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//===-- llvm/Value.h - Definition of the Value class ------------*- C++ -*-===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This file declares the Value class.
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//===----------------------------------------------------------------------===//
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#include "llvm/AbstractTypeUser.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/Casting.h"
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class ValueSymbolTable;
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class TypeSymbolTable;
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template<typename ValueTy> class StringMapEntry;
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template <typename ValueTy = Value>
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typedef StringMapEntry<Value*> ValueName;
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class AssemblyAnnotationWriter;
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class ValueHandleBase;
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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/// This is a very important LLVM class. It is the base class of all values
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/// computed by a program that may be used as operands to other values. Value is
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/// the super class of other important classes such as Instruction and Function.
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/// All Values have a Type. Type is not a subclass of Value. All types can have
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/// a name and they should belong to some Module. Setting the name on the Value
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/// automatically updates the module's symbol table.
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/// Every value has a "use list" that keeps track of which other Values are
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/// using this Value. A Value can also have an arbitrary number of ValueHandle
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/// objects that watch it and listen to RAUW and Destroy events. See
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/// llvm/Support/ValueHandle.h for details.
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/// @brief LLVM Value Representation
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const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
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unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
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/// SubclassOptionalData - This member is similar to SubclassData, however it
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/// is for holding information which may be used to aid optimization, but
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/// which may be cleared to zero without affecting conservative
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unsigned char SubclassOptionalData : 7;
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/// SubclassData - This member is defined by this class, but is not used for
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/// anything. Subclasses can use it to hold whatever state they find useful.
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/// This field is initialized to zero by the ctor.
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unsigned short SubclassData;
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friend class ValueSymbolTable; // Allow ValueSymbolTable to directly mod Name.
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friend class ValueHandleBase;
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friend class AbstractTypeUser;
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void operator=(const Value &); // Do not implement
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Value(const Value &); // Do not implement
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/// printCustom - Value subclasses can override this to implement custom
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/// printing behavior.
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virtual void printCustom(raw_ostream &O) const;
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Value(const Type *Ty, unsigned scid);
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/// dump - Support for debugging, callable in GDB: V->dump()
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/// print - Implement operator<< on Value.
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void print(raw_ostream &O, AssemblyAnnotationWriter *AAW = 0) const;
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/// All values are typed, get the type of this value.
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inline const Type *getType() const { return VTy; }
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/// All values hold a context through their type.
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LLVMContext &getContext() const;
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// All values can potentially be named...
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inline bool hasName() const { return Name != 0; }
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ValueName *getValueName() const { return Name; }
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/// getName() - Return a constant reference to the value's name. This is cheap
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/// and guaranteed to return the same reference as long as the value is not
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/// This is currently guaranteed to return a StringRef for which data() points
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/// to a valid null terminated string. The use of StringRef.data() is
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/// deprecated here, however, and clients should not rely on it. If such
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/// behavior is needed, clients should use expensive getNameStr(), or switch
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/// to an interface that does not depend on null termination.
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StringRef getName() const;
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/// getNameStr() - Return the name of the specified value, *constructing a
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/// string* to hold it. This is guaranteed to construct a string and is very
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/// expensive, clients should use getName() unless necessary.
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std::string getNameStr() const;
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/// setName() - Change the name of the value, choosing a new unique name if
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/// the provided name is taken.
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/// \arg Name - The new name; or "" if the value's name should be removed.
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void setName(const Twine &Name);
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/// takeName - transfer the name from V to this value, setting V's name to
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/// empty. It is an error to call V->takeName(V).
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void takeName(Value *V);
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/// replaceAllUsesWith - Go through the uses list for this definition and make
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/// each use point to "V" instead of "this". After this completes, 'this's
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/// use list is guaranteed to be empty.
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void replaceAllUsesWith(Value *V);
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// uncheckedReplaceAllUsesWith - Just like replaceAllUsesWith but dangerous.
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// Only use when in type resolution situations!
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void uncheckedReplaceAllUsesWith(Value *V);
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//----------------------------------------------------------------------
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// Methods for handling the chain of uses of this Value.
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typedef value_use_iterator<User> use_iterator;
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typedef value_use_iterator<const User> use_const_iterator;
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bool use_empty() const { return UseList == 0; }
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use_iterator use_begin() { return use_iterator(UseList); }
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use_const_iterator use_begin() const { return use_const_iterator(UseList); }
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use_iterator use_end() { return use_iterator(0); }
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use_const_iterator use_end() const { return use_const_iterator(0); }
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User *use_back() { return *use_begin(); }
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const User *use_back() const { return *use_begin(); }
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/// hasOneUse - Return true if there is exactly one user of this value. This
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/// is specialized because it is a common request and does not require
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/// traversing the whole use list.
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bool hasOneUse() const {
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use_const_iterator I = use_begin(), E = use_end();
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if (I == E) return false;
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/// hasNUses - Return true if this Value has exactly N users.
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bool hasNUses(unsigned N) const;
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/// hasNUsesOrMore - Return true if this value has N users or more. This is
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/// logically equivalent to getNumUses() >= N.
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bool hasNUsesOrMore(unsigned N) const;
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bool isUsedInBasicBlock(const BasicBlock *BB) const;
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/// getNumUses - This method computes the number of uses of this Value. This
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/// is a linear time operation. Use hasOneUse, hasNUses, or hasMoreThanNUses
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/// to check for specific values.
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unsigned getNumUses() const;
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/// addUse - This method should only be used by the Use class.
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void addUse(Use &U) { U.addToList(&UseList); }
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/// An enumeration for keeping track of the concrete subclass of Value that
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/// is actually instantiated. Values of this enumeration are kept in the
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/// Value classes SubclassID field. They are used for concrete type
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ArgumentVal, // This is an instance of Argument
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BasicBlockVal, // This is an instance of BasicBlock
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FunctionVal, // This is an instance of Function
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GlobalAliasVal, // This is an instance of GlobalAlias
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GlobalVariableVal, // This is an instance of GlobalVariable
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UndefValueVal, // This is an instance of UndefValue
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BlockAddressVal, // This is an instance of BlockAddress
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ConstantExprVal, // This is an instance of ConstantExpr
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ConstantAggregateZeroVal, // This is an instance of ConstantAggregateNull
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ConstantIntVal, // This is an instance of ConstantInt
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ConstantFPVal, // This is an instance of ConstantFP
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ConstantArrayVal, // This is an instance of ConstantArray
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ConstantStructVal, // This is an instance of ConstantStruct
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ConstantUnionVal, // This is an instance of ConstantUnion
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ConstantVectorVal, // This is an instance of ConstantVector
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ConstantPointerNullVal, // This is an instance of ConstantPointerNull
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MDNodeVal, // This is an instance of MDNode
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MDStringVal, // This is an instance of MDString
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NamedMDNodeVal, // This is an instance of NamedMDNode
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InlineAsmVal, // This is an instance of InlineAsm
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PseudoSourceValueVal, // This is an instance of PseudoSourceValue
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FixedStackPseudoSourceValueVal, // This is an instance of
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// FixedStackPseudoSourceValue
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InstructionVal, // This is an instance of Instruction
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// Enum values starting at InstructionVal are used for Instructions;
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// don't add new values here!
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ConstantFirstVal = FunctionVal,
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ConstantLastVal = ConstantPointerNullVal
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/// getValueID - Return an ID for the concrete type of this object. This is
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/// used to implement the classof checks. This should not be used for any
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/// other purpose, as the values may change as LLVM evolves. Also, note that
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/// for instructions, the Instruction's opcode is added to InstructionVal. So
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/// this means three things:
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/// # there is no value with code InstructionVal (no opcode==0).
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/// # there are more possible values for the value type than in ValueTy enum.
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/// # the InstructionVal enumerator must be the highest valued enumerator in
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/// the ValueTy enum.
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unsigned getValueID() const {
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/// getRawSubclassOptionalData - Return the raw optional flags value
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/// contained in this value. This should only be used when testing two
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/// Values for equivalence.
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unsigned getRawSubclassOptionalData() const {
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return SubclassOptionalData;
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/// hasSameSubclassOptionalData - Test whether the optional flags contained
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/// in this value are equal to the optional flags in the given value.
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bool hasSameSubclassOptionalData(const Value *V) const {
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return SubclassOptionalData == V->SubclassOptionalData;
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/// intersectOptionalDataWith - Clear any optional flags in this value
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/// that are not also set in the given value.
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void intersectOptionalDataWith(const Value *V) {
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SubclassOptionalData &= V->SubclassOptionalData;
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// Methods for support type inquiry through isa, cast, and dyn_cast:
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static inline bool classof(const Value *) {
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return true; // Values are always values.
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/// getRawType - This should only be used to implement the vmcore library.
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const Type *getRawType() const { return VTy.getRawType(); }
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/// stripPointerCasts - This method strips off any unneeded pointer
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/// casts from the specified value, returning the original uncasted value.
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/// Note that the returned value has pointer type if the specified value does.
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Value *stripPointerCasts();
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const Value *stripPointerCasts() const {
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return const_cast<Value*>(this)->stripPointerCasts();
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/// getUnderlyingObject - This method strips off any GEP address adjustments
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/// and pointer casts from the specified value, returning the original object
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/// being addressed. Note that the returned value has pointer type if the
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/// specified value does. If the MaxLookup value is non-zero, it limits the
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/// number of instructions to be stripped off.
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Value *getUnderlyingObject(unsigned MaxLookup = 6);
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const Value *getUnderlyingObject(unsigned MaxLookup = 6) const {
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return const_cast<Value*>(this)->getUnderlyingObject(MaxLookup);
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/// DoPHITranslation - If this value is a PHI node with CurBB as its parent,
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/// return the value in the PHI node corresponding to PredBB. If not, return
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/// ourself. This is useful if you want to know the value something has in a
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/// predecessor block.
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Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
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const Value *DoPHITranslation(const BasicBlock *CurBB,
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const BasicBlock *PredBB) const{
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return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
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unsigned short getSubclassDataFromValue() const { return SubclassData; }
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void setValueSubclassData(unsigned short D) { SubclassData = D; }
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inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
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void Use::set(Value *V) {
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if (Val) removeFromList();
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if (V) V->addUse(*this);
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// isa - Provide some specializations of isa so that we don't have to include
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// the subtype header files to test to see if the value is a subclass...
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template <> inline bool isa_impl<Constant, Value>(const Value &Val) {
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return Val.getValueID() >= Value::ConstantFirstVal &&
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Val.getValueID() <= Value::ConstantLastVal;
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template <> inline bool isa_impl<Argument, Value>(const Value &Val) {
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return Val.getValueID() == Value::ArgumentVal;
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template <> inline bool isa_impl<InlineAsm, Value>(const Value &Val) {
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return Val.getValueID() == Value::InlineAsmVal;
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template <> inline bool isa_impl<Instruction, Value>(const Value &Val) {
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return Val.getValueID() >= Value::InstructionVal;
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template <> inline bool isa_impl<BasicBlock, Value>(const Value &Val) {
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return Val.getValueID() == Value::BasicBlockVal;
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template <> inline bool isa_impl<Function, Value>(const Value &Val) {
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return Val.getValueID() == Value::FunctionVal;
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template <> inline bool isa_impl<GlobalVariable, Value>(const Value &Val) {
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return Val.getValueID() == Value::GlobalVariableVal;
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template <> inline bool isa_impl<GlobalAlias, Value>(const Value &Val) {
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return Val.getValueID() == Value::GlobalAliasVal;
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template <> inline bool isa_impl<GlobalValue, Value>(const Value &Val) {
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return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
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isa<GlobalAlias>(Val);
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template <> inline bool isa_impl<MDNode, Value>(const Value &Val) {
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return Val.getValueID() == Value::MDNodeVal;
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// Value* is only 4-byte aligned.
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class PointerLikeTypeTraits<Value*> {
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static inline void *getAsVoidPointer(PT P) { return P; }
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static inline PT getFromVoidPointer(void *P) {
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return static_cast<PT>(P);
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enum { NumLowBitsAvailable = 2 };
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} // End llvm namespace