[PATCH] Overhaul __builtin_constant_p processing (take 2)

[Roger Sayle]

Hi Neil,
> I think it's really important we stop this gradual rot.

I'm happy to entertain other suggestions for fixing PR opt/8423.

You'll have to trust me that we'll probably eventually recover this
loss by combining it with GCSE's local_cprop, but that won't happen
over night.  I'd be more concerned about the slow downs that we
haven't predicted, and don't have any plans to remedy.

Alternatively, my still unreviewed patch "More aggressive jump
bypassing", http://gcc.gnu.org/ml/gcc-patches/2003-01/msg01164.html,
knocked over 12 seconds of the bootstrap time of just the C, C++
and FORTRAN compilers as measured by Andreas' SPEC2000 benchmarking
scripts when run last June.  Of course, Moore's law also predicts
that computers are 25% faster now than they were then... :>

Roger
--