lib/Analysis/LazyBranchProbabilityInfo.cpp

   1 //===- LazyBranchProbabilityInfo.cpp - Lazy Branch Probability 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 BranchProbabilityInfoWrapperPass.
  10 // The difference is that with this pass the branch probabilities are not
  11 // computed when the analysis pass is executed but rather when the BPI results
  12 // is explicitly requested by the analysis client.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/Analysis/LazyBranchProbabilityInfo.h"
  17 #include "llvm/Analysis/LoopInfo.h"
  18 #include "llvm/Analysis/TargetLibraryInfo.h"
  19 #include "llvm/IR/Dominators.h"
  20
  21 using namespace llvm;
  22
  23 #define DEBUG_TYPE "lazy-branch-prob"
  24
  25 INITIALIZE_PASS_BEGIN(LazyBranchProbabilityInfoPass, DEBUG_TYPE,
  26                       "Lazy Branch Probability Analysis", true, true)
  27 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
  28 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
  29 INITIALIZE_PASS_END(LazyBranchProbabilityInfoPass, DEBUG_TYPE,
  30                     "Lazy Branch Probability Analysis", true, true)
  31
  32 char LazyBranchProbabilityInfoPass::ID = 0;
  33
  34 LazyBranchProbabilityInfoPass::LazyBranchProbabilityInfoPass()
  35     : FunctionPass(ID) {
  36   initializeLazyBranchProbabilityInfoPassPass(*PassRegistry::getPassRegistry());
  37 }
  38
  39 void LazyBranchProbabilityInfoPass::print(raw_ostream &OS,
  40                                           const Module *) const {
  41   LBPI->getCalculated().print(OS);
  42 }
  43
  44 void LazyBranchProbabilityInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
  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.addRequired<DominatorTreeWrapperPass>();
  49   AU.addRequired<LoopInfoWrapperPass>();
  50   AU.addRequired<TargetLibraryInfoWrapperPass>();
  51   AU.setPreservesAll();
  52 }
  53
  54 void LazyBranchProbabilityInfoPass::releaseMemory() { LBPI.reset(); }
  55
  56 bool LazyBranchProbabilityInfoPass::runOnFunction(Function &F) {
  57   LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
  58   TargetLibraryInfo &TLI =
  59       getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
  60   LBPI = std::make_unique<LazyBranchProbabilityInfo>(&F, &LI, &TLI);
  61   return false;
  62 }
  63
  64 void LazyBranchProbabilityInfoPass::getLazyBPIAnalysisUsage(AnalysisUsage &AU) {
  65   AU.addRequired<LazyBranchProbabilityInfoPass>();
  66   AU.addRequired<LoopInfoWrapperPass>();
  67   AU.addRequired<TargetLibraryInfoWrapperPass>();
  68 }
  69
  70 void llvm::initializeLazyBPIPassPass(PassRegistry &Registry) {
  71   INITIALIZE_PASS_DEPENDENCY(LazyBranchProbabilityInfoPass);
  72   INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
  73   INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass);
  74 }