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/MachineBasicBlock.h"
35 #include "llvm/CodeGen/MachineFunctionPass.h"
39 // Implementation in LoopInfoImpl.h
41 extern template class LoopBase<MachineBasicBlock, MachineLoop>;
43 class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
47 /// getTopBlock - Return the "top" block in the loop, which is the first
48 /// block in the linear layout, ignoring any parts of the loop not
49 /// contiguous with the part the contains the header.
50 MachineBasicBlock *getTopBlock();
52 /// getBottomBlock - Return the "bottom" block in the loop, which is the last
53 /// block in the linear layout, ignoring any parts of the loop not
54 /// contiguous with the part the contains the header.
55 MachineBasicBlock *getBottomBlock();
60 friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
61 explicit MachineLoop(MachineBasicBlock *MBB)
62 : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
65 // Implementation in LoopInfoImpl.h
66 extern template class LoopInfoBase<MachineBasicBlock, MachineLoop>;
68 class MachineLoopInfo : public MachineFunctionPass {
69 LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
70 friend class LoopBase<MachineBasicBlock, MachineLoop>;
72 void operator=(const MachineLoopInfo &) = delete;
73 MachineLoopInfo(const MachineLoopInfo &) = delete;
76 static char ID; // Pass identification, replacement for typeid
78 MachineLoopInfo() : MachineFunctionPass(ID) {
79 initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
82 LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
84 /// iterator/begin/end - The interface to the top-level loops in the current
87 typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
88 inline iterator begin() const { return LI.begin(); }
89 inline iterator end() const { return LI.end(); }
90 bool empty() const { return LI.empty(); }
92 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
93 /// block is in no loop (for example the entry node), null is returned.
95 inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
96 return LI.getLoopFor(BB);
99 /// operator[] - same as getLoopFor...
101 inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
102 return LI.getLoopFor(BB);
105 /// getLoopDepth - Return the loop nesting level of the specified block...
107 inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
108 return LI.getLoopDepth(BB);
111 // isLoopHeader - True if the block is a loop header node
112 inline bool isLoopHeader(const MachineBasicBlock *BB) const {
113 return LI.isLoopHeader(BB);
116 /// runOnFunction - Calculate the natural loop information.
118 bool runOnMachineFunction(MachineFunction &F) override;
120 void releaseMemory() override { LI.releaseMemory(); }
122 void getAnalysisUsage(AnalysisUsage &AU) const override;
124 /// removeLoop - This removes the specified top-level loop from this loop info
125 /// object. The loop is not deleted, as it will presumably be inserted into
127 inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
129 /// changeLoopFor - Change the top-level loop that contains BB to the
130 /// specified loop. This should be used by transformations that restructure
131 /// the loop hierarchy tree.
132 inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
133 LI.changeLoopFor(BB, L);
136 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
137 /// list with the indicated loop.
138 inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
139 LI.changeTopLevelLoop(OldLoop, NewLoop);
142 /// addTopLevelLoop - This adds the specified loop to the collection of
144 inline void addTopLevelLoop(MachineLoop *New) {
145 LI.addTopLevelLoop(New);
148 /// removeBlock - This method completely removes BB from all data structures,
149 /// including all of the Loop objects it is nested in and our mapping from
150 /// MachineBasicBlocks to loops.
151 void removeBlock(MachineBasicBlock *BB) {
157 // Allow clients to walk the list of nested loops...
158 template <> struct GraphTraits<const MachineLoop*> {
159 typedef const MachineLoop NodeType;
160 typedef MachineLoopInfo::iterator ChildIteratorType;
162 static NodeType *getEntryNode(const MachineLoop *L) { return L; }
163 static inline ChildIteratorType child_begin(NodeType *N) {
166 static inline ChildIteratorType child_end(NodeType *N) {
171 template <> struct GraphTraits<MachineLoop*> {
172 typedef MachineLoop NodeType;
173 typedef MachineLoopInfo::iterator ChildIteratorType;
175 static NodeType *getEntryNode(MachineLoop *L) { return L; }
176 static inline ChildIteratorType child_begin(NodeType *N) {
179 static inline ChildIteratorType child_end(NodeType *N) {
184 } // End llvm namespace