forked from OSchip/llvm-project
209 lines
6.8 KiB
C++
209 lines
6.8 KiB
C++
//===- LTO.cpp ------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "LTO.h"
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#include "Config.h"
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#include "InputFiles.h"
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#include "Symbols.h"
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#include "lld/Common/Args.h"
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#include "lld/Common/ErrorHandler.h"
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#include "lld/Common/Strings.h"
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#include "lld/Common/TargetOptionsCommandFlags.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/Bitcode/BitcodeWriter.h"
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#include "llvm/IR/DiagnosticPrinter.h"
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#include "llvm/LTO/Caching.h"
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#include "llvm/LTO/Config.h"
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#include "llvm/LTO/LTO.h"
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#include "llvm/Object/SymbolicFile.h"
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#include "llvm/Support/CodeGen.h"
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#include "llvm/Support/Error.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <cstddef>
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#include <memory>
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#include <string>
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#include <system_error>
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#include <vector>
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using namespace llvm;
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using namespace llvm::object;
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using namespace lld;
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using namespace lld::coff;
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// Creates an empty file to and returns a raw_fd_ostream to write to it.
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static std::unique_ptr<raw_fd_ostream> openFile(StringRef file) {
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std::error_code ec;
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auto ret =
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std::make_unique<raw_fd_ostream>(file, ec, sys::fs::OpenFlags::OF_None);
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if (ec) {
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error("cannot open " + file + ": " + ec.message());
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return nullptr;
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}
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return ret;
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}
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static std::string getThinLTOOutputFile(StringRef path) {
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return lto::getThinLTOOutputFile(
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std::string(path), std::string(config->thinLTOPrefixReplace.first),
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std::string(config->thinLTOPrefixReplace.second));
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}
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static lto::Config createConfig() {
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lto::Config c;
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c.Options = initTargetOptionsFromCodeGenFlags();
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// Always emit a section per function/datum with LTO. LLVM LTO should get most
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// of the benefit of linker GC, but there are still opportunities for ICF.
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c.Options.FunctionSections = true;
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c.Options.DataSections = true;
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// Use static reloc model on 32-bit x86 because it usually results in more
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// compact code, and because there are also known code generation bugs when
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// using the PIC model (see PR34306).
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if (config->machine == COFF::IMAGE_FILE_MACHINE_I386)
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c.RelocModel = Reloc::Static;
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else
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c.RelocModel = Reloc::PIC_;
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c.DisableVerify = true;
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c.DiagHandler = diagnosticHandler;
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c.OptLevel = config->ltoo;
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c.CPU = getCPUStr();
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c.MAttrs = getMAttrs();
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c.CGOptLevel = args::getCGOptLevel(config->ltoo);
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if (config->saveTemps)
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checkError(c.addSaveTemps(std::string(config->outputFile) + ".",
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/*UseInputModulePath*/ true));
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return c;
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}
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BitcodeCompiler::BitcodeCompiler() {
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// Initialize indexFile.
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if (!config->thinLTOIndexOnlyArg.empty())
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indexFile = openFile(config->thinLTOIndexOnlyArg);
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// Initialize ltoObj.
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lto::ThinBackend backend;
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if (config->thinLTOIndexOnly) {
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auto OnIndexWrite = [&](StringRef S) { thinIndices.erase(S); };
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backend = lto::createWriteIndexesThinBackend(
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std::string(config->thinLTOPrefixReplace.first),
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std::string(config->thinLTOPrefixReplace.second),
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config->thinLTOEmitImportsFiles, indexFile.get(), OnIndexWrite);
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} else if (config->thinLTOJobs != 0) {
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backend = lto::createInProcessThinBackend(config->thinLTOJobs);
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}
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ltoObj = std::make_unique<lto::LTO>(createConfig(), backend,
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config->ltoPartitions);
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}
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BitcodeCompiler::~BitcodeCompiler() = default;
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static void undefine(Symbol *s) { replaceSymbol<Undefined>(s, s->getName()); }
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void BitcodeCompiler::add(BitcodeFile &f) {
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lto::InputFile &obj = *f.obj;
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unsigned symNum = 0;
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std::vector<Symbol *> symBodies = f.getSymbols();
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std::vector<lto::SymbolResolution> resols(symBodies.size());
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if (config->thinLTOIndexOnly)
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thinIndices.insert(obj.getName());
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// Provide a resolution to the LTO API for each symbol.
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for (const lto::InputFile::Symbol &objSym : obj.symbols()) {
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Symbol *sym = symBodies[symNum];
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lto::SymbolResolution &r = resols[symNum];
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++symNum;
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// Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
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// reports two symbols for module ASM defined. Without this check, lld
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// flags an undefined in IR with a definition in ASM as prevailing.
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// Once IRObjectFile is fixed to report only one symbol this hack can
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// be removed.
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r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f;
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r.VisibleToRegularObj = sym->isUsedInRegularObj;
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if (r.Prevailing)
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undefine(sym);
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}
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checkError(ltoObj->add(std::move(f.obj), resols));
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}
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// Merge all the bitcode files we have seen, codegen the result
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// and return the resulting objects.
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std::vector<StringRef> BitcodeCompiler::compile() {
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unsigned maxTasks = ltoObj->getMaxTasks();
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buf.resize(maxTasks);
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files.resize(maxTasks);
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// The /lldltocache option specifies the path to a directory in which to cache
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// native object files for ThinLTO incremental builds. If a path was
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// specified, configure LTO to use it as the cache directory.
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lto::NativeObjectCache cache;
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if (!config->ltoCache.empty())
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cache = check(lto::localCache(
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config->ltoCache, [&](size_t task, std::unique_ptr<MemoryBuffer> mb) {
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files[task] = std::move(mb);
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}));
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checkError(ltoObj->run(
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[&](size_t task) {
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return std::make_unique<lto::NativeObjectStream>(
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std::make_unique<raw_svector_ostream>(buf[task]));
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},
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cache));
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// Emit empty index files for non-indexed files
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for (StringRef s : thinIndices) {
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std::string path = getThinLTOOutputFile(s);
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openFile(path + ".thinlto.bc");
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if (config->thinLTOEmitImportsFiles)
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openFile(path + ".imports");
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}
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// ThinLTO with index only option is required to generate only the index
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// files. After that, we exit from linker and ThinLTO backend runs in a
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// distributed environment.
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if (config->thinLTOIndexOnly) {
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if (!config->ltoObjPath.empty())
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saveBuffer(buf[0], config->ltoObjPath);
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if (indexFile)
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indexFile->close();
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return {};
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}
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if (!config->ltoCache.empty())
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pruneCache(config->ltoCache, config->ltoCachePolicy);
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std::vector<StringRef> ret;
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for (unsigned i = 0; i != maxTasks; ++i) {
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if (buf[i].empty())
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continue;
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if (config->saveTemps) {
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if (i == 0)
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saveBuffer(buf[i], config->outputFile + ".lto.obj");
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else
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saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.obj");
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}
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ret.emplace_back(buf[i].data(), buf[i].size());
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}
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for (std::unique_ptr<MemoryBuffer> &file : files)
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if (file)
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ret.push_back(file->getBuffer());
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return ret;
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}
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