1 ///===- LazyMachineBlockFrequencyInfo.cpp - Lazy Machine Block Frequency --===// 2 /// 3 /// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 /// See https://llvm.org/LICENSE.txt for license information. 5 /// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 /// 7 ///===---------------------------------------------------------------------===// 8 /// \file 9 /// This is an alternative analysis pass to MachineBlockFrequencyInfo. The 10 /// difference is that with this pass the block frequencies are not computed 11 /// when the analysis pass is executed but rather when the BFI result is 12 /// explicitly requested by the analysis client. 13 /// 14 ///===---------------------------------------------------------------------===// 15 16 #include "llvm/CodeGen/LazyMachineBlockFrequencyInfo.h" 17 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h" 18 #include "llvm/InitializePasses.h" 19 20 using namespace llvm; 21 22 #define DEBUG_TYPE "lazy-machine-block-freq" 23 24 INITIALIZE_PASS_BEGIN(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE, 25 "Lazy Machine Block Frequency Analysis", true, true) 26 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfoWrapperPass) 27 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfoWrapperPass) 28 INITIALIZE_PASS_END(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE, 29 "Lazy Machine Block Frequency Analysis", true, true) 30 31 char LazyMachineBlockFrequencyInfoPass::ID = 0; 32 33 LazyMachineBlockFrequencyInfoPass::LazyMachineBlockFrequencyInfoPass() 34 : MachineFunctionPass(ID) { 35 initializeLazyMachineBlockFrequencyInfoPassPass( 36 *PassRegistry::getPassRegistry()); 37 } 38 39 void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage( 40 AnalysisUsage &AU) const { 41 AU.addRequired<MachineBranchProbabilityInfoWrapperPass>(); 42 AU.setPreservesAll(); 43 MachineFunctionPass::getAnalysisUsage(AU); 44 } 45 46 void LazyMachineBlockFrequencyInfoPass::releaseMemory() { 47 OwnedMBFI.reset(); 48 OwnedMLI.reset(); 49 OwnedMDT.reset(); 50 } 51 52 MachineBlockFrequencyInfo & 53 LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const { 54 auto *MBFIWrapper = 55 getAnalysisIfAvailable<MachineBlockFrequencyInfoWrapperPass>(); 56 if (MBFIWrapper) { 57 LLVM_DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n"); 58 return MBFIWrapper->getMBFI(); 59 } 60 61 auto &MBPI = getAnalysis<MachineBranchProbabilityInfoWrapperPass>().getMBPI(); 62 auto *MLIWrapper = getAnalysisIfAvailable<MachineLoopInfoWrapperPass>(); 63 auto *MLI = MLIWrapper ? &MLIWrapper->getLI() : nullptr; 64 auto *MDTWrapper = getAnalysisIfAvailable<MachineDominatorTreeWrapperPass>(); 65 auto *MDT = MDTWrapper ? &MDTWrapper->getDomTree() : nullptr; 66 LLVM_DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n"); 67 LLVM_DEBUG(if (MLI) dbgs() << "LoopInfo is available\n"); 68 69 if (!MLI) { 70 LLVM_DEBUG(dbgs() << "Building LoopInfo on the fly\n"); 71 // First create a dominator tree. 72 LLVM_DEBUG(if (MDT) dbgs() << "DominatorTree is available\n"); 73 74 if (!MDT) { 75 LLVM_DEBUG(dbgs() << "Building DominatorTree on the fly\n"); 76 OwnedMDT = std::make_unique<MachineDominatorTree>(); 77 OwnedMDT->getBase().recalculate(*MF); 78 MDT = OwnedMDT.get(); 79 } 80 81 // Generate LoopInfo from it. 82 OwnedMLI = std::make_unique<MachineLoopInfo>(); 83 OwnedMLI->analyze(MDT->getBase()); 84 MLI = OwnedMLI.get(); 85 } 86 87 OwnedMBFI = std::make_unique<MachineBlockFrequencyInfo>(); 88 OwnedMBFI->calculate(*MF, MBPI, *MLI); 89 return *OwnedMBFI; 90 } 91 92 bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction( 93 MachineFunction &F) { 94 MF = &F; 95 return false; 96 } 97