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Re: Vectorizer/alignment
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Hendrik Greving <hendrik dot greving dot intel at gmail dot com>
- Cc: David Edelsohn <dje dot gcc at gmail dot com>, Richard Henderson <rth at redhat dot com>, Richard Biener <richard dot guenther at gmail dot com>, Jakub Jelinek <jakub at redhat dot com>, GCC Development <gcc at gcc dot gnu dot org>
- Date: Mon, 11 Nov 2013 16:00:06 -0800
- Subject: Re: Vectorizer/alignment
- Authentication-results: sourceware.org; auth=none
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On Mon, Nov 11, 2013 at 2:48 PM, Hendrik Greving
<hendrik.greving.intel@gmail.com> wrote:
> Ok, thanks, that explains it... Apparently x86 splits the vector movs
> into 2 in ix86_expand_vector_move_misalign->ix86_avx256_split_vector_move_misalign.
> But I wanted to mention that e.g. icc, despite also putting g_a, g_b,
> g_c into .comm, actually generates AVX2 vmovdqu using ymm...
>
> Examples:
>
> foo.c:
>
> #include <stdio.h>
> #include <stdint.h>
> #include "foo.h"
>
> int g_a[LENGTH];
> int g_b[LENGTH];
> int g_c[LENGTH];
> void
> foo()
> {
> int i ;
> for (i = 0; i < LENGTH; i++) {
> g_c[i] = g_a[i] + g_b[i];
> }
> }
>
> icc:
> icc/13.1.3/bin/icc -S -O3 -march=core-avx2 foo.c -v -save-temps -vec-report=2
>
> gcc:
> gcc -S -O3 -march=core-avx2 foo.c -ftree-vectorizer-verbose=1 -dp -v -da
>
>
Please open a bug. We will fix it.
Thanks.
--
H.J.