forked from OSchip/llvm-project
105 lines
3.9 KiB
C++
105 lines
3.9 KiB
C++
//===-Caching.cpp - LLVM Link Time Optimizer Cache Handling ---------------===//
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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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// This file implements the Caching for ThinLTO.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/LTO/Caching.h"
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#ifdef HAVE_LLVM_REVISION
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#include "LLVMLTORevision.h"
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#endif
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/Path.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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using namespace llvm::lto;
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static void commitEntry(StringRef TempFilename, StringRef EntryPath) {
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// Rename to final destination (hopefully race condition won't matter here)
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auto EC = sys::fs::rename(TempFilename, EntryPath);
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if (EC) {
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// Renaming failed, probably not the same filesystem, copy and delete.
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{
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auto ReloadedBufferOrErr = MemoryBuffer::getFile(TempFilename);
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if (auto EC = ReloadedBufferOrErr.getError())
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report_fatal_error(Twine("Failed to open temp file '") + TempFilename +
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"': " + EC.message() + "\n");
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raw_fd_ostream OS(EntryPath, EC, sys::fs::F_None);
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if (EC)
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report_fatal_error(Twine("Failed to open ") + EntryPath +
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" to save cached entry\n");
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// I'm not sure what are the guarantee if two processes are doing this
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// at the same time.
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OS << (*ReloadedBufferOrErr)->getBuffer();
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}
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sys::fs::remove(TempFilename);
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}
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}
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CacheObjectOutput::~CacheObjectOutput() {
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if (EntryPath.empty())
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// The entry was never used by the client (tryLoadFromCache() wasn't called)
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return;
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// TempFilename is only set if getStream() was called, i.e. on cache miss when
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// tryLoadFromCache() returned false. And EntryPath is valid if a Key was
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// submitted, otherwise it has been set to CacheDirectoryPath in
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// tryLoadFromCache.
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if (!TempFilename.empty()) {
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if (EntryPath == CacheDirectoryPath)
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// The Key supplied to tryLoadFromCache was empty, do not commit the temp.
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EntryPath = TempFilename;
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else
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// We commit the tempfile into the cache now, by moving it to EntryPath.
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commitEntry(TempFilename, EntryPath);
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}
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// Load the entry from the cache now.
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auto ReloadedBufferOrErr = MemoryBuffer::getFile(EntryPath);
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if (auto EC = ReloadedBufferOrErr.getError())
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report_fatal_error(Twine("Can't reload cached file '") + EntryPath + "': " +
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EC.message() + "\n");
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// Supply the resulting buffer to the user.
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AddBuffer(std::move(*ReloadedBufferOrErr));
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}
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// Return an allocated stream for the output, or null in case of failure.
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std::unique_ptr<raw_pwrite_stream> CacheObjectOutput::getStream() {
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assert(!EntryPath.empty() && "API Violation: client didn't call "
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"tryLoadFromCache() before getStream()");
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// Write to a temporary to avoid race condition
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int TempFD;
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std::error_code EC =
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sys::fs::createTemporaryFile("Thin", "tmp.o", TempFD, TempFilename);
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if (EC) {
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errs() << "Error: " << EC.message() << "\n";
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report_fatal_error("ThinLTO: Can't get a temporary file");
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}
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return llvm::make_unique<raw_fd_ostream>(TempFD, /* ShouldClose */ true);
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}
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// Try loading from a possible cache first, return true on cache hit.
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bool CacheObjectOutput::tryLoadFromCache(StringRef Key) {
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assert(!CacheDirectoryPath.empty() &&
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"CacheObjectOutput was initialized without a cache path");
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if (Key.empty()) {
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// Client didn't compute a valid key. EntryPath has been set to
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// CacheDirectoryPath.
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EntryPath = CacheDirectoryPath;
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return false;
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}
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sys::path::append(EntryPath, CacheDirectoryPath, Key);
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return sys::fs::exists(EntryPath);
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}
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