From: Ian Lance Taylor <iant@google.com>
To: srimeruva@cse.iitb.ac.in
Cc: gcc-help@gcc.gnu.org
Subject: Re: match_dup as internal operands
Date: Wed, 21 Dec 2011 00:02:00 -0000 [thread overview]
Message-ID: <mcrvcpa6c0r.fsf@dhcp-172-18-216-180.mtv.corp.google.com> (raw)
In-Reply-To: <ab38551f74fe0b1a415229dc537655db.squirrel@www.cse.iitb.ac.in> (srimeruva@cse.iitb.ac.in's message of "Wed, 21 Dec 2011 02:31:59 +0530")
srimeruva@cse.iitb.ac.in writes:
> what is the advantage of using match_dup for internal operands as
>
> (define_expand "zero_extendhisi2"
> [(set (match_operand:SI 0 "register_operand" "")
> (and:SI (subreg:SI
> (match_operand:HI 1 "register_operand" "")
> 0)
> (match_dup 2)))]
> ""
> "operands[2]
> = force_reg (SImode, GEN_INT (65535)); ")
This would normally be used for a named pattern which does not expect
operand[2] to be filled in. Since there is no operand[2], using a
match_operand does not make sense. But since operand[2] needs to be
referenced in the generated pattern, it has to appear somehow.
match_dup is a reasonable compromise, because match_dup always matches.
Ian
next prev parent reply other threads:[~2011-12-20 23:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1324405305.17587.ezmlm@gcc.gnu.org>
2011-12-20 21:15 ` srimeruva
2011-12-21 0:02 ` Ian Lance Taylor [this message]
2012-02-04 7:06 ` constraints validation in reload pass srimeruva
2012-02-04 11:49 ` Georg-Johann Lay
2012-02-04 12:02 ` match_dup as internal operands Georg-Johann Lay
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=mcrvcpa6c0r.fsf@dhcp-172-18-216-180.mtv.corp.google.com \
--to=iant@google.com \
--cc=gcc-help@gcc.gnu.org \
--cc=srimeruva@cse.iitb.ac.in \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).