aboutsummaryrefslogtreecommitdiffstats
path: root/ELF/LTO.cpp
blob: b342b6195f1d0fa471492d5a3b6cf5e1f591d63c (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
//===- LTO.cpp ------------------------------------------------------------===//
//
//                             The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "LTO.h"
#include "Config.h"
#include "Error.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/LTO/Config.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Object/SymbolicFile.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cstddef>
#include <memory>
#include <string>
#include <system_error>
#include <vector>

using namespace llvm;
using namespace llvm::object;
using namespace llvm::ELF;

using namespace lld;
using namespace lld::elf;

// This is for use when debugging LTO.
static void saveBuffer(StringRef Buffer, const Twine &Path) {
  std::error_code EC;
  raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
  if (EC)
    error(EC, "cannot create " + Path);
  OS << Buffer;
}

static void diagnosticHandler(const DiagnosticInfo &DI) {
  SmallString<128> ErrStorage;
  raw_svector_ostream OS(ErrStorage);
  DiagnosticPrinterRawOStream DP(OS);
  DI.print(DP);
  warn(ErrStorage);
}

static void checkError(Error E) {
  handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) -> Error {
    error(EIB.message());
    return Error::success();
  });
}

static std::unique_ptr<lto::LTO> createLTO() {
  lto::Config Conf;

  // LLD supports the new relocations.
  Conf.Options = InitTargetOptionsFromCodeGenFlags();
  Conf.Options.RelaxELFRelocations = true;

  Conf.RelocModel = Config->Pic ? Reloc::PIC_ : Reloc::Static;
  Conf.DisableVerify = Config->DisableVerify;
  Conf.DiagHandler = diagnosticHandler;
  Conf.OptLevel = Config->LTOO;

  // Set up a custom pipeline if we've been asked to.
  Conf.OptPipeline = Config->LTONewPmPasses;
  Conf.AAPipeline = Config->LTOAAPipeline;

  if (Config->SaveTemps)
    checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".",
                                 /*UseInputModulePath*/ true));

  lto::ThinBackend Backend;
  if (Config->ThinLTOJobs != -1u)
    Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs);
  return llvm::make_unique<lto::LTO>(std::move(Conf), Backend,
                                     Config->LTOPartitions);
}

BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {}

BitcodeCompiler::~BitcodeCompiler() = default;

template <class ELFT> static void undefine(Symbol *S) {
  replaceBody<Undefined<ELFT>>(S, S->body()->getName(), /*IsLocal=*/false,
                               STV_DEFAULT, S->body()->Type, nullptr);
}

template <class ELFT> void BitcodeCompiler::add(BitcodeFile &F) {
  lto::InputFile &Obj = *F.Obj;
  unsigned SymNum = 0;
  std::vector<Symbol *> Syms = F.getSymbols();
  std::vector<lto::SymbolResolution> Resols(Syms.size());

  // Provide a resolution to the LTO API for each symbol.
  for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) {
    Symbol *Sym = Syms[SymNum];
    lto::SymbolResolution &R = Resols[SymNum];
    ++SymNum;
    SymbolBody *B = Sym->body();

    // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
    // reports two symbols for module ASM defined. Without this check, lld
    // flags an undefined in IR with a definition in ASM as prevailing.
    // Once IRObjectFile is fixed to report only one symbol this hack can
    // be removed.
    R.Prevailing =
        !(ObjSym.getFlags() & object::BasicSymbolRef::SF_Undefined) &&
        B->File == &F;

    R.VisibleToRegularObj =
        Sym->IsUsedInRegularObj || (R.Prevailing && Sym->includeInDynsym());
    if (R.Prevailing)
      undefine<ELFT>(Sym);
  }
  checkError(LTOObj->add(std::move(F.Obj), Resols));
}

// Merge all the bitcode files we have seen, codegen the result
// and return the resulting ObjectFile(s).
std::vector<InputFile *> BitcodeCompiler::compile() {
  std::vector<InputFile *> Ret;
  unsigned MaxTasks = LTOObj->getMaxTasks();
  Buff.resize(MaxTasks);

  checkError(LTOObj->run([&](size_t Task) {
    return llvm::make_unique<lto::NativeObjectStream>(
        llvm::make_unique<raw_svector_ostream>(Buff[Task]));
  }));

  for (unsigned I = 0; I != MaxTasks; ++I) {
    if (Buff[I].empty())
      continue;
    if (Config->SaveTemps) {
      if (MaxTasks == 1)
        saveBuffer(Buff[I], Config->OutputFile + ".lto.o");
      else
        saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.o");
    }
    InputFile *Obj = createObjectFile(MemoryBufferRef(Buff[I], "lto.tmp"));
    Ret.push_back(Obj);
  }
  return Ret;
}

template void BitcodeCompiler::template add<ELF32LE>(BitcodeFile &);
template void BitcodeCompiler::template add<ELF32BE>(BitcodeFile &);
template void BitcodeCompiler::template add<ELF64LE>(BitcodeFile &);
template void BitcodeCompiler::template add<ELF64BE>(BitcodeFile &);