Index: lib/LTO/Caching.cpp
===================================================================
--- lib/LTO/Caching.cpp
+++ lib/LTO/Caching.cpp
@@ -71,20 +71,7 @@
                              TempFilename + ": " +
                              MBOrErr.getError().message() + "\n");
 
-        // This is atomic on POSIX systems.
-        // On Windows, it can fail with permission denied if the destination
-        // file already exists. 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.
-        auto EC = sys::fs::rename(TempFilename, EntryPath);
-        if (EC == errc::permission_denied) {
-          auto MBCopy = MemoryBuffer::getMemBufferCopy(
-              (*MBOrErr)->getBuffer(), EntryPath);
-          MBOrErr = std::move(MBCopy);
-          sys::fs::remove(TempFilename);
-        } else if (EC) {
+        if (auto EC = sys::fs::rename(TempFilename, EntryPath)) {
           report_fatal_error(Twine("Failed to rename temporary file ") +
                              TempFilename + " to " + EntryPath + ": " +
                              EC.message() + "\n");