1 /* Move constant computations out of loops.
2 Copyright (C) 1987, 88, 89, 91-4, 1995 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
21 /* This is the loop optimization pass of the compiler.
22 It finds invariant computations within loops and moves them
23 to the beginning of the loop. Then it identifies basic and
24 general induction variables. Strength reduction is applied to the general
25 induction variables, and induction variable elimination is applied to
26 the basic induction variables.
28 It also finds cases where
29 a register is set within the loop by zero-extending a narrower value
30 and changes these to zero the entire register once before the loop
31 and merely copy the low part within the loop.
33 Most of the complexity is in heuristics to decide when it is worth
34 while to do these things. */
41 #include "insn-config.h"
42 #include "insn-flags.h"
44 #include "hard-reg-set.h"
50 /* Vector mapping INSN_UIDs to luids.
51 The luids are like uids but increase monotonically always.
52 We use them to see whether a jump comes from outside a given loop. */
56 /* Indexed by INSN_UID, contains the ordinal giving the (innermost) loop
57 number the insn is contained in. */
61 /* 1 + largest uid of any insn. */
65 /* 1 + luid of last insn. */
69 /* Number of loops detected in current function. Used as index to the
72 static int max_loop_num;
74 /* Indexed by loop number, contains the first and last insn of each loop. */
76 static rtx *loop_number_loop_starts, *loop_number_loop_ends;
78 /* For each loop, gives the containing loop number, -1 if none. */
82 /* Indexed by loop number, contains a nonzero value if the "loop" isn't
83 really a loop (an insn outside the loop branches into it). */
85 static char *loop_invalid;
87 /* Indexed by loop number, links together all LABEL_REFs which refer to
88 code labels outside the loop. Used by routines that need to know all
89 loop exits, such as final_biv_value and final_giv_value.
91 This does not include loop exits due to return instructions. This is
92 because all bivs and givs are pseudos, and hence must be dead after a
93 return, so the presense of a return does not affect any of the
94 optimizations that use this info. It is simpler to just not include return
95 instructions on this list. */
97 rtx *loop_number_exit_labels;
99 /* Holds the number of loop iterations. It is zero if the number could not be
100 calculated. Must be unsigned since the number of iterations can
101 be as high as 2^wordsize-1. For loops with a wider iterator, this number
102 will will be zero if the number of loop iterations is too large for an
103 unsigned integer to hold. */
105 unsigned HOST_WIDE_INT loop_n_iterations;
107 /* Nonzero if there is a subroutine call in the current loop.
108 (unknown_address_altered is also nonzero in this case.) */
110 static int loop_has_call;
112 /* Nonzero if there is a volatile memory reference in the current
115 static int loop_has_volatile;
117 /* Added loop_continue which is the NOTE_INSN_LOOP_CONT of the
118 current loop. A continue statement will generate a branch to
119 NEXT_INSN (loop_continue). */
121 static rtx loop_continue;
123 /* Indexed by register number, contains the number of times the reg
124 is set during the loop being scanned.
125 During code motion, a negative value indicates a reg that has been
126 made a candidate; in particular -2 means that it is an candidate that
127 we know is equal to a constant and -1 means that it is an candidate
128 not known equal to a constant.
129 After code motion, regs moved have 0 (which is accurate now)
130 while the failed candidates have the original number of times set.
132 Therefore, at all times, == 0 indicates an invariant register;
133 < 0 a conditionally invariant one. */
135 static short *n_times_set;
137 /* Original value of n_times_set; same except that this value
138 is not set negative for a reg whose sets have been made candidates
139 and not set to 0 for a reg that is moved. */
141 static short *n_times_used;
143 /* Index by register number, 1 indicates that the register
144 cannot be moved or strength reduced. */
146 static char *may_not_optimize;
148 /* Nonzero means reg N has already been moved out of one loop.
149 This reduces the desire to move it out of another. */
151 static char *moved_once;
153 /* Array of MEMs that are stored in this loop. If there are too many to fit
154 here, we just turn on unknown_address_altered. */
156 #define NUM_STORES 20
157 static rtx loop_store_mems[NUM_STORES];
159 /* Index of first available slot in above array. */
160 static int loop_store_mems_idx;
162 /* Nonzero if we don't know what MEMs were changed in the current loop.
163 This happens if the loop contains a call (in which case `loop_has_call'
164 will also be set) or if we store into more than NUM_STORES MEMs. */
166 static int unknown_address_altered;
168 /* Count of movable (i.e. invariant) instructions discovered in the loop. */
169 static int num_movables;
171 /* Count of memory write instructions discovered in the loop. */
172 static int num_mem_sets;
174 /* Number of loops contained within the current one, including itself. */
175 static int loops_enclosed;
177 /* Bound on pseudo register number before loop optimization.
178 A pseudo has valid regscan info if its number is < max_reg_before_loop. */
179 int max_reg_before_loop;
181 /* This obstack is used in product_cheap_p to allocate its rtl. It
182 may call gen_reg_rtx which, in turn, may reallocate regno_reg_rtx.
183 If we used the same obstack that it did, we would be deallocating
186 static struct obstack temp_obstack;
188 /* This is where the pointer to the obstack being used for RTL is stored. */
190 extern struct obstack *rtl_obstack;
192 #define obstack_chunk_alloc xmalloc
193 #define obstack_chunk_free free
195 extern char *oballoc ();
197 /* During the analysis of a loop, a chain of `struct movable's
198 is made to record all the movable insns found.
199 Then the entire chain can be scanned to decide which to move. */
203 rtx insn; /* A movable insn */
204 rtx set_src; /* The expression this reg is set from. */
205 rtx set_dest; /* The destination of this SET. */
206 rtx dependencies; /* When INSN is libcall, this is an EXPR_LIST
207 of any registers used within the LIBCALL. */
208 int consec; /* Number of consecutive following insns
209 that must be moved with this one. */
210 int regno; /* The register it sets */
211 short lifetime; /* lifetime of that register;
212 may be adjusted when matching movables
213 that load the same value are found. */
214 short savings; /* Number of insns we can move for this reg,
215 including other movables that force this
216 or match this one. */
217 unsigned int cond : 1; /* 1 if only conditionally movable */
218 unsigned int force : 1; /* 1 means MUST move this insn */
219 unsigned int global : 1; /* 1 means reg is live outside this loop */
220 /* If PARTIAL is 1, GLOBAL means something different:
221 that the reg is live outside the range from where it is set
222 to the following label. */
223 unsigned int done : 1; /* 1 inhibits further processing of this */
225 unsigned int partial : 1; /* 1 means this reg is used for zero-extending.
226 In particular, moving it does not make it
228 unsigned int move_insn : 1; /* 1 means that we call emit_move_insn to
229 load SRC, rather than copying INSN. */
230 unsigned int is_equiv : 1; /* 1 means a REG_EQUIV is present on INSN. */
231 enum machine_mode savemode; /* Nonzero means it is a mode for a low part
232 that we should avoid changing when clearing
233 the rest of the reg. */
234 struct movable *match; /* First entry for same value */
235 struct movable *forces; /* An insn that must be moved if this is */
236 struct movable *next;
239 FILE *loop_dump_stream;
241 /* Forward declarations. */
243 static void find_and_verify_loops ();
244 static void mark_loop_jump ();
245 static void prescan_loop ();
246 static int reg_in_basic_block_p ();
247 static int consec_sets_invariant_p ();
248 static rtx libcall_other_reg ();
249 static int labels_in_range_p ();
250 static void count_loop_regs_set ();
251 static void note_addr_stored ();
252 static int loop_reg_used_before_p ();
253 static void scan_loop ();
254 static void replace_call_address ();
255 static rtx skip_consec_insns ();
256 static int libcall_benefit ();
257 static void ignore_some_movables ();
258 static void force_movables ();
259 static void combine_movables ();
260 static int rtx_equal_for_loop_p ();
261 static void move_movables ();
262 static void strength_reduce ();
263 static int valid_initial_value_p ();
264 static void find_mem_givs ();
265 static void record_biv ();
266 static void check_final_value ();
267 static void record_giv ();
268 static void update_giv_derive ();
269 static int basic_induction_var ();
270 static rtx simplify_giv_expr ();
271 static int general_induction_var ();
272 static int consec_sets_giv ();
273 static int check_dbra_loop ();
274 static rtx express_from ();
275 static int combine_givs_p ();
276 static void combine_givs ();
277 static int product_cheap_p ();
278 static int maybe_eliminate_biv ();
279 static int maybe_eliminate_biv_1 ();
280 static int last_use_this_basic_block ();
281 static void record_initial ();
282 static void update_reg_last_use ();
284 /* Relative gain of eliminating various kinds of operations. */
291 /* Benefit penalty, if a giv is not replaceable, i.e. must emit an insn to
292 copy the value of the strength reduced giv to its original register. */
298 char *free_point = (char *) oballoc (1);
299 rtx reg = gen_rtx (REG, word_mode, 0);
301 add_cost = rtx_cost (gen_rtx (PLUS, word_mode, reg, reg), SET);
303 /* We multiply by 2 to reconcile the difference in scale between
304 these two ways of computing costs. Otherwise the cost of a copy
305 will be far less than the cost of an add. */
309 /* Free the objects we just allocated. */
312 /* Initialize the obstack used for rtl in product_cheap_p. */
313 gcc_obstack_init (&temp_obstack);
316 /* Entry point of this file. Perform loop optimization
317 on the current function. F is the first insn of the function
318 and DUMPFILE is a stream for output of a trace of actions taken
319 (or 0 if none should be output). */
322 loop_optimize (f, dumpfile)
323 /* f is the first instruction of a chain of insns for one function */
331 loop_dump_stream = dumpfile;
333 init_recog_no_volatile ();
334 init_alias_analysis ();
336 max_reg_before_loop = max_reg_num ();
338 moved_once = (char *) alloca (max_reg_before_loop);
339 bzero (moved_once, max_reg_before_loop);
343 /* Count the number of loops. */
346 for (insn = f; insn; insn = NEXT_INSN (insn))
348 if (GET_CODE (insn) == NOTE
349 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
353 /* Don't waste time if no loops. */
354 if (max_loop_num == 0)
357 /* Get size to use for tables indexed by uids.
358 Leave some space for labels allocated by find_and_verify_loops. */
359 max_uid_for_loop = get_max_uid () + 1 + max_loop_num * 32;
361 uid_luid = (int *) alloca (max_uid_for_loop * sizeof (int));
362 uid_loop_num = (int *) alloca (max_uid_for_loop * sizeof (int));
364 bzero ((char *) uid_luid, max_uid_for_loop * sizeof (int));
365 bzero ((char *) uid_loop_num, max_uid_for_loop * sizeof (int));
367 /* Allocate tables for recording each loop. We set each entry, so they need
369 loop_number_loop_starts = (rtx *) alloca (max_loop_num * sizeof (rtx));
370 loop_number_loop_ends = (rtx *) alloca (max_loop_num * sizeof (rtx));
371 loop_outer_loop = (int *) alloca (max_loop_num * sizeof (int));
372 loop_invalid = (char *) alloca (max_loop_num * sizeof (char));
373 loop_number_exit_labels = (rtx *) alloca (max_loop_num * sizeof (rtx));
375 /* Find and process each loop.
376 First, find them, and record them in order of their beginnings. */
377 find_and_verify_loops (f);
379 /* Now find all register lifetimes. This must be done after
380 find_and_verify_loops, because it might reorder the insns in the
382 reg_scan (f, max_reg_num (), 1);
384 /* See if we went too far. */
385 if (get_max_uid () > max_uid_for_loop)
388 /* Compute the mapping from uids to luids.
389 LUIDs are numbers assigned to insns, like uids,
390 except that luids increase monotonically through the code.
391 Don't assign luids to line-number NOTEs, so that the distance in luids
392 between two insns is not affected by -g. */
394 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
397 if (GET_CODE (insn) != NOTE
398 || NOTE_LINE_NUMBER (insn) <= 0)
399 uid_luid[INSN_UID (insn)] = ++i;
401 /* Give a line number note the same luid as preceding insn. */
402 uid_luid[INSN_UID (insn)] = i;
407 /* Don't leave gaps in uid_luid for insns that have been
408 deleted. It is possible that the first or last insn
409 using some register has been deleted by cross-jumping.
410 Make sure that uid_luid for that former insn's uid
411 points to the general area where that insn used to be. */
412 for (i = 0; i < max_uid_for_loop; i++)
414 uid_luid[0] = uid_luid[i];
415 if (uid_luid[0] != 0)
418 for (i = 0; i < max_uid_for_loop; i++)
419 if (uid_luid[i] == 0)
420 uid_luid[i] = uid_luid[i - 1];
422 /* Create a mapping from loops to BLOCK tree nodes. */
423 if (flag_unroll_loops && write_symbols != NO_DEBUG)
424 find_loop_tree_blocks ();
426 /* Now scan the loops, last ones first, since this means inner ones are done
427 before outer ones. */
428 for (i = max_loop_num-1; i >= 0; i--)
429 if (! loop_invalid[i] && loop_number_loop_ends[i])
430 scan_loop (loop_number_loop_starts[i], loop_number_loop_ends[i],
433 /* If debugging and unrolling loops, we must replicate the tree nodes
434 corresponding to the blocks inside the loop, so that the original one
435 to one mapping will remain. */
436 if (flag_unroll_loops && write_symbols != NO_DEBUG)
437 unroll_block_trees ();
440 /* Optimize one loop whose start is LOOP_START and end is END.
441 LOOP_START is the NOTE_INSN_LOOP_BEG and END is the matching
442 NOTE_INSN_LOOP_END. */
444 /* ??? Could also move memory writes out of loops if the destination address
445 is invariant, the source is invariant, the memory write is not volatile,
446 and if we can prove that no read inside the loop can read this address
447 before the write occurs. If there is a read of this address after the
448 write, then we can also mark the memory read as invariant. */
451 scan_loop (loop_start, end, nregs)
457 /* 1 if we are scanning insns that could be executed zero times. */
459 /* 1 if we are scanning insns that might never be executed
460 due to a subroutine call which might exit before they are reached. */
462 /* For a rotated loop that is entered near the bottom,
463 this is the label at the top. Otherwise it is zero. */
465 /* Jump insn that enters the loop, or 0 if control drops in. */
466 rtx loop_entry_jump = 0;
467 /* Place in the loop where control enters. */
469 /* Number of insns in the loop. */
474 /* The SET from an insn, if it is the only SET in the insn. */
476 /* Chain describing insns movable in current loop. */
477 struct movable *movables = 0;
478 /* Last element in `movables' -- so we can add elements at the end. */
479 struct movable *last_movable = 0;
480 /* Ratio of extra register life span we can justify
481 for saving an instruction. More if loop doesn't call subroutines
482 since in that case saving an insn makes more difference
483 and more registers are available. */
485 /* If we have calls, contains the insn in which a register was used
486 if it was used exactly once; contains const0_rtx if it was used more
488 rtx *reg_single_usage = 0;
489 /* Nonzero if we are scanning instructions in a sub-loop. */
492 n_times_set = (short *) alloca (nregs * sizeof (short));
493 n_times_used = (short *) alloca (nregs * sizeof (short));
494 may_not_optimize = (char *) alloca (nregs);
496 /* Determine whether this loop starts with a jump down to a test at
497 the end. This will occur for a small number of loops with a test
498 that is too complex to duplicate in front of the loop.
500 We search for the first insn or label in the loop, skipping NOTEs.
501 However, we must be careful not to skip past a NOTE_INSN_LOOP_BEG
502 (because we might have a loop executed only once that contains a
503 loop which starts with a jump to its exit test) or a NOTE_INSN_LOOP_END
504 (in case we have a degenerate loop).
506 Note that if we mistakenly think that a loop is entered at the top
507 when, in fact, it is entered at the exit test, the only effect will be
508 slightly poorer optimization. Making the opposite error can generate
509 incorrect code. Since very few loops now start with a jump to the
510 exit test, the code here to detect that case is very conservative. */
512 for (p = NEXT_INSN (loop_start);
514 && GET_CODE (p) != CODE_LABEL && GET_RTX_CLASS (GET_CODE (p)) != 'i'
515 && (GET_CODE (p) != NOTE
516 || (NOTE_LINE_NUMBER (p) != NOTE_INSN_LOOP_BEG
517 && NOTE_LINE_NUMBER (p) != NOTE_INSN_LOOP_END));
523 /* Set up variables describing this loop. */
524 prescan_loop (loop_start, end);
525 threshold = (loop_has_call ? 1 : 2) * (1 + n_non_fixed_regs);
527 /* If loop has a jump before the first label,
528 the true entry is the target of that jump.
529 Start scan from there.
530 But record in LOOP_TOP the place where the end-test jumps
531 back to so we can scan that after the end of the loop. */
532 if (GET_CODE (p) == JUMP_INSN)
536 /* Loop entry must be unconditional jump (and not a RETURN) */
538 && JUMP_LABEL (p) != 0
539 /* Check to see whether the jump actually
540 jumps out of the loop (meaning it's no loop).
541 This case can happen for things like
542 do {..} while (0). If this label was generated previously
543 by loop, we can't tell anything about it and have to reject
545 && INSN_UID (JUMP_LABEL (p)) < max_uid_for_loop
546 && INSN_LUID (JUMP_LABEL (p)) >= INSN_LUID (loop_start)
547 && INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (end))
549 loop_top = next_label (scan_start);
550 scan_start = JUMP_LABEL (p);
554 /* If SCAN_START was an insn created by loop, we don't know its luid
555 as required by loop_reg_used_before_p. So skip such loops. (This
556 test may never be true, but it's best to play it safe.)
558 Also, skip loops where we do not start scanning at a label. This
559 test also rejects loops starting with a JUMP_INSN that failed the
562 if (INSN_UID (scan_start) >= max_uid_for_loop
563 || GET_CODE (scan_start) != CODE_LABEL)
565 if (loop_dump_stream)
566 fprintf (loop_dump_stream, "\nLoop from %d to %d is phony.\n\n",
567 INSN_UID (loop_start), INSN_UID (end));
571 /* Count number of times each reg is set during this loop.
572 Set may_not_optimize[I] if it is not safe to move out
573 the setting of register I. If this loop has calls, set
574 reg_single_usage[I]. */
576 bzero ((char *) n_times_set, nregs * sizeof (short));
577 bzero (may_not_optimize, nregs);
581 reg_single_usage = (rtx *) alloca (nregs * sizeof (rtx));
582 bzero ((char *) reg_single_usage, nregs * sizeof (rtx));
585 count_loop_regs_set (loop_top ? loop_top : loop_start, end,
586 may_not_optimize, reg_single_usage, &insn_count, nregs);
588 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
589 may_not_optimize[i] = 1, n_times_set[i] = 1;
590 bcopy ((char *) n_times_set, (char *) n_times_used, nregs * sizeof (short));
592 if (loop_dump_stream)
594 fprintf (loop_dump_stream, "\nLoop from %d to %d: %d real insns.\n",
595 INSN_UID (loop_start), INSN_UID (end), insn_count);
597 fprintf (loop_dump_stream, "Continue at insn %d.\n",
598 INSN_UID (loop_continue));
601 /* Scan through the loop finding insns that are safe to move.
602 Set n_times_set negative for the reg being set, so that
603 this reg will be considered invariant for subsequent insns.
604 We consider whether subsequent insns use the reg
605 in deciding whether it is worth actually moving.
607 MAYBE_NEVER is nonzero if we have passed a conditional jump insn
608 and therefore it is possible that the insns we are scanning
609 would never be executed. At such times, we must make sure
610 that it is safe to execute the insn once instead of zero times.
611 When MAYBE_NEVER is 0, all insns will be executed at least once
612 so that is not a problem. */
618 /* At end of a straight-in loop, we are done.
619 At end of a loop entered at the bottom, scan the top. */
632 if (GET_RTX_CLASS (GET_CODE (p)) == 'i'
633 && find_reg_note (p, REG_LIBCALL, NULL_RTX))
635 else if (GET_RTX_CLASS (GET_CODE (p)) == 'i'
636 && find_reg_note (p, REG_RETVAL, NULL_RTX))
639 if (GET_CODE (p) == INSN
640 && (set = single_set (p))
641 && GET_CODE (SET_DEST (set)) == REG
642 && ! may_not_optimize[REGNO (SET_DEST (set))])
647 rtx src = SET_SRC (set);
648 rtx dependencies = 0;
650 /* Figure out what to use as a source of this insn. If a REG_EQUIV
651 note is given or if a REG_EQUAL note with a constant operand is
652 specified, use it as the source and mark that we should move
653 this insn by calling emit_move_insn rather that duplicating the
656 Otherwise, only use the REG_EQUAL contents if a REG_RETVAL note
658 temp = find_reg_note (p, REG_EQUIV, NULL_RTX);
660 src = XEXP (temp, 0), move_insn = 1;
663 temp = find_reg_note (p, REG_EQUAL, NULL_RTX);
664 if (temp && CONSTANT_P (XEXP (temp, 0)))
665 src = XEXP (temp, 0), move_insn = 1;
666 if (temp && find_reg_note (p, REG_RETVAL, NULL_RTX))
668 src = XEXP (temp, 0);
669 /* A libcall block can use regs that don't appear in
670 the equivalent expression. To move the libcall,
671 we must move those regs too. */
672 dependencies = libcall_other_reg (p, src);
676 /* Don't try to optimize a register that was made
677 by loop-optimization for an inner loop.
678 We don't know its life-span, so we can't compute the benefit. */
679 if (REGNO (SET_DEST (set)) >= max_reg_before_loop)
681 /* In order to move a register, we need to have one of three cases:
682 (1) it is used only in the same basic block as the set
683 (2) it is not a user variable and it is not used in the
684 exit test (this can cause the variable to be used
685 before it is set just like a user-variable).
686 (3) the set is guaranteed to be executed once the loop starts,
687 and the reg is not used until after that. */
688 else if (! ((! maybe_never
689 && ! loop_reg_used_before_p (set, p, loop_start,
691 || (! REG_USERVAR_P (SET_DEST (set))
692 && ! REG_LOOP_TEST_P (SET_DEST (set)))
693 || reg_in_basic_block_p (p, SET_DEST (set))))
695 else if ((tem = invariant_p (src))
696 && (dependencies == 0
697 || (tem2 = invariant_p (dependencies)) != 0)
698 && (n_times_set[REGNO (SET_DEST (set))] == 1
700 = consec_sets_invariant_p (SET_DEST (set),
701 n_times_set[REGNO (SET_DEST (set))],
703 /* If the insn can cause a trap (such as divide by zero),
704 can't move it unless it's guaranteed to be executed
705 once loop is entered. Even a function call might
706 prevent the trap insn from being reached
707 (since it might exit!) */
708 && ! ((maybe_never || call_passed)
709 && may_trap_p (src)))
711 register struct movable *m;
712 register int regno = REGNO (SET_DEST (set));
714 /* A potential lossage is where we have a case where two insns
715 can be combined as long as they are both in the loop, but
716 we move one of them outside the loop. For large loops,
717 this can lose. The most common case of this is the address
718 of a function being called.
720 Therefore, if this register is marked as being used exactly
721 once if we are in a loop with calls (a "large loop"), see if
722 we can replace the usage of this register with the source
723 of this SET. If we can, delete this insn.
725 Don't do this if P has a REG_RETVAL note or if we have
726 SMALL_REGISTER_CLASSES and SET_SRC is a hard register. */
728 if (reg_single_usage && reg_single_usage[regno] != 0
729 && reg_single_usage[regno] != const0_rtx
730 && regno_first_uid[regno] == INSN_UID (p)
731 && (regno_last_uid[regno]
732 == INSN_UID (reg_single_usage[regno]))
733 && n_times_set[REGNO (SET_DEST (set))] == 1
734 && ! side_effects_p (SET_SRC (set))
735 && ! find_reg_note (p, REG_RETVAL, NULL_RTX)
736 #ifdef SMALL_REGISTER_CLASSES
737 && ! (GET_CODE (SET_SRC (set)) == REG
738 && REGNO (SET_SRC (set)) < FIRST_PSEUDO_REGISTER)
740 /* This test is not redundant; SET_SRC (set) might be
741 a call-clobbered register and the life of REGNO
742 might span a call. */
743 && ! modified_between_p (SET_SRC (set), p,
744 reg_single_usage[regno])
745 && no_labels_between_p (p, reg_single_usage[regno])
746 && validate_replace_rtx (SET_DEST (set), SET_SRC (set),
747 reg_single_usage[regno]))
749 /* Replace any usage in a REG_EQUAL note. Must copy the
750 new source, so that we don't get rtx sharing between the
751 SET_SOURCE and REG_NOTES of insn p. */
752 REG_NOTES (reg_single_usage[regno])
753 = replace_rtx (REG_NOTES (reg_single_usage[regno]),
754 SET_DEST (set), copy_rtx (SET_SRC (set)));
757 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
758 NOTE_SOURCE_FILE (p) = 0;
759 n_times_set[regno] = 0;
763 m = (struct movable *) alloca (sizeof (struct movable));
767 m->dependencies = dependencies;
768 m->set_dest = SET_DEST (set);
770 m->consec = n_times_set[REGNO (SET_DEST (set))] - 1;
774 m->move_insn = move_insn;
775 m->is_equiv = (find_reg_note (p, REG_EQUIV, NULL_RTX) != 0);
776 m->savemode = VOIDmode;
778 /* Set M->cond if either invariant_p or consec_sets_invariant_p
779 returned 2 (only conditionally invariant). */
780 m->cond = ((tem | tem1 | tem2) > 1);
781 m->global = (uid_luid[regno_last_uid[regno]] > INSN_LUID (end)
782 || uid_luid[regno_first_uid[regno]] < INSN_LUID (loop_start));
784 m->lifetime = (uid_luid[regno_last_uid[regno]]
785 - uid_luid[regno_first_uid[regno]]);
786 m->savings = n_times_used[regno];
787 if (find_reg_note (p, REG_RETVAL, NULL_RTX))
788 m->savings += libcall_benefit (p);
789 n_times_set[regno] = move_insn ? -2 : -1;
790 /* Add M to the end of the chain MOVABLES. */
794 last_movable->next = m;
799 /* Skip this insn, not checking REG_LIBCALL notes. */
800 p = next_nonnote_insn (p);
801 /* Skip the consecutive insns, if there are any. */
802 p = skip_consec_insns (p, m->consec);
803 /* Back up to the last insn of the consecutive group. */
804 p = prev_nonnote_insn (p);
806 /* We must now reset m->move_insn, m->is_equiv, and possibly
807 m->set_src to correspond to the effects of all the
809 temp = find_reg_note (p, REG_EQUIV, NULL_RTX);
811 m->set_src = XEXP (temp, 0), m->move_insn = 1;
814 temp = find_reg_note (p, REG_EQUAL, NULL_RTX);
815 if (temp && CONSTANT_P (XEXP (temp, 0)))
816 m->set_src = XEXP (temp, 0), m->move_insn = 1;
821 m->is_equiv = (find_reg_note (p, REG_EQUIV, NULL_RTX) != 0);
824 /* If this register is always set within a STRICT_LOW_PART
825 or set to zero, then its high bytes are constant.
826 So clear them outside the loop and within the loop
827 just load the low bytes.
828 We must check that the machine has an instruction to do so.
829 Also, if the value loaded into the register
830 depends on the same register, this cannot be done. */
831 else if (SET_SRC (set) == const0_rtx
832 && GET_CODE (NEXT_INSN (p)) == INSN
833 && (set1 = single_set (NEXT_INSN (p)))
834 && GET_CODE (set1) == SET
835 && (GET_CODE (SET_DEST (set1)) == STRICT_LOW_PART)
836 && (GET_CODE (XEXP (SET_DEST (set1), 0)) == SUBREG)
837 && (SUBREG_REG (XEXP (SET_DEST (set1), 0))
839 && !reg_mentioned_p (SET_DEST (set), SET_SRC (set1)))
841 register int regno = REGNO (SET_DEST (set));
842 if (n_times_set[regno] == 2)
844 register struct movable *m;
845 m = (struct movable *) alloca (sizeof (struct movable));
848 m->set_dest = SET_DEST (set);
856 /* If the insn may not be executed on some cycles,
857 we can't clear the whole reg; clear just high part.
858 Not even if the reg is used only within this loop.
865 Clearing x before the inner loop could clobber a value
866 being saved from the last time around the outer loop.
867 However, if the reg is not used outside this loop
868 and all uses of the register are in the same
869 basic block as the store, there is no problem.
871 If this insn was made by loop, we don't know its
872 INSN_LUID and hence must make a conservative
874 m->global = (INSN_UID (p) >= max_uid_for_loop
875 || (uid_luid[regno_last_uid[regno]]
877 || (uid_luid[regno_first_uid[regno]]
879 || (labels_in_range_p
880 (p, uid_luid[regno_first_uid[regno]])));
881 if (maybe_never && m->global)
882 m->savemode = GET_MODE (SET_SRC (set1));
884 m->savemode = VOIDmode;
888 m->lifetime = (uid_luid[regno_last_uid[regno]]
889 - uid_luid[regno_first_uid[regno]]);
891 n_times_set[regno] = -1;
892 /* Add M to the end of the chain MOVABLES. */
896 last_movable->next = m;
901 /* Past a call insn, we get to insns which might not be executed
902 because the call might exit. This matters for insns that trap.
903 Call insns inside a REG_LIBCALL/REG_RETVAL block always return,
904 so they don't count. */
905 else if (GET_CODE (p) == CALL_INSN && ! in_libcall)
907 /* Past a label or a jump, we get to insns for which we
908 can't count on whether or how many times they will be
909 executed during each iteration. Therefore, we can
910 only move out sets of trivial variables
911 (those not used after the loop). */
912 /* This code appears in three places, once in scan_loop, and twice
913 in strength_reduce. */
914 else if ((GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN)
915 /* If we enter the loop in the middle, and scan around to the
916 beginning, don't set maybe_never for that. This must be an
917 unconditional jump, otherwise the code at the top of the
918 loop might never be executed. Unconditional jumps are
919 followed a by barrier then loop end. */
920 && ! (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == loop_top
921 && NEXT_INSN (NEXT_INSN (p)) == end
922 && simplejump_p (p)))
924 else if (GET_CODE (p) == NOTE)
926 /* At the virtual top of a converted loop, insns are again known to
927 be executed: logically, the loop begins here even though the exit
928 code has been duplicated. */
929 if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_VTOP && loop_depth == 0)
930 maybe_never = call_passed = 0;
931 else if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_BEG)
933 else if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_END)
938 /* If one movable subsumes another, ignore that other. */
940 ignore_some_movables (movables);
942 /* For each movable insn, see if the reg that it loads
943 leads when it dies right into another conditionally movable insn.
944 If so, record that the second insn "forces" the first one,
945 since the second can be moved only if the first is. */
947 force_movables (movables);
949 /* See if there are multiple movable insns that load the same value.
950 If there are, make all but the first point at the first one
951 through the `match' field, and add the priorities of them
952 all together as the priority of the first. */
954 combine_movables (movables, nregs);
956 /* Now consider each movable insn to decide whether it is worth moving.
957 Store 0 in n_times_set for each reg that is moved. */
959 move_movables (movables, threshold,
960 insn_count, loop_start, end, nregs);
962 /* Now candidates that still are negative are those not moved.
963 Change n_times_set to indicate that those are not actually invariant. */
964 for (i = 0; i < nregs; i++)
965 if (n_times_set[i] < 0)
966 n_times_set[i] = n_times_used[i];
968 if (flag_strength_reduce)
969 strength_reduce (scan_start, end, loop_top,
970 insn_count, loop_start, end);
973 /* Add elements to *OUTPUT to record all the pseudo-regs
974 mentioned in IN_THIS but not mentioned in NOT_IN_THIS. */
977 record_excess_regs (in_this, not_in_this, output)
978 rtx in_this, not_in_this;
985 code = GET_CODE (in_this);
999 if (REGNO (in_this) >= FIRST_PSEUDO_REGISTER
1000 && ! reg_mentioned_p (in_this, not_in_this))
1001 *output = gen_rtx (EXPR_LIST, VOIDmode, in_this, *output);
1005 fmt = GET_RTX_FORMAT (code);
1006 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1013 for (j = 0; j < XVECLEN (in_this, i); j++)
1014 record_excess_regs (XVECEXP (in_this, i, j), not_in_this, output);
1018 record_excess_regs (XEXP (in_this, i), not_in_this, output);
1024 /* Check what regs are referred to in the libcall block ending with INSN,
1025 aside from those mentioned in the equivalent value.
1026 If there are none, return 0.
1027 If there are one or more, return an EXPR_LIST containing all of them. */
1030 libcall_other_reg (insn, equiv)
1033 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1034 rtx p = XEXP (note, 0);
1037 /* First, find all the regs used in the libcall block
1038 that are not mentioned as inputs to the result. */
1042 if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
1043 || GET_CODE (p) == CALL_INSN)
1044 record_excess_regs (PATTERN (p), equiv, &output);
1051 /* Return 1 if all uses of REG
1052 are between INSN and the end of the basic block. */
1055 reg_in_basic_block_p (insn, reg)
1058 int regno = REGNO (reg);
1061 if (regno_first_uid[regno] != INSN_UID (insn))
1064 /* Search this basic block for the already recorded last use of the reg. */
1065 for (p = insn; p; p = NEXT_INSN (p))
1067 switch (GET_CODE (p))
1074 /* Ordinary insn: if this is the last use, we win. */
1075 if (regno_last_uid[regno] == INSN_UID (p))
1080 /* Jump insn: if this is the last use, we win. */
1081 if (regno_last_uid[regno] == INSN_UID (p))
1083 /* Otherwise, it's the end of the basic block, so we lose. */
1088 /* It's the end of the basic block, so we lose. */
1093 /* The "last use" doesn't follow the "first use"?? */
1097 /* Compute the benefit of eliminating the insns in the block whose
1098 last insn is LAST. This may be a group of insns used to compute a
1099 value directly or can contain a library call. */
1102 libcall_benefit (last)
1108 for (insn = XEXP (find_reg_note (last, REG_RETVAL, NULL_RTX), 0);
1109 insn != last; insn = NEXT_INSN (insn))
1111 if (GET_CODE (insn) == CALL_INSN)
1112 benefit += 10; /* Assume at least this many insns in a library
1114 else if (GET_CODE (insn) == INSN
1115 && GET_CODE (PATTERN (insn)) != USE
1116 && GET_CODE (PATTERN (insn)) != CLOBBER)
1123 /* Skip COUNT insns from INSN, counting library calls as 1 insn. */
1126 skip_consec_insns (insn, count)
1130 for (; count > 0; count--)
1134 /* If first insn of libcall sequence, skip to end. */
1135 /* Do this at start of loop, since INSN is guaranteed to
1137 if (GET_CODE (insn) != NOTE
1138 && (temp = find_reg_note (insn, REG_LIBCALL, NULL_RTX)))
1139 insn = XEXP (temp, 0);
1141 do insn = NEXT_INSN (insn);
1142 while (GET_CODE (insn) == NOTE);
1148 /* Ignore any movable whose insn falls within a libcall
1149 which is part of another movable.
1150 We make use of the fact that the movable for the libcall value
1151 was made later and so appears later on the chain. */
1154 ignore_some_movables (movables)
1155 struct movable *movables;
1157 register struct movable *m, *m1;
1159 for (m = movables; m; m = m->next)
1161 /* Is this a movable for the value of a libcall? */
1162 rtx note = find_reg_note (m->insn, REG_RETVAL, NULL_RTX);
1166 /* Check for earlier movables inside that range,
1167 and mark them invalid. We cannot use LUIDs here because
1168 insns created by loop.c for prior loops don't have LUIDs.
1169 Rather than reject all such insns from movables, we just
1170 explicitly check each insn in the libcall (since invariant
1171 libcalls aren't that common). */
1172 for (insn = XEXP (note, 0); insn != m->insn; insn = NEXT_INSN (insn))
1173 for (m1 = movables; m1 != m; m1 = m1->next)
1174 if (m1->insn == insn)
1180 /* For each movable insn, see if the reg that it loads
1181 leads when it dies right into another conditionally movable insn.
1182 If so, record that the second insn "forces" the first one,
1183 since the second can be moved only if the first is. */
1186 force_movables (movables)
1187 struct movable *movables;
1189 register struct movable *m, *m1;
1190 for (m1 = movables; m1; m1 = m1->next)
1191 /* Omit this if moving just the (SET (REG) 0) of a zero-extend. */
1192 if (!m1->partial && !m1->done)
1194 int regno = m1->regno;
1195 for (m = m1->next; m; m = m->next)
1196 /* ??? Could this be a bug? What if CSE caused the
1197 register of M1 to be used after this insn?
1198 Since CSE does not update regno_last_uid,
1199 this insn M->insn might not be where it dies.
1200 But very likely this doesn't matter; what matters is
1201 that M's reg is computed from M1's reg. */
1202 if (INSN_UID (m->insn) == regno_last_uid[regno]
1205 if (m != 0 && m->set_src == m1->set_dest
1206 /* If m->consec, m->set_src isn't valid. */
1210 /* Increase the priority of the moving the first insn
1211 since it permits the second to be moved as well. */
1215 m1->lifetime += m->lifetime;
1216 m1->savings += m1->savings;
1221 /* Find invariant expressions that are equal and can be combined into
1225 combine_movables (movables, nregs)
1226 struct movable *movables;
1229 register struct movable *m;
1230 char *matched_regs = (char *) alloca (nregs);
1231 enum machine_mode mode;
1233 /* Regs that are set more than once are not allowed to match
1234 or be matched. I'm no longer sure why not. */
1235 /* Perhaps testing m->consec_sets would be more appropriate here? */
1237 for (m = movables; m; m = m->next)
1238 if (m->match == 0 && n_times_used[m->regno] == 1 && !m->partial)
1240 register struct movable *m1;
1241 int regno = m->regno;
1243 bzero (matched_regs, nregs);
1244 matched_regs[regno] = 1;
1246 for (m1 = movables; m1; m1 = m1->next)
1247 if (m != m1 && m1->match == 0 && n_times_used[m1->regno] == 1
1248 /* A reg used outside the loop mustn't be eliminated. */
1250 /* A reg used for zero-extending mustn't be eliminated. */
1252 && (matched_regs[m1->regno]
1255 /* Can combine regs with different modes loaded from the
1256 same constant only if the modes are the same or
1257 if both are integer modes with M wider or the same
1258 width as M1. The check for integer is redundant, but
1259 safe, since the only case of differing destination
1260 modes with equal sources is when both sources are
1261 VOIDmode, i.e., CONST_INT. */
1262 (GET_MODE (m->set_dest) == GET_MODE (m1->set_dest)
1263 || (GET_MODE_CLASS (GET_MODE (m->set_dest)) == MODE_INT
1264 && GET_MODE_CLASS (GET_MODE (m1->set_dest)) == MODE_INT
1265 && (GET_MODE_BITSIZE (GET_MODE (m->set_dest))
1266 >= GET_MODE_BITSIZE (GET_MODE (m1->set_dest)))))
1267 /* See if the source of M1 says it matches M. */
1268 && ((GET_CODE (m1->set_src) == REG
1269 && matched_regs[REGNO (m1->set_src)])
1270 || rtx_equal_for_loop_p (m->set_src, m1->set_src,
1272 && ((m->dependencies == m1->dependencies)
1273 || rtx_equal_p (m->dependencies, m1->dependencies)))
1275 m->lifetime += m1->lifetime;
1276 m->savings += m1->savings;
1279 matched_regs[m1->regno] = 1;
1283 /* Now combine the regs used for zero-extension.
1284 This can be done for those not marked `global'
1285 provided their lives don't overlap. */
1287 for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT); mode != VOIDmode;
1288 mode = GET_MODE_WIDER_MODE (mode))
1290 register struct movable *m0 = 0;
1292 /* Combine all the registers for extension from mode MODE.
1293 Don't combine any that are used outside this loop. */
1294 for (m = movables; m; m = m->next)
1295 if (m->partial && ! m->global
1296 && mode == GET_MODE (SET_SRC (PATTERN (NEXT_INSN (m->insn)))))
1298 register struct movable *m1;
1299 int first = uid_luid[regno_first_uid[m->regno]];
1300 int last = uid_luid[regno_last_uid[m->regno]];
1304 /* First one: don't check for overlap, just record it. */
1309 /* Make sure they extend to the same mode.
1310 (Almost always true.) */
1311 if (GET_MODE (m->set_dest) != GET_MODE (m0->set_dest))
1314 /* We already have one: check for overlap with those
1315 already combined together. */
1316 for (m1 = movables; m1 != m; m1 = m1->next)
1317 if (m1 == m0 || (m1->partial && m1->match == m0))
1318 if (! (uid_luid[regno_first_uid[m1->regno]] > last
1319 || uid_luid[regno_last_uid[m1->regno]] < first))
1322 /* No overlap: we can combine this with the others. */
1323 m0->lifetime += m->lifetime;
1324 m0->savings += m->savings;
1333 /* Return 1 if regs X and Y will become the same if moved. */
1336 regs_match_p (x, y, movables)
1338 struct movable *movables;
1342 struct movable *mx, *my;
1344 for (mx = movables; mx; mx = mx->next)
1345 if (mx->regno == xn)
1348 for (my = movables; my; my = my->next)
1349 if (my->regno == yn)
1353 && ((mx->match == my->match && mx->match != 0)
1355 || mx == my->match));
1358 /* Return 1 if X and Y are identical-looking rtx's.
1359 This is the Lisp function EQUAL for rtx arguments.
1361 If two registers are matching movables or a movable register and an
1362 equivalent constant, consider them equal. */
1365 rtx_equal_for_loop_p (x, y, movables)
1367 struct movable *movables;
1371 register struct movable *m;
1372 register enum rtx_code code;
1377 if (x == 0 || y == 0)
1380 code = GET_CODE (x);
1382 /* If we have a register and a constant, they may sometimes be
1384 if (GET_CODE (x) == REG && n_times_set[REGNO (x)] == -2
1386 for (m = movables; m; m = m->next)
1387 if (m->move_insn && m->regno == REGNO (x)
1388 && rtx_equal_p (m->set_src, y))
1391 else if (GET_CODE (y) == REG && n_times_set[REGNO (y)] == -2
1393 for (m = movables; m; m = m->next)
1394 if (m->move_insn && m->regno == REGNO (y)
1395 && rtx_equal_p (m->set_src, x))
1398 /* Otherwise, rtx's of different codes cannot be equal. */
1399 if (code != GET_CODE (y))
1402 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1403 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1405 if (GET_MODE (x) != GET_MODE (y))
1408 /* These three types of rtx's can be compared nonrecursively. */
1410 return (REGNO (x) == REGNO (y) || regs_match_p (x, y, movables));
1412 if (code == LABEL_REF)
1413 return XEXP (x, 0) == XEXP (y, 0);
1414 if (code == SYMBOL_REF)
1415 return XSTR (x, 0) == XSTR (y, 0);
1417 /* Compare the elements. If any pair of corresponding elements
1418 fail to match, return 0 for the whole things. */
1420 fmt = GET_RTX_FORMAT (code);
1421 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1426 if (XWINT (x, i) != XWINT (y, i))
1431 if (XINT (x, i) != XINT (y, i))
1436 /* Two vectors must have the same length. */
1437 if (XVECLEN (x, i) != XVECLEN (y, i))
1440 /* And the corresponding elements must match. */
1441 for (j = 0; j < XVECLEN (x, i); j++)
1442 if (rtx_equal_for_loop_p (XVECEXP (x, i, j), XVECEXP (y, i, j), movables) == 0)
1447 if (rtx_equal_for_loop_p (XEXP (x, i), XEXP (y, i), movables) == 0)
1452 if (strcmp (XSTR (x, i), XSTR (y, i)))
1457 /* These are just backpointers, so they don't matter. */
1463 /* It is believed that rtx's at this level will never
1464 contain anything but integers and other rtx's,
1465 except for within LABEL_REFs and SYMBOL_REFs. */
1473 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to all
1474 insns in INSNS which use thet reference. */
1477 add_label_notes (x, insns)
1481 enum rtx_code code = GET_CODE (x);
1486 if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
1488 rtx next = next_real_insn (XEXP (x, 0));
1490 /* Don't record labels that refer to dispatch tables.
1491 This is not necessary, since the tablejump references the same label.
1492 And if we did record them, flow.c would make worse code. */
1494 || ! (GET_CODE (next) == JUMP_INSN
1495 && (GET_CODE (PATTERN (next)) == ADDR_VEC
1496 || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC)))
1498 for (insn = insns; insn; insn = NEXT_INSN (insn))
1499 if (reg_mentioned_p (XEXP (x, 0), insn))
1500 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_LABEL, XEXP (x, 0),
1506 fmt = GET_RTX_FORMAT (code);
1507 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1510 add_label_notes (XEXP (x, i), insns);
1511 else if (fmt[i] == 'E')
1512 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
1513 add_label_notes (XVECEXP (x, i, j), insns);
1517 /* Scan MOVABLES, and move the insns that deserve to be moved.
1518 If two matching movables are combined, replace one reg with the
1519 other throughout. */
1522 move_movables (movables, threshold, insn_count, loop_start, end, nregs)
1523 struct movable *movables;
1531 register struct movable *m;
1533 /* Map of pseudo-register replacements to handle combining
1534 when we move several insns that load the same value
1535 into different pseudo-registers. */
1536 rtx *reg_map = (rtx *) alloca (nregs * sizeof (rtx));
1537 char *already_moved = (char *) alloca (nregs);
1539 bzero (already_moved, nregs);
1540 bzero ((char *) reg_map, nregs * sizeof (rtx));
1544 for (m = movables; m; m = m->next)
1546 /* Describe this movable insn. */
1548 if (loop_dump_stream)
1550 fprintf (loop_dump_stream, "Insn %d: regno %d (life %d), ",
1551 INSN_UID (m->insn), m->regno, m->lifetime);
1553 fprintf (loop_dump_stream, "consec %d, ", m->consec);
1555 fprintf (loop_dump_stream, "cond ");
1557 fprintf (loop_dump_stream, "force ");
1559 fprintf (loop_dump_stream, "global ");
1561 fprintf (loop_dump_stream, "done ");
1563 fprintf (loop_dump_stream, "move-insn ");
1565 fprintf (loop_dump_stream, "matches %d ",
1566 INSN_UID (m->match->insn));
1568 fprintf (loop_dump_stream, "forces %d ",
1569 INSN_UID (m->forces->insn));
1572 /* Count movables. Value used in heuristics in strength_reduce. */
1575 /* Ignore the insn if it's already done (it matched something else).
1576 Otherwise, see if it is now safe to move. */
1580 || (1 == invariant_p (m->set_src)
1581 && (m->dependencies == 0
1582 || 1 == invariant_p (m->dependencies))
1584 || 1 == consec_sets_invariant_p (m->set_dest,
1587 && (! m->forces || m->forces->done))
1591 int savings = m->savings;
1593 /* We have an insn that is safe to move.
1594 Compute its desirability. */
1599 if (loop_dump_stream)
1600 fprintf (loop_dump_stream, "savings %d ", savings);
1602 if (moved_once[regno])
1606 if (loop_dump_stream)
1607 fprintf (loop_dump_stream, "halved since already moved ");
1610 /* An insn MUST be moved if we already moved something else
1611 which is safe only if this one is moved too: that is,
1612 if already_moved[REGNO] is nonzero. */
1614 /* An insn is desirable to move if the new lifetime of the
1615 register is no more than THRESHOLD times the old lifetime.
1616 If it's not desirable, it means the loop is so big
1617 that moving won't speed things up much,
1618 and it is liable to make register usage worse. */
1620 /* It is also desirable to move if it can be moved at no
1621 extra cost because something else was already moved. */
1623 if (already_moved[regno]
1624 || (threshold * savings * m->lifetime) >= insn_count
1625 || (m->forces && m->forces->done
1626 && n_times_used[m->forces->regno] == 1))
1629 register struct movable *m1;
1632 /* Now move the insns that set the reg. */
1634 if (m->partial && m->match)
1638 /* Find the end of this chain of matching regs.
1639 Thus, we load each reg in the chain from that one reg.
1640 And that reg is loaded with 0 directly,
1641 since it has ->match == 0. */
1642 for (m1 = m; m1->match; m1 = m1->match);
1643 newpat = gen_move_insn (SET_DEST (PATTERN (m->insn)),
1644 SET_DEST (PATTERN (m1->insn)));
1645 i1 = emit_insn_before (newpat, loop_start);
1647 /* Mark the moved, invariant reg as being allowed to
1648 share a hard reg with the other matching invariant. */
1649 REG_NOTES (i1) = REG_NOTES (m->insn);
1650 r1 = SET_DEST (PATTERN (m->insn));
1651 r2 = SET_DEST (PATTERN (m1->insn));
1652 regs_may_share = gen_rtx (EXPR_LIST, VOIDmode, r1,
1653 gen_rtx (EXPR_LIST, VOIDmode, r2,
1655 delete_insn (m->insn);
1660 if (loop_dump_stream)
1661 fprintf (loop_dump_stream, " moved to %d", INSN_UID (i1));
1663 /* If we are to re-generate the item being moved with a
1664 new move insn, first delete what we have and then emit
1665 the move insn before the loop. */
1666 else if (m->move_insn)
1670 for (count = m->consec; count >= 0; count--)
1672 /* If this is the first insn of a library call sequence,
1674 if (GET_CODE (p) != NOTE
1675 && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX)))
1678 /* If this is the last insn of a libcall sequence, then
1679 delete every insn in the sequence except the last.
1680 The last insn is handled in the normal manner. */
1681 if (GET_CODE (p) != NOTE
1682 && (temp = find_reg_note (p, REG_RETVAL, NULL_RTX)))
1684 temp = XEXP (temp, 0);
1686 temp = delete_insn (temp);
1689 p = delete_insn (p);
1690 while (p && GET_CODE (p) == NOTE)
1695 emit_move_insn (m->set_dest, m->set_src);
1696 temp = get_insns ();
1699 add_label_notes (m->set_src, temp);
1701 i1 = emit_insns_before (temp, loop_start);
1702 if (! find_reg_note (i1, REG_EQUAL, NULL_RTX))
1704 = gen_rtx (EXPR_LIST,
1705 m->is_equiv ? REG_EQUIV : REG_EQUAL,
1706 m->set_src, REG_NOTES (i1));
1708 if (loop_dump_stream)
1709 fprintf (loop_dump_stream, " moved to %d", INSN_UID (i1));
1711 /* The more regs we move, the less we like moving them. */
1716 for (count = m->consec; count >= 0; count--)
1720 /* If first insn of libcall sequence, skip to end. */
1721 /* Do this at start of loop, since p is guaranteed to
1723 if (GET_CODE (p) != NOTE
1724 && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX)))
1727 /* If last insn of libcall sequence, move all
1728 insns except the last before the loop. The last
1729 insn is handled in the normal manner. */
1730 if (GET_CODE (p) != NOTE
1731 && (temp = find_reg_note (p, REG_RETVAL, NULL_RTX)))
1735 rtx fn_address_insn = 0;
1738 for (temp = XEXP (temp, 0); temp != p;
1739 temp = NEXT_INSN (temp))
1745 if (GET_CODE (temp) == NOTE)
1748 body = PATTERN (temp);
1750 /* Find the next insn after TEMP,
1751 not counting USE or NOTE insns. */
1752 for (next = NEXT_INSN (temp); next != p;
1753 next = NEXT_INSN (next))
1754 if (! (GET_CODE (next) == INSN
1755 && GET_CODE (PATTERN (next)) == USE)
1756 && GET_CODE (next) != NOTE)
1759 /* If that is the call, this may be the insn
1760 that loads the function address.
1762 Extract the function address from the insn
1763 that loads it into a register.
1764 If this insn was cse'd, we get incorrect code.
1766 So emit a new move insn that copies the
1767 function address into the register that the
1768 call insn will use. flow.c will delete any
1769 redundant stores that we have created. */
1770 if (GET_CODE (next) == CALL_INSN
1771 && GET_CODE (body) == SET
1772 && GET_CODE (SET_DEST (body)) == REG
1773 && (n = find_reg_note (temp, REG_EQUAL,
1776 fn_reg = SET_SRC (body);
1777 if (GET_CODE (fn_reg) != REG)
1778 fn_reg = SET_DEST (body);
1779 fn_address = XEXP (n, 0);
1780 fn_address_insn = temp;
1782 /* We have the call insn.
1783 If it uses the register we suspect it might,
1784 load it with the correct address directly. */
1785 if (GET_CODE (temp) == CALL_INSN
1787 && reg_referenced_p (fn_reg, body))
1788 emit_insn_after (gen_move_insn (fn_reg,
1792 if (GET_CODE (temp) == CALL_INSN)
1794 i1 = emit_call_insn_before (body, loop_start);
1795 /* Because the USAGE information potentially
1796 contains objects other than hard registers
1797 we need to copy it. */
1798 if (CALL_INSN_FUNCTION_USAGE (temp))
1799 CALL_INSN_FUNCTION_USAGE (i1) =
1800 copy_rtx (CALL_INSN_FUNCTION_USAGE (temp));
1803 i1 = emit_insn_before (body, loop_start);
1806 if (temp == fn_address_insn)
1807 fn_address_insn = i1;
1808 REG_NOTES (i1) = REG_NOTES (temp);
1812 if (m->savemode != VOIDmode)
1814 /* P sets REG to zero; but we should clear only
1815 the bits that are not covered by the mode
1817 rtx reg = m->set_dest;
1823 (GET_MODE (reg), and_optab, reg,
1824 GEN_INT ((((HOST_WIDE_INT) 1
1825 << GET_MODE_BITSIZE (m->savemode)))
1827 reg, 1, OPTAB_LIB_WIDEN);
1831 emit_move_insn (reg, tem);
1832 sequence = gen_sequence ();
1834 i1 = emit_insn_before (sequence, loop_start);
1836 else if (GET_CODE (p) == CALL_INSN)
1838 i1 = emit_call_insn_before (PATTERN (p), loop_start);
1839 /* Because the USAGE information potentially
1840 contains objects other than hard registers
1841 we need to copy it. */
1842 if (CALL_INSN_FUNCTION_USAGE (p))
1843 CALL_INSN_FUNCTION_USAGE (i1) =
1844 copy_rtx (CALL_INSN_FUNCTION_USAGE (p));
1847 i1 = emit_insn_before (PATTERN (p), loop_start);
1849 REG_NOTES (i1) = REG_NOTES (p);
1851 /* If there is a REG_EQUAL note present whose value is
1852 not loop invariant, then delete it, since it may
1853 cause problems with later optimization passes.
1854 It is possible for cse to create such notes
1855 like this as a result of record_jump_cond. */
1857 if ((temp = find_reg_note (i1, REG_EQUAL, NULL_RTX))
1858 && ! invariant_p (XEXP (temp, 0)))
1859 remove_note (i1, temp);
1864 if (loop_dump_stream)
1865 fprintf (loop_dump_stream, " moved to %d",
1869 /* This isn't needed because REG_NOTES is copied
1870 below and is wrong since P might be a PARALLEL. */
1871 if (REG_NOTES (i1) == 0
1872 && ! m->partial /* But not if it's a zero-extend clr. */
1873 && ! m->global /* and not if used outside the loop
1874 (since it might get set outside). */
1875 && CONSTANT_P (SET_SRC (PATTERN (p))))
1877 = gen_rtx (EXPR_LIST, REG_EQUAL,
1878 SET_SRC (PATTERN (p)), REG_NOTES (i1));
1881 /* If library call, now fix the REG_NOTES that contain
1882 insn pointers, namely REG_LIBCALL on FIRST
1883 and REG_RETVAL on I1. */
1884 if (temp = find_reg_note (i1, REG_RETVAL, NULL_RTX))
1886 XEXP (temp, 0) = first;
1887 temp = find_reg_note (first, REG_LIBCALL, NULL_RTX);
1888 XEXP (temp, 0) = i1;
1892 do p = NEXT_INSN (p);
1893 while (p && GET_CODE (p) == NOTE);
1896 /* The more regs we move, the less we like moving them. */
1900 /* Any other movable that loads the same register
1902 already_moved[regno] = 1;
1904 /* This reg has been moved out of one loop. */
1905 moved_once[regno] = 1;
1907 /* The reg set here is now invariant. */
1909 n_times_set[regno] = 0;
1913 /* Change the length-of-life info for the register
1914 to say it lives at least the full length of this loop.
1915 This will help guide optimizations in outer loops. */
1917 if (uid_luid[regno_first_uid[regno]] > INSN_LUID (loop_start))
1918 /* This is the old insn before all the moved insns.
1919 We can't use the moved insn because it is out of range
1920 in uid_luid. Only the old insns have luids. */
1921 regno_first_uid[regno] = INSN_UID (loop_start);
1922 if (uid_luid[regno_last_uid[regno]] < INSN_LUID (end))
1923 regno_last_uid[regno] = INSN_UID (end);
1925 /* Combine with this moved insn any other matching movables. */
1928 for (m1 = movables; m1; m1 = m1->next)
1933 /* Schedule the reg loaded by M1
1934 for replacement so that shares the reg of M.
1935 If the modes differ (only possible in restricted
1936 circumstances, make a SUBREG. */
1937 if (GET_MODE (m->set_dest) == GET_MODE (m1->set_dest))
1938 reg_map[m1->regno] = m->set_dest;
1941 = gen_lowpart_common (GET_MODE (m1->set_dest),
1944 /* Get rid of the matching insn
1945 and prevent further processing of it. */
1948 /* if library call, delete all insn except last, which
1950 if (temp = find_reg_note (m1->insn, REG_RETVAL,
1953 for (temp = XEXP (temp, 0); temp != m1->insn;
1954 temp = NEXT_INSN (temp))
1957 delete_insn (m1->insn);
1959 /* Any other movable that loads the same register
1961 already_moved[m1->regno] = 1;
1963 /* The reg merged here is now invariant,
1964 if the reg it matches is invariant. */
1966 n_times_set[m1->regno] = 0;
1969 else if (loop_dump_stream)
1970 fprintf (loop_dump_stream, "not desirable");
1972 else if (loop_dump_stream && !m->match)
1973 fprintf (loop_dump_stream, "not safe");
1975 if (loop_dump_stream)
1976 fprintf (loop_dump_stream, "\n");
1980 new_start = loop_start;
1982 /* Go through all the instructions in the loop, making
1983 all the register substitutions scheduled in REG_MAP. */
1984 for (p = new_start; p != end; p = NEXT_INSN (p))
1985 if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
1986 || GET_CODE (p) == CALL_INSN)
1988 replace_regs (PATTERN (p), reg_map, nregs, 0);
1989 replace_regs (REG_NOTES (p), reg_map, nregs, 0);
1995 /* Scan X and replace the address of any MEM in it with ADDR.
1996 REG is the address that MEM should have before the replacement. */
1999 replace_call_address (x, reg, addr)
2002 register enum rtx_code code;
2008 code = GET_CODE (x);
2022 /* Short cut for very common case. */
2023 replace_call_address (XEXP (x, 1), reg, addr);
2027 /* Short cut for very common case. */
2028 replace_call_address (XEXP (x, 0), reg, addr);
2032 /* If this MEM uses a reg other than the one we expected,
2033 something is wrong. */
2034 if (XEXP (x, 0) != reg)
2040 fmt = GET_RTX_FORMAT (code);
2041 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2044 replace_call_address (XEXP (x, i), reg, addr);
2048 for (j = 0; j < XVECLEN (x, i); j++)
2049 replace_call_address (XVECEXP (x, i, j), reg, addr);
2055 /* Return the number of memory refs to addresses that vary
2059 count_nonfixed_reads (x)
2062 register enum rtx_code code;
2070 code = GET_CODE (x);
2084 return ((invariant_p (XEXP (x, 0)) != 1)
2085 + count_nonfixed_reads (XEXP (x, 0)));
2089 fmt = GET_RTX_FORMAT (code);
2090 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2093 value += count_nonfixed_reads (XEXP (x, i));
2097 for (j = 0; j < XVECLEN (x, i); j++)
2098 value += count_nonfixed_reads (XVECEXP (x, i, j));
2106 /* P is an instruction that sets a register to the result of a ZERO_EXTEND.
2107 Replace it with an instruction to load just the low bytes
2108 if the machine supports such an instruction,
2109 and insert above LOOP_START an instruction to clear the register. */
2112 constant_high_bytes (p, loop_start)
2116 register int insn_code_number;
2118 /* Try to change (SET (REG ...) (ZERO_EXTEND (..:B ...)))
2119 to (SET (STRICT_LOW_PART (SUBREG:B (REG...))) ...). */
2121 new = gen_rtx (SET, VOIDmode,
2122 gen_rtx (STRICT_LOW_PART, VOIDmode,
2123 gen_rtx (SUBREG, GET_MODE (XEXP (SET_SRC (PATTERN (p)), 0)),
2124 SET_DEST (PATTERN (p)),
2126 XEXP (SET_SRC (PATTERN (p)), 0));
2127 insn_code_number = recog (new, p);
2129 if (insn_code_number)
2133 /* Clear destination register before the loop. */
2134 emit_insn_before (gen_rtx (SET, VOIDmode,
2135 SET_DEST (PATTERN (p)),
2139 /* Inside the loop, just load the low part. */
2145 /* Scan a loop setting the variables `unknown_address_altered',
2146 `num_mem_sets', `loop_continue', loops_enclosed', `loop_has_call',
2147 and `loop_has_volatile'.
2148 Also, fill in the array `loop_store_mems'. */
2151 prescan_loop (start, end)
2154 register int level = 1;
2157 unknown_address_altered = 0;
2159 loop_has_volatile = 0;
2160 loop_store_mems_idx = 0;
2166 for (insn = NEXT_INSN (start); insn != NEXT_INSN (end);
2167 insn = NEXT_INSN (insn))
2169 if (GET_CODE (insn) == NOTE)
2171 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
2174 /* Count number of loops contained in this one. */
2177 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
2186 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_CONT)
2189 loop_continue = insn;
2192 else if (GET_CODE (insn) == CALL_INSN)
2194 unknown_address_altered = 1;
2199 if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
2201 if (volatile_refs_p (PATTERN (insn)))
2202 loop_has_volatile = 1;
2204 note_stores (PATTERN (insn), note_addr_stored);
2210 /* Scan the function looking for loops. Record the start and end of each loop.
2211 Also mark as invalid loops any loops that contain a setjmp or are branched
2212 to from outside the loop. */
2215 find_and_verify_loops (f)
2219 int current_loop = -1;
2223 /* If there are jumps to undefined labels,
2224 treat them as jumps out of any/all loops.
2225 This also avoids writing past end of tables when there are no loops. */
2226 uid_loop_num[0] = -1;
2228 /* Find boundaries of loops, mark which loops are contained within
2229 loops, and invalidate loops that have setjmp. */
2231 for (insn = f; insn; insn = NEXT_INSN (insn))
2233 if (GET_CODE (insn) == NOTE)
2234 switch (NOTE_LINE_NUMBER (insn))
2236 case NOTE_INSN_LOOP_BEG:
2237 loop_number_loop_starts[++next_loop] = insn;
2238 loop_number_loop_ends[next_loop] = 0;
2239 loop_outer_loop[next_loop] = current_loop;
2240 loop_invalid[next_loop] = 0;
2241 loop_number_exit_labels[next_loop] = 0;
2242 current_loop = next_loop;
2245 case NOTE_INSN_SETJMP:
2246 /* In this case, we must invalidate our current loop and any
2248 for (loop = current_loop; loop != -1; loop = loop_outer_loop[loop])
2250 loop_invalid[loop] = 1;
2251 if (loop_dump_stream)
2252 fprintf (loop_dump_stream,
2253 "\nLoop at %d ignored due to setjmp.\n",
2254 INSN_UID (loop_number_loop_starts[loop]));
2258 case NOTE_INSN_LOOP_END:
2259 if (current_loop == -1)
2262 loop_number_loop_ends[current_loop] = insn;
2263 current_loop = loop_outer_loop[current_loop];
2268 /* Note that this will mark the NOTE_INSN_LOOP_END note as being in the
2269 enclosing loop, but this doesn't matter. */
2270 uid_loop_num[INSN_UID (insn)] = current_loop;
2273 /* Any loop containing a label used in an initializer must be invalidated,
2274 because it can be jumped into from anywhere. */
2276 for (label = forced_labels; label; label = XEXP (label, 1))
2280 for (loop_num = uid_loop_num[INSN_UID (XEXP (label, 0))];
2282 loop_num = loop_outer_loop[loop_num])
2283 loop_invalid[loop_num] = 1;
2286 /* Now scan all insn's in the function. If any JUMP_INSN branches into a
2287 loop that it is not contained within, that loop is marked invalid.
2288 If any INSN or CALL_INSN uses a label's address, then the loop containing
2289 that label is marked invalid, because it could be jumped into from
2292 Also look for blocks of code ending in an unconditional branch that
2293 exits the loop. If such a block is surrounded by a conditional
2294 branch around the block, move the block elsewhere (see below) and
2295 invert the jump to point to the code block. This may eliminate a
2296 label in our loop and will simplify processing by both us and a
2297 possible second cse pass. */
2299 for (insn = f; insn; insn = NEXT_INSN (insn))
2300 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
2302 int this_loop_num = uid_loop_num[INSN_UID (insn)];
2304 if (GET_CODE (insn) == INSN || GET_CODE (insn) == CALL_INSN)
2306 rtx note = find_reg_note (insn, REG_LABEL, NULL_RTX);
2311 for (loop_num = uid_loop_num[INSN_UID (XEXP (note, 0))];
2313 loop_num = loop_outer_loop[loop_num])
2314 loop_invalid[loop_num] = 1;
2318 if (GET_CODE (insn) != JUMP_INSN)
2321 mark_loop_jump (PATTERN (insn), this_loop_num);
2323 /* See if this is an unconditional branch outside the loop. */
2324 if (this_loop_num != -1
2325 && (GET_CODE (PATTERN (insn)) == RETURN
2326 || (simplejump_p (insn)
2327 && (uid_loop_num[INSN_UID (JUMP_LABEL (insn))]
2329 && get_max_uid () < max_uid_for_loop)
2332 rtx our_next = next_real_insn (insn);
2334 /* Go backwards until we reach the start of the loop, a label,
2336 for (p = PREV_INSN (insn);
2337 GET_CODE (p) != CODE_LABEL
2338 && ! (GET_CODE (p) == NOTE
2339 && NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_BEG)
2340 && GET_CODE (p) != JUMP_INSN;
2344 /* If we stopped on a JUMP_INSN to the next insn after INSN,
2345 we have a block of code to try to move.
2347 We look backward and then forward from the target of INSN
2348 to find a BARRIER at the same loop depth as the target.
2349 If we find such a BARRIER, we make a new label for the start
2350 of the block, invert the jump in P and point it to that label,
2351 and move the block of code to the spot we found. */
2353 if (GET_CODE (p) == JUMP_INSN
2354 && JUMP_LABEL (p) != 0
2355 /* Just ignore jumps to labels that were never emitted.
2356 These always indicate compilation errors. */
2357 && INSN_UID (JUMP_LABEL (p)) != 0
2359 && ! simplejump_p (p)
2360 && next_real_insn (JUMP_LABEL (p)) == our_next)
2363 = JUMP_LABEL (insn) ? JUMP_LABEL (insn) : get_last_insn ();
2364 int target_loop_num = uid_loop_num[INSN_UID (target)];
2367 for (loc = target; loc; loc = PREV_INSN (loc))
2368 if (GET_CODE (loc) == BARRIER
2369 && uid_loop_num[INSN_UID (loc)] == target_loop_num)
2373 for (loc = target; loc; loc = NEXT_INSN (loc))
2374 if (GET_CODE (loc) == BARRIER
2375 && uid_loop_num[INSN_UID (loc)] == target_loop_num)
2380 rtx cond_label = JUMP_LABEL (p);
2381 rtx new_label = get_label_after (p);
2383 /* Ensure our label doesn't go away. */
2384 LABEL_NUSES (cond_label)++;
2386 /* Verify that uid_loop_num is large enough and that
2388 if (invert_jump (p, new_label))
2392 /* Include the BARRIER after INSN and copy the
2394 new_label = squeeze_notes (new_label, NEXT_INSN (insn));
2395 reorder_insns (new_label, NEXT_INSN (insn), loc);
2397 /* All those insns are now in TARGET_LOOP_NUM. */
2398 for (q = new_label; q != NEXT_INSN (NEXT_INSN (insn));
2400 uid_loop_num[INSN_UID (q)] = target_loop_num;
2402 /* The label jumped to by INSN is no longer a loop exit.
2403 Unless INSN does not have a label (e.g., it is a
2404 RETURN insn), search loop_number_exit_labels to find
2405 its label_ref, and remove it. Also turn off
2406 LABEL_OUTSIDE_LOOP_P bit. */
2407 if (JUMP_LABEL (insn))
2410 r = loop_number_exit_labels[this_loop_num];
2411 r; q = r, r = LABEL_NEXTREF (r))
2412 if (XEXP (r, 0) == JUMP_LABEL (insn))
2414 LABEL_OUTSIDE_LOOP_P (r) = 0;
2416 LABEL_NEXTREF (q) = LABEL_NEXTREF (r);
2418 loop_number_exit_labels[this_loop_num]
2419 = LABEL_NEXTREF (r);
2423 /* If we didn't find it, then something is wrong. */
2428 /* P is now a jump outside the loop, so it must be put
2429 in loop_number_exit_labels, and marked as such.
2430 The easiest way to do this is to just call
2431 mark_loop_jump again for P. */
2432 mark_loop_jump (PATTERN (p), this_loop_num);
2434 /* If INSN now jumps to the insn after it,
2436 if (JUMP_LABEL (insn) != 0
2437 && (next_real_insn (JUMP_LABEL (insn))
2438 == next_real_insn (insn)))
2442 /* Continue the loop after where the conditional
2443 branch used to jump, since the only branch insn
2444 in the block (if it still remains) is an inter-loop
2445 branch and hence needs no processing. */
2446 insn = NEXT_INSN (cond_label);
2448 if (--LABEL_NUSES (cond_label) == 0)
2449 delete_insn (cond_label);
2451 /* This loop will be continued with NEXT_INSN (insn). */
2452 insn = PREV_INSN (insn);
2459 /* If any label in X jumps to a loop different from LOOP_NUM and any of the
2460 loops it is contained in, mark the target loop invalid.
2462 For speed, we assume that X is part of a pattern of a JUMP_INSN. */
2465 mark_loop_jump (x, loop_num)
2473 switch (GET_CODE (x))
2486 /* There could be a label reference in here. */
2487 mark_loop_jump (XEXP (x, 0), loop_num);
2493 mark_loop_jump (XEXP (x, 0), loop_num);
2494 mark_loop_jump (XEXP (x, 1), loop_num);
2499 mark_loop_jump (XEXP (x, 0), loop_num);
2503 dest_loop = uid_loop_num[INSN_UID (XEXP (x, 0))];
2505 /* Link together all labels that branch outside the loop. This
2506 is used by final_[bg]iv_value and the loop unrolling code. Also
2507 mark this LABEL_REF so we know that this branch should predict
2510 if (dest_loop != loop_num && loop_num != -1)
2512 LABEL_OUTSIDE_LOOP_P (x) = 1;
2513 LABEL_NEXTREF (x) = loop_number_exit_labels[loop_num];
2514 loop_number_exit_labels[loop_num] = x;
2517 /* If this is inside a loop, but not in the current loop or one enclosed
2518 by it, it invalidates at least one loop. */
2520 if (dest_loop == -1)
2523 /* We must invalidate every nested loop containing the target of this
2524 label, except those that also contain the jump insn. */
2526 for (; dest_loop != -1; dest_loop = loop_outer_loop[dest_loop])
2528 /* Stop when we reach a loop that also contains the jump insn. */
2529 for (outer_loop = loop_num; outer_loop != -1;
2530 outer_loop = loop_outer_loop[outer_loop])
2531 if (dest_loop == outer_loop)
2534 /* If we get here, we know we need to invalidate a loop. */
2535 if (loop_dump_stream && ! loop_invalid[dest_loop])
2536 fprintf (loop_dump_stream,
2537 "\nLoop at %d ignored due to multiple entry points.\n",
2538 INSN_UID (loop_number_loop_starts[dest_loop]));
2540 loop_invalid[dest_loop] = 1;
2545 /* If this is not setting pc, ignore. */
2546 if (SET_DEST (x) == pc_rtx)
2547 mark_loop_jump (SET_SRC (x), loop_num);
2551 mark_loop_jump (XEXP (x, 1), loop_num);
2552 mark_loop_jump (XEXP (x, 2), loop_num);
2557 for (i = 0; i < XVECLEN (x, 0); i++)
2558 mark_loop_jump (XVECEXP (x, 0, i), loop_num);
2562 for (i = 0; i < XVECLEN (x, 1); i++)
2563 mark_loop_jump (XVECEXP (x, 1, i), loop_num);
2567 /* Treat anything else (such as a symbol_ref)
2568 as a branch out of this loop, but not into any loop. */
2571 loop_number_exit_labels[loop_num] = x;
2577 /* Return nonzero if there is a label in the range from
2578 insn INSN to and including the insn whose luid is END
2579 INSN must have an assigned luid (i.e., it must not have
2580 been previously created by loop.c). */
2583 labels_in_range_p (insn, end)
2587 while (insn && INSN_LUID (insn) <= end)
2589 if (GET_CODE (insn) == CODE_LABEL)
2591 insn = NEXT_INSN (insn);
2597 /* Record that a memory reference X is being set. */
2600 note_addr_stored (x)
2605 if (x == 0 || GET_CODE (x) != MEM)
2608 /* Count number of memory writes.
2609 This affects heuristics in strength_reduce. */
2612 /* BLKmode MEM means all memory is clobbered. */
2613 if (GET_MODE (x) == BLKmode)
2614 unknown_address_altered = 1;
2616 if (unknown_address_altered)
2619 for (i = 0; i < loop_store_mems_idx; i++)
2620 if (rtx_equal_p (XEXP (loop_store_mems[i], 0), XEXP (x, 0))
2621 && MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (loop_store_mems[i]))
2623 /* We are storing at the same address as previously noted. Save the
2625 if (GET_MODE_SIZE (GET_MODE (x))
2626 > GET_MODE_SIZE (GET_MODE (loop_store_mems[i])))
2627 loop_store_mems[i] = x;
2631 if (i == NUM_STORES)
2632 unknown_address_altered = 1;
2634 else if (i == loop_store_mems_idx)
2635 loop_store_mems[loop_store_mems_idx++] = x;
2638 /* Return nonzero if the rtx X is invariant over the current loop.
2640 The value is 2 if we refer to something only conditionally invariant.
2642 If `unknown_address_altered' is nonzero, no memory ref is invariant.
2643 Otherwise, a memory ref is invariant if it does not conflict with
2644 anything stored in `loop_store_mems'. */
2651 register enum rtx_code code;
2653 int conditional = 0;
2657 code = GET_CODE (x);
2667 /* A LABEL_REF is normally invariant, however, if we are unrolling
2668 loops, and this label is inside the loop, then it isn't invariant.
2669 This is because each unrolled copy of the loop body will have
2670 a copy of this label. If this was invariant, then an insn loading
2671 the address of this label into a register might get moved outside
2672 the loop, and then each loop body would end up using the same label.
2674 We don't know the loop bounds here though, so just fail for all
2676 if (flag_unroll_loops)
2683 case UNSPEC_VOLATILE:
2687 /* We used to check RTX_UNCHANGING_P (x) here, but that is invalid
2688 since the reg might be set by initialization within the loop. */
2689 if (x == frame_pointer_rtx || x == hard_frame_pointer_rtx
2690 || x == arg_pointer_rtx)
2693 && REGNO (x) < FIRST_PSEUDO_REGISTER && call_used_regs[REGNO (x)])
2695 if (n_times_set[REGNO (x)] < 0)
2697 return n_times_set[REGNO (x)] == 0;
2700 /* Volatile memory references must be rejected. Do this before
2701 checking for read-only items, so that volatile read-only items
2702 will be rejected also. */
2703 if (MEM_VOLATILE_P (x))
2706 /* Read-only items (such as constants in a constant pool) are
2707 invariant if their address is. */
2708 if (RTX_UNCHANGING_P (x))
2711 /* If we filled the table (or had a subroutine call), any location
2712 in memory could have been clobbered. */
2713 if (unknown_address_altered)
2716 /* See if there is any dependence between a store and this load. */
2717 for (i = loop_store_mems_idx - 1; i >= 0; i--)
2718 if (true_dependence (loop_store_mems[i], x))
2721 /* It's not invalidated by a store in memory
2722 but we must still verify the address is invariant. */
2726 /* Don't mess with insns declared volatile. */
2727 if (MEM_VOLATILE_P (x))
2731 fmt = GET_RTX_FORMAT (code);
2732 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2736 int tem = invariant_p (XEXP (x, i));
2742 else if (fmt[i] == 'E')
2745 for (j = 0; j < XVECLEN (x, i); j++)
2747 int tem = invariant_p (XVECEXP (x, i, j));
2757 return 1 + conditional;
2761 /* Return nonzero if all the insns in the loop that set REG
2762 are INSN and the immediately following insns,
2763 and if each of those insns sets REG in an invariant way
2764 (not counting uses of REG in them).
2766 The value is 2 if some of these insns are only conditionally invariant.
2768 We assume that INSN itself is the first set of REG
2769 and that its source is invariant. */
2772 consec_sets_invariant_p (reg, n_sets, insn)
2776 register rtx p = insn;
2777 register int regno = REGNO (reg);
2779 /* Number of sets we have to insist on finding after INSN. */
2780 int count = n_sets - 1;
2781 int old = n_times_set[regno];
2785 /* If N_SETS hit the limit, we can't rely on its value. */
2789 n_times_set[regno] = 0;
2793 register enum rtx_code code;
2797 code = GET_CODE (p);
2799 /* If library call, skip to end of of it. */
2800 if (code == INSN && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX)))
2805 && (set = single_set (p))
2806 && GET_CODE (SET_DEST (set)) == REG
2807 && REGNO (SET_DEST (set)) == regno)
2809 this = invariant_p (SET_SRC (set));
2812 else if (temp = find_reg_note (p, REG_EQUAL, NULL_RTX))
2814 /* If this is a libcall, then any invariant REG_EQUAL note is OK.
2815 If this is an ordinary insn, then only CONSTANT_P REG_EQUAL
2817 this = (CONSTANT_P (XEXP (temp, 0))
2818 || (find_reg_note (p, REG_RETVAL, NULL_RTX)
2819 && invariant_p (XEXP (temp, 0))));
2826 else if (code != NOTE)
2828 n_times_set[regno] = old;
2833 n_times_set[regno] = old;
2834 /* If invariant_p ever returned 2, we return 2. */
2835 return 1 + (value & 2);
2839 /* I don't think this condition is sufficient to allow INSN
2840 to be moved, so we no longer test it. */
2842 /* Return 1 if all insns in the basic block of INSN and following INSN
2843 that set REG are invariant according to TABLE. */
2846 all_sets_invariant_p (reg, insn, table)
2850 register rtx p = insn;
2851 register int regno = REGNO (reg);
2855 register enum rtx_code code;
2857 code = GET_CODE (p);
2858 if (code == CODE_LABEL || code == JUMP_INSN)
2860 if (code == INSN && GET_CODE (PATTERN (p)) == SET
2861 && GET_CODE (SET_DEST (PATTERN (p))) == REG
2862 && REGNO (SET_DEST (PATTERN (p))) == regno)
2864 if (!invariant_p (SET_SRC (PATTERN (p)), table))
2871 /* Look at all uses (not sets) of registers in X. For each, if it is
2872 the single use, set USAGE[REGNO] to INSN; if there was a previous use in
2873 a different insn, set USAGE[REGNO] to const0_rtx. */
2876 find_single_use_in_loop (insn, x, usage)
2881 enum rtx_code code = GET_CODE (x);
2882 char *fmt = GET_RTX_FORMAT (code);
2887 = (usage[REGNO (x)] != 0 && usage[REGNO (x)] != insn)
2888 ? const0_rtx : insn;
2890 else if (code == SET)
2892 /* Don't count SET_DEST if it is a REG; otherwise count things
2893 in SET_DEST because if a register is partially modified, it won't
2894 show up as a potential movable so we don't care how USAGE is set
2896 if (GET_CODE (SET_DEST (x)) != REG)
2897 find_single_use_in_loop (insn, SET_DEST (x), usage);
2898 find_single_use_in_loop (insn, SET_SRC (x), usage);
2901 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2903 if (fmt[i] == 'e' && XEXP (x, i) != 0)
2904 find_single_use_in_loop (insn, XEXP (x, i), usage);
2905 else if (fmt[i] == 'E')
2906 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2907 find_single_use_in_loop (insn, XVECEXP (x, i, j), usage);
2911 /* Increment N_TIMES_SET at the index of each register
2912 that is modified by an insn between FROM and TO.
2913 If the value of an element of N_TIMES_SET becomes 127 or more,
2914 stop incrementing it, to avoid overflow.
2916 Store in SINGLE_USAGE[I] the single insn in which register I is
2917 used, if it is only used once. Otherwise, it is set to 0 (for no
2918 uses) or const0_rtx for more than one use. This parameter may be zero,
2919 in which case this processing is not done.
2921 Store in *COUNT_PTR the number of actual instruction
2922 in the loop. We use this to decide what is worth moving out. */
2924 /* last_set[n] is nonzero iff reg n has been set in the current basic block.
2925 In that case, it is the insn that last set reg n. */
2928 count_loop_regs_set (from, to, may_not_move, single_usage, count_ptr, nregs)
2929 register rtx from, to;
2935 register rtx *last_set = (rtx *) alloca (nregs * sizeof (rtx));
2937 register int count = 0;
2940 bzero ((char *) last_set, nregs * sizeof (rtx));
2941 for (insn = from; insn != to; insn = NEXT_INSN (insn))
2943 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
2947 /* If requested, record registers that have exactly one use. */
2950 find_single_use_in_loop (insn, PATTERN (insn), single_usage);
2952 /* Include uses in REG_EQUAL notes. */
2953 if (REG_NOTES (insn))
2954 find_single_use_in_loop (insn, REG_NOTES (insn), single_usage);
2957 if (GET_CODE (PATTERN (insn)) == CLOBBER
2958 && GET_CODE (XEXP (PATTERN (insn), 0)) == REG)
2959 /* Don't move a reg that has an explicit clobber.
2960 We might do so sometimes, but it's not worth the pain. */
2961 may_not_move[REGNO (XEXP (PATTERN (insn), 0))] = 1;
2963 if (GET_CODE (PATTERN (insn)) == SET
2964 || GET_CODE (PATTERN (insn)) == CLOBBER)
2966 dest = SET_DEST (PATTERN (insn));
2967 while (GET_CODE (dest) == SUBREG
2968 || GET_CODE (dest) == ZERO_EXTRACT
2969 || GET_CODE (dest) == SIGN_EXTRACT
2970 || GET_CODE (dest) == STRICT_LOW_PART)
2971 dest = XEXP (dest, 0);
2972 if (GET_CODE (dest) == REG)
2974 register int regno = REGNO (dest);
2975 /* If this is the first setting of this reg
2976 in current basic block, and it was set before,
2977 it must be set in two basic blocks, so it cannot
2978 be moved out of the loop. */
2979 if (n_times_set[regno] > 0 && last_set[regno] == 0)
2980 may_not_move[regno] = 1;
2981 /* If this is not first setting in current basic block,
2982 see if reg was used in between previous one and this.
2983 If so, neither one can be moved. */
2984 if (last_set[regno] != 0
2985 && reg_used_between_p (dest, last_set[regno], insn))
2986 may_not_move[regno] = 1;
2987 if (n_times_set[regno] < 127)
2988 ++n_times_set[regno];
2989 last_set[regno] = insn;
2992 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
2995 for (i = XVECLEN (PATTERN (insn), 0) - 1; i >= 0; i--)
2997 register rtx x = XVECEXP (PATTERN (insn), 0, i);
2998 if (GET_CODE (x) == CLOBBER && GET_CODE (XEXP (x, 0)) == REG)
2999 /* Don't move a reg that has an explicit clobber.
3000 It's not worth the pain to try to do it correctly. */
3001 may_not_move[REGNO (XEXP (x, 0))] = 1;
3003 if (GET_CODE (x) == SET || GET_CODE (x) == CLOBBER)
3005 dest = SET_DEST (x);
3006 while (GET_CODE (dest) == SUBREG
3007 || GET_CODE (dest) == ZERO_EXTRACT
3008 || GET_CODE (dest) == SIGN_EXTRACT
3009 || GET_CODE (dest) == STRICT_LOW_PART)
3010 dest = XEXP (dest, 0);
3011 if (GET_CODE (dest) == REG)
3013 register int regno = REGNO (dest);
3014 if (n_times_set[regno] > 0 && last_set[regno] == 0)
3015 may_not_move[regno] = 1;
3016 if (last_set[regno] != 0
3017 && reg_used_between_p (dest, last_set[regno], insn))
3018 may_not_move[regno] = 1;
3019 if (n_times_set[regno] < 127)
3020 ++n_times_set[regno];
3021 last_set[regno] = insn;
3028 if (GET_CODE (insn) == CODE_LABEL || GET_CODE (insn) == JUMP_INSN)
3029 bzero ((char *) last_set, nregs * sizeof (rtx));
3034 /* Given a loop that is bounded by LOOP_START and LOOP_END
3035 and that is entered at SCAN_START,
3036 return 1 if the register set in SET contained in insn INSN is used by
3037 any insn that precedes INSN in cyclic order starting
3038 from the loop entry point.
3040 We don't want to use INSN_LUID here because if we restrict INSN to those
3041 that have a valid INSN_LUID, it means we cannot move an invariant out
3042 from an inner loop past two loops. */
3045 loop_reg_used_before_p (set, insn, loop_start, scan_start, loop_end)
3046 rtx set, insn, loop_start, scan_start, loop_end;
3048 rtx reg = SET_DEST (set);
3051 /* Scan forward checking for register usage. If we hit INSN, we
3052 are done. Otherwise, if we hit LOOP_END, wrap around to LOOP_START. */
3053 for (p = scan_start; p != insn; p = NEXT_INSN (p))
3055 if (GET_RTX_CLASS (GET_CODE (p)) == 'i'
3056 && reg_overlap_mentioned_p (reg, PATTERN (p)))
3066 /* A "basic induction variable" or biv is a pseudo reg that is set
3067 (within this loop) only by incrementing or decrementing it. */
3068 /* A "general induction variable" or giv is a pseudo reg whose
3069 value is a linear function of a biv. */
3071 /* Bivs are recognized by `basic_induction_var';
3072 Givs by `general_induct_var'. */
3074 /* Indexed by register number, indicates whether or not register is an
3075 induction variable, and if so what type. */
3077 enum iv_mode *reg_iv_type;
3079 /* Indexed by register number, contains pointer to `struct induction'
3080 if register is an induction variable. This holds general info for
3081 all induction variables. */
3083 struct induction **reg_iv_info;
3085 /* Indexed by register number, contains pointer to `struct iv_class'
3086 if register is a basic induction variable. This holds info describing
3087 the class (a related group) of induction variables that the biv belongs
3090 struct iv_class **reg_biv_class;
3092 /* The head of a list which links together (via the next field)
3093 every iv class for the current loop. */
3095 struct iv_class *loop_iv_list;
3097 /* Communication with routines called via `note_stores'. */
3099 static rtx note_insn;
3101 /* Dummy register to have non-zero DEST_REG for DEST_ADDR type givs. */
3103 static rtx addr_placeholder;
3105 /* ??? Unfinished optimizations, and possible future optimizations,
3106 for the strength reduction code. */
3108 /* ??? There is one more optimization you might be interested in doing: to
3109 allocate pseudo registers for frequently-accessed memory locations.
3110 If the same memory location is referenced each time around, it might
3111 be possible to copy it into a register before and out after.
3112 This is especially useful when the memory location is a variable which
3113 is in a stack slot because somewhere its address is taken. If the
3114 loop doesn't contain a function call and the variable isn't volatile,
3115 it is safe to keep the value in a register for the duration of the
3116 loop. One tricky thing is that the copying of the value back from the
3117 register has to be done on all exits from the loop. You need to check that
3118 all the exits from the loop go to the same place. */
3120 /* ??? The interaction of biv elimination, and recognition of 'constant'
3121 bivs, may cause problems. */
3123 /* ??? Add heuristics so that DEST_ADDR strength reduction does not cause
3124 performance problems.
3126 Perhaps don't eliminate things that can be combined with an addressing
3127 mode. Find all givs that have the same biv, mult_val, and add_val;
3128 then for each giv, check to see if its only use dies in a following
3129 memory address. If so, generate a new memory address and check to see
3130 if it is valid. If it is valid, then store the modified memory address,
3131 otherwise, mark the giv as not done so that it will get its own iv. */
3133 /* ??? Could try to optimize branches when it is known that a biv is always
3136 /* ??? When replace a biv in a compare insn, we should replace with closest
3137 giv so that an optimized branch can still be recognized by the combiner,
3138 e.g. the VAX acb insn. */
3140 /* ??? Many of the checks involving uid_luid could be simplified if regscan
3141 was rerun in loop_optimize whenever a register was added or moved.
3142 Also, some of the optimizations could be a little less conservative. */
3144 /* Perform strength reduction and induction variable elimination. */
3146 /* Pseudo registers created during this function will be beyond the last
3147 valid index in several tables including n_times_set and regno_last_uid.
3148 This does not cause a problem here, because the added registers cannot be
3149 givs outside of their loop, and hence will never be reconsidered.
3150 But scan_loop must check regnos to make sure they are in bounds. */
3153 strength_reduce (scan_start, end, loop_top, insn_count,
3154 loop_start, loop_end)
3167 /* This is 1 if current insn is not executed at least once for every loop
3169 int not_every_iteration = 0;
3170 /* This is 1 if current insn may be executed more than once for every
3172 int maybe_multiple = 0;
3173 /* Temporary list pointers for traversing loop_iv_list. */
3174 struct iv_class *bl, **backbl;
3175 /* Ratio of extra register life span we can justify
3176 for saving an instruction. More if loop doesn't call subroutines
3177 since in that case saving an insn makes more difference
3178 and more registers are available. */
3179 /* ??? could set this to last value of threshold in move_movables */
3180 int threshold = (loop_has_call ? 1 : 2) * (3 + n_non_fixed_regs);
3181 /* Map of pseudo-register replacements. */
3185 rtx end_insert_before;
3188 reg_iv_type = (enum iv_mode *) alloca (max_reg_before_loop
3189 * sizeof (enum iv_mode *));
3190 bzero ((char *) reg_iv_type, max_reg_before_loop * sizeof (enum iv_mode *));
3191 reg_iv_info = (struct induction **)
3192 alloca (max_reg_before_loop * sizeof (struct induction *));
3193 bzero ((char *) reg_iv_info, (max_reg_before_loop
3194 * sizeof (struct induction *)));
3195 reg_biv_class = (struct iv_class **)
3196 alloca (max_reg_before_loop * sizeof (struct iv_class *));
3197 bzero ((char *) reg_biv_class, (max_reg_before_loop
3198 * sizeof (struct iv_class *)));
3201 addr_placeholder = gen_reg_rtx (Pmode);
3203 /* Save insn immediately after the loop_end. Insns inserted after loop_end
3204 must be put before this insn, so that they will appear in the right
3205 order (i.e. loop order).
3207 If loop_end is the end of the current function, then emit a
3208 NOTE_INSN_DELETED after loop_end and set end_insert_before to the
3210 if (NEXT_INSN (loop_end) != 0)
3211 end_insert_before = NEXT_INSN (loop_end);
3213 end_insert_before = emit_note_after (NOTE_INSN_DELETED, loop_end);
3215 /* Scan through loop to find all possible bivs. */
3221 /* At end of a straight-in loop, we are done.
3222 At end of a loop entered at the bottom, scan the top. */
3223 if (p == scan_start)
3231 if (p == scan_start)
3235 if (GET_CODE (p) == INSN
3236 && (set = single_set (p))
3237 && GET_CODE (SET_DEST (set)) == REG)
3239 dest_reg = SET_DEST (set);
3240 if (REGNO (dest_reg) < max_reg_before_loop
3241 && REGNO (dest_reg) >= FIRST_PSEUDO_REGISTER
3242 && reg_iv_type[REGNO (dest_reg)] != NOT_BASIC_INDUCT)
3244 if (basic_induction_var (SET_SRC (set), GET_MODE (SET_SRC (set)),
3245 dest_reg, p, &inc_val, &mult_val))
3247 /* It is a possible basic induction variable.
3248 Create and initialize an induction structure for it. */
3251 = (struct induction *) alloca (sizeof (struct induction));
3253 record_biv (v, p, dest_reg, inc_val, mult_val,
3254 not_every_iteration, maybe_multiple);
3255 reg_iv_type[REGNO (dest_reg)] = BASIC_INDUCT;
3257 else if (REGNO (dest_reg) < max_reg_before_loop)
3258 reg_iv_type[REGNO (dest_reg)] = NOT_BASIC_INDUCT;
3262 /* Past CODE_LABEL, we get to insns that may be executed multiple
3263 times. The only way we can be sure that they can't is if every
3264 every jump insn between here and the end of the loop either
3265 returns, exits the loop, or is a forward jump. */
3267 if (GET_CODE (p) == CODE_LABEL)
3275 insn = NEXT_INSN (insn);
3276 if (insn == scan_start)
3284 if (insn == scan_start)
3288 if (GET_CODE (insn) == JUMP_INSN
3289 && GET_CODE (PATTERN (insn)) != RETURN
3290 && (! condjump_p (insn)
3291 || (JUMP_LABEL (insn) != 0
3292 && (INSN_UID (JUMP_LABEL (insn)) >= max_uid_for_loop
3293 || INSN_UID (insn) >= max_uid_for_loop
3294 || (INSN_LUID (JUMP_LABEL (insn))
3295 < INSN_LUID (insn))))))
3303 /* Past a label or a jump, we get to insns for which we can't count
3304 on whether or how many times they will be executed during each
3306 /* This code appears in three places, once in scan_loop, and twice
3307 in strength_reduce. */
3308 if ((GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN)
3309 /* If we enter the loop in the middle, and scan around to the
3310 beginning, don't set not_every_iteration for that.
3311 This can be any kind of jump, since we want to know if insns
3312 will be executed if the loop is executed. */
3313 && ! (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == loop_top
3314 && ((NEXT_INSN (NEXT_INSN (p)) == loop_end && simplejump_p (p))
3315 || (NEXT_INSN (p) == loop_end && condjump_p (p)))))
3316 not_every_iteration = 1;
3318 else if (GET_CODE (p) == NOTE)
3320 /* At the virtual top of a converted loop, insns are again known to
3321 be executed each iteration: logically, the loop begins here
3322 even though the exit code has been duplicated. */
3323 if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_VTOP && loop_depth == 0)
3324 not_every_iteration = 0;
3325 else if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_BEG)
3327 else if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_END)
3331 /* Unlike in the code motion pass where MAYBE_NEVER indicates that
3332 an insn may never be executed, NOT_EVERY_ITERATION indicates whether
3333 or not an insn is known to be executed each iteration of the
3334 loop, whether or not any iterations are known to occur.
3336 Therefore, if we have just passed a label and have no more labels
3337 between here and the test insn of the loop, we know these insns
3338 will be executed each iteration. This can also happen if we
3339 have just passed a jump, for example, when there are nested loops. */
3341 if (not_every_iteration && GET_CODE (p) == CODE_LABEL
3342 && no_labels_between_p (p, loop_end))
3343 not_every_iteration = 0;
3346 /* Scan loop_iv_list to remove all regs that proved not to be bivs.
3347 Make a sanity check against n_times_set. */
3348 for (backbl = &loop_iv_list, bl = *backbl; bl; bl = bl->next)
3350 if (reg_iv_type[bl->regno] != BASIC_INDUCT
3351 /* Above happens if register modified by subreg, etc. */
3352 /* Make sure it is not recognized as a basic induction var: */
3353 || n_times_set[bl->regno] != bl->biv_count
3354 /* If never incremented, it is invariant that we decided not to
3355 move. So leave it alone. */
3356 || ! bl->incremented)
3358 if (loop_dump_stream)
3359 fprintf (loop_dump_stream, "Reg %d: biv discarded, %s\n",
3361 (reg_iv_type[bl->regno] != BASIC_INDUCT
3362 ? "not induction variable"
3363 : (! bl->incremented ? "never incremented"
3366 reg_iv_type[bl->regno] = NOT_BASIC_INDUCT;
3373 if (loop_dump_stream)
3374 fprintf (loop_dump_stream, "Reg %d: biv verified\n", bl->regno);
3378 /* Exit if there are no bivs. */
3381 /* Can still unroll the loop anyways, but indicate that there is no
3382 strength reduction info available. */
3383 if (flag_unroll_loops)
3384 unroll_loop (loop_end, insn_count, loop_start, end_insert_before, 0);
3389 /* Find initial value for each biv by searching backwards from loop_start,
3390 halting at first label. Also record any test condition. */
3393 for (p = loop_start; p && GET_CODE (p) != CODE_LABEL; p = PREV_INSN (p))
3397 if (GET_CODE (p) == CALL_INSN)
3400 if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
3401 || GET_CODE (p) == CALL_INSN)
3402 note_stores (PATTERN (p), record_initial);
3404 /* Record any test of a biv that branches around the loop if no store
3405 between it and the start of loop. We only care about tests with
3406 constants and registers and only certain of those. */
3407 if (GET_CODE (p) == JUMP_INSN
3408 && JUMP_LABEL (p) != 0
3409 && next_real_insn (JUMP_LABEL (p)) == next_real_insn (loop_end)
3410 && (test = get_condition_for_loop (p)) != 0
3411 && GET_CODE (XEXP (test, 0)) == REG
3412 && REGNO (XEXP (test, 0)) < max_reg_before_loop
3413 && (bl = reg_biv_class[REGNO (XEXP (test, 0))]) != 0
3414 && valid_initial_value_p (XEXP (test, 1), p, call_seen, loop_start)
3415 && bl->init_insn == 0)
3417 /* If an NE test, we have an initial value! */
3418 if (GET_CODE (test) == NE)
3421 bl->init_set = gen_rtx (SET, VOIDmode,
3422 XEXP (test, 0), XEXP (test, 1));
3425 bl->initial_test = test;
3429 /* Look at the each biv and see if we can say anything better about its
3430 initial value from any initializing insns set up above. (This is done
3431 in two passes to avoid missing SETs in a PARALLEL.) */
3432 for (bl = loop_iv_list; bl; bl = bl->next)
3436 if (! bl->init_insn)
3439 src = SET_SRC (bl->init_set);
3441 if (loop_dump_stream)
3442 fprintf (loop_dump_stream,
3443 "Biv %d initialized at insn %d: initial value ",
3444 bl->regno, INSN_UID (bl->init_insn));
3446 if ((GET_MODE (src) == GET_MODE (regno_reg_rtx[bl->regno])
3447 || GET_MODE (src) == VOIDmode)
3448 && valid_initial_value_p (src, bl->init_insn, call_seen, loop_start))
3450 bl->initial_value = src;
3452 if (loop_dump_stream)
3454 if (GET_CODE (src) == CONST_INT)
3455 fprintf (loop_dump_stream, "%d\n", INTVAL (src));
3458 print_rtl (loop_dump_stream, src);
3459 fprintf (loop_dump_stream, "\n");
3465 /* Biv initial value is not simple move,
3466 so let it keep initial value of "itself". */
3468 if (loop_dump_stream)
3469 fprintf (loop_dump_stream, "is complex\n");
3473 /* Search the loop for general induction variables. */
3475 /* A register is a giv if: it is only set once, it is a function of a
3476 biv and a constant (or invariant), and it is not a biv. */
3478 not_every_iteration = 0;
3484 /* At end of a straight-in loop, we are done.
3485 At end of a loop entered at the bottom, scan the top. */
3486 if (p == scan_start)
3494 if (p == scan_start)
3498 /* Look for a general induction variable in a register. */
3499 if (GET_CODE (p) == INSN
3500 && (set = single_set (p))
3501 && GET_CODE (SET_DEST (set)) == REG
3502 && ! may_not_optimize[REGNO (SET_DEST (set))])
3510 dest_reg = SET_DEST (set);
3511 if (REGNO (dest_reg) < FIRST_PSEUDO_REGISTER)
3514 if (/* SET_SRC is a giv. */
3515 ((benefit = general_induction_var (SET_SRC (set),
3518 /* Equivalent expression is a giv. */
3519 || ((regnote = find_reg_note (p, REG_EQUAL, NULL_RTX))
3520 && (benefit = general_induction_var (XEXP (regnote, 0),
3522 &add_val, &mult_val))))
3523 /* Don't try to handle any regs made by loop optimization.
3524 We have nothing on them in regno_first_uid, etc. */
3525 && REGNO (dest_reg) < max_reg_before_loop
3526 /* Don't recognize a BASIC_INDUCT_VAR here. */
3527 && dest_reg != src_reg
3528 /* This must be the only place where the register is set. */
3529 && (n_times_set[REGNO (dest_reg)] == 1
3530 /* or all sets must be consecutive and make a giv. */
3531 || (benefit = consec_sets_giv (benefit, p,
3533 &add_val, &mult_val))))
3537 = (struct induction *) alloca (sizeof (struct induction));
3540 /* If this is a library call, increase benefit. */
3541 if (find_reg_note (p, REG_RETVAL, NULL_RTX))
3542 benefit += libcall_benefit (p);
3544 /* Skip the consecutive insns, if there are any. */
3545 for (count = n_times_set[REGNO (dest_reg)] - 1;
3548 /* If first insn of libcall sequence, skip to end.
3549 Do this at start of loop, since INSN is guaranteed to
3551 if (GET_CODE (p) != NOTE
3552 && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX)))
3555 do p = NEXT_INSN (p);
3556 while (GET_CODE (p) == NOTE);
3559 record_giv (v, p, src_reg, dest_reg, mult_val, add_val, benefit,
3560 DEST_REG, not_every_iteration, NULL_PTR, loop_start,
3566 #ifndef DONT_REDUCE_ADDR
3567 /* Look for givs which are memory addresses. */
3568 /* This resulted in worse code on a VAX 8600. I wonder if it
3570 if (GET_CODE (p) == INSN)
3571 find_mem_givs (PATTERN (p), p, not_every_iteration, loop_start,
3575 /* Update the status of whether giv can derive other givs. This can
3576 change when we pass a label or an insn that updates a biv. */
3577 if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
3578 || GET_CODE (p) == CODE_LABEL)
3579 update_giv_derive (p);
3581 /* Past a label or a jump, we get to insns for which we can't count
3582 on whether or how many times they will be executed during each
3584 /* This code appears in three places, once in scan_loop, and twice
3585 in strength_reduce. */
3586 if ((GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN)
3587 /* If we enter the loop in the middle, and scan around
3588 to the beginning, don't set not_every_iteration for that.
3589 This can be any kind of jump, since we want to know if insns
3590 will be executed if the loop is executed. */
3591 && ! (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p) == loop_top
3592 && ((NEXT_INSN (NEXT_INSN (p)) == loop_end && simplejump_p (p))
3593 || (NEXT_INSN (p) == loop_end && condjump_p (p)))))
3594 not_every_iteration = 1;
3596 else if (GET_CODE (p) == NOTE)
3598 /* At the virtual top of a converted loop, insns are again known to
3599 be executed each iteration: logically, the loop begins here
3600 even though the exit code has been duplicated. */
3601 if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_VTOP && loop_depth == 0)
3602 not_every_iteration = 0;
3603 else if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_BEG)
3605 else if (NOTE_LINE_NUMBER (p) == NOTE_INSN_LOOP_END)
3609 /* Unlike in the code motion pass where MAYBE_NEVER indicates that
3610 an insn may never be executed, NOT_EVERY_ITERATION indicates whether
3611 or not an insn is known to be executed each iteration of the
3612 loop, whether or not any iterations are known to occur.
3614 Therefore, if we have just passed a label and have no more labels
3615 between here and the test insn of the loop, we know these insns
3616 will be executed each iteration. */
3618 if (not_every_iteration && GET_CODE (p) == CODE_LABEL
3619 && no_labels_between_p (p, loop_end))
3620 not_every_iteration = 0;
3623 /* Try to calculate and save the number of loop iterations. This is
3624 set to zero if the actual number can not be calculated. This must
3625 be called after all giv's have been identified, since otherwise it may
3626 fail if the iteration variable is a giv. */
3628 loop_n_iterations = loop_iterations (loop_start, loop_end);
3630 /* Now for each giv for which we still don't know whether or not it is
3631 replaceable, check to see if it is replaceable because its final value
3632 can be calculated. This must be done after loop_iterations is called,
3633 so that final_giv_value will work correctly. */
3635 for (bl = loop_iv_list; bl; bl = bl->next)
3637 struct induction *v;
3639 for (v = bl->giv; v; v = v->next_iv)
3640 if (! v->replaceable && ! v->not_replaceable)
3641 check_final_value (v, loop_start, loop_end);
3644 /* Try to prove that the loop counter variable (if any) is always
3645 nonnegative; if so, record that fact with a REG_NONNEG note
3646 so that "decrement and branch until zero" insn can be used. */
3647 check_dbra_loop (loop_end, insn_count, loop_start);
3649 /* Create reg_map to hold substitutions for replaceable giv regs. */
3650 reg_map = (rtx *) alloca (max_reg_before_loop * sizeof (rtx));
3651 bzero ((char *) reg_map, max_reg_before_loop * sizeof (rtx));
3653 /* Examine each iv class for feasibility of strength reduction/induction
3654 variable elimination. */
3656 for (bl = loop_iv_list; bl; bl = bl->next)
3658 struct induction *v;
3661 rtx final_value = 0;
3663 /* Test whether it will be possible to eliminate this biv
3664 provided all givs are reduced. This is possible if either
3665 the reg is not used outside the loop, or we can compute
3666 what its final value will be.
3668 For architectures with a decrement_and_branch_until_zero insn,
3669 don't do this if we put a REG_NONNEG note on the endtest for
3672 /* Compare against bl->init_insn rather than loop_start.
3673 We aren't concerned with any uses of the biv between
3674 init_insn and loop_start since these won't be affected
3675 by the value of the biv elsewhere in the function, so
3676 long as init_insn doesn't use the biv itself.
3677 March 14, 1989 -- self@bayes.arc.nasa.gov */
3679 if ((uid_luid[regno_last_uid[bl->regno]] < INSN_LUID (loop_end)
3681 && INSN_UID (bl->init_insn) < max_uid_for_loop
3682 && uid_luid[regno_first_uid[bl->regno]] >= INSN_LUID (bl->init_insn)
3683 #ifdef HAVE_decrement_and_branch_until_zero
3686 && ! reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
3687 || ((final_value = final_biv_value (bl, loop_start, loop_end))
3688 #ifdef HAVE_decrement_and_branch_until_zero
3692 bl->eliminable = maybe_eliminate_biv (bl, loop_start, end, 0,
3693 threshold, insn_count);
3696 if (loop_dump_stream)
3698 fprintf (loop_dump_stream,
3699 "Cannot eliminate biv %d.\n",
3701 fprintf (loop_dump_stream,
3702 "First use: insn %d, last use: insn %d.\n",
3703 regno_first_uid[bl->regno],
3704 regno_last_uid[bl->regno]);
3708 /* Combine all giv's for this iv_class. */
3711 /* This will be true at the end, if all givs which depend on this
3712 biv have been strength reduced.
3713 We can't (currently) eliminate the biv unless this is so. */
3716 /* Check each giv in this class to see if we will benefit by reducing
3717 it. Skip giv's combined with others. */
3718 for (v = bl->giv; v; v = v->next_iv)
3720 struct induction *tv;
3722 if (v->ignore || v->same)
3725 benefit = v->benefit;
3727 /* Reduce benefit if not replaceable, since we will insert
3728 a move-insn to replace the insn that calculates this giv.
3729 Don't do this unless the giv is a user variable, since it
3730 will often be marked non-replaceable because of the duplication
3731 of the exit code outside the loop. In such a case, the copies
3732 we insert are dead and will be deleted. So they don't have
3733 a cost. Similar situations exist. */
3734 /* ??? The new final_[bg]iv_value code does a much better job
3735 of finding replaceable giv's, and hence this code may no longer
3737 if (! v->replaceable && ! bl->eliminable
3738 && REG_USERVAR_P (v->dest_reg))
3739 benefit -= copy_cost;
3741 /* Decrease the benefit to count the add-insns that we will
3742 insert to increment the reduced reg for the giv. */
3743 benefit -= add_cost * bl->biv_count;
3745 /* Decide whether to strength-reduce this giv or to leave the code
3746 unchanged (recompute it from the biv each time it is used).
3747 This decision can be made independently for each giv. */
3749 /* ??? Perhaps attempt to guess whether autoincrement will handle
3750 some of the new add insns; if so, can increase BENEFIT
3751 (undo the subtraction of add_cost that was done above). */
3753 /* If an insn is not to be strength reduced, then set its ignore
3754 flag, and clear all_reduced. */
3756 /* A giv that depends on a reversed biv must be reduced if it is
3757 used after the loop exit, otherwise, it would have the wrong
3758 value after the loop exit. To make it simple, just reduce all
3759 of such giv's whether or not we know they are used after the loop
3762 if (v->lifetime * threshold * benefit < insn_count
3765 if (loop_dump_stream)
3766 fprintf (loop_dump_stream,
3767 "giv of insn %d not worth while, %d vs %d.\n",
3769 v->lifetime * threshold * benefit, insn_count);
3775 /* Check that we can increment the reduced giv without a
3776 multiply insn. If not, reject it. */
3778 for (tv = bl->biv; tv; tv = tv->next_iv)
3779 if (tv->mult_val == const1_rtx
3780 && ! product_cheap_p (tv->add_val, v->mult_val))
3782 if (loop_dump_stream)
3783 fprintf (loop_dump_stream,
3784 "giv of insn %d: would need a multiply.\n",
3785 INSN_UID (v->insn));
3793 /* Reduce each giv that we decided to reduce. */
3795 for (v = bl->giv; v; v = v->next_iv)
3797 struct induction *tv;
3798 if (! v->ignore && v->same == 0)
3800 v->new_reg = gen_reg_rtx (v->mode);
3802 /* For each place where the biv is incremented,
3803 add an insn to increment the new, reduced reg for the giv. */
3804 for (tv = bl->biv; tv; tv = tv->next_iv)
3806 if (tv->mult_val == const1_rtx)
3807 emit_iv_add_mult (tv->add_val, v->mult_val,
3808 v->new_reg, v->new_reg, tv->insn);
3809 else /* tv->mult_val == const0_rtx */
3810 /* A multiply is acceptable here
3811 since this is presumed to be seldom executed. */
3812 emit_iv_add_mult (tv->add_val, v->mult_val,
3813 v->add_val, v->new_reg, tv->insn);
3816 /* Add code at loop start to initialize giv's reduced reg. */
3818 emit_iv_add_mult (bl->initial_value, v->mult_val,
3819 v->add_val, v->new_reg, loop_start);
3823 /* Rescan all givs. If a giv is the same as a giv not reduced, mark it
3826 For each giv register that can be reduced now: if replaceable,
3827 substitute reduced reg wherever the old giv occurs;
3828 else add new move insn "giv_reg = reduced_reg".
3830 Also check for givs whose first use is their definition and whose
3831 last use is the definition of another giv. If so, it is likely
3832 dead and should not be used to eliminate a biv. */
3833 for (v = bl->giv; v; v = v->next_iv)
3835 if (v->same && v->same->ignore)
3841 if (v->giv_type == DEST_REG
3842 && regno_first_uid[REGNO (v->dest_reg)] == INSN_UID (v->insn))
3844 struct induction *v1;
3846 for (v1 = bl->giv; v1; v1 = v1->next_iv)
3847 if (regno_last_uid[REGNO (v->dest_reg)] == INSN_UID (v1->insn))
3851 /* Update expression if this was combined, in case other giv was
3854 v->new_reg = replace_rtx (v->new_reg,
3855 v->same->dest_reg, v->same->new_reg);
3857 if (v->giv_type == DEST_ADDR)
3858 /* Store reduced reg as the address in the memref where we found
3860 validate_change (v->insn, v->location, v->new_reg, 0);
3861 else if (v->replaceable)
3863 reg_map[REGNO (v->dest_reg)] = v->new_reg;
3866 /* I can no longer duplicate the original problem. Perhaps
3867 this is unnecessary now? */
3869 /* Replaceable; it isn't strictly necessary to delete the old
3870 insn and emit a new one, because v->dest_reg is now dead.
3872 However, especially when unrolling loops, the special
3873 handling for (set REG0 REG1) in the second cse pass may
3874 make v->dest_reg live again. To avoid this problem, emit
3875 an insn to set the original giv reg from the reduced giv.
3876 We can not delete the original insn, since it may be part
3877 of a LIBCALL, and the code in flow that eliminates dead
3878 libcalls will fail if it is deleted. */
3879 emit_insn_after (gen_move_insn (v->dest_reg, v->new_reg),
3885 /* Not replaceable; emit an insn to set the original giv reg from
3886 the reduced giv, same as above. */
3887 emit_insn_after (gen_move_insn (v->dest_reg, v->new_reg),
3891 /* When a loop is reversed, givs which depend on the reversed
3892 biv, and which are live outside the loop, must be set to their
3893 correct final value. This insn is only needed if the giv is
3894 not replaceable. The correct final value is the same as the
3895 value that the giv starts the reversed loop with. */
3896 if (bl->reversed && ! v->replaceable)
3897 emit_iv_add_mult (bl->initial_value, v->mult_val,
3898 v->add_val, v->dest_reg, end_insert_before);
3899 else if (v->final_value)
3903 /* If the loop has multiple exits, emit the insn before the
3904 loop to ensure that it will always be executed no matter
3905 how the loop exits. Otherwise, emit the insn after the loop,
3906 since this is slightly more efficient. */
3907 if (loop_number_exit_labels[uid_loop_num[INSN_UID (loop_start)]])
3908 insert_before = loop_start;
3910 insert_before = end_insert_before;
3911 emit_insn_before (gen_move_insn (v->dest_reg, v->final_value),
3915 /* If the insn to set the final value of the giv was emitted
3916 before the loop, then we must delete the insn inside the loop
3917 that sets it. If this is a LIBCALL, then we must delete
3918 every insn in the libcall. Note, however, that
3919 final_giv_value will only succeed when there are multiple
3920 exits if the giv is dead at each exit, hence it does not
3921 matter that the original insn remains because it is dead
3923 /* Delete the insn inside the loop that sets the giv since
3924 the giv is now set before (or after) the loop. */
3925 delete_insn (v->insn);
3929 if (loop_dump_stream)
3931 fprintf (loop_dump_stream, "giv at %d reduced to ",
3932 INSN_UID (v->insn));
3933 print_rtl (loop_dump_stream, v->new_reg);
3934 fprintf (loop_dump_stream, "\n");
3938 /* All the givs based on the biv bl have been reduced if they
3941 /* For each giv not marked as maybe dead that has been combined with a
3942 second giv, clear any "maybe dead" mark on that second giv.
3943 v->new_reg will either be or refer to the register of the giv it
3946 Doing this clearing avoids problems in biv elimination where a
3947 giv's new_reg is a complex value that can't be put in the insn but
3948 the giv combined with (with a reg as new_reg) is marked maybe_dead.
3949 Since the register will be used in either case, we'd prefer it be
3950 used from the simpler giv. */
3952 for (v = bl->giv; v; v = v->next_iv)
3953 if (! v->maybe_dead && v->same)
3954 v->same->maybe_dead = 0;
3956 /* Try to eliminate the biv, if it is a candidate.
3957 This won't work if ! all_reduced,
3958 since the givs we planned to use might not have been reduced.
3960 We have to be careful that we didn't initially think we could eliminate
3961 this biv because of a giv that we now think may be dead and shouldn't
3962 be used as a biv replacement.
3964 Also, there is the possibility that we may have a giv that looks
3965 like it can be used to eliminate a biv, but the resulting insn
3966 isn't valid. This can happen, for example, on the 88k, where a
3967 JUMP_INSN can compare a register only with zero. Attempts to
3968 replace it with a compare with a constant will fail.
3970 Note that in cases where this call fails, we may have replaced some
3971 of the occurrences of the biv with a giv, but no harm was done in
3972 doing so in the rare cases where it can occur. */
3974 if (all_reduced == 1 && bl->eliminable
3975 && maybe_eliminate_biv (bl, loop_start, end, 1,
3976 threshold, insn_count))
3979 /* ?? If we created a new test to bypass the loop entirely,
3980 or otherwise drop straight in, based on this test, then
3981 we might want to rewrite it also. This way some later
3982 pass has more hope of removing the initialization of this
3985 /* If final_value != 0, then the biv may be used after loop end
3986 and we must emit an insn to set it just in case.
3988 Reversed bivs already have an insn after the loop setting their
3989 value, so we don't need another one. We can't calculate the
3990 proper final value for such a biv here anyways. */
3991 if (final_value != 0 && ! bl->reversed)
3995 /* If the loop has multiple exits, emit the insn before the
3996 loop to ensure that it will always be executed no matter
3997 how the loop exits. Otherwise, emit the insn after the
3998 loop, since this is slightly more efficient. */
3999 if (loop_number_exit_labels[uid_loop_num[INSN_UID (loop_start)]])
4000 insert_before = loop_start;
4002 insert_before = end_insert_before;
4004 emit_insn_before (gen_move_insn (bl->biv->dest_reg, final_value),
4009 /* Delete all of the instructions inside the loop which set
4010 the biv, as they are all dead. If is safe to delete them,
4011 because an insn setting a biv will never be part of a libcall. */
4012 /* However, deleting them will invalidate the regno_last_uid info,
4013 so keeping them around is more convenient. Final_biv_value
4014 will only succeed when there are multiple exits if the biv
4015 is dead at each exit, hence it does not matter that the original
4016 insn remains, because it is dead anyways. */
4017 for (v = bl->biv; v; v = v->next_iv)
4018 delete_insn (v->insn);
4021 if (loop_dump_stream)
4022 fprintf (loop_dump_stream, "Reg %d: biv eliminated\n",
4027 /* Go through all the instructions in the loop, making all the
4028 register substitutions scheduled in REG_MAP. */
4030 for (p = loop_start; p != end; p = NEXT_INSN (p))
4031 if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
4032 || GET_CODE (p) == CALL_INSN)
4034 replace_regs (PATTERN (p), reg_map, max_reg_before_loop, 0);
4035 replace_regs (REG_NOTES (p), reg_map, max_reg_before_loop, 0);
4039 /* Unroll loops from within strength reduction so that we can use the
4040 induction variable information that strength_reduce has already
4043 if (flag_unroll_loops)
4044 unroll_loop (loop_end, insn_count, loop_start, end_insert_before, 1);
4046 if (loop_dump_stream)
4047 fprintf (loop_dump_stream, "\n");
4050 /* Return 1 if X is a valid source for an initial value (or as value being
4051 compared against in an initial test).
4053 X must be either a register or constant and must not be clobbered between
4054 the current insn and the start of the loop.
4056 INSN is the insn containing X. */
4059 valid_initial_value_p (x, insn, call_seen, loop_start)
4068 /* Only consider pseudos we know about initialized in insns whose luids
4070 if (GET_CODE (x) != REG
4071 || REGNO (x) >= max_reg_before_loop)
4074 /* Don't use call-clobbered registers across a call which clobbers it. On
4075 some machines, don't use any hard registers at all. */
4076 if (REGNO (x) < FIRST_PSEUDO_REGISTER
4077 #ifndef SMALL_REGISTER_CLASSES
4078 && call_used_regs[REGNO (x)] && call_seen
4083 /* Don't use registers that have been clobbered before the start of the
4085 if (reg_set_between_p (x, insn, loop_start))
4091 /* Scan X for memory refs and check each memory address
4092 as a possible giv. INSN is the insn whose pattern X comes from.
4093 NOT_EVERY_ITERATION is 1 if the insn might not be executed during
4094 every loop iteration. */
4097 find_mem_givs (x, insn, not_every_iteration, loop_start, loop_end)
4100 int not_every_iteration;
4101 rtx loop_start, loop_end;
4104 register enum rtx_code code;
4110 code = GET_CODE (x);
4134 benefit = general_induction_var (XEXP (x, 0),
4135 &src_reg, &add_val, &mult_val);
4137 /* Don't make a DEST_ADDR giv with mult_val == 1 && add_val == 0.
4138 Such a giv isn't useful. */
4139 if (benefit > 0 && (mult_val != const1_rtx || add_val != const0_rtx))
4141 /* Found one; record it. */
4143 = (struct induction *) oballoc (sizeof (struct induction));
4145 record_giv (v, insn, src_reg, addr_placeholder, mult_val,
4146 add_val, benefit, DEST_ADDR, not_every_iteration,
4147 &XEXP (x, 0), loop_start, loop_end);
4149 v->mem_mode = GET_MODE (x);
4155 /* Recursively scan the subexpressions for other mem refs. */
4157 fmt = GET_RTX_FORMAT (code);
4158 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
4160 find_mem_givs (XEXP (x, i), insn, not_every_iteration, loop_start,
4162 else if (fmt[i] == 'E')
4163 for (j = 0; j < XVECLEN (x, i); j++)
4164 find_mem_givs (XVECEXP (x, i, j), insn, not_every_iteration,
4165 loop_start, loop_end);
4168 /* Fill in the data about one biv update.
4169 V is the `struct induction' in which we record the biv. (It is
4170 allocated by the caller, with alloca.)
4171 INSN is the insn that sets it.
4172 DEST_REG is the biv's reg.
4174 MULT_VAL is const1_rtx if the biv is being incremented here, in which case
4175 INC_VAL is the increment. Otherwise, MULT_VAL is const0_rtx and the biv is
4176 being set to INC_VAL.
4178 NOT_EVERY_ITERATION is nonzero if this biv update is not know to be
4179 executed every iteration; MAYBE_MULTIPLE is nonzero if this biv update
4180 can be executed more than once per iteration. If MAYBE_MULTIPLE
4181 and NOT_EVERY_ITERATION are both zero, we know that the biv update is
4182 executed exactly once per iteration. */
4185 record_biv (v, insn, dest_reg, inc_val, mult_val,
4186 not_every_iteration, maybe_multiple)
4187 struct induction *v;
4192 int not_every_iteration;
4195 struct iv_class *bl;
4198 v->src_reg = dest_reg;
4199 v->dest_reg = dest_reg;
4200 v->mult_val = mult_val;
4201 v->add_val = inc_val;
4202 v->mode = GET_MODE (dest_reg);
4203 v->always_computable = ! not_every_iteration;
4204 v->maybe_multiple = maybe_multiple;
4206 /* Add this to the reg's iv_class, creating a class
4207 if this is the first incrementation of the reg. */
4209 bl = reg_biv_class[REGNO (dest_reg)];
4212 /* Create and initialize new iv_class. */
4214 bl = (struct iv_class *) oballoc (sizeof (struct iv_class));
4216 bl->regno = REGNO (dest_reg);
4222 /* Set initial value to the reg itself. */
4223 bl->initial_value = dest_reg;
4224 /* We haven't seen the initializing insn yet */
4227 bl->initial_test = 0;
4228 bl->incremented = 0;
4232 bl->total_benefit = 0;
4234 /* Add this class to loop_iv_list. */
4235 bl->next = loop_iv_list;
4238 /* Put it in the array of biv register classes. */
4239 reg_biv_class[REGNO (dest_reg)] = bl;
4242 /* Update IV_CLASS entry for this biv. */
4243 v->next_iv = bl->biv;
4246 if (mult_val == const1_rtx)
4247 bl->incremented = 1;
4249 if (loop_dump_stream)
4251 fprintf (loop_dump_stream,
4252 "Insn %d: possible biv, reg %d,",
4253 INSN_UID (insn), REGNO (dest_reg));
4254 if (GET_CODE (inc_val) == CONST_INT)
4255 fprintf (loop_dump_stream, " const = %d\n",
4259 fprintf (loop_dump_stream, " const = ");
4260 print_rtl (loop_dump_stream, inc_val);
4261 fprintf (loop_dump_stream, "\n");
4266 /* Fill in the data about one giv.
4267 V is the `struct induction' in which we record the giv. (It is
4268 allocated by the caller, with alloca.)
4269 INSN is the insn that sets it.
4270 BENEFIT estimates the savings from deleting this insn.
4271 TYPE is DEST_REG or DEST_ADDR; it says whether the giv is computed
4272 into a register or is used as a memory address.
4274 SRC_REG is the biv reg which the giv is computed from.
4275 DEST_REG is the giv's reg (if the giv is stored in a reg).
4276 MULT_VAL and ADD_VAL are the coefficients used to compute the giv.
4277 LOCATION points to the place where this giv's value appears in INSN. */
4280 record_giv (v, insn, src_reg, dest_reg, mult_val, add_val, benefit,
4281 type, not_every_iteration, location, loop_start, loop_end)
4282 struct induction *v;
4286 rtx mult_val, add_val;
4289 int not_every_iteration;
4291 rtx loop_start, loop_end;
4293 struct induction *b;
4294 struct iv_class *bl;
4295 rtx set = single_set (insn);
4299 v->src_reg = src_reg;
4301 v->dest_reg = dest_reg;
4302 v->mult_val = mult_val;
4303 v->add_val = add_val;
4304 v->benefit = benefit;
4305 v->location = location;
4307 v->combined_with = 0;
4308 v->maybe_multiple = 0;
4310 v->derive_adjustment = 0;
4317 /* The v->always_computable field is used in update_giv_derive, to
4318 determine whether a giv can be used to derive another giv. For a
4319 DEST_REG giv, INSN computes a new value for the giv, so its value
4320 isn't computable if INSN insn't executed every iteration.
4321 However, for a DEST_ADDR giv, INSN merely uses the value of the giv;
4322 it does not compute a new value. Hence the value is always computable
4323 regardless of whether INSN is executed each iteration. */
4325 if (type == DEST_ADDR)
4326 v->always_computable = 1;
4328 v->always_computable = ! not_every_iteration;
4330 if (type == DEST_ADDR)
4332 v->mode = GET_MODE (*location);
4336 else /* type == DEST_REG */
4338 v->mode = GET_MODE (SET_DEST (set));
4340 v->lifetime = (uid_luid[regno_last_uid[REGNO (dest_reg)]]
4341 - uid_luid[regno_first_uid[REGNO (dest_reg)]]);
4343 v->times_used = n_times_used[REGNO (dest_reg)];
4345 /* If the lifetime is zero, it means that this register is
4346 really a dead store. So mark this as a giv that can be
4347 ignored. This will not prevent the biv from being eliminated. */
4348 if (v->lifetime == 0)
4351 reg_iv_type[REGNO (dest_reg)] = GENERAL_INDUCT;
4352 reg_iv_info[REGNO (dest_reg)] = v;
4355 /* Add the giv to the class of givs computed from one biv. */
4357 bl = reg_biv_class[REGNO (src_reg)];
4360 v->next_iv = bl->giv;
4362 /* Don't count DEST_ADDR. This is supposed to count the number of
4363 insns that calculate givs. */
4364 if (type == DEST_REG)
4366 bl->total_benefit += benefit;
4369 /* Fatal error, biv missing for this giv? */
4372 if (type == DEST_ADDR)
4376 /* The giv can be replaced outright by the reduced register only if all
4377 of the following conditions are true:
4378 - the insn that sets the giv is always executed on any iteration
4379 on which the giv is used at all
4380 (there are two ways to deduce this:
4381 either the insn is executed on every iteration,
4382 or all uses follow that insn in the same basic block),
4383 - the giv is not used outside the loop
4384 - no assignments to the biv occur during the giv's lifetime. */
4386 if (regno_first_uid[REGNO (dest_reg)] == INSN_UID (insn)
4387 /* Previous line always fails if INSN was moved by loop opt. */
4388 && uid_luid[regno_last_uid[REGNO (dest_reg)]] < INSN_LUID (loop_end)
4389 && (! not_every_iteration
4390 || last_use_this_basic_block (dest_reg, insn)))
4392 /* Now check that there are no assignments to the biv within the
4393 giv's lifetime. This requires two separate checks. */
4395 /* Check each biv update, and fail if any are between the first
4396 and last use of the giv.
4398 If this loop contains an inner loop that was unrolled, then
4399 the insn modifying the biv may have been emitted by the loop
4400 unrolling code, and hence does not have a valid luid. Just
4401 mark the biv as not replaceable in this case. It is not very
4402 useful as a biv, because it is used in two different loops.
4403 It is very unlikely that we would be able to optimize the giv
4404 using this biv anyways. */
4407 for (b = bl->biv; b; b = b->next_iv)
4409 if (INSN_UID (b->insn) >= max_uid_for_loop
4410 || ((uid_luid[INSN_UID (b->insn)]
4411 >= uid_luid[regno_first_uid[REGNO (dest_reg)]])
4412 && (uid_luid[INSN_UID (b->insn)]
4413 <= uid_luid[regno_last_uid[REGNO (dest_reg)]])))
4416 v->not_replaceable = 1;
4421 /* If there are any backwards branches that go from after the
4422 biv update to before it, then this giv is not replaceable. */
4424 for (b = bl->biv; b; b = b->next_iv)
4425 if (back_branch_in_range_p (b->insn, loop_start, loop_end))
4428 v->not_replaceable = 1;
4434 /* May still be replaceable, we don't have enough info here to
4437 v->not_replaceable = 0;
4441 if (loop_dump_stream)
4443 if (type == DEST_REG)
4444 fprintf (loop_dump_stream, "Insn %d: giv reg %d",
4445 INSN_UID (insn), REGNO (dest_reg));
4447 fprintf (loop_dump_stream, "Insn %d: dest address",
4450 fprintf (loop_dump_stream, " src reg %d benefit %d",
4451 REGNO (src_reg), v->benefit);
4452 fprintf (loop_dump_stream, " used %d lifetime %d",
4453 v->times_used, v->lifetime);
4456 fprintf (loop_dump_stream, " replaceable");
4458 if (GET_CODE (mult_val) == CONST_INT)
4459 fprintf (loop_dump_stream, " mult %d",
4463 fprintf (loop_dump_stream, " mult ");
4464 print_rtl (loop_dump_stream, mult_val);
4467 if (GET_CODE (add_val) == CONST_INT)
4468 fprintf (loop_dump_stream, " add %d",
4472 fprintf (loop_dump_stream, " add ");
4473 print_rtl (loop_dump_stream, add_val);
4477 if (loop_dump_stream)
4478 fprintf (loop_dump_stream, "\n");
4483 /* All this does is determine whether a giv can be made replaceable because
4484 its final value can be calculated. This code can not be part of record_giv
4485 above, because final_giv_value requires that the number of loop iterations
4486 be known, and that can not be accurately calculated until after all givs
4487 have been identified. */
4490 check_final_value (v, loop_start, loop_end)
4491 struct induction *v;
4492 rtx loop_start, loop_end;
4494 struct iv_class *bl;
4495 rtx final_value = 0;
4497 bl = reg_biv_class[REGNO (v->src_reg)];
4499 /* DEST_ADDR givs will never reach here, because they are always marked
4500 replaceable above in record_giv. */
4502 /* The giv can be replaced outright by the reduced register only if all
4503 of the following conditions are true:
4504 - the insn that sets the giv is always executed on any iteration
4505 on which the giv is used at all
4506 (there are two ways to deduce this:
4507 either the insn is executed on every iteration,
4508 or all uses follow that insn in the same basic block),
4509 - its final value can be calculated (this condition is different
4510 than the one above in record_giv)
4511 - no assignments to the biv occur during the giv's lifetime. */
4514 /* This is only called now when replaceable is known to be false. */
4515 /* Clear replaceable, so that it won't confuse final_giv_value. */
4519 if ((final_value = final_giv_value (v, loop_start, loop_end))
4520 && (v->always_computable || last_use_this_basic_block (v->dest_reg, v->insn)))
4522 int biv_increment_seen = 0;
4528 /* When trying to determine whether or not a biv increment occurs
4529 during the lifetime of the giv, we can ignore uses of the variable
4530 outside the loop because final_value is true. Hence we can not
4531 use regno_last_uid and regno_first_uid as above in record_giv. */
4533 /* Search the loop to determine whether any assignments to the
4534 biv occur during the giv's lifetime. Start with the insn
4535 that sets the giv, and search around the loop until we come
4536 back to that insn again.
4538 Also fail if there is a jump within the giv's lifetime that jumps
4539 to somewhere outside the lifetime but still within the loop. This
4540 catches spaghetti code where the execution order is not linear, and
4541 hence the above test fails. Here we assume that the giv lifetime
4542 does not extend from one iteration of the loop to the next, so as
4543 to make the test easier. Since the lifetime isn't known yet,
4544 this requires two loops. See also record_giv above. */
4546 last_giv_use = v->insn;
4552 p = NEXT_INSN (loop_start);
4556 if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
4557 || GET_CODE (p) == CALL_INSN)
4559 if (biv_increment_seen)
4561 if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
4564 v->not_replaceable = 1;
4568 else if (GET_CODE (PATTERN (p)) == SET
4569 && SET_DEST (PATTERN (p)) == v->src_reg)
4570 biv_increment_seen = 1;
4571 else if (reg_mentioned_p (v->dest_reg, PATTERN (p)))
4576 /* Now that the lifetime of the giv is known, check for branches
4577 from within the lifetime to outside the lifetime if it is still
4587 p = NEXT_INSN (loop_start);
4588 if (p == last_giv_use)
4591 if (GET_CODE (p) == JUMP_INSN && JUMP_LABEL (p)
4592 && LABEL_NAME (JUMP_LABEL (p))
4593 && ((INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (v->insn)
4594 && INSN_LUID (JUMP_LABEL (p)) > INSN_LUID (loop_start))
4595 || (INSN_LUID (JUMP_LABEL (p)) > INSN_LUID (last_giv_use)
4596 && INSN_LUID (JUMP_LABEL (p)) < INSN_LUID (loop_end))))
4599 v->not_replaceable = 1;
4601 if (loop_dump_stream)
4602 fprintf (loop_dump_stream,
4603 "Found branch outside giv lifetime.\n");
4610 /* If it is replaceable, then save the final value. */
4612 v->final_value = final_value;
4615 if (loop_dump_stream && v->replaceable)
4616 fprintf (loop_dump_stream, "Insn %d: giv reg %d final_value replaceable\n",
4617 INSN_UID (v->insn), REGNO (v->dest_reg));
4620 /* Update the status of whether a giv can derive other givs.
4622 We need to do something special if there is or may be an update to the biv
4623 between the time the giv is defined and the time it is used to derive
4626 In addition, a giv that is only conditionally set is not allowed to
4627 derive another giv once a label has been passed.
4629 The cases we look at are when a label or an update to a biv is passed. */
4632 update_giv_derive (p)
4635 struct iv_class *bl;
4636 struct induction *biv, *giv;
4640 /* Search all IV classes, then all bivs, and finally all givs.
4642 There are three cases we are concerned with. First we have the situation
4643 of a giv that is only updated conditionally. In that case, it may not
4644 derive any givs after a label is passed.
4646 The second case is when a biv update occurs, or may occur, after the
4647 definition of a giv. For certain biv updates (see below) that are
4648 known to occur between the giv definition and use, we can adjust the
4649 giv definition. For others, or when the biv update is conditional,
4650 we must prevent the giv from deriving any other givs. There are two
4651 sub-cases within this case.
4653 If this is a label, we are concerned with any biv update that is done
4654 conditionally, since it may be done after the giv is defined followed by
4655 a branch here (actually, we need to pass both a jump and a label, but
4656 this extra tracking doesn't seem worth it).
4658 If this is a jump, we are concerned about any biv update that may be
4659 executed multiple times. We are actually only concerned about
4660 backward jumps, but it is probably not worth performing the test
4661 on the jump again here.
4663 If this is a biv update, we must adjust the giv status to show that a
4664 subsequent biv update was performed. If this adjustment cannot be done,
4665 the giv cannot derive further givs. */
4667 for (bl = loop_iv_list; bl; bl = bl->next)
4668 for (biv = bl->biv; biv; biv = biv->next_iv)
4669 if (GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN
4672 for (giv = bl->giv; giv; giv = giv->next_iv)
4674 /* If cant_derive is already true, there is no point in
4675 checking all of these conditions again. */
4676 if (giv->cant_derive)
4679 /* If this giv is conditionally set and we have passed a label,
4680 it cannot derive anything. */
4681 if (GET_CODE (p) == CODE_LABEL && ! giv->always_computable)
4682 giv->cant_derive = 1;
4684 /* Skip givs that have mult_val == 0, since
4685 they are really invariants. Also skip those that are
4686 replaceable, since we know their lifetime doesn't contain
4688 else if (giv->mult_val == const0_rtx || giv->replaceable)
4691 /* The only way we can allow this giv to derive another
4692 is if this is a biv increment and we can form the product
4693 of biv->add_val and giv->mult_val. In this case, we will
4694 be able to compute a compensation. */
4695 else if (biv->insn == p)
4699 if (biv->mult_val == const1_rtx)
4700 tem = simplify_giv_expr (gen_rtx (MULT, giv->mode,
4705 if (tem && giv->derive_adjustment)
4706 tem = simplify_giv_expr (gen_rtx (PLUS, giv->mode, tem,
4707 giv->derive_adjustment),
4710 giv->derive_adjustment = tem;
4712 giv->cant_derive = 1;
4714 else if ((GET_CODE (p) == CODE_LABEL && ! biv->always_computable)
4715 || (GET_CODE (p) == JUMP_INSN && biv->maybe_multiple))
4716 giv->cant_derive = 1;
4721 /* Check whether an insn is an increment legitimate for a basic induction var.
4722 X is the source of insn P, or a part of it.
4723 MODE is the mode in which X should be interpreted.
4725 DEST_REG is the putative biv, also the destination of the insn.
4726 We accept patterns of these forms:
4727 REG = REG + INVARIANT (includes REG = REG - CONSTANT)
4728 REG = INVARIANT + REG
4730 If X is suitable, we return 1, set *MULT_VAL to CONST1_RTX,
4731 and store the additive term into *INC_VAL.
4733 If X is an assignment of an invariant into DEST_REG, we set
4734 *MULT_VAL to CONST0_RTX, and store the invariant into *INC_VAL.
4736 We also want to detect a BIV when it corresponds to a variable
4737 whose mode was promoted via PROMOTED_MODE. In that case, an increment
4738 of the variable may be a PLUS that adds a SUBREG of that variable to
4739 an invariant and then sign- or zero-extends the result of the PLUS
4742 Most GIVs in such cases will be in the promoted mode, since that is the
4743 probably the natural computation mode (and almost certainly the mode
4744 used for addresses) on the machine. So we view the pseudo-reg containing
4745 the variable as the BIV, as if it were simply incremented.
4747 Note that treating the entire pseudo as a BIV will result in making
4748 simple increments to any GIVs based on it. However, if the variable
4749 overflows in its declared mode but not its promoted mode, the result will
4750 be incorrect. This is acceptable if the variable is signed, since
4751 overflows in such cases are undefined, but not if it is unsigned, since
4752 those overflows are defined. So we only check for SIGN_EXTEND and
4755 If we cannot find a biv, we return 0. */
4758 basic_induction_var (x, mode, dest_reg, p, inc_val, mult_val)
4760 enum machine_mode mode;
4766 register enum rtx_code code;
4770 code = GET_CODE (x);
4774 if (XEXP (x, 0) == dest_reg
4775 || (GET_CODE (XEXP (x, 0)) == SUBREG
4776 && SUBREG_PROMOTED_VAR_P (XEXP (x, 0))
4777 && SUBREG_REG (XEXP (x, 0)) == dest_reg))
4779 else if (XEXP (x, 1) == dest_reg
4780 || (GET_CODE (XEXP (x, 1)) == SUBREG
4781 && SUBREG_PROMOTED_VAR_P (XEXP (x, 1))
4782 && SUBREG_REG (XEXP (x, 1)) == dest_reg))
4787 if (invariant_p (arg) != 1)
4790 *inc_val = convert_modes (GET_MODE (dest_reg), GET_MODE (x), arg, 0);
4791 *mult_val = const1_rtx;
4795 /* If this is a SUBREG for a promoted variable, check the inner
4797 if (SUBREG_PROMOTED_VAR_P (x))
4798 return basic_induction_var (SUBREG_REG (x), GET_MODE (SUBREG_REG (x)),
4799 dest_reg, p, inc_val, mult_val);
4802 /* If this register is assigned in the previous insn, look at its
4803 source, but don't go outside the loop or past a label. */
4805 for (insn = PREV_INSN (p);
4806 (insn && GET_CODE (insn) == NOTE
4807 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_BEG);
4808 insn = PREV_INSN (insn))
4812 set = single_set (insn);
4815 && (SET_DEST (set) == x
4816 || (GET_CODE (SET_DEST (set)) == SUBREG
4817 && (GET_MODE_SIZE (GET_MODE (SET_DEST (set)))
4819 && SUBREG_REG (SET_DEST (set)) == x)))
4820 return basic_induction_var (SET_SRC (set),
4821 (GET_MODE (SET_SRC (set)) == VOIDmode
4823 : GET_MODE (SET_SRC (set))),
4826 /* ... fall through ... */
4828 /* Can accept constant setting of biv only when inside inner most loop.
4829 Otherwise, a biv of an inner loop may be incorrectly recognized
4830 as a biv of the outer loop,
4831 causing code to be moved INTO the inner loop. */
4833 if (invariant_p (x) != 1)
4838 if (loops_enclosed == 1)
4840 /* Possible bug here? Perhaps we don't know the mode of X. */
4841 *inc_val = convert_modes (GET_MODE (dest_reg), mode, x, 0);
4842 *mult_val = const0_rtx;
4849 return basic_induction_var (XEXP (x, 0), GET_MODE (XEXP (x, 0)),
4850 dest_reg, p, inc_val, mult_val);
4852 /* Similar, since this can be a sign extension. */
4853 for (insn = PREV_INSN (p);
4854 (insn && GET_CODE (insn) == NOTE
4855 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_BEG);
4856 insn = PREV_INSN (insn))
4860 set = single_set (insn);
4862 if (set && SET_DEST (set) == XEXP (x, 0)
4863 && GET_CODE (XEXP (x, 1)) == CONST_INT
4864 && INTVAL (XEXP (x, 1)) >= 0
4865 && GET_CODE (SET_SRC (set)) == ASHIFT
4866 && XEXP (x, 1) == XEXP (SET_SRC (set), 1))
4867 return basic_induction_var (XEXP (SET_SRC (set), 0),
4868 GET_MODE (XEXP (x, 0)),
4869 dest_reg, insn, inc_val, mult_val);
4877 /* A general induction variable (giv) is any quantity that is a linear
4878 function of a basic induction variable,
4879 i.e. giv = biv * mult_val + add_val.
4880 The coefficients can be any loop invariant quantity.
4881 A giv need not be computed directly from the biv;
4882 it can be computed by way of other givs. */
4884 /* Determine whether X computes a giv.
4885 If it does, return a nonzero value
4886 which is the benefit from eliminating the computation of X;
4887 set *SRC_REG to the register of the biv that it is computed from;
4888 set *ADD_VAL and *MULT_VAL to the coefficients,
4889 such that the value of X is biv * mult + add; */
4892 general_induction_var (x, src_reg, add_val, mult_val)
4902 /* If this is an invariant, forget it, it isn't a giv. */
4903 if (invariant_p (x) == 1)
4906 /* See if the expression could be a giv and get its form.
4907 Mark our place on the obstack in case we don't find a giv. */
4908 storage = (char *) oballoc (0);
4909 x = simplify_giv_expr (x, &benefit);
4916 switch (GET_CODE (x))
4920 /* Since this is now an invariant and wasn't before, it must be a giv
4921 with MULT_VAL == 0. It doesn't matter which BIV we associate this
4923 *src_reg = loop_iv_list->biv->dest_reg;
4924 *mult_val = const0_rtx;
4929 /* This is equivalent to a BIV. */
4931 *mult_val = const1_rtx;
4932 *add_val = const0_rtx;
4936 /* Either (plus (biv) (invar)) or
4937 (plus (mult (biv) (invar_1)) (invar_2)). */
4938 if (GET_CODE (XEXP (x, 0)) == MULT)
4940 *src_reg = XEXP (XEXP (x, 0), 0);
4941 *mult_val = XEXP (XEXP (x, 0), 1);
4945 *src_reg = XEXP (x, 0);
4946 *mult_val = const1_rtx;
4948 *add_val = XEXP (x, 1);
4952 /* ADD_VAL is zero. */
4953 *src_reg = XEXP (x, 0);
4954 *mult_val = XEXP (x, 1);
4955 *add_val = const0_rtx;
4962 /* Remove any enclosing USE from ADD_VAL and MULT_VAL (there will be
4963 unless they are CONST_INT). */
4964 if (GET_CODE (*add_val) == USE)
4965 *add_val = XEXP (*add_val, 0);
4966 if (GET_CODE (*mult_val) == USE)
4967 *mult_val = XEXP (*mult_val, 0);
4969 benefit += rtx_cost (orig_x, SET);
4971 /* Always return some benefit if this is a giv so it will be detected
4972 as such. This allows elimination of bivs that might otherwise
4973 not be eliminated. */
4974 return benefit == 0 ? 1 : benefit;
4977 /* Given an expression, X, try to form it as a linear function of a biv.
4978 We will canonicalize it to be of the form
4979 (plus (mult (BIV) (invar_1))
4981 with possible degeneracies.
4983 The invariant expressions must each be of a form that can be used as a
4984 machine operand. We surround then with a USE rtx (a hack, but localized
4985 and certainly unambiguous!) if not a CONST_INT for simplicity in this
4986 routine; it is the caller's responsibility to strip them.
4988 If no such canonicalization is possible (i.e., two biv's are used or an
4989 expression that is neither invariant nor a biv or giv), this routine
4992 For a non-zero return, the result will have a code of CONST_INT, USE,
4993 REG (for a BIV), PLUS, or MULT. No other codes will occur.
4995 *BENEFIT will be incremented by the benefit of any sub-giv encountered. */
4998 simplify_giv_expr (x, benefit)
5002 enum machine_mode mode = GET_MODE (x);
5006 /* If this is not an integer mode, or if we cannot do arithmetic in this
5007 mode, this can't be a giv. */
5008 if (mode != VOIDmode
5009 && (GET_MODE_CLASS (mode) != MODE_INT
5010 || GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT))
5013 switch (GET_CODE (x))
5016 arg0 = simplify_giv_expr (XEXP (x, 0), benefit);
5017 arg1 = simplify_giv_expr (XEXP (x, 1), benefit);
5018 if (arg0 == 0 || arg1 == 0)
5021 /* Put constant last, CONST_INT last if both constant. */
5022 if ((GET_CODE (arg0) == USE
5023 || GET_CODE (arg0) == CONST_INT)
5024 && GET_CODE (arg1) != CONST_INT)
5025 tem = arg0, arg0 = arg1, arg1 = tem;
5027 /* Handle addition of zero, then addition of an invariant. */
5028 if (arg1 == const0_rtx)
5030 else if (GET_CODE (arg1) == CONST_INT || GET_CODE (arg1) == USE)
5031 switch (GET_CODE (arg0))
5035 /* Both invariant. Only valid if sum is machine operand.
5036 First strip off possible USE on first operand. */
5037 if (GET_CODE (arg0) == USE)
5038 arg0 = XEXP (arg0, 0);
5041 if (CONSTANT_P (arg0) && GET_CODE (arg1) == CONST_INT)
5043 tem = plus_constant (arg0, INTVAL (arg1));
5044 if (GET_CODE (tem) != CONST_INT)
5045 tem = gen_rtx (USE, mode, tem);
5052 /* biv + invar or mult + invar. Return sum. */
5053 return gen_rtx (PLUS, mode, arg0, arg1);
5056 /* (a + invar_1) + invar_2. Associate. */
5057 return simplify_giv_expr (gen_rtx (PLUS, mode,
5059 gen_rtx (PLUS, mode,
5060 XEXP (arg0, 1), arg1)),
5067 /* Each argument must be either REG, PLUS, or MULT. Convert REG to
5068 MULT to reduce cases. */
5069 if (GET_CODE (arg0) == REG)
5070 arg0 = gen_rtx (MULT, mode, arg0, const1_rtx);
5071 if (GET_CODE (arg1) == REG)
5072 arg1 = gen_rtx (MULT, mode, arg1, const1_rtx);
5074 /* Now have PLUS + PLUS, PLUS + MULT, MULT + PLUS, or MULT + MULT.
5075 Put a MULT first, leaving PLUS + PLUS, MULT + PLUS, or MULT + MULT.
5076 Recurse to associate the second PLUS. */
5077 if (GET_CODE (arg1) == MULT)
5078 tem = arg0, arg0 = arg1, arg1 = tem;
5080 if (GET_CODE (arg1) == PLUS)
5081 return simplify_giv_expr (gen_rtx (PLUS, mode,
5082 gen_rtx (PLUS, mode,
5083 arg0, XEXP (arg1, 0)),
5087 /* Now must have MULT + MULT. Distribute if same biv, else not giv. */
5088 if (GET_CODE (arg0) != MULT || GET_CODE (arg1) != MULT)
5091 if (XEXP (arg0, 0) != XEXP (arg1, 0))
5094 return simplify_giv_expr (gen_rtx (MULT, mode,
5096 gen_rtx (PLUS, mode,
5102 /* Handle "a - b" as "a + b * (-1)". */
5103 return simplify_giv_expr (gen_rtx (PLUS, mode,
5105 gen_rtx (MULT, mode,
5106 XEXP (x, 1), constm1_rtx)),
5110 arg0 = simplify_giv_expr (XEXP (x, 0), benefit);
5111 arg1 = simplify_giv_expr (XEXP (x, 1), benefit);
5112 if (arg0 == 0 || arg1 == 0)
5115 /* Put constant last, CONST_INT last if both constant. */
5116 if ((GET_CODE (arg0) == USE || GET_CODE (arg0) == CONST_INT)
5117 && GET_CODE (arg1) != CONST_INT)
5118 tem = arg0, arg0 = arg1, arg1 = tem;
5120 /* If second argument is not now constant, not giv. */
5121 if (GET_CODE (arg1) != USE && GET_CODE (arg1) != CONST_INT)
5124 /* Handle multiply by 0 or 1. */
5125 if (arg1 == const0_rtx)
5128 else if (arg1 == const1_rtx)
5131 switch (GET_CODE (arg0))
5134 /* biv * invar. Done. */
5135 return gen_rtx (MULT, mode, arg0, arg1);
5138 /* Product of two constants. */
5139 return GEN_INT (INTVAL (arg0) * INTVAL (arg1));
5142 /* invar * invar. Not giv. */
5146 /* (a * invar_1) * invar_2. Associate. */
5147 return simplify_giv_expr (gen_rtx (MULT, mode,
5149 gen_rtx (MULT, mode,
5150 XEXP (arg0, 1), arg1)),
5154 /* (a + invar_1) * invar_2. Distribute. */
5155 return simplify_giv_expr (gen_rtx (PLUS, mode,
5156 gen_rtx (MULT, mode,
5157 XEXP (arg0, 0), arg1),
5158 gen_rtx (MULT, mode,
5159 XEXP (arg0, 1), arg1)),
5167 /* Shift by constant is multiply by power of two. */
5168 if (GET_CODE (XEXP (x, 1)) != CONST_INT)
5171 return simplify_giv_expr (gen_rtx (MULT, mode,
5173 GEN_INT ((HOST_WIDE_INT) 1
5174 << INTVAL (XEXP (x, 1)))),
5178 /* "-a" is "a * (-1)" */
5179 return simplify_giv_expr (gen_rtx (MULT, mode, XEXP (x, 0), constm1_rtx),
5183 /* "~a" is "-a - 1". Silly, but easy. */
5184 return simplify_giv_expr (gen_rtx (MINUS, mode,
5185 gen_rtx (NEG, mode, XEXP (x, 0)),
5190 /* Already in proper form for invariant. */
5194 /* If this is a new register, we can't deal with it. */
5195 if (REGNO (x) >= max_reg_before_loop)
5198 /* Check for biv or giv. */
5199 switch (reg_iv_type[REGNO (x)])
5203 case GENERAL_INDUCT:
5205 struct induction *v = reg_iv_info[REGNO (x)];
5207 /* Form expression from giv and add benefit. Ensure this giv
5208 can derive another and subtract any needed adjustment if so. */
5209 *benefit += v->benefit;
5213 tem = gen_rtx (PLUS, mode, gen_rtx (MULT, mode,
5214 v->src_reg, v->mult_val),
5216 if (v->derive_adjustment)
5217 tem = gen_rtx (MINUS, mode, tem, v->derive_adjustment);
5218 return simplify_giv_expr (tem, benefit);
5222 /* Fall through to general case. */
5224 /* If invariant, return as USE (unless CONST_INT).
5225 Otherwise, not giv. */
5226 if (GET_CODE (x) == USE)
5229 if (invariant_p (x) == 1)
5231 if (GET_CODE (x) == CONST_INT)
5234 return gen_rtx (USE, mode, x);
5241 /* Help detect a giv that is calculated by several consecutive insns;
5245 The caller has already identified the first insn P as having a giv as dest;
5246 we check that all other insns that set the same register follow
5247 immediately after P, that they alter nothing else,
5248 and that the result of the last is still a giv.
5250 The value is 0 if the reg set in P is not really a giv.
5251 Otherwise, the value is the amount gained by eliminating
5252 all the consecutive insns that compute the value.
5254 FIRST_BENEFIT is the amount gained by eliminating the first insn, P.
5255 SRC_REG is the reg of the biv; DEST_REG is the reg of the giv.
5257 The coefficients of the ultimate giv value are stored in
5258 *MULT_VAL and *ADD_VAL. */
5261 consec_sets_giv (first_benefit, p, src_reg, dest_reg,
5276 /* Indicate that this is a giv so that we can update the value produced in
5277 each insn of the multi-insn sequence.
5279 This induction structure will be used only by the call to
5280 general_induction_var below, so we can allocate it on our stack.
5281 If this is a giv, our caller will replace the induct var entry with
5282 a new induction structure. */
5284 = (struct induction *) alloca (sizeof (struct induction));
5285 v->src_reg = src_reg;
5286 v->mult_val = *mult_val;
5287 v->add_val = *add_val;
5288 v->benefit = first_benefit;
5290 v->derive_adjustment = 0;
5292 reg_iv_type[REGNO (dest_reg)] = GENERAL_INDUCT;
5293 reg_iv_info[REGNO (dest_reg)] = v;
5295 count = n_times_set[REGNO (dest_reg)] - 1;
5300 code = GET_CODE (p);
5302 /* If libcall, skip to end of call sequence. */
5303 if (code == INSN && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX)))
5307 && (set = single_set (p))
5308 && GET_CODE (SET_DEST (set)) == REG
5309 && SET_DEST (set) == dest_reg
5310 && ((benefit = general_induction_var (SET_SRC (set), &src_reg,
5312 /* Giv created by equivalent expression. */
5313 || ((temp = find_reg_note (p, REG_EQUAL, NULL_RTX))
5314 && (benefit = general_induction_var (XEXP (temp, 0), &src_reg,
5315 add_val, mult_val))))
5316 && src_reg == v->src_reg)
5318 if (find_reg_note (p, REG_RETVAL, NULL_RTX))
5319 benefit += libcall_benefit (p);
5322 v->mult_val = *mult_val;
5323 v->add_val = *add_val;
5324 v->benefit = benefit;
5326 else if (code != NOTE)
5328 /* Allow insns that set something other than this giv to a
5329 constant. Such insns are needed on machines which cannot
5330 include long constants and should not disqualify a giv. */
5332 && (set = single_set (p))
5333 && SET_DEST (set) != dest_reg
5334 && CONSTANT_P (SET_SRC (set)))
5337 reg_iv_type[REGNO (dest_reg)] = UNKNOWN_INDUCT;
5345 /* Return an rtx, if any, that expresses giv G2 as a function of the register
5346 represented by G1. If no such expression can be found, or it is clear that
5347 it cannot possibly be a valid address, 0 is returned.
5349 To perform the computation, we note that
5352 where `v' is the biv.
5354 So G2 = (c/a) * G1 + (d - b*c/a) */
5358 express_from (g1, g2)
5359 struct induction *g1, *g2;
5363 /* The value that G1 will be multiplied by must be a constant integer. Also,
5364 the only chance we have of getting a valid address is if b*c/a (see above
5365 for notation) is also an integer. */
5366 if (GET_CODE (g1->mult_val) != CONST_INT
5367 || GET_CODE (g2->mult_val) != CONST_INT
5368 || GET_CODE (g1->add_val) != CONST_INT
5369 || g1->mult_val == const0_rtx
5370 || INTVAL (g2->mult_val) % INTVAL (g1->mult_val) != 0)
5373 mult = GEN_INT (INTVAL (g2->mult_val) / INTVAL (g1->mult_val));
5374 add = plus_constant (g2->add_val, - INTVAL (g1->add_val) * INTVAL (mult));
5376 /* Form simplified final result. */
5377 if (mult == const0_rtx)
5379 else if (mult == const1_rtx)
5380 mult = g1->dest_reg;
5382 mult = gen_rtx (MULT, g2->mode, g1->dest_reg, mult);
5384 if (add == const0_rtx)
5387 return gen_rtx (PLUS, g2->mode, mult, add);
5391 /* Return 1 if giv G2 can be combined with G1. This means that G2 can use
5392 (either directly or via an address expression) a register used to represent
5393 G1. Set g2->new_reg to a represtation of G1 (normally just
5397 combine_givs_p (g1, g2)
5398 struct induction *g1, *g2;
5402 /* If these givs are identical, they can be combined. */
5403 if (rtx_equal_p (g1->mult_val, g2->mult_val)
5404 && rtx_equal_p (g1->add_val, g2->add_val))
5406 g2->new_reg = g1->dest_reg;
5411 /* If G2 can be expressed as a function of G1 and that function is valid
5412 as an address and no more expensive than using a register for G2,
5413 the expression of G2 in terms of G1 can be used. */
5414 if (g2->giv_type == DEST_ADDR
5415 && (tem = express_from (g1, g2)) != 0
5416 && memory_address_p (g2->mem_mode, tem)
5417 && ADDRESS_COST (tem) <= ADDRESS_COST (*g2->location))
5427 /* Check all pairs of givs for iv_class BL and see if any can be combined with
5428 any other. If so, point SAME to the giv combined with and set NEW_REG to
5429 be an expression (in terms of the other giv's DEST_REG) equivalent to the
5430 giv. Also, update BENEFIT and related fields for cost/benefit analysis. */
5434 struct iv_class *bl;
5436 struct induction *g1, *g2;
5439 for (g1 = bl->giv; g1; g1 = g1->next_iv)
5440 for (pass = 0; pass <= 1; pass++)
5441 for (g2 = bl->giv; g2; g2 = g2->next_iv)
5443 /* First try to combine with replaceable givs, then all givs. */
5444 && (g1->replaceable || pass == 1)
5445 /* If either has already been combined or is to be ignored, can't
5447 && ! g1->ignore && ! g2->ignore && ! g1->same && ! g2->same
5448 /* If something has been based on G2, G2 cannot itself be based
5449 on something else. */
5450 && ! g2->combined_with
5451 && combine_givs_p (g1, g2))
5453 /* g2->new_reg set by `combine_givs_p' */
5455 g1->combined_with = 1;
5456 g1->benefit += g2->benefit;
5457 /* ??? The new final_[bg]iv_value code does a much better job
5458 of finding replaceable giv's, and hence this code may no
5459 longer be necessary. */
5460 if (! g2->replaceable && REG_USERVAR_P (g2->dest_reg))
5461 g1->benefit -= copy_cost;
5462 g1->lifetime += g2->lifetime;
5463 g1->times_used += g2->times_used;
5465 if (loop_dump_stream)
5466 fprintf (loop_dump_stream, "giv at %d combined with giv at %d\n",
5467 INSN_UID (g2->insn), INSN_UID (g1->insn));
5471 /* EMIT code before INSERT_BEFORE to set REG = B * M + A. */
5474 emit_iv_add_mult (b, m, a, reg, insert_before)
5475 rtx b; /* initial value of basic induction variable */
5476 rtx m; /* multiplicative constant */
5477 rtx a; /* additive constant */
5478 rtx reg; /* destination register */
5484 /* Prevent unexpected sharing of these rtx. */
5488 /* Increase the lifetime of any invariants moved further in code. */
5489 update_reg_last_use (a, insert_before);
5490 update_reg_last_use (b, insert_before);
5491 update_reg_last_use (m, insert_before);
5494 result = expand_mult_add (b, reg, m, a, GET_MODE (reg), 0);
5496 emit_move_insn (reg, result);
5497 seq = gen_sequence ();
5500 emit_insn_before (seq, insert_before);
5503 /* Test whether A * B can be computed without
5504 an actual multiply insn. Value is 1 if so. */
5507 product_cheap_p (a, b)
5513 struct obstack *old_rtl_obstack = rtl_obstack;
5514 char *storage = (char *) obstack_alloc (&temp_obstack, 0);
5517 /* If only one is constant, make it B. */
5518 if (GET_CODE (a) == CONST_INT)
5519 tmp = a, a = b, b = tmp;
5521 /* If first constant, both constant, so don't need multiply. */
5522 if (GET_CODE (a) == CONST_INT)
5525 /* If second not constant, neither is constant, so would need multiply. */
5526 if (GET_CODE (b) != CONST_INT)
5529 /* One operand is constant, so might not need multiply insn. Generate the
5530 code for the multiply and see if a call or multiply, or long sequence
5531 of insns is generated. */
5533 rtl_obstack = &temp_obstack;
5535 expand_mult (GET_MODE (a), a, b, NULL_RTX, 0);
5536 tmp = gen_sequence ();
5539 if (GET_CODE (tmp) == SEQUENCE)
5541 if (XVEC (tmp, 0) == 0)
5543 else if (XVECLEN (tmp, 0) > 3)
5546 for (i = 0; i < XVECLEN (tmp, 0); i++)
5548 rtx insn = XVECEXP (tmp, 0, i);
5550 if (GET_CODE (insn) != INSN
5551 || (GET_CODE (PATTERN (insn)) == SET
5552 && GET_CODE (SET_SRC (PATTERN (insn))) == MULT)
5553 || (GET_CODE (PATTERN (insn)) == PARALLEL
5554 && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == SET
5555 && GET_CODE (SET_SRC (XVECEXP (PATTERN (insn), 0, 0))) == MULT))
5562 else if (GET_CODE (tmp) == SET
5563 && GET_CODE (SET_SRC (tmp)) == MULT)
5565 else if (GET_CODE (tmp) == PARALLEL
5566 && GET_CODE (XVECEXP (tmp, 0, 0)) == SET
5567 && GET_CODE (SET_SRC (XVECEXP (tmp, 0, 0))) == MULT)
5570 /* Free any storage we obtained in generating this multiply and restore rtl
5571 allocation to its normal obstack. */
5572 obstack_free (&temp_obstack, storage);
5573 rtl_obstack = old_rtl_obstack;
5578 /* Check to see if loop can be terminated by a "decrement and branch until
5579 zero" instruction. If so, add a REG_NONNEG note to the branch insn if so.
5580 Also try reversing an increment loop to a decrement loop
5581 to see if the optimization can be performed.
5582 Value is nonzero if optimization was performed. */
5584 /* This is useful even if the architecture doesn't have such an insn,
5585 because it might change a loops which increments from 0 to n to a loop
5586 which decrements from n to 0. A loop that decrements to zero is usually
5587 faster than one that increments from zero. */
5589 /* ??? This could be rewritten to use some of the loop unrolling procedures,
5590 such as approx_final_value, biv_total_increment, loop_iterations, and
5591 final_[bg]iv_value. */
5594 check_dbra_loop (loop_end, insn_count, loop_start)
5599 struct iv_class *bl;
5606 rtx before_comparison;
5609 /* If last insn is a conditional branch, and the insn before tests a
5610 register value, try to optimize it. Otherwise, we can't do anything. */
5612 comparison = get_condition_for_loop (PREV_INSN (loop_end));
5613 if (comparison == 0)
5616 /* Check all of the bivs to see if the compare uses one of them.
5617 Skip biv's set more than once because we can't guarantee that
5618 it will be zero on the last iteration. Also skip if the biv is
5619 used between its update and the test insn. */
5621 for (bl = loop_iv_list; bl; bl = bl->next)
5623 if (bl->biv_count == 1
5624 && bl->biv->dest_reg == XEXP (comparison, 0)
5625 && ! reg_used_between_p (regno_reg_rtx[bl->regno], bl->biv->insn,
5626 PREV_INSN (PREV_INSN (loop_end))))
5633 /* Look for the case where the basic induction variable is always
5634 nonnegative, and equals zero on the last iteration.
5635 In this case, add a reg_note REG_NONNEG, which allows the
5636 m68k DBRA instruction to be used. */
5638 if (((GET_CODE (comparison) == GT
5639 && GET_CODE (XEXP (comparison, 1)) == CONST_INT
5640 && INTVAL (XEXP (comparison, 1)) == -1)
5641 || (GET_CODE (comparison) == NE && XEXP (comparison, 1) == const0_rtx))
5642 && GET_CODE (bl->biv->add_val) == CONST_INT
5643 && INTVAL (bl->biv->add_val) < 0)
5645 /* Initial value must be greater than 0,
5646 init_val % -dec_value == 0 to ensure that it equals zero on
5647 the last iteration */
5649 if (GET_CODE (bl->initial_value) == CONST_INT
5650 && INTVAL (bl->initial_value) > 0
5651 && (INTVAL (bl->initial_value) %
5652 (-INTVAL (bl->biv->add_val))) == 0)
5654 /* register always nonnegative, add REG_NOTE to branch */
5655 REG_NOTES (PREV_INSN (loop_end))
5656 = gen_rtx (EXPR_LIST, REG_NONNEG, NULL_RTX,
5657 REG_NOTES (PREV_INSN (loop_end)));
5663 /* If the decrement is 1 and the value was tested as >= 0 before
5664 the loop, then we can safely optimize. */
5665 for (p = loop_start; p; p = PREV_INSN (p))
5667 if (GET_CODE (p) == CODE_LABEL)
5669 if (GET_CODE (p) != JUMP_INSN)
5672 before_comparison = get_condition_for_loop (p);
5673 if (before_comparison
5674 && XEXP (before_comparison, 0) == bl->biv->dest_reg
5675 && GET_CODE (before_comparison) == LT
5676 && XEXP (before_comparison, 1) == const0_rtx
5677 && ! reg_set_between_p (bl->biv->dest_reg, p, loop_start)
5678 && INTVAL (bl->biv->add_val) == -1)
5680 REG_NOTES (PREV_INSN (loop_end))
5681 = gen_rtx (EXPR_LIST, REG_NONNEG, NULL_RTX,
5682 REG_NOTES (PREV_INSN (loop_end)));
5689 else if (num_mem_sets <= 1)
5691 /* Try to change inc to dec, so can apply above optimization. */
5693 all registers modified are induction variables or invariant,
5694 all memory references have non-overlapping addresses
5695 (obviously true if only one write)
5696 allow 2 insns for the compare/jump at the end of the loop. */
5697 /* Also, we must avoid any instructions which use both the reversed
5698 biv and another biv. Such instructions will fail if the loop is
5699 reversed. We meet this condition by requiring that either
5700 no_use_except_counting is true, or else that there is only
5702 int num_nonfixed_reads = 0;
5703 /* 1 if the iteration var is used only to count iterations. */
5704 int no_use_except_counting = 0;
5705 /* 1 if the loop has no memory store, or it has a single memory store
5706 which is reversible. */
5707 int reversible_mem_store = 1;
5709 for (p = loop_start; p != loop_end; p = NEXT_INSN (p))
5710 if (GET_RTX_CLASS (GET_CODE (p)) == 'i')
5711 num_nonfixed_reads += count_nonfixed_reads (PATTERN (p));
5713 if (bl->giv_count == 0
5714 && ! loop_number_exit_labels[uid_loop_num[INSN_UID (loop_start)]])
5716 rtx bivreg = regno_reg_rtx[bl->regno];
5718 /* If there are no givs for this biv, and the only exit is the
5719 fall through at the end of the the loop, then
5720 see if perhaps there are no uses except to count. */
5721 no_use_except_counting = 1;
5722 for (p = loop_start; p != loop_end; p = NEXT_INSN (p))
5723 if (GET_RTX_CLASS (GET_CODE (p)) == 'i')
5725 rtx set = single_set (p);
5727 if (set && GET_CODE (SET_DEST (set)) == REG
5728 && REGNO (SET_DEST (set)) == bl->regno)
5729 /* An insn that sets the biv is okay. */
5731 else if (p == prev_nonnote_insn (prev_nonnote_insn (loop_end))
5732 || p == prev_nonnote_insn (loop_end))
5733 /* Don't bother about the end test. */
5735 else if (reg_mentioned_p (bivreg, PATTERN (p)))
5736 /* Any other use of the biv is no good. */
5738 no_use_except_counting = 0;
5744 /* If the loop has a single store, and the destination address is
5745 invariant, then we can't reverse the loop, because this address
5746 might then have the wrong value at loop exit.
5747 This would work if the source was invariant also, however, in that
5748 case, the insn should have been moved out of the loop. */
5750 if (num_mem_sets == 1)
5751 reversible_mem_store
5752 = (! unknown_address_altered
5753 && ! invariant_p (XEXP (loop_store_mems[0], 0)));
5755 /* This code only acts for innermost loops. Also it simplifies
5756 the memory address check by only reversing loops with
5757 zero or one memory access.
5758 Two memory accesses could involve parts of the same array,
5759 and that can't be reversed. */
5761 if (num_nonfixed_reads <= 1
5763 && !loop_has_volatile
5764 && reversible_mem_store
5765 && (no_use_except_counting
5766 || ((bl->giv_count + bl->biv_count + num_mem_sets
5767 + num_movables + 2 == insn_count)
5768 && (bl == loop_iv_list && bl->next == 0))))
5772 /* Loop can be reversed. */
5773 if (loop_dump_stream)
5774 fprintf (loop_dump_stream, "Can reverse loop\n");
5776 /* Now check other conditions:
5777 initial_value must be zero,
5778 final_value % add_val == 0, so that when reversed, the
5779 biv will be zero on the last iteration.
5781 This test can probably be improved since +/- 1 in the constant
5782 can be obtained by changing LT to LE and vice versa; this is
5785 if (comparison && bl->initial_value == const0_rtx
5786 && GET_CODE (XEXP (comparison, 1)) == CONST_INT
5787 /* LE gets turned into LT */
5788 && GET_CODE (comparison) == LT
5789 && (INTVAL (XEXP (comparison, 1))
5790 % INTVAL (bl->biv->add_val)) == 0)
5792 /* Register will always be nonnegative, with value
5793 0 on last iteration if loop reversed */
5795 /* Save some info needed to produce the new insns. */
5796 reg = bl->biv->dest_reg;
5797 jump_label = XEXP (SET_SRC (PATTERN (PREV_INSN (loop_end))), 1);
5798 new_add_val = GEN_INT (- INTVAL (bl->biv->add_val));
5800 final_value = XEXP (comparison, 1);
5801 start_value = GEN_INT (INTVAL (XEXP (comparison, 1))
5802 - INTVAL (bl->biv->add_val));
5804 /* Initialize biv to start_value before loop start.
5805 The old initializing insn will be deleted as a
5806 dead store by flow.c. */
5807 emit_insn_before (gen_move_insn (reg, start_value), loop_start);
5809 /* Add insn to decrement register, and delete insn
5810 that incremented the register. */
5811 p = emit_insn_before (gen_add2_insn (reg, new_add_val),
5813 delete_insn (bl->biv->insn);
5815 /* Update biv info to reflect its new status. */
5817 bl->initial_value = start_value;
5818 bl->biv->add_val = new_add_val;
5820 /* Inc LABEL_NUSES so that delete_insn will
5821 not delete the label. */
5822 LABEL_NUSES (XEXP (jump_label, 0)) ++;
5824 /* Emit an insn after the end of the loop to set the biv's
5825 proper exit value if it is used anywhere outside the loop. */
5826 if ((regno_last_uid[bl->regno]
5827 != INSN_UID (PREV_INSN (PREV_INSN (loop_end))))
5829 || regno_first_uid[bl->regno] != INSN_UID (bl->init_insn))
5830 emit_insn_after (gen_move_insn (reg, final_value),
5833 /* Delete compare/branch at end of loop. */
5834 delete_insn (PREV_INSN (loop_end));
5835 delete_insn (PREV_INSN (loop_end));
5837 /* Add new compare/branch insn at end of loop. */
5839 emit_cmp_insn (reg, const0_rtx, GE, NULL_RTX,
5840 GET_MODE (reg), 0, 0);
5841 emit_jump_insn (gen_bge (XEXP (jump_label, 0)));
5842 tem = gen_sequence ();
5844 emit_jump_insn_before (tem, loop_end);
5846 for (tem = PREV_INSN (loop_end);
5847 tem && GET_CODE (tem) != JUMP_INSN; tem = PREV_INSN (tem))
5851 JUMP_LABEL (tem) = XEXP (jump_label, 0);
5853 /* Increment of LABEL_NUSES done above. */
5854 /* Register is now always nonnegative,
5855 so add REG_NONNEG note to the branch. */
5856 REG_NOTES (tem) = gen_rtx (EXPR_LIST, REG_NONNEG, NULL_RTX,
5862 /* Mark that this biv has been reversed. Each giv which depends
5863 on this biv, and which is also live past the end of the loop
5864 will have to be fixed up. */
5868 if (loop_dump_stream)
5869 fprintf (loop_dump_stream,
5870 "Reversed loop and added reg_nonneg\n");
5880 /* Verify whether the biv BL appears to be eliminable,
5881 based on the insns in the loop that refer to it.
5882 LOOP_START is the first insn of the loop, and END is the end insn.
5884 If ELIMINATE_P is non-zero, actually do the elimination.
5886 THRESHOLD and INSN_COUNT are from loop_optimize and are used to
5887 determine whether invariant insns should be placed inside or at the
5888 start of the loop. */
5891 maybe_eliminate_biv (bl, loop_start, end, eliminate_p, threshold, insn_count)
5892 struct iv_class *bl;
5896 int threshold, insn_count;
5898 rtx reg = bl->biv->dest_reg;
5901 /* Scan all insns in the loop, stopping if we find one that uses the
5902 biv in a way that we cannot eliminate. */
5904 for (p = loop_start; p != end; p = NEXT_INSN (p))
5906 enum rtx_code code = GET_CODE (p);
5907 rtx where = threshold >= insn_count ? loop_start : p;
5909 if ((code == INSN || code == JUMP_INSN || code == CALL_INSN)
5910 && reg_mentioned_p (reg, PATTERN (p))
5911 && ! maybe_eliminate_biv_1 (PATTERN (p), p, bl, eliminate_p, where))
5913 if (loop_dump_stream)
5914 fprintf (loop_dump_stream,
5915 "Cannot eliminate biv %d: biv used in insn %d.\n",
5916 bl->regno, INSN_UID (p));
5923 if (loop_dump_stream)
5924 fprintf (loop_dump_stream, "biv %d %s eliminated.\n",
5925 bl->regno, eliminate_p ? "was" : "can be");
5932 /* If BL appears in X (part of the pattern of INSN), see if we can
5933 eliminate its use. If so, return 1. If not, return 0.
5935 If BIV does not appear in X, return 1.
5937 If ELIMINATE_P is non-zero, actually do the elimination. WHERE indicates
5938 where extra insns should be added. Depending on how many items have been
5939 moved out of the loop, it will either be before INSN or at the start of
5943 maybe_eliminate_biv_1 (x, insn, bl, eliminate_p, where)
5945 struct iv_class *bl;
5949 enum rtx_code code = GET_CODE (x);
5950 rtx reg = bl->biv->dest_reg;
5951 enum machine_mode mode = GET_MODE (reg);
5952 struct induction *v;
5961 /* If we haven't already been able to do something with this BIV,
5962 we can't eliminate it. */
5968 /* If this sets the BIV, it is not a problem. */
5969 if (SET_DEST (x) == reg)
5972 /* If this is an insn that defines a giv, it is also ok because
5973 it will go away when the giv is reduced. */
5974 for (v = bl->giv; v; v = v->next_iv)
5975 if (v->giv_type == DEST_REG && SET_DEST (x) == v->dest_reg)
5979 if (SET_DEST (x) == cc0_rtx && SET_SRC (x) == reg)
5981 /* Can replace with any giv that was reduced and
5982 that has (MULT_VAL != 0) and (ADD_VAL == 0).
5983 Require a constant for MULT_VAL, so we know it's nonzero. */
5985 for (v = bl->giv; v; v = v->next_iv)
5986 if (CONSTANT_P (v->mult_val) && v->mult_val != const0_rtx
5987 && v->add_val == const0_rtx
5988 && ! v->ignore && ! v->maybe_dead && v->always_computable
5994 /* If the giv has the opposite direction of change,
5995 then reverse the comparison. */
5996 if (INTVAL (v->mult_val) < 0)
5997 new = gen_rtx (COMPARE, GET_MODE (v->new_reg),
5998 const0_rtx, v->new_reg);
6002 /* We can probably test that giv's reduced reg. */
6003 if (validate_change (insn, &SET_SRC (x), new, 0))
6007 /* Look for a giv with (MULT_VAL != 0) and (ADD_VAL != 0);
6008 replace test insn with a compare insn (cmp REDUCED_GIV ADD_VAL).
6009 Require a constant for MULT_VAL, so we know it's nonzero. */
6011 for (v = bl->giv; v; v = v->next_iv)
6012 if (CONSTANT_P (v->mult_val) && v->mult_val != const0_rtx
6013 && ! v->ignore && ! v->maybe_dead && v->always_computable
6019 /* If the giv has the opposite direction of change,
6020 then reverse the comparison. */
6021 if (INTVAL (v->mult_val) < 0)
6022 new = gen_rtx (COMPARE, VOIDmode, copy_rtx (v->add_val),
6025 new = gen_rtx (COMPARE, VOIDmode, v->new_reg,
6026 copy_rtx (v->add_val));
6028 /* Replace biv with the giv's reduced register. */
6029 update_reg_last_use (v->add_val, insn);
6030 if (validate_change (insn, &SET_SRC (PATTERN (insn)), new, 0))
6033 /* Insn doesn't support that constant or invariant. Copy it
6034 into a register (it will be a loop invariant.) */
6035 tem = gen_reg_rtx (GET_MODE (v->new_reg));
6037 emit_insn_before (gen_move_insn (tem, copy_rtx (v->add_val)),
6040 if (validate_change (insn, &SET_SRC (PATTERN (insn)),
6041 gen_rtx (COMPARE, VOIDmode,
6042 v->new_reg, tem), 0))
6051 case GT: case GE: case GTU: case GEU:
6052 case LT: case LE: case LTU: case LEU:
6053 /* See if either argument is the biv. */
6054 if (XEXP (x, 0) == reg)
6055 arg = XEXP (x, 1), arg_operand = 1;
6056 else if (XEXP (x, 1) == reg)
6057 arg = XEXP (x, 0), arg_operand = 0;
6061 if (CONSTANT_P (arg))
6063 /* First try to replace with any giv that has constant positive
6064 mult_val and constant add_val. We might be able to support
6065 negative mult_val, but it seems complex to do it in general. */
6067 for (v = bl->giv; v; v = v->next_iv)
6068 if (CONSTANT_P (v->mult_val) && INTVAL (v->mult_val) > 0
6069 && CONSTANT_P (v->add_val)
6070 && ! v->ignore && ! v->maybe_dead && v->always_computable
6076 /* Replace biv with the giv's reduced reg. */
6077 XEXP (x, 1-arg_operand) = v->new_reg;
6079 /* If all constants are actually constant integers and
6080 the derived constant can be directly placed in the COMPARE,
6082 if (GET_CODE (arg) == CONST_INT
6083 && GET_CODE (v->mult_val) == CONST_INT
6084 && GET_CODE (v->add_val) == CONST_INT
6085 && validate_change (insn, &XEXP (x, arg_operand),
6086 GEN_INT (INTVAL (arg)
6087 * INTVAL (v->mult_val)
6088 + INTVAL (v->add_val)), 0))
6091 /* Otherwise, load it into a register. */
6092 tem = gen_reg_rtx (mode);
6093 emit_iv_add_mult (arg, v->mult_val, v->add_val, tem, where);
6094 if (validate_change (insn, &XEXP (x, arg_operand), tem, 0))
6097 /* If that failed, put back the change we made above. */
6098 XEXP (x, 1-arg_operand) = reg;
6101 /* Look for giv with positive constant mult_val and nonconst add_val.
6102 Insert insns to calculate new compare value. */
6104 for (v = bl->giv; v; v = v->next_iv)
6105 if (CONSTANT_P (v->mult_val) && INTVAL (v->mult_val) > 0
6106 && ! v->ignore && ! v->maybe_dead && v->always_computable
6114 tem = gen_reg_rtx (mode);
6116 /* Replace biv with giv's reduced register. */
6117 validate_change (insn, &XEXP (x, 1 - arg_operand),
6120 /* Compute value to compare against. */
6121 emit_iv_add_mult (arg, v->mult_val, v->add_val, tem, where);
6122 /* Use it in this insn. */
6123 validate_change (insn, &XEXP (x, arg_operand), tem, 1);
6124 if (apply_change_group ())
6128 else if (GET_CODE (arg) == REG || GET_CODE (arg) == MEM)
6130 if (invariant_p (arg) == 1)
6132 /* Look for giv with constant positive mult_val and nonconst
6133 add_val. Insert insns to compute new compare value. */
6135 for (v = bl->giv; v; v = v->next_iv)
6136 if (CONSTANT_P (v->mult_val) && INTVAL (v->mult_val) > 0
6137 && ! v->ignore && ! v->maybe_dead && v->always_computable
6145 tem = gen_reg_rtx (mode);
6147 /* Replace biv with giv's reduced register. */
6148 validate_change (insn, &XEXP (x, 1 - arg_operand),
6151 /* Compute value to compare against. */
6152 emit_iv_add_mult (arg, v->mult_val, v->add_val,
6154 validate_change (insn, &XEXP (x, arg_operand), tem, 1);
6155 if (apply_change_group ())
6160 /* This code has problems. Basically, you can't know when
6161 seeing if we will eliminate BL, whether a particular giv
6162 of ARG will be reduced. If it isn't going to be reduced,
6163 we can't eliminate BL. We can try forcing it to be reduced,
6164 but that can generate poor code.
6166 The problem is that the benefit of reducing TV, below should
6167 be increased if BL can actually be eliminated, but this means
6168 we might have to do a topological sort of the order in which
6169 we try to process biv. It doesn't seem worthwhile to do
6170 this sort of thing now. */
6173 /* Otherwise the reg compared with had better be a biv. */
6174 if (GET_CODE (arg) != REG
6175 || reg_iv_type[REGNO (arg)] != BASIC_INDUCT)
6178 /* Look for a pair of givs, one for each biv,
6179 with identical coefficients. */
6180 for (v = bl->giv; v; v = v->next_iv)
6182 struct induction *tv;
6184 if (v->ignore || v->maybe_dead || v->mode != mode)
6187 for (tv = reg_biv_class[REGNO (arg)]->giv; tv; tv = tv->next_iv)
6188 if (! tv->ignore && ! tv->maybe_dead
6189 && rtx_equal_p (tv->mult_val, v->mult_val)
6190 && rtx_equal_p (tv->add_val, v->add_val)
6191 && tv->mode == mode)
6196 /* Replace biv with its giv's reduced reg. */
6197 XEXP (x, 1-arg_operand) = v->new_reg;
6198 /* Replace other operand with the other giv's
6200 XEXP (x, arg_operand) = tv->new_reg;
6207 /* If we get here, the biv can't be eliminated. */
6211 /* If this address is a DEST_ADDR giv, it doesn't matter if the
6212 biv is used in it, since it will be replaced. */
6213 for (v = bl->giv; v; v = v->next_iv)
6214 if (v->giv_type == DEST_ADDR && v->location == &XEXP (x, 0))
6219 /* See if any subexpression fails elimination. */
6220 fmt = GET_RTX_FORMAT (code);
6221 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
6226 if (! maybe_eliminate_biv_1 (XEXP (x, i), insn, bl,
6227 eliminate_p, where))
6232 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
6233 if (! maybe_eliminate_biv_1 (XVECEXP (x, i, j), insn, bl,
6234 eliminate_p, where))
6243 /* Return nonzero if the last use of REG
6244 is in an insn following INSN in the same basic block. */
6247 last_use_this_basic_block (reg, insn)
6253 n && GET_CODE (n) != CODE_LABEL && GET_CODE (n) != JUMP_INSN;
6256 if (regno_last_uid[REGNO (reg)] == INSN_UID (n))
6262 /* Called via `note_stores' to record the initial value of a biv. Here we
6263 just record the location of the set and process it later. */
6266 record_initial (dest, set)
6270 struct iv_class *bl;
6272 if (GET_CODE (dest) != REG
6273 || REGNO (dest) >= max_reg_before_loop
6274 || reg_iv_type[REGNO (dest)] != BASIC_INDUCT)
6277 bl = reg_biv_class[REGNO (dest)];
6279 /* If this is the first set found, record it. */
6280 if (bl->init_insn == 0)
6282 bl->init_insn = note_insn;
6287 /* If any of the registers in X are "old" and currently have a last use earlier
6288 than INSN, update them to have a last use of INSN. Their actual last use
6289 will be the previous insn but it will not have a valid uid_luid so we can't
6293 update_reg_last_use (x, insn)
6297 /* Check for the case where INSN does not have a valid luid. In this case,
6298 there is no need to modify the regno_last_uid, as this can only happen
6299 when code is inserted after the loop_end to set a pseudo's final value,
6300 and hence this insn will never be the last use of x. */
6301 if (GET_CODE (x) == REG && REGNO (x) < max_reg_before_loop
6302 && INSN_UID (insn) < max_uid_for_loop
6303 && uid_luid[regno_last_uid[REGNO (x)]] < uid_luid[INSN_UID (insn)])
6304 regno_last_uid[REGNO (x)] = INSN_UID (insn);
6308 register char *fmt = GET_RTX_FORMAT (GET_CODE (x));
6309 for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
6312 update_reg_last_use (XEXP (x, i), insn);
6313 else if (fmt[i] == 'E')
6314 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
6315 update_reg_last_use (XVECEXP (x, i, j), insn);
6320 /* Given a jump insn JUMP, return the condition that will cause it to branch
6321 to its JUMP_LABEL. If the condition cannot be understood, or is an
6322 inequality floating-point comparison which needs to be reversed, 0 will
6325 If EARLIEST is non-zero, it is a pointer to a place where the earliest
6326 insn used in locating the condition was found. If a replacement test
6327 of the condition is desired, it should be placed in front of that
6328 insn and we will be sure that the inputs are still valid.
6330 The condition will be returned in a canonical form to simplify testing by
6331 callers. Specifically:
6333 (1) The code will always be a comparison operation (EQ, NE, GT, etc.).
6334 (2) Both operands will be machine operands; (cc0) will have been replaced.
6335 (3) If an operand is a constant, it will be the second operand.
6336 (4) (LE x const) will be replaced with (LT x <const+1>) and similarly
6337 for GE, GEU, and LEU. */
6340 get_condition (jump, earliest)
6349 int reverse_code = 0;
6350 int did_reverse_condition = 0;
6352 /* If this is not a standard conditional jump, we can't parse it. */
6353 if (GET_CODE (jump) != JUMP_INSN
6354 || ! condjump_p (jump) || simplejump_p (jump))
6357 code = GET_CODE (XEXP (SET_SRC (PATTERN (jump)), 0));
6358 op0 = XEXP (XEXP (SET_SRC (PATTERN (jump)), 0), 0);
6359 op1 = XEXP (XEXP (SET_SRC (PATTERN (jump)), 0), 1);
6364 /* If this branches to JUMP_LABEL when the condition is false, reverse
6366 if (GET_CODE (XEXP (SET_SRC (PATTERN (jump)), 2)) == LABEL_REF
6367 && XEXP (XEXP (SET_SRC (PATTERN (jump)), 2), 0) == JUMP_LABEL (jump))
6368 code = reverse_condition (code), did_reverse_condition ^= 1;
6370 /* If we are comparing a register with zero, see if the register is set
6371 in the previous insn to a COMPARE or a comparison operation. Perform
6372 the same tests as a function of STORE_FLAG_VALUE as find_comparison_args
6375 while (GET_RTX_CLASS (code) == '<' && op1 == CONST0_RTX (GET_MODE (op0)))
6377 /* Set non-zero when we find something of interest. */
6381 /* If comparison with cc0, import actual comparison from compare
6385 if ((prev = prev_nonnote_insn (prev)) == 0
6386 || GET_CODE (prev) != INSN
6387 || (set = single_set (prev)) == 0
6388 || SET_DEST (set) != cc0_rtx)
6391 op0 = SET_SRC (set);
6392 op1 = CONST0_RTX (GET_MODE (op0));
6398 /* If this is a COMPARE, pick up the two things being compared. */
6399 if (GET_CODE (op0) == COMPARE)
6401 op1 = XEXP (op0, 1);
6402 op0 = XEXP (op0, 0);
6405 else if (GET_CODE (op0) != REG)
6408 /* Go back to the previous insn. Stop if it is not an INSN. We also
6409 stop if it isn't a single set or if it has a REG_INC note because
6410 we don't want to bother dealing with it. */
6412 if ((prev = prev_nonnote_insn (prev)) == 0
6413 || GET_CODE (prev) != INSN
6414 || FIND_REG_INC_NOTE (prev, 0)
6415 || (set = single_set (prev)) == 0)
6418 /* If this is setting OP0, get what it sets it to if it looks
6420 if (SET_DEST (set) == op0)
6422 enum machine_mode inner_mode = GET_MODE (SET_SRC (set));
6424 if ((GET_CODE (SET_SRC (set)) == COMPARE
6427 && GET_MODE_CLASS (inner_mode) == MODE_INT
6428 && (GET_MODE_BITSIZE (inner_mode)
6429 <= HOST_BITS_PER_WIDE_INT)
6430 && (STORE_FLAG_VALUE
6431 & ((HOST_WIDE_INT) 1
6432 << (GET_MODE_BITSIZE (inner_mode) - 1))))
6433 #ifdef FLOAT_STORE_FLAG_VALUE
6435 && GET_MODE_CLASS (inner_mode) == MODE_FLOAT
6436 && FLOAT_STORE_FLAG_VALUE < 0)
6439 && GET_RTX_CLASS (GET_CODE (SET_SRC (set))) == '<')))
6441 else if (((code == EQ
6443 && (GET_MODE_BITSIZE (inner_mode)
6444 <= HOST_BITS_PER_WIDE_INT)
6445 && GET_MODE_CLASS (inner_mode) == MODE_INT
6446 && (STORE_FLAG_VALUE
6447 & ((HOST_WIDE_INT) 1
6448 << (GET_MODE_BITSIZE (inner_mode) - 1))))
6449 #ifdef FLOAT_STORE_FLAG_VALUE
6451 && GET_MODE_CLASS (inner_mode) == MODE_FLOAT
6452 && FLOAT_STORE_FLAG_VALUE < 0)
6455 && GET_RTX_CLASS (GET_CODE (SET_SRC (set))) == '<')
6457 /* We might have reversed a LT to get a GE here. But this wasn't
6458 actually the comparison of data, so we don't flag that we
6459 have had to reverse the condition. */
6460 did_reverse_condition ^= 1;
6468 else if (reg_set_p (op0, prev))
6469 /* If this sets OP0, but not directly, we have to give up. */
6474 if (GET_RTX_CLASS (GET_CODE (x)) == '<')
6475 code = GET_CODE (x);
6478 code = reverse_condition (code);
6479 did_reverse_condition ^= 1;
6483 op0 = XEXP (x, 0), op1 = XEXP (x, 1);
6489 /* If constant is first, put it last. */
6490 if (CONSTANT_P (op0))
6491 code = swap_condition (code), tem = op0, op0 = op1, op1 = tem;
6493 /* If OP0 is the result of a comparison, we weren't able to find what
6494 was really being compared, so fail. */
6495 if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC)
6498 /* Canonicalize any ordered comparison with integers involving equality
6499 if we can do computations in the relevant mode and we do not
6502 if (GET_CODE (op1) == CONST_INT
6503 && GET_MODE (op0) != VOIDmode
6504 && GET_MODE_BITSIZE (GET_MODE (op0)) <= HOST_BITS_PER_WIDE_INT)
6506 HOST_WIDE_INT const_val = INTVAL (op1);
6507 unsigned HOST_WIDE_INT uconst_val = const_val;
6508 unsigned HOST_WIDE_INT max_val
6509 = (unsigned HOST_WIDE_INT) GET_MODE_MASK (GET_MODE (op0));
6514 if (const_val != max_val >> 1)
6515 code = LT, op1 = GEN_INT (const_val + 1);
6520 != (((HOST_WIDE_INT) 1
6521 << (GET_MODE_BITSIZE (GET_MODE (op0)) - 1))))
6522 code = GT, op1 = GEN_INT (const_val - 1);
6526 if (uconst_val != max_val)
6527 code = LTU, op1 = GEN_INT (uconst_val + 1);
6531 if (uconst_val != 0)
6532 code = GTU, op1 = GEN_INT (uconst_val - 1);
6537 /* If this was floating-point and we reversed anything other than an
6538 EQ or NE, return zero. */
6539 if (TARGET_FLOAT_FORMAT == IEEE_FLOAT_FORMAT
6540 && did_reverse_condition && code != NE && code != EQ
6542 && GET_MODE_CLASS (GET_MODE (op0)) == MODE_FLOAT)
6546 /* Never return CC0; return zero instead. */
6551 return gen_rtx (code, VOIDmode, op0, op1);
6554 /* Similar to above routine, except that we also put an invariant last
6555 unless both operands are invariants. */
6558 get_condition_for_loop (x)
6561 rtx comparison = get_condition (x, NULL_PTR);
6564 || ! invariant_p (XEXP (comparison, 0))
6565 || invariant_p (XEXP (comparison, 1)))
6568 return gen_rtx (swap_condition (GET_CODE (comparison)), VOIDmode,
6569 XEXP (comparison, 1), XEXP (comparison, 0));