On 11/17/2017 08:13 AM, Richard Sandiford wrote:
> This patch adds support for aligning vectors by using a partial
> first iteration. E.g. if the start pointer is 3 elements beyond
> an aligned address, the first iteration will have a mask in which
> the first three elements are false.
>
> On SVE, the optimisation is only useful for vector-length-specific
> code. Vector-length-agnostic code doesn't try to align vectors
> since the vector length might not be a power of 2.
>
> Tested on aarch64-linux-gnu (with and without SVE), x86_64-linux-gnu
> and powerpc64le-linux-gnu. OK to install?
>
> Richard
>
>
> 2017-11-17 Richard Sandiford <richard.sandif...@linaro.org>
> Alan Hayward <alan.hayw...@arm.com>
> David Sherwood <david.sherw...@arm.com>
>
> gcc/
> * tree-vectorizer.h (_loop_vec_info::mask_skip_niters): New field.
> (LOOP_VINFO_MASK_SKIP_NITERS): New macro.
> (vect_use_loop_mask_for_alignment_p): New function.
> (vect_prepare_for_masked_peels, vect_gen_while_not): Declare.
> * tree-vect-loop-manip.c (vect_set_loop_masks_directly): Add an
> niters_skip argument. Make sure that the first niters_skip elements
> of the first iteration are inactive.
> (vect_set_loop_condition_masked): Handle LOOP_VINFO_MASK_SKIP_NITERS.
> Update call to vect_set_loop_masks_directly.
> (get_misalign_in_elems): New function, split out from...
> (vect_gen_prolog_loop_niters): ...here.
> (vect_update_init_of_dr): Take a code argument that specifies whether
> the adjustment should be added or subtracted.
> (vect_update_init_of_drs): Likewise.
> (vect_prepare_for_masked_peels): New function.
> (vect_do_peeling): Skip prologue peeling if we're using a mask
> instead. Update call to vect_update_inits_of_drs.
> * tree-vect-loop.c (_loop_vec_info::_loop_vec_info): Initialize
> mask_skip_niters.
> (vect_analyze_loop_2): Allow fully-masked loops with peeling for
> alignment. Do not include the number of peeled iterations in
> the minimum threshold in that case.
> (vectorizable_induction): Adjust the start value down by
> LOOP_VINFO_MASK_SKIP_NITERS iterations.
> (vect_transform_loop): Call vect_prepare_for_masked_peels.
> Take the number of skipped iterations into account when calculating
> the loop bounds.
> * tree-vect-stmts.c (vect_gen_while_not): New function.
OK.
jeff
