blob: 8d35dfe81b52e34b02521d64eec02c15086f9a44 [file] [log] [blame]
//===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization ------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This is a gold plugin for LLVM. It provides an LLVM implementation of the
// interface described in .
#include "llvm/ADT/Statistic.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Object/Error.h"
#include "llvm/Remarks/HotnessThresholdParser.h"
#include "llvm/Support/CachePruning.h"
#include "llvm/Support/Caching.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/Threading.h"
#include "llvm/Support/raw_ostream.h"
#include <list>
#include <map>
#include <plugin-api.h>
#include <string>
#include <system_error>
#include <utility>
#include <vector>
// FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
// Precise and Debian Wheezy (binutils 2.23 is required)
#define LDPO_PIE 3
#define LDPT_GET_SYMBOLS_V3 28
// FIXME: Remove when binutils 2.31 (containing gold 1.16) is the minimum
// required version.
using namespace llvm;
using namespace lto;
static codegen::RegisterCodeGenFlags CodeGenFlags;
// FIXME: Remove when binutils 2.31 (containing gold 1.16) is the minimum
// required version.
typedef enum ld_plugin_status (*ld_plugin_get_wrap_symbols)(
uint64_t *num_symbols, const char ***wrap_symbol_list);
static ld_plugin_status discard_message(int level, const char *format, ...) {
// Die loudly. Recent versions of Gold pass ld_plugin_message as the first
// callback in the transfer vector. This should never be called.
static ld_plugin_release_input_file release_input_file = nullptr;
static ld_plugin_get_input_file get_input_file = nullptr;
static ld_plugin_message message = discard_message;
static ld_plugin_get_wrap_symbols get_wrap_symbols = nullptr;
namespace {
struct claimed_file {
void *handle;
void *leader_handle;
std::vector<ld_plugin_symbol> syms;
off_t filesize;
std::string name;
/// RAII wrapper to manage opening and releasing of a ld_plugin_input_file.
struct PluginInputFile {
void *Handle;
std::unique_ptr<ld_plugin_input_file> File;
PluginInputFile(void *Handle) : Handle(Handle) {
File = std::make_unique<ld_plugin_input_file>();
if (get_input_file(Handle, File.get()) != LDPS_OK)
message(LDPL_FATAL, "Failed to get file information");
~PluginInputFile() {
// File would have been reset to nullptr if we moved this object
// to a new owner.
if (File)
if (release_input_file(Handle) != LDPS_OK)
message(LDPL_FATAL, "Failed to release file information");
ld_plugin_input_file &file() { return *File; }
PluginInputFile(PluginInputFile &&RHS) = default;
PluginInputFile &operator=(PluginInputFile &&RHS) = default;
struct ResolutionInfo {
bool CanOmitFromDynSym = true;
bool DefaultVisibility = true;
bool CanInline = true;
bool IsUsedInRegularObj = false;
static ld_plugin_add_symbols add_symbols = nullptr;
static ld_plugin_get_symbols get_symbols = nullptr;
static ld_plugin_add_input_file add_input_file = nullptr;
static ld_plugin_set_extra_library_path set_extra_library_path = nullptr;
static ld_plugin_get_view get_view = nullptr;
static bool IsExecutable = false;
static bool SplitSections = true;
static Optional<Reloc::Model> RelocationModel = None;
static std::string output_name = "";
static std::list<claimed_file> Modules;
static DenseMap<int, void *> FDToLeaderHandle;
static StringMap<ResolutionInfo> ResInfo;
static std::vector<std::string> Cleanup;
namespace options {
enum OutputType {
static OutputType TheOutputType = OT_NORMAL;
static unsigned OptLevel = 2;
// Currently only affects ThinLTO, where the default is the max cores in the
// system. See llvm::get_threadpool_strategy() for acceptable values.
static std::string Parallelism;
// Default regular LTO codegen parallelism (number of partitions).
static unsigned ParallelCodeGenParallelismLevel = 1;
#ifdef NDEBUG
static bool DisableVerify = true;
static bool DisableVerify = false;
static std::string obj_path;
static std::string extra_library_path;
static std::string triple;
static std::string mcpu;
// When the thinlto plugin option is specified, only read the function
// the information from intermediate files and write a combined
// global index for the ThinLTO backends.
static bool thinlto = false;
// If false, all ThinLTO backend compilations through code gen are performed
// using multiple threads in the gold-plugin, before handing control back to
// gold. If true, write individual backend index files which reflect
// the import decisions, and exit afterwards. The assumption is
// that the build system will launch the backend processes.
static bool thinlto_index_only = false;
// If non-empty, holds the name of a file in which to write the list of
// oject files gold selected for inclusion in the link after symbol
// resolution (i.e. they had selected symbols). This will only be non-empty
// in the thinlto_index_only case. It is used to identify files, which may
// have originally been within archive libraries specified via
// --start-lib/--end-lib pairs, that should be included in the final
// native link process (since intervening function importing and inlining
// may change the symbol resolution detected in the final link and which
// files to include out of --start-lib/--end-lib libraries as a result).
static std::string thinlto_linked_objects_file;
// If true, when generating individual index files for distributed backends,
// also generate a "${bitcodefile}.imports" file at the same location for each
// bitcode file, listing the files it imports from in plain text. This is to
// support distributed build file staging.
static bool thinlto_emit_imports_files = false;
// Option to control where files for a distributed backend (the individual
// index files and optional imports files) are created.
// If specified, expects a string of the form "oldprefix:newprefix", and
// instead of generating these files in the same directory path as the
// corresponding bitcode file, will use a path formed by replacing the
// bitcode file's path prefix matching oldprefix with newprefix.
static std::string thinlto_prefix_replace;
// Option to control the name of modules encoded in the individual index
// files for a distributed backend. This enables the use of minimized
// bitcode files for the thin link, assuming the name of the full bitcode
// file used in the backend differs just in some part of the file suffix.
// If specified, expects a string of the form "oldsuffix:newsuffix".
static std::string thinlto_object_suffix_replace;
// Optional path to a directory for caching ThinLTO objects.
static std::string cache_dir;
// Optional pruning policy for ThinLTO caches.
static std::string cache_policy;
// Additional options to pass into the code generator.
// Note: This array will contain all plugin options which are not claimed
// as plugin exclusive to pass to the code generator.
static std::vector<const char *> extra;
// Sample profile file path
static std::string sample_profile;
// New pass manager
static bool new_pass_manager = LLVM_ENABLE_NEW_PASS_MANAGER;
// Debug new pass manager
static bool debug_pass_manager = false;
// Directory to store the .dwo files.
static std::string dwo_dir;
/// Statistics output filename.
static std::string stats_file;
// Asserts that LTO link has whole program visibility
static bool whole_program_visibility = false;
// Optimization remarks filename, accepted passes and hotness options
static std::string RemarksFilename;
static std::string RemarksPasses;
static bool RemarksWithHotness = false;
static Optional<uint64_t> RemarksHotnessThreshold = 0;
static std::string RemarksFormat;
// Context sensitive PGO options.
static std::string cs_profile_path;
static bool cs_pgo_gen = false;
static void process_plugin_option(const char *opt_)
if (opt_ == nullptr)
llvm::StringRef opt = opt_;
if (opt.consume_front("mcpu=")) {
mcpu = std::string(opt);
} else if (opt.consume_front("extra-library-path=")) {
extra_library_path = std::string(opt);
} else if (opt.consume_front("mtriple=")) {
triple = std::string(opt);
} else if (opt.consume_front("obj-path=")) {
obj_path = std::string(opt);
} else if (opt == "emit-llvm") {
TheOutputType = OT_BC_ONLY;
} else if (opt == "save-temps") {
TheOutputType = OT_SAVE_TEMPS;
} else if (opt == "disable-output") {
TheOutputType = OT_DISABLE;
} else if (opt == "emit-asm") {
TheOutputType = OT_ASM_ONLY;
} else if (opt == "thinlto") {
thinlto = true;
} else if (opt == "thinlto-index-only") {
thinlto_index_only = true;
} else if (opt.consume_front("thinlto-index-only=")) {
thinlto_index_only = true;
thinlto_linked_objects_file = std::string(opt);
} else if (opt == "thinlto-emit-imports-files") {
thinlto_emit_imports_files = true;
} else if (opt.consume_front("thinlto-prefix-replace=")) {
thinlto_prefix_replace = std::string(opt);
if (thinlto_prefix_replace.find(';') == std::string::npos)
message(LDPL_FATAL, "thinlto-prefix-replace expects 'old;new' format");
} else if (opt.consume_front("thinlto-object-suffix-replace=")) {
thinlto_object_suffix_replace = std::string(opt);
if (thinlto_object_suffix_replace.find(';') == std::string::npos)
"thinlto-object-suffix-replace expects 'old;new' format");
} else if (opt.consume_front("cache-dir=")) {
cache_dir = std::string(opt);
} else if (opt.consume_front("cache-policy=")) {
cache_policy = std::string(opt);
} else if (opt.size() == 2 && opt[0] == 'O') {
if (opt[1] < '0' || opt[1] > '3')
message(LDPL_FATAL, "Optimization level must be between 0 and 3");
OptLevel = opt[1] - '0';
} else if (opt.consume_front("jobs=")) {
Parallelism = std::string(opt);
if (!get_threadpool_strategy(opt))
message(LDPL_FATAL, "Invalid parallelism level: %s",
} else if (opt.consume_front("lto-partitions=")) {
if (opt.getAsInteger(10, ParallelCodeGenParallelismLevel))
message(LDPL_FATAL, "Invalid codegen partition level: %s", opt_ + 5);
} else if (opt == "disable-verify") {
DisableVerify = true;
} else if (opt.consume_front("sample-profile=")) {
sample_profile = std::string(opt);
} else if (opt == "cs-profile-generate") {
cs_pgo_gen = true;
} else if (opt.consume_front("cs-profile-path=")) {
cs_profile_path = std::string(opt);
} else if (opt == "new-pass-manager") {
new_pass_manager = true;
} else if (opt == "legacy-pass-manager") {
new_pass_manager = false;
} else if (opt == "debug-pass-manager") {
debug_pass_manager = true;
} else if (opt == "whole-program-visibility") {
whole_program_visibility = true;
} else if (opt.consume_front("dwo_dir=")) {
dwo_dir = std::string(opt);
} else if (opt.consume_front("opt-remarks-filename=")) {
RemarksFilename = std::string(opt);
} else if (opt.consume_front("opt-remarks-passes=")) {
RemarksPasses = std::string(opt);
} else if (opt == "opt-remarks-with-hotness") {
RemarksWithHotness = true;
} else if (opt.consume_front("opt-remarks-hotness-threshold=")) {
auto ResultOrErr = remarks::parseHotnessThresholdOption(opt);
if (!ResultOrErr)
message(LDPL_FATAL, "Invalid remarks hotness threshold: %s", opt);
RemarksHotnessThreshold = *ResultOrErr;
} else if (opt.consume_front("opt-remarks-format=")) {
RemarksFormat = std::string(opt);
} else if (opt.consume_front("stats-file=")) {
stats_file = std::string(opt);
} else {
// Save this option to pass to the code generator.
// ParseCommandLineOptions() expects argv[0] to be program name. Lazily
// add that.
if (extra.empty())
static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
int *claimed);
static ld_plugin_status all_symbols_read_hook(void);
static ld_plugin_status cleanup_hook(void);
extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
ld_plugin_status onload(ld_plugin_tv *tv) {
// We're given a pointer to the first transfer vector. We read through them
// until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
// contain pointers to functions that we need to call to register our own
// hooks. The others are addresses of functions we can use to call into gold
// for services.
bool registeredClaimFile = false;
bool RegisteredAllSymbolsRead = false;
for (; tv->tv_tag != LDPT_NULL; ++tv) {
// Cast tv_tag to int to allow values not in "enum ld_plugin_tag", like, for
// example, LDPT_GET_SYMBOLS_V3 when building against an older plugin-api.h
// header.
switch (static_cast<int>(tv->tv_tag)) {
output_name = tv->tv_u.tv_string;
switch (tv->tv_u.tv_val) {
case LDPO_REL: // .o
IsExecutable = false;
SplitSections = false;
case LDPO_DYN: // .so
IsExecutable = false;
RelocationModel = Reloc::PIC_;
case LDPO_PIE: // position independent executable
IsExecutable = true;
RelocationModel = Reloc::PIC_;
case LDPO_EXEC: // .exe
IsExecutable = true;
RelocationModel = Reloc::Static;
message(LDPL_ERROR, "Unknown output file type %d", tv->tv_u.tv_val);
return LDPS_ERR;
ld_plugin_register_claim_file callback;
callback = tv->tv_u.tv_register_claim_file;
if (callback(claim_file_hook) != LDPS_OK)
return LDPS_ERR;
registeredClaimFile = true;
} break;
ld_plugin_register_all_symbols_read callback;
callback = tv->tv_u.tv_register_all_symbols_read;
if (callback(all_symbols_read_hook) != LDPS_OK)
return LDPS_ERR;
RegisteredAllSymbolsRead = true;
} break;
ld_plugin_register_cleanup callback;
callback = tv->tv_u.tv_register_cleanup;
if (callback(cleanup_hook) != LDPS_OK)
return LDPS_ERR;
} break;
get_input_file = tv->tv_u.tv_get_input_file;
release_input_file = tv->tv_u.tv_release_input_file;
add_symbols = tv->tv_u.tv_add_symbols;
// Do not override get_symbols_v3 with get_symbols_v2.
if (!get_symbols)
get_symbols = tv->tv_u.tv_get_symbols;
get_symbols = tv->tv_u.tv_get_symbols;
add_input_file = tv->tv_u.tv_add_input_file;
set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
get_view = tv->tv_u.tv_get_view;
message = tv->tv_u.tv_message;
// FIXME: When binutils 2.31 (containing gold 1.16) is the minimum
// required version, this should be changed to:
// get_wrap_symbols = tv->tv_u.tv_get_wrap_symbols;
get_wrap_symbols =
if (!registeredClaimFile) {
message(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
return LDPS_ERR;
if (!add_symbols) {
message(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
return LDPS_ERR;
if (!RegisteredAllSymbolsRead)
return LDPS_OK;
if (!get_input_file) {
message(LDPL_ERROR, "get_input_file not passed to LLVMgold.");
return LDPS_ERR;
if (!release_input_file) {
message(LDPL_ERROR, "release_input_file not passed to LLVMgold.");
return LDPS_ERR;
return LDPS_OK;
static void diagnosticHandler(const DiagnosticInfo &DI) {
std::string ErrStorage;
raw_string_ostream OS(ErrStorage);
DiagnosticPrinterRawOStream DP(OS);
ld_plugin_level Level;
switch (DI.getSeverity()) {
case DS_Error:
case DS_Warning:
case DS_Note:
case DS_Remark:
Level = LDPL_INFO;
message(Level, "LLVM gold plugin: %s", ErrStorage.c_str());
static void check(Error E, std::string Msg = "LLVM gold plugin") {
handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) -> Error {
message(LDPL_FATAL, "%s: %s", Msg.c_str(), EIB.message().c_str());
return Error::success();
template <typename T> static T check(Expected<T> E) {
if (E)
return std::move(*E);
return T();
/// Called by gold to see whether this file is one that our plugin can handle.
/// We'll try to open it and register all the symbols with add_symbol if
/// possible.
static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
int *claimed) {
MemoryBufferRef BufferRef;
std::unique_ptr<MemoryBuffer> Buffer;
if (get_view) {
const void *view;
if (get_view(file->handle, &view) != LDPS_OK) {
message(LDPL_ERROR, "Failed to get a view of %s", file->name);
return LDPS_ERR;
BufferRef =
MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
} else {
int64_t offset = 0;
// Gold has found what might be IR part-way inside of a file, such as
// an .a archive.
if (file->offset) {
offset = file->offset;
ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
file->name, file->filesize, offset);
if (std::error_code EC = BufferOrErr.getError()) {
message(LDPL_ERROR, EC.message().c_str());
return LDPS_ERR;
Buffer = std::move(BufferOrErr.get());
BufferRef = Buffer->getMemBufferRef();
*claimed = 1;
Expected<std::unique_ptr<InputFile>> ObjOrErr = InputFile::create(BufferRef);
if (!ObjOrErr) {
handleAllErrors(ObjOrErr.takeError(), [&](const ErrorInfoBase &EI) {
std::error_code EC = EI.convertToErrorCode();
if (EC == object::object_error::invalid_file_type ||
EC == object::object_error::bitcode_section_not_found)
*claimed = 0;
"LLVM gold plugin has failed to create LTO module: %s",
return *claimed ? LDPS_ERR : LDPS_OK;
std::unique_ptr<InputFile> Obj = std::move(*ObjOrErr);
claimed_file &cf = Modules.back();
cf.handle = file->handle;
// Keep track of the first handle for each file descriptor, since there are
// multiple in the case of an archive. This is used later in the case of
// ThinLTO parallel backends to ensure that each file is only opened and
// released once.
auto LeaderHandle =
FDToLeaderHandle.insert(std::make_pair(file->fd, file->handle)).first;
cf.leader_handle = LeaderHandle->second;
// Save the filesize since for parallel ThinLTO backends we can only
// invoke get_input_file once per archive (only for the leader handle).
cf.filesize = file->filesize;
// In the case of an archive library, all but the first member must have a
// non-zero offset, which we can append to the file name to obtain a
// unique name. = file->name;
if (file->offset) += ".llvm." + std::to_string(file->offset) + "." +
for (auto &Sym : Obj->symbols()) {
ld_plugin_symbol &sym = cf.syms.back();
sym.version = nullptr;
StringRef Name = Sym.getName(); = strdup(Name.str().c_str());
ResolutionInfo &Res = ResInfo[Name];
Res.CanOmitFromDynSym &= Sym.canBeOmittedFromSymbolTable();
sym.visibility = LDPV_DEFAULT;
GlobalValue::VisibilityTypes Vis = Sym.getVisibility();
if (Vis != GlobalValue::DefaultVisibility)
Res.DefaultVisibility = false;
switch (Vis) {
case GlobalValue::DefaultVisibility:
case GlobalValue::HiddenVisibility:
sym.visibility = LDPV_HIDDEN;
case GlobalValue::ProtectedVisibility:
sym.visibility = LDPV_PROTECTED;
if (Sym.isUndefined()) {
sym.def = LDPK_UNDEF;
if (Sym.isWeak())
} else if (Sym.isCommon())
sym.def = LDPK_COMMON;
else if (Sym.isWeak())
sym.def = LDPK_WEAKDEF;
sym.def = LDPK_DEF;
sym.size = 0;
sym.comdat_key = nullptr;
int CI = Sym.getComdatIndex();
if (CI != -1) {
// Not setting comdat_key for nodeduplicate ensuress we don't deduplicate.
std::pair<StringRef, Comdat::SelectionKind> C = Obj->getComdatTable()[CI];
if (C.second != Comdat::NoDeduplicate)
sym.comdat_key = strdup(C.first.str().c_str());
sym.resolution = LDPR_UNKNOWN;
if (!cf.syms.empty()) {
if (add_symbols(cf.handle, cf.syms.size(), != LDPS_OK) {
message(LDPL_ERROR, "Unable to add symbols!");
return LDPS_ERR;
// Handle any --wrap options passed to gold, which are than passed
// along to the plugin.
if (get_wrap_symbols) {
const char **wrap_symbols;
uint64_t count = 0;
if (get_wrap_symbols(&count, &wrap_symbols) != LDPS_OK) {
message(LDPL_ERROR, "Unable to get wrap symbols!");
return LDPS_ERR;
for (uint64_t i = 0; i < count; i++) {
StringRef Name = wrap_symbols[i];
ResolutionInfo &Res = ResInfo[Name];
ResolutionInfo &WrapRes = ResInfo["__wrap_" + Name.str()];
ResolutionInfo &RealRes = ResInfo["__real_" + Name.str()];
// Tell LTO not to inline symbols that will be overwritten.
Res.CanInline = false;
RealRes.CanInline = false;
// Tell LTO not to eliminate symbols that will be used after renaming.
Res.IsUsedInRegularObj = true;
WrapRes.IsUsedInRegularObj = true;
return LDPS_OK;
static void freeSymName(ld_plugin_symbol &Sym) {
free(Sym.comdat_key); = nullptr;
Sym.comdat_key = nullptr;
/// Helper to get a file's symbols and a view into it via gold callbacks.
static const void *getSymbolsAndView(claimed_file &F) {
ld_plugin_status status = get_symbols(F.handle, F.syms.size(),;
if (status == LDPS_NO_SYMS)
return nullptr;
if (status != LDPS_OK)
message(LDPL_FATAL, "Failed to get symbol information");
const void *View;
if (get_view(F.handle, &View) != LDPS_OK)
message(LDPL_FATAL, "Failed to get a view of file");
return View;
/// Parse the thinlto-object-suffix-replace option into the \p OldSuffix and
/// \p NewSuffix strings, if it was specified.
static void getThinLTOOldAndNewSuffix(std::string &OldSuffix,
std::string &NewSuffix) {
assert(options::thinlto_object_suffix_replace.empty() ||
options::thinlto_object_suffix_replace.find(';') != StringRef::npos);
StringRef SuffixReplace = options::thinlto_object_suffix_replace;
auto Split = SuffixReplace.split(';');
OldSuffix = std::string(Split.first);
NewSuffix = std::string(Split.second);
/// Given the original \p Path to an output file, replace any filename
/// suffix matching \p OldSuffix with \p NewSuffix.
static std::string getThinLTOObjectFileName(StringRef Path, StringRef OldSuffix,
StringRef NewSuffix) {
if (Path.consume_back(OldSuffix))
return (Path + NewSuffix).str();
return std::string(Path);
// Returns true if S is valid as a C language identifier.
static bool isValidCIdentifier(StringRef S) {
return !S.empty() && (isAlpha(S[0]) || S[0] == '_') &&
std::all_of(S.begin() + 1, S.end(),
[](char C) { return C == '_' || isAlnum(C); });
static bool isUndefined(ld_plugin_symbol &Sym) {
return Sym.def == LDPK_UNDEF || Sym.def == LDPK_WEAKUNDEF;
static void addModule(LTO &Lto, claimed_file &F, const void *View,
StringRef Filename) {
MemoryBufferRef BufferRef(StringRef((const char *)View, F.filesize),
Expected<std::unique_ptr<InputFile>> ObjOrErr = InputFile::create(BufferRef);
if (!ObjOrErr)
message(LDPL_FATAL, "Could not read bitcode from file : %s",
unsigned SymNum = 0;
std::unique_ptr<InputFile> Input = std::move(ObjOrErr.get());
auto InputFileSyms = Input->symbols();
assert(InputFileSyms.size() == F.syms.size());
std::vector<SymbolResolution> Resols(F.syms.size());
for (ld_plugin_symbol &Sym : F.syms) {
const InputFile::Symbol &InpSym = InputFileSyms[SymNum];
SymbolResolution &R = Resols[SymNum++];
ld_plugin_symbol_resolution Resolution =
ResolutionInfo &Res = ResInfo[];
switch (Resolution) {
llvm_unreachable("Unexpected resolution");
R.ExportDynamic = true;
R.Prevailing = !isUndefined(Sym);
R.Prevailing = !isUndefined(Sym);
R.VisibleToRegularObj = true;
R.Prevailing = !isUndefined(Sym);
// Identify symbols exported dynamically, and that therefore could be
// referenced by a shared library not visible to the linker.
R.ExportDynamic = true;
if (!Res.CanOmitFromDynSym)
R.VisibleToRegularObj = true;
// If the symbol has a C identifier section name, we need to mark
// it as visible to a regular object so that LTO will keep it around
// to ensure the linker generates special __start_<secname> and
// __stop_<secname> symbols which may be used elsewhere.
if (isValidCIdentifier(InpSym.getSectionName()))
R.VisibleToRegularObj = true;
if (Resolution != LDPR_RESOLVED_DYN && Resolution != LDPR_UNDEF &&
(IsExecutable || !Res.DefaultVisibility))
R.FinalDefinitionInLinkageUnit = true;
if (!Res.CanInline)
R.LinkerRedefined = true;
if (Res.IsUsedInRegularObj)
R.VisibleToRegularObj = true;
check(Lto.add(std::move(Input), Resols),
std::string("Failed to link module ") +;
static void recordFile(const std::string &Filename, bool TempOutFile) {
if (add_input_file(Filename.c_str()) != LDPS_OK)
"Unable to add .o file to the link. File left behind in: %s",
if (TempOutFile)
/// Return the desired output filename given a base input name, a flag
/// indicating whether a temp file should be generated, and an optional task id.
/// The new filename generated is returned in \p NewFilename.
static int getOutputFileName(StringRef InFilename, bool TempOutFile,
SmallString<128> &NewFilename, int TaskID) {
int FD = -1;
if (TempOutFile) {
std::error_code EC =
sys::fs::createTemporaryFile("lto-llvm", "o", FD, NewFilename);
if (EC)
message(LDPL_FATAL, "Could not create temporary file: %s",
} else {
NewFilename = InFilename;
if (TaskID > 0)
NewFilename += utostr(TaskID);
std::error_code EC =
sys::fs::openFileForWrite(NewFilename, FD, sys::fs::CD_CreateAlways);
if (EC)
message(LDPL_FATAL, "Could not open file %s: %s", NewFilename.c_str(),
return FD;
static CodeGenOpt::Level getCGOptLevel() {
switch (options::OptLevel) {
case 0:
return CodeGenOpt::None;
case 1:
return CodeGenOpt::Less;
case 2:
return CodeGenOpt::Default;
case 3:
return CodeGenOpt::Aggressive;
llvm_unreachable("Invalid optimization level");
/// Parse the thinlto_prefix_replace option into the \p OldPrefix and
/// \p NewPrefix strings, if it was specified.
static void getThinLTOOldAndNewPrefix(std::string &OldPrefix,
std::string &NewPrefix) {
StringRef PrefixReplace = options::thinlto_prefix_replace;
assert(PrefixReplace.empty() || PrefixReplace.find(';') != StringRef::npos);
auto Split = PrefixReplace.split(';');
OldPrefix = std::string(Split.first);
NewPrefix = std::string(Split.second);
/// Creates instance of LTO.
/// OnIndexWrite is callback to let caller know when LTO writes index files.
/// LinkedObjectsFile is an output stream to write the list of object files for
/// the final ThinLTO linking. Can be nullptr.
static std::unique_ptr<LTO> createLTO(IndexWriteCallback OnIndexWrite,
raw_fd_ostream *LinkedObjectsFile) {
Config Conf;
ThinBackend Backend;
Conf.CPU = options::mcpu;
Conf.Options = codegen::InitTargetOptionsFromCodeGenFlags(Triple());
// Disable the new X86 relax relocations since gold might not support them.
// FIXME: Check the gold version or add a new option to enable them.
Conf.Options.RelaxELFRelocations = false;
// Toggle function/data sections.
if (!codegen::getExplicitFunctionSections())
Conf.Options.FunctionSections = SplitSections;
if (!codegen::getExplicitDataSections())
Conf.Options.DataSections = SplitSections;
Conf.MAttrs = codegen::getMAttrs();
Conf.RelocModel = RelocationModel;
Conf.CodeModel = codegen::getExplicitCodeModel();
Conf.CGOptLevel = getCGOptLevel();
Conf.DisableVerify = options::DisableVerify;
Conf.OptLevel = options::OptLevel;
Conf.PTO.LoopVectorization = options::OptLevel > 1;
Conf.PTO.SLPVectorization = options::OptLevel > 1;
Conf.AlwaysEmitRegularLTOObj = !options::obj_path.empty();
if (options::thinlto_index_only) {
std::string OldPrefix, NewPrefix;
getThinLTOOldAndNewPrefix(OldPrefix, NewPrefix);
Backend = createWriteIndexesThinBackend(OldPrefix, NewPrefix,
LinkedObjectsFile, OnIndexWrite);
} else {
Backend = createInProcessThinBackend(
Conf.OverrideTriple = options::triple;
Conf.DefaultTriple = sys::getDefaultTargetTriple();
Conf.DiagHandler = diagnosticHandler;
switch (options::TheOutputType) {
case options::OT_NORMAL:
case options::OT_DISABLE:
Conf.PreOptModuleHook = [](size_t Task, const Module &M) { return false; };
case options::OT_BC_ONLY:
Conf.PostInternalizeModuleHook = [](size_t Task, const Module &M) {
std::error_code EC;
SmallString<128> TaskFilename;
getOutputFileName(output_name, /* TempOutFile */ false, TaskFilename,
raw_fd_ostream OS(TaskFilename, EC, sys::fs::OpenFlags::OF_None);
if (EC)
message(LDPL_FATAL, "Failed to write the output file.");
WriteBitcodeToFile(M, OS, /* ShouldPreserveUseListOrder */ false);
return false;
case options::OT_SAVE_TEMPS:
check(Conf.addSaveTemps(output_name + ".",
/* UseInputModulePath */ true));
case options::OT_ASM_ONLY:
Conf.CGFileType = CGFT_AssemblyFile;
if (!options::sample_profile.empty())
Conf.SampleProfile = options::sample_profile;
if (!options::cs_profile_path.empty())
Conf.CSIRProfile = options::cs_profile_path;
Conf.RunCSIRInstr = options::cs_pgo_gen;
Conf.DwoDir = options::dwo_dir;
// Set up optimization remarks handling.
Conf.RemarksFilename = options::RemarksFilename;
Conf.RemarksPasses = options::RemarksPasses;
Conf.RemarksWithHotness = options::RemarksWithHotness;
Conf.RemarksHotnessThreshold = options::RemarksHotnessThreshold;
Conf.RemarksFormat = options::RemarksFormat;
// Use new pass manager if set in driver
Conf.UseNewPM = options::new_pass_manager;
// Debug new pass manager if requested
Conf.DebugPassManager = options::debug_pass_manager;
Conf.HasWholeProgramVisibility = options::whole_program_visibility;
Conf.StatsFile = options::stats_file;
return std::make_unique<LTO>(std::move(Conf), Backend,
// Write empty files that may be expected by a distributed build
// system when invoked with thinlto_index_only. This is invoked when
// the linker has decided not to include the given module in the
// final link. Frequently the distributed build system will want to
// confirm that all expected outputs are created based on all of the
// modules provided to the linker.
// If SkipModule is true then .thinlto.bc should contain just
// SkipModuleByDistributedBackend flag which requests distributed backend
// to skip the compilation of the corresponding module and produce an empty
// object file.
static void writeEmptyDistributedBuildOutputs(const std::string &ModulePath,
const std::string &OldPrefix,
const std::string &NewPrefix,
bool SkipModule) {
std::string NewModulePath =
getThinLTOOutputFile(ModulePath, OldPrefix, NewPrefix);
std::error_code EC;
raw_fd_ostream OS(NewModulePath + ".thinlto.bc", EC,
if (EC)
message(LDPL_FATAL, "Failed to write '%s': %s",
(NewModulePath + ".thinlto.bc").c_str(), EC.message().c_str());
if (SkipModule) {
ModuleSummaryIndex Index(/*HaveGVs*/ false);
WriteIndexToFile(Index, OS, nullptr);
if (options::thinlto_emit_imports_files) {
raw_fd_ostream OS(NewModulePath + ".imports", EC,
if (EC)
message(LDPL_FATAL, "Failed to write '%s': %s",
(NewModulePath + ".imports").c_str(), EC.message().c_str());
// Creates and returns output stream with a list of object files for final
// linking of distributed ThinLTO.
static std::unique_ptr<raw_fd_ostream> CreateLinkedObjectsFile() {
if (options::thinlto_linked_objects_file.empty())
return nullptr;
std::error_code EC;
auto LinkedObjectsFile = std::make_unique<raw_fd_ostream>(
options::thinlto_linked_objects_file, EC, sys::fs::OpenFlags::OF_None);
if (EC)
message(LDPL_FATAL, "Failed to create '%s': %s",
options::thinlto_linked_objects_file.c_str(), EC.message().c_str());
return LinkedObjectsFile;
/// Runs LTO and return a list of pairs <FileName, IsTemporary>.
static std::vector<std::pair<SmallString<128>, bool>> runLTO() {
// Map to own RAII objects that manage the file opening and releasing
// interfaces with gold. This is needed only for ThinLTO mode, since
// unlike regular LTO, where addModule will result in the opened file
// being merged into a new combined module, we need to keep these files open
// through Lto->run().
DenseMap<void *, std::unique_ptr<PluginInputFile>> HandleToInputFile;
// Owns string objects and tells if index file was already created.
StringMap<bool> ObjectToIndexFileState;
std::unique_ptr<raw_fd_ostream> LinkedObjects = CreateLinkedObjectsFile();
std::unique_ptr<LTO> Lto = createLTO(
[&ObjectToIndexFileState](const std::string &Identifier) {
ObjectToIndexFileState[Identifier] = true;
std::string OldPrefix, NewPrefix;
if (options::thinlto_index_only)
getThinLTOOldAndNewPrefix(OldPrefix, NewPrefix);
std::string OldSuffix, NewSuffix;
getThinLTOOldAndNewSuffix(OldSuffix, NewSuffix);
for (claimed_file &F : Modules) {
if (options::thinlto && !HandleToInputFile.count(F.leader_handle))
F.leader_handle, std::make_unique<PluginInputFile>(F.handle)));
// In case we are thin linking with a minimized bitcode file, ensure
// the module paths encoded in the index reflect where the backends
// will locate the full bitcode files for compiling/importing.
std::string Identifier =
getThinLTOObjectFileName(, OldSuffix, NewSuffix);
auto ObjFilename = ObjectToIndexFileState.insert({Identifier, false});
if (const void *View = getSymbolsAndView(F))
addModule(*Lto, F, View, ObjFilename.first->first());
else if (options::thinlto_index_only) {
ObjFilename.first->second = true;
writeEmptyDistributedBuildOutputs(Identifier, OldPrefix, NewPrefix,
/* SkipModule */ true);
SmallString<128> Filename;
// Note that getOutputFileName will append a unique ID for each task
if (!options::obj_path.empty())
Filename = options::obj_path;
else if (options::TheOutputType == options::OT_SAVE_TEMPS)
Filename = output_name + ".lto.o";
else if (options::TheOutputType == options::OT_ASM_ONLY)
Filename = output_name;
bool SaveTemps = !Filename.empty();
size_t MaxTasks = Lto->getMaxTasks();
std::vector<std::pair<SmallString<128>, bool>> Files(MaxTasks);
auto AddStream = [&](size_t Task) -> std::unique_ptr<CachedFileStream> {
Files[Task].second = !SaveTemps;
int FD = getOutputFileName(Filename, /* TempOutFile */ !SaveTemps,
Files[Task].first, Task);
return std::make_unique<CachedFileStream>(
std::make_unique<llvm::raw_fd_ostream>(FD, true));
auto AddBuffer = [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) {
*AddStream(Task)->OS << MB->getBuffer();
FileCache Cache;
if (!options::cache_dir.empty())
Cache = check(localCache("ThinLTO", "Thin", options::cache_dir, AddBuffer));
check(Lto->run(AddStream, Cache));
// Write empty output files that may be expected by the distributed build
// system.
if (options::thinlto_index_only)
for (auto &Identifier : ObjectToIndexFileState)
if (!Identifier.getValue())
OldPrefix, NewPrefix,
/* SkipModule */ false);
return Files;
/// gold informs us that all symbols have been read. At this point, we use
/// get_symbols to see if any of our definitions have been overridden by a
/// native object file. Then, perform optimization and codegen.
static ld_plugin_status allSymbolsReadHook() {
if (Modules.empty())
return LDPS_OK;
if (unsigned NumOpts = options::extra.size())
cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);
std::vector<std::pair<SmallString<128>, bool>> Files = runLTO();
if (options::TheOutputType == options::OT_DISABLE ||
options::TheOutputType == options::OT_BC_ONLY ||
options::TheOutputType == options::OT_ASM_ONLY)
return LDPS_OK;
if (options::thinlto_index_only) {
for (const auto &F : Files)
if (!F.first.empty())
recordFile(std::string(F.first.str()), F.second);
if (!options::extra_library_path.empty() &&
set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK)
message(LDPL_FATAL, "Unable to set the extra library path.");
return LDPS_OK;
static ld_plugin_status all_symbols_read_hook(void) {
ld_plugin_status Ret = allSymbolsReadHook();
if (options::TheOutputType == options::OT_BC_ONLY ||
options::TheOutputType == options::OT_ASM_ONLY ||
options::TheOutputType == options::OT_DISABLE) {
if (options::TheOutputType == options::OT_DISABLE) {
// Remove the output file here since ld.bfd creates the output file
// early.
std::error_code EC = sys::fs::remove(output_name);
if (EC)
message(LDPL_ERROR, "Failed to delete '%s': %s", output_name.c_str(),
return Ret;
static ld_plugin_status cleanup_hook(void) {
for (std::string &Name : Cleanup) {
std::error_code EC = sys::fs::remove(Name);
if (EC)
message(LDPL_ERROR, "Failed to delete '%s': %s", Name.c_str(),
// Prune cache
if (!options::cache_dir.empty()) {
CachePruningPolicy policy = check(parseCachePruningPolicy(options::cache_policy));
pruneCache(options::cache_dir, policy);
return LDPS_OK;