On Mon, 28 Oct 2019, Andre Vieira (lists) wrote:
> Hi,
>
> Reworked according to your comments, see inline for clarification.
>
> Is this OK for trunk?
+ gimple_seq seq = STMT_VINFO_PATTERN_DEF_SEQ (stmt_vinfo);
+ while (seq)
+ {
+ stmt_worklist.safe_push (seq);
+ seq = seq->next;
+ }
you're supposed to do to the following, not access the ->next
implementation detail:
for (gimple_stmt_iterator gsi = gsi_start (seq); !gsi_end_p (gsi);
gsi_next (&gsi))
stmt_worklist.safe_push (gsi_stmt (gsi));
+ /* Data references for gather loads and scatter stores do not use
the
+ updated offset we set using ADVANCE. Instead we have to make
sure
the
+ reference in the data references point to the corresponding copy
of
+ the original in the epilogue. */
+ if (STMT_VINFO_GATHER_SCATTER_P (stmt_vinfo))
+ {
+ DR_REF (dr)
+ = simplify_replace_tree (DR_REF (dr), NULL_TREE, NULL_TREE,
+ &find_in_mapping, &mapping);
+ DR_BASE_ADDRESS (dr)
+ = simplify_replace_tree (DR_BASE_ADDRESS (dr), NULL_TREE,
NULL_TREE,
+ &find_in_mapping, &mapping);
+ }
Hmm. So for other DRs we account for the previous vector loop
by adjusting DR_OFFSET? But STMT_VINFO_GATHER_SCATTER_P ends up
using (unconditionally) DR_REF here? In that case it seems
best to adjust DR_REF only but NULL out DR_BASE_ADDRESS and
DR_OFFSET? I wonder how prologue peeling deals with
STMT_VINFO_GATHER_SCATTER_P ... I see the caller of
vect_update_init_of_dr there does nothing for STMT_VINFO_GATHER_SCATTER_P.
I wonder if (as followup to not delay this further) we can
"offload" all the DR adjustment by storing ADVANCE in dr_vec_info
and accounting for that when we create the dataref pointers in
vectorizable_load/store? That way we could avoid saving/restoring
DR_OFFSET as well.
So, the patch is OK with the sequence iteration fixed. I think
sorting out the above can be done as followup.
Thanks,
Richard.
> gcc/ChangeLog:
> 2019-10-28 Andre Vieira <andre.simoesdiasvie...@arm.com>
>
> PR 88915
> * tree-ssa-loop-niter.h (simplify_replace_tree): Change declaration.
> * tree-ssa-loop-niter.c (simplify_replace_tree): Add context parameter
> and make the valueize function pointer also take a void pointer.
> * gcc/tree-ssa-sccvn.c (vn_valueize_wrapper): New function to wrap
> around vn_valueize, to call it without a context.
> (process_bb): Use vn_valueize_wrapper instead of vn_valueize.
> * tree-vect-loop.c (_loop_vec_info): Initialize epilogue_vinfos.
> (~_loop_vec_info): Release epilogue_vinfos.
> (vect_analyze_loop_costing): Use knowledge of main VF to estimate
> number of iterations of epilogue.
> (vect_analyze_loop_2): Adapt to analyse main loop for all supported
> vector sizes when vect-epilogues-nomask=1. Also keep track of lowest
> versioning threshold needed for main loop.
> (vect_analyze_loop): Likewise.
> (find_in_mapping): New helper function.
> (update_epilogue_loop_vinfo): New function.
> (vect_transform_loop): When vectorizing epilogues re-use analysis done
> on main loop and call update_epilogue_loop_vinfo to update it.
> * tree-vect-loop-manip.c (vect_update_inits_of_drs): No longer insert
> stmts on loop preheader edge.
> (vect_do_peeling): Enable skip-vectors when doing loop versioning if
> we decided to vectorize epilogues. Update epilogues NITERS and
> construct ADVANCE to update epilogues data references where needed.
> * tree-vectorizer.h (_loop_vec_info): Add epilogue_vinfos.
> (vect_do_peeling, vect_update_inits_of_drs,
> determine_peel_for_niter, vect_analyze_loop): Add or update declarations.
> * tree-vectorizer.c (try_vectorize_loop_1): Make sure to use already
> created loop_vec_info's for epilogues when available. Otherwise
> analyse
> epilogue separately.
>
>
>
> Cheers,
> Andre
>
> On 28/10/2019 14:16, Richard Biener wrote:
> > On Fri, 25 Oct 2019, Andre Vieira (lists) wrote:
> >
> >> Hi,
> >>
> >> This is the reworked patch after your comments.
> >>
> >> I have moved the epilogue check into the analysis form disguised under
> >> '!epilogue_vinfos.is_empty ()'. This because I realized that I am doing
> >> the
> >> "lowest threshold" check there.
> >>
> >> The only place where we may reject an epilogue_vinfo is when we know the
> >> number of scalar iterations and we realize the number of iterations left
> >> after
> >> the main loop are not enough to enter the vectorized epilogue so we
> >> optimize
> >> away that code-gen. The only way we know this to be true is if the number
> >> of
> >> scalar iterations are known and the peeling for alignment is known. So we
> >> know
> >> we will enter the main loop regardless, so whether the threshold we use is
> >> for
> >> a lower VF or not it shouldn't matter as much, I would even like to think
> >> that
> >> check isn't done, but I am not sure... Might be worth checking as an
> >> optimization.
> >>
> >>
> >> Is this OK for trunk?
> >
> > + for (epilogue_phi_gsi = gsi_start_phis (epilogue_bbs[i]);
> > + !gsi_end_p (epilogue_phi_gsi); gsi_next (&epilogue_phi_gsi))
> > + {
> > ..
> > + if (STMT_VINFO_PATTERN_DEF_SEQ (stmt_vinfo))
> > + pattern_worklist.safe_push (stmt_vinfo);
> > +
> > + related_vinfo = STMT_VINFO_RELATED_STMT (stmt_vinfo);
> > + while (related_vinfo && related_vinfo != stmt_vinfo)
> > + {
> >
> > I think PHIs cannot have patterns. You can assert
> > that STMT_VINFO_RELATED_STMT is NULL I think.
>
> Done.
> >
> > + related_vinfo = STMT_VINFO_RELATED_STMT (stmt_vinfo);
> > + while (related_vinfo && related_vinfo != stmt_vinfo)
> > + {
> > + related_worklist.safe_push (related_vinfo);
> > + /* Set BB such that the assert in
> > + 'get_initial_def_for_reduction' is able to determine that
> > + the BB of the related stmt is inside this loop. */
> > + gimple_set_bb (STMT_VINFO_STMT (related_vinfo),
> > + gimple_bb (new_stmt));
> > + related_vinfo = STMT_VINFO_RELATED_STMT (related_vinfo);
> > + }
> >
> > do we really keep references to "nested" patterns? Thus, do you
> > need this loop?
>
> Changed and added asserts. They didn't trigger so I suppose you are right, I
> didn't know at the time whether it was possible, so I just operated on the
> side of caution. Can remove the asserts and so on if you want.
> >
> > + /* The PATTERN_DEF_SEQs in the epilogue were constructed using the
> > + original main loop and thus need to be updated to refer to the
> > cloned
> > + variables used in the epilogue. */
> > + for (unsigned i = 0; i < pattern_worklist.length (); ++i)
> > + {
> > ...
> > + op = simplify_replace_tree (op, NULL_TREE, NULL_TREE,
> > + &find_in_mapping, &mapping);
> > + gimple_set_op (seq, j, op);
> >
> > you do this for the pattern-def seq but not for the related one.
> > I guess you ran into this for COND_EXPR conditions. I wondered
> > to use a shared worklist for both the def-seq and the main pattern
> > stmt or at least to split out the replacement so you can share it.
>
> I think that was it yeah, reworked it now to use the same list. Less code,
> thanks!
> >
> > + /* Data references for gather loads and scatter stores do not use
> > the
> > + updated offset we set using ADVANCE. Instead we have to make
> > sure the
> > + reference in the data references point to the corresponding copy
> > of
> > + the original in the epilogue. */
> > + if (STMT_VINFO_GATHER_SCATTER_P (stmt_vinfo))
> > + {
> > + int j;
> > + if (TREE_CODE (DR_REF (dr)) == MEM_REF)
> > + j = 0;
> > + else if (TREE_CODE (DR_REF (dr)) == ARRAY_REF)
> > + j = 1;
> > + else
> > + gcc_unreachable ();
> > +
> > + if (tree *new_op = mapping.get (TREE_OPERAND (DR_REF (dr), j)))
> > + {
> > + DR_REF (dr) = unshare_expr (DR_REF (dr));
> > + TREE_OPERAND (DR_REF (dr), j) = *new_op;
> > + }
> >
> > huh, do you really only ever see MEM_REF or ARRAY_REF here?
> > I would guess using simplify_replace_tree is safer.
> > There's also DR_BASE_ADDRESS - we seem to leave the DRs partially
> > updated, is that correct?
>
> Yeah can use simplify_replace_tree indeed. And I have changed it so it
> updates DR_BASE_ADDRESS. I think DR_BASE_ADDRESS never actually changed in
> the way we use data_references... Either way, replacing them if they do change
> is cleaner and more future proof.
> >
> > Otherwise looks OK to me.
> >
> > Thanks,
> > Richard.
> >
> >
> >> gcc/ChangeLog:
> >> 2019-10-25 Andre Vieira <andre.simoesdiasvie...@arm.com>
> >>
> >> PR 88915
> >> * tree-ssa-loop-niter.h (simplify_replace_tree): Change declaration.
> >> * tree-ssa-loop-niter.c (simplify_replace_tree): Add context parameter
> >> and make the valueize function pointer also take a void pointer.
> >> * gcc/tree-ssa-sccvn.c (vn_valueize_wrapper): New function to wrap
> >> around vn_valueize, to call it without a context.
> >> (process_bb): Use vn_valueize_wrapper instead of vn_valueize.
> >> * tree-vect-loop.c (_loop_vec_info): Initialize epilogue_vinfos.
> >> (~_loop_vec_info): Release epilogue_vinfos.
> >> (vect_analyze_loop_costing): Use knowledge of main VF to estimate
> >> number of iterations of epilogue.
> >> (vect_analyze_loop_2): Adapt to analyse main loop for all supported
> >> vector sizes when vect-epilogues-nomask=1. Also keep track of lowest
> >> versioning threshold needed for main loop.
> >> (vect_analyze_loop): Likewise.
> >> (find_in_mapping): New helper function.
> >> (update_epilogue_loop_vinfo): New function.
> >> (vect_transform_loop): When vectorizing epilogues re-use analysis done
> >> on main loop and call update_epilogue_loop_vinfo to update it.
> >> * tree-vect-loop-manip.c (vect_update_inits_of_drs): No longer insert
> >> stmts on loop preheader edge.
> >> (vect_do_peeling): Enable skip-vectors when doing loop versioning if
> >> we decided to vectorize epilogues. Update epilogues NITERS and
> >> construct ADVANCE to update epilogues data references where needed.
> >> * tree-vectorizer.h (_loop_vec_info): Add epilogue_vinfos.
> >> (vect_do_peeling, vect_update_inits_of_drs,
> >> determine_peel_for_niter, vect_analyze_loop): Add or update
> >> declarations.
> >> * tree-vectorizer.c (try_vectorize_loop_1): Make sure to use already
> >> created loop_vec_info's for epilogues when available. Otherwise
> >> analyse
> >> epilogue separately.
> >>
> >>
> >>
> >> Cheers,
> >> Andre
> >>
> >
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
