[PATCH 2/4] vect: Refit lane-reducing to be normal operation
Feng Xue OS
fxue@os.amperecomputing.com
Sat Jul 13 15:47:14 GMT 2024
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
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
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