On 11/17/2017 07:56 AM, Richard Sandiford wrote:
> This patch adds support for using a single fully-predicated loop instead
> of a vector loop and a scalar tail. An SVE WHILELO instruction generates
> the predicate for each iteration of the loop, given the current scalar
> iv value and the loop bound. This operation is wrapped up in a new internal
> function called WHILE_ULT. E.g.:
>
> WHILE_ULT (0, 3, { 0, 0, 0, 0}) -> { 1, 1, 1, 0 }
> WHILE_ULT (UINT_MAX - 1, UINT_MAX, { 0, 0, 0, 0 }) -> { 1, 0, 0, 0 }
>
> The third WHILE_ULT argument is needed to make the operation
> unambiguous: without it, WHILE_ULT (0, 3) for one vector type would
> seem equivalent to WHILE_ULT (0, 3) for another, even if the types have
> different numbers of elements.
>
> Note that the patch uses "mask" and "fully-masked" instead of
> "predicate" and "fully-predicated", to follow existing GCC terminology.
>
> This patch just handles the simple cases, punting for things like
> reductions and live-out values. Later patches remove most of these
> restrictions.
>
> 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/
> * optabs.def (while_ult_optab): New optab.
> * doc/md.texi (while_ult@var{m}@var{n}): Document.
> * internal-fn.def (WHILE_ULT): New internal function.
> * internal-fn.h (direct_internal_fn_supported_p): New override
> that takes two types as argument.
> * internal-fn.c (while_direct): New macro.
> (expand_while_optab_fn): New function.
> (convert_optab_supported_p): Likewise.
> (direct_while_optab_supported_p): New macro.
> * wide-int.h (wi::udiv_ceil): New function.
> * tree-vectorizer.h (rgroup_masks): New structure.
> (vec_loop_masks): New typedef.
> (_loop_vec_info): Add masks, mask_compare_type, can_fully_mask_p
> and fully_masked_p.
> (LOOP_VINFO_CAN_FULLY_MASK_P, LOOP_VINFO_FULLY_MASKED_P)
> (LOOP_VINFO_MASKS, LOOP_VINFO_MASK_COMPARE_TYPE): New macros.
> (vect_max_vf): New function.
> (slpeel_make_loop_iterate_ntimes): Delete.
> (vect_set_loop_condition, vect_get_loop_mask_type, vect_gen_while)
> (vect_halve_mask_nunits, vect_double_mask_nunits): Declare.
> )vect_record_loop_mask, vect_get_loop_mask): Likewise.
> * tree-vect-loop-manip.c: Include tree-ssa-loop-niter.h,
> internal-fn.h, stor-layout.h and optabs-query.h.
> (vect_set_loop_mask): New function.
> (add_preheader_seq): Likewise.
> (add_header_seq): Likewise.
> (vect_maybe_permute_loop_masks): Likewise.
> (vect_set_loop_masks_directly): Likewise.
> (vect_set_loop_condition_masked): Likewise.
> (vect_set_loop_condition_unmasked): New function, split out from
> slpeel_make_loop_iterate_ntimes.
> (slpeel_make_loop_iterate_ntimes): Rename to..
> (vect_set_loop_condition): ...this. Use vect_set_loop_condition_masked
> for fully-masked loops and vect_set_loop_condition_unmasked otherwise.
> (vect_do_peeling): Update call accordingly.
> (vect_gen_vector_loop_niters): Use VF as the step for fully-masked
> loops.
> * tree-vect-loop.c (_loop_vec_info::_loop_vec_info): Initialize
> mask_compare_type, can_fully_mask_p and fully_masked_p.
> (release_vec_loop_masks): New function.
> (_loop_vec_info): Use it to free the loop masks.
> (can_produce_all_loop_masks_p): New function.
> (vect_get_max_nscalars_per_iter): Likewise.
> (vect_verify_full_masking): Likewise.
> (vect_analyze_loop_2): Save LOOP_VINFO_CAN_FULLY_MASK_P around
> retries, and free the mask rgroups before retrying. Check loop-wide
> reasons for disallowing fully-masked loops. Make the final decision
> about whether use a fully-masked loop or not.
> (vect_estimate_min_profitable_iters): Do not assume that peeling
> for the number of iterations will be needed for fully-masked loops.
> (vectorizable_reduction): Disable fully-masked loops.
> (vectorizable_live_operation): Likewise.
> (vect_halve_mask_nunits): New function.
> (vect_double_mask_nunits): Likewise.
> (vect_record_loop_mask): Likewise.
> (vect_get_loop_mask): Likewise.
> (vect_transform_loop): Handle the case in which the final loop
> iteration might handle a partial vector. Call vect_set_loop_condition
> instead of slpeel_make_loop_iterate_ntimes.
> * tree-vect-stmts.c: Include tree-ssa-loop-niter.h and gimple-fold.h.
> (check_load_store_masking): New function.
> (prepare_load_store_mask): Likewise.
> (vectorizable_store): Handle fully-masked loops.
> (vectorizable_load): Likewise.
> (supportable_widening_operation): Use vect_halve_mask_nunits for
> booleans.
> (supportable_narrowing_operation): Likewise vect_double_mask_nunits.
> (vect_gen_while): New function.
> * config/aarch64/aarch64.md (umax<mode>3): New expander.
> (aarch64_uqdec<mode>): New insn.
> * config/aarch64/aarch64-sve.md (<perm_optab>_<mode>)
> (*aarch64_sve_<perm_insn><perm_hilo><mode>): New predicate patterns.
>
> gcc/testsuite/
> * gcc.dg/tree-ssa/cunroll-10.c: Disable vectorization.
> * gcc.dg/tree-ssa/peel1.c: Likewise.
> * gcc.dg/vect/vect-load-lanes-peeling-1.c: Remove XFAIL for
> variable-length vectors.
> * gcc.target/aarch64/sve_vcond_6.c: XFAIL test for AND.
> * gcc.target/aarch64/sve_vec_bool_cmp_1.c: Expect BIC instead of NOT.
> * gcc.target/aarch64/sve_slp_1.c: Check for a fully-masked loop.
> * gcc.target/aarch64/sve_slp_2.c: Likewise.
> * gcc.target/aarch64/sve_slp_3.c: Likewise.
> * gcc.target/aarch64/sve_slp_4.c: Likewise.
> * gcc.target/aarch64/sve_slp_6.c: Likewise.
> * gcc.target/aarch64/sve_slp_8.c: New test.
> * gcc.target/aarch64/sve_slp_8_run.c: Likewise.
> * gcc.target/aarch64/sve_slp_9.c: Likewise.
> * gcc.target/aarch64/sve_slp_9_run.c: Likewise.
> * gcc.target/aarch64/sve_slp_10.c: Likewise.
> * gcc.target/aarch64/sve_slp_10_run.c: Likewise.
> * gcc.target/aarch64/sve_slp_11.c: Likewise.
> * gcc.target/aarch64/sve_slp_11_run.c: Likewise.
> * gcc.target/aarch64/sve_slp_12.c: Likewise.
> * gcc.target/aarch64/sve_slp_12_run.c: Likewise.
> * gcc.target/aarch64/sve_ld1r_2.c: Likewise.
> * gcc.target/aarch64/sve_ld1r_2_run.c: Likewise.
> * gcc.target/aarch64/sve_while_1.c: Likewise.
> * gcc.target/aarch64/sve_while_2.c: Likewise.
> * gcc.target/aarch64/sve_while_3.c: Likewise.
> * gcc.target/aarch64/sve_while_4.c: Likewise.
Like other SVE related patches, I haven't looked at the aarch64 specific
bits, just the generic bits.
Sadly, I'm totally lost on this one.... I understand at a 30000ft
level what you're trying to do and many of the low level primitives made
sense. But I wasn't able to go from those primitives to the higher
level implementation details, even though the higher level
implementation details didn't seem all that large.
I trust your judgment on this stuff.
OK for the trunk.
Jeff
