1 files changed, 104 insertions, 0 deletions
diff --git a/llvm/lib/LTO/Caching.cpp b/llvm/lib/LTO/Caching.cpp
new file mode 100644
index 00000000000..118efde6a1f
--- /dev/null
+++ b/llvm/lib/LTO/Caching.cpp
@@ -0,0 +1,104 @@
+//===-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);
+}