From: Richard Sandiford <rsandifo@redhat.com>
To: Alexandre Oliva <aoliva@redhat.com>
Cc: Kazu Hirata <kazu@cs.umass.edu>, gcc-patches@gcc.gnu.org
Subject: Re: add h8sx support to h8300
Date: Thu, 15 Jul 2004 05:22:00 -0000 [thread overview]
Message-ID: <874qoawesn.fsf@redhat.com> (raw)
In-Reply-To: <orpt6yjsjg.fsf@free.redhat.lsd.ic.unicamp.br> (Alexandre Oliva's message of "14 Jul 2004 16:30:11 -0300")
Alexandre Oliva <aoliva@redhat.com> writes:
> On Jul 14, 2004, Richard Sandiford <rsandifo@redhat.com> wrote:
>> Alexandre Oliva <aoliva@redhat.com> writes:
>>>> ! if (!regs_ever_live[HFP_REG])
>>>> ! return NO_REGS;
>>>
>>> I had both HFP_REG and FP_REG at some point. I thought this would
>>> minimize the risk of running into the failure case. Don't you think
>>> so?
>
>> I wouldn't have thought checking for FP_REG was necessary. It really is
>> the liveness of er6 that we're concerned about.
>
> Then I totally misunderstand what's going on. I thought you were
> testing whether the frame pointer was used, not whether there was some
> random pseudo assigned to er6 by local or global. Which is it?
The idea is that, if nothing is using er6, there's no reason why it
can't be allocated for a movmd. The register allocators might normally
shy away from that because er6 is a call-saved register. "Hey, I've got
this call-clobbered register sitting free. Why not use that instead of
er6?". Even '!' wasn't enough to convince them otherwise.
[ And that's not surprising really. It's unusual to strongly prefer
a call-saved register over a call-clobbered when a pattern offers
both alternatives. ]
Of course, we don't have the same problem with er5 and er7 since we can
safely require 'f' and 'c' in all alternatives. er6 is the odd one out
because we have to offer a 'D' alternative as well.
Richard
next prev parent reply other threads:[~2004-07-14 19:48 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-21 14:24 Alexandre Oliva
2004-06-21 17:12 ` Kazu Hirata
2004-06-23 2:23 ` Alexandre Oliva
2004-07-07 22:11 ` Alexandre Oliva
2004-07-08 6:08 ` Richard Sandiford
2004-07-08 7:41 ` Alexandre Oliva
2004-07-08 9:39 ` Richard Sandiford
2004-07-08 18:16 ` Alexandre Oliva
2004-07-08 18:16 ` Richard Sandiford
2004-07-08 20:23 ` Alexandre Oliva
2004-07-12 20:14 ` Richard Sandiford
2004-07-14 12:49 ` Alexandre Oliva
2004-07-14 17:16 ` Richard Sandiford
2004-07-15 4:11 ` Alexandre Oliva
2004-07-15 5:22 ` Richard Sandiford [this message]
2004-07-15 16:25 ` Alexandre Oliva
2004-07-15 17:14 ` Richard Sandiford
2004-07-15 17:25 ` Richard Sandiford
2004-07-15 22:23 ` Alexandre Oliva
2004-07-08 21:20 ` Alexandre Oliva
2004-07-06 20:56 ` Alexandre Oliva
2004-07-07 2:37 ` Richard Henderson
2004-07-07 7:06 ` Alexandre Oliva
2004-07-07 9:06 ` Richard Henderson
2004-07-08 0:14 ` Alexandre Oliva
2004-07-08 1:22 ` Richard Henderson
2004-07-08 1:26 ` Alexandre Oliva
2004-07-08 2:01 ` Richard Henderson
2004-07-08 4:39 ` Alexandre Oliva
2004-07-08 18:59 ` Alexandre Oliva
2004-07-07 9:13 ` Joseph S. Myers
2004-07-07 19:44 ` Alexandre Oliva
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