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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 #include "llvm/Support/raw_ostream.h"
     23 using namespace llvm;
     24 
     25 // Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
     26 template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
     27 template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
     28 
     29 char MachineLoopInfo::ID = 0;
     30 INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
     31                 "Machine Natural Loop Construction", true, true)
     32 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
     33 INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
     34                 "Machine Natural Loop Construction", true, true)
     35 
     36 char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
     37 
     38 bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
     39   releaseMemory();
     40   LI.analyze(getAnalysis<MachineDominatorTree>().getBase());
     41   return false;
     42 }
     43 
     44 void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
     45   AU.setPreservesAll();
     46   AU.addRequired<MachineDominatorTree>();
     47   MachineFunctionPass::getAnalysisUsage(AU);
     48 }
     49 
     50 MachineBasicBlock *MachineLoop::getTopBlock() {
     51   MachineBasicBlock *TopMBB = getHeader();
     52   MachineFunction::iterator Begin = TopMBB->getParent()->begin();
     53   if (TopMBB->getIterator() != Begin) {
     54     MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator());
     55     while (contains(PriorMBB)) {
     56       TopMBB = PriorMBB;
     57       if (TopMBB->getIterator() == Begin)
     58         break;
     59       PriorMBB = &*std::prev(TopMBB->getIterator());
     60     }
     61   }
     62   return TopMBB;
     63 }
     64 
     65 MachineBasicBlock *MachineLoop::getBottomBlock() {
     66   MachineBasicBlock *BotMBB = getHeader();
     67   MachineFunction::iterator End = BotMBB->getParent()->end();
     68   if (BotMBB->getIterator() != std::prev(End)) {
     69     MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator());
     70     while (contains(NextMBB)) {
     71       BotMBB = NextMBB;
     72       if (BotMBB == &*std::next(BotMBB->getIterator()))
     73         break;
     74       NextMBB = &*std::next(BotMBB->getIterator());
     75     }
     76   }
     77   return BotMBB;
     78 }
     79 
     80 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
     81 LLVM_DUMP_METHOD void MachineLoop::dump() const {
     82   print(dbgs());
     83 }
     84 #endif
     85