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;
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 Metadata;
87 friend class AbstractTypeUser;
90 void operator=(const Value &); // Do not implement
91 Value(const Value &); // Do not implement
94 Value(const Type *Ty, unsigned scid);
97 /// dump - Support for debugging, callable in GDB: V->dump()
99 virtual void dump() const;
101 /// print - Implement operator<< on Value.
103 void print(raw_ostream &O, AssemblyAnnotationWriter *AAW = 0) const;
105 /// All values are typed, get the type of this value.
107 inline const Type *getType() const { return VTy; }
109 /// All values hold a context through their type.
110 LLVMContext &getContext() const;
112 // All values can potentially be named...
113 inline bool hasName() const { return Name != 0; }
114 ValueName *getValueName() const { return Name; }
116 /// getName() - Return a constant reference to the value's name. This is cheap
117 /// and guaranteed to return the same reference as long as the value is not
120 /// This is currently guaranteed to return a StringRef for which data() points
121 /// to a valid null terminated string. The use of StringRef.data() is
122 /// deprecated here, however, and clients should not rely on it. If such
123 /// behavior is needed, clients should use expensive getNameStr(), or switch
124 /// to an interface that does not depend on null termination.
125 StringRef getName() const;
127 /// getNameStr() - Return the name of the specified value, *constructing a
128 /// string* to hold it. This is guaranteed to construct a string and is very
129 /// expensive, clients should use getName() unless necessary.
130 std::string getNameStr() const;
132 /// setName() - Change the name of the value, choosing a new unique name if
133 /// the provided name is taken.
135 /// \arg Name - The new name; or "" if the value's name should be removed.
136 void setName(const Twine &Name);
139 /// takeName - transfer the name from V to this value, setting V's name to
140 /// empty. It is an error to call V->takeName(V).
141 void takeName(Value *V);
143 /// replaceAllUsesWith - Go through the uses list for this definition and make
144 /// each use point to "V" instead of "this". After this completes, 'this's
145 /// use list is guaranteed to be empty.
147 void replaceAllUsesWith(Value *V);
149 // uncheckedReplaceAllUsesWith - Just like replaceAllUsesWith but dangerous.
150 // Only use when in type resolution situations!
151 void uncheckedReplaceAllUsesWith(Value *V);
153 //----------------------------------------------------------------------
154 // Methods for handling the chain of uses of this Value.
156 typedef value_use_iterator<User> use_iterator;
157 typedef value_use_iterator<const User> use_const_iterator;
159 bool use_empty() const { return UseList == 0; }
160 use_iterator use_begin() { return use_iterator(UseList); }
161 use_const_iterator use_begin() const { return use_const_iterator(UseList); }
162 use_iterator use_end() { return use_iterator(0); }
163 use_const_iterator use_end() const { return use_const_iterator(0); }
164 User *use_back() { return *use_begin(); }
165 const User *use_back() const { return *use_begin(); }
167 /// hasOneUse - Return true if there is exactly one user of this value. This
168 /// is specialized because it is a common request and does not require
169 /// traversing the whole use list.
171 bool hasOneUse() const {
172 use_const_iterator I = use_begin(), E = use_end();
173 if (I == E) return false;
177 /// hasNUses - Return true if this Value has exactly N users.
179 bool hasNUses(unsigned N) const;
181 /// hasNUsesOrMore - Return true if this value has N users or more. This is
182 /// logically equivalent to getNumUses() >= N.
184 bool hasNUsesOrMore(unsigned N) const;
186 bool isUsedInBasicBlock(const BasicBlock *BB) const;
188 /// getNumUses - This method computes the number of uses of this Value. This
189 /// is a linear time operation. Use hasOneUse, hasNUses, or hasMoreThanNUses
190 /// to check for specific values.
191 unsigned getNumUses() const;
193 /// addUse - This method should only be used by the Use class.
195 void addUse(Use &U) { U.addToList(&UseList); }
197 /// An enumeration for keeping track of the concrete subclass of Value that
198 /// is actually instantiated. Values of this enumeration are kept in the
199 /// Value classes SubclassID field. They are used for concrete type
202 ArgumentVal, // This is an instance of Argument
203 BasicBlockVal, // This is an instance of BasicBlock
204 FunctionVal, // This is an instance of Function
205 GlobalAliasVal, // This is an instance of GlobalAlias
206 GlobalVariableVal, // This is an instance of GlobalVariable
207 UndefValueVal, // This is an instance of UndefValue
208 ConstantExprVal, // This is an instance of ConstantExpr
209 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateNull
210 ConstantIntVal, // This is an instance of ConstantInt
211 ConstantFPVal, // This is an instance of ConstantFP
212 ConstantArrayVal, // This is an instance of ConstantArray
213 ConstantStructVal, // This is an instance of ConstantStruct
214 ConstantVectorVal, // This is an instance of ConstantVector
215 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
216 MDNodeVal, // This is an instance of MDNode
217 MDStringVal, // This is an instance of MDString
218 NamedMDNodeVal, // This is an instance of NamedMDNode
219 InlineAsmVal, // This is an instance of InlineAsm
220 PseudoSourceValueVal, // This is an instance of PseudoSourceValue
221 InstructionVal, // This is an instance of Instruction
224 ConstantFirstVal = FunctionVal,
225 ConstantLastVal = ConstantPointerNullVal
228 /// getValueID - Return an ID for the concrete type of this object. This is
229 /// used to implement the classof checks. This should not be used for any
230 /// other purpose, as the values may change as LLVM evolves. Also, note that
231 /// for instructions, the Instruction's opcode is added to InstructionVal. So
232 /// this means three things:
233 /// # there is no value with code InstructionVal (no opcode==0).
234 /// # there are more possible values for the value type than in ValueTy enum.
235 /// # the InstructionVal enumerator must be the highest valued enumerator in
236 /// the ValueTy enum.
237 unsigned getValueID() const {
241 /// getRawSubclassOptionalData - Return the raw optional flags value
242 /// contained in this value. This should only be used when testing two
243 /// Values for equivalence.
244 unsigned getRawSubclassOptionalData() const {
245 return SubclassOptionalData;
248 /// hasSameSubclassOptionalData - Test whether the optional flags contained
249 /// in this value are equal to the optional flags in the given value.
250 bool hasSameSubclassOptionalData(const Value *V) const {
251 return SubclassOptionalData == V->SubclassOptionalData;
254 /// intersectOptionalDataWith - Clear any optional flags in this value
255 /// that are not also set in the given value.
256 void intersectOptionalDataWith(const Value *V) {
257 SubclassOptionalData &= V->SubclassOptionalData;
260 // Methods for support type inquiry through isa, cast, and dyn_cast:
261 static inline bool classof(const Value *) {
262 return true; // Values are always values.
265 /// getRawType - This should only be used to implement the vmcore library.
267 const Type *getRawType() const { return VTy.getRawType(); }
269 /// stripPointerCasts - This method strips off any unneeded pointer
270 /// casts from the specified value, returning the original uncasted value.
271 /// Note that the returned value has pointer type if the specified value does.
272 Value *stripPointerCasts();
273 const Value *stripPointerCasts() const {
274 return const_cast<Value*>(this)->stripPointerCasts();
277 /// getUnderlyingObject - This method strips off any GEP address adjustments
278 /// and pointer casts from the specified value, returning the original object
279 /// being addressed. Note that the returned value has pointer type if the
280 /// specified value does.
281 Value *getUnderlyingObject();
282 const Value *getUnderlyingObject() const {
283 return const_cast<Value*>(this)->getUnderlyingObject();
286 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
287 /// return the value in the PHI node corresponding to PredBB. If not, return
288 /// ourself. This is useful if you want to know the value something has in a
289 /// predecessor block.
290 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
292 const Value *DoPHITranslation(const BasicBlock *CurBB,
293 const BasicBlock *PredBB) const{
294 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
298 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
303 void Use::set(Value *V) {
304 if (Val) removeFromList();
306 if (V) V->addUse(*this);
310 // isa - Provide some specializations of isa so that we don't have to include
311 // the subtype header files to test to see if the value is a subclass...
313 template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
314 return Val.getValueID() >= Value::ConstantFirstVal &&
315 Val.getValueID() <= Value::ConstantLastVal;
317 template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
318 return Val.getValueID() == Value::ArgumentVal;
320 template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
321 return Val.getValueID() == Value::InlineAsmVal;
323 template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
324 return Val.getValueID() >= Value::InstructionVal;
326 template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
327 return Val.getValueID() == Value::BasicBlockVal;
329 template <> inline bool isa_impl<Function, Value>(const Value &Val) {
330 return Val.getValueID() == Value::FunctionVal;
332 template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
333 return Val.getValueID() == Value::GlobalVariableVal;
335 template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
336 return Val.getValueID() == Value::GlobalAliasVal;
338 template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
339 return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
340 isa<GlobalAlias>(Val);
344 // Value* is only 4-byte aligned.
346 class PointerLikeTypeTraits<Value*> {
349 static inline void *getAsVoidPointer(PT P) { return P; }
350 static inline PT getFromVoidPointer(void *P) {
351 return static_cast<PT>(P);
353 enum { NumLowBitsAvailable = 2 };
356 } // End llvm namespace