gcc-patches-ow...@gcc.gnu.org wrote on 13/12/2011 04:05:57 AM:
> On core2, unaligned vector load/store using movdqu is a very slow
operation.
> Experiments show it is six times slower than movdqa (aligned) and this is
> irrespective of whether the resulting data happens to be aligned or not.
> For Corei7, there is no performance difference between the two and on
AMDs,
> movdqu is only about 10% slower.
>
> This patch does not vectorize loops that need to generate the slow
unaligned
> memory load/stores on core2.
>
>
> Do not vectorize loops on Core2 that need to use unaligned
> vector load/stores.
> * tree-vect-stmts.c (is_slow_vect_unaligned_load_store): New function.
> (vect_analyze_stmt): Check if the vectorizable load/store is slow.
> * target.def (TARGET_SLOW_UNALIGNED_VECTOR_MEMOP): New target hook.
> * doc/m.texi.in: Document new target hook:
> TARGET_SLOW_UNALIGNED_VECTOR_MEMOP
> * doc/m.texi: Regenerate.
> * config/i386/i386.c (ix86_slow_unaligned_vector_memop): New function.
> (TARGET_SLOW_UNALIGNED_VECTOR_MEMOP): New macro.
>
> @@ -5065,27 +5112,43 @@ vect_analyze_stmt (gimple stmt, bool
*need_to_vect
> if (!bb_vinfo
> && (STMT_VINFO_RELEVANT_P (stmt_info)
> || STMT_VINFO_DEF_TYPE (stmt_info) == vect_reduction_def))
> + {
> ok = (vectorizable_type_promotion (stmt, NULL, NULL, NULL)
> || vectorizable_type_demotion (stmt, NULL, NULL, NULL)
> || vectorizable_conversion (stmt, NULL, NULL, NULL)
> || vectorizable_shift (stmt, NULL, NULL, NULL)
> || vectorizable_operation (stmt, NULL, NULL, NULL)
> || vectorizable_assignment (stmt, NULL, NULL, NULL)
> - || vectorizable_load (stmt, NULL, NULL, NULL, NULL)
> || vectorizable_call (stmt, NULL, NULL)
> - || vectorizable_store (stmt, NULL, NULL, NULL)
> - || vectorizable_reduction (stmt, NULL, NULL, NULL)
> + || vectorizable_reduction (stmt, NULL, NULL, NULL)
> || vectorizable_condition (stmt, NULL, NULL, NULL, 0));
> +
> + if (!ok)
> + {
> + ok = (vectorizable_load (stmt, NULL, NULL, NULL, NULL)
> + || vectorizable_store (stmt, NULL, NULL, NULL));
> +
> + if (ok && is_slow_vect_unaligned_load_store (stmt))
> + ok = false;
Why not call is_slow_vect_unaligned_load_store from
vectorizable_load/store?
Ira
> + }
> + }
> else
> {
> if (bb_vinfo)
> - ok = (vectorizable_type_promotion (stmt, NULL, NULL, node)
> - || vectorizable_type_demotion (stmt, NULL, NULL, node)
> - || vectorizable_shift (stmt, NULL, NULL, node)
> - || vectorizable_operation (stmt, NULL, NULL, node)
> - || vectorizable_assignment (stmt, NULL, NULL, node)
> - || vectorizable_load (stmt, NULL, NULL, node, NULL)
> - || vectorizable_store (stmt, NULL, NULL, node));
> + {
> + ok = (vectorizable_type_promotion (stmt, NULL, NULL, node)
> + || vectorizable_type_demotion (stmt, NULL, NULL, node)
> + || vectorizable_shift (stmt, NULL, NULL, node)
> + || vectorizable_operation (stmt, NULL, NULL, node)
> + || vectorizable_assignment (stmt, NULL, NULL, node));
> + if (!ok)
> + {
> + ok = (vectorizable_load (stmt, NULL, NULL, node, NULL)
> + || vectorizable_store (stmt, NULL, NULL, node));
> + if (ok && is_slow_vect_unaligned_load_store (stmt))
> + ok = false;
> + }
> + }
> }
