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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/57223] Auto-vectorization fails for nested multiple loops depending on type of array
Date: Thu, 26 Sep 2013 09:23:00 -0000 [thread overview]
Message-ID: <bug-57223-4-ctgSaImhi0@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-57223-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57223
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Usishchev Yury from comment #3)
> I'm testing it on current trunk, and second loop is not vectorized both with
> floating point and integer types.
> For floating point types it is not vectorized due to control flow in loop:
>
> <bb 15>:
> // ...
> if (t_56 > _61)
> goto <bb 16>;
> else
> goto <bb 17>;
> <bb 16>:
> <bb 17>:
> # iftmp.2_7 = PHI <_61(16), t_56(15)>
>
> This can be optimized to MIN_EXPR in phiopt pass, but is not because of NaNs:
>
> tree-ssa-phiopt.c:876:
> /* The optimization may be unsafe due to NaNs. */
> if (HONOR_NANS (TYPE_MODE (type)))
> return false;
>
> If compiled with -ffinite-math-only second loop still is not vectorised:
>
> not_always_good.c:16:7: note: not vectorized: latch block not empty.
>
> (same occurs with integer types). Latch block it that case is:
>
> <bb 14>:
> pretmp_176 = *prephitmp_173;
> goto <bb 13>;
>
> the statement here is generated in pre pass.
>
> For vectorization to work we can either not generate it in pre or move it
> into head of the loop in vectorizer.
>
> Right now i'm trying to find how to prevent pre from generating statements
> in empty latch blocks.
It already has code to avoid this in some situations.
next prev parent reply other threads:[~2013-09-26 9:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-57223-4@http.gcc.gnu.org/bugzilla/>
2013-05-09 5:06 ` snagavallis at outlook dot com
2013-05-09 5:11 ` snagavallis at outlook dot com
2013-09-26 8:45 ` y.usishchev at samsung dot com
2013-09-26 9:23 ` rguenth at gcc dot gnu.org [this message]
2013-09-26 14:47 ` rguenth at gcc dot gnu.org
2013-09-26 14:53 ` rguenth at gcc dot gnu.org
2013-09-26 14:57 ` rguenth at gcc dot gnu.org
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