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 if (!Name) return "";
119 return getName().begin();
121 /// getNameEnd - Return a pointer to the end of the name.
122 const char *getNameEnd() const {
123 if (!Name) return "";
124 return getName().end();
127 /// getName() - Return a constant reference to the value's name. This is cheap
128 /// and guaranteed to return the same reference as long as the value is not
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 /// clearOptionalData - Clear any optional optimization data from this Value.
159 /// Transformation passes must call this method whenever changing the IR
160 /// in a way that would affect the values produced by this Value, unless
161 /// it takes special care to ensure correctness in some other way.
162 void clearOptionalData() { SubclassOptionalData = 0; }
164 //----------------------------------------------------------------------
165 // Methods for handling the chain of uses of this Value.
167 typedef value_use_iterator<User> use_iterator;
168 typedef value_use_iterator<const User> use_const_iterator;
170 bool use_empty() const { return UseList == 0; }
171 use_iterator use_begin() { return use_iterator(UseList); }
172 use_const_iterator use_begin() const { return use_const_iterator(UseList); }
173 use_iterator use_end() { return use_iterator(0); }
174 use_const_iterator use_end() const { return use_const_iterator(0); }
175 User *use_back() { return *use_begin(); }
176 const User *use_back() const { return *use_begin(); }
178 /// hasOneUse - Return true if there is exactly one user of this value. This
179 /// is specialized because it is a common request and does not require
180 /// traversing the whole use list.
182 bool hasOneUse() const {
183 use_const_iterator I = use_begin(), E = use_end();
184 if (I == E) return false;
188 /// hasNUses - Return true if this Value has exactly N users.
190 bool hasNUses(unsigned N) const;
192 /// hasNUsesOrMore - Return true if this value has N users or more. This is
193 /// logically equivalent to getNumUses() >= N.
195 bool hasNUsesOrMore(unsigned N) const;
197 bool isUsedInBasicBlock(const BasicBlock *BB) const;
199 /// getNumUses - This method computes the number of uses of this Value. This
200 /// is a linear time operation. Use hasOneUse, hasNUses, or hasMoreThanNUses
201 /// to check for specific values.
202 unsigned getNumUses() const;
204 /// addUse - This method should only be used by the Use class.
206 void addUse(Use &U) { U.addToList(&UseList); }
208 /// An enumeration for keeping track of the concrete subclass of Value that
209 /// is actually instantiated. Values of this enumeration are kept in the
210 /// Value classes SubclassID field. They are used for concrete type
213 ArgumentVal, // This is an instance of Argument
214 BasicBlockVal, // This is an instance of BasicBlock
215 FunctionVal, // This is an instance of Function
216 GlobalAliasVal, // This is an instance of GlobalAlias
217 GlobalVariableVal, // This is an instance of GlobalVariable
218 UndefValueVal, // This is an instance of UndefValue
219 ConstantExprVal, // This is an instance of ConstantExpr
220 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateNull
221 ConstantIntVal, // This is an instance of ConstantInt
222 ConstantFPVal, // This is an instance of ConstantFP
223 ConstantArrayVal, // This is an instance of ConstantArray
224 ConstantStructVal, // This is an instance of ConstantStruct
225 ConstantVectorVal, // This is an instance of ConstantVector
226 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
227 MDNodeVal, // This is an instance of MDNode
228 MDStringVal, // This is an instance of MDString
229 InlineAsmVal, // This is an instance of InlineAsm
230 PseudoSourceValueVal, // This is an instance of PseudoSourceValue
231 InstructionVal, // This is an instance of Instruction
234 ConstantFirstVal = FunctionVal,
235 ConstantLastVal = ConstantPointerNullVal
238 /// getValueID - Return an ID for the concrete type of this object. This is
239 /// used to implement the classof checks. This should not be used for any
240 /// other purpose, as the values may change as LLVM evolves. Also, note that
241 /// for instructions, the Instruction's opcode is added to InstructionVal. So
242 /// this means three things:
243 /// # there is no value with code InstructionVal (no opcode==0).
244 /// # there are more possible values for the value type than in ValueTy enum.
245 /// # the InstructionVal enumerator must be the highest valued enumerator in
246 /// the ValueTy enum.
247 unsigned getValueID() const {
251 // Methods for support type inquiry through isa, cast, and dyn_cast:
252 static inline bool classof(const Value *) {
253 return true; // Values are always values.
256 /// getRawType - This should only be used to implement the vmcore library.
258 const Type *getRawType() const { return VTy.getRawType(); }
260 /// stripPointerCasts - This method strips off any unneeded pointer
261 /// casts from the specified value, returning the original uncasted value.
262 /// Note that the returned value has pointer type if the specified value does.
263 Value *stripPointerCasts();
264 const Value *stripPointerCasts() const {
265 return const_cast<Value*>(this)->stripPointerCasts();
268 /// getUnderlyingObject - This method strips off any GEP address adjustments
269 /// and pointer casts from the specified value, returning the original object
270 /// being addressed. Note that the returned value has pointer type if the
271 /// specified value does.
272 Value *getUnderlyingObject();
273 const Value *getUnderlyingObject() const {
274 return const_cast<Value*>(this)->getUnderlyingObject();
277 /// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
278 /// return the value in the PHI node corresponding to PredBB. If not, return
279 /// ourself. This is useful if you want to know the value something has in a
280 /// predecessor block.
281 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
283 const Value *DoPHITranslation(const BasicBlock *CurBB,
284 const BasicBlock *PredBB) const{
285 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
289 inline std::ostream &operator<<(std::ostream &OS, const Value &V) {
293 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
298 void Use::set(Value *V) {
299 if (Val) removeFromList();
301 if (V) V->addUse(*this);
305 // isa - Provide some specializations of isa so that we don't have to include
306 // the subtype header files to test to see if the value is a subclass...
308 template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
309 return Val.getValueID() >= Value::ConstantFirstVal &&
310 Val.getValueID() <= Value::ConstantLastVal;
312 template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
313 return Val.getValueID() == Value::ArgumentVal;
315 template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
316 return Val.getValueID() == Value::InlineAsmVal;
318 template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
319 return Val.getValueID() >= Value::InstructionVal;
321 template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
322 return Val.getValueID() == Value::BasicBlockVal;
324 template <> inline bool isa_impl<Function, Value>(const Value &Val) {
325 return Val.getValueID() == Value::FunctionVal;
327 template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
328 return Val.getValueID() == Value::GlobalVariableVal;
330 template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
331 return Val.getValueID() == Value::GlobalAliasVal;
333 template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
334 return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
335 isa<GlobalAlias>(Val);
339 // Value* is only 4-byte aligned.
341 class PointerLikeTypeTraits<Value*> {
344 static inline void *getAsVoidPointer(PT P) { return P; }
345 static inline PT getFromVoidPointer(void *P) {
346 return static_cast<PT>(P);
348 enum { NumLowBitsAvailable = 2 };
351 } // End llvm namespace