On Wed, 11 Oct 2023, Tamar Christina wrote:
> > -----Original Message-----
> > From: Richard Biener <rguent...@suse.de>
> > Sent: Tuesday, October 10, 2023 12:14 PM
> > To: Tamar Christina <tamar.christ...@arm.com>
> > Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; j...@ventanamicro.com
> > Subject: Re: [PATCH 2/3]middle-end: updated niters analysis to handle
> > multiple exits.
> >
> > On Mon, 2 Oct 2023, Tamar Christina wrote:
> >
> > > Hi All,
> > >
> > > This second part updates niters analysis to be able to analyze any
> > > number of exits. If we have multiple exits we determine the main exit
> > > by finding the first counting IV.
> > >
> > > The change allows the vectorizer to pass analysis for multiple loops,
> > > but we later gracefully reject them. It does however allow us to test
> > > if the exit handling is using the right exit everywhere.
> > >
> > > Additionally since we analyze all exits, we now return all conditions
> > > for them and determine which condition belongs to the main exit.
> > >
> > > The main condition is needed because the vectorizer needs to ignore
> > > the main IV condition during vectorization as it will replace it during
> > > codegen.
> > >
> > > To track versioned loops we extend the contract between ifcvt and the
> > > vectorizer to store the exit number in aux so that we can match it up
> > > again
> > during peeling.
> > >
> > > Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-linux-gnu,
> > > and no issues.
> > >
> > > Ok for master?
> > >
> > > Thanks,
> > > Tamar
> > >
> > > gcc/ChangeLog:
> > >
> > > * tree-if-conv.cc (tree_if_conversion): Record exits in aux.
> > > * tree-vect-loop-manip.cc (slpeel_tree_duplicate_loop_to_edge_cfg):
> > Use
> > > it.
> > > * tree-vect-loop.cc (vect_get_loop_niters): Determine main exit.
> > > (vec_init_loop_exit_info): Extend analysis when multiple exits.
> > > (vect_analyze_loop_form): Record conds and determine main cond.
> > > (vect_create_loop_vinfo): Extend bookkeeping of conds.
> > > (vect_analyze_loop): Release conds.
> > > * tree-vectorizer.h (LOOP_VINFO_LOOP_CONDS,
> > > LOOP_VINFO_LOOP_IV_COND): New.
> > > (struct vect_loop_form_info): Add conds, alt_loop_conds;
> > > (struct loop_vec_info): Add conds, loop_iv_cond.
> > >
> > > --- inline copy of patch --
> > > diff --git a/gcc/tree-if-conv.cc b/gcc/tree-if-conv.cc index
> > >
> > 799f071965e5c41eb352b5530cf1d9c7ecf7bf25..3dc2290467797ebbfcef55
> > 903531
> > > b22829f4fdbd 100644
> > > --- a/gcc/tree-if-conv.cc
> > > +++ b/gcc/tree-if-conv.cc
> > > @@ -3795,6 +3795,13 @@ tree_if_conversion (class loop *loop,
> > vec<gimple *> *preds)
> > > }
> > > if (need_to_ifcvt)
> > > {
> > > + /* Before we rewrite edges we'll record their original position in
> > > the
> > > + edge map such that we can map the edges between the ifcvt and the
> > > + non-ifcvt loop during peeling. */
> > > + uintptr_t idx = 0;
> > > + for (edge exit : get_loop_exit_edges (loop))
> > > + exit->aux = (void*)idx++;
> > > +
> > > /* Now all statements are if-convertible. Combine all the basic
> > > blocks into one huge basic block doing the if-conversion
> > > on-the-fly. */
> > > diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
> > > index
> > >
> > e06717272aafc6d31cbdcb94840ac25de616da6d..77f8e668bcc8beca99ba4
> > 052e1b1
> > > 2e0d17300262 100644
> > > --- a/gcc/tree-vect-loop-manip.cc
> > > +++ b/gcc/tree-vect-loop-manip.cc
> > > @@ -1470,6 +1470,18 @@ slpeel_tree_duplicate_loop_to_edge_cfg (class
> > loop *loop, edge loop_exit,
> > > scalar_loop = loop;
> > > scalar_exit = loop_exit;
> > > }
> > > + else if (scalar_loop == loop)
> > > + scalar_exit = loop_exit;
> > > + else
> > > + {
> > > + /* Loop has been version, match exits up using the aux index. */
> > > + for (edge exit : get_loop_exit_edges (scalar_loop))
> > > + if (exit->aux == loop_exit->aux)
> > > + {
> > > + scalar_exit = exit;
> > > + break;
> > > + }
> > > + }
> > >
> > > bbs = XNEWVEC (basic_block, scalar_loop->num_nodes + 1);
> > > pbbs = bbs + 1;
> > > @@ -1501,6 +1513,8 @@ slpeel_tree_duplicate_loop_to_edge_cfg (class
> > loop *loop, edge loop_exit,
> > > exit = loop_exit;
> > > basic_block new_preheader = new_bbs[0];
> > >
> > > + /* Record the new loop exit information. new_loop doesn't have SCEV
> > data and
> > > + so we must initialize the exit information. */
> > > if (new_e)
> > > *new_e = new_exit;
> > >
> > > diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc index
> > >
> > 6e60d84143626a8e1d801bb580f4dcebc73c7ba7..f1caa5f207d3b13da58c3
> > a313b11
> > > d1ef98374349 100644
> > > --- a/gcc/tree-vect-loop.cc
> > > +++ b/gcc/tree-vect-loop.cc
> > > @@ -851,79 +851,106 @@ vect_fixup_scalar_cycles_with_patterns
> > (loop_vec_info loop_vinfo)
> > > in NUMBER_OF_ITERATIONSM1. Place the condition under which the
> > > niter information holds in ASSUMPTIONS.
> > >
> > > - Return the loop exit condition. */
> > > + Return the loop exit conditions. */
> > >
> > >
> > > -static gcond *
> > > -vect_get_loop_niters (class loop *loop, edge exit, tree *assumptions,
> > > +static vec<gcond *>
> > > +vect_get_loop_niters (class loop *loop, tree *assumptions, const_edge
> > > +main_exit,
> > > tree *number_of_iterations, tree
> > *number_of_iterationsm1)
> >
> > Any reason you swap exit and main_exit? IMHO the input better pairs with
> > the other input 'loop'.
> >
>
> No, I think I was just rearranging thing to fit more on a line. I'll put
> them next
> to their exits.
>
> >
> > > {
> > > + auto_vec<edge> exits = get_loop_exit_edges (loop); vec<gcond *>
> > > + conds; conds.create (exits.length ());
> > > class tree_niter_desc niter_desc;
> > > tree niter_assumptions, niter, may_be_zero;
> > > - gcond *cond = get_loop_exit_condition (loop);
> > >
> > > *assumptions = boolean_true_node;
> > > *number_of_iterationsm1 = chrec_dont_know;
> > > *number_of_iterations = chrec_dont_know;
> > > +
> > > DUMP_VECT_SCOPE ("get_loop_niters");
> > >
> > > - if (!exit)
> > > - return cond;
> > > + if (exits.is_empty ())
> > > + return conds;
> > > +
> > > + if (dump_enabled_p ())
> > > + dump_printf_loc (MSG_NOTE, vect_location, "Loop has %d exits.\n",
> > > + exits.length ());
> > > +
> > > + edge exit;
> > > + unsigned int i;
> > > + FOR_EACH_VEC_ELT (exits, i, exit)
> > > + {
> > > + gcond *cond = get_loop_exit_condition (exit);
> > > + if (cond)
> > > + conds.safe_push (cond);
> > > +
> > > + if (dump_enabled_p ())
> > > + dump_printf_loc (MSG_NOTE, vect_location, "Analyzing exit %d...\n",
> > > +i);
> > >
> > > - may_be_zero = NULL_TREE;
> > > - if (!number_of_iterations_exit_assumptions (loop, exit, &niter_desc,
> > NULL)
> > > - || chrec_contains_undetermined (niter_desc.niter))
> > > - return cond;
> > > + may_be_zero = NULL_TREE;
> > > + if (!number_of_iterations_exit_assumptions (loop, exit,
> > > &niter_desc,
> > NULL)
> > > + || chrec_contains_undetermined (niter_desc.niter))
> > > + continue;
> > >
> > > - niter_assumptions = niter_desc.assumptions;
> > > - may_be_zero = niter_desc.may_be_zero;
> > > - niter = niter_desc.niter;
> > > + niter_assumptions = niter_desc.assumptions;
> > > + may_be_zero = niter_desc.may_be_zero;
> > > + niter = niter_desc.niter;
> > >
> > > - if (may_be_zero && integer_zerop (may_be_zero))
> > > - may_be_zero = NULL_TREE;
> > > + if (may_be_zero && integer_zerop (may_be_zero))
> > > + may_be_zero = NULL_TREE;
> > >
> > > - if (may_be_zero)
> > > - {
> > > - if (COMPARISON_CLASS_P (may_be_zero))
> > > + if (may_be_zero)
> > > {
> > > - /* Try to combine may_be_zero with assumptions, this can simplify
> > > - computation of niter expression. */
> > > - if (niter_assumptions && !integer_nonzerop (niter_assumptions))
> > > - niter_assumptions = fold_build2 (TRUTH_AND_EXPR,
> > boolean_type_node,
> > > - niter_assumptions,
> > > - fold_build1 (TRUTH_NOT_EXPR,
> > > - boolean_type_node,
> > > - may_be_zero));
> > > + if (COMPARISON_CLASS_P (may_be_zero))
> > > + {
> > > + /* Try to combine may_be_zero with assumptions, this can simplify
> > > + computation of niter expression. */
> > > + if (niter_assumptions && !integer_nonzerop (niter_assumptions))
> > > + niter_assumptions = fold_build2 (TRUTH_AND_EXPR,
> > boolean_type_node,
> > > + niter_assumptions,
> > > + fold_build1
> > (TRUTH_NOT_EXPR,
> > > +
> > boolean_type_node,
> > > + may_be_zero));
> > > + else
> > > + niter = fold_build3 (COND_EXPR, TREE_TYPE (niter),
> > may_be_zero,
> > > + build_int_cst (TREE_TYPE (niter), 0),
> > > + rewrite_to_non_trapping_overflow (niter));
> > > +
> > > + may_be_zero = NULL_TREE;
> > > + }
> > > + else if (integer_nonzerop (may_be_zero) && exit == main_exit)
> > > + {
> > > + *number_of_iterationsm1 = build_int_cst (TREE_TYPE (niter), 0);
> > > + *number_of_iterations = build_int_cst (TREE_TYPE (niter), 1);
> > > + continue;
> > > + }
> > > else
> > > - niter = fold_build3 (COND_EXPR, TREE_TYPE (niter), may_be_zero,
> > > - build_int_cst (TREE_TYPE (niter), 0),
> > > - rewrite_to_non_trapping_overflow (niter));
> > > + continue;
> > > + }
> > >
> > > - may_be_zero = NULL_TREE;
> > > - }
> > > - else if (integer_nonzerop (may_be_zero))
> > > + /* Loop assumptions are based off the normal exit. */
> > > + if (exit == main_exit)
> >
> > It's a bit hard to follow in patch form but I wonder why you even analyze
> > the
> > number of iterations of the non-main exits riskying possibly clobbering the
> > *number_* outputs which we later assume to be for the main exit?
> >
>
> My original goal here was that if we can't analyze the other exits, we
> probably
> can't vectorize them. So I don't really need the results but I thought it
> useful to
> check. I can skip them.
Please. I don't think they need to be countable.
Richard.
> Thanks,
> Tamar
>
> > > {
> > > - *number_of_iterationsm1 = build_int_cst (TREE_TYPE (niter), 0);
> > > - *number_of_iterations = build_int_cst (TREE_TYPE (niter), 1);
> > > - return cond;
> > > + *assumptions = niter_assumptions;
> > > + *number_of_iterationsm1 = niter;
> > > +
> > > + /* We want the number of loop header executions which is the
> > number
> > > + of latch executions plus one.
> > > + ??? For UINT_MAX latch executions this number overflows to zero
> > > + for loops like do { n++; } while (n != 0); */
> > > + if (niter && !chrec_contains_undetermined (niter))
> > > + niter = fold_build2 (PLUS_EXPR, TREE_TYPE (niter),
> > > + unshare_expr (niter),
> > > + build_int_cst (TREE_TYPE (niter), 1));
> > > + *number_of_iterations = niter;
> > > }
> > > - else
> > > - return cond;
> > > }
> > >
> > > - *assumptions = niter_assumptions;
> > > - *number_of_iterationsm1 = niter;
> > > -
> > > - /* We want the number of loop header executions which is the number
> > > - of latch executions plus one.
> > > - ??? For UINT_MAX latch executions this number overflows to zero
> > > - for loops like do { n++; } while (n != 0); */
> > > - if (niter && !chrec_contains_undetermined (niter))
> > > - niter = fold_build2 (PLUS_EXPR, TREE_TYPE (niter), unshare_expr
> > > (niter),
> > > - build_int_cst (TREE_TYPE (niter), 1));
> > > - *number_of_iterations = niter;
> > > + if (dump_enabled_p ())
> > > + dump_printf_loc (MSG_NOTE, vect_location, "All loop exits
> > > + successfully analyzed.\n");
> > >
> > > - return cond;
> > > + return conds;
> > > }
> > >
> > > /* Determine the main loop exit for the vectorizer. */ @@ -936,8
> > > +963,25 @@ vec_init_loop_exit_info (class loop *loop)
> > > auto_vec<edge> exits = get_loop_exit_edges (loop);
> > > if (exits.length () == 1)
> > > return exits[0];
> > > - else
> > > - return NULL;
> > > +
> > > + /* If we have multiple exits we only support counting IV at the moment.
> > Analyze
> > > + all exits and return one */
> > > + class tree_niter_desc niter_desc;
> > > + edge candidate = NULL;
> > > + for (edge exit : exits)
> > > + {
> > > + if (!get_loop_exit_condition (exit))
> > > + continue;
> > > +
> > > + if (number_of_iterations_exit_assumptions (loop, exit, &niter_desc,
> > NULL)
> > > + && !chrec_contains_undetermined (niter_desc.niter))
> > > + {
> > > + if (!niter_desc.may_be_zero || !candidate)
> > > + candidate = exit;
> > > + }
> > > + }
> > > +
> > > + return candidate;
> > > }
> > >
> > > /* Function bb_in_loop_p
> > > @@ -1788,21 +1832,31 @@ vect_analyze_loop_form (class loop *loop,
> > vect_loop_form_info *info)
> > > "not vectorized: latch block not empty.\n");
> > >
> > > /* Make sure the exit is not abnormal. */
> > > - edge e = single_exit (loop);
> > > - if (e->flags & EDGE_ABNORMAL)
> > > + if (exit_e->flags & EDGE_ABNORMAL)
> > > return opt_result::failure_at (vect_location,
> > > "not vectorized:"
> > > " abnormal loop exit edge.\n");
> > >
> > > - info->loop_cond
> > > - = vect_get_loop_niters (loop, e, &info->assumptions,
> > > + info->conds
> > > + = vect_get_loop_niters (loop, &info->assumptions, exit_e,
> > > &info->number_of_iterations,
> > > &info->number_of_iterationsm1);
> > > - if (!info->loop_cond)
> > > +
> > > + if (info->conds.is_empty ())
> > > return opt_result::failure_at
> > > (vect_location,
> > > "not vectorized: complicated exit condition.\n");
> > >
> > > + /* Determine what the primary and alternate exit conds are. */
> > > + info->alt_loop_conds.create (info->conds.length () - 1);
> > > + for (gcond *cond : info->conds)
> > > + {
> > > + if (exit_e->src != gimple_bb (cond))
> > > + info->alt_loop_conds.quick_push (cond);
> > > + else
> > > + info->loop_cond = cond;
> > > + }
> > > +
> >
> > IMHO it would be simpler to have the primary exit condition in
> > info->conds[0] and the rest after that? That avoids having two
> > arrays and one scalar in vect_loop_form_info.
> >
> > > if (integer_zerop (info->assumptions)
> > > || !info->number_of_iterations
> > > || chrec_contains_undetermined (info->number_of_iterations)) @@
> > > -1847,8 +1901,13 @@ vect_create_loop_vinfo (class loop *loop,
> > vec_info_shared *shared,
> > > if (!integer_onep (info->assumptions) && !main_loop_info)
> > > LOOP_VINFO_NITERS_ASSUMPTIONS (loop_vinfo) = info->assumptions;
> > >
> > > - stmt_vec_info loop_cond_info = loop_vinfo->lookup_stmt
> > > (info->loop_cond);
> > > - STMT_VINFO_TYPE (loop_cond_info) = loop_exit_ctrl_vec_info_type;
> > > + for (gcond *cond : info->conds)
> > > + {
> > > + stmt_vec_info loop_cond_info = loop_vinfo->lookup_stmt (cond);
> > > + STMT_VINFO_TYPE (loop_cond_info) = loop_exit_ctrl_vec_info_type;
> > > + }
> > > + LOOP_VINFO_LOOP_CONDS (loop_vinfo).safe_splice
> > > + (info->alt_loop_conds); LOOP_VINFO_LOOP_IV_COND (loop_vinfo) =
> > > + info->loop_cond;
> > > LOOP_VINFO_IV_EXIT (loop_vinfo) = info->loop_exit;
> > >
> > > @@ -3594,7 +3653,11 @@ vect_analyze_loop (class loop *loop,
> > vec_info_shared *shared)
> > > && LOOP_VINFO_PEELING_FOR_NITER
> > (first_loop_vinfo)
> > > && !loop->simduid);
> > > if (!vect_epilogues)
> > > - return first_loop_vinfo;
> > > + {
> > > + loop_form_info.conds.release ();
> > > + loop_form_info.alt_loop_conds.release ();
> > > + return first_loop_vinfo;
> > > + }
> >
> > I think there's 'inner' where you leak these. Maybe use auto_vec<> in
> > vect_loop_form_info instead?
> >
> > Otherwise looks OK.
> >
> > Thanks,
> > Richard.
> >
> > > /* Now analyze first_loop_vinfo for epilogue vectorization. */
> > > poly_uint64 lowest_th = LOOP_VINFO_VERSIONING_THRESHOLD
> > > (first_loop_vinfo); @@ -3694,6 +3757,9 @@ vect_analyze_loop (class loop
> > *loop, vec_info_shared *shared)
> > > (first_loop_vinfo->epilogue_vinfos[0]-
> > >vector_mode));
> > > }
> > >
> > > + loop_form_info.conds.release ();
> > > + loop_form_info.alt_loop_conds.release ();
> > > +
> > > return first_loop_vinfo;
> > > }
> > >
> > > diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h index
> > >
> > afa7a8e30891c782a0e5e3740ecc4377f5a31e54..55b6771b271d5072fa132
> > 7d595e1
> > > dddb112cfdf6 100644
> > > --- a/gcc/tree-vectorizer.h
> > > +++ b/gcc/tree-vectorizer.h
> > > @@ -882,6 +882,12 @@ public:
> > > we need to peel off iterations at the end to form an epilogue loop.
> > > */
> > > bool peeling_for_niter;
> > >
> > > + /* List of loop additional IV conditionals found in the loop. */
> > > + auto_vec<gcond *> conds;
> > > +
> > > + /* Main loop IV cond. */
> > > + gcond* loop_iv_cond;
> > > +
> > > /* True if there are no loop carried data dependencies in the loop.
> > > If loop->safelen <= 1, then this is always true, either the loop
> > > didn't have any loop carried data dependencies, or the loop is
> > > being @@ -984,6 +990,8 @@ public:
> > > #define LOOP_VINFO_REDUCTION_CHAINS(L) (L)->reduction_chains
> > > #define LOOP_VINFO_PEELING_FOR_GAPS(L) (L)->peeling_for_gaps
> > > #define LOOP_VINFO_PEELING_FOR_NITER(L) (L)->peeling_for_niter
> > > +#define LOOP_VINFO_LOOP_CONDS(L) (L)->conds
> > > +#define LOOP_VINFO_LOOP_IV_COND(L) (L)->loop_iv_cond
> > > #define LOOP_VINFO_NO_DATA_DEPENDENCIES(L) (L)-
> > >no_data_dependencies
> > > #define LOOP_VINFO_SCALAR_LOOP(L) (L)->scalar_loop
> > > #define LOOP_VINFO_SCALAR_LOOP_SCALING(L) (L)->scalar_loop_scaling
> > > @@ -2373,7 +2381,9 @@ struct vect_loop_form_info
> > > tree number_of_iterations;
> > > tree number_of_iterationsm1;
> > > tree assumptions;
> > > + vec<gcond *> conds;
> > > gcond *loop_cond;
> > > + vec<gcond *> alt_loop_conds;
> > > gcond *inner_loop_cond;
> > > edge loop_exit;
> > > };
> > >
> > >
> > >
> > >
> > >
> >
> > --
> > Richard Biener <rguent...@suse.de>
> > SUSE Software Solutions Germany GmbH,
> > Frankenstrasse 146, 90461 Nuernberg, Germany;
> > GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG
> > Nuernberg)
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
