MachineLoopInfo.cpp revision 4c5e43da7792f75567b693105cc53e3f1992ad98 
1//===- MachineLoopInfo.cpp - Natural Loop Calculator ----------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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// the loops identified may actually be several natural loops that share the
13// same header node... not just a single natural loop.
14//
15//===----------------------------------------------------------------------===//
16
17#include "llvm/CodeGen/MachineLoopInfo.h"
18#include "llvm/Analysis/LoopInfoImpl.h"
19#include "llvm/CodeGen/MachineDominators.h"
20#include "llvm/CodeGen/Passes.h"
21#include "llvm/Support/Debug.h"
22#include "llvm/Support/raw_ostream.h"
23using namespace llvm;
24
25// Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
26template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
27template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
28
29char MachineLoopInfo::ID = 0;
30INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
31                "Machine Natural Loop Construction", true, true)
32INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
33INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
34                "Machine Natural Loop Construction", true, true)
35
36char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
37
38bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
39  releaseMemory();
40  LI.Analyze(getAnalysis<MachineDominatorTree>().getBase());
41  return false;
42}
43
44void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
45  AU.setPreservesAll();
46  AU.addRequired<MachineDominatorTree>();
47  MachineFunctionPass::getAnalysisUsage(AU);
48}
49
50MachineBasicBlock *MachineLoop::getTopBlock() {
51  MachineBasicBlock *TopMBB = getHeader();
52  MachineFunction::iterator Begin = TopMBB->getParent()->begin();
53  if (TopMBB != Begin) {
54    MachineBasicBlock *PriorMBB = std::prev(MachineFunction::iterator(TopMBB));
55    while (contains(PriorMBB)) {
56      TopMBB = PriorMBB;
57      if (TopMBB == Begin) break;
58      PriorMBB = std::prev(MachineFunction::iterator(TopMBB));
59    }
60  }
61  return TopMBB;
62}
63
64MachineBasicBlock *MachineLoop::getBottomBlock() {
65  MachineBasicBlock *BotMBB = getHeader();
66  MachineFunction::iterator End = BotMBB->getParent()->end();
67  if (BotMBB != std::prev(End)) {
68    MachineBasicBlock *NextMBB = std::next(MachineFunction::iterator(BotMBB));
69    while (contains(NextMBB)) {
70      BotMBB = NextMBB;
71      if (BotMBB == std::next(MachineFunction::iterator(BotMBB))) break;
72      NextMBB = std::next(MachineFunction::iterator(BotMBB));
73    }
74  }
75  return BotMBB;
76}
77
78#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
79void MachineLoop::dump() const {
80  print(dbgs());
81}
82#endif
83