1 /* RTL-level loop invariant motion.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008 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/>. */
20 /* This implements the loop invariant motion pass. It is very simple
21 (no calls, no loads/stores, etc.). This should be sufficient to cleanup
22 things like address arithmetics -- other more complicated invariants should
23 be eliminated on GIMPLE either in tree-ssa-loop-im.c or in tree-ssa-pre.c.
25 We proceed loop by loop -- it is simpler than trying to handle things
26 globally and should not lose much. First we inspect all sets inside loop
27 and create a dependency graph on insns (saying "to move this insn, you must
28 also move the following insns").
30 We then need to determine what to move. We estimate the number of registers
31 used and move as many invariants as possible while we still have enough free
32 registers. We prefer the expensive invariants.
34 Then we move the selected invariants out of the loop, creating a new
35 temporaries for them if necessary. */
39 #include "coretypes.h"
43 #include "hard-reg-set.h"
45 #include "basic-block.h"
56 /* The data stored for the loop. */
60 struct loop *outermost_exit; /* The outermost exit of the loop. */
61 bool has_call; /* True if the loop contains a call. */
64 #define LOOP_DATA(LOOP) ((struct loop_data *) (LOOP)->aux)
66 /* The description of an use. */
70 rtx *pos; /* Position of the use. */
71 rtx insn; /* The insn in that the use occurs. */
73 struct use *next; /* Next use in the list. */
76 /* The description of a def. */
80 struct use *uses; /* The list of uses that are uniquely reached
82 unsigned n_uses; /* Number of such uses. */
83 unsigned invno; /* The corresponding invariant. */
86 /* The data stored for each invariant. */
90 /* The number of the invariant. */
93 /* The number of the invariant with the same value. */
96 /* If we moved the invariant out of the loop, the register that contains its
100 /* The definition of the invariant. */
103 /* The insn in that it is defined. */
106 /* Whether it is always executed. */
107 bool always_executed;
109 /* Whether to move the invariant. */
112 /* Cost of the invariant. */
115 /* The invariants it depends on. */
118 /* Used for detecting already visited invariants during determining
119 costs of movements. */
123 /* Table of invariants indexed by the df_ref uid field. */
125 static unsigned int invariant_table_size = 0;
126 static struct invariant ** invariant_table;
128 /* Entry for hash table of invariant expressions. */
130 struct invariant_expr_entry
133 struct invariant *inv;
139 enum machine_mode mode;
145 /* The actual stamp for marking already visited invariants during determining
146 costs of movements. */
148 static unsigned actual_stamp;
150 typedef struct invariant *invariant_p;
152 DEF_VEC_P(invariant_p);
153 DEF_VEC_ALLOC_P(invariant_p, heap);
155 /* The invariants. */
157 static VEC(invariant_p,heap) *invariants;
159 /* Check the size of the invariant table and realloc if necessary. */
162 check_invariant_table_size (void)
164 if (invariant_table_size < DF_DEFS_TABLE_SIZE())
166 unsigned int new_size = DF_DEFS_TABLE_SIZE () + (DF_DEFS_TABLE_SIZE () / 4);
167 invariant_table = xrealloc (invariant_table,
168 sizeof (struct rtx_iv *) * new_size);
169 memset (&invariant_table[invariant_table_size], 0,
170 (new_size - invariant_table_size) * sizeof (struct rtx_iv *));
171 invariant_table_size = new_size;
175 /* Test for possibility of invariantness of X. */
178 check_maybe_invariant (rtx x)
180 enum rtx_code code = GET_CODE (x);
196 case UNSPEC_VOLATILE:
204 /* Load/store motion is done elsewhere. ??? Perhaps also add it here?
205 It should not be hard, and might be faster than "elsewhere". */
207 /* Just handle the most trivial case where we load from an unchanging
208 location (most importantly, pic tables). */
209 if (MEM_READONLY_P (x) && !MEM_VOLATILE_P (x))
215 /* Don't mess with insns declared volatile. */
216 if (MEM_VOLATILE_P (x))
224 fmt = GET_RTX_FORMAT (code);
225 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
229 if (!check_maybe_invariant (XEXP (x, i)))
232 else if (fmt[i] == 'E')
234 for (j = 0; j < XVECLEN (x, i); j++)
235 if (!check_maybe_invariant (XVECEXP (x, i, j)))
243 /* Returns the invariant definition for USE, or NULL if USE is not
246 static struct invariant *
247 invariant_for_use (struct df_ref *use)
249 struct df_link *defs;
251 basic_block bb = DF_REF_BB (use), def_bb;
253 if (use->flags & DF_REF_READ_WRITE)
256 defs = DF_REF_CHAIN (use);
257 if (!defs || defs->next)
260 check_invariant_table_size ();
261 if (!invariant_table[DF_REF_ID(def)])
264 def_bb = DF_REF_BB (def);
265 if (!dominated_by_p (CDI_DOMINATORS, bb, def_bb))
267 return invariant_table[DF_REF_ID(def)];
270 /* Computes hash value for invariant expression X in INSN. */
273 hash_invariant_expr_1 (rtx insn, rtx x)
275 enum rtx_code code = GET_CODE (x);
278 hashval_t val = code;
281 struct invariant *inv;
291 return hash_rtx (x, GET_MODE (x), &do_not_record_p, NULL, false);
294 use = df_find_use (insn, x);
296 return hash_rtx (x, GET_MODE (x), &do_not_record_p, NULL, false);
297 inv = invariant_for_use (use);
299 return hash_rtx (x, GET_MODE (x), &do_not_record_p, NULL, false);
301 gcc_assert (inv->eqto != ~0u);
308 fmt = GET_RTX_FORMAT (code);
309 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
312 val ^= hash_invariant_expr_1 (insn, XEXP (x, i));
313 else if (fmt[i] == 'E')
315 for (j = 0; j < XVECLEN (x, i); j++)
316 val ^= hash_invariant_expr_1 (insn, XVECEXP (x, i, j));
318 else if (fmt[i] == 'i' || fmt[i] == 'n')
325 /* Returns true if the invariant expressions E1 and E2 used in insns INSN1
326 and INSN2 have always the same value. */
329 invariant_expr_equal_p (rtx insn1, rtx e1, rtx insn2, rtx e2)
331 enum rtx_code code = GET_CODE (e1);
334 struct df_ref *use1, *use2;
335 struct invariant *inv1 = NULL, *inv2 = NULL;
338 /* If mode of only one of the operands is VOIDmode, it is not equivalent to
339 the other one. If both are VOIDmode, we rely on the caller of this
340 function to verify that their modes are the same. */
341 if (code != GET_CODE (e2) || GET_MODE (e1) != GET_MODE (e2))
352 return rtx_equal_p (e1, e2);
355 use1 = df_find_use (insn1, e1);
356 use2 = df_find_use (insn2, e2);
358 inv1 = invariant_for_use (use1);
360 inv2 = invariant_for_use (use2);
363 return rtx_equal_p (e1, e2);
368 gcc_assert (inv1->eqto != ~0u);
369 gcc_assert (inv2->eqto != ~0u);
370 return inv1->eqto == inv2->eqto;
376 fmt = GET_RTX_FORMAT (code);
377 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
384 if (!invariant_expr_equal_p (insn1, sub1, insn2, sub2))
388 else if (fmt[i] == 'E')
390 if (XVECLEN (e1, i) != XVECLEN (e2, i))
393 for (j = 0; j < XVECLEN (e1, i); j++)
395 sub1 = XVECEXP (e1, i, j);
396 sub2 = XVECEXP (e2, i, j);
398 if (!invariant_expr_equal_p (insn1, sub1, insn2, sub2))
402 else if (fmt[i] == 'i' || fmt[i] == 'n')
404 if (XINT (e1, i) != XINT (e2, i))
407 /* Unhandled type of subexpression, we fail conservatively. */
415 /* Returns hash value for invariant expression entry E. */
418 hash_invariant_expr (const void *e)
420 const struct invariant_expr_entry *entry = e;
425 /* Compares invariant expression entries E1 and E2. */
428 eq_invariant_expr (const void *e1, const void *e2)
430 const struct invariant_expr_entry *entry1 = e1;
431 const struct invariant_expr_entry *entry2 = e2;
433 if (entry1->mode != entry2->mode)
436 return invariant_expr_equal_p (entry1->inv->insn, entry1->expr,
437 entry2->inv->insn, entry2->expr);
440 /* Checks whether invariant with value EXPR in machine mode MODE is
441 recorded in EQ. If this is the case, return the invariant. Otherwise
442 insert INV to the table for this expression and return INV. */
444 static struct invariant *
445 find_or_insert_inv (htab_t eq, rtx expr, enum machine_mode mode,
446 struct invariant *inv)
448 hashval_t hash = hash_invariant_expr_1 (inv->insn, expr);
449 struct invariant_expr_entry *entry;
450 struct invariant_expr_entry pentry;
456 slot = htab_find_slot_with_hash (eq, &pentry, hash, INSERT);
462 entry = XNEW (struct invariant_expr_entry);
472 /* Finds invariants identical to INV and records the equivalence. EQ is the
473 hash table of the invariants. */
476 find_identical_invariants (htab_t eq, struct invariant *inv)
480 struct invariant *dep;
482 enum machine_mode mode;
484 if (inv->eqto != ~0u)
487 EXECUTE_IF_SET_IN_BITMAP (inv->depends_on, 0, depno, bi)
489 dep = VEC_index (invariant_p, invariants, depno);
490 find_identical_invariants (eq, dep);
493 set = single_set (inv->insn);
494 expr = SET_SRC (set);
495 mode = GET_MODE (expr);
496 if (mode == VOIDmode)
497 mode = GET_MODE (SET_DEST (set));
498 inv->eqto = find_or_insert_inv (eq, expr, mode, inv)->invno;
500 if (dump_file && inv->eqto != inv->invno)
502 "Invariant %d is equivalent to invariant %d.\n",
503 inv->invno, inv->eqto);
506 /* Find invariants with the same value and record the equivalences. */
509 merge_identical_invariants (void)
512 struct invariant *inv;
513 htab_t eq = htab_create (VEC_length (invariant_p, invariants),
514 hash_invariant_expr, eq_invariant_expr, free);
516 for (i = 0; VEC_iterate (invariant_p, invariants, i, inv); i++)
517 find_identical_invariants (eq, inv);
522 /* Determines the basic blocks inside LOOP that are always executed and
523 stores their bitmap to ALWAYS_REACHED. MAY_EXIT is a bitmap of
524 basic blocks that may either exit the loop, or contain the call that
525 does not have to return. BODY is body of the loop obtained by
526 get_loop_body_in_dom_order. */
529 compute_always_reached (struct loop *loop, basic_block *body,
530 bitmap may_exit, bitmap always_reached)
534 for (i = 0; i < loop->num_nodes; i++)
536 if (dominated_by_p (CDI_DOMINATORS, loop->latch, body[i]))
537 bitmap_set_bit (always_reached, i);
539 if (bitmap_bit_p (may_exit, i))
544 /* Finds exits out of the LOOP with body BODY. Marks blocks in that we may
545 exit the loop by cfg edge to HAS_EXIT and MAY_EXIT. In MAY_EXIT
546 additionally mark blocks that may exit due to a call. */
549 find_exits (struct loop *loop, basic_block *body,
550 bitmap may_exit, bitmap has_exit)
555 struct loop *outermost_exit = loop, *aexit;
556 bool has_call = false;
559 for (i = 0; i < loop->num_nodes; i++)
561 if (body[i]->loop_father == loop)
563 FOR_BB_INSNS (body[i], insn)
566 && (RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)
567 || !RTL_CONST_OR_PURE_CALL_P (insn)))
570 bitmap_set_bit (may_exit, i);
575 FOR_EACH_EDGE (e, ei, body[i]->succs)
577 if (flow_bb_inside_loop_p (loop, e->dest))
580 bitmap_set_bit (may_exit, i);
581 bitmap_set_bit (has_exit, i);
582 outermost_exit = find_common_loop (outermost_exit,
583 e->dest->loop_father);
588 /* Use the data stored for the subloop to decide whether we may exit
589 through it. It is sufficient to do this for header of the loop,
590 as other basic blocks inside it must be dominated by it. */
591 if (body[i]->loop_father->header != body[i])
594 if (LOOP_DATA (body[i]->loop_father)->has_call)
597 bitmap_set_bit (may_exit, i);
599 aexit = LOOP_DATA (body[i]->loop_father)->outermost_exit;
602 bitmap_set_bit (may_exit, i);
603 bitmap_set_bit (has_exit, i);
605 if (flow_loop_nested_p (aexit, outermost_exit))
606 outermost_exit = aexit;
610 loop->aux = xcalloc (1, sizeof (struct loop_data));
611 LOOP_DATA (loop)->outermost_exit = outermost_exit;
612 LOOP_DATA (loop)->has_call = has_call;
615 /* Check whether we may assign a value to X from a register. */
618 may_assign_reg_p (rtx x)
620 return (GET_MODE (x) != VOIDmode
621 && GET_MODE (x) != BLKmode
622 && can_copy_p (GET_MODE (x))
624 || !HARD_REGISTER_P (x)
625 || REGNO_REG_CLASS (REGNO (x)) != NO_REGS));
628 /* Finds definitions that may correspond to invariants in LOOP with body
632 find_defs (struct loop *loop, basic_block *body)
635 bitmap blocks = BITMAP_ALLOC (NULL);
637 for (i = 0; i < loop->num_nodes; i++)
638 bitmap_set_bit (blocks, body[i]->index);
640 df_remove_problem (df_chain);
641 df_process_deferred_rescans ();
642 df_chain_add_problem (DF_UD_CHAIN);
643 df_set_blocks (blocks);
648 df_dump_region (dump_file);
649 fprintf (dump_file, "*****starting processing of loop ******\n");
650 print_rtl_with_bb (dump_file, get_insns ());
651 fprintf (dump_file, "*****ending processing of loop ******\n");
653 check_invariant_table_size ();
655 BITMAP_FREE (blocks);
658 /* Creates a new invariant for definition DEF in INSN, depending on invariants
659 in DEPENDS_ON. ALWAYS_EXECUTED is true if the insn is always executed,
660 unless the program ends due to a function call. The newly created invariant
663 static struct invariant *
664 create_new_invariant (struct def *def, rtx insn, bitmap depends_on,
665 bool always_executed)
667 struct invariant *inv = XNEW (struct invariant);
668 rtx set = single_set (insn);
671 inv->always_executed = always_executed;
672 inv->depends_on = depends_on;
674 /* If the set is simple, usually by moving it we move the whole store out of
675 the loop. Otherwise we save only cost of the computation. */
677 inv->cost = rtx_cost (set, SET);
679 inv->cost = rtx_cost (SET_SRC (set), SET);
686 inv->invno = VEC_length (invariant_p, invariants);
689 def->invno = inv->invno;
690 VEC_safe_push (invariant_p, heap, invariants, inv);
695 "Set in insn %d is invariant (%d), cost %d, depends on ",
696 INSN_UID (insn), inv->invno, inv->cost);
697 dump_bitmap (dump_file, inv->depends_on);
703 /* Record USE at DEF. */
706 record_use (struct def *def, rtx *use, rtx insn)
708 struct use *u = XNEW (struct use);
710 gcc_assert (REG_P (*use));
719 /* Finds the invariants USE depends on and store them to the DEPENDS_ON
720 bitmap. Returns true if all dependencies of USE are known to be
721 loop invariants, false otherwise. */
724 check_dependency (basic_block bb, struct df_ref *use, bitmap depends_on)
728 struct df_link *defs;
729 struct def *def_data;
730 struct invariant *inv;
732 if (use->flags & DF_REF_READ_WRITE)
735 defs = DF_REF_CHAIN (use);
743 check_invariant_table_size ();
744 inv = invariant_table[DF_REF_ID(def)];
749 gcc_assert (def_data != NULL);
751 def_bb = DF_REF_BB (def);
752 /* Note that in case bb == def_bb, we know that the definition
753 dominates insn, because def has invariant_table[DF_REF_ID(def)]
754 defined and we process the insns in the basic block bb
756 if (!dominated_by_p (CDI_DOMINATORS, bb, def_bb))
759 bitmap_set_bit (depends_on, def_data->invno);
764 /* Finds the invariants INSN depends on and store them to the DEPENDS_ON
765 bitmap. Returns true if all dependencies of INSN are known to be
766 loop invariants, false otherwise. */
769 check_dependencies (rtx insn, bitmap depends_on)
771 struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
772 struct df_ref **use_rec;
773 basic_block bb = BLOCK_FOR_INSN (insn);
775 for (use_rec = DF_INSN_INFO_USES (insn_info); *use_rec; use_rec++)
776 if (!check_dependency (bb, *use_rec, depends_on))
778 for (use_rec = DF_INSN_INFO_EQ_USES (insn_info); *use_rec; use_rec++)
779 if (!check_dependency (bb, *use_rec, depends_on))
785 /* Finds invariant in INSN. ALWAYS_REACHED is true if the insn is always
786 executed. ALWAYS_EXECUTED is true if the insn is always executed,
787 unless the program ends due to a function call. */
790 find_invariant_insn (rtx insn, bool always_reached, bool always_executed)
797 struct invariant *inv;
800 /* We can't move a CC0 setter without the user. */
801 if (sets_cc0_p (insn))
805 set = single_set (insn);
808 dest = SET_DEST (set);
811 || HARD_REGISTER_P (dest))
814 if (!may_assign_reg_p (SET_DEST (set))
815 || !check_maybe_invariant (SET_SRC (set)))
818 /* If the insn can throw exception, we cannot move it at all without changing
820 if (can_throw_internal (insn))
823 /* We cannot make trapping insn executed, unless it was executed before. */
824 if (may_trap_after_code_motion_p (PATTERN (insn)) && !always_reached)
827 depends_on = BITMAP_ALLOC (NULL);
828 if (!check_dependencies (insn, depends_on))
830 BITMAP_FREE (depends_on);
835 def = XCNEW (struct def);
839 inv = create_new_invariant (def, insn, depends_on, always_executed);
843 ref = df_find_def (insn, dest);
844 check_invariant_table_size ();
845 invariant_table[DF_REF_ID(ref)] = inv;
849 /* Record registers used in INSN that have a unique invariant definition. */
852 record_uses (rtx insn)
854 struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
855 struct df_ref **use_rec;
856 struct invariant *inv;
858 for (use_rec = DF_INSN_INFO_USES (insn_info); *use_rec; use_rec++)
860 struct df_ref *use = *use_rec;
861 inv = invariant_for_use (use);
863 record_use (inv->def, DF_REF_REAL_LOC (use), DF_REF_INSN (use));
865 for (use_rec = DF_INSN_INFO_EQ_USES (insn_info); *use_rec; use_rec++)
867 struct df_ref *use = *use_rec;
868 inv = invariant_for_use (use);
870 record_use (inv->def, DF_REF_REAL_LOC (use), DF_REF_INSN (use));
874 /* Finds invariants in INSN. ALWAYS_REACHED is true if the insn is always
875 executed. ALWAYS_EXECUTED is true if the insn is always executed,
876 unless the program ends due to a function call. */
879 find_invariants_insn (rtx insn, bool always_reached, bool always_executed)
881 find_invariant_insn (insn, always_reached, always_executed);
885 /* Finds invariants in basic block BB. ALWAYS_REACHED is true if the
886 basic block is always executed. ALWAYS_EXECUTED is true if the basic
887 block is always executed, unless the program ends due to a function
891 find_invariants_bb (basic_block bb, bool always_reached, bool always_executed)
895 FOR_BB_INSNS (bb, insn)
900 find_invariants_insn (insn, always_reached, always_executed);
904 && (RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)
905 || ! RTL_CONST_OR_PURE_CALL_P (insn)))
906 always_reached = false;
910 /* Finds invariants in LOOP with body BODY. ALWAYS_REACHED is the bitmap of
911 basic blocks in BODY that are always executed. ALWAYS_EXECUTED is the
912 bitmap of basic blocks in BODY that are always executed unless the program
913 ends due to a function call. */
916 find_invariants_body (struct loop *loop, basic_block *body,
917 bitmap always_reached, bitmap always_executed)
921 for (i = 0; i < loop->num_nodes; i++)
922 find_invariants_bb (body[i],
923 bitmap_bit_p (always_reached, i),
924 bitmap_bit_p (always_executed, i));
927 /* Finds invariants in LOOP. */
930 find_invariants (struct loop *loop)
932 bitmap may_exit = BITMAP_ALLOC (NULL);
933 bitmap always_reached = BITMAP_ALLOC (NULL);
934 bitmap has_exit = BITMAP_ALLOC (NULL);
935 bitmap always_executed = BITMAP_ALLOC (NULL);
936 basic_block *body = get_loop_body_in_dom_order (loop);
938 find_exits (loop, body, may_exit, has_exit);
939 compute_always_reached (loop, body, may_exit, always_reached);
940 compute_always_reached (loop, body, has_exit, always_executed);
942 find_defs (loop, body);
943 find_invariants_body (loop, body, always_reached, always_executed);
944 merge_identical_invariants ();
946 BITMAP_FREE (always_reached);
947 BITMAP_FREE (always_executed);
948 BITMAP_FREE (may_exit);
949 BITMAP_FREE (has_exit);
953 /* Frees a list of uses USE. */
956 free_use_list (struct use *use)
960 for (; use; use = next)
967 /* Calculates cost and number of registers needed for moving invariant INV
968 out of the loop and stores them to *COST and *REGS_NEEDED. */
971 get_inv_cost (struct invariant *inv, int *comp_cost, unsigned *regs_needed)
974 unsigned aregs_needed;
976 struct invariant *dep;
979 /* Find the representative of the class of the equivalent invariants. */
980 inv = VEC_index (invariant_p, invariants, inv->eqto);
985 || inv->stamp == actual_stamp)
987 inv->stamp = actual_stamp;
990 (*comp_cost) += inv->cost;
994 /* Hoisting constant pool constants into stack regs may cost more than
995 just single register. On x87, the balance is affected both by the
996 small number of FP registers, and by its register stack organization,
997 that forces us to add compensation code in and around the loop to
998 shuffle the operands to the top of stack before use, and pop them
999 from the stack after the loop finishes.
1001 To model this effect, we increase the number of registers needed for
1002 stack registers by two: one register push, and one register pop.
1003 This usually has the effect that FP constant loads from the constant
1004 pool are not moved out of the loop.
1006 Note that this also means that dependent invariants can not be moved.
1007 However, the primary purpose of this pass is to move loop invariant
1008 address arithmetic out of loops, and address arithmetic that depends
1009 on floating point constants is unlikely to ever occur. */
1010 rtx set = single_set (inv->insn);
1012 && IS_STACK_MODE (GET_MODE (SET_SRC (set)))
1013 && constant_pool_constant_p (SET_SRC (set)))
1014 (*regs_needed) += 2;
1018 EXECUTE_IF_SET_IN_BITMAP (inv->depends_on, 0, depno, bi)
1020 dep = VEC_index (invariant_p, invariants, depno);
1022 get_inv_cost (dep, &acomp_cost, &aregs_needed);
1025 /* We need to check always_executed, since if the original value of
1026 the invariant may be preserved, we may need to keep it in a
1027 separate register. TODO check whether the register has an
1028 use outside of the loop. */
1029 && dep->always_executed
1030 && !dep->def->uses->next)
1032 /* If this is a single use, after moving the dependency we will not
1033 need a new register. */
1037 (*regs_needed) += aregs_needed;
1038 (*comp_cost) += acomp_cost;
1042 /* Calculates gain for eliminating invariant INV. REGS_USED is the number
1043 of registers used in the loop, NEW_REGS is the number of new variables
1044 already added due to the invariant motion. The number of registers needed
1045 for it is stored in *REGS_NEEDED. */
1048 gain_for_invariant (struct invariant *inv, unsigned *regs_needed,
1049 unsigned new_regs, unsigned regs_used)
1051 int comp_cost, size_cost;
1053 get_inv_cost (inv, &comp_cost, regs_needed);
1056 size_cost = (estimate_reg_pressure_cost (new_regs + *regs_needed, regs_used)
1057 - estimate_reg_pressure_cost (new_regs, regs_used));
1059 return comp_cost - size_cost;
1062 /* Finds invariant with best gain for moving. Returns the gain, stores
1063 the invariant in *BEST and number of registers needed for it to
1064 *REGS_NEEDED. REGS_USED is the number of registers used in the loop.
1065 NEW_REGS is the number of new variables already added due to invariant
1069 best_gain_for_invariant (struct invariant **best, unsigned *regs_needed,
1070 unsigned new_regs, unsigned regs_used)
1072 struct invariant *inv;
1073 int gain = 0, again;
1074 unsigned aregs_needed, invno;
1076 for (invno = 0; VEC_iterate (invariant_p, invariants, invno, inv); invno++)
1081 /* Only consider the "representatives" of equivalent invariants. */
1082 if (inv->eqto != inv->invno)
1085 again = gain_for_invariant (inv, &aregs_needed, new_regs, regs_used);
1090 *regs_needed = aregs_needed;
1097 /* Marks invariant INVNO and all its dependencies for moving. */
1100 set_move_mark (unsigned invno)
1102 struct invariant *inv = VEC_index (invariant_p, invariants, invno);
1105 /* Find the representative of the class of the equivalent invariants. */
1106 inv = VEC_index (invariant_p, invariants, inv->eqto);
1113 fprintf (dump_file, "Decided to move invariant %d\n", invno);
1115 EXECUTE_IF_SET_IN_BITMAP (inv->depends_on, 0, invno, bi)
1117 set_move_mark (invno);
1121 /* Determines which invariants to move. */
1124 find_invariants_to_move (void)
1126 unsigned i, regs_used, regs_needed = 0, new_regs;
1127 struct invariant *inv = NULL;
1128 unsigned int n_regs = DF_REG_SIZE (df);
1130 if (!VEC_length (invariant_p, invariants))
1133 /* We do not really do a good job in estimating number of registers used;
1134 we put some initial bound here to stand for induction variables etc.
1135 that we do not detect. */
1138 for (i = 0; i < n_regs; i++)
1140 if (!DF_REGNO_FIRST_DEF (i) && DF_REGNO_LAST_USE (i))
1142 /* This is a value that is used but not changed inside loop. */
1148 while (best_gain_for_invariant (&inv, ®s_needed, new_regs, regs_used) > 0)
1150 set_move_mark (inv->invno);
1151 new_regs += regs_needed;
1155 /* Move invariant INVNO out of the LOOP. Returns true if this succeeds, false
1159 move_invariant_reg (struct loop *loop, unsigned invno)
1161 struct invariant *inv = VEC_index (invariant_p, invariants, invno);
1162 struct invariant *repr = VEC_index (invariant_p, invariants, inv->eqto);
1164 basic_block preheader = loop_preheader_edge (loop)->src;
1165 rtx reg, set, dest, note;
1173 /* If this is a representative of the class of equivalent invariants,
1174 really move the invariant. Otherwise just replace its use with
1175 the register used for the representative. */
1178 if (inv->depends_on)
1180 EXECUTE_IF_SET_IN_BITMAP (inv->depends_on, 0, i, bi)
1182 if (!move_invariant_reg (loop, i))
1187 /* Move the set out of the loop. If the set is always executed (we could
1188 omit this condition if we know that the register is unused outside of the
1189 loop, but it does not seem worth finding out) and it has no uses that
1190 would not be dominated by it, we may just move it (TODO). Otherwise we
1191 need to create a temporary register. */
1192 set = single_set (inv->insn);
1193 dest = SET_DEST (set);
1194 reg = gen_reg_rtx_and_attrs (dest);
1196 /* Try replacing the destination by a new pseudoregister. */
1197 if (!validate_change (inv->insn, &SET_DEST (set), reg, false))
1199 df_insn_rescan (inv->insn);
1201 emit_insn_after (gen_move_insn (dest, reg), inv->insn);
1202 reorder_insns (inv->insn, inv->insn, BB_END (preheader));
1204 /* If there is a REG_EQUAL note on the insn we just moved, and
1205 insn is in a basic block that is not always executed, the note
1206 may no longer be valid after we move the insn.
1207 Note that uses in REG_EQUAL notes are taken into account in
1208 the computation of invariants. Hence it is safe to retain the
1209 note even if the note contains register references. */
1210 if (! inv->always_executed
1211 && (note = find_reg_note (inv->insn, REG_EQUAL, NULL_RTX)))
1212 remove_note (inv->insn, note);
1216 if (!move_invariant_reg (loop, repr->invno))
1219 set = single_set (inv->insn);
1220 emit_insn_after (gen_move_insn (SET_DEST (set), reg), inv->insn);
1221 delete_insn (inv->insn);
1227 /* Replace the uses we know to be dominated. It saves work for copy
1228 propagation, and also it is necessary so that dependent invariants
1229 are computed right. */
1232 for (use = inv->def->uses; use; use = use->next)
1235 df_insn_rescan (use->insn);
1242 /* If we failed, clear move flag, so that we do not try to move inv
1245 fprintf (dump_file, "Failed to move invariant %d\n", invno);
1247 inv->reg = NULL_RTX;
1252 /* Move selected invariant out of the LOOP. Newly created regs are marked
1253 in TEMPORARY_REGS. */
1256 move_invariants (struct loop *loop)
1258 struct invariant *inv;
1261 for (i = 0; VEC_iterate (invariant_p, invariants, i, inv); i++)
1262 move_invariant_reg (loop, i);
1265 /* Initializes invariant motion data. */
1268 init_inv_motion_data (void)
1272 invariants = VEC_alloc (invariant_p, heap, 100);
1275 /* Frees the data allocated by invariant motion. */
1278 free_inv_motion_data (void)
1282 struct invariant *inv;
1284 check_invariant_table_size ();
1285 for (i = 0; i < DF_DEFS_TABLE_SIZE (); i++)
1287 inv = invariant_table[i];
1291 gcc_assert (def != NULL);
1293 free_use_list (def->uses);
1295 invariant_table[i] = NULL;
1299 for (i = 0; VEC_iterate (invariant_p, invariants, i, inv); i++)
1301 BITMAP_FREE (inv->depends_on);
1304 VEC_free (invariant_p, heap, invariants);
1307 /* Move the invariants out of the LOOP. */
1310 move_single_loop_invariants (struct loop *loop)
1312 init_inv_motion_data ();
1314 find_invariants (loop);
1315 find_invariants_to_move ();
1316 move_invariants (loop);
1318 free_inv_motion_data ();
1321 /* Releases the auxiliary data for LOOP. */
1324 free_loop_data (struct loop *loop)
1326 struct loop_data *data = LOOP_DATA (loop);
1332 /* Move the invariants out of the loops. */
1335 move_loop_invariants (void)
1340 df_set_flags (DF_EQ_NOTES + DF_DEFER_INSN_RESCAN);
1341 /* Process the loops, innermost first. */
1342 FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
1344 move_single_loop_invariants (loop);
1347 FOR_EACH_LOOP (li, loop, 0)
1349 free_loop_data (loop);
1352 free (invariant_table);
1353 invariant_table = NULL;
1354 invariant_table_size = 0;
1356 #ifdef ENABLE_CHECKING
1357 verify_flow_info ();