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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"
#ifdef HAVE_LLVM_REVISION
#include "LLVMLTORevision.h"
#endif
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/FileSystem.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.
{
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);
}
}
CacheObjectOutput::~CacheObjectOutput() {
if (EntryPath.empty())
// The entry was never used by the client (tryLoadFromCache() wasn't called)
return;
// TempFilename is only set if getStream() was called, i.e. on cache miss when
// tryLoadFromCache() returned false. And EntryPath is valid if a Key was
// submitted, otherwise it has been set to CacheDirectoryPath in
// tryLoadFromCache.
if (!TempFilename.empty()) {
if (EntryPath == CacheDirectoryPath)
// The Key supplied to tryLoadFromCache was empty, do not commit the temp.
EntryPath = TempFilename;
else
// We commit the tempfile into the cache now, by moving it to EntryPath.
commitEntry(TempFilename, EntryPath);
}
// Load the entry from the cache now.
auto ReloadedBufferOrErr = MemoryBuffer::getFile(EntryPath);
if (auto EC = ReloadedBufferOrErr.getError())
report_fatal_error(Twine("Can't reload cached file '") + EntryPath + "': " +
EC.message() + "\n");
// Supply the resulting buffer to the user.
AddBuffer(std::move(*ReloadedBufferOrErr));
}
// Return an allocated stream for the output, or null in case of failure.
std::unique_ptr<raw_pwrite_stream> CacheObjectOutput::getStream() {
assert(!EntryPath.empty() && "API Violation: client didn't call "
"tryLoadFromCache() before getStream()");
// Write to a temporary to avoid race condition
int TempFD;
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");
}
return llvm::make_unique<raw_fd_ostream>(TempFD, /* ShouldClose */ true);
}
// Try loading from a possible cache first, return true on cache hit.
bool CacheObjectOutput::tryLoadFromCache(StringRef Key) {
assert(!CacheDirectoryPath.empty() &&
"CacheObjectOutput was initialized without a cache path");
if (Key.empty()) {
// Client didn't compute a valid key. EntryPath has been set to
// CacheDirectoryPath.
EntryPath = CacheDirectoryPath;
return false;
}
sys::path::append(EntryPath, CacheDirectoryPath, Key);
return sys::fs::exists(EntryPath);
}
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