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Re: [PATCH] Fix PR53295
On Sat, May 12, 2012 at 9:53 AM, Toon Moene <toon@moene.org> wrote:
> On 05/11/2012 01:59 PM, Richard Guenther wrote:
>
>> This fixes the dependency of vectorization of strided loads on
>> gather support. ?For that to work we need to lift the restriction
>> in data-ref analysis that requries a constant DR_STEP. ?Fortunately
>> fallout is small.
>
>
> Would this also vectorize strided loops when the architecture doesn't have a
> gather instruction ?
gather is different from strided loops. Gather is a[b[i]] while strided loops
are for (i=0;; i+=stride) ...= a[i] with stride being non-constant.
Your testcase requires gather support.
Richard.
> If so, it doesn't work for the attached case, which *does* vectorize with a
> gather instruction:
>
> $ /tmp/c/bin/gfortran -g -O3 -ftree-vectorizer-verbose=2 -mavx2 -S
> verintlin.f
>
> Analyzing loop at verintlin.f:68
>
> Analyzing loop at verintlin.f:69
>
>
> Vectorizing loop at verintlin.f:69
>
> 69: LOOP VECTORIZED.
> verintlin.f:1: note: vectorized 1 loops in function.
>
> whereas:
>
> $ /tmp/c/bin/gfortran -g -O3 -ftree-vectorizer-verbose=2 -mavx -S
> verintlin.f
>
> Analyzing loop at verintlin.f:68
>
> Analyzing loop at verintlin.f:69
>
> 69: not vectorized: not suitable for gather load D.2051_74 =
> *parg_73(D)[D.2050_72];
>
> 69: not vectorized: not suitable for gather load D.2051_74 =
> *parg_73(D)[D.2050_72];
>
> verintlin.f:1: note: vectorized 0 loops in function.
>
> --
> Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
> Saturnushof 14, 3738 XG ?Maartensdijk, The Netherlands
> At home: http://moene.org/~toon/; weather: http://moene.org/~hirlam/
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