Optimize nonoptimizing compilation IV

[Neil Booth]

Jan Hubicka wrote:-

> Hi,
> this patch avoids optimize_mode_swithcing when no instructions needing
> it are present in the insn stream.  It saves 7% out of insn-attrtab
> build time at -O0.  Together with the tidy_fallthru_eges we are already
> faster than gcc-3.0 (and with this patch only we are faster than
> gcc-3.2)

Cool.  Is CPP beginning to be a significant part of the time at -O0?
We should be able to get it to at least 30% I expect.

Neil.