1 //===- LTO.cpp ------------------------------------------------------------===//
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 #include "LTO.h"
10 #include "Config.h"
11 #include "InputFiles.h"
12
13 #include "lld/Common/ErrorHandler.h"
14 #include "lld/Common/Strings.h"
15 #include "lld/Common/TargetOptionsCommandFlags.h"
16 #include "llvm/LTO/LTO.h"
17 #include "llvm/Support/raw_ostream.h"
18
19 using namespace lld;
20 using namespace lld::macho;
21 using namespace llvm;
22
createConfig()23 static lto::Config createConfig() {
24 lto::Config c;
25 c.Options = initTargetOptionsFromCodeGenFlags();
26 return c;
27 }
28
BitcodeCompiler()29 BitcodeCompiler::BitcodeCompiler() {
30 auto backend =
31 lto::createInProcessThinBackend(llvm::heavyweight_hardware_concurrency());
32 ltoObj = std::make_unique<lto::LTO>(createConfig(), backend);
33 }
34
add(BitcodeFile & f)35 void BitcodeCompiler::add(BitcodeFile &f) {
36 ArrayRef<lto::InputFile::Symbol> objSyms = f.obj->symbols();
37 std::vector<lto::SymbolResolution> resols;
38 resols.reserve(objSyms.size());
39
40 // Provide a resolution to the LTO API for each symbol.
41 for (const lto::InputFile::Symbol &objSym : objSyms) {
42 resols.emplace_back();
43 lto::SymbolResolution &r = resols.back();
44
45 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
46 // reports two symbols for module ASM defined. Without this check, lld
47 // flags an undefined in IR with a definition in ASM as prevailing.
48 // Once IRObjectFile is fixed to report only one symbol this hack can
49 // be removed.
50 r.Prevailing = !objSym.isUndefined();
51
52 // TODO: set the other resolution configs properly
53 r.VisibleToRegularObj = true;
54 }
55 checkError(ltoObj->add(std::move(f.obj), resols));
56 }
57
58 // Merge all the bitcode files we have seen, codegen the result
59 // and return the resulting ObjectFile(s).
compile()60 std::vector<ObjFile *> BitcodeCompiler::compile() {
61 unsigned maxTasks = ltoObj->getMaxTasks();
62 buf.resize(maxTasks);
63
64 checkError(ltoObj->run([&](size_t task) {
65 return std::make_unique<lto::NativeObjectStream>(
66 std::make_unique<raw_svector_ostream>(buf[task]));
67 }));
68
69 if (config->saveTemps) {
70 if (!buf[0].empty())
71 saveBuffer(buf[0], config->outputFile + ".lto.o");
72 for (unsigned i = 1; i != maxTasks; ++i)
73 saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.o");
74 }
75
76 // TODO: set modTime properly
77 std::vector<ObjFile *> ret;
78 for (unsigned i = 0; i != maxTasks; ++i)
79 if (!buf[i].empty())
80 ret.push_back(
81 make<ObjFile>(MemoryBufferRef(buf[i], "lto.tmp"), /*modTime=*/0, ""));
82
83 return ret;
84 }
85