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//===-Caching.cpp - LLVM Link Time Optimizer Cache Handling ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Caching for ThinLTO.
//
//===----------------------------------------------------------------------===//
#include "llvm/LTO/Caching.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
using namespace llvm::lto;
static void commitEntry(StringRef TempFilename, StringRef EntryPath) {
// Rename to final destination (hopefully race condition won't matter here)
auto EC = sys::fs::rename(TempFilename, EntryPath);
if (EC) {
// Renaming failed, probably not the same filesystem, copy and delete.
// FIXME: Avoid needing to do this by creating the temporary file in the
// cache directory.
{
auto ReloadedBufferOrErr = MemoryBuffer::getFile(TempFilename);
if (auto EC = ReloadedBufferOrErr.getError())
report_fatal_error(Twine("Failed to open temp file '") + TempFilename +
"': " + EC.message() + "\n");
raw_fd_ostream OS(EntryPath, EC, sys::fs::F_None);
if (EC)
report_fatal_error(Twine("Failed to open ") + EntryPath +
" to save cached entry\n");
// I'm not sure what are the guarantee if two processes are doing this
// at the same time.
OS << (*ReloadedBufferOrErr)->getBuffer();
}
sys::fs::remove(TempFilename);
}
}
NativeObjectCache lto::localCache(std::string CacheDirectoryPath,
AddFileFn AddFile) {
return [=](unsigned Task, StringRef Key) -> AddStreamFn {
// First, see if we have a cache hit.
SmallString<64> EntryPath;
sys::path::append(EntryPath, CacheDirectoryPath, Key);
if (sys::fs::exists(EntryPath)) {
AddFile(Task, EntryPath);
return AddStreamFn();
}
// This native object stream is responsible for commiting the resulting
// file to the cache and calling AddFile to add it to the link.
struct CacheStream : NativeObjectStream {
AddFileFn AddFile;
std::string TempFilename;
std::string EntryPath;
unsigned Task;
CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddFileFn AddFile,
std::string TempFilename, std::string EntryPath,
unsigned Task)
: NativeObjectStream(std::move(OS)), AddFile(AddFile),
TempFilename(TempFilename), EntryPath(EntryPath), Task(Task) {}
~CacheStream() {
// Make sure the file is closed before committing it.
OS.reset();
commitEntry(TempFilename, EntryPath);
AddFile(Task, EntryPath);
}
};
return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> {
// Write to a temporary to avoid race condition
int TempFD;
SmallString<64> TempFilename;
std::error_code EC =
sys::fs::createTemporaryFile("Thin", "tmp.o", TempFD, TempFilename);
if (EC) {
errs() << "Error: " << EC.message() << "\n";
report_fatal_error("ThinLTO: Can't get a temporary file");
}
// This CacheStream will move the temporary file into the cache when done.
return llvm::make_unique<CacheStream>(
llvm::make_unique<raw_fd_ostream>(TempFD, /* ShouldClose */ true),
AddFile, TempFilename.str(), EntryPath.str(), Task);
};
};
}
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