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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/Analysis/LoopInfoImpl.h"
     19 #include "llvm/CodeGen/MachineDominators.h"
     20 #include "llvm/CodeGen/Passes.h"
     21 #include "llvm/Support/Debug.h"
     22 using namespace llvm;
     23 
     24 // Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
     25 template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
     26 template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
     27 
     28 char MachineLoopInfo::ID = 0;
     29 INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
     30                 "Machine Natural Loop Construction", true, true)
     31 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
     32 INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
     33                 "Machine Natural Loop Construction", true, true)
     34 
     35 char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
     36 
     37 bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
     38   releaseMemory();
     39   LI.Analyze(getAnalysis<MachineDominatorTree>().getBase());
     40   return false;
     41 }
     42 
     43 void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
     44   AU.setPreservesAll();
     45   AU.addRequired<MachineDominatorTree>();
     46   MachineFunctionPass::getAnalysisUsage(AU);
     47 }
     48 
     49 MachineBasicBlock *MachineLoop::getTopBlock() {
     50   MachineBasicBlock *TopMBB = getHeader();
     51   MachineFunction::iterator Begin = TopMBB->getParent()->begin();
     52   if (TopMBB != Begin) {
     53     MachineBasicBlock *PriorMBB = std::prev(MachineFunction::iterator(TopMBB));
     54     while (contains(PriorMBB)) {
     55       TopMBB = PriorMBB;
     56       if (TopMBB == Begin) break;
     57       PriorMBB = std::prev(MachineFunction::iterator(TopMBB));
     58     }
     59   }
     60   return TopMBB;
     61 }
     62 
     63 MachineBasicBlock *MachineLoop::getBottomBlock() {
     64   MachineBasicBlock *BotMBB = getHeader();
     65   MachineFunction::iterator End = BotMBB->getParent()->end();
     66   if (BotMBB != std::prev(End)) {
     67     MachineBasicBlock *NextMBB = std::next(MachineFunction::iterator(BotMBB));
     68     while (contains(NextMBB)) {
     69       BotMBB = NextMBB;
     70       if (BotMBB == std::next(MachineFunction::iterator(BotMBB))) break;
     71       NextMBB = std::next(MachineFunction::iterator(BotMBB));
     72     }
     73   }
     74   return BotMBB;
     75 }
     76 
     77 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
     78 void MachineLoop::dump() const {
     79   print(dbgs());
     80 }
     81 #endif
     82