LLVM API Documentation
00001 //===-- llvm/BasicBlock.h - Represent a basic block in the VM ---*- C++ -*-===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // 00011 // This file contains the declaration of the BasicBlock class, which represents 00012 // a single basic block in the VM. 00013 // 00014 // Note that basic blocks themselves are Value's, because they are referenced 00015 // by instructions like branches and can go in switch tables and stuff... 00016 // 00017 ///===---------------------------------------------------------------------===// 00018 // 00019 // Note that well formed basic blocks are formed of a list of instructions 00020 // followed by a single TerminatorInst instruction. TerminatorInst's may not 00021 // occur in the middle of basic blocks, and must terminate the blocks. 00022 // 00023 // This code allows malformed basic blocks to occur, because it may be useful 00024 // in the intermediate stage modification to a program. 00025 // 00026 //===----------------------------------------------------------------------===// 00027 00028 #ifndef LLVM_BASICBLOCK_H 00029 #define LLVM_BASICBLOCK_H 00030 00031 #include "llvm/Instruction.h" 00032 #include "llvm/SymbolTableListTraits.h" 00033 #include "llvm/ADT/ilist" 00034 00035 namespace llvm { 00036 00037 class TerminatorInst; 00038 template <class Term, class BB> class SuccIterator; // Successor Iterator 00039 template <class Ptr, class USE_iterator> class PredIterator; 00040 00041 template<> struct ilist_traits<Instruction> 00042 : public SymbolTableListTraits<Instruction, BasicBlock, Function> { 00043 // createSentinel is used to create a node that marks the end of the list... 00044 static Instruction *createSentinel(); 00045 static void destroySentinel(Instruction *I) { delete I; } 00046 static iplist<Instruction> &getList(BasicBlock *BB); 00047 }; 00048 00049 class BasicBlock : public Value { // Basic blocks are data objects also 00050 public: 00051 typedef iplist<Instruction> InstListType; 00052 private : 00053 InstListType InstList; 00054 BasicBlock *Prev, *Next; // Next and Prev links for our intrusive linked list 00055 00056 void setParent(Function *parent); 00057 void setNext(BasicBlock *N) { Next = N; } 00058 void setPrev(BasicBlock *N) { Prev = N; } 00059 friend class SymbolTableListTraits<BasicBlock, Function, Function>; 00060 00061 BasicBlock(const BasicBlock &); // Do not implement 00062 void operator=(const BasicBlock &); // Do not implement 00063 00064 public: 00065 /// Instruction iterators... 00066 typedef InstListType::iterator iterator; 00067 typedef InstListType::const_iterator const_iterator; 00068 00069 /// BasicBlock ctor - If the function parameter is specified, the basic block 00070 /// is automatically inserted at either the end of the function (if 00071 /// InsertBefore is null), or before the specified basic block. 00072 /// 00073 BasicBlock(const std::string &Name = "", Function *Parent = 0, 00074 BasicBlock *InsertBefore = 0); 00075 ~BasicBlock(); 00076 00077 /// getParent - Return the enclosing method, or null if none 00078 /// 00079 const Function *getParent() const { return InstList.getParent(); } 00080 Function *getParent() { return InstList.getParent(); } 00081 00082 // getNext/Prev - Return the next or previous basic block in the list. 00083 BasicBlock *getNext() { return Next; } 00084 const BasicBlock *getNext() const { return Next; } 00085 BasicBlock *getPrev() { return Prev; } 00086 const BasicBlock *getPrev() const { return Prev; } 00087 00088 /// getTerminator() - If this is a well formed basic block, then this returns 00089 /// a pointer to the terminator instruction. If it is not, then you get a 00090 /// null pointer back. 00091 /// 00092 TerminatorInst *getTerminator(); 00093 const TerminatorInst *const getTerminator() const; 00094 00095 /// removeFromParent - This method unlinks 'this' from the containing 00096 /// function, but does not delete it. 00097 /// 00098 void removeFromParent(); 00099 00100 /// eraseFromParent - This method unlinks 'this' from the containing function 00101 /// and deletes it. 00102 /// 00103 void eraseFromParent(); 00104 00105 /// moveBefore - Unlink this instruction from its current function and 00106 /// insert it into the function that MovePos lives in, right before 00107 /// MovePos. 00108 void moveBefore(BasicBlock *MovePos); 00109 00110 /// getSinglePredecessor - If this basic block has a single predecessor block, 00111 /// return the block, otherwise return a null pointer. 00112 BasicBlock *getSinglePredecessor(); 00113 const BasicBlock *getSinglePredecessor() const { 00114 return const_cast<BasicBlock*>(this)->getSinglePredecessor(); 00115 } 00116 00117 //===--------------------------------------------------------------------===// 00118 /// Instruction iterator methods 00119 /// 00120 inline iterator begin() { return InstList.begin(); } 00121 inline const_iterator begin() const { return InstList.begin(); } 00122 inline iterator end () { return InstList.end(); } 00123 inline const_iterator end () const { return InstList.end(); } 00124 00125 inline size_t size() const { return InstList.size(); } 00126 inline bool empty() const { return InstList.empty(); } 00127 inline const Instruction &front() const { return InstList.front(); } 00128 inline Instruction &front() { return InstList.front(); } 00129 inline const Instruction &back() const { return InstList.back(); } 00130 inline Instruction &back() { return InstList.back(); } 00131 00132 /// getInstList() - Return the underlying instruction list container. You 00133 /// need to access it directly if you want to modify it currently. 00134 /// 00135 const InstListType &getInstList() const { return InstList; } 00136 InstListType &getInstList() { return InstList; } 00137 00138 virtual void print(std::ostream &OS) const { print(OS, 0); } 00139 void print(std::ostream &OS, AssemblyAnnotationWriter *AAW) const; 00140 00141 /// Methods for support type inquiry through isa, cast, and dyn_cast: 00142 static inline bool classof(const BasicBlock *) { return true; } 00143 static inline bool classof(const Value *V) { 00144 return V->getValueType() == Value::BasicBlockVal; 00145 } 00146 00147 /// dropAllReferences() - This function causes all the subinstructions to "let 00148 /// go" of all references that they are maintaining. This allows one to 00149 /// 'delete' a whole class at a time, even though there may be circular 00150 /// references... first all references are dropped, and all use counts go to 00151 /// zero. Then everything is delete'd for real. Note that no operations are 00152 /// valid on an object that has "dropped all references", except operator 00153 /// delete. 00154 /// 00155 void dropAllReferences(); 00156 00157 /// removePredecessor - This method is used to notify a BasicBlock that the 00158 /// specified Predecessor of the block is no longer able to reach it. This is 00159 /// actually not used to update the Predecessor list, but is actually used to 00160 /// update the PHI nodes that reside in the block. Note that this should be 00161 /// called while the predecessor still refers to this block. 00162 /// 00163 void removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs = false); 00164 00165 /// splitBasicBlock - This splits a basic block into two at the specified 00166 /// instruction. Note that all instructions BEFORE the specified iterator 00167 /// stay as part of the original basic block, an unconditional branch is added 00168 /// to the original BB, and the rest of the instructions in the BB are moved 00169 /// to the new BB, including the old terminator. The newly formed BasicBlock 00170 /// is returned. This function invalidates the specified iterator. 00171 /// 00172 /// Note that this only works on well formed basic blocks (must have a 00173 /// terminator), and 'I' must not be the end of instruction list (which would 00174 /// cause a degenerate basic block to be formed, having a terminator inside of 00175 /// the basic block). 00176 /// 00177 BasicBlock *splitBasicBlock(iterator I, const std::string &BBName = ""); 00178 }; 00179 00180 } // End llvm namespace 00181 00182 #endif