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c9b1e25493
The primary advantage is that loop optimizations will be applied in a stable order. This helps debugging and unit test creation. It is also a better overall implementation without pathologically bad performance on deep functions. On large functions (llvm-stress --size=200000 | opt -loops) Before: 0.1263s After: 0.0225s On deep functions (after tweaking llvm-stress, thanks Nadav): Before: 0.2281s After: 0.0227s See r158790 for more comments. The loop tree is now consistently generated in forward order, but loop passes are applied in reverse order over the program. If we have a loop optimization that prefers forward order, that can easily be achieved by adding a different type of LoopPassManager. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159183 91177308-0d34-0410-b5e6-96231b3b80d8
80 lines
2.8 KiB
C++
80 lines
2.8 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/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Analysis/LoopInfoImpl.h"
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#include "llvm/Support/Debug.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 != Begin) {
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MachineBasicBlock *PriorMBB = prior(MachineFunction::iterator(TopMBB));
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while (contains(PriorMBB)) {
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TopMBB = PriorMBB;
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if (TopMBB == Begin) break;
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PriorMBB = prior(MachineFunction::iterator(TopMBB));
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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 != prior(End)) {
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MachineBasicBlock *NextMBB = llvm::next(MachineFunction::iterator(BotMBB));
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while (contains(NextMBB)) {
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BotMBB = NextMBB;
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if (BotMBB == llvm::next(MachineFunction::iterator(BotMBB))) break;
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NextMBB = llvm::next(MachineFunction::iterator(BotMBB));
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}
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}
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return BotMBB;
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}
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void MachineLoop::dump() const {
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print(dbgs());
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}
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