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"
36 class ValueSymbolTable;
37 class TypeSymbolTable;
38 template<typename ValueTy> class StringMapEntry;
39 template <typename ValueTy = Value>
41 typedef StringMapEntry<Value*> ValueName;
43 class AssemblyAnnotationWriter;
44 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?
68 /// SubclassOptionalData - This member is similar to SubclassData, however it
69 /// is for holding information which may be used to aid optimization, but
70 /// which may be cleared to zero without affecting conservative
72 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 SymbolTable; // Allow SymbolTable to directly poke Name.
84 friend class ValueHandleBase;
87 void operator=(const Value &); // Do not implement
88 Value(const Value &); // Do not implement
91 Value(const Type *Ty, unsigned scid);
94 /// dump - Support for debugging, callable in GDB: V->dump()
96 virtual void dump() const;
98 /// print - Implement operator<< on Value.
100 void print(std::ostream &O, AssemblyAnnotationWriter *AAW = 0) const;
101 void print(raw_ostream &O, AssemblyAnnotationWriter *AAW = 0) const;
103 /// All values are typed, get the type of this value.
105 inline const Type *getType() const { return VTy; }
107 /// All values hold a context through their type.
108 LLVMContext &getContext() const;
110 // All values can potentially be named...
111 inline bool hasName() const { return Name != 0; }
112 ValueName *getValueName() const { return Name; }
114 /// getNameStart - Return a pointer to a null terminated string for this name.
115 /// Note that names can have null characters within the string as well as at
116 /// their end. This always returns a non-null pointer.
117 const char *getNameStart() const;
118 /// getNameEnd - Return a pointer to the end of the name.
119 const char *getNameEnd() const { return getNameStart() + getNameLen(); }
121 /// getNameLen - Return the length of the string, correctly handling nul
122 /// characters embedded into them.
123 unsigned getNameLen() const;
125 /// getName()/getNameStr() - Return the name of the specified value,
126 /// *constructing a string* to hold it. Because these are guaranteed to
127 /// construct a string, they are very expensive and should be avoided.
128 StringRef getName() const { return StringRef(getNameStart(), getNameLen()); }
129 std::string getNameStr() const;
131 /// setName() - Change the name of the value, choosing a new unique name if
132 /// the provided name is taken.
134 /// \arg Name - The new name; or "" if the value's name should be removed.
135 void setName(const Twine &Name);
138 /// takeName - transfer the name from V to this value, setting V's name to
139 /// empty. It is an error to call V->takeName(V).
140 void takeName(Value *V);
142 /// replaceAllUsesWith - Go through the uses list for this definition and make
143 /// each use point to "V" instead of "this". After this completes, 'this's
144 /// use list is guaranteed to be empty.
146 void replaceAllUsesWith(Value *V);
148 // uncheckedReplaceAllUsesWith - Just like replaceAllUsesWith but dangerous.
149 // Only use when in type resolution situations!
150 void uncheckedReplaceAllUsesWith(Value *V);
152 /// clearOptionalData - Clear any optional optimization data from this Value.
153 /// Transformation passes must call this method whenever changing the IR
154 /// in a way that would affect the values produced by this Value, unless
155 /// it takes special care to ensure correctness in some other way.
156 void clearOptionalData() { SubclassOptionalData = 0; }
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 ConstantExprVal, // This is an instance of ConstantExpr
214 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateNull
215 ConstantIntVal, // This is an instance of ConstantInt
216 ConstantFPVal, // This is an instance of ConstantFP
217 ConstantArrayVal, // This is an instance of ConstantArray
218 ConstantStructVal, // This is an instance of ConstantStruct
219 ConstantVectorVal, // This is an instance of ConstantVector
220 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
221 MDNodeVal, // This is an instance of MDNode
222 MDStringVal, // This is an instance of MDString
223 InlineAsmVal, // This is an instance of InlineAsm
224 PseudoSourceValueVal, // This is an instance of PseudoSourceValue
225 InstructionVal, // This is an instance of Instruction
228 ConstantFirstVal = FunctionVal,
229 ConstantLastVal = ConstantPointerNullVal
232 /// getValueID - Return an ID for the concrete type of this object. This is
233 /// used to implement the classof checks. This should not be used for any
234 /// other purpose, as the values may change as LLVM evolves. Also, note that
235 /// for instructions, the Instruction's opcode is added to InstructionVal. So
236 /// this means three things:
237 /// # there is no value with code InstructionVal (no opcode==0).
238 /// # there are more possible values for the value type than in ValueTy enum.
239 /// # the InstructionVal enumerator must be the highest valued enumerator in
240 /// the ValueTy enum.
241 unsigned getValueID() const {
245 // Methods for support type inquiry through isa, cast, and dyn_cast:
246 static inline bool classof(const Value *) {
247 return true; // Values are always values.
250 /// getRawType - This should only be used to implement the vmcore library.
252 const Type *getRawType() const { return VTy.getRawType(); }
254 /// stripPointerCasts - This method strips off any unneeded pointer
255 /// casts from the specified value, returning the original uncasted value.
256 /// Note that the returned value has pointer type if the specified value does.
257 Value *stripPointerCasts();
258 const Value *stripPointerCasts() const {
259 return const_cast<Value*>(this)->stripPointerCasts();
262 /// getUnderlyingObject - This method strips off any GEP address adjustments
263 /// and pointer casts from the specified value, returning the original object
264 /// being addressed. Note that the returned value has pointer type if the
265 /// specified value does.
266 Value *getUnderlyingObject();
267 const Value *getUnderlyingObject() const {
268 return const_cast<Value*>(this)->getUnderlyingObject();
271 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
272 /// return the value in the PHI node corresponding to PredBB. If not, return
273 /// ourself. This is useful if you want to know the value something has in a
274 /// predecessor block.
275 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
277 const Value *DoPHITranslation(const BasicBlock *CurBB,
278 const BasicBlock *PredBB) const{
279 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
283 inline std::ostream &operator<<(std::ostream &OS, const Value &V) {
287 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
292 void Use::set(Value *V) {
293 if (Val) removeFromList();
295 if (V) V->addUse(*this);
299 // isa - Provide some specializations of isa so that we don't have to include
300 // the subtype header files to test to see if the value is a subclass...
302 template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
303 return Val.getValueID() >= Value::ConstantFirstVal &&
304 Val.getValueID() <= Value::ConstantLastVal;
306 template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
307 return Val.getValueID() == Value::ArgumentVal;
309 template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
310 return Val.getValueID() == Value::InlineAsmVal;
312 template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
313 return Val.getValueID() >= Value::InstructionVal;
315 template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
316 return Val.getValueID() == Value::BasicBlockVal;
318 template <> inline bool isa_impl<Function, Value>(const Value &Val) {
319 return Val.getValueID() == Value::FunctionVal;
321 template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
322 return Val.getValueID() == Value::GlobalVariableVal;
324 template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
325 return Val.getValueID() == Value::GlobalAliasVal;
327 template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
328 return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
329 isa<GlobalAlias>(Val);
333 // Value* is only 4-byte aligned.
335 class PointerLikeTypeTraits<Value*> {
338 static inline void *getAsVoidPointer(PT P) { return P; }
339 static inline PT getFromVoidPointer(void *P) {
340 return static_cast<PT>(P);
342 enum { NumLowBitsAvailable = 2 };
345 } // End llvm namespace