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Re: [RFC] Turn on -mapp-regs by default on Solaris
- From: David S. Miller <davem at davemloft dot net>
- To: ebotcazou at libertysurf dot fr
- Cc: gcc-patches at gcc dot gnu dot org, rth at redhat dot com
- Date: Wed, 18 May 2005 13:02:33 -0700 (PDT)
- Subject: Re: [RFC] Turn on -mapp-regs by default on Solaris
- References: <email@example.com><firstname.lastname@example.org>
From: Eric Botcazou <email@example.com>
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.