The vectoriser aligned vectors to TYPE_ALIGN unconditionally, although
there was also a hard-coded assumption that this was equal to the type
size. This was inconvenient for SVE for two reasons:
- When compiling for a specific power-of-2 SVE vector length, we might
want to align to a full vector. However, the TYPE_ALIGN is governed
by the ABI alignment, which is 128 bits regardless of size.
- For vector-length-agnostic code it doesn't usually make sense to align,
since the runtime vector length might not be a power of two. Even for
power of two sizes, there's no guarantee that aligning to the previous
16 bytes will be an improveent.
This patch therefore adds a target hook to control the preferred
vectoriser (as opposed to ABI) alignment.
2017-09-22 Richard Sandiford <richard.sandiford@linaro.org>
Alan Hayward <alan.hayward@arm.com>
David Sherwood <david.sherwood@arm.com>
gcc/
* target.def (preferred_vector_alignment): New hook.
* doc/tm.texi.in (TARGET_VECTORIZE_PREFERRED_VECTOR_ALIGNMENT): New
hook.
* doc/tm.texi: Regenerate.
* targhooks.h (default_preferred_vector_alignment): Declare.
* targhooks.c (default_preferred_vector_alignment): New function.
* tree-vectorizer.h (dataref_aux): Add a target_alignment field.
Expand commentary.
(DR_TARGET_ALIGNMENT): New macro.
(aligned_access_p): Update commentary.
(vect_known_alignment_in_bytes): New function.
* tree-vect-data-refs.c (vect_calculate_required_alignment): New
function.
(vect_compute_data_ref_alignment): Set DR_TARGET_ALIGNMENT.
Calculate the misalignment based on the target alignment rather than
the vector size.
(vect_update_misalignment_for_peel): Use DR_TARGET_ALIGMENT
rather than TYPE_ALIGN / BITS_PER_UNIT to update the misalignment.
(vect_enhance_data_refs_alignment): Mask the byte misalignment with
the target alignment, rather than masking the element misalignment
with the number of elements in a vector. Also use the target
alignment when calculating the maximum number of peels.
(vect_find_same_alignment_drs): Use vect_calculate_required_alignment
instead of TYPE_ALIGN_UNIT.
(vect_duplicate_ssa_name_ptr_info): Remove stmt_info parameter.
Measure DR_MISALIGNMENT relative to DR_TARGET_ALIGNMENT.
(vect_create_addr_base_for_vector_ref): Update call accordingly.
(vect_create_data_ref_ptr): Likewise.
(vect_setup_realignment): Realign by ANDing with
-DR_TARGET_MISALIGNMENT.
* tree-vect-loop-manip.c (vect_gen_prolog_loop_niters): Calculate
the number of peels based on DR_TARGET_ALIGNMENT.
* tree-vect-stmts.c (get_group_load_store_type): Compare the gap
with the guaranteed alignment boundary when deciding whether
overrun is OK.
(vectorizable_mask_load_store): Interpret DR_MISALIGNMENT
relative to DR_TARGET_ALIGNMENT instead of TYPE_ALIGN_UNIT.
(ensure_base_align): Remove stmt_info parameter. Get the
target base alignment from DR_TARGET_ALIGNMENT.
(vectorizable_store): Update call accordingly. Interpret
DR_MISALIGNMENT relative to DR_TARGET_ALIGNMENT instead of
TYPE_ALIGN_UNIT.
(vectorizable_load): Likewise.
gcc/testsuite/
* gcc.dg/vect/vect-outer-3a.c: Adjust dump scan for new wording
of alignment message.
* gcc.dg/vect/vect-outer-3a-big-array.c: Likewise.
Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r253101
