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/* Heuristics and transform for loop blocking and strip mining on
polyhedral representation.
Copyright (C) 2009 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 "tm.h"
#include "ggc.h"
#include "tree.h"
#include "rtl.h"
#include "output.h"
#include "basic-block.h"
#include "diagnostic.h"
#include "tree-flow.h"
#include "toplev.h"
#include "tree-dump.h"
#include "timevar.h"
#include "cfgloop.h"
#include "tree-chrec.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "tree-pass.h"
#include "domwalk.h"
#include "value-prof.h"
#include "pointer-set.h"
#include "gimple.h"
#include "params.h"
#ifdef HAVE_cloog
#include "cloog/cloog.h"
#include "ppl_c.h"
#include "sese.h"
#include "graphite-ppl.h"
#include "graphite.h"
#include "graphite-poly.h"
/* Strip mines with a factor STRIDE the loop around PBB at depth
LOOP_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_loop_depth (poly_bb_p pbb, int loop_depth, int stride)
{
ppl_dimension_type iter, dim;
ppl_Polyhedron_t res = PBB_TRANSFORMED_SCATTERING (pbb);
ppl_dimension_type strip = psct_scattering_dim_for_loop_depth (pbb,
loop_depth);
psct_add_scattering_dimension (pbb, strip);
iter = psct_iterator_dim (pbb, loop_depth);
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);
}
return true;
}
/* Returns true when strip mining with STRIDE of the loop around PBB
at depth LOOP_DEPTH is profitable. */
static bool
pbb_strip_mine_profitable_p (poly_bb_p pbb,
graphite_dim_t loop_depth,
int stride)
{
Value niter, strip_stride;
bool res;
value_init (strip_stride);
value_init (niter);
value_set_si (strip_stride, stride);
pbb_number_of_iterations (pbb, loop_depth, niter);
res = value_gt (niter, strip_stride);
value_clear (strip_stride);
value_clear (niter);
return res;
}
/* Strip mines all the loops around PBB. Nothing profitable in all this:
this is just a driver function. */
static bool
pbb_do_strip_mine (poly_bb_p pbb)
{
graphite_dim_t loop_depth;
int stride = 64;
bool transform_done = false;
for (loop_depth = 0; loop_depth < pbb_dim_iter_domain (pbb); loop_depth++)
if (pbb_strip_mine_profitable_p (pbb, loop_depth, stride))
transform_done |= pbb_strip_mine_loop_depth (pbb, loop_depth, stride);
return transform_done;
}
/* Strip mines all the loops in SCOP. Nothing profitable in all this:
this is just a driver function. */
bool
scop_do_strip_mine (scop_p scop)
{
poly_bb_p pbb;
int i;
bool transform_done = false;
store_scattering (scop);
for (i = 0; VEC_iterate (poly_bb_p, SCOP_BBS (scop), i, pbb); i++)
transform_done |= pbb_do_strip_mine (pbb);
if (!transform_done)
return false;
if (!graphite_legal_transform (scop))
{
restore_scattering (scop);
return false;
}
return true;
}
#endif
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