llvm/lib/CodeGen/TailDuplication.cpp

   1 //===- TailDuplication.cpp - Duplicate blocks into predecessors' tails ----===//
   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 /// \file This pass duplicates basic blocks ending in unconditional branches
  10 /// into the tails of their predecessors, using the TailDuplicator utility
  11 /// class.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Analysis/ProfileSummaryInfo.h"
  16 #include "llvm/CodeGen/LazyMachineBlockFrequencyInfo.h"
  17 #include "llvm/CodeGen/MBFIWrapper.h"
  18 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineFunctionPass.h"
  21 #include "llvm/CodeGen/TailDuplicator.h"
  22 #include "llvm/InitializePasses.h"
  23 #include "llvm/Pass.h"
  24 #include "llvm/PassRegistry.h"
  25
  26 using namespace llvm;
  27
  28 #define DEBUG_TYPE "tailduplication"
  29
  30 namespace {
  31
  32 class TailDuplicateBase : public MachineFunctionPass {
  33   TailDuplicator Duplicator;
  34   std::unique_ptr<MBFIWrapper> MBFIW;
  35   bool PreRegAlloc;
  36 public:
  37   TailDuplicateBase(char &PassID, bool PreRegAlloc)
  38     : MachineFunctionPass(PassID), PreRegAlloc(PreRegAlloc) {}
  39
  40   bool runOnMachineFunction(MachineFunction &MF) override;
  41
  42   void getAnalysisUsage(AnalysisUsage &AU) const override {
  43     AU.addRequired<MachineBranchProbabilityInfo>();
  44     AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
  45     AU.addRequired<ProfileSummaryInfoWrapperPass>();
  46     MachineFunctionPass::getAnalysisUsage(AU);
  47   }
  48 };
  49
  50 class TailDuplicate : public TailDuplicateBase {
  51 public:
  52   static char ID;
  53   TailDuplicate() : TailDuplicateBase(ID, false) {
  54     initializeTailDuplicatePass(*PassRegistry::getPassRegistry());
  55   }
  56 };
  57
  58 class EarlyTailDuplicate : public TailDuplicateBase {
  59 public:
  60   static char ID;
  61   EarlyTailDuplicate() : TailDuplicateBase(ID, true) {
  62     initializeEarlyTailDuplicatePass(*PassRegistry::getPassRegistry());
  63   }
  64
  65   MachineFunctionProperties getClearedProperties() const override {
  66     return MachineFunctionProperties()
  67       .set(MachineFunctionProperties::Property::NoPHIs);
  68   }
  69 };
  70
  71 } // end anonymous namespace
  72
  73 char TailDuplicate::ID;
  74 char EarlyTailDuplicate::ID;
  75
  76 char &llvm::TailDuplicateID = TailDuplicate::ID;
  77 char &llvm::EarlyTailDuplicateID = EarlyTailDuplicate::ID;
  78
  79 INITIALIZE_PASS(TailDuplicate, DEBUG_TYPE, "Tail Duplication", false, false)
  80 INITIALIZE_PASS(EarlyTailDuplicate, "early-tailduplication",
  81                 "Early Tail Duplication", false, false)
  82
  83 bool TailDuplicateBase::runOnMachineFunction(MachineFunction &MF) {
  84   if (skipFunction(MF.getFunction()))
  85     return false;
  86
  87   auto MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
  88   auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
  89   auto *MBFI = (PSI && PSI->hasProfileSummary()) ?
  90                &getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI() :
  91                nullptr;
  92   if (MBFI)
  93     MBFIW = std::make_unique<MBFIWrapper>(*MBFI);
  94   Duplicator.initMF(MF, PreRegAlloc, MBPI, MBFI ? MBFIW.get() : nullptr, PSI,
  95                     /*LayoutMode=*/false);
  96
  97   bool MadeChange = false;
  98   while (Duplicator.tailDuplicateBlocks())
  99     MadeChange = true;
 100
 101   return MadeChange;
 102 }