lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp

   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
  18 using namespace llvm;
  19
  20 #define DEBUG_TYPE "lazy-machine-block-freq"
  21
  22 INITIALIZE_PASS_BEGIN(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE,
  23                       "Lazy Machine Block Frequency Analysis", true, true)
  24 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
  25 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
  26 INITIALIZE_PASS_END(LazyMachineBlockFrequencyInfoPass, DEBUG_TYPE,
  27                     "Lazy Machine Block Frequency Analysis", true, true)
  28
  29 char LazyMachineBlockFrequencyInfoPass::ID = 0;
  30
  31 LazyMachineBlockFrequencyInfoPass::LazyMachineBlockFrequencyInfoPass()
  32     : MachineFunctionPass(ID) {
  33   initializeLazyMachineBlockFrequencyInfoPassPass(
  34       *PassRegistry::getPassRegistry());
  35 }
  36
  37 void LazyMachineBlockFrequencyInfoPass::print(raw_ostream &OS,
  38                                               const Module *M) const {
  39   getBFI().print(OS, M);
  40 }
  41
  42 void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
  43     AnalysisUsage &AU) const {
  44   AU.addRequired<MachineBranchProbabilityInfo>();
  45   AU.setPreservesAll();
  46   MachineFunctionPass::getAnalysisUsage(AU);
  47 }
  48
  49 void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
  50   OwnedMBFI.reset();
  51   OwnedMLI.reset();
  52   OwnedMDT.reset();
  53 }
  54
  55 MachineBlockFrequencyInfo &
  56 LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
  57   auto *MBFI = getAnalysisIfAvailable<MachineBlockFrequencyInfo>();
  58   if (MBFI) {
  59     LLVM_DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
  60     return *MBFI;
  61   }
  62
  63   auto &MBPI = getAnalysis<MachineBranchProbabilityInfo>();
  64   auto *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
  65   auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
  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->getBase().analyze(MDT->getBase());
  84     MLI = OwnedMLI.get();
  85   }
  86
  87   OwnedMBFI = std::make_unique<MachineBlockFrequencyInfo>();
  88   OwnedMBFI->calculate(*MF, MBPI, *MLI);
  89   return *OwnedMBFI.get();
  90 }
  91
  92 bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
  93     MachineFunction &F) {
  94   MF = &F;
  95   return false;
  96 }