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 int jmp_uses_reg_or_mem PROTO((rtx));
253 static void mark_label_ref PROTO((rtx, rtx, int));
254 static void life_analysis PROTO((rtx, int));
255 void allocate_for_life_analysis PROTO((void));
256 static void init_regset_vector PROTO((regset *, int, int, struct obstack *));
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 static rtx find_use_as_address PROTO((rtx, rtx, HOST_WIDE_INT));
271 void dump_flow_info PROTO((FILE *));
273 /* Find basic blocks of the current function and perform data flow analysis.
274 F is the first insn of the function and NREGS the number of register numbers
278 flow_analysis (f, nregs, file)
285 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
287 #ifdef ELIMINABLE_REGS
288 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
291 /* Record which registers will be eliminated. We use this in
294 CLEAR_HARD_REG_SET (elim_reg_set);
296 #ifdef ELIMINABLE_REGS
297 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
298 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
300 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
303 /* Count the basic blocks. Also find maximum insn uid value used. */
306 register RTX_CODE prev_code = JUMP_INSN;
307 register RTX_CODE code;
309 max_uid_for_flow = 0;
311 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
313 code = GET_CODE (insn);
314 if (INSN_UID (insn) > max_uid_for_flow)
315 max_uid_for_flow = INSN_UID (insn);
316 if (code == CODE_LABEL
317 || (GET_RTX_CLASS (code) == 'i'
318 && (prev_code == JUMP_INSN
319 || (prev_code == CALL_INSN
320 && nonlocal_label_list != 0)
321 || prev_code == BARRIER)))
324 if (code == CALL_INSN && find_reg_note (insn, REG_RETVAL, NULL_RTX))
333 /* Leave space for insns we make in some cases for auto-inc. These cases
334 are rare, so we don't need too much space. */
335 max_uid_for_flow += max_uid_for_flow / 10;
338 /* Allocate some tables that last till end of compiling this function
339 and some needed only in find_basic_blocks and life_analysis. */
342 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
343 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
344 basic_block_drops_in = (char *) alloca (n_basic_blocks);
345 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
347 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
348 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
349 bzero (uid_volatile, max_uid_for_flow + 1);
351 find_basic_blocks (f, nonlocal_label_list);
352 life_analysis (f, nregs);
354 dump_flow_info (file);
356 basic_block_drops_in = 0;
357 uid_block_number = 0;
358 basic_block_loop_depth = 0;
361 /* Find all basic blocks of the function whose first insn is F.
362 Store the correct data in the tables that describe the basic blocks,
363 set up the chains of references for each CODE_LABEL, and
364 delete any entire basic blocks that cannot be reached.
366 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
369 find_basic_blocks (f, nonlocal_label_list)
370 rtx f, nonlocal_label_list;
374 register char *block_live = (char *) alloca (n_basic_blocks);
375 register char *block_marked = (char *) alloca (n_basic_blocks);
376 /* List of label_refs to all labels whose addresses are taken
378 rtx label_value_list;
379 int label_value_list_marked_live;
381 enum rtx_code prev_code, code;
387 label_value_list = 0;
388 label_value_list_marked_live = 0;
389 block_live_static = block_live;
390 bzero (block_live, n_basic_blocks);
391 bzero (block_marked, n_basic_blocks);
393 /* Initialize with just block 0 reachable and no blocks marked. */
394 if (n_basic_blocks > 0)
397 /* Initialize the ref chain of each label to 0. Record where all the
398 blocks start and end and their depth in loops. For each insn, record
399 the block it is in. Also mark as reachable any blocks headed by labels
400 that must not be deleted. */
402 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
403 insn; insn = NEXT_INSN (insn))
405 code = GET_CODE (insn);
408 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
410 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
414 /* A basic block starts at label, or after something that can jump. */
415 else if (code == CODE_LABEL
416 || (GET_RTX_CLASS (code) == 'i'
417 && (prev_code == JUMP_INSN
418 || (prev_code == CALL_INSN
419 && nonlocal_label_list != 0
420 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
421 || prev_code == BARRIER)))
423 basic_block_head[++i] = insn;
424 basic_block_end[i] = insn;
425 basic_block_loop_depth[i] = depth;
427 if (code == CODE_LABEL)
429 LABEL_REFS (insn) = insn;
430 /* Any label that cannot be deleted
431 is considered to start a reachable block. */
432 if (LABEL_PRESERVE_P (insn))
437 else if (GET_RTX_CLASS (code) == 'i')
439 basic_block_end[i] = insn;
440 basic_block_loop_depth[i] = depth;
443 if (GET_RTX_CLASS (code) == 'i')
445 /* Make a list of all labels referred to other than by jumps. */
446 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
447 if (REG_NOTE_KIND (note) == REG_LABEL)
448 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
452 BLOCK_NUM (insn) = i;
458 /* During the second pass, `n_basic_blocks' is only an upper bound.
459 Only perform the sanity check for the first pass, and on the second
460 pass ensure `n_basic_blocks' is set to the correct value. */
461 if (pass == 1 && i + 1 != n_basic_blocks)
463 n_basic_blocks = i + 1;
465 for (x = forced_labels; x; x = XEXP (x, 1))
466 if (! LABEL_REF_NONLOCAL_P (x))
467 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
469 for (x = exception_handler_labels; x; x = XEXP (x, 1))
470 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
472 /* Record which basic blocks control can drop in to. */
474 for (i = 0; i < n_basic_blocks; i++)
476 for (insn = PREV_INSN (basic_block_head[i]);
477 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
480 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
483 /* Now find which basic blocks can actually be reached
484 and put all jump insns' LABEL_REFS onto the ref-chains
485 of their target labels. */
487 if (n_basic_blocks > 0)
489 int something_marked = 1;
492 /* Find all indirect jump insns and mark them as possibly jumping to all
493 the labels whose addresses are explicitly used. This is because,
494 when there are computed gotos, we can't tell which labels they jump
495 to, of all the possibilities.
497 Tablejumps and casesi insns are OK and we can recognize them by
498 a (use (label_ref)). */
500 for (insn = f; insn; insn = NEXT_INSN (insn))
501 if (GET_CODE (insn) == JUMP_INSN)
503 rtx pat = PATTERN (insn);
504 int computed_jump = 0;
506 if (GET_CODE (pat) == PARALLEL)
508 int len = XVECLEN (pat, 0);
509 int has_use_labelref = 0;
511 for (i = len - 1; i >= 0; i--)
512 if (GET_CODE (XVECEXP (pat, 0, i)) == USE
513 && (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
515 has_use_labelref = 1;
517 if (! has_use_labelref)
518 for (i = len - 1; i >= 0; i--)
519 if (GET_CODE (XVECEXP (pat, 0, i)) == SET
520 && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
521 && jmp_uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
524 else if (GET_CODE (pat) == SET
525 && SET_DEST (pat) == pc_rtx
526 && jmp_uses_reg_or_mem (SET_SRC (pat)))
531 if (label_value_list_marked_live == 0)
533 label_value_list_marked_live = 1;
535 /* This could be made smarter by only considering
536 these live, if the computed goto is live. */
538 /* Don't delete the labels (in this function) that
539 are referenced by non-jump instructions. */
541 for (x = label_value_list; x; x = XEXP (x, 1))
542 if (! LABEL_REF_NONLOCAL_P (x))
543 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
546 for (x = label_value_list; x; x = XEXP (x, 1))
547 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
550 for (x = forced_labels; x; x = XEXP (x, 1))
551 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
556 /* Find all call insns and mark them as possibly jumping
557 to all the nonlocal goto handler labels. */
559 for (insn = f; insn; insn = NEXT_INSN (insn))
560 if (GET_CODE (insn) == CALL_INSN
561 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
563 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
564 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
567 /* ??? This could be made smarter:
568 in some cases it's possible to tell that certain
569 calls will not do a nonlocal goto.
571 For example, if the nested functions that do the
572 nonlocal gotos do not have their addresses taken, then
573 only calls to those functions or to other nested
574 functions that use them could possibly do nonlocal
578 /* All blocks associated with labels in label_value_list are
579 trivially considered as marked live, if the list is empty.
580 We do this to speed up the below code. */
582 if (label_value_list == 0)
583 label_value_list_marked_live = 1;
585 /* Pass over all blocks, marking each block that is reachable
586 and has not yet been marked.
587 Keep doing this until, in one pass, no blocks have been marked.
588 Then blocks_live and blocks_marked are identical and correct.
589 In addition, all jumps actually reachable have been marked. */
591 while (something_marked)
593 something_marked = 0;
594 for (i = 0; i < n_basic_blocks; i++)
595 if (block_live[i] && !block_marked[i])
598 something_marked = 1;
599 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
600 block_live[i + 1] = 1;
601 insn = basic_block_end[i];
602 if (GET_CODE (insn) == JUMP_INSN)
603 mark_label_ref (PATTERN (insn), insn, 0);
605 if (label_value_list_marked_live == 0)
606 /* Now that we know that this block is live, mark as
607 live, all the blocks that we might be able to get
610 for (insn = basic_block_head[i];
611 insn != NEXT_INSN (basic_block_end[i]);
612 insn = NEXT_INSN (insn))
614 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
616 for (note = REG_NOTES (insn);
618 note = XEXP (note, 1))
619 if (REG_NOTE_KIND (note) == REG_LABEL)
622 block_live[BLOCK_NUM (x)] = 1;
629 /* ??? See if we have a "live" basic block that is not reachable.
630 This can happen if it is headed by a label that is preserved or
631 in one of the label lists, but no call or computed jump is in
632 the loop. It's not clear if we can delete the block or not,
633 but don't for now. However, we will mess up register status if
634 it remains unreachable, so add a fake reachability from the
637 for (i = 1; i < n_basic_blocks; i++)
638 if (block_live[i] && ! basic_block_drops_in[i]
639 && GET_CODE (basic_block_head[i]) == CODE_LABEL
640 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
641 basic_block_drops_in[i] = 1;
643 /* Now delete the code for any basic blocks that can't be reached.
644 They can occur because jump_optimize does not recognize
645 unreachable loops as unreachable. */
648 for (i = 0; i < n_basic_blocks; i++)
653 /* Delete the insns in a (non-live) block. We physically delete
654 every non-note insn except the start and end (so
655 basic_block_head/end needn't be updated), we turn the latter
656 into NOTE_INSN_DELETED notes.
657 We use to "delete" the insns by turning them into notes, but
658 we may be deleting lots of insns that subsequent passes would
659 otherwise have to process. Secondly, lots of deleted blocks in
660 a row can really slow down propagate_block since it will
661 otherwise process insn-turned-notes multiple times when it
662 looks for loop begin/end notes. */
663 if (basic_block_head[i] != basic_block_end[i])
665 /* It would be quicker to delete all of these with a single
666 unchaining, rather than one at a time, but we need to keep
668 insn = NEXT_INSN (basic_block_head[i]);
669 while (insn != basic_block_end[i])
671 if (GET_CODE (insn) == BARRIER)
673 else if (GET_CODE (insn) != NOTE)
674 insn = flow_delete_insn (insn);
676 insn = NEXT_INSN (insn);
679 insn = basic_block_head[i];
680 if (GET_CODE (insn) != NOTE)
682 /* Turn the head into a deleted insn note. */
683 if (GET_CODE (insn) == BARRIER)
685 PUT_CODE (insn, NOTE);
686 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
687 NOTE_SOURCE_FILE (insn) = 0;
689 insn = basic_block_end[i];
690 if (GET_CODE (insn) != NOTE)
692 /* Turn the tail into a deleted insn note. */
693 if (GET_CODE (insn) == BARRIER)
695 PUT_CODE (insn, NOTE);
696 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
697 NOTE_SOURCE_FILE (insn) = 0;
699 /* BARRIERs are between basic blocks, not part of one.
700 Delete a BARRIER if the preceding jump is deleted.
701 We cannot alter a BARRIER into a NOTE
702 because it is too short; but we can really delete
703 it because it is not part of a basic block. */
704 if (NEXT_INSN (insn) != 0
705 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
706 delete_insn (NEXT_INSN (insn));
708 /* Each time we delete some basic blocks,
709 see if there is a jump around them that is
710 being turned into a no-op. If so, delete it. */
712 if (block_live[i - 1])
715 for (j = i + 1; j < n_basic_blocks; j++)
719 insn = basic_block_end[i - 1];
720 if (GET_CODE (insn) == JUMP_INSN
721 /* An unconditional jump is the only possibility
722 we must check for, since a conditional one
723 would make these blocks live. */
724 && simplejump_p (insn)
725 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
726 && INSN_UID (label) != 0
727 && BLOCK_NUM (label) == j)
729 PUT_CODE (insn, NOTE);
730 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
731 NOTE_SOURCE_FILE (insn) = 0;
732 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
734 delete_insn (NEXT_INSN (insn));
741 /* There are pathological cases where one function calling hundreds of
742 nested inline functions can generate lots and lots of unreachable
743 blocks that jump can't delete. Since we don't use sparse matrices
744 a lot of memory will be needed to compile such functions.
745 Implementing sparse matrices is a fair bit of work and it is not
746 clear that they win more than they lose (we don't want to
747 unnecessarily slow down compilation of normal code). By making
748 another pass for the pathological case, we can greatly speed up
749 their compilation without hurting normal code. This works because
750 all the insns in the unreachable blocks have either been deleted or
752 Note that we're talking about reducing memory usage by 10's of
753 megabytes and reducing compilation time by several minutes. */
754 /* ??? The choice of when to make another pass is a bit arbitrary,
755 and was derived from empirical data. */
760 n_basic_blocks -= deleted;
761 /* `n_basic_blocks' may not be correct at this point: two previously
762 separate blocks may now be merged. That's ok though as we
763 recalculate it during the second pass. It certainly can't be
764 any larger than the current value. */
770 /* Subroutines of find_basic_blocks. */
772 /* Return 1 if X, the SRC_SRC of SET of (pc) contain a REG or MEM that is
773 not in the constant pool and not in the condition of an IF_THEN_ELSE. */
776 jmp_uses_reg_or_mem (x)
779 enum rtx_code code = GET_CODE (x);
794 return ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
795 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)));
798 return (jmp_uses_reg_or_mem (XEXP (x, 1))
799 || jmp_uses_reg_or_mem (XEXP (x, 2)));
801 case PLUS: case MINUS: case MULT:
802 return (jmp_uses_reg_or_mem (XEXP (x, 0))
803 || jmp_uses_reg_or_mem (XEXP (x, 1)));
806 fmt = GET_RTX_FORMAT (code);
807 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
810 && jmp_uses_reg_or_mem (XEXP (x, i)))
814 for (j = 0; j < XVECLEN (x, i); j++)
815 if (jmp_uses_reg_or_mem (XVECEXP (x, i, j)))
822 /* Check expression X for label references;
823 if one is found, add INSN to the label's chain of references.
825 CHECKDUP means check for and avoid creating duplicate references
826 from the same insn. Such duplicates do no serious harm but
827 can slow life analysis. CHECKDUP is set only when duplicates
831 mark_label_ref (x, insn, checkdup)
835 register RTX_CODE code;
839 /* We can be called with NULL when scanning label_value_list. */
844 if (code == LABEL_REF)
846 register rtx label = XEXP (x, 0);
848 if (GET_CODE (label) != CODE_LABEL)
850 /* If the label was never emitted, this insn is junk,
851 but avoid a crash trying to refer to BLOCK_NUM (label).
852 This can happen as a result of a syntax error
853 and a diagnostic has already been printed. */
854 if (INSN_UID (label) == 0)
856 CONTAINING_INSN (x) = insn;
857 /* if CHECKDUP is set, check for duplicate ref from same insn
860 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
861 if (CONTAINING_INSN (y) == insn)
863 LABEL_NEXTREF (x) = LABEL_REFS (label);
864 LABEL_REFS (label) = x;
865 block_live_static[BLOCK_NUM (label)] = 1;
869 fmt = GET_RTX_FORMAT (code);
870 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
873 mark_label_ref (XEXP (x, i), insn, 0);
877 for (j = 0; j < XVECLEN (x, i); j++)
878 mark_label_ref (XVECEXP (x, i, j), insn, 1);
883 /* Delete INSN by patching it out.
884 Return the next insn. */
887 flow_delete_insn (insn)
890 /* ??? For the moment we assume we don't have to watch for NULLs here
891 since the start/end of basic blocks aren't deleted like this. */
892 NEXT_INSN (PREV_INSN (insn)) = NEXT_INSN (insn);
893 PREV_INSN (NEXT_INSN (insn)) = PREV_INSN (insn);
894 return NEXT_INSN (insn);
897 /* Determine which registers are live at the start of each
898 basic block of the function whose first insn is F.
899 NREGS is the number of registers used in F.
900 We allocate the vector basic_block_live_at_start
901 and the regsets that it points to, and fill them with the data.
902 regset_size and regset_bytes are also set here. */
905 life_analysis (f, nregs)
911 /* For each basic block, a bitmask of regs
912 live on exit from the block. */
913 regset *basic_block_live_at_end;
914 /* For each basic block, a bitmask of regs
915 live on entry to a successor-block of this block.
916 If this does not match basic_block_live_at_end,
917 that must be updated, and the block must be rescanned. */
918 regset *basic_block_new_live_at_end;
919 /* For each basic block, a bitmask of regs
920 whose liveness at the end of the basic block
921 can make a difference in which regs are live on entry to the block.
922 These are the regs that are set within the basic block,
923 possibly excluding those that are used after they are set. */
924 regset *basic_block_significant;
928 struct obstack flow_obstack;
930 gcc_obstack_init (&flow_obstack);
934 bzero (regs_ever_live, sizeof regs_ever_live);
936 /* Allocate and zero out many data structures
937 that will record the data from lifetime analysis. */
939 allocate_for_life_analysis ();
941 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
942 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
944 /* Set up several regset-vectors used internally within this function.
945 Their meanings are documented above, with their declarations. */
947 basic_block_live_at_end
948 = (regset *) alloca (n_basic_blocks * sizeof (regset));
950 /* Don't use alloca since that leads to a crash rather than an error message
951 if there isn't enough space.
952 Don't use oballoc since we may need to allocate other things during
953 this function on the temporary obstack. */
954 init_regset_vector (basic_block_live_at_end, n_basic_blocks, regset_bytes,
957 basic_block_new_live_at_end
958 = (regset *) alloca (n_basic_blocks * sizeof (regset));
959 init_regset_vector (basic_block_new_live_at_end, n_basic_blocks, regset_bytes,
962 basic_block_significant
963 = (regset *) alloca (n_basic_blocks * sizeof (regset));
964 init_regset_vector (basic_block_significant, n_basic_blocks, regset_bytes,
967 /* Record which insns refer to any volatile memory
968 or for any reason can't be deleted just because they are dead stores.
969 Also, delete any insns that copy a register to itself. */
971 for (insn = f; insn; insn = NEXT_INSN (insn))
973 enum rtx_code code1 = GET_CODE (insn);
974 if (code1 == CALL_INSN)
975 INSN_VOLATILE (insn) = 1;
976 else if (code1 == INSN || code1 == JUMP_INSN)
978 /* Delete (in effect) any obvious no-op moves. */
979 if (GET_CODE (PATTERN (insn)) == SET
980 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
981 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
982 && (REGNO (SET_DEST (PATTERN (insn)))
983 == REGNO (SET_SRC (PATTERN (insn))))
984 /* Insns carrying these notes are useful later on. */
985 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
987 PUT_CODE (insn, NOTE);
988 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
989 NOTE_SOURCE_FILE (insn) = 0;
991 /* Delete (in effect) any obvious no-op moves. */
992 else if (GET_CODE (PATTERN (insn)) == SET
993 && GET_CODE (SET_DEST (PATTERN (insn))) == SUBREG
994 && GET_CODE (SUBREG_REG (SET_DEST (PATTERN (insn)))) == REG
995 && GET_CODE (SET_SRC (PATTERN (insn))) == SUBREG
996 && GET_CODE (SUBREG_REG (SET_SRC (PATTERN (insn)))) == REG
997 && (REGNO (SUBREG_REG (SET_DEST (PATTERN (insn))))
998 == REGNO (SUBREG_REG (SET_SRC (PATTERN (insn)))))
999 && SUBREG_WORD (SET_DEST (PATTERN (insn))) ==
1000 SUBREG_WORD (SET_SRC (PATTERN (insn)))
1001 /* Insns carrying these notes are useful later on. */
1002 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1004 PUT_CODE (insn, NOTE);
1005 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1006 NOTE_SOURCE_FILE (insn) = 0;
1008 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
1010 /* If nothing but SETs of registers to themselves,
1011 this insn can also be deleted. */
1012 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
1014 rtx tem = XVECEXP (PATTERN (insn), 0, i);
1016 if (GET_CODE (tem) == USE
1017 || GET_CODE (tem) == CLOBBER)
1020 if (GET_CODE (tem) != SET
1021 || GET_CODE (SET_DEST (tem)) != REG
1022 || GET_CODE (SET_SRC (tem)) != REG
1023 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
1027 if (i == XVECLEN (PATTERN (insn), 0)
1028 /* Insns carrying these notes are useful later on. */
1029 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1031 PUT_CODE (insn, NOTE);
1032 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1033 NOTE_SOURCE_FILE (insn) = 0;
1036 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1038 else if (GET_CODE (PATTERN (insn)) != USE)
1039 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1040 /* A SET that makes space on the stack cannot be dead.
1041 (Such SETs occur only for allocating variable-size data,
1042 so they will always have a PLUS or MINUS according to the
1043 direction of stack growth.)
1044 Even if this function never uses this stack pointer value,
1045 signal handlers do! */
1046 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
1047 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1048 #ifdef STACK_GROWS_DOWNWARD
1049 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
1051 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1053 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
1054 INSN_VOLATILE (insn) = 1;
1058 if (n_basic_blocks > 0)
1059 #ifdef EXIT_IGNORE_STACK
1060 if (! EXIT_IGNORE_STACK
1061 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
1064 /* If exiting needs the right stack value,
1065 consider the stack pointer live at the end of the function. */
1066 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1067 STACK_POINTER_REGNUM);
1068 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1069 STACK_POINTER_REGNUM);
1072 /* Mark the frame pointer is needed at the end of the function. If
1073 we end up eliminating it, it will be removed from the live list
1074 of each basic block by reload. */
1076 if (n_basic_blocks > 0)
1078 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1079 FRAME_POINTER_REGNUM);
1080 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1081 FRAME_POINTER_REGNUM);
1082 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1083 /* If they are different, also mark the hard frame pointer as live */
1084 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1085 HARD_FRAME_POINTER_REGNUM);
1086 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1087 HARD_FRAME_POINTER_REGNUM);
1091 /* Mark all global registers and all registers used by the epilogue
1092 as being live at the end of the function since they may be
1093 referenced by our caller. */
1095 if (n_basic_blocks > 0)
1096 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1098 #ifdef EPILOGUE_USES
1099 || EPILOGUE_USES (i)
1103 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1], i);
1104 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1], i);
1107 /* Propagate life info through the basic blocks
1108 around the graph of basic blocks.
1110 This is a relaxation process: each time a new register
1111 is live at the end of the basic block, we must scan the block
1112 to determine which registers are, as a consequence, live at the beginning
1113 of that block. These registers must then be marked live at the ends
1114 of all the blocks that can transfer control to that block.
1115 The process continues until it reaches a fixed point. */
1122 for (i = n_basic_blocks - 1; i >= 0; i--)
1124 int consider = first_pass;
1125 int must_rescan = first_pass;
1130 /* Set CONSIDER if this block needs thinking about at all
1131 (that is, if the regs live now at the end of it
1132 are not the same as were live at the end of it when
1133 we last thought about it).
1134 Set must_rescan if it needs to be thought about
1135 instruction by instruction (that is, if any additional
1136 reg that is live at the end now but was not live there before
1137 is one of the significant regs of this basic block). */
1139 EXECUTE_IF_AND_COMPL_IN_REG_SET (basic_block_new_live_at_end[i],
1140 basic_block_live_at_end[i],
1144 if (REGNO_REG_SET_P (basic_block_significant[i], j))
1155 /* The live_at_start of this block may be changing,
1156 so another pass will be required after this one. */
1161 /* No complete rescan needed;
1162 just record those variables newly known live at end
1163 as live at start as well. */
1164 IOR_AND_COMPL_REG_SET (basic_block_live_at_start[i],
1165 basic_block_new_live_at_end[i],
1166 basic_block_live_at_end[i]);
1168 IOR_AND_COMPL_REG_SET (basic_block_live_at_end[i],
1169 basic_block_new_live_at_end[i],
1170 basic_block_live_at_end[i]);
1174 /* Update the basic_block_live_at_start
1175 by propagation backwards through the block. */
1176 COPY_REG_SET (basic_block_live_at_end[i],
1177 basic_block_new_live_at_end[i]);
1178 COPY_REG_SET (basic_block_live_at_start[i],
1179 basic_block_live_at_end[i]);
1180 propagate_block (basic_block_live_at_start[i],
1181 basic_block_head[i], basic_block_end[i], 0,
1182 first_pass ? basic_block_significant[i]
1188 register rtx jump, head;
1190 /* Update the basic_block_new_live_at_end's of the block
1191 that falls through into this one (if any). */
1192 head = basic_block_head[i];
1193 if (basic_block_drops_in[i])
1194 IOR_REG_SET (basic_block_new_live_at_end[i-1],
1195 basic_block_live_at_start[i]);
1197 /* Update the basic_block_new_live_at_end's of
1198 all the blocks that jump to this one. */
1199 if (GET_CODE (head) == CODE_LABEL)
1200 for (jump = LABEL_REFS (head);
1202 jump = LABEL_NEXTREF (jump))
1204 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1205 IOR_REG_SET (basic_block_new_live_at_end[from_block],
1206 basic_block_live_at_start[i]);
1216 /* The only pseudos that are live at the beginning of the function are
1217 those that were not set anywhere in the function. local-alloc doesn't
1218 know how to handle these correctly, so mark them as not local to any
1221 if (n_basic_blocks > 0)
1222 EXECUTE_IF_SET_IN_REG_SET (basic_block_live_at_start[0],
1223 FIRST_PSEUDO_REGISTER, i,
1225 REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL;
1228 /* Now the life information is accurate.
1229 Make one more pass over each basic block
1230 to delete dead stores, create autoincrement addressing
1231 and record how many times each register is used, is set, or dies.
1233 To save time, we operate directly in basic_block_live_at_end[i],
1234 thus destroying it (in fact, converting it into a copy of
1235 basic_block_live_at_start[i]). This is ok now because
1236 basic_block_live_at_end[i] is no longer used past this point. */
1240 for (i = 0; i < n_basic_blocks; i++)
1242 propagate_block (basic_block_live_at_end[i],
1243 basic_block_head[i], basic_block_end[i], 1,
1251 /* Something live during a setjmp should not be put in a register
1252 on certain machines which restore regs from stack frames
1253 rather than from the jmpbuf.
1254 But we don't need to do this for the user's variables, since
1255 ANSI says only volatile variables need this. */
1256 #ifdef LONGJMP_RESTORE_FROM_STACK
1257 EXECUTE_IF_SET_IN_REG_SET (regs_live_at_setjmp,
1258 FIRST_PSEUDO_REGISTER, i,
1260 if (regno_reg_rtx[i] != 0
1261 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1263 REG_LIVE_LENGTH (i) = -1;
1264 REG_BASIC_BLOCK (i) = -1;
1270 /* We have a problem with any pseudoreg that
1271 lives across the setjmp. ANSI says that if a
1272 user variable does not change in value
1273 between the setjmp and the longjmp, then the longjmp preserves it.
1274 This includes longjmp from a place where the pseudo appears dead.
1275 (In principle, the value still exists if it is in scope.)
1276 If the pseudo goes in a hard reg, some other value may occupy
1277 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1278 Conclusion: such a pseudo must not go in a hard reg. */
1279 EXECUTE_IF_SET_IN_REG_SET (regs_live_at_setjmp,
1280 FIRST_PSEUDO_REGISTER, i,
1282 if (regno_reg_rtx[i] != 0)
1284 REG_LIVE_LENGTH (i) = -1;
1285 REG_BASIC_BLOCK (i) = -1;
1289 obstack_free (&flow_obstack, NULL_PTR);
1292 /* Subroutines of life analysis. */
1294 /* Allocate the permanent data structures that represent the results
1295 of life analysis. Not static since used also for stupid life analysis. */
1298 allocate_for_life_analysis ()
1302 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1303 regset_bytes = regset_size * sizeof (*(regset) 0);
1305 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
1306 information, explicitly reset it here. The allocation should have
1307 already happened on the previous reg_scan pass. Make sure in case
1308 some more registers were allocated. */
1309 allocate_reg_info (max_regno, FALSE, FALSE);
1311 for (i = 0; i < max_regno; i++)
1314 basic_block_live_at_start
1315 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1316 init_regset_vector (basic_block_live_at_start, n_basic_blocks, regset_bytes,
1319 regs_live_at_setjmp = OBSTACK_ALLOC_REG_SET (function_obstack);
1320 CLEAR_REG_SET (regs_live_at_setjmp);
1323 /* Make each element of VECTOR point at a regset,
1324 taking the space for all those regsets from SPACE.
1325 SPACE is of type regset, but it is really as long as NELTS regsets.
1326 BYTES_PER_ELT is the number of bytes in one regset. */
1329 init_regset_vector (vector, nelts, bytes_per_elt, alloc_obstack)
1333 struct obstack *alloc_obstack;
1337 for (i = 0; i < nelts; i++)
1339 vector[i] = OBSTACK_ALLOC_REG_SET (alloc_obstack);
1340 CLEAR_REG_SET (vector[i]);
1344 /* Compute the registers live at the beginning of a basic block
1345 from those live at the end.
1347 When called, OLD contains those live at the end.
1348 On return, it contains those live at the beginning.
1349 FIRST and LAST are the first and last insns of the basic block.
1351 FINAL is nonzero if we are doing the final pass which is not
1352 for computing the life info (since that has already been done)
1353 but for acting on it. On this pass, we delete dead stores,
1354 set up the logical links and dead-variables lists of instructions,
1355 and merge instructions for autoincrement and autodecrement addresses.
1357 SIGNIFICANT is nonzero only the first time for each basic block.
1358 If it is nonzero, it points to a regset in which we store
1359 a 1 for each register that is set within the block.
1361 BNUM is the number of the basic block. */
1364 propagate_block (old, first, last, final, significant, bnum)
1365 register regset old;
1377 /* The following variables are used only if FINAL is nonzero. */
1378 /* This vector gets one element for each reg that has been live
1379 at any point in the basic block that has been scanned so far.
1380 SOMETIMES_MAX says how many elements are in use so far. */
1381 register int *regs_sometimes_live;
1382 int sometimes_max = 0;
1383 /* This regset has 1 for each reg that we have seen live so far.
1384 It and REGS_SOMETIMES_LIVE are updated together. */
1387 /* The loop depth may change in the middle of a basic block. Since we
1388 scan from end to beginning, we start with the depth at the end of the
1389 current basic block, and adjust as we pass ends and starts of loops. */
1390 loop_depth = basic_block_loop_depth[bnum];
1392 dead = ALLOCA_REG_SET ();
1393 live = ALLOCA_REG_SET ();
1398 /* Include any notes at the end of the block in the scan.
1399 This is in case the block ends with a call to setjmp. */
1401 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1403 /* Look for loop boundaries, we are going forward here. */
1404 last = NEXT_INSN (last);
1405 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1407 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1416 maxlive = ALLOCA_REG_SET ();
1417 COPY_REG_SET (maxlive, old);
1418 regs_sometimes_live = (int *) alloca (max_regno * sizeof (int));
1420 /* Process the regs live at the end of the block.
1421 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1422 Also mark them as not local to any one basic block. */
1423 EXECUTE_IF_SET_IN_REG_SET (old, 0, i,
1425 REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL;
1426 regs_sometimes_live[sometimes_max] = i;
1431 /* Scan the block an insn at a time from end to beginning. */
1433 for (insn = last; ; insn = prev)
1435 prev = PREV_INSN (insn);
1437 if (GET_CODE (insn) == NOTE)
1439 /* Look for loop boundaries, remembering that we are going
1441 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1443 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1446 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1447 Abort now rather than setting register status incorrectly. */
1448 if (loop_depth == 0)
1451 /* If this is a call to `setjmp' et al,
1452 warn if any non-volatile datum is live. */
1454 if (final && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1455 IOR_REG_SET (regs_live_at_setjmp, old);
1458 /* Update the life-status of regs for this insn.
1459 First DEAD gets which regs are set in this insn
1460 then LIVE gets which regs are used in this insn.
1461 Then the regs live before the insn
1462 are those live after, with DEAD regs turned off,
1463 and then LIVE regs turned on. */
1465 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1468 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1470 = (insn_dead_p (PATTERN (insn), old, 0)
1471 /* Don't delete something that refers to volatile storage! */
1472 && ! INSN_VOLATILE (insn));
1474 = (insn_is_dead && note != 0
1475 && libcall_dead_p (PATTERN (insn), old, note, insn));
1477 /* If an instruction consists of just dead store(s) on final pass,
1478 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1479 We could really delete it with delete_insn, but that
1480 can cause trouble for first or last insn in a basic block. */
1481 if (final && insn_is_dead)
1483 PUT_CODE (insn, NOTE);
1484 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1485 NOTE_SOURCE_FILE (insn) = 0;
1487 /* CC0 is now known to be dead. Either this insn used it,
1488 in which case it doesn't anymore, or clobbered it,
1489 so the next insn can't use it. */
1492 /* If this insn is copying the return value from a library call,
1493 delete the entire library call. */
1494 if (libcall_is_dead)
1496 rtx first = XEXP (note, 0);
1498 while (INSN_DELETED_P (first))
1499 first = NEXT_INSN (first);
1504 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1505 NOTE_SOURCE_FILE (p) = 0;
1511 CLEAR_REG_SET (dead);
1512 CLEAR_REG_SET (live);
1514 /* See if this is an increment or decrement that can be
1515 merged into a following memory address. */
1518 register rtx x = PATTERN (insn);
1519 /* Does this instruction increment or decrement a register? */
1520 if (final && GET_CODE (x) == SET
1521 && GET_CODE (SET_DEST (x)) == REG
1522 && (GET_CODE (SET_SRC (x)) == PLUS
1523 || GET_CODE (SET_SRC (x)) == MINUS)
1524 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1525 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1526 /* Ok, look for a following memory ref we can combine with.
1527 If one is found, change the memory ref to a PRE_INC
1528 or PRE_DEC, cancel this insn, and return 1.
1529 Return 0 if nothing has been done. */
1530 && try_pre_increment_1 (insn))
1533 #endif /* AUTO_INC_DEC */
1535 /* If this is not the final pass, and this insn is copying the
1536 value of a library call and it's dead, don't scan the
1537 insns that perform the library call, so that the call's
1538 arguments are not marked live. */
1539 if (libcall_is_dead)
1541 /* Mark the dest reg as `significant'. */
1542 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1544 insn = XEXP (note, 0);
1545 prev = PREV_INSN (insn);
1547 else if (GET_CODE (PATTERN (insn)) == SET
1548 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1549 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1550 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1551 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1552 /* We have an insn to pop a constant amount off the stack.
1553 (Such insns use PLUS regardless of the direction of the stack,
1554 and any insn to adjust the stack by a constant is always a pop.)
1555 These insns, if not dead stores, have no effect on life. */
1559 /* LIVE gets the regs used in INSN;
1560 DEAD gets those set by it. Dead insns don't make anything
1563 mark_set_regs (old, dead, PATTERN (insn),
1564 final ? insn : NULL_RTX, significant);
1566 /* If an insn doesn't use CC0, it becomes dead since we
1567 assume that every insn clobbers it. So show it dead here;
1568 mark_used_regs will set it live if it is referenced. */
1572 mark_used_regs (old, live, PATTERN (insn), final, insn);
1574 /* Sometimes we may have inserted something before INSN (such as
1575 a move) when we make an auto-inc. So ensure we will scan
1578 prev = PREV_INSN (insn);
1581 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1587 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1589 note = XEXP (note, 1))
1590 if (GET_CODE (XEXP (note, 0)) == USE)
1591 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1594 /* Each call clobbers all call-clobbered regs that are not
1595 global or fixed. Note that the function-value reg is a
1596 call-clobbered reg, and mark_set_regs has already had
1597 a chance to handle it. */
1599 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1600 if (call_used_regs[i] && ! global_regs[i]
1602 SET_REGNO_REG_SET (dead, i);
1604 /* The stack ptr is used (honorarily) by a CALL insn. */
1605 SET_REGNO_REG_SET (live, STACK_POINTER_REGNUM);
1607 /* Calls may also reference any of the global registers,
1608 so they are made live. */
1609 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1611 mark_used_regs (old, live,
1612 gen_rtx (REG, reg_raw_mode[i], i),
1615 /* Calls also clobber memory. */
1619 /* Update OLD for the registers used or set. */
1620 AND_COMPL_REG_SET (old, dead);
1621 IOR_REG_SET (old, live);
1623 if (GET_CODE (insn) == CALL_INSN && final)
1625 /* Any regs live at the time of a call instruction
1626 must not go in a register clobbered by calls.
1627 Find all regs now live and record this for them. */
1629 register int *p = regs_sometimes_live;
1631 for (i = 0; i < sometimes_max; i++, p++)
1632 if (REGNO_REG_SET_P (old, *p))
1633 REG_N_CALLS_CROSSED (*p)++;
1637 /* On final pass, add any additional sometimes-live regs
1638 into MAXLIVE and REGS_SOMETIMES_LIVE.
1639 Also update counts of how many insns each reg is live at. */
1646 EXECUTE_IF_AND_COMPL_IN_REG_SET (live, maxlive, 0, regno,
1648 regs_sometimes_live[sometimes_max++] = regno;
1649 SET_REGNO_REG_SET (maxlive, regno);
1652 p = regs_sometimes_live;
1653 for (i = 0; i < sometimes_max; i++)
1656 if (REGNO_REG_SET_P (old, regno))
1657 REG_LIVE_LENGTH (regno)++;
1666 if (num_scratch > max_scratch)
1667 max_scratch = num_scratch;
1670 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1671 (SET expressions whose destinations are registers dead after the insn).
1672 NEEDED is the regset that says which regs are alive after the insn.
1674 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1677 insn_dead_p (x, needed, call_ok)
1682 register RTX_CODE code = GET_CODE (x);
1683 /* If setting something that's a reg or part of one,
1684 see if that register's altered value will be live. */
1688 register rtx r = SET_DEST (x);
1689 /* A SET that is a subroutine call cannot be dead. */
1690 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1694 if (GET_CODE (r) == CC0)
1698 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1699 && rtx_equal_p (r, last_mem_set))
1702 while (GET_CODE (r) == SUBREG
1703 || GET_CODE (r) == STRICT_LOW_PART
1704 || GET_CODE (r) == ZERO_EXTRACT
1705 || GET_CODE (r) == SIGN_EXTRACT)
1708 if (GET_CODE (r) == REG)
1710 register int regno = REGNO (r);
1712 /* Don't delete insns to set global regs. */
1713 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1714 /* Make sure insns to set frame pointer aren't deleted. */
1715 || regno == FRAME_POINTER_REGNUM
1716 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1717 || regno == HARD_FRAME_POINTER_REGNUM
1719 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1720 /* Make sure insns to set arg pointer are never deleted
1721 (if the arg pointer isn't fixed, there will be a USE for
1722 it, so we can treat it normally). */
1723 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1725 || REGNO_REG_SET_P (needed, regno))
1728 /* If this is a hard register, verify that subsequent words are
1730 if (regno < FIRST_PSEUDO_REGISTER)
1732 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1735 if (REGNO_REG_SET_P (needed, regno+n))
1742 /* If performing several activities,
1743 insn is dead if each activity is individually dead.
1744 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1745 that's inside a PARALLEL doesn't make the insn worth keeping. */
1746 else if (code == PARALLEL)
1748 register int i = XVECLEN (x, 0);
1749 for (i--; i >= 0; i--)
1751 rtx elt = XVECEXP (x, 0, i);
1752 if (!insn_dead_p (elt, needed, call_ok)
1753 && GET_CODE (elt) != CLOBBER
1754 && GET_CODE (elt) != USE)
1759 /* We do not check CLOBBER or USE here.
1760 An insn consisting of just a CLOBBER or just a USE
1761 should not be deleted. */
1765 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1766 return 1 if the entire library call is dead.
1767 This is true if X copies a register (hard or pseudo)
1768 and if the hard return reg of the call insn is dead.
1769 (The caller should have tested the destination of X already for death.)
1771 If this insn doesn't just copy a register, then we don't
1772 have an ordinary libcall. In that case, cse could not have
1773 managed to substitute the source for the dest later on,
1774 so we can assume the libcall is dead.
1776 NEEDED is the bit vector of pseudoregs live before this insn.
1777 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1780 libcall_dead_p (x, needed, note, insn)
1786 register RTX_CODE code = GET_CODE (x);
1790 register rtx r = SET_SRC (x);
1791 if (GET_CODE (r) == REG)
1793 rtx call = XEXP (note, 0);
1796 /* Find the call insn. */
1797 while (call != insn && GET_CODE (call) != CALL_INSN)
1798 call = NEXT_INSN (call);
1800 /* If there is none, do nothing special,
1801 since ordinary death handling can understand these insns. */
1805 /* See if the hard reg holding the value is dead.
1806 If this is a PARALLEL, find the call within it. */
1807 call = PATTERN (call);
1808 if (GET_CODE (call) == PARALLEL)
1810 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1811 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1812 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1815 /* This may be a library call that is returning a value
1816 via invisible pointer. Do nothing special, since
1817 ordinary death handling can understand these insns. */
1821 call = XVECEXP (call, 0, i);
1824 return insn_dead_p (call, needed, 1);
1830 /* Return 1 if register REGNO was used before it was set.
1831 In other words, if it is live at function entry.
1832 Don't count global register variables or variables in registers
1833 that can be used for function arg passing, though. */
1836 regno_uninitialized (regno)
1839 if (n_basic_blocks == 0
1840 || (regno < FIRST_PSEUDO_REGISTER
1841 && (global_regs[regno] || FUNCTION_ARG_REGNO_P (regno))))
1844 return REGNO_REG_SET_P (basic_block_live_at_start[0], regno);
1847 /* 1 if register REGNO was alive at a place where `setjmp' was called
1848 and was set more than once or is an argument.
1849 Such regs may be clobbered by `longjmp'. */
1852 regno_clobbered_at_setjmp (regno)
1855 if (n_basic_blocks == 0)
1858 return ((REG_N_SETS (regno) > 1
1859 || REGNO_REG_SET_P (basic_block_live_at_start[0], regno))
1860 && REGNO_REG_SET_P (regs_live_at_setjmp, regno));
1863 /* Process the registers that are set within X.
1864 Their bits are set to 1 in the regset DEAD,
1865 because they are dead prior to this insn.
1867 If INSN is nonzero, it is the insn being processed
1868 and the fact that it is nonzero implies this is the FINAL pass
1869 in propagate_block. In this case, various info about register
1870 usage is stored, LOG_LINKS fields of insns are set up. */
1873 mark_set_regs (needed, dead, x, insn, significant)
1880 register RTX_CODE code = GET_CODE (x);
1882 if (code == SET || code == CLOBBER)
1883 mark_set_1 (needed, dead, x, insn, significant);
1884 else if (code == PARALLEL)
1887 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1889 code = GET_CODE (XVECEXP (x, 0, i));
1890 if (code == SET || code == CLOBBER)
1891 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1896 /* Process a single SET rtx, X. */
1899 mark_set_1 (needed, dead, x, insn, significant)
1907 register rtx reg = SET_DEST (x);
1909 /* Modifying just one hardware register of a multi-reg value
1910 or just a byte field of a register
1911 does not mean the value from before this insn is now dead.
1912 But it does mean liveness of that register at the end of the block
1915 Within mark_set_1, however, we treat it as if the register is
1916 indeed modified. mark_used_regs will, however, also treat this
1917 register as being used. Thus, we treat these insns as setting a
1918 new value for the register as a function of its old value. This
1919 cases LOG_LINKS to be made appropriately and this will help combine. */
1921 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1922 || GET_CODE (reg) == SIGN_EXTRACT
1923 || GET_CODE (reg) == STRICT_LOW_PART)
1924 reg = XEXP (reg, 0);
1926 /* If we are writing into memory or into a register mentioned in the
1927 address of the last thing stored into memory, show we don't know
1928 what the last store was. If we are writing memory, save the address
1929 unless it is volatile. */
1930 if (GET_CODE (reg) == MEM
1931 || (GET_CODE (reg) == REG
1932 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1935 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1936 /* There are no REG_INC notes for SP, so we can't assume we'll see
1937 everything that invalidates it. To be safe, don't eliminate any
1938 stores though SP; none of them should be redundant anyway. */
1939 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1942 if (GET_CODE (reg) == REG
1943 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1944 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1945 && regno != HARD_FRAME_POINTER_REGNUM
1947 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1948 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1950 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1951 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1953 int some_needed = REGNO_REG_SET_P (needed, regno);
1954 int some_not_needed = ! some_needed;
1956 /* Mark it as a significant register for this basic block. */
1958 SET_REGNO_REG_SET (significant, regno);
1960 /* Mark it as as dead before this insn. */
1961 SET_REGNO_REG_SET (dead, regno);
1963 /* A hard reg in a wide mode may really be multiple registers.
1964 If so, mark all of them just like the first. */
1965 if (regno < FIRST_PSEUDO_REGISTER)
1969 /* Nothing below is needed for the stack pointer; get out asap.
1970 Eg, log links aren't needed, since combine won't use them. */
1971 if (regno == STACK_POINTER_REGNUM)
1974 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1977 int regno_n = regno + n;
1978 int needed_regno = REGNO_REG_SET_P (needed, regno_n);
1980 SET_REGNO_REG_SET (significant, regno_n);
1982 SET_REGNO_REG_SET (dead, regno_n);
1983 some_needed |= needed_regno;
1984 some_not_needed |= ! needed_regno;
1987 /* Additional data to record if this is the final pass. */
1990 register rtx y = reg_next_use[regno];
1991 register int blocknum = BLOCK_NUM (insn);
1993 /* If this is a hard reg, record this function uses the reg. */
1995 if (regno < FIRST_PSEUDO_REGISTER)
1998 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
2000 for (i = regno; i < endregno; i++)
2002 /* The next use is no longer "next", since a store
2004 reg_next_use[i] = 0;
2006 regs_ever_live[i] = 1;
2012 /* The next use is no longer "next", since a store
2014 reg_next_use[regno] = 0;
2016 /* Keep track of which basic blocks each reg appears in. */
2018 if (REG_BASIC_BLOCK (regno) == REG_BLOCK_UNKNOWN)
2019 REG_BASIC_BLOCK (regno) = blocknum;
2020 else if (REG_BASIC_BLOCK (regno) != blocknum)
2021 REG_BASIC_BLOCK (regno) = REG_BLOCK_GLOBAL;
2023 /* Count (weighted) references, stores, etc. This counts a
2024 register twice if it is modified, but that is correct. */
2025 REG_N_SETS (regno)++;
2027 REG_N_REFS (regno) += loop_depth;
2029 /* The insns where a reg is live are normally counted
2030 elsewhere, but we want the count to include the insn
2031 where the reg is set, and the normal counting mechanism
2032 would not count it. */
2033 REG_LIVE_LENGTH (regno)++;
2036 if (! some_not_needed)
2038 /* Make a logical link from the next following insn
2039 that uses this register, back to this insn.
2040 The following insns have already been processed.
2042 We don't build a LOG_LINK for hard registers containing
2043 in ASM_OPERANDs. If these registers get replaced,
2044 we might wind up changing the semantics of the insn,
2045 even if reload can make what appear to be valid assignments
2047 if (y && (BLOCK_NUM (y) == blocknum)
2048 && (regno >= FIRST_PSEUDO_REGISTER
2049 || asm_noperands (PATTERN (y)) < 0))
2051 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
2053 else if (! some_needed)
2055 /* Note that dead stores have already been deleted when possible
2056 If we get here, we have found a dead store that cannot
2057 be eliminated (because the same insn does something useful).
2058 Indicate this by marking the reg being set as dying here. */
2060 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2061 REG_N_DEATHS (REGNO (reg))++;
2065 /* This is a case where we have a multi-word hard register
2066 and some, but not all, of the words of the register are
2067 needed in subsequent insns. Write REG_UNUSED notes
2068 for those parts that were not needed. This case should
2073 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2075 if (!REGNO_REG_SET_P (needed, regno + i))
2077 = gen_rtx (EXPR_LIST, REG_UNUSED,
2078 gen_rtx (REG, reg_raw_mode[regno + i],
2084 else if (GET_CODE (reg) == REG)
2085 reg_next_use[regno] = 0;
2087 /* If this is the last pass and this is a SCRATCH, show it will be dying
2088 here and count it. */
2089 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2092 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2099 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2103 find_auto_inc (needed, x, insn)
2108 rtx addr = XEXP (x, 0);
2109 HOST_WIDE_INT offset = 0;
2112 /* Here we detect use of an index register which might be good for
2113 postincrement, postdecrement, preincrement, or predecrement. */
2115 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2116 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2118 if (GET_CODE (addr) == REG)
2121 register int size = GET_MODE_SIZE (GET_MODE (x));
2124 int regno = REGNO (addr);
2126 /* Is the next use an increment that might make auto-increment? */
2127 if ((incr = reg_next_use[regno]) != 0
2128 && (set = single_set (incr)) != 0
2129 && GET_CODE (set) == SET
2130 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2131 /* Can't add side effects to jumps; if reg is spilled and
2132 reloaded, there's no way to store back the altered value. */
2133 && GET_CODE (insn) != JUMP_INSN
2134 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2135 && XEXP (y, 0) == addr
2136 && GET_CODE (XEXP (y, 1)) == CONST_INT
2138 #ifdef HAVE_POST_INCREMENT
2139 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2141 #ifdef HAVE_POST_DECREMENT
2142 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2144 #ifdef HAVE_PRE_INCREMENT
2145 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2147 #ifdef HAVE_PRE_DECREMENT
2148 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2151 /* Make sure this reg appears only once in this insn. */
2152 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2153 use != 0 && use != (rtx) 1))
2155 rtx q = SET_DEST (set);
2156 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2157 ? (offset ? PRE_INC : POST_INC)
2158 : (offset ? PRE_DEC : POST_DEC));
2160 if (dead_or_set_p (incr, addr))
2162 /* This is the simple case. Try to make the auto-inc. If
2163 we can't, we are done. Otherwise, we will do any
2164 needed updates below. */
2165 if (! validate_change (insn, &XEXP (x, 0),
2166 gen_rtx (inc_code, Pmode, addr),
2170 else if (GET_CODE (q) == REG
2171 /* PREV_INSN used here to check the semi-open interval
2173 && ! reg_used_between_p (q, PREV_INSN (insn), incr)
2174 /* We must also check for sets of q as q may be
2175 a call clobbered hard register and there may
2176 be a call between PREV_INSN (insn) and incr. */
2177 && ! reg_set_between_p (q, PREV_INSN (insn), incr))
2179 /* We have *p followed sometime later by q = p+size.
2180 Both p and q must be live afterward,
2181 and q is not used between INSN and it's assignment.
2182 Change it to q = p, ...*q..., q = q+size.
2183 Then fall into the usual case. */
2187 emit_move_insn (q, addr);
2188 insns = get_insns ();
2191 /* If anything in INSNS have UID's that don't fit within the
2192 extra space we allocate earlier, we can't make this auto-inc.
2193 This should never happen. */
2194 for (temp = insns; temp; temp = NEXT_INSN (temp))
2196 if (INSN_UID (temp) > max_uid_for_flow)
2198 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2201 /* If we can't make the auto-inc, or can't make the
2202 replacement into Y, exit. There's no point in making
2203 the change below if we can't do the auto-inc and doing
2204 so is not correct in the pre-inc case. */
2206 validate_change (insn, &XEXP (x, 0),
2207 gen_rtx (inc_code, Pmode, q),
2209 validate_change (incr, &XEXP (y, 0), q, 1);
2210 if (! apply_change_group ())
2213 /* We now know we'll be doing this change, so emit the
2214 new insn(s) and do the updates. */
2215 emit_insns_before (insns, insn);
2217 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2218 basic_block_head[BLOCK_NUM (insn)] = insns;
2220 /* INCR will become a NOTE and INSN won't contain a
2221 use of ADDR. If a use of ADDR was just placed in
2222 the insn before INSN, make that the next use.
2223 Otherwise, invalidate it. */
2224 if (GET_CODE (PREV_INSN (insn)) == INSN
2225 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2226 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2227 reg_next_use[regno] = PREV_INSN (insn);
2229 reg_next_use[regno] = 0;
2234 /* REGNO is now used in INCR which is below INSN, but
2235 it previously wasn't live here. If we don't mark
2236 it as needed, we'll put a REG_DEAD note for it
2237 on this insn, which is incorrect. */
2238 SET_REGNO_REG_SET (needed, regno);
2240 /* If there are any calls between INSN and INCR, show
2241 that REGNO now crosses them. */
2242 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2243 if (GET_CODE (temp) == CALL_INSN)
2244 REG_N_CALLS_CROSSED (regno)++;
2249 /* If we haven't returned, it means we were able to make the
2250 auto-inc, so update the status. First, record that this insn
2251 has an implicit side effect. */
2254 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2256 /* Modify the old increment-insn to simply copy
2257 the already-incremented value of our register. */
2258 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2261 /* If that makes it a no-op (copying the register into itself) delete
2262 it so it won't appear to be a "use" and a "set" of this
2264 if (SET_DEST (set) == addr)
2266 PUT_CODE (incr, NOTE);
2267 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2268 NOTE_SOURCE_FILE (incr) = 0;
2271 if (regno >= FIRST_PSEUDO_REGISTER)
2273 /* Count an extra reference to the reg. When a reg is
2274 incremented, spilling it is worse, so we want to make
2275 that less likely. */
2276 REG_N_REFS (regno) += loop_depth;
2278 /* Count the increment as a setting of the register,
2279 even though it isn't a SET in rtl. */
2280 REG_N_SETS (regno)++;
2285 #endif /* AUTO_INC_DEC */
2287 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2288 This is done assuming the registers needed from X
2289 are those that have 1-bits in NEEDED.
2291 On the final pass, FINAL is 1. This means try for autoincrement
2292 and count the uses and deaths of each pseudo-reg.
2294 INSN is the containing instruction. If INSN is dead, this function is not
2298 mark_used_regs (needed, live, x, final, insn)
2305 register RTX_CODE code;
2310 code = GET_CODE (x);
2331 /* If we are clobbering a MEM, mark any registers inside the address
2333 if (GET_CODE (XEXP (x, 0)) == MEM)
2334 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2338 /* CYGNUS LOCAL dje/8176 */
2339 /* Invalidate the data for the last MEM stored, but only if MEM is
2340 something that can be stored into. */
2341 if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
2342 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
2343 ; /* needn't clear last_mem_set */
2346 /* END CYGNUS LOCAL */
2350 find_auto_inc (needed, x, insn);
2355 if (GET_CODE (SUBREG_REG (x)) == REG
2356 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2357 && (GET_MODE_SIZE (GET_MODE (x))
2358 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))))
2359 REG_CHANGES_SIZE (REGNO (SUBREG_REG (x))) = 1;
2361 /* While we're here, optimize this case. */
2364 /* In case the SUBREG is not of a register, don't optimize */
2365 if (GET_CODE (x) != REG)
2367 mark_used_regs (needed, live, x, final, insn);
2371 /* ... fall through ... */
2374 /* See a register other than being set
2375 => mark it as needed. */
2379 REGSET_ELT_TYPE some_needed = REGNO_REG_SET_P (needed, regno);
2380 REGSET_ELT_TYPE some_not_needed = ! some_needed;
2382 SET_REGNO_REG_SET (live, regno);
2384 /* A hard reg in a wide mode may really be multiple registers.
2385 If so, mark all of them just like the first. */
2386 if (regno < FIRST_PSEUDO_REGISTER)
2390 /* For stack ptr or fixed arg pointer,
2391 nothing below can be necessary, so waste no more time. */
2392 if (regno == STACK_POINTER_REGNUM
2393 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2394 || regno == HARD_FRAME_POINTER_REGNUM
2396 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2397 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2399 || regno == FRAME_POINTER_REGNUM)
2401 /* If this is a register we are going to try to eliminate,
2402 don't mark it live here. If we are successful in
2403 eliminating it, it need not be live unless it is used for
2404 pseudos, in which case it will have been set live when
2405 it was allocated to the pseudos. If the register will not
2406 be eliminated, reload will set it live at that point. */
2408 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2409 regs_ever_live[regno] = 1;
2412 /* No death notes for global register variables;
2413 their values are live after this function exits. */
2414 if (global_regs[regno])
2417 reg_next_use[regno] = insn;
2421 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2424 int regno_n = regno + n;
2425 int needed_regno = REGNO_REG_SET_P (needed, regno_n);
2427 SET_REGNO_REG_SET (live, regno_n);
2428 some_needed |= needed_regno;
2429 some_not_needed |= ! needed_regno;
2434 /* Record where each reg is used, so when the reg
2435 is set we know the next insn that uses it. */
2437 reg_next_use[regno] = insn;
2439 if (regno < FIRST_PSEUDO_REGISTER)
2441 /* If a hard reg is being used,
2442 record that this function does use it. */
2444 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2448 regs_ever_live[regno + --i] = 1;
2453 /* Keep track of which basic block each reg appears in. */
2455 register int blocknum = BLOCK_NUM (insn);
2457 if (REG_BASIC_BLOCK (regno) == REG_BLOCK_UNKNOWN)
2458 REG_BASIC_BLOCK (regno) = blocknum;
2459 else if (REG_BASIC_BLOCK (regno) != blocknum)
2460 REG_BASIC_BLOCK (regno) = REG_BLOCK_GLOBAL;
2462 /* Count (weighted) number of uses of each reg. */
2464 REG_N_REFS (regno) += loop_depth;
2467 /* Record and count the insns in which a reg dies.
2468 If it is used in this insn and was dead below the insn
2469 then it dies in this insn. If it was set in this insn,
2470 we do not make a REG_DEAD note; likewise if we already
2471 made such a note. */
2474 && ! dead_or_set_p (insn, x)
2476 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2480 /* Check for the case where the register dying partially
2481 overlaps the register set by this insn. */
2482 if (regno < FIRST_PSEUDO_REGISTER
2483 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2485 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2487 some_needed |= dead_or_set_regno_p (insn, regno + n);
2490 /* If none of the words in X is needed, make a REG_DEAD
2491 note. Otherwise, we must make partial REG_DEAD notes. */
2495 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2496 REG_N_DEATHS (regno)++;
2502 /* Don't make a REG_DEAD note for a part of a register
2503 that is set in the insn. */
2505 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2507 if (!REGNO_REG_SET_P (needed, regno + i)
2508 && ! dead_or_set_regno_p (insn, regno + i))
2510 = gen_rtx (EXPR_LIST, REG_DEAD,
2511 gen_rtx (REG, reg_raw_mode[regno + i],
2522 register rtx testreg = SET_DEST (x);
2525 /* If storing into MEM, don't show it as being used. But do
2526 show the address as being used. */
2527 if (GET_CODE (testreg) == MEM)
2531 find_auto_inc (needed, testreg, insn);
2533 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2534 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2538 /* Storing in STRICT_LOW_PART is like storing in a reg
2539 in that this SET might be dead, so ignore it in TESTREG.
2540 but in some other ways it is like using the reg.
2542 Storing in a SUBREG or a bit field is like storing the entire
2543 register in that if the register's value is not used
2544 then this SET is not needed. */
2545 while (GET_CODE (testreg) == STRICT_LOW_PART
2546 || GET_CODE (testreg) == ZERO_EXTRACT
2547 || GET_CODE (testreg) == SIGN_EXTRACT
2548 || GET_CODE (testreg) == SUBREG)
2550 if (GET_CODE (testreg) == SUBREG
2551 && GET_CODE (SUBREG_REG (testreg)) == REG
2552 && REGNO (SUBREG_REG (testreg)) >= FIRST_PSEUDO_REGISTER
2553 && (GET_MODE_SIZE (GET_MODE (testreg))
2554 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (testreg)))))
2555 REG_CHANGES_SIZE (REGNO (SUBREG_REG (testreg))) = 1;
2557 /* Modifying a single register in an alternate mode
2558 does not use any of the old value. But these other
2559 ways of storing in a register do use the old value. */
2560 if (GET_CODE (testreg) == SUBREG
2561 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2566 testreg = XEXP (testreg, 0);
2569 /* If this is a store into a register,
2570 recursively scan the value being stored. */
2572 if (GET_CODE (testreg) == REG
2573 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2574 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2575 && regno != HARD_FRAME_POINTER_REGNUM
2577 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2578 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2581 /* We used to exclude global_regs here, but that seems wrong.
2582 Storing in them is like storing in mem. */
2584 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2586 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2593 /* If exiting needs the right stack value, consider this insn as
2594 using the stack pointer. In any event, consider it as using
2595 all global registers and all registers used by return. */
2597 #ifdef EXIT_IGNORE_STACK
2598 if (! EXIT_IGNORE_STACK
2599 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2601 SET_REGNO_REG_SET (live, STACK_POINTER_REGNUM);
2603 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2605 #ifdef EPILOGUE_USES
2606 || EPILOGUE_USES (i)
2609 SET_REGNO_REG_SET (live, i);
2613 /* Recursively scan the operands of this expression. */
2616 register char *fmt = GET_RTX_FORMAT (code);
2619 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2623 /* Tail recursive case: save a function call level. */
2629 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2631 else if (fmt[i] == 'E')
2634 for (j = 0; j < XVECLEN (x, i); j++)
2635 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2644 try_pre_increment_1 (insn)
2647 /* Find the next use of this reg. If in same basic block,
2648 make it do pre-increment or pre-decrement if appropriate. */
2649 rtx x = PATTERN (insn);
2650 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2651 * INTVAL (XEXP (SET_SRC (x), 1)));
2652 int regno = REGNO (SET_DEST (x));
2653 rtx y = reg_next_use[regno];
2655 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2656 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2657 mode would be better. */
2658 && ! dead_or_set_p (y, SET_DEST (x))
2659 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2662 /* We have found a suitable auto-increment
2663 and already changed insn Y to do it.
2664 So flush this increment-instruction. */
2665 PUT_CODE (insn, NOTE);
2666 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2667 NOTE_SOURCE_FILE (insn) = 0;
2668 /* Count a reference to this reg for the increment
2669 insn we are deleting. When a reg is incremented.
2670 spilling it is worse, so we want to make that
2672 if (regno >= FIRST_PSEUDO_REGISTER)
2674 REG_N_REFS (regno) += loop_depth;
2675 REG_N_SETS (regno)++;
2682 /* Try to change INSN so that it does pre-increment or pre-decrement
2683 addressing on register REG in order to add AMOUNT to REG.
2684 AMOUNT is negative for pre-decrement.
2685 Returns 1 if the change could be made.
2686 This checks all about the validity of the result of modifying INSN. */
2689 try_pre_increment (insn, reg, amount)
2691 HOST_WIDE_INT amount;
2695 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2696 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2698 /* Nonzero if we can try to make a post-increment or post-decrement.
2699 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2700 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2701 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2704 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2707 /* From the sign of increment, see which possibilities are conceivable
2708 on this target machine. */
2709 #ifdef HAVE_PRE_INCREMENT
2713 #ifdef HAVE_POST_INCREMENT
2718 #ifdef HAVE_PRE_DECREMENT
2722 #ifdef HAVE_POST_DECREMENT
2727 if (! (pre_ok || post_ok))
2730 /* It is not safe to add a side effect to a jump insn
2731 because if the incremented register is spilled and must be reloaded
2732 there would be no way to store the incremented value back in memory. */
2734 if (GET_CODE (insn) == JUMP_INSN)
2739 use = find_use_as_address (PATTERN (insn), reg, 0);
2740 if (post_ok && (use == 0 || use == (rtx) 1))
2742 use = find_use_as_address (PATTERN (insn), reg, -amount);
2746 if (use == 0 || use == (rtx) 1)
2749 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2752 /* See if this combination of instruction and addressing mode exists. */
2753 if (! validate_change (insn, &XEXP (use, 0),
2755 ? (do_post ? POST_INC : PRE_INC)
2756 : (do_post ? POST_DEC : PRE_DEC),
2760 /* Record that this insn now has an implicit side effect on X. */
2761 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2765 #endif /* AUTO_INC_DEC */
2767 /* Find the place in the rtx X where REG is used as a memory address.
2768 Return the MEM rtx that so uses it.
2769 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2770 (plus REG (const_int PLUSCONST)).
2772 If such an address does not appear, return 0.
2773 If REG appears more than once, or is used other than in such an address,
2777 find_use_as_address (x, reg, plusconst)
2780 HOST_WIDE_INT plusconst;
2782 enum rtx_code code = GET_CODE (x);
2783 char *fmt = GET_RTX_FORMAT (code);
2785 register rtx value = 0;
2788 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2791 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2792 && XEXP (XEXP (x, 0), 0) == reg
2793 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2794 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2797 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2799 /* If REG occurs inside a MEM used in a bit-field reference,
2800 that is unacceptable. */
2801 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2802 return (rtx) (HOST_WIDE_INT) 1;
2806 return (rtx) (HOST_WIDE_INT) 1;
2808 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2812 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2816 return (rtx) (HOST_WIDE_INT) 1;
2821 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2823 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2827 return (rtx) (HOST_WIDE_INT) 1;
2835 /* Write information about registers and basic blocks into FILE.
2836 This is part of making a debugging dump. */
2839 dump_flow_info (file)
2843 static char *reg_class_names[] = REG_CLASS_NAMES;
2845 fprintf (file, "%d registers.\n", max_regno);
2847 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2850 enum reg_class class, altclass;
2851 fprintf (file, "\nRegister %d used %d times across %d insns",
2852 i, REG_N_REFS (i), REG_LIVE_LENGTH (i));
2853 if (REG_BASIC_BLOCK (i) >= 0)
2854 fprintf (file, " in block %d", REG_BASIC_BLOCK (i));
2855 if (REG_N_DEATHS (i) != 1)
2856 fprintf (file, "; dies in %d places", REG_N_DEATHS (i));
2857 if (REG_N_CALLS_CROSSED (i) == 1)
2858 fprintf (file, "; crosses 1 call");
2859 else if (REG_N_CALLS_CROSSED (i))
2860 fprintf (file, "; crosses %d calls", REG_N_CALLS_CROSSED (i));
2861 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2862 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2863 class = reg_preferred_class (i);
2864 altclass = reg_alternate_class (i);
2865 if (class != GENERAL_REGS || altclass != ALL_REGS)
2867 if (altclass == ALL_REGS || class == ALL_REGS)
2868 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2869 else if (altclass == NO_REGS)
2870 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2872 fprintf (file, "; pref %s, else %s",
2873 reg_class_names[(int) class],
2874 reg_class_names[(int) altclass]);
2876 if (REGNO_POINTER_FLAG (i))
2877 fprintf (file, "; pointer");
2878 fprintf (file, ".\n");
2880 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2881 for (i = 0; i < n_basic_blocks; i++)
2883 register rtx head, jump;
2885 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2887 INSN_UID (basic_block_head[i]),
2888 INSN_UID (basic_block_end[i]));
2889 /* The control flow graph's storage is freed
2890 now when flow_analysis returns.
2891 Don't try to print it if it is gone. */
2892 if (basic_block_drops_in)
2894 fprintf (file, "Reached from blocks: ");
2895 head = basic_block_head[i];
2896 if (GET_CODE (head) == CODE_LABEL)
2897 for (jump = LABEL_REFS (head);
2899 jump = LABEL_NEXTREF (jump))
2901 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2902 fprintf (file, " %d", from_block);
2904 if (basic_block_drops_in[i])
2905 fprintf (file, " previous");
2907 fprintf (file, "\nRegisters live at start:");
2908 for (regno = 0; regno < max_regno; regno++)
2909 if (REGNO_REG_SET_P (basic_block_live_at_start[i], regno))
2910 fprintf (file, " %d", regno);
2911 fprintf (file, "\n");
2913 fprintf (file, "\n");
OSDN Git Service
