On Tue, Aug 15, 2023 at 1:47 PM Kewen.Lin <li...@linux.ibm.com> wrote:
>
> 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?
I'd leave those together, they share too much code.
> >
> > 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
