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 //===----------------------------------------------------------------------===//
11 // This file contains the declaration of the BasicBlock class, which represents
12 // a single basic block in the VM.
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...
17 ///===---------------------------------------------------------------------===//
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.
23 // This code allows malformed basic blocks to occur, because it may be useful
24 // in the intermediate stage modification to a program.
26 //===----------------------------------------------------------------------===//
28 #ifndef LLVM_BASICBLOCK_H
29 #define LLVM_BASICBLOCK_H
31 #include "llvm/Instruction.h"
32 #include "llvm/SymbolTableListTraits.h"
33 #include "llvm/ADT/ilist"
38 template <class Term, class BB> class SuccIterator; // Successor Iterator
39 template <class Ptr, class USE_iterator> class PredIterator;
41 template<> 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);
49 class BasicBlock : public Value { // Basic blocks are data objects also
51 typedef iplist<Instruction> InstListType;
53 InstListType InstList;
54 BasicBlock *Prev, *Next; // Next and Prev links for our intrusive linked list
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>;
61 BasicBlock(const BasicBlock &); // Do not implement
62 void operator=(const BasicBlock &); // Do not implement
65 /// Instruction iterators...
66 typedef InstListType::iterator iterator;
67 typedef InstListType::const_iterator const_iterator;
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.
73 BasicBlock(const std::string &Name = "", Function *Parent = 0,
74 BasicBlock *InsertBefore = 0);
77 /// getParent - Return the enclosing method, or null if none
79 const Function *getParent() const { return InstList.getParent(); }
80 Function *getParent() { return InstList.getParent(); }
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; }
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.
92 TerminatorInst *getTerminator();
93 const TerminatorInst *const getTerminator() const;
95 /// removeFromParent - This method unlinks 'this' from the containing
96 /// function, but does not delete it.
98 void removeFromParent();
100 /// eraseFromParent - This method unlinks 'this' from the containing function
103 void eraseFromParent();
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();
112 //===--------------------------------------------------------------------===//
113 /// Instruction iterator methods
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(); }
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(); }
127 /// getInstList() - Return the underlying instruction list container. You
128 /// need to access it directly if you want to modify it currently.
130 const InstListType &getInstList() const { return InstList; }
131 InstListType &getInstList() { return InstList; }
133 virtual void print(std::ostream &OS) const { print(OS, 0); }
134 void print(std::ostream &OS, AssemblyAnnotationWriter *AAW) const;
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;
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
150 void dropAllReferences();
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.
158 void removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs = false);
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 new BB, and the rest of the instructions in the BB are moved to the
164 /// new BB, including the old terminator. The newly formed BasicBlock is
165 /// returned. This function invalidates the specified iterator.
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).
172 BasicBlock *splitBasicBlock(iterator I, const std::string &BBName = "");
175 } // End llvm namespace