gcc/loop-init.c

   1 /* Loop optimizer initialization routines and RTL loop optimization passes.
   2    Copyright (C) 2002-2014 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 3, 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 COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "rtl.h"
  25 #include "tree.h"
  26 #include "regs.h"
  27 #include "obstack.h"
  28 #include "basic-block.h"
  29 #include "cfgloop.h"
  30 #include "tree-pass.h"
  31 #include "flags.h"
  32 #include "df.h"
  33 #include "ggc.h"
  34 #include "tree-ssa-loop-niter.h"
  35
  36 \f
  37 /* Apply FLAGS to the loop state.  */
  38
  39 static void
  40 apply_loop_flags (unsigned flags)
  41 {
  42   if (flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
  43     {
  44       /* If the loops may have multiple latches, we cannot canonicalize
  45          them further (and most of the loop manipulation functions will
  46          not work).  However, we avoid modifying cfg, which some
  47          passes may want.  */
  48       gcc_assert ((flags & ~(LOOPS_MAY_HAVE_MULTIPLE_LATCHES
  49                              | LOOPS_HAVE_RECORDED_EXITS)) == 0);
  50       loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
  51     }
  52   else
  53     disambiguate_loops_with_multiple_latches ();
  54
  55   /* Create pre-headers.  */
  56   if (flags & LOOPS_HAVE_PREHEADERS)
  57     {
  58       int cp_flags = CP_SIMPLE_PREHEADERS;
  59
  60       if (flags & LOOPS_HAVE_FALLTHRU_PREHEADERS)
  61         cp_flags |= CP_FALLTHRU_PREHEADERS;
  62
  63       create_preheaders (cp_flags);
  64     }
  65
  66   /* Force all latches to have only single successor.  */
  67   if (flags & LOOPS_HAVE_SIMPLE_LATCHES)
  68     force_single_succ_latches ();
  69
  70   /* Mark irreducible loops.  */
  71   if (flags & LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
  72     mark_irreducible_loops ();
  73
  74   if (flags & LOOPS_HAVE_RECORDED_EXITS)
  75     record_loop_exits ();
  76 }
  77
  78 /* Initialize loop structures.  This is used by the tree and RTL loop
  79    optimizers.  FLAGS specify what properties to compute and/or ensure for
  80    loops.  */
  81
  82 void
  83 loop_optimizer_init (unsigned flags)
  84 {
  85   timevar_push (TV_LOOP_INIT);
  86
  87   if (!current_loops)
  88     {
  89       gcc_assert (!(cfun->curr_properties & PROP_loops));
  90
  91       /* Find the loops.  */
  92       current_loops = flow_loops_find (NULL);
  93     }
  94   else
  95     {
  96       bool recorded_exits = loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS);
  97       bool needs_fixup = loops_state_satisfies_p (LOOPS_NEED_FIXUP);
  98
  99       gcc_assert (cfun->curr_properties & PROP_loops);
 100
 101       /* Ensure that the dominators are computed, like flow_loops_find does.  */
 102       calculate_dominance_info (CDI_DOMINATORS);
 103
 104 #ifdef ENABLE_CHECKING
 105       if (!needs_fixup)
 106         verify_loop_structure ();
 107 #endif
 108
 109       /* Clear all flags.  */
 110       if (recorded_exits)
 111         release_recorded_exits ();
 112       loops_state_clear (~0U);
 113
 114       if (needs_fixup)
 115         {
 116           /* Apply LOOPS_MAY_HAVE_MULTIPLE_LATCHES early as fix_loop_structure
 117              re-applies flags.  */
 118           loops_state_set (flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
 119           fix_loop_structure (NULL);
 120         }
 121     }
 122
 123   /* Apply flags to loops.  */
 124   apply_loop_flags (flags);
 125
 126   /* Dump loops.  */
 127   flow_loops_dump (dump_file, NULL, 1);
 128
 129 #ifdef ENABLE_CHECKING
 130   verify_loop_structure ();
 131 #endif
 132
 133   timevar_pop (TV_LOOP_INIT);
 134 }
 135
 136 /* Finalize loop structures.  */
 137
 138 void
 139 loop_optimizer_finalize (void)
 140 {
 141   struct loop *loop;
 142   basic_block bb;
 143
 144   timevar_push (TV_LOOP_FINI);
 145
 146   if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
 147     release_recorded_exits ();
 148
 149   free_numbers_of_iterations_estimates ();
 150
 151   /* If we should preserve loop structure, do not free it but clear
 152      flags that advanced properties are there as we are not preserving
 153      that in full.  */
 154   if (cfun->curr_properties & PROP_loops)
 155     {
 156       loops_state_clear (LOOP_CLOSED_SSA
 157                          | LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS
 158                          | LOOPS_HAVE_PREHEADERS
 159                          | LOOPS_HAVE_SIMPLE_LATCHES
 160                          | LOOPS_HAVE_FALLTHRU_PREHEADERS);
 161       loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
 162       goto loop_fini_done;
 163     }
 164
 165   gcc_assert (current_loops != NULL);
 166
 167   FOR_EACH_LOOP (loop, 0)
 168     free_simple_loop_desc (loop);
 169
 170   /* Clean up.  */
 171   flow_loops_free (current_loops);
 172   ggc_free (current_loops);
 173   current_loops = NULL;
 174
 175   FOR_ALL_BB_FN (bb, cfun)
 176     {
 177       bb->loop_father = NULL;
 178     }
 179
 180 loop_fini_done:
 181   timevar_pop (TV_LOOP_FINI);
 182 }
 183
 184 /* The structure of loops might have changed.  Some loops might get removed
 185    (and their headers and latches were set to NULL), loop exists might get
 186    removed (thus the loop nesting may be wrong), and some blocks and edges
 187    were changed (so the information about bb --> loop mapping does not have
 188    to be correct).  But still for the remaining loops the header dominates
 189    the latch, and loops did not get new subloops (new loops might possibly
 190    get created, but we are not interested in them).  Fix up the mess.
 191
 192    If CHANGED_BBS is not NULL, basic blocks whose loop depth has changed are
 193    marked in it.
 194
 195    Returns the number of new discovered loops.  */
 196
 197 unsigned
 198 fix_loop_structure (bitmap changed_bbs)
 199 {
 200   basic_block bb;
 201   int record_exits = 0;
 202   struct loop *loop;
 203   unsigned old_nloops, i;
 204
 205   timevar_push (TV_LOOP_INIT);
 206
 207   /* We need exact and fast dominance info to be available.  */
 208   gcc_assert (dom_info_state (CDI_DOMINATORS) == DOM_OK);
 209
 210   if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
 211     {
 212       release_recorded_exits ();
 213       record_exits = LOOPS_HAVE_RECORDED_EXITS;
 214     }
 215
 216   /* Remember the depth of the blocks in the loop hierarchy, so that we can
 217      recognize blocks whose loop nesting relationship has changed.  */
 218   if (changed_bbs)
 219     FOR_EACH_BB_FN (bb, cfun)
 220       bb->aux = (void *) (size_t) loop_depth (bb->loop_father);
 221
 222   /* Remove the dead loops from structures.  We start from the innermost
 223      loops, so that when we remove the loops, we know that the loops inside
 224      are preserved, and do not waste time relinking loops that will be
 225      removed later.  */
 226   FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
 227     {
 228       /* Detect the case that the loop is no longer present even though
 229          it wasn't marked for removal.
 230          ???  If we do that we can get away with not marking loops for
 231          removal at all.  And possibly avoid some spurious removals.  */
 232       if (loop->header
 233           && bb_loop_header_p (loop->header))
 234         continue;
 235
 236       if (dump_file && (dump_flags & TDF_DETAILS))
 237         fprintf (dump_file, "fix_loop_structure: removing loop %d\n",
 238                  loop->num);
 239
 240       while (loop->inner)
 241         {
 242           struct loop *ploop = loop->inner;
 243           flow_loop_tree_node_remove (ploop);
 244           flow_loop_tree_node_add (loop_outer (loop), ploop);
 245         }
 246
 247       /* Remove the loop.  */
 248       if (loop->header)
 249         loop->former_header = loop->header;
 250       else
 251         gcc_assert (loop->former_header != NULL);
 252       loop->header = NULL;
 253       flow_loop_tree_node_remove (loop);
 254     }
 255
 256   /* Remember the number of loops so we can return how many new loops
 257      flow_loops_find discovered.  */
 258   old_nloops = number_of_loops (cfun);
 259
 260   /* Re-compute loop structure in-place.  */
 261   flow_loops_find (current_loops);
 262
 263   /* Mark the blocks whose loop has changed.  */
 264   if (changed_bbs)
 265     {
 266       FOR_EACH_BB_FN (bb, cfun)
 267         {
 268           if ((void *) (size_t) loop_depth (bb->loop_father) != bb->aux)
 269             bitmap_set_bit (changed_bbs, bb->index);
 270
 271           bb->aux = NULL;
 272         }
 273     }
 274
 275   /* Finally free deleted loops.  */
 276   FOR_EACH_VEC_ELT (*get_loops (cfun), i, loop)
 277     if (loop && loop->header == NULL)
 278       {
 279         if (dump_file
 280             && ((unsigned) loop->former_header->index
 281                 < basic_block_info_for_fn (cfun)->length ()))
 282           {
 283             basic_block former_header
 284               = BASIC_BLOCK_FOR_FN (cfun, loop->former_header->index);
 285             /* If the old header still exists we want to check if the
 286                original loop is re-discovered or the old header is now
 287                part of a newly discovered loop.
 288                In both cases we should have avoided removing the loop.  */
 289             if (former_header == loop->former_header)
 290               {
 291                 if (former_header->loop_father->header == former_header)
 292                   fprintf (dump_file, "fix_loop_structure: rediscovered "
 293                            "removed loop %d as loop %d with old header %d\n",
 294                            loop->num, former_header->loop_father->num,
 295                            former_header->index);
 296                 else if ((unsigned) former_header->loop_father->num
 297                          >= old_nloops)
 298                   fprintf (dump_file, "fix_loop_structure: header %d of "
 299                            "removed loop %d is part of the newly "
 300                            "discovered loop %d with header %d\n",
 301                            former_header->index, loop->num,
 302                            former_header->loop_father->num,
 303                            former_header->loop_father->header->index);
 304               }
 305           }
 306         (*get_loops (cfun))[i] = NULL;
 307         flow_loop_free (loop);
 308       }
 309
 310   loops_state_clear (LOOPS_NEED_FIXUP);
 311
 312   /* Apply flags to loops.  */
 313   apply_loop_flags (current_loops->state | record_exits);
 314
 315 #ifdef ENABLE_CHECKING
 316   verify_loop_structure ();
 317 #endif
 318
 319   timevar_pop (TV_LOOP_INIT);
 320
 321   return number_of_loops (cfun) - old_nloops;
 322 }
 323 \f
 324 /* The RTL loop superpass.  The actual passes are subpasses.  See passes.c for
 325    more on that.  */
 326
 327 namespace {
 328
 329 const pass_data pass_data_loop2 =
 330 {
 331   RTL_PASS, /* type */
 332   "loop2", /* name */
 333   OPTGROUP_LOOP, /* optinfo_flags */
 334   TV_LOOP, /* tv_id */
 335   0, /* properties_required */
 336   0, /* properties_provided */
 337   0, /* properties_destroyed */
 338   0, /* todo_flags_start */
 339   0, /* todo_flags_finish */
 340 };
 341
 342 class pass_loop2 : public rtl_opt_pass
 343 {
 344 public:
 345   pass_loop2 (gcc::context *ctxt)
 346     : rtl_opt_pass (pass_data_loop2, ctxt)
 347   {}
 348
 349   /* opt_pass methods: */
 350   virtual bool gate (function *);
 351
 352 }; // class pass_loop2
 353
 354 bool
 355 pass_loop2::gate (function *fun)
 356 {
 357   if (optimize > 0
 358       && (flag_move_loop_invariants
 359           || flag_unswitch_loops
 360           || flag_unroll_loops
 361 #ifdef HAVE_doloop_end
 362           || (flag_branch_on_count_reg && HAVE_doloop_end)
 363 #endif
 364       ))
 365     return true;
 366   else
 367     {
 368       /* No longer preserve loops, remove them now.  */
 369       fun->curr_properties &= ~PROP_loops;
 370       if (current_loops)
 371         loop_optimizer_finalize ();
 372       return false;
 373     }
 374 }
 375
 376 } // anon namespace
 377
 378 rtl_opt_pass *
 379 make_pass_loop2 (gcc::context *ctxt)
 380 {
 381   return new pass_loop2 (ctxt);
 382 }
 383
 384 \f
 385 /* Initialization of the RTL loop passes.  */
 386 static unsigned int
 387 rtl_loop_init (void)
 388 {
 389   gcc_assert (current_ir_type () == IR_RTL_CFGLAYOUT);
 390
 391   if (dump_file)
 392     {
 393       dump_reg_info (dump_file);
 394       dump_flow_info (dump_file, dump_flags);
 395     }
 396
 397   loop_optimizer_init (LOOPS_NORMAL);
 398   return 0;
 399 }
 400
 401 namespace {
 402
 403 const pass_data pass_data_rtl_loop_init =
 404 {
 405   RTL_PASS, /* type */
 406   "loop2_init", /* name */
 407   OPTGROUP_LOOP, /* optinfo_flags */
 408   TV_LOOP, /* tv_id */
 409   0, /* properties_required */
 410   0, /* properties_provided */
 411   0, /* properties_destroyed */
 412   0, /* todo_flags_start */
 413   0, /* todo_flags_finish */
 414 };
 415
 416 class pass_rtl_loop_init : public rtl_opt_pass
 417 {
 418 public:
 419   pass_rtl_loop_init (gcc::context *ctxt)
 420     : rtl_opt_pass (pass_data_rtl_loop_init, ctxt)
 421   {}
 422
 423   /* opt_pass methods: */
 424   virtual unsigned int execute (function *) { return rtl_loop_init (); }
 425
 426 }; // class pass_rtl_loop_init
 427
 428 } // anon namespace
 429
 430 rtl_opt_pass *
 431 make_pass_rtl_loop_init (gcc::context *ctxt)
 432 {
 433   return new pass_rtl_loop_init (ctxt);
 434 }
 435
 436 \f
 437 /* Finalization of the RTL loop passes.  */
 438
 439 namespace {
 440
 441 const pass_data pass_data_rtl_loop_done =
 442 {
 443   RTL_PASS, /* type */
 444   "loop2_done", /* name */
 445   OPTGROUP_LOOP, /* optinfo_flags */
 446   TV_LOOP, /* tv_id */
 447   0, /* properties_required */
 448   0, /* properties_provided */
 449   PROP_loops, /* properties_destroyed */
 450   0, /* todo_flags_start */
 451   0, /* todo_flags_finish */
 452 };
 453
 454 class pass_rtl_loop_done : public rtl_opt_pass
 455 {
 456 public:
 457   pass_rtl_loop_done (gcc::context *ctxt)
 458     : rtl_opt_pass (pass_data_rtl_loop_done, ctxt)
 459   {}
 460
 461   /* opt_pass methods: */
 462   virtual unsigned int execute (function *);
 463
 464 }; // class pass_rtl_loop_done
 465
 466 unsigned int
 467 pass_rtl_loop_done::execute (function *fun)
 468 {
 469   /* No longer preserve loops, remove them now.  */
 470   fun->curr_properties &= ~PROP_loops;
 471   loop_optimizer_finalize ();
 472   free_dominance_info (CDI_DOMINATORS);
 473
 474   cleanup_cfg (0);
 475   if (dump_file)
 476     {
 477       dump_reg_info (dump_file);
 478       dump_flow_info (dump_file, dump_flags);
 479     }
 480
 481   return 0;
 482 }
 483
 484 } // anon namespace
 485
 486 rtl_opt_pass *
 487 make_pass_rtl_loop_done (gcc::context *ctxt)
 488 {
 489   return new pass_rtl_loop_done (ctxt);
 490 }
 491
 492 \f
 493 /* Loop invariant code motion.  */
 494
 495 namespace {
 496
 497 const pass_data pass_data_rtl_move_loop_invariants =
 498 {
 499   RTL_PASS, /* type */
 500   "loop2_invariant", /* name */
 501   OPTGROUP_LOOP, /* optinfo_flags */
 502   TV_LOOP_MOVE_INVARIANTS, /* tv_id */
 503   0, /* properties_required */
 504   0, /* properties_provided */
 505   0, /* properties_destroyed */
 506   0, /* todo_flags_start */
 507   ( TODO_df_verify | TODO_df_finish ), /* todo_flags_finish */
 508 };
 509
 510 class pass_rtl_move_loop_invariants : public rtl_opt_pass
 511 {
 512 public:
 513   pass_rtl_move_loop_invariants (gcc::context *ctxt)
 514     : rtl_opt_pass (pass_data_rtl_move_loop_invariants, ctxt)
 515   {}
 516
 517   /* opt_pass methods: */
 518   virtual bool gate (function *) { return flag_move_loop_invariants; }
 519   virtual unsigned int execute (function *fun)
 520     {
 521       if (number_of_loops (fun) > 1)
 522         move_loop_invariants ();
 523       return 0;
 524     }
 525
 526 }; // class pass_rtl_move_loop_invariants
 527
 528 } // anon namespace
 529
 530 rtl_opt_pass *
 531 make_pass_rtl_move_loop_invariants (gcc::context *ctxt)
 532 {
 533   return new pass_rtl_move_loop_invariants (ctxt);
 534 }
 535
 536 \f
 537 namespace {
 538
 539 const pass_data pass_data_rtl_unroll_loops =
 540 {
 541   RTL_PASS, /* type */
 542   "loop2_unroll", /* name */
 543   OPTGROUP_LOOP, /* optinfo_flags */
 544   TV_LOOP_UNROLL, /* tv_id */
 545   0, /* properties_required */
 546   0, /* properties_provided */
 547   0, /* properties_destroyed */
 548   0, /* todo_flags_start */
 549   0, /* todo_flags_finish */
 550 };
 551
 552 class pass_rtl_unroll_loops : public rtl_opt_pass
 553 {
 554 public:
 555   pass_rtl_unroll_loops (gcc::context *ctxt)
 556     : rtl_opt_pass (pass_data_rtl_unroll_loops, ctxt)
 557   {}
 558
 559   /* opt_pass methods: */
 560   virtual bool gate (function *)
 561     {
 562       return (flag_peel_loops || flag_unroll_loops || flag_unroll_all_loops);
 563     }
 564
 565   virtual unsigned int execute (function *);
 566
 567 }; // class pass_rtl_unroll_loops
 568
 569 unsigned int
 570 pass_rtl_unroll_loops::execute (function *fun)
 571 {
 572   if (number_of_loops (fun) > 1)
 573     {
 574       int flags = 0;
 575       if (dump_file)
 576         df_dump (dump_file);
 577
 578       if (flag_unroll_loops)
 579         flags |= UAP_UNROLL;
 580       if (flag_unroll_all_loops)
 581         flags |= UAP_UNROLL_ALL;
 582
 583       unroll_loops (flags);
 584     }
 585   return 0;
 586 }
 587
 588 } // anon namespace
 589
 590 rtl_opt_pass *
 591 make_pass_rtl_unroll_loops (gcc::context *ctxt)
 592 {
 593   return new pass_rtl_unroll_loops (ctxt);
 594 }
 595
 596 \f
 597 namespace {
 598
 599 const pass_data pass_data_rtl_doloop =
 600 {
 601   RTL_PASS, /* type */
 602   "loop2_doloop", /* name */
 603   OPTGROUP_LOOP, /* optinfo_flags */
 604   TV_LOOP_DOLOOP, /* tv_id */
 605   0, /* properties_required */
 606   0, /* properties_provided */
 607   0, /* properties_destroyed */
 608   0, /* todo_flags_start */
 609   0, /* todo_flags_finish */
 610 };
 611
 612 class pass_rtl_doloop : public rtl_opt_pass
 613 {
 614 public:
 615   pass_rtl_doloop (gcc::context *ctxt)
 616     : rtl_opt_pass (pass_data_rtl_doloop, ctxt)
 617   {}
 618
 619   /* opt_pass methods: */
 620   virtual bool gate (function *);
 621   virtual unsigned int execute (function *);
 622
 623 }; // class pass_rtl_doloop
 624
 625 bool
 626 pass_rtl_doloop::gate (function *)
 627 {
 628 #ifdef HAVE_doloop_end
 629   return (flag_branch_on_count_reg && HAVE_doloop_end);
 630 #else
 631   return false;
 632 #endif
 633 }
 634
 635 unsigned int
 636 pass_rtl_doloop::execute (function *fun ATTRIBUTE_UNUSED)
 637 {
 638 #ifdef HAVE_doloop_end
 639   if (number_of_loops (fun) > 1)
 640     doloop_optimize_loops ();
 641 #endif
 642   return 0;
 643 }
 644
 645 } // anon namespace
 646
 647 rtl_opt_pass *
 648 make_pass_rtl_doloop (gcc::context *ctxt)
 649 {
 650   return new pass_rtl_doloop (ctxt);
 651 }