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      1 //===- LazyBlockFrequencyInfo.cpp - Lazy Block Frequency Analysis ---------===//
      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 //
      9 // This is an alternative analysis pass to BlockFrequencyInfoWrapperPass.  The
     10 // difference is that with this pass the block frequencies are not computed when
     11 // the analysis pass is executed but rather when the BFI result is explicitly
     12 // requested by the analysis client.
     13 //
     14 //===----------------------------------------------------------------------===//
     15 
     16 #include "llvm/Analysis/LazyBlockFrequencyInfo.h"
     17 #include "llvm/Analysis/LazyBranchProbabilityInfo.h"
     18 #include "llvm/Analysis/LoopInfo.h"
     19 #include "llvm/IR/Dominators.h"
     20 #include "llvm/InitializePasses.h"
     21 
     22 using namespace llvm;
     23 
     24 #define DEBUG_TYPE "lazy-block-freq"
     25 
     26 INITIALIZE_PASS_BEGIN(LazyBlockFrequencyInfoPass, DEBUG_TYPE,
     27                       "Lazy Block Frequency Analysis", true, true)
     28 INITIALIZE_PASS_DEPENDENCY(LazyBPIPass)
     29 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
     30 INITIALIZE_PASS_END(LazyBlockFrequencyInfoPass, DEBUG_TYPE,
     31                     "Lazy Block Frequency Analysis", true, true)
     32 
     33 char LazyBlockFrequencyInfoPass::ID = 0;
     34 
     35 LazyBlockFrequencyInfoPass::LazyBlockFrequencyInfoPass() : FunctionPass(ID) {
     36   initializeLazyBlockFrequencyInfoPassPass(*PassRegistry::getPassRegistry());
     37 }
     38 
     39 void LazyBlockFrequencyInfoPass::print(raw_ostream &OS, const Module *) const {
     40   LBFI.getCalculated().print(OS);
     41 }
     42 
     43 void LazyBlockFrequencyInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
     44   LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU);
     45   // We require DT so it's available when LI is available. The LI updating code
     46   // asserts that DT is also present so if we don't make sure that we have DT
     47   // here, that assert will trigger.
     48   AU.addRequiredTransitive<DominatorTreeWrapperPass>();
     49   AU.addRequiredTransitive<LoopInfoWrapperPass>();
     50   AU.setPreservesAll();
     51 }
     52 
     53 void LazyBlockFrequencyInfoPass::releaseMemory() { LBFI.releaseMemory(); }
     54 
     55 bool LazyBlockFrequencyInfoPass::runOnFunction(Function &F) {
     56   auto &BPIPass = getAnalysis<LazyBranchProbabilityInfoPass>();
     57   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
     58   LBFI.setAnalysis(&F, &BPIPass, &LI);
     59   return false;
     60 }
     61 
     62 void LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AnalysisUsage &AU) {
     63   LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AU);
     64   AU.addRequiredTransitive<LazyBlockFrequencyInfoPass>();
     65   AU.addRequiredTransitive<LoopInfoWrapperPass>();
     66 }
     67 
     68 void llvm::initializeLazyBFIPassPass(PassRegistry &Registry) {
     69   initializeLazyBPIPassPass(Registry);
     70   INITIALIZE_PASS_DEPENDENCY(LazyBlockFrequencyInfoPass);
     71   INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
     72 }
     73