Re: Reload patch to improve 386 code

[Jeffrey A Law <law at cygnus dot com>]

Another reply to an old message from Bernd...

  In message <Pine.SOL.3.90.970819095143.291G-100000@starsky.informatik.rwth-aachen.de>you write:
  > Then, there are some simplifications that could be done. I don't like the
  > inheritance code, find_equiv_reg and all that. IMHO reload shouldn't try to
  > be very clever about this sort of thing - the reload_cse_regs pass can be made
  > more clever.
While reload_cse_regs can help this stuff, I'm not sure that it totally
eliminates the need for the reload inheritance stuff.  In fact, I'm
sure Joern can show you lots of case where improving inheritance leads
to better code.

So, I'm not sure it's time to ditch the inheritance code yet.  Given
the structure of the locally spilling reload code, I do see how reload
inheriting gets noticably more complicated.

One thing we should try is a cook off between the locally spilling reload
code (with inheritance disabled) and the existing reload code.  If
the locally spilling reloader generally wins, I'll support disabling
inheritance to get the benefit of local spilling.  Then we can go
back later and try to make inheritance work with your reload code.

[ Then again, if you've made inheritance work, then there's no need
  for the cook off :-)  I guess I'll find out when I start actually
  looking at the code. ]


jeff