Re: [PATCH, vec-tails 07/10] Support loop epilogue combining

[Jeff Law <law at redhat dot com>]

On 06/28/2016 06:24 AM, Ilya Enkovich wrote:

> Here is an updated patch version.
>
> Thanks,
> Ilya
> --
> gcc/
>
> 2016-05-28  Ilya Enkovich  <ilya.enkovich@intel.com>
>
> 	* dbgcnt.def (vect_tail_combine): New.
> 	* params.def (PARAM_VECT_COST_INCREASE_COMBINE_THRESHOLD): New.
> 	* tree-vect-data-refs.c (vect_get_new_ssa_name): Support vect_mask_var.
> 	* tree-vect-loop-manip.c (slpeel_tree_peel_loop_to_edge): Support
> 	epilogue combined with loop body.
> 	(vect_do_peeling_for_loop_bound): LIkewise.
> 	(vect_do_peeling_for_alignment): ???
> 	* tree-vect-loop.c Include alias.h and dbgcnt.h.
> 	(vect_estimate_min_profitable_iters): Add ret_min_profitable_combine_niters
> 	arg, compute number of iterations for which loop epilogue combining is
> 	profitable.
> 	(vect_generate_tmps_on_preheader): Support combined apilogue.
> 	(vect_gen_ivs_for_masking): New.
> 	(vect_get_mask_index_for_elems): New.
> 	(vect_get_mask_index_for_type): New.
> 	(vect_gen_loop_masks): New.
> 	(vect_mask_reduction_stmt): New.
> 	(vect_mask_mask_load_store_stmt): New.
> 	(vect_mask_load_store_stmt): New.
> 	(vect_combine_loop_epilogue): New.
> 	(vect_transform_loop): Support combined apilogue.
>
>
> diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
> index 41b9380..08fad82 100644
> --- a/gcc/tree-vect-loop.c
> +++ b/gcc/tree-vect-loop.c
> @@ -6895,6 +7044,489 @@ vect_generate_tmps_on_preheader (loop_vec_info loop_vinfo,
>    return;
>  }
 +
> +/* Function vect_gen_loop_masks.
> +
> +   Create masks to mask a loop described by LOOP_VINFO.  Masks
> +   are created according to LOOP_VINFO_REQUIRED_MASKS and are stored
> +   into MASKS vector.
> +
> +   Index of a mask in a vector is computed according to a number
> +   of masks's elements.  Masks are sorted by number of its elements
> +   in descending order.  Index 0 is used to access a mask with
> +   current_vector_size elements.  Among masks with the same number
> +   of elements the one with lower index is used to mask iterations
> +   with smaller iteration counter.  Note that you may get NULL elements
> +   for masks which are not required.  Use vect_get_mask_index_for_elems
> +   or vect_get_mask_index_for_type to access resulting vector.  */
> +
> +static void
> +vect_gen_loop_masks (loop_vec_info loop_vinfo, vec<tree> *masks)
I find myself wondering if this ought to be broken down a bit (without 
changing the underlying semantics).

> +
> +  /* Create narrowed masks.  */
> +  cur_mask_elems = iv_elems;
> +  nmasks = ivs.length ();
> +  while (cur_mask_elems < max_mask_elems)
> +    {
> +      prev_mask = vect_get_mask_index_for_elems (cur_mask_elems);
> +
> +      cur_mask_elems <<= 1;
> +      nmasks >>= 1;
> +
> +      cur_mask = vect_get_mask_index_for_elems (cur_mask_elems);
> +
> +      mask_type = build_truth_vector_type (cur_mask_elems, vec_size);
> +
> +      for (unsigned i = 0; i < nmasks; i++)
> +	{
> +	  tree mask_low = (*masks)[prev_mask++];
> +	  tree mask_hi = (*masks)[prev_mask++];
> +	  mask = vect_get_new_ssa_name (mask_type, vect_mask_var);
> +	  stmt = gimple_build_assign (mask, VEC_PACK_TRUNC_EXPR,
> +				      mask_low, mask_hi);
> +	  gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);
> +	  (*masks)[cur_mask++] = mask;
> +	}
> +    }
For example, pull this into its own function as well as the code to 
create widened masks.  In fact, didn't I see those functions in one of 
the other patches as their own separate subroutines?

It's not a huge deal and I don't think it requires another round of 
review.  I just found myself scrolling through multiple pages of this 
function and thought it'd be slightly easier to grok if were simply smaller.


> +
> +/* Function vect_mask_reduction_stmt.
> +
> +   Mask given vectorized reduction statement STMT using
> +   MASK.  In case scalar reduction statement is vectorized
> +   into several vector statements then PREV holds a
> +   preceding vetor statement copy for STMT.
s/vetor/vector/

With the one function split up and the typo fix I think this is OK for 
the trunk when the set as a whole is ready.

jeff