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"
34 typedef UseTy<BasicBlock> BasicBlockUse;
36 class BasicBlock : public Value { // Basic blocks are data objects also
38 typedef ValueHolder<Instruction, BasicBlock> InstListType;
40 InstListType InstList;
42 friend class ValueHolder<BasicBlock,Method>;
43 void setParent(Method *parent);
46 typedef cfg::succ_iterator succ_iterator; // Include CFG.h to use these
47 typedef cfg::pred_iterator pred_iterator;
48 typedef cfg::succ_const_iterator succ_const_iterator;
49 typedef cfg::pred_const_iterator pred_const_iterator;
51 BasicBlock(const string &Name = "", Method *Parent = 0);
54 // Specialize setName to take care of symbol table majik
55 virtual void setName(const string &name);
57 const Method *getParent() const { return (const Method*)InstList.getParent();}
58 Method *getParent() { return (Method*)InstList.getParent(); }
60 const InstListType &getInstList() const { return InstList; }
61 InstListType &getInstList() { return InstList; }
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 // hasConstantPoolReferences() - This predicate is true if there is a
71 // reference to this basic block in the constant pool for this method. For
72 // example, if a block is reached through a switch table, that table resides
73 // in the constant pool, and the basic block is reference from it.
75 bool hasConstantPoolReferences() const;
77 // dropAllReferences() - This function causes all the subinstructions to "let
78 // go" of all references that they are maintaining. This allows one to
79 // 'delete' a whole class at a time, even though there may be circular
80 // references... first all references are dropped, and all use counts go to
81 // zero. Then everything is delete'd for real. Note that no operations are
82 // valid on an object that has "dropped all references", except operator
85 void dropAllReferences();
87 // splitBasicBlock - This splits a basic block into two at the specified
88 // instruction. Note that all instructions BEFORE the specified iterator stay
89 // as part of the original basic block, an unconditional branch is added to
90 // the new BB, and the rest of the instructions in the BB are moved to the new
91 // BB, including the old terminator. The newly formed BasicBlock is returned.
92 // This function invalidates the specified iterator.
94 // Note that this only works on well formed basic blocks (must have a
95 // terminator), and 'I' must not be the end of instruction list (which would
96 // cause a degenerate basic block to be formed, having a terminator inside of
99 BasicBlock *splitBasicBlock(InstListType::iterator I);