From: Richard Henderson <rth@redhat.com>
To: Mike Stump <mrs@apple.com>
Cc: Geoff Keating <geoffk@geoffk.org>,
mark@codesourcery.com, steby@enea.se, gcc@gcc.gnu.org
Subject: Re: GCC floating point usage
Date: Wed, 16 Oct 2002 13:43:00 -0000 [thread overview]
Message-ID: <20021016201445.GC22988@redhat.com> (raw)
In-Reply-To: <0638B6F4-E09D-11D6-8136-000393941EE6@apple.com>
On Tue, Oct 15, 2002 at 05:20:07PM -0700, Mike Stump wrote:
> A routine that is compiled with no-implicit-fp is valid to use in a
> no-FP task, provided there is no explicit fp in it. A routine that
> isn't compiled with this flag isn't valid to use in a non-FP task.
No, that's not correct.
A routine that doesn't use FP is valid to use in a no-FP task.
A routine that does use explicit fp is not valid to use in a no-FP task.
I think that the proper solution to this to have a mode in which
the compiler does not *prefer* to use FP registers for integral
data. But the assembler would set a bit if any FP registers are
used, which would then be collected by the linker to indicate
whether or not the process as a whole uses FP registers.
In this way, if gcc does happen to use an FP register, due to
queer register pressure/preferencing, then we're still ok, because
the process *is* marked as an FP process.
Anything less is asking for trouble.
The only other solution is to use -msoft-float. The argument that
that changes calling conventions is nonsense -- given that this
is supposed to be a no-FP process, we've already established that
we're not supposed to be using FP whatsoever.
r~
next prev parent reply other threads:[~2002-10-16 20:14 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-14 9:59 Stefan Bylund
2002-10-14 10:16 ` David Edelsohn
2002-10-14 10:25 ` Zack Weinberg
2002-10-14 10:55 ` Dale Johannesen
2002-10-14 22:22 ` Mark Mitchell
2002-10-15 15:35 ` Geoff Keating
2002-10-15 16:10 ` Mark Mitchell
2002-10-15 17:20 ` Geoff Keating
2002-10-15 18:09 ` Mark Mitchell
2002-10-16 7:40 ` Joel Sherrill
2002-10-15 19:04 ` Mike Stump
2002-10-16 12:06 ` Mark Mitchell
2002-10-16 13:35 ` Geoff Keating
2002-10-16 14:29 ` Mark Mitchell
2002-10-16 14:56 ` Michael Matz
2002-10-16 15:03 ` Mark Mitchell
2002-10-16 15:27 ` David Edelsohn
2002-10-16 15:36 ` Mark Mitchell
2002-10-16 16:35 ` Zack Weinberg
2002-10-16 16:36 ` Mark Mitchell
2002-10-16 16:46 ` David Edelsohn
2002-10-17 8:37 ` Paul Koning
2002-10-16 17:57 ` Mike Stump
2002-10-17 4:12 ` Mike Stump
2002-10-16 13:43 ` Richard Henderson [this message]
2002-10-16 14:35 ` Mark Mitchell
2002-10-16 14:56 ` Joel Sherrill
2002-10-16 16:38 ` Richard Henderson
2002-10-16 16:53 ` Zack Weinberg
2002-10-16 17:52 ` Michael Matz
2002-10-16 22:50 ` Richard Henderson
2002-10-21 12:21 ` Jeff Law
2002-10-16 17:29 ` Mike Stump
2002-10-17 2:19 ` Richard Henderson
2002-10-15 17:19 ` Mike Stump
2002-10-15 18:41 ` Zack Weinberg
2002-10-16 1:48 ` Fergus Henderson
2002-10-14 10:37 ` Stefan Bylund
2002-10-14 11:28 ` Mike Stump
2002-10-14 12:39 ` Joel Sherrill
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