130 lines
4.1 KiB
C++
130 lines
4.1 KiB
C++
//===- MachineLoopInfo.cpp - Natural Loop Calculator ----------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the MachineLoopInfo class that is used to identify natural
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// loops and determine the loop depth of various nodes of the CFG. Note that
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// the loops identified may actually be several natural loops that share the
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// same header node... not just a single natural loop.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/Analysis/LoopInfoImpl.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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// Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops.
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template class llvm::LoopBase<MachineBasicBlock, MachineLoop>;
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template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>;
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char MachineLoopInfo::ID = 0;
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INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",
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"Machine Natural Loop Construction", true, true)
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INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
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INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",
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"Machine Natural Loop Construction", true, true)
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char &llvm::MachineLoopInfoID = MachineLoopInfo::ID;
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bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) {
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releaseMemory();
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LI.analyze(getAnalysis<MachineDominatorTree>().getBase());
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return false;
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}
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void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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AU.addRequired<MachineDominatorTree>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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MachineBasicBlock *MachineLoop::getTopBlock() {
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MachineBasicBlock *TopMBB = getHeader();
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MachineFunction::iterator Begin = TopMBB->getParent()->begin();
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if (TopMBB->getIterator() != Begin) {
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MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator());
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while (contains(PriorMBB)) {
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TopMBB = PriorMBB;
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if (TopMBB->getIterator() == Begin)
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break;
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PriorMBB = &*std::prev(TopMBB->getIterator());
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}
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}
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return TopMBB;
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}
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MachineBasicBlock *MachineLoop::getBottomBlock() {
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MachineBasicBlock *BotMBB = getHeader();
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MachineFunction::iterator End = BotMBB->getParent()->end();
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if (BotMBB->getIterator() != std::prev(End)) {
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MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator());
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while (contains(NextMBB)) {
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BotMBB = NextMBB;
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if (BotMBB == &*std::next(BotMBB->getIterator()))
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break;
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NextMBB = &*std::next(BotMBB->getIterator());
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}
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}
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return BotMBB;
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}
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MachineBasicBlock *MachineLoop::findLoopControlBlock() {
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if (MachineBasicBlock *Latch = getLoopLatch()) {
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if (isLoopExiting(Latch))
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return Latch;
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else
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return getExitingBlock();
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}
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return nullptr;
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}
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MachineBasicBlock *
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MachineLoopInfo::findLoopPreheader(MachineLoop *L,
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bool SpeculativePreheader) const {
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if (MachineBasicBlock *PB = L->getLoopPreheader())
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return PB;
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if (!SpeculativePreheader)
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return nullptr;
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MachineBasicBlock *HB = L->getHeader(), *LB = L->getLoopLatch();
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if (HB->pred_size() != 2 || HB->hasAddressTaken())
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return nullptr;
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// Find the predecessor of the header that is not the latch block.
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MachineBasicBlock *Preheader = nullptr;
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for (MachineBasicBlock *P : HB->predecessors()) {
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if (P == LB)
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continue;
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// Sanity.
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if (Preheader)
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return nullptr;
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Preheader = P;
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}
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// Check if the preheader candidate is a successor of any other loop
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// headers. We want to avoid having two loop setups in the same block.
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for (MachineBasicBlock *S : Preheader->successors()) {
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if (S == HB)
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continue;
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MachineLoop *T = getLoopFor(S);
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if (T && T->getHeader() == S)
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return nullptr;
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}
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return Preheader;
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void MachineLoop::dump() const {
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print(dbgs());
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}
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#endif
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