From: Jeff Law <jeffreyalaw@gmail.com>
To: Richard Biener <richard.guenther@gmail.com>,
Philipp Tomsich <philipp.tomsich@vrull.eu>
Cc: Manolis Tsamis <manolis.tsamis@vrull.eu>,
Andrew MacLeod <amacleod@redhat.com>,
gcc-patches@gcc.gnu.org
Subject: Re: [PATCH v1] [RFC] Improve folding for comparisons with zero in tree-ssa-forwprop.
Date: Mon, 24 Apr 2023 17:05:14 -0600 [thread overview]
Message-ID: <8bd8b246-a252-0e05-414c-ab1e35975aea@gmail.com> (raw)
In-Reply-To: <CAFiYyc1Ton4hYUjzWkTP-mOh8_wAW0MFnnNZtbMyDXY4qihccA@mail.gmail.com>
On 4/24/23 02:06, Richard Biener via Gcc-patches wrote:
> On Fri, Apr 21, 2023 at 11:01 PM Philipp Tomsich
> <philipp.tomsich@vrull.eu> wrote:
>>
>> Any guidance on the next steps for this patch?
>
> I think we want to perform this transform later, in particular when
> the test is a loop exit test we do not want to do it as it prevents
> coalescing of the IV on the backedge at out-of-SSA time.
>
> That means doing the transform in folding and/or before inlining
> (the test could become a loop exit test) would be a no-go. In fact
> for SSA coalescing we'd want the reverse transform in some cases, see
> PRs 86270 and 70359.
>
> If we can reliably undo for the loop case I suppose we can do the
> canonicalization to compare against zero. In any case please split
> up the patch (note
I've also
> hoped we could eventually get rid of that part of
> tree-ssa-forwprop.cc
in favor
> of match.pd patterns since it uses GENERIC folding :/).
>
Do we have enough information to do this at expansion time? That would
avoid introducing the target dependencies to drive this in gimple.
Jeff
next prev parent reply other threads:[~2023-04-24 23:05 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-16 15:27 Manolis Tsamis
2023-03-16 16:41 ` Jeff Law
2023-03-16 20:32 ` Philipp Tomsich
2023-03-17 8:31 ` Richard Biener
2023-03-17 13:15 ` Philipp Tomsich
2023-03-17 14:03 ` Richard Biener
2023-03-17 20:43 ` Andrew Waterman
2023-03-17 14:12 ` Andrew MacLeod
2023-03-20 14:01 ` Manolis Tsamis
2023-03-23 23:27 ` Jeff Law
2023-04-21 21:01 ` Philipp Tomsich
2023-04-24 8:06 ` Richard Biener
2023-04-24 23:05 ` Jeff Law [this message]
2023-04-25 7:21 ` Richard Biener
2023-04-26 2:30 ` Jeff Law
2023-04-26 6:41 ` Richard Biener
2023-08-02 14:07 ` Manolis Tsamis
2023-08-03 7:04 ` Richard Biener
2023-08-03 15:21 ` Jeff Law
2023-08-04 6:37 ` Richard Biener
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