llvm-capstone/lld/ELF/Driver.h
Fangrui Song a96fe1bf3b [ELF][LTO] Call madvise(MADV_DONTNEED) on MemoryBuffer instances
@tejohnson noticed that freeing MemoryBuffer instances right before
`lto->compile` can save RSS, likely because the memory can be reused by
LTO indexing (e.g. ThinLTO import/export lists).).

For ELFFileBase instances, symbol and section names are backed by MemoryBuffer,
so destroying MemoryBuffer would make some infrequent passes (parseSymbolVersion,
reportBackrefs) crash and make debugging difficult.
For a BitcodeFile, its content is completely unused, but destroying its
MemoryBuffer makes the buffer identifier inaccessible and may introduce
constraints for future changes.
This patch leverages madvise(MADV_DONTNEED) which achieves the major gain
without the latent issues.

`Maximum resident set size (kbytes): ` for a large --thinlto-index-only link:

* current behavior: 10146104KiB
* destroy MemoryBuffer instances: 8555240KiB
* madvise(MADV_DONTNEED) just bitcodeFiles  and lazyBitcodeFiles: 8737372KiB
* madvise(MADV_DONTNEED) all MemoryBuffers: 8739796KiB  (16% decrease)

Depends on D116366

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D116367
2021-12-30 11:36:58 -08:00

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2.1 KiB
C++

//===- Driver.h -------------------------------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
#ifndef LLD_ELF_DRIVER_H
#define LLD_ELF_DRIVER_H
#include "LTO.h"
#include "SymbolTable.h"
#include "lld/Common/LLVM.h"
#include "lld/Common/Reproduce.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Support/raw_ostream.h"
namespace lld {
namespace elf {
extern std::unique_ptr<class LinkerDriver> driver;
class LinkerDriver {
public:
void linkerMain(ArrayRef<const char *> args);
void addFile(StringRef path, bool withLOption);
void addLibrary(StringRef name);
private:
void createFiles(llvm::opt::InputArgList &args);
void inferMachineType();
template <class ELFT> void link(llvm::opt::InputArgList &args);
template <class ELFT> void compileBitcodeFiles(bool skipLinkedOutput);
// True if we are in --whole-archive and --no-whole-archive.
bool inWholeArchive = false;
// True if we are in --start-lib and --end-lib.
bool inLib = false;
// For LTO.
std::unique_ptr<BitcodeCompiler> lto;
std::vector<InputFile *> files;
};
// Parses command line options.
class ELFOptTable : public llvm::opt::OptTable {
public:
ELFOptTable();
llvm::opt::InputArgList parse(ArrayRef<const char *> argv);
};
// Create enum with OPT_xxx values for each option in Options.td
enum {
OPT_INVALID = 0,
#define OPTION(_1, _2, ID, _4, _5, _6, _7, _8, _9, _10, _11, _12) OPT_##ID,
#include "Options.inc"
#undef OPTION
};
void printHelp();
std::string createResponseFile(const llvm::opt::InputArgList &args);
llvm::Optional<std::string> findFromSearchPaths(StringRef path);
llvm::Optional<std::string> searchScript(StringRef path);
llvm::Optional<std::string> searchLibraryBaseName(StringRef path);
llvm::Optional<std::string> searchLibrary(StringRef path);
} // namespace elf
} // namespace lld
#endif