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"
123 #define obstack_chunk_alloc xmalloc
124 #define obstack_chunk_free free
126 /* List of labels that must never be deleted. */
127 extern rtx forced_labels;
129 /* Get the basic block number of an insn.
130 This info should not be expected to remain available
131 after the end of life_analysis. */
133 /* This is the limit of the allocated space in the following two arrays. */
135 static int max_uid_for_flow;
137 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
139 /* This is where the BLOCK_NUM values are really stored.
140 This is set up by find_basic_blocks and used there and in life_analysis,
143 static int *uid_block_number;
145 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
147 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
148 static char *uid_volatile;
150 /* Number of basic blocks in the current function. */
154 /* Maximum register number used in this function, plus one. */
158 /* Maximum number of SCRATCH rtx's used in any basic block of this
163 /* Number of SCRATCH rtx's in the current block. */
165 static int num_scratch;
167 /* Indexed by n, gives number of basic block that (REG n) is used in.
168 If the value is REG_BLOCK_GLOBAL (-2),
169 it means (REG n) is used in more than one basic block.
170 REG_BLOCK_UNKNOWN (-1) means it hasn't been seen yet so we don't know.
171 This information remains valid for the rest of the compilation
172 of the current function; it is used to control register allocation. */
174 int *reg_basic_block;
176 /* Indexed by n, gives number of times (REG n) is used or set, each
177 weighted by its loop-depth.
178 This information remains valid for the rest of the compilation
179 of the current function; it is used to control register allocation. */
183 /* Indexed by N; says whether a pseudo register N was ever used
184 within a SUBREG that changes the size of the reg. Some machines prohibit
185 such objects to be in certain (usually floating-point) registers. */
187 char *reg_changes_size;
189 /* Indexed by N, gives number of places register N dies.
190 This information remains valid for the rest of the compilation
191 of the current function; it is used to control register allocation. */
195 /* Indexed by N, gives 1 if that reg is live across any CALL_INSNs.
196 This information remains valid for the rest of the compilation
197 of the current function; it is used to control register allocation. */
199 int *reg_n_calls_crossed;
201 /* Total number of instructions at which (REG n) is live.
202 The larger this is, the less priority (REG n) gets for
203 allocation in a real register.
204 This information remains valid for the rest of the compilation
205 of the current function; it is used to control register allocation.
207 local-alloc.c may alter this number to change the priority.
209 Negative values are special.
210 -1 is used to mark a pseudo reg which has a constant or memory equivalent
211 and is used infrequently enough that it should not get a hard register.
212 -2 is used to mark a pseudo reg for a parameter, when a frame pointer
213 is not required. global.c makes an allocno for this but does
214 not try to assign a hard register to it. */
216 int *reg_live_length;
218 /* Element N is the next insn that uses (hard or pseudo) register number N
219 within the current basic block; or zero, if there is no such insn.
220 This is valid only during the final backward scan in propagate_block. */
222 static rtx *reg_next_use;
224 /* Size of a regset for the current function,
225 in (1) bytes and (2) elements. */
230 /* Element N is first insn in basic block N.
231 This info lasts until we finish compiling the function. */
233 rtx *basic_block_head;
235 /* Element N is last insn in basic block N.
236 This info lasts until we finish compiling the function. */
238 rtx *basic_block_end;
240 /* Element N is a regset describing the registers live
241 at the start of basic block N.
242 This info lasts until we finish compiling the function. */
244 regset *basic_block_live_at_start;
246 /* Regset of regs live when calls to `setjmp'-like functions happen. */
248 regset regs_live_at_setjmp;
250 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
251 that have to go in the same hard reg.
252 The first two regs in the list are a pair, and the next two
253 are another pair, etc. */
256 /* Element N is nonzero if control can drop into basic block N
257 from the preceding basic block. Freed after life_analysis. */
259 static char *basic_block_drops_in;
261 /* Element N is depth within loops of the last insn in basic block number N.
262 Freed after life_analysis. */
264 static short *basic_block_loop_depth;
266 /* Element N nonzero if basic block N can actually be reached.
267 Vector exists only during find_basic_blocks. */
269 static char *block_live_static;
271 /* Depth within loops of basic block being scanned for lifetime analysis,
272 plus one. This is the weight attached to references to registers. */
274 static int loop_depth;
276 /* During propagate_block, this is non-zero if the value of CC0 is live. */
280 /* During propagate_block, this contains the last MEM stored into. It
281 is used to eliminate consecutive stores to the same location. */
283 static rtx last_mem_set;
285 /* Set of registers that may be eliminable. These are handled specially
286 in updating regs_ever_live. */
288 static HARD_REG_SET elim_reg_set;
290 /* Forward declarations */
291 static void find_basic_blocks PROTO((rtx, rtx));
292 static int jmp_uses_reg_or_mem PROTO((rtx));
293 static void mark_label_ref PROTO((rtx, rtx, int));
294 static void life_analysis PROTO((rtx, int));
295 void allocate_for_life_analysis PROTO((void));
296 static void init_regset_vector PROTO((regset *, regset, int, int));
297 static void propagate_block PROTO((regset, rtx, rtx, int,
299 static rtx flow_delete_insn PROTO((rtx));
300 static int insn_dead_p PROTO((rtx, regset, int));
301 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
302 static void mark_set_regs PROTO((regset, regset, rtx,
304 static void mark_set_1 PROTO((regset, regset, rtx,
306 static void find_auto_inc PROTO((regset, rtx, rtx));
307 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
308 static int try_pre_increment_1 PROTO((rtx));
309 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
310 static rtx find_use_as_address PROTO((rtx, rtx, HOST_WIDE_INT));
311 void dump_flow_info PROTO((FILE *));
313 /* Find basic blocks of the current function and perform data flow analysis.
314 F is the first insn of the function and NREGS the number of register numbers
318 flow_analysis (f, nregs, file)
325 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
327 #ifdef ELIMINABLE_REGS
328 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
331 /* Record which registers will be eliminated. We use this in
334 CLEAR_HARD_REG_SET (elim_reg_set);
336 #ifdef ELIMINABLE_REGS
337 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
338 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
340 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
343 /* Count the basic blocks. Also find maximum insn uid value used. */
346 register RTX_CODE prev_code = JUMP_INSN;
347 register RTX_CODE code;
349 max_uid_for_flow = 0;
351 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
353 code = GET_CODE (insn);
354 if (INSN_UID (insn) > max_uid_for_flow)
355 max_uid_for_flow = INSN_UID (insn);
356 if (code == CODE_LABEL
357 || (GET_RTX_CLASS (code) == 'i'
358 && (prev_code == JUMP_INSN
359 || (prev_code == CALL_INSN
360 && nonlocal_label_list != 0)
361 || prev_code == BARRIER)))
364 if (code == CALL_INSN && find_reg_note (insn, REG_RETVAL, NULL_RTX))
373 /* Leave space for insns we make in some cases for auto-inc. These cases
374 are rare, so we don't need too much space. */
375 max_uid_for_flow += max_uid_for_flow / 10;
378 /* Allocate some tables that last till end of compiling this function
379 and some needed only in find_basic_blocks and life_analysis. */
382 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
383 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
384 basic_block_drops_in = (char *) alloca (n_basic_blocks);
385 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
387 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
388 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
389 bzero (uid_volatile, max_uid_for_flow + 1);
391 find_basic_blocks (f, nonlocal_label_list);
392 life_analysis (f, nregs);
394 dump_flow_info (file);
396 basic_block_drops_in = 0;
397 uid_block_number = 0;
398 basic_block_loop_depth = 0;
401 /* Find all basic blocks of the function whose first insn is F.
402 Store the correct data in the tables that describe the basic blocks,
403 set up the chains of references for each CODE_LABEL, and
404 delete any entire basic blocks that cannot be reached.
406 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
409 find_basic_blocks (f, nonlocal_label_list)
410 rtx f, nonlocal_label_list;
414 register char *block_live = (char *) alloca (n_basic_blocks);
415 register char *block_marked = (char *) alloca (n_basic_blocks);
416 /* List of label_refs to all labels whose addresses are taken
418 rtx label_value_list;
420 enum rtx_code prev_code, code;
426 label_value_list = 0;
427 block_live_static = block_live;
428 bzero (block_live, n_basic_blocks);
429 bzero (block_marked, n_basic_blocks);
431 /* Initialize with just block 0 reachable and no blocks marked. */
432 if (n_basic_blocks > 0)
435 /* Initialize the ref chain of each label to 0. Record where all the
436 blocks start and end and their depth in loops. For each insn, record
437 the block it is in. Also mark as reachable any blocks headed by labels
438 that must not be deleted. */
440 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
441 insn; insn = NEXT_INSN (insn))
443 code = GET_CODE (insn);
446 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
448 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
452 /* A basic block starts at label, or after something that can jump. */
453 else if (code == CODE_LABEL
454 || (GET_RTX_CLASS (code) == 'i'
455 && (prev_code == JUMP_INSN
456 || (prev_code == CALL_INSN
457 && nonlocal_label_list != 0
458 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
459 || prev_code == BARRIER)))
461 basic_block_head[++i] = insn;
462 basic_block_end[i] = insn;
463 basic_block_loop_depth[i] = depth;
465 if (code == CODE_LABEL)
467 LABEL_REFS (insn) = insn;
468 /* Any label that cannot be deleted
469 is considered to start a reachable block. */
470 if (LABEL_PRESERVE_P (insn))
475 else if (GET_RTX_CLASS (code) == 'i')
477 basic_block_end[i] = insn;
478 basic_block_loop_depth[i] = depth;
481 if (GET_RTX_CLASS (code) == 'i')
483 /* Make a list of all labels referred to other than by jumps. */
484 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
485 if (REG_NOTE_KIND (note) == REG_LABEL)
486 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
490 BLOCK_NUM (insn) = i;
496 /* During the second pass, `n_basic_blocks' is only an upper bound.
497 Only perform the sanity check for the first pass, and on the second
498 pass ensure `n_basic_blocks' is set to the correct value. */
499 if (pass == 1 && i + 1 != n_basic_blocks)
501 n_basic_blocks = i + 1;
503 /* Don't delete the labels (in this function)
504 that are referenced by non-jump instructions. */
506 for (x = label_value_list; x; x = XEXP (x, 1))
507 if (! LABEL_REF_NONLOCAL_P (x))
508 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
510 for (x = forced_labels; x; x = XEXP (x, 1))
511 if (! LABEL_REF_NONLOCAL_P (x))
512 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
514 for (x = exception_handler_labels; x; x = XEXP (x, 1))
515 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
517 /* Record which basic blocks control can drop in to. */
519 for (i = 0; i < n_basic_blocks; i++)
521 for (insn = PREV_INSN (basic_block_head[i]);
522 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
525 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
528 /* Now find which basic blocks can actually be reached
529 and put all jump insns' LABEL_REFS onto the ref-chains
530 of their target labels. */
532 if (n_basic_blocks > 0)
534 int something_marked = 1;
537 /* Find all indirect jump insns and mark them as possibly jumping to all
538 the labels whose addresses are explicitly used. This is because,
539 when there are computed gotos, we can't tell which labels they jump
540 to, of all the possibilities.
542 Tablejumps and casesi insns are OK and we can recognize them by
543 a (use (label_ref)). */
545 for (insn = f; insn; insn = NEXT_INSN (insn))
546 if (GET_CODE (insn) == JUMP_INSN)
548 rtx pat = PATTERN (insn);
549 int computed_jump = 0;
551 if (GET_CODE (pat) == PARALLEL)
553 int len = XVECLEN (pat, 0);
554 int has_use_labelref = 0;
556 for (i = len - 1; i >= 0; i--)
557 if (GET_CODE (XVECEXP (pat, 0, i)) == USE
558 && (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
560 has_use_labelref = 1;
562 if (! has_use_labelref)
563 for (i = len - 1; i >= 0; i--)
564 if (GET_CODE (XVECEXP (pat, 0, i)) == SET
565 && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
566 && jmp_uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
569 else if (GET_CODE (pat) == SET
570 && SET_DEST (pat) == pc_rtx
571 && jmp_uses_reg_or_mem (SET_SRC (pat)))
576 for (x = label_value_list; x; x = XEXP (x, 1))
577 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
580 for (x = forced_labels; x; x = XEXP (x, 1))
581 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
586 /* Find all call insns and mark them as possibly jumping
587 to all the nonlocal goto handler labels. */
589 for (insn = f; insn; insn = NEXT_INSN (insn))
590 if (GET_CODE (insn) == CALL_INSN
591 && ! find_reg_note (insn, REG_RETVAL, NULL_RTX))
593 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
594 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
597 /* ??? This could be made smarter:
598 in some cases it's possible to tell that certain
599 calls will not do a nonlocal goto.
601 For example, if the nested functions that do the
602 nonlocal gotos do not have their addresses taken, then
603 only calls to those functions or to other nested
604 functions that use them could possibly do nonlocal
608 /* Pass over all blocks, marking each block that is reachable
609 and has not yet been marked.
610 Keep doing this until, in one pass, no blocks have been marked.
611 Then blocks_live and blocks_marked are identical and correct.
612 In addition, all jumps actually reachable have been marked. */
614 while (something_marked)
616 something_marked = 0;
617 for (i = 0; i < n_basic_blocks; i++)
618 if (block_live[i] && !block_marked[i])
621 something_marked = 1;
622 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
623 block_live[i + 1] = 1;
624 insn = basic_block_end[i];
625 if (GET_CODE (insn) == JUMP_INSN)
626 mark_label_ref (PATTERN (insn), insn, 0);
630 /* ??? See if we have a "live" basic block that is not reachable.
631 This can happen if it is headed by a label that is preserved or
632 in one of the label lists, but no call or computed jump is in
633 the loop. It's not clear if we can delete the block or not,
634 but don't for now. However, we will mess up register status if
635 it remains unreachable, so add a fake reachability from the
638 for (i = 1; i < n_basic_blocks; i++)
639 if (block_live[i] && ! basic_block_drops_in[i]
640 && GET_CODE (basic_block_head[i]) == CODE_LABEL
641 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
642 basic_block_drops_in[i] = 1;
644 /* Now delete the code for any basic blocks that can't be reached.
645 They can occur because jump_optimize does not recognize
646 unreachable loops as unreachable. */
649 for (i = 0; i < n_basic_blocks; i++)
654 /* Delete the insns in a (non-live) block. We physically delete
655 every non-note insn except the start and end (so
656 basic_block_head/end needn't be updated), we turn the latter
657 into NOTE_INSN_DELETED notes.
658 We use to "delete" the insns by turning them into notes, but
659 we may be deleting lots of insns that subsequent passes would
660 otherwise have to process. Secondly, lots of deleted blocks in
661 a row can really slow down propagate_block since it will
662 otherwise process insn-turned-notes multiple times when it
663 looks for loop begin/end notes. */
664 if (basic_block_head[i] != basic_block_end[i])
666 /* It would be quicker to delete all of these with a single
667 unchaining, rather than one at a time, but we need to keep
669 insn = NEXT_INSN (basic_block_head[i]);
670 while (insn != basic_block_end[i])
672 if (GET_CODE (insn) == BARRIER)
674 else if (GET_CODE (insn) != NOTE)
675 insn = flow_delete_insn (insn);
677 insn = NEXT_INSN (insn);
680 insn = basic_block_head[i];
681 if (GET_CODE (insn) != NOTE)
683 /* Turn the head into a deleted insn note. */
684 if (GET_CODE (insn) == BARRIER)
686 PUT_CODE (insn, NOTE);
687 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
688 NOTE_SOURCE_FILE (insn) = 0;
690 insn = basic_block_end[i];
691 if (GET_CODE (insn) != NOTE)
693 /* Turn the tail into a deleted insn note. */
694 if (GET_CODE (insn) == BARRIER)
696 PUT_CODE (insn, NOTE);
697 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
698 NOTE_SOURCE_FILE (insn) = 0;
700 /* BARRIERs are between basic blocks, not part of one.
701 Delete a BARRIER if the preceding jump is deleted.
702 We cannot alter a BARRIER into a NOTE
703 because it is too short; but we can really delete
704 it because it is not part of a basic block. */
705 if (NEXT_INSN (insn) != 0
706 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
707 delete_insn (NEXT_INSN (insn));
709 /* Each time we delete some basic blocks,
710 see if there is a jump around them that is
711 being turned into a no-op. If so, delete it. */
713 if (block_live[i - 1])
716 for (j = i + 1; j < n_basic_blocks; j++)
720 insn = basic_block_end[i - 1];
721 if (GET_CODE (insn) == JUMP_INSN
722 /* An unconditional jump is the only possibility
723 we must check for, since a conditional one
724 would make these blocks live. */
725 && simplejump_p (insn)
726 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
727 && INSN_UID (label) != 0
728 && BLOCK_NUM (label) == j)
730 PUT_CODE (insn, NOTE);
731 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
732 NOTE_SOURCE_FILE (insn) = 0;
733 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
735 delete_insn (NEXT_INSN (insn));
742 /* There are pathological cases where one function calling hundreds of
743 nested inline functions can generate lots and lots of unreachable
744 blocks that jump can't delete. Since we don't use sparse matrices
745 a lot of memory will be needed to compile such functions.
746 Implementing sparse matrices is a fair bit of work and it is not
747 clear that they win more than they lose (we don't want to
748 unnecessarily slow down compilation of normal code). By making
749 another pass for the pathological case, we can greatly speed up
750 their compilation without hurting normal code. This works because
751 all the insns in the unreachable blocks have either been deleted or
753 Note that we're talking about reducing memory usage by 10's of
754 megabytes and reducing compilation time by several minutes. */
755 /* ??? The choice of when to make another pass is a bit arbitrary,
756 and was derived from empirical data. */
761 n_basic_blocks -= deleted;
762 /* `n_basic_blocks' may not be correct at this point: two previously
763 separate blocks may now be merged. That's ok though as we
764 recalculate it during the second pass. It certainly can't be
765 any larger than the current value. */
771 /* Subroutines of find_basic_blocks. */
773 /* Return 1 if X, the SRC_SRC of SET of (pc) contain a REG or MEM that is
774 not in the constant pool and not in the condition of an IF_THEN_ELSE. */
777 jmp_uses_reg_or_mem (x)
780 enum rtx_code code = GET_CODE (x);
795 return ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
796 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)));
799 return (jmp_uses_reg_or_mem (XEXP (x, 1))
800 || jmp_uses_reg_or_mem (XEXP (x, 2)));
802 case PLUS: case MINUS: case MULT:
803 return (jmp_uses_reg_or_mem (XEXP (x, 0))
804 || jmp_uses_reg_or_mem (XEXP (x, 1)));
807 fmt = GET_RTX_FORMAT (code);
808 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
811 && jmp_uses_reg_or_mem (XEXP (x, i)))
815 for (j = 0; j < XVECLEN (x, i); j++)
816 if (jmp_uses_reg_or_mem (XVECEXP (x, i, j)))
823 /* Check expression X for label references;
824 if one is found, add INSN to the label's chain of references.
826 CHECKDUP means check for and avoid creating duplicate references
827 from the same insn. Such duplicates do no serious harm but
828 can slow life analysis. CHECKDUP is set only when duplicates
832 mark_label_ref (x, insn, checkdup)
836 register RTX_CODE code;
840 /* We can be called with NULL when scanning label_value_list. */
845 if (code == LABEL_REF)
847 register rtx label = XEXP (x, 0);
849 if (GET_CODE (label) != CODE_LABEL)
851 /* If the label was never emitted, this insn is junk,
852 but avoid a crash trying to refer to BLOCK_NUM (label).
853 This can happen as a result of a syntax error
854 and a diagnostic has already been printed. */
855 if (INSN_UID (label) == 0)
857 CONTAINING_INSN (x) = insn;
858 /* if CHECKDUP is set, check for duplicate ref from same insn
861 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
862 if (CONTAINING_INSN (y) == insn)
864 LABEL_NEXTREF (x) = LABEL_REFS (label);
865 LABEL_REFS (label) = x;
866 block_live_static[BLOCK_NUM (label)] = 1;
870 fmt = GET_RTX_FORMAT (code);
871 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
874 mark_label_ref (XEXP (x, i), insn, 0);
878 for (j = 0; j < XVECLEN (x, i); j++)
879 mark_label_ref (XVECEXP (x, i, j), insn, 1);
884 /* Delete INSN by patching it out.
885 Return the next insn. */
888 flow_delete_insn (insn)
891 /* ??? For the moment we assume we don't have to watch for NULLs here
892 since the start/end of basic blocks aren't deleted like this. */
893 NEXT_INSN (PREV_INSN (insn)) = NEXT_INSN (insn);
894 PREV_INSN (NEXT_INSN (insn)) = PREV_INSN (insn);
895 return NEXT_INSN (insn);
898 /* Determine which registers are live at the start of each
899 basic block of the function whose first insn is F.
900 NREGS is the number of registers used in F.
901 We allocate the vector basic_block_live_at_start
902 and the regsets that it points to, and fill them with the data.
903 regset_size and regset_bytes are also set here. */
906 life_analysis (f, nregs)
913 /* For each basic block, a bitmask of regs
914 live on exit from the block. */
915 regset *basic_block_live_at_end;
916 /* For each basic block, a bitmask of regs
917 live on entry to a successor-block of this block.
918 If this does not match basic_block_live_at_end,
919 that must be updated, and the block must be rescanned. */
920 regset *basic_block_new_live_at_end;
921 /* For each basic block, a bitmask of regs
922 whose liveness at the end of the basic block
923 can make a difference in which regs are live on entry to the block.
924 These are the regs that are set within the basic block,
925 possibly excluding those that are used after they are set. */
926 regset *basic_block_significant;
930 struct obstack flow_obstack;
932 gcc_obstack_init (&flow_obstack);
936 bzero (regs_ever_live, sizeof regs_ever_live);
938 /* Allocate and zero out many data structures
939 that will record the data from lifetime analysis. */
941 allocate_for_life_analysis ();
943 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
944 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
946 /* Set up several regset-vectors used internally within this function.
947 Their meanings are documented above, with their declarations. */
949 basic_block_live_at_end
950 = (regset *) alloca (n_basic_blocks * sizeof (regset));
952 /* Don't use alloca since that leads to a crash rather than an error message
953 if there isn't enough space.
954 Don't use oballoc since we may need to allocate other things during
955 this function on the temporary obstack. */
956 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
957 bzero ((char *) tem, n_basic_blocks * regset_bytes);
958 init_regset_vector (basic_block_live_at_end, tem,
959 n_basic_blocks, regset_bytes);
961 basic_block_new_live_at_end
962 = (regset *) alloca (n_basic_blocks * sizeof (regset));
963 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
964 bzero ((char *) tem, n_basic_blocks * regset_bytes);
965 init_regset_vector (basic_block_new_live_at_end, tem,
966 n_basic_blocks, regset_bytes);
968 basic_block_significant
969 = (regset *) alloca (n_basic_blocks * sizeof (regset));
970 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
971 bzero ((char *) tem, n_basic_blocks * regset_bytes);
972 init_regset_vector (basic_block_significant, tem,
973 n_basic_blocks, regset_bytes);
975 /* Record which insns refer to any volatile memory
976 or for any reason can't be deleted just because they are dead stores.
977 Also, delete any insns that copy a register to itself. */
979 for (insn = f; insn; insn = NEXT_INSN (insn))
981 enum rtx_code code1 = GET_CODE (insn);
982 if (code1 == CALL_INSN)
983 INSN_VOLATILE (insn) = 1;
984 else if (code1 == INSN || code1 == JUMP_INSN)
986 /* Delete (in effect) any obvious no-op moves. */
987 if (GET_CODE (PATTERN (insn)) == SET
988 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
989 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
990 && REGNO (SET_DEST (PATTERN (insn))) ==
991 REGNO (SET_SRC (PATTERN (insn)))
992 /* Insns carrying these notes are useful later on. */
993 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
995 PUT_CODE (insn, NOTE);
996 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
997 NOTE_SOURCE_FILE (insn) = 0;
999 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
1001 /* If nothing but SETs of registers to themselves,
1002 this insn can also be deleted. */
1003 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
1005 rtx tem = XVECEXP (PATTERN (insn), 0, i);
1007 if (GET_CODE (tem) == USE
1008 || GET_CODE (tem) == CLOBBER)
1011 if (GET_CODE (tem) != SET
1012 || GET_CODE (SET_DEST (tem)) != REG
1013 || GET_CODE (SET_SRC (tem)) != REG
1014 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
1018 if (i == XVECLEN (PATTERN (insn), 0)
1019 /* Insns carrying these notes are useful later on. */
1020 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1022 PUT_CODE (insn, NOTE);
1023 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1024 NOTE_SOURCE_FILE (insn) = 0;
1027 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1029 else if (GET_CODE (PATTERN (insn)) != USE)
1030 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1031 /* A SET that makes space on the stack cannot be dead.
1032 (Such SETs occur only for allocating variable-size data,
1033 so they will always have a PLUS or MINUS according to the
1034 direction of stack growth.)
1035 Even if this function never uses this stack pointer value,
1036 signal handlers do! */
1037 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
1038 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1039 #ifdef STACK_GROWS_DOWNWARD
1040 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
1042 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1044 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
1045 INSN_VOLATILE (insn) = 1;
1049 if (n_basic_blocks > 0)
1050 #ifdef EXIT_IGNORE_STACK
1051 if (! EXIT_IGNORE_STACK
1052 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
1055 /* If exiting needs the right stack value,
1056 consider the stack pointer live at the end of the function. */
1057 basic_block_live_at_end[n_basic_blocks - 1]
1058 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1059 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1060 basic_block_new_live_at_end[n_basic_blocks - 1]
1061 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1062 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1065 /* Mark the frame pointer is needed at the end of the function. If
1066 we end up eliminating it, it will be removed from the live list
1067 of each basic block by reload. */
1069 if (n_basic_blocks > 0)
1071 basic_block_live_at_end[n_basic_blocks - 1]
1072 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1073 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
1074 basic_block_new_live_at_end[n_basic_blocks - 1]
1075 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1076 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
1077 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1078 /* If they are different, also mark the hard frame pointer as live */
1079 basic_block_live_at_end[n_basic_blocks - 1]
1080 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1081 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
1083 basic_block_new_live_at_end[n_basic_blocks - 1]
1084 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1085 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
1090 /* Mark all global registers as being live at the end of the function
1091 since they may be referenced by our caller. */
1093 if (n_basic_blocks > 0)
1094 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1097 basic_block_live_at_end[n_basic_blocks - 1]
1098 [i / REGSET_ELT_BITS]
1099 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
1100 basic_block_new_live_at_end[n_basic_blocks - 1]
1101 [i / REGSET_ELT_BITS]
1102 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
1105 /* Propagate life info through the basic blocks
1106 around the graph of basic blocks.
1108 This is a relaxation process: each time a new register
1109 is live at the end of the basic block, we must scan the block
1110 to determine which registers are, as a consequence, live at the beginning
1111 of that block. These registers must then be marked live at the ends
1112 of all the blocks that can transfer control to that block.
1113 The process continues until it reaches a fixed point. */
1120 for (i = n_basic_blocks - 1; i >= 0; i--)
1122 int consider = first_pass;
1123 int must_rescan = first_pass;
1128 /* Set CONSIDER if this block needs thinking about at all
1129 (that is, if the regs live now at the end of it
1130 are not the same as were live at the end of it when
1131 we last thought about it).
1132 Set must_rescan if it needs to be thought about
1133 instruction by instruction (that is, if any additional
1134 reg that is live at the end now but was not live there before
1135 is one of the significant regs of this basic block). */
1137 for (j = 0; j < regset_size; j++)
1139 register REGSET_ELT_TYPE x
1140 = (basic_block_new_live_at_end[i][j]
1141 & ~basic_block_live_at_end[i][j]);
1144 if (x & basic_block_significant[i][j])
1156 /* The live_at_start of this block may be changing,
1157 so another pass will be required after this one. */
1162 /* No complete rescan needed;
1163 just record those variables newly known live at end
1164 as live at start as well. */
1165 for (j = 0; j < regset_size; j++)
1167 register REGSET_ELT_TYPE x
1168 = (basic_block_new_live_at_end[i][j]
1169 & ~basic_block_live_at_end[i][j]);
1170 basic_block_live_at_start[i][j] |= x;
1171 basic_block_live_at_end[i][j] |= x;
1176 /* Update the basic_block_live_at_start
1177 by propagation backwards through the block. */
1178 bcopy ((char *) basic_block_new_live_at_end[i],
1179 (char *) basic_block_live_at_end[i], regset_bytes);
1180 bcopy ((char *) basic_block_live_at_end[i],
1181 (char *) basic_block_live_at_start[i], regset_bytes);
1182 propagate_block (basic_block_live_at_start[i],
1183 basic_block_head[i], basic_block_end[i], 0,
1184 first_pass ? basic_block_significant[i]
1190 register rtx jump, head;
1192 /* Update the basic_block_new_live_at_end's of the block
1193 that falls through into this one (if any). */
1194 head = basic_block_head[i];
1195 if (basic_block_drops_in[i])
1198 for (j = 0; j < regset_size; j++)
1199 basic_block_new_live_at_end[i-1][j]
1200 |= basic_block_live_at_start[i][j];
1203 /* Update the basic_block_new_live_at_end's of
1204 all the blocks that jump to this one. */
1205 if (GET_CODE (head) == CODE_LABEL)
1206 for (jump = LABEL_REFS (head);
1208 jump = LABEL_NEXTREF (jump))
1210 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1212 for (j = 0; j < regset_size; j++)
1213 basic_block_new_live_at_end[from_block][j]
1214 |= basic_block_live_at_start[i][j];
1224 /* The only pseudos that are live at the beginning of the function are
1225 those that were not set anywhere in the function. local-alloc doesn't
1226 know how to handle these correctly, so mark them as not local to any
1229 if (n_basic_blocks > 0)
1230 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1231 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1232 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1233 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1235 /* Now the life information is accurate.
1236 Make one more pass over each basic block
1237 to delete dead stores, create autoincrement addressing
1238 and record how many times each register is used, is set, or dies.
1240 To save time, we operate directly in basic_block_live_at_end[i],
1241 thus destroying it (in fact, converting it into a copy of
1242 basic_block_live_at_start[i]). This is ok now because
1243 basic_block_live_at_end[i] is no longer used past this point. */
1247 for (i = 0; i < n_basic_blocks; i++)
1249 propagate_block (basic_block_live_at_end[i],
1250 basic_block_head[i], basic_block_end[i], 1,
1258 /* Something live during a setjmp should not be put in a register
1259 on certain machines which restore regs from stack frames
1260 rather than from the jmpbuf.
1261 But we don't need to do this for the user's variables, since
1262 ANSI says only volatile variables need this. */
1263 #ifdef LONGJMP_RESTORE_FROM_STACK
1264 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1265 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1266 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1267 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1269 reg_live_length[i] = -1;
1270 reg_basic_block[i] = -1;
1275 /* We have a problem with any pseudoreg that
1276 lives across the setjmp. ANSI says that if a
1277 user variable does not change in value
1278 between the setjmp and the longjmp, then the longjmp preserves it.
1279 This includes longjmp from a place where the pseudo appears dead.
1280 (In principle, the value still exists if it is in scope.)
1281 If the pseudo goes in a hard reg, some other value may occupy
1282 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1283 Conclusion: such a pseudo must not go in a hard reg. */
1284 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1285 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1286 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1287 && regno_reg_rtx[i] != 0)
1289 reg_live_length[i] = -1;
1290 reg_basic_block[i] = -1;
1293 obstack_free (&flow_obstack, NULL_PTR);
1296 /* Subroutines of life analysis. */
1298 /* Allocate the permanent data structures that represent the results
1299 of life analysis. Not static since used also for stupid life analysis. */
1302 allocate_for_life_analysis ()
1305 register regset tem;
1307 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1308 regset_bytes = regset_size * sizeof (*(regset) 0);
1310 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1311 bzero ((char *) reg_n_refs, max_regno * sizeof (int));
1313 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1314 bzero ((char *) reg_n_sets, max_regno * sizeof (short));
1316 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1317 bzero ((char *) reg_n_deaths, max_regno * sizeof (short));
1319 reg_changes_size = (char *) oballoc (max_regno * sizeof (char));
1320 bzero (reg_changes_size, max_regno * sizeof (char));;
1322 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1323 bzero ((char *) reg_live_length, max_regno * sizeof (int));
1325 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1326 bzero ((char *) reg_n_calls_crossed, max_regno * sizeof (int));
1328 reg_basic_block = (int *) oballoc (max_regno * sizeof (int));
1329 for (i = 0; i < max_regno; i++)
1330 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1332 basic_block_live_at_start
1333 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1334 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1335 bzero ((char *) tem, n_basic_blocks * regset_bytes);
1336 init_regset_vector (basic_block_live_at_start, tem,
1337 n_basic_blocks, regset_bytes);
1339 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1340 bzero ((char *) regs_live_at_setjmp, regset_bytes);
1343 /* Make each element of VECTOR point at a regset,
1344 taking the space for all those regsets from SPACE.
1345 SPACE is of type regset, but it is really as long as NELTS regsets.
1346 BYTES_PER_ELT is the number of bytes in one regset. */
1349 init_regset_vector (vector, space, nelts, bytes_per_elt)
1356 register regset p = space;
1358 for (i = 0; i < nelts; i++)
1361 p += bytes_per_elt / sizeof (*p);
1365 /* Compute the registers live at the beginning of a basic block
1366 from those live at the end.
1368 When called, OLD contains those live at the end.
1369 On return, it contains those live at the beginning.
1370 FIRST and LAST are the first and last insns of the basic block.
1372 FINAL is nonzero if we are doing the final pass which is not
1373 for computing the life info (since that has already been done)
1374 but for acting on it. On this pass, we delete dead stores,
1375 set up the logical links and dead-variables lists of instructions,
1376 and merge instructions for autoincrement and autodecrement addresses.
1378 SIGNIFICANT is nonzero only the first time for each basic block.
1379 If it is nonzero, it points to a regset in which we store
1380 a 1 for each register that is set within the block.
1382 BNUM is the number of the basic block. */
1385 propagate_block (old, first, last, final, significant, bnum)
1386 register regset old;
1398 /* The following variables are used only if FINAL is nonzero. */
1399 /* This vector gets one element for each reg that has been live
1400 at any point in the basic block that has been scanned so far.
1401 SOMETIMES_MAX says how many elements are in use so far.
1402 In each element, OFFSET is the byte-number within a regset
1403 for the register described by the element, and BIT is a mask
1404 for that register's bit within the byte. */
1405 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1406 int sometimes_max = 0;
1407 /* This regset has 1 for each reg that we have seen live so far.
1408 It and REGS_SOMETIMES_LIVE are updated together. */
1411 /* The loop depth may change in the middle of a basic block. Since we
1412 scan from end to beginning, we start with the depth at the end of the
1413 current basic block, and adjust as we pass ends and starts of loops. */
1414 loop_depth = basic_block_loop_depth[bnum];
1416 dead = (regset) alloca (regset_bytes);
1417 live = (regset) alloca (regset_bytes);
1422 /* Include any notes at the end of the block in the scan.
1423 This is in case the block ends with a call to setjmp. */
1425 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1427 /* Look for loop boundaries, we are going forward here. */
1428 last = NEXT_INSN (last);
1429 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1431 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1437 register int i, offset;
1438 REGSET_ELT_TYPE bit;
1441 maxlive = (regset) alloca (regset_bytes);
1442 bcopy ((char *) old, (char *) maxlive, regset_bytes);
1444 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1446 /* Process the regs live at the end of the block.
1447 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1448 Also mark them as not local to any one basic block. */
1450 for (offset = 0, i = 0; offset < regset_size; offset++)
1451 for (bit = 1; bit; bit <<= 1, i++)
1455 if (old[offset] & bit)
1457 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1458 regs_sometimes_live[sometimes_max].offset = offset;
1459 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1465 /* Scan the block an insn at a time from end to beginning. */
1467 for (insn = last; ; insn = prev)
1469 prev = PREV_INSN (insn);
1471 if (GET_CODE (insn) == NOTE)
1473 /* Look for loop boundaries, remembering that we are going
1475 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1477 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1480 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1481 Abort now rather than setting register status incorrectly. */
1482 if (loop_depth == 0)
1485 /* If this is a call to `setjmp' et al,
1486 warn if any non-volatile datum is live. */
1488 if (final && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1491 for (i = 0; i < regset_size; i++)
1492 regs_live_at_setjmp[i] |= old[i];
1496 /* Update the life-status of regs for this insn.
1497 First DEAD gets which regs are set in this insn
1498 then LIVE gets which regs are used in this insn.
1499 Then the regs live before the insn
1500 are those live after, with DEAD regs turned off,
1501 and then LIVE regs turned on. */
1503 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1506 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1508 = (insn_dead_p (PATTERN (insn), old, 0)
1509 /* Don't delete something that refers to volatile storage! */
1510 && ! INSN_VOLATILE (insn));
1512 = (insn_is_dead && note != 0
1513 && libcall_dead_p (PATTERN (insn), old, note, insn));
1515 /* If an instruction consists of just dead store(s) on final pass,
1516 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1517 We could really delete it with delete_insn, but that
1518 can cause trouble for first or last insn in a basic block. */
1519 if (final && insn_is_dead)
1521 PUT_CODE (insn, NOTE);
1522 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1523 NOTE_SOURCE_FILE (insn) = 0;
1525 /* CC0 is now known to be dead. Either this insn used it,
1526 in which case it doesn't anymore, or clobbered it,
1527 so the next insn can't use it. */
1530 /* If this insn is copying the return value from a library call,
1531 delete the entire library call. */
1532 if (libcall_is_dead)
1534 rtx first = XEXP (note, 0);
1536 while (INSN_DELETED_P (first))
1537 first = NEXT_INSN (first);
1542 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1543 NOTE_SOURCE_FILE (p) = 0;
1549 for (i = 0; i < regset_size; i++)
1551 dead[i] = 0; /* Faster than bzero here */
1552 live[i] = 0; /* since regset_size is usually small */
1555 /* See if this is an increment or decrement that can be
1556 merged into a following memory address. */
1559 register rtx x = PATTERN (insn);
1560 /* Does this instruction increment or decrement a register? */
1561 if (final && GET_CODE (x) == SET
1562 && GET_CODE (SET_DEST (x)) == REG
1563 && (GET_CODE (SET_SRC (x)) == PLUS
1564 || GET_CODE (SET_SRC (x)) == MINUS)
1565 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1566 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1567 /* Ok, look for a following memory ref we can combine with.
1568 If one is found, change the memory ref to a PRE_INC
1569 or PRE_DEC, cancel this insn, and return 1.
1570 Return 0 if nothing has been done. */
1571 && try_pre_increment_1 (insn))
1574 #endif /* AUTO_INC_DEC */
1576 /* If this is not the final pass, and this insn is copying the
1577 value of a library call and it's dead, don't scan the
1578 insns that perform the library call, so that the call's
1579 arguments are not marked live. */
1580 if (libcall_is_dead)
1582 /* Mark the dest reg as `significant'. */
1583 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1585 insn = XEXP (note, 0);
1586 prev = PREV_INSN (insn);
1588 else if (GET_CODE (PATTERN (insn)) == SET
1589 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1590 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1591 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1592 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1593 /* We have an insn to pop a constant amount off the stack.
1594 (Such insns use PLUS regardless of the direction of the stack,
1595 and any insn to adjust the stack by a constant is always a pop.)
1596 These insns, if not dead stores, have no effect on life. */
1600 /* LIVE gets the regs used in INSN;
1601 DEAD gets those set by it. Dead insns don't make anything
1604 mark_set_regs (old, dead, PATTERN (insn),
1605 final ? insn : NULL_RTX, significant);
1607 /* If an insn doesn't use CC0, it becomes dead since we
1608 assume that every insn clobbers it. So show it dead here;
1609 mark_used_regs will set it live if it is referenced. */
1613 mark_used_regs (old, live, PATTERN (insn), final, insn);
1615 /* Sometimes we may have inserted something before INSN (such as
1616 a move) when we make an auto-inc. So ensure we will scan
1619 prev = PREV_INSN (insn);
1622 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1628 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1630 note = XEXP (note, 1))
1631 if (GET_CODE (XEXP (note, 0)) == USE)
1632 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1635 /* Each call clobbers all call-clobbered regs that are not
1636 global or fixed. Note that the function-value reg is a
1637 call-clobbered reg, and mark_set_regs has already had
1638 a chance to handle it. */
1640 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1641 if (call_used_regs[i] && ! global_regs[i]
1643 dead[i / REGSET_ELT_BITS]
1644 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1646 /* The stack ptr is used (honorarily) by a CALL insn. */
1647 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1648 |= ((REGSET_ELT_TYPE) 1
1649 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1651 /* Calls may also reference any of the global registers,
1652 so they are made live. */
1653 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1655 mark_used_regs (old, live,
1656 gen_rtx (REG, reg_raw_mode[i], i),
1659 /* Calls also clobber memory. */
1663 /* Update OLD for the registers used or set. */
1664 for (i = 0; i < regset_size; i++)
1670 if (GET_CODE (insn) == CALL_INSN && final)
1672 /* Any regs live at the time of a call instruction
1673 must not go in a register clobbered by calls.
1674 Find all regs now live and record this for them. */
1676 register struct sometimes *p = regs_sometimes_live;
1678 for (i = 0; i < sometimes_max; i++, p++)
1679 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1680 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1684 /* On final pass, add any additional sometimes-live regs
1685 into MAXLIVE and REGS_SOMETIMES_LIVE.
1686 Also update counts of how many insns each reg is live at. */
1690 for (i = 0; i < regset_size; i++)
1692 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1698 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1699 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1701 regs_sometimes_live[sometimes_max].offset = i;
1702 regs_sometimes_live[sometimes_max].bit = regno;
1703 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1710 register struct sometimes *p = regs_sometimes_live;
1711 for (i = 0; i < sometimes_max; i++, p++)
1713 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1714 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1724 if (num_scratch > max_scratch)
1725 max_scratch = num_scratch;
1728 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1729 (SET expressions whose destinations are registers dead after the insn).
1730 NEEDED is the regset that says which regs are alive after the insn.
1732 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1735 insn_dead_p (x, needed, call_ok)
1740 register RTX_CODE code = GET_CODE (x);
1741 /* If setting something that's a reg or part of one,
1742 see if that register's altered value will be live. */
1746 register rtx r = SET_DEST (x);
1747 /* A SET that is a subroutine call cannot be dead. */
1748 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1752 if (GET_CODE (r) == CC0)
1756 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1757 && rtx_equal_p (r, last_mem_set))
1760 while (GET_CODE (r) == SUBREG
1761 || GET_CODE (r) == STRICT_LOW_PART
1762 || GET_CODE (r) == ZERO_EXTRACT
1763 || GET_CODE (r) == SIGN_EXTRACT)
1766 if (GET_CODE (r) == REG)
1768 register int regno = REGNO (r);
1769 register int offset = regno / REGSET_ELT_BITS;
1770 register REGSET_ELT_TYPE bit
1771 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1773 /* Don't delete insns to set global regs. */
1774 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1775 /* Make sure insns to set frame pointer aren't deleted. */
1776 || regno == FRAME_POINTER_REGNUM
1777 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1778 || regno == HARD_FRAME_POINTER_REGNUM
1780 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1781 /* Make sure insns to set arg pointer are never deleted
1782 (if the arg pointer isn't fixed, there will be a USE for
1783 it, so we can treat it normally). */
1784 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1786 || (needed[offset] & bit) != 0)
1789 /* If this is a hard register, verify that subsequent words are
1791 if (regno < FIRST_PSEUDO_REGISTER)
1793 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1796 if ((needed[(regno + n) / REGSET_ELT_BITS]
1797 & ((REGSET_ELT_TYPE) 1
1798 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1805 /* If performing several activities,
1806 insn is dead if each activity is individually dead.
1807 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1808 that's inside a PARALLEL doesn't make the insn worth keeping. */
1809 else if (code == PARALLEL)
1811 register int i = XVECLEN (x, 0);
1812 for (i--; i >= 0; i--)
1814 rtx elt = XVECEXP (x, 0, i);
1815 if (!insn_dead_p (elt, needed, call_ok)
1816 && GET_CODE (elt) != CLOBBER
1817 && GET_CODE (elt) != USE)
1822 /* We do not check CLOBBER or USE here.
1823 An insn consisting of just a CLOBBER or just a USE
1824 should not be deleted. */
1828 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1829 return 1 if the entire library call is dead.
1830 This is true if X copies a register (hard or pseudo)
1831 and if the hard return reg of the call insn is dead.
1832 (The caller should have tested the destination of X already for death.)
1834 If this insn doesn't just copy a register, then we don't
1835 have an ordinary libcall. In that case, cse could not have
1836 managed to substitute the source for the dest later on,
1837 so we can assume the libcall is dead.
1839 NEEDED is the bit vector of pseudoregs live before this insn.
1840 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1843 libcall_dead_p (x, needed, note, insn)
1849 register RTX_CODE code = GET_CODE (x);
1853 register rtx r = SET_SRC (x);
1854 if (GET_CODE (r) == REG)
1856 rtx call = XEXP (note, 0);
1859 /* Find the call insn. */
1860 while (call != insn && GET_CODE (call) != CALL_INSN)
1861 call = NEXT_INSN (call);
1863 /* If there is none, do nothing special,
1864 since ordinary death handling can understand these insns. */
1868 /* See if the hard reg holding the value is dead.
1869 If this is a PARALLEL, find the call within it. */
1870 call = PATTERN (call);
1871 if (GET_CODE (call) == PARALLEL)
1873 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1874 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1875 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1878 /* This may be a library call that is returning a value
1879 via invisible pointer. Do nothing special, since
1880 ordinary death handling can understand these insns. */
1884 call = XVECEXP (call, 0, i);
1887 return insn_dead_p (call, needed, 1);
1893 /* Return 1 if register REGNO was used before it was set.
1894 In other words, if it is live at function entry.
1895 Don't count global register variables, though. */
1898 regno_uninitialized (regno)
1901 if (n_basic_blocks == 0
1902 || (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1905 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1906 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1909 /* 1 if register REGNO was alive at a place where `setjmp' was called
1910 and was set more than once or is an argument.
1911 Such regs may be clobbered by `longjmp'. */
1914 regno_clobbered_at_setjmp (regno)
1917 if (n_basic_blocks == 0)
1920 return ((reg_n_sets[regno] > 1
1921 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1922 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1923 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1924 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1927 /* Process the registers that are set within X.
1928 Their bits are set to 1 in the regset DEAD,
1929 because they are dead prior to this insn.
1931 If INSN is nonzero, it is the insn being processed
1932 and the fact that it is nonzero implies this is the FINAL pass
1933 in propagate_block. In this case, various info about register
1934 usage is stored, LOG_LINKS fields of insns are set up. */
1937 mark_set_regs (needed, dead, x, insn, significant)
1944 register RTX_CODE code = GET_CODE (x);
1946 if (code == SET || code == CLOBBER)
1947 mark_set_1 (needed, dead, x, insn, significant);
1948 else if (code == PARALLEL)
1951 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1953 code = GET_CODE (XVECEXP (x, 0, i));
1954 if (code == SET || code == CLOBBER)
1955 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1960 /* Process a single SET rtx, X. */
1963 mark_set_1 (needed, dead, x, insn, significant)
1971 register rtx reg = SET_DEST (x);
1973 /* Modifying just one hardware register of a multi-reg value
1974 or just a byte field of a register
1975 does not mean the value from before this insn is now dead.
1976 But it does mean liveness of that register at the end of the block
1979 Within mark_set_1, however, we treat it as if the register is
1980 indeed modified. mark_used_regs will, however, also treat this
1981 register as being used. Thus, we treat these insns as setting a
1982 new value for the register as a function of its old value. This
1983 cases LOG_LINKS to be made appropriately and this will help combine. */
1985 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1986 || GET_CODE (reg) == SIGN_EXTRACT
1987 || GET_CODE (reg) == STRICT_LOW_PART)
1988 reg = XEXP (reg, 0);
1990 /* If we are writing into memory or into a register mentioned in the
1991 address of the last thing stored into memory, show we don't know
1992 what the last store was. If we are writing memory, save the address
1993 unless it is volatile. */
1994 if (GET_CODE (reg) == MEM
1995 || (GET_CODE (reg) == REG
1996 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1999 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
2000 /* There are no REG_INC notes for SP, so we can't assume we'll see
2001 everything that invalidates it. To be safe, don't eliminate any
2002 stores though SP; none of them should be redundant anyway. */
2003 && ! reg_mentioned_p (stack_pointer_rtx, reg))
2006 if (GET_CODE (reg) == REG
2007 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
2008 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2009 && regno != HARD_FRAME_POINTER_REGNUM
2011 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2012 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2014 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
2015 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
2017 register int offset = regno / REGSET_ELT_BITS;
2018 register REGSET_ELT_TYPE bit
2019 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2020 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
2021 REGSET_ELT_TYPE some_not_needed = (~ needed[offset]) & bit;
2023 /* Mark it as a significant register for this basic block. */
2025 significant[offset] |= bit;
2027 /* Mark it as as dead before this insn. */
2028 dead[offset] |= bit;
2030 /* A hard reg in a wide mode may really be multiple registers.
2031 If so, mark all of them just like the first. */
2032 if (regno < FIRST_PSEUDO_REGISTER)
2036 /* Nothing below is needed for the stack pointer; get out asap.
2037 Eg, log links aren't needed, since combine won't use them. */
2038 if (regno == STACK_POINTER_REGNUM)
2041 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
2044 REGSET_ELT_TYPE n_bit
2045 = (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2048 significant[(regno + n) / REGSET_ELT_BITS] |= n_bit;
2050 dead[(regno + n) / REGSET_ELT_BITS] |= n_bit;
2052 |= (needed[(regno + n) / REGSET_ELT_BITS] & n_bit);
2054 |= ((~ needed[(regno + n) / REGSET_ELT_BITS]) & n_bit);
2057 /* Additional data to record if this is the final pass. */
2060 register rtx y = reg_next_use[regno];
2061 register int blocknum = BLOCK_NUM (insn);
2063 /* If this is a hard reg, record this function uses the reg. */
2065 if (regno < FIRST_PSEUDO_REGISTER)
2068 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
2070 for (i = regno; i < endregno; i++)
2072 /* The next use is no longer "next", since a store
2074 reg_next_use[i] = 0;
2076 regs_ever_live[i] = 1;
2082 /* The next use is no longer "next", since a store
2084 reg_next_use[regno] = 0;
2086 /* Keep track of which basic blocks each reg appears in. */
2088 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2089 reg_basic_block[regno] = blocknum;
2090 else if (reg_basic_block[regno] != blocknum)
2091 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2093 /* Count (weighted) references, stores, etc. This counts a
2094 register twice if it is modified, but that is correct. */
2095 reg_n_sets[regno]++;
2097 reg_n_refs[regno] += loop_depth;
2099 /* The insns where a reg is live are normally counted
2100 elsewhere, but we want the count to include the insn
2101 where the reg is set, and the normal counting mechanism
2102 would not count it. */
2103 reg_live_length[regno]++;
2106 if (! some_not_needed)
2108 /* Make a logical link from the next following insn
2109 that uses this register, back to this insn.
2110 The following insns have already been processed.
2112 We don't build a LOG_LINK for hard registers containing
2113 in ASM_OPERANDs. If these registers get replaced,
2114 we might wind up changing the semantics of the insn,
2115 even if reload can make what appear to be valid assignments
2117 if (y && (BLOCK_NUM (y) == blocknum)
2118 && (regno >= FIRST_PSEUDO_REGISTER
2119 || asm_noperands (PATTERN (y)) < 0))
2121 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
2123 else if (! some_needed)
2125 /* Note that dead stores have already been deleted when possible
2126 If we get here, we have found a dead store that cannot
2127 be eliminated (because the same insn does something useful).
2128 Indicate this by marking the reg being set as dying here. */
2130 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2131 reg_n_deaths[REGNO (reg)]++;
2135 /* This is a case where we have a multi-word hard register
2136 and some, but not all, of the words of the register are
2137 needed in subsequent insns. Write REG_UNUSED notes
2138 for those parts that were not needed. This case should
2143 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2145 if ((needed[(regno + i) / REGSET_ELT_BITS]
2146 & ((REGSET_ELT_TYPE) 1
2147 << ((regno + i) % REGSET_ELT_BITS))) == 0)
2149 = gen_rtx (EXPR_LIST, REG_UNUSED,
2150 gen_rtx (REG, reg_raw_mode[regno + i],
2156 else if (GET_CODE (reg) == REG)
2157 reg_next_use[regno] = 0;
2159 /* If this is the last pass and this is a SCRATCH, show it will be dying
2160 here and count it. */
2161 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2164 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2171 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2175 find_auto_inc (needed, x, insn)
2180 rtx addr = XEXP (x, 0);
2181 HOST_WIDE_INT offset = 0;
2184 /* Here we detect use of an index register which might be good for
2185 postincrement, postdecrement, preincrement, or predecrement. */
2187 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2188 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2190 if (GET_CODE (addr) == REG)
2193 register int size = GET_MODE_SIZE (GET_MODE (x));
2196 int regno = REGNO (addr);
2198 /* Is the next use an increment that might make auto-increment? */
2199 if ((incr = reg_next_use[regno]) != 0
2200 && (set = single_set (incr)) != 0
2201 && GET_CODE (set) == SET
2202 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2203 /* Can't add side effects to jumps; if reg is spilled and
2204 reloaded, there's no way to store back the altered value. */
2205 && GET_CODE (insn) != JUMP_INSN
2206 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2207 && XEXP (y, 0) == addr
2208 && GET_CODE (XEXP (y, 1)) == CONST_INT
2210 #ifdef HAVE_POST_INCREMENT
2211 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2213 #ifdef HAVE_POST_DECREMENT
2214 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2216 #ifdef HAVE_PRE_INCREMENT
2217 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2219 #ifdef HAVE_PRE_DECREMENT
2220 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2223 /* Make sure this reg appears only once in this insn. */
2224 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2225 use != 0 && use != (rtx) 1))
2227 rtx q = SET_DEST (set);
2228 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2229 ? (offset ? PRE_INC : POST_INC)
2230 : (offset ? PRE_DEC : POST_DEC));
2232 if (dead_or_set_p (incr, addr))
2234 /* This is the simple case. Try to make the auto-inc. If
2235 we can't, we are done. Otherwise, we will do any
2236 needed updates below. */
2237 if (! validate_change (insn, &XEXP (x, 0),
2238 gen_rtx (inc_code, Pmode, addr),
2242 else if (GET_CODE (q) == REG
2243 /* PREV_INSN used here to check the semi-open interval
2245 && ! reg_used_between_p (q, PREV_INSN (insn), incr)
2246 /* We must also check for sets of q as q may be
2247 a call clobbered hard register and there may
2248 be a call between PREV_INSN (insn) and incr. */
2249 && ! reg_set_between_p (q, PREV_INSN (insn), incr))
2251 /* We have *p followed sometime later by q = p+size.
2252 Both p and q must be live afterward,
2253 and q is not used between INSN and it's assignment.
2254 Change it to q = p, ...*q..., q = q+size.
2255 Then fall into the usual case. */
2259 emit_move_insn (q, addr);
2260 insns = get_insns ();
2263 /* If anything in INSNS have UID's that don't fit within the
2264 extra space we allocate earlier, we can't make this auto-inc.
2265 This should never happen. */
2266 for (temp = insns; temp; temp = NEXT_INSN (temp))
2268 if (INSN_UID (temp) > max_uid_for_flow)
2270 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2273 /* If we can't make the auto-inc, or can't make the
2274 replacement into Y, exit. There's no point in making
2275 the change below if we can't do the auto-inc and doing
2276 so is not correct in the pre-inc case. */
2278 validate_change (insn, &XEXP (x, 0),
2279 gen_rtx (inc_code, Pmode, q),
2281 validate_change (incr, &XEXP (y, 0), q, 1);
2282 if (! apply_change_group ())
2285 /* We now know we'll be doing this change, so emit the
2286 new insn(s) and do the updates. */
2287 emit_insns_before (insns, insn);
2289 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2290 basic_block_head[BLOCK_NUM (insn)] = insns;
2292 /* INCR will become a NOTE and INSN won't contain a
2293 use of ADDR. If a use of ADDR was just placed in
2294 the insn before INSN, make that the next use.
2295 Otherwise, invalidate it. */
2296 if (GET_CODE (PREV_INSN (insn)) == INSN
2297 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2298 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2299 reg_next_use[regno] = PREV_INSN (insn);
2301 reg_next_use[regno] = 0;
2306 /* REGNO is now used in INCR which is below INSN, but
2307 it previously wasn't live here. If we don't mark
2308 it as needed, we'll put a REG_DEAD note for it
2309 on this insn, which is incorrect. */
2310 needed[regno / REGSET_ELT_BITS]
2311 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2313 /* If there are any calls between INSN and INCR, show
2314 that REGNO now crosses them. */
2315 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2316 if (GET_CODE (temp) == CALL_INSN)
2317 reg_n_calls_crossed[regno]++;
2322 /* If we haven't returned, it means we were able to make the
2323 auto-inc, so update the status. First, record that this insn
2324 has an implicit side effect. */
2327 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2329 /* Modify the old increment-insn to simply copy
2330 the already-incremented value of our register. */
2331 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2334 /* If that makes it a no-op (copying the register into itself) delete
2335 it so it won't appear to be a "use" and a "set" of this
2337 if (SET_DEST (set) == addr)
2339 PUT_CODE (incr, NOTE);
2340 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2341 NOTE_SOURCE_FILE (incr) = 0;
2344 if (regno >= FIRST_PSEUDO_REGISTER)
2346 /* Count an extra reference to the reg. When a reg is
2347 incremented, spilling it is worse, so we want to make
2348 that less likely. */
2349 reg_n_refs[regno] += loop_depth;
2351 /* Count the increment as a setting of the register,
2352 even though it isn't a SET in rtl. */
2353 reg_n_sets[regno]++;
2358 #endif /* AUTO_INC_DEC */
2360 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2361 This is done assuming the registers needed from X
2362 are those that have 1-bits in NEEDED.
2364 On the final pass, FINAL is 1. This means try for autoincrement
2365 and count the uses and deaths of each pseudo-reg.
2367 INSN is the containing instruction. If INSN is dead, this function is not
2371 mark_used_regs (needed, live, x, final, insn)
2378 register RTX_CODE code;
2383 code = GET_CODE (x);
2404 /* If we are clobbering a MEM, mark any registers inside the address
2406 if (GET_CODE (XEXP (x, 0)) == MEM)
2407 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2411 /* Invalidate the data for the last MEM stored. We could do this only
2412 if the addresses conflict, but this doesn't seem worthwhile. */
2417 find_auto_inc (needed, x, insn);
2422 if (GET_CODE (SUBREG_REG (x)) == REG
2423 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2424 && (GET_MODE_SIZE (GET_MODE (x))
2425 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))))
2426 reg_changes_size[REGNO (SUBREG_REG (x))] = 1;
2428 /* While we're here, optimize this case. */
2431 /* In case the SUBREG is not of a register, don't optimize */
2432 if (GET_CODE (x) != REG)
2434 mark_used_regs (needed, live, x, final, insn);
2438 /* ... fall through ... */
2441 /* See a register other than being set
2442 => mark it as needed. */
2446 register int offset = regno / REGSET_ELT_BITS;
2447 register REGSET_ELT_TYPE bit
2448 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2449 REGSET_ELT_TYPE some_needed = needed[offset] & bit;
2450 REGSET_ELT_TYPE some_not_needed = (~ needed[offset]) & bit;
2452 live[offset] |= bit;
2454 /* A hard reg in a wide mode may really be multiple registers.
2455 If so, mark all of them just like the first. */
2456 if (regno < FIRST_PSEUDO_REGISTER)
2460 /* For stack ptr or fixed arg pointer,
2461 nothing below can be necessary, so waste no more time. */
2462 if (regno == STACK_POINTER_REGNUM
2463 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2464 || regno == HARD_FRAME_POINTER_REGNUM
2466 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2467 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2469 || regno == FRAME_POINTER_REGNUM)
2471 /* If this is a register we are going to try to eliminate,
2472 don't mark it live here. If we are successful in
2473 eliminating it, it need not be live unless it is used for
2474 pseudos, in which case it will have been set live when
2475 it was allocated to the pseudos. If the register will not
2476 be eliminated, reload will set it live at that point. */
2478 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2479 regs_ever_live[regno] = 1;
2482 /* No death notes for global register variables;
2483 their values are live after this function exits. */
2484 if (global_regs[regno])
2487 reg_next_use[regno] = insn;
2491 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2494 REGSET_ELT_TYPE n_bit
2495 = (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2497 live[(regno + n) / REGSET_ELT_BITS] |= n_bit;
2498 some_needed |= (needed[(regno + n) / REGSET_ELT_BITS] & n_bit);
2500 |= ((~ needed[(regno + n) / REGSET_ELT_BITS]) & n_bit);
2505 /* Record where each reg is used, so when the reg
2506 is set we know the next insn that uses it. */
2508 reg_next_use[regno] = insn;
2510 if (regno < FIRST_PSEUDO_REGISTER)
2512 /* If a hard reg is being used,
2513 record that this function does use it. */
2515 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2519 regs_ever_live[regno + --i] = 1;
2524 /* Keep track of which basic block each reg appears in. */
2526 register int blocknum = BLOCK_NUM (insn);
2528 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2529 reg_basic_block[regno] = blocknum;
2530 else if (reg_basic_block[regno] != blocknum)
2531 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2533 /* Count (weighted) number of uses of each reg. */
2535 reg_n_refs[regno] += loop_depth;
2538 /* Record and count the insns in which a reg dies.
2539 If it is used in this insn and was dead below the insn
2540 then it dies in this insn. If it was set in this insn,
2541 we do not make a REG_DEAD note; likewise if we already
2542 made such a note. */
2545 && ! dead_or_set_p (insn, x)
2547 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2551 /* Check for the case where the register dying partially
2552 overlaps the register set by this insn. */
2553 if (regno < FIRST_PSEUDO_REGISTER
2554 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2556 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2558 some_needed |= dead_or_set_regno_p (insn, regno + n);
2561 /* If none of the words in X is needed, make a REG_DEAD
2562 note. Otherwise, we must make partial REG_DEAD notes. */
2566 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2567 reg_n_deaths[regno]++;
2573 /* Don't make a REG_DEAD note for a part of a register
2574 that is set in the insn. */
2576 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2578 if ((needed[(regno + i) / REGSET_ELT_BITS]
2579 & ((REGSET_ELT_TYPE) 1
2580 << ((regno + i) % REGSET_ELT_BITS))) == 0
2581 && ! dead_or_set_regno_p (insn, regno + i))
2583 = gen_rtx (EXPR_LIST, REG_DEAD,
2584 gen_rtx (REG, reg_raw_mode[regno + i],
2595 register rtx testreg = SET_DEST (x);
2598 /* If storing into MEM, don't show it as being used. But do
2599 show the address as being used. */
2600 if (GET_CODE (testreg) == MEM)
2604 find_auto_inc (needed, testreg, insn);
2606 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2607 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2611 /* Storing in STRICT_LOW_PART is like storing in a reg
2612 in that this SET might be dead, so ignore it in TESTREG.
2613 but in some other ways it is like using the reg.
2615 Storing in a SUBREG or a bit field is like storing the entire
2616 register in that if the register's value is not used
2617 then this SET is not needed. */
2618 while (GET_CODE (testreg) == STRICT_LOW_PART
2619 || GET_CODE (testreg) == ZERO_EXTRACT
2620 || GET_CODE (testreg) == SIGN_EXTRACT
2621 || GET_CODE (testreg) == SUBREG)
2623 if (GET_CODE (testreg) == SUBREG
2624 && GET_CODE (SUBREG_REG (testreg)) == REG
2625 && REGNO (SUBREG_REG (testreg)) >= FIRST_PSEUDO_REGISTER
2626 && (GET_MODE_SIZE (GET_MODE (testreg))
2627 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (testreg)))))
2628 reg_changes_size[REGNO (SUBREG_REG (testreg))] = 1;
2630 /* Modifying a single register in an alternate mode
2631 does not use any of the old value. But these other
2632 ways of storing in a register do use the old value. */
2633 if (GET_CODE (testreg) == SUBREG
2634 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2639 testreg = XEXP (testreg, 0);
2642 /* If this is a store into a register,
2643 recursively scan the value being stored. */
2645 if (GET_CODE (testreg) == REG
2646 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2647 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2648 && regno != HARD_FRAME_POINTER_REGNUM
2650 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2651 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2654 /* We used to exclude global_regs here, but that seems wrong.
2655 Storing in them is like storing in mem. */
2657 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2659 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2666 /* If exiting needs the right stack value, consider this insn as
2667 using the stack pointer. In any event, consider it as using
2668 all global registers. */
2670 #ifdef EXIT_IGNORE_STACK
2671 if (! EXIT_IGNORE_STACK
2672 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2674 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2675 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2677 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2679 live[i / REGSET_ELT_BITS]
2680 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2684 /* Recursively scan the operands of this expression. */
2687 register char *fmt = GET_RTX_FORMAT (code);
2690 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2694 /* Tail recursive case: save a function call level. */
2700 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2702 else if (fmt[i] == 'E')
2705 for (j = 0; j < XVECLEN (x, i); j++)
2706 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2715 try_pre_increment_1 (insn)
2718 /* Find the next use of this reg. If in same basic block,
2719 make it do pre-increment or pre-decrement if appropriate. */
2720 rtx x = PATTERN (insn);
2721 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2722 * INTVAL (XEXP (SET_SRC (x), 1)));
2723 int regno = REGNO (SET_DEST (x));
2724 rtx y = reg_next_use[regno];
2726 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2727 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2728 mode would be better. */
2729 && ! dead_or_set_p (y, SET_DEST (x))
2730 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2733 /* We have found a suitable auto-increment
2734 and already changed insn Y to do it.
2735 So flush this increment-instruction. */
2736 PUT_CODE (insn, NOTE);
2737 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2738 NOTE_SOURCE_FILE (insn) = 0;
2739 /* Count a reference to this reg for the increment
2740 insn we are deleting. When a reg is incremented.
2741 spilling it is worse, so we want to make that
2743 if (regno >= FIRST_PSEUDO_REGISTER)
2745 reg_n_refs[regno] += loop_depth;
2746 reg_n_sets[regno]++;
2753 /* Try to change INSN so that it does pre-increment or pre-decrement
2754 addressing on register REG in order to add AMOUNT to REG.
2755 AMOUNT is negative for pre-decrement.
2756 Returns 1 if the change could be made.
2757 This checks all about the validity of the result of modifying INSN. */
2760 try_pre_increment (insn, reg, amount)
2762 HOST_WIDE_INT amount;
2766 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2767 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2769 /* Nonzero if we can try to make a post-increment or post-decrement.
2770 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2771 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2772 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2775 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2778 /* From the sign of increment, see which possibilities are conceivable
2779 on this target machine. */
2780 #ifdef HAVE_PRE_INCREMENT
2784 #ifdef HAVE_POST_INCREMENT
2789 #ifdef HAVE_PRE_DECREMENT
2793 #ifdef HAVE_POST_DECREMENT
2798 if (! (pre_ok || post_ok))
2801 /* It is not safe to add a side effect to a jump insn
2802 because if the incremented register is spilled and must be reloaded
2803 there would be no way to store the incremented value back in memory. */
2805 if (GET_CODE (insn) == JUMP_INSN)
2810 use = find_use_as_address (PATTERN (insn), reg, 0);
2811 if (post_ok && (use == 0 || use == (rtx) 1))
2813 use = find_use_as_address (PATTERN (insn), reg, -amount);
2817 if (use == 0 || use == (rtx) 1)
2820 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2823 /* See if this combination of instruction and addressing mode exists. */
2824 if (! validate_change (insn, &XEXP (use, 0),
2826 ? (do_post ? POST_INC : PRE_INC)
2827 : (do_post ? POST_DEC : PRE_DEC),
2831 /* Record that this insn now has an implicit side effect on X. */
2832 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2836 #endif /* AUTO_INC_DEC */
2838 /* Find the place in the rtx X where REG is used as a memory address.
2839 Return the MEM rtx that so uses it.
2840 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2841 (plus REG (const_int PLUSCONST)).
2843 If such an address does not appear, return 0.
2844 If REG appears more than once, or is used other than in such an address,
2848 find_use_as_address (x, reg, plusconst)
2851 HOST_WIDE_INT plusconst;
2853 enum rtx_code code = GET_CODE (x);
2854 char *fmt = GET_RTX_FORMAT (code);
2856 register rtx value = 0;
2859 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2862 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2863 && XEXP (XEXP (x, 0), 0) == reg
2864 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2865 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2868 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2870 /* If REG occurs inside a MEM used in a bit-field reference,
2871 that is unacceptable. */
2872 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2873 return (rtx) (HOST_WIDE_INT) 1;
2877 return (rtx) (HOST_WIDE_INT) 1;
2879 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2883 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2887 return (rtx) (HOST_WIDE_INT) 1;
2892 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2894 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2898 return (rtx) (HOST_WIDE_INT) 1;
2906 /* Write information about registers and basic blocks into FILE.
2907 This is part of making a debugging dump. */
2910 dump_flow_info (file)
2914 static char *reg_class_names[] = REG_CLASS_NAMES;
2916 fprintf (file, "%d registers.\n", max_regno);
2918 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2921 enum reg_class class, altclass;
2922 fprintf (file, "\nRegister %d used %d times across %d insns",
2923 i, reg_n_refs[i], reg_live_length[i]);
2924 if (reg_basic_block[i] >= 0)
2925 fprintf (file, " in block %d", reg_basic_block[i]);
2926 if (reg_n_deaths[i] != 1)
2927 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2928 if (reg_n_calls_crossed[i] == 1)
2929 fprintf (file, "; crosses 1 call");
2930 else if (reg_n_calls_crossed[i])
2931 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2932 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2933 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2934 class = reg_preferred_class (i);
2935 altclass = reg_alternate_class (i);
2936 if (class != GENERAL_REGS || altclass != ALL_REGS)
2938 if (altclass == ALL_REGS || class == ALL_REGS)
2939 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2940 else if (altclass == NO_REGS)
2941 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2943 fprintf (file, "; pref %s, else %s",
2944 reg_class_names[(int) class],
2945 reg_class_names[(int) altclass]);
2947 if (REGNO_POINTER_FLAG (i))
2948 fprintf (file, "; pointer");
2949 fprintf (file, ".\n");
2951 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2952 for (i = 0; i < n_basic_blocks; i++)
2954 register rtx head, jump;
2956 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2958 INSN_UID (basic_block_head[i]),
2959 INSN_UID (basic_block_end[i]));
2960 /* The control flow graph's storage is freed
2961 now when flow_analysis returns.
2962 Don't try to print it if it is gone. */
2963 if (basic_block_drops_in)
2965 fprintf (file, "Reached from blocks: ");
2966 head = basic_block_head[i];
2967 if (GET_CODE (head) == CODE_LABEL)
2968 for (jump = LABEL_REFS (head);
2970 jump = LABEL_NEXTREF (jump))
2972 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2973 fprintf (file, " %d", from_block);
2975 if (basic_block_drops_in[i])
2976 fprintf (file, " previous");
2978 fprintf (file, "\nRegisters live at start:");
2979 for (regno = 0; regno < max_regno; regno++)
2981 register int offset = regno / REGSET_ELT_BITS;
2982 register REGSET_ELT_TYPE bit
2983 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2984 if (basic_block_live_at_start[i][offset] & bit)
2985 fprintf (file, " %d", regno);
2987 fprintf (file, "\n");
2989 fprintf (file, "\n");