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/ADT/Twine.h"
21 #include "llvm/Support/Casting.h"
35 class ValueSymbolTable;
36 class TypeSymbolTable;
37 template<typename ValueTy> class StringMapEntry;
38 template <typename ValueTy = Value>
40 typedef StringMapEntry<Value*> ValueName;
42 class AssemblyAnnotationWriter;
43 class ValueHandleBase;
45 class MetadataContextImpl;
47 //===----------------------------------------------------------------------===//
49 //===----------------------------------------------------------------------===//
51 /// This is a very important LLVM class. It is the base class of all values
52 /// computed by a program that may be used as operands to other values. Value is
53 /// the super class of other important classes such as Instruction and Function.
54 /// All Values have a Type. Type is not a subclass of Value. All types can have
55 /// a name and they should belong to some Module. Setting the name on the Value
56 /// automatically updates the module's symbol table.
58 /// Every value has a "use list" that keeps track of which other Values are
59 /// using this Value. A Value can also have an arbitrary number of ValueHandle
60 /// objects that watch it and listen to RAUW and Destroy events see
61 /// llvm/Support/ValueHandle.h for details.
63 /// @brief LLVM Value Representation
65 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
66 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
67 unsigned char HasMetadata : 1; // Has a metadata attached to this ?
69 /// SubclassOptionalData - This member is similar to SubclassData, however it
70 /// is for holding information which may be used to aid optimization, but
71 /// which may be cleared to zero without affecting conservative
73 unsigned char SubclassOptionalData : 7;
75 /// SubclassData - This member is defined by this class, but is not used for
76 /// anything. Subclasses can use it to hold whatever state they find useful.
77 /// This field is initialized to zero by the ctor.
78 unsigned short SubclassData;
83 friend class ValueSymbolTable; // Allow ValueSymbolTable to directly mod Name.
84 friend class SymbolTable; // Allow SymbolTable to directly poke Name.
85 friend class ValueHandleBase;
86 friend class MetadataContextImpl;
87 friend class AbstractTypeUser;
90 void operator=(const Value &); // Do not implement
91 Value(const Value &); // Do not implement
94 /// printCustom - Value subclasses can override this to implement custom
95 /// printing behavior.
96 virtual void printCustom(raw_ostream &O) const;
99 Value(const Type *Ty, unsigned scid);
102 /// dump - Support for debugging, callable in GDB: V->dump()
106 /// print - Implement operator<< on Value.
108 void print(raw_ostream &O, AssemblyAnnotationWriter *AAW = 0) const;
110 /// All values are typed, get the type of this value.
112 inline const Type *getType() const { return VTy; }
114 /// All values hold a context through their type.
115 LLVMContext &getContext() const;
117 // All values can potentially be named...
118 inline bool hasName() const { return Name != 0; }
119 ValueName *getValueName() const { return Name; }
121 /// getName() - Return a constant reference to the value's name. This is cheap
122 /// and guaranteed to return the same reference as long as the value is not
125 /// This is currently guaranteed to return a StringRef for which data() points
126 /// to a valid null terminated string. The use of StringRef.data() is
127 /// deprecated here, however, and clients should not rely on it. If such
128 /// behavior is needed, clients should use expensive getNameStr(), or switch
129 /// to an interface that does not depend on null termination.
130 StringRef getName() const;
132 /// getNameStr() - Return the name of the specified value, *constructing a
133 /// string* to hold it. This is guaranteed to construct a string and is very
134 /// expensive, clients should use getName() unless necessary.
135 std::string getNameStr() const;
137 /// setName() - Change the name of the value, choosing a new unique name if
138 /// the provided name is taken.
140 /// \arg Name - The new name; or "" if the value's name should be removed.
141 void setName(const Twine &Name);
144 /// takeName - transfer the name from V to this value, setting V's name to
145 /// empty. It is an error to call V->takeName(V).
146 void takeName(Value *V);
148 /// replaceAllUsesWith - Go through the uses list for this definition and make
149 /// each use point to "V" instead of "this". After this completes, 'this's
150 /// use list is guaranteed to be empty.
152 void replaceAllUsesWith(Value *V);
154 // uncheckedReplaceAllUsesWith - Just like replaceAllUsesWith but dangerous.
155 // Only use when in type resolution situations!
156 void uncheckedReplaceAllUsesWith(Value *V);
158 //----------------------------------------------------------------------
159 // Methods for handling the chain of uses of this Value.
161 typedef value_use_iterator<User> use_iterator;
162 typedef value_use_iterator<const User> use_const_iterator;
164 bool use_empty() const { return UseList == 0; }
165 use_iterator use_begin() { return use_iterator(UseList); }
166 use_const_iterator use_begin() const { return use_const_iterator(UseList); }
167 use_iterator use_end() { return use_iterator(0); }
168 use_const_iterator use_end() const { return use_const_iterator(0); }
169 User *use_back() { return *use_begin(); }
170 const User *use_back() const { return *use_begin(); }
172 /// hasOneUse - Return true if there is exactly one user of this value. This
173 /// is specialized because it is a common request and does not require
174 /// traversing the whole use list.
176 bool hasOneUse() const {
177 use_const_iterator I = use_begin(), E = use_end();
178 if (I == E) return false;
182 /// hasNUses - Return true if this Value has exactly N users.
184 bool hasNUses(unsigned N) const;
186 /// hasNUsesOrMore - Return true if this value has N users or more. This is
187 /// logically equivalent to getNumUses() >= N.
189 bool hasNUsesOrMore(unsigned N) const;
191 bool isUsedInBasicBlock(const BasicBlock *BB) const;
193 /// getNumUses - This method computes the number of uses of this Value. This
194 /// is a linear time operation. Use hasOneUse, hasNUses, or hasMoreThanNUses
195 /// to check for specific values.
196 unsigned getNumUses() const;
198 /// addUse - This method should only be used by the Use class.
200 void addUse(Use &U) { U.addToList(&UseList); }
202 /// An enumeration for keeping track of the concrete subclass of Value that
203 /// is actually instantiated. Values of this enumeration are kept in the
204 /// Value classes SubclassID field. They are used for concrete type
207 ArgumentVal, // This is an instance of Argument
208 BasicBlockVal, // This is an instance of BasicBlock
209 FunctionVal, // This is an instance of Function
210 GlobalAliasVal, // This is an instance of GlobalAlias
211 GlobalVariableVal, // This is an instance of GlobalVariable
212 UndefValueVal, // This is an instance of UndefValue
213 BlockAddressVal, // This is an instance of BlockAddress
214 ConstantExprVal, // This is an instance of ConstantExpr
215 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateNull
216 ConstantIntVal, // This is an instance of ConstantInt
217 ConstantFPVal, // This is an instance of ConstantFP
218 ConstantArrayVal, // This is an instance of ConstantArray
219 ConstantStructVal, // This is an instance of ConstantStruct
220 ConstantVectorVal, // This is an instance of ConstantVector
221 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
222 MDNodeVal, // This is an instance of MDNode
223 MDStringVal, // This is an instance of MDString
224 NamedMDNodeVal, // This is an instance of NamedMDNode
225 InlineAsmVal, // This is an instance of InlineAsm
226 PseudoSourceValueVal, // This is an instance of PseudoSourceValue
227 InstructionVal, // This is an instance of Instruction
230 ConstantFirstVal = FunctionVal,
231 ConstantLastVal = ConstantPointerNullVal
234 /// getValueID - Return an ID for the concrete type of this object. This is
235 /// used to implement the classof checks. This should not be used for any
236 /// other purpose, as the values may change as LLVM evolves. Also, note that
237 /// for instructions, the Instruction's opcode is added to InstructionVal. So
238 /// this means three things:
239 /// # there is no value with code InstructionVal (no opcode==0).
240 /// # there are more possible values for the value type than in ValueTy enum.
241 /// # the InstructionVal enumerator must be the highest valued enumerator in
242 /// the ValueTy enum.
243 unsigned getValueID() const {
247 /// getRawSubclassOptionalData - Return the raw optional flags value
248 /// contained in this value. This should only be used when testing two
249 /// Values for equivalence.
250 unsigned getRawSubclassOptionalData() const {
251 return SubclassOptionalData;
254 /// hasSameSubclassOptionalData - Test whether the optional flags contained
255 /// in this value are equal to the optional flags in the given value.
256 bool hasSameSubclassOptionalData(const Value *V) const {
257 return SubclassOptionalData == V->SubclassOptionalData;
260 /// intersectOptionalDataWith - Clear any optional flags in this value
261 /// that are not also set in the given value.
262 void intersectOptionalDataWith(const Value *V) {
263 SubclassOptionalData &= V->SubclassOptionalData;
266 // Methods for support type inquiry through isa, cast, and dyn_cast:
267 static inline bool classof(const Value *) {
268 return true; // Values are always values.
271 /// getRawType - This should only be used to implement the vmcore library.
273 const Type *getRawType() const { return VTy.getRawType(); }
275 /// stripPointerCasts - This method strips off any unneeded pointer
276 /// casts from the specified value, returning the original uncasted value.
277 /// Note that the returned value has pointer type if the specified value does.
278 Value *stripPointerCasts();
279 const Value *stripPointerCasts() const {
280 return const_cast<Value*>(this)->stripPointerCasts();
283 /// getUnderlyingObject - This method strips off any GEP address adjustments
284 /// and pointer casts from the specified value, returning the original object
285 /// being addressed. Note that the returned value has pointer type if the
286 /// specified value does.
287 Value *getUnderlyingObject();
288 const Value *getUnderlyingObject() const {
289 return const_cast<Value*>(this)->getUnderlyingObject();
292 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
293 /// return the value in the PHI node corresponding to PredBB. If not, return
294 /// ourself. This is useful if you want to know the value something has in a
295 /// predecessor block.
296 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
298 const Value *DoPHITranslation(const BasicBlock *CurBB,
299 const BasicBlock *PredBB) const{
300 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
303 /// hasMetadata - Return true if metadata is attached with this value.
304 bool hasMetadata() const { return HasMetadata; }
307 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
312 void Use::set(Value *V) {
313 if (Val) removeFromList();
315 if (V) V->addUse(*this);
319 // isa - Provide some specializations of isa so that we don't have to include
320 // the subtype header files to test to see if the value is a subclass...
322 template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
323 return Val.getValueID() >= Value::ConstantFirstVal &&
324 Val.getValueID() <= Value::ConstantLastVal;
326 template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
327 return Val.getValueID() == Value::ArgumentVal;
329 template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
330 return Val.getValueID() == Value::InlineAsmVal;
332 template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
333 return Val.getValueID() >= Value::InstructionVal;
335 template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
336 return Val.getValueID() == Value::BasicBlockVal;
338 template <> inline bool isa_impl<Function, Value>(const Value &Val) {
339 return Val.getValueID() == Value::FunctionVal;
341 template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
342 return Val.getValueID() == Value::GlobalVariableVal;
344 template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
345 return Val.getValueID() == Value::GlobalAliasVal;
347 template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
348 return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
349 isa<GlobalAlias>(Val);
353 // Value* is only 4-byte aligned.
355 class PointerLikeTypeTraits<Value*> {
358 static inline void *getAsVoidPointer(PT P) { return P; }
359 static inline PT getFromVoidPointer(void *P) {
360 return static_cast<PT>(P);
362 enum { NumLowBitsAvailable = 2 };
365 } // End llvm namespace