Not actually solving those testcases but currently scatters/gathers
are costed as a single vector load/store. Micro-architectural Intel
seems to have gotten to the point (with skylake) to hide all but
the scalar loads/stores which seem to take up as many load/store
ports as expected. I'm not expecting further improvements ontop
of that so the following patch reflects this.
When the vectorizer would open-code gathers/scatters extra cost
of vector element insertion / extraction would be accounted for
(if the CPU doesn't have scatter/gather support).
Bootstrap / regtest running on x86_64-unknown-linux-gnu.
Any objection at this stage?
Thanks,
Richard.
2017-05-28 Richard Biener <rguent...@suse.de>
PR tree-optimization/57796
* tree-vect-stmts.c (vect_model_store_cost): Cost scatters
as N scalar stores.
(vect_model_load_cost): Cost gathers as N scalar loads.
Index: gcc/tree-vect-stmts.c
===================================================================
--- gcc/tree-vect-stmts.c (revision 246500)
+++ gcc/tree-vect-stmts.c (working copy)
@@ -929,7 +929,8 @@ vect_model_store_cost (stmt_vec_info stm
tree vectype = STMT_VINFO_VECTYPE (stmt_info);
/* Costs of the stores. */
- if (memory_access_type == VMAT_ELEMENTWISE)
+ if (memory_access_type == VMAT_ELEMENTWISE
+ || memory_access_type == VMAT_GATHER_SCATTER)
/* N scalar stores plus extracting the elements. */
inside_cost += record_stmt_cost (body_cost_vec,
ncopies * TYPE_VECTOR_SUBPARTS (vectype),
@@ -1056,7 +1057,8 @@ vect_model_load_cost (stmt_vec_info stmt
}
/* The loads themselves. */
- if (memory_access_type == VMAT_ELEMENTWISE)
+ if (memory_access_type == VMAT_ELEMENTWISE
+ || memory_access_type == VMAT_GATHER_SCATTER)
{
/* N scalar loads plus gathering them into a vector. */
tree vectype = STMT_VINFO_VECTYPE (stmt_info);
