1 //===-- llvm/BasicBlock.h - Represent a basic block in the VM ----*- C++ -*--=//
3 // This file contains the declaration of the BasicBlock class, which represents
4 // a single basic block in the VM.
6 // Note that basic blocks themselves are Def's, because they are referenced
7 // by instructions like branches and can go in switch tables and stuff...
9 // This may see wierd at first, but it's really pretty cool. :)
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 of analysis or modification of a program.
20 //===----------------------------------------------------------------------===//
22 #ifndef LLVM_BASICBLOCK_H
23 #define LLVM_BASICBLOCK_H
25 #include "llvm/Value.h" // Get the definition of Value
26 #include "llvm/ValueHolder.h"
27 #include "llvm/CFGdecls.h"
32 class MachineCodeForBasicBlock;
34 class BasicBlock : public Value { // Basic blocks are data objects also
36 typedef ValueHolder<Instruction, BasicBlock, Method> InstListType;
38 InstListType InstList;
39 MachineCodeForBasicBlock* machineInstrVec;
41 friend class ValueHolder<BasicBlock,Method,Method>;
42 void setParent(Method *parent);
45 // Instruction iterators...
46 typedef InstListType::iterator iterator;
47 typedef InstListType::const_iterator const_iterator;
48 typedef reverse_iterator<const_iterator> const_reverse_iterator;
49 typedef reverse_iterator<iterator> reverse_iterator;
51 typedef cfg::succ_iterator succ_iterator; // Include CFG.h to use these
52 typedef cfg::pred_iterator pred_iterator;
53 typedef cfg::succ_const_iterator succ_const_iterator;
54 typedef cfg::pred_const_iterator pred_const_iterator;
56 BasicBlock(const string &Name = "", Method *Parent = 0);
59 // Specialize setName to take care of symbol table majik
60 virtual void setName(const string &name, SymbolTable *ST = 0);
62 const Method *getParent() const { return InstList.getParent(); }
63 Method *getParent() { return InstList.getParent(); }
65 // getTerminator() - If this is a well formed basic block, then this returns
66 // a pointer to the terminator instruction. If it is not, then you get a null
69 TerminatorInst *getTerminator();
70 const TerminatorInst *const getTerminator() const;
73 // Machine code accessor...
74 inline MachineCodeForBasicBlock& getMachineInstrVec() const {
75 return *machineInstrVec;
78 //===--------------------------------------------------------------------===//
79 // Instruction iterator methods
80 inline iterator begin() { return InstList.begin(); }
81 inline const_iterator begin() const { return InstList.begin(); }
82 inline iterator end () { return InstList.end(); }
83 inline const_iterator end () const { return InstList.end(); }
85 inline reverse_iterator rbegin() { return InstList.rbegin(); }
86 inline const_reverse_iterator rbegin() const { return InstList.rbegin(); }
87 inline reverse_iterator rend () { return InstList.rend(); }
88 inline const_reverse_iterator rend () const { return InstList.rend(); }
90 inline unsigned size() const { return InstList.size(); }
91 inline bool empty() const { return InstList.empty(); }
92 inline const Instruction *front() const { return InstList.front(); }
93 inline Instruction *front() { return InstList.front(); }
94 inline const Instruction *back() const { return InstList.back(); }
95 inline Instruction *back() { return InstList.back(); }
97 // getInstList() - Return the underlying instruction list container. You need
98 // to access it directly if you want to modify it currently.
100 const InstListType &getInstList() const { return InstList; }
101 InstListType &getInstList() { return InstList; }
103 // hasConstantPoolReferences() - This predicate is true if there is a
104 // reference to this basic block in the constant pool for this method. For
105 // example, if a block is reached through a switch table, that table resides
106 // in the constant pool, and the basic block is reference from it.
108 bool hasConstantPoolReferences() const;
110 // dropAllReferences() - This function causes all the subinstructions to "let
111 // go" of all references that they are maintaining. This allows one to
112 // 'delete' a whole class at a time, even though there may be circular
113 // references... first all references are dropped, and all use counts go to
114 // zero. Then everything is delete'd for real. Note that no operations are
115 // valid on an object that has "dropped all references", except operator
118 void dropAllReferences();
120 // removePredecessor - This method is used to notify a BasicBlock that the
121 // specified Predecessor of the block is no longer able to reach it. This is
122 // actually not used to update the Predecessor list, but is actually used to
123 // update the PHI nodes that reside in the block. Note that this should be
124 // called while the predecessor still refers to this block.
126 void removePredecessor(BasicBlock *Pred);
128 // splitBasicBlock - This splits a basic block into two at the specified
129 // instruction. Note that all instructions BEFORE the specified iterator stay
130 // as part of the original basic block, an unconditional branch is added to
131 // the new BB, and the rest of the instructions in the BB are moved to the new
132 // BB, including the old terminator. The newly formed BasicBlock is returned.
133 // This function invalidates the specified iterator.
135 // Note that this only works on well formed basic blocks (must have a
136 // terminator), and 'I' must not be the end of instruction list (which would
137 // cause a degenerate basic block to be formed, having a terminator inside of
140 BasicBlock *splitBasicBlock(iterator I);