PTH: Cache directory and negative 'stat' calls.  This gives us a 1% performance improvement on Cocoa.h (fsyntax-only+PTH).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64490 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed