llvm-project/llvm/tools/llvm-debuginfod-find/llvm-debuginfod-find.cpp
Chandler Carruth dd647e3e60
Rework the Option library to reduce dynamic relocations (#119198)
Apologies for the large change, I looked for ways to break this up and
all of the ones I saw added real complexity. This change focuses on the
option's prefixed names and the array of prefixes. These are present in
every option and the dominant source of dynamic relocations for PIE or
PIC users of LLVM and Clang tooling. In some cases, 100s or 1000s of
them for the Clang driver which has a huge number of options.

This PR addresses this by building a string table and a prefixes table
that can be referenced with indices rather than pointers that require
dynamic relocations. This removes almost 7k dynmaic relocations from the
`clang` binary, roughly 8% of the remaining dynmaic relocations outside
of vtables. For busy-boxing use cases where many different option tables
are linked into the same binary, the savings add up a bit more.

The string table is a straightforward mechanism, but the prefixes
required some subtlety. They are encoded in a Pascal-string fashion with
a size followed by a sequence of offsets. This works relatively well for
the small realistic prefixes arrays in use.

Lots of code has to change in order to land this though: both all the
option library code has to be updated to use the string table and
prefixes table, and all the users of the options library have to be
updated to correctly instantiate the objects.

Some follow-up patches in the works to provide an abstraction for this
style of code, and to start using the same technique for some of the
other strings here now that the infrastructure is in place.
2024-12-11 15:44:44 -08:00

162 lines
5.2 KiB
C++

//===-- llvm-debuginfod-find.cpp - Simple CLI for libdebuginfod-client ----===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file contains the llvm-debuginfod-find tool. This tool
/// queries the debuginfod servers in the DEBUGINFOD_URLS environment
/// variable (delimited by space (" ")) for the executable,
/// debuginfo, or specified source file of the binary matching the
/// given build-id.
///
//===----------------------------------------------------------------------===//
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Debuginfod/BuildIDFetcher.h"
#include "llvm/Debuginfod/Debuginfod.h"
#include "llvm/Debuginfod/HTTPClient.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Option/Option.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/LLVMDriver.h"
using namespace llvm;
// Command-line option boilerplate.
namespace {
enum ID {
OPT_INVALID = 0, // This is not an option ID.
#define OPTION(...) LLVM_MAKE_OPT_ID(__VA_ARGS__),
#include "Opts.inc"
#undef OPTION
};
#define OPTTABLE_STR_TABLE_CODE
#include "Opts.inc"
#undef OPTTABLE_STR_TABLE_CODE
#define OPTTABLE_PREFIXES_TABLE_CODE
#include "Opts.inc"
#undef OPTTABLE_PREFIXES_TABLE_CODE
using namespace llvm::opt;
static constexpr opt::OptTable::Info InfoTable[] = {
#define OPTION(...) LLVM_CONSTRUCT_OPT_INFO(__VA_ARGS__),
#include "Opts.inc"
#undef OPTION
};
class DebuginfodFindOptTable : public opt::GenericOptTable {
public:
DebuginfodFindOptTable()
: GenericOptTable(OptionStrTable, OptionPrefixesTable, InfoTable) {}
};
} // end anonymous namespace
static std::string InputBuildID;
static bool FetchExecutable;
static bool FetchDebuginfo;
static std::string FetchSource;
static bool DumpToStdout;
static std::vector<std::string> DebugFileDirectory;
static void parseArgs(int argc, char **argv) {
DebuginfodFindOptTable Tbl;
llvm::BumpPtrAllocator A;
llvm::StringSaver Saver{A};
opt::InputArgList Args =
Tbl.parseArgs(argc, argv, OPT_UNKNOWN, Saver, [&](StringRef Msg) {
llvm::errs() << Msg << '\n';
std::exit(1);
});
if (Args.hasArg(OPT_help)) {
Tbl.printHelp(
llvm::outs(), "llvm-debuginfod-find [options] <input build_id>",
"llvm-debuginfod-find: Fetch debuginfod artifacts\n\n"
"This program is a frontend to the debuginfod client library. The "
"cache directory, request timeout (in seconds), and debuginfod server "
"urls are set by these environment variables:\n"
"DEBUGINFOD_CACHE_PATH (default set by sys::path::cache_directory)\n"
"DEBUGINFOD_TIMEOUT (defaults to 90s)\n"
"DEBUGINFOD_URLS=[comma separated URLs] (defaults to empty)");
std::exit(0);
}
InputBuildID = Args.getLastArgValue(OPT_INPUT);
FetchExecutable = Args.hasArg(OPT_fetch_executable);
FetchDebuginfo = Args.hasArg(OPT_fetch_debuginfo);
DumpToStdout = Args.hasArg(OPT_dump_to_stdout);
FetchSource = Args.getLastArgValue(OPT_fetch_source, "");
DebugFileDirectory = Args.getAllArgValues(OPT_debug_file_directory);
}
[[noreturn]] static void helpExit() {
errs() << "Must specify exactly one of --executable, "
"--source=/path/to/file, or --debuginfo.\n";
exit(1);
}
ExitOnError ExitOnDebuginfodFindError;
static std::string fetchDebugInfo(object::BuildIDRef BuildID);
int llvm_debuginfod_find_main(int argc, char **argv,
const llvm::ToolContext &) {
// InitLLVM X(argc, argv);
HTTPClient::initialize();
parseArgs(argc, argv);
if (FetchExecutable + FetchDebuginfo + (FetchSource != "") != 1)
helpExit();
std::string IDString;
if (!tryGetFromHex(InputBuildID, IDString)) {
errs() << "Build ID " << InputBuildID << " is not a hex string.\n";
exit(1);
}
object::BuildID ID(IDString.begin(), IDString.end());
std::string Path;
if (FetchSource != "")
Path =
ExitOnDebuginfodFindError(getCachedOrDownloadSource(ID, FetchSource));
else if (FetchExecutable)
Path = ExitOnDebuginfodFindError(getCachedOrDownloadExecutable(ID));
else if (FetchDebuginfo)
Path = fetchDebugInfo(ID);
else
llvm_unreachable("We have already checked that exactly one of the above "
"conditions is true.");
if (DumpToStdout) {
// Print the contents of the artifact.
ErrorOr<std::unique_ptr<MemoryBuffer>> Buf = MemoryBuffer::getFile(
Path, /*IsText=*/false, /*RequiresNullTerminator=*/false);
ExitOnDebuginfodFindError(errorCodeToError(Buf.getError()));
outs() << Buf.get()->getBuffer();
} else
// Print the path to the cached artifact file.
outs() << Path << "\n";
return 0;
}
// Find a debug file in local build ID directories and via debuginfod.
std::string fetchDebugInfo(object::BuildIDRef BuildID) {
if (std::optional<std::string> Path =
DebuginfodFetcher(DebugFileDirectory).fetch(BuildID))
return *Path;
errs() << "Build ID " << llvm::toHex(BuildID, /*Lowercase=*/true)
<< " could not be found.\n";
exit(1);
}