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
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:
TailDuplicateBase(char & PassID,bool PreRegAlloc)37 TailDuplicateBase(char &PassID, bool PreRegAlloc)
38 : MachineFunctionPass(PassID), PreRegAlloc(PreRegAlloc) {}
39
40 bool runOnMachineFunction(MachineFunction &MF) override;
41
getAnalysisUsage(AnalysisUsage & AU) const42 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;
TailDuplicate()53 TailDuplicate() : TailDuplicateBase(ID, false) {
54 initializeTailDuplicatePass(*PassRegistry::getPassRegistry());
55 }
56 };
57
58 class EarlyTailDuplicate : public TailDuplicateBase {
59 public:
60 static char ID;
EarlyTailDuplicate()61 EarlyTailDuplicate() : TailDuplicateBase(ID, true) {
62 initializeEarlyTailDuplicatePass(*PassRegistry::getPassRegistry());
63 }
64
getClearedProperties() const65 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
runOnMachineFunction(MachineFunction & MF)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 }
103