From: "Ulrich Weigand" <uweigand@de.ibm.com>
To: stevenb.gcc@gmail.com (Steven Bosscher)
Cc: gcc@gcc.gnu.org (GCC Mailing List),
eric.weddington@atmel.com, bonzini@gnu.org (Paolo Bonzini)
Subject: Re: Semantics of PARALLEL that sets and uses CC0
Date: Mon, 09 Aug 2010 18:00:00 -0000 [thread overview]
Message-ID: <201008091739.o79HdVSW013616@d12av02.megacenter.de.ibm.com> (raw)
In-Reply-To: <AANLkTinRfnNu7UNzUg_GXDhzn4wk+CCYhek7qiBZRYK+@mail.gmail.com> from "Steven Bosscher" at Aug 09, 2010 04:26:04 PM
Steven Bosscher wrote:
> Forgive me if I overlooked it, but I can't find in the manuals what
> the semantics would be of the following define_expand, from avr.md:
>
> (define_expand "cbranchsi4"
> [(parallel [(set (cc0)
> (compare (match_operand:SI 1 "register_operand" "")
> (match_operand:SI 2 "nonmemory_operand" "")))
> (clobber (match_scratch:QI 4 ""))])
> (set (pc)
> (if_then_else
> (match_operator 0 "ordered_comparison_operator" [(cc0)
> (const_int 0)])
> (label_ref (match_operand 3 "" ""))
> (pc)))]
> "")
>
> The expander performs a SET of CC0 in the first pattern inside the
> PARALLEL, and there is a USE of CC0 in the second pattern of the
> PARALLEL.
That's incorrect; the second pattern of the PARALLEL is just a CLOBBER.
The USE of CC0 happens in a completely separate second INSN that is
emitted by this define_expand. (Note that as opposed to define_insn,
define_expand can emit more than a single insn.)
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE
Ulrich.Weigand@de.ibm.com
next prev parent reply other threads:[~2010-08-09 17:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-09 17:53 Steven Bosscher
2010-08-09 18:00 ` Ulrich Weigand [this message]
2010-08-09 20:57 ` Paolo Bonzini
2010-08-09 21:04 ` Steven Bosscher
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