on 2023/8/15 15:53, Richard Biener wrote:
> On Tue, Aug 15, 2023 at 4:44 AM Kewen.Lin <li...@linux.ibm.com> wrote:
>>
>> on 2023/8/14 22:16, Richard Sandiford wrote:
>>> "Kewen.Lin" <li...@linux.ibm.com> writes:
>>>> Hi Richard,
>>>>
>>>> on 2023/8/14 20:20, Richard Sandiford wrote:
>>>>> Thanks for the clean-ups. But...
>>>>>
>>>>> "Kewen.Lin" <li...@linux.ibm.com> writes:
>>>>>> Hi,
>>>>>>
>>>>>> Following Richi's suggestion [1], this patch is to move the
>>>>>> handlings on VMAT_GATHER_SCATTER in the final loop nest
>>>>>> of function vectorizable_load to its own loop. Basically
>>>>>> it duplicates the final loop nest, clean up some useless
>>>>>> set up code for the case of VMAT_GATHER_SCATTER, remove some
>>>>>> unreachable code. Also remove the corresponding handlings
>>>>>> in the final loop nest.
>>>>>>
>>>>>> Bootstrapped and regtested on x86_64-redhat-linux,
>>>>>> aarch64-linux-gnu and powerpc64{,le}-linux-gnu.
>>>>>>
>>>>>> [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-June/623329.html
>>>>>>
>>>>>> Is it ok for trunk?
>>>>>>
>>>>>> BR,
>>>>>> Kewen
>>>>>> -----
>>>>>>
>>>>>> gcc/ChangeLog:
>>>>>>
>>>>>> * tree-vect-stmts.cc (vectorizable_load): Move the handlings on
>>>>>> VMAT_GATHER_SCATTER in the final loop nest to its own loop,
>>>>>> and update the final nest accordingly.
>>>>>> ---
>>>>>> gcc/tree-vect-stmts.cc | 361 +++++++++++++++++++++++++----------------
>>>>>> 1 file changed, 219 insertions(+), 142 deletions(-)
>>>>>
>>>>> ...that seems like quite a lot of +s. Is there nothing we can do to
>>>>> avoid the cut-&-paste?
>>>>
>>>> Thanks for the comments! I'm not sure if I get your question, if we
>>>> want to move out the handlings of VMAT_GATHER_SCATTER, the new +s seem
>>>> inevitable? Your concern is mainly about git blame history?
>>>
>>> No, it was more that 219-142=77, so it seems like a lot of lines
>>> are being duplicated rather than simply being moved. (Unlike for
>>> VMAT_LOAD_STORE_LANES, which was even a slight LOC saving, and so
>>> was a clear improvement.)
>>>
>>> So I was just wondering if there was any obvious factoring-out that
>>> could be done to reduce the duplication.
>>
>> ah, thanks for the clarification!
>>
>> I think the main duplication are on the loop body beginning and end,
>> let's take a look at them in details:
>>
>> + if (memory_access_type == VMAT_GATHER_SCATTER)
>> + {
>> + gcc_assert (alignment_support_scheme == dr_aligned
>> + || alignment_support_scheme == dr_unaligned_supported);
>> + gcc_assert (!grouped_load && !slp_perm);
>> +
>> + unsigned int inside_cost = 0, prologue_cost = 0;
>>
>> // These above are newly added.
>>
>> + for (j = 0; j < ncopies; j++)
>> + {
>> + /* 1. Create the vector or array pointer update chain. */
>> + if (j == 0 && !costing_p)
>> + {
>> + if (STMT_VINFO_GATHER_SCATTER_P (stmt_info))
>> + vect_get_gather_scatter_ops (loop_vinfo, loop, stmt_info,
>> + slp_node, &gs_info,
>> &dataref_ptr,
>> + &vec_offsets);
>> + else
>> + dataref_ptr
>> + = vect_create_data_ref_ptr (vinfo, first_stmt_info,
>> aggr_type,
>> + at_loop, offset, &dummy, gsi,
>> + &ptr_incr, false, bump);
>> + }
>> + else if (!costing_p)
>> + {
>> + gcc_assert (!LOOP_VINFO_USING_SELECT_VL_P (loop_vinfo));
>> + if (!STMT_VINFO_GATHER_SCATTER_P (stmt_info))
>> + dataref_ptr = bump_vector_ptr (vinfo, dataref_ptr, ptr_incr,
>> + gsi, stmt_info, bump);
>> + }
>>
>> // These are for dataref_ptr, in the final looop nest we deal with more cases
>> on simd_lane_access_p and diff_first_stmt_info, but don't handle
>> STMT_VINFO_GATHER_SCATTER_P any more, very few (one case) can be shared
>> between,
>> IMHO factoring out it seems like a overkill.
>>
>> +
>> + if (mask && !costing_p)
>> + vec_mask = vec_masks[j];
>>
>> // It's merged out from j == 0 and j != 0
>>
>> +
>> + gimple *new_stmt = NULL;
>> + for (i = 0; i < vec_num; i++)
>> + {
>> + tree final_mask = NULL_TREE;
>> + tree final_len = NULL_TREE;
>> + tree bias = NULL_TREE;
>> + if (!costing_p)
>> + {
>> + if (loop_masks)
>> + final_mask
>> + = vect_get_loop_mask (loop_vinfo, gsi, loop_masks,
>> + vec_num * ncopies, vectype,
>> + vec_num * j + i);
>> + if (vec_mask)
>> + final_mask = prepare_vec_mask (loop_vinfo, mask_vectype,
>> + final_mask, vec_mask,
>> gsi);
>> +
>> + if (i > 0 && !STMT_VINFO_GATHER_SCATTER_P (stmt_info))
>> + dataref_ptr = bump_vector_ptr (vinfo, dataref_ptr,
>> ptr_incr,
>> + gsi, stmt_info, bump);
>> + }
>>
>> // This part is directly copied from the original, the original gets updated
>> by
>> removing && !STMT_VINFO_GATHER_SCATTER_P. Due to its size, I didn't consider
>> this before, do you prefer me to factor this part out?
>>
>> + if (gs_info.ifn != IFN_LAST)
>> + {
>> ...
>> + }
>> + else
>> + {
>> + /* Emulated gather-scatter. */
>> ...
>>
>> // This part is just moved from the original.
>>
>> + vec_dest = vect_create_destination_var (scalar_dest, vectype);
>> + /* DATA_REF is null if we've already built the statement. */
>> + if (data_ref)
>> + {
>> + vect_copy_ref_info (data_ref, DR_REF (first_dr_info->dr));
>> + new_stmt = gimple_build_assign (vec_dest, data_ref);
>> + }
>> + new_temp = make_ssa_name (vec_dest, new_stmt);
>> + gimple_set_lhs (new_stmt, new_temp);
>> + vect_finish_stmt_generation (vinfo, stmt_info, new_stmt, gsi);
>> +
>> + /* Store vector loads in the corresponding SLP_NODE. */
>> + if (slp)
>> + slp_node->push_vec_def (new_stmt);
>> +
>> + if (!slp && !costing_p)
>> + STMT_VINFO_VEC_STMTS (stmt_info).safe_push (new_stmt);
>> + }
>> +
>> + if (!slp && !costing_p)
>> + *vec_stmt = STMT_VINFO_VEC_STMTS (stmt_info)[0];
>>
>> // This part is some subsequent handlings, it's duplicated from the original
>> but removing some more useless code. I guess this part is not worthy
>> being factored out?
>>
>> + if (costing_p)
>> + {
>> + if (dump_enabled_p ())
>> + dump_printf_loc (MSG_NOTE, vect_location,
>> + "vect_model_load_cost: inside_cost = %u, "
>> + "prologue_cost = %u .\n",
>> + inside_cost, prologue_cost);
>> + }
>> + return true;
>> + }
>>
>> // Duplicating the dumping, I guess it's unnecessary to be factored out.
>>
>> oh, I just noticed that this should be shorten as
>> "if (costing_p && dump_enabled_p ())" instead, just the same as what's
>> adopted for VMAT_LOAD_STORE_LANES dumping.
>
> Just to mention, the original motivational idea was even though we
> duplicate some
> code we make it overall more readable and thus maintainable. In the end we
> might have vectorizable_load () for analysis but have not only
> load_vec_info_type but one for each VMAT_* which means multiple separate
> vect_transform_load () functions. Currently vectorizable_load is structured
> very inconsistently, having the transforms all hang off a single
> switch (vmat-kind) {} would be an improvement IMHO.
Thanks for the comments! With these two patches, now the final loop nest are
only handling VMAT_CONTIGUOUS, VMAT_CONTIGUOUS_REVERSE and
VMAT_CONTIGUOUS_PERMUTE.
IMHO, their handlings are highly bundled, re-structuring them can have more
duplicated code and potential incomplete bug fix risks as Richard pointed out.
But if I read the above comments right, our final goal seems to separate all of
them? I wonder if you both prefer to further separate them?
>
> But sure some of our internal APIs are verbose and maybe badly factored,
> any improvement there is welcome. Inventing new random APIs just to
> save a few lines of code without actually making the code more readable
> is IMHO bad.
>
> But, if we can for example enhance prepare_vec_mask to handle both loop
> and conditional mask and handle querying the mask that would be fine
> (of course you need to check all uses to see if that makes sense).
OK, will keep in mind, also add the example to my TODO list. :)
BR,
Kewen
