1 //===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements sparse conditional constant propagation and merging:
12 // Specifically, this:
13 // * Assumes values are constant unless proven otherwise
14 // * Assumes BasicBlocks are dead unless proven otherwise
15 // * Proves values to be constant, and replaces them with constants
16 // * Proves conditional branches to be unconditional
18 //===----------------------------------------------------------------------===//
20 #include "llvm/Transforms/Scalar/SCCP.h"
21 #include "llvm/ADT/ArrayRef.h"
22 #include "llvm/ADT/DenseMap.h"
23 #include "llvm/ADT/DenseSet.h"
24 #include "llvm/ADT/PointerIntPair.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"
29 #include "llvm/Analysis/ConstantFolding.h"
30 #include "llvm/Analysis/GlobalsModRef.h"
31 #include "llvm/Analysis/TargetLibraryInfo.h"
32 #include "llvm/Transforms/Utils/Local.h"
33 #include "llvm/Analysis/ValueLattice.h"
34 #include "llvm/Analysis/ValueLatticeUtils.h"
35 #include "llvm/IR/BasicBlock.h"
36 #include "llvm/IR/CallSite.h"
37 #include "llvm/IR/Constant.h"
38 #include "llvm/IR/Constants.h"
39 #include "llvm/IR/DataLayout.h"
40 #include "llvm/IR/DerivedTypes.h"
41 #include "llvm/IR/Function.h"
42 #include "llvm/IR/GlobalVariable.h"
43 #include "llvm/IR/InstVisitor.h"
44 #include "llvm/IR/InstrTypes.h"
45 #include "llvm/IR/Instruction.h"
46 #include "llvm/IR/Instructions.h"
47 #include "llvm/IR/Module.h"
48 #include "llvm/IR/PassManager.h"
49 #include "llvm/IR/Type.h"
50 #include "llvm/IR/User.h"
51 #include "llvm/IR/Value.h"
52 #include "llvm/Pass.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/Debug.h"
55 #include "llvm/Support/ErrorHandling.h"
56 #include "llvm/Support/raw_ostream.h"
57 #include "llvm/Transforms/Scalar.h"
58 #include "llvm/Transforms/Utils/PredicateInfo.h"
65 #define DEBUG_TYPE "sccp"
67 STATISTIC(NumInstRemoved, "Number of instructions removed");
68 STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
70 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
71 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
72 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
76 /// LatticeVal class - This class represents the different lattice values that
77 /// an LLVM value may occupy. It is a simple class with value semantics.
81 /// unknown - This LLVM Value has no known value yet.
84 /// constant - This LLVM Value has a specific constant value.
87 /// forcedconstant - This LLVM Value was thought to be undef until
88 /// ResolvedUndefsIn. This is treated just like 'constant', but if merged
89 /// with another (different) constant, it goes to overdefined, instead of
93 /// overdefined - This instruction is not known to be constant, and we know
98 /// Val: This stores the current lattice value along with the Constant* for
99 /// the constant if this is a 'constant' or 'forcedconstant' value.
100 PointerIntPair<Constant *, 2, LatticeValueTy> Val;
102 LatticeValueTy getLatticeValue() const {
107 LatticeVal() : Val(nullptr, unknown) {}
109 bool isUnknown() const { return getLatticeValue() == unknown; }
111 bool isConstant() const {
112 return getLatticeValue() == constant || getLatticeValue() == forcedconstant;
115 bool isOverdefined() const { return getLatticeValue() == overdefined; }
117 Constant *getConstant() const {
118 assert(isConstant() && "Cannot get the constant of a non-constant!");
119 return Val.getPointer();
122 /// markOverdefined - Return true if this is a change in status.
123 bool markOverdefined() {
127 Val.setInt(overdefined);
131 /// markConstant - Return true if this is a change in status.
132 bool markConstant(Constant *V) {
133 if (getLatticeValue() == constant) { // Constant but not forcedconstant.
134 assert(getConstant() == V && "Marking constant with different value");
139 Val.setInt(constant);
140 assert(V && "Marking constant with NULL");
143 assert(getLatticeValue() == forcedconstant &&
144 "Cannot move from overdefined to constant!");
145 // Stay at forcedconstant if the constant is the same.
146 if (V == getConstant()) return false;
148 // Otherwise, we go to overdefined. Assumptions made based on the
149 // forced value are possibly wrong. Assuming this is another constant
150 // could expose a contradiction.
151 Val.setInt(overdefined);
156 /// getConstantInt - If this is a constant with a ConstantInt value, return it
157 /// otherwise return null.
158 ConstantInt *getConstantInt() const {
160 return dyn_cast<ConstantInt>(getConstant());
164 /// getBlockAddress - If this is a constant with a BlockAddress value, return
165 /// it, otherwise return null.
166 BlockAddress *getBlockAddress() const {
168 return dyn_cast<BlockAddress>(getConstant());
172 void markForcedConstant(Constant *V) {
173 assert(isUnknown() && "Can't force a defined value!");
174 Val.setInt(forcedconstant);
178 ValueLatticeElement toValueLattice() const {
180 return ValueLatticeElement::getOverdefined();
182 return ValueLatticeElement::get(getConstant());
183 return ValueLatticeElement();
187 //===----------------------------------------------------------------------===//
189 /// SCCPSolver - This class is a general purpose solver for Sparse Conditional
190 /// Constant Propagation.
192 class SCCPSolver : public InstVisitor<SCCPSolver> {
193 const DataLayout &DL;
194 const TargetLibraryInfo *TLI;
195 SmallPtrSet<BasicBlock *, 8> BBExecutable; // The BBs that are executable.
196 DenseMap<Value *, LatticeVal> ValueState; // The state each value is in.
197 // The state each parameter is in.
198 DenseMap<Value *, ValueLatticeElement> ParamState;
200 /// StructValueState - This maintains ValueState for values that have
201 /// StructType, for example for formal arguments, calls, insertelement, etc.
202 DenseMap<std::pair<Value *, unsigned>, LatticeVal> StructValueState;
204 /// GlobalValue - If we are tracking any values for the contents of a global
205 /// variable, we keep a mapping from the constant accessor to the element of
206 /// the global, to the currently known value. If the value becomes
207 /// overdefined, it's entry is simply removed from this map.
208 DenseMap<GlobalVariable *, LatticeVal> TrackedGlobals;
210 /// TrackedRetVals - If we are tracking arguments into and the return
211 /// value out of a function, it will have an entry in this map, indicating
212 /// what the known return value for the function is.
213 DenseMap<Function *, LatticeVal> TrackedRetVals;
215 /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
216 /// that return multiple values.
217 DenseMap<std::pair<Function *, unsigned>, LatticeVal> TrackedMultipleRetVals;
219 /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
220 /// represented here for efficient lookup.
221 SmallPtrSet<Function *, 16> MRVFunctionsTracked;
223 /// MustTailFunctions - Each function here is a callee of non-removable
224 /// musttail call site.
225 SmallPtrSet<Function *, 16> MustTailCallees;
227 /// TrackingIncomingArguments - This is the set of functions for whose
228 /// arguments we make optimistic assumptions about and try to prove as
230 SmallPtrSet<Function *, 16> TrackingIncomingArguments;
232 /// The reason for two worklists is that overdefined is the lowest state
233 /// on the lattice, and moving things to overdefined as fast as possible
234 /// makes SCCP converge much faster.
236 /// By having a separate worklist, we accomplish this because everything
237 /// possibly overdefined will become overdefined at the soonest possible
239 SmallVector<Value *, 64> OverdefinedInstWorkList;
240 SmallVector<Value *, 64> InstWorkList;
242 // The BasicBlock work list
243 SmallVector<BasicBlock *, 64> BBWorkList;
245 /// KnownFeasibleEdges - Entries in this set are edges which have already had
246 /// PHI nodes retriggered.
247 using Edge = std::pair<BasicBlock *, BasicBlock *>;
248 DenseSet<Edge> KnownFeasibleEdges;
250 DenseMap<Function *, std::unique_ptr<PredicateInfo>> PredInfos;
251 DenseMap<Value *, SmallPtrSet<User *, 2>> AdditionalUsers;
254 void addPredInfo(Function &F, std::unique_ptr<PredicateInfo> PI) {
255 PredInfos[&F] = std::move(PI);
258 const PredicateBase *getPredicateInfoFor(Instruction *I) {
259 auto PI = PredInfos.find(I->getFunction());
260 if (PI == PredInfos.end())
262 return PI->second->getPredicateInfoFor(I);
265 SCCPSolver(const DataLayout &DL, const TargetLibraryInfo *tli)
266 : DL(DL), TLI(tli) {}
268 /// MarkBlockExecutable - This method can be used by clients to mark all of
269 /// the blocks that are known to be intrinsically live in the processed unit.
271 /// This returns true if the block was not considered live before.
272 bool MarkBlockExecutable(BasicBlock *BB) {
273 if (!BBExecutable.insert(BB).second)
275 LLVM_DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << '\n');
276 BBWorkList.push_back(BB); // Add the block to the work list!
280 /// TrackValueOfGlobalVariable - Clients can use this method to
281 /// inform the SCCPSolver that it should track loads and stores to the
282 /// specified global variable if it can. This is only legal to call if
283 /// performing Interprocedural SCCP.
284 void TrackValueOfGlobalVariable(GlobalVariable *GV) {
285 // We only track the contents of scalar globals.
286 if (GV->getValueType()->isSingleValueType()) {
287 LatticeVal &IV = TrackedGlobals[GV];
288 if (!isa<UndefValue>(GV->getInitializer()))
289 IV.markConstant(GV->getInitializer());
293 /// AddTrackedFunction - If the SCCP solver is supposed to track calls into
294 /// and out of the specified function (which cannot have its address taken),
295 /// this method must be called.
296 void AddTrackedFunction(Function *F) {
297 // Add an entry, F -> undef.
298 if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
299 MRVFunctionsTracked.insert(F);
300 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
301 TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
304 TrackedRetVals.insert(std::make_pair(F, LatticeVal()));
307 /// AddMustTailCallee - If the SCCP solver finds that this function is called
308 /// from non-removable musttail call site.
309 void AddMustTailCallee(Function *F) {
310 MustTailCallees.insert(F);
313 /// Returns true if the given function is called from non-removable musttail
315 bool isMustTailCallee(Function *F) {
316 return MustTailCallees.count(F);
319 void AddArgumentTrackedFunction(Function *F) {
320 TrackingIncomingArguments.insert(F);
323 /// Returns true if the given function is in the solver's set of
324 /// argument-tracked functions.
325 bool isArgumentTrackedFunction(Function *F) {
326 return TrackingIncomingArguments.count(F);
329 /// Solve - Solve for constants and executable blocks.
332 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
333 /// that branches on undef values cannot reach any of their successors.
334 /// However, this is not a safe assumption. After we solve dataflow, this
335 /// method should be use to handle this. If this returns true, the solver
337 bool ResolvedUndefsIn(Function &F);
339 bool isBlockExecutable(BasicBlock *BB) const {
340 return BBExecutable.count(BB);
343 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
344 // block to the 'To' basic block is currently feasible.
345 bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
347 std::vector<LatticeVal> getStructLatticeValueFor(Value *V) const {
348 std::vector<LatticeVal> StructValues;
349 auto *STy = dyn_cast<StructType>(V->getType());
350 assert(STy && "getStructLatticeValueFor() can be called only on structs");
351 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
352 auto I = StructValueState.find(std::make_pair(V, i));
353 assert(I != StructValueState.end() && "Value not in valuemap!");
354 StructValues.push_back(I->second);
359 const LatticeVal &getLatticeValueFor(Value *V) const {
360 assert(!V->getType()->isStructTy() &&
361 "Should use getStructLatticeValueFor");
362 DenseMap<Value *, LatticeVal>::const_iterator I = ValueState.find(V);
363 assert(I != ValueState.end() &&
364 "V not found in ValueState nor Paramstate map!");
368 /// getTrackedRetVals - Get the inferred return value map.
369 const DenseMap<Function*, LatticeVal> &getTrackedRetVals() {
370 return TrackedRetVals;
373 /// getTrackedGlobals - Get and return the set of inferred initializers for
374 /// global variables.
375 const DenseMap<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
376 return TrackedGlobals;
379 /// getMRVFunctionsTracked - Get the set of functions which return multiple
380 /// values tracked by the pass.
381 const SmallPtrSet<Function *, 16> getMRVFunctionsTracked() {
382 return MRVFunctionsTracked;
385 /// getMustTailCallees - Get the set of functions which are called
386 /// from non-removable musttail call sites.
387 const SmallPtrSet<Function *, 16> getMustTailCallees() {
388 return MustTailCallees;
391 /// markOverdefined - Mark the specified value overdefined. This
392 /// works with both scalars and structs.
393 void markOverdefined(Value *V) {
394 if (auto *STy = dyn_cast<StructType>(V->getType()))
395 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
396 markOverdefined(getStructValueState(V, i), V);
398 markOverdefined(ValueState[V], V);
401 // isStructLatticeConstant - Return true if all the lattice values
402 // corresponding to elements of the structure are not overdefined,
404 bool isStructLatticeConstant(Function *F, StructType *STy) {
405 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
406 const auto &It = TrackedMultipleRetVals.find(std::make_pair(F, i));
407 assert(It != TrackedMultipleRetVals.end());
408 LatticeVal LV = It->second;
409 if (LV.isOverdefined())
416 // pushToWorkList - Helper for markConstant/markForcedConstant/markOverdefined
417 void pushToWorkList(LatticeVal &IV, Value *V) {
418 if (IV.isOverdefined())
419 return OverdefinedInstWorkList.push_back(V);
420 InstWorkList.push_back(V);
423 // markConstant - Make a value be marked as "constant". If the value
424 // is not already a constant, add it to the instruction work list so that
425 // the users of the instruction are updated later.
426 bool markConstant(LatticeVal &IV, Value *V, Constant *C) {
427 if (!IV.markConstant(C)) return false;
428 LLVM_DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
429 pushToWorkList(IV, V);
433 bool markConstant(Value *V, Constant *C) {
434 assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
435 return markConstant(ValueState[V], V, C);
438 void markForcedConstant(Value *V, Constant *C) {
439 assert(!V->getType()->isStructTy() && "structs should use mergeInValue");
440 LatticeVal &IV = ValueState[V];
441 IV.markForcedConstant(C);
442 LLVM_DEBUG(dbgs() << "markForcedConstant: " << *C << ": " << *V << '\n');
443 pushToWorkList(IV, V);
446 // markOverdefined - Make a value be marked as "overdefined". If the
447 // value is not already overdefined, add it to the overdefined instruction
448 // work list so that the users of the instruction are updated later.
449 bool markOverdefined(LatticeVal &IV, Value *V) {
450 if (!IV.markOverdefined()) return false;
452 LLVM_DEBUG(dbgs() << "markOverdefined: ";
453 if (auto *F = dyn_cast<Function>(V)) dbgs()
454 << "Function '" << F->getName() << "'\n";
455 else dbgs() << *V << '\n');
456 // Only instructions go on the work list
457 pushToWorkList(IV, V);
461 bool mergeInValue(LatticeVal &IV, Value *V, LatticeVal MergeWithV) {
462 if (IV.isOverdefined() || MergeWithV.isUnknown())
463 return false; // Noop.
464 if (MergeWithV.isOverdefined())
465 return markOverdefined(IV, V);
467 return markConstant(IV, V, MergeWithV.getConstant());
468 if (IV.getConstant() != MergeWithV.getConstant())
469 return markOverdefined(IV, V);
473 bool mergeInValue(Value *V, LatticeVal MergeWithV) {
474 assert(!V->getType()->isStructTy() &&
475 "non-structs should use markConstant");
476 return mergeInValue(ValueState[V], V, MergeWithV);
479 /// getValueState - Return the LatticeVal object that corresponds to the
480 /// value. This function handles the case when the value hasn't been seen yet
481 /// by properly seeding constants etc.
482 LatticeVal &getValueState(Value *V) {
483 assert(!V->getType()->isStructTy() && "Should use getStructValueState");
485 std::pair<DenseMap<Value*, LatticeVal>::iterator, bool> I =
486 ValueState.insert(std::make_pair(V, LatticeVal()));
487 LatticeVal &LV = I.first->second;
490 return LV; // Common case, already in the map.
492 if (auto *C = dyn_cast<Constant>(V)) {
493 // Undef values remain unknown.
494 if (!isa<UndefValue>(V))
495 LV.markConstant(C); // Constants are constant
498 // All others are underdefined by default.
502 ValueLatticeElement &getParamState(Value *V) {
503 assert(!V->getType()->isStructTy() && "Should use getStructValueState");
505 std::pair<DenseMap<Value*, ValueLatticeElement>::iterator, bool>
506 PI = ParamState.insert(std::make_pair(V, ValueLatticeElement()));
507 ValueLatticeElement &LV = PI.first->second;
509 LV = getValueState(V).toValueLattice();
514 /// getStructValueState - Return the LatticeVal object that corresponds to the
515 /// value/field pair. This function handles the case when the value hasn't
516 /// been seen yet by properly seeding constants etc.
517 LatticeVal &getStructValueState(Value *V, unsigned i) {
518 assert(V->getType()->isStructTy() && "Should use getValueState");
519 assert(i < cast<StructType>(V->getType())->getNumElements() &&
520 "Invalid element #");
522 std::pair<DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator,
523 bool> I = StructValueState.insert(
524 std::make_pair(std::make_pair(V, i), LatticeVal()));
525 LatticeVal &LV = I.first->second;
528 return LV; // Common case, already in the map.
530 if (auto *C = dyn_cast<Constant>(V)) {
531 Constant *Elt = C->getAggregateElement(i);
534 LV.markOverdefined(); // Unknown sort of constant.
535 else if (isa<UndefValue>(Elt))
536 ; // Undef values remain unknown.
538 LV.markConstant(Elt); // Constants are constant.
541 // All others are underdefined by default.
545 /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
546 /// work list if it is not already executable.
547 bool markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
548 if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
549 return false; // This edge is already known to be executable!
551 if (!MarkBlockExecutable(Dest)) {
552 // If the destination is already executable, we just made an *edge*
553 // feasible that wasn't before. Revisit the PHI nodes in the block
554 // because they have potentially new operands.
555 LLVM_DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
556 << " -> " << Dest->getName() << '\n');
558 for (PHINode &PN : Dest->phis())
564 // getFeasibleSuccessors - Return a vector of booleans to indicate which
565 // successors are reachable from a given terminator instruction.
566 void getFeasibleSuccessors(TerminatorInst &TI, SmallVectorImpl<bool> &Succs);
568 // OperandChangedState - This method is invoked on all of the users of an
569 // instruction that was just changed state somehow. Based on this
570 // information, we need to update the specified user of this instruction.
571 void OperandChangedState(Instruction *I) {
572 if (BBExecutable.count(I->getParent())) // Inst is executable?
576 // Add U as additional user of V.
577 void addAdditionalUser(Value *V, User *U) {
578 auto Iter = AdditionalUsers.insert({V, {}});
579 Iter.first->second.insert(U);
582 // Mark I's users as changed, including AdditionalUsers.
583 void markUsersAsChanged(Value *I) {
584 for (User *U : I->users())
585 if (auto *UI = dyn_cast<Instruction>(U))
586 OperandChangedState(UI);
588 auto Iter = AdditionalUsers.find(I);
589 if (Iter != AdditionalUsers.end()) {
590 for (User *U : Iter->second)
591 if (auto *UI = dyn_cast<Instruction>(U))
592 OperandChangedState(UI);
597 friend class InstVisitor<SCCPSolver>;
599 // visit implementations - Something changed in this instruction. Either an
600 // operand made a transition, or the instruction is newly executable. Change
601 // the value type of I to reflect these changes if appropriate.
602 void visitPHINode(PHINode &I);
606 void visitReturnInst(ReturnInst &I);
607 void visitTerminatorInst(TerminatorInst &TI);
609 void visitCastInst(CastInst &I);
610 void visitSelectInst(SelectInst &I);
611 void visitBinaryOperator(Instruction &I);
612 void visitCmpInst(CmpInst &I);
613 void visitExtractValueInst(ExtractValueInst &EVI);
614 void visitInsertValueInst(InsertValueInst &IVI);
616 void visitCatchSwitchInst(CatchSwitchInst &CPI) {
617 markOverdefined(&CPI);
618 visitTerminatorInst(CPI);
621 // Instructions that cannot be folded away.
623 void visitStoreInst (StoreInst &I);
624 void visitLoadInst (LoadInst &I);
625 void visitGetElementPtrInst(GetElementPtrInst &I);
627 void visitCallInst (CallInst &I) {
631 void visitInvokeInst (InvokeInst &II) {
633 visitTerminatorInst(II);
636 void visitCallSite (CallSite CS);
637 void visitResumeInst (TerminatorInst &I) { /*returns void*/ }
638 void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
639 void visitFenceInst (FenceInst &I) { /*returns void*/ }
641 void visitInstruction(Instruction &I) {
642 // All the instructions we don't do any special handling for just
643 // go to overdefined.
644 LLVM_DEBUG(dbgs() << "SCCP: Don't know how to handle: " << I << '\n');
649 } // end anonymous namespace
651 // getFeasibleSuccessors - Return a vector of booleans to indicate which
652 // successors are reachable from a given terminator instruction.
653 void SCCPSolver::getFeasibleSuccessors(TerminatorInst &TI,
654 SmallVectorImpl<bool> &Succs) {
655 Succs.resize(TI.getNumSuccessors());
656 if (auto *BI = dyn_cast<BranchInst>(&TI)) {
657 if (BI->isUnconditional()) {
662 LatticeVal BCValue = getValueState(BI->getCondition());
663 ConstantInt *CI = BCValue.getConstantInt();
665 // Overdefined condition variables, and branches on unfoldable constant
666 // conditions, mean the branch could go either way.
667 if (!BCValue.isUnknown())
668 Succs[0] = Succs[1] = true;
672 // Constant condition variables mean the branch can only go a single way.
673 Succs[CI->isZero()] = true;
677 // Unwinding instructions successors are always executable.
678 if (TI.isExceptional()) {
679 Succs.assign(TI.getNumSuccessors(), true);
683 if (auto *SI = dyn_cast<SwitchInst>(&TI)) {
684 if (!SI->getNumCases()) {
688 LatticeVal SCValue = getValueState(SI->getCondition());
689 ConstantInt *CI = SCValue.getConstantInt();
691 if (!CI) { // Overdefined or unknown condition?
692 // All destinations are executable!
693 if (!SCValue.isUnknown())
694 Succs.assign(TI.getNumSuccessors(), true);
698 Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
702 // In case of indirect branch and its address is a blockaddress, we mark
703 // the target as executable.
704 if (auto *IBR = dyn_cast<IndirectBrInst>(&TI)) {
705 // Casts are folded by visitCastInst.
706 LatticeVal IBRValue = getValueState(IBR->getAddress());
707 BlockAddress *Addr = IBRValue.getBlockAddress();
708 if (!Addr) { // Overdefined or unknown condition?
709 // All destinations are executable!
710 if (!IBRValue.isUnknown())
711 Succs.assign(TI.getNumSuccessors(), true);
715 BasicBlock* T = Addr->getBasicBlock();
716 assert(Addr->getFunction() == T->getParent() &&
717 "Block address of a different function ?");
718 for (unsigned i = 0; i < IBR->getNumSuccessors(); ++i) {
719 // This is the target.
720 if (IBR->getDestination(i) == T) {
726 // If we didn't find our destination in the IBR successor list, then we
727 // have undefined behavior. Its ok to assume no successor is executable.
731 LLVM_DEBUG(dbgs() << "Unknown terminator instruction: " << TI << '\n');
732 llvm_unreachable("SCCP: Don't know how to handle this terminator!");
735 // isEdgeFeasible - Return true if the control flow edge from the 'From' basic
736 // block to the 'To' basic block is currently feasible.
737 bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
738 // Check if we've called markEdgeExecutable on the edge yet. (We could
739 // be more aggressive and try to consider edges which haven't been marked
740 // yet, but there isn't any need.)
741 return KnownFeasibleEdges.count(Edge(From, To));
744 // visit Implementations - Something changed in this instruction, either an
745 // operand made a transition, or the instruction is newly executable. Change
746 // the value type of I to reflect these changes if appropriate. This method
747 // makes sure to do the following actions:
749 // 1. If a phi node merges two constants in, and has conflicting value coming
750 // from different branches, or if the PHI node merges in an overdefined
751 // value, then the PHI node becomes overdefined.
752 // 2. If a phi node merges only constants in, and they all agree on value, the
753 // PHI node becomes a constant value equal to that.
754 // 3. If V <- x (op) y && isConstant(x) && isConstant(y) V = Constant
755 // 4. If V <- x (op) y && (isOverdefined(x) || isOverdefined(y)) V = Overdefined
756 // 5. If V <- MEM or V <- CALL or V <- (unknown) then V = Overdefined
757 // 6. If a conditional branch has a value that is constant, make the selected
758 // destination executable
759 // 7. If a conditional branch has a value that is overdefined, make all
760 // successors executable.
761 void SCCPSolver::visitPHINode(PHINode &PN) {
762 // If this PN returns a struct, just mark the result overdefined.
763 // TODO: We could do a lot better than this if code actually uses this.
764 if (PN.getType()->isStructTy())
765 return (void)markOverdefined(&PN);
767 if (getValueState(&PN).isOverdefined())
768 return; // Quick exit
770 // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
771 // and slow us down a lot. Just mark them overdefined.
772 if (PN.getNumIncomingValues() > 64)
773 return (void)markOverdefined(&PN);
775 // Look at all of the executable operands of the PHI node. If any of them
776 // are overdefined, the PHI becomes overdefined as well. If they are all
777 // constant, and they agree with each other, the PHI becomes the identical
778 // constant. If they are constant and don't agree, the PHI is overdefined.
779 // If there are no executable operands, the PHI remains unknown.
780 Constant *OperandVal = nullptr;
781 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
782 LatticeVal IV = getValueState(PN.getIncomingValue(i));
783 if (IV.isUnknown()) continue; // Doesn't influence PHI node.
785 if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
788 if (IV.isOverdefined()) // PHI node becomes overdefined!
789 return (void)markOverdefined(&PN);
791 if (!OperandVal) { // Grab the first value.
792 OperandVal = IV.getConstant();
796 // There is already a reachable operand. If we conflict with it,
797 // then the PHI node becomes overdefined. If we agree with it, we
800 // Check to see if there are two different constants merging, if so, the PHI
801 // node is overdefined.
802 if (IV.getConstant() != OperandVal)
803 return (void)markOverdefined(&PN);
806 // If we exited the loop, this means that the PHI node only has constant
807 // arguments that agree with each other(and OperandVal is the constant) or
808 // OperandVal is null because there are no defined incoming arguments. If
809 // this is the case, the PHI remains unknown.
811 markConstant(&PN, OperandVal); // Acquire operand value
814 void SCCPSolver::visitReturnInst(ReturnInst &I) {
815 if (I.getNumOperands() == 0) return; // ret void
817 Function *F = I.getParent()->getParent();
818 Value *ResultOp = I.getOperand(0);
820 // If we are tracking the return value of this function, merge it in.
821 if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
822 DenseMap<Function*, LatticeVal>::iterator TFRVI =
823 TrackedRetVals.find(F);
824 if (TFRVI != TrackedRetVals.end()) {
825 mergeInValue(TFRVI->second, F, getValueState(ResultOp));
830 // Handle functions that return multiple values.
831 if (!TrackedMultipleRetVals.empty()) {
832 if (auto *STy = dyn_cast<StructType>(ResultOp->getType()))
833 if (MRVFunctionsTracked.count(F))
834 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
835 mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
836 getStructValueState(ResultOp, i));
840 void SCCPSolver::visitTerminatorInst(TerminatorInst &TI) {
841 SmallVector<bool, 16> SuccFeasible;
842 getFeasibleSuccessors(TI, SuccFeasible);
844 BasicBlock *BB = TI.getParent();
846 // Mark all feasible successors executable.
847 for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
849 markEdgeExecutable(BB, TI.getSuccessor(i));
852 void SCCPSolver::visitCastInst(CastInst &I) {
853 LatticeVal OpSt = getValueState(I.getOperand(0));
854 if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
856 else if (OpSt.isConstant()) {
857 // Fold the constant as we build.
858 Constant *C = ConstantFoldCastOperand(I.getOpcode(), OpSt.getConstant(),
860 if (isa<UndefValue>(C))
862 // Propagate constant value
867 void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
868 // If this returns a struct, mark all elements over defined, we don't track
869 // structs in structs.
870 if (EVI.getType()->isStructTy())
871 return (void)markOverdefined(&EVI);
873 // If this is extracting from more than one level of struct, we don't know.
874 if (EVI.getNumIndices() != 1)
875 return (void)markOverdefined(&EVI);
877 Value *AggVal = EVI.getAggregateOperand();
878 if (AggVal->getType()->isStructTy()) {
879 unsigned i = *EVI.idx_begin();
880 LatticeVal EltVal = getStructValueState(AggVal, i);
881 mergeInValue(getValueState(&EVI), &EVI, EltVal);
883 // Otherwise, must be extracting from an array.
884 return (void)markOverdefined(&EVI);
888 void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
889 auto *STy = dyn_cast<StructType>(IVI.getType());
891 return (void)markOverdefined(&IVI);
893 // If this has more than one index, we can't handle it, drive all results to
895 if (IVI.getNumIndices() != 1)
896 return (void)markOverdefined(&IVI);
898 Value *Aggr = IVI.getAggregateOperand();
899 unsigned Idx = *IVI.idx_begin();
901 // Compute the result based on what we're inserting.
902 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
903 // This passes through all values that aren't the inserted element.
905 LatticeVal EltVal = getStructValueState(Aggr, i);
906 mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
910 Value *Val = IVI.getInsertedValueOperand();
911 if (Val->getType()->isStructTy())
912 // We don't track structs in structs.
913 markOverdefined(getStructValueState(&IVI, i), &IVI);
915 LatticeVal InVal = getValueState(Val);
916 mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
921 void SCCPSolver::visitSelectInst(SelectInst &I) {
922 // If this select returns a struct, just mark the result overdefined.
923 // TODO: We could do a lot better than this if code actually uses this.
924 if (I.getType()->isStructTy())
925 return (void)markOverdefined(&I);
927 LatticeVal CondValue = getValueState(I.getCondition());
928 if (CondValue.isUnknown())
931 if (ConstantInt *CondCB = CondValue.getConstantInt()) {
932 Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
933 mergeInValue(&I, getValueState(OpVal));
937 // Otherwise, the condition is overdefined or a constant we can't evaluate.
938 // See if we can produce something better than overdefined based on the T/F
940 LatticeVal TVal = getValueState(I.getTrueValue());
941 LatticeVal FVal = getValueState(I.getFalseValue());
943 // select ?, C, C -> C.
944 if (TVal.isConstant() && FVal.isConstant() &&
945 TVal.getConstant() == FVal.getConstant())
946 return (void)markConstant(&I, FVal.getConstant());
948 if (TVal.isUnknown()) // select ?, undef, X -> X.
949 return (void)mergeInValue(&I, FVal);
950 if (FVal.isUnknown()) // select ?, X, undef -> X.
951 return (void)mergeInValue(&I, TVal);
955 // Handle Binary Operators.
956 void SCCPSolver::visitBinaryOperator(Instruction &I) {
957 LatticeVal V1State = getValueState(I.getOperand(0));
958 LatticeVal V2State = getValueState(I.getOperand(1));
960 LatticeVal &IV = ValueState[&I];
961 if (IV.isOverdefined()) return;
963 if (V1State.isConstant() && V2State.isConstant()) {
964 Constant *C = ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
965 V2State.getConstant());
967 if (isa<UndefValue>(C))
969 return (void)markConstant(IV, &I, C);
972 // If something is undef, wait for it to resolve.
973 if (!V1State.isOverdefined() && !V2State.isOverdefined())
976 // Otherwise, one of our operands is overdefined. Try to produce something
977 // better than overdefined with some tricks.
978 // If this is 0 / Y, it doesn't matter that the second operand is
979 // overdefined, and we can replace it with zero.
980 if (I.getOpcode() == Instruction::UDiv || I.getOpcode() == Instruction::SDiv)
981 if (V1State.isConstant() && V1State.getConstant()->isNullValue())
982 return (void)markConstant(IV, &I, V1State.getConstant());
987 // it doesn't matter that the other operand is overdefined.
988 if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Mul ||
989 I.getOpcode() == Instruction::Or) {
990 LatticeVal *NonOverdefVal = nullptr;
991 if (!V1State.isOverdefined())
992 NonOverdefVal = &V1State;
993 else if (!V2State.isOverdefined())
994 NonOverdefVal = &V2State;
997 if (NonOverdefVal->isUnknown())
1000 if (I.getOpcode() == Instruction::And ||
1001 I.getOpcode() == Instruction::Mul) {
1004 if (NonOverdefVal->getConstant()->isNullValue())
1005 return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1008 if (ConstantInt *CI = NonOverdefVal->getConstantInt())
1009 if (CI->isMinusOne())
1010 return (void)markConstant(IV, &I, NonOverdefVal->getConstant());
1015 markOverdefined(&I);
1018 // Handle ICmpInst instruction.
1019 void SCCPSolver::visitCmpInst(CmpInst &I) {
1020 LatticeVal &IV = ValueState[&I];
1021 if (IV.isOverdefined()) return;
1023 Value *Op1 = I.getOperand(0);
1024 Value *Op2 = I.getOperand(1);
1026 // For parameters, use ParamState which includes constant range info if
1028 auto V1Param = ParamState.find(Op1);
1029 ValueLatticeElement V1State = (V1Param != ParamState.end())
1031 : getValueState(Op1).toValueLattice();
1033 auto V2Param = ParamState.find(Op2);
1034 ValueLatticeElement V2State = V2Param != ParamState.end()
1036 : getValueState(Op2).toValueLattice();
1038 Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
1040 if (isa<UndefValue>(C))
1044 mergeInValue(&I, CV);
1048 // If operands are still unknown, wait for it to resolve.
1049 if (!V1State.isOverdefined() && !V2State.isOverdefined() && !IV.isConstant())
1052 markOverdefined(&I);
1055 // Handle getelementptr instructions. If all operands are constants then we
1056 // can turn this into a getelementptr ConstantExpr.
1057 void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
1058 if (ValueState[&I].isOverdefined()) return;
1060 SmallVector<Constant*, 8> Operands;
1061 Operands.reserve(I.getNumOperands());
1063 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
1064 LatticeVal State = getValueState(I.getOperand(i));
1065 if (State.isUnknown())
1066 return; // Operands are not resolved yet.
1068 if (State.isOverdefined())
1069 return (void)markOverdefined(&I);
1071 assert(State.isConstant() && "Unknown state!");
1072 Operands.push_back(State.getConstant());
1075 Constant *Ptr = Operands[0];
1076 auto Indices = makeArrayRef(Operands.begin() + 1, Operands.end());
1078 ConstantExpr::getGetElementPtr(I.getSourceElementType(), Ptr, Indices);
1079 if (isa<UndefValue>(C))
1081 markConstant(&I, C);
1084 void SCCPSolver::visitStoreInst(StoreInst &SI) {
1085 // If this store is of a struct, ignore it.
1086 if (SI.getOperand(0)->getType()->isStructTy())
1089 if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
1092 GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
1093 DenseMap<GlobalVariable*, LatticeVal>::iterator I = TrackedGlobals.find(GV);
1094 if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
1096 // Get the value we are storing into the global, then merge it.
1097 mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
1098 if (I->second.isOverdefined())
1099 TrackedGlobals.erase(I); // No need to keep tracking this!
1102 // Handle load instructions. If the operand is a constant pointer to a constant
1103 // global, we can replace the load with the loaded constant value!
1104 void SCCPSolver::visitLoadInst(LoadInst &I) {
1105 // If this load is of a struct, just mark the result overdefined.
1106 if (I.getType()->isStructTy())
1107 return (void)markOverdefined(&I);
1109 LatticeVal PtrVal = getValueState(I.getOperand(0));
1110 if (PtrVal.isUnknown()) return; // The pointer is not resolved yet!
1112 LatticeVal &IV = ValueState[&I];
1113 if (IV.isOverdefined()) return;
1115 if (!PtrVal.isConstant() || I.isVolatile())
1116 return (void)markOverdefined(IV, &I);
1118 Constant *Ptr = PtrVal.getConstant();
1120 // load null is undefined.
1121 if (isa<ConstantPointerNull>(Ptr)) {
1122 if (NullPointerIsDefined(I.getFunction(), I.getPointerAddressSpace()))
1123 return (void)markOverdefined(IV, &I);
1128 // Transform load (constant global) into the value loaded.
1129 if (auto *GV = dyn_cast<GlobalVariable>(Ptr)) {
1130 if (!TrackedGlobals.empty()) {
1131 // If we are tracking this global, merge in the known value for it.
1132 DenseMap<GlobalVariable*, LatticeVal>::iterator It =
1133 TrackedGlobals.find(GV);
1134 if (It != TrackedGlobals.end()) {
1135 mergeInValue(IV, &I, It->second);
1141 // Transform load from a constant into a constant if possible.
1142 if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, I.getType(), DL)) {
1143 if (isa<UndefValue>(C))
1145 return (void)markConstant(IV, &I, C);
1148 // Otherwise we cannot say for certain what value this load will produce.
1150 markOverdefined(IV, &I);
1153 void SCCPSolver::visitCallSite(CallSite CS) {
1154 Function *F = CS.getCalledFunction();
1155 Instruction *I = CS.getInstruction();
1157 if (auto *II = dyn_cast<IntrinsicInst>(I)) {
1158 if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
1159 if (ValueState[I].isOverdefined())
1162 auto *PI = getPredicateInfoFor(I);
1166 auto *PBranch = dyn_cast<PredicateBranch>(getPredicateInfoFor(I));
1168 mergeInValue(ValueState[I], I, getValueState(PI->OriginalOp));
1172 Value *CopyOf = I->getOperand(0);
1173 Value *Cond = PBranch->Condition;
1175 // Everything below relies on the condition being a comparison.
1176 auto *Cmp = dyn_cast<CmpInst>(Cond);
1178 mergeInValue(ValueState[I], I, getValueState(PI->OriginalOp));
1182 Value *CmpOp0 = Cmp->getOperand(0);
1183 Value *CmpOp1 = Cmp->getOperand(1);
1184 if (CopyOf != CmpOp0 && CopyOf != CmpOp1) {
1185 mergeInValue(ValueState[I], I, getValueState(PI->OriginalOp));
1189 if (CmpOp0 != CopyOf)
1190 std::swap(CmpOp0, CmpOp1);
1192 LatticeVal OriginalVal = getValueState(CopyOf);
1193 LatticeVal EqVal = getValueState(CmpOp1);
1194 LatticeVal &IV = ValueState[I];
1195 if (PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_EQ) {
1196 addAdditionalUser(CmpOp1, I);
1197 if (OriginalVal.isConstant())
1198 mergeInValue(IV, I, OriginalVal);
1200 mergeInValue(IV, I, EqVal);
1203 if (!PBranch->TrueEdge && Cmp->getPredicate() == CmpInst::ICMP_NE) {
1204 addAdditionalUser(CmpOp1, I);
1205 if (OriginalVal.isConstant())
1206 mergeInValue(IV, I, OriginalVal);
1208 mergeInValue(IV, I, EqVal);
1212 return (void)mergeInValue(IV, I, getValueState(PBranch->OriginalOp));
1216 // The common case is that we aren't tracking the callee, either because we
1217 // are not doing interprocedural analysis or the callee is indirect, or is
1218 // external. Handle these cases first.
1219 if (!F || F->isDeclaration()) {
1221 // Void return and not tracking callee, just bail.
1222 if (I->getType()->isVoidTy()) return;
1224 // Otherwise, if we have a single return value case, and if the function is
1225 // a declaration, maybe we can constant fold it.
1226 if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
1227 canConstantFoldCallTo(CS, F)) {
1228 SmallVector<Constant*, 8> Operands;
1229 for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
1231 LatticeVal State = getValueState(*AI);
1233 if (State.isUnknown())
1234 return; // Operands are not resolved yet.
1235 if (State.isOverdefined())
1236 return (void)markOverdefined(I);
1237 assert(State.isConstant() && "Unknown state!");
1238 Operands.push_back(State.getConstant());
1241 if (getValueState(I).isOverdefined())
1244 // If we can constant fold this, mark the result of the call as a
1246 if (Constant *C = ConstantFoldCall(CS, F, Operands, TLI)) {
1248 if (isa<UndefValue>(C))
1250 return (void)markConstant(I, C);
1254 // Otherwise, we don't know anything about this call, mark it overdefined.
1255 return (void)markOverdefined(I);
1258 // If this is a local function that doesn't have its address taken, mark its
1259 // entry block executable and merge in the actual arguments to the call into
1260 // the formal arguments of the function.
1261 if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
1262 MarkBlockExecutable(&F->front());
1264 // Propagate information from this call site into the callee.
1265 CallSite::arg_iterator CAI = CS.arg_begin();
1266 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
1267 AI != E; ++AI, ++CAI) {
1268 // If this argument is byval, and if the function is not readonly, there
1269 // will be an implicit copy formed of the input aggregate.
1270 if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
1271 markOverdefined(&*AI);
1275 if (auto *STy = dyn_cast<StructType>(AI->getType())) {
1276 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1277 LatticeVal CallArg = getStructValueState(*CAI, i);
1278 mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
1281 // Most other parts of the Solver still only use the simpler value
1282 // lattice, so we propagate changes for parameters to both lattices.
1283 LatticeVal ConcreteArgument = getValueState(*CAI);
1285 getParamState(&*AI).mergeIn(ConcreteArgument.toValueLattice(), DL);
1286 bool ValueChanged = mergeInValue(&*AI, ConcreteArgument);
1287 // Add argument to work list, if the state of a parameter changes but
1288 // ValueState does not change (because it is already overdefined there),
1289 // We have to take changes in ParamState into account, as it is used
1290 // when evaluating Cmp instructions.
1291 if (!ValueChanged && ParamChanged)
1292 pushToWorkList(ValueState[&*AI], &*AI);
1297 // If this is a single/zero retval case, see if we're tracking the function.
1298 if (auto *STy = dyn_cast<StructType>(F->getReturnType())) {
1299 if (!MRVFunctionsTracked.count(F))
1300 goto CallOverdefined; // Not tracking this callee.
1302 // If we are tracking this callee, propagate the result of the function
1303 // into this call site.
1304 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1305 mergeInValue(getStructValueState(I, i), I,
1306 TrackedMultipleRetVals[std::make_pair(F, i)]);
1308 DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
1309 if (TFRVI == TrackedRetVals.end())
1310 goto CallOverdefined; // Not tracking this callee.
1312 // If so, propagate the return value of the callee into this call result.
1313 mergeInValue(I, TFRVI->second);
1317 void SCCPSolver::Solve() {
1318 // Process the work lists until they are empty!
1319 while (!BBWorkList.empty() || !InstWorkList.empty() ||
1320 !OverdefinedInstWorkList.empty()) {
1321 // Process the overdefined instruction's work list first, which drives other
1322 // things to overdefined more quickly.
1323 while (!OverdefinedInstWorkList.empty()) {
1324 Value *I = OverdefinedInstWorkList.pop_back_val();
1326 LLVM_DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
1328 // "I" got into the work list because it either made the transition from
1329 // bottom to constant, or to overdefined.
1331 // Anything on this worklist that is overdefined need not be visited
1332 // since all of its users will have already been marked as overdefined
1333 // Update all of the users of this instruction's value.
1335 markUsersAsChanged(I);
1338 // Process the instruction work list.
1339 while (!InstWorkList.empty()) {
1340 Value *I = InstWorkList.pop_back_val();
1342 LLVM_DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
1344 // "I" got into the work list because it made the transition from undef to
1347 // Anything on this worklist that is overdefined need not be visited
1348 // since all of its users will have already been marked as overdefined.
1349 // Update all of the users of this instruction's value.
1351 if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
1352 markUsersAsChanged(I);
1355 // Process the basic block work list.
1356 while (!BBWorkList.empty()) {
1357 BasicBlock *BB = BBWorkList.back();
1358 BBWorkList.pop_back();
1360 LLVM_DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
1362 // Notify all instructions in this basic block that they are newly
1369 /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
1370 /// that branches on undef values cannot reach any of their successors.
1371 /// However, this is not a safe assumption. After we solve dataflow, this
1372 /// method should be use to handle this. If this returns true, the solver
1373 /// should be rerun.
1375 /// This method handles this by finding an unresolved branch and marking it one
1376 /// of the edges from the block as being feasible, even though the condition
1377 /// doesn't say it would otherwise be. This allows SCCP to find the rest of the
1378 /// CFG and only slightly pessimizes the analysis results (by marking one,
1379 /// potentially infeasible, edge feasible). This cannot usefully modify the
1380 /// constraints on the condition of the branch, as that would impact other users
1383 /// This scan also checks for values that use undefs, whose results are actually
1384 /// defined. For example, 'zext i8 undef to i32' should produce all zeros
1385 /// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
1386 /// even if X isn't defined.
1387 bool SCCPSolver::ResolvedUndefsIn(Function &F) {
1388 for (BasicBlock &BB : F) {
1389 if (!BBExecutable.count(&BB))
1392 for (Instruction &I : BB) {
1393 // Look for instructions which produce undef values.
1394 if (I.getType()->isVoidTy()) continue;
1396 if (auto *STy = dyn_cast<StructType>(I.getType())) {
1397 // Only a few things that can be structs matter for undef.
1399 // Tracked calls must never be marked overdefined in ResolvedUndefsIn.
1400 if (CallSite CS = CallSite(&I))
1401 if (Function *F = CS.getCalledFunction())
1402 if (MRVFunctionsTracked.count(F))
1405 // extractvalue and insertvalue don't need to be marked; they are
1406 // tracked as precisely as their operands.
1407 if (isa<ExtractValueInst>(I) || isa<InsertValueInst>(I))
1410 // Send the results of everything else to overdefined. We could be
1411 // more precise than this but it isn't worth bothering.
1412 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1413 LatticeVal &LV = getStructValueState(&I, i);
1415 markOverdefined(LV, &I);
1420 LatticeVal &LV = getValueState(&I);
1421 if (!LV.isUnknown()) continue;
1423 // extractvalue is safe; check here because the argument is a struct.
1424 if (isa<ExtractValueInst>(I))
1427 // Compute the operand LatticeVals, for convenience below.
1428 // Anything taking a struct is conservatively assumed to require
1429 // overdefined markings.
1430 if (I.getOperand(0)->getType()->isStructTy()) {
1431 markOverdefined(&I);
1434 LatticeVal Op0LV = getValueState(I.getOperand(0));
1436 if (I.getNumOperands() == 2) {
1437 if (I.getOperand(1)->getType()->isStructTy()) {
1438 markOverdefined(&I);
1442 Op1LV = getValueState(I.getOperand(1));
1444 // If this is an instructions whose result is defined even if the input is
1445 // not fully defined, propagate the information.
1446 Type *ITy = I.getType();
1447 switch (I.getOpcode()) {
1448 case Instruction::Add:
1449 case Instruction::Sub:
1450 case Instruction::Trunc:
1451 case Instruction::FPTrunc:
1452 case Instruction::BitCast:
1453 break; // Any undef -> undef
1454 case Instruction::FSub:
1455 case Instruction::FAdd:
1456 case Instruction::FMul:
1457 case Instruction::FDiv:
1458 case Instruction::FRem:
1459 // Floating-point binary operation: be conservative.
1460 if (Op0LV.isUnknown() && Op1LV.isUnknown())
1461 markForcedConstant(&I, Constant::getNullValue(ITy));
1463 markOverdefined(&I);
1465 case Instruction::ZExt:
1466 case Instruction::SExt:
1467 case Instruction::FPToUI:
1468 case Instruction::FPToSI:
1469 case Instruction::FPExt:
1470 case Instruction::PtrToInt:
1471 case Instruction::IntToPtr:
1472 case Instruction::SIToFP:
1473 case Instruction::UIToFP:
1474 // undef -> 0; some outputs are impossible
1475 markForcedConstant(&I, Constant::getNullValue(ITy));
1477 case Instruction::Mul:
1478 case Instruction::And:
1479 // Both operands undef -> undef
1480 if (Op0LV.isUnknown() && Op1LV.isUnknown())
1482 // undef * X -> 0. X could be zero.
1483 // undef & X -> 0. X could be zero.
1484 markForcedConstant(&I, Constant::getNullValue(ITy));
1486 case Instruction::Or:
1487 // Both operands undef -> undef
1488 if (Op0LV.isUnknown() && Op1LV.isUnknown())
1490 // undef | X -> -1. X could be -1.
1491 markForcedConstant(&I, Constant::getAllOnesValue(ITy));
1493 case Instruction::Xor:
1494 // undef ^ undef -> 0; strictly speaking, this is not strictly
1495 // necessary, but we try to be nice to people who expect this
1496 // behavior in simple cases
1497 if (Op0LV.isUnknown() && Op1LV.isUnknown()) {
1498 markForcedConstant(&I, Constant::getNullValue(ITy));
1501 // undef ^ X -> undef
1503 case Instruction::SDiv:
1504 case Instruction::UDiv:
1505 case Instruction::SRem:
1506 case Instruction::URem:
1507 // X / undef -> undef. No change.
1508 // X % undef -> undef. No change.
1509 if (Op1LV.isUnknown()) break;
1511 // X / 0 -> undef. No change.
1512 // X % 0 -> undef. No change.
1513 if (Op1LV.isConstant() && Op1LV.getConstant()->isZeroValue())
1516 // undef / X -> 0. X could be maxint.
1517 // undef % X -> 0. X could be 1.
1518 markForcedConstant(&I, Constant::getNullValue(ITy));
1520 case Instruction::AShr:
1521 // X >>a undef -> undef.
1522 if (Op1LV.isUnknown()) break;
1524 // Shifting by the bitwidth or more is undefined.
1525 if (Op1LV.isConstant()) {
1526 if (auto *ShiftAmt = Op1LV.getConstantInt())
1527 if (ShiftAmt->getLimitedValue() >=
1528 ShiftAmt->getType()->getScalarSizeInBits())
1533 markForcedConstant(&I, Constant::getNullValue(ITy));
1535 case Instruction::LShr:
1536 case Instruction::Shl:
1537 // X << undef -> undef.
1538 // X >> undef -> undef.
1539 if (Op1LV.isUnknown()) break;
1541 // Shifting by the bitwidth or more is undefined.
1542 if (Op1LV.isConstant()) {
1543 if (auto *ShiftAmt = Op1LV.getConstantInt())
1544 if (ShiftAmt->getLimitedValue() >=
1545 ShiftAmt->getType()->getScalarSizeInBits())
1551 markForcedConstant(&I, Constant::getNullValue(ITy));
1553 case Instruction::Select:
1554 Op1LV = getValueState(I.getOperand(1));
1555 // undef ? X : Y -> X or Y. There could be commonality between X/Y.
1556 if (Op0LV.isUnknown()) {
1557 if (!Op1LV.isConstant()) // Pick the constant one if there is any.
1558 Op1LV = getValueState(I.getOperand(2));
1559 } else if (Op1LV.isUnknown()) {
1560 // c ? undef : undef -> undef. No change.
1561 Op1LV = getValueState(I.getOperand(2));
1562 if (Op1LV.isUnknown())
1564 // Otherwise, c ? undef : x -> x.
1566 // Leave Op1LV as Operand(1)'s LatticeValue.
1569 if (Op1LV.isConstant())
1570 markForcedConstant(&I, Op1LV.getConstant());
1572 markOverdefined(&I);
1574 case Instruction::Load:
1575 // A load here means one of two things: a load of undef from a global,
1576 // a load from an unknown pointer. Either way, having it return undef
1579 case Instruction::ICmp:
1580 // X == undef -> undef. Other comparisons get more complicated.
1581 Op0LV = getValueState(I.getOperand(0));
1582 Op1LV = getValueState(I.getOperand(1));
1584 if ((Op0LV.isUnknown() || Op1LV.isUnknown()) &&
1585 cast<ICmpInst>(&I)->isEquality())
1587 markOverdefined(&I);
1589 case Instruction::Call:
1590 case Instruction::Invoke:
1591 // There are two reasons a call can have an undef result
1592 // 1. It could be tracked.
1593 // 2. It could be constant-foldable.
1594 // Because of the way we solve return values, tracked calls must
1595 // never be marked overdefined in ResolvedUndefsIn.
1596 if (Function *F = CallSite(&I).getCalledFunction())
1597 if (TrackedRetVals.count(F))
1600 // If the call is constant-foldable, we mark it overdefined because
1601 // we do not know what return values are valid.
1602 markOverdefined(&I);
1605 // If we don't know what should happen here, conservatively mark it
1607 markOverdefined(&I);
1612 // Check to see if we have a branch or switch on an undefined value. If so
1613 // we force the branch to go one way or the other to make the successor
1614 // values live. It doesn't really matter which way we force it.
1615 TerminatorInst *TI = BB.getTerminator();
1616 if (auto *BI = dyn_cast<BranchInst>(TI)) {
1617 if (!BI->isConditional()) continue;
1618 if (!getValueState(BI->getCondition()).isUnknown())
1621 // If the input to SCCP is actually branch on undef, fix the undef to
1623 if (isa<UndefValue>(BI->getCondition())) {
1624 BI->setCondition(ConstantInt::getFalse(BI->getContext()));
1625 markEdgeExecutable(&BB, TI->getSuccessor(1));
1629 // Otherwise, it is a branch on a symbolic value which is currently
1630 // considered to be undef. Make sure some edge is executable, so a
1631 // branch on "undef" always flows somewhere.
1632 // FIXME: Distinguish between dead code and an LLVM "undef" value.
1633 BasicBlock *DefaultSuccessor = TI->getSuccessor(1);
1634 if (markEdgeExecutable(&BB, DefaultSuccessor))
1640 if (auto *IBR = dyn_cast<IndirectBrInst>(TI)) {
1641 // Indirect branch with no successor ?. Its ok to assume it branches
1643 if (IBR->getNumSuccessors() < 1)
1646 if (!getValueState(IBR->getAddress()).isUnknown())
1649 // If the input to SCCP is actually branch on undef, fix the undef to
1650 // the first successor of the indirect branch.
1651 if (isa<UndefValue>(IBR->getAddress())) {
1652 IBR->setAddress(BlockAddress::get(IBR->getSuccessor(0)));
1653 markEdgeExecutable(&BB, IBR->getSuccessor(0));
1657 // Otherwise, it is a branch on a symbolic value which is currently
1658 // considered to be undef. Make sure some edge is executable, so a
1659 // branch on "undef" always flows somewhere.
1660 // FIXME: IndirectBr on "undef" doesn't actually need to go anywhere:
1661 // we can assume the branch has undefined behavior instead.
1662 BasicBlock *DefaultSuccessor = IBR->getSuccessor(0);
1663 if (markEdgeExecutable(&BB, DefaultSuccessor))
1669 if (auto *SI = dyn_cast<SwitchInst>(TI)) {
1670 if (!SI->getNumCases() || !getValueState(SI->getCondition()).isUnknown())
1673 // If the input to SCCP is actually switch on undef, fix the undef to
1674 // the first constant.
1675 if (isa<UndefValue>(SI->getCondition())) {
1676 SI->setCondition(SI->case_begin()->getCaseValue());
1677 markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
1681 // Otherwise, it is a branch on a symbolic value which is currently
1682 // considered to be undef. Make sure some edge is executable, so a
1683 // branch on "undef" always flows somewhere.
1684 // FIXME: Distinguish between dead code and an LLVM "undef" value.
1685 BasicBlock *DefaultSuccessor = SI->case_begin()->getCaseSuccessor();
1686 if (markEdgeExecutable(&BB, DefaultSuccessor))
1696 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
1697 Constant *Const = nullptr;
1698 if (V->getType()->isStructTy()) {
1699 std::vector<LatticeVal> IVs = Solver.getStructLatticeValueFor(V);
1700 if (llvm::any_of(IVs,
1701 [](const LatticeVal &LV) { return LV.isOverdefined(); }))
1703 std::vector<Constant *> ConstVals;
1704 auto *ST = dyn_cast<StructType>(V->getType());
1705 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1706 LatticeVal V = IVs[i];
1707 ConstVals.push_back(V.isConstant()
1709 : UndefValue::get(ST->getElementType(i)));
1711 Const = ConstantStruct::get(ST, ConstVals);
1713 const LatticeVal &IV = Solver.getLatticeValueFor(V);
1714 if (IV.isOverdefined())
1717 Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
1719 assert(Const && "Constant is nullptr here!");
1721 // Replacing `musttail` instructions with constant breaks `musttail` invariant
1722 // unless the call itself can be removed
1723 CallInst *CI = dyn_cast<CallInst>(V);
1724 if (CI && CI->isMustTailCall() && !CI->isSafeToRemove()) {
1726 Function *F = CS.getCalledFunction();
1728 // Don't zap returns of the callee
1730 Solver.AddMustTailCallee(F);
1732 LLVM_DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI
1733 << " as a constant\n");
1737 LLVM_DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n');
1739 // Replaces all of the uses of a variable with uses of the constant.
1740 V->replaceAllUsesWith(Const);
1744 // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
1745 // and return true if the function was modified.
1746 static bool runSCCP(Function &F, const DataLayout &DL,
1747 const TargetLibraryInfo *TLI) {
1748 LLVM_DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
1749 SCCPSolver Solver(DL, TLI);
1751 // Mark the first block of the function as being executable.
1752 Solver.MarkBlockExecutable(&F.front());
1754 // Mark all arguments to the function as being overdefined.
1755 for (Argument &AI : F.args())
1756 Solver.markOverdefined(&AI);
1758 // Solve for constants.
1759 bool ResolvedUndefs = true;
1760 while (ResolvedUndefs) {
1762 LLVM_DEBUG(dbgs() << "RESOLVING UNDEFs\n");
1763 ResolvedUndefs = Solver.ResolvedUndefsIn(F);
1766 bool MadeChanges = false;
1768 // If we decided that there are basic blocks that are dead in this function,
1769 // delete their contents now. Note that we cannot actually delete the blocks,
1770 // as we cannot modify the CFG of the function.
1772 for (BasicBlock &BB : F) {
1773 if (!Solver.isBlockExecutable(&BB)) {
1774 LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << BB);
1777 NumInstRemoved += removeAllNonTerminatorAndEHPadInstructions(&BB);
1783 // Iterate over all of the instructions in a function, replacing them with
1784 // constants if we have found them to be of constant values.
1785 for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
1786 Instruction *Inst = &*BI++;
1787 if (Inst->getType()->isVoidTy() || isa<TerminatorInst>(Inst))
1790 if (tryToReplaceWithConstant(Solver, Inst)) {
1791 if (isInstructionTriviallyDead(Inst))
1792 Inst->eraseFromParent();
1793 // Hey, we just changed something!
1803 PreservedAnalyses SCCPPass::run(Function &F, FunctionAnalysisManager &AM) {
1804 const DataLayout &DL = F.getParent()->getDataLayout();
1805 auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
1806 if (!runSCCP(F, DL, &TLI))
1807 return PreservedAnalyses::all();
1809 auto PA = PreservedAnalyses();
1810 PA.preserve<GlobalsAA>();
1811 PA.preserveSet<CFGAnalyses>();
1817 //===--------------------------------------------------------------------===//
1819 /// SCCP Class - This class uses the SCCPSolver to implement a per-function
1820 /// Sparse Conditional Constant Propagator.
1822 class SCCPLegacyPass : public FunctionPass {
1824 // Pass identification, replacement for typeid
1827 SCCPLegacyPass() : FunctionPass(ID) {
1828 initializeSCCPLegacyPassPass(*PassRegistry::getPassRegistry());
1831 void getAnalysisUsage(AnalysisUsage &AU) const override {
1832 AU.addRequired<TargetLibraryInfoWrapperPass>();
1833 AU.addPreserved<GlobalsAAWrapperPass>();
1834 AU.setPreservesCFG();
1837 // runOnFunction - Run the Sparse Conditional Constant Propagation
1838 // algorithm, and return true if the function was modified.
1839 bool runOnFunction(Function &F) override {
1840 if (skipFunction(F))
1842 const DataLayout &DL = F.getParent()->getDataLayout();
1843 const TargetLibraryInfo *TLI =
1844 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1845 return runSCCP(F, DL, TLI);
1849 } // end anonymous namespace
1851 char SCCPLegacyPass::ID = 0;
1853 INITIALIZE_PASS_BEGIN(SCCPLegacyPass, "sccp",
1854 "Sparse Conditional Constant Propagation", false, false)
1855 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
1856 INITIALIZE_PASS_END(SCCPLegacyPass, "sccp",
1857 "Sparse Conditional Constant Propagation", false, false)
1859 // createSCCPPass - This is the public interface to this file.
1860 FunctionPass *llvm::createSCCPPass() { return new SCCPLegacyPass(); }
1862 static void findReturnsToZap(Function &F,
1863 SmallVector<ReturnInst *, 8> &ReturnsToZap,
1864 SCCPSolver &Solver) {
1865 // We can only do this if we know that nothing else can call the function.
1866 if (!Solver.isArgumentTrackedFunction(&F))
1869 // There is a non-removable musttail call site of this function. Zapping
1870 // returns is not allowed.
1871 if (Solver.isMustTailCallee(&F)) {
1872 LLVM_DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName()
1873 << " due to present musttail call of it\n");
1877 for (BasicBlock &BB : F) {
1878 if (CallInst *CI = BB.getTerminatingMustTailCall()) {
1879 LLVM_DEBUG(dbgs() << "Can't zap return of the block due to present "
1880 << "musttail call : " << *CI << "\n");
1885 if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1886 if (!isa<UndefValue>(RI->getOperand(0)))
1887 ReturnsToZap.push_back(RI);
1891 bool llvm::runIPSCCP(
1892 Module &M, const DataLayout &DL, const TargetLibraryInfo *TLI,
1893 function_ref<std::unique_ptr<PredicateInfo>(Function &)> getPredicateInfo) {
1894 SCCPSolver Solver(DL, TLI);
1896 // Loop over all functions, marking arguments to those with their addresses
1897 // taken or that are external as overdefined.
1898 for (Function &F : M) {
1899 if (F.isDeclaration())
1902 Solver.addPredInfo(F, getPredicateInfo(F));
1903 // Determine if we can track the function's return values. If so, add the
1904 // function to the solver's set of return-tracked functions.
1905 if (canTrackReturnsInterprocedurally(&F))
1906 Solver.AddTrackedFunction(&F);
1908 // Determine if we can track the function's arguments. If so, add the
1909 // function to the solver's set of argument-tracked functions.
1910 if (canTrackArgumentsInterprocedurally(&F)) {
1911 Solver.AddArgumentTrackedFunction(&F);
1915 // Assume the function is called.
1916 Solver.MarkBlockExecutable(&F.front());
1918 // Assume nothing about the incoming arguments.
1919 for (Argument &AI : F.args())
1920 Solver.markOverdefined(&AI);
1923 // Determine if we can track any of the module's global variables. If so, add
1924 // the global variables we can track to the solver's set of tracked global
1926 for (GlobalVariable &G : M.globals()) {
1927 G.removeDeadConstantUsers();
1928 if (canTrackGlobalVariableInterprocedurally(&G))
1929 Solver.TrackValueOfGlobalVariable(&G);
1932 // Solve for constants.
1933 bool ResolvedUndefs = true;
1935 while (ResolvedUndefs) {
1936 LLVM_DEBUG(dbgs() << "RESOLVING UNDEFS\n");
1937 ResolvedUndefs = false;
1938 for (Function &F : M)
1939 if (Solver.ResolvedUndefsIn(F)) {
1940 // We run Solve() after we resolved an undef in a function, because
1941 // we might deduce a fact that eliminates an undef in another function.
1943 ResolvedUndefs = true;
1947 bool MadeChanges = false;
1949 // Iterate over all of the instructions in the module, replacing them with
1950 // constants if we have found them to be of constant values.
1951 SmallVector<BasicBlock*, 512> BlocksToErase;
1953 for (Function &F : M) {
1954 if (F.isDeclaration())
1957 if (Solver.isBlockExecutable(&F.front()))
1958 for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
1960 if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI)) {
1966 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
1967 if (!Solver.isBlockExecutable(&*BB)) {
1968 LLVM_DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
1973 if (&*BB != &F.front())
1974 BlocksToErase.push_back(&*BB);
1978 for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
1979 Instruction *Inst = &*BI++;
1980 if (Inst->getType()->isVoidTy())
1982 if (tryToReplaceWithConstant(Solver, Inst)) {
1983 if (Inst->isSafeToRemove())
1984 Inst->eraseFromParent();
1985 // Hey, we just changed something!
1992 // Change dead blocks to unreachable. We do it after replacing constants in
1993 // all executable blocks, because changeToUnreachable may remove PHI nodes
1994 // in executable blocks we found values for. The function's entry block is
1995 // not part of BlocksToErase, so we have to handle it separately.
1996 for (BasicBlock *BB : BlocksToErase)
1998 changeToUnreachable(BB->getFirstNonPHI(), /*UseLLVMTrap=*/false);
1999 if (!Solver.isBlockExecutable(&F.front()))
2000 NumInstRemoved += changeToUnreachable(F.front().getFirstNonPHI(),
2001 /*UseLLVMTrap=*/false);
2003 // Now that all instructions in the function are constant folded, erase dead
2004 // blocks, because we can now use ConstantFoldTerminator to get rid of
2006 for (unsigned i = 0, e = BlocksToErase.size(); i != e; ++i) {
2007 // If there are any PHI nodes in this successor, drop entries for BB now.
2008 BasicBlock *DeadBB = BlocksToErase[i];
2009 for (Value::user_iterator UI = DeadBB->user_begin(),
2010 UE = DeadBB->user_end();
2012 // Grab the user and then increment the iterator early, as the user
2013 // will be deleted. Step past all adjacent uses from the same user.
2014 auto *I = dyn_cast<Instruction>(*UI);
2015 do { ++UI; } while (UI != UE && *UI == I);
2017 // Ignore blockaddress users; BasicBlock's dtor will handle them.
2020 bool Folded = ConstantFoldTerminator(I->getParent());
2022 // If the branch can't be folded, we must have forced an edge
2023 // for an indeterminate value. Force the terminator to fold
2027 if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
2028 Dest = SI->case_begin()->getCaseSuccessor();
2029 C = SI->case_begin()->getCaseValue();
2030 } else if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
2031 Dest = BI->getSuccessor(1);
2032 C = ConstantInt::getFalse(BI->getContext());
2033 } else if (IndirectBrInst *IBR = dyn_cast<IndirectBrInst>(I)) {
2034 Dest = IBR->getSuccessor(0);
2035 C = BlockAddress::get(IBR->getSuccessor(0));
2037 llvm_unreachable("Unexpected terminator instruction");
2039 assert(Solver.isEdgeFeasible(I->getParent(), Dest) &&
2040 "Didn't find feasible edge?");
2043 I->setOperand(0, C);
2044 Folded = ConstantFoldTerminator(I->getParent());
2047 "Expect TermInst on constantint or blockaddress to be folded");
2051 // Finally, delete the basic block.
2052 F.getBasicBlockList().erase(DeadBB);
2054 BlocksToErase.clear();
2056 for (BasicBlock &BB : F) {
2057 for (BasicBlock::iterator BI = BB.begin(), E = BB.end(); BI != E;) {
2058 Instruction *Inst = &*BI++;
2059 if (const PredicateBase *PI = Solver.getPredicateInfoFor(Inst)) {
2060 if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
2061 if (II->getIntrinsicID() == Intrinsic::ssa_copy) {
2062 Value *Op = II->getOperand(0);
2063 Inst->replaceAllUsesWith(Op);
2064 Inst->eraseFromParent();
2068 Inst->replaceAllUsesWith(PI->OriginalOp);
2069 Inst->eraseFromParent();
2075 // If we inferred constant or undef return values for a function, we replaced
2076 // all call uses with the inferred value. This means we don't need to bother
2077 // actually returning anything from the function. Replace all return
2078 // instructions with return undef.
2080 // Do this in two stages: first identify the functions we should process, then
2081 // actually zap their returns. This is important because we can only do this
2082 // if the address of the function isn't taken. In cases where a return is the
2083 // last use of a function, the order of processing functions would affect
2084 // whether other functions are optimizable.
2085 SmallVector<ReturnInst*, 8> ReturnsToZap;
2087 const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
2088 for (const auto &I : RV) {
2089 Function *F = I.first;
2090 if (I.second.isOverdefined() || F->getReturnType()->isVoidTy())
2092 findReturnsToZap(*F, ReturnsToZap, Solver);
2095 for (const auto &F : Solver.getMRVFunctionsTracked()) {
2096 assert(F->getReturnType()->isStructTy() &&
2097 "The return type should be a struct");
2098 StructType *STy = cast<StructType>(F->getReturnType());
2099 if (Solver.isStructLatticeConstant(F, STy))
2100 findReturnsToZap(*F, ReturnsToZap, Solver);
2103 // Zap all returns which we've identified as zap to change.
2104 for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
2105 Function *F = ReturnsToZap[i]->getParent()->getParent();
2106 ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
2109 // If we inferred constant or undef values for globals variables, we can
2110 // delete the global and any stores that remain to it.
2111 const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
2112 for (DenseMap<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
2113 E = TG.end(); I != E; ++I) {
2114 GlobalVariable *GV = I->first;
2115 assert(!I->second.isOverdefined() &&
2116 "Overdefined values should have been taken out of the map!");
2117 LLVM_DEBUG(dbgs() << "Found that GV '" << GV->getName()
2118 << "' is constant!\n");
2119 while (!GV->use_empty()) {
2120 StoreInst *SI = cast<StoreInst>(GV->user_back());
2121 SI->eraseFromParent();
2123 M.getGlobalList().erase(GV);