Driver: Make argument parsing fast.

On a synthetic command line consisting of almost all defined options,
this drops wall time from .00494 to .00336 and user time from .00258
to .00105.

On the same benchmark, clang-driver is about 15% faster than the
primary gcc driver and almost twice as fast as the gcc driver driver.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67564 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed