https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77621

--- Comment #18 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 20 Sep 2016, ubizjak at gmail dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77621
> 
> --- Comment #17 from UroŇ° Bizjak <ubizjak at gmail dot com> ---
> (In reply to rguent...@suse.de from comment #16)
> 
> > At least you won't get called for the scalar loop copy and you have
> > definite acccess to vectype.
> 
> Thanks for the hint, the following patch is effective as well:

Looks good to me.

> --cut here--
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 60b81bb..9d72681 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -49554,9 +49554,7 @@ ix86_preferred_simd_mode (machine_mode mode)
>         return V4SFmode;
> 
>      case DFmode:
> -      if (!TARGET_VECTORIZE_DOUBLE)
> -       return word_mode;
> -      else if (TARGET_AVX512F)
> +      if (TARGET_AVX512F)
>         return V8DFmode;
>        else if (TARGET_AVX && !TARGET_PREFER_AVX128)
>         return V4DFmode;
> @@ -49647,6 +49645,11 @@ ix86_add_stmt_cost (void *data, int count, enum
> vect_cost_for_stmt kind,
>    tree vectype = stmt_info ? stmt_vectype (stmt_info) : NULL_TREE;
>    int stmt_cost = ix86_builtin_vectorization_cost (kind, vectype, misalign);
> 
> +  /* Penalize DFmode vector operations for !TARGET_VECTORIZE_DOUBLE.  */
> +  if (kind == vector_stmt && !TARGET_VECTORIZE_DOUBLE
> +      && vectype && GET_MODE_INNER (TYPE_MODE (vectype)) == DFmode)
> +    stmt_cost *= 5;  /* FIXME: The value here is arbitrary.  */
> +
>    /* Statements in an inner loop relative to the loop being
>       vectorized are weighted more heavily.  The value here is
>        arbitrary and could potentially be improved with analysis.  */
> --cut here--

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