> -----Original Message-----
> From: Richard Biener <[email protected]>
> Sent: Monday, July 6, 2026 4:03 PM
> To: Liu, Hongtao <[email protected]>
> Cc: [email protected]
> Subject: Re: [PATCH] i386: Move SLP-node costing into
> ix86_vector_costs::add_slp_cost
>
> On Wed, 1 Jul 2026, liuhongt wrote:
>
> > Override the add_slp_cost hook so the x86 cost model gets the recorded
> > stmt costs grouped per SLP node. The node-dependent costing that used
> > to live in add_stmt_cost -- the
> > vec_construct/vec_deconstruct/scalar_to_vec
> > construction cost and the cross-lane vec_perm accounting -- is moved
> > to add_slp_cost, which handles those kinds and delegates the rest to
> > add_stmt_cost. The shared tail (default-cost fallback,
> > Bonnell/Silvermont fixups and frequency scaling) is factored into
> > finish_stmt_cost, called by both paths.
> >
> > This is a refactor with no intended functional change.
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > Ok for trunk?
>
> Sorry for not commenting earlier
>
> > gcc/ChangeLog:
> >
> > * config/i386/i386.cc (ix86_vector_costs): Declare add_slp_cost,
> > ix86_slp_construct_cost, ix86_slp_account_perm and
> finish_stmt_cost.
> > (ix86_vector_costs::add_stmt_cost): Move the vec_construct and
> > vec_perm node costing out; finish via finish_stmt_cost.
> > (ix86_vector_costs::ix86_slp_construct_cost): New.
> > (ix86_vector_costs::ix86_slp_account_perm): New.
> > (ix86_vector_costs::finish_stmt_cost): New.
> > (ix86_vector_costs::add_slp_cost): New.
> > ---
> > gcc/config/i386/i386.cc | 166
> > ++++++++++++++++++++++++++++++++--------
> > 1 file changed, 135 insertions(+), 31 deletions(-)
> >
> > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index
> > e66958db7ac..94c2b3c0090 100644
> > --- a/gcc/config/i386/i386.cc
> > +++ b/gcc/config/i386/i386.cc
> > @@ -26165,6 +26165,9 @@ public:
> > stmt_vec_info stmt_info, slp_tree node,
> > tree vectype, int misalign,
> > vect_cost_model_location where) override;
> > + unsigned int add_slp_cost (slp_tree node,
> > + const array_slice<stmt_info_for_cost> &)
> > + override;
> > void finish_cost (const vector_costs *) override;
> > bool better_main_loop_than_p (const vector_costs *) const override;
> > bool better_epilogue_loop_than_p (const vector_costs *other, @@
> > -26174,6 +26177,20 @@ private:
> >
> > /* Estimate register pressure of the vectorized code. */
> > void ix86_vect_estimate_reg_pressure ();
> > + /* Cost of a vec_construct/vec_deconstruct/scalar_to_vec of SLP NODE,
> > + or -1 to fall back to the default vector cost. */
> > + int ix86_slp_construct_cost (slp_tree node, vect_cost_for_stmt kind,
> > + tree vectype, machine_mode mode, bool fp,
> > + vect_cost_model_location where);
> > + /* Account a vec_perm of SLP NODE to the cross-lane permute
> > +counters. */
> > + void ix86_slp_account_perm (slp_tree node, int count, tree vectype,
> > + stmt_vec_info stmt_info,
> > + vect_cost_model_location where);
> > + /* Common cost finalization shared by add_stmt_cost and
> > +add_slp_cost. */
> > + unsigned int finish_stmt_cost (int stmt_cost, int count,
> > + vect_cost_for_stmt kind,
> > + stmt_vec_info stmt_info, machine_mode
> mode,
> > + tree vectype, vect_cost_model_location
> where);
> > /* Number of GENERAL_REGS/SSE_REGS used in the vectorizer, it's used for
> > estimation of register pressure.
> > ??? Currently it's only used by vec_construct/scalar_to_vec @@
> > -26255,7 +26272,6 @@ ix86_vector_costs::add_stmt_cost (int count,
> vect_cost_for_stmt kind,
> > tree vectype, int,
> > vect_cost_model_location where) {
> > - unsigned retval = 0;
> > bool scalar_p
> > = (kind == scalar_stmt || kind == scalar_load || kind == scalar_store);
> > int stmt_cost = - 1;
> > @@ -26732,18 +26748,35 @@ ix86_vector_costs::add_stmt_cost (int
> count, vect_cost_for_stmt kind,
> > + ix86_vec_cost (mode, ix86_cost->sse_op);
> > }
> >
> > + /* vec_construct/vec_deconstruct/scalar_to_vec and vec_perm are costed
> > + per SLP node in add_slp_cost, which does the node-specific work before
> > + finishing here. */
> > + return finish_stmt_cost (stmt_cost, count, kind, stmt_info, mode,
> vectype,
> > + where);
> > +}
> > +
> > +/* See the comment above the declaration for details. */
> > +
> > +int
> > +ix86_vector_costs::ix86_slp_construct_cost (slp_tree node,
> > + vect_cost_for_stmt kind,
> > + tree vectype, machine_mode mode,
> > + bool fp,
> > + vect_cost_model_location where) {
> > + int stmt_cost = -1;
> > +
> > /* If we do elementwise loads into a vector then we are bound by
> > latency and execution resources for the many scalar loads
> > (AGU and load ports). Try to account for this by scaling the
> > construction cost by the number of elements involved. */
> > if ((kind == vec_construct || kind == vec_deconstruct)
> > - && ((node
> > - && (((SLP_TREE_MEMORY_ACCESS_TYPE (node) ==
> VMAT_ELEMENTWISE
> > - || SLP_TREE_MEMORY_ACCESS_TYPE (node) ==
> VMAT_STRIDED_SLP)
> > - && (TREE_CODE (DR_STEP (STMT_VINFO_DATA_REF
> > - (SLP_TREE_REPRESENTATIVE
> (node))))
> > - != INTEGER_CST))
> > - || mat_gather_scatter_p (SLP_TREE_MEMORY_ACCESS_TYPE
> (node))))))
> > + && (((SLP_TREE_MEMORY_ACCESS_TYPE (node) ==
> VMAT_ELEMENTWISE
> > + || SLP_TREE_MEMORY_ACCESS_TYPE (node) ==
> VMAT_STRIDED_SLP)
> > + && (TREE_CODE (DR_STEP (STMT_VINFO_DATA_REF
> > + (SLP_TREE_REPRESENTATIVE (node))))
> > + != INTEGER_CST))
> > + || mat_gather_scatter_p (SLP_TREE_MEMORY_ACCESS_TYPE
> (node))))
> > {
> > auto lsdata = static_cast<vect_load_store_data *> (node->data);
> > tree ls_type = lsdata->ls_type ? lsdata->ls_type : vectype; @@
> > -26755,7 +26788,6 @@ ix86_vector_costs::add_stmt_cost (int count,
> vect_cost_for_stmt kind,
> > / GET_MODE_BITSIZE (TYPE_MODE (ls_eltype)) + 1);
> > }
> > else if ((kind == vec_construct || kind == scalar_to_vec)
> > - && node
> > && SLP_TREE_DEF_TYPE (node) == vect_external_def)
> > {
> > stmt_cost = ix86_default_vector_cost (kind, mode); @@ -26823,34
> > +26855,58 @@ ix86_vector_costs::add_stmt_cost (int count,
> vect_cost_for_stmt kind,
> > if (TREE_CODE (op) == SSA_NAME)
> > TREE_VISITED (op) = 0;
> > }
> > - if (stmt_cost == -1)
> > - stmt_cost = ix86_default_vector_cost (kind, mode);
> >
> > + return stmt_cost;
> > +}
> > +
> > +/* See the comment above the declaration for details. */
> > +
> > +void
> > +ix86_vector_costs::ix86_slp_account_perm (slp_tree node, int count,
> > + tree vectype,
> > + stmt_vec_info stmt_info,
> > + vect_cost_model_location where) {
> > /* BIT_FIELD_REF <vect_**, 64, 0> with count 0 costs 0 in body. */
> > - if (kind == vec_perm && vectype && count != 0)
> > - {
> > - unsigned vec_size = GET_MODE_SIZE (TYPE_MODE (vectype));
> > - unsigned nunits = TYPE_VECTOR_SUBPARTS (vectype);
> > - unsigned *num_vec_perm = NULL;
> > + if (!vectype || count == 0)
> > + return;
> >
> > - if (vec_size == 32)
> > - num_vec_perm = m_num_avx256_vec_perm;
> > - else if (vec_size == 64)
> > - num_vec_perm = m_num_avx512_vec_perm;
> > + unsigned vec_size = GET_MODE_SIZE (TYPE_MODE (vectype)); unsigned
> > + nunits = TYPE_VECTOR_SUBPARTS (vectype); unsigned *num_vec_perm =
> > + NULL;
> >
> > - if (num_vec_perm && ix86_count_cross_lane_perm_p (m_vinfo, node,
> nunits))
> > + if (vec_size == 32)
> > + num_vec_perm = m_num_avx256_vec_perm; else if (vec_size == 64)
> > + num_vec_perm = m_num_avx512_vec_perm;
> > +
> > + if (num_vec_perm && ix86_count_cross_lane_perm_p (m_vinfo, node,
> nunits))
> > + {
> > + num_vec_perm[where] += count;
> > + if (dump_file && (dump_flags & TDF_DETAILS))
> > {
> > - num_vec_perm[where] += count;
> > - if (dump_file && (dump_flags & TDF_DETAILS))
> > - {
> > - fprintf (dump_file,
> > - "Detected avx%u cross-lane permutation: ", vec_size * 8);
> > - if (stmt_info)
> > - print_gimple_expr (dump_file, stmt_info->stmt, 0, TDF_SLIM);
> > - fprintf (dump_file, " \n");
> > - }
> > + fprintf (dump_file,
> > + "Detected avx%u cross-lane permutation: ", vec_size * 8);
> > + if (stmt_info)
> > + print_gimple_expr (dump_file, stmt_info->stmt, 0, TDF_SLIM);
> > + fprintf (dump_file, " \n");
> > }
> > }
> > +}
> > +
> > +/* Apply the default-cost fallback, uarch fixups and frequency scaling to
> > + STMT_COST (-1 if not yet computed), accumulate into m_costs[WHERE]
> and
> > + return the result. */
> > +
> > +unsigned int
> > +ix86_vector_costs::finish_stmt_cost (int stmt_cost, int count,
> > + vect_cost_for_stmt kind,
> > + stmt_vec_info stmt_info,
> > + machine_mode mode, tree vectype,
> > + vect_cost_model_location where) {
> > + if (stmt_cost == -1)
> > + stmt_cost = ix86_default_vector_cost (kind, mode);
> >
> > /* Penalize DFmode vector operations for Bonnell. */
> > if (TARGET_CPU_P (BONNELL) && kind == vector_stmt @@ -26860,7
> > +26916,8 @@ ix86_vector_costs::add_stmt_cost (int count,
> vect_cost_for_stmt kind,
> > /* Statements in an inner loop relative to the loop being
> > vectorized are weighted more heavily. The value here is
> > arbitrary and could potentially be improved with analysis. */
> > - retval = adjust_cost_for_freq (stmt_info, where, count *
> > stmt_cost);
> > + unsigned int retval
> > + = adjust_cost_for_freq (stmt_info, where, count * stmt_cost);
> >
> > /* We need to multiply all vector stmt cost by 1.7 (estimated cost)
> > for Silvermont as it has out of order integer pipeline and can
> > execute @@ -26879,6 +26936,53 @@ ix86_vector_costs::add_stmt_cost
> (int count, vect_cost_for_stmt kind,
> > return retval;
> > }
> >
> > +/* Cost the entries of COST_VEC, which all belong to a single SLP node.
> > + vec_construct/vec_deconstruct/scalar_to_vec and vec_perm get x86-
> specific
> > + node-level costing here; everything else is handed to
> > +add_stmt_cost. */
> > +
> > +unsigned int
> > +ix86_vector_costs::add_slp_cost (slp_tree,
> > + const array_slice<stmt_info_for_cost>
> &cost_vec) {
> > + unsigned int sum = 0;
> > + for (auto item : cost_vec)
>
> So my original intent of the ::add_slp_cost hook was to make it possible to
> key
> only on the 'node' - the passed cost_vec should have been possibly just an
> afterthought.
>
> So if you iterate over the cost_vec and ignore the common node here there's
> no immediate benefit to how we deal with this previously?
I thought you wanted to move all SLP-related processing into add_slp_cost, so
that there would be no need to check for the existence of the node in
add_stmt_cost, and additionally, the case of fold_left_reduction could be
handled in add_slp_cost
>
> As said I didn't yet get to experiment on how that works out, but I'd have
> expected sth like
>
> if (mat_gather_scatter_p (SLP_TREE_MEMORY_ACCESS_TYPE (node)))
> ix86_slp_account_gather_scatter (node, cost_vec);
> else if (SLP_TREE_MEMORY_ACCESS_TYPE (node) == VMAT_STRIDED_SLP)
> ...
> else
> return ::add_slp_cost (node, cost_vec);
>
> but maybe this doesn't work out to simplify things.
>
> > + {
> > + tree vectype = item.vectype;
> > + /* vec_perm is accounted even without a node (treated as cross-lane);
> > + the construct cases need a node. */
> > + if (item.kind == vec_perm
> > + || (item.node
> > + && (item.kind == vec_construct
> > + || item.kind == vec_deconstruct
> > + || item.kind == scalar_to_vec)))
> > + {
> > + machine_mode mode = vectype ? TYPE_MODE (vectype) : TImode;
> > + bool fp = vectype ? FLOAT_TYPE_P (vectype) : false;
> > + int stmt_cost = -1;
> > +
> > + if (item.kind == vec_perm)
> > + ix86_slp_account_perm (item.node, item.count, vectype,
> > + item.stmt_info, item.where);
> > + else
> > + stmt_cost = ix86_slp_construct_cost (item.node, item.kind, vectype,
> > + mode, fp, item.where);
> > +
> > + unsigned int cost
> > + = finish_stmt_cost (stmt_cost, item.count, item.kind,
> > + item.stmt_info, mode, vectype, item.where);
> > + if (dump_file && (dump_flags & TDF_DETAILS))
> > + dump_stmt_cost (dump_file, item.count, item.kind, item.stmt_info,
> > + item.node, vectype, item.misalign, cost,
> > + item.where);
> > + sum += cost;
> > + }
> > + else
> > + sum += ::add_stmt_cost (this, item.count, item.kind, item.stmt_info,
> > + item.node, vectype, item.misalign,
> item.where);
> > + }
> > + return sum;
> > +}
> > +
> > void
> > ix86_vector_costs::ix86_vect_estimate_reg_pressure () {
> >
>
> --
> Richard Biener <[email protected]>
> SUSE Software Solutions Germany GmbH,
> Frankenstrasse 146, 90461 Nuernberg, Germany;
> GF: Jochen Jaser, Andrew McDonald; (HRB 36809, AG Nuernberg)
