From: Ulrich Weigand <weigand@immd1.informatik.uni-erlangen.de>
To: geoffk@geoffk.org (Geoff Keating)
Cc: weigand@immd1.informatik.uni-erlangen.de (Ulrich Weigand),
gcc@gcc.gnu.org
Subject: Re: condition codes, haifa-sched and virtual-stack-vars
Date: Wed, 30 Jan 2002 17:13:00 -0000 [thread overview]
Message-ID: <200201302316.AAA17136@faui1a.informatik.uni-erlangen.de> (raw)
In-Reply-To: <jmlmefo5as.fsf@desire.geoffk.org> from "Geoff Keating" at Jan 30, 2002 02:14:03 PM
Geoff Keating wrote:
> Ulrich Weigand <weigand@immd1.informatik.uni-erlangen.de> writes:
>
> > The problem is that reload simply calls gen_add2_insn whenever it
> > feels like it, without consideration that this might introduce
> > a CC clobber at an inappropriate point ...
>
> On xstormy16, this problem existed with the carry register. I believe
> it was fixed by having a reload_inhi pattern and an appropriate
> definition of SECONDARY_RELOAD_CLASS. The result appears to work.
This is interesting, but I'm not sure I understand *why* it works ;-)
The reload_inhi pattern tries to allocate the carry register as the
secondary reload scratch register. Now, in the interesting case
where the carry register is in fact live at the location where the
insn is inserted, this would mean that reload would need to spill
the carry register and later on restore its old value, right?
(Because there is only a single register in this class ...)
However, I'm not sure how the carry register can be spilled,
given that there is no mov* insn that touches it, unless I'm
missing something ...
Bye,
Ulrich
--
Dr. Ulrich Weigand
weigand@informatik.uni-erlangen.de
next prev parent reply other threads:[~2002-01-30 23:18 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-30 15:19 Ulrich Weigand
2002-01-30 16:50 ` Geoff Keating
2002-01-30 17:13 ` Ulrich Weigand [this message]
2002-01-31 13:59 ` Geoff Keating
2002-01-30 19:31 ` Richard Henderson
2002-01-31 16:07 ` Ulrich Weigand
[not found] <no.id>
2002-01-30 17:36 ` Ulrich Weigand
-- strict thread matches above, loose matches on Subject: below --
2002-01-30 12:31 Greg McGary
2002-01-30 12:42 ` law
2002-01-30 13:30 ` Greg McGary
2002-01-30 14:15 ` law
2002-01-31 7:49 ` Richard Earnshaw
2002-01-30 13:56 ` Alexandre Oliva
2002-01-30 17:13 ` Greg McGary
2002-01-30 17:20 ` Alexandre Oliva
2002-01-30 18:00 ` law
2002-01-30 19:23 ` Greg McGary
2002-01-31 5:53 ` Alexandre Oliva
2002-01-30 18:41 ` Richard Henderson
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