gcc/loop-init.c

   1 /* Loop optimizer initialization routines and RTL loop optimization passes.
   2    Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 2, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to the Free
  18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301, USA.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tm.h"
  25 #include "rtl.h"
  26 #include "hard-reg-set.h"
  27 #include "obstack.h"
  28 #include "basic-block.h"
  29 #include "cfgloop.h"
  30 #include "cfglayout.h"
  31 #include "tree-pass.h"
  32 #include "timevar.h"
  33 #include "flags.h"
  34
  35 \f
  36 /* Initialize loop optimizer.  This is used by the tree and RTL loop
  37    optimizers.  FLAGS specify what properties to compute and/or ensure for
  38    loops.  */
  39
  40 struct loops *
  41 loop_optimizer_init (unsigned flags)
  42 {
  43   struct loops *loops = XCNEW (struct loops);
  44   edge e;
  45   edge_iterator ei;
  46   static bool first_time = true;
  47
  48   if (first_time)
  49     {
  50       first_time = false;
  51       init_set_costs ();
  52     }
  53
  54   /* Avoid annoying special cases of edges going to exit
  55      block.  */
  56
  57   for (ei = ei_start (EXIT_BLOCK_PTR->preds); (e = ei_safe_edge (ei)); )
  58     if ((e->flags & EDGE_FALLTHRU) && !single_succ_p (e->src))
  59       split_edge (e);
  60     else
  61       ei_next (&ei);
  62
  63   /* Find the loops.  */
  64
  65   if (flow_loops_find (loops) <= 1)
  66     {
  67       /* No loops.  */
  68       flow_loops_free (loops);
  69       free (loops);
  70
  71       return NULL;
  72     }
  73
  74   /* Not going to update these.  */
  75   free (loops->cfg.rc_order);
  76   loops->cfg.rc_order = NULL;
  77   free (loops->cfg.dfs_order);
  78   loops->cfg.dfs_order = NULL;
  79
  80   /* Create pre-headers.  */
  81   if (flags & LOOPS_HAVE_PREHEADERS)
  82     create_preheaders (loops, CP_SIMPLE_PREHEADERS);
  83
  84   /* Force all latches to have only single successor.  */
  85   if (flags & LOOPS_HAVE_SIMPLE_LATCHES)
  86     force_single_succ_latches (loops);
  87
  88   /* Mark irreducible loops.  */
  89   if (flags & LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
  90     mark_irreducible_loops (loops);
  91
  92   if (flags & LOOPS_HAVE_MARKED_SINGLE_EXITS)
  93     mark_single_exit_loops (loops);
  94
  95   /* Dump loops.  */
  96   flow_loops_dump (loops, dump_file, NULL, 1);
  97
  98 #ifdef ENABLE_CHECKING
  99   verify_dominators (CDI_DOMINATORS);
 100   verify_loop_structure (loops);
 101 #endif
 102
 103   return loops;
 104 }
 105
 106 /* Finalize loop optimizer.  */
 107 void
 108 loop_optimizer_finalize (struct loops *loops)
 109 {
 110   unsigned i;
 111
 112   if (!loops)
 113     return;
 114
 115   for (i = 1; i < loops->num; i++)
 116     if (loops->parray[i])
 117       free_simple_loop_desc (loops->parray[i]);
 118
 119   /* Clean up.  */
 120   flow_loops_free (loops);
 121   free (loops);
 122
 123   /* Checking.  */
 124 #ifdef ENABLE_CHECKING
 125   verify_flow_info ();
 126 #endif
 127 }
 128
 129 \f
 130 /* Gate for the RTL loop superpass.  The actual passes are subpasses.
 131    See passes.c for more on that.  */
 132
 133 static bool
 134 gate_handle_loop2 (void)
 135 {
 136   return (optimize > 0 && flag_loop_optimize2
 137           && (flag_move_loop_invariants
 138               || flag_unswitch_loops
 139               || flag_peel_loops
 140               || flag_unroll_loops
 141               || flag_branch_on_count_reg));
 142 }
 143
 144 struct tree_opt_pass pass_loop2 =
 145 {
 146   "loop2",                              /* name */
 147   gate_handle_loop2,                    /* gate */
 148   NULL,                                 /* execute */
 149   NULL,                                 /* sub */
 150   NULL,                                 /* next */
 151   0,                                    /* static_pass_number */
 152   TV_LOOP,                              /* tv_id */
 153   0,                                    /* properties_required */
 154   0,                                    /* properties_provided */
 155   0,                                    /* properties_destroyed */
 156   0,                                    /* todo_flags_start */
 157   TODO_dump_func |
 158   TODO_ggc_collect,                     /* todo_flags_finish */
 159   'L'                                   /* letter */
 160 };
 161
 162 \f
 163 /* Initialization of the RTL loop passes.  */
 164 static void
 165 rtl_loop_init (void)
 166 {
 167   if (dump_file)
 168     dump_flow_info (dump_file);
 169
 170   /* Initialize structures for layout changes.  */
 171   cfg_layout_initialize (0);
 172
 173   current_loops = loop_optimizer_init (LOOPS_NORMAL);
 174 }
 175
 176 struct tree_opt_pass pass_rtl_loop_init =
 177 {
 178   "loop2_init",                           /* name */
 179   NULL,                                 /* gate */
 180   rtl_loop_init,                        /* execute */
 181   NULL,                                 /* sub */
 182   NULL,                                 /* next */
 183   0,                                    /* static_pass_number */
 184   TV_LOOP,                              /* tv_id */
 185   0,                                    /* properties_required */
 186   0,                                    /* properties_provided */
 187   0,                                    /* properties_destroyed */
 188   0,                                    /* todo_flags_start */
 189   TODO_dump_func,                       /* todo_flags_finish */
 190   'L'                                   /* letter */
 191 };
 192
 193 \f
 194 /* Finalization of the RTL loop passes.  */
 195 static void
 196 rtl_loop_done (void)
 197 {
 198   basic_block bb;
 199
 200   if (current_loops)
 201     loop_optimizer_finalize (current_loops);
 202
 203   free_dominance_info (CDI_DOMINATORS);
 204
 205   /* Finalize layout changes.  */
 206   FOR_EACH_BB (bb)
 207     if (bb->next_bb != EXIT_BLOCK_PTR)
 208       bb->aux = bb->next_bb;
 209   cfg_layout_finalize ();
 210
 211   cleanup_cfg (CLEANUP_EXPENSIVE);
 212   delete_trivially_dead_insns (get_insns (), max_reg_num ());
 213   reg_scan (get_insns (), max_reg_num ());
 214   if (dump_file)
 215     dump_flow_info (dump_file);
 216
 217   current_loops = NULL;
 218 }
 219
 220 struct tree_opt_pass pass_rtl_loop_done =
 221 {
 222   "loop2_done",                          /* name */
 223   NULL,                                 /* gate */
 224   rtl_loop_done,                        /* execute */
 225   NULL,                                 /* sub */
 226   NULL,                                 /* next */
 227   0,                                    /* static_pass_number */
 228   TV_LOOP,                              /* tv_id */
 229   0,                                    /* properties_required */
 230   0,                                    /* properties_provided */
 231   0,                                    /* properties_destroyed */
 232   0,                                    /* todo_flags_start */
 233   TODO_dump_func,                       /* todo_flags_finish */
 234   'L'                                   /* letter */
 235 };
 236
 237 \f
 238 /* Loop invariant code motion.  */
 239 static bool
 240 gate_rtl_move_loop_invariants (void)
 241 {
 242   return flag_move_loop_invariants;
 243 }
 244
 245 static void
 246 rtl_move_loop_invariants (void)
 247 {
 248   if (current_loops)
 249     move_loop_invariants (current_loops);
 250 }
 251
 252 struct tree_opt_pass pass_rtl_move_loop_invariants =
 253 {
 254   "loop2_invariant",                     /* name */
 255   gate_rtl_move_loop_invariants,        /* gate */
 256   rtl_move_loop_invariants,             /* execute */
 257   NULL,                                 /* sub */
 258   NULL,                                 /* next */
 259   0,                                    /* static_pass_number */
 260   TV_LOOP,                              /* tv_id */
 261   0,                                    /* properties_required */
 262   0,                                    /* properties_provided */
 263   0,                                    /* properties_destroyed */
 264   0,                                    /* todo_flags_start */
 265   TODO_dump_func,                       /* todo_flags_finish */
 266   'L'                                   /* letter */
 267 };
 268
 269 \f
 270 /* Loop unswitching for RTL.  */
 271 static bool
 272 gate_rtl_unswitch (void)
 273 {
 274   return flag_unswitch_loops;
 275 }
 276
 277 static void
 278 rtl_unswitch (void)
 279 {
 280   if (current_loops)
 281     unswitch_loops (current_loops);
 282 }
 283
 284 struct tree_opt_pass pass_rtl_unswitch =
 285 {
 286   "loop2_unswitch",                      /* name */
 287   gate_rtl_unswitch,                    /* gate */
 288   rtl_unswitch,                         /* execute */
 289   NULL,                                 /* sub */
 290   NULL,                                 /* next */
 291   0,                                    /* static_pass_number */
 292   TV_LOOP,                              /* tv_id */
 293   0,                                    /* properties_required */
 294   0,                                    /* properties_provided */
 295   0,                                    /* properties_destroyed */
 296   0,                                    /* todo_flags_start */
 297   TODO_dump_func,                       /* todo_flags_finish */
 298   'L'                                   /* letter */
 299 };
 300
 301 \f
 302 /* Loop unswitching for RTL.  */
 303 static bool
 304 gate_rtl_unroll_and_peel_loops (void)
 305 {
 306   return (flag_peel_loops || flag_unroll_loops || flag_unroll_all_loops);
 307 }
 308
 309 static void
 310 rtl_unroll_and_peel_loops (void)
 311 {
 312   if (current_loops)
 313     {
 314       int flags = 0;
 315
 316       if (flag_peel_loops)
 317         flags |= UAP_PEEL;
 318       if (flag_unroll_loops)
 319         flags |= UAP_UNROLL;
 320       if (flag_unroll_all_loops)
 321         flags |= UAP_UNROLL_ALL;
 322
 323       unroll_and_peel_loops (current_loops, flags);
 324     }
 325 }
 326
 327 struct tree_opt_pass pass_rtl_unroll_and_peel_loops =
 328 {
 329   "loop2_unroll",                        /* name */
 330   gate_rtl_unroll_and_peel_loops,       /* gate */
 331   rtl_unroll_and_peel_loops,            /* execute */
 332   NULL,                                 /* sub */
 333   NULL,                                 /* next */
 334   0,                                    /* static_pass_number */
 335   TV_LOOP,                              /* tv_id */
 336   0,                                    /* properties_required */
 337   0,                                    /* properties_provided */
 338   0,                                    /* properties_destroyed */
 339   0,                                    /* todo_flags_start */
 340   TODO_dump_func,                       /* todo_flags_finish */
 341   'L'                                   /* letter */
 342 };
 343
 344 \f
 345 /* The doloop optimization.  */
 346 static bool
 347 gate_rtl_doloop (void)
 348 {
 349 #ifdef HAVE_doloop_end
 350   return (flag_branch_on_count_reg && HAVE_doloop_end);
 351 #else
 352   return 0;
 353 #endif
 354 }
 355
 356 static void
 357 rtl_doloop (void)
 358 {
 359 #ifdef HAVE_doloop_end
 360   if (current_loops)
 361     doloop_optimize_loops (current_loops);
 362 #endif
 363 }
 364
 365 struct tree_opt_pass pass_rtl_doloop =
 366 {
 367   "loop2_doloop",                        /* name */
 368   gate_rtl_doloop,                      /* gate */
 369   rtl_doloop,                           /* execute */
 370   NULL,                                 /* sub */
 371   NULL,                                 /* next */
 372   0,                                    /* static_pass_number */
 373   TV_LOOP,                              /* tv_id */
 374   0,                                    /* properties_required */
 375   0,                                    /* properties_provided */
 376   0,                                    /* properties_destroyed */
 377   0,                                    /* todo_flags_start */
 378   TODO_dump_func,                       /* todo_flags_finish */
 379   'L'                                   /* letter */
 380 };
 381