transform matrix for locality purposes.
TODO: Completion of partial transforms. */
-/* Gather statistics for loop interchange. Initializes SUM the sum of
- all the data dependence distances carried by loop LOOP_NUMBER.
- NB_DEPS_NOT_CARRIED_BY_LOOP is initialized to the number of
- dependence relations for which the loop LOOP_NUMBER is not carrying
- any dependence. */
+/* Gather statistics for loop interchange. LOOP_NUMBER is a relative
+ index in the considered loop nest. The first loop in the
+ considered loop nest is FIRST_LOOP, and consequently the index of
+ the considered loop is obtained by FIRST_LOOP + LOOP_NUMBER.
+
+ Initializes:
+ - DEPENDENCE_STEPS the sum of all the data dependence distances
+ carried by loop LOOP_NUMBER,
+
+ - NB_DEPS_NOT_CARRIED_BY_LOOP the number of dependence relations
+ for which the loop LOOP_NUMBER is not carrying any dependence,
+
+ - ACCESS_STRIDES the sum of all the strides in LOOP_NUMBER.
+
+ Example: for the following loop,
+
+ | loop_1 runs 1335 times
+ | loop_2 runs 1335 times
+ | A[{{0, +, 1}_1, +, 1335}_2]
+ | B[{{0, +, 1}_1, +, 1335}_2]
+ | endloop_2
+ | A[{0, +, 1336}_1]
+ | endloop_1
+
+ gather_interchange_stats (in loop_1) will return
+ DEPENDENCE_STEPS = 3002
+ NB_DEPS_NOT_CARRIED_BY_LOOP = 5
+ ACCESS_STRIDES = 10694
+
+ gather_interchange_stats (in loop_2) will return
+ DEPENDENCE_STEPS = 3000
+ NB_DEPS_NOT_CARRIED_BY_LOOP = 7
+ ACCESS_STRIDES = 8010
+ */
static void
gather_interchange_stats (varray_type dependence_relations,
+ varray_type datarefs,
unsigned int loop_number,
- unsigned int *sum,
- unsigned int *nb_deps_not_carried_by_loop)
+ unsigned int first_loop,
+ unsigned int *dependence_steps,
+ unsigned int *nb_deps_not_carried_by_loop,
+ unsigned int *access_strides)
{
unsigned int i;
- *sum = 0;
+ *dependence_steps = 0;
*nb_deps_not_carried_by_loop = 0;
+ *access_strides = 0;
+
for (i = 0; i < VARRAY_ACTIVE_SIZE (dependence_relations); i++)
{
int dist;
(struct data_dependence_relation *)
VARRAY_GENERIC_PTR (dependence_relations, i);
+ /* Compute the dependence strides. */
+
if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
{
- /* Some constants will need tweaking, but not something that should
- be user-accessible. Thus, no --param. */
- *sum += 100;
+ (*dependence_steps) += 0;
continue;
}
is no reuse of the data. */
if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
{
- /* Ditto on the no --param here */
- *sum += 1000;
+ (*dependence_steps) += 0;
continue;
}
dist = DDR_DIST_VECT (ddr)[loop_number];
if (dist == 0)
- *nb_deps_not_carried_by_loop++;
+ (*nb_deps_not_carried_by_loop) += 1;
else if (dist < 0)
- *sum += -dist;
+ (*dependence_steps) += -dist;
else
- *sum += dist;
+ (*dependence_steps) += dist;
+ }
+
+ /* Compute the access strides. */
+ for (i = 0; i < VARRAY_ACTIVE_SIZE (datarefs); i++)
+ {
+ unsigned int it;
+ struct data_reference *dr = VARRAY_GENERIC_PTR (datarefs, i);
+ tree stmt = DR_STMT (dr);
+ struct loop *stmt_loop = loop_containing_stmt (stmt);
+ struct loop *inner_loop = current_loops->parray[first_loop + 1];
+
+ if (!flow_loop_nested_p (inner_loop, stmt_loop)
+ && inner_loop->num != stmt_loop->num)
+ continue;
+
+ for (it = 0; it < DR_NUM_DIMENSIONS (dr); it++)
+ {
+ tree chrec = DR_ACCESS_FN (dr, it);
+ tree tstride = evolution_part_in_loop_num
+ (chrec, first_loop + loop_number);
+
+ if (tstride == NULL_TREE
+ || TREE_CODE (tstride) != INTEGER_CST)
+ continue;
+
+ (*access_strides) += int_cst_value (tstride);
+ }
}
}
/* Apply to TRANS any loop interchange that minimize inner loop steps.
- DEPTH is the depth of the loop nest, and DEPENDENCE_RELATIONS is an array
- of dependence relations.
Returns the new transform matrix. The smaller the reuse vector
- distances in the inner loops, the fewer the cache misses. */
+ distances in the inner loops, the fewer the cache misses.
+ FIRST_LOOP is the loop->num of the first loop in the analyzed loop
+ nest. */
+
static lambda_trans_matrix
try_interchange_loops (lambda_trans_matrix trans,
unsigned int depth,
- varray_type dependence_relations)
+ varray_type dependence_relations,
+ varray_type datarefs,
+ unsigned int first_loop)
{
unsigned int loop_i, loop_j;
- unsigned int steps_i, steps_j;
+ unsigned int dependence_steps_i, dependence_steps_j;
+ unsigned int access_strides_i, access_strides_j;
unsigned int nb_deps_not_carried_by_i, nb_deps_not_carried_by_j;
struct data_dependence_relation *ddr;
for (loop_j = 1; loop_j < depth; loop_j++)
for (loop_i = 0; loop_i < loop_j; loop_i++)
{
- gather_interchange_stats (dependence_relations, loop_i, &steps_i,
- &nb_deps_not_carried_by_i);
- gather_interchange_stats (dependence_relations, loop_j, &steps_j,
- &nb_deps_not_carried_by_j);
+ gather_interchange_stats (dependence_relations, datarefs,
+ loop_i, first_loop,
+ &dependence_steps_i,
+ &nb_deps_not_carried_by_i,
+ &access_strides_i);
+ gather_interchange_stats (dependence_relations, datarefs,
+ loop_j, first_loop,
+ &dependence_steps_j,
+ &nb_deps_not_carried_by_j,
+ &access_strides_j);
/* Heuristics for loop interchange profitability:
- 1. Inner loops should have smallest steps.
- 2. Inner loops should contain more dependence relations not
- carried by the loop.
+
+ 1. (spatial locality) Inner loops should have smallest
+ dependence steps.
+
+ 2. (spatial locality) Inner loops should contain more
+ dependence relations not carried by the loop.
+
+ 3. (temporal locality) Inner loops should have smallest
+ array access strides.
*/
- if (steps_i < steps_j
- || nb_deps_not_carried_by_i > nb_deps_not_carried_by_j)
+ if (dependence_steps_i < dependence_steps_j
+ || nb_deps_not_carried_by_i > nb_deps_not_carried_by_j
+ || access_strides_i < access_strides_j)
{
lambda_matrix_row_exchange (LTM_MATRIX (trans), loop_i, loop_j);
-
/* Validate the resulting matrix. When the transformation
- is not valid, reverse to the previous matrix.
-
- FIXME: In this case of transformation it could be
- faster to verify the validity of the interchange
- without applying the transform to the matrix. But for
- the moment do it cleanly: this is just a prototype. */
+ is not valid, reverse to the previous transformation. */
if (!lambda_transform_legal_p (trans, depth, dependence_relations))
lambda_matrix_row_exchange (LTM_MATRIX (trans), loop_i, loop_j);
}
}
-
+
return trans;
}
lambda_loopnest before, after;
lambda_trans_matrix trans;
bool problem = false;
+ bool need_perfect_nest = false;
/* If it's not a loop nest, we don't want it.
We also don't handle sibling loops properly,
which are loops of the following form:
} */
if (!loop_nest->inner)
continue;
- for (temp = loop_nest; temp; temp = temp->inner)
+ depth = 1;
+ for (temp = loop_nest->inner; temp; temp = temp->inner)
{
flow_loop_scan (temp, LOOP_ALL);
/* If we have a sibling loop or multiple exit edges, jump ship. */
/* Build the transformation matrix. */
trans = lambda_trans_matrix_new (depth, depth);
lambda_matrix_id (LTM_MATRIX (trans), depth);
- trans = try_interchange_loops (trans, depth, dependence_relations);
+ trans = try_interchange_loops (trans, depth, dependence_relations,
+ datarefs, loop_nest->num);
+
+ if (lambda_trans_matrix_id_p (trans))
+ {
+ if (dump_file)
+ fprintf (dump_file, "Won't transform loop. Optimal transform is the identity transform\n");
+ continue;
+ }
/* Check whether the transformation is legal. */
if (!lambda_transform_legal_p (trans, depth, dependence_relations))
fprintf (dump_file, "Can't transform loop, transform is illegal:\n");
continue;
}
- before = gcc_loopnest_to_lambda_loopnest (loop_nest, &oldivs,
- &invariants);
+ if (!perfect_nest_p (loop_nest))
+ need_perfect_nest = true;
+ before = gcc_loopnest_to_lambda_loopnest (loops,
+ loop_nest, &oldivs,
+ &invariants,
+ need_perfect_nest);
if (!before)
continue;
free_dependence_relations (dependence_relations);
free_data_refs (datarefs);
}
+ rewrite_into_loop_closed_ssa ();
+ free_df ();
}
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