Value.cpp revision 5034dd318a9dfa0dc45a3ac01e58e60f2aa2498d
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 "LLVMContextImpl.h" 15#include "llvm/Constant.h" 16#include "llvm/Constants.h" 17#include "llvm/DerivedTypes.h" 18#include "llvm/InstrTypes.h" 19#include "llvm/Instructions.h" 20#include "llvm/Operator.h" 21#include "llvm/Module.h" 22#include "llvm/ValueSymbolTable.h" 23#include "llvm/ADT/SmallString.h" 24#include "llvm/Support/Debug.h" 25#include "llvm/Support/GetElementPtrTypeIterator.h" 26#include "llvm/Support/ErrorHandling.h" 27#include "llvm/Support/LeakDetector.h" 28#include "llvm/Support/ManagedStatic.h" 29#include "llvm/Support/ValueHandle.h" 30#include "llvm/ADT/DenseMap.h" 31#include <algorithm> 32using namespace llvm; 33 34//===----------------------------------------------------------------------===// 35// Value Class 36//===----------------------------------------------------------------------===// 37 38static inline const Type *checkType(const Type *Ty) { 39 assert(Ty && "Value defined with a null type: Error!"); 40 return Ty; 41} 42 43Value::Value(const Type *ty, unsigned scid) 44 : SubclassID(scid), HasValueHandle(0), 45 SubclassOptionalData(0), SubclassData(0), VTy(checkType(ty)), 46 UseList(0), Name(0) { 47 if (isa<CallInst>(this) || isa<InvokeInst>(this)) 48 assert((VTy->isFirstClassType() || VTy->isVoidTy() || 49 ty->isOpaqueTy() || VTy->isStructTy()) && 50 "invalid CallInst type!"); 51 else if (!isa<Constant>(this) && !isa<BasicBlock>(this)) 52 assert((VTy->isFirstClassType() || VTy->isVoidTy() || 53 ty->isOpaqueTy()) && 54 "Cannot create non-first-class values except for constants!"); 55} 56 57Value::~Value() { 58 // Notify all ValueHandles (if present) that this value is going away. 59 if (HasValueHandle) 60 ValueHandleBase::ValueIsDeleted(this); 61 62#ifndef NDEBUG // Only in -g mode... 63 // Check to make sure that there are no uses of this value that are still 64 // around when the value is destroyed. If there are, then we have a dangling 65 // reference and something is wrong. This code is here to print out what is 66 // still being referenced. The value in question should be printed as 67 // a <badref> 68 // 69 if (!use_empty()) { 70 dbgs() << "While deleting: " << *VTy << " %" << getNameStr() << "\n"; 71 for (use_iterator I = use_begin(), E = use_end(); I != E; ++I) 72 dbgs() << "Use still stuck around after Def is destroyed:" 73 << **I << "\n"; 74 } 75#endif 76 assert(use_empty() && "Uses remain when a value is destroyed!"); 77 78 // If this value is named, destroy the name. This should not be in a symtab 79 // at this point. 80 if (Name) 81 Name->Destroy(); 82 83 // There should be no uses of this object anymore, remove it. 84 LeakDetector::removeGarbageObject(this); 85} 86 87/// hasNUses - Return true if this Value has exactly N users. 88/// 89bool Value::hasNUses(unsigned N) const { 90 const_use_iterator UI = use_begin(), E = use_end(); 91 92 for (; N; --N, ++UI) 93 if (UI == E) return false; // Too few. 94 return UI == E; 95} 96 97/// hasNUsesOrMore - Return true if this value has N users or more. This is 98/// logically equivalent to getNumUses() >= N. 99/// 100bool Value::hasNUsesOrMore(unsigned N) const { 101 const_use_iterator UI = use_begin(), E = use_end(); 102 103 for (; N; --N, ++UI) 104 if (UI == E) return false; // Too few. 105 106 return true; 107} 108 109/// isUsedInBasicBlock - Return true if this value is used in the specified 110/// basic block. 111bool Value::isUsedInBasicBlock(const BasicBlock *BB) const { 112 for (const_use_iterator I = use_begin(), E = use_end(); I != E; ++I) { 113 const Instruction *User = dyn_cast<Instruction>(*I); 114 if (User && User->getParent() == BB) 115 return true; 116 } 117 return false; 118} 119 120 121/// getNumUses - This method computes the number of uses of this Value. This 122/// is a linear time operation. Use hasOneUse or hasNUses to check for specific 123/// values. 124unsigned Value::getNumUses() const { 125 return (unsigned)std::distance(use_begin(), use_end()); 126} 127 128static bool getSymTab(Value *V, ValueSymbolTable *&ST) { 129 ST = 0; 130 if (Instruction *I = dyn_cast<Instruction>(V)) { 131 if (BasicBlock *P = I->getParent()) 132 if (Function *PP = P->getParent()) 133 ST = &PP->getValueSymbolTable(); 134 } else if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { 135 if (Function *P = BB->getParent()) 136 ST = &P->getValueSymbolTable(); 137 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 138 if (Module *P = GV->getParent()) 139 ST = &P->getValueSymbolTable(); 140 } else if (Argument *A = dyn_cast<Argument>(V)) { 141 if (Function *P = A->getParent()) 142 ST = &P->getValueSymbolTable(); 143 } else if (isa<MDString>(V)) 144 return true; 145 else { 146 assert(isa<Constant>(V) && "Unknown value type!"); 147 return true; // no name is setable for this. 148 } 149 return false; 150} 151 152StringRef Value::getName() const { 153 // Make sure the empty string is still a C string. For historical reasons, 154 // some clients want to call .data() on the result and expect it to be null 155 // terminated. 156 if (!Name) return StringRef("", 0); 157 return Name->getKey(); 158} 159 160std::string Value::getNameStr() const { 161 return getName().str(); 162} 163 164void Value::setName(const Twine &NewName) { 165 // Fast path for common IRBuilder case of setName("") when there is no name. 166 if (NewName.isTriviallyEmpty() && !hasName()) 167 return; 168 169 SmallString<256> NameData; 170 StringRef NameRef = NewName.toStringRef(NameData); 171 172 // Name isn't changing? 173 if (getName() == NameRef) 174 return; 175 176 assert(!getType()->isVoidTy() && "Cannot assign a name to void values!"); 177 178 // Get the symbol table to update for this object. 179 ValueSymbolTable *ST; 180 if (getSymTab(this, ST)) 181 return; // Cannot set a name on this value (e.g. constant). 182 183 if (!ST) { // No symbol table to update? Just do the change. 184 if (NameRef.empty()) { 185 // Free the name for this value. 186 Name->Destroy(); 187 Name = 0; 188 return; 189 } 190 191 if (Name) 192 Name->Destroy(); 193 194 // NOTE: Could optimize for the case the name is shrinking to not deallocate 195 // then reallocated. 196 197 // Create the new name. 198 Name = ValueName::Create(NameRef.begin(), NameRef.end()); 199 Name->setValue(this); 200 return; 201 } 202 203 // NOTE: Could optimize for the case the name is shrinking to not deallocate 204 // then reallocated. 205 if (hasName()) { 206 // Remove old name. 207 ST->removeValueName(Name); 208 Name->Destroy(); 209 Name = 0; 210 211 if (NameRef.empty()) 212 return; 213 } 214 215 // Name is changing to something new. 216 Name = ST->createValueName(NameRef, this); 217} 218 219 220/// takeName - transfer the name from V to this value, setting V's name to 221/// empty. It is an error to call V->takeName(V). 222void Value::takeName(Value *V) { 223 ValueSymbolTable *ST = 0; 224 // If this value has a name, drop it. 225 if (hasName()) { 226 // Get the symtab this is in. 227 if (getSymTab(this, ST)) { 228 // We can't set a name on this value, but we need to clear V's name if 229 // it has one. 230 if (V->hasName()) V->setName(""); 231 return; // Cannot set a name on this value (e.g. constant). 232 } 233 234 // Remove old name. 235 if (ST) 236 ST->removeValueName(Name); 237 Name->Destroy(); 238 Name = 0; 239 } 240 241 // Now we know that this has no name. 242 243 // If V has no name either, we're done. 244 if (!V->hasName()) return; 245 246 // Get this's symtab if we didn't before. 247 if (!ST) { 248 if (getSymTab(this, ST)) { 249 // Clear V's name. 250 V->setName(""); 251 return; // Cannot set a name on this value (e.g. constant). 252 } 253 } 254 255 // Get V's ST, this should always succed, because V has a name. 256 ValueSymbolTable *VST; 257 bool Failure = getSymTab(V, VST); 258 assert(!Failure && "V has a name, so it should have a ST!"); Failure=Failure; 259 260 // If these values are both in the same symtab, we can do this very fast. 261 // This works even if both values have no symtab yet. 262 if (ST == VST) { 263 // Take the name! 264 Name = V->Name; 265 V->Name = 0; 266 Name->setValue(this); 267 return; 268 } 269 270 // Otherwise, things are slightly more complex. Remove V's name from VST and 271 // then reinsert it into ST. 272 273 if (VST) 274 VST->removeValueName(V->Name); 275 Name = V->Name; 276 V->Name = 0; 277 Name->setValue(this); 278 279 if (ST) 280 ST->reinsertValue(this); 281} 282 283 284// uncheckedReplaceAllUsesWith - This is exactly the same as replaceAllUsesWith, 285// except that it doesn't have all of the asserts. The asserts fail because we 286// are half-way done resolving types, which causes some types to exist as two 287// different Type*'s at the same time. This is a sledgehammer to work around 288// this problem. 289// 290void Value::uncheckedReplaceAllUsesWith(Value *New) { 291 // Notify all ValueHandles (if present) that this value is going away. 292 if (HasValueHandle) 293 ValueHandleBase::ValueIsRAUWd(this, New); 294 295 while (!use_empty()) { 296 Use &U = *UseList; 297 // Must handle Constants specially, we cannot call replaceUsesOfWith on a 298 // constant because they are uniqued. 299 if (Constant *C = dyn_cast<Constant>(U.getUser())) { 300 if (!isa<GlobalValue>(C)) { 301 C->replaceUsesOfWithOnConstant(this, New, &U); 302 continue; 303 } 304 } 305 306 U.set(New); 307 } 308} 309 310void Value::replaceAllUsesWith(Value *New) { 311 assert(New && "Value::replaceAllUsesWith(<null>) is invalid!"); 312 assert(New != this && "this->replaceAllUsesWith(this) is NOT valid!"); 313 assert(New->getType() == getType() && 314 "replaceAllUses of value with new value of different type!"); 315 316 uncheckedReplaceAllUsesWith(New); 317} 318 319Value *Value::stripPointerCasts() { 320 if (!getType()->isPointerTy()) 321 return this; 322 323 // Even though we don't look through PHI nodes, we could be called on an 324 // instruction in an unreachable block, which may be on a cycle. 325 SmallPtrSet<Value *, 4> Visited; 326 327 Value *V = this; 328 Visited.insert(V); 329 do { 330 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { 331 if (!GEP->hasAllZeroIndices()) 332 return V; 333 V = GEP->getPointerOperand(); 334 } else if (Operator::getOpcode(V) == Instruction::BitCast) { 335 V = cast<Operator>(V)->getOperand(0); 336 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) { 337 if (GA->mayBeOverridden()) 338 return V; 339 V = GA->getAliasee(); 340 } else { 341 return V; 342 } 343 assert(V->getType()->isPointerTy() && "Unexpected operand type!"); 344 } while (Visited.insert(V)); 345 346 return V; 347} 348 349/// isDereferenceablePointer - Test if this value is always a pointer to 350/// allocated and suitably aligned memory for a simple load or store. 351bool Value::isDereferenceablePointer() const { 352 // Note that it is not safe to speculate into a malloc'd region because 353 // malloc may return null. 354 // It's also not always safe to follow a bitcast, for example: 355 // bitcast i8* (alloca i8) to i32* 356 // would result in a 4-byte load from a 1-byte alloca. Some cases could 357 // be handled using TargetData to check sizes and alignments though. 358 359 // These are obviously ok. 360 if (isa<AllocaInst>(this)) return true; 361 362 // Global variables which can't collapse to null are ok. 363 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this)) 364 return !GV->hasExternalWeakLinkage(); 365 366 // For GEPs, determine if the indexing lands within the allocated object. 367 if (const GEPOperator *GEP = dyn_cast<GEPOperator>(this)) { 368 // Conservatively require that the base pointer be fully dereferenceable. 369 if (!GEP->getOperand(0)->isDereferenceablePointer()) 370 return false; 371 // Check the indices. 372 gep_type_iterator GTI = gep_type_begin(GEP); 373 for (User::const_op_iterator I = GEP->op_begin()+1, 374 E = GEP->op_end(); I != E; ++I) { 375 Value *Index = *I; 376 const Type *Ty = *GTI++; 377 // Struct indices can't be out of bounds. 378 if (isa<StructType>(Ty)) 379 continue; 380 ConstantInt *CI = dyn_cast<ConstantInt>(Index); 381 if (!CI) 382 return false; 383 // Zero is always ok. 384 if (CI->isZero()) 385 continue; 386 // Check to see that it's within the bounds of an array. 387 const ArrayType *ATy = dyn_cast<ArrayType>(Ty); 388 if (!ATy) 389 return false; 390 if (CI->getValue().getActiveBits() > 64) 391 return false; 392 if (CI->getZExtValue() >= ATy->getNumElements()) 393 return false; 394 } 395 // Indices check out; this is dereferenceable. 396 return true; 397 } 398 399 // If we don't know, assume the worst. 400 return false; 401} 402 403/// DoPHITranslation - If this value is a PHI node with CurBB as its parent, 404/// return the value in the PHI node corresponding to PredBB. If not, return 405/// ourself. This is useful if you want to know the value something has in a 406/// predecessor block. 407Value *Value::DoPHITranslation(const BasicBlock *CurBB, 408 const BasicBlock *PredBB) { 409 PHINode *PN = dyn_cast<PHINode>(this); 410 if (PN && PN->getParent() == CurBB) 411 return PN->getIncomingValueForBlock(PredBB); 412 return this; 413} 414 415LLVMContext &Value::getContext() const { return VTy->getContext(); } 416 417//===----------------------------------------------------------------------===// 418// ValueHandleBase Class 419//===----------------------------------------------------------------------===// 420 421/// AddToExistingUseList - Add this ValueHandle to the use list for VP, where 422/// List is known to point into the existing use list. 423void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) { 424 assert(List && "Handle list is null?"); 425 426 // Splice ourselves into the list. 427 Next = *List; 428 *List = this; 429 setPrevPtr(List); 430 if (Next) { 431 Next->setPrevPtr(&Next); 432 assert(VP == Next->VP && "Added to wrong list?"); 433 } 434} 435 436void ValueHandleBase::AddToExistingUseListAfter(ValueHandleBase *List) { 437 assert(List && "Must insert after existing node"); 438 439 Next = List->Next; 440 setPrevPtr(&List->Next); 441 List->Next = this; 442 if (Next) 443 Next->setPrevPtr(&Next); 444} 445 446/// AddToUseList - Add this ValueHandle to the use list for VP. 447void ValueHandleBase::AddToUseList() { 448 assert(VP && "Null pointer doesn't have a use list!"); 449 450 LLVMContextImpl *pImpl = VP->getContext().pImpl; 451 452 if (VP->HasValueHandle) { 453 // If this value already has a ValueHandle, then it must be in the 454 // ValueHandles map already. 455 ValueHandleBase *&Entry = pImpl->ValueHandles[VP]; 456 assert(Entry != 0 && "Value doesn't have any handles?"); 457 AddToExistingUseList(&Entry); 458 return; 459 } 460 461 // Ok, it doesn't have any handles yet, so we must insert it into the 462 // DenseMap. However, doing this insertion could cause the DenseMap to 463 // reallocate itself, which would invalidate all of the PrevP pointers that 464 // point into the old table. Handle this by checking for reallocation and 465 // updating the stale pointers only if needed. 466 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles; 467 const void *OldBucketPtr = Handles.getPointerIntoBucketsArray(); 468 469 ValueHandleBase *&Entry = Handles[VP]; 470 assert(Entry == 0 && "Value really did already have handles?"); 471 AddToExistingUseList(&Entry); 472 VP->HasValueHandle = true; 473 474 // If reallocation didn't happen or if this was the first insertion, don't 475 // walk the table. 476 if (Handles.isPointerIntoBucketsArray(OldBucketPtr) || 477 Handles.size() == 1) { 478 return; 479 } 480 481 // Okay, reallocation did happen. Fix the Prev Pointers. 482 for (DenseMap<Value*, ValueHandleBase*>::iterator I = Handles.begin(), 483 E = Handles.end(); I != E; ++I) { 484 assert(I->second && I->first == I->second->VP && "List invariant broken!"); 485 I->second->setPrevPtr(&I->second); 486 } 487} 488 489/// RemoveFromUseList - Remove this ValueHandle from its current use list. 490void ValueHandleBase::RemoveFromUseList() { 491 assert(VP && VP->HasValueHandle && "Pointer doesn't have a use list!"); 492 493 // Unlink this from its use list. 494 ValueHandleBase **PrevPtr = getPrevPtr(); 495 assert(*PrevPtr == this && "List invariant broken"); 496 497 *PrevPtr = Next; 498 if (Next) { 499 assert(Next->getPrevPtr() == &Next && "List invariant broken"); 500 Next->setPrevPtr(PrevPtr); 501 return; 502 } 503 504 // If the Next pointer was null, then it is possible that this was the last 505 // ValueHandle watching VP. If so, delete its entry from the ValueHandles 506 // map. 507 LLVMContextImpl *pImpl = VP->getContext().pImpl; 508 DenseMap<Value*, ValueHandleBase*> &Handles = pImpl->ValueHandles; 509 if (Handles.isPointerIntoBucketsArray(PrevPtr)) { 510 Handles.erase(VP); 511 VP->HasValueHandle = false; 512 } 513} 514 515 516void ValueHandleBase::ValueIsDeleted(Value *V) { 517 assert(V->HasValueHandle && "Should only be called if ValueHandles present"); 518 519 // Get the linked list base, which is guaranteed to exist since the 520 // HasValueHandle flag is set. 521 LLVMContextImpl *pImpl = V->getContext().pImpl; 522 ValueHandleBase *Entry = pImpl->ValueHandles[V]; 523 assert(Entry && "Value bit set but no entries exist"); 524 525 // We use a local ValueHandleBase as an iterator so that ValueHandles can add 526 // and remove themselves from the list without breaking our iteration. This 527 // is not really an AssertingVH; we just have to give ValueHandleBase a kind. 528 // Note that we deliberately do not the support the case when dropping a value 529 // handle results in a new value handle being permanently added to the list 530 // (as might occur in theory for CallbackVH's): the new value handle will not 531 // be processed and the checking code will mete out righteous punishment if 532 // the handle is still present once we have finished processing all the other 533 // value handles (it is fine to momentarily add then remove a value handle). 534 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) { 535 Iterator.RemoveFromUseList(); 536 Iterator.AddToExistingUseListAfter(Entry); 537 assert(Entry->Next == &Iterator && "Loop invariant broken."); 538 539 switch (Entry->getKind()) { 540 case Assert: 541 break; 542 case Tracking: 543 // Mark that this value has been deleted by setting it to an invalid Value 544 // pointer. 545 Entry->operator=(DenseMapInfo<Value *>::getTombstoneKey()); 546 break; 547 case Weak: 548 // Weak just goes to null, which will unlink it from the list. 549 Entry->operator=(0); 550 break; 551 case Callback: 552 // Forward to the subclass's implementation. 553 static_cast<CallbackVH*>(Entry)->deleted(); 554 break; 555 } 556 } 557 558 // All callbacks, weak references, and assertingVHs should be dropped by now. 559 if (V->HasValueHandle) { 560#ifndef NDEBUG // Only in +Asserts mode... 561 dbgs() << "While deleting: " << *V->getType() << " %" << V->getNameStr() 562 << "\n"; 563 if (pImpl->ValueHandles[V]->getKind() == Assert) 564 llvm_unreachable("An asserting value handle still pointed to this" 565 " value!"); 566 567#endif 568 llvm_unreachable("All references to V were not removed?"); 569 } 570} 571 572 573void ValueHandleBase::ValueIsRAUWd(Value *Old, Value *New) { 574 assert(Old->HasValueHandle &&"Should only be called if ValueHandles present"); 575 assert(Old != New && "Changing value into itself!"); 576 577 // Get the linked list base, which is guaranteed to exist since the 578 // HasValueHandle flag is set. 579 LLVMContextImpl *pImpl = Old->getContext().pImpl; 580 ValueHandleBase *Entry = pImpl->ValueHandles[Old]; 581 582 assert(Entry && "Value bit set but no entries exist"); 583 584 // We use a local ValueHandleBase as an iterator so that 585 // ValueHandles can add and remove themselves from the list without 586 // breaking our iteration. This is not really an AssertingVH; we 587 // just have to give ValueHandleBase some kind. 588 for (ValueHandleBase Iterator(Assert, *Entry); Entry; Entry = Iterator.Next) { 589 Iterator.RemoveFromUseList(); 590 Iterator.AddToExistingUseListAfter(Entry); 591 assert(Entry->Next == &Iterator && "Loop invariant broken."); 592 593 switch (Entry->getKind()) { 594 case Assert: 595 // Asserting handle does not follow RAUW implicitly. 596 break; 597 case Tracking: 598 // Tracking goes to new value like a WeakVH. Note that this may make it 599 // something incompatible with its templated type. We don't want to have a 600 // virtual (or inline) interface to handle this though, so instead we make 601 // the TrackingVH accessors guarantee that a client never sees this value. 602 603 // FALLTHROUGH 604 case Weak: 605 // Weak goes to the new value, which will unlink it from Old's list. 606 Entry->operator=(New); 607 break; 608 case Callback: 609 // Forward to the subclass's implementation. 610 static_cast<CallbackVH*>(Entry)->allUsesReplacedWith(New); 611 break; 612 } 613 } 614 615#ifndef NDEBUG 616 // If any new tracking or weak value handles were added while processing the 617 // list, then complain about it now. 618 if (Old->HasValueHandle) 619 for (Entry = pImpl->ValueHandles[Old]; Entry; Entry = Entry->Next) 620 switch (Entry->getKind()) { 621 case Tracking: 622 case Weak: 623 dbgs() << "After RAUW from " << *Old->getType() << " %" 624 << Old->getNameStr() << " to " << *New->getType() << " %" 625 << New->getNameStr() << "\n"; 626 llvm_unreachable("A tracking or weak value handle still pointed to the" 627 " old value!\n"); 628 default: 629 break; 630 } 631#endif 632} 633 634/// ~CallbackVH. Empty, but defined here to avoid emitting the vtable 635/// more than once. 636CallbackVH::~CallbackVH() {} 637 638 639//===----------------------------------------------------------------------===// 640// User Class 641//===----------------------------------------------------------------------===// 642 643// replaceUsesOfWith - Replaces all references to the "From" definition with 644// references to the "To" definition. 645// 646void User::replaceUsesOfWith(Value *From, Value *To) { 647 if (From == To) return; // Duh what? 648 649 assert((!isa<Constant>(this) || isa<GlobalValue>(this)) && 650 "Cannot call User::replaceUsesOfWith on a constant!"); 651 652 for (unsigned i = 0, E = getNumOperands(); i != E; ++i) 653 if (getOperand(i) == From) { // Is This operand is pointing to oldval? 654 // The side effects of this setOperand call include linking to 655 // "To", adding "this" to the uses list of To, and 656 // most importantly, removing "this" from the use list of "From". 657 setOperand(i, To); // Fix it now... 658 } 659} 660