1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 88, 92-96, 1997 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, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
22 /* This file contains the data flow analysis pass of the compiler.
23 It computes data flow information
24 which tells combine_instructions which insns to consider combining
25 and controls register allocation.
27 Additional data flow information that is too bulky to record
28 is generated during the analysis, and is used at that time to
29 create autoincrement and autodecrement addressing.
31 The first step is dividing the function into basic blocks.
32 find_basic_blocks does this. Then life_analysis determines
33 where each register is live and where it is dead.
35 ** find_basic_blocks **
37 find_basic_blocks divides the current function's rtl
38 into basic blocks. It records the beginnings and ends of the
39 basic blocks in the vectors basic_block_head and basic_block_end,
40 and the number of blocks in n_basic_blocks.
42 find_basic_blocks also finds any unreachable loops
47 life_analysis is called immediately after find_basic_blocks.
48 It uses the basic block information to determine where each
49 hard or pseudo register is live.
51 ** live-register info **
53 The information about where each register is live is in two parts:
54 the REG_NOTES of insns, and the vector basic_block_live_at_start.
56 basic_block_live_at_start has an element for each basic block,
57 and the element is a bit-vector with a bit for each hard or pseudo
58 register. The bit is 1 if the register is live at the beginning
61 Two types of elements can be added to an insn's REG_NOTES.
62 A REG_DEAD note is added to an insn's REG_NOTES for any register
63 that meets both of two conditions: The value in the register is not
64 needed in subsequent insns and the insn does not replace the value in
65 the register (in the case of multi-word hard registers, the value in
66 each register must be replaced by the insn to avoid a REG_DEAD note).
68 In the vast majority of cases, an object in a REG_DEAD note will be
69 used somewhere in the insn. The (rare) exception to this is if an
70 insn uses a multi-word hard register and only some of the registers are
71 needed in subsequent insns. In that case, REG_DEAD notes will be
72 provided for those hard registers that are not subsequently needed.
73 Partial REG_DEAD notes of this type do not occur when an insn sets
74 only some of the hard registers used in such a multi-word operand;
75 omitting REG_DEAD notes for objects stored in an insn is optional and
76 the desire to do so does not justify the complexity of the partial
79 REG_UNUSED notes are added for each register that is set by the insn
80 but is unused subsequently (if every register set by the insn is unused
81 and the insn does not reference memory or have some other side-effect,
82 the insn is deleted instead). If only part of a multi-word hard
83 register is used in a subsequent insn, REG_UNUSED notes are made for
84 the parts that will not be used.
86 To determine which registers are live after any insn, one can
87 start from the beginning of the basic block and scan insns, noting
88 which registers are set by each insn and which die there.
90 ** Other actions of life_analysis **
92 life_analysis sets up the LOG_LINKS fields of insns because the
93 information needed to do so is readily available.
95 life_analysis deletes insns whose only effect is to store a value
98 life_analysis notices cases where a reference to a register as
99 a memory address can be combined with a preceding or following
100 incrementation or decrementation of the register. The separate
101 instruction to increment or decrement is deleted and the address
102 is changed to a POST_INC or similar rtx.
104 Each time an incrementing or decrementing address is created,
105 a REG_INC element is added to the insn's REG_NOTES list.
107 life_analysis fills in certain vectors containing information about
108 register usage: reg_n_refs, reg_n_deaths, reg_n_sets, reg_live_length,
109 reg_n_calls_crosses and reg_basic_block. */
114 #include "basic-block.h"
115 #include "insn-config.h"
117 #include "hard-reg-set.h"
123 #define obstack_chunk_alloc xmalloc
124 #define obstack_chunk_free free
126 /* The contents of the current function definition are allocated
127 in this obstack, and all are freed at the end of the function.
128 For top-level functions, this is temporary_obstack.
129 Separate obstacks are made for nested functions. */
131 extern struct obstack *function_obstack;
133 /* List of labels that must never be deleted. */
134 extern rtx forced_labels;
136 /* Get the basic block number of an insn.
137 This info should not be expected to remain available
138 after the end of life_analysis. */
140 /* This is the limit of the allocated space in the following two arrays. */
142 static int max_uid_for_flow;
144 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
146 /* This is where the BLOCK_NUM values are really stored.
147 This is set up by find_basic_blocks and used there and in life_analysis,
150 static int *uid_block_number;
152 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
154 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
155 static char *uid_volatile;
157 /* Number of basic blocks in the current function. */
161 /* Maximum register number used in this function, plus one. */
165 /* Maximum number of SCRATCH rtx's used in any basic block of this
170 /* Number of SCRATCH rtx's in the current block. */
172 static int num_scratch;
174 /* Indexed by n, giving various register information */
176 reg_info *reg_n_info;
178 /* Element N is the next insn that uses (hard or pseudo) register number N
179 within the current basic block; or zero, if there is no such insn.
180 This is valid only during the final backward scan in propagate_block. */
182 static rtx *reg_next_use;
184 /* Size of a regset for the current function,
185 in (1) bytes and (2) elements. */
190 /* Element N is first insn in basic block N.
191 This info lasts until we finish compiling the function. */
193 rtx *basic_block_head;
195 /* Element N is last insn in basic block N.
196 This info lasts until we finish compiling the function. */
198 rtx *basic_block_end;
200 /* Element N is a regset describing the registers live
201 at the start of basic block N.
202 This info lasts until we finish compiling the function. */
204 regset *basic_block_live_at_start;
206 /* Regset of regs live when calls to `setjmp'-like functions happen. */
208 regset regs_live_at_setjmp;
210 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
211 that have to go in the same hard reg.
212 The first two regs in the list are a pair, and the next two
213 are another pair, etc. */
216 /* Element N is nonzero if control can drop into basic block N
217 from the preceding basic block. Freed after life_analysis. */
219 static char *basic_block_drops_in;
221 /* Element N is depth within loops of the last insn in basic block number N.
222 Freed after life_analysis. */
224 static short *basic_block_loop_depth;
226 /* Element N nonzero if basic block N can actually be reached.
227 Vector exists only during find_basic_blocks. */
229 static char *block_live_static;
231 /* Depth within loops of basic block being scanned for lifetime analysis,
232 plus one. This is the weight attached to references to registers. */
234 static int loop_depth;
236 /* During propagate_block, this is non-zero if the value of CC0 is live. */
240 /* During propagate_block, this contains the last MEM stored into. It
241 is used to eliminate consecutive stores to the same location. */
243 static rtx last_mem_set;
245 /* Set of registers that may be eliminable. These are handled specially
246 in updating regs_ever_live. */
248 static HARD_REG_SET elim_reg_set;
250 /* Forward declarations */
251 static void find_basic_blocks PROTO((rtx, rtx));
252 static void mark_label_ref PROTO((rtx, rtx, int));
253 static void life_analysis PROTO((rtx, int));
254 void allocate_for_life_analysis PROTO((void));
255 void init_regset_vector PROTO((regset *, int, struct obstack *));
256 void free_regset_vector PROTO((regset *, int));
257 static void propagate_block PROTO((regset, rtx, rtx, int,
259 static rtx flow_delete_insn PROTO((rtx));
260 static int insn_dead_p PROTO((rtx, regset, int));
261 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
262 static void mark_set_regs PROTO((regset, regset, rtx,
264 static void mark_set_1 PROTO((regset, regset, rtx,
266 static void find_auto_inc PROTO((regset, rtx, rtx));
267 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
268 static int try_pre_increment_1 PROTO((rtx));
269 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
270 void dump_flow_info PROTO((FILE *));
272 /* Find basic blocks of the current function and perform data flow analysis.
273 F is the first insn of the function and NREGS the number of register numbers
277 flow_analysis (f, nregs, file)
284 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
286 #ifdef ELIMINABLE_REGS
287 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
290 /* Record which registers will be eliminated. We use this in
293 CLEAR_HARD_REG_SET (elim_reg_set);
295 #ifdef ELIMINABLE_REGS
296 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
297 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
299 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
302 /* Count the basic blocks. Also find maximum insn uid value used. */
305 register RTX_CODE prev_code = JUMP_INSN;
306 register RTX_CODE code;
308 max_uid_for_flow = 0;
310 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
312 code = GET_CODE (insn);
313 if (INSN_UID (insn) > max_uid_for_flow)
314 max_uid_for_flow = INSN_UID (insn);
315 if (code == CODE_LABEL
316 || (GET_RTX_CLASS (code) == 'i'
317 && (prev_code == JUMP_INSN
318 || (prev_code == CALL_INSN
319 && nonlocal_label_list != 0)
320 || prev_code == BARRIER)))
323 if (code == CALL_INSN && find_reg_note (insn, REG_RETVAL, NULL_RTX))
332 /* Leave space for insns we make in some cases for auto-inc. These cases
333 are rare, so we don't need too much space. */
334 max_uid_for_flow += max_uid_for_flow / 10;
337 /* Allocate some tables that last till end of compiling this function
338 and some needed only in find_basic_blocks and life_analysis. */
341 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
342 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
343 basic_block_drops_in = (char *) alloca (n_basic_blocks);
344 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
346 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
347 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
348 bzero (uid_volatile, max_uid_for_flow + 1);
350 find_basic_blocks (f, nonlocal_label_list);
351 life_analysis (f, nregs);
353 dump_flow_info (file);
355 basic_block_drops_in = 0;
356 uid_block_number = 0;
357 basic_block_loop_depth = 0;
360 /* Find all basic blocks of the function whose first insn is F.
361 Store the correct data in the tables that describe the basic blocks,
362 set up the chains of references for each CODE_LABEL, and
363 delete any entire basic blocks that cannot be reached.
365 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
368 find_basic_blocks (f, nonlocal_label_list)
369 rtx f, nonlocal_label_list;
373 register char *block_live = (char *) alloca (n_basic_blocks);
374 register char *block_marked = (char *) alloca (n_basic_blocks);
375 /* List of label_refs to all labels whose addresses are taken
377 rtx label_value_list;
378 int label_value_list_marked_live;
380 enum rtx_code prev_code, code;
386 label_value_list = 0;
387 label_value_list_marked_live = 0;
388 block_live_static = block_live;
389 bzero (block_live, n_basic_blocks);
390 bzero (block_marked, n_basic_blocks);
392 /* Initialize with just block 0 reachable and no blocks marked. */
393 if (n_basic_blocks > 0)
396 /* Initialize the ref chain of each label to 0. Record where all the
397 blocks start and end and their depth in loops. For each insn, record
398 the block it is in. Also mark as reachable any blocks headed by labels
399 that must not be deleted. */
401 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
402 insn; insn = NEXT_INSN (insn))
404 code = GET_CODE (insn);
407 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
409 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
413 /* A basic block starts at label, or after something that can jump. */
414 else if (code == CODE_LABEL
415 || (GET_RTX_CLASS (code) == 'i'
416 && (prev_code == JUMP_INSN
417 || (prev_code == CALL_INSN
418 && nonlocal_label_list != 0
419 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
420 || prev_code == BARRIER)))
422 basic_block_head[++i] = insn;
423 basic_block_end[i] = insn;
424 basic_block_loop_depth[i] = depth;
426 if (code == CODE_LABEL)
428 LABEL_REFS (insn) = insn;
429 /* Any label that cannot be deleted
430 is considered to start a reachable block. */
431 if (LABEL_PRESERVE_P (insn))
436 else if (GET_RTX_CLASS (code) == 'i')
438 basic_block_end[i] = insn;
439 basic_block_loop_depth[i] = depth;
442 if (GET_RTX_CLASS (code) == 'i')
444 /* Make a list of all labels referred to other than by jumps. */
445 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
446 if (REG_NOTE_KIND (note) == REG_LABEL)
447 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
451 BLOCK_NUM (insn) = i;
457 /* During the second pass, `n_basic_blocks' is only an upper bound.
458 Only perform the sanity check for the first pass, and on the second
459 pass ensure `n_basic_blocks' is set to the correct value. */
460 if (pass == 1 && i + 1 != n_basic_blocks)
462 n_basic_blocks = i + 1;
464 for (x = forced_labels; x; x = XEXP (x, 1))
465 if (! LABEL_REF_NONLOCAL_P (x))
466 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
468 for (x = exception_handler_labels; x; x = XEXP (x, 1))
469 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
471 /* Record which basic blocks control can drop in to. */
473 for (i = 0; i < n_basic_blocks; i++)
475 for (insn = PREV_INSN (basic_block_head[i]);
476 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
479 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
482 /* Now find which basic blocks can actually be reached
483 and put all jump insns' LABEL_REFS onto the ref-chains
484 of their target labels. */
486 if (n_basic_blocks > 0)
488 int something_marked = 1;
491 /* Find all indirect jump insns and mark them as possibly jumping to all
492 the labels whose addresses are explicitly used. This is because,
493 when there are computed gotos, we can't tell which labels they jump
494 to, of all the possibilities. */
496 for (insn = f; insn; insn = NEXT_INSN (insn))
497 if (computed_jump_p (insn))
499 if (label_value_list_marked_live == 0)
501 label_value_list_marked_live = 1;
503 /* This could be made smarter by only considering
504 these live, if the computed goto is live. */
506 /* Don't delete the labels (in this function) that
507 are referenced by non-jump instructions. */
509 for (x = label_value_list; x; x = XEXP (x, 1))
510 if (! LABEL_REF_NONLOCAL_P (x))
511 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
514 for (x = label_value_list; x; x = XEXP (x, 1))
515 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
518 for (x = forced_labels; x; x = XEXP (x, 1))
519 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
523 /* Find all call insns and mark them as possibly jumping
524 to all the nonlocal goto handler labels. */
526 for (insn = f; insn; insn = NEXT_INSN (insn))
527 if (GET_CODE (insn) == CALL_INSN
528 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
530 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
531 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
534 /* ??? This could be made smarter:
535 in some cases it's possible to tell that certain
536 calls will not do a nonlocal goto.
538 For example, if the nested functions that do the
539 nonlocal gotos do not have their addresses taken, then
540 only calls to those functions or to other nested
541 functions that use them could possibly do nonlocal
545 /* All blocks associated with labels in label_value_list are
546 trivially considered as marked live, if the list is empty.
547 We do this to speed up the below code. */
549 if (label_value_list == 0)
550 label_value_list_marked_live = 1;
552 /* Pass over all blocks, marking each block that is reachable
553 and has not yet been marked.
554 Keep doing this until, in one pass, no blocks have been marked.
555 Then blocks_live and blocks_marked are identical and correct.
556 In addition, all jumps actually reachable have been marked. */
558 while (something_marked)
560 something_marked = 0;
561 for (i = 0; i < n_basic_blocks; i++)
562 if (block_live[i] && !block_marked[i])
565 something_marked = 1;
566 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
567 block_live[i + 1] = 1;
568 insn = basic_block_end[i];
569 if (GET_CODE (insn) == JUMP_INSN)
570 mark_label_ref (PATTERN (insn), insn, 0);
572 if (label_value_list_marked_live == 0)
573 /* Now that we know that this block is live, mark as
574 live, all the blocks that we might be able to get
577 for (insn = basic_block_head[i];
578 insn != NEXT_INSN (basic_block_end[i]);
579 insn = NEXT_INSN (insn))
581 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
583 for (note = REG_NOTES (insn);
585 note = XEXP (note, 1))
586 if (REG_NOTE_KIND (note) == REG_LABEL)
589 block_live[BLOCK_NUM (x)] = 1;
596 /* ??? See if we have a "live" basic block that is not reachable.
597 This can happen if it is headed by a label that is preserved or
598 in one of the label lists, but no call or computed jump is in
599 the loop. It's not clear if we can delete the block or not,
600 but don't for now. However, we will mess up register status if
601 it remains unreachable, so add a fake reachability from the
604 for (i = 1; i < n_basic_blocks; i++)
605 if (block_live[i] && ! basic_block_drops_in[i]
606 && GET_CODE (basic_block_head[i]) == CODE_LABEL
607 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
608 basic_block_drops_in[i] = 1;
610 /* Now delete the code for any basic blocks that can't be reached.
611 They can occur because jump_optimize does not recognize
612 unreachable loops as unreachable. */
615 for (i = 0; i < n_basic_blocks; i++)
620 /* Delete the insns in a (non-live) block. We physically delete
621 every non-note insn except the start and end (so
622 basic_block_head/end needn't be updated), we turn the latter
623 into NOTE_INSN_DELETED notes.
624 We use to "delete" the insns by turning them into notes, but
625 we may be deleting lots of insns that subsequent passes would
626 otherwise have to process. Secondly, lots of deleted blocks in
627 a row can really slow down propagate_block since it will
628 otherwise process insn-turned-notes multiple times when it
629 looks for loop begin/end notes. */
630 if (basic_block_head[i] != basic_block_end[i])
632 /* It would be quicker to delete all of these with a single
633 unchaining, rather than one at a time, but we need to keep
635 insn = NEXT_INSN (basic_block_head[i]);
636 while (insn != basic_block_end[i])
638 if (GET_CODE (insn) == BARRIER)
640 else if (GET_CODE (insn) != NOTE)
641 insn = flow_delete_insn (insn);
643 insn = NEXT_INSN (insn);
646 insn = basic_block_head[i];
647 if (GET_CODE (insn) != NOTE)
649 /* Turn the head into a deleted insn note. */
650 if (GET_CODE (insn) == BARRIER)
652 PUT_CODE (insn, NOTE);
653 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
654 NOTE_SOURCE_FILE (insn) = 0;
656 insn = basic_block_end[i];
657 if (GET_CODE (insn) != NOTE)
659 /* Turn the tail into a deleted insn note. */
660 if (GET_CODE (insn) == BARRIER)
662 PUT_CODE (insn, NOTE);
663 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
664 NOTE_SOURCE_FILE (insn) = 0;
666 /* BARRIERs are between basic blocks, not part of one.
667 Delete a BARRIER if the preceding jump is deleted.
668 We cannot alter a BARRIER into a NOTE
669 because it is too short; but we can really delete
670 it because it is not part of a basic block. */
671 if (NEXT_INSN (insn) != 0
672 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
673 delete_insn (NEXT_INSN (insn));
675 /* Each time we delete some basic blocks,
676 see if there is a jump around them that is
677 being turned into a no-op. If so, delete it. */
679 if (block_live[i - 1])
682 for (j = i + 1; j < n_basic_blocks; j++)
686 insn = basic_block_end[i - 1];
687 if (GET_CODE (insn) == JUMP_INSN
688 /* An unconditional jump is the only possibility
689 we must check for, since a conditional one
690 would make these blocks live. */
691 && simplejump_p (insn)
692 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
693 && INSN_UID (label) != 0
694 && BLOCK_NUM (label) == j)
696 PUT_CODE (insn, NOTE);
697 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
698 NOTE_SOURCE_FILE (insn) = 0;
699 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
701 delete_insn (NEXT_INSN (insn));
708 /* There are pathological cases where one function calling hundreds of
709 nested inline functions can generate lots and lots of unreachable
710 blocks that jump can't delete. Since we don't use sparse matrices
711 a lot of memory will be needed to compile such functions.
712 Implementing sparse matrices is a fair bit of work and it is not
713 clear that they win more than they lose (we don't want to
714 unnecessarily slow down compilation of normal code). By making
715 another pass for the pathological case, we can greatly speed up
716 their compilation without hurting normal code. This works because
717 all the insns in the unreachable blocks have either been deleted or
719 Note that we're talking about reducing memory usage by 10's of
720 megabytes and reducing compilation time by several minutes. */
721 /* ??? The choice of when to make another pass is a bit arbitrary,
722 and was derived from empirical data. */
727 n_basic_blocks -= deleted;
728 /* `n_basic_blocks' may not be correct at this point: two previously
729 separate blocks may now be merged. That's ok though as we
730 recalculate it during the second pass. It certainly can't be
731 any larger than the current value. */
737 /* Subroutines of find_basic_blocks. */
739 /* Check expression X for label references;
740 if one is found, add INSN to the label's chain of references.
742 CHECKDUP means check for and avoid creating duplicate references
743 from the same insn. Such duplicates do no serious harm but
744 can slow life analysis. CHECKDUP is set only when duplicates
748 mark_label_ref (x, insn, checkdup)
752 register RTX_CODE code;
756 /* We can be called with NULL when scanning label_value_list. */
761 if (code == LABEL_REF)
763 register rtx label = XEXP (x, 0);
765 if (GET_CODE (label) != CODE_LABEL)
767 /* If the label was never emitted, this insn is junk,
768 but avoid a crash trying to refer to BLOCK_NUM (label).
769 This can happen as a result of a syntax error
770 and a diagnostic has already been printed. */
771 if (INSN_UID (label) == 0)
773 CONTAINING_INSN (x) = insn;
774 /* if CHECKDUP is set, check for duplicate ref from same insn
777 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
778 if (CONTAINING_INSN (y) == insn)
780 LABEL_NEXTREF (x) = LABEL_REFS (label);
781 LABEL_REFS (label) = x;
782 block_live_static[BLOCK_NUM (label)] = 1;
786 fmt = GET_RTX_FORMAT (code);
787 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
790 mark_label_ref (XEXP (x, i), insn, 0);
794 for (j = 0; j < XVECLEN (x, i); j++)
795 mark_label_ref (XVECEXP (x, i, j), insn, 1);
800 /* Delete INSN by patching it out.
801 Return the next insn. */
804 flow_delete_insn (insn)
807 /* ??? For the moment we assume we don't have to watch for NULLs here
808 since the start/end of basic blocks aren't deleted like this. */
809 NEXT_INSN (PREV_INSN (insn)) = NEXT_INSN (insn);
810 PREV_INSN (NEXT_INSN (insn)) = PREV_INSN (insn);
811 return NEXT_INSN (insn);
814 /* Determine which registers are live at the start of each
815 basic block of the function whose first insn is F.
816 NREGS is the number of registers used in F.
817 We allocate the vector basic_block_live_at_start
818 and the regsets that it points to, and fill them with the data.
819 regset_size and regset_bytes are also set here. */
822 life_analysis (f, nregs)
828 /* For each basic block, a bitmask of regs
829 live on exit from the block. */
830 regset *basic_block_live_at_end;
831 /* For each basic block, a bitmask of regs
832 live on entry to a successor-block of this block.
833 If this does not match basic_block_live_at_end,
834 that must be updated, and the block must be rescanned. */
835 regset *basic_block_new_live_at_end;
836 /* For each basic block, a bitmask of regs
837 whose liveness at the end of the basic block
838 can make a difference in which regs are live on entry to the block.
839 These are the regs that are set within the basic block,
840 possibly excluding those that are used after they are set. */
841 regset *basic_block_significant;
845 struct obstack flow_obstack;
847 gcc_obstack_init (&flow_obstack);
851 bzero (regs_ever_live, sizeof regs_ever_live);
853 /* Allocate and zero out many data structures
854 that will record the data from lifetime analysis. */
856 allocate_for_life_analysis ();
858 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
859 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
861 /* Set up several regset-vectors used internally within this function.
862 Their meanings are documented above, with their declarations. */
864 basic_block_live_at_end
865 = (regset *) alloca (n_basic_blocks * sizeof (regset));
867 /* Don't use alloca since that leads to a crash rather than an error message
868 if there isn't enough space.
869 Don't use oballoc since we may need to allocate other things during
870 this function on the temporary obstack. */
871 init_regset_vector (basic_block_live_at_end, n_basic_blocks, &flow_obstack);
873 basic_block_new_live_at_end
874 = (regset *) alloca (n_basic_blocks * sizeof (regset));
875 init_regset_vector (basic_block_new_live_at_end, n_basic_blocks,
878 basic_block_significant
879 = (regset *) alloca (n_basic_blocks * sizeof (regset));
880 init_regset_vector (basic_block_significant, n_basic_blocks, &flow_obstack);
882 /* Record which insns refer to any volatile memory
883 or for any reason can't be deleted just because they are dead stores.
884 Also, delete any insns that copy a register to itself. */
886 for (insn = f; insn; insn = NEXT_INSN (insn))
888 enum rtx_code code1 = GET_CODE (insn);
889 if (code1 == CALL_INSN)
890 INSN_VOLATILE (insn) = 1;
891 else if (code1 == INSN || code1 == JUMP_INSN)
893 /* Delete (in effect) any obvious no-op moves. */
894 if (GET_CODE (PATTERN (insn)) == SET
895 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
896 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
897 && (REGNO (SET_DEST (PATTERN (insn)))
898 == REGNO (SET_SRC (PATTERN (insn))))
899 /* Insns carrying these notes are useful later on. */
900 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
902 PUT_CODE (insn, NOTE);
903 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
904 NOTE_SOURCE_FILE (insn) = 0;
906 /* Delete (in effect) any obvious no-op moves. */
907 else if (GET_CODE (PATTERN (insn)) == SET
908 && GET_CODE (SET_DEST (PATTERN (insn))) == SUBREG
909 && GET_CODE (SUBREG_REG (SET_DEST (PATTERN (insn)))) == REG
910 && GET_CODE (SET_SRC (PATTERN (insn))) == SUBREG
911 && GET_CODE (SUBREG_REG (SET_SRC (PATTERN (insn)))) == REG
912 && (REGNO (SUBREG_REG (SET_DEST (PATTERN (insn))))
913 == REGNO (SUBREG_REG (SET_SRC (PATTERN (insn)))))
914 && SUBREG_WORD (SET_DEST (PATTERN (insn))) ==
915 SUBREG_WORD (SET_SRC (PATTERN (insn)))
916 /* Insns carrying these notes are useful later on. */
917 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
919 PUT_CODE (insn, NOTE);
920 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
921 NOTE_SOURCE_FILE (insn) = 0;
923 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
925 /* If nothing but SETs of registers to themselves,
926 this insn can also be deleted. */
927 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
929 rtx tem = XVECEXP (PATTERN (insn), 0, i);
931 if (GET_CODE (tem) == USE
932 || GET_CODE (tem) == CLOBBER)
935 if (GET_CODE (tem) != SET
936 || GET_CODE (SET_DEST (tem)) != REG
937 || GET_CODE (SET_SRC (tem)) != REG
938 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
942 if (i == XVECLEN (PATTERN (insn), 0)
943 /* Insns carrying these notes are useful later on. */
944 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
946 PUT_CODE (insn, NOTE);
947 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
948 NOTE_SOURCE_FILE (insn) = 0;
951 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
953 else if (GET_CODE (PATTERN (insn)) != USE)
954 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
955 /* A SET that makes space on the stack cannot be dead.
956 (Such SETs occur only for allocating variable-size data,
957 so they will always have a PLUS or MINUS according to the
958 direction of stack growth.)
959 Even if this function never uses this stack pointer value,
960 signal handlers do! */
961 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
962 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
963 #ifdef STACK_GROWS_DOWNWARD
964 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
966 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
968 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
969 INSN_VOLATILE (insn) = 1;
973 if (n_basic_blocks > 0)
974 #ifdef EXIT_IGNORE_STACK
975 if (! EXIT_IGNORE_STACK
976 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
979 /* If exiting needs the right stack value,
980 consider the stack pointer live at the end of the function. */
981 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
982 STACK_POINTER_REGNUM);
983 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
984 STACK_POINTER_REGNUM);
987 /* Mark the frame pointer is needed at the end of the function. If
988 we end up eliminating it, it will be removed from the live list
989 of each basic block by reload. */
991 if (n_basic_blocks > 0)
993 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
994 FRAME_POINTER_REGNUM);
995 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
996 FRAME_POINTER_REGNUM);
997 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
998 /* If they are different, also mark the hard frame pointer as live */
999 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1000 HARD_FRAME_POINTER_REGNUM);
1001 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1002 HARD_FRAME_POINTER_REGNUM);
1006 /* Mark all global registers and all registers used by the epilogue
1007 as being live at the end of the function since they may be
1008 referenced by our caller. */
1010 if (n_basic_blocks > 0)
1011 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1013 #ifdef EPILOGUE_USES
1014 || EPILOGUE_USES (i)
1018 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1], i);
1019 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1], i);
1022 /* Propagate life info through the basic blocks
1023 around the graph of basic blocks.
1025 This is a relaxation process: each time a new register
1026 is live at the end of the basic block, we must scan the block
1027 to determine which registers are, as a consequence, live at the beginning
1028 of that block. These registers must then be marked live at the ends
1029 of all the blocks that can transfer control to that block.
1030 The process continues until it reaches a fixed point. */
1037 for (i = n_basic_blocks - 1; i >= 0; i--)
1039 int consider = first_pass;
1040 int must_rescan = first_pass;
1045 /* Set CONSIDER if this block needs thinking about at all
1046 (that is, if the regs live now at the end of it
1047 are not the same as were live at the end of it when
1048 we last thought about it).
1049 Set must_rescan if it needs to be thought about
1050 instruction by instruction (that is, if any additional
1051 reg that is live at the end now but was not live there before
1052 is one of the significant regs of this basic block). */
1054 EXECUTE_IF_AND_COMPL_IN_REG_SET
1055 (basic_block_new_live_at_end[i],
1056 basic_block_live_at_end[i], 0, j,
1059 if (REGNO_REG_SET_P (basic_block_significant[i], j))
1070 /* The live_at_start of this block may be changing,
1071 so another pass will be required after this one. */
1076 /* No complete rescan needed;
1077 just record those variables newly known live at end
1078 as live at start as well. */
1079 IOR_AND_COMPL_REG_SET (basic_block_live_at_start[i],
1080 basic_block_new_live_at_end[i],
1081 basic_block_live_at_end[i]);
1083 IOR_AND_COMPL_REG_SET (basic_block_live_at_end[i],
1084 basic_block_new_live_at_end[i],
1085 basic_block_live_at_end[i]);
1089 /* Update the basic_block_live_at_start
1090 by propagation backwards through the block. */
1091 COPY_REG_SET (basic_block_live_at_end[i],
1092 basic_block_new_live_at_end[i]);
1093 COPY_REG_SET (basic_block_live_at_start[i],
1094 basic_block_live_at_end[i]);
1095 propagate_block (basic_block_live_at_start[i],
1096 basic_block_head[i], basic_block_end[i], 0,
1097 first_pass ? basic_block_significant[i]
1103 register rtx jump, head;
1105 /* Update the basic_block_new_live_at_end's of the block
1106 that falls through into this one (if any). */
1107 head = basic_block_head[i];
1108 if (basic_block_drops_in[i])
1109 IOR_REG_SET (basic_block_new_live_at_end[i-1],
1110 basic_block_live_at_start[i]);
1112 /* Update the basic_block_new_live_at_end's of
1113 all the blocks that jump to this one. */
1114 if (GET_CODE (head) == CODE_LABEL)
1115 for (jump = LABEL_REFS (head);
1117 jump = LABEL_NEXTREF (jump))
1119 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1120 IOR_REG_SET (basic_block_new_live_at_end[from_block],
1121 basic_block_live_at_start[i]);
1131 /* The only pseudos that are live at the beginning of the function are
1132 those that were not set anywhere in the function. local-alloc doesn't
1133 know how to handle these correctly, so mark them as not local to any
1136 if (n_basic_blocks > 0)
1137 EXECUTE_IF_SET_IN_REG_SET (basic_block_live_at_start[0],
1138 FIRST_PSEUDO_REGISTER, i,
1140 REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL;
1143 /* Now the life information is accurate.
1144 Make one more pass over each basic block
1145 to delete dead stores, create autoincrement addressing
1146 and record how many times each register is used, is set, or dies.
1148 To save time, we operate directly in basic_block_live_at_end[i],
1149 thus destroying it (in fact, converting it into a copy of
1150 basic_block_live_at_start[i]). This is ok now because
1151 basic_block_live_at_end[i] is no longer used past this point. */
1155 for (i = 0; i < n_basic_blocks; i++)
1157 propagate_block (basic_block_live_at_end[i],
1158 basic_block_head[i], basic_block_end[i], 1,
1166 /* Something live during a setjmp should not be put in a register
1167 on certain machines which restore regs from stack frames
1168 rather than from the jmpbuf.
1169 But we don't need to do this for the user's variables, since
1170 ANSI says only volatile variables need this. */
1171 #ifdef LONGJMP_RESTORE_FROM_STACK
1172 EXECUTE_IF_SET_IN_REG_SET (regs_live_at_setjmp,
1173 FIRST_PSEUDO_REGISTER, i,
1175 if (regno_reg_rtx[i] != 0
1176 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1178 REG_LIVE_LENGTH (i) = -1;
1179 REG_BASIC_BLOCK (i) = -1;
1185 /* We have a problem with any pseudoreg that
1186 lives across the setjmp. ANSI says that if a
1187 user variable does not change in value
1188 between the setjmp and the longjmp, then the longjmp preserves it.
1189 This includes longjmp from a place where the pseudo appears dead.
1190 (In principle, the value still exists if it is in scope.)
1191 If the pseudo goes in a hard reg, some other value may occupy
1192 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1193 Conclusion: such a pseudo must not go in a hard reg. */
1194 EXECUTE_IF_SET_IN_REG_SET (regs_live_at_setjmp,
1195 FIRST_PSEUDO_REGISTER, i,
1197 if (regno_reg_rtx[i] != 0)
1199 REG_LIVE_LENGTH (i) = -1;
1200 REG_BASIC_BLOCK (i) = -1;
1205 free_regset_vector (basic_block_live_at_end, n_basic_blocks);
1206 free_regset_vector (basic_block_new_live_at_end, n_basic_blocks);
1207 free_regset_vector (basic_block_significant, n_basic_blocks);
1208 basic_block_live_at_end = (regset *)0;
1209 basic_block_new_live_at_end = (regset *)0;
1210 basic_block_significant = (regset *)0;
1212 obstack_free (&flow_obstack, NULL_PTR);
1215 /* Subroutines of life analysis. */
1217 /* Allocate the permanent data structures that represent the results
1218 of life analysis. Not static since used also for stupid life analysis. */
1221 allocate_for_life_analysis ()
1225 /* Recalculate the register space, in case it has grown. Old style
1226 vector oriented regsets would set regset_{size,bytes} here also. */
1227 allocate_reg_info (max_regno, FALSE, FALSE);
1229 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
1230 information, explicitly reset it here. The allocation should have
1231 already happened on the previous reg_scan pass. Make sure in case
1232 some more registers were allocated. */
1233 for (i = 0; i < max_regno; i++)
1236 basic_block_live_at_start
1237 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1238 init_regset_vector (basic_block_live_at_start, n_basic_blocks,
1241 regs_live_at_setjmp = OBSTACK_ALLOC_REG_SET (function_obstack);
1242 CLEAR_REG_SET (regs_live_at_setjmp);
1245 /* Make each element of VECTOR point at a regset. The vector has
1246 NELTS elements, and space is allocated from the ALLOC_OBSTACK
1250 init_regset_vector (vector, nelts, alloc_obstack)
1253 struct obstack *alloc_obstack;
1257 for (i = 0; i < nelts; i++)
1259 vector[i] = OBSTACK_ALLOC_REG_SET (alloc_obstack);
1260 CLEAR_REG_SET (vector[i]);
1264 /* Release any additional space allocated for each element of VECTOR point
1265 other than the regset header itself. The vector has NELTS elements. */
1268 free_regset_vector (vector, nelts)
1274 for (i = 0; i < nelts; i++)
1275 FREE_REG_SET (vector[i]);
1278 /* Compute the registers live at the beginning of a basic block
1279 from those live at the end.
1281 When called, OLD contains those live at the end.
1282 On return, it contains those live at the beginning.
1283 FIRST and LAST are the first and last insns of the basic block.
1285 FINAL is nonzero if we are doing the final pass which is not
1286 for computing the life info (since that has already been done)
1287 but for acting on it. On this pass, we delete dead stores,
1288 set up the logical links and dead-variables lists of instructions,
1289 and merge instructions for autoincrement and autodecrement addresses.
1291 SIGNIFICANT is nonzero only the first time for each basic block.
1292 If it is nonzero, it points to a regset in which we store
1293 a 1 for each register that is set within the block.
1295 BNUM is the number of the basic block. */
1298 propagate_block (old, first, last, final, significant, bnum)
1299 register regset old;
1311 /* The following variables are used only if FINAL is nonzero. */
1312 /* This vector gets one element for each reg that has been live
1313 at any point in the basic block that has been scanned so far.
1314 SOMETIMES_MAX says how many elements are in use so far. */
1315 register int *regs_sometimes_live;
1316 int sometimes_max = 0;
1317 /* This regset has 1 for each reg that we have seen live so far.
1318 It and REGS_SOMETIMES_LIVE are updated together. */
1321 /* The loop depth may change in the middle of a basic block. Since we
1322 scan from end to beginning, we start with the depth at the end of the
1323 current basic block, and adjust as we pass ends and starts of loops. */
1324 loop_depth = basic_block_loop_depth[bnum];
1326 dead = ALLOCA_REG_SET ();
1327 live = ALLOCA_REG_SET ();
1332 /* Include any notes at the end of the block in the scan.
1333 This is in case the block ends with a call to setjmp. */
1335 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1337 /* Look for loop boundaries, we are going forward here. */
1338 last = NEXT_INSN (last);
1339 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1341 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1350 maxlive = ALLOCA_REG_SET ();
1351 COPY_REG_SET (maxlive, old);
1352 regs_sometimes_live = (int *) alloca (max_regno * sizeof (int));
1354 /* Process the regs live at the end of the block.
1355 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1356 Also mark them as not local to any one basic block. */
1357 EXECUTE_IF_SET_IN_REG_SET (old, 0, i,
1359 REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL;
1360 regs_sometimes_live[sometimes_max] = i;
1365 /* Scan the block an insn at a time from end to beginning. */
1367 for (insn = last; ; insn = prev)
1369 prev = PREV_INSN (insn);
1371 if (GET_CODE (insn) == NOTE)
1373 /* Look for loop boundaries, remembering that we are going
1375 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1377 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1380 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1381 Abort now rather than setting register status incorrectly. */
1382 if (loop_depth == 0)
1385 /* If this is a call to `setjmp' et al,
1386 warn if any non-volatile datum is live. */
1388 if (final && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1389 IOR_REG_SET (regs_live_at_setjmp, old);
1392 /* Update the life-status of regs for this insn.
1393 First DEAD gets which regs are set in this insn
1394 then LIVE gets which regs are used in this insn.
1395 Then the regs live before the insn
1396 are those live after, with DEAD regs turned off,
1397 and then LIVE regs turned on. */
1399 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1402 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1404 = (insn_dead_p (PATTERN (insn), old, 0)
1405 /* Don't delete something that refers to volatile storage! */
1406 && ! INSN_VOLATILE (insn));
1408 = (insn_is_dead && note != 0
1409 && libcall_dead_p (PATTERN (insn), old, note, insn));
1411 /* If an instruction consists of just dead store(s) on final pass,
1412 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1413 We could really delete it with delete_insn, but that
1414 can cause trouble for first or last insn in a basic block. */
1415 if (final && insn_is_dead)
1417 PUT_CODE (insn, NOTE);
1418 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1419 NOTE_SOURCE_FILE (insn) = 0;
1421 /* CC0 is now known to be dead. Either this insn used it,
1422 in which case it doesn't anymore, or clobbered it,
1423 so the next insn can't use it. */
1426 /* If this insn is copying the return value from a library call,
1427 delete the entire library call. */
1428 if (libcall_is_dead)
1430 rtx first = XEXP (note, 0);
1432 while (INSN_DELETED_P (first))
1433 first = NEXT_INSN (first);
1438 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1439 NOTE_SOURCE_FILE (p) = 0;
1445 CLEAR_REG_SET (dead);
1446 CLEAR_REG_SET (live);
1448 /* See if this is an increment or decrement that can be
1449 merged into a following memory address. */
1452 register rtx x = PATTERN (insn);
1453 /* Does this instruction increment or decrement a register? */
1454 if (final && GET_CODE (x) == SET
1455 && GET_CODE (SET_DEST (x)) == REG
1456 && (GET_CODE (SET_SRC (x)) == PLUS
1457 || GET_CODE (SET_SRC (x)) == MINUS)
1458 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1459 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1460 /* Ok, look for a following memory ref we can combine with.
1461 If one is found, change the memory ref to a PRE_INC
1462 or PRE_DEC, cancel this insn, and return 1.
1463 Return 0 if nothing has been done. */
1464 && try_pre_increment_1 (insn))
1467 #endif /* AUTO_INC_DEC */
1469 /* If this is not the final pass, and this insn is copying the
1470 value of a library call and it's dead, don't scan the
1471 insns that perform the library call, so that the call's
1472 arguments are not marked live. */
1473 if (libcall_is_dead)
1475 /* Mark the dest reg as `significant'. */
1476 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1478 insn = XEXP (note, 0);
1479 prev = PREV_INSN (insn);
1481 else if (GET_CODE (PATTERN (insn)) == SET
1482 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1483 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1484 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1485 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1486 /* We have an insn to pop a constant amount off the stack.
1487 (Such insns use PLUS regardless of the direction of the stack,
1488 and any insn to adjust the stack by a constant is always a pop.)
1489 These insns, if not dead stores, have no effect on life. */
1493 /* LIVE gets the regs used in INSN;
1494 DEAD gets those set by it. Dead insns don't make anything
1497 mark_set_regs (old, dead, PATTERN (insn),
1498 final ? insn : NULL_RTX, significant);
1500 /* If an insn doesn't use CC0, it becomes dead since we
1501 assume that every insn clobbers it. So show it dead here;
1502 mark_used_regs will set it live if it is referenced. */
1506 mark_used_regs (old, live, PATTERN (insn), final, insn);
1508 /* Sometimes we may have inserted something before INSN (such as
1509 a move) when we make an auto-inc. So ensure we will scan
1512 prev = PREV_INSN (insn);
1515 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1521 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1523 note = XEXP (note, 1))
1524 if (GET_CODE (XEXP (note, 0)) == USE)
1525 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1528 /* Each call clobbers all call-clobbered regs that are not
1529 global or fixed. Note that the function-value reg is a
1530 call-clobbered reg, and mark_set_regs has already had
1531 a chance to handle it. */
1533 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1534 if (call_used_regs[i] && ! global_regs[i]
1536 SET_REGNO_REG_SET (dead, i);
1538 /* The stack ptr is used (honorarily) by a CALL insn. */
1539 SET_REGNO_REG_SET (live, STACK_POINTER_REGNUM);
1541 /* Calls may also reference any of the global registers,
1542 so they are made live. */
1543 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1545 mark_used_regs (old, live,
1546 gen_rtx (REG, reg_raw_mode[i], i),
1549 /* Calls also clobber memory. */
1553 /* Update OLD for the registers used or set. */
1554 AND_COMPL_REG_SET (old, dead);
1555 IOR_REG_SET (old, live);
1557 if (GET_CODE (insn) == CALL_INSN && final)
1559 /* Any regs live at the time of a call instruction
1560 must not go in a register clobbered by calls.
1561 Find all regs now live and record this for them. */
1563 register int *p = regs_sometimes_live;
1565 for (i = 0; i < sometimes_max; i++, p++)
1566 if (REGNO_REG_SET_P (old, *p))
1567 REG_N_CALLS_CROSSED (*p)++;
1571 /* On final pass, add any additional sometimes-live regs
1572 into MAXLIVE and REGS_SOMETIMES_LIVE.
1573 Also update counts of how many insns each reg is live at. */
1580 EXECUTE_IF_AND_COMPL_IN_REG_SET
1581 (live, maxlive, 0, regno,
1583 regs_sometimes_live[sometimes_max++] = regno;
1584 SET_REGNO_REG_SET (maxlive, regno);
1587 p = regs_sometimes_live;
1588 for (i = 0; i < sometimes_max; i++)
1591 if (REGNO_REG_SET_P (old, regno))
1592 REG_LIVE_LENGTH (regno)++;
1601 FREE_REG_SET (dead);
1602 FREE_REG_SET (live);
1604 FREE_REG_SET (maxlive);
1606 if (num_scratch > max_scratch)
1607 max_scratch = num_scratch;
1610 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1611 (SET expressions whose destinations are registers dead after the insn).
1612 NEEDED is the regset that says which regs are alive after the insn.
1614 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1617 insn_dead_p (x, needed, call_ok)
1622 register RTX_CODE code = GET_CODE (x);
1623 /* If setting something that's a reg or part of one,
1624 see if that register's altered value will be live. */
1628 register rtx r = SET_DEST (x);
1629 /* A SET that is a subroutine call cannot be dead. */
1630 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1634 if (GET_CODE (r) == CC0)
1638 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1639 && rtx_equal_p (r, last_mem_set))
1642 while (GET_CODE (r) == SUBREG
1643 || GET_CODE (r) == STRICT_LOW_PART
1644 || GET_CODE (r) == ZERO_EXTRACT
1645 || GET_CODE (r) == SIGN_EXTRACT)
1648 if (GET_CODE (r) == REG)
1650 register int regno = REGNO (r);
1652 /* Don't delete insns to set global regs. */
1653 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1654 /* Make sure insns to set frame pointer aren't deleted. */
1655 || regno == FRAME_POINTER_REGNUM
1656 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1657 || regno == HARD_FRAME_POINTER_REGNUM
1659 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1660 /* Make sure insns to set arg pointer are never deleted
1661 (if the arg pointer isn't fixed, there will be a USE for
1662 it, so we can treat it normally). */
1663 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1665 || REGNO_REG_SET_P (needed, regno))
1668 /* If this is a hard register, verify that subsequent words are
1670 if (regno < FIRST_PSEUDO_REGISTER)
1672 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1675 if (REGNO_REG_SET_P (needed, regno+n))
1682 /* If performing several activities,
1683 insn is dead if each activity is individually dead.
1684 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1685 that's inside a PARALLEL doesn't make the insn worth keeping. */
1686 else if (code == PARALLEL)
1688 register int i = XVECLEN (x, 0);
1689 for (i--; i >= 0; i--)
1691 rtx elt = XVECEXP (x, 0, i);
1692 if (!insn_dead_p (elt, needed, call_ok)
1693 && GET_CODE (elt) != CLOBBER
1694 && GET_CODE (elt) != USE)
1699 /* We do not check CLOBBER or USE here.
1700 An insn consisting of just a CLOBBER or just a USE
1701 should not be deleted. */
1705 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1706 return 1 if the entire library call is dead.
1707 This is true if X copies a register (hard or pseudo)
1708 and if the hard return reg of the call insn is dead.
1709 (The caller should have tested the destination of X already for death.)
1711 If this insn doesn't just copy a register, then we don't
1712 have an ordinary libcall. In that case, cse could not have
1713 managed to substitute the source for the dest later on,
1714 so we can assume the libcall is dead.
1716 NEEDED is the bit vector of pseudoregs live before this insn.
1717 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1720 libcall_dead_p (x, needed, note, insn)
1726 register RTX_CODE code = GET_CODE (x);
1730 register rtx r = SET_SRC (x);
1731 if (GET_CODE (r) == REG)
1733 rtx call = XEXP (note, 0);
1736 /* Find the call insn. */
1737 while (call != insn && GET_CODE (call) != CALL_INSN)
1738 call = NEXT_INSN (call);
1740 /* If there is none, do nothing special,
1741 since ordinary death handling can understand these insns. */
1745 /* See if the hard reg holding the value is dead.
1746 If this is a PARALLEL, find the call within it. */
1747 call = PATTERN (call);
1748 if (GET_CODE (call) == PARALLEL)
1750 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1751 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1752 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1755 /* This may be a library call that is returning a value
1756 via invisible pointer. Do nothing special, since
1757 ordinary death handling can understand these insns. */
1761 call = XVECEXP (call, 0, i);
1764 return insn_dead_p (call, needed, 1);
1770 /* Return 1 if register REGNO was used before it was set.
1771 In other words, if it is live at function entry.
1772 Don't count global register variables or variables in registers
1773 that can be used for function arg passing, though. */
1776 regno_uninitialized (regno)
1779 if (n_basic_blocks == 0
1780 || (regno < FIRST_PSEUDO_REGISTER
1781 && (global_regs[regno] || FUNCTION_ARG_REGNO_P (regno))))
1784 return REGNO_REG_SET_P (basic_block_live_at_start[0], regno);
1787 /* 1 if register REGNO was alive at a place where `setjmp' was called
1788 and was set more than once or is an argument.
1789 Such regs may be clobbered by `longjmp'. */
1792 regno_clobbered_at_setjmp (regno)
1795 if (n_basic_blocks == 0)
1798 return ((REG_N_SETS (regno) > 1
1799 || REGNO_REG_SET_P (basic_block_live_at_start[0], regno))
1800 && REGNO_REG_SET_P (regs_live_at_setjmp, regno));
1803 /* Process the registers that are set within X.
1804 Their bits are set to 1 in the regset DEAD,
1805 because they are dead prior to this insn.
1807 If INSN is nonzero, it is the insn being processed
1808 and the fact that it is nonzero implies this is the FINAL pass
1809 in propagate_block. In this case, various info about register
1810 usage is stored, LOG_LINKS fields of insns are set up. */
1813 mark_set_regs (needed, dead, x, insn, significant)
1820 register RTX_CODE code = GET_CODE (x);
1822 if (code == SET || code == CLOBBER)
1823 mark_set_1 (needed, dead, x, insn, significant);
1824 else if (code == PARALLEL)
1827 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1829 code = GET_CODE (XVECEXP (x, 0, i));
1830 if (code == SET || code == CLOBBER)
1831 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1836 /* Process a single SET rtx, X. */
1839 mark_set_1 (needed, dead, x, insn, significant)
1847 register rtx reg = SET_DEST (x);
1849 /* Modifying just one hardware register of a multi-reg value
1850 or just a byte field of a register
1851 does not mean the value from before this insn is now dead.
1852 But it does mean liveness of that register at the end of the block
1855 Within mark_set_1, however, we treat it as if the register is
1856 indeed modified. mark_used_regs will, however, also treat this
1857 register as being used. Thus, we treat these insns as setting a
1858 new value for the register as a function of its old value. This
1859 cases LOG_LINKS to be made appropriately and this will help combine. */
1861 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1862 || GET_CODE (reg) == SIGN_EXTRACT
1863 || GET_CODE (reg) == STRICT_LOW_PART)
1864 reg = XEXP (reg, 0);
1866 /* If we are writing into memory or into a register mentioned in the
1867 address of the last thing stored into memory, show we don't know
1868 what the last store was. If we are writing memory, save the address
1869 unless it is volatile. */
1870 if (GET_CODE (reg) == MEM
1871 || (GET_CODE (reg) == REG
1872 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1875 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1876 /* There are no REG_INC notes for SP, so we can't assume we'll see
1877 everything that invalidates it. To be safe, don't eliminate any
1878 stores though SP; none of them should be redundant anyway. */
1879 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1882 if (GET_CODE (reg) == REG
1883 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1884 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1885 && regno != HARD_FRAME_POINTER_REGNUM
1887 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1888 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1890 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1891 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1893 int some_needed = REGNO_REG_SET_P (needed, regno);
1894 int some_not_needed = ! some_needed;
1896 /* Mark it as a significant register for this basic block. */
1898 SET_REGNO_REG_SET (significant, regno);
1900 /* Mark it as as dead before this insn. */
1901 SET_REGNO_REG_SET (dead, regno);
1903 /* A hard reg in a wide mode may really be multiple registers.
1904 If so, mark all of them just like the first. */
1905 if (regno < FIRST_PSEUDO_REGISTER)
1909 /* Nothing below is needed for the stack pointer; get out asap.
1910 Eg, log links aren't needed, since combine won't use them. */
1911 if (regno == STACK_POINTER_REGNUM)
1914 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1917 int regno_n = regno + n;
1918 int needed_regno = REGNO_REG_SET_P (needed, regno_n);
1920 SET_REGNO_REG_SET (significant, regno_n);
1922 SET_REGNO_REG_SET (dead, regno_n);
1923 some_needed |= needed_regno;
1924 some_not_needed |= ! needed_regno;
1927 /* Additional data to record if this is the final pass. */
1930 register rtx y = reg_next_use[regno];
1931 register int blocknum = BLOCK_NUM (insn);
1933 /* If this is a hard reg, record this function uses the reg. */
1935 if (regno < FIRST_PSEUDO_REGISTER)
1938 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
1940 for (i = regno; i < endregno; i++)
1942 /* The next use is no longer "next", since a store
1944 reg_next_use[i] = 0;
1946 regs_ever_live[i] = 1;
1952 /* The next use is no longer "next", since a store
1954 reg_next_use[regno] = 0;
1956 /* Keep track of which basic blocks each reg appears in. */
1958 if (REG_BASIC_BLOCK (regno) == REG_BLOCK_UNKNOWN)
1959 REG_BASIC_BLOCK (regno) = blocknum;
1960 else if (REG_BASIC_BLOCK (regno) != blocknum)
1961 REG_BASIC_BLOCK (regno) = REG_BLOCK_GLOBAL;
1963 /* Count (weighted) references, stores, etc. This counts a
1964 register twice if it is modified, but that is correct. */
1965 REG_N_SETS (regno)++;
1967 REG_N_REFS (regno) += loop_depth;
1969 /* The insns where a reg is live are normally counted
1970 elsewhere, but we want the count to include the insn
1971 where the reg is set, and the normal counting mechanism
1972 would not count it. */
1973 REG_LIVE_LENGTH (regno)++;
1976 if (! some_not_needed)
1978 /* Make a logical link from the next following insn
1979 that uses this register, back to this insn.
1980 The following insns have already been processed.
1982 We don't build a LOG_LINK for hard registers containing
1983 in ASM_OPERANDs. If these registers get replaced,
1984 we might wind up changing the semantics of the insn,
1985 even if reload can make what appear to be valid assignments
1987 if (y && (BLOCK_NUM (y) == blocknum)
1988 && (regno >= FIRST_PSEUDO_REGISTER
1989 || asm_noperands (PATTERN (y)) < 0))
1991 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
1993 else if (! some_needed)
1995 /* Note that dead stores have already been deleted when possible
1996 If we get here, we have found a dead store that cannot
1997 be eliminated (because the same insn does something useful).
1998 Indicate this by marking the reg being set as dying here. */
2000 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2001 REG_N_DEATHS (REGNO (reg))++;
2005 /* This is a case where we have a multi-word hard register
2006 and some, but not all, of the words of the register are
2007 needed in subsequent insns. Write REG_UNUSED notes
2008 for those parts that were not needed. This case should
2013 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2015 if (!REGNO_REG_SET_P (needed, regno + i))
2017 = gen_rtx (EXPR_LIST, REG_UNUSED,
2018 gen_rtx (REG, reg_raw_mode[regno + i],
2024 else if (GET_CODE (reg) == REG)
2025 reg_next_use[regno] = 0;
2027 /* If this is the last pass and this is a SCRATCH, show it will be dying
2028 here and count it. */
2029 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2032 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2039 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2043 find_auto_inc (needed, x, insn)
2048 rtx addr = XEXP (x, 0);
2049 HOST_WIDE_INT offset = 0;
2052 /* Here we detect use of an index register which might be good for
2053 postincrement, postdecrement, preincrement, or predecrement. */
2055 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2056 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2058 if (GET_CODE (addr) == REG)
2061 register int size = GET_MODE_SIZE (GET_MODE (x));
2064 int regno = REGNO (addr);
2066 /* Is the next use an increment that might make auto-increment? */
2067 if ((incr = reg_next_use[regno]) != 0
2068 && (set = single_set (incr)) != 0
2069 && GET_CODE (set) == SET
2070 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2071 /* Can't add side effects to jumps; if reg is spilled and
2072 reloaded, there's no way to store back the altered value. */
2073 && GET_CODE (insn) != JUMP_INSN
2074 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2075 && XEXP (y, 0) == addr
2076 && GET_CODE (XEXP (y, 1)) == CONST_INT
2078 #ifdef HAVE_POST_INCREMENT
2079 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2081 #ifdef HAVE_POST_DECREMENT
2082 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2084 #ifdef HAVE_PRE_INCREMENT
2085 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2087 #ifdef HAVE_PRE_DECREMENT
2088 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2091 /* Make sure this reg appears only once in this insn. */
2092 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2093 use != 0 && use != (rtx) 1))
2095 rtx q = SET_DEST (set);
2096 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2097 ? (offset ? PRE_INC : POST_INC)
2098 : (offset ? PRE_DEC : POST_DEC));
2100 if (dead_or_set_p (incr, addr))
2102 /* This is the simple case. Try to make the auto-inc. If
2103 we can't, we are done. Otherwise, we will do any
2104 needed updates below. */
2105 if (! validate_change (insn, &XEXP (x, 0),
2106 gen_rtx (inc_code, Pmode, addr),
2110 else if (GET_CODE (q) == REG
2111 /* PREV_INSN used here to check the semi-open interval
2113 && ! reg_used_between_p (q, PREV_INSN (insn), incr)
2114 /* We must also check for sets of q as q may be
2115 a call clobbered hard register and there may
2116 be a call between PREV_INSN (insn) and incr. */
2117 && ! reg_set_between_p (q, PREV_INSN (insn), incr))
2119 /* We have *p followed sometime later by q = p+size.
2120 Both p and q must be live afterward,
2121 and q is not used between INSN and it's assignment.
2122 Change it to q = p, ...*q..., q = q+size.
2123 Then fall into the usual case. */
2127 emit_move_insn (q, addr);
2128 insns = get_insns ();
2131 /* If anything in INSNS have UID's that don't fit within the
2132 extra space we allocate earlier, we can't make this auto-inc.
2133 This should never happen. */
2134 for (temp = insns; temp; temp = NEXT_INSN (temp))
2136 if (INSN_UID (temp) > max_uid_for_flow)
2138 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2141 /* If we can't make the auto-inc, or can't make the
2142 replacement into Y, exit. There's no point in making
2143 the change below if we can't do the auto-inc and doing
2144 so is not correct in the pre-inc case. */
2146 validate_change (insn, &XEXP (x, 0),
2147 gen_rtx (inc_code, Pmode, q),
2149 validate_change (incr, &XEXP (y, 0), q, 1);
2150 if (! apply_change_group ())
2153 /* We now know we'll be doing this change, so emit the
2154 new insn(s) and do the updates. */
2155 emit_insns_before (insns, insn);
2157 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2158 basic_block_head[BLOCK_NUM (insn)] = insns;
2160 /* INCR will become a NOTE and INSN won't contain a
2161 use of ADDR. If a use of ADDR was just placed in
2162 the insn before INSN, make that the next use.
2163 Otherwise, invalidate it. */
2164 if (GET_CODE (PREV_INSN (insn)) == INSN
2165 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2166 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2167 reg_next_use[regno] = PREV_INSN (insn);
2169 reg_next_use[regno] = 0;
2174 /* REGNO is now used in INCR which is below INSN, but
2175 it previously wasn't live here. If we don't mark
2176 it as needed, we'll put a REG_DEAD note for it
2177 on this insn, which is incorrect. */
2178 SET_REGNO_REG_SET (needed, regno);
2180 /* If there are any calls between INSN and INCR, show
2181 that REGNO now crosses them. */
2182 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2183 if (GET_CODE (temp) == CALL_INSN)
2184 REG_N_CALLS_CROSSED (regno)++;
2189 /* If we haven't returned, it means we were able to make the
2190 auto-inc, so update the status. First, record that this insn
2191 has an implicit side effect. */
2194 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2196 /* Modify the old increment-insn to simply copy
2197 the already-incremented value of our register. */
2198 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2201 /* If that makes it a no-op (copying the register into itself) delete
2202 it so it won't appear to be a "use" and a "set" of this
2204 if (SET_DEST (set) == addr)
2206 PUT_CODE (incr, NOTE);
2207 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2208 NOTE_SOURCE_FILE (incr) = 0;
2211 if (regno >= FIRST_PSEUDO_REGISTER)
2213 /* Count an extra reference to the reg. When a reg is
2214 incremented, spilling it is worse, so we want to make
2215 that less likely. */
2216 REG_N_REFS (regno) += loop_depth;
2218 /* Count the increment as a setting of the register,
2219 even though it isn't a SET in rtl. */
2220 REG_N_SETS (regno)++;
2225 #endif /* AUTO_INC_DEC */
2227 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2228 This is done assuming the registers needed from X
2229 are those that have 1-bits in NEEDED.
2231 On the final pass, FINAL is 1. This means try for autoincrement
2232 and count the uses and deaths of each pseudo-reg.
2234 INSN is the containing instruction. If INSN is dead, this function is not
2238 mark_used_regs (needed, live, x, final, insn)
2245 register RTX_CODE code;
2250 code = GET_CODE (x);
2271 /* If we are clobbering a MEM, mark any registers inside the address
2273 if (GET_CODE (XEXP (x, 0)) == MEM)
2274 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2278 /* Invalidate the data for the last MEM stored, but only if MEM is
2279 something that can be stored into. */
2280 if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
2281 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
2282 ; /* needn't clear last_mem_set */
2288 find_auto_inc (needed, x, insn);
2293 if (GET_CODE (SUBREG_REG (x)) == REG
2294 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2295 && (GET_MODE_SIZE (GET_MODE (x))
2296 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))))
2297 REG_CHANGES_SIZE (REGNO (SUBREG_REG (x))) = 1;
2299 /* While we're here, optimize this case. */
2302 /* In case the SUBREG is not of a register, don't optimize */
2303 if (GET_CODE (x) != REG)
2305 mark_used_regs (needed, live, x, final, insn);
2309 /* ... fall through ... */
2312 /* See a register other than being set
2313 => mark it as needed. */
2317 int some_needed = REGNO_REG_SET_P (needed, regno);
2318 int some_not_needed = ! some_needed;
2320 SET_REGNO_REG_SET (live, regno);
2322 /* A hard reg in a wide mode may really be multiple registers.
2323 If so, mark all of them just like the first. */
2324 if (regno < FIRST_PSEUDO_REGISTER)
2328 /* For stack ptr or fixed arg pointer,
2329 nothing below can be necessary, so waste no more time. */
2330 if (regno == STACK_POINTER_REGNUM
2331 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2332 || regno == HARD_FRAME_POINTER_REGNUM
2334 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2335 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2337 || regno == FRAME_POINTER_REGNUM)
2339 /* If this is a register we are going to try to eliminate,
2340 don't mark it live here. If we are successful in
2341 eliminating it, it need not be live unless it is used for
2342 pseudos, in which case it will have been set live when
2343 it was allocated to the pseudos. If the register will not
2344 be eliminated, reload will set it live at that point. */
2346 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2347 regs_ever_live[regno] = 1;
2350 /* No death notes for global register variables;
2351 their values are live after this function exits. */
2352 if (global_regs[regno])
2355 reg_next_use[regno] = insn;
2359 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2362 int regno_n = regno + n;
2363 int needed_regno = REGNO_REG_SET_P (needed, regno_n);
2365 SET_REGNO_REG_SET (live, regno_n);
2366 some_needed |= needed_regno;
2367 some_not_needed |= ! needed_regno;
2372 /* Record where each reg is used, so when the reg
2373 is set we know the next insn that uses it. */
2375 reg_next_use[regno] = insn;
2377 if (regno < FIRST_PSEUDO_REGISTER)
2379 /* If a hard reg is being used,
2380 record that this function does use it. */
2382 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2386 regs_ever_live[regno + --i] = 1;
2391 /* Keep track of which basic block each reg appears in. */
2393 register int blocknum = BLOCK_NUM (insn);
2395 if (REG_BASIC_BLOCK (regno) == REG_BLOCK_UNKNOWN)
2396 REG_BASIC_BLOCK (regno) = blocknum;
2397 else if (REG_BASIC_BLOCK (regno) != blocknum)
2398 REG_BASIC_BLOCK (regno) = REG_BLOCK_GLOBAL;
2400 /* Count (weighted) number of uses of each reg. */
2402 REG_N_REFS (regno) += loop_depth;
2405 /* Record and count the insns in which a reg dies.
2406 If it is used in this insn and was dead below the insn
2407 then it dies in this insn. If it was set in this insn,
2408 we do not make a REG_DEAD note; likewise if we already
2409 made such a note. */
2412 && ! dead_or_set_p (insn, x)
2414 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2418 /* Check for the case where the register dying partially
2419 overlaps the register set by this insn. */
2420 if (regno < FIRST_PSEUDO_REGISTER
2421 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2423 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2425 some_needed |= dead_or_set_regno_p (insn, regno + n);
2428 /* If none of the words in X is needed, make a REG_DEAD
2429 note. Otherwise, we must make partial REG_DEAD notes. */
2433 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2434 REG_N_DEATHS (regno)++;
2440 /* Don't make a REG_DEAD note for a part of a register
2441 that is set in the insn. */
2443 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2445 if (!REGNO_REG_SET_P (needed, regno + i)
2446 && ! dead_or_set_regno_p (insn, regno + i))
2448 = gen_rtx (EXPR_LIST, REG_DEAD,
2449 gen_rtx (REG, reg_raw_mode[regno + i],
2460 register rtx testreg = SET_DEST (x);
2463 /* If storing into MEM, don't show it as being used. But do
2464 show the address as being used. */
2465 if (GET_CODE (testreg) == MEM)
2469 find_auto_inc (needed, testreg, insn);
2471 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2472 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2476 /* Storing in STRICT_LOW_PART is like storing in a reg
2477 in that this SET might be dead, so ignore it in TESTREG.
2478 but in some other ways it is like using the reg.
2480 Storing in a SUBREG or a bit field is like storing the entire
2481 register in that if the register's value is not used
2482 then this SET is not needed. */
2483 while (GET_CODE (testreg) == STRICT_LOW_PART
2484 || GET_CODE (testreg) == ZERO_EXTRACT
2485 || GET_CODE (testreg) == SIGN_EXTRACT
2486 || GET_CODE (testreg) == SUBREG)
2488 if (GET_CODE (testreg) == SUBREG
2489 && GET_CODE (SUBREG_REG (testreg)) == REG
2490 && REGNO (SUBREG_REG (testreg)) >= FIRST_PSEUDO_REGISTER
2491 && (GET_MODE_SIZE (GET_MODE (testreg))
2492 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (testreg)))))
2493 REG_CHANGES_SIZE (REGNO (SUBREG_REG (testreg))) = 1;
2495 /* Modifying a single register in an alternate mode
2496 does not use any of the old value. But these other
2497 ways of storing in a register do use the old value. */
2498 if (GET_CODE (testreg) == SUBREG
2499 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2504 testreg = XEXP (testreg, 0);
2507 /* If this is a store into a register,
2508 recursively scan the value being stored. */
2510 if (GET_CODE (testreg) == REG
2511 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2512 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2513 && regno != HARD_FRAME_POINTER_REGNUM
2515 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2516 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2519 /* We used to exclude global_regs here, but that seems wrong.
2520 Storing in them is like storing in mem. */
2522 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2524 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2531 /* If exiting needs the right stack value, consider this insn as
2532 using the stack pointer. In any event, consider it as using
2533 all global registers and all registers used by return. */
2535 #ifdef EXIT_IGNORE_STACK
2536 if (! EXIT_IGNORE_STACK
2537 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2539 SET_REGNO_REG_SET (live, STACK_POINTER_REGNUM);
2541 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2543 #ifdef EPILOGUE_USES
2544 || EPILOGUE_USES (i)
2547 SET_REGNO_REG_SET (live, i);
2551 /* Recursively scan the operands of this expression. */
2554 register char *fmt = GET_RTX_FORMAT (code);
2557 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2561 /* Tail recursive case: save a function call level. */
2567 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2569 else if (fmt[i] == 'E')
2572 for (j = 0; j < XVECLEN (x, i); j++)
2573 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2582 try_pre_increment_1 (insn)
2585 /* Find the next use of this reg. If in same basic block,
2586 make it do pre-increment or pre-decrement if appropriate. */
2587 rtx x = PATTERN (insn);
2588 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2589 * INTVAL (XEXP (SET_SRC (x), 1)));
2590 int regno = REGNO (SET_DEST (x));
2591 rtx y = reg_next_use[regno];
2593 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2594 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2595 mode would be better. */
2596 && ! dead_or_set_p (y, SET_DEST (x))
2597 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2600 /* We have found a suitable auto-increment
2601 and already changed insn Y to do it.
2602 So flush this increment-instruction. */
2603 PUT_CODE (insn, NOTE);
2604 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2605 NOTE_SOURCE_FILE (insn) = 0;
2606 /* Count a reference to this reg for the increment
2607 insn we are deleting. When a reg is incremented.
2608 spilling it is worse, so we want to make that
2610 if (regno >= FIRST_PSEUDO_REGISTER)
2612 REG_N_REFS (regno) += loop_depth;
2613 REG_N_SETS (regno)++;
2620 /* Try to change INSN so that it does pre-increment or pre-decrement
2621 addressing on register REG in order to add AMOUNT to REG.
2622 AMOUNT is negative for pre-decrement.
2623 Returns 1 if the change could be made.
2624 This checks all about the validity of the result of modifying INSN. */
2627 try_pre_increment (insn, reg, amount)
2629 HOST_WIDE_INT amount;
2633 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2634 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2636 /* Nonzero if we can try to make a post-increment or post-decrement.
2637 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2638 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2639 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2642 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2645 /* From the sign of increment, see which possibilities are conceivable
2646 on this target machine. */
2647 #ifdef HAVE_PRE_INCREMENT
2651 #ifdef HAVE_POST_INCREMENT
2656 #ifdef HAVE_PRE_DECREMENT
2660 #ifdef HAVE_POST_DECREMENT
2665 if (! (pre_ok || post_ok))
2668 /* It is not safe to add a side effect to a jump insn
2669 because if the incremented register is spilled and must be reloaded
2670 there would be no way to store the incremented value back in memory. */
2672 if (GET_CODE (insn) == JUMP_INSN)
2677 use = find_use_as_address (PATTERN (insn), reg, 0);
2678 if (post_ok && (use == 0 || use == (rtx) 1))
2680 use = find_use_as_address (PATTERN (insn), reg, -amount);
2684 if (use == 0 || use == (rtx) 1)
2687 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2690 /* See if this combination of instruction and addressing mode exists. */
2691 if (! validate_change (insn, &XEXP (use, 0),
2693 ? (do_post ? POST_INC : PRE_INC)
2694 : (do_post ? POST_DEC : PRE_DEC),
2698 /* Record that this insn now has an implicit side effect on X. */
2699 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2703 #endif /* AUTO_INC_DEC */
2705 /* Find the place in the rtx X where REG is used as a memory address.
2706 Return the MEM rtx that so uses it.
2707 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2708 (plus REG (const_int PLUSCONST)).
2710 If such an address does not appear, return 0.
2711 If REG appears more than once, or is used other than in such an address,
2715 find_use_as_address (x, reg, plusconst)
2718 HOST_WIDE_INT plusconst;
2720 enum rtx_code code = GET_CODE (x);
2721 char *fmt = GET_RTX_FORMAT (code);
2723 register rtx value = 0;
2726 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2729 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2730 && XEXP (XEXP (x, 0), 0) == reg
2731 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2732 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2735 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2737 /* If REG occurs inside a MEM used in a bit-field reference,
2738 that is unacceptable. */
2739 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2740 return (rtx) (HOST_WIDE_INT) 1;
2744 return (rtx) (HOST_WIDE_INT) 1;
2746 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2750 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2754 return (rtx) (HOST_WIDE_INT) 1;
2759 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2761 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2765 return (rtx) (HOST_WIDE_INT) 1;
2773 /* Write information about registers and basic blocks into FILE.
2774 This is part of making a debugging dump. */
2777 dump_flow_info (file)
2781 static char *reg_class_names[] = REG_CLASS_NAMES;
2783 fprintf (file, "%d registers.\n", max_regno);
2785 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2788 enum reg_class class, altclass;
2789 fprintf (file, "\nRegister %d used %d times across %d insns",
2790 i, REG_N_REFS (i), REG_LIVE_LENGTH (i));
2791 if (REG_BASIC_BLOCK (i) >= 0)
2792 fprintf (file, " in block %d", REG_BASIC_BLOCK (i));
2793 if (REG_N_DEATHS (i) != 1)
2794 fprintf (file, "; dies in %d places", REG_N_DEATHS (i));
2795 if (REG_N_CALLS_CROSSED (i) == 1)
2796 fprintf (file, "; crosses 1 call");
2797 else if (REG_N_CALLS_CROSSED (i))
2798 fprintf (file, "; crosses %d calls", REG_N_CALLS_CROSSED (i));
2799 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2800 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2801 class = reg_preferred_class (i);
2802 altclass = reg_alternate_class (i);
2803 if (class != GENERAL_REGS || altclass != ALL_REGS)
2805 if (altclass == ALL_REGS || class == ALL_REGS)
2806 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2807 else if (altclass == NO_REGS)
2808 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2810 fprintf (file, "; pref %s, else %s",
2811 reg_class_names[(int) class],
2812 reg_class_names[(int) altclass]);
2814 if (REGNO_POINTER_FLAG (i))
2815 fprintf (file, "; pointer");
2816 fprintf (file, ".\n");
2818 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2819 for (i = 0; i < n_basic_blocks; i++)
2821 register rtx head, jump;
2823 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2825 INSN_UID (basic_block_head[i]),
2826 INSN_UID (basic_block_end[i]));
2827 /* The control flow graph's storage is freed
2828 now when flow_analysis returns.
2829 Don't try to print it if it is gone. */
2830 if (basic_block_drops_in)
2832 fprintf (file, "Reached from blocks: ");
2833 head = basic_block_head[i];
2834 if (GET_CODE (head) == CODE_LABEL)
2835 for (jump = LABEL_REFS (head);
2837 jump = LABEL_NEXTREF (jump))
2839 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2840 fprintf (file, " %d", from_block);
2842 if (basic_block_drops_in[i])
2843 fprintf (file, " previous");
2845 fprintf (file, "\nRegisters live at start:");
2846 for (regno = 0; regno < max_regno; regno++)
2847 if (REGNO_REG_SET_P (basic_block_live_at_start[i], regno))
2848 fprintf (file, " %d", regno);
2849 fprintf (file, "\n");
2851 fprintf (file, "\n");
2855 /* Like print_rtl, but also print out live information for the start of each
2859 print_rtl_with_bb (outf, rtx_first)
2863 register rtx tmp_rtx;
2866 fprintf (outf, "(nil)\n");
2871 enum bb_state { NOT_IN_BB, IN_ONE_BB, IN_MULTIPLE_BB };
2872 int max_uid = get_max_uid ();
2873 int *start = alloca (max_uid * sizeof (int));
2874 int *end = alloca (max_uid * sizeof (int));
2875 char *in_bb_p = alloca (max_uid * sizeof (enum bb_state));
2877 for (i = 0; i < max_uid; i++)
2879 start[i] = end[i] = -1;
2880 in_bb_p[i] = NOT_IN_BB;
2883 for (i = n_basic_blocks-1; i >= 0; i--)
2886 start[INSN_UID (basic_block_head[i])] = i;
2887 end[INSN_UID (basic_block_end[i])] = i;
2888 for (x = basic_block_head[i]; x != NULL_RTX; x = NEXT_INSN (x))
2890 in_bb_p[ INSN_UID(x)]
2891 = (in_bb_p[ INSN_UID(x)] == NOT_IN_BB)
2892 ? IN_ONE_BB : IN_MULTIPLE_BB;
2893 if (x == basic_block_end[i])
2898 for (tmp_rtx = rtx_first; NULL != tmp_rtx; tmp_rtx = NEXT_INSN (tmp_rtx))
2900 if ((bb = start[INSN_UID (tmp_rtx)]) >= 0)
2902 fprintf (outf, ";; Start of basic block %d, registers live:",
2905 EXECUTE_IF_SET_IN_REG_SET (basic_block_live_at_start[bb], 0, i,
2907 fprintf (outf, " %d", i);
2908 if (i < FIRST_PSEUDO_REGISTER)
2909 fprintf (outf, " [%s]",
2915 if (in_bb_p[ INSN_UID(tmp_rtx)] == NOT_IN_BB
2916 && GET_CODE (tmp_rtx) != NOTE
2917 && GET_CODE (tmp_rtx) != BARRIER)
2918 fprintf (outf, ";; Insn is not within a basic block\n");
2919 else if (in_bb_p[ INSN_UID(tmp_rtx)] == IN_MULTIPLE_BB)
2920 fprintf (outf, ";; Insn is in multiple basic blocks\n");
2922 print_rtl_single (outf, tmp_rtx);
2924 if ((bb = end[INSN_UID (tmp_rtx)]) >= 0)
2925 fprintf (outf, ";; End of basic block %d\n", bb);