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 void setName(const Twine &Name);
132 void setName(const char *Name, unsigned NameLen);
133 void setName(const char *Name); // Takes a null-terminated string.
136 /// takeName - transfer the name from V to this value, setting V's name to
137 /// empty. It is an error to call V->takeName(V).
138 void takeName(Value *V);
140 /// replaceAllUsesWith - Go through the uses list for this definition and make
141 /// each use point to "V" instead of "this". After this completes, 'this's
142 /// use list is guaranteed to be empty.
144 void replaceAllUsesWith(Value *V);
146 // uncheckedReplaceAllUsesWith - Just like replaceAllUsesWith but dangerous.
147 // Only use when in type resolution situations!
148 void uncheckedReplaceAllUsesWith(Value *V);
150 /// clearOptionalData - Clear any optional optimization data from this Value.
151 /// Transformation passes must call this method whenever changing the IR
152 /// in a way that would affect the values produced by this Value, unless
153 /// it takes special care to ensure correctness in some other way.
154 void clearOptionalData() { SubclassOptionalData = 0; }
156 //----------------------------------------------------------------------
157 // Methods for handling the chain of uses of this Value.
159 typedef value_use_iterator<User> use_iterator;
160 typedef value_use_iterator<const User> use_const_iterator;
162 bool use_empty() const { return UseList == 0; }
163 use_iterator use_begin() { return use_iterator(UseList); }
164 use_const_iterator use_begin() const { return use_const_iterator(UseList); }
165 use_iterator use_end() { return use_iterator(0); }
166 use_const_iterator use_end() const { return use_const_iterator(0); }
167 User *use_back() { return *use_begin(); }
168 const User *use_back() const { return *use_begin(); }
170 /// hasOneUse - Return true if there is exactly one user of this value. This
171 /// is specialized because it is a common request and does not require
172 /// traversing the whole use list.
174 bool hasOneUse() const {
175 use_const_iterator I = use_begin(), E = use_end();
176 if (I == E) return false;
180 /// hasNUses - Return true if this Value has exactly N users.
182 bool hasNUses(unsigned N) const;
184 /// hasNUsesOrMore - Return true if this value has N users or more. This is
185 /// logically equivalent to getNumUses() >= N.
187 bool hasNUsesOrMore(unsigned N) const;
189 bool isUsedInBasicBlock(const BasicBlock *BB) const;
191 /// getNumUses - This method computes the number of uses of this Value. This
192 /// is a linear time operation. Use hasOneUse, hasNUses, or hasMoreThanNUses
193 /// to check for specific values.
194 unsigned getNumUses() const;
196 /// addUse - This method should only be used by the Use class.
198 void addUse(Use &U) { U.addToList(&UseList); }
200 /// An enumeration for keeping track of the concrete subclass of Value that
201 /// is actually instantiated. Values of this enumeration are kept in the
202 /// Value classes SubclassID field. They are used for concrete type
205 ArgumentVal, // This is an instance of Argument
206 BasicBlockVal, // This is an instance of BasicBlock
207 FunctionVal, // This is an instance of Function
208 GlobalAliasVal, // This is an instance of GlobalAlias
209 GlobalVariableVal, // This is an instance of GlobalVariable
210 UndefValueVal, // This is an instance of UndefValue
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 InlineAsmVal, // This is an instance of InlineAsm
222 PseudoSourceValueVal, // This is an instance of PseudoSourceValue
223 InstructionVal, // This is an instance of Instruction
226 ConstantFirstVal = FunctionVal,
227 ConstantLastVal = ConstantPointerNullVal
230 /// getValueID - Return an ID for the concrete type of this object. This is
231 /// used to implement the classof checks. This should not be used for any
232 /// other purpose, as the values may change as LLVM evolves. Also, note that
233 /// for instructions, the Instruction's opcode is added to InstructionVal. So
234 /// this means three things:
235 /// # there is no value with code InstructionVal (no opcode==0).
236 /// # there are more possible values for the value type than in ValueTy enum.
237 /// # the InstructionVal enumerator must be the highest valued enumerator in
238 /// the ValueTy enum.
239 unsigned getValueID() const {
243 // Methods for support type inquiry through isa, cast, and dyn_cast:
244 static inline bool classof(const Value *) {
245 return true; // Values are always values.
248 /// getRawType - This should only be used to implement the vmcore library.
250 const Type *getRawType() const { return VTy.getRawType(); }
252 /// stripPointerCasts - This method strips off any unneeded pointer
253 /// casts from the specified value, returning the original uncasted value.
254 /// Note that the returned value has pointer type if the specified value does.
255 Value *stripPointerCasts();
256 const Value *stripPointerCasts() const {
257 return const_cast<Value*>(this)->stripPointerCasts();
260 /// getUnderlyingObject - This method strips off any GEP address adjustments
261 /// and pointer casts from the specified value, returning the original object
262 /// being addressed. Note that the returned value has pointer type if the
263 /// specified value does.
264 Value *getUnderlyingObject();
265 const Value *getUnderlyingObject() const {
266 return const_cast<Value*>(this)->getUnderlyingObject();
269 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
270 /// return the value in the PHI node corresponding to PredBB. If not, return
271 /// ourself. This is useful if you want to know the value something has in a
272 /// predecessor block.
273 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
275 const Value *DoPHITranslation(const BasicBlock *CurBB,
276 const BasicBlock *PredBB) const{
277 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
281 inline std::ostream &operator<<(std::ostream &OS, const Value &V) {
285 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
290 void Use::set(Value *V) {
291 if (Val) removeFromList();
293 if (V) V->addUse(*this);
297 // isa - Provide some specializations of isa so that we don't have to include
298 // the subtype header files to test to see if the value is a subclass...
300 template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
301 return Val.getValueID() >= Value::ConstantFirstVal &&
302 Val.getValueID() <= Value::ConstantLastVal;
304 template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
305 return Val.getValueID() == Value::ArgumentVal;
307 template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
308 return Val.getValueID() == Value::InlineAsmVal;
310 template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
311 return Val.getValueID() >= Value::InstructionVal;
313 template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
314 return Val.getValueID() == Value::BasicBlockVal;
316 template <> inline bool isa_impl<Function, Value>(const Value &Val) {
317 return Val.getValueID() == Value::FunctionVal;
319 template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
320 return Val.getValueID() == Value::GlobalVariableVal;
322 template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
323 return Val.getValueID() == Value::GlobalAliasVal;
325 template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
326 return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
327 isa<GlobalAlias>(Val);
331 // Value* is only 4-byte aligned.
333 class PointerLikeTypeTraits<Value*> {
336 static inline void *getAsVoidPointer(PT P) { return P; }
337 static inline PT getFromVoidPointer(void *P) {
338 return static_cast<PT>(P);
340 enum { NumLowBitsAvailable = 2 };
343 } // End llvm namespace