2 Copyright (C) 2004-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 3, or (at your option) any
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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/>. */
22 #include "coretypes.h"
31 #include "hard-reg-set.h"
34 #include "dominance.h"
36 #include "basic-block.h"
37 #include "tree-ssa-alias.h"
38 #include "internal-fn.h"
39 #include "gimple-expr.h"
43 #include "gimple-ssa.h"
45 #include "tree-phinodes.h"
46 #include "ssa-iterators.h"
47 #include "tree-ssa-loop-niter.h"
48 #include "tree-ssa-loop.h"
49 #include "tree-into-ssa.h"
52 #include "tree-pass.h"
53 #include "tree-inline.h"
55 /* This file implements the loop unswitching, i.e. transformation of loops like
68 where inv is the loop invariant, into
87 Inv is considered invariant iff the values it compares are both invariant;
88 tree-ssa-loop-im.c ensures that all the suitable conditions are in this
91 static struct loop
*tree_unswitch_loop (struct loop
*, basic_block
, tree
);
92 static bool tree_unswitch_single_loop (struct loop
*, int);
93 static tree
tree_may_unswitch_on (basic_block
, struct loop
*);
95 /* Main entry point. Perform loop unswitching on all suitable loops. */
98 tree_ssa_unswitch_loops (void)
101 bool changed
= false;
102 HOST_WIDE_INT iterations
;
104 /* Go through inner loops (only original ones). */
105 FOR_EACH_LOOP (loop
, LI_ONLY_INNERMOST
)
107 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
108 fprintf (dump_file
, ";; Considering loop %d\n", loop
->num
);
110 /* Do not unswitch in cold regions. */
111 if (optimize_loop_for_size_p (loop
))
113 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
114 fprintf (dump_file
, ";; Not unswitching cold loops\n");
118 /* The loop should not be too large, to limit code growth. */
119 if (tree_num_loop_insns (loop
, &eni_size_weights
)
120 > (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS
))
122 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
123 fprintf (dump_file
, ";; Not unswitching, loop too big\n");
127 /* If the loop is not expected to iterate, there is no need
129 iterations
= estimated_loop_iterations_int (loop
);
130 if (iterations
>= 0 && iterations
<= 1)
132 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
133 fprintf (dump_file
, ";; Not unswitching, loop is not expected to iterate\n");
137 changed
|= tree_unswitch_single_loop (loop
, 0);
141 return TODO_cleanup_cfg
;
145 /* Checks whether we can unswitch LOOP on condition at end of BB -- one of its
146 basic blocks (for what it means see comments below). */
149 tree_may_unswitch_on (basic_block bb
, struct loop
*loop
)
156 /* BB must end in a simple conditional jump. */
157 stmt
= last_stmt (bb
);
158 if (!stmt
|| gimple_code (stmt
) != GIMPLE_COND
)
161 /* To keep the things simple, we do not directly remove the conditions,
162 but just replace tests with 0 != 0 resp. 1 != 0. Prevent the infinite
163 loop where we would unswitch again on such a condition. */
164 if (gimple_cond_true_p (stmt
) || gimple_cond_false_p (stmt
))
167 /* Condition must be invariant. */
168 FOR_EACH_SSA_TREE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
)
170 def
= SSA_NAME_DEF_STMT (use
);
171 def_bb
= gimple_bb (def
);
173 && flow_bb_inside_loop_p (loop
, def_bb
))
177 cond
= build2 (gimple_cond_code (stmt
), boolean_type_node
,
178 gimple_cond_lhs (stmt
), gimple_cond_rhs (stmt
));
183 /* Simplifies COND using checks in front of the entry of the LOOP. Just very
184 simplish (sufficient to prevent us from duplicating loop in unswitching
188 simplify_using_entry_checks (struct loop
*loop
, tree cond
)
190 edge e
= loop_preheader_edge (loop
);
195 stmt
= last_stmt (e
->src
);
197 && gimple_code (stmt
) == GIMPLE_COND
198 && gimple_cond_code (stmt
) == TREE_CODE (cond
)
199 && operand_equal_p (gimple_cond_lhs (stmt
),
200 TREE_OPERAND (cond
, 0), 0)
201 && operand_equal_p (gimple_cond_rhs (stmt
),
202 TREE_OPERAND (cond
, 1), 0))
203 return (e
->flags
& EDGE_TRUE_VALUE
205 : boolean_false_node
);
207 if (!single_pred_p (e
->src
))
210 e
= single_pred_edge (e
->src
);
211 if (e
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
))
216 /* Unswitch single LOOP. NUM is number of unswitchings done; we do not allow
217 it to grow too much, it is too easy to create example on that the code would
218 grow exponentially. */
221 tree_unswitch_single_loop (struct loop
*loop
, int num
)
226 tree cond
= NULL_TREE
;
228 bool changed
= false;
231 bbs
= get_loop_body (loop
);
232 found
= loop
->num_nodes
;
236 /* Find a bb to unswitch on. */
237 for (; i
< loop
->num_nodes
; i
++)
238 if ((cond
= tree_may_unswitch_on (bbs
[i
], loop
)))
241 if (i
== loop
->num_nodes
)
244 && num
> PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL
)
245 && (dump_flags
& TDF_DETAILS
))
246 fprintf (dump_file
, ";; Not unswitching anymore, hit max level\n");
248 if (found
== loop
->num_nodes
)
256 cond
= simplify_using_entry_checks (loop
, cond
);
257 stmt
= last_stmt (bbs
[i
]);
258 if (integer_nonzerop (cond
))
260 /* Remove false path. */
261 gimple_cond_set_condition_from_tree (stmt
, boolean_true_node
);
264 else if (integer_zerop (cond
))
266 /* Remove true path. */
267 gimple_cond_set_condition_from_tree (stmt
, boolean_false_node
);
270 /* Do not unswitch too much. */
271 else if (num
> PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL
))
276 /* In nested tree_unswitch_single_loop first optimize all conditions
277 using entry checks, then discover still reachable blocks in the
278 loop and find the condition only among those still reachable bbs. */
281 if (found
== loop
->num_nodes
)
298 basic_block
*tos
, *worklist
;
300 /* When called recursively, first do a quick discovery
301 of reachable bbs after the above changes and only
302 consider conditions in still reachable bbs. */
303 tos
= worklist
= XNEWVEC (basic_block
, loop
->num_nodes
);
305 for (i
= 0; i
< loop
->num_nodes
; i
++)
306 bbs
[i
]->flags
&= ~BB_REACHABLE
;
308 /* Start with marking header. */
310 bbs
[0]->flags
|= BB_REACHABLE
;
312 /* Iterate: find everything reachable from what we've already seen
313 within the same innermost loop. Don't look through false edges
314 if condition is always true or true edges if condition is
316 while (tos
!= worklist
)
318 basic_block b
= *--tos
;
323 if (EDGE_COUNT (b
->succs
) == 2)
325 gimple stmt
= last_stmt (b
);
327 && gimple_code (stmt
) == GIMPLE_COND
)
329 if (gimple_cond_true_p (stmt
))
330 flags
= EDGE_FALSE_VALUE
;
331 else if (gimple_cond_false_p (stmt
))
332 flags
= EDGE_TRUE_VALUE
;
336 FOR_EACH_EDGE (e
, ei
, b
->succs
)
338 basic_block dest
= e
->dest
;
340 if (dest
->loop_father
== loop
341 && !(dest
->flags
& BB_REACHABLE
)
342 && !(e
->flags
& flags
))
345 dest
->flags
|= BB_REACHABLE
;
352 /* Find a bb to unswitch on. */
353 for (; found
< loop
->num_nodes
; found
++)
354 if ((bbs
[found
]->flags
& BB_REACHABLE
)
355 && (cond
= tree_may_unswitch_on (bbs
[found
], loop
)))
358 if (found
== loop
->num_nodes
)
365 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
366 fprintf (dump_file
, ";; Unswitching loop\n");
368 initialize_original_copy_tables ();
369 /* Unswitch the loop on this condition. */
370 nloop
= tree_unswitch_loop (loop
, bbs
[found
], cond
);
373 free_original_copy_tables ();
378 /* Update the SSA form after unswitching. */
379 update_ssa (TODO_update_ssa
);
380 free_original_copy_tables ();
382 /* Invoke itself on modified loops. */
383 tree_unswitch_single_loop (nloop
, num
+ 1);
384 tree_unswitch_single_loop (loop
, num
+ 1);
389 /* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON. We only support
390 unswitching of innermost loops. COND is the condition determining which
391 loop is entered -- the new loop is entered if COND is true. Returns NULL
392 if impossible, new loop otherwise. */
395 tree_unswitch_loop (struct loop
*loop
,
396 basic_block unswitch_on
, tree cond
)
399 edge edge_true
, edge_false
;
401 /* Some sanity checking. */
402 gcc_assert (flow_bb_inside_loop_p (loop
, unswitch_on
));
403 gcc_assert (EDGE_COUNT (unswitch_on
->succs
) == 2);
404 gcc_assert (loop
->inner
== NULL
);
406 extract_true_false_edges_from_block (unswitch_on
, &edge_true
, &edge_false
);
407 prob_true
= edge_true
->probability
;
408 return loop_version (loop
, unshare_expr (cond
),
409 NULL
, prob_true
, prob_true
,
410 REG_BR_PROB_BASE
- prob_true
, false);
413 /* Loop unswitching pass. */
417 const pass_data pass_data_tree_unswitch
=
419 GIMPLE_PASS
, /* type */
420 "unswitch", /* name */
421 OPTGROUP_LOOP
, /* optinfo_flags */
422 TV_TREE_LOOP_UNSWITCH
, /* tv_id */
423 PROP_cfg
, /* properties_required */
424 0, /* properties_provided */
425 0, /* properties_destroyed */
426 0, /* todo_flags_start */
427 0, /* todo_flags_finish */
430 class pass_tree_unswitch
: public gimple_opt_pass
433 pass_tree_unswitch (gcc::context
*ctxt
)
434 : gimple_opt_pass (pass_data_tree_unswitch
, ctxt
)
437 /* opt_pass methods: */
438 virtual bool gate (function
*) { return flag_unswitch_loops
!= 0; }
439 virtual unsigned int execute (function
*);
441 }; // class pass_tree_unswitch
444 pass_tree_unswitch::execute (function
*fun
)
446 if (number_of_loops (fun
) <= 1)
449 return tree_ssa_unswitch_loops ();
455 make_pass_tree_unswitch (gcc::context
*ctxt
)
457 return new pass_tree_unswitch (ctxt
);