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1 //===-- Value.cpp - Implement the Value class -----------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the Value, ValueHandle, and User classes.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/IR/Value.h"
15 #include "LLVMContextImpl.h"
16 #include "llvm/ADT/DenseMap.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/IR/CallSite.h"
19 #include "llvm/IR/Constant.h"
20 #include "llvm/IR/Constants.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/DerivedTypes.h"
23 #include "llvm/IR/GetElementPtrTypeIterator.h"
24 #include "llvm/IR/InstrTypes.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/Operator.h"
29 #include "llvm/IR/Statepoint.h"
30 #include "llvm/IR/ValueHandle.h"
31 #include "llvm/IR/ValueSymbolTable.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/ManagedStatic.h"
35 #include "llvm/Support/raw_ostream.h"
36 #include <algorithm>
37 
38 using namespace llvm;
39 
40 //===----------------------------------------------------------------------===//
41 //                                Value Class
42 //===----------------------------------------------------------------------===//
checkType(Type * Ty)43 static inline Type *checkType(Type *Ty) {
44   assert(Ty && "Value defined with a null type: Error!");
45   return Ty;
46 }
47 
Value(Type * ty,unsigned scid)48 Value::Value(Type *ty, unsigned scid)
49     : VTy(checkType(ty)), UseList(nullptr), SubclassID(scid),
50       HasValueHandle(0), SubclassOptionalData(0), SubclassData(0),
51       NumUserOperands(0), IsUsedByMD(false), HasName(false) {
52   // FIXME: Why isn't this in the subclass gunk??
53   // Note, we cannot call isa<CallInst> before the CallInst has been
54   // constructed.
55   if (SubclassID == Instruction::Call || SubclassID == Instruction::Invoke)
56     assert((VTy->isFirstClassType() || VTy->isVoidTy() || VTy->isStructTy()) &&
57            "invalid CallInst type!");
58   else if (SubclassID != BasicBlockVal &&
59            (SubclassID < ConstantFirstVal || SubclassID > ConstantLastVal))
60     assert((VTy->isFirstClassType() || VTy->isVoidTy()) &&
61            "Cannot create non-first-class values except for constants!");
62   static_assert(sizeof(Value) == 3 * sizeof(void *) + 2 * sizeof(unsigned),
63                 "Value too big");
64 }
65 
~Value()66 Value::~Value() {
67   // Notify all ValueHandles (if present) that this value is going away.
68   if (HasValueHandle)
69     ValueHandleBase::ValueIsDeleted(this);
70   if (isUsedByMetadata())
71     ValueAsMetadata::handleDeletion(this);
72 
73 #ifndef NDEBUG      // Only in -g mode...
74   // Check to make sure that there are no uses of this value that are still
75   // around when the value is destroyed.  If there are, then we have a dangling
76   // reference and something is wrong.  This code is here to print out where
77   // the value is still being referenced.
78   //
79   if (!use_empty()) {
80     dbgs() << "While deleting: " << *VTy << " %" << getName() << "\n";
81     for (auto *U : users())
82       dbgs() << "Use still stuck around after Def is destroyed:" << *U << "\n";
83   }
84 #endif
85   assert(use_empty() && "Uses remain when a value is destroyed!");
86 
87   // If this value is named, destroy the name.  This should not be in a symtab
88   // at this point.
89   destroyValueName();
90 }
91 
destroyValueName()92 void Value::destroyValueName() {
93   ValueName *Name = getValueName();
94   if (Name)
95     Name->Destroy();
96   setValueName(nullptr);
97 }
98 
hasNUses(unsigned N) const99 bool Value::hasNUses(unsigned N) const {
100   const_use_iterator UI = use_begin(), E = use_end();
101 
102   for (; N; --N, ++UI)
103     if (UI == E) return false;  // Too few.
104   return UI == E;
105 }
106 
hasNUsesOrMore(unsigned N) const107 bool Value::hasNUsesOrMore(unsigned N) const {
108   const_use_iterator UI = use_begin(), E = use_end();
109 
110   for (; N; --N, ++UI)
111     if (UI == E) return false;  // Too few.
112 
113   return true;
114 }
115 
isUsedInBasicBlock(const BasicBlock * BB) const116 bool Value::isUsedInBasicBlock(const BasicBlock *BB) const {
117   // This can be computed either by scanning the instructions in BB, or by
118   // scanning the use list of this Value. Both lists can be very long, but
119   // usually one is quite short.
120   //
121   // Scan both lists simultaneously until one is exhausted. This limits the
122   // search to the shorter list.
123   BasicBlock::const_iterator BI = BB->begin(), BE = BB->end();
124   const_user_iterator UI = user_begin(), UE = user_end();
125   for (; BI != BE && UI != UE; ++BI, ++UI) {
126     // Scan basic block: Check if this Value is used by the instruction at BI.
127     if (std::find(BI->op_begin(), BI->op_end(), this) != BI->op_end())
128       return true;
129     // Scan use list: Check if the use at UI is in BB.
130     const Instruction *User = dyn_cast<Instruction>(*UI);
131     if (User && User->getParent() == BB)
132       return true;
133   }
134   return false;
135 }
136 
getNumUses() const137 unsigned Value::getNumUses() const {
138   return (unsigned)std::distance(use_begin(), use_end());
139 }
140 
getSymTab(Value * V,ValueSymbolTable * & ST)141 static bool getSymTab(Value *V, ValueSymbolTable *&ST) {
142   ST = nullptr;
143   if (Instruction *I = dyn_cast<Instruction>(V)) {
144     if (BasicBlock *P = I->getParent())
145       if (Function *PP = P->getParent())
146         ST = &PP->getValueSymbolTable();
147   } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
148     if (Function *P = BB->getParent())
149       ST = &P->getValueSymbolTable();
150   } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
151     if (Module *P = GV->getParent())
152       ST = &P->getValueSymbolTable();
153   } else if (Argument *A = dyn_cast<Argument>(V)) {
154     if (Function *P = A->getParent())
155       ST = &P->getValueSymbolTable();
156   } else {
157     assert(isa<Constant>(V) && "Unknown value type!");
158     return true;  // no name is setable for this.
159   }
160   return false;
161 }
162 
getValueName() const163 ValueName *Value::getValueName() const {
164   if (!HasName) return nullptr;
165 
166   LLVMContext &Ctx = getContext();
167   auto I = Ctx.pImpl->ValueNames.find(this);
168   assert(I != Ctx.pImpl->ValueNames.end() &&
169          "No name entry found!");
170 
171   return I->second;
172 }
173 
setValueName(ValueName * VN)174 void Value::setValueName(ValueName *VN) {
175   LLVMContext &Ctx = getContext();
176 
177   assert(HasName == Ctx.pImpl->ValueNames.count(this) &&
178          "HasName bit out of sync!");
179 
180   if (!VN) {
181     if (HasName)
182       Ctx.pImpl->ValueNames.erase(this);
183     HasName = false;
184     return;
185   }
186 
187   HasName = true;
188   Ctx.pImpl->ValueNames[this] = VN;
189 }
190 
getName() const191 StringRef Value::getName() const {
192   // Make sure the empty string is still a C string. For historical reasons,
193   // some clients want to call .data() on the result and expect it to be null
194   // terminated.
195   if (!hasName())
196     return StringRef("", 0);
197   return getValueName()->getKey();
198 }
199 
setNameImpl(const Twine & NewName)200 void Value::setNameImpl(const Twine &NewName) {
201   // Fast-path: LLVMContext can be set to strip out non-GlobalValue names
202   if (getContext().shouldDiscardValueNames() && !isa<GlobalValue>(this))
203     return;
204 
205   // Fast path for common IRBuilder case of setName("") when there is no name.
206   if (NewName.isTriviallyEmpty() && !hasName())
207     return;
208 
209   SmallString<256> NameData;
210   StringRef NameRef = NewName.toStringRef(NameData);
211   assert(NameRef.find_first_of(0) == StringRef::npos &&
212          "Null bytes are not allowed in names");
213 
214   // Name isn't changing?
215   if (getName() == NameRef)
216     return;
217 
218   assert(!getType()->isVoidTy() && "Cannot assign a name to void values!");
219 
220   // Get the symbol table to update for this object.
221   ValueSymbolTable *ST;
222   if (getSymTab(this, ST))
223     return;  // Cannot set a name on this value (e.g. constant).
224 
225   if (!ST) { // No symbol table to update?  Just do the change.
226     if (NameRef.empty()) {
227       // Free the name for this value.
228       destroyValueName();
229       return;
230     }
231 
232     // NOTE: Could optimize for the case the name is shrinking to not deallocate
233     // then reallocated.
234     destroyValueName();
235 
236     // Create the new name.
237     setValueName(ValueName::Create(NameRef));
238     getValueName()->setValue(this);
239     return;
240   }
241 
242   // NOTE: Could optimize for the case the name is shrinking to not deallocate
243   // then reallocated.
244   if (hasName()) {
245     // Remove old name.
246     ST->removeValueName(getValueName());
247     destroyValueName();
248 
249     if (NameRef.empty())
250       return;
251   }
252 
253   // Name is changing to something new.
254   setValueName(ST->createValueName(NameRef, this));
255 }
256 
setName(const Twine & NewName)257 void Value::setName(const Twine &NewName) {
258   setNameImpl(NewName);
259   if (Function *F = dyn_cast<Function>(this))
260     F->recalculateIntrinsicID();
261 }
262 
takeName(Value * V)263 void Value::takeName(Value *V) {
264   ValueSymbolTable *ST = nullptr;
265   // If this value has a name, drop it.
266   if (hasName()) {
267     // Get the symtab this is in.
268     if (getSymTab(this, ST)) {
269       // We can't set a name on this value, but we need to clear V's name if
270       // it has one.
271       if (V->hasName()) V->setName("");
272       return;  // Cannot set a name on this value (e.g. constant).
273     }
274 
275     // Remove old name.
276     if (ST)
277       ST->removeValueName(getValueName());
278     destroyValueName();
279   }
280 
281   // Now we know that this has no name.
282 
283   // If V has no name either, we're done.
284   if (!V->hasName()) return;
285 
286   // Get this's symtab if we didn't before.
287   if (!ST) {
288     if (getSymTab(this, ST)) {
289       // Clear V's name.
290       V->setName("");
291       return;  // Cannot set a name on this value (e.g. constant).
292     }
293   }
294 
295   // Get V's ST, this should always succed, because V has a name.
296   ValueSymbolTable *VST;
297   bool Failure = getSymTab(V, VST);
298   assert(!Failure && "V has a name, so it should have a ST!"); (void)Failure;
299 
300   // If these values are both in the same symtab, we can do this very fast.
301   // This works even if both values have no symtab yet.
302   if (ST == VST) {
303     // Take the name!
304     setValueName(V->getValueName());
305     V->setValueName(nullptr);
306     getValueName()->setValue(this);
307     return;
308   }
309 
310   // Otherwise, things are slightly more complex.  Remove V's name from VST and
311   // then reinsert it into ST.
312 
313   if (VST)
314     VST->removeValueName(V->getValueName());
315   setValueName(V->getValueName());
316   V->setValueName(nullptr);
317   getValueName()->setValue(this);
318 
319   if (ST)
320     ST->reinsertValue(this);
321 }
322 
assertModuleIsMaterialized() const323 void Value::assertModuleIsMaterialized() const {
324 #ifndef NDEBUG
325   const GlobalValue *GV = dyn_cast<GlobalValue>(this);
326   if (!GV)
327     return;
328   const Module *M = GV->getParent();
329   if (!M)
330     return;
331   assert(M->isMaterialized());
332 #endif
333 }
334 
335 #ifndef NDEBUG
contains(SmallPtrSetImpl<ConstantExpr * > & Cache,ConstantExpr * Expr,Constant * C)336 static bool contains(SmallPtrSetImpl<ConstantExpr *> &Cache, ConstantExpr *Expr,
337                      Constant *C) {
338   if (!Cache.insert(Expr).second)
339     return false;
340 
341   for (auto &O : Expr->operands()) {
342     if (O == C)
343       return true;
344     auto *CE = dyn_cast<ConstantExpr>(O);
345     if (!CE)
346       continue;
347     if (contains(Cache, CE, C))
348       return true;
349   }
350   return false;
351 }
352 
contains(Value * Expr,Value * V)353 static bool contains(Value *Expr, Value *V) {
354   if (Expr == V)
355     return true;
356 
357   auto *C = dyn_cast<Constant>(V);
358   if (!C)
359     return false;
360 
361   auto *CE = dyn_cast<ConstantExpr>(Expr);
362   if (!CE)
363     return false;
364 
365   SmallPtrSet<ConstantExpr *, 4> Cache;
366   return contains(Cache, CE, C);
367 }
368 #endif // NDEBUG
369 
replaceAllUsesWith(Value * New)370 void Value::replaceAllUsesWith(Value *New) {
371   assert(New && "Value::replaceAllUsesWith(<null>) is invalid!");
372   assert(!contains(New, this) &&
373          "this->replaceAllUsesWith(expr(this)) is NOT valid!");
374   assert(New->getType() == getType() &&
375          "replaceAllUses of value with new value of different type!");
376 
377   // Notify all ValueHandles (if present) that this value is going away.
378   if (HasValueHandle)
379     ValueHandleBase::ValueIsRAUWd(this, New);
380   if (isUsedByMetadata())
381     ValueAsMetadata::handleRAUW(this, New);
382 
383   while (!use_empty()) {
384     Use &U = *UseList;
385     // Must handle Constants specially, we cannot call replaceUsesOfWith on a
386     // constant because they are uniqued.
387     if (auto *C = dyn_cast<Constant>(U.getUser())) {
388       if (!isa<GlobalValue>(C)) {
389         C->handleOperandChange(this, New);
390         continue;
391       }
392     }
393 
394     U.set(New);
395   }
396 
397   if (BasicBlock *BB = dyn_cast<BasicBlock>(this))
398     BB->replaceSuccessorsPhiUsesWith(cast<BasicBlock>(New));
399 }
400 
401 // Like replaceAllUsesWith except it does not handle constants or basic blocks.
402 // This routine leaves uses within BB.
replaceUsesOutsideBlock(Value * New,BasicBlock * BB)403 void Value::replaceUsesOutsideBlock(Value *New, BasicBlock *BB) {
404   assert(New && "Value::replaceUsesOutsideBlock(<null>, BB) is invalid!");
405   assert(!contains(New, this) &&
406          "this->replaceUsesOutsideBlock(expr(this), BB) is NOT valid!");
407   assert(New->getType() == getType() &&
408          "replaceUses of value with new value of different type!");
409   assert(BB && "Basic block that may contain a use of 'New' must be defined\n");
410 
411   use_iterator UI = use_begin(), E = use_end();
412   for (; UI != E;) {
413     Use &U = *UI;
414     ++UI;
415     auto *Usr = dyn_cast<Instruction>(U.getUser());
416     if (Usr && Usr->getParent() == BB)
417       continue;
418     U.set(New);
419   }
420 }
421 
422 namespace {
423 // Various metrics for how much to strip off of pointers.
424 enum PointerStripKind {
425   PSK_ZeroIndices,
426   PSK_ZeroIndicesAndAliases,
427   PSK_InBoundsConstantIndices,
428   PSK_InBounds
429 };
430 
431 template <PointerStripKind StripKind>
stripPointerCastsAndOffsets(Value * V)432 static Value *stripPointerCastsAndOffsets(Value *V) {
433   if (!V->getType()->isPointerTy())
434     return V;
435 
436   // Even though we don't look through PHI nodes, we could be called on an
437   // instruction in an unreachable block, which may be on a cycle.
438   SmallPtrSet<Value *, 4> Visited;
439 
440   Visited.insert(V);
441   do {
442     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
443       switch (StripKind) {
444       case PSK_ZeroIndicesAndAliases:
445       case PSK_ZeroIndices:
446         if (!GEP->hasAllZeroIndices())
447           return V;
448         break;
449       case PSK_InBoundsConstantIndices:
450         if (!GEP->hasAllConstantIndices())
451           return V;
452         // fallthrough
453       case PSK_InBounds:
454         if (!GEP->isInBounds())
455           return V;
456         break;
457       }
458       V = GEP->getPointerOperand();
459     } else if (Operator::getOpcode(V) == Instruction::BitCast ||
460                Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
461       V = cast<Operator>(V)->getOperand(0);
462     } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
463       if (StripKind == PSK_ZeroIndices || GA->isInterposable())
464         return V;
465       V = GA->getAliasee();
466     } else {
467       if (auto CS = CallSite(V))
468         if (Value *RV = CS.getReturnedArgOperand()) {
469           V = RV;
470           continue;
471         }
472 
473       return V;
474     }
475     assert(V->getType()->isPointerTy() && "Unexpected operand type!");
476   } while (Visited.insert(V).second);
477 
478   return V;
479 }
480 } // end anonymous namespace
481 
stripPointerCasts()482 Value *Value::stripPointerCasts() {
483   return stripPointerCastsAndOffsets<PSK_ZeroIndicesAndAliases>(this);
484 }
485 
stripPointerCastsNoFollowAliases()486 Value *Value::stripPointerCastsNoFollowAliases() {
487   return stripPointerCastsAndOffsets<PSK_ZeroIndices>(this);
488 }
489 
stripInBoundsConstantOffsets()490 Value *Value::stripInBoundsConstantOffsets() {
491   return stripPointerCastsAndOffsets<PSK_InBoundsConstantIndices>(this);
492 }
493 
stripAndAccumulateInBoundsConstantOffsets(const DataLayout & DL,APInt & Offset)494 Value *Value::stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
495                                                         APInt &Offset) {
496   if (!getType()->isPointerTy())
497     return this;
498 
499   assert(Offset.getBitWidth() == DL.getPointerSizeInBits(cast<PointerType>(
500                                      getType())->getAddressSpace()) &&
501          "The offset must have exactly as many bits as our pointer.");
502 
503   // Even though we don't look through PHI nodes, we could be called on an
504   // instruction in an unreachable block, which may be on a cycle.
505   SmallPtrSet<Value *, 4> Visited;
506   Visited.insert(this);
507   Value *V = this;
508   do {
509     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
510       if (!GEP->isInBounds())
511         return V;
512       APInt GEPOffset(Offset);
513       if (!GEP->accumulateConstantOffset(DL, GEPOffset))
514         return V;
515       Offset = GEPOffset;
516       V = GEP->getPointerOperand();
517     } else if (Operator::getOpcode(V) == Instruction::BitCast) {
518       V = cast<Operator>(V)->getOperand(0);
519     } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
520       V = GA->getAliasee();
521     } else {
522       if (auto CS = CallSite(V))
523         if (Value *RV = CS.getReturnedArgOperand()) {
524           V = RV;
525           continue;
526         }
527 
528       return V;
529     }
530     assert(V->getType()->isPointerTy() && "Unexpected operand type!");
531   } while (Visited.insert(V).second);
532 
533   return V;
534 }
535 
stripInBoundsOffsets()536 Value *Value::stripInBoundsOffsets() {
537   return stripPointerCastsAndOffsets<PSK_InBounds>(this);
538 }
539 
getPointerDereferenceableBytes(const DataLayout & DL,bool & CanBeNull) const540 unsigned Value::getPointerDereferenceableBytes(const DataLayout &DL,
541                                                bool &CanBeNull) const {
542   assert(getType()->isPointerTy() && "must be pointer");
543 
544   unsigned DerefBytes = 0;
545   CanBeNull = false;
546   if (const Argument *A = dyn_cast<Argument>(this)) {
547     DerefBytes = A->getDereferenceableBytes();
548     if (DerefBytes == 0 && A->hasByValAttr() && A->getType()->isSized()) {
549       DerefBytes = DL.getTypeStoreSize(A->getType());
550       CanBeNull = false;
551     }
552     if (DerefBytes == 0) {
553       DerefBytes = A->getDereferenceableOrNullBytes();
554       CanBeNull = true;
555     }
556   } else if (auto CS = ImmutableCallSite(this)) {
557     DerefBytes = CS.getDereferenceableBytes(0);
558     if (DerefBytes == 0) {
559       DerefBytes = CS.getDereferenceableOrNullBytes(0);
560       CanBeNull = true;
561     }
562   } else if (const LoadInst *LI = dyn_cast<LoadInst>(this)) {
563     if (MDNode *MD = LI->getMetadata(LLVMContext::MD_dereferenceable)) {
564       ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
565       DerefBytes = CI->getLimitedValue();
566     }
567     if (DerefBytes == 0) {
568       if (MDNode *MD =
569               LI->getMetadata(LLVMContext::MD_dereferenceable_or_null)) {
570         ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
571         DerefBytes = CI->getLimitedValue();
572       }
573       CanBeNull = true;
574     }
575   } else if (auto *AI = dyn_cast<AllocaInst>(this)) {
576     if (AI->getAllocatedType()->isSized()) {
577       DerefBytes = DL.getTypeStoreSize(AI->getAllocatedType());
578       CanBeNull = false;
579     }
580   } else if (auto *GV = dyn_cast<GlobalVariable>(this)) {
581     if (GV->getValueType()->isSized() && !GV->hasExternalWeakLinkage()) {
582       // TODO: Don't outright reject hasExternalWeakLinkage but set the
583       // CanBeNull flag.
584       DerefBytes = DL.getTypeStoreSize(GV->getValueType());
585       CanBeNull = false;
586     }
587   }
588   return DerefBytes;
589 }
590 
getPointerAlignment(const DataLayout & DL) const591 unsigned Value::getPointerAlignment(const DataLayout &DL) const {
592   assert(getType()->isPointerTy() && "must be pointer");
593 
594   unsigned Align = 0;
595   if (auto *GO = dyn_cast<GlobalObject>(this)) {
596     Align = GO->getAlignment();
597     if (Align == 0) {
598       if (auto *GVar = dyn_cast<GlobalVariable>(GO)) {
599         Type *ObjectType = GVar->getValueType();
600         if (ObjectType->isSized()) {
601           // If the object is defined in the current Module, we'll be giving
602           // it the preferred alignment. Otherwise, we have to assume that it
603           // may only have the minimum ABI alignment.
604           if (GVar->isStrongDefinitionForLinker())
605             Align = DL.getPreferredAlignment(GVar);
606           else
607             Align = DL.getABITypeAlignment(ObjectType);
608         }
609       }
610     }
611   } else if (const Argument *A = dyn_cast<Argument>(this)) {
612     Align = A->getParamAlignment();
613 
614     if (!Align && A->hasStructRetAttr()) {
615       // An sret parameter has at least the ABI alignment of the return type.
616       Type *EltTy = cast<PointerType>(A->getType())->getElementType();
617       if (EltTy->isSized())
618         Align = DL.getABITypeAlignment(EltTy);
619     }
620   } else if (const AllocaInst *AI = dyn_cast<AllocaInst>(this)) {
621     Align = AI->getAlignment();
622     if (Align == 0) {
623       Type *AllocatedType = AI->getAllocatedType();
624       if (AllocatedType->isSized())
625         Align = DL.getPrefTypeAlignment(AllocatedType);
626     }
627   } else if (auto CS = ImmutableCallSite(this))
628     Align = CS.getAttributes().getParamAlignment(AttributeSet::ReturnIndex);
629   else if (const LoadInst *LI = dyn_cast<LoadInst>(this))
630     if (MDNode *MD = LI->getMetadata(LLVMContext::MD_align)) {
631       ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
632       Align = CI->getLimitedValue();
633     }
634 
635   return Align;
636 }
637 
DoPHITranslation(const BasicBlock * CurBB,const BasicBlock * PredBB)638 Value *Value::DoPHITranslation(const BasicBlock *CurBB,
639                                const BasicBlock *PredBB) {
640   PHINode *PN = dyn_cast<PHINode>(this);
641   if (PN && PN->getParent() == CurBB)
642     return PN->getIncomingValueForBlock(PredBB);
643   return this;
644 }
645 
getContext() const646 LLVMContext &Value::getContext() const { return VTy->getContext(); }
647 
reverseUseList()648 void Value::reverseUseList() {
649   if (!UseList || !UseList->Next)
650     // No need to reverse 0 or 1 uses.
651     return;
652 
653   Use *Head = UseList;
654   Use *Current = UseList->Next;
655   Head->Next = nullptr;
656   while (Current) {
657     Use *Next = Current->Next;
658     Current->Next = Head;
659     Head->setPrev(&Current->Next);
660     Head = Current;
661     Current = Next;
662   }
663   UseList = Head;
664   Head->setPrev(&UseList);
665 }
666 
667 //===----------------------------------------------------------------------===//
668 //                             ValueHandleBase Class
669 //===----------------------------------------------------------------------===//
670 
AddToExistingUseList(ValueHandleBase ** List)671 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
672   assert(List && "Handle list is null?");
673 
674   // Splice ourselves into the list.
675   Next = *List;
676   *List = this;
677   setPrevPtr(List);
678   if (Next) {
679     Next->setPrevPtr(&Next);
680     assert(V == Next->V && "Added to wrong list?");
681   }
682 }
683 
AddToExistingUseListAfter(ValueHandleBase * List)684 void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) {
685   assert(List && "Must insert after existing node");
686 
687   Next = List->Next;
688   setPrevPtr(&List->Next);
689   List->Next = this;
690   if (Next)
691     Next->setPrevPtr(&Next);
692 }
693 
AddToUseList()694 void ValueHandleBase::AddToUseList() {
695   assert(V && "Null pointer doesn't have a use list!");
696 
697   LLVMContextImpl *pImpl = V->getContext().pImpl;
698 
699   if (V->HasValueHandle) {
700     // If this value already has a ValueHandle, then it must be in the
701     // ValueHandles map already.
702     ValueHandleBase *&Entry = pImpl->ValueHandles[V];
703     assert(Entry && "Value doesn't have any handles?");
704     AddToExistingUseList(&Entry);
705     return;
706   }
707 
708   // Ok, it doesn't have any handles yet, so we must insert it into the
709   // DenseMap.  However, doing this insertion could cause the DenseMap to
710   // reallocate itself, which would invalidate all of the PrevP pointers that
711   // point into the old table.  Handle this by checking for reallocation and
712   // updating the stale pointers only if needed.
713   DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
714   const void *OldBucketPtr = Handles.getPointerIntoBucketsArray();
715 
716   ValueHandleBase *&Entry = Handles[V];
717   assert(!Entry && "Value really did already have handles?");
718   AddToExistingUseList(&Entry);
719   V->HasValueHandle = true;
720 
721   // If reallocation didn't happen or if this was the first insertion, don't
722   // walk the table.
723   if (Handles.isPointerIntoBucketsArray(OldBucketPtr) ||
724       Handles.size() == 1) {
725     return;
726   }
727 
728   // Okay, reallocation did happen.  Fix the Prev Pointers.
729   for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(),
730        E = Handles.end(); I != E; ++I) {
731     assert(I->second && I->first == I->second->V &&
732            "List invariant broken!");
733     I->second->setPrevPtr(&I->second);
734   }
735 }
736 
RemoveFromUseList()737 void ValueHandleBase::RemoveFromUseList() {
738   assert(V && V->HasValueHandle &&
739          "Pointer doesn't have a use list!");
740 
741   // Unlink this from its use list.
742   ValueHandleBase **PrevPtr = getPrevPtr();
743   assert(*PrevPtr == this && "List invariant broken");
744 
745   *PrevPtr = Next;
746   if (Next) {
747     assert(Next->getPrevPtr() == &Next && "List invariant broken");
748     Next->setPrevPtr(PrevPtr);
749     return;
750   }
751 
752   // If the Next pointer was null, then it is possible that this was the last
753   // ValueHandle watching VP.  If so, delete its entry from the ValueHandles
754   // map.
755   LLVMContextImpl *pImpl = V->getContext().pImpl;
756   DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles;
757   if (Handles.isPointerIntoBucketsArray(PrevPtr)) {
758     Handles.erase(V);
759     V->HasValueHandle = false;
760   }
761 }
762 
ValueIsDeleted(Value * V)763 void ValueHandleBase::ValueIsDeleted(Value *V) {
764   assert(V->HasValueHandle && "Should only be called if ValueHandles present");
765 
766   // Get the linked list base, which is guaranteed to exist since the
767   // HasValueHandle flag is set.
768   LLVMContextImpl *pImpl = V->getContext().pImpl;
769   ValueHandleBase *Entry = pImpl->ValueHandles[V];
770   assert(Entry && "Value bit set but no entries exist");
771 
772   // We use a local ValueHandleBase as an iterator so that ValueHandles can add
773   // and remove themselves from the list without breaking our iteration.  This
774   // is not really an AssertingVH; we just have to give ValueHandleBase a kind.
775   // Note that we deliberately do not the support the case when dropping a value
776   // handle results in a new value handle being permanently added to the list
777   // (as might occur in theory for CallbackVH's): the new value handle will not
778   // be processed and the checking code will mete out righteous punishment if
779   // the handle is still present once we have finished processing all the other
780   // value handles (it is fine to momentarily add then remove a value handle).
781   for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
782     Iterator.RemoveFromUseList();
783     Iterator.AddToExistingUseListAfter(Entry);
784     assert(Entry->Next == &Iterator && "Loop invariant broken.");
785 
786     switch (Entry->getKind()) {
787     case Assert:
788       break;
789     case Tracking:
790       // Mark that this value has been deleted by setting it to an invalid Value
791       // pointer.
792       Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey());
793       break;
794     case Weak:
795       // Weak just goes to null, which will unlink it from the list.
796       Entry->operator=(nullptr);
797       break;
798     case Callback:
799       // Forward to the subclass's implementation.
800       static_cast<CallbackVH*>(Entry)->deleted();
801       break;
802     }
803   }
804 
805   // All callbacks, weak references, and assertingVHs should be dropped by now.
806   if (V->HasValueHandle) {
807 #ifndef NDEBUG      // Only in +Asserts mode...
808     dbgs() << "While deleting: " << *V->getType() << " %" << V->getName()
809            << "\n";
810     if (pImpl->ValueHandles[V]->getKind() == Assert)
811       llvm_unreachable("An asserting value handle still pointed to this"
812                        " value!");
813 
814 #endif
815     llvm_unreachable("All references to V were not removed?");
816   }
817 }
818 
ValueIsRAUWd(Value * Old,Value * New)819 void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) {
820   assert(Old->HasValueHandle &&"Should only be called if ValueHandles present");
821   assert(Old != New && "Changing value into itself!");
822   assert(Old->getType() == New->getType() &&
823          "replaceAllUses of value with new value of different type!");
824 
825   // Get the linked list base, which is guaranteed to exist since the
826   // HasValueHandle flag is set.
827   LLVMContextImpl *pImpl = Old->getContext().pImpl;
828   ValueHandleBase *Entry = pImpl->ValueHandles[Old];
829 
830   assert(Entry && "Value bit set but no entries exist");
831 
832   // We use a local ValueHandleBase as an iterator so that
833   // ValueHandles can add and remove themselves from the list without
834   // breaking our iteration.  This is not really an AssertingVH; we
835   // just have to give ValueHandleBase some kind.
836   for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) {
837     Iterator.RemoveFromUseList();
838     Iterator.AddToExistingUseListAfter(Entry);
839     assert(Entry->Next == &Iterator && "Loop invariant broken.");
840 
841     switch (Entry->getKind()) {
842     case Assert:
843       // Asserting handle does not follow RAUW implicitly.
844       break;
845     case Tracking:
846       // Tracking goes to new value like a WeakVH. Note that this may make it
847       // something incompatible with its templated type. We don't want to have a
848       // virtual (or inline) interface to handle this though, so instead we make
849       // the TrackingVH accessors guarantee that a client never sees this value.
850 
851       // FALLTHROUGH
852     case Weak:
853       // Weak goes to the new value, which will unlink it from Old's list.
854       Entry->operator=(New);
855       break;
856     case Callback:
857       // Forward to the subclass's implementation.
858       static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New);
859       break;
860     }
861   }
862 
863 #ifndef NDEBUG
864   // If any new tracking or weak value handles were added while processing the
865   // list, then complain about it now.
866   if (Old->HasValueHandle)
867     for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next)
868       switch (Entry->getKind()) {
869       case Tracking:
870       case Weak:
871         dbgs() << "After RAUW from " << *Old->getType() << " %"
872                << Old->getName() << " to " << *New->getType() << " %"
873                << New->getName() << "\n";
874         llvm_unreachable("A tracking or weak value handle still pointed to the"
875                          " old value!\n");
876       default:
877         break;
878       }
879 #endif
880 }
881 
882 // Pin the vtable to this file.
anchor()883 void CallbackVH::anchor() {}
884