1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
21 /* This file contains the data flow analysis pass of the compiler.
22 It computes data flow information
23 which tells combine_instructions which insns to consider combining
24 and controls register allocation.
26 Additional data flow information that is too bulky to record
27 is generated during the analysis, and is used at that time to
28 create autoincrement and autodecrement addressing.
30 The first step is dividing the function into basic blocks.
31 find_basic_blocks does this. Then life_analysis determines
32 where each register is live and where it is dead.
34 ** find_basic_blocks **
36 find_basic_blocks divides the current function's rtl
37 into basic blocks. It records the beginnings and ends of the
38 basic blocks in the vectors basic_block_head and basic_block_end,
39 and the number of blocks in n_basic_blocks.
41 find_basic_blocks also finds any unreachable loops
46 life_analysis is called immediately after find_basic_blocks.
47 It uses the basic block information to determine where each
48 hard or pseudo register is live.
50 ** live-register info **
52 The information about where each register is live is in two parts:
53 the REG_NOTES of insns, and the vector basic_block_live_at_start.
55 basic_block_live_at_start has an element for each basic block,
56 and the element is a bit-vector with a bit for each hard or pseudo
57 register. The bit is 1 if the register is live at the beginning
60 Two types of elements can be added to an insn's REG_NOTES.
61 A REG_DEAD note is added to an insn's REG_NOTES for any register
62 that meets both of two conditions: The value in the register is not
63 needed in subsequent insns and the insn does not replace the value in
64 the register (in the case of multi-word hard registers, the value in
65 each register must be replaced by the insn to avoid a REG_DEAD note).
67 In the vast majority of cases, an object in a REG_DEAD note will be
68 used somewhere in the insn. The (rare) exception to this is if an
69 insn uses a multi-word hard register and only some of the registers are
70 needed in subsequent insns. In that case, REG_DEAD notes will be
71 provided for those hard registers that are not subsequently needed.
72 Partial REG_DEAD notes of this type do not occur when an insn sets
73 only some of the hard registers used in such a multi-word operand;
74 omitting REG_DEAD notes for objects stored in an insn is optional and
75 the desire to do so does not justify the complexity of the partial
78 REG_UNUSED notes are added for each register that is set by the insn
79 but is unused subsequently (if every register set by the insn is unused
80 and the insn does not reference memory or have some other side-effect,
81 the insn is deleted instead). If only part of a multi-word hard
82 register is used in a subsequent insn, REG_UNUSED notes are made for
83 the parts that will not be used.
85 To determine which registers are live after any insn, one can
86 start from the beginning of the basic block and scan insns, noting
87 which registers are set by each insn and which die there.
89 ** Other actions of life_analysis **
91 life_analysis sets up the LOG_LINKS fields of insns because the
92 information needed to do so is readily available.
94 life_analysis deletes insns whose only effect is to store a value
97 life_analysis notices cases where a reference to a register as
98 a memory address can be combined with a preceding or following
99 incrementation or decrementation of the register. The separate
100 instruction to increment or decrement is deleted and the address
101 is changed to a POST_INC or similar rtx.
103 Each time an incrementing or decrementing address is created,
104 a REG_INC element is added to the insn's REG_NOTES list.
106 life_analysis fills in certain vectors containing information about
107 register usage: reg_n_refs, reg_n_deaths, reg_n_sets, reg_live_length,
108 reg_n_calls_crosses and reg_basic_block. */
113 #include "basic-block.h"
114 #include "insn-config.h"
116 #include "hard-reg-set.h"
121 #define obstack_chunk_alloc xmalloc
122 #define obstack_chunk_free free
124 /* List of labels that must never be deleted. */
125 extern rtx forced_labels;
127 /* Get the basic block number of an insn.
128 This info should not be expected to remain available
129 after the end of life_analysis. */
131 /* This is the limit of the allocated space in the following two arrays. */
133 static int max_uid_for_flow;
135 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
137 /* This is where the BLOCK_NUM values are really stored.
138 This is set up by find_basic_blocks and used there and in life_analysis,
141 static int *uid_block_number;
143 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
145 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
146 static char *uid_volatile;
148 /* Number of basic blocks in the current function. */
152 /* Maximum register number used in this function, plus one. */
156 /* Maximum number of SCRATCH rtx's used in any basic block of this function. */
160 /* Number of SCRATCH rtx's in the current block. */
162 static int num_scratch;
164 /* Indexed by n, gives number of basic block that (REG n) is used in.
165 If the value is REG_BLOCK_GLOBAL (-2),
166 it means (REG n) is used in more than one basic block.
167 REG_BLOCK_UNKNOWN (-1) means it hasn't been seen yet so we don't know.
168 This information remains valid for the rest of the compilation
169 of the current function; it is used to control register allocation. */
171 int *reg_basic_block;
173 /* Indexed by n, gives number of times (REG n) is used or set, each
174 weighted by its loop-depth.
175 This information remains valid for the rest of the compilation
176 of the current function; it is used to control register allocation. */
180 /* Indexed by N; says whether a psuedo register N was ever used
181 within a SUBREG that changes the size of the reg. Some machines prohibit
182 such objects to be in certain (usually floating-point) registers. */
184 char *reg_changes_size;
186 /* Indexed by N, gives number of places register N dies.
187 This information remains valid for the rest of the compilation
188 of the current function; it is used to control register allocation. */
192 /* Indexed by N, gives 1 if that reg is live across any CALL_INSNs.
193 This information remains valid for the rest of the compilation
194 of the current function; it is used to control register allocation. */
196 int *reg_n_calls_crossed;
198 /* Total number of instructions at which (REG n) is live.
199 The larger this is, the less priority (REG n) gets for
200 allocation in a real register.
201 This information remains valid for the rest of the compilation
202 of the current function; it is used to control register allocation.
204 local-alloc.c may alter this number to change the priority.
206 Negative values are special.
207 -1 is used to mark a pseudo reg which has a constant or memory equivalent
208 and is used infrequently enough that it should not get a hard register.
209 -2 is used to mark a pseudo reg for a parameter, when a frame pointer
210 is not required. global.c makes an allocno for this but does
211 not try to assign a hard register to it. */
213 int *reg_live_length;
215 /* Element N is the next insn that uses (hard or pseudo) register number N
216 within the current basic block; or zero, if there is no such insn.
217 This is valid only during the final backward scan in propagate_block. */
219 static rtx *reg_next_use;
221 /* Size of a regset for the current function,
222 in (1) bytes and (2) elements. */
227 /* Element N is first insn in basic block N.
228 This info lasts until we finish compiling the function. */
230 rtx *basic_block_head;
232 /* Element N is last insn in basic block N.
233 This info lasts until we finish compiling the function. */
235 rtx *basic_block_end;
237 /* Element N is a regset describing the registers live
238 at the start of basic block N.
239 This info lasts until we finish compiling the function. */
241 regset *basic_block_live_at_start;
243 /* Regset of regs live when calls to `setjmp'-like functions happen. */
245 regset regs_live_at_setjmp;
247 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
248 that have to go in the same hard reg.
249 The first two regs in the list are a pair, and the next two
250 are another pair, etc. */
253 /* Element N is nonzero if control can drop into basic block N
254 from the preceding basic block. Freed after life_analysis. */
256 static char *basic_block_drops_in;
258 /* Element N is depth within loops of the last insn in basic block number N.
259 Freed after life_analysis. */
261 static short *basic_block_loop_depth;
263 /* Element N nonzero if basic block N can actually be reached.
264 Vector exists only during find_basic_blocks. */
266 static char *block_live_static;
268 /* Depth within loops of basic block being scanned for lifetime analysis,
269 plus one. This is the weight attached to references to registers. */
271 static int loop_depth;
273 /* During propagate_block, this is non-zero if the value of CC0 is live. */
277 /* During propagate_block, this contains the last MEM stored into. It
278 is used to eliminate consecutive stores to the same location. */
280 static rtx last_mem_set;
282 /* Set of registers that may be eliminable. These are handled specially
283 in updating regs_ever_live. */
285 static HARD_REG_SET elim_reg_set;
287 /* Forward declarations */
288 static void find_basic_blocks PROTO((rtx, rtx));
289 static int uses_reg_or_mem PROTO((rtx));
290 static void mark_label_ref PROTO((rtx, rtx, int));
291 static void life_analysis PROTO((rtx, int));
292 void allocate_for_life_analysis PROTO((void));
293 static void init_regset_vector PROTO((regset *, regset, int, int));
294 static void propagate_block PROTO((regset, rtx, rtx, int,
296 static rtx flow_delete_insn PROTO((rtx));
297 static int insn_dead_p PROTO((rtx, regset, int));
298 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
299 static void mark_set_regs PROTO((regset, regset, rtx,
301 static void mark_set_1 PROTO((regset, regset, rtx,
303 static void find_auto_inc PROTO((regset, rtx, rtx));
304 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
305 static int try_pre_increment_1 PROTO((rtx));
306 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
307 static rtx find_use_as_address PROTO((rtx, rtx, HOST_WIDE_INT));
308 void dump_flow_info PROTO((FILE *));
310 /* Find basic blocks of the current function and perform data flow analysis.
311 F is the first insn of the function and NREGS the number of register numbers
315 flow_analysis (f, nregs, file)
322 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
324 #ifdef ELIMINABLE_REGS
325 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
328 /* Record which registers will be eliminated. We use this in
331 CLEAR_HARD_REG_SET (elim_reg_set);
333 #ifdef ELIMINABLE_REGS
334 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
335 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
337 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
340 /* Count the basic blocks. Also find maximum insn uid value used. */
343 register RTX_CODE prev_code = JUMP_INSN;
344 register RTX_CODE code;
346 max_uid_for_flow = 0;
348 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
350 code = GET_CODE (insn);
351 if (INSN_UID (insn) > max_uid_for_flow)
352 max_uid_for_flow = INSN_UID (insn);
353 if (code == CODE_LABEL
354 || (GET_RTX_CLASS (code) == 'i'
355 && (prev_code == JUMP_INSN
356 || (prev_code == CALL_INSN
357 && nonlocal_label_list != 0)
358 || prev_code == BARRIER)))
366 /* Leave space for insns we make in some cases for auto-inc. These cases
367 are rare, so we don't need too much space. */
368 max_uid_for_flow += max_uid_for_flow / 10;
371 /* Allocate some tables that last till end of compiling this function
372 and some needed only in find_basic_blocks and life_analysis. */
375 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
376 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
377 basic_block_drops_in = (char *) alloca (n_basic_blocks);
378 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
380 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
381 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
382 bzero (uid_volatile, max_uid_for_flow + 1);
384 find_basic_blocks (f, nonlocal_label_list);
385 life_analysis (f, nregs);
387 dump_flow_info (file);
389 basic_block_drops_in = 0;
390 uid_block_number = 0;
391 basic_block_loop_depth = 0;
394 /* Find all basic blocks of the function whose first insn is F.
395 Store the correct data in the tables that describe the basic blocks,
396 set up the chains of references for each CODE_LABEL, and
397 delete any entire basic blocks that cannot be reached.
399 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
402 find_basic_blocks (f, nonlocal_label_list)
403 rtx f, nonlocal_label_list;
407 register char *block_live = (char *) alloca (n_basic_blocks);
408 register char *block_marked = (char *) alloca (n_basic_blocks);
409 /* List of label_refs to all labels whose addresses are taken
411 rtx label_value_list;
413 enum rtx_code prev_code, code;
419 label_value_list = 0;
420 block_live_static = block_live;
421 bzero (block_live, n_basic_blocks);
422 bzero (block_marked, n_basic_blocks);
424 /* Initialize with just block 0 reachable and no blocks marked. */
425 if (n_basic_blocks > 0)
428 /* Initialize the ref chain of each label to 0. Record where all the
429 blocks start and end and their depth in loops. For each insn, record
430 the block it is in. Also mark as reachable any blocks headed by labels
431 that must not be deleted. */
433 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
434 insn; insn = NEXT_INSN (insn))
436 code = GET_CODE (insn);
439 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
441 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
445 /* A basic block starts at label, or after something that can jump. */
446 else if (code == CODE_LABEL
447 || (GET_RTX_CLASS (code) == 'i'
448 && (prev_code == JUMP_INSN
449 || (prev_code == CALL_INSN
450 && nonlocal_label_list != 0)
451 || prev_code == BARRIER)))
453 basic_block_head[++i] = insn;
454 basic_block_end[i] = insn;
455 basic_block_loop_depth[i] = depth;
457 if (code == CODE_LABEL)
459 LABEL_REFS (insn) = insn;
460 /* Any label that cannot be deleted
461 is considered to start a reachable block. */
462 if (LABEL_PRESERVE_P (insn))
467 else if (GET_RTX_CLASS (code) == 'i')
469 basic_block_end[i] = insn;
470 basic_block_loop_depth[i] = depth;
473 if (GET_RTX_CLASS (code) == 'i')
475 /* Make a list of all labels referred to other than by jumps. */
476 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
477 if (REG_NOTE_KIND (note) == REG_LABEL)
478 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
482 BLOCK_NUM (insn) = i;
488 if (i + 1 != n_basic_blocks)
491 /* Don't delete the labels (in this function)
492 that are referenced by non-jump instructions. */
494 for (x = label_value_list; x; x = XEXP (x, 1))
495 if (! LABEL_REF_NONLOCAL_P (x))
496 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
498 for (x = forced_labels; x; x = XEXP (x, 1))
499 if (! LABEL_REF_NONLOCAL_P (x))
500 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
502 /* Record which basic blocks control can drop in to. */
504 for (i = 0; i < n_basic_blocks; i++)
506 for (insn = PREV_INSN (basic_block_head[i]);
507 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
510 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
513 /* Now find which basic blocks can actually be reached
514 and put all jump insns' LABEL_REFS onto the ref-chains
515 of their target labels. */
517 if (n_basic_blocks > 0)
519 int something_marked = 1;
522 /* Find all indirect jump insns and mark them as possibly jumping to all
523 the labels whose addresses are explicitly used. This is because,
524 when there are computed gotos, we can't tell which labels they jump
525 to, of all the possibilities.
527 Tablejumps and casesi insns are OK and we can recognize them by
528 a (use (label_ref)). */
530 for (insn = f; insn; insn = NEXT_INSN (insn))
531 if (GET_CODE (insn) == JUMP_INSN)
533 rtx pat = PATTERN (insn);
534 int computed_jump = 0;
536 if (GET_CODE (pat) == PARALLEL)
538 int len = XVECLEN (pat, 0);
539 int has_use_labelref = 0;
541 for (i = len - 1; i >= 0; i--)
542 if (GET_CODE (XVECEXP (pat, 0, i)) == USE
543 && (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
545 has_use_labelref = 1;
547 if (! has_use_labelref)
548 for (i = len - 1; i >= 0; i--)
549 if (GET_CODE (XVECEXP (pat, 0, i)) == SET
550 && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
551 && uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
554 else if (GET_CODE (pat) == SET
555 && SET_DEST (pat) == pc_rtx
556 && uses_reg_or_mem (SET_SRC (pat)))
561 for (x = label_value_list; x; x = XEXP (x, 1))
562 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
565 for (x = forced_labels; x; x = XEXP (x, 1))
566 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
571 /* Find all call insns and mark them as possibly jumping
572 to all the nonlocal goto handler labels. */
574 for (insn = f; insn; insn = NEXT_INSN (insn))
575 if (GET_CODE (insn) == CALL_INSN)
577 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
578 /* Don't try marking labels that
579 were deleted as unreferenced. */
580 if (GET_CODE (XEXP (x, 0)) == CODE_LABEL)
581 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
584 /* ??? This could be made smarter:
585 in some cases it's possible to tell that certain
586 calls will not do a nonlocal goto.
588 For example, if the nested functions that do the
589 nonlocal gotos do not have their addresses taken, then
590 only calls to those functions or to other nested
591 functions that use them could possibly do nonlocal
595 /* Pass over all blocks, marking each block that is reachable
596 and has not yet been marked.
597 Keep doing this until, in one pass, no blocks have been marked.
598 Then blocks_live and blocks_marked are identical and correct.
599 In addition, all jumps actually reachable have been marked. */
601 while (something_marked)
603 something_marked = 0;
604 for (i = 0; i < n_basic_blocks; i++)
605 if (block_live[i] && !block_marked[i])
608 something_marked = 1;
609 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
610 block_live[i + 1] = 1;
611 insn = basic_block_end[i];
612 if (GET_CODE (insn) == JUMP_INSN)
613 mark_label_ref (PATTERN (insn), insn, 0);
617 /* ??? See if we have a "live" basic block that is not reachable.
618 This can happen if it is headed by a label that is preserved or
619 in one of the label lists, but no call or computed jump is in
620 the loop. It's not clear if we can delete the block or not,
621 but don't for now. However, we will mess up register status if
622 it remains unreachable, so add a fake reachability from the
625 for (i = 1; i < n_basic_blocks; i++)
626 if (block_live[i] && ! basic_block_drops_in[i]
627 && GET_CODE (basic_block_head[i]) == CODE_LABEL
628 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
629 basic_block_drops_in[i] = 1;
631 /* Now delete the code for any basic blocks that can't be reached.
632 They can occur because jump_optimize does not recognize
633 unreachable loops as unreachable. */
636 for (i = 0; i < n_basic_blocks; i++)
641 /* Delete the insns in a (non-live) block. We physically delete
642 every non-note insn except the start and end (so
643 basic_block_head/end needn't be updated), we turn the latter
644 into NOTE_INSN_DELETED notes.
645 We use to "delete" the insns by turning them into notes, but
646 we may be deleting lots of insns that subsequent passes would
647 otherwise have to process. Secondly, lots of deleted blocks in
648 a row can really slow down propagate_block since it will
649 otherwise process insn-turned-notes multiple times when it
650 looks for loop begin/end notes. */
651 if (basic_block_head[i] != basic_block_end[i])
653 insn = NEXT_INSN (basic_block_head[i]);
654 while (insn != basic_block_end[i])
656 if (GET_CODE (insn) == BARRIER)
658 else if (GET_CODE (insn) != NOTE)
659 insn = flow_delete_insn (insn);
661 insn = NEXT_INSN (insn);
664 insn = basic_block_head[i];
665 if (GET_CODE (insn) != NOTE)
667 /* Turn the head into a deleted insn note. */
668 if (GET_CODE (insn) == BARRIER)
670 PUT_CODE (insn, NOTE);
671 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
672 NOTE_SOURCE_FILE (insn) = 0;
674 insn = basic_block_end[i];
675 if (GET_CODE (insn) != NOTE)
677 /* Turn the tail into a deleted insn note. */
678 if (GET_CODE (insn) == BARRIER)
680 PUT_CODE (insn, NOTE);
681 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
682 NOTE_SOURCE_FILE (insn) = 0;
684 /* BARRIERs are between basic blocks, not part of one.
685 Delete a BARRIER if the preceding jump is deleted.
686 We cannot alter a BARRIER into a NOTE
687 because it is too short; but we can really delete
688 it because it is not part of a basic block. */
689 if (NEXT_INSN (insn) != 0
690 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
691 delete_insn (NEXT_INSN (insn));
693 /* Each time we delete some basic blocks,
694 see if there is a jump around them that is
695 being turned into a no-op. If so, delete it. */
697 if (block_live[i - 1])
700 for (j = i + 1; j < n_basic_blocks; j++)
704 insn = basic_block_end[i - 1];
705 if (GET_CODE (insn) == JUMP_INSN
706 /* An unconditional jump is the only possibility
707 we must check for, since a conditional one
708 would make these blocks live. */
709 && simplejump_p (insn)
710 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
711 && INSN_UID (label) != 0
712 && BLOCK_NUM (label) == j)
714 PUT_CODE (insn, NOTE);
715 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
716 NOTE_SOURCE_FILE (insn) = 0;
717 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
719 delete_insn (NEXT_INSN (insn));
726 /* There are pathalogical cases where one function calling hundreds of
727 nested inline functions can generate lots and lots of unreachable
728 blocks that jump can't delete. Since we don't use sparse matrices
729 a lot of memory will be needed to compile such functions.
730 Implementing sparse matrices is a fair bit of work and it is not
731 clear that they win more than they lose (we don't want to
732 unnecessarily slow down compilation of normal code). By making
733 another pass for the pathalogical case, we can greatly speed up
734 their compilation without hurting normal code. This works because
735 all the insns in the unreachable blocks have either been deleted or
736 turned into notes. */
737 /* ??? The choice of when to make another pass is a bit arbitrary,
738 and was derived from empirical data. */
740 && (deleted > n_basic_blocks / 2 || deleted > 1000))
743 n_basic_blocks -= deleted;
749 /* Subroutines of find_basic_blocks. */
751 /* Return 1 if X contain a REG or MEM that is not in the constant pool. */
757 enum rtx_code code = GET_CODE (x);
763 && ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
764 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))))
767 fmt = GET_RTX_FORMAT (code);
768 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
771 && uses_reg_or_mem (XEXP (x, i)))
775 for (j = 0; j < XVECLEN (x, i); j++)
776 if (uses_reg_or_mem (XVECEXP (x, i, j)))
783 /* Check expression X for label references;
784 if one is found, add INSN to the label's chain of references.
786 CHECKDUP means check for and avoid creating duplicate references
787 from the same insn. Such duplicates do no serious harm but
788 can slow life analysis. CHECKDUP is set only when duplicates
792 mark_label_ref (x, insn, checkdup)
796 register RTX_CODE code;
800 /* We can be called with NULL when scanning label_value_list. */
805 if (code == LABEL_REF)
807 register rtx label = XEXP (x, 0);
809 if (GET_CODE (label) != CODE_LABEL)
811 /* If the label was never emitted, this insn is junk,
812 but avoid a crash trying to refer to BLOCK_NUM (label).
813 This can happen as a result of a syntax error
814 and a diagnostic has already been printed. */
815 if (INSN_UID (label) == 0)
817 CONTAINING_INSN (x) = insn;
818 /* if CHECKDUP is set, check for duplicate ref from same insn
821 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
822 if (CONTAINING_INSN (y) == insn)
824 LABEL_NEXTREF (x) = LABEL_REFS (label);
825 LABEL_REFS (label) = x;
826 block_live_static[BLOCK_NUM (label)] = 1;
830 fmt = GET_RTX_FORMAT (code);
831 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
834 mark_label_ref (XEXP (x, i), insn, 0);
838 for (j = 0; j < XVECLEN (x, i); j++)
839 mark_label_ref (XVECEXP (x, i, j), insn, 1);
844 /* Delete INSN by patching it out.
845 Return the next insn. */
848 flow_delete_insn (insn)
851 /* ??? For the moment we assume we don't have to watch for NULLs here
852 since the start/end of basic blocks aren't deleted like this. */
853 NEXT_INSN (PREV_INSN (insn)) = NEXT_INSN (insn);
854 PREV_INSN (NEXT_INSN (insn)) = PREV_INSN (insn);
855 return NEXT_INSN (insn);
858 /* Determine which registers are live at the start of each
859 basic block of the function whose first insn is F.
860 NREGS is the number of registers used in F.
861 We allocate the vector basic_block_live_at_start
862 and the regsets that it points to, and fill them with the data.
863 regset_size and regset_bytes are also set here. */
866 life_analysis (f, nregs)
873 /* For each basic block, a bitmask of regs
874 live on exit from the block. */
875 regset *basic_block_live_at_end;
876 /* For each basic block, a bitmask of regs
877 live on entry to a successor-block of this block.
878 If this does not match basic_block_live_at_end,
879 that must be updated, and the block must be rescanned. */
880 regset *basic_block_new_live_at_end;
881 /* For each basic block, a bitmask of regs
882 whose liveness at the end of the basic block
883 can make a difference in which regs are live on entry to the block.
884 These are the regs that are set within the basic block,
885 possibly excluding those that are used after they are set. */
886 regset *basic_block_significant;
890 struct obstack flow_obstack;
892 gcc_obstack_init (&flow_obstack);
896 bzero (regs_ever_live, sizeof regs_ever_live);
898 /* Allocate and zero out many data structures
899 that will record the data from lifetime analysis. */
901 allocate_for_life_analysis ();
903 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
904 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
906 /* Set up several regset-vectors used internally within this function.
907 Their meanings are documented above, with their declarations. */
909 basic_block_live_at_end
910 = (regset *) alloca (n_basic_blocks * sizeof (regset));
912 /* Don't use alloca since that leads to a crash rather than an error message
913 if there isn't enough space.
914 Don't use oballoc since we may need to allocate other things during
915 this function on the temporary obstack. */
916 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
917 bzero ((char *) tem, n_basic_blocks * regset_bytes);
918 init_regset_vector (basic_block_live_at_end, tem,
919 n_basic_blocks, regset_bytes);
921 basic_block_new_live_at_end
922 = (regset *) alloca (n_basic_blocks * sizeof (regset));
923 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
924 bzero ((char *) tem, n_basic_blocks * regset_bytes);
925 init_regset_vector (basic_block_new_live_at_end, tem,
926 n_basic_blocks, regset_bytes);
928 basic_block_significant
929 = (regset *) alloca (n_basic_blocks * sizeof (regset));
930 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
931 bzero ((char *) tem, n_basic_blocks * regset_bytes);
932 init_regset_vector (basic_block_significant, tem,
933 n_basic_blocks, regset_bytes);
935 /* Record which insns refer to any volatile memory
936 or for any reason can't be deleted just because they are dead stores.
937 Also, delete any insns that copy a register to itself. */
939 for (insn = f; insn; insn = NEXT_INSN (insn))
941 enum rtx_code code1 = GET_CODE (insn);
942 if (code1 == CALL_INSN)
943 INSN_VOLATILE (insn) = 1;
944 else if (code1 == INSN || code1 == JUMP_INSN)
946 /* Delete (in effect) any obvious no-op moves. */
947 if (GET_CODE (PATTERN (insn)) == SET
948 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
949 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
950 && REGNO (SET_DEST (PATTERN (insn))) ==
951 REGNO (SET_SRC (PATTERN (insn)))
952 /* Insns carrying these notes are useful later on. */
953 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
955 PUT_CODE (insn, NOTE);
956 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
957 NOTE_SOURCE_FILE (insn) = 0;
959 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
961 /* If nothing but SETs of registers to themselves,
962 this insn can also be deleted. */
963 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
965 rtx tem = XVECEXP (PATTERN (insn), 0, i);
967 if (GET_CODE (tem) == USE
968 || GET_CODE (tem) == CLOBBER)
971 if (GET_CODE (tem) != SET
972 || GET_CODE (SET_DEST (tem)) != REG
973 || GET_CODE (SET_SRC (tem)) != REG
974 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
978 if (i == XVECLEN (PATTERN (insn), 0)
979 /* Insns carrying these notes are useful later on. */
980 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
982 PUT_CODE (insn, NOTE);
983 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
984 NOTE_SOURCE_FILE (insn) = 0;
987 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
989 else if (GET_CODE (PATTERN (insn)) != USE)
990 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
991 /* A SET that makes space on the stack cannot be dead.
992 (Such SETs occur only for allocating variable-size data,
993 so they will always have a PLUS or MINUS according to the
994 direction of stack growth.)
995 Even if this function never uses this stack pointer value,
996 signal handlers do! */
997 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
998 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
999 #ifdef STACK_GROWS_DOWNWARD
1000 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
1002 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1004 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
1005 INSN_VOLATILE (insn) = 1;
1009 if (n_basic_blocks > 0)
1010 #ifdef EXIT_IGNORE_STACK
1011 if (! EXIT_IGNORE_STACK
1012 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
1015 /* If exiting needs the right stack value,
1016 consider the stack pointer live at the end of the function. */
1017 basic_block_live_at_end[n_basic_blocks - 1]
1018 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1019 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1020 basic_block_new_live_at_end[n_basic_blocks - 1]
1021 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1022 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1025 /* Mark the frame pointer is needed at the end of the function. If
1026 we end up eliminating it, it will be removed from the live list
1027 of each basic block by reload. */
1029 if (n_basic_blocks > 0)
1031 basic_block_live_at_end[n_basic_blocks - 1]
1032 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1033 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
1034 basic_block_new_live_at_end[n_basic_blocks - 1]
1035 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1036 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
1037 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1038 /* If they are different, also mark the hard frame pointer as live */
1039 basic_block_live_at_end[n_basic_blocks - 1]
1040 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1041 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
1043 basic_block_new_live_at_end[n_basic_blocks - 1]
1044 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
1045 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
1050 /* Mark all global registers as being live at the end of the function
1051 since they may be referenced by our caller. */
1053 if (n_basic_blocks > 0)
1054 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1057 basic_block_live_at_end[n_basic_blocks - 1]
1058 [i / REGSET_ELT_BITS]
1059 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
1060 basic_block_new_live_at_end[n_basic_blocks - 1]
1061 [i / REGSET_ELT_BITS]
1062 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
1065 /* Propagate life info through the basic blocks
1066 around the graph of basic blocks.
1068 This is a relaxation process: each time a new register
1069 is live at the end of the basic block, we must scan the block
1070 to determine which registers are, as a consequence, live at the beginning
1071 of that block. These registers must then be marked live at the ends
1072 of all the blocks that can transfer control to that block.
1073 The process continues until it reaches a fixed point. */
1080 for (i = n_basic_blocks - 1; i >= 0; i--)
1082 int consider = first_pass;
1083 int must_rescan = first_pass;
1088 /* Set CONSIDER if this block needs thinking about at all
1089 (that is, if the regs live now at the end of it
1090 are not the same as were live at the end of it when
1091 we last thought about it).
1092 Set must_rescan if it needs to be thought about
1093 instruction by instruction (that is, if any additional
1094 reg that is live at the end now but was not live there before
1095 is one of the significant regs of this basic block). */
1097 for (j = 0; j < regset_size; j++)
1099 register REGSET_ELT_TYPE x
1100 = (basic_block_new_live_at_end[i][j]
1101 & ~basic_block_live_at_end[i][j]);
1104 if (x & basic_block_significant[i][j])
1116 /* The live_at_start of this block may be changing,
1117 so another pass will be required after this one. */
1122 /* No complete rescan needed;
1123 just record those variables newly known live at end
1124 as live at start as well. */
1125 for (j = 0; j < regset_size; j++)
1127 register REGSET_ELT_TYPE x
1128 = (basic_block_new_live_at_end[i][j]
1129 & ~basic_block_live_at_end[i][j]);
1130 basic_block_live_at_start[i][j] |= x;
1131 basic_block_live_at_end[i][j] |= x;
1136 /* Update the basic_block_live_at_start
1137 by propagation backwards through the block. */
1138 bcopy ((char *) basic_block_new_live_at_end[i],
1139 (char *) basic_block_live_at_end[i], regset_bytes);
1140 bcopy ((char *) basic_block_live_at_end[i],
1141 (char *) basic_block_live_at_start[i], regset_bytes);
1142 propagate_block (basic_block_live_at_start[i],
1143 basic_block_head[i], basic_block_end[i], 0,
1144 first_pass ? basic_block_significant[i]
1150 register rtx jump, head;
1152 /* Update the basic_block_new_live_at_end's of the block
1153 that falls through into this one (if any). */
1154 head = basic_block_head[i];
1155 if (basic_block_drops_in[i])
1158 for (j = 0; j < regset_size; j++)
1159 basic_block_new_live_at_end[i-1][j]
1160 |= basic_block_live_at_start[i][j];
1163 /* Update the basic_block_new_live_at_end's of
1164 all the blocks that jump to this one. */
1165 if (GET_CODE (head) == CODE_LABEL)
1166 for (jump = LABEL_REFS (head);
1168 jump = LABEL_NEXTREF (jump))
1170 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1172 for (j = 0; j < regset_size; j++)
1173 basic_block_new_live_at_end[from_block][j]
1174 |= basic_block_live_at_start[i][j];
1184 /* The only pseudos that are live at the beginning of the function are
1185 those that were not set anywhere in the function. local-alloc doesn't
1186 know how to handle these correctly, so mark them as not local to any
1189 if (n_basic_blocks > 0)
1190 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1191 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1192 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1193 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1195 /* Now the life information is accurate.
1196 Make one more pass over each basic block
1197 to delete dead stores, create autoincrement addressing
1198 and record how many times each register is used, is set, or dies.
1200 To save time, we operate directly in basic_block_live_at_end[i],
1201 thus destroying it (in fact, converting it into a copy of
1202 basic_block_live_at_start[i]). This is ok now because
1203 basic_block_live_at_end[i] is no longer used past this point. */
1207 for (i = 0; i < n_basic_blocks; i++)
1209 propagate_block (basic_block_live_at_end[i],
1210 basic_block_head[i], basic_block_end[i], 1,
1218 /* Something live during a setjmp should not be put in a register
1219 on certain machines which restore regs from stack frames
1220 rather than from the jmpbuf.
1221 But we don't need to do this for the user's variables, since
1222 ANSI says only volatile variables need this. */
1223 #ifdef LONGJMP_RESTORE_FROM_STACK
1224 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1225 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1226 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1227 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1229 reg_live_length[i] = -1;
1230 reg_basic_block[i] = -1;
1235 /* We have a problem with any pseudoreg that
1236 lives across the setjmp. ANSI says that if a
1237 user variable does not change in value
1238 between the setjmp and the longjmp, then the longjmp preserves it.
1239 This includes longjmp from a place where the pseudo appears dead.
1240 (In principle, the value still exists if it is in scope.)
1241 If the pseudo goes in a hard reg, some other value may occupy
1242 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1243 Conclusion: such a pseudo must not go in a hard reg. */
1244 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1245 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1246 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1247 && regno_reg_rtx[i] != 0)
1249 reg_live_length[i] = -1;
1250 reg_basic_block[i] = -1;
1253 obstack_free (&flow_obstack, NULL_PTR);
1256 /* Subroutines of life analysis. */
1258 /* Allocate the permanent data structures that represent the results
1259 of life analysis. Not static since used also for stupid life analysis. */
1262 allocate_for_life_analysis ()
1265 register regset tem;
1267 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1268 regset_bytes = regset_size * sizeof (*(regset)0);
1270 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1271 bzero ((char *) reg_n_refs, max_regno * sizeof (int));
1273 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1274 bzero ((char *) reg_n_sets, max_regno * sizeof (short));
1276 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1277 bzero ((char *) reg_n_deaths, max_regno * sizeof (short));
1279 reg_changes_size = (char *) oballoc (max_regno * sizeof (char));
1280 bzero (reg_changes_size, max_regno * sizeof (char));;
1282 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1283 bzero ((char *) reg_live_length, max_regno * sizeof (int));
1285 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1286 bzero ((char *) reg_n_calls_crossed, max_regno * sizeof (int));
1288 reg_basic_block = (int *) oballoc (max_regno * sizeof (int));
1289 for (i = 0; i < max_regno; i++)
1290 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1292 basic_block_live_at_start
1293 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1294 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1295 bzero ((char *) tem, n_basic_blocks * regset_bytes);
1296 init_regset_vector (basic_block_live_at_start, tem,
1297 n_basic_blocks, regset_bytes);
1299 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1300 bzero ((char *) regs_live_at_setjmp, regset_bytes);
1303 /* Make each element of VECTOR point at a regset,
1304 taking the space for all those regsets from SPACE.
1305 SPACE is of type regset, but it is really as long as NELTS regsets.
1306 BYTES_PER_ELT is the number of bytes in one regset. */
1309 init_regset_vector (vector, space, nelts, bytes_per_elt)
1316 register regset p = space;
1318 for (i = 0; i < nelts; i++)
1321 p += bytes_per_elt / sizeof (*p);
1325 /* Compute the registers live at the beginning of a basic block
1326 from those live at the end.
1328 When called, OLD contains those live at the end.
1329 On return, it contains those live at the beginning.
1330 FIRST and LAST are the first and last insns of the basic block.
1332 FINAL is nonzero if we are doing the final pass which is not
1333 for computing the life info (since that has already been done)
1334 but for acting on it. On this pass, we delete dead stores,
1335 set up the logical links and dead-variables lists of instructions,
1336 and merge instructions for autoincrement and autodecrement addresses.
1338 SIGNIFICANT is nonzero only the first time for each basic block.
1339 If it is nonzero, it points to a regset in which we store
1340 a 1 for each register that is set within the block.
1342 BNUM is the number of the basic block. */
1345 propagate_block (old, first, last, final, significant, bnum)
1346 register regset old;
1358 /* The following variables are used only if FINAL is nonzero. */
1359 /* This vector gets one element for each reg that has been live
1360 at any point in the basic block that has been scanned so far.
1361 SOMETIMES_MAX says how many elements are in use so far.
1362 In each element, OFFSET is the byte-number within a regset
1363 for the register described by the element, and BIT is a mask
1364 for that register's bit within the byte. */
1365 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1366 int sometimes_max = 0;
1367 /* This regset has 1 for each reg that we have seen live so far.
1368 It and REGS_SOMETIMES_LIVE are updated together. */
1371 /* The loop depth may change in the middle of a basic block. Since we
1372 scan from end to beginning, we start with the depth at the end of the
1373 current basic block, and adjust as we pass ends and starts of loops. */
1374 loop_depth = basic_block_loop_depth[bnum];
1376 dead = (regset) alloca (regset_bytes);
1377 live = (regset) alloca (regset_bytes);
1382 /* Include any notes at the end of the block in the scan.
1383 This is in case the block ends with a call to setjmp. */
1385 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1387 /* Look for loop boundaries, we are going forward here. */
1388 last = NEXT_INSN (last);
1389 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1391 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1397 register int i, offset;
1398 REGSET_ELT_TYPE bit;
1401 maxlive = (regset) alloca (regset_bytes);
1402 bcopy ((char *) old, (char *) maxlive, regset_bytes);
1404 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1406 /* Process the regs live at the end of the block.
1407 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1408 Also mark them as not local to any one basic block. */
1410 for (offset = 0, i = 0; offset < regset_size; offset++)
1411 for (bit = 1; bit; bit <<= 1, i++)
1415 if (old[offset] & bit)
1417 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1418 regs_sometimes_live[sometimes_max].offset = offset;
1419 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1425 /* Scan the block an insn at a time from end to beginning. */
1427 for (insn = last; ; insn = prev)
1429 prev = PREV_INSN (insn);
1431 if (GET_CODE (insn) == NOTE)
1433 /* Look for loop boundaries, remembering that we are going
1435 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1437 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1440 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1441 Abort now rather than setting register status incorrectly. */
1442 if (loop_depth == 0)
1445 /* If this is a call to `setjmp' et al,
1446 warn if any non-volatile datum is live. */
1448 if (final && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1451 for (i = 0; i < regset_size; i++)
1452 regs_live_at_setjmp[i] |= old[i];
1456 /* Update the life-status of regs for this insn.
1457 First DEAD gets which regs are set in this insn
1458 then LIVE gets which regs are used in this insn.
1459 Then the regs live before the insn
1460 are those live after, with DEAD regs turned off,
1461 and then LIVE regs turned on. */
1463 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1466 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1468 = (insn_dead_p (PATTERN (insn), old, 0)
1469 /* Don't delete something that refers to volatile storage! */
1470 && ! INSN_VOLATILE (insn));
1472 = (insn_is_dead && note != 0
1473 && libcall_dead_p (PATTERN (insn), old, note, insn));
1475 /* If an instruction consists of just dead store(s) on final pass,
1476 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1477 We could really delete it with delete_insn, but that
1478 can cause trouble for first or last insn in a basic block. */
1479 if (final && insn_is_dead)
1481 PUT_CODE (insn, NOTE);
1482 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1483 NOTE_SOURCE_FILE (insn) = 0;
1485 /* CC0 is now known to be dead. Either this insn used it,
1486 in which case it doesn't anymore, or clobbered it,
1487 so the next insn can't use it. */
1490 /* If this insn is copying the return value from a library call,
1491 delete the entire library call. */
1492 if (libcall_is_dead)
1494 rtx first = XEXP (note, 0);
1496 while (INSN_DELETED_P (first))
1497 first = NEXT_INSN (first);
1502 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1503 NOTE_SOURCE_FILE (p) = 0;
1509 for (i = 0; i < regset_size; i++)
1511 dead[i] = 0; /* Faster than bzero here */
1512 live[i] = 0; /* since regset_size is usually small */
1515 /* See if this is an increment or decrement that can be
1516 merged into a following memory address. */
1519 register rtx x = PATTERN (insn);
1520 /* Does this instruction increment or decrement a register? */
1521 if (final && GET_CODE (x) == SET
1522 && GET_CODE (SET_DEST (x)) == REG
1523 && (GET_CODE (SET_SRC (x)) == PLUS
1524 || GET_CODE (SET_SRC (x)) == MINUS)
1525 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1526 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1527 /* Ok, look for a following memory ref we can combine with.
1528 If one is found, change the memory ref to a PRE_INC
1529 or PRE_DEC, cancel this insn, and return 1.
1530 Return 0 if nothing has been done. */
1531 && try_pre_increment_1 (insn))
1534 #endif /* AUTO_INC_DEC */
1536 /* If this is not the final pass, and this insn is copying the
1537 value of a library call and it's dead, don't scan the
1538 insns that perform the library call, so that the call's
1539 arguments are not marked live. */
1540 if (libcall_is_dead)
1542 /* Mark the dest reg as `significant'. */
1543 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1545 insn = XEXP (note, 0);
1546 prev = PREV_INSN (insn);
1548 else if (GET_CODE (PATTERN (insn)) == SET
1549 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1550 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1551 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1552 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1553 /* We have an insn to pop a constant amount off the stack.
1554 (Such insns use PLUS regardless of the direction of the stack,
1555 and any insn to adjust the stack by a constant is always a pop.)
1556 These insns, if not dead stores, have no effect on life. */
1560 /* LIVE gets the regs used in INSN;
1561 DEAD gets those set by it. Dead insns don't make anything
1564 mark_set_regs (old, dead, PATTERN (insn),
1565 final ? insn : NULL_RTX, significant);
1567 /* If an insn doesn't use CC0, it becomes dead since we
1568 assume that every insn clobbers it. So show it dead here;
1569 mark_used_regs will set it live if it is referenced. */
1573 mark_used_regs (old, live, PATTERN (insn), final, insn);
1575 /* Sometimes we may have inserted something before INSN (such as
1576 a move) when we make an auto-inc. So ensure we will scan
1579 prev = PREV_INSN (insn);
1582 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1588 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1590 note = XEXP (note, 1))
1591 if (GET_CODE (XEXP (note, 0)) == USE)
1592 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1595 /* Each call clobbers all call-clobbered regs that are not
1596 global. Note that the function-value reg is a
1597 call-clobbered reg, and mark_set_regs has already had
1598 a chance to handle it. */
1600 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1601 if (call_used_regs[i] && ! global_regs[i])
1602 dead[i / REGSET_ELT_BITS]
1603 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1605 /* The stack ptr is used (honorarily) by a CALL insn. */
1606 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1607 |= ((REGSET_ELT_TYPE) 1
1608 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1610 /* Calls may also reference any of the global registers,
1611 so they are made live. */
1612 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1614 mark_used_regs (old, live,
1615 gen_rtx (REG, reg_raw_mode[i], i),
1618 /* Calls also clobber memory. */
1622 /* Update OLD for the registers used or set. */
1623 for (i = 0; i < regset_size; i++)
1629 if (GET_CODE (insn) == CALL_INSN && final)
1631 /* Any regs live at the time of a call instruction
1632 must not go in a register clobbered by calls.
1633 Find all regs now live and record this for them. */
1635 register struct sometimes *p = regs_sometimes_live;
1637 for (i = 0; i < sometimes_max; i++, p++)
1638 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1639 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1643 /* On final pass, add any additional sometimes-live regs
1644 into MAXLIVE and REGS_SOMETIMES_LIVE.
1645 Also update counts of how many insns each reg is live at. */
1649 for (i = 0; i < regset_size; i++)
1651 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1657 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1658 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1660 regs_sometimes_live[sometimes_max].offset = i;
1661 regs_sometimes_live[sometimes_max].bit = regno;
1662 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1669 register struct sometimes *p = regs_sometimes_live;
1670 for (i = 0; i < sometimes_max; i++, p++)
1672 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1673 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1683 if (num_scratch > max_scratch)
1684 max_scratch = num_scratch;
1687 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1688 (SET expressions whose destinations are registers dead after the insn).
1689 NEEDED is the regset that says which regs are alive after the insn.
1691 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1694 insn_dead_p (x, needed, call_ok)
1699 register RTX_CODE code = GET_CODE (x);
1700 /* If setting something that's a reg or part of one,
1701 see if that register's altered value will be live. */
1705 register rtx r = SET_DEST (x);
1706 /* A SET that is a subroutine call cannot be dead. */
1707 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1711 if (GET_CODE (r) == CC0)
1715 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1716 && rtx_equal_p (r, last_mem_set))
1719 while (GET_CODE (r) == SUBREG
1720 || GET_CODE (r) == STRICT_LOW_PART
1721 || GET_CODE (r) == ZERO_EXTRACT
1722 || GET_CODE (r) == SIGN_EXTRACT)
1725 if (GET_CODE (r) == REG)
1727 register int regno = REGNO (r);
1728 register int offset = regno / REGSET_ELT_BITS;
1729 register REGSET_ELT_TYPE bit
1730 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1732 /* Don't delete insns to set global regs. */
1733 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1734 /* Make sure insns to set frame pointer aren't deleted. */
1735 || regno == FRAME_POINTER_REGNUM
1736 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1737 || regno == HARD_FRAME_POINTER_REGNUM
1739 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1740 /* Make sure insns to set arg pointer are never deleted
1741 (if the arg pointer isn't fixed, there will be a USE for
1742 it, so we can treat it normally). */
1743 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1745 || (needed[offset] & bit) != 0)
1748 /* If this is a hard register, verify that subsequent words are
1750 if (regno < FIRST_PSEUDO_REGISTER)
1752 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1755 if ((needed[(regno + n) / REGSET_ELT_BITS]
1756 & ((REGSET_ELT_TYPE) 1
1757 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1764 /* If performing several activities,
1765 insn is dead if each activity is individually dead.
1766 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1767 that's inside a PARALLEL doesn't make the insn worth keeping. */
1768 else if (code == PARALLEL)
1770 register int i = XVECLEN (x, 0);
1771 for (i--; i >= 0; i--)
1773 rtx elt = XVECEXP (x, 0, i);
1774 if (!insn_dead_p (elt, needed, call_ok)
1775 && GET_CODE (elt) != CLOBBER
1776 && GET_CODE (elt) != USE)
1781 /* We do not check CLOBBER or USE here.
1782 An insn consisting of just a CLOBBER or just a USE
1783 should not be deleted. */
1787 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1788 return 1 if the entire library call is dead.
1789 This is true if X copies a register (hard or pseudo)
1790 and if the hard return reg of the call insn is dead.
1791 (The caller should have tested the destination of X already for death.)
1793 If this insn doesn't just copy a register, then we don't
1794 have an ordinary libcall. In that case, cse could not have
1795 managed to substitute the source for the dest later on,
1796 so we can assume the libcall is dead.
1798 NEEDED is the bit vector of pseudoregs live before this insn.
1799 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1802 libcall_dead_p (x, needed, note, insn)
1808 register RTX_CODE code = GET_CODE (x);
1812 register rtx r = SET_SRC (x);
1813 if (GET_CODE (r) == REG)
1815 rtx call = XEXP (note, 0);
1818 /* Find the call insn. */
1819 while (call != insn && GET_CODE (call) != CALL_INSN)
1820 call = NEXT_INSN (call);
1822 /* If there is none, do nothing special,
1823 since ordinary death handling can understand these insns. */
1827 /* See if the hard reg holding the value is dead.
1828 If this is a PARALLEL, find the call within it. */
1829 call = PATTERN (call);
1830 if (GET_CODE (call) == PARALLEL)
1832 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1833 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1834 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1837 /* This may be a library call that is returning a value
1838 via invisible pointer. Do nothing special, since
1839 ordinary death handling can understand these insns. */
1843 call = XVECEXP (call, 0, i);
1846 return insn_dead_p (call, needed, 1);
1852 /* Return 1 if register REGNO was used before it was set.
1853 In other words, if it is live at function entry.
1854 Don't count global regster variables, though. */
1857 regno_uninitialized (regno)
1860 if (n_basic_blocks == 0
1861 || (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1864 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1865 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1868 /* 1 if register REGNO was alive at a place where `setjmp' was called
1869 and was set more than once or is an argument.
1870 Such regs may be clobbered by `longjmp'. */
1873 regno_clobbered_at_setjmp (regno)
1876 if (n_basic_blocks == 0)
1879 return ((reg_n_sets[regno] > 1
1880 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1881 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1882 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1883 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1886 /* Process the registers that are set within X.
1887 Their bits are set to 1 in the regset DEAD,
1888 because they are dead prior to this insn.
1890 If INSN is nonzero, it is the insn being processed
1891 and the fact that it is nonzero implies this is the FINAL pass
1892 in propagate_block. In this case, various info about register
1893 usage is stored, LOG_LINKS fields of insns are set up. */
1896 mark_set_regs (needed, dead, x, insn, significant)
1903 register RTX_CODE code = GET_CODE (x);
1905 if (code == SET || code == CLOBBER)
1906 mark_set_1 (needed, dead, x, insn, significant);
1907 else if (code == PARALLEL)
1910 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1912 code = GET_CODE (XVECEXP (x, 0, i));
1913 if (code == SET || code == CLOBBER)
1914 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1919 /* Process a single SET rtx, X. */
1922 mark_set_1 (needed, dead, x, insn, significant)
1930 register rtx reg = SET_DEST (x);
1932 /* Modifying just one hardware register of a multi-reg value
1933 or just a byte field of a register
1934 does not mean the value from before this insn is now dead.
1935 But it does mean liveness of that register at the end of the block
1938 Within mark_set_1, however, we treat it as if the register is
1939 indeed modified. mark_used_regs will, however, also treat this
1940 register as being used. Thus, we treat these insns as setting a
1941 new value for the register as a function of its old value. This
1942 cases LOG_LINKS to be made appropriately and this will help combine. */
1944 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1945 || GET_CODE (reg) == SIGN_EXTRACT
1946 || GET_CODE (reg) == STRICT_LOW_PART)
1947 reg = XEXP (reg, 0);
1949 /* If we are writing into memory or into a register mentioned in the
1950 address of the last thing stored into memory, show we don't know
1951 what the last store was. If we are writing memory, save the address
1952 unless it is volatile. */
1953 if (GET_CODE (reg) == MEM
1954 || (GET_CODE (reg) == REG
1955 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1958 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1959 /* There are no REG_INC notes for SP, so we can't assume we'll see
1960 everything that invalidates it. To be safe, don't eliminate any
1961 stores though SP; none of them should be redundant anyway. */
1962 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1965 if (GET_CODE (reg) == REG
1966 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1967 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1968 && regno != HARD_FRAME_POINTER_REGNUM
1970 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1971 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1973 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1974 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1976 register int offset = regno / REGSET_ELT_BITS;
1977 register REGSET_ELT_TYPE bit
1978 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1979 REGSET_ELT_TYPE all_needed = (needed[offset] & bit);
1980 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
1982 /* Mark it as a significant register for this basic block. */
1984 significant[offset] |= bit;
1986 /* Mark it as as dead before this insn. */
1987 dead[offset] |= bit;
1989 /* A hard reg in a wide mode may really be multiple registers.
1990 If so, mark all of them just like the first. */
1991 if (regno < FIRST_PSEUDO_REGISTER)
1995 /* Nothing below is needed for the stack pointer; get out asap.
1996 Eg, log links aren't needed, since combine won't use them. */
1997 if (regno == STACK_POINTER_REGNUM)
2000 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
2004 significant[(regno + n) / REGSET_ELT_BITS]
2005 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2006 dead[(regno + n) / REGSET_ELT_BITS]
2007 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2009 |= (needed[(regno + n) / REGSET_ELT_BITS]
2010 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2012 &= (needed[(regno + n) / REGSET_ELT_BITS]
2013 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2016 /* Additional data to record if this is the final pass. */
2019 register rtx y = reg_next_use[regno];
2020 register int blocknum = BLOCK_NUM (insn);
2022 /* The next use is no longer "next", since a store intervenes. */
2023 reg_next_use[regno] = 0;
2025 /* If this is a hard reg, record this function uses the reg. */
2027 if (regno < FIRST_PSEUDO_REGISTER)
2030 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
2032 for (i = regno; i < endregno; i++)
2034 regs_ever_live[i] = 1;
2040 /* Keep track of which basic blocks each reg appears in. */
2042 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2043 reg_basic_block[regno] = blocknum;
2044 else if (reg_basic_block[regno] != blocknum)
2045 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2047 /* Count (weighted) references, stores, etc. This counts a
2048 register twice if it is modified, but that is correct. */
2049 reg_n_sets[regno]++;
2051 reg_n_refs[regno] += loop_depth;
2053 /* The insns where a reg is live are normally counted
2054 elsewhere, but we want the count to include the insn
2055 where the reg is set, and the normal counting mechanism
2056 would not count it. */
2057 reg_live_length[regno]++;
2062 /* Make a logical link from the next following insn
2063 that uses this register, back to this insn.
2064 The following insns have already been processed.
2066 We don't build a LOG_LINK for hard registers containing
2067 in ASM_OPERANDs. If these registers get replaced,
2068 we might wind up changing the semantics of the insn,
2069 even if reload can make what appear to be valid assignments
2071 if (y && (BLOCK_NUM (y) == blocknum)
2072 && (regno >= FIRST_PSEUDO_REGISTER
2073 || asm_noperands (PATTERN (y)) < 0))
2075 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
2077 else if (! some_needed)
2079 /* Note that dead stores have already been deleted when possible
2080 If we get here, we have found a dead store that cannot
2081 be eliminated (because the same insn does something useful).
2082 Indicate this by marking the reg being set as dying here. */
2084 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2085 reg_n_deaths[REGNO (reg)]++;
2089 /* This is a case where we have a multi-word hard register
2090 and some, but not all, of the words of the register are
2091 needed in subsequent insns. Write REG_UNUSED notes
2092 for those parts that were not needed. This case should
2097 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2099 if ((needed[(regno + i) / REGSET_ELT_BITS]
2100 & ((REGSET_ELT_TYPE) 1
2101 << ((regno + i) % REGSET_ELT_BITS))) == 0)
2103 = gen_rtx (EXPR_LIST, REG_UNUSED,
2104 gen_rtx (REG, reg_raw_mode[regno + i],
2110 else if (GET_CODE (reg) == REG)
2111 reg_next_use[regno] = 0;
2113 /* If this is the last pass and this is a SCRATCH, show it will be dying
2114 here and count it. */
2115 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2118 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2125 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2129 find_auto_inc (needed, x, insn)
2134 rtx addr = XEXP (x, 0);
2135 HOST_WIDE_INT offset = 0;
2138 /* Here we detect use of an index register which might be good for
2139 postincrement, postdecrement, preincrement, or predecrement. */
2141 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2142 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2144 if (GET_CODE (addr) == REG)
2147 register int size = GET_MODE_SIZE (GET_MODE (x));
2150 int regno = REGNO (addr);
2152 /* Is the next use an increment that might make auto-increment? */
2153 if ((incr = reg_next_use[regno]) != 0
2154 && (set = single_set (incr)) != 0
2155 && GET_CODE (set) == SET
2156 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2157 /* Can't add side effects to jumps; if reg is spilled and
2158 reloaded, there's no way to store back the altered value. */
2159 && GET_CODE (insn) != JUMP_INSN
2160 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2161 && XEXP (y, 0) == addr
2162 && GET_CODE (XEXP (y, 1)) == CONST_INT
2164 #ifdef HAVE_POST_INCREMENT
2165 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2167 #ifdef HAVE_POST_DECREMENT
2168 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2170 #ifdef HAVE_PRE_INCREMENT
2171 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2173 #ifdef HAVE_PRE_DECREMENT
2174 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2177 /* Make sure this reg appears only once in this insn. */
2178 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2179 use != 0 && use != (rtx) 1))
2181 rtx q = SET_DEST (set);
2182 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2183 ? (offset ? PRE_INC : POST_INC)
2184 : (offset ? PRE_DEC : POST_DEC));
2186 if (dead_or_set_p (incr, addr))
2188 /* This is the simple case. Try to make the auto-inc. If
2189 we can't, we are done. Otherwise, we will do any
2190 needed updates below. */
2191 if (! validate_change (insn, &XEXP (x, 0),
2192 gen_rtx (inc_code, Pmode, addr),
2196 else if (GET_CODE (q) == REG
2197 /* PREV_INSN used here to check the semi-open interval
2199 && ! reg_used_between_p (q, PREV_INSN (insn), incr))
2201 /* We have *p followed sometime later by q = p+size.
2202 Both p and q must be live afterward,
2203 and q is not used between INSN and it's assignment.
2204 Change it to q = p, ...*q..., q = q+size.
2205 Then fall into the usual case. */
2209 emit_move_insn (q, addr);
2210 insns = get_insns ();
2213 /* If anything in INSNS have UID's that don't fit within the
2214 extra space we allocate earlier, we can't make this auto-inc.
2215 This should never happen. */
2216 for (temp = insns; temp; temp = NEXT_INSN (temp))
2218 if (INSN_UID (temp) > max_uid_for_flow)
2220 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2223 /* If we can't make the auto-inc, or can't make the
2224 replacement into Y, exit. There's no point in making
2225 the change below if we can't do the auto-inc and doing
2226 so is not correct in the pre-inc case. */
2228 validate_change (insn, &XEXP (x, 0),
2229 gen_rtx (inc_code, Pmode, q),
2231 validate_change (incr, &XEXP (y, 0), q, 1);
2232 if (! apply_change_group ())
2235 /* We now know we'll be doing this change, so emit the
2236 new insn(s) and do the updates. */
2237 emit_insns_before (insns, insn);
2239 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2240 basic_block_head[BLOCK_NUM (insn)] = insns;
2242 /* INCR will become a NOTE and INSN won't contain a
2243 use of ADDR. If a use of ADDR was just placed in
2244 the insn before INSN, make that the next use.
2245 Otherwise, invalidate it. */
2246 if (GET_CODE (PREV_INSN (insn)) == INSN
2247 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2248 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2249 reg_next_use[regno] = PREV_INSN (insn);
2251 reg_next_use[regno] = 0;
2256 /* REGNO is now used in INCR which is below INSN, but
2257 it previously wasn't live here. If we don't mark
2258 it as needed, we'll put a REG_DEAD note for it
2259 on this insn, which is incorrect. */
2260 needed[regno / REGSET_ELT_BITS]
2261 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2263 /* If there are any calls between INSN and INCR, show
2264 that REGNO now crosses them. */
2265 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2266 if (GET_CODE (temp) == CALL_INSN)
2267 reg_n_calls_crossed[regno]++;
2270 /* If we haven't returned, it means we were able to make the
2271 auto-inc, so update the status. First, record that this insn
2272 has an implicit side effect. */
2275 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2277 /* Modify the old increment-insn to simply copy
2278 the already-incremented value of our register. */
2279 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2282 /* If that makes it a no-op (copying the register into itself) delete
2283 it so it won't appear to be a "use" and a "set" of this
2285 if (SET_DEST (set) == addr)
2287 PUT_CODE (incr, NOTE);
2288 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2289 NOTE_SOURCE_FILE (incr) = 0;
2292 if (regno >= FIRST_PSEUDO_REGISTER)
2294 /* Count an extra reference to the reg. When a reg is
2295 incremented, spilling it is worse, so we want to make
2296 that less likely. */
2297 reg_n_refs[regno] += loop_depth;
2299 /* Count the increment as a setting of the register,
2300 even though it isn't a SET in rtl. */
2301 reg_n_sets[regno]++;
2306 #endif /* AUTO_INC_DEC */
2308 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2309 This is done assuming the registers needed from X
2310 are those that have 1-bits in NEEDED.
2312 On the final pass, FINAL is 1. This means try for autoincrement
2313 and count the uses and deaths of each pseudo-reg.
2315 INSN is the containing instruction. If INSN is dead, this function is not
2319 mark_used_regs (needed, live, x, final, insn)
2326 register RTX_CODE code;
2331 code = GET_CODE (x);
2352 /* If we are clobbering a MEM, mark any registers inside the address
2354 if (GET_CODE (XEXP (x, 0)) == MEM)
2355 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2359 /* Invalidate the data for the last MEM stored. We could do this only
2360 if the addresses conflict, but this doesn't seem worthwhile. */
2365 find_auto_inc (needed, x, insn);
2370 if (GET_CODE (SUBREG_REG (x)) == REG
2371 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2372 && (GET_MODE_SIZE (GET_MODE (x))
2373 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
2374 && (INTEGRAL_MODE_P (GET_MODE (x))
2375 || INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (x)))))
2376 reg_changes_size[REGNO (SUBREG_REG (x))] = 1;
2378 /* While we're here, optimize this case. */
2381 /* ... fall through ... */
2384 /* See a register other than being set
2385 => mark it as needed. */
2389 register int offset = regno / REGSET_ELT_BITS;
2390 register REGSET_ELT_TYPE bit
2391 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2392 REGSET_ELT_TYPE all_needed = needed[offset] & bit;
2393 REGSET_ELT_TYPE some_needed = needed[offset] & bit;
2395 live[offset] |= bit;
2396 /* A hard reg in a wide mode may really be multiple registers.
2397 If so, mark all of them just like the first. */
2398 if (regno < FIRST_PSEUDO_REGISTER)
2402 /* For stack ptr or fixed arg pointer,
2403 nothing below can be necessary, so waste no more time. */
2404 if (regno == STACK_POINTER_REGNUM
2405 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2406 || regno == HARD_FRAME_POINTER_REGNUM
2408 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2409 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2411 || regno == FRAME_POINTER_REGNUM)
2413 /* If this is a register we are going to try to eliminate,
2414 don't mark it live here. If we are successful in
2415 eliminating it, it need not be live unless it is used for
2416 pseudos, in which case it will have been set live when
2417 it was allocated to the pseudos. If the register will not
2418 be eliminated, reload will set it live at that point. */
2420 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2421 regs_ever_live[regno] = 1;
2424 /* No death notes for global register variables;
2425 their values are live after this function exits. */
2426 if (global_regs[regno])
2429 reg_next_use[regno] = insn;
2433 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2436 live[(regno + n) / REGSET_ELT_BITS]
2437 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2439 |= (needed[(regno + n) / REGSET_ELT_BITS]
2440 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2442 &= (needed[(regno + n) / REGSET_ELT_BITS]
2443 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2448 /* Record where each reg is used, so when the reg
2449 is set we know the next insn that uses it. */
2451 reg_next_use[regno] = insn;
2453 if (regno < FIRST_PSEUDO_REGISTER)
2455 /* If a hard reg is being used,
2456 record that this function does use it. */
2458 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2462 regs_ever_live[regno + --i] = 1;
2467 /* Keep track of which basic block each reg appears in. */
2469 register int blocknum = BLOCK_NUM (insn);
2471 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2472 reg_basic_block[regno] = blocknum;
2473 else if (reg_basic_block[regno] != blocknum)
2474 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2476 /* Count (weighted) number of uses of each reg. */
2478 reg_n_refs[regno] += loop_depth;
2481 /* Record and count the insns in which a reg dies.
2482 If it is used in this insn and was dead below the insn
2483 then it dies in this insn. If it was set in this insn,
2484 we do not make a REG_DEAD note; likewise if we already
2485 made such a note. */
2488 && ! dead_or_set_p (insn, x)
2490 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2494 /* Check for the case where the register dying partially
2495 overlaps the register set by this insn. */
2496 if (regno < FIRST_PSEUDO_REGISTER
2497 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2499 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2501 some_needed |= dead_or_set_regno_p (insn, regno + n);
2504 /* If none of the words in X is needed, make a REG_DEAD
2505 note. Otherwise, we must make partial REG_DEAD notes. */
2509 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2510 reg_n_deaths[regno]++;
2516 /* Don't make a REG_DEAD note for a part of a register
2517 that is set in the insn. */
2519 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2521 if ((needed[(regno + i) / REGSET_ELT_BITS]
2522 & ((REGSET_ELT_TYPE) 1
2523 << ((regno + i) % REGSET_ELT_BITS))) == 0
2524 && ! dead_or_set_regno_p (insn, regno + i))
2526 = gen_rtx (EXPR_LIST, REG_DEAD,
2527 gen_rtx (REG, reg_raw_mode[regno + i],
2538 register rtx testreg = SET_DEST (x);
2541 /* If storing into MEM, don't show it as being used. But do
2542 show the address as being used. */
2543 if (GET_CODE (testreg) == MEM)
2547 find_auto_inc (needed, testreg, insn);
2549 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2550 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2554 /* Storing in STRICT_LOW_PART is like storing in a reg
2555 in that this SET might be dead, so ignore it in TESTREG.
2556 but in some other ways it is like using the reg.
2558 Storing in a SUBREG or a bit field is like storing the entire
2559 register in that if the register's value is not used
2560 then this SET is not needed. */
2561 while (GET_CODE (testreg) == STRICT_LOW_PART
2562 || GET_CODE (testreg) == ZERO_EXTRACT
2563 || GET_CODE (testreg) == SIGN_EXTRACT
2564 || GET_CODE (testreg) == SUBREG)
2566 /* Modifying a single register in an alternate mode
2567 does not use any of the old value. But these other
2568 ways of storing in a register do use the old value. */
2569 if (GET_CODE (testreg) == SUBREG
2570 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2575 testreg = XEXP (testreg, 0);
2578 /* If this is a store into a register,
2579 recursively scan the value being stored. */
2581 if (GET_CODE (testreg) == REG
2582 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2583 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2584 && regno != HARD_FRAME_POINTER_REGNUM
2586 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2587 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2590 /* We used to exclude global_regs here, but that seems wrong.
2591 Storing in them is like storing in mem. */
2593 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2595 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2602 /* If exiting needs the right stack value, consider this insn as
2603 using the stack pointer. In any event, consider it as using
2604 all global registers. */
2606 #ifdef EXIT_IGNORE_STACK
2607 if (! EXIT_IGNORE_STACK
2608 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2610 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2611 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2613 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2615 live[i / REGSET_ELT_BITS]
2616 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2620 /* Recursively scan the operands of this expression. */
2623 register char *fmt = GET_RTX_FORMAT (code);
2626 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2630 /* Tail recursive case: save a function call level. */
2636 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2638 else if (fmt[i] == 'E')
2641 for (j = 0; j < XVECLEN (x, i); j++)
2642 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2651 try_pre_increment_1 (insn)
2654 /* Find the next use of this reg. If in same basic block,
2655 make it do pre-increment or pre-decrement if appropriate. */
2656 rtx x = PATTERN (insn);
2657 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2658 * INTVAL (XEXP (SET_SRC (x), 1)));
2659 int regno = REGNO (SET_DEST (x));
2660 rtx y = reg_next_use[regno];
2662 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2663 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2664 mode would be better. */
2665 && ! dead_or_set_p (y, SET_DEST (x))
2666 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2669 /* We have found a suitable auto-increment
2670 and already changed insn Y to do it.
2671 So flush this increment-instruction. */
2672 PUT_CODE (insn, NOTE);
2673 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2674 NOTE_SOURCE_FILE (insn) = 0;
2675 /* Count a reference to this reg for the increment
2676 insn we are deleting. When a reg is incremented.
2677 spilling it is worse, so we want to make that
2679 if (regno >= FIRST_PSEUDO_REGISTER)
2681 reg_n_refs[regno] += loop_depth;
2682 reg_n_sets[regno]++;
2689 /* Try to change INSN so that it does pre-increment or pre-decrement
2690 addressing on register REG in order to add AMOUNT to REG.
2691 AMOUNT is negative for pre-decrement.
2692 Returns 1 if the change could be made.
2693 This checks all about the validity of the result of modifying INSN. */
2696 try_pre_increment (insn, reg, amount)
2698 HOST_WIDE_INT amount;
2702 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2703 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2705 /* Nonzero if we can try to make a post-increment or post-decrement.
2706 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2707 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2708 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2711 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2714 /* From the sign of increment, see which possibilities are conceivable
2715 on this target machine. */
2716 #ifdef HAVE_PRE_INCREMENT
2720 #ifdef HAVE_POST_INCREMENT
2725 #ifdef HAVE_PRE_DECREMENT
2729 #ifdef HAVE_POST_DECREMENT
2734 if (! (pre_ok || post_ok))
2737 /* It is not safe to add a side effect to a jump insn
2738 because if the incremented register is spilled and must be reloaded
2739 there would be no way to store the incremented value back in memory. */
2741 if (GET_CODE (insn) == JUMP_INSN)
2746 use = find_use_as_address (PATTERN (insn), reg, 0);
2747 if (post_ok && (use == 0 || use == (rtx) 1))
2749 use = find_use_as_address (PATTERN (insn), reg, -amount);
2753 if (use == 0 || use == (rtx) 1)
2756 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2759 /* See if this combination of instruction and addressing mode exists. */
2760 if (! validate_change (insn, &XEXP (use, 0),
2762 ? (do_post ? POST_INC : PRE_INC)
2763 : (do_post ? POST_DEC : PRE_DEC),
2767 /* Record that this insn now has an implicit side effect on X. */
2768 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2772 #endif /* AUTO_INC_DEC */
2774 /* Find the place in the rtx X where REG is used as a memory address.
2775 Return the MEM rtx that so uses it.
2776 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2777 (plus REG (const_int PLUSCONST)).
2779 If such an address does not appear, return 0.
2780 If REG appears more than once, or is used other than in such an address,
2784 find_use_as_address (x, reg, plusconst)
2787 HOST_WIDE_INT plusconst;
2789 enum rtx_code code = GET_CODE (x);
2790 char *fmt = GET_RTX_FORMAT (code);
2792 register rtx value = 0;
2795 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2798 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2799 && XEXP (XEXP (x, 0), 0) == reg
2800 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2801 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2804 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2806 /* If REG occurs inside a MEM used in a bit-field reference,
2807 that is unacceptable. */
2808 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2809 return (rtx) (HOST_WIDE_INT) 1;
2813 return (rtx) (HOST_WIDE_INT) 1;
2815 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2819 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2823 return (rtx) (HOST_WIDE_INT) 1;
2828 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2830 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2834 return (rtx) (HOST_WIDE_INT) 1;
2842 /* Write information about registers and basic blocks into FILE.
2843 This is part of making a debugging dump. */
2846 dump_flow_info (file)
2850 static char *reg_class_names[] = REG_CLASS_NAMES;
2852 fprintf (file, "%d registers.\n", max_regno);
2854 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2857 enum reg_class class, altclass;
2858 fprintf (file, "\nRegister %d used %d times across %d insns",
2859 i, reg_n_refs[i], reg_live_length[i]);
2860 if (reg_basic_block[i] >= 0)
2861 fprintf (file, " in block %d", reg_basic_block[i]);
2862 if (reg_n_deaths[i] != 1)
2863 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2864 if (reg_n_calls_crossed[i] == 1)
2865 fprintf (file, "; crosses 1 call");
2866 else if (reg_n_calls_crossed[i])
2867 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2868 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2869 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2870 class = reg_preferred_class (i);
2871 altclass = reg_alternate_class (i);
2872 if (class != GENERAL_REGS || altclass != ALL_REGS)
2874 if (altclass == ALL_REGS || class == ALL_REGS)
2875 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2876 else if (altclass == NO_REGS)
2877 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2879 fprintf (file, "; pref %s, else %s",
2880 reg_class_names[(int) class],
2881 reg_class_names[(int) altclass]);
2883 if (REGNO_POINTER_FLAG (i))
2884 fprintf (file, "; pointer");
2885 fprintf (file, ".\n");
2887 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2888 for (i = 0; i < n_basic_blocks; i++)
2890 register rtx head, jump;
2892 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2894 INSN_UID (basic_block_head[i]),
2895 INSN_UID (basic_block_end[i]));
2896 /* The control flow graph's storage is freed
2897 now when flow_analysis returns.
2898 Don't try to print it if it is gone. */
2899 if (basic_block_drops_in)
2901 fprintf (file, "Reached from blocks: ");
2902 head = basic_block_head[i];
2903 if (GET_CODE (head) == CODE_LABEL)
2904 for (jump = LABEL_REFS (head);
2906 jump = LABEL_NEXTREF (jump))
2908 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2909 fprintf (file, " %d", from_block);
2911 if (basic_block_drops_in[i])
2912 fprintf (file, " previous");
2914 fprintf (file, "\nRegisters live at start:");
2915 for (regno = 0; regno < max_regno; regno++)
2917 register int offset = regno / REGSET_ELT_BITS;
2918 register REGSET_ELT_TYPE bit
2919 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2920 if (basic_block_live_at_start[i][offset] & bit)
2921 fprintf (file, " %d", regno);
2923 fprintf (file, "\n");
2925 fprintf (file, "\n");