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