1 //===-- llvm/BasicBlock.h - Represent a basic block in the VM ---*- C++ -*-===//
5 /// This file contains the declaration of the BasicBlock class, which represents
6 /// a single basic block in the VM.
8 /// Note that basic blocks themselves are Value's, because they are referenced
9 /// by instructions like branches and can go in switch tables and stuff...
11 ///===---------------------------------------------------------------------===//
13 /// Note that well formed basic blocks are formed of a list of instructions
14 /// followed by a single TerminatorInst instruction. TerminatorInst's may not
15 /// occur in the middle of basic blocks, and must terminate the blocks.
17 /// This code allows malformed basic blocks to occur, because it may be useful
18 /// in the intermediate stage modification to a program.
20 //===----------------------------------------------------------------------===//
22 #ifndef LLVM_BASICBLOCK_H
23 #define LLVM_BASICBLOCK_H
25 #include "llvm/Instruction.h"
26 #include "llvm/SymbolTableListTraits.h"
27 #include "Support/ilist"
30 template <class _Term, class _BB> class SuccIterator; // Successor Iterator
31 template <class _Ptr, class _USE_iterator> class PredIterator;
33 template<> struct ilist_traits<Instruction>
34 : public SymbolTableListTraits<Instruction, BasicBlock, Function> {
35 // createNode is used to create a node that marks the end of the list...
36 static Instruction *createNode();
37 static iplist<Instruction> &getList(BasicBlock *BB);
40 struct BasicBlock : public Value { // Basic blocks are data objects also
41 typedef iplist<Instruction> InstListType;
43 InstListType InstList;
44 BasicBlock *Prev, *Next; // Next and Prev links for our intrusive linked list
46 void setParent(Function *parent);
47 void setNext(BasicBlock *N) { Next = N; }
48 void setPrev(BasicBlock *N) { Prev = N; }
49 friend class SymbolTableListTraits<BasicBlock, Function, Function>;
51 BasicBlock(const BasicBlock &); // Do not implement
52 void operator=(const BasicBlock &); // Do not implement
55 /// Instruction iterators...
56 typedef InstListType::iterator iterator;
57 typedef InstListType::const_iterator const_iterator;
58 typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
59 typedef std::reverse_iterator<iterator> reverse_iterator;
61 /// BasicBlock ctor - If the function parameter is specified, the basic block
62 /// is automatically inserted at the end of the function.
64 BasicBlock(const std::string &Name = "", Function *Parent = 0);
66 /// BasicBlock ctor - If the InsertBefore parameter is specified, the basic
67 /// block is automatically inserted right before the specified block.
68 BasicBlock(const std::string &Name, BasicBlock *InsertBefore);
71 // Specialize setName to take care of symbol table majik
72 virtual void setName(const std::string &name, SymbolTable *ST = 0);
74 /// getParent - Return the enclosing method, or null if none
76 const Function *getParent() const { return InstList.getParent(); }
77 Function *getParent() { return InstList.getParent(); }
79 // getNext/Prev - Return the next or previous basic block in the list.
80 BasicBlock *getNext() { return Next; }
81 const BasicBlock *getNext() const { return Next; }
82 BasicBlock *getPrev() { return Prev; }
83 const BasicBlock *getPrev() const { return Prev; }
85 /// getTerminator() - If this is a well formed basic block, then this returns
86 /// a pointer to the terminator instruction. If it is not, then you get a
87 /// null pointer back.
89 TerminatorInst *getTerminator();
90 const TerminatorInst *const getTerminator() const;
92 // Provide a scoped predecessor and successor iterator
93 typedef PredIterator<BasicBlock, Value::use_iterator> pred_iterator;
94 typedef PredIterator<const BasicBlock,
95 Value::use_const_iterator> pred_const_iterator;
97 typedef SuccIterator<TerminatorInst*, BasicBlock> succ_iterator;
98 typedef SuccIterator<const TerminatorInst*,
99 const BasicBlock> succ_const_iterator;
102 //===--------------------------------------------------------------------===//
103 /// Instruction iterator methods
105 inline iterator begin() { return InstList.begin(); }
106 inline const_iterator begin() const { return InstList.begin(); }
107 inline iterator end () { return InstList.end(); }
108 inline const_iterator end () const { return InstList.end(); }
110 inline reverse_iterator rbegin() { return InstList.rbegin(); }
111 inline const_reverse_iterator rbegin() const { return InstList.rbegin(); }
112 inline reverse_iterator rend () { return InstList.rend(); }
113 inline const_reverse_iterator rend () const { return InstList.rend(); }
115 inline unsigned size() const { return InstList.size(); }
116 inline bool empty() const { return InstList.empty(); }
117 inline const Instruction &front() const { return InstList.front(); }
118 inline Instruction &front() { return InstList.front(); }
119 inline const Instruction &back() const { return InstList.back(); }
120 inline Instruction &back() { return InstList.back(); }
122 /// getInstList() - Return the underlying instruction list container. You
123 /// need to access it directly if you want to modify it currently.
125 const InstListType &getInstList() const { return InstList; }
126 InstListType &getInstList() { return InstList; }
128 virtual void print(std::ostream &OS) const;
130 /// Methods for support type inquiry through isa, cast, and dyn_cast:
131 static inline bool classof(const BasicBlock *BB) { return true; }
132 static inline bool classof(const Value *V) {
133 return V->getValueType() == Value::BasicBlockVal;
136 /// hasConstantReferences() - This predicate is true if there is a
137 /// reference to this basic block in the constant pool for this method. For
138 /// example, if a block is reached through a switch table, that table resides
139 /// in the constant pool, and the basic block is reference from it.
141 bool hasConstantReferences() const;
143 /// dropAllReferences() - This function causes all the subinstructions to "let
144 /// go" of all references that they are maintaining. This allows one to
145 /// 'delete' a whole class at a time, even though there may be circular
146 /// references... first all references are dropped, and all use counts go to
147 /// zero. Then everything is delete'd for real. Note that no operations are
148 /// valid on an object that has "dropped all references", except operator
151 void dropAllReferences();
153 /// removePredecessor - This method is used to notify a BasicBlock that the
154 /// specified Predecessor of the block is no longer able to reach it. This is
155 /// actually not used to update the Predecessor list, but is actually used to
156 /// update the PHI nodes that reside in the block. Note that this should be
157 /// called while the predecessor still refers to this block.
159 void removePredecessor(BasicBlock *Pred);
161 /// splitBasicBlock - This splits a basic block into two at the specified
162 /// instruction. Note that all instructions BEFORE the specified iterator
163 /// stay as part of the original basic block, an unconditional branch is added
164 /// to the new BB, and the rest of the instructions in the BB are moved to the
165 /// new BB, including the old terminator. The newly formed BasicBlock is
166 /// returned. This function invalidates the specified iterator.
168 /// Note that this only works on well formed basic blocks (must have a
169 /// terminator), and 'I' must not be the end of instruction list (which would
170 /// cause a degenerate basic block to be formed, having a terminator inside of
171 /// the basic block).
173 BasicBlock *splitBasicBlock(iterator I, const std::string &BBName = "");