599eabdb42
2004-09-08 Daniel Berlin <dberlin@dberlin.org> * Makefile.in (tree-loop-linear.o): Added. (OBJS-common): Add tree-loop-linear.o * common.opt: New flag, ftree-loop-linear. * timevar.def: New timevar, TV_TREE_LOOP_LINEAR. * tree-flow.h: Add prototype for linear_transform_loops. * tree-optimize.c: Add linear transform after vectorization. * tree-pass.h: Add struct pass_linear_transform. * tree-ssa-loop.c: Add pass_linear_transform. * tree-loop-linear.c: New file. * lambda-code.c: gcc_assertify. (gcc_loop_to_lambda_loop): Handle all exit tests. Handle case where we have (invariant >= induction var). (find_induction_var_from_exit_cond): Ditto. From-SVN: r87190
283 lines
8.6 KiB
C
283 lines
8.6 KiB
C
/* Linear Loop transforms
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Copyright (C) 2003, 2004 Free Software Foundation, Inc.
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Contributed by Daniel Berlin <dberlin@dberlin.org>.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "errors.h"
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#include "ggc.h"
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#include "tree.h"
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#include "target.h"
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#include "rtl.h"
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#include "basic-block.h"
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#include "diagnostic.h"
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#include "tree-flow.h"
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#include "tree-dump.h"
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#include "timevar.h"
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#include "cfgloop.h"
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#include "expr.h"
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#include "optabs.h"
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#include "tree-chrec.h"
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#include "tree-data-ref.h"
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#include "tree-scalar-evolution.h"
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#include "tree-pass.h"
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#include "varray.h"
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#include "lambda.h"
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/* Linear loop transforms include any composition of interchange,
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scaling, skewing, and reversal. They are used to change the
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iteration order of loop nests in order to optimize data locality of
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traversals, or remove dependences that prevent
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parallelization/vectorization/etc.
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TODO: Determine reuse vectors/matrix and use it to determine optimal
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transform matrix for locality purposes.
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TODO: Completion of partial transforms. */
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/* Gather statistics for loop interchange. Initializes SUM the sum of
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all the data dependence distances carried by loop LOOP_NUMBER.
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NB_DEPS_NOT_CARRIED_BY_LOOP is initialized to the number of
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dependence relations for which the loop LOOP_NUMBER is not carrying
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any dependence. */
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static void
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gather_interchange_stats (varray_type dependence_relations,
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unsigned int loop_number,
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unsigned int *sum,
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unsigned int *nb_deps_not_carried_by_loop)
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{
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unsigned int i;
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*sum = 0;
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*nb_deps_not_carried_by_loop = 0;
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for (i = 0; i < VARRAY_ACTIVE_SIZE (dependence_relations); i++)
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{
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int dist;
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struct data_dependence_relation *ddr =
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(struct data_dependence_relation *)
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VARRAY_GENERIC_PTR (dependence_relations, i);
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if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
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{
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/* Some constants will need tweaking, but not something that should
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be user-accessible. Thus, no --param. */
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*sum += 100;
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continue;
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}
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/* When we know that there is no dependence, we know that there
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is no reuse of the data. */
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if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
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{
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/* Ditto on the no --param here */
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*sum += 1000;
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continue;
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}
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dist = DDR_DIST_VECT (ddr)[loop_number];
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if (dist == 0)
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*nb_deps_not_carried_by_loop++;
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else if (dist < 0)
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*sum += -dist;
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else
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*sum += dist;
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}
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}
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/* Apply to TRANS any loop interchange that minimize inner loop steps.
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DEPTH is the depth of the loop nest, and DEPENDENCE_RELATIONS is an array
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of dependence relations.
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Returns the new transform matrix. The smaller the reuse vector
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distances in the inner loops, the fewer the cache misses. */
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static lambda_trans_matrix
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try_interchange_loops (lambda_trans_matrix trans,
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unsigned int depth,
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varray_type dependence_relations)
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{
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unsigned int loop_i, loop_j;
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unsigned int steps_i, steps_j;
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unsigned int nb_deps_not_carried_by_i, nb_deps_not_carried_by_j;
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struct data_dependence_relation *ddr;
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/* When there is an unknown relation in the dependence_relations, we
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know that it is no worth looking at this loop nest: give up. */
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ddr = (struct data_dependence_relation *)
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VARRAY_GENERIC_PTR (dependence_relations, 0);
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if (ddr == NULL || DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
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return trans;
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/* LOOP_I is always the outer loop. */
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for (loop_j = 1; loop_j < depth; loop_j++)
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for (loop_i = 0; loop_i < loop_j; loop_i++)
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{
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gather_interchange_stats (dependence_relations, loop_i, &steps_i,
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&nb_deps_not_carried_by_i);
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gather_interchange_stats (dependence_relations, loop_j, &steps_j,
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&nb_deps_not_carried_by_j);
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/* Heuristics for loop interchange profitability:
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1. Inner loops should have smallest steps.
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2. Inner loops should contain more dependence relations not
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carried by the loop.
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*/
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if (steps_i < steps_j
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|| nb_deps_not_carried_by_i > nb_deps_not_carried_by_j)
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{
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lambda_matrix_row_exchange (LTM_MATRIX (trans), loop_i, loop_j);
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/* Validate the resulting matrix. When the transformation
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is not valid, reverse to the previous matrix.
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FIXME: In this case of transformation it could be
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faster to verify the validity of the interchange
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without applying the transform to the matrix. But for
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the moment do it cleanly: this is just a prototype. */
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if (!lambda_transform_legal_p (trans, depth, dependence_relations))
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lambda_matrix_row_exchange (LTM_MATRIX (trans), loop_i, loop_j);
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}
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}
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return trans;
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}
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/* Perform a set of linear transforms on LOOPS. */
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void
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linear_transform_loops (struct loops *loops)
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{
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unsigned int i;
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for (i = 1; i < loops->num; i++)
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{
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unsigned int depth = 0;
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varray_type datarefs;
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varray_type dependence_relations;
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struct loop *loop_nest = loops->parray[i];
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struct loop *temp;
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VEC (tree) *oldivs;
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VEC (tree) *invariants;
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lambda_loopnest before, after;
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lambda_trans_matrix trans;
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bool problem = false;
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/* If it's not a loop nest, we don't want it.
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We also don't handle sibling loops properly,
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which are loops of the following form:
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for (i = 0; i < 50; i++)
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{
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for (j = 0; j < 50; j++)
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{
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...
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}
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for (j = 0; j < 50; j++)
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{
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...
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}
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} */
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if (!loop_nest->inner)
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continue;
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for (temp = loop_nest; temp; temp = temp->inner)
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{
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flow_loop_scan (temp, LOOP_ALL);
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/* If we have a sibling loop or multiple exit edges, jump ship. */
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if (temp->next || temp->num_exits != 1)
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{
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problem = true;
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break;
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}
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depth ++;
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}
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if (problem)
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continue;
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/* Analyze data references and dependence relations using scev. */
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VARRAY_GENERIC_PTR_INIT (datarefs, 10, "datarefs");
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VARRAY_GENERIC_PTR_INIT (dependence_relations, 10,
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"dependence_relations");
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compute_data_dependences_for_loop (depth, loop_nest,
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&datarefs, &dependence_relations);
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if (dump_file && (dump_flags & TDF_DETAILS))
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{
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unsigned int j;
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for (j = 0; j < VARRAY_ACTIVE_SIZE (dependence_relations); j++)
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{
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struct data_dependence_relation *ddr =
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(struct data_dependence_relation *)
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VARRAY_GENERIC_PTR (dependence_relations, j);
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if (DDR_ARE_DEPENDENT (ddr) == NULL_TREE)
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{
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fprintf (dump_file, "DISTANCE_V (");
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print_lambda_vector (dump_file, DDR_DIST_VECT (ddr),
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loops->num);
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fprintf (dump_file, ")\n");
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fprintf (dump_file, "DIRECTION_V (");
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print_lambda_vector (dump_file, DDR_DIR_VECT (ddr),
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loops->num);
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fprintf (dump_file, ")\n");
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}
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}
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fprintf (dump_file, "\n\n");
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}
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/* Build the transformation matrix. */
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trans = lambda_trans_matrix_new (depth, depth);
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lambda_matrix_id (LTM_MATRIX (trans), depth);
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trans = try_interchange_loops (trans, depth, dependence_relations);
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/* Check whether the transformation is legal. */
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if (!lambda_transform_legal_p (trans, depth, dependence_relations))
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{
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if (dump_file)
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fprintf (dump_file, "Can't transform loop, transform is illegal:\n");
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continue;
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}
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before = gcc_loopnest_to_lambda_loopnest (loop_nest, &oldivs,
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&invariants);
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if (!before)
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continue;
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if (dump_file)
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{
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fprintf (dump_file, "Before:\n");
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print_lambda_loopnest (dump_file, before, 'i');
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}
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after = lambda_loopnest_transform (before, trans);
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if (dump_file)
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{
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fprintf (dump_file, "After:\n");
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print_lambda_loopnest (dump_file, after, 'u');
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}
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lambda_loopnest_to_gcc_loopnest (loop_nest, oldivs, invariants,
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after, trans);
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oldivs = NULL;
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invariants = NULL;
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free_dependence_relations (dependence_relations);
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free_data_refs (datarefs);
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}
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}
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