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_MACHINELOOPINFO_H
31 #define LLVM_CODEGEN_MACHINELOOPINFO_H
33 #include "llvm/Analysis/LoopInfo.h"
34 #include "llvm/CodeGen/MachineFunctionPass.h"
38 // Implementation in LoopInfoImpl.h
41 __extension__ extern template class LoopBase<MachineBasicBlock, MachineLoop>;
44 class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
48 /// getTopBlock - Return the "top" block in the loop, which is the first
49 /// block in the linear layout, ignoring any parts of the loop not
50 /// contiguous with the part the contains the header.
51 MachineBasicBlock *getTopBlock();
53 /// getBottomBlock - Return the "bottom" block in the loop, which is the last
54 /// block in the linear layout, ignoring any parts of the loop not
55 /// contiguous with the part the contains the header.
56 MachineBasicBlock *getBottomBlock();
61 friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
62 explicit MachineLoop(MachineBasicBlock *MBB)
63 : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
66 // Implementation in LoopInfoImpl.h
68 __extension__ extern template
69 class LoopInfoBase<MachineBasicBlock, MachineLoop>;
72 class MachineLoopInfo : public MachineFunctionPass {
73 LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
74 friend class LoopBase<MachineBasicBlock, MachineLoop>;
76 void operator=(const MachineLoopInfo &) LLVM_DELETED_FUNCTION;
77 MachineLoopInfo(const MachineLoopInfo &) LLVM_DELETED_FUNCTION;
80 static char ID; // Pass identification, replacement for typeid
82 MachineLoopInfo() : MachineFunctionPass(ID) {
83 initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
86 LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
88 /// iterator/begin/end - The interface to the top-level loops in the current
91 typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
92 inline iterator begin() const { return LI.begin(); }
93 inline iterator end() const { return LI.end(); }
94 bool empty() const { return LI.empty(); }
96 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
97 /// block is in no loop (for example the entry node), null is returned.
99 inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
100 return LI.getLoopFor(BB);
103 /// operator[] - same as getLoopFor...
105 inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
106 return LI.getLoopFor(BB);
109 /// getLoopDepth - Return the loop nesting level of the specified block...
111 inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
112 return LI.getLoopDepth(BB);
115 // isLoopHeader - True if the block is a loop header node
116 inline bool isLoopHeader(MachineBasicBlock *BB) const {
117 return LI.isLoopHeader(BB);
120 /// runOnFunction - Calculate the natural loop information.
122 virtual bool runOnMachineFunction(MachineFunction &F);
124 virtual void releaseMemory() { LI.releaseMemory(); }
126 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
128 /// removeLoop - This removes the specified top-level loop from this loop info
129 /// object. The loop is not deleted, as it will presumably be inserted into
131 inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
133 /// changeLoopFor - Change the top-level loop that contains BB to the
134 /// specified loop. This should be used by transformations that restructure
135 /// the loop hierarchy tree.
136 inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
137 LI.changeLoopFor(BB, L);
140 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
141 /// list with the indicated loop.
142 inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
143 LI.changeTopLevelLoop(OldLoop, NewLoop);
146 /// addTopLevelLoop - This adds the specified loop to the collection of
148 inline void addTopLevelLoop(MachineLoop *New) {
149 LI.addTopLevelLoop(New);
152 /// removeBlock - This method completely removes BB from all data structures,
153 /// including all of the Loop objects it is nested in and our mapping from
154 /// MachineBasicBlocks to loops.
155 void removeBlock(MachineBasicBlock *BB) {
161 // Allow clients to walk the list of nested loops...
162 template <> struct GraphTraits<const MachineLoop*> {
163 typedef const MachineLoop NodeType;
164 typedef MachineLoopInfo::iterator ChildIteratorType;
166 static NodeType *getEntryNode(const MachineLoop *L) { return L; }
167 static inline ChildIteratorType child_begin(NodeType *N) {
170 static inline ChildIteratorType child_end(NodeType *N) {
175 template <> struct GraphTraits<MachineLoop*> {
176 typedef MachineLoop NodeType;
177 typedef MachineLoopInfo::iterator ChildIteratorType;
179 static NodeType *getEntryNode(MachineLoop *L) { return L; }
180 static inline ChildIteratorType child_begin(NodeType *N) {
183 static inline ChildIteratorType child_end(NodeType *N) {
188 } // End llvm namespace