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
42 __extension__ extern template class LoopBase<MachineBasicBlock, MachineLoop>;
45 class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
49 /// getTopBlock - Return the "top" block in the loop, which is the first
50 /// block in the linear layout, ignoring any parts of the loop not
51 /// contiguous with the part the contains the header.
52 MachineBasicBlock *getTopBlock();
54 /// getBottomBlock - Return the "bottom" block in the loop, which is the last
55 /// block in the linear layout, ignoring any parts of the loop not
56 /// contiguous with the part the contains the header.
57 MachineBasicBlock *getBottomBlock();
62 friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
63 explicit MachineLoop(MachineBasicBlock *MBB)
64 : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
67 // Implementation in LoopInfoImpl.h
69 __extension__ extern template
70 class LoopInfoBase<MachineBasicBlock, MachineLoop>;
73 class MachineLoopInfo : public MachineFunctionPass {
74 LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
75 friend class LoopBase<MachineBasicBlock, MachineLoop>;
77 void operator=(const MachineLoopInfo &) = delete;
78 MachineLoopInfo(const MachineLoopInfo &) = delete;
81 static char ID; // Pass identification, replacement for typeid
83 MachineLoopInfo() : MachineFunctionPass(ID) {
84 initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
87 LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
89 /// iterator/begin/end - The interface to the top-level loops in the current
92 typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
93 inline iterator begin() const { return LI.begin(); }
94 inline iterator end() const { return LI.end(); }
95 bool empty() const { return LI.empty(); }
97 /// getLoopFor - Return the inner most loop that BB lives in. If a basic
98 /// block is in no loop (for example the entry node), null is returned.
100 inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
101 return LI.getLoopFor(BB);
104 /// operator[] - same as getLoopFor...
106 inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
107 return LI.getLoopFor(BB);
110 /// getLoopDepth - Return the loop nesting level of the specified block...
112 inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
113 return LI.getLoopDepth(BB);
116 // isLoopHeader - True if the block is a loop header node
117 inline bool isLoopHeader(MachineBasicBlock *BB) const {
118 return LI.isLoopHeader(BB);
121 /// runOnFunction - Calculate the natural loop information.
123 bool runOnMachineFunction(MachineFunction &F) override;
125 void releaseMemory() override { LI.releaseMemory(); }
127 void getAnalysisUsage(AnalysisUsage &AU) const override;
129 /// removeLoop - This removes the specified top-level loop from this loop info
130 /// object. The loop is not deleted, as it will presumably be inserted into
132 inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
134 /// changeLoopFor - Change the top-level loop that contains BB to the
135 /// specified loop. This should be used by transformations that restructure
136 /// the loop hierarchy tree.
137 inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
138 LI.changeLoopFor(BB, L);
141 /// changeTopLevelLoop - Replace the specified loop in the top-level loops
142 /// list with the indicated loop.
143 inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
144 LI.changeTopLevelLoop(OldLoop, NewLoop);
147 /// addTopLevelLoop - This adds the specified loop to the collection of
149 inline void addTopLevelLoop(MachineLoop *New) {
150 LI.addTopLevelLoop(New);
153 /// removeBlock - This method completely removes BB from all data structures,
154 /// including all of the Loop objects it is nested in and our mapping from
155 /// MachineBasicBlocks to loops.
156 void removeBlock(MachineBasicBlock *BB) {
162 // Allow clients to walk the list of nested loops...
163 template <> struct GraphTraits<const MachineLoop*> {
164 typedef const MachineLoop NodeType;
165 typedef MachineLoopInfo::iterator ChildIteratorType;
167 static NodeType *getEntryNode(const MachineLoop *L) { return L; }
168 static inline ChildIteratorType child_begin(NodeType *N) {
171 static inline ChildIteratorType child_end(NodeType *N) {
176 template <> struct GraphTraits<MachineLoop*> {
177 typedef MachineLoop NodeType;
178 typedef MachineLoopInfo::iterator ChildIteratorType;
180 static NodeType *getEntryNode(MachineLoop *L) { return L; }
181 static inline ChildIteratorType child_begin(NodeType *N) {
184 static inline ChildIteratorType child_end(NodeType *N) {
189 } // End llvm namespace