From: Dan Nicolaescu <dann@godzilla.ics.uci.edu>
To: Jan Hubicka <jh@suse.cz>
Cc: gcc@gcc.gnu.org
Subject: Re: Optimization advice for maintainers: go for low-hanging fruit
Date: Fri, 20 Dec 2002 11:01:00 -0000 [thread overview]
Message-ID: <200212201808.gBKI8RU31264@amrm2.ics.uci.edu> (raw)
In-Reply-To: <20021220120653.GA25206@kam.mff.cuni.cz>
Jan Hubicka <jh@suse.cz> writes:
> > I've been staring at a lot of g++-generated x86 assembler, trying to
> > coax g++ into creating better code, and creating a bunch of
> > optimization-related PRs. Overall, I'm disappointed by gcc's ability
> > to optimize some very simple things like constant-folding.
> >
> > The most distressing thing about the failures is that gcc is
> > invariably capable of performing all the optimizations I care about,
> > just not consistently. Seemingly irrelevant random features of the
> > source code seem to inhibit optimizations from being performed.
>
> Can you send some testcases where GCC fails to do the transformation?
Look at the audit trail for PR8967, the example there shows that life
analysis fails to eliminate some insns in one case.
Also please take a look at PR9016, the 4 functions in that generate
the same (optimal) assembly on SPARC, but some of them don't get
optimized well on x86.
next prev parent reply other threads:[~2002-12-20 17:02 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-12-20 3:44 Martin Buchholz
2002-12-20 8:17 ` Jan Hubicka
2002-12-20 11:01 ` Dan Nicolaescu [this message]
2002-12-23 18:06 ` Joe Buck
2002-12-24 6:34 ` Martin Buchholz
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=200212201808.gBKI8RU31264@amrm2.ics.uci.edu \
--to=dann@godzilla.ics.uci.edu \
--cc=gcc@gcc.gnu.org \
--cc=jh@suse.cz \
/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).