1 /* Loop invariant motion.
2 Copyright (C) 2003, 2004, 2005, 2006, 2007 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 2, 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 COPYING. If not, write to the Free
18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
23 #include "coretypes.h"
28 #include "hard-reg-set.h"
29 #include "basic-block.h"
31 #include "diagnostic.h"
32 #include "tree-flow.h"
33 #include "tree-dump.h"
38 #include "tree-pass.h"
43 /* TODO: Support for predicated code motion. I.e.
54 Where COND and INV are is invariants, but evaluating INV may trap or be
55 invalid from some other reason if !COND. This may be transformed to
65 /* A type for the list of statements that have to be moved in order to be able
66 to hoist an invariant computation. */
74 /* The auxiliary data kept for each statement. */
78 struct loop
*max_loop
; /* The outermost loop in that the statement
81 struct loop
*tgt_loop
; /* The loop out of that we want to move the
84 struct loop
*always_executed_in
;
85 /* The outermost loop for that we are sure
86 the statement is executed if the loop
89 bool sm_done
; /* True iff the store motion for a memory
90 reference in the statement has already
93 unsigned cost
; /* Cost of the computation performed by the
96 struct depend
*depends
; /* List of statements that must be also hoisted
97 out of the loop when this statement is
98 hoisted; i.e. those that define the operands
99 of the statement and are inside of the
103 #define LIM_DATA(STMT) (TREE_CODE (STMT) == PHI_NODE \
105 : (struct lim_aux_data *) (stmt_ann (STMT)->common.aux))
107 /* Description of a memory reference location for store motion. */
111 tree
*ref
; /* The reference itself. */
112 tree stmt
; /* The statement in that it occurs. */
113 struct mem_ref_loc
*next
; /* Next use in the chain. */
116 /* Description of a memory reference for store motion. */
120 tree mem
; /* The memory itself. */
121 hashval_t hash
; /* Its hash value. */
122 bool is_stored
; /* True if there is a store to the location
124 struct mem_ref_loc
*locs
; /* The locations where it is found. */
125 bitmap vops
; /* Vops corresponding to this memory
127 struct mem_ref
*next
; /* Next memory reference in the list.
128 Memory references are stored in a hash
129 table, but the hash function depends
130 on values of pointers. Thus we cannot use
131 htab_traverse, since then we would get
132 miscompares during bootstrap (although the
133 produced code would be correct). */
136 /* Minimum cost of an expensive expression. */
137 #define LIM_EXPENSIVE ((unsigned) PARAM_VALUE (PARAM_LIM_EXPENSIVE))
139 /* The outermost loop for that execution of the header guarantees that the
140 block will be executed. */
141 #define ALWAYS_EXECUTED_IN(BB) ((struct loop *) (BB)->aux)
143 /* Calls CBCK for each index in memory reference ADDR_P. There are two
144 kinds situations handled; in each of these cases, the memory reference
145 and DATA are passed to the callback:
147 Access to an array: ARRAY_{RANGE_}REF (base, index). In this case we also
148 pass the pointer to the index to the callback.
150 Pointer dereference: INDIRECT_REF (addr). In this case we also pass the
151 pointer to addr to the callback.
153 If the callback returns false, the whole search stops and false is returned.
154 Otherwise the function returns true after traversing through the whole
155 reference *ADDR_P. */
158 for_each_index (tree
*addr_p
, bool (*cbck
) (tree
, tree
*, void *), void *data
)
162 for (; ; addr_p
= nxt
)
164 switch (TREE_CODE (*addr_p
))
167 return cbck (*addr_p
, addr_p
, data
);
169 case MISALIGNED_INDIRECT_REF
:
170 case ALIGN_INDIRECT_REF
:
172 nxt
= &TREE_OPERAND (*addr_p
, 0);
173 return cbck (*addr_p
, nxt
, data
);
176 case VIEW_CONVERT_EXPR
:
179 nxt
= &TREE_OPERAND (*addr_p
, 0);
183 /* If the component has varying offset, it behaves like index
185 idx
= &TREE_OPERAND (*addr_p
, 2);
187 && !cbck (*addr_p
, idx
, data
))
190 nxt
= &TREE_OPERAND (*addr_p
, 0);
194 case ARRAY_RANGE_REF
:
195 nxt
= &TREE_OPERAND (*addr_p
, 0);
196 if (!cbck (*addr_p
, &TREE_OPERAND (*addr_p
, 1), data
))
211 idx
= &TMR_BASE (*addr_p
);
213 && !cbck (*addr_p
, idx
, data
))
215 idx
= &TMR_INDEX (*addr_p
);
217 && !cbck (*addr_p
, idx
, data
))
227 /* If it is possible to hoist the statement STMT unconditionally,
228 returns MOVE_POSSIBLE.
229 If it is possible to hoist the statement STMT, but we must avoid making
230 it executed if it would not be executed in the original program (e.g.
231 because it may trap), return MOVE_PRESERVE_EXECUTION.
232 Otherwise return MOVE_IMPOSSIBLE. */
235 movement_possibility (tree stmt
)
239 if (flag_unswitch_loops
240 && TREE_CODE (stmt
) == COND_EXPR
)
242 /* If we perform unswitching, force the operands of the invariant
243 condition to be moved out of the loop. */
244 return MOVE_POSSIBLE
;
247 if (TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
)
248 return MOVE_IMPOSSIBLE
;
250 if (stmt_ends_bb_p (stmt
))
251 return MOVE_IMPOSSIBLE
;
253 if (stmt_ann (stmt
)->has_volatile_ops
)
254 return MOVE_IMPOSSIBLE
;
256 lhs
= GIMPLE_STMT_OPERAND (stmt
, 0);
257 if (TREE_CODE (lhs
) == SSA_NAME
258 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs
))
259 return MOVE_IMPOSSIBLE
;
261 rhs
= GIMPLE_STMT_OPERAND (stmt
, 1);
263 if (TREE_SIDE_EFFECTS (rhs
))
264 return MOVE_IMPOSSIBLE
;
266 if (TREE_CODE (lhs
) != SSA_NAME
267 || tree_could_trap_p (rhs
))
268 return MOVE_PRESERVE_EXECUTION
;
270 if (get_call_expr_in (stmt
))
272 /* While pure or const call is guaranteed to have no side effects, we
273 cannot move it arbitrarily. Consider code like
275 char *s = something ();
285 Here the strlen call cannot be moved out of the loop, even though
286 s is invariant. In addition to possibly creating a call with
287 invalid arguments, moving out a function call that is not executed
288 may cause performance regressions in case the call is costly and
289 not executed at all. */
290 return MOVE_PRESERVE_EXECUTION
;
292 return MOVE_POSSIBLE
;
295 /* Suppose that operand DEF is used inside the LOOP. Returns the outermost
296 loop to that we could move the expression using DEF if it did not have
297 other operands, i.e. the outermost loop enclosing LOOP in that the value
298 of DEF is invariant. */
301 outermost_invariant_loop (tree def
, struct loop
*loop
)
305 struct loop
*max_loop
;
307 if (TREE_CODE (def
) != SSA_NAME
)
308 return superloop_at_depth (loop
, 1);
310 def_stmt
= SSA_NAME_DEF_STMT (def
);
311 def_bb
= bb_for_stmt (def_stmt
);
313 return superloop_at_depth (loop
, 1);
315 max_loop
= find_common_loop (loop
, def_bb
->loop_father
);
317 if (LIM_DATA (def_stmt
) && LIM_DATA (def_stmt
)->max_loop
)
318 max_loop
= find_common_loop (max_loop
,
319 LIM_DATA (def_stmt
)->max_loop
->outer
);
320 if (max_loop
== loop
)
322 max_loop
= superloop_at_depth (loop
, max_loop
->depth
+ 1);
327 /* Returns the outermost superloop of LOOP in that the expression EXPR is
331 outermost_invariant_loop_expr (tree expr
, struct loop
*loop
)
333 enum tree_code_class
class = TREE_CODE_CLASS (TREE_CODE (expr
));
335 struct loop
*max_loop
= superloop_at_depth (loop
, 1), *aloop
;
337 if (TREE_CODE (expr
) == SSA_NAME
338 || TREE_CODE (expr
) == INTEGER_CST
339 || is_gimple_min_invariant (expr
))
340 return outermost_invariant_loop (expr
, loop
);
342 if (class != tcc_unary
343 && class != tcc_binary
344 && class != tcc_expression
345 && class != tcc_vl_exp
346 && class != tcc_comparison
)
349 nops
= TREE_OPERAND_LENGTH (expr
);
350 for (i
= 0; i
< nops
; i
++)
352 aloop
= outermost_invariant_loop_expr (TREE_OPERAND (expr
, i
), loop
);
356 if (flow_loop_nested_p (max_loop
, aloop
))
363 /* DATA is a structure containing information associated with a statement
364 inside LOOP. DEF is one of the operands of this statement.
366 Find the outermost loop enclosing LOOP in that value of DEF is invariant
367 and record this in DATA->max_loop field. If DEF itself is defined inside
368 this loop as well (i.e. we need to hoist it out of the loop if we want
369 to hoist the statement represented by DATA), record the statement in that
370 DEF is defined to the DATA->depends list. Additionally if ADD_COST is true,
371 add the cost of the computation of DEF to the DATA->cost.
373 If DEF is not invariant in LOOP, return false. Otherwise return TRUE. */
376 add_dependency (tree def
, struct lim_aux_data
*data
, struct loop
*loop
,
379 tree def_stmt
= SSA_NAME_DEF_STMT (def
);
380 basic_block def_bb
= bb_for_stmt (def_stmt
);
381 struct loop
*max_loop
;
387 max_loop
= outermost_invariant_loop (def
, loop
);
391 if (flow_loop_nested_p (data
->max_loop
, max_loop
))
392 data
->max_loop
= max_loop
;
394 if (!LIM_DATA (def_stmt
))
398 /* Only add the cost if the statement defining DEF is inside LOOP,
399 i.e. if it is likely that by moving the invariants dependent
400 on it, we will be able to avoid creating a new register for
401 it (since it will be only used in these dependent invariants). */
402 && def_bb
->loop_father
== loop
)
403 data
->cost
+= LIM_DATA (def_stmt
)->cost
;
405 dep
= XNEW (struct depend
);
406 dep
->stmt
= def_stmt
;
407 dep
->next
= data
->depends
;
413 /* Returns an estimate for a cost of statement STMT. TODO -- the values here
414 are just ad-hoc constants. The estimates should be based on target-specific
418 stmt_cost (tree stmt
)
423 /* Always try to create possibilities for unswitching. */
424 if (TREE_CODE (stmt
) == COND_EXPR
)
425 return LIM_EXPENSIVE
;
427 rhs
= GENERIC_TREE_OPERAND (stmt
, 1);
429 /* Hoisting memory references out should almost surely be a win. */
430 if (stmt_references_memory_p (stmt
))
433 switch (TREE_CODE (rhs
))
436 /* We should be hoisting calls if possible. */
438 /* Unless the call is a builtin_constant_p; this always folds to a
439 constant, so moving it is useless. */
440 rhs
= get_callee_fndecl (rhs
);
441 if (DECL_BUILT_IN_CLASS (rhs
) == BUILT_IN_NORMAL
442 && DECL_FUNCTION_CODE (rhs
) == BUILT_IN_CONSTANT_P
)
459 /* Division and multiplication are usually expensive. */
470 /* Determine the outermost loop to that it is possible to hoist a statement
471 STMT and store it to LIM_DATA (STMT)->max_loop. To do this we determine
472 the outermost loop in that the value computed by STMT is invariant.
473 If MUST_PRESERVE_EXEC is true, additionally choose such a loop that
474 we preserve the fact whether STMT is executed. It also fills other related
475 information to LIM_DATA (STMT).
477 The function returns false if STMT cannot be hoisted outside of the loop it
478 is defined in, and true otherwise. */
481 determine_max_movement (tree stmt
, bool must_preserve_exec
)
483 basic_block bb
= bb_for_stmt (stmt
);
484 struct loop
*loop
= bb
->loop_father
;
486 struct lim_aux_data
*lim_data
= LIM_DATA (stmt
);
490 if (must_preserve_exec
)
491 level
= ALWAYS_EXECUTED_IN (bb
);
493 level
= superloop_at_depth (loop
, 1);
494 lim_data
->max_loop
= level
;
496 FOR_EACH_SSA_TREE_OPERAND (val
, stmt
, iter
, SSA_OP_USE
)
497 if (!add_dependency (val
, lim_data
, loop
, true))
500 FOR_EACH_SSA_TREE_OPERAND (val
, stmt
, iter
, SSA_OP_VIRTUAL_USES
)
501 if (!add_dependency (val
, lim_data
, loop
, false))
504 lim_data
->cost
+= stmt_cost (stmt
);
509 /* Suppose that some statement in ORIG_LOOP is hoisted to the loop LEVEL,
510 and that one of the operands of this statement is computed by STMT.
511 Ensure that STMT (together with all the statements that define its
512 operands) is hoisted at least out of the loop LEVEL. */
515 set_level (tree stmt
, struct loop
*orig_loop
, struct loop
*level
)
517 struct loop
*stmt_loop
= bb_for_stmt (stmt
)->loop_father
;
520 stmt_loop
= find_common_loop (orig_loop
, stmt_loop
);
521 if (LIM_DATA (stmt
) && LIM_DATA (stmt
)->tgt_loop
)
522 stmt_loop
= find_common_loop (stmt_loop
,
523 LIM_DATA (stmt
)->tgt_loop
->outer
);
524 if (flow_loop_nested_p (stmt_loop
, level
))
527 gcc_assert (LIM_DATA (stmt
));
528 gcc_assert (level
== LIM_DATA (stmt
)->max_loop
529 || flow_loop_nested_p (LIM_DATA (stmt
)->max_loop
, level
));
531 LIM_DATA (stmt
)->tgt_loop
= level
;
532 for (dep
= LIM_DATA (stmt
)->depends
; dep
; dep
= dep
->next
)
533 set_level (dep
->stmt
, orig_loop
, level
);
536 /* Determines an outermost loop from that we want to hoist the statement STMT.
537 For now we chose the outermost possible loop. TODO -- use profiling
538 information to set it more sanely. */
541 set_profitable_level (tree stmt
)
543 set_level (stmt
, bb_for_stmt (stmt
)->loop_father
, LIM_DATA (stmt
)->max_loop
);
546 /* Returns true if STMT is not a pure call. */
549 nonpure_call_p (tree stmt
)
551 tree call
= get_call_expr_in (stmt
);
556 return TREE_SIDE_EFFECTS (call
) != 0;
559 /* Releases the memory occupied by DATA. */
562 free_lim_aux_data (struct lim_aux_data
*data
)
564 struct depend
*dep
, *next
;
566 for (dep
= data
->depends
; dep
; dep
= next
)
574 /* Determine the outermost loops in that statements in basic block BB are
575 invariant, and record them to the LIM_DATA associated with the statements.
576 Callback for walk_dominator_tree. */
579 determine_invariantness_stmt (struct dom_walk_data
*dw_data ATTRIBUTE_UNUSED
,
583 block_stmt_iterator bsi
;
585 bool maybe_never
= ALWAYS_EXECUTED_IN (bb
) == NULL
;
586 struct loop
*outermost
= ALWAYS_EXECUTED_IN (bb
);
588 if (!bb
->loop_father
->outer
)
591 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
592 fprintf (dump_file
, "Basic block %d (loop %d -- depth %d):\n\n",
593 bb
->index
, bb
->loop_father
->num
, bb
->loop_father
->depth
);
595 for (bsi
= bsi_start (bb
); !bsi_end_p (bsi
); bsi_next (&bsi
))
597 stmt
= bsi_stmt (bsi
);
599 pos
= movement_possibility (stmt
);
600 if (pos
== MOVE_IMPOSSIBLE
)
602 if (nonpure_call_p (stmt
))
610 /* If divisor is invariant, convert a/b to a*(1/b), allowing reciprocal
611 to be hoisted out of loop, saving expensive divide. */
612 if (pos
== MOVE_POSSIBLE
613 && (rhs
= GENERIC_TREE_OPERAND (stmt
, 1)) != NULL
614 && TREE_CODE (rhs
) == RDIV_EXPR
615 && flag_unsafe_math_optimizations
616 && !flag_trapping_math
617 && outermost_invariant_loop_expr (TREE_OPERAND (rhs
, 1),
618 loop_containing_stmt (stmt
)) != NULL
619 && outermost_invariant_loop_expr (rhs
,
620 loop_containing_stmt (stmt
)) == NULL
)
622 tree lhs
, stmt1
, stmt2
, var
, name
, tmp
;
624 lhs
= GENERIC_TREE_OPERAND (stmt
, 0);
626 /* stmt must be GIMPLE_MODIFY_STMT. */
627 var
= create_tmp_var (TREE_TYPE (rhs
), "reciptmp");
628 add_referenced_var (var
);
630 tmp
= build2 (RDIV_EXPR
, TREE_TYPE (rhs
),
631 build_real (TREE_TYPE (rhs
), dconst1
),
632 TREE_OPERAND (rhs
, 1));
633 stmt1
= build_gimple_modify_stmt (var
, tmp
);
634 name
= make_ssa_name (var
, stmt1
);
635 GIMPLE_STMT_OPERAND (stmt1
, 0) = name
;
636 tmp
= build2 (MULT_EXPR
, TREE_TYPE (rhs
),
637 name
, TREE_OPERAND (rhs
, 0));
638 stmt2
= build_gimple_modify_stmt (lhs
, tmp
);
640 /* Replace division stmt with reciprocal and multiply stmts.
641 The multiply stmt is not invariant, so update iterator
642 and avoid rescanning. */
643 bsi_replace (&bsi
, stmt1
, true);
644 bsi_insert_after (&bsi
, stmt2
, BSI_NEW_STMT
);
645 SSA_NAME_DEF_STMT (lhs
) = stmt2
;
647 /* Continue processing with invariant reciprocal statement. */
651 stmt_ann (stmt
)->common
.aux
= xcalloc (1, sizeof (struct lim_aux_data
));
652 LIM_DATA (stmt
)->always_executed_in
= outermost
;
654 if (maybe_never
&& pos
== MOVE_PRESERVE_EXECUTION
)
657 if (!determine_max_movement (stmt
, pos
== MOVE_PRESERVE_EXECUTION
))
659 LIM_DATA (stmt
)->max_loop
= NULL
;
663 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
665 print_generic_stmt_indented (dump_file
, stmt
, 0, 2);
666 fprintf (dump_file
, " invariant up to level %d, cost %d.\n\n",
667 LIM_DATA (stmt
)->max_loop
->depth
,
668 LIM_DATA (stmt
)->cost
);
671 if (LIM_DATA (stmt
)->cost
>= LIM_EXPENSIVE
)
672 set_profitable_level (stmt
);
676 /* For each statement determines the outermost loop in that it is invariant,
677 statements on whose motion it depends and the cost of the computation.
678 This information is stored to the LIM_DATA structure associated with
682 determine_invariantness (void)
684 struct dom_walk_data walk_data
;
686 memset (&walk_data
, 0, sizeof (struct dom_walk_data
));
687 walk_data
.before_dom_children_before_stmts
= determine_invariantness_stmt
;
689 init_walk_dominator_tree (&walk_data
);
690 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
691 fini_walk_dominator_tree (&walk_data
);
694 /* Hoist the statements in basic block BB out of the loops prescribed by
695 data stored in LIM_DATA structures associated with each statement. Callback
696 for walk_dominator_tree. */
699 move_computations_stmt (struct dom_walk_data
*dw_data ATTRIBUTE_UNUSED
,
703 block_stmt_iterator bsi
;
707 if (!bb
->loop_father
->outer
)
710 for (bsi
= bsi_start (bb
); !bsi_end_p (bsi
); )
712 stmt
= bsi_stmt (bsi
);
714 if (!LIM_DATA (stmt
))
720 cost
= LIM_DATA (stmt
)->cost
;
721 level
= LIM_DATA (stmt
)->tgt_loop
;
722 free_lim_aux_data (LIM_DATA (stmt
));
723 stmt_ann (stmt
)->common
.aux
= NULL
;
731 /* We do not really want to move conditionals out of the loop; we just
732 placed it here to force its operands to be moved if necessary. */
733 if (TREE_CODE (stmt
) == COND_EXPR
)
736 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
738 fprintf (dump_file
, "Moving statement\n");
739 print_generic_stmt (dump_file
, stmt
, 0);
740 fprintf (dump_file
, "(cost %u) out of loop %d.\n\n",
743 bsi_insert_on_edge (loop_preheader_edge (level
), stmt
);
744 bsi_remove (&bsi
, false);
748 /* Hoist the statements out of the loops prescribed by data stored in
749 LIM_DATA structures associated with each statement.*/
752 move_computations (void)
754 struct dom_walk_data walk_data
;
756 memset (&walk_data
, 0, sizeof (struct dom_walk_data
));
757 walk_data
.before_dom_children_before_stmts
= move_computations_stmt
;
759 init_walk_dominator_tree (&walk_data
);
760 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
761 fini_walk_dominator_tree (&walk_data
);
763 bsi_commit_edge_inserts ();
764 if (need_ssa_update_p ())
765 rewrite_into_loop_closed_ssa (NULL
, TODO_update_ssa
);
768 /* Checks whether the statement defining variable *INDEX can be hoisted
769 out of the loop passed in DATA. Callback for for_each_index. */
772 may_move_till (tree ref
, tree
*index
, void *data
)
774 struct loop
*loop
= data
, *max_loop
;
776 /* If REF is an array reference, check also that the step and the lower
777 bound is invariant in LOOP. */
778 if (TREE_CODE (ref
) == ARRAY_REF
)
780 tree step
= array_ref_element_size (ref
);
781 tree lbound
= array_ref_low_bound (ref
);
783 max_loop
= outermost_invariant_loop_expr (step
, loop
);
787 max_loop
= outermost_invariant_loop_expr (lbound
, loop
);
792 max_loop
= outermost_invariant_loop (*index
, loop
);
799 /* Forces statements defining (invariant) SSA names in expression EXPR to be
800 moved out of the LOOP. ORIG_LOOP is the loop in that EXPR is used. */
803 force_move_till_expr (tree expr
, struct loop
*orig_loop
, struct loop
*loop
)
805 enum tree_code_class
class = TREE_CODE_CLASS (TREE_CODE (expr
));
808 if (TREE_CODE (expr
) == SSA_NAME
)
810 tree stmt
= SSA_NAME_DEF_STMT (expr
);
811 if (IS_EMPTY_STMT (stmt
))
814 set_level (stmt
, orig_loop
, loop
);
818 if (class != tcc_unary
819 && class != tcc_binary
820 && class != tcc_expression
821 && class != tcc_vl_exp
822 && class != tcc_comparison
)
825 nops
= TREE_OPERAND_LENGTH (expr
);
826 for (i
= 0; i
< nops
; i
++)
827 force_move_till_expr (TREE_OPERAND (expr
, i
), orig_loop
, loop
);
830 /* Forces statement defining invariants in REF (and *INDEX) to be moved out of
831 the LOOP. The reference REF is used in the loop ORIG_LOOP. Callback for
837 struct loop
*orig_loop
;
841 force_move_till (tree ref
, tree
*index
, void *data
)
844 struct fmt_data
*fmt_data
= data
;
846 if (TREE_CODE (ref
) == ARRAY_REF
)
848 tree step
= array_ref_element_size (ref
);
849 tree lbound
= array_ref_low_bound (ref
);
851 force_move_till_expr (step
, fmt_data
->orig_loop
, fmt_data
->loop
);
852 force_move_till_expr (lbound
, fmt_data
->orig_loop
, fmt_data
->loop
);
855 if (TREE_CODE (*index
) != SSA_NAME
)
858 stmt
= SSA_NAME_DEF_STMT (*index
);
859 if (IS_EMPTY_STMT (stmt
))
862 set_level (stmt
, fmt_data
->orig_loop
, fmt_data
->loop
);
867 /* Records memory reference location *REF to the list MEM_REFS. The reference
868 occurs in statement STMT. */
871 record_mem_ref_loc (struct mem_ref_loc
**mem_refs
, tree stmt
, tree
*ref
)
873 struct mem_ref_loc
*aref
= XNEW (struct mem_ref_loc
);
878 aref
->next
= *mem_refs
;
882 /* Releases list of memory reference locations MEM_REFS. */
885 free_mem_ref_locs (struct mem_ref_loc
*mem_refs
)
887 struct mem_ref_loc
*act
;
892 mem_refs
= mem_refs
->next
;
897 /* Rewrites memory references in list MEM_REFS by variable TMP_VAR. */
900 rewrite_mem_refs (tree tmp_var
, struct mem_ref_loc
*mem_refs
)
905 for (; mem_refs
; mem_refs
= mem_refs
->next
)
907 FOR_EACH_SSA_TREE_OPERAND (var
, mem_refs
->stmt
, iter
, SSA_OP_ALL_VIRTUALS
)
908 mark_sym_for_renaming (SSA_NAME_VAR (var
));
910 *mem_refs
->ref
= tmp_var
;
911 update_stmt (mem_refs
->stmt
);
915 /* The name and the length of the currently generated variable
917 #define MAX_LSM_NAME_LENGTH 40
918 static char lsm_tmp_name
[MAX_LSM_NAME_LENGTH
+ 1];
919 static int lsm_tmp_name_length
;
921 /* Adds S to lsm_tmp_name. */
924 lsm_tmp_name_add (const char *s
)
926 int l
= strlen (s
) + lsm_tmp_name_length
;
927 if (l
> MAX_LSM_NAME_LENGTH
)
930 strcpy (lsm_tmp_name
+ lsm_tmp_name_length
, s
);
931 lsm_tmp_name_length
= l
;
934 /* Stores the name for temporary variable that replaces REF to
938 gen_lsm_tmp_name (tree ref
)
942 switch (TREE_CODE (ref
))
944 case MISALIGNED_INDIRECT_REF
:
945 case ALIGN_INDIRECT_REF
:
947 gen_lsm_tmp_name (TREE_OPERAND (ref
, 0));
948 lsm_tmp_name_add ("_");
952 case VIEW_CONVERT_EXPR
:
953 case ARRAY_RANGE_REF
:
954 gen_lsm_tmp_name (TREE_OPERAND (ref
, 0));
958 gen_lsm_tmp_name (TREE_OPERAND (ref
, 0));
959 lsm_tmp_name_add ("_RE");
963 gen_lsm_tmp_name (TREE_OPERAND (ref
, 0));
964 lsm_tmp_name_add ("_IM");
968 gen_lsm_tmp_name (TREE_OPERAND (ref
, 0));
969 lsm_tmp_name_add ("_");
970 name
= get_name (TREE_OPERAND (ref
, 1));
973 lsm_tmp_name_add ("_");
974 lsm_tmp_name_add (name
);
977 gen_lsm_tmp_name (TREE_OPERAND (ref
, 0));
978 lsm_tmp_name_add ("_I");
982 ref
= SSA_NAME_VAR (ref
);
987 name
= get_name (ref
);
990 lsm_tmp_name_add (name
);
994 lsm_tmp_name_add ("S");
998 lsm_tmp_name_add ("R");
1006 /* Determines name for temporary variable that replaces REF.
1007 The name is accumulated into the lsm_tmp_name variable. */
1010 get_lsm_tmp_name (tree ref
)
1012 lsm_tmp_name_length
= 0;
1013 gen_lsm_tmp_name (ref
);
1014 lsm_tmp_name_add ("_lsm");
1015 return lsm_tmp_name
;
1018 /* Records request for store motion of memory reference REF from LOOP.
1019 MEM_REFS is the list of occurrences of the reference REF inside LOOP;
1020 these references are rewritten by a new temporary variable.
1021 Exits from the LOOP are stored in EXITS. The initialization of the
1022 temporary variable is put to the preheader of the loop, and assignments
1023 to the reference from the temporary variable are emitted to exits. */
1026 schedule_sm (struct loop
*loop
, VEC (edge
, heap
) *exits
, tree ref
,
1027 struct mem_ref_loc
*mem_refs
)
1029 struct mem_ref_loc
*aref
;
1033 struct fmt_data fmt_data
;
1036 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1038 fprintf (dump_file
, "Executing store motion of ");
1039 print_generic_expr (dump_file
, ref
, 0);
1040 fprintf (dump_file
, " from loop %d\n", loop
->num
);
1043 tmp_var
= make_rename_temp (TREE_TYPE (ref
),
1044 get_lsm_tmp_name (ref
));
1046 fmt_data
.loop
= loop
;
1047 fmt_data
.orig_loop
= loop
;
1048 for_each_index (&ref
, force_move_till
, &fmt_data
);
1050 rewrite_mem_refs (tmp_var
, mem_refs
);
1051 for (aref
= mem_refs
; aref
; aref
= aref
->next
)
1052 if (LIM_DATA (aref
->stmt
))
1053 LIM_DATA (aref
->stmt
)->sm_done
= true;
1055 /* Emit the load & stores. */
1056 load
= build_gimple_modify_stmt (tmp_var
, ref
);
1057 get_stmt_ann (load
)->common
.aux
= xcalloc (1, sizeof (struct lim_aux_data
));
1058 LIM_DATA (load
)->max_loop
= loop
;
1059 LIM_DATA (load
)->tgt_loop
= loop
;
1061 /* Put this into the latch, so that we are sure it will be processed after
1062 all dependencies. */
1063 bsi_insert_on_edge (loop_latch_edge (loop
), load
);
1065 for (i
= 0; VEC_iterate (edge
, exits
, i
, ex
); i
++)
1067 store
= build_gimple_modify_stmt (unshare_expr (ref
), tmp_var
);
1068 bsi_insert_on_edge (ex
, store
);
1072 /* Check whether memory reference REF can be hoisted out of the LOOP. If this
1073 is true, prepare the statements that load the value of the memory reference
1074 to a temporary variable in the loop preheader, store it back on the loop
1075 exits, and replace all the references inside LOOP by this temporary variable.
1076 EXITS is the list of exits of LOOP. CLOBBERED_VOPS is the bitmap of virtual
1077 operands that are clobbered by a call or accessed through multiple references
1081 determine_lsm_ref (struct loop
*loop
, VEC (edge
, heap
) *exits
,
1082 bitmap clobbered_vops
, struct mem_ref
*ref
)
1084 struct mem_ref_loc
*aref
;
1085 struct loop
*must_exec
;
1087 /* In case the memory is not stored to, there is nothing for SM to do. */
1088 if (!ref
->is_stored
)
1091 /* If the reference is aliased with any different ref, or killed by call
1092 in function, then fail. */
1093 if (bitmap_intersect_p (ref
->vops
, clobbered_vops
))
1096 if (tree_could_trap_p (ref
->mem
))
1098 /* If the memory access is unsafe (i.e. it might trap), ensure that some
1099 of the statements in that it occurs is always executed when the loop
1100 is entered. This way we know that by moving the load from the
1101 reference out of the loop we will not cause the error that would not
1104 TODO -- in fact we would like to check for anticipability of the
1105 reference, i.e. that on each path from loop entry to loop exit at
1106 least one of the statements containing the memory reference is
1109 for (aref
= ref
->locs
; aref
; aref
= aref
->next
)
1111 if (!LIM_DATA (aref
->stmt
))
1114 must_exec
= LIM_DATA (aref
->stmt
)->always_executed_in
;
1118 if (must_exec
== loop
1119 || flow_loop_nested_p (must_exec
, loop
))
1127 schedule_sm (loop
, exits
, ref
->mem
, ref
->locs
);
1130 /* Hoists memory references MEM_REFS out of LOOP. CLOBBERED_VOPS is the list
1131 of vops clobbered by call in loop or accessed by multiple memory references.
1132 EXITS is the list of exit edges of the LOOP. */
1135 hoist_memory_references (struct loop
*loop
, struct mem_ref
*mem_refs
,
1136 bitmap clobbered_vops
, VEC (edge
, heap
) *exits
)
1138 struct mem_ref
*ref
;
1140 for (ref
= mem_refs
; ref
; ref
= ref
->next
)
1141 determine_lsm_ref (loop
, exits
, clobbered_vops
, ref
);
1144 /* Checks whether LOOP (with exits stored in EXITS array) is suitable
1145 for a store motion optimization (i.e. whether we can insert statement
1149 loop_suitable_for_sm (struct loop
*loop ATTRIBUTE_UNUSED
,
1150 VEC (edge
, heap
) *exits
)
1155 for (i
= 0; VEC_iterate (edge
, exits
, i
, ex
); i
++)
1156 if (ex
->flags
& EDGE_ABNORMAL
)
1162 /* A hash function for struct mem_ref object OBJ. */
1165 memref_hash (const void *obj
)
1167 const struct mem_ref
*mem
= obj
;
1172 /* An equality function for struct mem_ref object OBJ1 with
1173 memory reference OBJ2. */
1176 memref_eq (const void *obj1
, const void *obj2
)
1178 const struct mem_ref
*mem1
= obj1
;
1180 return operand_equal_p (mem1
->mem
, (tree
) obj2
, 0);
1183 /* Gathers memory references in statement STMT in LOOP, storing the
1184 information about them in MEM_REFS hash table. Note vops accessed through
1185 unrecognized statements in CLOBBERED_VOPS. The newly created references
1186 are also stored to MEM_REF_LIST. */
1189 gather_mem_refs_stmt (struct loop
*loop
, htab_t mem_refs
,
1190 bitmap clobbered_vops
, tree stmt
,
1191 struct mem_ref
**mem_ref_list
)
1193 tree
*lhs
, *rhs
, *mem
= NULL
;
1196 struct mem_ref
*ref
= NULL
;
1201 if (ZERO_SSA_OPERANDS (stmt
, SSA_OP_ALL_VIRTUALS
))
1204 /* Recognize MEM = (SSA_NAME | invariant) and SSA_NAME = MEM patterns. */
1205 if (TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
)
1208 lhs
= &GIMPLE_STMT_OPERAND (stmt
, 0);
1209 rhs
= &GIMPLE_STMT_OPERAND (stmt
, 1);
1211 if (TREE_CODE (*lhs
) == SSA_NAME
)
1213 if (!is_gimple_addressable (*rhs
))
1219 else if (TREE_CODE (*rhs
) == SSA_NAME
1220 || is_gimple_min_invariant (*rhs
))
1228 /* If we cannot create an SSA name for the result, give up. */
1229 if (!is_gimple_reg_type (TREE_TYPE (*mem
))
1230 || TREE_THIS_VOLATILE (*mem
))
1233 /* If we cannot move the reference out of the loop, fail. */
1234 if (!for_each_index (mem
, may_move_till
, loop
))
1237 hash
= iterative_hash_expr (*mem
, 0);
1238 slot
= htab_find_slot_with_hash (mem_refs
, *mem
, hash
, INSERT
);
1244 ref
= XNEW (struct mem_ref
);
1248 ref
->is_stored
= false;
1249 ref
->vops
= BITMAP_ALLOC (NULL
);
1250 ref
->next
= *mem_ref_list
;
1251 *mem_ref_list
= ref
;
1254 ref
->is_stored
|= is_stored
;
1256 FOR_EACH_SSA_TREE_OPERAND (vname
, stmt
, oi
, SSA_OP_VIRTUAL_USES
)
1257 bitmap_set_bit (ref
->vops
, DECL_UID (SSA_NAME_VAR (vname
)));
1258 record_mem_ref_loc (&ref
->locs
, stmt
, mem
);
1262 FOR_EACH_SSA_TREE_OPERAND (vname
, stmt
, oi
, SSA_OP_VIRTUAL_USES
)
1263 bitmap_set_bit (clobbered_vops
, DECL_UID (SSA_NAME_VAR (vname
)));
1266 /* Gathers memory references in LOOP. Notes vops accessed through unrecognized
1267 statements in CLOBBERED_VOPS. The list of the references found by
1268 the function is returned. */
1270 static struct mem_ref
*
1271 gather_mem_refs (struct loop
*loop
, bitmap clobbered_vops
)
1273 basic_block
*body
= get_loop_body (loop
);
1274 block_stmt_iterator bsi
;
1276 struct mem_ref
*mem_ref_list
= NULL
;
1277 htab_t mem_refs
= htab_create (100, memref_hash
, memref_eq
, NULL
);
1279 for (i
= 0; i
< loop
->num_nodes
; i
++)
1281 for (bsi
= bsi_start (body
[i
]); !bsi_end_p (bsi
); bsi_next (&bsi
))
1282 gather_mem_refs_stmt (loop
, mem_refs
, clobbered_vops
, bsi_stmt (bsi
),
1288 htab_delete (mem_refs
);
1289 return mem_ref_list
;
1292 /* Finds the vops accessed by more than one of the memory references described
1293 in MEM_REFS and marks them in CLOBBERED_VOPS. */
1296 find_more_ref_vops (struct mem_ref
*mem_refs
, bitmap clobbered_vops
)
1298 bitmap_head tmp
, all_vops
;
1299 struct mem_ref
*ref
;
1301 bitmap_initialize (&tmp
, &bitmap_default_obstack
);
1302 bitmap_initialize (&all_vops
, &bitmap_default_obstack
);
1304 for (ref
= mem_refs
; ref
; ref
= ref
->next
)
1306 /* The vops that are already in all_vops are accessed by more than
1307 one memory reference. */
1308 bitmap_and (&tmp
, &all_vops
, ref
->vops
);
1309 bitmap_ior_into (clobbered_vops
, &tmp
);
1310 bitmap_clear (&tmp
);
1312 bitmap_ior_into (&all_vops
, ref
->vops
);
1315 bitmap_clear (&all_vops
);
1318 /* Releases the memory occupied by REF. */
1321 free_mem_ref (struct mem_ref
*ref
)
1323 free_mem_ref_locs (ref
->locs
);
1324 BITMAP_FREE (ref
->vops
);
1328 /* Releases the memory occupied by REFS. */
1331 free_mem_refs (struct mem_ref
*refs
)
1333 struct mem_ref
*ref
, *next
;
1335 for (ref
= refs
; ref
; ref
= next
)
1342 /* Try to perform store motion for all memory references modified inside
1346 determine_lsm_loop (struct loop
*loop
)
1348 VEC (edge
, heap
) *exits
= get_loop_exit_edges (loop
);
1349 bitmap clobbered_vops
;
1350 struct mem_ref
*mem_refs
;
1352 if (!loop_suitable_for_sm (loop
, exits
))
1354 VEC_free (edge
, heap
, exits
);
1358 /* Find the memory references in LOOP. */
1359 clobbered_vops
= BITMAP_ALLOC (NULL
);
1360 mem_refs
= gather_mem_refs (loop
, clobbered_vops
);
1362 /* Find the vops that are used for more than one reference. */
1363 find_more_ref_vops (mem_refs
, clobbered_vops
);
1365 /* Hoist all suitable memory references. */
1366 hoist_memory_references (loop
, mem_refs
, clobbered_vops
, exits
);
1368 free_mem_refs (mem_refs
);
1369 VEC_free (edge
, heap
, exits
);
1370 BITMAP_FREE (clobbered_vops
);
1373 /* Try to perform store motion for all memory references modified inside
1377 determine_lsm (void)
1382 /* Pass the loops from the outermost and perform the store motion as
1385 FOR_EACH_LOOP (li
, loop
, 0)
1387 determine_lsm_loop (loop
);
1390 bsi_commit_edge_inserts ();
1393 /* Fills ALWAYS_EXECUTED_IN information for basic blocks of LOOP, i.e.
1394 for each such basic block bb records the outermost loop for that execution
1395 of its header implies execution of bb. CONTAINS_CALL is the bitmap of
1396 blocks that contain a nonpure call. */
1399 fill_always_executed_in (struct loop
*loop
, sbitmap contains_call
)
1401 basic_block bb
= NULL
, *bbs
, last
= NULL
;
1404 struct loop
*inn_loop
= loop
;
1406 if (!loop
->header
->aux
)
1408 bbs
= get_loop_body_in_dom_order (loop
);
1410 for (i
= 0; i
< loop
->num_nodes
; i
++)
1415 if (dominated_by_p (CDI_DOMINATORS
, loop
->latch
, bb
))
1418 if (TEST_BIT (contains_call
, bb
->index
))
1421 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1422 if (!flow_bb_inside_loop_p (loop
, e
->dest
))
1427 /* A loop might be infinite (TODO use simple loop analysis
1428 to disprove this if possible). */
1429 if (bb
->flags
& BB_IRREDUCIBLE_LOOP
)
1432 if (!flow_bb_inside_loop_p (inn_loop
, bb
))
1435 if (bb
->loop_father
->header
== bb
)
1437 if (!dominated_by_p (CDI_DOMINATORS
, loop
->latch
, bb
))
1440 /* In a loop that is always entered we may proceed anyway.
1441 But record that we entered it and stop once we leave it. */
1442 inn_loop
= bb
->loop_father
;
1449 if (last
== loop
->header
)
1451 last
= get_immediate_dominator (CDI_DOMINATORS
, last
);
1457 for (loop
= loop
->inner
; loop
; loop
= loop
->next
)
1458 fill_always_executed_in (loop
, contains_call
);
1461 /* Compute the global information needed by the loop invariant motion pass. */
1464 tree_ssa_lim_initialize (void)
1466 sbitmap contains_call
= sbitmap_alloc (last_basic_block
);
1467 block_stmt_iterator bsi
;
1471 sbitmap_zero (contains_call
);
1474 for (bsi
= bsi_start (bb
); !bsi_end_p (bsi
); bsi_next (&bsi
))
1476 if (nonpure_call_p (bsi_stmt (bsi
)))
1480 if (!bsi_end_p (bsi
))
1481 SET_BIT (contains_call
, bb
->index
);
1484 for (loop
= current_loops
->tree_root
->inner
; loop
; loop
= loop
->next
)
1485 fill_always_executed_in (loop
, contains_call
);
1487 sbitmap_free (contains_call
);
1490 /* Cleans up after the invariant motion pass. */
1493 tree_ssa_lim_finalize (void)
1503 /* Moves invariants from loops. Only "expensive" invariants are moved out --
1504 i.e. those that are likely to be win regardless of the register pressure. */
1509 tree_ssa_lim_initialize ();
1511 /* For each statement determine the outermost loop in that it is
1512 invariant and cost for computing the invariant. */
1513 determine_invariantness ();
1515 /* For each memory reference determine whether it is possible to hoist it
1516 out of the loop. Force the necessary invariants to be moved out of the
1520 /* Move the expressions that are expensive enough. */
1521 move_computations ();
1523 tree_ssa_lim_finalize ();