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"
33 typedef UseTy<BasicBlock> BasicBlockUse;
35 class BasicBlock : public Value { // Basic blocks are data objects also
37 typedef ValueHolder<Instruction, BasicBlock> InstListType;
39 InstListType InstList;
41 friend class ValueHolder<BasicBlock,Method>;
42 void setParent(Method *parent);
45 BasicBlock(const string &Name = "", Method *Parent = 0);
48 // Specialize setName to take care of symbol table majik
49 virtual void setName(const string &name);
51 const Method *getParent() const { return (const Method*)InstList.getParent();}
52 Method *getParent() { return (Method*)InstList.getParent(); }
54 const InstListType &getInstList() const { return InstList; }
55 InstListType &getInstList() { return InstList; }
57 // getTerminator() - If this is a well formed basic block, then this returns
58 // a pointer to the terminator instruction. If it is not, then you get a null
61 TerminatorInst *getTerminator();
62 const TerminatorInst *const getTerminator() const;
64 // hasConstantPoolReferences() - This predicate is true if there is a
65 // reference to this basic block in the constant pool for this method. For
66 // example, if a block is reached through a switch table, that table resides
67 // in the constant pool, and the basic block is reference from it.
69 bool hasConstantPoolReferences() const;
71 // dropAllReferences() - This function causes all the subinstructions to "let
72 // go" of all references that they are maintaining. This allows one to
73 // 'delete' a whole class at a time, even though there may be circular
74 // references... first all references are dropped, and all use counts go to
75 // zero. Then everything is delete'd for real. Note that no operations are
76 // valid on an object that has "dropped all references", except operator
79 void dropAllReferences();
81 // splitBasicBlock - This splits a basic block into two at the specified
82 // instruction. Note that all instructions BEFORE the specified iterator stay
83 // as part of the original basic block, an unconditional branch is added to
84 // the new BB, and the rest of the instructions in the BB are moved to the new
85 // BB, including the old terminator. The newly formed BasicBlock is returned.
86 // This function invalidates the specified iterator.
88 // Note that this only works on well formed basic blocks (must have a
89 // terminator), and 'I' must not be the end of instruction list (which would
90 // cause a degenerate basic block to be formed, having a terminator inside of
93 BasicBlock *splitBasicBlock(InstListType::iterator I);