The following makes sure that for a SLP reductions all lanes have the same STMT_VINFO_REDUC_IDX. Once we move that info and can adjust it we can implement swapping. It also makes the existing protection against operand swapping trigger for all stmts participating in a reduction, not just the final one marked as reduction-def.
Bootstrapped and tested on x86_64-unknown-linux-gnu. The first version had a thinko and the two remaining FAILs were because of SLP reduction chains where a same reduc_idx isn't really relevant. I'll see what the CI says to this. Richard. * tree-vect-slp.cc (vect_build_slp_tree_1): Compare STMT_VINFO_REDUC_IDX. (vect_build_slp_tree_2): Prevent operand swapping for all stmts participating in a reduction. --- gcc/tree-vect-slp.cc | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc index cb8604eb611..a02795e9d8f 100644 --- a/gcc/tree-vect-slp.cc +++ b/gcc/tree-vect-slp.cc @@ -1072,6 +1072,7 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap, stmt_vec_info first_load = NULL, prev_first_load = NULL; bool first_stmt_ldst_p = false, ldst_p = false; bool first_stmt_phi_p = false, phi_p = false; + int first_reduc_idx = -1; bool maybe_soft_fail = false; tree soft_fail_nunits_vectype = NULL_TREE; @@ -1204,6 +1205,7 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap, first_stmt_code = rhs_code; first_stmt_ldst_p = ldst_p; first_stmt_phi_p = phi_p; + first_reduc_idx = STMT_VINFO_REDUC_IDX (stmt_info); /* Shift arguments should be equal in all the packed stmts for a vector shift with scalar shift operand. */ @@ -1267,6 +1269,24 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap, } else { + if (first_reduc_idx != STMT_VINFO_REDUC_IDX (stmt_info) + /* For SLP reduction groups the index isn't necessarily + uniform but only that of the first stmt matters. */ + && !(first_reduc_idx != -1 + && STMT_VINFO_REDUC_IDX (stmt_info) != -1 + && REDUC_GROUP_FIRST_ELEMENT (stmt_info))) + { + if (dump_enabled_p ()) + { + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, + "Build SLP failed: different reduc_idx " + "%d instead of %d in %G", + STMT_VINFO_REDUC_IDX (stmt_info), + first_reduc_idx, stmt); + } + /* Mismatch. */ + continue; + } if (first_stmt_code != rhs_code && alt_stmt_code == ERROR_MARK) alt_stmt_code = rhs_code; @@ -2535,8 +2555,7 @@ out: && oprnds_info[1]->first_dt == vect_internal_def && is_gimple_assign (stmt_info->stmt) /* Swapping operands for reductions breaks assumptions later on. */ - && STMT_VINFO_DEF_TYPE (stmt_info) != vect_reduction_def - && STMT_VINFO_DEF_TYPE (stmt_info) != vect_double_reduction_def) + && STMT_VINFO_REDUC_IDX (stmt_info) == -1) { /* See whether we can swap the matching or the non-matching stmt operands. */ -- 2.43.0