1 /* Heuristics and transform for loop blocking and strip mining on
2 polyhedral representation.
4 Copyright (C) 2009 Free Software Foundation, Inc.
5 Contributed by Sebastian Pop <sebastian.pop@amd.com> and
6 Pranav Garg <pranav.garg2107@gmail.com>.
8 This file is part of GCC.
10 GCC is free software; you can redistribute it and/or modify
11 it under the terms of the GNU General Public License as published by
12 the Free Software Foundation; either version 3, or (at your option)
15 GCC is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
20 You should have received a copy of the GNU General Public License
21 along with GCC; see the file COPYING3. If not see
22 <http://www.gnu.org/licenses/>. */
25 #include "coretypes.h"
31 #include "basic-block.h"
32 #include "diagnostic.h"
33 #include "tree-flow.h"
35 #include "tree-dump.h"
38 #include "tree-chrec.h"
39 #include "tree-data-ref.h"
40 #include "tree-scalar-evolution.h"
41 #include "tree-pass.h"
43 #include "value-prof.h"
44 #include "pointer-set.h"
51 #include "graphite-ppl.h"
53 #include "graphite-poly.h"
56 /* Strip mines with a factor STRIDE the scattering (time) dimension
57 around PBB at depth TIME_DEPTH.
59 The following example comes from the wiki page:
60 http://gcc.gnu.org/wiki/Graphite/Strip_mine
62 The strip mine of a loop with a tile of 64 can be obtained with a
63 scattering function as follows:
65 $ cat ./albert_strip_mine.cloog
69 # parameter {n | n >= 0}
76 1 # Number of statements:
89 1 # Scattering functions
100 #the output of CLooG is like this:
101 #$ cloog ./albert_strip_mine.cloog
102 # for (NEW=0;NEW<=floord(n,64);NEW++) {
103 # for (OLD=max(64*NEW,0);OLD<=min(64*NEW+63,n);OLD++) {
110 pbb_strip_mine_time_depth (poly_bb_p pbb, int time_depth, int stride)
112 ppl_dimension_type iter, dim, strip;
113 ppl_Polyhedron_t res = PBB_TRANSFORMED_SCATTERING (pbb);
114 /* STRIP is the dimension that iterates with stride STRIDE. */
115 /* ITER is the dimension that enumerates single iterations inside
116 one strip that has at most STRIDE iterations. */
120 psct_add_scattering_dimension (pbb, strip);
121 psct_add_scattering_dimension (pbb, strip + 1);
123 ppl_Polyhedron_space_dimension (res, &dim);
125 /* Lower bound of the striped loop. */
127 ppl_Constraint_t new_cstr;
128 ppl_Linear_Expression_t expr;
130 ppl_new_Linear_Expression_with_dimension (&expr, dim);
131 ppl_set_coef (expr, strip, -1 * stride);
132 ppl_set_coef (expr, iter, 1);
134 ppl_new_Constraint (&new_cstr, expr, PPL_CONSTRAINT_TYPE_GREATER_OR_EQUAL);
135 ppl_delete_Linear_Expression (expr);
136 ppl_Polyhedron_add_constraint (res, new_cstr);
137 ppl_delete_Constraint (new_cstr);
140 /* Upper bound of the striped loop. */
142 ppl_Constraint_t new_cstr;
143 ppl_Linear_Expression_t expr;
145 ppl_new_Linear_Expression_with_dimension (&expr, dim);
146 ppl_set_coef (expr, strip, stride);
147 ppl_set_coef (expr, iter, -1);
148 ppl_set_inhomogeneous (expr, stride - 1);
150 ppl_new_Constraint (&new_cstr, expr, PPL_CONSTRAINT_TYPE_GREATER_OR_EQUAL);
151 ppl_delete_Linear_Expression (expr);
152 ppl_Polyhedron_add_constraint (res, new_cstr);
153 ppl_delete_Constraint (new_cstr);
156 /* Static scheduling for ITER level.
157 This is mandatory to keep the 2d + 1 canonical scheduling format. */
159 ppl_Constraint_t new_cstr;
160 ppl_Linear_Expression_t expr;
162 ppl_new_Linear_Expression_with_dimension (&expr, dim);
163 ppl_set_coef (expr, strip + 1, 1);
164 ppl_set_inhomogeneous (expr, 0);
166 ppl_new_Constraint (&new_cstr, expr, PPL_CONSTRAINT_TYPE_EQUAL);
167 ppl_delete_Linear_Expression (expr);
168 ppl_Polyhedron_add_constraint (res, new_cstr);
169 ppl_delete_Constraint (new_cstr);
175 /* Returns true when strip mining with STRIDE of the loop LST is
179 lst_strip_mine_profitable_p (lst_p lst, int stride)
181 mpz_t niter, strip_stride;
184 gcc_assert (LST_LOOP_P (lst));
185 mpz_init (strip_stride);
188 mpz_set_si (strip_stride, stride);
189 lst_niter_for_loop (lst, niter);
190 res = (mpz_cmp (niter, strip_stride) > 0);
192 mpz_clear (strip_stride);
197 /* Strip-mines all the loops of LST that are considered profitable to
198 strip-mine. Return true if it did strip-mined some loops. */
201 lst_do_strip_mine_loop (lst_p lst, int depth)
205 int stride = PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE);
211 if (LST_LOOP_P (lst))
215 FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
216 res |= lst_do_strip_mine_loop (l, depth);
222 return pbb_strip_mine_time_depth (pbb, psct_dynamic_dim (pbb, depth),
226 /* Strip-mines all the loops of LST that are considered profitable to
227 strip-mine. Return true if it did strip-mined some loops. */
230 lst_do_strip_mine (lst_p lst)
235 int stride = PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE);
239 || !LST_LOOP_P (lst))
242 FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
243 res |= lst_do_strip_mine (l);
245 depth = lst_depth (lst);
247 && lst_strip_mine_profitable_p (lst, stride))
249 res |= lst_do_strip_mine_loop (lst, lst_depth (lst));
250 lst_add_loop_under_loop (lst);
256 /* Strip mines all the loops in SCOP. Returns true when some loops
257 have been strip-mined. */
260 scop_do_strip_mine (scop_p scop)
262 return lst_do_strip_mine (SCOP_TRANSFORMED_SCHEDULE (scop));
265 /* Loop blocks all the loops in SCOP. Returns true when we manage to
269 scop_do_block (scop_p scop)
271 bool strip_mined = false;
272 bool interchanged = false;
274 store_scattering (scop);
276 strip_mined = lst_do_strip_mine (SCOP_TRANSFORMED_SCHEDULE (scop));
277 interchanged = scop_do_interchange (scop);
279 /* If we don't interchange loops, the strip mine alone will not be
280 profitable, and the transform is not a loop blocking: so revert
284 restore_scattering (scop);
287 else if (strip_mined && interchanged
288 && dump_file && (dump_flags & TDF_DETAILS))
289 fprintf (dump_file, "SCoP will be loop blocked.\n");
291 return strip_mined || interchanged;