1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 88, 92, 93, 94, 95, 1996 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"
122 #define obstack_chunk_alloc xmalloc
123 #define obstack_chunk_free free
125 /* List of labels that must never be deleted. */
126 extern rtx forced_labels;
128 /* Get the basic block number of an insn.
129 This info should not be expected to remain available
130 after the end of life_analysis. */
132 /* This is the limit of the allocated space in the following two arrays. */
134 static int max_uid_for_flow;
136 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
138 /* This is where the BLOCK_NUM values are really stored.
139 This is set up by find_basic_blocks and used there and in life_analysis,
142 static int *uid_block_number;
144 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
146 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
147 static char *uid_volatile;
149 /* Number of basic blocks in the current function. */
153 /* Maximum register number used in this function, plus one. */
157 /* Maximum number of SCRATCH rtx's used in any basic block of this function. */
161 /* Number of SCRATCH rtx's in the current block. */
163 static int num_scratch;
165 /* Indexed by n, gives number of basic block that (REG n) is used in.
166 If the value is REG_BLOCK_GLOBAL (-2),
167 it means (REG n) is used in more than one basic block.
168 REG_BLOCK_UNKNOWN (-1) means it hasn't been seen yet so we don't know.
169 This information remains valid for the rest of the compilation
170 of the current function; it is used to control register allocation. */
172 int *reg_basic_block;
174 /* Indexed by n, gives number of times (REG n) is used or set, each
175 weighted by its loop-depth.
176 This information remains valid for the rest of the compilation
177 of the current function; it is used to control register allocation. */
181 /* Indexed by N; says whether a pseudo register N was ever used
182 within a SUBREG that changes the size of the reg. Some machines prohibit
183 such objects to be in certain (usually floating-point) registers. */
185 char *reg_changes_size;
187 /* Indexed by N, gives number of places register N dies.
188 This information remains valid for the rest of the compilation
189 of the current function; it is used to control register allocation. */
193 /* Indexed by N, gives 1 if that reg is live across any CALL_INSNs.
194 This information remains valid for the rest of the compilation
195 of the current function; it is used to control register allocation. */
197 int *reg_n_calls_crossed;
199 /* Total number of instructions at which (REG n) is live.
200 The larger this is, the less priority (REG n) gets for
201 allocation in a real register.
202 This information remains valid for the rest of the compilation
203 of the current function; it is used to control register allocation.
205 local-alloc.c may alter this number to change the priority.
207 Negative values are special.
208 -1 is used to mark a pseudo reg which has a constant or memory equivalent
209 and is used infrequently enough that it should not get a hard register.
210 -2 is used to mark a pseudo reg for a parameter, when a frame pointer
211 is not required. global.c makes an allocno for this but does
212 not try to assign a hard register to it. */
214 int *reg_live_length;
216 /* Element N is the next insn that uses (hard or pseudo) register number N
217 within the current basic block; or zero, if there is no such insn.
218 This is valid only during the final backward scan in propagate_block. */
220 static rtx *reg_next_use;
222 /* Size of a regset for the current function,
223 in (1) bytes and (2) elements. */
228 /* Element N is first insn in basic block N.
229 This info lasts until we finish compiling the function. */
231 rtx *basic_block_head;
233 /* Element N is last insn in basic block N.
234 This info lasts until we finish compiling the function. */
236 rtx *basic_block_end;
238 /* Element N is a regset describing the registers live
239 at the start of basic block N.
240 This info lasts until we finish compiling the function. */
242 regset *basic_block_live_at_start;
244 /* Regset of regs live when calls to `setjmp'-like functions happen. */
246 regset regs_live_at_setjmp;
248 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
249 that have to go in the same hard reg.
250 The first two regs in the list are a pair, and the next two
251 are another pair, etc. */
254 /* Element N is nonzero if control can drop into basic block N
255 from the preceding basic block. Freed after life_analysis. */
257 static char *basic_block_drops_in;
259 /* Element N is depth within loops of the last insn in basic block number N.
260 Freed after life_analysis. */
262 static short *basic_block_loop_depth;
264 /* Element N nonzero if basic block N can actually be reached.
265 Vector exists only during find_basic_blocks. */
267 static char *block_live_static;
269 /* Depth within loops of basic block being scanned for lifetime analysis,
270 plus one. This is the weight attached to references to registers. */
272 static int loop_depth;
274 /* During propagate_block, this is non-zero if the value of CC0 is live. */
278 /* During propagate_block, this contains the last MEM stored into. It
279 is used to eliminate consecutive stores to the same location. */
281 static rtx last_mem_set;
283 /* Set of registers that may be eliminable. These are handled specially
284 in updating regs_ever_live. */
286 static HARD_REG_SET elim_reg_set;
288 /* Forward declarations */
289 static void find_basic_blocks PROTO((rtx, rtx));
290 static int jmp_uses_reg_or_mem PROTO((rtx));
291 static void mark_label_ref PROTO((rtx, rtx, int));
292 static void life_analysis PROTO((rtx, int));
293 void allocate_for_life_analysis PROTO((void));
294 static void init_regset_vector PROTO((regset *, regset, int, int));
295 static void propagate_block PROTO((regset, rtx, rtx, int,
297 static rtx flow_delete_insn PROTO((rtx));
298 static int insn_dead_p PROTO((rtx, regset, int));
299 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
300 static void mark_set_regs PROTO((regset, regset, rtx,
302 static void mark_set_1 PROTO((regset, regset, rtx,
304 static void find_auto_inc PROTO((regset, rtx, rtx));
305 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
306 static int try_pre_increment_1 PROTO((rtx));
307 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
308 static rtx find_use_as_address PROTO((rtx, rtx, HOST_WIDE_INT));
309 void dump_flow_info PROTO((FILE *));
311 /* Find basic blocks of the current function and perform data flow analysis.
312 F is the first insn of the function and NREGS the number of register numbers
316 flow_analysis (f, nregs, file)
323 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
325 #ifdef ELIMINABLE_REGS
326 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
329 /* Record which registers will be eliminated. We use this in
332 CLEAR_HARD_REG_SET (elim_reg_set);
334 #ifdef ELIMINABLE_REGS
335 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
336 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
338 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
341 /* Count the basic blocks. Also find maximum insn uid value used. */
344 register RTX_CODE prev_code = JUMP_INSN;
345 register RTX_CODE code;
347 max_uid_for_flow = 0;
349 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
351 code = GET_CODE (insn);
352 if (INSN_UID (insn) > max_uid_for_flow)
353 max_uid_for_flow = INSN_UID (insn);
354 if (code == CODE_LABEL
355 || (GET_RTX_CLASS (code) == 'i'
356 && (prev_code == JUMP_INSN
357 || (prev_code == CALL_INSN
358 && nonlocal_label_list != 0)
359 || prev_code == BARRIER)))
362 if (code == CALL_INSN && find_reg_note (insn, REG_RETVAL, NULL_RTX))
371 /* Leave space for insns we make in some cases for auto-inc. These cases
372 are rare, so we don't need too much space. */
373 max_uid_for_flow += max_uid_for_flow / 10;
376 /* Allocate some tables that last till end of compiling this function
377 and some needed only in find_basic_blocks and life_analysis. */
380 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
381 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
382 basic_block_drops_in = (char *) alloca (n_basic_blocks);
383 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
385 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
386 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
387 bzero (uid_volatile, max_uid_for_flow + 1);
389 find_basic_blocks (f, nonlocal_label_list);
390 life_analysis (f, nregs);
392 dump_flow_info (file);
394 basic_block_drops_in = 0;
395 uid_block_number = 0;
396 basic_block_loop_depth = 0;
399 /* Find all basic blocks of the function whose first insn is F.
400 Store the correct data in the tables that describe the basic blocks,
401 set up the chains of references for each CODE_LABEL, and
402 delete any entire basic blocks that cannot be reached.
404 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
407 find_basic_blocks (f, nonlocal_label_list)
408 rtx f, nonlocal_label_list;
412 register char *block_live = (char *) alloca (n_basic_blocks);
413 register char *block_marked = (char *) alloca (n_basic_blocks);
414 /* List of label_refs to all labels whose addresses are taken
416 rtx label_value_list;
418 enum rtx_code prev_code, code;
424 label_value_list = 0;
425 block_live_static = block_live;
426 bzero (block_live, n_basic_blocks);
427 bzero (block_marked, n_basic_blocks);
429 /* Initialize with just block 0 reachable and no blocks marked. */
430 if (n_basic_blocks > 0)
433 /* Initialize the ref chain of each label to 0. Record where all the
434 blocks start and end and their depth in loops. For each insn, record
435 the block it is in. Also mark as reachable any blocks headed by labels
436 that must not be deleted. */
438 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
439 insn; insn = NEXT_INSN (insn))
441 code = GET_CODE (insn);
444 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
446 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
450 /* A basic block starts at label, or after something that can jump. */
451 else if (code == CODE_LABEL
452 || (GET_RTX_CLASS (code) == 'i'
453 && (prev_code == JUMP_INSN
454 || (prev_code == CALL_INSN
455 && nonlocal_label_list != 0
456 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
457 || prev_code == BARRIER)))
459 basic_block_head[++i] = insn;
460 basic_block_end[i] = insn;
461 basic_block_loop_depth[i] = depth;
463 if (code == CODE_LABEL)
465 LABEL_REFS (insn) = insn;
466 /* Any label that cannot be deleted
467 is considered to start a reachable block. */
468 if (LABEL_PRESERVE_P (insn))
473 else if (GET_RTX_CLASS (code) == 'i')
475 basic_block_end[i] = insn;
476 basic_block_loop_depth[i] = depth;
479 if (GET_RTX_CLASS (code) == 'i')
481 /* Make a list of all labels referred to other than by jumps. */
482 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
483 if (REG_NOTE_KIND (note) == REG_LABEL)
484 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
488 BLOCK_NUM (insn) = i;
494 /* During the second pass, `n_basic_blocks' is only an upper bound.
495 Only perform the sanity check for the first pass, and on the second
496 pass ensure `n_basic_blocks' is set to the correct value. */
497 if (pass == 1 && i + 1 != n_basic_blocks)
499 n_basic_blocks = i + 1;
501 /* Don't delete the labels (in this function)
502 that are referenced by non-jump instructions. */
504 for (x = label_value_list; x; x = XEXP (x, 1))
505 if (! LABEL_REF_NONLOCAL_P (x))
506 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
508 for (x = forced_labels; x; x = XEXP (x, 1))
509 if (! LABEL_REF_NONLOCAL_P (x))
510 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
512 /* Record which basic blocks control can drop in to. */
514 for (i = 0; i < n_basic_blocks; i++)
516 for (insn = PREV_INSN (basic_block_head[i]);
517 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
520 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
523 /* Now find which basic blocks can actually be reached
524 and put all jump insns' LABEL_REFS onto the ref-chains
525 of their target labels. */
527 if (n_basic_blocks > 0)
529 int something_marked = 1;
532 /* Find all indirect jump insns and mark them as possibly jumping to all
533 the labels whose addresses are explicitly used. This is because,
534 when there are computed gotos, we can't tell which labels they jump
535 to, of all the possibilities.
537 Tablejumps and casesi insns are OK and we can recognize them by
538 a (use (label_ref)). */
540 for (insn = f; insn; insn = NEXT_INSN (insn))
541 if (GET_CODE (insn) == JUMP_INSN)
543 rtx pat = PATTERN (insn);
544 int computed_jump = 0;
546 if (GET_CODE (pat) == PARALLEL)
548 int len = XVECLEN (pat, 0);
549 int has_use_labelref = 0;
551 for (i = len - 1; i >= 0; i--)
552 if (GET_CODE (XVECEXP (pat, 0, i)) == USE
553 && (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
555 has_use_labelref = 1;
557 if (! has_use_labelref)
558 for (i = len - 1; i >= 0; i--)
559 if (GET_CODE (XVECEXP (pat, 0, i)) == SET
560 && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
561 && jmp_uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
564 else if (GET_CODE (pat) == SET
565 && SET_DEST (pat) == pc_rtx
566 && jmp_uses_reg_or_mem (SET_SRC (pat)))
571 for (x = label_value_list; x; x = XEXP (x, 1))
572 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
575 for (x = forced_labels; x; x = XEXP (x, 1))
576 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
581 /* Find all call insns and mark them as possibly jumping
582 to all the nonlocal goto handler labels. */
584 for (insn = f; insn; insn = NEXT_INSN (insn))
585 if (GET_CODE (insn) == CALL_INSN
586 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
588 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
589 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
592 /* ??? This could be made smarter:
593 in some cases it's possible to tell that certain
594 calls will not do a nonlocal goto.
596 For example, if the nested functions that do the
597 nonlocal gotos do not have their addresses taken, then
598 only calls to those functions or to other nested
599 functions that use them could possibly do nonlocal
603 /* Pass over all blocks, marking each block that is reachable
604 and has not yet been marked.
605 Keep doing this until, in one pass, no blocks have been marked.
606 Then blocks_live and blocks_marked are identical and correct.
607 In addition, all jumps actually reachable have been marked. */
609 while (something_marked)
611 something_marked = 0;
612 for (i = 0; i < n_basic_blocks; i++)
613 if (block_live[i] && !block_marked[i])
616 something_marked = 1;
617 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
618 block_live[i + 1] = 1;
619 insn = basic_block_end[i];
620 if (GET_CODE (insn) == JUMP_INSN)
621 mark_label_ref (PATTERN (insn), insn, 0);
625 /* ??? See if we have a "live" basic block that is not reachable.
626 This can happen if it is headed by a label that is preserved or
627 in one of the label lists, but no call or computed jump is in
628 the loop. It's not clear if we can delete the block or not,
629 but don't for now. However, we will mess up register status if
630 it remains unreachable, so add a fake reachability from the
633 for (i = 1; i < n_basic_blocks; i++)
634 if (block_live[i] && ! basic_block_drops_in[i]
635 && GET_CODE (basic_block_head[i]) == CODE_LABEL
636 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
637 basic_block_drops_in[i] = 1;
639 /* Now delete the code for any basic blocks that can't be reached.
640 They can occur because jump_optimize does not recognize
641 unreachable loops as unreachable. */
644 for (i = 0; i < n_basic_blocks; i++)
649 /* Delete the insns in a (non-live) block. We physically delete
650 every non-note insn except the start and end (so
651 basic_block_head/end needn't be updated), we turn the latter
652 into NOTE_INSN_DELETED notes.
653 We use to "delete" the insns by turning them into notes, but
654 we may be deleting lots of insns that subsequent passes would
655 otherwise have to process. Secondly, lots of deleted blocks in
656 a row can really slow down propagate_block since it will
657 otherwise process insn-turned-notes multiple times when it
658 looks for loop begin/end notes. */
659 if (basic_block_head[i] != basic_block_end[i])
661 /* It would be quicker to delete all of these with a single
662 unchaining, rather than one at a time, but we need to keep
664 insn = NEXT_INSN (basic_block_head[i]);
665 while (insn != basic_block_end[i])
667 if (GET_CODE (insn) == BARRIER)
669 else if (GET_CODE (insn) != NOTE)
670 insn = flow_delete_insn (insn);
672 insn = NEXT_INSN (insn);
675 insn = basic_block_head[i];
676 if (GET_CODE (insn) != NOTE)
678 /* Turn the head into a deleted insn note. */
679 if (GET_CODE (insn) == BARRIER)
681 PUT_CODE (insn, NOTE);
682 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
683 NOTE_SOURCE_FILE (insn) = 0;
685 insn = basic_block_end[i];
686 if (GET_CODE (insn) != NOTE)
688 /* Turn the tail into a deleted insn note. */
689 if (GET_CODE (insn) == BARRIER)
691 PUT_CODE (insn, NOTE);
692 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
693 NOTE_SOURCE_FILE (insn) = 0;
695 /* BARRIERs are between basic blocks, not part of one.
696 Delete a BARRIER if the preceding jump is deleted.
697 We cannot alter a BARRIER into a NOTE
698 because it is too short; but we can really delete
699 it because it is not part of a basic block. */
700 if (NEXT_INSN (insn) != 0
701 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
702 delete_insn (NEXT_INSN (insn));
704 /* Each time we delete some basic blocks,
705 see if there is a jump around them that is
706 being turned into a no-op. If so, delete it. */
708 if (block_live[i - 1])
711 for (j = i + 1; j < n_basic_blocks; j++)
715 insn = basic_block_end[i - 1];
716 if (GET_CODE (insn) == JUMP_INSN
717 /* An unconditional jump is the only possibility
718 we must check for, since a conditional one
719 would make these blocks live. */
720 && simplejump_p (insn)
721 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
722 && INSN_UID (label) != 0
723 && BLOCK_NUM (label) == j)
725 PUT_CODE (insn, NOTE);
726 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
727 NOTE_SOURCE_FILE (insn) = 0;
728 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
730 delete_insn (NEXT_INSN (insn));
737 /* There are pathological cases where one function calling hundreds of
738 nested inline functions can generate lots and lots of unreachable
739 blocks that jump can't delete. Since we don't use sparse matrices
740 a lot of memory will be needed to compile such functions.
741 Implementing sparse matrices is a fair bit of work and it is not
742 clear that they win more than they lose (we don't want to
743 unnecessarily slow down compilation of normal code). By making
744 another pass for the pathological case, we can greatly speed up
745 their compilation without hurting normal code. This works because
746 all the insns in the unreachable blocks have either been deleted or
748 Note that we're talking about reducing memory usage by 10's of
749 megabytes and reducing compilation time by several minutes. */
750 /* ??? The choice of when to make another pass is a bit arbitrary,
751 and was derived from empirical data. */
756 n_basic_blocks -= deleted;
757 /* `n_basic_blocks' may not be correct at this point: two previously
758 separate blocks may now be merged. That's ok though as we
759 recalculate it during the second pass. It certainly can't be
760 any larger than the current value. */
766 /* Subroutines of find_basic_blocks. */
768 /* Return 1 if X, the SRC_SRC of SET of (pc) contain a REG or MEM that is
769 not in the constant pool and not in the condition of an IF_THEN_ELSE. */
772 jmp_uses_reg_or_mem (x)
775 enum rtx_code code = GET_CODE (x);
790 return ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
791 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)));
794 return (jmp_uses_reg_or_mem (XEXP (x, 1))
795 || jmp_uses_reg_or_mem (XEXP (x, 2)));
797 case PLUS: case MINUS: case MULT:
798 return (jmp_uses_reg_or_mem (XEXP (x, 0))
799 || jmp_uses_reg_or_mem (XEXP (x, 1)));
802 fmt = GET_RTX_FORMAT (code);
803 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
806 && jmp_uses_reg_or_mem (XEXP (x, i)))
810 for (j = 0; j < XVECLEN (x, i); j++)
811 if (jmp_uses_reg_or_mem (XVECEXP (x, i, j)))
818 /* Check expression X for label references;
819 if one is found, add INSN to the label's chain of references.
821 CHECKDUP means check for and avoid creating duplicate references
822 from the same insn. Such duplicates do no serious harm but
823 can slow life analysis. CHECKDUP is set only when duplicates
827 mark_label_ref (x, insn, checkdup)
831 register RTX_CODE code;
835 /* We can be called with NULL when scanning label_value_list. */
840 if (code == LABEL_REF)
842 register rtx label = XEXP (x, 0);
844 if (GET_CODE (label) != CODE_LABEL)
846 /* If the label was never emitted, this insn is junk,
847 but avoid a crash trying to refer to BLOCK_NUM (label).
848 This can happen as a result of a syntax error
849 and a diagnostic has already been printed. */
850 if (INSN_UID (label) == 0)
852 CONTAINING_INSN (x) = insn;
853 /* if CHECKDUP is set, check for duplicate ref from same insn
856 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
857 if (CONTAINING_INSN (y) == insn)
859 LABEL_NEXTREF (x) = LABEL_REFS (label);
860 LABEL_REFS (label) = x;
861 block_live_static[BLOCK_NUM (label)] = 1;
865 fmt = GET_RTX_FORMAT (code);
866 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
869 mark_label_ref (XEXP (x, i), insn, 0);
873 for (j = 0; j < XVECLEN (x, i); j++)
874 mark_label_ref (XVECEXP (x, i, j), insn, 1);
879 /* Delete INSN by patching it out.
880 Return the next insn. */
883 flow_delete_insn (insn)
886 /* ??? For the moment we assume we don't have to watch for NULLs here
887 since the start/end of basic blocks aren't deleted like this. */
888 NEXT_INSN (PREV_INSN (insn)) = NEXT_INSN (insn);
889 PREV_INSN (NEXT_INSN (insn)) = PREV_INSN (insn);
890 return NEXT_INSN (insn);
893 /* Determine which registers are live at the start of each
894 basic block of the function whose first insn is F.
895 NREGS is the number of registers used in F.
896 We allocate the vector basic_block_live_at_start
897 and the regsets that it points to, and fill them with the data.
898 regset_size and regset_bytes are also set here. */
901 life_analysis (f, nregs)
908 /* For each basic block, a bitmask of regs
909 live on exit from the block. */
910 regset *basic_block_live_at_end;
911 /* For each basic block, a bitmask of regs
912 live on entry to a successor-block of this block.
913 If this does not match basic_block_live_at_end,
914 that must be updated, and the block must be rescanned. */
915 regset *basic_block_new_live_at_end;
916 /* For each basic block, a bitmask of regs
917 whose liveness at the end of the basic block
918 can make a difference in which regs are live on entry to the block.
919 These are the regs that are set within the basic block,
920 possibly excluding those that are used after they are set. */
921 regset *basic_block_significant;
925 struct obstack flow_obstack;
927 gcc_obstack_init (&flow_obstack);
931 bzero (regs_ever_live, sizeof regs_ever_live);
933 /* Allocate and zero out many data structures
934 that will record the data from lifetime analysis. */
936 allocate_for_life_analysis ();
938 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
939 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
941 /* Set up several regset-vectors used internally within this function.
942 Their meanings are documented above, with their declarations. */
944 basic_block_live_at_end
945 = (regset *) alloca (n_basic_blocks * sizeof (regset));
947 /* Don't use alloca since that leads to a crash rather than an error message
948 if there isn't enough space.
949 Don't use oballoc since we may need to allocate other things during
950 this function on the temporary obstack. */
951 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
952 bzero ((char *) tem, n_basic_blocks * regset_bytes);
953 init_regset_vector (basic_block_live_at_end, tem,
954 n_basic_blocks, regset_bytes);
956 basic_block_new_live_at_end
957 = (regset *) alloca (n_basic_blocks * sizeof (regset));
958 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
959 bzero ((char *) tem, n_basic_blocks * regset_bytes);
960 init_regset_vector (basic_block_new_live_at_end, tem,
961 n_basic_blocks, regset_bytes);
963 basic_block_significant
964 = (regset *) alloca (n_basic_blocks * sizeof (regset));
965 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
966 bzero ((char *) tem, n_basic_blocks * regset_bytes);
967 init_regset_vector (basic_block_significant, tem,
968 n_basic_blocks, regset_bytes);
970 /* Record which insns refer to any volatile memory
971 or for any reason can't be deleted just because they are dead stores.
972 Also, delete any insns that copy a register to itself. */
974 for (insn = f; insn; insn = NEXT_INSN (insn))
976 enum rtx_code code1 = GET_CODE (insn);
977 if (code1 == CALL_INSN)
978 INSN_VOLATILE (insn) = 1;
979 else if (code1 == INSN || code1 == JUMP_INSN)
981 /* Delete (in effect) any obvious no-op moves. */
982 if (GET_CODE (PATTERN (insn)) == SET
983 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
984 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
985 && REGNO (SET_DEST (PATTERN (insn))) ==
986 REGNO (SET_SRC (PATTERN (insn)))
987 /* Insns carrying these notes are useful later on. */
988 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
990 PUT_CODE (insn, NOTE);
991 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
992 NOTE_SOURCE_FILE (insn) = 0;
994 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
996 /* If nothing but SETs of registers to themselves,
997 this insn can also be deleted. */
998 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
1000 rtx tem = XVECEXP (PATTERN (insn), 0, i);
1002 if (GET_CODE (tem) == USE
1003 || GET_CODE (tem) == CLOBBER)
1006 if (GET_CODE (tem) != SET
1007 || GET_CODE (SET_DEST (tem)) != REG
1008 || GET_CODE (SET_SRC (tem)) != REG
1009 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
1013 if (i == XVECLEN (PATTERN (insn), 0)
1014 /* Insns carrying these notes are useful later on. */
1015 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1017 PUT_CODE (insn, NOTE);
1018 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1019 NOTE_SOURCE_FILE (insn) = 0;
1022 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1024 else if (GET_CODE (PATTERN (insn)) != USE)
1025 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1026 /* A SET that makes space on the stack cannot be dead.
1027 (Such SETs occur only for allocating variable-size data,
1028 so they will always have a PLUS or MINUS according to the
1029 direction of stack growth.)
1030 Even if this function never uses this stack pointer value,
1031 signal handlers do! */
1032 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
1033 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1034 #ifdef STACK_GROWS_DOWNWARD
1035 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
1037 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1039 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
1040 INSN_VOLATILE (insn) = 1;
1044 if (n_basic_blocks > 0)
1045 #ifdef EXIT_IGNORE_STACK
1046 if (! EXIT_IGNORE_STACK
1047 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
1050 /* If exiting needs the right stack value,
1051 consider the stack pointer live at the end of the function. */
1052 basic_block_live_at_end[n_basic_blocks - 1]
1053 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1054 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1055 basic_block_new_live_at_end[n_basic_blocks - 1]
1056 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1057 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1060 /* Mark the frame pointer is needed at the end of the function. If
1061 we end up eliminating it, it will be removed from the live list
1062 of each basic block by reload. */
1064 if (n_basic_blocks > 0)
1066 basic_block_live_at_end[n_basic_blocks - 1]
1067 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1068 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
1069 basic_block_new_live_at_end[n_basic_blocks - 1]
1070 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1071 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
1072 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1073 /* If they are different, also mark the hard frame pointer as live */
1074 basic_block_live_at_end[n_basic_blocks - 1]
1075 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1076 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
1078 basic_block_new_live_at_end[n_basic_blocks - 1]
1079 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1080 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
1085 /* Mark all global registers as being live at the end of the function
1086 since they may be referenced by our caller. */
1088 if (n_basic_blocks > 0)
1089 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1092 basic_block_live_at_end[n_basic_blocks - 1]
1093 [i / REGSET_ELT_BITS]
1094 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
1095 basic_block_new_live_at_end[n_basic_blocks - 1]
1096 [i / REGSET_ELT_BITS]
1097 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
1100 /* Propagate life info through the basic blocks
1101 around the graph of basic blocks.
1103 This is a relaxation process: each time a new register
1104 is live at the end of the basic block, we must scan the block
1105 to determine which registers are, as a consequence, live at the beginning
1106 of that block. These registers must then be marked live at the ends
1107 of all the blocks that can transfer control to that block.
1108 The process continues until it reaches a fixed point. */
1115 for (i = n_basic_blocks - 1; i >= 0; i--)
1117 int consider = first_pass;
1118 int must_rescan = first_pass;
1123 /* Set CONSIDER if this block needs thinking about at all
1124 (that is, if the regs live now at the end of it
1125 are not the same as were live at the end of it when
1126 we last thought about it).
1127 Set must_rescan if it needs to be thought about
1128 instruction by instruction (that is, if any additional
1129 reg that is live at the end now but was not live there before
1130 is one of the significant regs of this basic block). */
1132 for (j = 0; j < regset_size; j++)
1134 register REGSET_ELT_TYPE x
1135 = (basic_block_new_live_at_end[i][j]
1136 & ~basic_block_live_at_end[i][j]);
1139 if (x & basic_block_significant[i][j])
1151 /* The live_at_start of this block may be changing,
1152 so another pass will be required after this one. */
1157 /* No complete rescan needed;
1158 just record those variables newly known live at end
1159 as live at start as well. */
1160 for (j = 0; j < regset_size; j++)
1162 register REGSET_ELT_TYPE x
1163 = (basic_block_new_live_at_end[i][j]
1164 & ~basic_block_live_at_end[i][j]);
1165 basic_block_live_at_start[i][j] |= x;
1166 basic_block_live_at_end[i][j] |= x;
1171 /* Update the basic_block_live_at_start
1172 by propagation backwards through the block. */
1173 bcopy ((char *) basic_block_new_live_at_end[i],
1174 (char *) basic_block_live_at_end[i], regset_bytes);
1175 bcopy ((char *) basic_block_live_at_end[i],
1176 (char *) basic_block_live_at_start[i], regset_bytes);
1177 propagate_block (basic_block_live_at_start[i],
1178 basic_block_head[i], basic_block_end[i], 0,
1179 first_pass ? basic_block_significant[i]
1185 register rtx jump, head;
1187 /* Update the basic_block_new_live_at_end's of the block
1188 that falls through into this one (if any). */
1189 head = basic_block_head[i];
1190 if (basic_block_drops_in[i])
1193 for (j = 0; j < regset_size; j++)
1194 basic_block_new_live_at_end[i-1][j]
1195 |= basic_block_live_at_start[i][j];
1198 /* Update the basic_block_new_live_at_end's of
1199 all the blocks that jump to this one. */
1200 if (GET_CODE (head) == CODE_LABEL)
1201 for (jump = LABEL_REFS (head);
1203 jump = LABEL_NEXTREF (jump))
1205 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1207 for (j = 0; j < regset_size; j++)
1208 basic_block_new_live_at_end[from_block][j]
1209 |= basic_block_live_at_start[i][j];
1219 /* The only pseudos that are live at the beginning of the function are
1220 those that were not set anywhere in the function. local-alloc doesn't
1221 know how to handle these correctly, so mark them as not local to any
1224 if (n_basic_blocks > 0)
1225 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1226 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1227 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1228 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1230 /* Now the life information is accurate.
1231 Make one more pass over each basic block
1232 to delete dead stores, create autoincrement addressing
1233 and record how many times each register is used, is set, or dies.
1235 To save time, we operate directly in basic_block_live_at_end[i],
1236 thus destroying it (in fact, converting it into a copy of
1237 basic_block_live_at_start[i]). This is ok now because
1238 basic_block_live_at_end[i] is no longer used past this point. */
1242 for (i = 0; i < n_basic_blocks; i++)
1244 propagate_block (basic_block_live_at_end[i],
1245 basic_block_head[i], basic_block_end[i], 1,
1253 /* Something live during a setjmp should not be put in a register
1254 on certain machines which restore regs from stack frames
1255 rather than from the jmpbuf.
1256 But we don't need to do this for the user's variables, since
1257 ANSI says only volatile variables need this. */
1258 #ifdef LONGJMP_RESTORE_FROM_STACK
1259 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1260 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1261 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1262 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1264 reg_live_length[i] = -1;
1265 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 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1280 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1281 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1282 && regno_reg_rtx[i] != 0)
1284 reg_live_length[i] = -1;
1285 reg_basic_block[i] = -1;
1288 obstack_free (&flow_obstack, NULL_PTR);
1291 /* Subroutines of life analysis. */
1293 /* Allocate the permanent data structures that represent the results
1294 of life analysis. Not static since used also for stupid life analysis. */
1297 allocate_for_life_analysis ()
1300 register regset tem;
1302 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1303 regset_bytes = regset_size * sizeof (*(regset)0);
1305 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1306 bzero ((char *) reg_n_refs, max_regno * sizeof (int));
1308 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1309 bzero ((char *) reg_n_sets, max_regno * sizeof (short));
1311 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1312 bzero ((char *) reg_n_deaths, max_regno * sizeof (short));
1314 reg_changes_size = (char *) oballoc (max_regno * sizeof (char));
1315 bzero (reg_changes_size, max_regno * sizeof (char));;
1317 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1318 bzero ((char *) reg_live_length, max_regno * sizeof (int));
1320 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1321 bzero ((char *) reg_n_calls_crossed, max_regno * sizeof (int));
1323 reg_basic_block = (int *) oballoc (max_regno * sizeof (int));
1324 for (i = 0; i < max_regno; i++)
1325 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1327 basic_block_live_at_start
1328 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1329 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1330 bzero ((char *) tem, n_basic_blocks * regset_bytes);
1331 init_regset_vector (basic_block_live_at_start, tem,
1332 n_basic_blocks, regset_bytes);
1334 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1335 bzero ((char *) regs_live_at_setjmp, regset_bytes);
1338 /* Make each element of VECTOR point at a regset,
1339 taking the space for all those regsets from SPACE.
1340 SPACE is of type regset, but it is really as long as NELTS regsets.
1341 BYTES_PER_ELT is the number of bytes in one regset. */
1344 init_regset_vector (vector, space, nelts, bytes_per_elt)
1351 register regset p = space;
1353 for (i = 0; i < nelts; i++)
1356 p += bytes_per_elt / sizeof (*p);
1360 /* Compute the registers live at the beginning of a basic block
1361 from those live at the end.
1363 When called, OLD contains those live at the end.
1364 On return, it contains those live at the beginning.
1365 FIRST and LAST are the first and last insns of the basic block.
1367 FINAL is nonzero if we are doing the final pass which is not
1368 for computing the life info (since that has already been done)
1369 but for acting on it. On this pass, we delete dead stores,
1370 set up the logical links and dead-variables lists of instructions,
1371 and merge instructions for autoincrement and autodecrement addresses.
1373 SIGNIFICANT is nonzero only the first time for each basic block.
1374 If it is nonzero, it points to a regset in which we store
1375 a 1 for each register that is set within the block.
1377 BNUM is the number of the basic block. */
1380 propagate_block (old, first, last, final, significant, bnum)
1381 register regset old;
1393 /* The following variables are used only if FINAL is nonzero. */
1394 /* This vector gets one element for each reg that has been live
1395 at any point in the basic block that has been scanned so far.
1396 SOMETIMES_MAX says how many elements are in use so far.
1397 In each element, OFFSET is the byte-number within a regset
1398 for the register described by the element, and BIT is a mask
1399 for that register's bit within the byte. */
1400 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1401 int sometimes_max = 0;
1402 /* This regset has 1 for each reg that we have seen live so far.
1403 It and REGS_SOMETIMES_LIVE are updated together. */
1406 /* The loop depth may change in the middle of a basic block. Since we
1407 scan from end to beginning, we start with the depth at the end of the
1408 current basic block, and adjust as we pass ends and starts of loops. */
1409 loop_depth = basic_block_loop_depth[bnum];
1411 dead = (regset) alloca (regset_bytes);
1412 live = (regset) alloca (regset_bytes);
1417 /* Include any notes at the end of the block in the scan.
1418 This is in case the block ends with a call to setjmp. */
1420 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1422 /* Look for loop boundaries, we are going forward here. */
1423 last = NEXT_INSN (last);
1424 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1426 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1432 register int i, offset;
1433 REGSET_ELT_TYPE bit;
1436 maxlive = (regset) alloca (regset_bytes);
1437 bcopy ((char *) old, (char *) maxlive, regset_bytes);
1439 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1441 /* Process the regs live at the end of the block.
1442 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1443 Also mark them as not local to any one basic block. */
1445 for (offset = 0, i = 0; offset < regset_size; offset++)
1446 for (bit = 1; bit; bit <<= 1, i++)
1450 if (old[offset] & bit)
1452 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1453 regs_sometimes_live[sometimes_max].offset = offset;
1454 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1460 /* Scan the block an insn at a time from end to beginning. */
1462 for (insn = last; ; insn = prev)
1464 prev = PREV_INSN (insn);
1466 if (GET_CODE (insn) == NOTE)
1468 /* Look for loop boundaries, remembering that we are going
1470 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1472 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1475 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1476 Abort now rather than setting register status incorrectly. */
1477 if (loop_depth == 0)
1480 /* If this is a call to `setjmp' et al,
1481 warn if any non-volatile datum is live. */
1483 if (final && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1486 for (i = 0; i < regset_size; i++)
1487 regs_live_at_setjmp[i] |= old[i];
1491 /* Update the life-status of regs for this insn.
1492 First DEAD gets which regs are set in this insn
1493 then LIVE gets which regs are used in this insn.
1494 Then the regs live before the insn
1495 are those live after, with DEAD regs turned off,
1496 and then LIVE regs turned on. */
1498 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1501 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1503 = (insn_dead_p (PATTERN (insn), old, 0)
1504 /* Don't delete something that refers to volatile storage! */
1505 && ! INSN_VOLATILE (insn));
1507 = (insn_is_dead && note != 0
1508 && libcall_dead_p (PATTERN (insn), old, note, insn));
1510 /* If an instruction consists of just dead store(s) on final pass,
1511 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1512 We could really delete it with delete_insn, but that
1513 can cause trouble for first or last insn in a basic block. */
1514 if (final && insn_is_dead)
1516 PUT_CODE (insn, NOTE);
1517 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1518 NOTE_SOURCE_FILE (insn) = 0;
1520 /* CC0 is now known to be dead. Either this insn used it,
1521 in which case it doesn't anymore, or clobbered it,
1522 so the next insn can't use it. */
1525 /* If this insn is copying the return value from a library call,
1526 delete the entire library call. */
1527 if (libcall_is_dead)
1529 rtx first = XEXP (note, 0);
1531 while (INSN_DELETED_P (first))
1532 first = NEXT_INSN (first);
1537 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1538 NOTE_SOURCE_FILE (p) = 0;
1544 for (i = 0; i < regset_size; i++)
1546 dead[i] = 0; /* Faster than bzero here */
1547 live[i] = 0; /* since regset_size is usually small */
1550 /* See if this is an increment or decrement that can be
1551 merged into a following memory address. */
1554 register rtx x = PATTERN (insn);
1555 /* Does this instruction increment or decrement a register? */
1556 if (final && GET_CODE (x) == SET
1557 && GET_CODE (SET_DEST (x)) == REG
1558 && (GET_CODE (SET_SRC (x)) == PLUS
1559 || GET_CODE (SET_SRC (x)) == MINUS)
1560 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1561 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1562 /* Ok, look for a following memory ref we can combine with.
1563 If one is found, change the memory ref to a PRE_INC
1564 or PRE_DEC, cancel this insn, and return 1.
1565 Return 0 if nothing has been done. */
1566 && try_pre_increment_1 (insn))
1569 #endif /* AUTO_INC_DEC */
1571 /* If this is not the final pass, and this insn is copying the
1572 value of a library call and it's dead, don't scan the
1573 insns that perform the library call, so that the call's
1574 arguments are not marked live. */
1575 if (libcall_is_dead)
1577 /* Mark the dest reg as `significant'. */
1578 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1580 insn = XEXP (note, 0);
1581 prev = PREV_INSN (insn);
1583 else if (GET_CODE (PATTERN (insn)) == SET
1584 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1585 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1586 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1587 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1588 /* We have an insn to pop a constant amount off the stack.
1589 (Such insns use PLUS regardless of the direction of the stack,
1590 and any insn to adjust the stack by a constant is always a pop.)
1591 These insns, if not dead stores, have no effect on life. */
1595 /* LIVE gets the regs used in INSN;
1596 DEAD gets those set by it. Dead insns don't make anything
1599 mark_set_regs (old, dead, PATTERN (insn),
1600 final ? insn : NULL_RTX, significant);
1602 /* If an insn doesn't use CC0, it becomes dead since we
1603 assume that every insn clobbers it. So show it dead here;
1604 mark_used_regs will set it live if it is referenced. */
1608 mark_used_regs (old, live, PATTERN (insn), final, insn);
1610 /* Sometimes we may have inserted something before INSN (such as
1611 a move) when we make an auto-inc. So ensure we will scan
1614 prev = PREV_INSN (insn);
1617 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1623 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1625 note = XEXP (note, 1))
1626 if (GET_CODE (XEXP (note, 0)) == USE)
1627 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1630 /* Each call clobbers all call-clobbered regs that are not
1631 global or fixed. Note that the function-value reg is a
1632 call-clobbered reg, and mark_set_regs has already had
1633 a chance to handle it. */
1635 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1636 if (call_used_regs[i] && ! global_regs[i]
1638 dead[i / REGSET_ELT_BITS]
1639 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1641 /* The stack ptr is used (honorarily) by a CALL insn. */
1642 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1643 |= ((REGSET_ELT_TYPE) 1
1644 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1646 /* Calls may also reference any of the global registers,
1647 so they are made live. */
1648 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1650 mark_used_regs (old, live,
1651 gen_rtx (REG, reg_raw_mode[i], i),
1654 /* Calls also clobber memory. */
1658 /* Update OLD for the registers used or set. */
1659 for (i = 0; i < regset_size; i++)
1665 if (GET_CODE (insn) == CALL_INSN && final)
1667 /* Any regs live at the time of a call instruction
1668 must not go in a register clobbered by calls.
1669 Find all regs now live and record this for them. */
1671 register struct sometimes *p = regs_sometimes_live;
1673 for (i = 0; i < sometimes_max; i++, p++)
1674 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1675 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1679 /* On final pass, add any additional sometimes-live regs
1680 into MAXLIVE and REGS_SOMETIMES_LIVE.
1681 Also update counts of how many insns each reg is live at. */
1685 for (i = 0; i < regset_size; i++)
1687 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1693 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1694 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1696 regs_sometimes_live[sometimes_max].offset = i;
1697 regs_sometimes_live[sometimes_max].bit = regno;
1698 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1705 register struct sometimes *p = regs_sometimes_live;
1706 for (i = 0; i < sometimes_max; i++, p++)
1708 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1709 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1719 if (num_scratch > max_scratch)
1720 max_scratch = num_scratch;
1723 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1724 (SET expressions whose destinations are registers dead after the insn).
1725 NEEDED is the regset that says which regs are alive after the insn.
1727 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1730 insn_dead_p (x, needed, call_ok)
1735 register RTX_CODE code = GET_CODE (x);
1736 /* If setting something that's a reg or part of one,
1737 see if that register's altered value will be live. */
1741 register rtx r = SET_DEST (x);
1742 /* A SET that is a subroutine call cannot be dead. */
1743 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1747 if (GET_CODE (r) == CC0)
1751 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1752 && rtx_equal_p (r, last_mem_set))
1755 while (GET_CODE (r) == SUBREG
1756 || GET_CODE (r) == STRICT_LOW_PART
1757 || GET_CODE (r) == ZERO_EXTRACT
1758 || GET_CODE (r) == SIGN_EXTRACT)
1761 if (GET_CODE (r) == REG)
1763 register int regno = REGNO (r);
1764 register int offset = regno / REGSET_ELT_BITS;
1765 register REGSET_ELT_TYPE bit
1766 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1768 /* Don't delete insns to set global regs. */
1769 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1770 /* Make sure insns to set frame pointer aren't deleted. */
1771 || regno == FRAME_POINTER_REGNUM
1772 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1773 || regno == HARD_FRAME_POINTER_REGNUM
1775 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1776 /* Make sure insns to set arg pointer are never deleted
1777 (if the arg pointer isn't fixed, there will be a USE for
1778 it, so we can treat it normally). */
1779 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1781 || (needed[offset] & bit) != 0)
1784 /* If this is a hard register, verify that subsequent words are
1786 if (regno < FIRST_PSEUDO_REGISTER)
1788 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1791 if ((needed[(regno + n) / REGSET_ELT_BITS]
1792 & ((REGSET_ELT_TYPE) 1
1793 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1800 /* If performing several activities,
1801 insn is dead if each activity is individually dead.
1802 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1803 that's inside a PARALLEL doesn't make the insn worth keeping. */
1804 else if (code == PARALLEL)
1806 register int i = XVECLEN (x, 0);
1807 for (i--; i >= 0; i--)
1809 rtx elt = XVECEXP (x, 0, i);
1810 if (!insn_dead_p (elt, needed, call_ok)
1811 && GET_CODE (elt) != CLOBBER
1812 && GET_CODE (elt) != USE)
1817 /* We do not check CLOBBER or USE here.
1818 An insn consisting of just a CLOBBER or just a USE
1819 should not be deleted. */
1823 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1824 return 1 if the entire library call is dead.
1825 This is true if X copies a register (hard or pseudo)
1826 and if the hard return reg of the call insn is dead.
1827 (The caller should have tested the destination of X already for death.)
1829 If this insn doesn't just copy a register, then we don't
1830 have an ordinary libcall. In that case, cse could not have
1831 managed to substitute the source for the dest later on,
1832 so we can assume the libcall is dead.
1834 NEEDED is the bit vector of pseudoregs live before this insn.
1835 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1838 libcall_dead_p (x, needed, note, insn)
1844 register RTX_CODE code = GET_CODE (x);
1848 register rtx r = SET_SRC (x);
1849 if (GET_CODE (r) == REG)
1851 rtx call = XEXP (note, 0);
1854 /* Find the call insn. */
1855 while (call != insn && GET_CODE (call) != CALL_INSN)
1856 call = NEXT_INSN (call);
1858 /* If there is none, do nothing special,
1859 since ordinary death handling can understand these insns. */
1863 /* See if the hard reg holding the value is dead.
1864 If this is a PARALLEL, find the call within it. */
1865 call = PATTERN (call);
1866 if (GET_CODE (call) == PARALLEL)
1868 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1869 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1870 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1873 /* This may be a library call that is returning a value
1874 via invisible pointer. Do nothing special, since
1875 ordinary death handling can understand these insns. */
1879 call = XVECEXP (call, 0, i);
1882 return insn_dead_p (call, needed, 1);
1888 /* Return 1 if register REGNO was used before it was set.
1889 In other words, if it is live at function entry.
1890 Don't count global register variables, though. */
1893 regno_uninitialized (regno)
1896 if (n_basic_blocks == 0
1897 || (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1900 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1901 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1904 /* 1 if register REGNO was alive at a place where `setjmp' was called
1905 and was set more than once or is an argument.
1906 Such regs may be clobbered by `longjmp'. */
1909 regno_clobbered_at_setjmp (regno)
1912 if (n_basic_blocks == 0)
1915 return ((reg_n_sets[regno] > 1
1916 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1917 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1918 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1919 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1922 /* Process the registers that are set within X.
1923 Their bits are set to 1 in the regset DEAD,
1924 because they are dead prior to this insn.
1926 If INSN is nonzero, it is the insn being processed
1927 and the fact that it is nonzero implies this is the FINAL pass
1928 in propagate_block. In this case, various info about register
1929 usage is stored, LOG_LINKS fields of insns are set up. */
1932 mark_set_regs (needed, dead, x, insn, significant)
1939 register RTX_CODE code = GET_CODE (x);
1941 if (code == SET || code == CLOBBER)
1942 mark_set_1 (needed, dead, x, insn, significant);
1943 else if (code == PARALLEL)
1946 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1948 code = GET_CODE (XVECEXP (x, 0, i));
1949 if (code == SET || code == CLOBBER)
1950 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1955 /* Process a single SET rtx, X. */
1958 mark_set_1 (needed, dead, x, insn, significant)
1966 register rtx reg = SET_DEST (x);
1968 /* Modifying just one hardware register of a multi-reg value
1969 or just a byte field of a register
1970 does not mean the value from before this insn is now dead.
1971 But it does mean liveness of that register at the end of the block
1974 Within mark_set_1, however, we treat it as if the register is
1975 indeed modified. mark_used_regs will, however, also treat this
1976 register as being used. Thus, we treat these insns as setting a
1977 new value for the register as a function of its old value. This
1978 cases LOG_LINKS to be made appropriately and this will help combine. */
1980 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1981 || GET_CODE (reg) == SIGN_EXTRACT
1982 || GET_CODE (reg) == STRICT_LOW_PART)
1983 reg = XEXP (reg, 0);
1985 /* If we are writing into memory or into a register mentioned in the
1986 address of the last thing stored into memory, show we don't know
1987 what the last store was. If we are writing memory, save the address
1988 unless it is volatile. */
1989 if (GET_CODE (reg) == MEM
1990 || (GET_CODE (reg) == REG
1991 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1994 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1995 /* There are no REG_INC notes for SP, so we can't assume we'll see
1996 everything that invalidates it. To be safe, don't eliminate any
1997 stores though SP; none of them should be redundant anyway. */
1998 && ! reg_mentioned_p (stack_pointer_rtx, reg))
2001 if (GET_CODE (reg) == REG
2002 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
2003 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2004 && regno != HARD_FRAME_POINTER_REGNUM
2006 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2007 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2009 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
2010 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
2012 register int offset = regno / REGSET_ELT_BITS;
2013 register REGSET_ELT_TYPE bit
2014 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2015 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
2016 REGSET_ELT_TYPE some_not_needed = (~ needed[offset]) & bit;
2018 /* Mark it as a significant register for this basic block. */
2020 significant[offset] |= bit;
2022 /* Mark it as as dead before this insn. */
2023 dead[offset] |= bit;
2025 /* A hard reg in a wide mode may really be multiple registers.
2026 If so, mark all of them just like the first. */
2027 if (regno < FIRST_PSEUDO_REGISTER)
2031 /* Nothing below is needed for the stack pointer; get out asap.
2032 Eg, log links aren't needed, since combine won't use them. */
2033 if (regno == STACK_POINTER_REGNUM)
2036 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
2039 REGSET_ELT_TYPE n_bit
2040 = (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2043 significant[(regno + n) / REGSET_ELT_BITS] |= n_bit;
2045 dead[(regno + n) / REGSET_ELT_BITS] |= n_bit;
2047 |= (needed[(regno + n) / REGSET_ELT_BITS] & n_bit);
2049 |= ((~ needed[(regno + n) / REGSET_ELT_BITS]) & n_bit);
2052 /* Additional data to record if this is the final pass. */
2055 register rtx y = reg_next_use[regno];
2056 register int blocknum = BLOCK_NUM (insn);
2058 /* If this is a hard reg, record this function uses the reg. */
2060 if (regno < FIRST_PSEUDO_REGISTER)
2063 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
2065 for (i = regno; i < endregno; i++)
2067 /* The next use is no longer "next", since a store
2069 reg_next_use[i] = 0;
2071 regs_ever_live[i] = 1;
2077 /* The next use is no longer "next", since a store
2079 reg_next_use[regno] = 0;
2081 /* Keep track of which basic blocks each reg appears in. */
2083 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2084 reg_basic_block[regno] = blocknum;
2085 else if (reg_basic_block[regno] != blocknum)
2086 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2088 /* Count (weighted) references, stores, etc. This counts a
2089 register twice if it is modified, but that is correct. */
2090 reg_n_sets[regno]++;
2092 reg_n_refs[regno] += loop_depth;
2094 /* The insns where a reg is live are normally counted
2095 elsewhere, but we want the count to include the insn
2096 where the reg is set, and the normal counting mechanism
2097 would not count it. */
2098 reg_live_length[regno]++;
2101 if (! some_not_needed)
2103 /* Make a logical link from the next following insn
2104 that uses this register, back to this insn.
2105 The following insns have already been processed.
2107 We don't build a LOG_LINK for hard registers containing
2108 in ASM_OPERANDs. If these registers get replaced,
2109 we might wind up changing the semantics of the insn,
2110 even if reload can make what appear to be valid assignments
2112 if (y && (BLOCK_NUM (y) == blocknum)
2113 && (regno >= FIRST_PSEUDO_REGISTER
2114 || asm_noperands (PATTERN (y)) < 0))
2116 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
2118 else if (! some_needed)
2120 /* Note that dead stores have already been deleted when possible
2121 If we get here, we have found a dead store that cannot
2122 be eliminated (because the same insn does something useful).
2123 Indicate this by marking the reg being set as dying here. */
2125 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2126 reg_n_deaths[REGNO (reg)]++;
2130 /* This is a case where we have a multi-word hard register
2131 and some, but not all, of the words of the register are
2132 needed in subsequent insns. Write REG_UNUSED notes
2133 for those parts that were not needed. This case should
2138 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2140 if ((needed[(regno + i) / REGSET_ELT_BITS]
2141 & ((REGSET_ELT_TYPE) 1
2142 << ((regno + i) % REGSET_ELT_BITS))) == 0)
2144 = gen_rtx (EXPR_LIST, REG_UNUSED,
2145 gen_rtx (REG, reg_raw_mode[regno + i],
2151 else if (GET_CODE (reg) == REG)
2152 reg_next_use[regno] = 0;
2154 /* If this is the last pass and this is a SCRATCH, show it will be dying
2155 here and count it. */
2156 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2159 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2166 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2170 find_auto_inc (needed, x, insn)
2175 rtx addr = XEXP (x, 0);
2176 HOST_WIDE_INT offset = 0;
2179 /* Here we detect use of an index register which might be good for
2180 postincrement, postdecrement, preincrement, or predecrement. */
2182 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2183 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2185 if (GET_CODE (addr) == REG)
2188 register int size = GET_MODE_SIZE (GET_MODE (x));
2191 int regno = REGNO (addr);
2193 /* Is the next use an increment that might make auto-increment? */
2194 if ((incr = reg_next_use[regno]) != 0
2195 && (set = single_set (incr)) != 0
2196 && GET_CODE (set) == SET
2197 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2198 /* Can't add side effects to jumps; if reg is spilled and
2199 reloaded, there's no way to store back the altered value. */
2200 && GET_CODE (insn) != JUMP_INSN
2201 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2202 && XEXP (y, 0) == addr
2203 && GET_CODE (XEXP (y, 1)) == CONST_INT
2205 #ifdef HAVE_POST_INCREMENT
2206 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2208 #ifdef HAVE_POST_DECREMENT
2209 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2211 #ifdef HAVE_PRE_INCREMENT
2212 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2214 #ifdef HAVE_PRE_DECREMENT
2215 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2218 /* Make sure this reg appears only once in this insn. */
2219 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2220 use != 0 && use != (rtx) 1))
2222 rtx q = SET_DEST (set);
2223 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2224 ? (offset ? PRE_INC : POST_INC)
2225 : (offset ? PRE_DEC : POST_DEC));
2227 if (dead_or_set_p (incr, addr))
2229 /* This is the simple case. Try to make the auto-inc. If
2230 we can't, we are done. Otherwise, we will do any
2231 needed updates below. */
2232 if (! validate_change (insn, &XEXP (x, 0),
2233 gen_rtx (inc_code, Pmode, addr),
2237 else if (GET_CODE (q) == REG
2238 /* PREV_INSN used here to check the semi-open interval
2240 && ! reg_used_between_p (q, PREV_INSN (insn), incr)
2241 /* We must also check for sets of q as q may be
2242 a call clobbered hard register and there may
2243 be a call between PREV_INSN (insn) and incr. */
2244 && ! reg_set_between_p (q, PREV_INSN (insn), incr))
2246 /* We have *p followed sometime later by q = p+size.
2247 Both p and q must be live afterward,
2248 and q is not used between INSN and it's assignment.
2249 Change it to q = p, ...*q..., q = q+size.
2250 Then fall into the usual case. */
2254 emit_move_insn (q, addr);
2255 insns = get_insns ();
2258 /* If anything in INSNS have UID's that don't fit within the
2259 extra space we allocate earlier, we can't make this auto-inc.
2260 This should never happen. */
2261 for (temp = insns; temp; temp = NEXT_INSN (temp))
2263 if (INSN_UID (temp) > max_uid_for_flow)
2265 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2268 /* If we can't make the auto-inc, or can't make the
2269 replacement into Y, exit. There's no point in making
2270 the change below if we can't do the auto-inc and doing
2271 so is not correct in the pre-inc case. */
2273 validate_change (insn, &XEXP (x, 0),
2274 gen_rtx (inc_code, Pmode, q),
2276 validate_change (incr, &XEXP (y, 0), q, 1);
2277 if (! apply_change_group ())
2280 /* We now know we'll be doing this change, so emit the
2281 new insn(s) and do the updates. */
2282 emit_insns_before (insns, insn);
2284 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2285 basic_block_head[BLOCK_NUM (insn)] = insns;
2287 /* INCR will become a NOTE and INSN won't contain a
2288 use of ADDR. If a use of ADDR was just placed in
2289 the insn before INSN, make that the next use.
2290 Otherwise, invalidate it. */
2291 if (GET_CODE (PREV_INSN (insn)) == INSN
2292 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2293 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2294 reg_next_use[regno] = PREV_INSN (insn);
2296 reg_next_use[regno] = 0;
2301 /* REGNO is now used in INCR which is below INSN, but
2302 it previously wasn't live here. If we don't mark
2303 it as needed, we'll put a REG_DEAD note for it
2304 on this insn, which is incorrect. */
2305 needed[regno / REGSET_ELT_BITS]
2306 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2308 /* If there are any calls between INSN and INCR, show
2309 that REGNO now crosses them. */
2310 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2311 if (GET_CODE (temp) == CALL_INSN)
2312 reg_n_calls_crossed[regno]++;
2317 /* If we haven't returned, it means we were able to make the
2318 auto-inc, so update the status. First, record that this insn
2319 has an implicit side effect. */
2322 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2324 /* Modify the old increment-insn to simply copy
2325 the already-incremented value of our register. */
2326 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2329 /* If that makes it a no-op (copying the register into itself) delete
2330 it so it won't appear to be a "use" and a "set" of this
2332 if (SET_DEST (set) == addr)
2334 PUT_CODE (incr, NOTE);
2335 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2336 NOTE_SOURCE_FILE (incr) = 0;
2339 if (regno >= FIRST_PSEUDO_REGISTER)
2341 /* Count an extra reference to the reg. When a reg is
2342 incremented, spilling it is worse, so we want to make
2343 that less likely. */
2344 reg_n_refs[regno] += loop_depth;
2346 /* Count the increment as a setting of the register,
2347 even though it isn't a SET in rtl. */
2348 reg_n_sets[regno]++;
2353 #endif /* AUTO_INC_DEC */
2355 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2356 This is done assuming the registers needed from X
2357 are those that have 1-bits in NEEDED.
2359 On the final pass, FINAL is 1. This means try for autoincrement
2360 and count the uses and deaths of each pseudo-reg.
2362 INSN is the containing instruction. If INSN is dead, this function is not
2366 mark_used_regs (needed, live, x, final, insn)
2373 register RTX_CODE code;
2378 code = GET_CODE (x);
2399 /* If we are clobbering a MEM, mark any registers inside the address
2401 if (GET_CODE (XEXP (x, 0)) == MEM)
2402 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2406 /* Invalidate the data for the last MEM stored. We could do this only
2407 if the addresses conflict, but this doesn't seem worthwhile. */
2412 find_auto_inc (needed, x, insn);
2417 if (GET_CODE (SUBREG_REG (x)) == REG
2418 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2419 && (GET_MODE_SIZE (GET_MODE (x))
2420 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))))
2421 reg_changes_size[REGNO (SUBREG_REG (x))] = 1;
2423 /* While we're here, optimize this case. */
2426 /* In case the SUBREG is not of a register, don't optimize */
2427 if (GET_CODE (x) != REG)
2429 mark_used_regs (needed, live, x, final, insn);
2433 /* ... fall through ... */
2436 /* See a register other than being set
2437 => mark it as needed. */
2441 register int offset = regno / REGSET_ELT_BITS;
2442 register REGSET_ELT_TYPE bit
2443 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2444 REGSET_ELT_TYPE some_needed = needed[offset] & bit;
2445 REGSET_ELT_TYPE some_not_needed = (~ needed[offset]) & bit;
2447 live[offset] |= bit;
2449 /* A hard reg in a wide mode may really be multiple registers.
2450 If so, mark all of them just like the first. */
2451 if (regno < FIRST_PSEUDO_REGISTER)
2455 /* For stack ptr or fixed arg pointer,
2456 nothing below can be necessary, so waste no more time. */
2457 if (regno == STACK_POINTER_REGNUM
2458 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2459 || regno == HARD_FRAME_POINTER_REGNUM
2461 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2462 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2464 || regno == FRAME_POINTER_REGNUM)
2466 /* If this is a register we are going to try to eliminate,
2467 don't mark it live here. If we are successful in
2468 eliminating it, it need not be live unless it is used for
2469 pseudos, in which case it will have been set live when
2470 it was allocated to the pseudos. If the register will not
2471 be eliminated, reload will set it live at that point. */
2473 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2474 regs_ever_live[regno] = 1;
2477 /* No death notes for global register variables;
2478 their values are live after this function exits. */
2479 if (global_regs[regno])
2482 reg_next_use[regno] = insn;
2486 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2489 REGSET_ELT_TYPE n_bit
2490 = (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2492 live[(regno + n) / REGSET_ELT_BITS] |= n_bit;
2493 some_needed |= (needed[(regno + n) / REGSET_ELT_BITS] & n_bit);
2495 |= ((~ needed[(regno + n) / REGSET_ELT_BITS]) & n_bit);
2500 /* Record where each reg is used, so when the reg
2501 is set we know the next insn that uses it. */
2503 reg_next_use[regno] = insn;
2505 if (regno < FIRST_PSEUDO_REGISTER)
2507 /* If a hard reg is being used,
2508 record that this function does use it. */
2510 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2514 regs_ever_live[regno + --i] = 1;
2519 /* Keep track of which basic block each reg appears in. */
2521 register int blocknum = BLOCK_NUM (insn);
2523 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2524 reg_basic_block[regno] = blocknum;
2525 else if (reg_basic_block[regno] != blocknum)
2526 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2528 /* Count (weighted) number of uses of each reg. */
2530 reg_n_refs[regno] += loop_depth;
2533 /* Record and count the insns in which a reg dies.
2534 If it is used in this insn and was dead below the insn
2535 then it dies in this insn. If it was set in this insn,
2536 we do not make a REG_DEAD note; likewise if we already
2537 made such a note. */
2540 && ! dead_or_set_p (insn, x)
2542 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2546 /* Check for the case where the register dying partially
2547 overlaps the register set by this insn. */
2548 if (regno < FIRST_PSEUDO_REGISTER
2549 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2551 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2553 some_needed |= dead_or_set_regno_p (insn, regno + n);
2556 /* If none of the words in X is needed, make a REG_DEAD
2557 note. Otherwise, we must make partial REG_DEAD notes. */
2561 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2562 reg_n_deaths[regno]++;
2568 /* Don't make a REG_DEAD note for a part of a register
2569 that is set in the insn. */
2571 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2573 if ((needed[(regno + i) / REGSET_ELT_BITS]
2574 & ((REGSET_ELT_TYPE) 1
2575 << ((regno + i) % REGSET_ELT_BITS))) == 0
2576 && ! dead_or_set_regno_p (insn, regno + i))
2578 = gen_rtx (EXPR_LIST, REG_DEAD,
2579 gen_rtx (REG, reg_raw_mode[regno + i],
2590 register rtx testreg = SET_DEST (x);
2593 /* If storing into MEM, don't show it as being used. But do
2594 show the address as being used. */
2595 if (GET_CODE (testreg) == MEM)
2599 find_auto_inc (needed, testreg, insn);
2601 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2602 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2606 /* Storing in STRICT_LOW_PART is like storing in a reg
2607 in that this SET might be dead, so ignore it in TESTREG.
2608 but in some other ways it is like using the reg.
2610 Storing in a SUBREG or a bit field is like storing the entire
2611 register in that if the register's value is not used
2612 then this SET is not needed. */
2613 while (GET_CODE (testreg) == STRICT_LOW_PART
2614 || GET_CODE (testreg) == ZERO_EXTRACT
2615 || GET_CODE (testreg) == SIGN_EXTRACT
2616 || GET_CODE (testreg) == SUBREG)
2618 if (GET_CODE (testreg) == SUBREG
2619 && GET_CODE (SUBREG_REG (testreg)) == REG
2620 && REGNO (SUBREG_REG (testreg)) >= FIRST_PSEUDO_REGISTER
2621 && (GET_MODE_SIZE (GET_MODE (testreg))
2622 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (testreg)))))
2623 reg_changes_size[REGNO (SUBREG_REG (testreg))] = 1;
2625 /* Modifying a single register in an alternate mode
2626 does not use any of the old value. But these other
2627 ways of storing in a register do use the old value. */
2628 if (GET_CODE (testreg) == SUBREG
2629 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2634 testreg = XEXP (testreg, 0);
2637 /* If this is a store into a register,
2638 recursively scan the value being stored. */
2640 if (GET_CODE (testreg) == REG
2641 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2642 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2643 && regno != HARD_FRAME_POINTER_REGNUM
2645 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2646 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2649 /* We used to exclude global_regs here, but that seems wrong.
2650 Storing in them is like storing in mem. */
2652 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2654 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2661 /* If exiting needs the right stack value, consider this insn as
2662 using the stack pointer. In any event, consider it as using
2663 all global registers. */
2665 #ifdef EXIT_IGNORE_STACK
2666 if (! EXIT_IGNORE_STACK
2667 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2669 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2670 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2672 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2674 live[i / REGSET_ELT_BITS]
2675 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2679 /* Recursively scan the operands of this expression. */
2682 register char *fmt = GET_RTX_FORMAT (code);
2685 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2689 /* Tail recursive case: save a function call level. */
2695 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2697 else if (fmt[i] == 'E')
2700 for (j = 0; j < XVECLEN (x, i); j++)
2701 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2710 try_pre_increment_1 (insn)
2713 /* Find the next use of this reg. If in same basic block,
2714 make it do pre-increment or pre-decrement if appropriate. */
2715 rtx x = PATTERN (insn);
2716 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2717 * INTVAL (XEXP (SET_SRC (x), 1)));
2718 int regno = REGNO (SET_DEST (x));
2719 rtx y = reg_next_use[regno];
2721 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2722 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2723 mode would be better. */
2724 && ! dead_or_set_p (y, SET_DEST (x))
2725 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2728 /* We have found a suitable auto-increment
2729 and already changed insn Y to do it.
2730 So flush this increment-instruction. */
2731 PUT_CODE (insn, NOTE);
2732 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2733 NOTE_SOURCE_FILE (insn) = 0;
2734 /* Count a reference to this reg for the increment
2735 insn we are deleting. When a reg is incremented.
2736 spilling it is worse, so we want to make that
2738 if (regno >= FIRST_PSEUDO_REGISTER)
2740 reg_n_refs[regno] += loop_depth;
2741 reg_n_sets[regno]++;
2748 /* Try to change INSN so that it does pre-increment or pre-decrement
2749 addressing on register REG in order to add AMOUNT to REG.
2750 AMOUNT is negative for pre-decrement.
2751 Returns 1 if the change could be made.
2752 This checks all about the validity of the result of modifying INSN. */
2755 try_pre_increment (insn, reg, amount)
2757 HOST_WIDE_INT amount;
2761 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2762 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2764 /* Nonzero if we can try to make a post-increment or post-decrement.
2765 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2766 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2767 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2770 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2773 /* From the sign of increment, see which possibilities are conceivable
2774 on this target machine. */
2775 #ifdef HAVE_PRE_INCREMENT
2779 #ifdef HAVE_POST_INCREMENT
2784 #ifdef HAVE_PRE_DECREMENT
2788 #ifdef HAVE_POST_DECREMENT
2793 if (! (pre_ok || post_ok))
2796 /* It is not safe to add a side effect to a jump insn
2797 because if the incremented register is spilled and must be reloaded
2798 there would be no way to store the incremented value back in memory. */
2800 if (GET_CODE (insn) == JUMP_INSN)
2805 use = find_use_as_address (PATTERN (insn), reg, 0);
2806 if (post_ok && (use == 0 || use == (rtx) 1))
2808 use = find_use_as_address (PATTERN (insn), reg, -amount);
2812 if (use == 0 || use == (rtx) 1)
2815 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2818 /* See if this combination of instruction and addressing mode exists. */
2819 if (! validate_change (insn, &XEXP (use, 0),
2821 ? (do_post ? POST_INC : PRE_INC)
2822 : (do_post ? POST_DEC : PRE_DEC),
2826 /* Record that this insn now has an implicit side effect on X. */
2827 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2831 #endif /* AUTO_INC_DEC */
2833 /* Find the place in the rtx X where REG is used as a memory address.
2834 Return the MEM rtx that so uses it.
2835 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2836 (plus REG (const_int PLUSCONST)).
2838 If such an address does not appear, return 0.
2839 If REG appears more than once, or is used other than in such an address,
2843 find_use_as_address (x, reg, plusconst)
2846 HOST_WIDE_INT plusconst;
2848 enum rtx_code code = GET_CODE (x);
2849 char *fmt = GET_RTX_FORMAT (code);
2851 register rtx value = 0;
2854 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2857 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2858 && XEXP (XEXP (x, 0), 0) == reg
2859 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2860 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2863 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2865 /* If REG occurs inside a MEM used in a bit-field reference,
2866 that is unacceptable. */
2867 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2868 return (rtx) (HOST_WIDE_INT) 1;
2872 return (rtx) (HOST_WIDE_INT) 1;
2874 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2878 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2882 return (rtx) (HOST_WIDE_INT) 1;
2887 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2889 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2893 return (rtx) (HOST_WIDE_INT) 1;
2901 /* Write information about registers and basic blocks into FILE.
2902 This is part of making a debugging dump. */
2905 dump_flow_info (file)
2909 static char *reg_class_names[] = REG_CLASS_NAMES;
2911 fprintf (file, "%d registers.\n", max_regno);
2913 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2916 enum reg_class class, altclass;
2917 fprintf (file, "\nRegister %d used %d times across %d insns",
2918 i, reg_n_refs[i], reg_live_length[i]);
2919 if (reg_basic_block[i] >= 0)
2920 fprintf (file, " in block %d", reg_basic_block[i]);
2921 if (reg_n_deaths[i] != 1)
2922 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2923 if (reg_n_calls_crossed[i] == 1)
2924 fprintf (file, "; crosses 1 call");
2925 else if (reg_n_calls_crossed[i])
2926 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2927 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2928 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2929 class = reg_preferred_class (i);
2930 altclass = reg_alternate_class (i);
2931 if (class != GENERAL_REGS || altclass != ALL_REGS)
2933 if (altclass == ALL_REGS || class == ALL_REGS)
2934 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2935 else if (altclass == NO_REGS)
2936 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2938 fprintf (file, "; pref %s, else %s",
2939 reg_class_names[(int) class],
2940 reg_class_names[(int) altclass]);
2942 if (REGNO_POINTER_FLAG (i))
2943 fprintf (file, "; pointer");
2944 fprintf (file, ".\n");
2946 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2947 for (i = 0; i < n_basic_blocks; i++)
2949 register rtx head, jump;
2951 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2953 INSN_UID (basic_block_head[i]),
2954 INSN_UID (basic_block_end[i]));
2955 /* The control flow graph's storage is freed
2956 now when flow_analysis returns.
2957 Don't try to print it if it is gone. */
2958 if (basic_block_drops_in)
2960 fprintf (file, "Reached from blocks: ");
2961 head = basic_block_head[i];
2962 if (GET_CODE (head) == CODE_LABEL)
2963 for (jump = LABEL_REFS (head);
2965 jump = LABEL_NEXTREF (jump))
2967 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2968 fprintf (file, " %d", from_block);
2970 if (basic_block_drops_in[i])
2971 fprintf (file, " previous");
2973 fprintf (file, "\nRegisters live at start:");
2974 for (regno = 0; regno < max_regno; regno++)
2976 register int offset = regno / REGSET_ELT_BITS;
2977 register REGSET_ELT_TYPE bit
2978 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2979 if (basic_block_live_at_start[i][offset] & bit)
2980 fprintf (file, " %d", regno);
2982 fprintf (file, "\n");
2984 fprintf (file, "\n");