From: Segher Boessenkool <segher@kernel.crashing.org>
To: luoxhu--- via Gcc-patches <gcc-patches@gcc.gnu.org>,
luoxhu@linux.ibm.com, wschmidt@linux.ibm.com, linkw@gcc.gnu.org,
joseph@codesourcery.com, richard.sandiford@arm.com
Subject: Re: [PATCH] Fold (add -1; zero_ext; add +1) operations to zero_ext when not zero (PR37451, PR61837)
Date: Thu, 16 Apr 2020 20:21:40 -0500 [thread overview]
Message-ID: <20200417012140.GJ26902@gate.crashing.org> (raw)
In-Reply-To: <mptmu7dnm3r.fsf@arm.com>
On Wed, Apr 15, 2020 at 10:18:16AM +0100, Richard Sandiford wrote:
> luoxhu--- via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> > - count = simplify_gen_binary (PLUS, mode, count, const1_rtx);
> > + {
> > + /* Fold (add -1; zero_ext; add +1) operations to zero_ext based on addop0
> > + is never zero, as gimple pass loop ch will do optimization to simplify
> > + the loop to NO loop for loop condition is false. */
>
> IMO the code needs to prove this, rather than just assume that previous
> passes have made it so.
Well, it should gcc_assert it, probably.
It is the left-hand side of a+b... it cannot be 0, because niter always
is simplified!
Segher
next prev parent reply other threads:[~2020-04-17 1:21 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 8:47 luoxhu
2020-04-15 9:18 ` Richard Sandiford
2020-04-17 1:21 ` Segher Boessenkool [this message]
2020-04-17 16:32 ` Segher Boessenkool
2020-04-20 8:21 ` luoxhu
2020-04-20 9:05 ` luoxhu
2020-05-12 6:48 ` [PATCH v2] Fold (add -1; zero_ext; add +1) operations to zero_ext when not overflow (PR37451, part of PR61837) luoxhu
2020-05-12 14:58 ` Segher Boessenkool
2020-05-12 18:24 ` Richard Sandiford
2020-05-14 2:48 ` luoxhu
2020-05-14 11:15 ` Richard Sandiford
2020-04-15 9:37 ` [PATCH] Fold (add -1; zero_ext; add +1) operations to zero_ext when not zero (PR37451, PR61837) Jakub Jelinek
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=20200417012140.GJ26902@gate.crashing.org \
--to=segher@kernel.crashing.org \
--cc=gcc-patches@gcc.gnu.org \
--cc=joseph@codesourcery.com \
--cc=linkw@gcc.gnu.org \
--cc=luoxhu@linux.ibm.com \
--cc=richard.sandiford@arm.com \
--cc=wschmidt@linux.ibm.com \
/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).