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#include "Symbols.h"
13#include "lld/Common/Args.h"
14#include "lld/Common/ErrorHandler.h"
15#include "lld/Common/Strings.h"
16#include "lld/Common/TargetOptionsCommandFlags.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SmallString.h"
19#include "llvm/ADT/StringRef.h"
20#include "llvm/ADT/Twine.h"
21#include "llvm/IR/DiagnosticPrinter.h"
22#include "llvm/LTO/Config.h"
23#include "llvm/LTO/LTO.h"
24#include "llvm/Object/SymbolicFile.h"
25#include "llvm/Support/Caching.h"
26#include "llvm/Support/CodeGen.h"
27#include "llvm/Support/Error.h"
28#include "llvm/Support/FileSystem.h"
29#include "llvm/Support/MemoryBuffer.h"
30#include "llvm/Support/raw_ostream.h"
31#include <algorithm>
32#include <cstddef>
33#include <memory>
34#include <string>
35#include <system_error>
36#include <vector>
37
38using namespace llvm;
39
40namespace lld::wasm {
41static std::unique_ptr<lto::LTO> createLTO() {
42 lto::Config c;
43 c.Options = initTargetOptionsFromCodeGenFlags();
44
45 // Always emit a section per function/data with LTO.
46 c.Options.FunctionSections = true;
47 c.Options.DataSections = true;
48
49 c.DisableVerify = config->disableVerify;
50 c.DiagHandler = diagnosticHandler;
51 c.OptLevel = config->ltoo;
52 c.MAttrs = getMAttrs();
53 c.CGOptLevel = config->ltoCgo;
54 c.DebugPassManager = config->ltoDebugPassManager;
55
56 if (config->relocatable)
57 c.RelocModel = std::nullopt;
58 else if (ctx.isPic)
59 c.RelocModel = Reloc::PIC_;
60 else
61 c.RelocModel = Reloc::Static;
62
63 if (config->saveTemps)
64 checkError(e: c.addSaveTemps(OutputFileName: config->outputFile.str() + ".",
65 /*UseInputModulePath*/ true));
66 lto::ThinBackend backend = lto::createInProcessThinBackend(
67 Parallelism: llvm::heavyweight_hardware_concurrency(Num: config->thinLTOJobs));
68 return std::make_unique<lto::LTO>(args: std::move(c), args&: backend,
69 args&: config->ltoPartitions);
70}
71
72BitcodeCompiler::BitcodeCompiler() : ltoObj(createLTO()) {}
73
74BitcodeCompiler::~BitcodeCompiler() = default;
75
76static void undefine(Symbol *s) {
77 if (auto f = dyn_cast<DefinedFunction>(Val: s))
78 replaceSymbol<UndefinedFunction>(s: f, arg: f->getName(), arg: std::nullopt,
79 arg: std::nullopt, arg: 0, arg: f->getFile(),
80 arg&: f->signature);
81 else if (isa<DefinedData>(Val: s))
82 replaceSymbol<UndefinedData>(s, arg: s->getName(), arg: 0, arg: s->getFile());
83 else
84 llvm_unreachable("unexpected symbol kind");
85}
86
87void BitcodeCompiler::add(BitcodeFile &f) {
88 lto::InputFile &obj = *f.obj;
89 unsigned symNum = 0;
90 ArrayRef<Symbol *> syms = f.getSymbols();
91 std::vector<lto::SymbolResolution> resols(syms.size());
92
93 // Provide a resolution to the LTO API for each symbol.
94 for (const lto::InputFile::Symbol &objSym : obj.symbols()) {
95 Symbol *sym = syms[symNum];
96 lto::SymbolResolution &r = resols[symNum];
97 ++symNum;
98
99 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
100 // reports two symbols for module ASM defined. Without this check, lld
101 // flags an undefined in IR with a definition in ASM as prevailing.
102 // Once IRObjectFile is fixed to report only one symbol this hack can
103 // be removed.
104 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f;
105 r.VisibleToRegularObj = config->relocatable || sym->isUsedInRegularObj ||
106 sym->isNoStrip() ||
107 (r.Prevailing && sym->isExported());
108 if (r.Prevailing)
109 undefine(s: sym);
110
111 // We tell LTO to not apply interprocedural optimization for wrapped
112 // (with --wrap) symbols because otherwise LTO would inline them while
113 // their values are still not final.
114 r.LinkerRedefined = !sym->canInline;
115 }
116 checkError(e: ltoObj->add(Obj: std::move(f.obj), Res: resols));
117}
118
119// Merge all the bitcode files we have seen, codegen the result
120// and return the resulting objects.
121std::vector<StringRef> BitcodeCompiler::compile() {
122 unsigned maxTasks = ltoObj->getMaxTasks();
123 buf.resize(new_size: maxTasks);
124 files.resize(new_size: maxTasks);
125
126 // The --thinlto-cache-dir option specifies the path to a directory in which
127 // to cache native object files for ThinLTO incremental builds. If a path was
128 // specified, configure LTO to use it as the cache directory.
129 FileCache cache;
130 if (!config->thinLTOCacheDir.empty())
131 cache = check(e: localCache(CacheNameRef: "ThinLTO", TempFilePrefixRef: "Thin", CacheDirectoryPathRef: config->thinLTOCacheDir,
132 AddBuffer: [&](size_t task, const Twine &moduleName,
133 std::unique_ptr<MemoryBuffer> mb) {
134 files[task] = std::move(mb);
135 }));
136
137 checkError(e: ltoObj->run(
138 AddStream: [&](size_t task, const Twine &moduleName) {
139 return std::make_unique<CachedFileStream>(
140 args: std::make_unique<raw_svector_ostream>(args&: buf[task]));
141 },
142 Cache: cache));
143
144 if (!config->thinLTOCacheDir.empty())
145 pruneCache(Path: config->thinLTOCacheDir, Policy: config->thinLTOCachePolicy, Files: files);
146
147 std::vector<StringRef> ret;
148 for (unsigned i = 0; i != maxTasks; ++i) {
149 if (buf[i].empty())
150 continue;
151 if (config->saveTemps) {
152 if (i == 0)
153 saveBuffer(buffer: buf[i], path: config->outputFile + ".lto.o");
154 else
155 saveBuffer(buffer: buf[i], path: config->outputFile + Twine(i) + ".lto.o");
156 }
157 ret.emplace_back(args: buf[i].data(), args: buf[i].size());
158 }
159
160 for (std::unique_ptr<MemoryBuffer> &file : files)
161 if (file)
162 ret.push_back(x: file->getBuffer());
163
164 return ret;
165}
166
167} // namespace lld::wasm
168