BasicBlock.h revision 05bb8831d3cd5299ba8e0c3fecfd7cf682f0ace1 
1//===-- llvm/BasicBlock.h - Represent a basic block in the VM ---*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
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.
7//
8//===----------------------------------------------------------------------===//
9//
10//
11// This file contains the declaration of the BasicBlock class, which represents
12// a single basic block in the VM.
13//
14// Note that basic blocks themselves are Value's, because they are referenced
15// by instructions like branches and can go in switch tables and stuff...
16//
17///===---------------------------------------------------------------------===//
18//
19// Note that well formed basic blocks are formed of a list of instructions
20// followed by a single TerminatorInst instruction.  TerminatorInst's may not
21// occur in the middle of basic blocks, and must terminate the blocks.
22//
23// This code allows malformed basic blocks to occur, because it may be useful
24// in the intermediate stage modification to a program.
25//
26//===----------------------------------------------------------------------===//
27
28#ifndef LLVM_BASICBLOCK_H
29#define LLVM_BASICBLOCK_H
30
31#include "llvm/Instruction.h"
32#include "llvm/SymbolTableListTraits.h"
33#include "llvm/ADT/ilist"
34
35namespace llvm {
36
37class TerminatorInst;
38template <class Term, class BB> class SuccIterator;  // Successor Iterator
39template <class Ptr, class USE_iterator> class PredIterator;
40
41template<> struct ilist_traits<Instruction>
42  : public SymbolTableListTraits<Instruction, BasicBlock, Function> {
43  // createSentinel is used to create a node that marks the end of the list...
44  static Instruction *createSentinel();
45  static void destroySentinel(Instruction *I) { delete I; }
46  static iplist<Instruction> &getList(BasicBlock *BB);
47};
48
49class BasicBlock : public Value {       // Basic blocks are data objects also
50public:
51  typedef iplist<Instruction> InstListType;
52private :
53  InstListType InstList;
54  BasicBlock *Prev, *Next; // Next and Prev links for our intrusive linked list
55
56  void setParent(Function *parent);
57  void setNext(BasicBlock *N) { Next = N; }
58  void setPrev(BasicBlock *N) { Prev = N; }
59  friend class SymbolTableListTraits<BasicBlock, Function, Function>;
60
61  BasicBlock(const BasicBlock &);     // Do not implement
62  void operator=(const BasicBlock &); // Do not implement
63
64public:
65  /// Instruction iterators...
66  typedef InstListType::iterator                              iterator;
67  typedef InstListType::const_iterator                  const_iterator;
68
69  /// BasicBlock ctor - If the function parameter is specified, the basic block
70  /// is automatically inserted at either the end of the function (if
71  /// InsertBefore is null), or before the specified basic block.
72  ///
73  BasicBlock(const std::string &Name = "", Function *Parent = 0,
74             BasicBlock *InsertBefore = 0);
75  ~BasicBlock();
76
77  /// getParent - Return the enclosing method, or null if none
78  ///
79  const Function *getParent() const { return InstList.getParent(); }
80        Function *getParent()       { return InstList.getParent(); }
81
82  // getNext/Prev - Return the next or previous basic block in the list.
83        BasicBlock *getNext()       { return Next; }
84  const BasicBlock *getNext() const { return Next; }
85        BasicBlock *getPrev()       { return Prev; }
86  const BasicBlock *getPrev() const { return Prev; }
87
88  /// getTerminator() - If this is a well formed basic block, then this returns
89  /// a pointer to the terminator instruction.  If it is not, then you get a
90  /// null pointer back.
91  ///
92  TerminatorInst *getTerminator();
93  const TerminatorInst *const getTerminator() const;
94
95  /// removeFromParent - This method unlinks 'this' from the containing
96  /// function, but does not delete it.
97  ///
98  void removeFromParent();
99
100  /// eraseFromParent - This method unlinks 'this' from the containing function
101  /// and deletes it.
102  ///
103  void eraseFromParent();
104
105  /// getSinglePredecessor - If this basic block has a single predecessor block,
106  /// return the block, otherwise return a null pointer.
107  BasicBlock *getSinglePredecessor();
108  const BasicBlock *getSinglePredecessor() const {
109    return const_cast<BasicBlock*>(this)->getSinglePredecessor();
110  }
111
112  //===--------------------------------------------------------------------===//
113  /// Instruction iterator methods
114  ///
115  inline iterator                begin()       { return InstList.begin(); }
116  inline const_iterator          begin() const { return InstList.begin(); }
117  inline iterator                end  ()       { return InstList.end();   }
118  inline const_iterator          end  () const { return InstList.end();   }
119
120  inline size_t                   size() const { return InstList.size();  }
121  inline bool                    empty() const { return InstList.empty(); }
122  inline const Instruction      &front() const { return InstList.front(); }
123  inline       Instruction      &front()       { return InstList.front(); }
124  inline const Instruction       &back() const { return InstList.back();  }
125  inline       Instruction       &back()       { return InstList.back();  }
126
127  /// getInstList() - Return the underlying instruction list container.  You
128  /// need to access it directly if you want to modify it currently.
129  ///
130  const InstListType &getInstList() const { return InstList; }
131        InstListType &getInstList()       { return InstList; }
132
133  virtual void print(std::ostream &OS) const { print(OS, 0); }
134  void print(std::ostream &OS, AssemblyAnnotationWriter *AAW) const;
135
136  /// Methods for support type inquiry through isa, cast, and dyn_cast:
137  static inline bool classof(const BasicBlock *BB) { return true; }
138  static inline bool classof(const Value *V) {
139    return V->getValueType() == Value::BasicBlockVal;
140  }
141
142  /// dropAllReferences() - This function causes all the subinstructions to "let
143  /// go" of all references that they are maintaining.  This allows one to
144  /// 'delete' a whole class at a time, even though there may be circular
145  /// references... first all references are dropped, and all use counts go to
146  /// zero.  Then everything is delete'd for real.  Note that no operations are
147  /// valid on an object that has "dropped all references", except operator
148  /// delete.
149  ///
150  void dropAllReferences();
151
152  /// removePredecessor - This method is used to notify a BasicBlock that the
153  /// specified Predecessor of the block is no longer able to reach it.  This is
154  /// actually not used to update the Predecessor list, but is actually used to
155  /// update the PHI nodes that reside in the block.  Note that this should be
156  /// called while the predecessor still refers to this block.
157  ///
158  void removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs = false);
159
160  /// splitBasicBlock - This splits a basic block into two at the specified
161  /// instruction.  Note that all instructions BEFORE the specified iterator
162  /// stay as part of the original basic block, an unconditional branch is added
163  /// to the original BB, and the rest of the instructions in the BB are moved
164  /// to the new BB, including the old terminator.  The newly formed BasicBlock
165  /// is returned.  This function invalidates the specified iterator.
166  ///
167  /// Note that this only works on well formed basic blocks (must have a
168  /// terminator), and 'I' must not be the end of instruction list (which would
169  /// cause a degenerate basic block to be formed, having a terminator inside of
170  /// the basic block).
171  ///
172  BasicBlock *splitBasicBlock(iterator I, const std::string &BBName = "");
173};
174
175} // End llvm namespace
176
177#endif
178