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From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/113134] gcc does not version loops with early break conditions that don't have side-effects
Date: Thu, 28 Dec 2023 04:30:34 +0000 [thread overview]
Message-ID: <bug-113134-4-293RCijMku@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-113134-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113134
--- Comment #9 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to JuzheZhong from comment #8)
> Suppose the loop mask is generated by whilelo instruction of ARM SVE.
>
> Suppose we have 8 elements in a single whole vector.
>
> mask = whilo (0, res) if res = 6, then mask = 11111000.
> data = 12345678
>
> Then if it is early break. You are reversing both data and mask as follows:
>
> new_mask = 00011111
> new_data = 87654321
>
> Then use the EXTRACT_LAST, we will get value = 1 for early break.
>
> Am I right ?
Yeah, the idea being the scalar loop will then run from 1 to 6 to do any side
effects that we couldn't apply.
We went with this approach first because it works for non-masked architectures
too. In GCC-15 we'll try to implement staying entirely inside a vector loop by
splitting the mask in elements until first active and element from first active
so we can correctly mask the operations.
next prev parent reply other threads:[~2023-12-28 4:30 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-25 11:29 [Bug c/113134] New: Middle end early break vectorization: Fail to vectorize a simple early break code juzhe.zhong at rivai dot ai
2023-12-25 12:35 ` [Bug c/113134] " tnfchris at gcc dot gnu.org
2023-12-27 15:21 ` [Bug c/113134] gcc does not version loops with side-effect early breaks tnfchris at gcc dot gnu.org
2023-12-28 1:21 ` [Bug c/113134] gcc does not version loops with early break conditions that don't have side-effects juzhe.zhong at rivai dot ai
2023-12-28 3:48 ` tnfchris at gcc dot gnu.org
2023-12-28 3:55 ` juzhe.zhong at rivai dot ai
2023-12-28 4:02 ` tnfchris at gcc dot gnu.org
2023-12-28 4:05 ` tnfchris at gcc dot gnu.org
2023-12-28 4:23 ` juzhe.zhong at rivai dot ai
2023-12-28 4:30 ` tnfchris at gcc dot gnu.org [this message]
2023-12-28 4:35 ` juzhe.zhong at rivai dot ai
2023-12-28 4:45 ` tnfchris at gcc dot gnu.org
2023-12-28 4:46 ` juzhe.zhong at rivai dot ai
2023-12-28 4:49 ` tnfchris at gcc dot gnu.org
2023-12-28 4:51 ` juzhe.zhong at rivai dot ai
2023-12-28 4:53 ` tnfchris at gcc dot gnu.org
2023-12-28 5:08 ` tnfchris at gcc dot gnu.org
2023-12-28 9:11 ` juzhe.zhong at rivai dot ai
2023-12-28 21:20 ` [Bug tree-optimization/113134] " pinskia at gcc dot gnu.org
2024-01-08 8:11 ` rguenth at gcc dot gnu.org
2024-01-31 11:48 ` juzhe.zhong at rivai dot ai
2024-01-31 12:04 ` rguenth at gcc dot gnu.org
2024-02-02 3:38 ` juzhe.zhong at rivai dot ai
2024-02-02 8:49 ` juzhe.zhong at rivai dot ai
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