LLVM  10.0.0svn
SCCP.cpp
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1 //===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements sparse conditional constant propagation and merging:
10 //
11 // Specifically, this:
12 // * Assumes values are constant unless proven otherwise
13 // * Assumes BasicBlocks are dead unless proven otherwise
14 // * Proves values to be constant, and replaces them with constants
15 // * Proves conditional branches to be unconditional
16 //
17 //===----------------------------------------------------------------------===//
18 
20 #include "llvm/ADT/ArrayRef.h"
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/DenseSet.h"
23 #include "llvm/ADT/MapVector.h"
25 #include "llvm/ADT/STLExtras.h"
26 #include "llvm/ADT/SmallPtrSet.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/ADT/Statistic.h"
35 #include "llvm/IR/BasicBlock.h"
36 #include "llvm/IR/CallSite.h"
37 #include "llvm/IR/Constant.h"
38 #include "llvm/IR/Constants.h"
39 #include "llvm/IR/DataLayout.h"
40 #include "llvm/IR/DerivedTypes.h"
41 #include "llvm/IR/Function.h"
42 #include "llvm/IR/GlobalVariable.h"
43 #include "llvm/IR/InstVisitor.h"
44 #include "llvm/IR/InstrTypes.h"
45 #include "llvm/IR/Instruction.h"
46 #include "llvm/IR/Instructions.h"
47 #include "llvm/IR/Module.h"
48 #include "llvm/IR/PassManager.h"
49 #include "llvm/IR/Type.h"
50 #include "llvm/IR/User.h"
51 #include "llvm/IR/Value.h"
52 #include "llvm/Pass.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/Debug.h"
57 #include "llvm/Transforms/Scalar.h"
59 #include <cassert>
60 #include <utility>
61 #include <vector>
62 
63 using namespace llvm;
64 
65 #define DEBUG_TYPE "sccp"
66 
67 STATISTIC(NumInstRemoved, "Number of instructions removed");
68 STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
69 
70 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
71 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
72 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
73 
74 namespace {
75 
76 /// LatticeVal class - This class represents the different lattice values that
77 /// an LLVM value may occupy. It is a simple class with value semantics.
78 ///
79 class LatticeVal {
80  enum LatticeValueTy {
81  /// unknown - This LLVM Value has no known value yet.
82  unknown,
83 
84  /// constant - This LLVM Value has a specific constant value.
85  constant,
86 
87  /// forcedconstant - This LLVM Value was thought to be undef until
88  /// ResolvedUndefsIn. This is treated just like 'constant', but if merged
89  /// with another (different) constant, it goes to overdefined, instead of
90  /// asserting.
91  forcedconstant,
92 
93  /// overdefined - This instruction is not known to be constant, and we know
94  /// it has a value.
95  overdefined
96  };
97 
98  /// Val: This stores the current lattice value along with the Constant* for
99  /// the constant if this is a 'constant' or 'forcedconstant' value.
101 
102  LatticeValueTy getLatticeValue() const {
103  return Val.getInt();
104  }
105 
106 public:
107  LatticeVal() : Val(nullptr, unknown) {}
108 
109  bool isUnknown() const { return getLatticeValue() == unknown; }
110 
111  bool isConstant() const {
112  return getLatticeValue() == constant || getLatticeValue() == forcedconstant;
113  }
114 
115  bool isOverdefined() const { return getLatticeValue() == overdefined; }
116 
117  Constant *getConstant() const {
118  assert(isConstant() && "Cannot get the constant of a non-constant!");
119  return Val.getPointer();
120  }
121 
122  /// markOverdefined - Return true if this is a change in status.
123  bool markOverdefined() {
124  if (isOverdefined())
125  return false;
126 
127  Val.setInt(overdefined);
128  return true;
129  }
130 
131  /// markConstant - Return true if this is a change in status.
132  bool markConstant(Constant *V) {
133  if (getLatticeValue() == constant) { // Constant but not forcedconstant.
134  assert(getConstant() == V && "Marking constant with different value");
135  return false;
136  }
137 
138  if (isUnknown()) {
139  Val.setInt(constant);
140  assert(V && "Marking constant with NULL");
141  Val.setPointer(V);
142  } else {
143  assert(getLatticeValue() == forcedconstant &&
144  "Cannot move from overdefined to constant!");
145  // Stay at forcedconstant if the constant is the same.
146  if (V == getConstant()) return false;
147 
148  // Otherwise, we go to overdefined. Assumptions made based on the
149  // forced value are possibly wrong. Assuming this is another constant
150  // could expose a contradiction.
151  Val.setInt(overdefined);
152  }
153  return true;
154  }
155 
156  /// getConstantInt - If this is a constant with a ConstantInt value, return it
157  /// otherwise return null.
158  ConstantInt *getConstantInt() const {
159  if (isConstant())
160  return dyn_cast<ConstantInt>(getConstant());
161  return nullptr;
162  }
163 
164  /// getBlockAddress - If this is a constant with a BlockAddress value, return
165  /// it, otherwise return null.
166  BlockAddress *getBlockAddress() const {
167  if (isConstant())
168  return dyn_cast<BlockAddress>(getConstant());
169  return nullptr;
170  }
171 
172  void markForcedConstant(Constant *V) {
173  assert(isUnknown() && "Can't force a defined value!");
174  Val.setInt(forcedconstant);
175  Val.setPointer(V);
176  }
177 
178  ValueLatticeElement toValueLattice() const {
179  if (isOverdefined())
181  if (isConstant())
182  return ValueLatticeElement::get(getConstant());
183  return ValueLatticeElement();
184  }
185 };
186 
187 //===----------------------------------------------------------------------===//
188 //
189 /// SCCPSolver - This class is a general purpose solver for Sparse Conditional
190 /// Constant Propagation.
191 ///
192 class SCCPSolver : public InstVisitor<SCCPSolver> {
193  const DataLayout &DL;
194  std::function<const TargetLibraryInfo &(Function &)> GetTLI;
195  SmallPtrSet<BasicBlock *, 8> BBExecutable; // The BBs that are executable.
196  DenseMap<Value *, LatticeVal> ValueState; // The state each value is in.
197  // The state each parameter is in.
199 
200  /// StructValueState - This maintains ValueState for values that have
201  /// StructType, for example for formal arguments, calls, insertelement, etc.
202  DenseMap<std::pair<Value *, unsigned>, LatticeVal> StructValueState;
203 
204  /// GlobalValue - If we are tracking any values for the contents of a global
205  /// variable, we keep a mapping from the constant accessor to the element of
206  /// the global, to the currently known value. If the value becomes
207  /// overdefined, it's entry is simply removed from this map.
209 
210  /// TrackedRetVals - If we are tracking arguments into and the return
211  /// value out of a function, it will have an entry in this map, indicating
212  /// what the known return value for the function is.
213  MapVector<Function *, LatticeVal> TrackedRetVals;
214 
215  /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
216  /// that return multiple values.
217  MapVector<std::pair<Function *, unsigned>, LatticeVal> TrackedMultipleRetVals;
218 
219  /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
220  /// represented here for efficient lookup.
221  SmallPtrSet<Function *, 16> MRVFunctionsTracked;
222 
223  /// MustTailFunctions - Each function here is a callee of non-removable
224  /// musttail call site.
225  SmallPtrSet<Function *, 16> MustTailCallees;
226 
227  /// TrackingIncomingArguments - This is the set of functions for whose
228  /// arguments we make optimistic assumptions about and try to prove as
229  /// constants.
230  SmallPtrSet<Function *, 16> TrackingIncomingArguments;
231 
232  /// The reason for two worklists is that overdefined is the lowest state
233  /// on the lattice, and moving things to overdefined as fast as possible
234  /// makes SCCP converge much faster.
235  ///
236  /// By having a separate worklist, we accomplish this because everything
237  /// possibly overdefined will become overdefined at the soonest possible
238  /// point.
239  SmallVector<Value *, 64> OverdefinedInstWorkList;
240  SmallVector<Value *, 64> InstWorkList;
241 
242  // The BasicBlock work list
244 
245  /// KnownFeasibleEdges - Entries in this set are edges which have already had
246  /// PHI nodes retriggered.
247  using Edge = std::pair<BasicBlock *, BasicBlock *>;
248  DenseSet<Edge> KnownFeasibleEdges;
249 
252 
253 public:
254  void addAnalysis(Function &F, AnalysisResultsForFn A) {
255  AnalysisResults.insert({&F, std::move(A)});
256  }
257 
258  const PredicateBase *getPredicateInfoFor(Instruction *I) {
259  auto A = AnalysisResults.find(I->getParent()->getParent());
260  if (A == AnalysisResults.end())
261  return nullptr;
262  return A->second.PredInfo->getPredicateInfoFor(I);
263  }
264 
265  DomTreeUpdater getDTU(Function &F) {
266  auto A = AnalysisResults.find(&F);
267  assert(A != AnalysisResults.end() && "Need analysis results for function.");
268  return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy};
269  }
270 
271  SCCPSolver(const DataLayout &DL,
272  std::function<const TargetLibraryInfo &(Function &)> GetTLI)
273  : DL(DL), GetTLI(std::move(GetTLI)) {}
274 
275  /// MarkBlockExecutable - This method can be used by clients to mark all of
276  /// the blocks that are known to be intrinsically live in the processed unit.
277  ///
278  /// This returns true if the block was not considered live before.
279  bool MarkBlockExecutable(BasicBlock *BB) {
280  if (!BBExecutable.insert(BB).second)
281  return false;
282  LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n');
283  BBWorkList.push_back(BB); // Add the block to the work list!
284  return true;
285  }
286 
287  /// TrackValueOfGlobalVariable - Clients can use this method to
288  /// inform the SCCPSolver that it should track loads and stores to the
289  /// specified global variable if it can. This is only legal to call if
290  /// performing Interprocedural SCCP.
291  void TrackValueOfGlobalVariable(GlobalVariable *GV) {
292  // We only track the contents of scalar globals.
293  if (GV->getValueType()->isSingleValueType()) {
294  LatticeVal &IV = TrackedGlobals[GV];
295  if (!isa<UndefValue>(GV->getInitializer()))
296  IV.markConstant(GV->getInitializer());
297  }
298  }
299 
300  /// AddTrackedFunction - If the SCCP solver is supposed to track calls into
301  /// and out of the specified function (which cannot have its address taken),
302  /// this method must be called.
303  void AddTrackedFunction(Function *F) {
304  // Add an entry, F -> undef.
305  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
306  MRVFunctionsTracked.insert(F);
307  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
308  TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
309  LatticeVal()));
310  } else
311  TrackedRetVals.insert(std::make_pair(F, LatticeVal()));
312  }
313 
314  /// AddMustTailCallee - If the SCCP solver finds that this function is called
315  /// from non-removable musttail call site.
316  void AddMustTailCallee(Function *F) {
317  MustTailCallees.insert(F);
318  }
319 
320  /// Returns true if the given function is called from non-removable musttail
321  /// call site.
322  bool isMustTailCallee(Function *F) {
323  return MustTailCallees.count(F);
324  }
325 
326  void AddArgumentTrackedFunction(Function *F) {
327  TrackingIncomingArguments.insert(F);
328  }
329 
330  /// Returns true if the given function is in the solver's set of
331  /// argument-tracked functions.
332  bool isArgumentTrackedFunction(Function *F) {
333  return TrackingIncomingArguments.count(F);
334  }
335 
336  /// Solve - Solve for constants and executable blocks.
337  void Solve();
338 
339  /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
340  /// that branches on undef values cannot reach any of their successors.
341  /// However, this is not a safe assumption. After we solve dataflow, this
342  /// method should be use to handle this. If this returns true, the solver
343  /// should be rerun.
344  bool ResolvedUndefsIn(Function &F);
345 
346  bool isBlockExecutable(BasicBlock *BB) const {
347  return BBExecutable.count(BB);
348  }
349 
350  // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
351  // block to the 'To' basic block is currently feasible.
352  bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
353 
354  std::vector<LatticeVal> getStructLatticeValueFor(Value *V) const {
355  std::vector<LatticeVal> StructValues;
356  auto *STy = dyn_cast<StructType>(V->getType());
357  assert(STy && "getStructLatticeValueFor() can be called only on structs");
358  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
359  auto I = StructValueState.find(std::make_pair(V, i));
360  assert(I != StructValueState.end() && "Value not in valuemap!");
361  StructValues.push_back(I->second);
362  }
363  return StructValues;
364  }
365 
366  const LatticeVal &getLatticeValueFor(Value *V) const {
367  assert(!V->getType()->isStructTy() &&
368  "Should use getStructLatticeValueFor");
370  assert(I != ValueState.end() &&
371  "V not found in ValueState nor Paramstate map!");
372  return I->second;
373  }
374 
375  /// getTrackedRetVals - Get the inferred return value map.
376  const MapVector<Function*, LatticeVal> &getTrackedRetVals() {
377  return TrackedRetVals;
378  }
379 
380  /// getTrackedGlobals - Get and return the set of inferred initializers for
381  /// global variables.
382  const DenseMap<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
383  return TrackedGlobals;
384  }
385 
386  /// getMRVFunctionsTracked - Get the set of functions which return multiple
387  /// values tracked by the pass.
388  const SmallPtrSet<Function *, 16> getMRVFunctionsTracked() {
389  return MRVFunctionsTracked;
390  }
391 
392  /// getMustTailCallees - Get the set of functions which are called
393  /// from non-removable musttail call sites.
394  const SmallPtrSet<Function *, 16> getMustTailCallees() {
395  return MustTailCallees;
396  }
397 
398  /// markOverdefined - Mark the specified value overdefined. This
399  /// works with both scalars and structs.
400  void markOverdefined(Value *V) {
401  if (auto *STy = dyn_cast<StructType>(V->getType()))
402  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
403  markOverdefined(getStructValueState(V, i), V);
404  else
405  markOverdefined(ValueState[V], V);
406  }
407 
408  // isStructLatticeConstant - Return true if all the lattice values
409  // corresponding to elements of the structure are not overdefined,
410  // false otherwise.
411  bool isStructLatticeConstant(Function *F, StructType *STy) {
412  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
413  const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i));
414  assert(It != TrackedMultipleRetVals.end());
415  LatticeVal LV = It->second;
416  if (LV.isOverdefined())
417  return false;
418  }
419  return true;
420  }
421 
422 private:
423  // pushToWorkList - Helper for markConstant/markForcedConstant/markOverdefined
424  void pushToWorkList(LatticeVal &IV, Value *V) {
425  if (IV.isOverdefined())
426  return OverdefinedInstWorkList.push_back(V);
427  InstWorkList.push_back(V);
428  }
429 
430  // markConstant - Make a value be marked as "constant". If the value
431  // is not already a constant, add it to the instruction work list so that
432  // the users of the instruction are updated later.
433  bool markConstant(LatticeVal &IV, Value *V, Constant *C) {
434  if (!IV.markConstant(C)) return false;
435  LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
436  pushToWorkList(IV, V);
437  return true;
438  }
439 
440  bool markConstant(Value *V, Constant *C) {
441  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
442  return markConstant(ValueState[V], V, C);
443  }
444 
445  void markForcedConstant(Value *V, Constant *C) {
446  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
447  LatticeVal &IV = ValueState[V];
448  IV.markForcedConstant(C);
449  LLVM_DEBUG(dbgs() << "markForcedConstant: " << *C << ": " << *V << '\n');
450  pushToWorkList(IV, V);
451  }
452 
453  // markOverdefined - Make a value be marked as "overdefined". If the
454  // value is not already overdefined, add it to the overdefined instruction
455  // work list so that the users of the instruction are updated later.
456  bool markOverdefined(LatticeVal &IV, Value *V) {
457  if (!IV.markOverdefined()) return false;
458 
459  LLVM_DEBUG(dbgs() << "markOverdefined: ";
460  if (auto *F = dyn_cast<Function>(V)) dbgs()
461  << "Function '" << F->getName() << "'\n";
462  else dbgs() << *V << '\n');
463  // Only instructions go on the work list
464  pushToWorkList(IV, V);
465  return true;
466  }
467 
468  bool mergeInValue(LatticeVal &IV, Value *V, LatticeVal MergeWithV) {
469  if (IV.isOverdefined() || MergeWithV.isUnknown())
470  return false; // Noop.
471  if (MergeWithV.isOverdefined())
472  return markOverdefined(IV, V);
473  if (IV.isUnknown())
474  return markConstant(IV, V, MergeWithV.getConstant());
475  if (IV.getConstant() != MergeWithV.getConstant())
476  return markOverdefined(IV, V);
477  return false;
478  }
479 
480  bool mergeInValue(Value *V, LatticeVal MergeWithV) {
481  assert(!V->getType()->isStructTy() &&
482  "non-structs should use markConstant");
483  return mergeInValue(ValueState[V], V, MergeWithV);
484  }
485 
486  /// getValueState - Return the LatticeVal object that corresponds to the
487  /// value. This function handles the case when the value hasn't been seen yet
488  /// by properly seeding constants etc.
489  LatticeVal &getValueState(Value *V) {
490  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
491 
492  std::pair<DenseMap<Value*, LatticeVal>::iterator, bool> I =
493  ValueState.insert(std::make_pair(V, LatticeVal()));
494  LatticeVal &LV = I.first->second;
495 
496  if (!I.second)
497  return LV; // Common case, already in the map.
498 
499  if (auto *C = dyn_cast<Constant>(V)) {
500  // Undef values remain unknown.
501  if (!isa<UndefValue>(V))
502  LV.markConstant(C); // Constants are constant
503  }
504 
505  // All others are underdefined by default.
506  return LV;
507  }
508 
509  ValueLatticeElement &getParamState(Value *V) {
510  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
511 
512  std::pair<DenseMap<Value*, ValueLatticeElement>::iterator, bool>
513  PI = ParamState.insert(std::make_pair(V, ValueLatticeElement()));
514  ValueLatticeElement &LV = PI.first->second;
515  if (PI.second)
516  LV = getValueState(V).toValueLattice();
517 
518  return LV;
519  }
520 
521  /// getStructValueState - Return the LatticeVal object that corresponds to the
522  /// value/field pair. This function handles the case when the value hasn't
523  /// been seen yet by properly seeding constants etc.
524  LatticeVal &getStructValueState(Value *V, unsigned i) {
525  assert(V->getType()->isStructTy() && "Should use getValueState");
526  assert(i < cast<StructType>(V->getType())->getNumElements() &&
527  "Invalid element #");
528 
529  std::pair<DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator,
530  bool> I = StructValueState.insert(
531  std::make_pair(std::make_pair(V, i), LatticeVal()));
532  LatticeVal &LV = I.first->second;
533 
534  if (!I.second)
535  return LV; // Common case, already in the map.
536 
537  if (auto *C = dyn_cast<Constant>(V)) {
538  Constant *Elt = C->getAggregateElement(i);
539 
540  if (!Elt)
541  LV.markOverdefined(); // Unknown sort of constant.
542  else if (isa<UndefValue>(Elt))
543  ; // Undef values remain unknown.
544  else
545  LV.markConstant(Elt); // Constants are constant.
546  }
547 
548  // All others are underdefined by default.
549  return LV;
550  }
551 
552  /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
553  /// work list if it is not already executable.
554  bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
555  if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
556  return false; // This edge is already known to be executable!
557 
558  if (!MarkBlockExecutable(Dest)) {
559  // If the destination is already executable, we just made an *edge*
560  // feasible that wasn't before. Revisit the PHI nodes in the block
561  // because they have potentially new operands.
562  LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
563  << " -> " << Dest->getName() << '\n');
564 
565  for (PHINode &PN : Dest->phis())
566  visitPHINode(PN);
567  }
568  return true;
569  }
570 
571  // getFeasibleSuccessors - Return a vector of booleans to indicate which
572  // successors are reachable from a given terminator instruction.
573  void getFeasibleSuccessors(Instruction &TI, SmallVectorImpl<bool> &Succs);
574 
575  // OperandChangedState - This method is invoked on all of the users of an
576  // instruction that was just changed state somehow. Based on this
577  // information, we need to update the specified user of this instruction.
578  void OperandChangedState(Instruction *I) {
579  if (BBExecutable.count(I->getParent())) // Inst is executable?
580  visit(*I);
581  }
582 
583  // Add U as additional user of V.
584  void addAdditionalUser(Value *V, User *U) {
585  auto Iter = AdditionalUsers.insert({V, {}});
586  Iter.first->second.insert(U);
587  }
588 
589  // Mark I's users as changed, including AdditionalUsers.
590  void markUsersAsChanged(Value *I) {
591  for (User *U : I->users())
592  if (auto *UI = dyn_cast<Instruction>(U))
593  OperandChangedState(UI);
594 
595  auto Iter = AdditionalUsers.find(I);
596  if (Iter != AdditionalUsers.end()) {
597  for (User *U : Iter->second)
598  if (auto *UI = dyn_cast<Instruction>(U))
599  OperandChangedState(UI);
600  }
601  }
602 
603 private:
604  friend class InstVisitor<SCCPSolver>;
605 
606  // visit implementations - Something changed in this instruction. Either an
607  // operand made a transition, or the instruction is newly executable. Change
608  // the value type of I to reflect these changes if appropriate.
609  void visitPHINode(PHINode &I);
610 
611  // Terminators
612 
613  void visitReturnInst(ReturnInst &I);
614  void visitTerminator(Instruction &TI);
615 
616  void visitCastInst(CastInst &I);
617  void visitSelectInst(SelectInst &I);
618  void visitUnaryOperator(Instruction &I);
619  void visitBinaryOperator(Instruction &I);
620  void visitCmpInst(CmpInst &I);
621  void visitExtractValueInst(ExtractValueInst &EVI);
622  void visitInsertValueInst(InsertValueInst &IVI);
623 
624  void visitCatchSwitchInst(CatchSwitchInst &CPI) {
625  markOverdefined(&CPI);
626  visitTerminator(CPI);
627  }
628 
629  // Instructions that cannot be folded away.
630 
631  void visitStoreInst (StoreInst &I);
632  void visitLoadInst (LoadInst &I);
633  void visitGetElementPtrInst(GetElementPtrInst &I);
634 
635  void visitCallInst (CallInst &I) {
636  visitCallSite(&I);
637  }
638 
639  void visitInvokeInst (InvokeInst &II) {
640  visitCallSite(&II);
641  visitTerminator(II);
642  }
643 
644  void visitCallBrInst (CallBrInst &CBI) {
645  visitCallSite(&CBI);
646  visitTerminator(CBI);
647  }
648 
649  void visitCallSite (CallSite CS);
650  void visitResumeInst (ResumeInst &I) { /*returns void*/ }
651  void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ }
652  void visitFenceInst (FenceInst &I) { /*returns void*/ }
653 
654  void visitInstruction(Instruction &I) {
655  // All the instructions we don't do any special handling for just
656  // go to overdefined.
657  LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n');
658  markOverdefined(&I);
659  }
660 };
661 
662 } // end anonymous namespace
663 
664 // getFeasibleSuccessors - Return a vector of booleans to indicate which
665 // successors are reachable from a given terminator instruction.
666 void SCCPSolver::getFeasibleSuccessors(Instruction &TI,
667  SmallVectorImpl<bool> &Succs) {
668  Succs.resize(TI.getNumSuccessors());
669  if (auto *BI = dyn_cast<BranchInst>(&TI)) {
670  if (BI->isUnconditional()) {
671  Succs[0] = true;
672  return;
673  }
674 
675  LatticeVal BCValue = getValueState(BI->getCondition());
676  ConstantInt *CI = BCValue.getConstantInt();
677  if (!CI) {
678  // Overdefined condition variables, and branches on unfoldable constant
679  // conditions, mean the branch could go either way.
680  if (!BCValue.isUnknown())
681  Succs[0] = Succs[1] = true;
682  return;
683  }
684 
685  // Constant condition variables mean the branch can only go a single way.
686  Succs[CI->isZero()] = true;
687  return;
688  }
689 
690  // Unwinding instructions successors are always executable.
691  if (TI.isExceptionalTerminator()) {
692  Succs.assign(TI.getNumSuccessors(), true);
693  return;
694  }
695 
696  if (auto *SI = dyn_cast<SwitchInst>(&TI)) {
697  if (!SI->getNumCases()) {
698  Succs[0] = true;
699  return;
700  }
701  LatticeVal SCValue = getValueState(SI->getCondition());
702  ConstantInt *CI = SCValue.getConstantInt();
703 
704  if (!CI) { // Overdefined or unknown condition?
705  // All destinations are executable!
706  if (!SCValue.isUnknown())
707  Succs.assign(TI.getNumSuccessors(), true);
708  return;
709  }
710 
711  Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
712  return;
713  }
714 
715  // In case of indirect branch and its address is a blockaddress, we mark
716  // the target as executable.
717  if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) {
718  // Casts are folded by visitCastInst.
719  LatticeVal IBRValue = getValueState(IBR->getAddress());
720  BlockAddress *Addr = IBRValue.getBlockAddress();
721  if (!Addr) { // Overdefined or unknown condition?
722  // All destinations are executable!
723  if (!IBRValue.isUnknown())
724  Succs.assign(TI.getNumSuccessors(), true);
725  return;
726  }
727 
728  BasicBlock* T = Addr->getBasicBlock();
729  assert(Addr->getFunction() == T->getParent() &&
730  "Block address of a different function ?");
731  for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) {
732  // This is the target.
733  if (IBR->getDestination(i) == T) {
734  Succs[i] = true;
735  return;
736  }
737  }
738 
739  // If we didn't find our destination in the IBR successor list, then we
740  // have undefined behavior. Its ok to assume no successor is executable.
741  return;
742  }
743 
744  // In case of callbr, we pessimistically assume that all successors are
745  // feasible.
746  if (isa<CallBrInst>(&TI)) {
747  Succs.assign(TI.getNumSuccessors(), true);
748  return;
749  }
750 
751  LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n');
752  llvm_unreachable("SCCP: Don't know how to handle this terminator!");
753 }
754 
755 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
756 // block to the 'To' basic block is currently feasible.
757 bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
758  // Check if we've called markEdgeExecutable on the edge yet. (We could
759  // be more aggressive and try to consider edges which haven't been marked
760  // yet, but there isn't any need.)
761  return KnownFeasibleEdges.count(Edge(From, To));
762 }
763 
764 // visit Implementations - Something changed in this instruction, either an
765 // operand made a transition, or the instruction is newly executable. Change
766 // the value type of I to reflect these changes if appropriate. This method
767 // makes sure to do the following actions:
768 //
769 // 1. If a phi node merges two constants in, and has conflicting value coming
770 // from different branches, or if the PHI node merges in an overdefined
771 // value, then the PHI node becomes overdefined.
772 // 2. If a phi node merges only constants in, and they all agree on value, the
773 // PHI node becomes a constant value equal to that.
774 // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant
775 // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined
776 // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined
777 // 6. If a conditional branch has a value that is constant, make the selected
778 // destination executable
779 // 7. If a conditional branch has a value that is overdefined, make all
780 // successors executable.
781 void SCCPSolver::visitPHINode(PHINode &PN) {
782  // If this PN returns a struct, just mark the result overdefined.
783  // TODO: We could do a lot better than this if code actually uses this.
784  if (PN.getType()->isStructTy())
785  return (void)markOverdefined(&PN);
786 
787  if (getValueState(&PN).isOverdefined())
788  return; // Quick exit
789 
790  // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
791  // and slow us down a lot. Just mark them overdefined.
792  if (PN.getNumIncomingValues() > 64)
793  return (void)markOverdefined(&PN);
794 
795  // Look at all of the executable operands of the PHI node. If any of them
796  // are overdefined, the PHI becomes overdefined as well. If they are all
797  // constant, and they agree with each other, the PHI becomes the identical
798  // constant. If they are constant and don't agree, the PHI is overdefined.
799  // If there are no executable operands, the PHI remains unknown.
800  Constant *OperandVal = nullptr;
801  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
802  LatticeVal IV = getValueState(PN.getIncomingValue(i));
803  if (IV.isUnknown()) continue; // Doesn't influence PHI node.
804 
805  if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
806  continue;
807 
808  if (IV.isOverdefined()) // PHI node becomes overdefined!
809  return (void)markOverdefined(&PN);
810 
811  if (!OperandVal) { // Grab the first value.
812  OperandVal = IV.getConstant();
813  continue;
814  }
815 
816  // There is already a reachable operand. If we conflict with it,
817  // then the PHI node becomes overdefined. If we agree with it, we
818  // can continue on.
819 
820  // Check to see if there are two different constants merging, if so, the PHI
821  // node is overdefined.
822  if (IV.getConstant() != OperandVal)
823  return (void)markOverdefined(&PN);
824  }
825 
826  // If we exited the loop, this means that the PHI node only has constant
827  // arguments that agree with each other(and OperandVal is the constant) or
828  // OperandVal is null because there are no defined incoming arguments. If
829  // this is the case, the PHI remains unknown.
830  if (OperandVal)
831  markConstant(&PN, OperandVal); // Acquire operand value
832 }
833 
834 void SCCPSolver::visitReturnInst(ReturnInst &I) {
835  if (I.getNumOperands() == 0) return; // ret void
836 
837  Function *F = I.getParent()->getParent();
838  Value *ResultOp = I.getOperand(0);
839 
840  // If we are tracking the return value of this function, merge it in.
841  if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
843  TrackedRetVals.find(F);
844  if (TFRVI != TrackedRetVals.end()) {
845  mergeInValue(TFRVI->second, F, getValueState(ResultOp));
846  return;
847  }
848  }
849 
850  // Handle functions that return multiple values.
851  if (!TrackedMultipleRetVals.empty()) {
852  if (auto *STy = dyn_cast<StructType>(ResultOp->getType()))
853  if (MRVFunctionsTracked.count(F))
854  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
855  mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
856  getStructValueState(ResultOp, i));
857  }
858 }
859 
860 void SCCPSolver::visitTerminator(Instruction &TI) {
861  SmallVector<bool, 16> SuccFeasible;
862  getFeasibleSuccessors(TI, SuccFeasible);
863 
864  BasicBlock *BB = TI.getParent();
865 
866  // Mark all feasible successors executable.
867  for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
868  if (SuccFeasible[i])
869  markEdgeExecutable(BB, TI.getSuccessor(i));
870 }
871 
872 void SCCPSolver::visitCastInst(CastInst &I) {
873  LatticeVal OpSt = getValueState(I.getOperand(0));
874  if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
875  markOverdefined(&I);
876  else if (OpSt.isConstant()) {
877  // Fold the constant as we build.
878  Constant *C = ConstantFoldCastOperand(I.getOpcode(), OpSt.getConstant(),
879  I.getType(), DL);
880  if (isa<UndefValue>(C))
881  return;
882  // Propagate constant value
883  markConstant(&I, C);
884  }
885 }
886 
887 void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
888  // If this returns a struct, mark all elements over defined, we don't track
889  // structs in structs.
890  if (EVI.getType()->isStructTy())
891  return (void)markOverdefined(&EVI);
892 
893  // If this is extracting from more than one level of struct, we don't know.
894  if (EVI.getNumIndices() != 1)
895  return (void)markOverdefined(&EVI);
896 
897  Value *AggVal = EVI.getAggregateOperand();
898  if (AggVal->getType()->isStructTy()) {
899  unsigned i = *EVI.idx_begin();
900  LatticeVal EltVal = getStructValueState(AggVal, i);
901  mergeInValue(getValueState(&EVI), &EVI, EltVal);
902  } else {
903  // Otherwise, must be extracting from an array.
904  return (void)markOverdefined(&EVI);
905  }
906 }
907 
908 void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
909  auto *STy = dyn_cast<StructType>(IVI.getType());
910  if (!STy)
911  return (void)markOverdefined(&IVI);
912 
913  // If this has more than one index, we can't handle it, drive all results to
914  // undef.
915  if (IVI.getNumIndices() != 1)
916  return (void)markOverdefined(&IVI);
917 
918  Value *Aggr = IVI.getAggregateOperand();
919  unsigned Idx = *IVI.idx_begin();
920 
921  // Compute the result based on what we're inserting.
922  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
923  // This passes through all values that aren't the inserted element.
924  if (i != Idx) {
925  LatticeVal EltVal = getStructValueState(Aggr, i);
926  mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
927  continue;
928  }
929 
930  Value *Val = IVI.getInsertedValueOperand();
931  if (Val->getType()->isStructTy())
932  // We don't track structs in structs.
933  markOverdefined(getStructValueState(&IVI, i), &IVI);
934  else {
935  LatticeVal InVal = getValueState(Val);
936  mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
937  }
938  }
939 }
940 
941 void SCCPSolver::visitSelectInst(SelectInst &I) {
942  // If this select returns a struct, just mark the result overdefined.
943  // TODO: We could do a lot better than this if code actually uses this.
944  if (I.getType()->isStructTy())
945  return (void)markOverdefined(&I);
946 
947  LatticeVal CondValue = getValueState(I.getCondition());
948  if (CondValue.isUnknown())
949  return;
950 
951  if (ConstantInt *CondCB = CondValue.getConstantInt()) {
952  Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
953  mergeInValue(&I, getValueState(OpVal));
954  return;
955  }
956 
957  // Otherwise, the condition is overdefined or a constant we can't evaluate.
958  // See if we can produce something better than overdefined based on the T/F
959  // value.
960  LatticeVal TVal = getValueState(I.getTrueValue());
961  LatticeVal FVal = getValueState(I.getFalseValue());
962 
963  // select ?, C, C -> C.
964  if (TVal.isConstant() && FVal.isConstant() &&
965  TVal.getConstant() == FVal.getConstant())
966  return (void)markConstant(&I, FVal.getConstant());
967 
968  if (TVal.isUnknown()) // select ?, undef, X -> X.
969  return (void)mergeInValue(&I, FVal);
970  if (FVal.isUnknown()) // select ?, X, undef -> X.
971  return (void)mergeInValue(&I, TVal);
972  markOverdefined(&I);
973 }
974 
975 // Handle Unary Operators.
976 void SCCPSolver::visitUnaryOperator(Instruction &I) {
977  LatticeVal V0State = getValueState(I.getOperand(0));
978 
979  LatticeVal &IV = ValueState[&I];
980  if (IV.isOverdefined()) return;
981 
982  if (V0State.isConstant()) {
983  Constant *C = ConstantExpr::get(I.getOpcode(), V0State.getConstant());
984 
985  // op Y -> undef.
986  if (isa<UndefValue>(C))
987  return;
988  return (void)markConstant(IV, &I, C);
989  }
990 
991  // If something is undef, wait for it to resolve.
992  if (!V0State.isOverdefined())
993  return;
994 
995  markOverdefined(&I);
996 }
997 
998 // Handle Binary Operators.
999 void SCCPSolver::visitBinaryOperator(Instruction &I) {
1000  LatticeVal V1State = getValueState(I.getOperand(0));
1001  LatticeVal V2State = getValueState(I.getOperand(1));
1002 
1003  LatticeVal &IV = ValueState[&I];
1004  if (IV.isOverdefined()) return;
1005 
1006  if (V1State.isConstant() && V2State.isConstant()) {
1007  Constant *C = ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
1008  V2State.getConstant());
1009  // X op Y -> undef.
1010  if (isa<UndefValue>(C))
1011  return;
1012  return (void)markConstant(IV, &I, C);
1013  }
1014 
1015  // If something is undef, wait for it to resolve.
1016  if (!V1State.isOverdefined() && !V2State.isOverdefined())
1017  return;
1018 
1019  // Otherwise, one of our operands is overdefined. Try to produce something
1020  // better than overdefined with some tricks.
1021  // If this is 0 / Y, it doesn't matter that the second operand is
1022  // overdefined, and we can replace it with zero.
1023  if (I.getOpcode() == Instruction::UDiv || I.getOpcode() == Instruction::SDiv)
1024  if (V1State.isConstant() && V1State.getConstant()->isNullValue())
1025  return (void)markConstant(IV, &I, V1State.getConstant());
1026 
1027  // If this is:
1028  // -> AND/MUL with 0
1029  // -> OR with -1
1030  // it doesn't matter that the other operand is overdefined.
1031  if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Mul ||
1032  I.getOpcode() == Instruction::Or) {
1033  LatticeVal *NonOverdefVal = nullptr;
1034  if (!V1State.isOverdefined())
1035  NonOverdefVal = &V1State;
1036  else if (!V2State.isOverdefined())
1037  NonOverdefVal = &V2State;
1038 
1039  if (NonOverdefVal) {
1040  if (NonOverdefVal->isUnknown())
1041  return;
1042 
1043  if (I.getOpcode() == Instruction::And ||
1044  I.getOpcode() == Instruction::Mul) {
1045  // X and 0 = 0
1046  // X * 0 = 0
1047  if (NonOverdefVal->getConstant()->isNullValue())
1048  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1049  } else {
1050  // X or -1 = -1
1051  if (ConstantInt *CI = NonOverdefVal->getConstantInt())
1052  if (CI->isMinusOne())
1053  return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1054  }
1055  }
1056  }
1057 
1058  markOverdefined(&I);
1059 }
1060 
1061 // Handle ICmpInst instruction.
1062 void SCCPSolver::visitCmpInst(CmpInst &I) {
1063  // Do not cache this lookup, getValueState calls later in the function might
1064  // invalidate the reference.
1065  if (ValueState[&I].isOverdefined()) return;
1066 
1067  Value *Op1 = I.getOperand(0);
1068  Value *Op2 = I.getOperand(1);
1069 
1070  // For parameters, use ParamState which includes constant range info if
1071  // available.
1072  auto V1Param = ParamState.find(Op1);
1073  ValueLatticeElement V1State = (V1Param != ParamState.end())
1074  ? V1Param->second
1075  : getValueState(Op1).toValueLattice();
1076 
1077  auto V2Param = ParamState.find(Op2);
1078  ValueLatticeElement V2State = V2Param != ParamState.end()
1079  ? V2Param->second
1080  : getValueState(Op2).toValueLattice();
1081 
1082  Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
1083  if (C) {
1084  if (isa<UndefValue>(C))
1085  return;
1086  LatticeVal CV;
1087  CV.markConstant(C);
1088  mergeInValue(&I, CV);
1089  return;
1090  }
1091 
1092  // If operands are still unknown, wait for it to resolve.
1093  if (!V1State.isOverdefined() && !V2State.isOverdefined() &&
1094  !ValueState[&I].isConstant())
1095  return;
1096 
1097  markOverdefined(&I);
1098 }
1099 
1100 // Handle getelementptr instructions. If all operands are constants then we
1101 // can turn this into a getelementptr ConstantExpr.
1102 void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
1103  if (ValueState[&I].isOverdefined()) return;
1104 
1106  Operands.reserve(I.getNumOperands());
1107 
1108  for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
1109  LatticeVal State = getValueState(I.getOperand(i));
1110  if (State.isUnknown())
1111  return; // Operands are not resolved yet.
1112 
1113  if (State.isOverdefined())
1114  return (void)markOverdefined(&I);
1115 
1116  assert(State.isConstant() && "Unknown state!");
1117  Operands.push_back(State.getConstant());
1118  }
1119 
1120  Constant *Ptr = Operands[0];
1121  auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end());
1122  Constant *C =
1124  if (isa<UndefValue>(C))
1125  return;
1126  markConstant(&I, C);
1127 }
1128 
1129 void SCCPSolver::visitStoreInst(StoreInst &SI) {
1130  // If this store is of a struct, ignore it.
1131  if (SI.getOperand(0)->getType()->isStructTy())
1132  return;
1133 
1134  if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
1135  return;
1136 
1137  GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
1139  if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
1140 
1141  // Get the value we are storing into the global, then merge it.
1142  mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
1143  if (I->second.isOverdefined())
1144  TrackedGlobals.erase(I); // No need to keep tracking this!
1145 }
1146 
1147 // Handle load instructions. If the operand is a constant pointer to a constant
1148 // global, we can replace the load with the loaded constant value!
1149 void SCCPSolver::visitLoadInst(LoadInst &I) {
1150  // If this load is of a struct, just mark the result overdefined.
1151  if (I.getType()->isStructTy())
1152  return (void)markOverdefined(&I);
1153 
1154  LatticeVal PtrVal = getValueState(I.getOperand(0));
1155  if (PtrVal.isUnknown()) return; // The pointer is not resolved yet!
1156 
1157  LatticeVal &IV = ValueState[&I];
1158  if (IV.isOverdefined()) return;
1159 
1160  if (!PtrVal.isConstant() || I.isVolatile())
1161  return (void)markOverdefined(IV, &I);
1162 
1163  Constant *Ptr = PtrVal.getConstant();
1164 
1165  // load null is undefined.
1166  if (isa<ConstantPointerNull>(Ptr)) {
1168  return (void)markOverdefined(IV, &I);
1169  else
1170  return;
1171  }
1172 
1173  // Transform load (constant global) into the value loaded.
1174  if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) {
1175  if (!TrackedGlobals.empty()) {
1176  // If we are tracking this global, merge in the known value for it.
1178  TrackedGlobals.find(GV);
1179  if (It != TrackedGlobals.end()) {
1180  mergeInValue(IV, &I, It->second);
1181  return;
1182  }
1183  }
1184  }
1185 
1186  // Transform load from a constant into a constant if possible.
1187  if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) {
1188  if (isa<UndefValue>(C))
1189  return;
1190  return (void)markConstant(IV, &I, C);
1191  }
1192 
1193  // Otherwise we cannot say for certain what value this load will produce.
1194  // Bail out.
1195  markOverdefined(IV, &I);
1196 }
1197 
1198 void SCCPSolver::visitCallSite(CallSite CS) {
1199  Function *F = CS.getCalledFunction();
1200  Instruction *I = CS.getInstruction();
1201 
1202  if (auto *II = dyn_cast<IntrinsicInst>(I)) {
1203  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
1204  if (ValueState[I].isOverdefined())
1205  return;
1206 
1207  auto *PI = getPredicateInfoFor(I);
1208  if (!PI)
1209  return;
1210 
1211  Value *CopyOf = I->getOperand(0);
1212  auto *PBranch = dyn_cast<PredicateBranch>(PI);
1213  if (!PBranch) {
1214  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1215  return;
1216  }
1217 
1218  Value *Cond = PBranch->Condition;
1219 
1220  // Everything below relies on the condition being a comparison.
1221  auto *Cmp = dyn_cast<CmpInst>(Cond);
1222  if (!Cmp) {
1223  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1224  return;
1225  }
1226 
1227  Value *CmpOp0 = Cmp->getOperand(0);
1228  Value *CmpOp1 = Cmp->getOperand(1);
1229  if (CopyOf != CmpOp0 && CopyOf != CmpOp1) {
1230  mergeInValue(ValueState[I], I, getValueState(CopyOf));
1231  return;
1232  }
1233 
1234  if (CmpOp0 != CopyOf)
1235  std::swap(CmpOp0, CmpOp1);
1236 
1237  LatticeVal OriginalVal = getValueState(CopyOf);
1238  LatticeVal EqVal = getValueState(CmpOp1);
1239  LatticeVal &IV = ValueState[I];
1240  if (PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_EQ) {
1241  addAdditionalUser(CmpOp1, I);
1242  if (OriginalVal.isConstant())
1243  mergeInValue(IV, I, OriginalVal);
1244  else
1245  mergeInValue(IV, I, EqVal);
1246  return;
1247  }
1248  if (!PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_NE) {
1249  addAdditionalUser(CmpOp1, I);
1250  if (OriginalVal.isConstant())
1251  mergeInValue(IV, I, OriginalVal);
1252  else
1253  mergeInValue(IV, I, EqVal);
1254  return;
1255  }
1256 
1257  return (void)mergeInValue(IV, I, getValueState(CopyOf));
1258  }
1259  }
1260 
1261  // The common case is that we aren't tracking the callee, either because we
1262  // are not doing interprocedural analysis or the callee is indirect, or is
1263  // external. Handle these cases first.
1264  if (!F || F->isDeclaration()) {
1265 CallOverdefined:
1266  // Void return and not tracking callee, just bail.
1267  if (I->getType()->isVoidTy()) return;
1268 
1269  // Otherwise, if we have a single return value case, and if the function is
1270  // a declaration, maybe we can constant fold it.
1271  if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
1272  canConstantFoldCallTo(cast<CallBase>(CS.getInstruction()), F)) {
1274  for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
1275  AI != E; ++AI) {
1276  if (AI->get()->getType()->isStructTy())
1277  return markOverdefined(I); // Can't handle struct args.
1278  LatticeVal State = getValueState(*AI);
1279 
1280  if (State.isUnknown())
1281  return; // Operands are not resolved yet.
1282  if (State.isOverdefined())
1283  return (void)markOverdefined(I);
1284  assert(State.isConstant() && "Unknown state!");
1285  Operands.push_back(State.getConstant());
1286  }
1287 
1288  if (getValueState(I).isOverdefined())
1289  return;
1290 
1291  // If we can constant fold this, mark the result of the call as a
1292  // constant.
1293  if (Constant *C = ConstantFoldCall(cast<CallBase>(CS.getInstruction()), F,
1294  Operands, &GetTLI(*F))) {
1295  // call -> undef.
1296  if (isa<UndefValue>(C))
1297  return;
1298  return (void)markConstant(I, C);
1299  }
1300  }
1301 
1302  // Otherwise, we don't know anything about this call, mark it overdefined.
1303  return (void)markOverdefined(I);
1304  }
1305 
1306  // If this is a local function that doesn't have its address taken, mark its
1307  // entry block executable and merge in the actual arguments to the call into
1308  // the formal arguments of the function.
1309  if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
1310  MarkBlockExecutable(&F->front());
1311 
1312  // Propagate information from this call site into the callee.
1313  CallSite::arg_iterator CAI = CS.arg_begin();
1314  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
1315  AI != E; ++AI, ++CAI) {
1316  // If this argument is byval, and if the function is not readonly, there
1317  // will be an implicit copy formed of the input aggregate.
1318  if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
1319  markOverdefined(&*AI);
1320  continue;
1321  }
1322 
1323  if (auto *STy = dyn_cast<StructType>(AI->getType())) {
1324  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1325  LatticeVal CallArg = getStructValueState(*CAI, i);
1326  mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
1327  }
1328  } else {
1329  // Most other parts of the Solver still only use the simpler value
1330  // lattice, so we propagate changes for parameters to both lattices.
1331  LatticeVal ConcreteArgument = getValueState(*CAI);
1332  bool ParamChanged =
1333  getParamState(&*AI).mergeIn(ConcreteArgument.toValueLattice(), DL);
1334  bool ValueChanged = mergeInValue(&*AI, ConcreteArgument);
1335  // Add argument to work list, if the state of a parameter changes but
1336  // ValueState does not change (because it is already overdefined there),
1337  // We have to take changes in ParamState into account, as it is used
1338  // when evaluating Cmp instructions.
1339  if (!ValueChanged && ParamChanged)
1340  pushToWorkList(ValueState[&*AI], &*AI);
1341  }
1342  }
1343  }
1344 
1345  // If this is a single/zero retval case, see if we're tracking the function.
1346  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
1347  if (!MRVFunctionsTracked.count(F))
1348  goto CallOverdefined; // Not tracking this callee.
1349 
1350  // If we are tracking this callee, propagate the result of the function
1351  // into this call site.
1352  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1353  mergeInValue(getStructValueState(I, i), I,
1354  TrackedMultipleRetVals[std::make_pair(F, i)]);
1355  } else {
1356  MapVector<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
1357  if (TFRVI == TrackedRetVals.end())
1358  goto CallOverdefined; // Not tracking this callee.
1359 
1360  // If so, propagate the return value of the callee into this call result.
1361  mergeInValue(I, TFRVI->second);
1362  }
1363 }
1364 
1365 void SCCPSolver::Solve() {
1366  // Process the work lists until they are empty!
1367  while (!BBWorkList.empty() || !InstWorkList.empty() ||
1368  !OverdefinedInstWorkList.empty()) {
1369  // Process the overdefined instruction's work list first, which drives other
1370  // things to overdefined more quickly.
1371  while (!OverdefinedInstWorkList.empty()) {
1372  Value *I = OverdefinedInstWorkList.pop_back_val();
1373 
1374  LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
1375 
1376  // "I" got into the work list because it either made the transition from
1377  // bottom to constant, or to overdefined.
1378  //
1379  // Anything on this worklist that is overdefined need not be visited
1380  // since all of its users will have already been marked as overdefined
1381  // Update all of the users of this instruction's value.
1382  //
1383  markUsersAsChanged(I);
1384  }
1385 
1386  // Process the instruction work list.
1387  while (!InstWorkList.empty()) {
1388  Value *I = InstWorkList.pop_back_val();
1389 
1390  LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
1391 
1392  // "I" got into the work list because it made the transition from undef to
1393  // constant.
1394  //
1395  // Anything on this worklist that is overdefined need not be visited
1396  // since all of its users will have already been marked as overdefined.
1397  // Update all of the users of this instruction's value.
1398  //
1399  if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
1400  markUsersAsChanged(I);
1401  }
1402 
1403  // Process the basic block work list.
1404  while (!BBWorkList.empty()) {
1405  BasicBlock *BB = BBWorkList.back();
1406  BBWorkList.pop_back();
1407 
1408  LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
1409 
1410  // Notify all instructions in this basic block that they are newly
1411  // executable.
1412  visit(BB);
1413  }
1414  }
1415 }
1416 
1417 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
1418 /// that branches on undef values cannot reach any of their successors.
1419 /// However, this is not a safe assumption. After we solve dataflow, this
1420 /// method should be use to handle this. If this returns true, the solver
1421 /// should be rerun.
1422 ///
1423 /// This method handles this by finding an unresolved branch and marking it one
1424 /// of the edges from the block as being feasible, even though the condition
1425 /// doesn't say it would otherwise be. This allows SCCP to find the rest of the
1426 /// CFG and only slightly pessimizes the analysis results (by marking one,
1427 /// potentially infeasible, edge feasible). This cannot usefully modify the
1428 /// constraints on the condition of the branch, as that would impact other users
1429 /// of the value.
1430 ///
1431 /// This scan also checks for values that use undefs, whose results are actually
1432 /// defined. For example, 'zext i8 undef to i32' should produce all zeros
1433 /// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
1434 /// even if X isn't defined.
1435 bool SCCPSolver::ResolvedUndefsIn(Function &F) {
1436  for (BasicBlock &BB : F) {
1437  if (!BBExecutable.count(&BB))
1438  continue;
1439 
1440  for (Instruction &I : BB) {
1441  // Look for instructions which produce undef values.
1442  if (I.getType()->isVoidTy()) continue;
1443 
1444  if (auto *STy = dyn_cast<StructType>(I.getType())) {
1445  // Only a few things that can be structs matter for undef.
1446 
1447  // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
1448  if (CallSite CS = CallSite(&I))
1449  if (Function *F = CS.getCalledFunction())
1450  if (MRVFunctionsTracked.count(F))
1451  continue;
1452 
1453  // extractvalue and insertvalue don't need to be marked; they are
1454  // tracked as precisely as their operands.
1455  if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
1456  continue;
1457 
1458  // Send the results of everything else to overdefined. We could be
1459  // more precise than this but it isn't worth bothering.
1460  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1461  LatticeVal &LV = getStructValueState(&I, i);
1462  if (LV.isUnknown())
1463  markOverdefined(LV, &I);
1464  }
1465  continue;
1466  }
1467 
1468  LatticeVal &LV = getValueState(&I);
1469  if (!LV.isUnknown())
1470  continue;
1471 
1472  // There are two reasons a call can have an undef result
1473  // 1. It could be tracked.
1474  // 2. It could be constant-foldable.
1475  // Because of the way we solve return values, tracked calls must
1476  // never be marked overdefined in ResolvedUndefsIn.
1477  if (CallSite CS = CallSite(&I)) {
1478  if (Function *F = CS.getCalledFunction())
1479  if (TrackedRetVals.count(F))
1480  continue;
1481 
1482  // If the call is constant-foldable, we mark it overdefined because
1483  // we do not know what return values are valid.
1484  markOverdefined(&I);
1485  return true;
1486  }
1487 
1488  // extractvalue is safe; check here because the argument is a struct.
1489  if (isa<ExtractValueInst>(I))
1490  continue;
1491 
1492  // Compute the operand LatticeVals, for convenience below.
1493  // Anything taking a struct is conservatively assumed to require
1494  // overdefined markings.
1495  if (I.getOperand(0)->getType()->isStructTy()) {
1496  markOverdefined(&I);
1497  return true;
1498  }
1499  LatticeVal Op0LV = getValueState(I.getOperand(0));
1500  LatticeVal Op1LV;
1501  if (I.getNumOperands() == 2) {
1502  if (I.getOperand(1)->getType()->isStructTy()) {
1503  markOverdefined(&I);
1504  return true;
1505  }
1506 
1507  Op1LV = getValueState(I.getOperand(1));
1508  }
1509  // If this is an instructions whose result is defined even if the input is
1510  // not fully defined, propagate the information.
1511  Type *ITy = I.getType();
1512  switch (I.getOpcode()) {
1513  case Instruction::Add:
1514  case Instruction::Sub:
1515  case Instruction::Trunc:
1516  case Instruction::FPTrunc:
1517  case Instruction::BitCast:
1518  break; // Any undef -> undef
1519  case Instruction::FSub:
1520  case Instruction::FAdd:
1521  case Instruction::FMul:
1522  case Instruction::FDiv:
1523  case Instruction::FRem:
1524  // Floating-point binary operation: be conservative.
1525  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1526  markForcedConstant(&I, Constant::getNullValue(ITy));
1527  else
1528  markOverdefined(&I);
1529  return true;
1530  case Instruction::FNeg:
1531  break; // fneg undef -> undef
1532  case Instruction::ZExt:
1533  case Instruction::SExt:
1534  case Instruction::FPToUI:
1535  case Instruction::FPToSI:
1536  case Instruction::FPExt:
1537  case Instruction::PtrToInt:
1538  case Instruction::IntToPtr:
1539  case Instruction::SIToFP:
1540  case Instruction::UIToFP:
1541  // undef -> 0; some outputs are impossible
1542  markForcedConstant(&I, Constant::getNullValue(ITy));
1543  return true;
1544  case Instruction::Mul:
1545  case Instruction::And:
1546  // Both operands undef -> undef
1547  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1548  break;
1549  // undef * X -> 0. X could be zero.
1550  // undef & X -> 0. X could be zero.
1551  markForcedConstant(&I, Constant::getNullValue(ITy));
1552  return true;
1553  case Instruction::Or:
1554  // Both operands undef -> undef
1555  if (Op0LV.isUnknown() && Op1LV.isUnknown())
1556  break;
1557  // undef | X -> -1. X could be -1.
1558  markForcedConstant(&I, Constant::getAllOnesValue(ITy));
1559  return true;
1560  case Instruction::Xor:
1561  // undef ^ undef -> 0; strictly speaking, this is not strictly
1562  // necessary, but we try to be nice to people who expect this
1563  // behavior in simple cases
1564  if (Op0LV.isUnknown() && Op1LV.isUnknown()) {
1565  markForcedConstant(&I, Constant::getNullValue(ITy));
1566  return true;
1567  }
1568  // undef ^ X -> undef
1569  break;
1570  case Instruction::SDiv:
1571  case Instruction::UDiv:
1572  case Instruction::SRem:
1573  case Instruction::URem:
1574  // X / undef -> undef. No change.
1575  // X % undef -> undef. No change.
1576  if (Op1LV.isUnknown()) break;
1577 
1578  // X / 0 -> undef. No change.
1579  // X % 0 -> undef. No change.
1580  if (Op1LV.isConstant() && Op1LV.getConstant()->isZeroValue())
1581  break;
1582 
1583  // undef / X -> 0. X could be maxint.
1584  // undef % X -> 0. X could be 1.
1585  markForcedConstant(&I, Constant::getNullValue(ITy));
1586  return true;
1587  case Instruction::AShr:
1588  // X >>a undef -> undef.
1589  if (Op1LV.isUnknown()) break;
1590 
1591  // Shifting by the bitwidth or more is undefined.
1592  if (Op1LV.isConstant()) {
1593  if (auto *ShiftAmt = Op1LV.getConstantInt())
1594  if (ShiftAmt->getLimitedValue() >=
1595  ShiftAmt->getType()->getScalarSizeInBits())
1596  break;
1597  }
1598 
1599  // undef >>a X -> 0
1600  markForcedConstant(&I, Constant::getNullValue(ITy));
1601  return true;
1602  case Instruction::LShr:
1603  case Instruction::Shl:
1604  // X << undef -> undef.
1605  // X >> undef -> undef.
1606  if (Op1LV.isUnknown()) break;
1607 
1608  // Shifting by the bitwidth or more is undefined.
1609  if (Op1LV.isConstant()) {
1610  if (auto *ShiftAmt = Op1LV.getConstantInt())
1611  if (ShiftAmt->getLimitedValue() >=
1612  ShiftAmt->getType()->getScalarSizeInBits())
1613  break;
1614  }
1615 
1616  // undef << X -> 0
1617  // undef >> X -> 0
1618  markForcedConstant(&I, Constant::getNullValue(ITy));
1619  return true;
1620  case Instruction::Select:
1621  Op1LV = getValueState(I.getOperand(1));
1622  // undef ? X : Y -> X or Y. There could be commonality between X/Y.
1623  if (Op0LV.isUnknown()) {
1624  if (!Op1LV.isConstant()) // Pick the constant one if there is any.
1625  Op1LV = getValueState(I.getOperand(2));
1626  } else if (Op1LV.isUnknown()) {
1627  // c ? undef : undef -> undef. No change.
1628  Op1LV = getValueState(I.getOperand(2));
1629  if (Op1LV.isUnknown())
1630  break;
1631  // Otherwise, c ? undef : x -> x.
1632  } else {
1633  // Leave Op1LV as Operand(1)'s LatticeValue.
1634  }
1635 
1636  if (Op1LV.isConstant())
1637  markForcedConstant(&I, Op1LV.getConstant());
1638  else
1639  markOverdefined(&I);
1640  return true;
1641  case Instruction::Load:
1642  // A load here means one of two things: a load of undef from a global,
1643  // a load from an unknown pointer. Either way, having it return undef
1644  // is okay.
1645  break;
1646  case Instruction::ICmp:
1647  // X == undef -> undef. Other comparisons get more complicated.
1648  Op0LV = getValueState(I.getOperand(0));
1649  Op1LV = getValueState(I.getOperand(1));
1650 
1651  if ((Op0LV.isUnknown() || Op1LV.isUnknown()) &&
1652  cast<ICmpInst>(&I)->isEquality())
1653  break;
1654  markOverdefined(&I);
1655  return true;
1656  case Instruction::Call:
1657  case Instruction::Invoke:
1658  case Instruction::CallBr:
1659  llvm_unreachable("Call-like instructions should have be handled early");
1660  default:
1661  // If we don't know what should happen here, conservatively mark it
1662  // overdefined.
1663  markOverdefined(&I);
1664  return true;
1665  }
1666  }
1667 
1668  // Check to see if we have a branch or switch on an undefined value. If so
1669  // we force the branch to go one way or the other to make the successor
1670  // values live. It doesn't really matter which way we force it.
1671  Instruction *TI = BB.getTerminator();
1672  if (auto *BI = dyn_cast<BranchInst>(TI)) {
1673  if (!BI->isConditional()) continue;
1674  if (!getValueState(BI->getCondition()).isUnknown())
1675  continue;
1676 
1677  // If the input to SCCP is actually branch on undef, fix the undef to
1678  // false.
1679  if (isa<UndefValue>(BI->getCondition())) {
1680  BI->setCondition(ConstantInt::getFalse(BI->getContext()));
1681  markEdgeExecutable(&BB, TI->getSuccessor(1));
1682  return true;
1683  }
1684 
1685  // Otherwise, it is a branch on a symbolic value which is currently
1686  // considered to be undef. Make sure some edge is executable, so a
1687  // branch on "undef" always flows somewhere.
1688  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1689  BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
1690  if (markEdgeExecutable(&BB, DefaultSuccessor))
1691  return true;
1692 
1693  continue;
1694  }
1695 
1696  if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
1697  // Indirect branch with no successor ?. Its ok to assume it branches
1698  // to no target.
1699  if (IBR->getNumSuccessors() < 1)
1700  continue;
1701 
1702  if (!getValueState(IBR->getAddress()).isUnknown())
1703  continue;
1704 
1705  // If the input to SCCP is actually branch on undef, fix the undef to
1706  // the first successor of the indirect branch.
1707  if (isa<UndefValue>(IBR->getAddress())) {
1708  IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
1709  markEdgeExecutable(&BB, IBR->getSuccessor(0));
1710  return true;
1711  }
1712 
1713  // Otherwise, it is a branch on a symbolic value which is currently
1714  // considered to be undef. Make sure some edge is executable, so a
1715  // branch on "undef" always flows somewhere.
1716  // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
1717  // we can assume the branch has undefined behavior instead.
1718  BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
1719  if (markEdgeExecutable(&BB, DefaultSuccessor))
1720  return true;
1721 
1722  continue;
1723  }
1724 
1725  if (auto *SI = dyn_cast<SwitchInst>(TI)) {
1726  if (!SI->getNumCases() || !getValueState(SI->getCondition()).isUnknown())
1727  continue;
1728 
1729  // If the input to SCCP is actually switch on undef, fix the undef to
1730  // the first constant.
1731  if (isa<UndefValue>(SI->getCondition())) {
1732  SI->setCondition(SI->case_begin()->getCaseValue());
1733  markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
1734  return true;
1735  }
1736 
1737  // Otherwise, it is a branch on a symbolic value which is currently
1738  // considered to be undef. Make sure some edge is executable, so a
1739  // branch on "undef" always flows somewhere.
1740  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1741  BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
1742  if (markEdgeExecutable(&BB, DefaultSuccessor))
1743  return true;
1744 
1745  continue;
1746  }
1747  }
1748 
1749  return false;
1750 }
1751 
1752 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
1753  Constant *Const = nullptr;
1754  if (V->getType()->isStructTy()) {
1755  std::vector<LatticeVal> IVs = Solver.getStructLatticeValueFor(V);
1756  if (llvm::any_of(IVs,
1757  [](const LatticeVal &LV) { return LV.isOverdefined(); }))
1758  return false;
1759  std::vector<Constant *> ConstVals;
1760  auto *ST = cast<StructType>(V->getType());
1761  for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1762  LatticeVal V = IVs[i];
1763  ConstVals.push_back(V.isConstant()
1764  ? V.getConstant()
1765  : UndefValue::get(ST->getElementType(i)));
1766  }
1767  Const = ConstantStruct::get(ST, ConstVals);
1768  } else {
1769  const LatticeVal &IV = Solver.getLatticeValueFor(V);
1770  if (IV.isOverdefined())
1771  return false;
1772 
1773  Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
1774  }
1775  assert(Const && "Constant is nullptr here!");
1776 
1777  // Replacing `musttail` instructions with constant breaks `musttail` invariant
1778  // unless the call itself can be removed
1779  CallInst *CI = dyn_cast<CallInst>(V);
1780  if (CI && CI->isMustTailCall() && !CI->isSafeToRemove()) {
1781  CallSite CS(CI);
1782  Function *F = CS.getCalledFunction();
1783 
1784  // Don't zap returns of the callee
1785  if (F)
1786  Solver.AddMustTailCallee(F);
1787 
1788  LLVM_DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI
1789  << " as a constant\n");
1790  return false;
1791  }
1792 
1793  LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
1794 
1795  // Replaces all of the uses of a variable with uses of the constant.
1796  V->replaceAllUsesWith(Const);
1797  return true;
1798 }
1799 
1800 // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
1801 // and return true if the function was modified.
1802 static bool runSCCP(Function &F, const DataLayout &DL,
1803  const TargetLibraryInfo *TLI) {
1804  LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
1805  SCCPSolver Solver(
1806  DL, [TLI](Function &F) -> const TargetLibraryInfo & { return *TLI; });
1807 
1808  // Mark the first block of the function as being executable.
1809  Solver.MarkBlockExecutable(&F.front());
1810 
1811  // Mark all arguments to the function as being overdefined.
1812  for (Argument &AI : F.args())
1813  Solver.markOverdefined(&AI);
1814 
1815  // Solve for constants.
1816  bool ResolvedUndefs = true;
1817  while (ResolvedUndefs) {
1818  Solver.Solve();
1819  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n");
1820  ResolvedUndefs = Solver.ResolvedUndefsIn(F);
1821  }
1822 
1823  bool MadeChanges = false;
1824 
1825  // If we decided that there are basic blocks that are dead in this function,
1826  // delete their contents now. Note that we cannot actually delete the blocks,
1827  // as we cannot modify the CFG of the function.
1828 
1829  for (BasicBlock &BB : F) {
1830  if (!Solver.isBlockExecutable(&BB)) {
1831  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1832 
1833  ++NumDeadBlocks;
1834  NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB);
1835 
1836  MadeChanges = true;
1837  continue;
1838  }
1839 
1840  // Iterate over all of the instructions in a function, replacing them with
1841  // constants if we have found them to be of constant values.
1842  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
1843  Instruction *Inst = &*BI++;
1844  if (Inst->getType()->isVoidTy() || Inst->isTerminator())
1845  continue;
1846 
1847  if (tryToReplaceWithConstant(Solver, Inst)) {
1848  if (isInstructionTriviallyDead(Inst))
1849  Inst->eraseFromParent();
1850  // Hey, we just changed something!
1851  MadeChanges = true;
1852  ++NumInstRemoved;
1853  }
1854  }
1855  }
1856 
1857  return MadeChanges;
1858 }
1859 
1861  const DataLayout &DL = F.getParent()->getDataLayout();
1862  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
1863  if (!runSCCP(F, DL, &TLI))
1864  return PreservedAnalyses::all();
1865 
1866  auto PA = PreservedAnalyses();
1867  PA.preserve<GlobalsAA>();
1868  PA.preserveSet<CFGAnalyses>();
1869  return PA;
1870 }
1871 
1872 namespace {
1873 
1874 //===--------------------------------------------------------------------===//
1875 //
1876 /// SCCP Class - This class uses the SCCPSolver to implement a per-function
1877 /// Sparse Conditional Constant Propagator.
1878 ///
1879 class SCCPLegacyPass : public FunctionPass {
1880 public:
1881  // Pass identification, replacement for typeid
1882  static char ID;
1883 
1884  SCCPLegacyPass() : FunctionPass(ID) {
1886  }
1887 
1888  void getAnalysisUsage(AnalysisUsage &AU) const override {
1891  AU.setPreservesCFG();
1892  }
1893 
1894  // runOnFunction - Run the Sparse Conditional Constant Propagation
1895  // algorithm, and return true if the function was modified.
1896  bool runOnFunction(Function &F) override {
1897  if (skipFunction(F))
1898  return false;
1899  const DataLayout &DL = F.getParent()->getDataLayout();
1900  const TargetLibraryInfo *TLI =
1901  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
1902  return runSCCP(F, DL, TLI);
1903  }
1904 };
1905 
1906 } // end anonymous namespace
1907 
1908 char SCCPLegacyPass::ID = 0;
1909 
1910 INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp",
1911  "Sparse Conditional Constant Propagation", false, false)
1913 INITIALIZE_PASS_END(SCCPLegacyPass, "sccp",
1914  "Sparse Conditional Constant Propagation", false, false)
1915 
1916 // createSCCPPass - This is the public interface to this file.
1917 FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); }
1918 
1920  SmallVector<ReturnInst *, 8> &ReturnsToZap,
1921  SCCPSolver &Solver) {
1922  // We can only do this if we know that nothing else can call the function.
1923  if (!Solver.isArgumentTrackedFunction(&F))
1924  return;
1925 
1926  // There is a non-removable musttail call site of this function. Zapping
1927  // returns is not allowed.
1928  if (Solver.isMustTailCallee(&F)) {
1929  LLVM_DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName()
1930  << " due to present musttail call of it\n");
1931  return;
1932  }
1933 
1934  assert(
1935  all_of(F.users(),
1936  [&Solver](User *U) {
1937  if (isa<Instruction>(U) &&
1938  !Solver.isBlockExecutable(cast<Instruction>(U)->getParent()))
1939  return true;
1940  // Non-callsite uses are not impacted by zapping. Also, constant
1941  // uses (like blockaddresses) could stuck around, without being
1942  // used in the underlying IR, meaning we do not have lattice
1943  // values for them.
1944  if (!CallSite(U))
1945  return true;
1946  if (U->getType()->isStructTy()) {
1947  return all_of(
1948  Solver.getStructLatticeValueFor(U),
1949  [](const LatticeVal &LV) { return !LV.isOverdefined(); });
1950  }
1951  return !Solver.getLatticeValueFor(U).isOverdefined();
1952  }) &&
1953  "We can only zap functions where all live users have a concrete value");
1954 
1955  for (BasicBlock &BB : F) {
1956  if (CallInst *CI = BB.getTerminatingMustTailCall()) {
1957  LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "
1958  << "musttail call : " << *CI << "\n");
1959  (void)CI;
1960  return;
1961  }
1962 
1963  if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1964  if (!isa<UndefValue>(RI->getOperand(0)))
1965  ReturnsToZap.push_back(RI);
1966  }
1967 }
1968 
1969 // Update the condition for terminators that are branching on indeterminate
1970 // values, forcing them to use a specific edge.
1971 static void forceIndeterminateEdge(Instruction* I, SCCPSolver &Solver) {
1972  BasicBlock *Dest = nullptr;
1973  Constant *C = nullptr;
1974  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
1975  if (!isa<ConstantInt>(SI->getCondition())) {
1976  // Indeterminate switch; use first case value.
1977  Dest = SI->case_begin()->getCaseSuccessor();
1978  C = SI->case_begin()->getCaseValue();
1979  }
1980  } else if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
1981  if (!isa<ConstantInt>(BI->getCondition())) {
1982  // Indeterminate branch; use false.
1983  Dest = BI->getSuccessor(1);
1984  C = ConstantInt::getFalse(BI->getContext());
1985  }
1986  } else if (IndirectBrInst *IBR = dyn_cast<IndirectBrInst>(I)) {
1987  if (!isa<BlockAddress>(IBR->getAddress()->stripPointerCasts())) {
1988  // Indeterminate indirectbr; use successor 0.
1989  Dest = IBR->getSuccessor(0);
1990  C = BlockAddress::get(IBR->getSuccessor(0));
1991  }
1992  } else {
1993  llvm_unreachable("Unexpected terminator instruction");
1994  }
1995  if (C) {
1996  assert(Solver.isEdgeFeasible(I->getParent(), Dest) &&
1997  "Didn't find feasible edge?");
1998  (void)Dest;
1999 
2000  I->setOperand(0, C);
2001  }
2002 }
2003 
2005  Module &M, const DataLayout &DL,
2006  std::function<const TargetLibraryInfo &(Function &)> GetTLI,
2007  function_ref<AnalysisResultsForFn(Function &)> getAnalysis) {
2008  SCCPSolver Solver(DL, GetTLI);
2009 
2010  // Loop over all functions, marking arguments to those with their addresses
2011  // taken or that are external as overdefined.
2012  for (Function &F : M) {
2013  if (F.isDeclaration())
2014  continue;
2015 
2016  Solver.addAnalysis(F, getAnalysis(F));
2017 
2018  // Determine if we can track the function's return values. If so, add the
2019  // function to the solver's set of return-tracked functions.
2021  Solver.AddTrackedFunction(&F);
2022 
2023  // Determine if we can track the function's arguments. If so, add the
2024  // function to the solver's set of argument-tracked functions.
2026  Solver.AddArgumentTrackedFunction(&F);
2027  continue;
2028  }
2029 
2030  // Assume the function is called.
2031  Solver.MarkBlockExecutable(&F.front());
2032 
2033  // Assume nothing about the incoming arguments.
2034  for (Argument &AI : F.args())
2035  Solver.markOverdefined(&AI);
2036  }
2037 
2038  // Determine if we can track any of the module's global variables. If so, add
2039  // the global variables we can track to the solver's set of tracked global
2040  // variables.
2041  for (GlobalVariable &G : M.globals()) {
2042  G.removeDeadConstantUsers();
2044  Solver.TrackValueOfGlobalVariable(&G);
2045  }
2046 
2047  // Solve for constants.
2048  bool ResolvedUndefs = true;
2049  Solver.Solve();
2050  while (ResolvedUndefs) {
2051  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n");
2052  ResolvedUndefs = false;
2053  for (Function &F : M)
2054  if (Solver.ResolvedUndefsIn(F)) {
2055  // We run Solve() after we resolved an undef in a function, because
2056  // we might deduce a fact that eliminates an undef in another function.
2057  Solver.Solve();
2058  ResolvedUndefs = true;
2059  }
2060  }
2061 
2062  bool MadeChanges = false;
2063 
2064  // Iterate over all of the instructions in the module, replacing them with
2065  // constants if we have found them to be of constant values.
2066 
2067  for (Function &F : M) {
2068  if (F.isDeclaration())
2069  continue;
2070 
2071  SmallVector<BasicBlock *, 512> BlocksToErase;
2072 
2073  if (Solver.isBlockExecutable(&F.front()))
2074  for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
2075  ++AI) {
2076  if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
2077  ++IPNumArgsElimed;
2078  continue;
2079  }
2080  }
2081 
2082  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
2083  if (!Solver.isBlockExecutable(&*BB)) {
2084  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
2085  ++NumDeadBlocks;
2086 
2087  MadeChanges = true;
2088 
2089  if (&*BB != &F.front())
2090  BlocksToErase.push_back(&*BB);
2091  continue;
2092  }
2093 
2094  for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
2095  Instruction *Inst = &*BI++;
2096  if (Inst->getType()->isVoidTy())
2097  continue;
2098  if (tryToReplaceWithConstant(Solver, Inst)) {
2099  if (Inst->isSafeToRemove())
2100  Inst->eraseFromParent();
2101  // Hey, we just changed something!
2102  MadeChanges = true;
2103  ++IPNumInstRemoved;
2104  }
2105  }
2106  }
2107 
2108  DomTreeUpdater DTU = Solver.getDTU(F);
2109  // Change dead blocks to unreachable. We do it after replacing constants
2110  // in all executable blocks, because changeToUnreachable may remove PHI
2111  // nodes in executable blocks we found values for. The function's entry
2112  // block is not part of BlocksToErase, so we have to handle it separately.
2113  for (BasicBlock *BB : BlocksToErase) {
2114  NumInstRemoved +=
2115  changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false,
2116  /*PreserveLCSSA=*/false, &DTU);
2117  }
2118  if (!Solver.isBlockExecutable(&F.front()))
2119  NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
2120  /*UseLLVMTrap=*/false,
2121  /*PreserveLCSSA=*/false, &DTU);
2122 
2123  // Now that all instructions in the function are constant folded,
2124  // use ConstantFoldTerminator to get rid of in-edges, record DT updates and
2125  // delete dead BBs.
2126  for (BasicBlock *DeadBB : BlocksToErase) {
2127  // If there are any PHI nodes in this successor, drop entries for BB now.
2128  for (Value::user_iterator UI = DeadBB->user_begin(),
2129  UE = DeadBB->user_end();
2130  UI != UE;) {
2131  // Grab the user and then increment the iterator early, as the user
2132  // will be deleted. Step past all adjacent uses from the same user.
2133  auto *I = dyn_cast<Instruction>(*UI);
2134  do { ++UI; } while (UI != UE && *UI == I);
2135 
2136  // Ignore blockaddress users; BasicBlock's dtor will handle them.
2137  if (!I) continue;
2138 
2139  // If we have forced an edge for an indeterminate value, then force the
2140  // terminator to fold to that edge.
2141  forceIndeterminateEdge(I, Solver);
2142  BasicBlock *InstBB = I->getParent();
2143  bool Folded = ConstantFoldTerminator(InstBB,
2144  /*DeleteDeadConditions=*/false,
2145  /*TLI=*/nullptr, &DTU);
2146  assert(Folded &&
2147  "Expect TermInst on constantint or blockaddress to be folded");
2148  (void) Folded;
2149  // If we folded the terminator to an unconditional branch to another
2150  // dead block, replace it with Unreachable, to avoid trying to fold that
2151  // branch again.
2152  BranchInst *BI = cast<BranchInst>(InstBB->getTerminator());
2153  if (BI && BI->isUnconditional() &&
2154  !Solver.isBlockExecutable(BI->getSuccessor(0))) {
2155  InstBB->getTerminator()->eraseFromParent();
2156  new UnreachableInst(InstBB->getContext(), InstBB);
2157  }
2158  }
2159  // Mark dead BB for deletion.
2160  DTU.deleteBB(DeadBB);
2161  }
2162 
2163  for (BasicBlock &BB : F) {
2164  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
2165  Instruction *Inst = &*BI++;
2166  if (Solver.getPredicateInfoFor(Inst)) {
2167  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
2168  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
2169  Value *Op = II->getOperand(0);
2170  Inst->replaceAllUsesWith(Op);
2171  Inst->eraseFromParent();
2172  }
2173  }
2174  }
2175  }
2176  }
2177  }
2178 
2179  // If we inferred constant or undef return values for a function, we replaced
2180  // all call uses with the inferred value. This means we don't need to bother
2181  // actually returning anything from the function. Replace all return
2182  // instructions with return undef.
2183  //
2184  // Do this in two stages: first identify the functions we should process, then
2185  // actually zap their returns. This is important because we can only do this
2186  // if the address of the function isn't taken. In cases where a return is the
2187  // last use of a function, the order of processing functions would affect
2188  // whether other functions are optimizable.
2189  SmallVector<ReturnInst*, 8> ReturnsToZap;
2190 
2191  const MapVector<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
2192  for (const auto &I : RV) {
2193  Function *F = I.first;
2194  if (I.second.isOverdefined() || F->getReturnType()->isVoidTy())
2195  continue;
2196  findReturnsToZap(*F, ReturnsToZap, Solver);
2197  }
2198 
2199  for (const auto &F : Solver.getMRVFunctionsTracked()) {
2200  assert(F->getReturnType()->isStructTy() &&
2201  "The return type should be a struct");
2202  StructType *STy = cast<StructType>(F->getReturnType());
2203  if (Solver.isStructLatticeConstant(F, STy))
2204  findReturnsToZap(*F, ReturnsToZap, Solver);
2205  }
2206 
2207  // Zap all returns which we've identified as zap to change.
2208  for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
2209  Function *F = ReturnsToZap[i]->getParent()->getParent();
2210  ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
2211  }
2212 
2213  // If we inferred constant or undef values for globals variables, we can
2214  // delete the global and any stores that remain to it.
2215  const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
2217  E = TG.end(); I != E; ++I) {
2218  GlobalVariable *GV = I->first;
2219  assert(!I->second.isOverdefined() &&
2220  "Overdefined values should have been taken out of the map!");
2221  LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName()
2222  << "' is constant!\n");
2223  while (!GV->use_empty()) {
2224  StoreInst *SI = cast<StoreInst>(GV->user_back());
2225  SI->eraseFromParent();
2226  }
2227  M.getGlobalList().erase(GV);
2228  ++IPNumGlobalConst;
2229  }
2230 
2231  return MadeChanges;
2232 }
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:486
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:111
static ConstantInt * getFalse(LLVMContext &Context)
Definition: Constants.cpp:616
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:722
void setInt(IntType IntVal) LLVM_LVALUE_FUNCTION
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:87
sccp
Definition: SCCP.cpp:1913
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:777
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:66
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:460
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:350
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:104
bool isTerminator() const
Definition: Instruction.h:128
This class implements a map that also provides access to all stored values in a deterministic order...
Definition: MapVector.h:37
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1165
BasicBlock * getSuccessor(unsigned i) const
arg_iterator arg_end()
Definition: Function.h:709
STATISTIC(NumFunctions, "Total number of functions")
F(f)
An instruction for reading from memory.
Definition: Instructions.h:169
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:144
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:1919
static Constant * getNullValue(Type *Ty)
Constructor to create a &#39;0&#39; constant of arbitrary type.
Definition: Constants.cpp:289
std::unique_ptr< PredicateInfo > PredInfo
Definition: SCCP.h:43
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:195
The address of a basic block.
Definition: Constants.h:839
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
bool isVolatile() const
Return true if this is a load from a volatile memory location.
Definition: Instructions.h:233
Definition: BitVector.h:937
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:238
void initializeSCCPLegacyPassPass(PassRegistry &)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: SCCP.cpp:1860
static void forceIndeterminateEdge(Instruction *I, SCCPSolver &Solver)
Definition: SCCP.cpp:1971
bool empty() const
Definition: MapVector.h:79
FunctionPass * createSCCPPass()
Definition: SCCP.cpp:1917
mir Rename Register Operands
Type * getSourceElementType() const
Definition: Instructions.h:978
Helper struct for bundling up the analysis results per function for IPSCCP.
Definition: SCCP.h:42
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:246
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:325
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:429
iterator find(const KeyT &Key)
Definition: MapVector.h:147
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
Value * getOperand(unsigned i) const
Definition: User.h:169
void setPointer(PointerTy PtrVal) LLVM_LVALUE_FUNCTION
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:359
bool canTrackReturnsInterprocedurally(Function *F)
Determine if the values of the given function&#39;s returns can be tracked interprocedurally.
bool isVoidTy() const
Return true if this is &#39;void&#39;.
Definition: Type.h:141
an instruction for type-safe pointer arithmetic to access elements of arrays and structs ...
Definition: Instructions.h:881
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:154
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:46
void deleteBB(BasicBlock *DelBB)
Delete DelBB.
Conditional or Unconditional Branch instruction.
static BlockAddress * get(Function *F, BasicBlock *BB)
Return a BlockAddress for the specified function and basic block.
Definition: Constants.cpp:1465
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:1172
Analysis pass providing a never-invalidated alias analysis result.
constexpr double e
Definition: MathExtras.h:57
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:1075
arg_iterator arg_begin()
Definition: Function.h:700
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:1752
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:343
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1446
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
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.
bool runIPSCCP(Module &M, const DataLayout &DL, std::function< const TargetLibraryInfo &(Function &)> GetTLI, function_ref< AnalysisResultsForFn(Function &)> getAnalysis)
Definition: SCCP.cpp:2004
CallBr instruction, tracking function calls that may not return control but instead transfer it to a ...
bool canConstantFoldCallTo(const CallBase *Call, const Function *F)
canConstantFoldCallTo - Return true if its even possible to fold a call to the specified function...
idx_iterator idx_begin() const
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: MapVector.h:117
Iterator for intrusive lists based on ilist_node.
unsigned getNumOperands() const
Definition: User.h:191
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:417
This is the shared class of boolean and integer constants.
Definition: Constants.h:83
BlockVerifier::State From
INITIALIZE_PASS_BEGIN(IPSCCPLegacyPass, "ipsccp", "Interprocedural Sparse Conditional Constant Propagation", false, false) INITIALIZE_PASS_END(IPSCCPLegacyPass
Constant * getCompare(CmpInst::Predicate Pred, Type *Ty, const ValueLatticeElement &Other) const
Compares this symbolic value with Other using Pred and returns either true, false or undef constants...
Definition: ValueLattice.h:293
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:837
Module.h This file contains the declarations for the Module class.
Provides information about what library functions are available for the current target.
bool canTrackGlobalVariableInterprocedurally(GlobalVariable *GV)
Determine if the value maintained in the given global variable can be tracked interprocedurally.
size_type count(const KeyT &Key) const
Definition: MapVector.h:142
const DataFlowGraph & G
Definition: RDFGraph.cpp:202
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:374
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
unsigned removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB)
Remove all instructions from a basic block other than it&#39;s terminator and any present EH pad instruct...
Definition: Local.cpp:1877
typename VectorType::iterator iterator
Definition: MapVector.h:49
User::op_iterator arg_iterator
The type of iterator to use when looping over actual arguments at this call site. ...
Definition: CallSite.h:220
unsigned getNumIncomingValues() const
Return the number of incoming edges.
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:1604
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:420
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:115
const Value * getFalseValue() const
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h: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:389
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:329
size_type count(const_arg_type_t< ValueT > V) const
Return 1 if the specified key is in the set, 0 otherwise.
Definition: DenseSet.h:91
bool isUnconditional() const
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:231
Analysis pass providing the TargetLibraryInfo.
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:295
Multiway switch.
iterator end()
Definition: MapVector.h:71
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const BasicBlock & front() const
Definition: Function.h:692
bool isSingleValueType() const
Return true if the type is a valid type for a register in codegen.
Definition: Type.h:250
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:359
LLVM Value Representation.
Definition: Value.h:74
static const Function * getParent(const Value *V)
Invoke instruction.
print Print MemDeps of function
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:1898
bool use_empty() const
Definition: Value.h:343
static bool runSCCP(Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI)
Definition: SCCP.cpp:1802
iterator_range< arg_iterator > args()
Definition: Function.h:724
bool isStructTy() const
True if this is an instance of StructType.
Definition: Type.h:218
User * user_back()
Definition: Value.h:406
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:1837