/* Heuristics and transform for loop blocking and strip mining on polyhedral representation. Copyright (C) 2009 Free Software Foundation, Inc. Contributed by Sebastian Pop and Pranav Garg . 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 . */ #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 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 around PBB at DEPTH is profitable. */ static bool pbb_strip_mine_profitable_p (poly_bb_p pbb, graphite_dim_t depth, int stride) { mpz_t niter, strip_stride; bool res; mpz_init (strip_stride); mpz_init (niter); mpz_set_si (strip_stride, stride); pbb_number_of_iterations_at_time (pbb, psct_dynamic_dim (pbb, depth), niter); res = (mpz_cmp (niter, strip_stride) > 0); mpz_clear (strip_stride); mpz_clear (niter); return res; } /* Strip-mines all the loops of LST that are considered profitable to strip-mine. Return true if it did strip-mined some loops. */ static bool lst_do_strip_mine_loop (lst_p lst, int depth) { int i; lst_p l; int stride = PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE); poly_bb_p pbb; if (!lst) return false; if (LST_LOOP_P (lst)) { bool res = false; for (i = 0; VEC_iterate (lst_p, LST_SEQ (lst), i, l); i++) res |= lst_do_strip_mine_loop (l, depth); 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 that are considered profitable to strip-mine. Return true if it did strip-mined some loops. */ static bool lst_do_strip_mine (lst_p lst) { int i; lst_p l; bool res = false; int stride = PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE); int depth; if (!lst || !LST_LOOP_P (lst)) return false; for (i = 0; VEC_iterate (lst_p, LST_SEQ (lst), i, l); i++) res |= lst_do_strip_mine (l); depth = lst_depth (lst); if (depth >= 0 && pbb_strip_mine_profitable_p (LST_PBB (lst_find_first_pbb (lst)), depth, stride)) { res |= lst_do_strip_mine_loop (lst, lst_depth (lst)); lst_add_loop_under_loop (lst); } return res; } /* 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) { bool transform_done = false; store_scattering (scop); transform_done = lst_do_strip_mine (SCOP_TRANSFORMED_SCHEDULE (scop)); if (!transform_done) return false; if (!graphite_legal_transform (scop)) { restore_scattering (scop); return false; } return transform_done; } /* 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)); interchanged = scop_do_interchange (scop); /* If we don't interchange loops, then the strip mine is not profitable, and the transform is not a loop blocking. */ if (!interchanged || !graphite_legal_transform (scop)) { 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