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 /// Return the "top" block in the loop, which is the first block in the linear
48 /// layout, ignoring any parts of the loop not contiguous with the part that
49 /// contains the header.
50 MachineBasicBlock *getTopBlock();
52 /// Return the "bottom" block in the loop, which is the last block in the
53 /// linear layout, ignoring any parts of the loop not contiguous with the part
54 /// that 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 /// The iterator interface to the top-level loops in the current function.
85 typedef LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator iterator;
86 inline iterator begin() const { return LI.begin(); }
87 inline iterator end() const { return LI.end(); }
88 bool empty() const { return LI.empty(); }
90 /// Return the innermost loop that BB lives in. If a basic block is in no loop
91 /// (for example the entry node), null is returned.
92 inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
93 return LI.getLoopFor(BB);
96 /// Same as getLoopFor.
97 inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
98 return LI.getLoopFor(BB);
101 /// Return the loop nesting level of the specified block.
102 inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
103 return LI.getLoopDepth(BB);
106 /// True if the block is a loop header node.
107 inline bool isLoopHeader(const MachineBasicBlock *BB) const {
108 return LI.isLoopHeader(BB);
111 /// Calculate the natural loop information.
112 bool runOnMachineFunction(MachineFunction &F) override;
114 void releaseMemory() override { LI.releaseMemory(); }
116 void getAnalysisUsage(AnalysisUsage &AU) const override;
118 /// This removes the specified top-level loop from this loop info object. The
119 /// loop is not deleted, as it will presumably be inserted into another loop.
120 inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
122 /// Change the top-level loop that contains BB to the specified loop. This
123 /// should be used by transformations that restructure the loop hierarchy
125 inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
126 LI.changeLoopFor(BB, L);
129 /// Replace the specified loop in the top-level loops list with the indicated
131 inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
132 LI.changeTopLevelLoop(OldLoop, NewLoop);
135 /// This adds the specified loop to the collection of top-level loops.
136 inline void addTopLevelLoop(MachineLoop *New) {
137 LI.addTopLevelLoop(New);
140 /// This method completely removes BB from all data structures, including all
141 /// of the Loop objects it is nested in and our mapping from
142 /// MachineBasicBlocks to loops.
143 void removeBlock(MachineBasicBlock *BB) {
149 // Allow clients to walk the list of nested loops...
150 template <> struct GraphTraits<const MachineLoop*> {
151 typedef const MachineLoop NodeType;
152 typedef MachineLoopInfo::iterator ChildIteratorType;
154 static NodeType *getEntryNode(const MachineLoop *L) { return L; }
155 static inline ChildIteratorType child_begin(NodeType *N) {
158 static inline ChildIteratorType child_end(NodeType *N) {
163 template <> struct GraphTraits<MachineLoop*> {
164 typedef MachineLoop NodeType;
165 typedef MachineLoopInfo::iterator ChildIteratorType;
167 static NodeType *getEntryNode(MachineLoop *L) { return L; }
168 static inline ChildIteratorType child_begin(NodeType *N) {
171 static inline ChildIteratorType child_end(NodeType *N) {
176 } // End llvm namespace