/* Linear Loop transforms
- Copyright (C) 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
Contributed by Daniel Berlin <dberlin@dberlin.org>.
This file is part of GCC.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
-#include "errors.h"
#include "ggc.h"
#include "tree.h"
#include "target.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "tree-pass.h"
-#include "varray.h"
#include "lambda.h"
/* Linear loop transforms include any composition of interchange,
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 is the loop being
+ considered. The first loop in the considered loop nest is
+ FIRST_LOOP, and consequently, the index of the considered loop is
+ obtained by LOOP->DEPTH - FIRST_LOOP->DEPTH
+
+ Initializes:
+ - DEPENDENCE_STEPS the sum of all the data dependence distances
+ carried by loop LOOP,
+
+ - NB_DEPS_NOT_CARRIED_BY_LOOP the number of dependence relations
+ for which the loop LOOP is not carrying any dependence,
+
+ - ACCESS_STRIDES the sum of all the strides in LOOP.
+
+ 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,
- unsigned int loop_number,
- unsigned int *sum,
- unsigned int *nb_deps_not_carried_by_loop)
+gather_interchange_stats (VEC (ddr_p, heap) *dependence_relations,
+ VEC (data_reference_p, heap) *datarefs,
+ struct loop *loop,
+ struct loop *first_loop,
+ unsigned int *dependence_steps,
+ unsigned int *nb_deps_not_carried_by_loop,
+ unsigned int *access_strides)
{
- unsigned int i;
+ unsigned int i, j;
+ struct data_dependence_relation *ddr;
+ struct data_reference *dr;
- *sum = 0;
+ *dependence_steps = 0;
*nb_deps_not_carried_by_loop = 0;
- for (i = 0; i < VARRAY_ACTIVE_SIZE (dependence_relations); i++)
+ *access_strides = 0;
+
+ for (i = 0; VEC_iterate (ddr_p, dependence_relations, i, ddr); i++)
{
- int dist;
- struct data_dependence_relation *ddr =
- (struct data_dependence_relation *)
- VARRAY_GENERIC_PTR (dependence_relations, i);
+ /* If we don't know anything about this dependence, or the distance
+ vector is NULL, or there is no dependence, then there is no reuse of
+ data. */
+ if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know
+ || DDR_ARE_DEPENDENT (ddr) == chrec_known
+ || DDR_NUM_DIST_VECTS (ddr) == 0)
+ continue;
- if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
+ for (j = 0; j < DDR_NUM_DIST_VECTS (ddr); j++)
{
- /* Some constants will need tweaking, but not something that should
- be user-accessible. Thus, no --param. */
- *sum += 100;
- continue;
+ int dist = DDR_DIST_VECT (ddr, j)[loop->depth - first_loop->depth];
+
+ if (dist == 0)
+ (*nb_deps_not_carried_by_loop) += 1;
+
+ else if (dist < 0)
+ (*dependence_steps) += -dist;
+
+ else
+ (*dependence_steps) += dist;
}
+ }
- /* When we know that there is no dependence, we know that there
- is no reuse of the data. */
- if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
+ /* Compute the access strides. */
+ for (i = 0; VEC_iterate (data_reference_p, datarefs, i, dr); i++)
+ {
+ unsigned int it;
+ tree stmt = DR_STMT (dr);
+ struct loop *stmt_loop = loop_containing_stmt (stmt);
+ struct loop *inner_loop = first_loop->inner;
+
+ if (inner_loop != stmt_loop
+ && !flow_loop_nested_p (inner_loop, stmt_loop))
+ continue;
+ for (it = 0; it < DR_NUM_DIMENSIONS (dr); it++)
{
- /* Ditto on the no --param here */
- *sum += 1000;
- continue;
+ tree chrec = DR_ACCESS_FN (dr, it);
+ tree tstride = evolution_part_in_loop_num
+ (chrec, loop->num);
+
+ if (tstride == NULL_TREE
+ || TREE_CODE (tstride) != INTEGER_CST)
+ continue;
+
+ (*access_strides) += int_cst_value (tstride);
}
-
- dist = DDR_DIST_VECT (ddr)[loop_number];
- if (dist == 0)
- *nb_deps_not_carried_by_loop++;
- else if (dist < 0)
- *sum += -dist;
- else
- *sum += dist;
}
}
-/* 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.
+/* Attempt to apply interchange transformations to TRANS to maximize the
+ spatial and temporal locality of the loop.
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)
+ VEC (ddr_p, heap) *dependence_relations,
+ VEC (data_reference_p, heap) *datarefs,
+ struct loop *first_loop)
{
- unsigned int loop_i, loop_j;
- unsigned int steps_i, steps_j;
+ struct loop *loop_i;
+ struct loop *loop_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;
+ if (VEC_length (ddr_p, dependence_relations) == 0)
+ return trans;
+
/* When there is an unknown relation in the dependence_relations, we
know that it is no worth looking at this loop nest: give up. */
- ddr = (struct data_dependence_relation *)
- VARRAY_GENERIC_PTR (dependence_relations, 0);
+ ddr = VEC_index (ddr_p, dependence_relations, 0);
if (ddr == NULL || DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
return trans;
/* LOOP_I is always the outer loop. */
- for (loop_j = 1; loop_j < depth; loop_j++)
- for (loop_i = 0; loop_i < loop_j; loop_i++)
+ for (loop_j = first_loop->inner;
+ loop_j;
+ loop_j = loop_j->inner)
+ for (loop_i = first_loop;
+ loop_i->depth < loop_j->depth;
+ loop_i = loop_i->inner)
{
- 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);
-
+ lambda_matrix_row_exchange (LTM_MATRIX (trans),
+ loop_i->depth - first_loop->depth,
+ loop_j->depth - first_loop->depth);
/* 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);
+ lambda_matrix_row_exchange (LTM_MATRIX (trans),
+ loop_i->depth - first_loop->depth,
+ loop_j->depth - first_loop->depth);
}
}
-
+
return trans;
}
void
linear_transform_loops (struct loops *loops)
{
+ bool modified = false;
unsigned int i;
-
+ VEC(tree,heap) *oldivs = NULL;
+ VEC(tree,heap) *invariants = NULL;
+
for (i = 1; i < loops->num; i++)
{
unsigned int depth = 0;
- varray_type datarefs;
- varray_type dependence_relations;
+ VEC (ddr_p, heap) *dependence_relations;
+ VEC (data_reference_p, heap) *datarefs;
struct loop *loop_nest = loops->parray[i];
struct loop *temp;
- VEC (tree) *oldivs;
- VEC (tree) *invariants;
lambda_loopnest before, after;
lambda_trans_matrix trans;
bool problem = false;
...
}
} */
- if (!loop_nest->inner)
+ if (!loop_nest || !loop_nest->inner)
continue;
- for (temp = loop_nest; temp; temp = temp->inner)
+ VEC_truncate (tree, oldivs, 0);
+ VEC_truncate (tree, invariants, 0);
+ 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. */
- if (temp->next || temp->num_exits != 1)
+ if (temp->next || !temp->single_exit)
{
problem = true;
break;
/* Analyze data references and dependence relations using scev. */
- VARRAY_GENERIC_PTR_INIT (datarefs, 10, "datarefs");
- VARRAY_GENERIC_PTR_INIT (dependence_relations, 10,
- "dependence_relations");
-
-
- compute_data_dependences_for_loop (depth, loop_nest,
- &datarefs, &dependence_relations);
+ datarefs = VEC_alloc (data_reference_p, heap, 10);
+ dependence_relations = VEC_alloc (ddr_p, heap, 10 * 10);
+ compute_data_dependences_for_loop (loop_nest, true, &datarefs,
+ &dependence_relations);
+
if (dump_file && (dump_flags & TDF_DETAILS))
- {
- unsigned int j;
- for (j = 0; j < VARRAY_ACTIVE_SIZE (dependence_relations); j++)
- {
- struct data_dependence_relation *ddr =
- (struct data_dependence_relation *)
- VARRAY_GENERIC_PTR (dependence_relations, j);
-
- if (DDR_ARE_DEPENDENT (ddr) == NULL_TREE)
- {
- fprintf (dump_file, "DISTANCE_V (");
- print_lambda_vector (dump_file, DDR_DIST_VECT (ddr),
- loops->num);
- fprintf (dump_file, ")\n");
- fprintf (dump_file, "DIRECTION_V (");
- print_lambda_vector (dump_file, DDR_DIR_VECT (ddr),
- loops->num);
- fprintf (dump_file, ")\n");
- }
- }
- fprintf (dump_file, "\n\n");
- }
+ dump_ddrs (dump_file, dependence_relations);
+
/* 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);
+
+ 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,
+
+ before = gcc_loopnest_to_lambda_loopnest (loops, loop_nest, &oldivs,
&invariants);
+
if (!before)
continue;
}
after = lambda_loopnest_transform (before, trans);
+
if (dump_file)
{
fprintf (dump_file, "After:\n");
print_lambda_loopnest (dump_file, after, 'u');
}
+
lambda_loopnest_to_gcc_loopnest (loop_nest, oldivs, invariants,
after, trans);
- oldivs = NULL;
- invariants = NULL;
+ modified = true;
+
+ if (dump_file)
+ fprintf (dump_file, "Successfully transformed loop.\n");
+
free_dependence_relations (dependence_relations);
free_data_refs (datarefs);
}
+
+ VEC_free (tree, heap, oldivs);
+ VEC_free (tree, heap, invariants);
+ scev_reset ();
+
+ if (modified)
+ rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa_full_phi);
}
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