[RFC] Turn on -mapp-regs by default on Solaris

[David S. Miller]

From: Eric Botcazou <ebotcazou@libertysurf.fr>
Date: Wed, 18 May 2005 10:18:07 +0200

> [I've also discovered that Sun switched the default code V9 model in their 
> Studio 10 compiler (at least on Solaris 10) from MedAny to MedMid.]

In my mind, MedLow gives the best setup for %99 of the cases when
people compile.  The %1 can specify medmid or medany explicitly.

Sun doesn't do MedLow by default, because Solaris only makes half of
the lower 32-bit address space available (in 64-bit mode) to work
around some bug in older UltraSPARC chips which they refuse to
document.  I think the chip bug has something to do with executing a
call instruction that wraps the computed PC around negatively back up
to the top of the 64-bit address space.  This plus some other
preconditions likely wedge the chip.

As a result, MedLow becomes much less useful.