From: dewar@gnat.com (Robert Dewar)
To: denisc@overta.ru, ja_walker@earthlink.net
Cc: gcc@gcc.gnu.org
Subject: Re: Synthetic register related: consequences of changing Frame layout.
Date: Sun, 05 Jan 2003 11:42:00 -0000 [thread overview]
Message-ID: <20030105114048.DAAFDF2E18@nile.gnat.com> (raw)
> In principle, you are correct. The differences are small. I believe that in
> many instances, instructions accessing stack slots as spilled registers are
> six bytes long, not three bytes long as for Synthetic registers. I believe
> that the compiler does not differentiate between spilled register stack slot
> memory and any other kind of memory, and so generates unnecessary register
> content motion between registers and stack slots, under the mistaken idea
> that this is more efficient.
This is completely wrong. Have you even looked at how code is currently
generated. Registers are spilled to the local stack frame, and of course
you get the normal 3-byte instructions to transfer to and from the spill
locations. There is too much general "I believe" guesswork in your approach
and not enough hard knowledge. I suggest that before you start hacking away
at the configuration file, you carefully examine actual generated code at
the machine level (gdb is quite nice for this).
next reply other threads:[~2003-01-05 11:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-05 11:42 Robert Dewar [this message]
2003-01-06 5:01 ` Andy Walker
-- strict thread matches above, loose matches on Subject: below --
2003-01-04 7:04 Andy Walker
2003-01-04 17:55 ` Denis Chertykov
2003-01-05 5:44 ` Andy Walker
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=20030105114048.DAAFDF2E18@nile.gnat.com \
--to=dewar@gnat.com \
--cc=denisc@overta.ru \
--cc=gcc@gcc.gnu.org \
--cc=ja_walker@earthlink.net \
/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).