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82b6d2e64d
We extend an underlying file before mmap'ing it, but it's not needed on Windows. Extending file is slow on Windows, so we should avoid doing that. The difference gets larger as the size of an output file gets larger. It shove off 2 seconds out of 25 seconds when linking chrome.dll with LLD, for example. llvm-svn: 231452
114 lines
3.4 KiB
C++
114 lines
3.4 KiB
C++
//===- FileOutputBuffer.cpp - File Output Buffer ----------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Utility for creating a in-memory buffer that will be written to a file.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/Errc.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Support/FileOutputBuffer.h"
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#include "llvm/Support/raw_ostream.h"
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#include <system_error>
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#if !defined(_MSC_VER) && !defined(__MINGW32__)
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#include <unistd.h>
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#else
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#include <io.h>
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#endif
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using llvm::sys::fs::mapped_file_region;
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namespace llvm {
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FileOutputBuffer::FileOutputBuffer(std::unique_ptr<mapped_file_region> R,
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StringRef Path, StringRef TmpPath)
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: Region(std::move(R)), FinalPath(Path), TempPath(TmpPath) {}
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FileOutputBuffer::~FileOutputBuffer() {
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sys::fs::remove(Twine(TempPath));
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}
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std::error_code
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FileOutputBuffer::create(StringRef FilePath, size_t Size,
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std::unique_ptr<FileOutputBuffer> &Result,
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unsigned Flags) {
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// If file already exists, it must be a regular file (to be mappable).
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sys::fs::file_status Stat;
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std::error_code EC = sys::fs::status(FilePath, Stat);
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switch (Stat.type()) {
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case sys::fs::file_type::file_not_found:
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// If file does not exist, we'll create one.
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break;
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case sys::fs::file_type::regular_file: {
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// If file is not currently writable, error out.
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// FIXME: There is no sys::fs:: api for checking this.
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// FIXME: In posix, you use the access() call to check this.
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}
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break;
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default:
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if (EC)
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return EC;
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else
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return make_error_code(errc::operation_not_permitted);
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}
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// Delete target file.
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EC = sys::fs::remove(FilePath);
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if (EC)
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return EC;
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unsigned Mode = sys::fs::all_read | sys::fs::all_write;
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// If requested, make the output file executable.
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if (Flags & F_executable)
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Mode |= sys::fs::all_exe;
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// Create new file in same directory but with random name.
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SmallString<128> TempFilePath;
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int FD;
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EC = sys::fs::createUniqueFile(Twine(FilePath) + ".tmp%%%%%%%", FD,
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TempFilePath, Mode);
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if (EC)
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return EC;
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#ifndef LLVM_ON_WIN32
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// On Windows, CreateFileMapping (the mmap function on Windows)
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// automatically extends the underlying file. We don't need to
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// extend the file beforehand. _chsize (ftruncate on Windows) is
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// pretty slow just like it writes specified amount of bytes,
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// so we should avoid calling that.
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EC = sys::fs::resize_file(FD, Size);
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if (EC)
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return EC;
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#endif
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auto MappedFile = llvm::make_unique<mapped_file_region>(
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FD, mapped_file_region::readwrite, Size, 0, EC);
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int Ret = close(FD);
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if (EC)
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return EC;
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if (Ret)
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return std::error_code(errno, std::generic_category());
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Result.reset(
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new FileOutputBuffer(std::move(MappedFile), FilePath, TempFilePath));
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return std::error_code();
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}
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std::error_code FileOutputBuffer::commit() {
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// Unmap buffer, letting OS flush dirty pages to file on disk.
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Region.reset();
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// Rename file to final name.
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return sys::fs::rename(Twine(TempPath), Twine(FinalPath));
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}
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} // namespace
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