1 //===-- llvm/Value.h - Definition of the Value class ------------*- C++ -*-===// 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 declares the Value class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_VALUE_H 15 #define LLVM_VALUE_H 16 17 #include "llvm/Use.h" 18 #include "llvm/ADT/StringRef.h" 19 #include "llvm/Support/Casting.h" 20 #include <string> 21 22 namespace llvm { 23 24 class Constant; 25 class Argument; 26 class Instruction; 27 class BasicBlock; 28 class GlobalValue; 29 class Function; 30 class GlobalVariable; 31 class GlobalAlias; 32 class InlineAsm; 33 class ValueSymbolTable; 34 template<typename ValueTy> class StringMapEntry; 35 template <typename ValueTy = Value> 36 class AssertingVH; 37 typedef StringMapEntry<Value*> ValueName; 38 class raw_ostream; 39 class AssemblyAnnotationWriter; 40 class ValueHandleBase; 41 class LLVMContext; 42 class Twine; 43 class MDNode; 44 class Type; 45 46 //===----------------------------------------------------------------------===// 47 // Value Class 48 //===----------------------------------------------------------------------===// 49 50 /// This is a very important LLVM class. It is the base class of all values 51 /// computed by a program that may be used as operands to other values. Value is 52 /// the super class of other important classes such as Instruction and Function. 53 /// All Values have a Type. Type is not a subclass of Value. Some values can 54 /// have a name and they belong to some Module. Setting the name on the Value 55 /// automatically updates the module's symbol table. 56 /// 57 /// Every value has a "use list" that keeps track of which other Values are 58 /// using this Value. A Value can also have an arbitrary number of ValueHandle 59 /// objects that watch it and listen to RAUW and Destroy events. See 60 /// llvm/Support/ValueHandle.h for details. 61 /// 62 /// @brief LLVM Value Representation 63 class Value { 64 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast) 65 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this? 66 protected: 67 /// SubclassOptionalData - This member is similar to SubclassData, however it 68 /// is for holding information which may be used to aid optimization, but 69 /// which may be cleared to zero without affecting conservative 70 /// interpretation. 71 unsigned char SubclassOptionalData : 7; 72 73 private: 74 /// SubclassData - This member is defined by this class, but is not used for 75 /// anything. Subclasses can use it to hold whatever state they find useful. 76 /// This field is initialized to zero by the ctor. 77 unsigned short SubclassData; 78 79 Type *VTy; 80 Use *UseList; 81 82 friend class ValueSymbolTable; // Allow ValueSymbolTable to directly mod Name. 83 friend class ValueHandleBase; 84 ValueName *Name; 85 86 void operator=(const Value &); // Do not implement 87 Value(const Value &); // Do not implement 88 89 protected: 90 /// printCustom - Value subclasses can override this to implement custom 91 /// printing behavior. 92 virtual void printCustom(raw_ostream &O) const; 93 94 Value(Type *Ty, unsigned scid); 95 public: 96 virtual ~Value(); 97 98 /// dump - Support for debugging, callable in GDB: V->dump() 99 // 100 void dump() const; 101 102 /// print - Implement operator<< on Value. 103 /// 104 void print(raw_ostream &O, AssemblyAnnotationWriter *AAW = 0) const; 105 106 /// All values are typed, get the type of this value. 107 /// 108 Type *getType() const { return VTy; } 109 110 /// All values hold a context through their type. 111 LLVMContext &getContext() const; 112 113 // All values can potentially be named... 114 bool hasName() const { return Name != 0; } 115 ValueName *getValueName() const { return Name; } 116 117 /// getName() - Return a constant reference to the value's name. This is cheap 118 /// and guaranteed to return the same reference as long as the value is not 119 /// modified. 120 /// 121 /// This is currently guaranteed to return a StringRef for which data() points 122 /// to a valid null terminated string. The use of StringRef.data() is 123 /// deprecated here, however, and clients should not rely on it. If such 124 /// behavior is needed, clients should use expensive getNameStr(), or switch 125 /// to an interface that does not depend on null termination. 126 StringRef getName() const; 127 128 /// getNameStr() - Return the name of the specified value, *constructing a 129 /// string* to hold it. This is guaranteed to construct a string and is very 130 /// expensive, clients should use getName() unless necessary. 131 std::string getNameStr() const; 132 133 /// setName() - Change the name of the value, choosing a new unique name if 134 /// the provided name is taken. 135 /// 136 /// \arg Name - The new name; or "" if the value's name should be removed. 137 void setName(const Twine &Name); 138 139 140 /// takeName - transfer the name from V to this value, setting V's name to 141 /// empty. It is an error to call V->takeName(V). 142 void takeName(Value *V); 143 144 /// replaceAllUsesWith - Go through the uses list for this definition and make 145 /// each use point to "V" instead of "this". After this completes, 'this's 146 /// use list is guaranteed to be empty. 147 /// 148 void replaceAllUsesWith(Value *V); 149 150 //---------------------------------------------------------------------- 151 // Methods for handling the chain of uses of this Value. 152 // 153 typedef value_use_iterator<User> use_iterator; 154 typedef value_use_iterator<const User> const_use_iterator; 155 156 bool use_empty() const { return UseList == 0; } 157 use_iterator use_begin() { return use_iterator(UseList); } 158 const_use_iterator use_begin() const { return const_use_iterator(UseList); } 159 use_iterator use_end() { return use_iterator(0); } 160 const_use_iterator use_end() const { return const_use_iterator(0); } 161 User *use_back() { return *use_begin(); } 162 const User *use_back() const { return *use_begin(); } 163 164 /// hasOneUse - Return true if there is exactly one user of this value. This 165 /// is specialized because it is a common request and does not require 166 /// traversing the whole use list. 167 /// 168 bool hasOneUse() const { 169 const_use_iterator I = use_begin(), E = use_end(); 170 if (I == E) return false; 171 return ++I == E; 172 } 173 174 /// hasNUses - Return true if this Value has exactly N users. 175 /// 176 bool hasNUses(unsigned N) const; 177 178 /// hasNUsesOrMore - Return true if this value has N users or more. This is 179 /// logically equivalent to getNumUses() >= N. 180 /// 181 bool hasNUsesOrMore(unsigned N) const; 182 183 bool isUsedInBasicBlock(const BasicBlock *BB) const; 184 185 /// getNumUses - This method computes the number of uses of this Value. This 186 /// is a linear time operation. Use hasOneUse, hasNUses, or hasNUsesOrMore 187 /// to check for specific values. 188 unsigned getNumUses() const; 189 190 /// addUse - This method should only be used by the Use class. 191 /// 192 void addUse(Use &U) { U.addToList(&UseList); } 193 194 /// An enumeration for keeping track of the concrete subclass of Value that 195 /// is actually instantiated. Values of this enumeration are kept in the 196 /// Value classes SubclassID field. They are used for concrete type 197 /// identification. 198 enum ValueTy { 199 ArgumentVal, // This is an instance of Argument 200 BasicBlockVal, // This is an instance of BasicBlock 201 FunctionVal, // This is an instance of Function 202 GlobalAliasVal, // This is an instance of GlobalAlias 203 GlobalVariableVal, // This is an instance of GlobalVariable 204 UndefValueVal, // This is an instance of UndefValue 205 BlockAddressVal, // This is an instance of BlockAddress 206 ConstantExprVal, // This is an instance of ConstantExpr 207 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateZero 208 ConstantIntVal, // This is an instance of ConstantInt 209 ConstantFPVal, // This is an instance of ConstantFP 210 ConstantArrayVal, // This is an instance of ConstantArray 211 ConstantStructVal, // This is an instance of ConstantStruct 212 ConstantVectorVal, // This is an instance of ConstantVector 213 ConstantPointerNullVal, // This is an instance of ConstantPointerNull 214 MDNodeVal, // This is an instance of MDNode 215 MDStringVal, // This is an instance of MDString 216 InlineAsmVal, // This is an instance of InlineAsm 217 PseudoSourceValueVal, // This is an instance of PseudoSourceValue 218 FixedStackPseudoSourceValueVal, // This is an instance of 219 // FixedStackPseudoSourceValue 220 InstructionVal, // This is an instance of Instruction 221 // Enum values starting at InstructionVal are used for Instructions; 222 // don't add new values here! 223 224 // Markers: 225 ConstantFirstVal = FunctionVal, 226 ConstantLastVal = ConstantPointerNullVal 227 }; 228 229 /// getValueID - Return an ID for the concrete type of this object. This is 230 /// used to implement the classof checks. This should not be used for any 231 /// other purpose, as the values may change as LLVM evolves. Also, note that 232 /// for instructions, the Instruction's opcode is added to InstructionVal. So 233 /// this means three things: 234 /// # there is no value with code InstructionVal (no opcode==0). 235 /// # there are more possible values for the value type than in ValueTy enum. 236 /// # the InstructionVal enumerator must be the highest valued enumerator in 237 /// the ValueTy enum. 238 unsigned getValueID() const { 239 return SubclassID; 240 } 241 242 /// getRawSubclassOptionalData - Return the raw optional flags value 243 /// contained in this value. This should only be used when testing two 244 /// Values for equivalence. 245 unsigned getRawSubclassOptionalData() const { 246 return SubclassOptionalData; 247 } 248 249 /// clearSubclassOptionalData - Clear the optional flags contained in 250 /// this value. 251 void clearSubclassOptionalData() { 252 SubclassOptionalData = 0; 253 } 254 255 /// hasSameSubclassOptionalData - Test whether the optional flags contained 256 /// in this value are equal to the optional flags in the given value. 257 bool hasSameSubclassOptionalData(const Value *V) const { 258 return SubclassOptionalData == V->SubclassOptionalData; 259 } 260 261 /// intersectOptionalDataWith - Clear any optional flags in this value 262 /// that are not also set in the given value. 263 void intersectOptionalDataWith(const Value *V) { 264 SubclassOptionalData &= V->SubclassOptionalData; 265 } 266 267 /// hasValueHandle - Return true if there is a value handle associated with 268 /// this value. 269 bool hasValueHandle() const { return HasValueHandle; } 270 271 // Methods for support type inquiry through isa, cast, and dyn_cast: 272 static inline bool classof(const Value *) { 273 return true; // Values are always values. 274 } 275 276 /// stripPointerCasts - This method strips off any unneeded pointer 277 /// casts from the specified value, returning the original uncasted value. 278 /// Note that the returned value has pointer type if the specified value does. 279 Value *stripPointerCasts(); 280 const Value *stripPointerCasts() const { 281 return const_cast<Value*>(this)->stripPointerCasts(); 282 } 283 284 /// isDereferenceablePointer - Test if this value is always a pointer to 285 /// allocated and suitably aligned memory for a simple load or store. 286 bool isDereferenceablePointer() const; 287 288 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent, 289 /// return the value in the PHI node corresponding to PredBB. If not, return 290 /// ourself. This is useful if you want to know the value something has in a 291 /// predecessor block. 292 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB); 293 294 const Value *DoPHITranslation(const BasicBlock *CurBB, 295 const BasicBlock *PredBB) const{ 296 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB); 297 } 298 299 /// MaximumAlignment - This is the greatest alignment value supported by 300 /// load, store, and alloca instructions, and global values. 301 static const unsigned MaximumAlignment = 1u << 29; 302 303 /// mutateType - Mutate the type of this Value to be of the specified type. 304 /// Note that this is an extremely dangerous operation which can create 305 /// completely invalid IR very easily. It is strongly recommended that you 306 /// recreate IR objects with the right types instead of mutating them in 307 /// place. 308 void mutateType(Type *Ty) { 309 VTy = Ty; 310 } 311 312 protected: 313 unsigned short getSubclassDataFromValue() const { return SubclassData; } 314 void setValueSubclassData(unsigned short D) { SubclassData = D; } 315 }; 316 317 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) { 318 V.print(OS); 319 return OS; 320 } 321 322 void Use::set(Value *V) { 323 if (Val) removeFromList(); 324 Val = V; 325 if (V) V->addUse(*this); 326 } 327 328 329 // isa - Provide some specializations of isa so that we don't have to include 330 // the subtype header files to test to see if the value is a subclass... 331 // 332 template <> struct isa_impl<Constant, Value> { 333 static inline bool doit(const Value &Val) { 334 return Val.getValueID() >= Value::ConstantFirstVal && 335 Val.getValueID() <= Value::ConstantLastVal; 336 } 337 }; 338 339 template <> struct isa_impl<Argument, Value> { 340 static inline bool doit (const Value &Val) { 341 return Val.getValueID() == Value::ArgumentVal; 342 } 343 }; 344 345 template <> struct isa_impl<InlineAsm, Value> { 346 static inline bool doit(const Value &Val) { 347 return Val.getValueID() == Value::InlineAsmVal; 348 } 349 }; 350 351 template <> struct isa_impl<Instruction, Value> { 352 static inline bool doit(const Value &Val) { 353 return Val.getValueID() >= Value::InstructionVal; 354 } 355 }; 356 357 template <> struct isa_impl<BasicBlock, Value> { 358 static inline bool doit(const Value &Val) { 359 return Val.getValueID() == Value::BasicBlockVal; 360 } 361 }; 362 363 template <> struct isa_impl<Function, Value> { 364 static inline bool doit(const Value &Val) { 365 return Val.getValueID() == Value::FunctionVal; 366 } 367 }; 368 369 template <> struct isa_impl<GlobalVariable, Value> { 370 static inline bool doit(const Value &Val) { 371 return Val.getValueID() == Value::GlobalVariableVal; 372 } 373 }; 374 375 template <> struct isa_impl<GlobalAlias, Value> { 376 static inline bool doit(const Value &Val) { 377 return Val.getValueID() == Value::GlobalAliasVal; 378 } 379 }; 380 381 template <> struct isa_impl<GlobalValue, Value> { 382 static inline bool doit(const Value &Val) { 383 return isa<GlobalVariable>(Val) || isa<Function>(Val) || 384 isa<GlobalAlias>(Val); 385 } 386 }; 387 388 template <> struct isa_impl<MDNode, Value> { 389 static inline bool doit(const Value &Val) { 390 return Val.getValueID() == Value::MDNodeVal; 391 } 392 }; 393 394 // Value* is only 4-byte aligned. 395 template<> 396 class PointerLikeTypeTraits<Value*> { 397 typedef Value* PT; 398 public: 399 static inline void *getAsVoidPointer(PT P) { return P; } 400 static inline PT getFromVoidPointer(void *P) { 401 return static_cast<PT>(P); 402 } 403 enum { NumLowBitsAvailable = 2 }; 404 }; 405 406 } // End llvm namespace 407 408 #endif 409
