Speed-up clang compilation for preprocessed files

Hi!

What I'm doing:
  1. Run `clang++ -### -c test.cc`
  2. Run `clang -cc1 -E <flags from previous command> -o test.E`
  3. Run `clang++ -c test.E -o test.o`

I want to speed-up the third step. Since I have done all the
preprocessing stuff, I suggest that there is a more efficient way of
calling clang to compile already preprocessed file. How can I do that?

Thanks in advance.
Ivan.

Preprocessor is built-in into clang, so if your source code does not preprocessor directives, there is no extra expences.