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"
33 class BasicBlock : public Value { // Basic blocks are data objects also
35 typedef ValueHolder<Instruction, BasicBlock, Method> InstListType;
37 InstListType InstList;
39 friend class ValueHolder<BasicBlock,Method,Method>;
40 void setParent(Method *parent);
43 // Instruction iterators...
44 typedef InstListType::iterator iterator;
45 typedef InstListType::const_iterator const_iterator;
46 typedef reverse_iterator<const_iterator> const_reverse_iterator;
47 typedef reverse_iterator<iterator> reverse_iterator;
49 typedef cfg::succ_iterator succ_iterator; // Include CFG.h to use these
50 typedef cfg::pred_iterator pred_iterator;
51 typedef cfg::succ_const_iterator succ_const_iterator;
52 typedef cfg::pred_const_iterator pred_const_iterator;
54 BasicBlock(const string &Name = "", Method *Parent = 0);
57 // Specialize setName to take care of symbol table majik
58 virtual void setName(const string &name);
60 const Method *getParent() const { return InstList.getParent(); }
61 Method *getParent() { return InstList.getParent(); }
63 // getTerminator() - If this is a well formed basic block, then this returns
64 // a pointer to the terminator instruction. If it is not, then you get a null
67 TerminatorInst *getTerminator();
68 const TerminatorInst *const getTerminator() const;
70 //===--------------------------------------------------------------------===//
71 // Instruction iterator methods
72 inline iterator begin() { return InstList.begin(); }
73 inline const_iterator begin() const { return InstList.begin(); }
74 inline iterator end () { return InstList.end(); }
75 inline const_iterator end () const { return InstList.end(); }
77 inline reverse_iterator rbegin() { return InstList.rbegin(); }
78 inline const_reverse_iterator rbegin() const { return InstList.rbegin(); }
79 inline reverse_iterator rend () { return InstList.rend(); }
80 inline const_reverse_iterator rend () const { return InstList.rend(); }
82 inline unsigned size() const { return InstList.size(); }
83 inline bool empty() const { return InstList.empty(); }
84 inline const Instruction *front() const { return InstList.front(); }
85 inline Instruction *front() { return InstList.front(); }
86 inline const Instruction *back() const { return InstList.back(); }
87 inline Instruction *back() { return InstList.back(); }
89 // getInstList() - Return the underlying instruction list container. You need
90 // to access it directly if you want to modify it currently.
92 const InstListType &getInstList() const { return InstList; }
93 InstListType &getInstList() { return InstList; }
95 // hasConstantPoolReferences() - This predicate is true if there is a
96 // reference to this basic block in the constant pool for this method. For
97 // example, if a block is reached through a switch table, that table resides
98 // in the constant pool, and the basic block is reference from it.
100 bool hasConstantPoolReferences() const;
102 // dropAllReferences() - This function causes all the subinstructions to "let
103 // go" of all references that they are maintaining. This allows one to
104 // 'delete' a whole class at a time, even though there may be circular
105 // references... first all references are dropped, and all use counts go to
106 // zero. Then everything is delete'd for real. Note that no operations are
107 // valid on an object that has "dropped all references", except operator
110 void dropAllReferences();
112 // removePredecessor - This method is used to notify a BasicBlock that the
113 // specified Predecessor of the block is no longer able to reach it. This is
114 // actually not used to update the Predecessor list, but is actually used to
115 // update the PHI nodes that reside in the block. Note that this should be
116 // called while the predecessor still refers to this block.
118 void removePredecessor(BasicBlock *Pred);
120 // splitBasicBlock - This splits a basic block into two at the specified
121 // instruction. Note that all instructions BEFORE the specified iterator stay
122 // as part of the original basic block, an unconditional branch is added to
123 // the new BB, and the rest of the instructions in the BB are moved to the new
124 // BB, including the old terminator. The newly formed BasicBlock is returned.
125 // This function invalidates the specified iterator.
127 // Note that this only works on well formed basic blocks (must have a
128 // terminator), and 'I' must not be the end of instruction list (which would
129 // cause a degenerate basic block to be formed, having a terminator inside of
132 BasicBlock *splitBasicBlock(iterator I);