Re: Reload patch to improve 386 code

[Joern Rennecke <amylaar at cygnus dot co dot uk>]

> 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.

Actually, it's not that simple.  The test cases are confidential, and I
don't have time right now to look for other test cases or synthesize
artifical ones.

> 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.


This is not acceptable for the SH target.  Reload inheritance is of paramount
importance.  The x86 doesn't suffer from these problems because it's so
CISCy that almost every address generated for a typical C program is valid...