On Mon, 6 Jul 2026, Liu, Hongtao wrote:
>
>
> > -----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
'node' is already (almost - there's one exception) always present
unless we're doing scalar costing. But no, the goal has been
to remove the "reverse matching" we now do to compose back the
pieces (from, say, emulated gather/scatter) to the overall operation
that is costed.
The current costing inter-mangles the bits, of course so it will
be a bit of mix-and-match to get the pieces isolated and possibly
split out for sharing. I don't know yet whether the result is
simpler than before (and I have to fix that one case where we fail
to pass in 'node').
That said, sorry if I have misled you.
Richard.
> >
> > 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)
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald; (HRB 36809, AG Nuernberg)
