1 files changed, 150 insertions, 0 deletions
diff --git a/llvm/lib/LTO/Caching.cpp b/llvm/lib/LTO/Caching.cpp
new file mode 100644
index 0000000000000..12dcd182de2d0
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+++ b/llvm/lib/LTO/Caching.cpp
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+//===-Caching.cpp - LLVM Link Time Optimizer Cache Handling ---------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Caching for ThinLTO.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/Caching.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/raw_ostream.h"
+
+#if !defined(_MSC_VER) && !defined(__MINGW32__)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+
+using namespace llvm;
+using namespace llvm::lto;
+
+Expected<NativeObjectCache> lto::localCache(StringRef CacheDirectoryPath,
+                                            AddBufferFn AddBuffer) {
+  if (std::error_code EC = sys::fs::create_directories(CacheDirectoryPath))
+    return errorCodeToError(EC);
+
+  return [=](unsigned Task, StringRef Key) -> AddStreamFn {
+    // This choice of file name allows the cache to be pruned (see pruneCache()
+    // in include/llvm/Support/CachePruning.h).
+    SmallString<64> EntryPath;
+    sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key);
+    // First, see if we have a cache hit.
+    SmallString<64> ResultPath;
+    Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead(
+        Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath);
+    std::error_code EC;
+    if (FDOrErr) {
+      ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
+          MemoryBuffer::getOpenFile(*FDOrErr, EntryPath,
+                                    /*FileSize=*/-1,
+                                    /*RequiresNullTerminator=*/false);
+      sys::fs::closeFile(*FDOrErr);
+      if (MBOrErr) {
+        AddBuffer(Task, std::move(*MBOrErr));
+        return AddStreamFn();
+      }
+      EC = MBOrErr.getError();
+    } else {
+      EC = errorToErrorCode(FDOrErr.takeError());
+    }
+
+    // On Windows we can fail to open a cache file with a permission denied
+    // error. This generally means that another process has requested to delete
+    // the file while it is still open, but it could also mean that another
+    // process has opened the file without the sharing permissions we need.
+    // Since the file is probably being deleted we handle it in the same way as
+    // if the file did not exist at all.
+    if (EC != errc::no_such_file_or_directory && EC != errc::permission_denied)
+      report_fatal_error(Twine("Failed to open cache file ") + EntryPath +
+                         ": " + EC.message() + "\n");
+
+    // This native object stream is responsible for commiting the resulting
+    // file to the cache and calling AddBuffer to add it to the link.
+    struct CacheStream : NativeObjectStream {
+      AddBufferFn AddBuffer;
+      sys::fs::TempFile TempFile;
+      std::string EntryPath;
+      unsigned Task;
+
+      CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer,
+                  sys::fs::TempFile TempFile, std::string EntryPath,
+                  unsigned Task)
+          : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)),
+            TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)),
+            Task(Task) {}
+
+      ~CacheStream() {
+        // Make sure the stream is closed before committing it.
+        OS.reset();
+
+        // Open the file first to avoid racing with a cache pruner.
+        ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
+            MemoryBuffer::getOpenFile(
+                sys::fs::convertFDToNativeFile(TempFile.FD), TempFile.TmpName,
+                /*FileSize=*/-1, /*RequiresNullTerminator=*/false);
+        if (!MBOrErr)
+          report_fatal_error(Twine("Failed to open new cache file ") +
+                             TempFile.TmpName + ": " +
+                             MBOrErr.getError().message() + "\n");
+
+        // On POSIX systems, this will atomically replace the destination if
+        // it already exists. We try to emulate this on Windows, but this may
+        // fail with a permission denied error (for example, if the destination
+        // is currently opened by another process that does not give us the
+        // sharing permissions we need). Since the existing file should be
+        // semantically equivalent to the one we are trying to write, we give
+        // AddBuffer a copy of the bytes we wrote in that case. We do this
+        // instead of just using the existing file, because the pruner might
+        // delete the file before we get a chance to use it.
+        Error E = TempFile.keep(EntryPath);
+        E = handleErrors(std::move(E), [&](const ECError &E) -> Error {
+          std::error_code EC = E.convertToErrorCode();
+          if (EC != errc::permission_denied)
+            return errorCodeToError(EC);
+
+          auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(),
+                                                       EntryPath);
+          MBOrErr = std::move(MBCopy);
+
+          // FIXME: should we consume the discard error?
+          consumeError(TempFile.discard());
+
+          return Error::success();
+        });
+
+        if (E)
+          report_fatal_error(Twine("Failed to rename temporary file ") +
+                             TempFile.TmpName + " to " + EntryPath + ": " +
+                             toString(std::move(E)) + "\n");
+
+        AddBuffer(Task, std::move(*MBOrErr));
+      }
+    };
+
+    return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> {
+      // Write to a temporary to avoid race condition
+      SmallString<64> TempFilenameModel;
+      sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o");
+      Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create(
+          TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write);
+      if (!Temp) {
+        errs() << "Error: " << toString(Temp.takeError()) << "\n";
+        report_fatal_error("ThinLTO: Can't get a temporary file");
+      }
+
+      // This CacheStream will move the temporary file into the cache when done.
+      return std::make_unique<CacheStream>(
+          std::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false),
+          AddBuffer, std::move(*Temp), EntryPath.str(), Task);
+    };
+  };
+}