1 //===-- llvm/Value.h - Definition of the Value class ------------*- C++ -*-===//
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 declares the Value class.
12 //===----------------------------------------------------------------------===//
17 #include "llvm/AbstractTypeUser.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/Support/Casting.h"
34 class ValueSymbolTable;
35 class TypeSymbolTable;
36 template<typename ValueTy> class StringMapEntry;
37 template <typename ValueTy = Value>
39 typedef StringMapEntry<Value*> ValueName;
41 class AssemblyAnnotationWriter;
42 class ValueHandleBase;
46 //===----------------------------------------------------------------------===//
48 //===----------------------------------------------------------------------===//
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. All types can have
54 /// a name and they should belong to some Module. Setting the name on the Value
55 /// automatically updates the module's symbol table.
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.
62 /// @brief LLVM Value Representation
64 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
65 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
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
71 unsigned char SubclassOptionalData : 7;
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;
82 friend class ValueSymbolTable; // Allow ValueSymbolTable to directly mod Name.
83 friend class ValueHandleBase;
84 friend class AbstractTypeUser;
87 void operator=(const Value &); // Do not implement
88 Value(const Value &); // Do not implement
91 /// printCustom - Value subclasses can override this to implement custom
92 /// printing behavior.
93 virtual void printCustom(raw_ostream &O) const;
96 Value(const Type *Ty, unsigned scid);
99 /// dump - Support for debugging, callable in GDB: V->dump()
103 /// print - Implement operator<< on Value.
105 void print(raw_ostream &O, AssemblyAnnotationWriter *AAW = 0) const;
107 /// All values are typed, get the type of this value.
109 inline const Type *getType() const { return VTy; }
111 /// All values hold a context through their type.
112 LLVMContext &getContext() const;
114 // All values can potentially be named...
115 inline bool hasName() const { return Name != 0; }
116 ValueName *getValueName() const { return Name; }
118 /// getName() - Return a constant reference to the value's name. This is cheap
119 /// and guaranteed to return the same reference as long as the value is not
122 /// This is currently guaranteed to return a StringRef for which data() points
123 /// to a valid null terminated string. The use of StringRef.data() is
124 /// deprecated here, however, and clients should not rely on it. If such
125 /// behavior is needed, clients should use expensive getNameStr(), or switch
126 /// to an interface that does not depend on null termination.
127 StringRef getName() const;
129 /// getNameStr() - Return the name of the specified value, *constructing a
130 /// string* to hold it. This is guaranteed to construct a string and is very
131 /// expensive, clients should use getName() unless necessary.
132 std::string getNameStr() const;
134 /// setName() - Change the name of the value, choosing a new unique name if
135 /// the provided name is taken.
137 /// \arg Name - The new name; or "" if the value's name should be removed.
138 void setName(const Twine &Name);
141 /// takeName - transfer the name from V to this value, setting V's name to
142 /// empty. It is an error to call V->takeName(V).
143 void takeName(Value *V);
145 /// replaceAllUsesWith - Go through the uses list for this definition and make
146 /// each use point to "V" instead of "this". After this completes, 'this's
147 /// use list is guaranteed to be empty.
149 void replaceAllUsesWith(Value *V);
151 // uncheckedReplaceAllUsesWith - Just like replaceAllUsesWith but dangerous.
152 // Only use when in type resolution situations!
153 void uncheckedReplaceAllUsesWith(Value *V);
155 //----------------------------------------------------------------------
156 // Methods for handling the chain of uses of this Value.
158 typedef value_use_iterator<User> use_iterator;
159 typedef value_use_iterator<const User> use_const_iterator;
161 bool use_empty() const { return UseList == 0; }
162 use_iterator use_begin() { return use_iterator(UseList); }
163 use_const_iterator use_begin() const { return use_const_iterator(UseList); }
164 use_iterator use_end() { return use_iterator(0); }
165 use_const_iterator use_end() const { return use_const_iterator(0); }
166 User *use_back() { return *use_begin(); }
167 const User *use_back() const { return *use_begin(); }
169 /// hasOneUse - Return true if there is exactly one user of this value. This
170 /// is specialized because it is a common request and does not require
171 /// traversing the whole use list.
173 bool hasOneUse() const {
174 use_const_iterator I = use_begin(), E = use_end();
175 if (I == E) return false;
179 /// hasNUses - Return true if this Value has exactly N users.
181 bool hasNUses(unsigned N) const;
183 /// hasNUsesOrMore - Return true if this value has N users or more. This is
184 /// logically equivalent to getNumUses() >= N.
186 bool hasNUsesOrMore(unsigned N) const;
188 bool isUsedInBasicBlock(const BasicBlock *BB) const;
190 /// getNumUses - This method computes the number of uses of this Value. This
191 /// is a linear time operation. Use hasOneUse, hasNUses, or hasMoreThanNUses
192 /// to check for specific values.
193 unsigned getNumUses() const;
195 /// addUse - This method should only be used by the Use class.
197 void addUse(Use &U) { U.addToList(&UseList); }
199 /// An enumeration for keeping track of the concrete subclass of Value that
200 /// is actually instantiated. Values of this enumeration are kept in the
201 /// Value classes SubclassID field. They are used for concrete type
204 ArgumentVal, // This is an instance of Argument
205 BasicBlockVal, // This is an instance of BasicBlock
206 FunctionVal, // This is an instance of Function
207 GlobalAliasVal, // This is an instance of GlobalAlias
208 GlobalVariableVal, // This is an instance of GlobalVariable
209 UndefValueVal, // This is an instance of UndefValue
210 BlockAddressVal, // This is an instance of BlockAddress
211 ConstantExprVal, // This is an instance of ConstantExpr
212 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateNull
213 ConstantIntVal, // This is an instance of ConstantInt
214 ConstantFPVal, // This is an instance of ConstantFP
215 ConstantArrayVal, // This is an instance of ConstantArray
216 ConstantStructVal, // This is an instance of ConstantStruct
217 ConstantVectorVal, // This is an instance of ConstantVector
218 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
219 MDNodeVal, // This is an instance of MDNode
220 MDStringVal, // This is an instance of MDString
221 NamedMDNodeVal, // This is an instance of NamedMDNode
222 InlineAsmVal, // This is an instance of InlineAsm
223 PseudoSourceValueVal, // This is an instance of PseudoSourceValue
224 FixedStackPseudoSourceValueVal, // This is an instance of
225 // FixedStackPseudoSourceValue
226 InstructionVal, // This is an instance of Instruction
227 // Enum values starting at InstructionVal are used for Instructions;
228 // don't add new values here!
231 ConstantFirstVal = FunctionVal,
232 ConstantLastVal = ConstantPointerNullVal
235 /// getValueID - Return an ID for the concrete type of this object. This is
236 /// used to implement the classof checks. This should not be used for any
237 /// other purpose, as the values may change as LLVM evolves. Also, note that
238 /// for instructions, the Instruction's opcode is added to InstructionVal. So
239 /// this means three things:
240 /// # there is no value with code InstructionVal (no opcode==0).
241 /// # there are more possible values for the value type than in ValueTy enum.
242 /// # the InstructionVal enumerator must be the highest valued enumerator in
243 /// the ValueTy enum.
244 unsigned getValueID() const {
248 /// getRawSubclassOptionalData - Return the raw optional flags value
249 /// contained in this value. This should only be used when testing two
250 /// Values for equivalence.
251 unsigned getRawSubclassOptionalData() const {
252 return SubclassOptionalData;
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;
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;
267 // Methods for support type inquiry through isa, cast, and dyn_cast:
268 static inline bool classof(const Value *) {
269 return true; // Values are always values.
272 /// getRawType - This should only be used to implement the vmcore library.
274 const Type *getRawType() const { return VTy.getRawType(); }
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();
284 /// getUnderlyingObject - This method strips off any GEP address adjustments
285 /// and pointer casts from the specified value, returning the original object
286 /// being addressed. Note that the returned value has pointer type if the
287 /// specified value does.
288 Value *getUnderlyingObject();
289 const Value *getUnderlyingObject() const {
290 return const_cast<Value*>(this)->getUnderlyingObject();
293 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
294 /// return the value in the PHI node corresponding to PredBB. If not, return
295 /// ourself. This is useful if you want to know the value something has in a
296 /// predecessor block.
297 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
299 const Value *DoPHITranslation(const BasicBlock *CurBB,
300 const BasicBlock *PredBB) const{
301 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
305 unsigned short getSubclassDataFromValue() const { return SubclassData; }
306 void setValueSubclassData(unsigned short D) { SubclassData = D; }
309 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
314 void Use::set(Value *V) {
315 if (Val) removeFromList();
317 if (V) V->addUse(*this);
321 // isa - Provide some specializations of isa so that we don't have to include
322 // the subtype header files to test to see if the value is a subclass...
324 template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
325 return Val.getValueID() >= Value::ConstantFirstVal &&
326 Val.getValueID() <= Value::ConstantLastVal;
328 template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
329 return Val.getValueID() == Value::ArgumentVal;
331 template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
332 return Val.getValueID() == Value::InlineAsmVal;
334 template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
335 return Val.getValueID() >= Value::InstructionVal;
337 template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
338 return Val.getValueID() == Value::BasicBlockVal;
340 template <> inline bool isa_impl<Function, Value>(const Value &Val) {
341 return Val.getValueID() == Value::FunctionVal;
343 template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
344 return Val.getValueID() == Value::GlobalVariableVal;
346 template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
347 return Val.getValueID() == Value::GlobalAliasVal;
349 template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
350 return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
351 isa<GlobalAlias>(Val);
355 // Value* is only 4-byte aligned.
357 class PointerLikeTypeTraits<Value*> {
360 static inline void *getAsVoidPointer(PT P) { return P; }
361 static inline PT getFromVoidPointer(void *P) {
362 return static_cast<PT>(P);
364 enum { NumLowBitsAvailable = 2 };
367 } // End llvm namespace