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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"
20 #include "llvm/Support/Debug.h"
21 using namespace llvm;
22 
23 namespace llvm {
24 #define MLB class LoopBase<MachineBasicBlock, MachineLoop>
25 TEMPLATE_INSTANTIATION(MLB);
26 #undef MLB
27 #define MLIB class LoopInfoBase<MachineBasicBlock, MachineLoop>
28 TEMPLATE_INSTANTIATION(MLIB);
29 #undef MLIB
30 }
31 
32 char MachineLoopInfo::ID = 0;
33 INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
34                 "Machine Natural Loop Construction", true, true)
35 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
36 INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
37                 "Machine Natural Loop Construction", true, true)
38 
39 char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
40 
runOnMachineFunction(MachineFunction &)41 bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
42   releaseMemory();
43   LI.Calculate(getAnalysis<MachineDominatorTree>().getBase());    // Update
44   return false;
45 }
46 
getAnalysisUsage(AnalysisUsage & AU) const47 void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
48   AU.setPreservesAll();
49   AU.addRequired<MachineDominatorTree>();
50   MachineFunctionPass::getAnalysisUsage(AU);
51 }
52 
getTopBlock()53 MachineBasicBlock *MachineLoop::getTopBlock() {
54   MachineBasicBlock *TopMBB = getHeader();
55   MachineFunction::iterator Begin = TopMBB->getParent()->begin();
56   if (TopMBB != Begin) {
57     MachineBasicBlock *PriorMBB = prior(MachineFunction::iterator(TopMBB));
58     while (contains(PriorMBB)) {
59       TopMBB = PriorMBB;
60       if (TopMBB == Begin) break;
61       PriorMBB = prior(MachineFunction::iterator(TopMBB));
62     }
63   }
64   return TopMBB;
65 }
66 
getBottomBlock()67 MachineBasicBlock *MachineLoop::getBottomBlock() {
68   MachineBasicBlock *BotMBB = getHeader();
69   MachineFunction::iterator End = BotMBB->getParent()->end();
70   if (BotMBB != prior(End)) {
71     MachineBasicBlock *NextMBB = llvm::next(MachineFunction::iterator(BotMBB));
72     while (contains(NextMBB)) {
73       BotMBB = NextMBB;
74       if (BotMBB == llvm::next(MachineFunction::iterator(BotMBB))) break;
75       NextMBB = llvm::next(MachineFunction::iterator(BotMBB));
76     }
77   }
78   return BotMBB;
79 }
80 
dump() const81 void MachineLoop::dump() const {
82   print(dbgs());
83 }
84