public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "ramana at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/47764] The constant load instruction should be hoisted out of loop
Date: Wed, 10 Aug 2011 22:18:00 -0000 [thread overview]
Message-ID: <bug-47764-4-jNaPywPAGo@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-47764-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47764
Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ramana at gcc dot gnu.org
--- Comment #4 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2011-08-10 22:17:23 UTC ---
(In reply to comment #3)
> > Any ideas of how this improvement could be implemented, Carrot?
>
> The root cause of this problem is that arm/thumb store instruction can't
> directly store a immediate number to memory, but gcc doesn't realize this early
> enough. In most part of the rtl phase, the following form is kept.
>
> (insn 41 38 42 3 (set (mem:HI (plus:SI (reg/f:SI 169)
> (const_int 60 [0x3c])) [2 MEM[(struct deflate_state *)D.2085
> _3 + 60B]+0 S2 A16])
> (const_int 0 [0])) src/trees.c:45 696 {*thumb2_movhi_insn}
> (expr_list:REG_DEAD (reg/f:SI 169)
> (nil)))
>
> Until register allocation it finds the restriction of the store instruction and
> split it into two instructions, load 0 into register and store register to
> memory. But it's too late to do a loop optimization.
Eh, how is splitting this early going to help with hoisting this out of a loop
?
Ramana
next prev parent reply other threads:[~2011-08-10 22:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-16 7:35 [Bug target/47764] New: " carrot at google dot com
2011-02-18 11:49 ` [Bug target/47764] " ibolton at gcc dot gnu.org
2011-02-19 7:06 ` pinskia at gcc dot gnu.org
2011-02-21 4:10 ` carrot at google dot com
2011-08-10 22:18 ` ramana at gcc dot gnu.org [this message]
2013-01-24 7:25 ` [Bug rtl-optimization/47764] " ubizjak at gmail dot com
2014-12-17 0:38 ` carrot at google dot com
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-47764-4-jNaPywPAGo@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).