1 //===- llvm/CodeGen/MachineLoopInfo.h - Natural Loop Calculator -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the MachineLoopInfo class that is used to identify natural
11 // loops and determine the loop depth of various nodes of the CFG. Note that
12 // natural loops may actually be several loops that share the same header node.
14 // This analysis calculates the nesting structure of loops in a function. For
15 // each natural loop identified, this analysis identifies natural loops
16 // contained entirely within the loop and the basic blocks the make up the loop.
18 // It can calculate on the fly various bits of information, for example:
20 // * whether there is a preheader for the loop
21 // * the number of back edges to the header
22 // * whether or not a particular block branches out of the loop
23 // * the successor blocks of the loop
28 //===----------------------------------------------------------------------===//
30 #ifndef LLVM_CODEGEN_MACHINE_LOOP_INFO_H
31 #define LLVM_CODEGEN_MACHINE_LOOP_INFO_H
33 #include "llvm/CodeGen/MachineFunctionPass.h"
34 #include "llvm/Analysis/LoopInfo.h"
38 class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
42 /// getTopBlock - Return the "top" block in the loop, which is the first
43 /// block in the linear layout, ignoring any parts of the loop not
44 /// contiguous with the part the contains the header.
45 MachineBasicBlock *getTopBlock();
47 /// getBottomBlock - Return the "bottom" block in the loop, which is the last
48 /// block in the linear layout, ignoring any parts of the loop not
49 /// contiguous with the part the contains the header.
50 MachineBasicBlock *getBottomBlock();
55 friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
56 explicit MachineLoop(MachineBasicBlock *MBB)
57 : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
60 class MachineLoopInfo : public MachineFunctionPass {
61 LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
62 friend class LoopBase<MachineBasicBlock, MachineLoop>;
64 void operator=(const MachineLoopInfo &); // do not implement
65 MachineLoopInfo(const MachineLoopInfo &); // do not implement
67 LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
70 static char ID; // Pass identification, replacement for typeid
72 MachineLoopInfo() : MachineFunctionPass(&ID) {}
74 /// iterator/begin/end - The interface to the top-level loops in the current
77 typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
78 inline iterator begin() const { return LI.begin(); }
79 inline iterator end() const { return LI.end(); }
80 bool empty() const { return LI.empty(); }
82 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
83 /// block is in no loop (for example the entry node), null is returned.
85 inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
86 return LI.getLoopFor(BB);
89 /// operator[] - same as getLoopFor...
91 inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
92 return LI.getLoopFor(BB);
95 /// getLoopDepth - Return the loop nesting level of the specified block...
97 inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
98 return LI.getLoopDepth(BB);
101 // isLoopHeader - True if the block is a loop header node
102 inline bool isLoopHeader(MachineBasicBlock *BB) const {
103 return LI.isLoopHeader(BB);
106 /// runOnFunction - Calculate the natural loop information.
108 virtual bool runOnMachineFunction(MachineFunction &F);
110 virtual void releaseMemory() { LI.releaseMemory(); }
112 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
114 /// removeLoop - This removes the specified top-level loop from this loop info
115 /// object. The loop is not deleted, as it will presumably be inserted into
117 inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
119 /// changeLoopFor - Change the top-level loop that contains BB to the
120 /// specified loop. This should be used by transformations that restructure
121 /// the loop hierarchy tree.
122 inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
123 LI.changeLoopFor(BB, L);
126 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
127 /// list with the indicated loop.
128 inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
129 LI.changeTopLevelLoop(OldLoop, NewLoop);
132 /// addTopLevelLoop - This adds the specified loop to the collection of
134 inline void addTopLevelLoop(MachineLoop *New) {
135 LI.addTopLevelLoop(New);
138 /// removeBlock - This method completely removes BB from all data structures,
139 /// including all of the Loop objects it is nested in and our mapping from
140 /// MachineBasicBlocks to loops.
141 void removeBlock(MachineBasicBlock *BB) {
147 // Allow clients to walk the list of nested loops...
148 template <> struct GraphTraits<const MachineLoop*> {
149 typedef const MachineLoop NodeType;
150 typedef MachineLoopInfo::iterator ChildIteratorType;
152 static NodeType *getEntryNode(const MachineLoop *L) { return L; }
153 static inline ChildIteratorType child_begin(NodeType *N) {
156 static inline ChildIteratorType child_end(NodeType *N) {
161 template <> struct GraphTraits<MachineLoop*> {
162 typedef MachineLoop NodeType;
163 typedef MachineLoopInfo::iterator ChildIteratorType;
165 static NodeType *getEntryNode(MachineLoop *L) { return L; }
166 static inline ChildIteratorType child_begin(NodeType *N) {
169 static inline ChildIteratorType child_end(NodeType *N) {
174 } // End llvm namespace