On Sat, Jul 13, 2024 at 5:47 PM Feng Xue OS <f...@os.amperecomputing.com> wrote:
>
> Vector stmts number of an operation is calculated based on output vectype.
> This is over-estimated for lane-reducing operation, which would cause vector
> def/use mismatched when we want to support loop reduction mixed with lane-
> reducing and normal operations. One solution is to refit lane-reducing
> to make it behave like a normal one, by adding new pass-through copies to
> fix possible def/use gap. And resultant superfluous statements could be
> optimized away after vectorization. For example:
>
> int sum = 1;
> for (i)
> {
> sum += d0[i] * d1[i]; // dot-prod <vector(16) char>
> }
>
> The vector size is 128-bit，vectorization factor is 16. Reduction
> statements would be transformed as:
>
> vector<4> int sum_v0 = { 0, 0, 0, 1 };
> vector<4> int sum_v1 = { 0, 0, 0, 0 };
> vector<4> int sum_v2 = { 0, 0, 0, 0 };
> vector<4> int sum_v3 = { 0, 0, 0, 0 };
>
> for (i / 16)
> {
> sum_v0 = DOT_PROD (d0_v0[i: 0 ~ 15], d1_v0[i: 0 ~ 15], sum_v0);
> sum_v1 = sum_v1; // copy
> sum_v2 = sum_v2; // copy
> sum_v3 = sum_v3; // copy
> }
>
> sum_v = sum_v0 + sum_v1 + sum_v2 + sum_v3; // = sum_v0
OK.
Thanks,
Richard.
> Thanks,
> Feng
> ---
> gcc/
> * tree-vect-loop.cc (vect_reduction_update_partial_vector_usage):
> Calculate effective vector stmts number with generic
> vect_get_num_copies.
> (vect_transform_reduction): Insert copies for lane-reducing so as to
> fix over-estimated vector stmts number.
> (vect_transform_cycle_phi): Calculate vector PHI number only based on
> output vectype.
> * tree-vect-slp.cc (vect_slp_analyze_node_operations_1): Remove
> adjustment on vector stmts number specific to slp reduction.
> ---
> gcc/tree-vect-loop.cc | 134 +++++++++++++++++++++++++++++++++++-------
> gcc/tree-vect-slp.cc | 27 +++------
> 2 files changed, 121 insertions(+), 40 deletions(-)
>
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index a64b5082bd1..5ac83e76975 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -7468,12 +7468,8 @@ vect_reduction_update_partial_vector_usage
> (loop_vec_info loop_vinfo,
> = get_masked_reduction_fn (reduc_fn, vectype_in);
> vec_loop_masks *masks = &LOOP_VINFO_MASKS (loop_vinfo);
> vec_loop_lens *lens = &LOOP_VINFO_LENS (loop_vinfo);
> - unsigned nvectors;
> -
> - if (slp_node)
> - nvectors = SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node);
> - else
> - nvectors = vect_get_num_copies (loop_vinfo, vectype_in);
> + unsigned nvectors = vect_get_num_copies (loop_vinfo, slp_node,
> + vectype_in);
>
> if (mask_reduc_fn == IFN_MASK_LEN_FOLD_LEFT_PLUS)
> vect_record_loop_len (loop_vinfo, lens, nvectors, vectype_in, 1);
> @@ -8595,12 +8591,15 @@ vect_transform_reduction (loop_vec_info loop_vinfo,
> stmt_vec_info phi_info = STMT_VINFO_REDUC_DEF (vect_orig_stmt (stmt_info));
> gphi *reduc_def_phi = as_a <gphi *> (phi_info->stmt);
> int reduc_index = STMT_VINFO_REDUC_IDX (stmt_info);
> - tree vectype_in = STMT_VINFO_REDUC_VECTYPE_IN (reduc_info);
> + tree vectype_in = STMT_VINFO_REDUC_VECTYPE_IN (stmt_info);
> +
> + if (!vectype_in)
> + vectype_in = STMT_VINFO_VECTYPE (stmt_info);
>
> if (slp_node)
> {
> ncopies = 1;
> - vec_num = SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node);
> + vec_num = vect_get_num_copies (loop_vinfo, slp_node, vectype_in);
> }
> else
> {
> @@ -8658,13 +8657,40 @@ vect_transform_reduction (loop_vec_info loop_vinfo,
> bool lane_reducing = lane_reducing_op_p (code);
> gcc_assert (single_defuse_cycle || lane_reducing);
>
> + if (lane_reducing)
> + {
> + /* The last operand of lane-reducing op is for reduction. */
> + gcc_assert (reduc_index == (int) op.num_ops - 1);
> + }
> +
> /* Create the destination vector */
> tree scalar_dest = gimple_get_lhs (stmt_info->stmt);
> tree vec_dest = vect_create_destination_var (scalar_dest, vectype_out);
>
> + if (lane_reducing && !slp_node && !single_defuse_cycle)
> + {
> + /* Note: there are still vectorizable cases that can not be handled by
> + single-lane slp. Probably it would take some time to evolve the
> + feature to a mature state. So we have to keep the below non-slp code
> + path as failsafe for lane-reducing support. */
> + gcc_assert (op.num_ops <= 3);
> + for (unsigned i = 0; i < op.num_ops; i++)
> + {
> + unsigned oprnd_ncopies = ncopies;
> +
> + if ((int) i == reduc_index)
> + {
> + tree vectype = STMT_VINFO_VECTYPE (stmt_info);
> + oprnd_ncopies = vect_get_num_copies (loop_vinfo, vectype);
> + }
> +
> + vect_get_vec_defs_for_operand (loop_vinfo, stmt_info, oprnd_ncopies,
> + op.ops[i], &vec_oprnds[i]);
> + }
> + }
> /* Get NCOPIES vector definitions for all operands except the reduction
> definition. */
> - if (!cond_fn_p)
> + else if (!cond_fn_p)
> {
> gcc_assert (reduc_index >= 0 && reduc_index <= 2);
> vect_get_vec_defs (loop_vinfo, stmt_info, slp_node, ncopies,
> @@ -8702,6 +8728,61 @@ vect_transform_reduction (loop_vec_info loop_vinfo,
> reduc_index == 2 ? op.ops[2] : NULL_TREE,
> &vec_oprnds[2]);
> }
> + else if (lane_reducing)
> + {
> + /* For normal reduction, consistency between vectorized def/use is
> + naturally ensured when mapping from scalar statement. But if lane-
> + reducing op is involved in reduction, thing would become somewhat
> + complicated in that the op's result and operand for accumulation are
> + limited to less lanes than other operands, which certainly causes
> + def/use mismatch on adjacent statements around the op if do not have
> + any kind of specific adjustment. One approach is to refit lane-
> + reducing op in the way of introducing new trivial pass-through copies
> + to fix possible def/use gap, so as to make it behave like a normal
> op.
> + And vector reduction PHIs are always generated to the full extent, no
> + matter lane-reducing op exists or not. If some copies or PHIs are
> + actually superfluous, they would be cleaned up by passes after
> + vectorization. An example for single-lane slp is given as below.
> + Similarly, this handling is applicable for multiple-lane slp as well.
> +
> + int sum = 1;
> + for (i)
> + {
> + sum += d0[i] * d1[i]; // dot-prod <vector(16) char>
> + }
> +
> + The vector size is 128-bit，vectorization factor is 16. Reduction
> + statements would be transformed as:
> +
> + vector<4> int sum_v0 = { 0, 0, 0, 1 };
> + vector<4> int sum_v1 = { 0, 0, 0, 0 };
> + vector<4> int sum_v2 = { 0, 0, 0, 0 };
> + vector<4> int sum_v3 = { 0, 0, 0, 0 };
> +
> + for (i / 16)
> + {
> + sum_v0 = DOT_PROD (d0_v0[i: 0 ~ 15], d1_v0[i: 0 ~ 15], sum_v0);
> + sum_v1 = sum_v1; // copy
> + sum_v2 = sum_v2; // copy
> + sum_v3 = sum_v3; // copy
> + }
> +
> + sum_v = sum_v0 + sum_v1 + sum_v2 + sum_v3; // = sum_v0
> + */
> + unsigned effec_ncopies = vec_oprnds[0].length ();
> + unsigned total_ncopies = vec_oprnds[reduc_index].length ();
> +
> + gcc_assert (effec_ncopies <= total_ncopies);
> +
> + if (effec_ncopies < total_ncopies)
> + {
> + for (unsigned i = 0; i < op.num_ops - 1; i++)
> + {
> + gcc_assert (vec_oprnds[i].length () == effec_ncopies);
> + vec_oprnds[i].safe_grow_cleared (total_ncopies);
> + }
> + }
> + }
>
> bool emulated_mixed_dot_prod = vect_is_emulated_mixed_dot_prod (stmt_info);
> unsigned num = vec_oprnds[reduc_index == 0 ? 1 : 0].length ();
> @@ -8710,7 +8791,27 @@ vect_transform_reduction (loop_vec_info loop_vinfo,
> {
> gimple *new_stmt;
> tree vop[3] = { vec_oprnds[0][i], vec_oprnds[1][i], NULL_TREE };
> - if (masked_loop_p && !mask_by_cond_expr)
> + if (!vop[0] || !vop[1])
> + {
> + tree reduc_vop = vec_oprnds[reduc_index][i];
> +
> + /* If could not generate an effective vector statement for current
> + portion of reduction operand, insert a trivial copy to simply
> + handle over the operand to other dependent statements. */
> + gcc_assert (reduc_vop);
> +
> + if (slp_node && TREE_CODE (reduc_vop) == SSA_NAME
> + && !SSA_NAME_IS_DEFAULT_DEF (reduc_vop))
> + new_stmt = SSA_NAME_DEF_STMT (reduc_vop);
> + else
> + {
> + new_temp = make_ssa_name (vec_dest);
> + new_stmt = gimple_build_assign (new_temp, reduc_vop);
> + vect_finish_stmt_generation (loop_vinfo, stmt_info, new_stmt,
> + gsi);
> + }
> + }
> + else if (masked_loop_p && !mask_by_cond_expr)
> {
> /* No conditional ifns have been defined for lane-reducing op
> yet. */
> @@ -8810,23 +8911,16 @@ vect_transform_cycle_phi (loop_vec_info loop_vinfo,
> /* Leave the scalar phi in place. */
> return true;
>
> - tree vectype_in = STMT_VINFO_REDUC_VECTYPE_IN (reduc_info);
> - /* For a nested cycle we do not fill the above. */
> - if (!vectype_in)
> - vectype_in = STMT_VINFO_VECTYPE (stmt_info);
> - gcc_assert (vectype_in);
> -
> if (slp_node)
> {
> - /* The size vect_schedule_slp_instance computes is off for us. */
> - vec_num = vect_get_num_vectors (LOOP_VINFO_VECT_FACTOR (loop_vinfo)
> - * SLP_TREE_LANES (slp_node),
> vectype_in);
> + vec_num = SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node);
> ncopies = 1;
> }
> else
> {
> vec_num = 1;
> - ncopies = vect_get_num_copies (loop_vinfo, vectype_in);
> + ncopies = vect_get_num_copies (loop_vinfo,
> + STMT_VINFO_VECTYPE (stmt_info));
> }
>
> /* Check whether we should use a single PHI node and accumulate
> diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
> index 4dadbc6854d..55ae496cbb2 100644
> --- a/gcc/tree-vect-slp.cc
> +++ b/gcc/tree-vect-slp.cc
> @@ -6554,26 +6554,13 @@ vect_slp_analyze_node_operations_1 (vec_info *vinfo,
> slp_tree node,
> {
> stmt_vec_info stmt_info = SLP_TREE_REPRESENTATIVE (node);
>
> - /* Calculate the number of vector statements to be created for the
> - scalar stmts in this node. For SLP reductions it is equal to the
> - number of vector statements in the children (which has already been
> - calculated by the recursive call). Otherwise it is the number of
> - scalar elements in one scalar iteration (DR_GROUP_SIZE) multiplied by
> - VF divided by the number of elements in a vector. */
> - if (SLP_TREE_CODE (node) != VEC_PERM_EXPR
> - && !STMT_VINFO_DATA_REF (stmt_info)
> - && REDUC_GROUP_FIRST_ELEMENT (stmt_info))
> - {
> - for (unsigned i = 0; i < SLP_TREE_CHILDREN (node).length (); ++i)
> - if (SLP_TREE_DEF_TYPE (SLP_TREE_CHILDREN (node)[i]) ==
> vect_internal_def)
> - {
> - SLP_TREE_NUMBER_OF_VEC_STMTS (node)
> - = SLP_TREE_NUMBER_OF_VEC_STMTS (SLP_TREE_CHILDREN (node)[i]);
> - break;
> - }
> - }
> - else
> - SLP_TREE_NUMBER_OF_VEC_STMTS (node) = vect_get_num_copies (vinfo, node);
> + /* Calculate the number of vector statements to be created for the scalar
> + stmts in this node. It is the number of scalar elements in one scalar
> + iteration (DR_GROUP_SIZE) multiplied by VF divided by the number of
> + elements in a vector. For single-defuse-cycle, lane-reducing op, and
> + PHI statement that starts reduction comprised of only lane-reducing ops,
> + the number is more than effective vector statements actually required.
> */
> + SLP_TREE_NUMBER_OF_VEC_STMTS (node) = vect_get_num_copies (vinfo, node);
>
> /* Handle purely internal nodes. */
> if (SLP_TREE_CODE (node) == VEC_PERM_EXPR)
> --
> 2.17.1
