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Re: [gomp4 simd, RFC] Simple fix to override vectorization cost estimation.
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Sergey Ostanevich <sergos dot gnu at gmail dot com>
- Cc: Richard Biener <rguenther at suse dot de>, Yuri Rumyantsev <ysrumyan at gmail dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>, Igor Zamyatin <izamyatin at gmail dot com>, Areg Melik-Adamyan <areg dot melikadamyan at gmail dot com>
- Date: Tue, 12 Nov 2013 12:05:51 +0100
- Subject: Re: [gomp4 simd, RFC] Simple fix to override vectorization cost estimation.
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- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Tue, Nov 12, 2013 at 02:48:46PM +0400, Sergey Ostanevich wrote:
> You are right regarding the cost model if we talk about vectorizer alone.
> But the #pragma omp simd goes beyond the vectorizer - it introduces
> parallel context in a place user defines, similar to #pragma omp parallel.
> Are we applying any cost model for omp parallel region?
> You can consider this pragma as a helper for developer for 'easily'
> introduce parallelism in his code, hence any type of cost model -
> whatever quality it is - will plays against this paradigm, forcing user
> to play around our cost model to let it make the loop simd-parallel.
So what do other compilers do here? Does icc also totally ignore all
cost analysis for #pragma omp simd or #pragma simd and vectorizes even when
it would be obviously undesirable?