[PATCH] remove target dependency for atomicity.h on ix86

[Loren James Rittle]

> 2003-04-22  Matthias Klose <doko@debian.org>
>
>	* config/cpu/i486/atomicity.h, config/cpu/generic/atomicity.h:
>	Select implementation according to predefined __<cpu> macros.

I do not wish to dampen enthusiasm of someone that wants to fix this
problem (and indeed I do believe that there is a deep problem here
when one considers the way we do atomicity implementation selection at
configure time verses non-multilib compilation flag changes).
However, I must reject this patch for a more fundamental reason than
that mentioned by Phil: all parts of your final program must be using
the exact same implementation of atomicity or else you risk
introducing subtle run-time errors (this includes everything the user
compiled directly and available in the compiled library image).
I.e. the current situation is reproducible bad (for the reason
contained in the initial parenthetical statement) and I'd rather have
that situation than introduce subtle non-reproducible errors.

If you really want to work on this problem until we have a solution we
can install in time for gcc 3.4's release, then you will have my full
support and attention.  I don't see how we could possibly fix this
issue in time for 3.3 but I'm willing to be proven wrong.

BTW, yes, IMHO, we've been screwed by using a C atomicity ABI in our
C++ library in a manner that exposes the details of the implementation
in headers used directly by users (and, yes, I replicated the mistake,
or rather failed to fix it, when I attempted to fix the general
portability issues with stl_mutex.h just before the 3.0 release).  If
all use of the ABI was buried inside the compiled version of the
library, then we could just multilib it (and, as a bonus, do it in a
way that only the final program link options affected the selection).

Thanks,
Loren