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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /gcc/graphite-blocking.c
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diff --git a/gcc/graphite-blocking.c b/gcc/graphite-blocking.c
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+/* Heuristics and transform for loop blocking and strip mining on
+ polyhedral representation.
+
+ Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+ Contributed by Sebastian Pop <sebastian.pop@amd.com> and
+ Pranav Garg <pranav.garg2107@gmail.com>.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree-flow.h"
+#include "tree-dump.h"
+#include "cfgloop.h"
+#include "tree-chrec.h"
+#include "tree-data-ref.h"
+#include "sese.h"
+
+#ifdef HAVE_cloog
+#include "ppl_c.h"
+#include "graphite-ppl.h"
+#include "graphite-poly.h"
+
+
+/* Strip mines with a factor STRIDE the scattering (time) dimension
+ around PBB at depth TIME_DEPTH.
+
+ The following example comes from the wiki page:
+ http://gcc.gnu.org/wiki/Graphite/Strip_mine
+
+ The strip mine of a loop with a tile of 64 can be obtained with a
+ scattering function as follows:
+
+ $ cat ./albert_strip_mine.cloog
+ # language: C
+ c
+
+ # parameter {n | n >= 0}
+ 1 3
+ # n 1
+ 1 1 0
+ 1
+ n
+
+ 1 # Number of statements:
+
+ 1
+ # {i | 0 <= i <= n}
+ 2 4
+ # i n 1
+ 1 1 0 0
+ 1 -1 1 0
+
+ 0 0 0
+ 1
+ i
+
+ 1 # Scattering functions
+
+ 3 6
+ # NEW OLD i n 1
+ 1 -64 0 1 0 0
+ 1 64 0 -1 0 63
+ 0 0 1 -1 0 0
+
+ 1
+ NEW OLD
+
+ #the output of CLooG is like this:
+ #$ cloog ./albert_strip_mine.cloog
+ # for (NEW=0;NEW<=floord(n,64);NEW++) {
+ # for (OLD=max(64*NEW,0);OLD<=min(64*NEW+63,n);OLD++) {
+ # S1(i = OLD) ;
+ # }
+ # }
+*/
+
+static bool
+pbb_strip_mine_time_depth (poly_bb_p pbb, int time_depth, int stride)
+{
+ ppl_dimension_type iter, dim, strip;
+ ppl_Polyhedron_t res = PBB_TRANSFORMED_SCATTERING (pbb);
+ /* STRIP is the dimension that iterates with stride STRIDE. */
+ /* ITER is the dimension that enumerates single iterations inside
+ one strip that has at most STRIDE iterations. */
+ strip = time_depth;
+ iter = strip + 2;
+
+ psct_add_scattering_dimension (pbb, strip);
+ psct_add_scattering_dimension (pbb, strip + 1);
+
+ ppl_Polyhedron_space_dimension (res, &dim);
+
+ /* Lower bound of the striped loop. */
+ {
+ ppl_Constraint_t new_cstr;
+ ppl_Linear_Expression_t expr;
+
+ ppl_new_Linear_Expression_with_dimension (&expr, dim);
+ ppl_set_coef (expr, strip, -1 * stride);
+ ppl_set_coef (expr, iter, 1);
+
+ ppl_new_Constraint (&new_cstr, expr, PPL_CONSTRAINT_TYPE_GREATER_OR_EQUAL);
+ ppl_delete_Linear_Expression (expr);
+ ppl_Polyhedron_add_constraint (res, new_cstr);
+ ppl_delete_Constraint (new_cstr);
+ }
+
+ /* Upper bound of the striped loop. */
+ {
+ ppl_Constraint_t new_cstr;
+ ppl_Linear_Expression_t expr;
+
+ ppl_new_Linear_Expression_with_dimension (&expr, dim);
+ ppl_set_coef (expr, strip, stride);
+ ppl_set_coef (expr, iter, -1);
+ ppl_set_inhomogeneous (expr, stride - 1);
+
+ ppl_new_Constraint (&new_cstr, expr, PPL_CONSTRAINT_TYPE_GREATER_OR_EQUAL);
+ ppl_delete_Linear_Expression (expr);
+ ppl_Polyhedron_add_constraint (res, new_cstr);
+ ppl_delete_Constraint (new_cstr);
+ }
+
+ /* Static scheduling for ITER level.
+ This is mandatory to keep the 2d + 1 canonical scheduling format. */
+ {
+ ppl_Constraint_t new_cstr;
+ ppl_Linear_Expression_t expr;
+
+ ppl_new_Linear_Expression_with_dimension (&expr, dim);
+ ppl_set_coef (expr, strip + 1, 1);
+ ppl_set_inhomogeneous (expr, 0);
+
+ ppl_new_Constraint (&new_cstr, expr, PPL_CONSTRAINT_TYPE_EQUAL);
+ ppl_delete_Linear_Expression (expr);
+ ppl_Polyhedron_add_constraint (res, new_cstr);
+ ppl_delete_Constraint (new_cstr);
+ }
+
+ return true;
+}
+
+/* Returns true when strip mining with STRIDE of the loop LST is
+ profitable. */
+
+static bool
+lst_strip_mine_profitable_p (lst_p lst, int stride)
+{
+ mpz_t niter, strip_stride;
+ bool res;
+
+ gcc_assert (LST_LOOP_P (lst));
+ mpz_init (strip_stride);
+ mpz_init (niter);
+
+ mpz_set_si (strip_stride, stride);
+ lst_niter_for_loop (lst, niter);
+ res = (mpz_cmp (niter, strip_stride) > 0);
+
+ mpz_clear (strip_stride);
+ mpz_clear (niter);
+ return res;
+}
+
+/* Strip-mines all the loops of LST with STRIDE. Return true if it
+ did strip-mined some loops. */
+
+static bool
+lst_do_strip_mine_loop (lst_p lst, int depth, int stride)
+{
+ int i;
+ lst_p l;
+ poly_bb_p pbb;
+
+ if (!lst)
+ return false;
+
+ if (LST_LOOP_P (lst))
+ {
+ bool res = false;
+
+ FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
+ res |= lst_do_strip_mine_loop (l, depth, stride);
+
+ return res;
+ }
+
+ pbb = LST_PBB (lst);
+ return pbb_strip_mine_time_depth (pbb, psct_dynamic_dim (pbb, depth),
+ stride);
+}
+
+/* Strip-mines all the loops of LST with STRIDE. When STRIDE is zero,
+ read the stride from the PARAM_LOOP_BLOCK_TILE_SIZE. Return true
+ if it did strip-mined some loops.
+
+ Strip mining transforms a loop
+
+ | for (i = 0; i < N; i++)
+ | S (i);
+
+ into the following loop nest:
+
+ | for (k = 0; k < N; k += STRIDE)
+ | for (j = 0; j < STRIDE; j++)
+ | S (i = k + j);
+*/
+
+static bool
+lst_do_strip_mine (lst_p lst, int stride)
+{
+ int i;
+ lst_p l;
+ bool res = false;
+ int depth;
+
+ if (!stride)
+ stride = PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE);
+
+ if (!lst
+ || !LST_LOOP_P (lst))
+ return false;
+
+ FOR_EACH_VEC_ELT (lst_p, LST_SEQ (lst), i, l)
+ res |= lst_do_strip_mine (l, stride);
+
+ depth = lst_depth (lst);
+ if (depth >= 0
+ && lst_strip_mine_profitable_p (lst, stride))
+ {
+ res |= lst_do_strip_mine_loop (lst, lst_depth (lst), stride);
+ lst_add_loop_under_loop (lst);
+ }
+
+ return res;
+}
+
+/* Strip mines all the loops in SCOP. Returns true when some loops
+ have been strip-mined. */
+
+bool
+scop_do_strip_mine (scop_p scop, int stride)
+{
+ return lst_do_strip_mine (SCOP_TRANSFORMED_SCHEDULE (scop), stride);
+}
+
+/* Loop blocks all the loops in SCOP. Returns true when we manage to
+ block some loops. */
+
+bool
+scop_do_block (scop_p scop)
+{
+ bool strip_mined = false;
+ bool interchanged = false;
+
+ store_scattering (scop);
+
+ strip_mined = lst_do_strip_mine (SCOP_TRANSFORMED_SCHEDULE (scop), 0);
+ interchanged = scop_do_interchange (scop);
+
+ /* If we don't interchange loops, the strip mine alone will not be
+ profitable, and the transform is not a loop blocking: so revert
+ the transform. */
+ if (!interchanged)
+ {
+ restore_scattering (scop);
+ return false;
+ }
+ else if (strip_mined && interchanged
+ && dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "SCoP will be loop blocked.\n");
+
+ return strip_mined || interchanged;
+}
+
+#endif