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From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/109072] [12/13 Regression] SLP costs for vec duplicate too high since g:4963079769c99c4073adfd799885410ad484cbbe
Date: Thu, 09 Mar 2023 14:13:37 +0000 [thread overview]
Message-ID: <bug-109072-4-Y4wObRWqa3@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-109072-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109072
rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2023-03-09
CC| |rguenth at gcc dot gnu.org
--- Comment #1 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #0)
> The SLP costs went from:
>
> Vector cost: 2
> Scalar cost: 4
>
> to:
>
> Vector cost: 12
> Scalar cost: 4
>
> it looks like it's no longer costing it as a duplicate but instead 4 vec
> inserts.
We do cost it as a duplicate, but we only try to vectorize up to
the stores, rather than up to the load back. So we're costing
the difference between:
fmov s1, s0
stp s1, s1, [x0]
stp s1, s1, [x0, 8]
(no idea why we have an fmov, pretend we don't) and:
fmov s1, s0
dup v1.4s, v1.s[0]
str q1, [x0]
If we want the latter as a general principle, the PR is
easy to fix. But if we don't, we'd need to make the
vectoriser start at the load or (alternatively) fold
to a constructor independently of vectorisation.
next prev parent reply other threads:[~2023-03-09 14:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-08 22:32 [Bug target/109072] New: " tnfchris at gcc dot gnu.org
2023-03-09 10:19 ` [Bug target/109072] " rguenth at gcc dot gnu.org
2023-03-09 14:13 ` rsandifo at gcc dot gnu.org [this message]
2023-03-09 14:30 ` tnfchris at gcc dot gnu.org
2023-03-09 14:46 ` rsandifo at gcc dot gnu.org
2023-03-09 15:04 ` tnfchris at gcc dot gnu.org
2023-03-09 16:22 ` rsandifo at gcc dot gnu.org
2023-03-09 17:35 ` rsandifo at gcc dot gnu.org
2023-03-10 7:40 ` rguenth at gcc dot gnu.org
2023-03-10 8:50 ` rsandifo at gcc dot gnu.org
2023-03-15 14:29 ` rguenth at gcc dot gnu.org
2023-03-28 11:35 ` cvs-commit at gcc dot gnu.org
2023-03-28 12:59 ` [Bug target/109072] [12 " rsandifo at gcc dot gnu.org
2023-04-03 8:58 ` cvs-commit at gcc dot gnu.org
2023-04-03 9:03 ` rsandifo at gcc dot gnu.org
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