MachineLoopInfo.cpp revision 7896c9f436a4eda5ec15e882a7505ba482a2fcd0 
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/CodeGen/MachineDominators.h"
19#include "llvm/CodeGen/Passes.h"
20using namespace llvm;
21
22#define MLB class LoopBase<MachineBasicBlock, MachineLoop>
23TEMPLATE_INSTANTIATION(MLB);
24#undef MLB
25#define MLIB class LoopInfoBase<MachineBasicBlock, MachineLoop>
26TEMPLATE_INSTANTIATION(MLIB);
27#undef MLIB
28
29char MachineLoopInfo::ID = 0;
30static RegisterPass<MachineLoopInfo>
31X("machine-loops", "Machine Natural Loop Construction", true);
32
33const PassInfo *const llvm::MachineLoopInfoID = &X;
34
35bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
36  releaseMemory();
37  LI.Calculate(getAnalysis<MachineDominatorTree>().getBase());    // Update
38  return false;
39}
40
41void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
42  AU.setPreservesAll();
43  AU.addRequired<MachineDominatorTree>();
44  MachineFunctionPass::getAnalysisUsage(AU);
45}
46
47MachineBasicBlock *MachineLoop::getTopBlock() {
48  MachineBasicBlock *TopMBB = getHeader();
49  MachineFunction::iterator Begin = TopMBB->getParent()->begin();
50  if (TopMBB != Begin) {
51    MachineBasicBlock *PriorMBB = prior(MachineFunction::iterator(TopMBB));
52    while (contains(PriorMBB)) {
53      TopMBB = PriorMBB;
54      if (TopMBB == Begin) break;
55      PriorMBB = prior(MachineFunction::iterator(TopMBB));
56    }
57  }
58  return TopMBB;
59}
60
61MachineBasicBlock *MachineLoop::getBottomBlock() {
62  MachineBasicBlock *BotMBB = getHeader();
63  MachineFunction::iterator End = BotMBB->getParent()->end();
64  if (BotMBB != prior(End)) {
65    MachineBasicBlock *NextMBB = llvm::next(MachineFunction::iterator(BotMBB));
66    while (contains(NextMBB)) {
67      BotMBB = NextMBB;
68      if (BotMBB == llvm::next(MachineFunction::iterator(BotMBB))) break;
69      NextMBB = llvm::next(MachineFunction::iterator(BotMBB));
70    }
71  }
72  return BotMBB;
73}
74