> -----Original Message-----
> From: Richard Biener <[email protected]>
> Sent: 24 August 2026 12:10
> To: [email protected]
> Cc: Tamar Christina <[email protected]>
> Subject: [PATCH][v2] tree-optimization/126984 - ICE with complex SLP
> patterns
>
> As VEC_PERM nodes no longer have a representative if those are at
> the SLP pattern root we have to get at one by other means to be
> able to create the scalar pattern to use.
>
> I've noticed that complex_pattern::build isn't really a full build
> but is used as common helper and receives a garbled node only. So
> I made that not an overload of build but a true helper, leaving
> complex_pattern as pure abstract class. The complex_pattern CTOR
> then guesses the representative and stores it in a new member.
>
> Bootstrap and regtest pending on aarch64-linux-gnu.
>
> I have left the ??? comment as it's still "guessing", but at
> least in a common place.
>
> Richard.
>
> PR tree-optimization/126984
> * tree-vect-slp-patterns.cc (complex_pattern::build):
> Rename to ...
> (complex_pattern::build_common): ... this.
> (complex_pattern::build): Likewise and adjust.
> (complex_pattern::m_rep): New.
> (complex_pattern::complex_pattern): Initialize m_rep.
> (complex_add_pattern::build): Call build_common instead
> of complex_pattern::build.
> (complex_mul_pattern::build): Likewise.
> (complex_fms_pattern::build): Likewise.
>
> * gcc.dg/vect/vect-pr126984.c: New testcase.
LGTM.
Thanks,
Tamar
> ---
> gcc/testsuite/gcc.dg/vect/vect-pr126984.c | 16 +++++++++++++
> gcc/tree-vect-slp-patterns.cc | 29 +++++++++++++----------
> 2 files changed, 33 insertions(+), 12 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-pr126984.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-pr126984.c
> b/gcc/testsuite/gcc.dg/vect/vect-pr126984.c
> new file mode 100644
> index 00000000000..ed7dc059cfa
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-pr126984.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-ffast-math" } */
> +/* { dg-additional-options "-march=armv9-a" { target { aarch64-*-* } } } */
> +
> +double *a;
> +double b, c, d, e, f;
> +int g, h;
> +void l() {
> + double i, j, k;
> + for (; g; g++, h += 2) {
> + k = a[h];
> + j = a[h + 1];
> + a[h] = b * f - c * e + d * k - i * j;
> + a[h + 1] = b * e + c * f + d * j + i * k;
> + }
> +}
> diff --git a/gcc/tree-vect-slp-patterns.cc b/gcc/tree-vect-slp-patterns.cc
> index bf9efacf161..c53325fecdc 100644
> --- a/gcc/tree-vect-slp-patterns.cc
> +++ b/gcc/tree-vect-slp-patterns.cc
> @@ -483,15 +483,23 @@ class complex_pattern : public vect_pattern
> {
> protected:
> auto_vec<slp_tree> m_workset;
> + stmt_vec_info m_rep;
> +
> complex_pattern (slp_tree *node, vec<slp_tree> *m_ops, internal_fn ifn)
> : vect_pattern (node, m_ops, ifn)
> {
> + /* ??? We should not have to guess here, analysis should have
> + it and pass it as CTOR argument. */
> + if (SLP_TREE_PERMUTE_P (*node))
> + m_rep = SLP_TREE_REPRESENTATIVE (SLP_TREE_CHILDREN
> (*node)[0]);
> + else
> + m_rep = SLP_TREE_REPRESENTATIVE (*node);
> this->m_workset.safe_push (*node);
> }
>
> - public:
> - void build (vec_info *) override;
> + void build_common (vec_info *);
>
> + public:
> static internal_fn
> matches (complex_operation_t op, slp_tree_to_load_perm_map_t *,
> slp_tree *,
> vec<slp_tree> *);
> @@ -518,10 +526,8 @@ class complex_pattern : public vect_pattern
> */
>
> void
> -complex_pattern::build (vec_info *vinfo)
> +complex_pattern::build_common (vec_info *vinfo)
> {
> - stmt_vec_info stmt_info;
> -
> auto_vec<tree> args;
> args.create (this->m_num_args);
> args.quick_grow_cleared (this->m_num_args);
> @@ -534,8 +540,7 @@ complex_pattern::build (vec_info *vinfo)
> FOR_EACH_VEC_ELT (this->m_workset, ix, node)
> {
> /* Calculate the location of the statement in NODE to replace. */
> - stmt_info = SLP_TREE_SCALAR_STMTS (node)[0];
> - gimple* old_stmt = STMT_VINFO_STMT (stmt_info);
> + gimple* old_stmt = STMT_VINFO_STMT (m_rep);
> tree lhs_old_stmt = gimple_get_lhs (old_stmt);
> tree type = TREE_TYPE (lhs_old_stmt);
>
> @@ -556,14 +561,14 @@ complex_pattern::build (vec_info *vinfo)
> the nodes as such we need to manually update them. Any changes
> will be
> undone if SLP is cancelled. */
> call_stmt_info
> - = vinfo->add_pattern_stmt (call_stmt, vect_orig_stmt (stmt_info));
> + = vinfo->add_pattern_stmt (call_stmt, vect_orig_stmt (m_rep));
>
> /* Make sure to mark the representative statement pure_slp and
> relevant and transfer reduction info. */
> STMT_VINFO_RELEVANT (call_stmt_info) = vect_used_in_scope;
> STMT_SLP_TYPE (call_stmt_info) = pure_slp;
>
> - gimple_set_bb (call_stmt, gimple_bb (stmt_info->stmt));
> + gimple_set_bb (call_stmt, gimple_bb (m_rep->stmt));
> STMT_VINFO_VECTYPE (call_stmt_info) = SLP_TREE_VECTYPE (node);
>
> /* Since we are replacing all the statements in the group with the same
> @@ -626,7 +631,7 @@ complex_add_pattern::build (vec_info *vinfo)
> vect_free_slp_tree (this->m_ops[0]);
> vect_free_slp_tree (this->m_ops[1]);
>
> - complex_pattern::build (vinfo);
> + build_common (vinfo);
> }
>
> /* Pattern matcher for trying to match complex addition pattern in SLP tree.
> @@ -1243,7 +1248,7 @@ complex_mul_pattern::build (vec_info *vinfo)
> }
>
> /* And then rewrite the node itself. */
> - complex_pattern::build (vinfo);
> + build_common (vinfo);
> }
>
>
> /******************************************************************
> *************
> @@ -1500,7 +1505,7 @@ complex_fms_pattern::build (vec_info *vinfo)
> SLP_TREE_CHILDREN (*this->m_node).quick_push (this->m_ops[0]);
>
> /* And then rewrite the node itself. */
> - complex_pattern::build (vinfo);
> + build_common (vinfo);
> }
>
>
> /******************************************************************
> *************
> --
> 2.51.0
