Re: [PATCH 14/25] Disable inefficient vectorization of elementwise loads/stores.

[Andrew Stubbs <ams at codesourcery dot com>]

On 17/09/18 12:43, Richard Sandiford wrote:
> OK, sounds like the cost of vec_construct is too low then.  But looking
> at the port, I see you have:
>
> /* Implement TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST.  */
>
> int
> gcn_vectorization_cost (enum vect_cost_for_stmt ARG_UNUSED (type_of_cost),
> 			tree ARG_UNUSED (vectype), int ARG_UNUSED (misalign))
> {
>    /* Always vectorize.  */
>    return 1;
> }
>
> which short-circuits the cost-model altogether.  Isn't that part
> of the problem?

Well, it's possible that that's a little simplistic. ;-)

Although, actually the elementwise issue predates the existence of 
gcn_vectorization_cost, and the default does appear to penalize 
vec_construct somewhat.

Actually, the default definition doesn't seem to do much besides 
increase vec_construct, so I'm not sure now why I needed to change it? 
Hmm, more experiments to do.

Thanks for the pointer.

Andrew