llvm/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 #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(MachineBranchProbabilityInfo)
  27 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
  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::print(raw_ostream &OS,
  40                                               const Module *M) const {
  41   getBFI().print(OS, M);
  42 }
  43
  44 void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
  45     AnalysisUsage &AU) const {
  46   AU.addRequired<MachineBranchProbabilityInfo>();
  47   AU.setPreservesAll();
  48   MachineFunctionPass::getAnalysisUsage(AU);
  49 }
  50
  51 void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
  52   OwnedMBFI.reset();
  53   OwnedMLI.reset();
  54   OwnedMDT.reset();
  55 }
  56
  57 MachineBlockFrequencyInfo &
  58 LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
  59   auto *MBFI = getAnalysisIfAvailable<MachineBlockFrequencyInfo>();
  60   if (MBFI) {
  61     LLVM_DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
  62     return *MBFI;
  63   }
  64
  65   auto &MBPI = getAnalysis<MachineBranchProbabilityInfo>();
  66   auto *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
  67   auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
  68   LLVM_DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n");
  69   LLVM_DEBUG(if (MLI) dbgs() << "LoopInfo is available\n");
  70
  71   if (!MLI) {
  72     LLVM_DEBUG(dbgs() << "Building LoopInfo on the fly\n");
  73     // First create a dominator tree.
  74     LLVM_DEBUG(if (MDT) dbgs() << "DominatorTree is available\n");
  75
  76     if (!MDT) {
  77       LLVM_DEBUG(dbgs() << "Building DominatorTree on the fly\n");
  78       OwnedMDT = std::make_unique<MachineDominatorTree>();
  79       OwnedMDT->getBase().recalculate(*MF);
  80       MDT = OwnedMDT.get();
  81     }
  82
  83     // Generate LoopInfo from it.
  84     OwnedMLI = std::make_unique<MachineLoopInfo>();
  85     OwnedMLI->getBase().analyze(MDT->getBase());
  86     MLI = OwnedMLI.get();
  87   }
  88
  89   OwnedMBFI = std::make_unique<MachineBlockFrequencyInfo>();
  90   OwnedMBFI->calculate(*MF, MBPI, *MLI);
  91   return *OwnedMBFI;
  92 }
  93
  94 bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
  95     MachineFunction &F) {
  96   MF = &F;
  97   return false;
  98 }