1 //===-- llvm/Metadata.h - Constant class subclass definitions ---*- 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 //===----------------------------------------------------------------------===//
11 /// This file contains the declarations for the subclasses of Constant,
12 /// which represent the different flavors of constant values that live in LLVM.
13 /// Note that Constants are immutable (once created they never change) and are
14 /// fully shared by structural equivalence. This means that two structurally
15 /// equivalent constants will always have the same address. Constant's are
16 /// created on demand as needed and never deleted: thus clients don't have to
17 /// worry about the lifetime of the objects.
19 //===----------------------------------------------------------------------===//
24 #include "llvm/Constant.h"
25 #include "llvm/Type.h"
26 #include "llvm/ADT/FoldingSet.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/ValueHandle.h"
33 //===----------------------------------------------------------------------===//
34 /// MDNode - a tuple of other values.
35 /// These contain a list of the Constants that represent the metadata. The
36 /// operand list is always empty, query the element list instead.
38 /// This class will attempt to keep track of values as they are modified. When
39 /// a value is replaced the element will be replaced with it, and when the
40 /// value is deleted the element is set to a null pointer. In order to preserve
41 /// structural equivalence while the elements mutate, the MDNode may call
42 /// replaceAllUsesWith on itself. Because of this, users of MDNode must use a
43 /// WeakVH or CallbackVH to hold the node pointer if there is a chance that one
44 /// of the elements held by the node may change.
46 class MDNode : public Constant, public FoldingSetNode {
47 MDNode(const MDNode &); // DO NOT IMPLEMENT
49 friend class ElementVH;
50 struct ElementVH : public CallbackVH {
53 ElementVH(Value *V, MDNode *Parent)
54 : CallbackVH(V), OwningNode(Parent) {}
58 /// deleted - Set this entry in the MDNode to 'null'. This will reallocate
60 virtual void deleted() {
61 OwningNode->replaceElement(this->operator Value*(), 0);
64 /// allUsesReplacedWith - Modify the MDNode by replacing this entry with
65 /// new_value. This will reallocate the MDNode.
66 virtual void allUsesReplacedWith(Value *new_value) {
67 OwningNode->replaceElement(this->operator Value*(), new_value);
71 void replaceElement(Value *From, Value *To);
73 SmallVector<ElementVH, 4> Node;
74 typedef SmallVectorImpl<ElementVH>::iterator elem_iterator;
76 explicit MDNode(Value*const* Vals, unsigned NumVals);
78 typedef SmallVectorImpl<ElementVH>::const_iterator const_elem_iterator;
80 /// get() - Static factory methods - Return objects of the specified value.
82 static MDNode *get(Value*const* Vals, unsigned NumVals);
84 Value *getElement(unsigned i) const {
88 unsigned getNumElements() const {
92 bool elem_empty() const {
96 const_elem_iterator elem_begin() const {
100 const_elem_iterator elem_end() const {
104 /// getType() specialization - Type is always MetadataTy.
106 inline const Type *getType() const {
107 return Type::MetadataTy;
110 /// isNullValue - Return true if this is the value that would be returned by
111 /// getNullValue. This always returns false because getNullValue will never
112 /// produce metadata.
113 virtual bool isNullValue() const {
117 /// Profile - calculate a unique identifier for this MDNode to collapse
119 void Profile(FoldingSetNodeID &ID) const;
121 virtual void destroyConstant();
122 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U) {
123 LLVM_UNREACHABLE("This should never be called because MDNodes have no ops");
126 /// Methods for support type inquiry through isa, cast, and dyn_cast:
127 static inline bool classof(const MDNode *) { return true; }
128 static bool classof(const Value *V) {
129 return V->getValueID() == MDNodeVal;
133 } // end llvm namespace