TailDuplication.cpp revision 360784 
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/MachineBranchProbabilityInfo.h"
18#include "llvm/CodeGen/MachineFunction.h"
19#include "llvm/CodeGen/MachineFunctionPass.h"
20#include "llvm/CodeGen/MachineRegisterInfo.h"
21#include "llvm/CodeGen/Passes.h"
22#include "llvm/CodeGen/TailDuplicator.h"
23#include "llvm/InitializePasses.h"
24#include "llvm/Pass.h"
25
26using namespace llvm;
27
28#define DEBUG_TYPE "tailduplication"
29
30namespace {
31
32class TailDuplicateBase : public MachineFunctionPass {
33  TailDuplicator Duplicator;
34  bool PreRegAlloc;
35public:
36  TailDuplicateBase(char &PassID, bool PreRegAlloc)
37    : MachineFunctionPass(PassID), PreRegAlloc(PreRegAlloc) {}
38
39  bool runOnMachineFunction(MachineFunction &MF) override;
40
41  void getAnalysisUsage(AnalysisUsage &AU) const override {
42    AU.addRequired<MachineBranchProbabilityInfo>();
43    AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
44    AU.addRequired<ProfileSummaryInfoWrapperPass>();
45    MachineFunctionPass::getAnalysisUsage(AU);
46  }
47};
48
49class TailDuplicate : public TailDuplicateBase {
50public:
51  static char ID;
52  TailDuplicate() : TailDuplicateBase(ID, false) {
53    initializeTailDuplicatePass(*PassRegistry::getPassRegistry());
54  }
55};
56
57class EarlyTailDuplicate : public TailDuplicateBase {
58public:
59  static char ID;
60  EarlyTailDuplicate() : TailDuplicateBase(ID, true) {
61    initializeEarlyTailDuplicatePass(*PassRegistry::getPassRegistry());
62  }
63
64  MachineFunctionProperties getClearedProperties() const override {
65    return MachineFunctionProperties()
66      .set(MachineFunctionProperties::Property::NoPHIs);
67  }
68};
69
70} // end anonymous namespace
71
72char TailDuplicate::ID;
73char EarlyTailDuplicate::ID;
74
75char &llvm::TailDuplicateID = TailDuplicate::ID;
76char &llvm::EarlyTailDuplicateID = EarlyTailDuplicate::ID;
77
78INITIALIZE_PASS(TailDuplicate, DEBUG_TYPE, "Tail Duplication", false, false)
79INITIALIZE_PASS(EarlyTailDuplicate, "early-tailduplication",
80                "Early Tail Duplication", false, false)
81
82bool TailDuplicateBase::runOnMachineFunction(MachineFunction &MF) {
83  if (skipFunction(MF.getFunction()))
84    return false;
85
86  auto MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
87  auto *PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
88  auto *MBFI = (PSI && PSI->hasProfileSummary()) ?
89               &getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI() :
90               nullptr;
91  Duplicator.initMF(MF, PreRegAlloc, MBPI, MBFI, PSI, /*LayoutMode=*/false);
92
93  bool MadeChange = false;
94  while (Duplicator.tailDuplicateBlocks())
95    MadeChange = true;
96
97  return MadeChange;
98}
99