempt to constant fold a cast with the specified operand.
bool onlyReadsMemory() const
Determine if the function does not access or only reads memory.
Definition: Function.h:481
IterTy arg_end() const
Definition: CallSite.h:588
uint64_t CallInst * C
Return a value (possibly void), from a function.
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:67
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:110
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:594
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:722
void setInt(IntType IntVal)
static bool isConstant(const MachineInstr &MI)
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
This instruction extracts a struct member or array element value from an aggregate value...
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This class represents an incoming formal argument to a Function.
Definition: Argument.h:29
Base class for instruction visitors.
Definition: InstVisitor.h:80
Value * getAggregateOperand()
Interprocedural Sparse Conditional Constant Propagation
Definition: SCCP.cpp:85
sccp
Definition: SCCP.cpp:1905
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:776
iterator erase(iterator where)
Definition: ilist.h:265
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
IterTy arg_begin() const
Definition: CallSite.h:584
This class represents lattice values for constants.
Definition: AllocatorList.h:23
PointerTy getPointer() const
This is the interface for a simple mod/ref and alias analysis over globals.
unsigned getNumIndices() const
bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions=false, const TargetLibraryInfo *TLI=nullptr, DomTreeUpdater *DTU=nullptr)
If a terminator instruction is predicated on a constant value, convert it into an unconditional branc...
Definition: Local.cpp:109
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:65
static Constant * getGetElementPtr(Type *Ty, Constant *C, ArrayRef< Constant *> IdxList, bool InBounds=false, Optional< unsigned > InRangeIndex=None, Type *OnlyIfReducedTy=nullptr)
Getelementptr form.
Definition: Constants.h:1153
BasicBlock * getSuccessor(unsigned Idx) const
Return the specified successor. This instruction must be a terminator.
An instruction for ordering other memory operations.
Definition: Instructions.h:454
bool canTrackArgumentsInterprocedurally(Function *F)
Determine if the values of the given function&#39;s arguments can be tracked interprocedurally.
Constant * ConstantFoldCall(const CallBase *Call, Function *F, ArrayRef< Constant *> Operands, const TargetLibraryInfo *TLI=nullptr)
ConstantFoldCall - Attempt to constant fold a call to the specified function with the specified argum...
Implements a dense probed hash-table based set.
Definition: DenseSet.h:249
unsigned getNumElements() const
Random access to the elements.
Definition: DerivedTypes.h:345
bool isSafeToRemove() const
Return true if the instruction can be removed if the result is unused.
static ValueLatticeElement get(Constant *C)
Definition: ValueLattice.h:119
This class represents a function call, abstracting a target machine&#39;s calling convention.
const Value * getTrueValue() const
An efficient, type-erasing, non-owning reference to a callable.
Definition: STLExtras.h:116
bool isTerminator() const
Definition: Instruction.h:128
BasicBlock * getSuccessor(unsigned i) const
arg_iterator arg_end()
Definition: Function.h:696
STATISTIC(NumFunctions, "Total number of functions")
F(f)
An instruction for reading from memory.
Definition: Instructions.h:167
FunTy * getCalledFunction() const
Return the function being called if this is a direct call, otherwise return null (if it&#39;s an indirect...
Definition: CallSite.h:111
const Instruction * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:137
void reserve(size_type N)
Definition: SmallVector.h:369
bool isMustTailCall() const
LLVMContext & getContext() const
Get the context in which this basic block lives.
Definition: BasicBlock.cpp:32
static void findReturnsToZap(Function &F, SmallVector< ReturnInst *, 8 > &ReturnsToZap, SCCPSolver &Solver)
Definition: SCCP.cpp:1911
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:274
std::unique_ptr< PredicateInfo > PredInfo
Definition: SCCP.h:43
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:221
The address of a basic block.
Definition: Constants.h:839
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
void setPointer(PointerTy PtrVal)
bool isVolatile() const
Return true if this is a load from a volatile memory location.
Definition: Instructions.h:231
This class represents the LLVM &#39;select&#39; instruction.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:369
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:439
ArrayRef< T > makeArrayRef(const T &OneElt)
Construct an ArrayRef from a single element.
Definition: ArrayRef.h:450
Class to represent struct types.
Definition: DerivedTypes.h:233
void initializeSCCPLegacyPassPass(PassRegistry &)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: SCCP.cpp:1852
static void forceIndeterminateEdge(Instruction *I, SCCPSolver &Solver)
Definition: SCCP.cpp:1942
FunctionPass * createSCCPPass()
Definition: SCCP.cpp:1909
Type * getSourceElementType() const
Definition: Instructions.h:972
Helper struct for bundling up the analysis results per function for IPSCCP.
Definition: SCCP.h:42
static int64_t getConstant(const MachineInstr *MI)
void assign(size_type NumElts, const T &Elt)
Definition: SmallVector.h:412
InstrTy * getInstruction() const
Definition: CallSite.h:96
Instruction::CastOps getOpcode() const
Return the opcode of this CastInst.
Definition: InstrTypes.h:692
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
IntType getInt() const
Value * getInsertedValueOperand()
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:125
PostDominatorTree * PDT
Definition: SCCP.h:45
An instruction for storing to memory.
Definition: Instructions.h:320
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
Value * getOperand(unsigned i) const
Definition: User.h:169
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:344
bool canTrackReturnsInterprocedurally(Function *F)
Determine if the values of the given function&#39;s returns can be tracked interprocedurally.
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:140
an instruction for type-safe pointer arithmetic to access elements of arrays and structs ...
Definition: Instructions.h:875
static bool runOnFunction(Function &F, bool PostInlining)
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:168
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
LLVM Basic Block Representation.
Definition: BasicBlock.h:57
PointerIntPair - This class implements a pair of a pointer and small integer.
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
void deleteBB(BasicBlock *DelBB)
Delete DelBB.
Conditional or Unconditional Branch instruction.
static BlockAddress * get(Function *F, BasicBlock *BB)
Return a BlockAddress for the specified function and basic block.
Definition: Constants.cpp:1443
This function has undefined behavior.
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:41
LLVM_NODISCARD bool empty() const
Definition: SmallPtrSet.h:91
Resume the propagation of an exception.
This file contains the declarations for the subclasses of Constant, which represent the different fla...
Indirect Branch Instruction.
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:370
unsigned getNumIndices() const
Represent the analysis usage information of a pass.
bool any_of(R &&range, UnaryPredicate P)
Provide wrappers to std::any_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1199
Analysis pass providing a never-invalidated alias analysis result.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
static Constant * get(StructType *T, ArrayRef< Constant *> V)
Definition: Constants.cpp:1053
arg_iterator arg_begin()
Definition: Function.h:687
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:381
const Function * getFunction() const
Return the function this instruction belongs to.
Definition: Instruction.cpp:59
static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V)
Definition: SCCP.cpp:1745
Constant * ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty, const DataLayout &DL)
ConstantFoldLoadFromConstPtr - Return the value that a load from C would produce if it is constant an...
const Value * getCondition() const
static Constant * getAllOnesValue(Type *Ty)
Definition: Constants.cpp:328
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1424
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
bool isExceptionalTerminator() const
Definition: Instruction.h:135
size_t size() const
Definition: SmallVector.h:52
Value * getIncomingValue(unsigned i) const
Return incoming value number x.
This file implements the PredicateInfo analysis, which creates an Extended SSA form for operations us...
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
CallBr instruction, tracking function calls that may not return control but instead transfer it to a ...
bool canConstantFoldCallTo(const CallBase *Call, const Function *F)
canConstantFoldCallTo - Return true if its even possible to fold a call to the specified function...
idx_iterator idx_begin() const
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:191
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:417
This is the shared class of boolean and integer constants.
Definition: Constants.h:83
BlockVerifier::State From
INITIALIZE_PASS_BEGIN(IPSCCPLegacyPass, "ipsccp", "Interprocedural Sparse Conditional Constant Propagation", false, false) INITIALIZE_PASS_END(IPSCCPLegacyPass
Constant * getCompare(CmpInst::Predicate Pred, Type *Ty, const ValueLatticeElement &Other) const
Compares this symbolic value with Other using Pred and returns either true, false or undef constants...
Definition: ValueLattice.h:293
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
Module.h This file contains the declarations for the Module class.
Provides information about what library functions are available for the current target.
bool canTrackGlobalVariableInterprocedurally(GlobalVariable *GV)
Determine if the value maintained in the given global variable can be tracked interprocedurally.
const DataFlowGraph & G
Definition: RDFGraph.cpp:202
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:374
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
unsigned removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB)
Remove all instructions from a basic block other than it&#39;s terminator and any present EH pad instruct...
Definition: Local.cpp:1896
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:220
unsigned getNumIncomingValues() const
Return the number of incoming edges.
static const Function * getCalledFunction(const Value *V, bool LookThroughBitCast, bool &IsNoBuiltin)
bool NullPointerIsDefined(const Function *F, unsigned AS=0)
Check whether null pointer dereferencing is considered undefined behavior for a given function or an ...
Definition: Function.cpp:1524
void setOperand(unsigned i, Value *Val)
Definition: User.h:174
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:940
iterator_range< user_iterator > users()
Definition: Value.h:399
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
const Value * getFalseValue() const
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:807
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:55
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:214
BasicBlock * getIncomingBlock(unsigned i) const
Return incoming basic block number i.
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:106
#define I(x, y, z)
Definition: MD5.cpp:58
user_iterator_impl< User > user_iterator
Definition: Value.h:368
DominatorTree * DT
Definition: SCCP.h:44
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:332
idx_iterator idx_begin() const
Type * getValueType() const
Definition: GlobalValue.h:279
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:324
size_type count(const_arg_type_t< ValueT > V) const
Return 1 if the specified key is in the set, 0 otherwise.
Definition: DenseSet.h:91
bool isUnconditional() const
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:227
Analysis pass providing the TargetLibraryInfo.
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:290
Multiway switch.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const BasicBlock & front() const
Definition: Function.h:679
bool isSingleValueType() const
Return true if the type is a valid type for a register in codegen.
Definition: Type.h:249
bool runIPSCCP(Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI, function_ref< AnalysisResultsForFn(Function &)> getAnalysis)
Definition: SCCP.cpp:1975
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:575
bool isInstructionTriviallyDead(Instruction *I, const TargetLibraryInfo *TLI=nullptr)
Return true if the result produced by the instruction is not used, and the instruction has no side ef...
Definition: Local.cpp:353
LLVM Value Representation.
Definition: Value.h:72
Invoke instruction.
static ValueLatticeElement getOverdefined()
Definition: ValueLattice.h:136
A container for analyses that lazily runs them and caches their results.
This header defines various interfaces for pass management in LLVM.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap, bool PreserveLCSSA=false, DomTreeUpdater *DTU=nullptr, MemorySSAUpdater *MSSAU=nullptr)
Insert an unreachable instruction before the specified instruction, making it and the rest of the cod...
Definition: Local.cpp:1917
bool use_empty() const
Definition: Value.h:322
static bool runSCCP(Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI)
Definition: SCCP.cpp:1795
iterator_range< arg_iterator > args()
Definition: Function.h:705
bool isStructTy() const
True if this is an instance of StructType.
Definition: Type.h:217
User * user_back()
Definition: Value.h:385
const BasicBlock * getParent() const
Definition: Instruction.h:66
This instruction inserts a struct field of array element value into an aggregate value.
void resize(size_type N)
Definition: SmallVector.h:344
static Constant * get(unsigned Opcode, Constant *C1, unsigned Flags=0, Type *OnlyIfReducedTy=nullptr)
get - Return a unary operator constant expression, folding if possible.
Definition: Constants.cpp:1815