LLVM  12.0.0git
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"
36 #include "llvm/IR/BasicBlock.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/InitializePasses.h"
53 #include "llvm/Pass.h"
54 #include "llvm/Support/Casting.h"
55 #include "llvm/Support/Debug.h"
58 #include "llvm/Transforms/Scalar.h"
61 #include <cassert>
62 #include <utility>
63 #include <vector>
64 
65 using namespace llvm;
66 
67 #define DEBUG_TYPE "sccp"
68 
69 STATISTIC(NumInstRemoved, "Number of instructions removed");
70 STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
71 STATISTIC(NumInstReplaced,
72  "Number of instructions replaced with (simpler) instruction");
73 
74 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
75 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
76 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
77 STATISTIC(
78  IPNumInstReplaced,
79  "Number of instructions replaced with (simpler) instruction by IPSCCP");
80 
81 // The maximum number of range extensions allowed for operations requiring
82 // widening.
83 static const unsigned MaxNumRangeExtensions = 10;
84 
85 /// Returns MergeOptions with MaxWidenSteps set to MaxNumRangeExtensions.
88  MaxNumRangeExtensions);
89 }
90 namespace {
91 
92 // Helper to check if \p LV is either a constant or a constant
93 // range with a single element. This should cover exactly the same cases as the
94 // old ValueLatticeElement::isConstant() and is intended to be used in the
95 // transition to ValueLatticeElement.
96 bool isConstant(const ValueLatticeElement &LV) {
97  return LV.isConstant() ||
99 }
100 
101 // Helper to check if \p LV is either overdefined or a constant range with more
102 // than a single element. This should cover exactly the same cases as the old
103 // ValueLatticeElement::isOverdefined() and is intended to be used in the
104 // transition to ValueLatticeElement.
105 bool isOverdefined(const ValueLatticeElement &LV) {
106  return LV.isOverdefined() ||
108 }
109 
110 //===----------------------------------------------------------------------===//
111 //
112 /// SCCPSolver - This class is a general purpose solver for Sparse Conditional
113 /// Constant Propagation.
114 ///
115 class SCCPSolver : public InstVisitor<SCCPSolver> {
116  const DataLayout &DL;
117  std::function<const TargetLibraryInfo &(Function &)> GetTLI;
118  SmallPtrSet<BasicBlock *, 8> BBExecutable; // The BBs that are executable.
120  ValueState; // The state each value is in.
121 
122  /// StructValueState - This maintains ValueState for values that have
123  /// StructType, for example for formal arguments, calls, insertelement, etc.
125 
126  /// GlobalValue - If we are tracking any values for the contents of a global
127  /// variable, we keep a mapping from the constant accessor to the element of
128  /// the global, to the currently known value. If the value becomes
129  /// overdefined, it's entry is simply removed from this map.
131 
132  /// TrackedRetVals - If we are tracking arguments into and the return
133  /// value out of a function, it will have an entry in this map, indicating
134  /// what the known return value for the function is.
136 
137  /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
138  /// that return multiple values.
140  TrackedMultipleRetVals;
141 
142  /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
143  /// represented here for efficient lookup.
144  SmallPtrSet<Function *, 16> MRVFunctionsTracked;
145 
146  /// MustTailFunctions - Each function here is a callee of non-removable
147  /// musttail call site.
148  SmallPtrSet<Function *, 16> MustTailCallees;
149 
150  /// TrackingIncomingArguments - This is the set of functions for whose
151  /// arguments we make optimistic assumptions about and try to prove as
152  /// constants.
153  SmallPtrSet<Function *, 16> TrackingIncomingArguments;
154 
155  /// The reason for two worklists is that overdefined is the lowest state
156  /// on the lattice, and moving things to overdefined as fast as possible
157  /// makes SCCP converge much faster.
158  ///
159  /// By having a separate worklist, we accomplish this because everything
160  /// possibly overdefined will become overdefined at the soonest possible
161  /// point.
162  SmallVector<Value *, 64> OverdefinedInstWorkList;
163  SmallVector<Value *, 64> InstWorkList;
164 
165  // The BasicBlock work list
167 
168  /// KnownFeasibleEdges - Entries in this set are edges which have already had
169  /// PHI nodes retriggered.
170  using Edge = std::pair<BasicBlock *, BasicBlock *>;
171  DenseSet<Edge> KnownFeasibleEdges;
172 
175 
176  LLVMContext &Ctx;
177 
178 public:
179  void addAnalysis(Function &F, AnalysisResultsForFn A) {
180  AnalysisResults.insert({&F, std::move(A)});
181  }
182 
183  const PredicateBase *getPredicateInfoFor(Instruction *I) {
184  auto A = AnalysisResults.find(I->getParent()->getParent());
185  if (A == AnalysisResults.end())
186  return nullptr;
187  return A->second.PredInfo->getPredicateInfoFor(I);
188  }
189 
190  DomTreeUpdater getDTU(Function &F) {
191  auto A = AnalysisResults.find(&F);
192  assert(A != AnalysisResults.end() && "Need analysis results for function.");
193  return {A->second.DT, A->second.PDT, DomTreeUpdater::UpdateStrategy::Lazy};
194  }
195 
196  SCCPSolver(const DataLayout &DL,
197  std::function<const TargetLibraryInfo &(Function &)> GetTLI,
198  LLVMContext &Ctx)
199  : DL(DL), GetTLI(std::move(GetTLI)), Ctx(Ctx) {}
200 
201  /// MarkBlockExecutable - This method can be used by clients to mark all of
202  /// the blocks that are known to be intrinsically live in the processed unit.
203  ///
204  /// This returns true if the block was not considered live before.
205  bool MarkBlockExecutable(BasicBlock *BB) {
206  if (!BBExecutable.insert(BB).second)
207  return false;
208  LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n');
209  BBWorkList.push_back(BB); // Add the block to the work list!
210  return true;
211  }
212 
213  /// TrackValueOfGlobalVariable - Clients can use this method to
214  /// inform the SCCPSolver that it should track loads and stores to the
215  /// specified global variable if it can. This is only legal to call if
216  /// performing Interprocedural SCCP.
217  void TrackValueOfGlobalVariable(GlobalVariable *GV) {
218  // We only track the contents of scalar globals.
219  if (GV->getValueType()->isSingleValueType()) {
220  ValueLatticeElement &IV = TrackedGlobals[GV];
221  if (!isa<UndefValue>(GV->getInitializer()))
222  IV.markConstant(GV->getInitializer());
223  }
224  }
225 
226  /// AddTrackedFunction - If the SCCP solver is supposed to track calls into
227  /// and out of the specified function (which cannot have its address taken),
228  /// this method must be called.
229  void AddTrackedFunction(Function *F) {
230  // Add an entry, F -> undef.
231  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
232  MRVFunctionsTracked.insert(F);
233  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
234  TrackedMultipleRetVals.insert(
235  std::make_pair(std::make_pair(F, i), ValueLatticeElement()));
236  } else
237  TrackedRetVals.insert(std::make_pair(F, ValueLatticeElement()));
238  }
239 
240  /// AddMustTailCallee - If the SCCP solver finds that this function is called
241  /// from non-removable musttail call site.
242  void AddMustTailCallee(Function *F) {
243  MustTailCallees.insert(F);
244  }
245 
246  /// Returns true if the given function is called from non-removable musttail
247  /// call site.
248  bool isMustTailCallee(Function *F) {
249  return MustTailCallees.count(F);
250  }
251 
252  void AddArgumentTrackedFunction(Function *F) {
253  TrackingIncomingArguments.insert(F);
254  }
255 
256  /// Returns true if the given function is in the solver's set of
257  /// argument-tracked functions.
258  bool isArgumentTrackedFunction(Function *F) {
259  return TrackingIncomingArguments.count(F);
260  }
261 
262  /// Solve - Solve for constants and executable blocks.
263  void Solve();
264 
265  /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
266  /// that branches on undef values cannot reach any of their successors.
267  /// However, this is not a safe assumption. After we solve dataflow, this
268  /// method should be use to handle this. If this returns true, the solver
269  /// should be rerun.
270  bool ResolvedUndefsIn(Function &F);
271 
272  bool isBlockExecutable(BasicBlock *BB) const {
273  return BBExecutable.count(BB);
274  }
275 
276  // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
277  // block to the 'To' basic block is currently feasible.
278  bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
279 
280  std::vector<ValueLatticeElement> getStructLatticeValueFor(Value *V) const {
281  std::vector<ValueLatticeElement> StructValues;
282  auto *STy = dyn_cast<StructType>(V->getType());
283  assert(STy && "getStructLatticeValueFor() can be called only on structs");
284  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
285  auto I = StructValueState.find(std::make_pair(V, i));
286  assert(I != StructValueState.end() && "Value not in valuemap!");
287  StructValues.push_back(I->second);
288  }
289  return StructValues;
290  }
291 
292  void removeLatticeValueFor(Value *V) { ValueState.erase(V); }
293 
294  const ValueLatticeElement &getLatticeValueFor(Value *V) const {
295  assert(!V->getType()->isStructTy() &&
296  "Should use getStructLatticeValueFor");
298  ValueState.find(V);
299  assert(I != ValueState.end() &&
300  "V not found in ValueState nor Paramstate map!");
301  return I->second;
302  }
303 
304  /// getTrackedRetVals - Get the inferred return value map.
305  const MapVector<Function *, ValueLatticeElement> &getTrackedRetVals() {
306  return TrackedRetVals;
307  }
308 
309  /// getTrackedGlobals - Get and return the set of inferred initializers for
310  /// global variables.
311  const DenseMap<GlobalVariable *, ValueLatticeElement> &getTrackedGlobals() {
312  return TrackedGlobals;
313  }
314 
315  /// getMRVFunctionsTracked - Get the set of functions which return multiple
316  /// values tracked by the pass.
317  const SmallPtrSet<Function *, 16> getMRVFunctionsTracked() {
318  return MRVFunctionsTracked;
319  }
320 
321  /// getMustTailCallees - Get the set of functions which are called
322  /// from non-removable musttail call sites.
323  const SmallPtrSet<Function *, 16> getMustTailCallees() {
324  return MustTailCallees;
325  }
326 
327  /// markOverdefined - Mark the specified value overdefined. This
328  /// works with both scalars and structs.
329  void markOverdefined(Value *V) {
330  if (auto *STy = dyn_cast<StructType>(V->getType()))
331  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
332  markOverdefined(getStructValueState(V, i), V);
333  else
334  markOverdefined(ValueState[V], V);
335  }
336 
337  // isStructLatticeConstant - Return true if all the lattice values
338  // corresponding to elements of the structure are constants,
339  // false otherwise.
340  bool isStructLatticeConstant(Function *F, StructType *STy) {
341  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
342  const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i));
343  assert(It != TrackedMultipleRetVals.end());
344  ValueLatticeElement LV = It->second;
345  if (!isConstant(LV))
346  return false;
347  }
348  return true;
349  }
350 
351  /// Helper to return a Constant if \p LV is either a constant or a constant
352  /// range with a single element.
353  Constant *getConstant(const ValueLatticeElement &LV) const {
354  if (LV.isConstant())
355  return LV.getConstant();
356 
357  if (LV.isConstantRange()) {
358  auto &CR = LV.getConstantRange();
359  if (CR.getSingleElement())
360  return ConstantInt::get(Ctx, *CR.getSingleElement());
361  }
362  return nullptr;
363  }
364 
365 private:
366  ConstantInt *getConstantInt(const ValueLatticeElement &IV) const {
367  return dyn_cast_or_null<ConstantInt>(getConstant(IV));
368  }
369 
370  // pushToWorkList - Helper for markConstant/markOverdefined
371  void pushToWorkList(ValueLatticeElement &IV, Value *V) {
372  if (IV.isOverdefined())
373  return OverdefinedInstWorkList.push_back(V);
374  InstWorkList.push_back(V);
375  }
376 
377  // Helper to push \p V to the worklist, after updating it to \p IV. Also
378  // prints a debug message with the updated value.
379  void pushToWorkListMsg(ValueLatticeElement &IV, Value *V) {
380  LLVM_DEBUG(dbgs() << "updated " << IV << ": " << *V << '\n');
381  pushToWorkList(IV, V);
382  }
383 
384  // markConstant - Make a value be marked as "constant". If the value
385  // is not already a constant, add it to the instruction work list so that
386  // the users of the instruction are updated later.
387  bool markConstant(ValueLatticeElement &IV, Value *V, Constant *C,
388  bool MayIncludeUndef = false) {
389  if (!IV.markConstant(C, MayIncludeUndef))
390  return false;
391  LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
392  pushToWorkList(IV, V);
393  return true;
394  }
395 
396  bool markConstant(Value *V, Constant *C) {
397  assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
398  return markConstant(ValueState[V], V, C);
399  }
400 
401  // markOverdefined - Make a value be marked as "overdefined". If the
402  // value is not already overdefined, add it to the overdefined instruction
403  // work list so that the users of the instruction are updated later.
404  bool markOverdefined(ValueLatticeElement &IV, Value *V) {
405  if (!IV.markOverdefined()) return false;
406 
407  LLVM_DEBUG(dbgs() << "markOverdefined: ";
408  if (auto *F = dyn_cast<Function>(V)) dbgs()
409  << "Function '" << F->getName() << "'\n";
410  else dbgs() << *V << '\n');
411  // Only instructions go on the work list
412  pushToWorkList(IV, V);
413  return true;
414  }
415 
416  /// Merge \p MergeWithV into \p IV and push \p V to the worklist, if \p IV
417  /// changes.
418  bool mergeInValue(ValueLatticeElement &IV, Value *V,
419  ValueLatticeElement MergeWithV,
421  /*MayIncludeUndef=*/false, /*CheckWiden=*/false}) {
422  if (IV.mergeIn(MergeWithV, Opts)) {
423  pushToWorkList(IV, V);
424  LLVM_DEBUG(dbgs() << "Merged " << MergeWithV << " into " << *V << " : "
425  << IV << "\n");
426  return true;
427  }
428  return false;
429  }
430 
431  bool mergeInValue(Value *V, ValueLatticeElement MergeWithV,
433  /*MayIncludeUndef=*/false, /*CheckWiden=*/false}) {
434  assert(!V->getType()->isStructTy() &&
435  "non-structs should use markConstant");
436  return mergeInValue(ValueState[V], V, MergeWithV, Opts);
437  }
438 
439  /// getValueState - Return the ValueLatticeElement object that corresponds to
440  /// the value. This function handles the case when the value hasn't been seen
441  /// yet by properly seeding constants etc.
442  ValueLatticeElement &getValueState(Value *V) {
443  assert(!V->getType()->isStructTy() && "Should use getStructValueState");
444 
445  auto I = ValueState.insert(std::make_pair(V, ValueLatticeElement()));
446  ValueLatticeElement &LV = I.first->second;
447 
448  if (!I.second)
449  return LV; // Common case, already in the map.
450 
451  if (auto *C = dyn_cast<Constant>(V))
452  LV.markConstant(C); // Constants are constant
453 
454  // All others are unknown by default.
455  return LV;
456  }
457 
458  /// getStructValueState - Return the ValueLatticeElement object that
459  /// corresponds to the value/field pair. This function handles the case when
460  /// the value hasn't been seen yet by properly seeding constants etc.
461  ValueLatticeElement &getStructValueState(Value *V, unsigned i) {
462  assert(V->getType()->isStructTy() && "Should use getValueState");
463  assert(i < cast<StructType>(V->getType())->getNumElements() &&
464  "Invalid element #");
465 
466  auto I = StructValueState.insert(
467  std::make_pair(std::make_pair(V, i), ValueLatticeElement()));
468  ValueLatticeElement &LV = I.first->second;
469 
470  if (!I.second)
471  return LV; // Common case, already in the map.
472 
473  if (auto *C = dyn_cast<Constant>(V)) {
474  Constant *Elt = C->getAggregateElement(i);
475 
476  if (!Elt)
477  LV.markOverdefined(); // Unknown sort of constant.
478  else if (isa<UndefValue>(Elt))
479  ; // Undef values remain unknown.
480  else
481  LV.markConstant(Elt); // Constants are constant.
482  }
483 
484  // All others are underdefined by default.
485  return LV;
486  }
487 
488  /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
489  /// work list if it is not already executable.
490  bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
491  if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
492  return false; // This edge is already known to be executable!
493 
494  if (!MarkBlockExecutable(Dest)) {
495  // If the destination is already executable, we just made an *edge*
496  // feasible that wasn't before. Revisit the PHI nodes in the block
497  // because they have potentially new operands.
498  LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
499  << " -> " << Dest->getName() << '\n');
500 
501  for (PHINode &PN : Dest->phis())
502  visitPHINode(PN);
503  }
504  return true;
505  }
506 
507  // getFeasibleSuccessors - Return a vector of booleans to indicate which
508  // successors are reachable from a given terminator instruction.
509  void getFeasibleSuccessors(Instruction &TI, SmallVectorImpl<bool> &Succs);
510 
511  // OperandChangedState - This method is invoked on all of the users of an
512  // instruction that was just changed state somehow. Based on this
513  // information, we need to update the specified user of this instruction.
514  void OperandChangedState(Instruction *I) {
515  if (BBExecutable.count(I->getParent())) // Inst is executable?
516  visit(*I);
517  }
518 
519  // Add U as additional user of V.
520  void addAdditionalUser(Value *V, User *U) {
521  auto Iter = AdditionalUsers.insert({V, {}});
522  Iter.first->second.insert(U);
523  }
524 
525  // Mark I's users as changed, including AdditionalUsers.
526  void markUsersAsChanged(Value *I) {
527  // Functions include their arguments in the use-list. Changed function
528  // values mean that the result of the function changed. We only need to
529  // update the call sites with the new function result and do not have to
530  // propagate the call arguments.
531  if (isa<Function>(I)) {
532  for (User *U : I->users()) {
533  if (auto *CB = dyn_cast<CallBase>(U))
534  handleCallResult(*CB);
535  }
536  } else {
537  for (User *U : I->users())
538  if (auto *UI = dyn_cast<Instruction>(U))
539  OperandChangedState(UI);
540  }
541 
542  auto Iter = AdditionalUsers.find(I);
543  if (Iter != AdditionalUsers.end()) {
544  for (User *U : Iter->second)
545  if (auto *UI = dyn_cast<Instruction>(U))
546  OperandChangedState(UI);
547  }
548  }
549  void handleCallOverdefined(CallBase &CB);
550  void handleCallResult(CallBase &CB);
551  void handleCallArguments(CallBase &CB);
552 
553 private:
554  friend class InstVisitor<SCCPSolver>;
555 
556  // visit implementations - Something changed in this instruction. Either an
557  // operand made a transition, or the instruction is newly executable. Change
558  // the value type of I to reflect these changes if appropriate.
559  void visitPHINode(PHINode &I);
560 
561  // Terminators
562 
563  void visitReturnInst(ReturnInst &I);
564  void visitTerminator(Instruction &TI);
565 
566  void visitCastInst(CastInst &I);
567  void visitSelectInst(SelectInst &I);
568  void visitUnaryOperator(Instruction &I);
569  void visitBinaryOperator(Instruction &I);
570  void visitCmpInst(CmpInst &I);
571  void visitExtractValueInst(ExtractValueInst &EVI);
572  void visitInsertValueInst(InsertValueInst &IVI);
573 
574  void visitCatchSwitchInst(CatchSwitchInst &CPI) {
575  markOverdefined(&CPI);
576  visitTerminator(CPI);
577  }
578 
579  // Instructions that cannot be folded away.
580 
581  void visitStoreInst (StoreInst &I);
582  void visitLoadInst (LoadInst &I);
583  void visitGetElementPtrInst(GetElementPtrInst &I);
584 
585  void visitCallInst (CallInst &I) {
586  visitCallBase(I);
587  }
588 
589  void visitInvokeInst (InvokeInst &II) {
590  visitCallBase(II);
591  visitTerminator(II);
592  }
593 
594  void visitCallBrInst (CallBrInst &CBI) {
595  visitCallBase(CBI);
596  visitTerminator(CBI);
597  }
598 
599  void visitCallBase (CallBase &CB);
600  void visitResumeInst (ResumeInst &I) { /*returns void*/ }
601  void visitUnreachableInst(UnreachableInst &I) { /*returns void*/ }
602  void visitFenceInst (FenceInst &I) { /*returns void*/ }
603 
604  void visitInstruction(Instruction &I) {
605  // All the instructions we don't do any special handling for just
606  // go to overdefined.
607  LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n');
608  markOverdefined(&I);
609  }
610 };
611 
612 } // end anonymous namespace
613 
614 // getFeasibleSuccessors - Return a vector of booleans to indicate which
615 // successors are reachable from a given terminator instruction.
616 void SCCPSolver::getFeasibleSuccessors(Instruction &TI,
617  SmallVectorImpl<bool> &Succs) {
618  Succs.resize(TI.getNumSuccessors());
619  if (auto *BI = dyn_cast<BranchInst>(&TI)) {
620  if (BI->isUnconditional()) {
621  Succs[0] = true;
622  return;
623  }
624 
625  ValueLatticeElement BCValue = getValueState(BI->getCondition());
626  ConstantInt *CI = getConstantInt(BCValue);
627  if (!CI) {
628  // Overdefined condition variables, and branches on unfoldable constant
629  // conditions, mean the branch could go either way.
630  if (!BCValue.isUnknownOrUndef())
631  Succs[0] = Succs[1] = true;
632  return;
633  }
634 
635  // Constant condition variables mean the branch can only go a single way.
636  Succs[CI->isZero()] = true;
637  return;
638  }
639 
640  // Unwinding instructions successors are always executable.
641  if (TI.isExceptionalTerminator()) {
642  Succs.assign(TI.getNumSuccessors(), true);
643  return;
644  }
645 
646  if (auto *SI = dyn_cast<SwitchInst>(&TI)) {
647  if (!SI->getNumCases()) {
648  Succs[0] = true;
649  return;
650  }
651  ValueLatticeElement SCValue = getValueState(SI->getCondition());
652  ConstantInt *CI = getConstantInt(SCValue);
653 
654  if (!CI) { // Overdefined or unknown condition?
655  // All destinations are executable!
656  if (!SCValue.isUnknownOrUndef())
657  Succs.assign(TI.getNumSuccessors(), true);
658  return;
659  }
660 
661  Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
662  return;
663  }
664 
665  // In case of indirect branch and its address is a blockaddress, we mark
666  // the target as executable.
667  if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) {
668  // Casts are folded by visitCastInst.
669  ValueLatticeElement IBRValue = getValueState(IBR->getAddress());
670  BlockAddress *Addr = dyn_cast_or_null<BlockAddress>(getConstant(IBRValue));
671  if (!Addr) { // Overdefined or unknown condition?
672  // All destinations are executable!
673  if (!IBRValue.isUnknownOrUndef())
674  Succs.assign(TI.getNumSuccessors(), true);
675  return;
676  }
677 
678  BasicBlock* T = Addr->getBasicBlock();
679  assert(Addr->getFunction() == T->getParent() &&
680  "Block address of a different function ?");
681  for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) {
682  // This is the target.
683  if (IBR->getDestination(i) == T) {
684  Succs[i] = true;
685  return;
686  }
687  }
688 
689  // If we didn't find our destination in the IBR successor list, then we
690  // have undefined behavior. Its ok to assume no successor is executable.
691  return;
692  }
693 
694  // In case of callbr, we pessimistically assume that all successors are
695  // feasible.
696  if (isa<CallBrInst>(&TI)) {
697  Succs.assign(TI.getNumSuccessors(), true);
698  return;
699  }
700 
701  LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n');
702  llvm_unreachable("SCCP: Don't know how to handle this terminator!");
703 }
704 
705 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
706 // block to the 'To' basic block is currently feasible.
707 bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
708  // Check if we've called markEdgeExecutable on the edge yet. (We could
709  // be more aggressive and try to consider edges which haven't been marked
710  // yet, but there isn't any need.)
711  return KnownFeasibleEdges.count(Edge(From, To));
712 }
713 
714 // visit Implementations - Something changed in this instruction, either an
715 // operand made a transition, or the instruction is newly executable. Change
716 // the value type of I to reflect these changes if appropriate. This method
717 // makes sure to do the following actions:
718 //
719 // 1. If a phi node merges two constants in, and has conflicting value coming
720 // from different branches, or if the PHI node merges in an overdefined
721 // value, then the PHI node becomes overdefined.
722 // 2. If a phi node merges only constants in, and they all agree on value, the
723 // PHI node becomes a constant value equal to that.
724 // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant
725 // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined
726 // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined
727 // 6. If a conditional branch has a value that is constant, make the selected
728 // destination executable
729 // 7. If a conditional branch has a value that is overdefined, make all
730 // successors executable.
731 void SCCPSolver::visitPHINode(PHINode &PN) {
732  // If this PN returns a struct, just mark the result overdefined.
733  // TODO: We could do a lot better than this if code actually uses this.
734  if (PN.getType()->isStructTy())
735  return (void)markOverdefined(&PN);
736 
737  if (getValueState(&PN).isOverdefined())
738  return; // Quick exit
739 
740  // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
741  // and slow us down a lot. Just mark them overdefined.
742  if (PN.getNumIncomingValues() > 64)
743  return (void)markOverdefined(&PN);
744 
745  unsigned NumActiveIncoming = 0;
746 
747  // Look at all of the executable operands of the PHI node. If any of them
748  // are overdefined, the PHI becomes overdefined as well. If they are all
749  // constant, and they agree with each other, the PHI becomes the identical
750  // constant. If they are constant and don't agree, the PHI is a constant
751  // range. If there are no executable operands, the PHI remains unknown.
752  ValueLatticeElement PhiState = getValueState(&PN);
753  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
754  if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
755  continue;
756 
757  ValueLatticeElement IV = getValueState(PN.getIncomingValue(i));
758  PhiState.mergeIn(IV);
759  NumActiveIncoming++;
760  if (PhiState.isOverdefined())
761  break;
762  }
763 
764  // We allow up to 1 range extension per active incoming value and one
765  // additional extension. Note that we manually adjust the number of range
766  // extensions to match the number of active incoming values. This helps to
767  // limit multiple extensions caused by the same incoming value, if other
768  // incoming values are equal.
769  mergeInValue(&PN, PhiState,
770  ValueLatticeElement::MergeOptions().setMaxWidenSteps(
771  NumActiveIncoming + 1));
772  ValueLatticeElement &PhiStateRef = getValueState(&PN);
773  PhiStateRef.setNumRangeExtensions(
774  std::max(NumActiveIncoming, PhiStateRef.getNumRangeExtensions()));
775 }
776 
777 void SCCPSolver::visitReturnInst(ReturnInst &I) {
778  if (I.getNumOperands() == 0) return; // ret void
779 
780  Function *F = I.getParent()->getParent();
781  Value *ResultOp = I.getOperand(0);
782 
783  // If we are tracking the return value of this function, merge it in.
784  if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
785  auto TFRVI = TrackedRetVals.find(F);
786  if (TFRVI != TrackedRetVals.end()) {
787  mergeInValue(TFRVI->second, F, getValueState(ResultOp));
788  return;
789  }
790  }
791 
792  // Handle functions that return multiple values.
793  if (!TrackedMultipleRetVals.empty()) {
794  if (auto *STy = dyn_cast<StructType>(ResultOp->getType()))
795  if (MRVFunctionsTracked.count(F))
796  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
797  mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
798  getStructValueState(ResultOp, i));
799  }
800 }
801 
802 void SCCPSolver::visitTerminator(Instruction &TI) {
803  SmallVector<bool, 16> SuccFeasible;
804  getFeasibleSuccessors(TI, SuccFeasible);
805 
806  BasicBlock *BB = TI.getParent();
807 
808  // Mark all feasible successors executable.
809  for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
810  if (SuccFeasible[i])
811  markEdgeExecutable(BB, TI.getSuccessor(i));
812 }
813 
814 void SCCPSolver::visitCastInst(CastInst &I) {
815  // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would
816  // discover a concrete value later.
817  if (ValueState[&I].isOverdefined())
818  return;
819 
820  ValueLatticeElement OpSt = getValueState(I.getOperand(0));
821  if (Constant *OpC = getConstant(OpSt)) {
822  // Fold the constant as we build.
824  if (isa<UndefValue>(C))
825  return;
826  // Propagate constant value
827  markConstant(&I, C);
828  } else if (OpSt.isConstantRange() && I.getDestTy()->isIntegerTy()) {
829  auto &LV = getValueState(&I);
830  ConstantRange OpRange = OpSt.getConstantRange();
831  Type *DestTy = I.getDestTy();
832  ConstantRange Res =
833  OpRange.castOp(I.getOpcode(), DL.getTypeSizeInBits(DestTy));
834  mergeInValue(LV, &I, ValueLatticeElement::getRange(Res));
835  } else if (!OpSt.isUnknownOrUndef())
836  markOverdefined(&I);
837 }
838 
839 void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
840  // If this returns a struct, mark all elements over defined, we don't track
841  // structs in structs.
842  if (EVI.getType()->isStructTy())
843  return (void)markOverdefined(&EVI);
844 
845  // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would
846  // discover a concrete value later.
847  if (ValueState[&EVI].isOverdefined())
848  return (void)markOverdefined(&EVI);
849 
850  // If this is extracting from more than one level of struct, we don't know.
851  if (EVI.getNumIndices() != 1)
852  return (void)markOverdefined(&EVI);
853 
854  Value *AggVal = EVI.getAggregateOperand();
855  if (AggVal->getType()->isStructTy()) {
856  unsigned i = *EVI.idx_begin();
857  ValueLatticeElement EltVal = getStructValueState(AggVal, i);
858  mergeInValue(getValueState(&EVI), &EVI, EltVal);
859  } else {
860  // Otherwise, must be extracting from an array.
861  return (void)markOverdefined(&EVI);
862  }
863 }
864 
865 void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
866  auto *STy = dyn_cast<StructType>(IVI.getType());
867  if (!STy)
868  return (void)markOverdefined(&IVI);
869 
870  // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would
871  // discover a concrete value later.
872  if (isOverdefined(ValueState[&IVI]))
873  return (void)markOverdefined(&IVI);
874 
875  // If this has more than one index, we can't handle it, drive all results to
876  // undef.
877  if (IVI.getNumIndices() != 1)
878  return (void)markOverdefined(&IVI);
879 
880  Value *Aggr = IVI.getAggregateOperand();
881  unsigned Idx = *IVI.idx_begin();
882 
883  // Compute the result based on what we're inserting.
884  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
885  // This passes through all values that aren't the inserted element.
886  if (i != Idx) {
887  ValueLatticeElement EltVal = getStructValueState(Aggr, i);
888  mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
889  continue;
890  }
891 
892  Value *Val = IVI.getInsertedValueOperand();
893  if (Val->getType()->isStructTy())
894  // We don't track structs in structs.
895  markOverdefined(getStructValueState(&IVI, i), &IVI);
896  else {
897  ValueLatticeElement InVal = getValueState(Val);
898  mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
899  }
900  }
901 }
902 
903 void SCCPSolver::visitSelectInst(SelectInst &I) {
904  // If this select returns a struct, just mark the result overdefined.
905  // TODO: We could do a lot better than this if code actually uses this.
906  if (I.getType()->isStructTy())
907  return (void)markOverdefined(&I);
908 
909  // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would
910  // discover a concrete value later.
911  if (ValueState[&I].isOverdefined())
912  return (void)markOverdefined(&I);
913 
914  ValueLatticeElement CondValue = getValueState(I.getCondition());
915  if (CondValue.isUnknownOrUndef())
916  return;
917 
918  if (ConstantInt *CondCB = getConstantInt(CondValue)) {
919  Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
920  mergeInValue(&I, getValueState(OpVal));
921  return;
922  }
923 
924  // Otherwise, the condition is overdefined or a constant we can't evaluate.
925  // See if we can produce something better than overdefined based on the T/F
926  // value.
927  ValueLatticeElement TVal = getValueState(I.getTrueValue());
928  ValueLatticeElement FVal = getValueState(I.getFalseValue());
929 
930  bool Changed = ValueState[&I].mergeIn(TVal);
931  Changed |= ValueState[&I].mergeIn(FVal);
932  if (Changed)
933  pushToWorkListMsg(ValueState[&I], &I);
934 }
935 
936 // Handle Unary Operators.
937 void SCCPSolver::visitUnaryOperator(Instruction &I) {
938  ValueLatticeElement V0State = getValueState(I.getOperand(0));
939 
940  ValueLatticeElement &IV = ValueState[&I];
941  // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would
942  // discover a concrete value later.
943  if (isOverdefined(IV))
944  return (void)markOverdefined(&I);
945 
946  if (isConstant(V0State)) {
947  Constant *C = ConstantExpr::get(I.getOpcode(), getConstant(V0State));
948 
949  // op Y -> undef.
950  if (isa<UndefValue>(C))
951  return;
952  return (void)markConstant(IV, &I, C);
953  }
954 
955  // If something is undef, wait for it to resolve.
956  if (!isOverdefined(V0State))
957  return;
958 
959  markOverdefined(&I);
960 }
961 
962 // Handle Binary Operators.
963 void SCCPSolver::visitBinaryOperator(Instruction &I) {
964  ValueLatticeElement V1State = getValueState(I.getOperand(0));
965  ValueLatticeElement V2State = getValueState(I.getOperand(1));
966 
967  ValueLatticeElement &IV = ValueState[&I];
968  if (IV.isOverdefined())
969  return;
970 
971  // If something is undef, wait for it to resolve.
972  if (V1State.isUnknownOrUndef() || V2State.isUnknownOrUndef())
973  return;
974 
975  if (V1State.isOverdefined() && V2State.isOverdefined())
976  return (void)markOverdefined(&I);
977 
978  // If either of the operands is a constant, try to fold it to a constant.
979  // TODO: Use information from notconstant better.
980  if ((V1State.isConstant() || V2State.isConstant())) {
981  Value *V1 = isConstant(V1State) ? getConstant(V1State) : I.getOperand(0);
982  Value *V2 = isConstant(V2State) ? getConstant(V2State) : I.getOperand(1);
984  auto *C = dyn_cast_or_null<Constant>(R);
985  if (C) {
986  // X op Y -> undef.
987  if (isa<UndefValue>(C))
988  return;
989  // Conservatively assume that the result may be based on operands that may
990  // be undef. Note that we use mergeInValue to combine the constant with
991  // the existing lattice value for I, as different constants might be found
992  // after one of the operands go to overdefined, e.g. due to one operand
993  // being a special floating value.
994  ValueLatticeElement NewV;
995  NewV.markConstant(C, /*MayIncludeUndef=*/true);
996  return (void)mergeInValue(&I, NewV);
997  }
998  }
999 
1000  // Only use ranges for binary operators on integers.
1001  if (!I.getType()->isIntegerTy())
1002  return markOverdefined(&I);
1003 
1004  // Try to simplify to a constant range.
1005  ConstantRange A = ConstantRange::getFull(I.getType()->getScalarSizeInBits());
1006  ConstantRange B = ConstantRange::getFull(I.getType()->getScalarSizeInBits());
1007  if (V1State.isConstantRange())
1008  A = V1State.getConstantRange();
1009  if (V2State.isConstantRange())
1010  B = V2State.getConstantRange();
1011 
1012  ConstantRange R = A.binaryOp(cast<BinaryOperator>(&I)->getOpcode(), B);
1013  mergeInValue(&I, ValueLatticeElement::getRange(R));
1014 
1015  // TODO: Currently we do not exploit special values that produce something
1016  // better than overdefined with an overdefined operand for vector or floating
1017  // point types, like and <4 x i32> overdefined, zeroinitializer.
1018 }
1019 
1020 // Handle ICmpInst instruction.
1021 void SCCPSolver::visitCmpInst(CmpInst &I) {
1022  // Do not cache this lookup, getValueState calls later in the function might
1023  // invalidate the reference.
1024  if (isOverdefined(ValueState[&I]))
1025  return (void)markOverdefined(&I);
1026 
1027  Value *Op1 = I.getOperand(0);
1028  Value *Op2 = I.getOperand(1);
1029 
1030  // For parameters, use ParamState which includes constant range info if
1031  // available.
1032  auto V1State = getValueState(Op1);
1033  auto V2State = getValueState(Op2);
1034 
1035  Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
1036  if (C) {
1037  if (isa<UndefValue>(C))
1038  return;
1040  CV.markConstant(C);
1041  mergeInValue(&I, CV);
1042  return;
1043  }
1044 
1045  // If operands are still unknown, wait for it to resolve.
1046  if ((V1State.isUnknownOrUndef() || V2State.isUnknownOrUndef()) &&
1047  !isConstant(ValueState[&I]))
1048  return;
1049 
1050  markOverdefined(&I);
1051 }
1052 
1053 // Handle getelementptr instructions. If all operands are constants then we
1054 // can turn this into a getelementptr ConstantExpr.
1055 void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
1056  if (isOverdefined(ValueState[&I]))
1057  return (void)markOverdefined(&I);
1058 
1060  Operands.reserve(I.getNumOperands());
1061 
1062  for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
1063  ValueLatticeElement State = getValueState(I.getOperand(i));
1064  if (State.isUnknownOrUndef())
1065  return; // Operands are not resolved yet.
1066 
1067  if (isOverdefined(State))
1068  return (void)markOverdefined(&I);
1069 
1070  if (Constant *C = getConstant(State)) {
1071  Operands.push_back(C);
1072  continue;
1073  }
1074 
1075  return (void)markOverdefined(&I);
1076  }
1077 
1078  Constant *Ptr = Operands[0];
1079  auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end());
1080  Constant *C =
1081  ConstantExpr::getGetElementPtr(I.getSourceElementType(), Ptr, Indices);
1082  if (isa<UndefValue>(C))
1083  return;
1084  markConstant(&I, C);
1085 }
1086 
1087 void SCCPSolver::visitStoreInst(StoreInst &SI) {
1088  // If this store is of a struct, ignore it.
1089  if (SI.getOperand(0)->getType()->isStructTy())
1090  return;
1091 
1092  if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
1093  return;
1094 
1095  GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
1096  auto I = TrackedGlobals.find(GV);
1097  if (I == TrackedGlobals.end())
1098  return;
1099 
1100  // Get the value we are storing into the global, then merge it.
1101  mergeInValue(I->second, GV, getValueState(SI.getOperand(0)),
1103  if (I->second.isOverdefined())
1104  TrackedGlobals.erase(I); // No need to keep tracking this!
1105 }
1106 
1108  if (MDNode *Ranges = I->getMetadata(LLVMContext::MD_range))
1109  if (I->getType()->isIntegerTy())
1111  getConstantRangeFromMetadata(*Ranges));
1112  // TODO: Also handle MD_nonnull.
1114 }
1115 
1116 // Handle load instructions. If the operand is a constant pointer to a constant
1117 // global, we can replace the load with the loaded constant value!
1118 void SCCPSolver::visitLoadInst(LoadInst &I) {
1119  // If this load is of a struct or the load is volatile, just mark the result
1120  // as overdefined.
1121  if (I.getType()->isStructTy() || I.isVolatile())
1122  return (void)markOverdefined(&I);
1123 
1124  // ResolvedUndefsIn might mark I as overdefined. Bail out, even if we would
1125  // discover a concrete value later.
1126  if (ValueState[&I].isOverdefined())
1127  return (void)markOverdefined(&I);
1128 
1129  ValueLatticeElement PtrVal = getValueState(I.getOperand(0));
1130  if (PtrVal.isUnknownOrUndef())
1131  return; // The pointer is not resolved yet!
1132 
1133  ValueLatticeElement &IV = ValueState[&I];
1134 
1135  if (isConstant(PtrVal)) {
1136  Constant *Ptr = getConstant(PtrVal);
1137 
1138  // load null is undefined.
1139  if (isa<ConstantPointerNull>(Ptr)) {
1141  return (void)markOverdefined(IV, &I);
1142  else
1143  return;
1144  }
1145 
1146  // Transform load (constant global) into the value loaded.
1147  if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) {
1148  if (!TrackedGlobals.empty()) {
1149  // If we are tracking this global, merge in the known value for it.
1150  auto It = TrackedGlobals.find(GV);
1151  if (It != TrackedGlobals.end()) {
1152  mergeInValue(IV, &I, It->second, getMaxWidenStepsOpts());
1153  return;
1154  }
1155  }
1156  }
1157 
1158  // Transform load from a constant into a constant if possible.
1159  if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) {
1160  if (isa<UndefValue>(C))
1161  return;
1162  return (void)markConstant(IV, &I, C);
1163  }
1164  }
1165 
1166  // Fall back to metadata.
1167  mergeInValue(&I, getValueFromMetadata(&I));
1168 }
1169 
1170 void SCCPSolver::visitCallBase(CallBase &CB) {
1171  handleCallResult(CB);
1172  handleCallArguments(CB);
1173 }
1174 
1175 void SCCPSolver::handleCallOverdefined(CallBase &CB) {
1176  Function *F = CB.getCalledFunction();
1177 
1178  // Void return and not tracking callee, just bail.
1179  if (CB.getType()->isVoidTy())
1180  return;
1181 
1182  // Always mark struct return as overdefined.
1183  if (CB.getType()->isStructTy())
1184  return (void)markOverdefined(&CB);
1185 
1186  // Otherwise, if we have a single return value case, and if the function is
1187  // a declaration, maybe we can constant fold it.
1188  if (F && F->isDeclaration() && canConstantFoldCallTo(&CB, F)) {
1190  for (auto AI = CB.arg_begin(), E = CB.arg_end(); AI != E; ++AI) {
1191  if (AI->get()->getType()->isStructTy())
1192  return markOverdefined(&CB); // Can't handle struct args.
1193  ValueLatticeElement State = getValueState(*AI);
1194 
1195  if (State.isUnknownOrUndef())
1196  return; // Operands are not resolved yet.
1197  if (isOverdefined(State))
1198  return (void)markOverdefined(&CB);
1199  assert(isConstant(State) && "Unknown state!");
1200  Operands.push_back(getConstant(State));
1201  }
1202 
1203  if (isOverdefined(getValueState(&CB)))
1204  return (void)markOverdefined(&CB);
1205 
1206  // If we can constant fold this, mark the result of the call as a
1207  // constant.
1208  if (Constant *C = ConstantFoldCall(&CB, F, Operands, &GetTLI(*F))) {
1209  // call -> undef.
1210  if (isa<UndefValue>(C))
1211  return;
1212  return (void)markConstant(&CB, C);
1213  }
1214  }
1215 
1216  // Fall back to metadata.
1217  mergeInValue(&CB, getValueFromMetadata(&CB));
1218 }
1219 
1220 void SCCPSolver::handleCallArguments(CallBase &CB) {
1221  Function *F = CB.getCalledFunction();
1222  // If this is a local function that doesn't have its address taken, mark its
1223  // entry block executable and merge in the actual arguments to the call into
1224  // the formal arguments of the function.
1225  if (!TrackingIncomingArguments.empty() &&
1226  TrackingIncomingArguments.count(F)) {
1227  MarkBlockExecutable(&F->front());
1228 
1229  // Propagate information from this call site into the callee.
1230  auto CAI = CB.arg_begin();
1231  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
1232  ++AI, ++CAI) {
1233  // If this argument is byval, and if the function is not readonly, there
1234  // will be an implicit copy formed of the input aggregate.
1235  if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
1236  markOverdefined(&*AI);
1237  continue;
1238  }
1239 
1240  if (auto *STy = dyn_cast<StructType>(AI->getType())) {
1241  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1242  ValueLatticeElement CallArg = getStructValueState(*CAI, i);
1243  mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg,
1245  }
1246  } else
1247  mergeInValue(&*AI, getValueState(*CAI), getMaxWidenStepsOpts());
1248  }
1249  }
1250 }
1251 
1252 void SCCPSolver::handleCallResult(CallBase &CB) {
1253  Function *F = CB.getCalledFunction();
1254 
1255  if (auto *II = dyn_cast<IntrinsicInst>(&CB)) {
1256  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
1257  if (ValueState[&CB].isOverdefined())
1258  return;
1259 
1260  Value *CopyOf = CB.getOperand(0);
1261  ValueLatticeElement CopyOfVal = getValueState(CopyOf);
1262  auto *PI = getPredicateInfoFor(&CB);
1263  assert(PI && "Missing predicate info for ssa.copy");
1264 
1265  CmpInst *Cmp;
1266  bool TrueEdge;
1267  if (auto *PBranch = dyn_cast<PredicateBranch>(PI)) {
1268  Cmp = dyn_cast<CmpInst>(PBranch->Condition);
1269  TrueEdge = PBranch->TrueEdge;
1270  } else if (auto *PAssume = dyn_cast<PredicateAssume>(PI)) {
1271  Cmp = dyn_cast<CmpInst>(PAssume->Condition);
1272  TrueEdge = true;
1273  } else {
1274  mergeInValue(ValueState[&CB], &CB, CopyOfVal);
1275  return;
1276  }
1277 
1278  // Everything below relies on the condition being a comparison.
1279  if (!Cmp) {
1280  mergeInValue(ValueState[&CB], &CB, CopyOfVal);
1281  return;
1282  }
1283 
1284  Value *RenamedOp = PI->RenamedOp;
1285  Value *CmpOp0 = Cmp->getOperand(0);
1286  Value *CmpOp1 = Cmp->getOperand(1);
1287  // Bail out if neither of the operands matches RenamedOp.
1288  if (CmpOp0 != RenamedOp && CmpOp1 != RenamedOp) {
1289  mergeInValue(ValueState[&CB], &CB, getValueState(CopyOf));
1290  return;
1291  }
1292 
1293  auto Pred = Cmp->getPredicate();
1294  if (CmpOp1 == RenamedOp) {
1295  std::swap(CmpOp0, CmpOp1);
1296  Pred = Cmp->getSwappedPredicate();
1297  }
1298 
1299  // Wait until CmpOp1 is resolved.
1300  if (getValueState(CmpOp1).isUnknown()) {
1301  addAdditionalUser(CmpOp1, &CB);
1302  return;
1303  }
1304 
1305  // The code below relies on PredicateInfo only inserting copies for the
1306  // true branch when the branch condition is an AND and only inserting
1307  // copies for the false branch when the branch condition is an OR. This
1308  // ensures we can intersect the range from the condition with the range of
1309  // CopyOf.
1310  if (!TrueEdge)
1311  Pred = CmpInst::getInversePredicate(Pred);
1312 
1313  ValueLatticeElement CondVal = getValueState(CmpOp1);
1314  ValueLatticeElement &IV = ValueState[&CB];
1315  if (CondVal.isConstantRange() || CopyOfVal.isConstantRange()) {
1316  auto ImposedCR =
1317  ConstantRange::getFull(DL.getTypeSizeInBits(CopyOf->getType()));
1318 
1319  // Get the range imposed by the condition.
1320  if (CondVal.isConstantRange())
1322  Pred, CondVal.getConstantRange());
1323 
1324  // Combine range info for the original value with the new range from the
1325  // condition.
1326  auto CopyOfCR = CopyOfVal.isConstantRange()
1327  ? CopyOfVal.getConstantRange()
1328  : ConstantRange::getFull(
1329  DL.getTypeSizeInBits(CopyOf->getType()));
1330  auto NewCR = ImposedCR.intersectWith(CopyOfCR);
1331  // If the existing information is != x, do not use the information from
1332  // a chained predicate, as the != x information is more likely to be
1333  // helpful in practice.
1334  if (!CopyOfCR.contains(NewCR) && CopyOfCR.getSingleMissingElement())
1335  NewCR = CopyOfCR;
1336 
1337  addAdditionalUser(CmpOp1, &CB);
1338  // TODO: Actually filp MayIncludeUndef for the created range to false,
1339  // once most places in the optimizer respect the branches on
1340  // undef/poison are UB rule. The reason why the new range cannot be
1341  // undef is as follows below:
1342  // The new range is based on a branch condition. That guarantees that
1343  // neither of the compare operands can be undef in the branch targets,
1344  // unless we have conditions that are always true/false (e.g. icmp ule
1345  // i32, %a, i32_max). For the latter overdefined/empty range will be
1346  // inferred, but the branch will get folded accordingly anyways.
1347  mergeInValue(
1348  IV, &CB,
1349  ValueLatticeElement::getRange(NewCR, /*MayIncludeUndef=*/true));
1350  return;
1351  } else if (Pred == CmpInst::ICMP_EQ && CondVal.isConstant()) {
1352  // For non-integer values or integer constant expressions, only
1353  // propagate equal constants.
1354  addAdditionalUser(CmpOp1, &CB);
1355  mergeInValue(IV, &CB, CondVal);
1356  return;
1357  }
1358 
1359  return (void)mergeInValue(IV, &CB, CopyOfVal);
1360  }
1361  }
1362 
1363  // The common case is that we aren't tracking the callee, either because we
1364  // are not doing interprocedural analysis or the callee is indirect, or is
1365  // external. Handle these cases first.
1366  if (!F || F->isDeclaration())
1367  return handleCallOverdefined(CB);
1368 
1369  // If this is a single/zero retval case, see if we're tracking the function.
1370  if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
1371  if (!MRVFunctionsTracked.count(F))
1372  return handleCallOverdefined(CB); // Not tracking this callee.
1373 
1374  // If we are tracking this callee, propagate the result of the function
1375  // into this call site.
1376  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1377  mergeInValue(getStructValueState(&CB, i), &CB,
1378  TrackedMultipleRetVals[std::make_pair(F, i)],
1380  } else {
1381  auto TFRVI = TrackedRetVals.find(F);
1382  if (TFRVI == TrackedRetVals.end())
1383  return handleCallOverdefined(CB); // Not tracking this callee.
1384 
1385  // If so, propagate the return value of the callee into this call result.
1386  mergeInValue(&CB, TFRVI->second, getMaxWidenStepsOpts());
1387  }
1388 }
1389 
1390 void SCCPSolver::Solve() {
1391  // Process the work lists until they are empty!
1392  while (!BBWorkList.empty() || !InstWorkList.empty() ||
1393  !OverdefinedInstWorkList.empty()) {
1394  // Process the overdefined instruction's work list first, which drives other
1395  // things to overdefined more quickly.
1396  while (!OverdefinedInstWorkList.empty()) {
1397  Value *I = OverdefinedInstWorkList.pop_back_val();
1398 
1399  LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
1400 
1401  // "I" got into the work list because it either made the transition from
1402  // bottom to constant, or to overdefined.
1403  //
1404  // Anything on this worklist that is overdefined need not be visited
1405  // since all of its users will have already been marked as overdefined
1406  // Update all of the users of this instruction's value.
1407  //
1408  markUsersAsChanged(I);
1409  }
1410 
1411  // Process the instruction work list.
1412  while (!InstWorkList.empty()) {
1413  Value *I = InstWorkList.pop_back_val();
1414 
1415  LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
1416 
1417  // "I" got into the work list because it made the transition from undef to
1418  // constant.
1419  //
1420  // Anything on this worklist that is overdefined need not be visited
1421  // since all of its users will have already been marked as overdefined.
1422  // Update all of the users of this instruction's value.
1423  //
1424  if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
1425  markUsersAsChanged(I);
1426  }
1427 
1428  // Process the basic block work list.
1429  while (!BBWorkList.empty()) {
1430  BasicBlock *BB = BBWorkList.back();
1431  BBWorkList.pop_back();
1432 
1433  LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
1434 
1435  // Notify all instructions in this basic block that they are newly
1436  // executable.
1437  visit(BB);
1438  }
1439  }
1440 }
1441 
1442 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
1443 /// that branches on undef values cannot reach any of their successors.
1444 /// However, this is not a safe assumption. After we solve dataflow, this
1445 /// method should be use to handle this. If this returns true, the solver
1446 /// should be rerun.
1447 ///
1448 /// This method handles this by finding an unresolved branch and marking it one
1449 /// of the edges from the block as being feasible, even though the condition
1450 /// doesn't say it would otherwise be. This allows SCCP to find the rest of the
1451 /// CFG and only slightly pessimizes the analysis results (by marking one,
1452 /// potentially infeasible, edge feasible). This cannot usefully modify the
1453 /// constraints on the condition of the branch, as that would impact other users
1454 /// of the value.
1455 ///
1456 /// This scan also checks for values that use undefs. It conservatively marks
1457 /// them as overdefined.
1458 bool SCCPSolver::ResolvedUndefsIn(Function &F) {
1459  for (BasicBlock &BB : F) {
1460  if (!BBExecutable.count(&BB))
1461  continue;
1462 
1463  for (Instruction &I : BB) {
1464  // Look for instructions which produce undef values.
1465  if (I.getType()->isVoidTy()) continue;
1466 
1467  if (auto *STy = dyn_cast<StructType>(I.getType())) {
1468  // Only a few things that can be structs matter for undef.
1469 
1470  // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
1471  if (auto *CB = dyn_cast<CallBase>(&I))
1472  if (Function *F = CB->getCalledFunction())
1473  if (MRVFunctionsTracked.count(F))
1474  continue;
1475 
1476  // extractvalue and insertvalue don't need to be marked; they are
1477  // tracked as precisely as their operands.
1478  if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
1479  continue;
1480  // Send the results of everything else to overdefined. We could be
1481  // more precise than this but it isn't worth bothering.
1482  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1483  ValueLatticeElement &LV = getStructValueState(&I, i);
1484  if (LV.isUnknownOrUndef())
1485  markOverdefined(LV, &I);
1486  }
1487  continue;
1488  }
1489 
1490  ValueLatticeElement &LV = getValueState(&I);
1491  if (!LV.isUnknownOrUndef())
1492  continue;
1493 
1494  // There are two reasons a call can have an undef result
1495  // 1. It could be tracked.
1496  // 2. It could be constant-foldable.
1497  // Because of the way we solve return values, tracked calls must
1498  // never be marked overdefined in ResolvedUndefsIn.
1499  if (auto *CB = dyn_cast<CallBase>(&I))
1500  if (Function *F = CB->getCalledFunction())
1501  if (TrackedRetVals.count(F))
1502  continue;
1503 
1504  if (isa<LoadInst>(I)) {
1505  // A load here means one of two things: a load of undef from a global,
1506  // a load from an unknown pointer. Either way, having it return undef
1507  // is okay.
1508  continue;
1509  }
1510 
1511  markOverdefined(&I);
1512  return true;
1513  }
1514 
1515  // Check to see if we have a branch or switch on an undefined value. If so
1516  // we force the branch to go one way or the other to make the successor
1517  // values live. It doesn't really matter which way we force it.
1518  Instruction *TI = BB.getTerminator();
1519  if (auto *BI = dyn_cast<BranchInst>(TI)) {
1520  if (!BI->isConditional()) continue;
1521  if (!getValueState(BI->getCondition()).isUnknownOrUndef())
1522  continue;
1523 
1524  // If the input to SCCP is actually branch on undef, fix the undef to
1525  // false.
1526  if (isa<UndefValue>(BI->getCondition())) {
1527  BI->setCondition(ConstantInt::getFalse(BI->getContext()));
1528  markEdgeExecutable(&BB, TI->getSuccessor(1));
1529  return true;
1530  }
1531 
1532  // Otherwise, it is a branch on a symbolic value which is currently
1533  // considered to be undef. Make sure some edge is executable, so a
1534  // branch on "undef" always flows somewhere.
1535  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1536  BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
1537  if (markEdgeExecutable(&BB, DefaultSuccessor))
1538  return true;
1539 
1540  continue;
1541  }
1542 
1543  if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
1544  // Indirect branch with no successor ?. Its ok to assume it branches
1545  // to no target.
1546  if (IBR->getNumSuccessors() < 1)
1547  continue;
1548 
1549  if (!getValueState(IBR->getAddress()).isUnknownOrUndef())
1550  continue;
1551 
1552  // If the input to SCCP is actually branch on undef, fix the undef to
1553  // the first successor of the indirect branch.
1554  if (isa<UndefValue>(IBR->getAddress())) {
1555  IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
1556  markEdgeExecutable(&BB, IBR->getSuccessor(0));
1557  return true;
1558  }
1559 
1560  // Otherwise, it is a branch on a symbolic value which is currently
1561  // considered to be undef. Make sure some edge is executable, so a
1562  // branch on "undef" always flows somewhere.
1563  // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
1564  // we can assume the branch has undefined behavior instead.
1565  BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
1566  if (markEdgeExecutable(&BB, DefaultSuccessor))
1567  return true;
1568 
1569  continue;
1570  }
1571 
1572  if (auto *SI = dyn_cast<SwitchInst>(TI)) {
1573  if (!SI->getNumCases() ||
1574  !getValueState(SI->getCondition()).isUnknownOrUndef())
1575  continue;
1576 
1577  // If the input to SCCP is actually switch on undef, fix the undef to
1578  // the first constant.
1579  if (isa<UndefValue>(SI->getCondition())) {
1580  SI->setCondition(SI->case_begin()->getCaseValue());
1581  markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
1582  return true;
1583  }
1584 
1585  // Otherwise, it is a branch on a symbolic value which is currently
1586  // considered to be undef. Make sure some edge is executable, so a
1587  // branch on "undef" always flows somewhere.
1588  // FIXME: Distinguish between dead code and an LLVM "undef" value.
1589  BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
1590  if (markEdgeExecutable(&BB, DefaultSuccessor))
1591  return true;
1592 
1593  continue;
1594  }
1595  }
1596 
1597  return false;
1598 }
1599 
1600 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
1601  Constant *Const = nullptr;
1602  if (V->getType()->isStructTy()) {
1603  std::vector<ValueLatticeElement> IVs = Solver.getStructLatticeValueFor(V);
1604  if (any_of(IVs,
1605  [](const ValueLatticeElement &LV) { return isOverdefined(LV); }))
1606  return false;
1607  std::vector<Constant *> ConstVals;
1608  auto *ST = cast<StructType>(V->getType());
1609  for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1610  ValueLatticeElement V = IVs[i];
1611  ConstVals.push_back(isConstant(V)
1612  ? Solver.getConstant(V)
1613  : UndefValue::get(ST->getElementType(i)));
1614  }
1615  Const = ConstantStruct::get(ST, ConstVals);
1616  } else {
1617  const ValueLatticeElement &IV = Solver.getLatticeValueFor(V);
1618  if (isOverdefined(IV))
1619  return false;
1620 
1621  Const =
1622  isConstant(IV) ? Solver.getConstant(IV) : UndefValue::get(V->getType());
1623  }
1624  assert(Const && "Constant is nullptr here!");
1625 
1626  // Replacing `musttail` instructions with constant breaks `musttail` invariant
1627  // unless the call itself can be removed
1628  CallInst *CI = dyn_cast<CallInst>(V);
1629  if (CI && CI->isMustTailCall() && !CI->isSafeToRemove()) {
1630  Function *F = CI->getCalledFunction();
1631 
1632  // Don't zap returns of the callee
1633  if (F)
1634  Solver.AddMustTailCallee(F);
1635 
1636  LLVM_DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI
1637  << " as a constant\n");
1638  return false;
1639  }
1640 
1641  LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
1642 
1643  // Replaces all of the uses of a variable with uses of the constant.
1644  V->replaceAllUsesWith(Const);
1645  return true;
1646 }
1647 
1648 static bool simplifyInstsInBlock(SCCPSolver &Solver, BasicBlock &BB,
1649  SmallPtrSetImpl<Value *> &InsertedValues,
1650  Statistic &InstRemovedStat,
1651  Statistic &InstReplacedStat) {
1652  bool MadeChanges = false;
1653  for (Instruction &Inst : make_early_inc_range(BB)) {
1654  if (Inst.getType()->isVoidTy())
1655  continue;
1656  if (tryToReplaceWithConstant(Solver, &Inst)) {
1657  if (Inst.isSafeToRemove())
1658  Inst.eraseFromParent();
1659  // Hey, we just changed something!
1660  MadeChanges = true;
1661  ++InstRemovedStat;
1662  } else if (isa<SExtInst>(&Inst)) {
1663  Value *ExtOp = Inst.getOperand(0);
1664  if (isa<Constant>(ExtOp) || InsertedValues.count(ExtOp))
1665  continue;
1666  const ValueLatticeElement &IV = Solver.getLatticeValueFor(ExtOp);
1667  if (!IV.isConstantRange(/*UndefAllowed=*/false))
1668  continue;
1669  if (IV.getConstantRange().isAllNonNegative()) {
1670  auto *ZExt = new ZExtInst(ExtOp, Inst.getType(), "", &Inst);
1671  InsertedValues.insert(ZExt);
1672  Inst.replaceAllUsesWith(ZExt);
1673  Solver.removeLatticeValueFor(&Inst);
1674  Inst.eraseFromParent();
1675  InstReplacedStat++;
1676  MadeChanges = true;
1677  }
1678  }
1679  }
1680  return MadeChanges;
1681 }
1682 
1683 // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
1684 // and return true if the function was modified.
1685 static bool runSCCP(Function &F, const DataLayout &DL,
1686  const TargetLibraryInfo *TLI) {
1687  LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
1688  SCCPSolver Solver(
1689  DL, [TLI](Function &F) -> const TargetLibraryInfo & { return *TLI; },
1690  F.getContext());
1691 
1692  // Mark the first block of the function as being executable.
1693  Solver.MarkBlockExecutable(&F.front());
1694 
1695  // Mark all arguments to the function as being overdefined.
1696  for (Argument &AI : F.args())
1697  Solver.markOverdefined(&AI);
1698 
1699  // Solve for constants.
1700  bool ResolvedUndefs = true;
1701  while (ResolvedUndefs) {
1702  Solver.Solve();
1703  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n");
1704  ResolvedUndefs = Solver.ResolvedUndefsIn(F);
1705  }
1706 
1707  bool MadeChanges = false;
1708 
1709  // If we decided that there are basic blocks that are dead in this function,
1710  // delete their contents now. Note that we cannot actually delete the blocks,
1711  // as we cannot modify the CFG of the function.
1712 
1713  SmallPtrSet<Value *, 32> InsertedValues;
1714  for (BasicBlock &BB : F) {
1715  if (!Solver.isBlockExecutable(&BB)) {
1716  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1717 
1718  ++NumDeadBlocks;
1719  NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB);
1720 
1721  MadeChanges = true;
1722  continue;
1723  }
1724 
1725  MadeChanges |= simplifyInstsInBlock(Solver, BB, InsertedValues,
1726  NumInstRemoved, NumInstReplaced);
1727  }
1728 
1729  return MadeChanges;
1730 }
1731 
1733  const DataLayout &DL = F.getParent()->getDataLayout();
1734  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
1735  if (!runSCCP(F, DL, &TLI))
1736  return PreservedAnalyses::all();
1737 
1738  auto PA = PreservedAnalyses();
1739  PA.preserve<GlobalsAA>();
1740  PA.preserveSet<CFGAnalyses>();
1741  return PA;
1742 }
1743 
1744 namespace {
1745 
1746 //===--------------------------------------------------------------------===//
1747 //
1748 /// SCCP Class - This class uses the SCCPSolver to implement a per-function
1749 /// Sparse Conditional Constant Propagator.
1750 ///
1751 class SCCPLegacyPass : public FunctionPass {
1752 public:
1753  // Pass identification, replacement for typeid
1754  static char ID;
1755 
1756  SCCPLegacyPass() : FunctionPass(ID) {
1758  }
1759 
1760  void getAnalysisUsage(AnalysisUsage &AU) const override {
1763  AU.setPreservesCFG();
1764  }
1765 
1766  // runOnFunction - Run the Sparse Conditional Constant Propagation
1767  // algorithm, and return true if the function was modified.
1768  bool runOnFunction(Function &F) override {
1769  if (skipFunction(F))
1770  return false;
1771  const DataLayout &DL = F.getParent()->getDataLayout();
1772  const TargetLibraryInfo *TLI =
1773  &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
1774  return runSCCP(F, DL, TLI);
1775  }
1776 };
1777 
1778 } // end anonymous namespace
1779 
1780 char SCCPLegacyPass::ID = 0;
1781 
1782 INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp",
1783  "Sparse Conditional Constant Propagation", false, false)
1785 INITIALIZE_PASS_END(SCCPLegacyPass, "sccp",
1786  "Sparse Conditional Constant Propagation", false, false)
1787 
1788 // createSCCPPass - This is the public interface to this file.
1789 FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); }
1790 
1792  SmallVector<ReturnInst *, 8> &ReturnsToZap,
1793  SCCPSolver &Solver) {
1794  // We can only do this if we know that nothing else can call the function.
1795  if (!Solver.isArgumentTrackedFunction(&F))
1796  return;
1797 
1798  // There is a non-removable musttail call site of this function. Zapping
1799  // returns is not allowed.
1800  if (Solver.isMustTailCallee(&F)) {
1801  LLVM_DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName()
1802  << " due to present musttail call of it\n");
1803  return;
1804  }
1805 
1806  assert(
1807  all_of(F.users(),
1808  [&Solver](User *U) {
1809  if (isa<Instruction>(U) &&
1810  !Solver.isBlockExecutable(cast<Instruction>(U)->getParent()))
1811  return true;
1812  // Non-callsite uses are not impacted by zapping. Also, constant
1813  // uses (like blockaddresses) could stuck around, without being
1814  // used in the underlying IR, meaning we do not have lattice
1815  // values for them.
1816  if (!isa<CallBase>(U))
1817  return true;
1818  if (U->getType()->isStructTy()) {
1819  return all_of(Solver.getStructLatticeValueFor(U),
1820  [](const ValueLatticeElement &LV) {
1821  return !isOverdefined(LV);
1822  });
1823  }
1824  return !isOverdefined(Solver.getLatticeValueFor(U));
1825  }) &&
1826  "We can only zap functions where all live users have a concrete value");
1827 
1828  for (BasicBlock &BB : F) {
1829  if (CallInst *CI = BB.getTerminatingMustTailCall()) {
1830  LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "
1831  << "musttail call : " << *CI << "\n");
1832  (void)CI;
1833  return;
1834  }
1835 
1836  if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1837  if (!isa<UndefValue>(RI->getOperand(0)))
1838  ReturnsToZap.push_back(RI);
1839  }
1840 }
1841 
1842 // Update the condition for terminators that are branching on indeterminate
1843 // values, forcing them to use a specific edge.
1844 static void forceIndeterminateEdge(Instruction* I, SCCPSolver &Solver) {
1845  BasicBlock *Dest = nullptr;
1846  Constant *C = nullptr;
1847  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
1848  if (!isa<ConstantInt>(SI->getCondition())) {
1849  // Indeterminate switch; use first case value.
1850  Dest = SI->case_begin()->getCaseSuccessor();
1851  C = SI->case_begin()->getCaseValue();
1852  }
1853  } else if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
1854  if (!isa<ConstantInt>(BI->getCondition())) {
1855  // Indeterminate branch; use false.
1856  Dest = BI->getSuccessor(1);
1857  C = ConstantInt::getFalse(BI->getContext());
1858  }
1859  } else if (IndirectBrInst *IBR = dyn_cast<IndirectBrInst>(I)) {
1860  if (!isa<BlockAddress>(IBR->getAddress()->stripPointerCasts())) {
1861  // Indeterminate indirectbr; use successor 0.
1862  Dest = IBR->getSuccessor(0);
1863  C = BlockAddress::get(IBR->getSuccessor(0));
1864  }
1865  } else {
1866  llvm_unreachable("Unexpected terminator instruction");
1867  }
1868  if (C) {
1869  assert(Solver.isEdgeFeasible(I->getParent(), Dest) &&
1870  "Didn't find feasible edge?");
1871  (void)Dest;
1872 
1873  I->setOperand(0, C);
1874  }
1875 }
1876 
1878  Module &M, const DataLayout &DL,
1879  std::function<const TargetLibraryInfo &(Function &)> GetTLI,
1880  function_ref<AnalysisResultsForFn(Function &)> getAnalysis) {
1881  SCCPSolver Solver(DL, GetTLI, M.getContext());
1882 
1883  // Loop over all functions, marking arguments to those with their addresses
1884  // taken or that are external as overdefined.
1885  for (Function &F : M) {
1886  if (F.isDeclaration())
1887  continue;
1888 
1889  Solver.addAnalysis(F, getAnalysis(F));
1890 
1891  // Determine if we can track the function's return values. If so, add the
1892  // function to the solver's set of return-tracked functions.
1894  Solver.AddTrackedFunction(&F);
1895 
1896  // Determine if we can track the function's arguments. If so, add the
1897  // function to the solver's set of argument-tracked functions.
1899  Solver.AddArgumentTrackedFunction(&F);
1900  continue;
1901  }
1902 
1903  // Assume the function is called.
1904  Solver.MarkBlockExecutable(&F.front());
1905 
1906  // Assume nothing about the incoming arguments.
1907  for (Argument &AI : F.args())
1908  Solver.markOverdefined(&AI);
1909  }
1910 
1911  // Determine if we can track any of the module's global variables. If so, add
1912  // the global variables we can track to the solver's set of tracked global
1913  // variables.
1914  for (GlobalVariable &G : M.globals()) {
1915  G.removeDeadConstantUsers();
1917  Solver.TrackValueOfGlobalVariable(&G);
1918  }
1919 
1920  // Solve for constants.
1921  bool ResolvedUndefs = true;
1922  Solver.Solve();
1923  while (ResolvedUndefs) {
1924  LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n");
1925  ResolvedUndefs = false;
1926  for (Function &F : M)
1927  if (Solver.ResolvedUndefsIn(F)) {
1928  // We run Solve() after we resolved an undef in a function, because
1929  // we might deduce a fact that eliminates an undef in another function.
1930  Solver.Solve();
1931  ResolvedUndefs = true;
1932  }
1933  }
1934 
1935  bool MadeChanges = false;
1936 
1937  // Iterate over all of the instructions in the module, replacing them with
1938  // constants if we have found them to be of constant values.
1939 
1940  for (Function &F : M) {
1941  if (F.isDeclaration())
1942  continue;
1943 
1944  SmallVector<BasicBlock *, 512> BlocksToErase;
1945 
1946  if (Solver.isBlockExecutable(&F.front()))
1947  for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
1948  ++AI) {
1949  if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
1950  ++IPNumArgsElimed;
1951  continue;
1952  }
1953  }
1954 
1955  SmallPtrSet<Value *, 32> InsertedValues;
1956  for (BasicBlock &BB : F) {
1957  if (!Solver.isBlockExecutable(&BB)) {
1958  LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1959  ++NumDeadBlocks;
1960 
1961  MadeChanges = true;
1962 
1963  if (&BB != &F.front())
1964  BlocksToErase.push_back(&BB);
1965  continue;
1966  }
1967 
1968  MadeChanges |= simplifyInstsInBlock(Solver, BB, InsertedValues,
1969  IPNumInstRemoved, IPNumInstReplaced);
1970  }
1971 
1972  DomTreeUpdater DTU = Solver.getDTU(F);
1973  // Change dead blocks to unreachable. We do it after replacing constants
1974  // in all executable blocks, because changeToUnreachable may remove PHI
1975  // nodes in executable blocks we found values for. The function's entry
1976  // block is not part of BlocksToErase, so we have to handle it separately.
1977  for (BasicBlock *BB : BlocksToErase) {
1978  NumInstRemoved +=
1979  changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false,
1980  /*PreserveLCSSA=*/false, &DTU);
1981  }
1982  if (!Solver.isBlockExecutable(&F.front()))
1983  NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
1984  /*UseLLVMTrap=*/false,
1985  /*PreserveLCSSA=*/false, &DTU);
1986 
1987  // Now that all instructions in the function are constant folded,
1988  // use ConstantFoldTerminator to get rid of in-edges, record DT updates and
1989  // delete dead BBs.
1990  for (BasicBlock *DeadBB : BlocksToErase) {
1991  // If there are any PHI nodes in this successor, drop entries for BB now.
1992  for (Value::user_iterator UI = DeadBB->user_begin(),
1993  UE = DeadBB->user_end();
1994  UI != UE;) {
1995  // Grab the user and then increment the iterator early, as the user
1996  // will be deleted. Step past all adjacent uses from the same user.
1997  auto *I = dyn_cast<Instruction>(*UI);
1998  do { ++UI; } while (UI != UE && *UI == I);
1999 
2000  // Ignore blockaddress users; BasicBlock's dtor will handle them.
2001  if (!I) continue;
2002 
2003  // If we have forced an edge for an indeterminate value, then force the
2004  // terminator to fold to that edge.
2005  forceIndeterminateEdge(I, Solver);
2006  BasicBlock *InstBB = I->getParent();
2007  bool Folded = ConstantFoldTerminator(InstBB,
2008  /*DeleteDeadConditions=*/false,
2009  /*TLI=*/nullptr, &DTU);
2010  assert(Folded &&
2011  "Expect TermInst on constantint or blockaddress to be folded");
2012  (void) Folded;
2013  // If we folded the terminator to an unconditional branch to another
2014  // dead block, replace it with Unreachable, to avoid trying to fold that
2015  // branch again.
2016  BranchInst *BI = cast<BranchInst>(InstBB->getTerminator());
2017  if (BI && BI->isUnconditional() &&
2018  !Solver.isBlockExecutable(BI->getSuccessor(0))) {
2019  InstBB->getTerminator()->eraseFromParent();
2020  new UnreachableInst(InstBB->getContext(), InstBB);
2021  }
2022  }
2023  // Mark dead BB for deletion.
2024  DTU.deleteBB(DeadBB);
2025  }
2026 
2027  for (BasicBlock &BB : F) {
2028  for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
2029  Instruction *Inst = &*BI++;
2030  if (Solver.getPredicateInfoFor(Inst)) {
2031  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
2032  if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
2033  Value *Op = II->getOperand(0);
2034  Inst->replaceAllUsesWith(Op);
2035  Inst->eraseFromParent();
2036  }
2037  }
2038  }
2039  }
2040  }
2041  }
2042 
2043  // If we inferred constant or undef return values for a function, we replaced
2044  // all call uses with the inferred value. This means we don't need to bother
2045  // actually returning anything from the function. Replace all return
2046  // instructions with return undef.
2047  //
2048  // Do this in two stages: first identify the functions we should process, then
2049  // actually zap their returns. This is important because we can only do this
2050  // if the address of the function isn't taken. In cases where a return is the
2051  // last use of a function, the order of processing functions would affect
2052  // whether other functions are optimizable.
2053  SmallVector<ReturnInst*, 8> ReturnsToZap;
2054 
2055  for (const auto &I : Solver.getTrackedRetVals()) {
2056  Function *F = I.first;
2057  if (isOverdefined(I.second) || F->getReturnType()->isVoidTy())
2058  continue;
2059  findReturnsToZap(*F, ReturnsToZap, Solver);
2060  }
2061 
2062  for (auto F : Solver.getMRVFunctionsTracked()) {
2063  assert(F->getReturnType()->isStructTy() &&
2064  "The return type should be a struct");
2065  StructType *STy = cast<StructType>(F->getReturnType());
2066  if (Solver.isStructLatticeConstant(F, STy))
2067  findReturnsToZap(*F, ReturnsToZap, Solver);
2068  }
2069 
2070  // Zap all returns which we've identified as zap to change.
2071  for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
2072  Function *F = ReturnsToZap[i]->getParent()->getParent();
2073  ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
2074  }
2075 
2076  // If we inferred constant or undef values for globals variables, we can
2077  // delete the global and any stores that remain to it.
2078  for (auto &I : make_early_inc_range(Solver.getTrackedGlobals())) {
2079  GlobalVariable *GV = I.first;
2080  if (isOverdefined(I.second))
2081  continue;
2082  LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName()
2083  << "' is constant!\n");
2084  while (!GV->use_empty()) {
2085  StoreInst *SI = cast<StoreInst>(GV->user_back());
2086  SI->eraseFromParent();
2087  MadeChanges = true;
2088  }
2089  M.getGlobalList().erase(GV);
2090  ++IPNumGlobalConst;
2091  }
2092 
2093  return MadeChanges;
2094 }
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:506
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:80
static bool simplifyInstsInBlock(SCCPSolver &Solver, BasicBlock &BB, SmallPtrSetImpl< Value *> &InsertedValues, Statistic &InstRemovedStat, Statistic &InstReplacedStat)
Definition: SCCP.cpp:1648
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:749
This class is the base class for the comparison instructions.
Definition: InstrTypes.h:715
static bool isConstant(const MachineInstr &MI)
LLVM_NODISCARD std::enable_if_t< !is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type > dyn_cast(const Y &Val)
Definition: Casting.h:334
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
MergeOptions & setMaxWidenSteps(unsigned Steps=1)
Definition: ValueLattice.h:137
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:79
Interprocedural Sparse Conditional Constant Propagation
Definition: SCCP.cpp:88
sccp
Definition: SCCP.cpp:1785
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:769
static ValueLatticeElement getRange(ConstantRange CR, bool MayIncludeUndef=false)
Definition: ValueLattice.h:214
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
This class represents lattice values for constants.
Definition: AllocatorList.h:23
This is the interface for a simple mod/ref and alias analysis over globals.
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:110
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:67
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:1166
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:443
const ConstantRange & getConstantRange(bool UndefAllowed=true) const
Returns the constant range for this value.
Definition: ValueLattice.h:269
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:255
This class represents zero extension of integer types.
unsigned getNumElements() const
Random access to the elements.
Definition: DerivedTypes.h:328
bool isSafeToRemove() const
Return true if the instruction can be removed if the result is unused.
This class represents a function call, abstracting a target machine&#39;s calling convention.
iterator_range< early_inc_iterator_impl< detail::IterOfRange< RangeT > > > make_early_inc_range(RangeT &&Range)
Make a range that does early increment to allow mutation of the underlying range without disrupting i...
Definition: STLExtras.h:584
const Value * getTrueValue() const
An efficient, type-erasing, non-owning reference to a callable.
Definition: STLExtras.h:176
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:1491
BasicBlock * getSuccessor(unsigned i) const
arg_iterator arg_end()
Definition: Function.h:729
STATISTIC(NumFunctions, "Total number of functions")
Metadata node.
Definition: Metadata.h:870
bool markConstant(Constant *V, bool MayIncludeUndef=false)
Definition: ValueLattice.h:301
Base class for all callable instructions (InvokeInst and CallInst) Holds everything related to callin...
Definition: InstrTypes.h:1100
F(f)
bool isConstantRange(bool UndefAllowed=true) const
Returns true if this value is a constant range.
Definition: ValueLattice.h:249
User::op_iterator arg_end()
Return the iterator pointing to the end of the argument list.
Definition: InstrTypes.h:1230
An instruction for reading from memory.
Definition: Instructions.h:173
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:150
static ConstantRange makeAllowedICmpRegion(CmpInst::Predicate Pred, const ConstantRange &Other)
Produce the smallest range such that all values that may satisfy the given predicate with any value c...
void reserve(size_type N)
Definition: SmallVector.h:415
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:1791
MergeOptions & setCheckWiden(bool V=true)
Definition: ValueLattice.h:132
std::unique_ptr< PredicateInfo > PredInfo
Definition: SCCP.h:43
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:207
bool isUnknownOrUndef() const
Definition: ValueLattice.h:239
The address of a basic block.
Definition: Constants.h:850
AnalysisUsage & addRequired()
void setNumRangeExtensions(unsigned N)
Definition: ValueLattice.h:477
bool isVolatile() const
Return true if this is a load from a volatile memory location.
Definition: Instructions.h:210
This class represents the LLVM &#39;select&#39; instruction.
Predicate getInversePredicate() const
For example, EQ -> NE, UGT -> ULE, SLT -> SGE, OEQ -> UNE, UGT -> OLE, OLT -> UGE, etc.
Definition: InstrTypes.h:826
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:397
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:432
ArrayRef< T > makeArrayRef(const T &OneElt)
Construct an ArrayRef from a single element.
Definition: ArrayRef.h:458
Class to represent struct types.
Definition: DerivedTypes.h:218
Struct to control some aspects related to merging constant ranges.
Definition: ValueLattice.h:108
LLVMContext & getContext() const
Get the global data context.
Definition: Module.h:253
void initializeSCCPLegacyPassPass(PassRegistry &)
static Optional< unsigned > getOpcode(ArrayRef< VPValue *> Values)
Returns the opcode of Values or ~0 if they do not all agree.
Definition: VPlanSLP.cpp:196
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:43
bool isIntegerTy() const
True if this is an instance of IntegerType.
Definition: Type.h:198
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: SCCP.cpp:1732
static void forceIndeterminateEdge(Instruction *I, SCCPSolver &Solver)
Definition: SCCP.cpp:1844
FunctionPass * createSCCPPass()
Definition: SCCP.cpp:1789
mir Rename Register Operands
Helper struct for bundling up the analysis results per function for IPSCCP.
Definition: SCCP.h:42
unsigned getNumRangeExtensions() const
Definition: ValueLattice.h:476
void assign(size_type NumElts, const T &Elt)
Definition: SmallVector.h:458
Instruction::CastOps getOpcode() const
Return the opcode of this CastInst.
Definition: InstrTypes.h:685
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:244
#define T
static const unsigned MaxNumRangeExtensions
Definition: SCCP.cpp:83
MDNode * getMetadata(unsigned KindID) const
Get the metadata of given kind attached to this Instruction.
Definition: Instruction.h:279
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:160
PostDominatorTree * PDT
Definition: SCCP.h:45
An instruction for storing to memory.
Definition: Instructions.h:302
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:486
iterator find(const KeyT &Key)
Definition: MapVector.h:147
ConstantRange castOp(Instruction::CastOps CastOp, uint32_t BitWidth) const
Return a new range representing the possible values resulting from an application of the specified ca...
unsigned getNumSuccessors() const
Return the number of successors that this instruction has.
Value * getOperand(unsigned i) const
Definition: User.h:169
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:402
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:138
an instruction for type-safe pointer arithmetic to access elements of arrays and structs ...
Definition: Instructions.h:904
static bool runOnFunction(Function &F, bool PostInlining)
bool isAllNonNegative() const
Return true if all values in this range are non-negative.
Type * getReturnType() const
Returns the type of the ret val.
Definition: Function.h:170
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:154
ConstantRange getConstantRangeFromMetadata(const MDNode &RangeMD)
Parse out a conservative ConstantRange from !range metadata.
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
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.
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:68
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:1684
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
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:364
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:1498
const Instruction & back() const
Definition: BasicBlock.h:303
Analysis pass providing a never-invalidated alias analysis result.
constexpr double e
Definition: MathExtras.h:58
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:1219
arg_iterator arg_begin()
Definition: Function.h:720
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:375
const Function * getFunction() const
Return the function this instruction belongs to.
Definition: Instruction.cpp:72
static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V)
Definition: SCCP.cpp:1600
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
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:252
static UndefValue * get(Type *T)
Static factory methods - Return an &#39;undef&#39; object of the specified type.
Definition: Constants.cpp:1665
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:160
bool isExceptionalTerminator() const
Definition: Instruction.h:170
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...
Constant * getConstant() const
Definition: ValueLattice.h:255
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:1877
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...
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:439
This is the shared class of boolean and integer constants.
Definition: Constants.h:77
BlockVerifier::State From
Align max(MaybeAlign Lhs, Align Rhs)
Definition: Alignment.h:350
INITIALIZE_PASS_BEGIN(IPSCCPLegacyPass, "ipsccp", "Interprocedural Sparse Conditional Constant Propagation", false, false) INITIALIZE_PASS_END(IPSCCPLegacyPass
unsigned getScalarSizeInBits() const LLVM_READONLY
If this is a vector type, return the getPrimitiveSizeInBits value for the element type...
Definition: Type.cpp:137
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:883
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.
This class represents a range of values.
Definition: ConstantRange.h:47
const DataFlowGraph & G
Definition: RDFGraph.cpp:202
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:786
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:253
Type * getDestTy() const
Return the destination type, as a convenience.
Definition: InstrTypes.h:692
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:1922
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:1685
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:962
iterator_range< user_iterator > users()
Definition: Value.h:418
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:115
const Value * getFalseValue() const
bool mergeIn(const ValueLatticeElement &RHS, MergeOptions Opts=MergeOptions())
Updates this object to approximate both this object and RHS.
Definition: ValueLattice.h:385
User::op_iterator arg_begin()
Return the iterator pointing to the beginning of the argument list.
Definition: InstrTypes.h:1224
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:802
StringRef getName() const
Return a constant reference to the value&#39;s name.
Definition: Value.cpp:270
BasicBlock * getIncomingBlock(unsigned i) const
Return incoming basic block number i.
Function * getCalledFunction() const
Returns the function called, or null if this is an indirect function invocation.
Definition: InstrTypes.h:1314
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:107
#define I(x, y, z)
Definition: MD5.cpp:59
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
user_iterator_impl< User > user_iterator
Definition: Value.h:387
DominatorTree * DT
Definition: SCCP.h:44
idx_iterator idx_begin() const
Type * getValueType() const
Definition: GlobalValue.h:273
iterator_range< const_phi_iterator > phis() const
Returns a range that iterates over the phis in the basic block.
Definition: BasicBlock.h:345
bool isUnconditional() const
static Value * getNumElements(BasicBlock *Preheader, Value *BTC)
static ValueLatticeElement getValueFromMetadata(const Instruction *I)
Definition: SCCP.cpp:1107
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:227
bool isSingleElement() const
Return true if this set contains exactly one member.
Analysis pass providing the TargetLibraryInfo.
unsigned getPointerAddressSpace() const
Returns the address space of the pointer operand.
Definition: Instructions.h:271
Multiway switch.
Value * SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, const SimplifyQuery &Q)
Given operands for a BinaryOperator, fold the result or return null.
iterator end()
Definition: MapVector.h:71
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const BasicBlock & front() const
Definition: Function.h:712
bool isSingleValueType() const
Return true if the type is a valid type for a register in codegen.
Definition: Type.h:253
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:572
LLVM Value Representation.
Definition: Value.h:74
static const Function * getParent(const Value *V)
static ValueLatticeElement::MergeOptions getMaxWidenStepsOpts()
Returns MergeOptions with MaxWidenSteps set to MaxNumRangeExtensions.
Definition: SCCP.cpp:86
Invoke instruction.
print Print MemDeps of function
static ValueLatticeElement getOverdefined()
Definition: ValueLattice.h:231
Predicate getSwappedPredicate() const
For example, EQ->EQ, SLE->SGE, ULT->UGT, OEQ->OEQ, ULE->UGE, OLT->OGT, etc.
Definition: InstrTypes.h:842
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
ConstantRange binaryOp(Instruction::BinaryOps BinOp, const ConstantRange &Other) const
Return a new range representing the possible values resulting from an application of the specified bi...
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:1943
bool use_empty() const
Definition: Value.h:341
static bool runSCCP(Function &F, const DataLayout &DL, const TargetLibraryInfo *TLI)
Definition: SCCP.cpp:1685
iterator_range< arg_iterator > args()
Definition: Function.h:744
bool isStructTy() const
True if this is an instance of StructType.
Definition: Type.h:219
User * user_back()
Definition: Value.h:404
const BasicBlock * getParent() const
Definition: Instruction.h:94
This instruction inserts a struct field of array element value into an aggregate value.
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
void resize(size_type N)
Definition: SmallVector.h:390
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:2058