public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "david.meggy at icron dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/50110] Endian reversal when adding extzv instruction
Date: Tue, 10 Jan 2012 19:16:00 -0000 [thread overview]
Message-ID: <bug-50110-4-CuPTn49BKr@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-50110-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50110
David Meggy <david.meggy at icron dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
--- Comment #5 from David Meggy <david.meggy at icron dot com> 2012-01-10 19:16:15 UTC ---
Let me sum up this bug. It boiled down to a misunderstanding of how bit field
extract works on a big endian processor (I don't know if anyone else has
implemented this on a big endian processor). Since we have implemented the
starting bit in our hardware from the least significant bit, I've just modified
the output instruction to change the start bit to the least significant bit.
(define_insn "extzvsi"
[(set (match_operand:SI 0 "register_operand" "=r")
(zero_extract:SI (match_operand:SI 1 "register_operand" "r")
(match_operand 2 "const_int_operand" "")
(match_operand 3 "const_int_operand" "")))]
""
"ext\t%1,%2,32 - %2 - %3,%0"
)
This works quite well for us, and is giving us the code space savings we were
looking for, an ~1% code space reduction. Not bad for a tiny GCC patch, tiny
binutils patch, and a minor CPU opcode addition.
This bug can be closed. Marking as RESOLVED - INVALID, as it isn't a real bug,
but a documentation misunderstanding
prev parent reply other threads:[~2012-01-10 19:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-17 19:17 [Bug rtl-optimization/50110] New: " david.meggy at icron dot com
2011-08-17 19:23 ` [Bug rtl-optimization/50110] " david.meggy at icron dot com
2011-08-17 19:32 ` pinskia at gcc dot gnu.org
2011-08-17 20:35 ` david.meggy at icron dot com
2011-08-18 2:24 ` david.meggy at icron dot com
2012-01-10 19:16 ` david.meggy at icron dot com [this message]
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=bug-50110-4-CuPTn49BKr@http.gcc.gnu.org/bugzilla/ \
--to=gcc-bugzilla@gcc.gnu.org \
--cc=gcc-bugs@gcc.gnu.org \
/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).