1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 1988, 1992 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 short *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 short *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, gives number of places register N dies.
181 This information remains valid for the rest of the compilation
182 of the current function; it is used to control register allocation. */
186 /* Indexed by N, gives 1 if that reg is live across any CALL_INSNs.
187 This information remains valid for the rest of the compilation
188 of the current function; it is used to control register allocation. */
190 int *reg_n_calls_crossed;
192 /* Total number of instructions at which (REG n) is live.
193 The larger this is, the less priority (REG n) gets for
194 allocation in a real register.
195 This information remains valid for the rest of the compilation
196 of the current function; it is used to control register allocation.
198 local-alloc.c may alter this number to change the priority.
200 Negative values are special.
201 -1 is used to mark a pseudo reg which has a constant or memory equivalent
202 and is used infrequently enough that it should not get a hard register.
203 -2 is used to mark a pseudo reg for a parameter, when a frame pointer
204 is not required. global.c makes an allocno for this but does
205 not try to assign a hard register to it. */
207 int *reg_live_length;
209 /* Element N is the next insn that uses (hard or pseudo) register number N
210 within the current basic block; or zero, if there is no such insn.
211 This is valid only during the final backward scan in propagate_block. */
213 static rtx *reg_next_use;
215 /* Size of a regset for the current function,
216 in (1) bytes and (2) elements. */
221 /* Element N is first insn in basic block N.
222 This info lasts until we finish compiling the function. */
224 rtx *basic_block_head;
226 /* Element N is last insn in basic block N.
227 This info lasts until we finish compiling the function. */
229 rtx *basic_block_end;
231 /* Element N is a regset describing the registers live
232 at the start of basic block N.
233 This info lasts until we finish compiling the function. */
235 regset *basic_block_live_at_start;
237 /* Regset of regs live when calls to `setjmp'-like functions happen. */
239 regset regs_live_at_setjmp;
241 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
242 that have to go in the same hard reg.
243 The first two regs in the list are a pair, and the next two
244 are another pair, etc. */
247 /* Element N is nonzero if control can drop into basic block N
248 from the preceding basic block. Freed after life_analysis. */
250 static char *basic_block_drops_in;
252 /* Element N is depth within loops of the last insn in basic block number N.
253 Freed after life_analysis. */
255 static short *basic_block_loop_depth;
257 /* Element N nonzero if basic block N can actually be reached.
258 Vector exists only during find_basic_blocks. */
260 static char *block_live_static;
262 /* Depth within loops of basic block being scanned for lifetime analysis,
263 plus one. This is the weight attached to references to registers. */
265 static int loop_depth;
267 /* During propagate_block, this is non-zero if the value of CC0 is live. */
271 /* During propagate_block, this contains the last MEM stored into. It
272 is used to eliminate consecutive stores to the same location. */
274 static rtx last_mem_set;
276 /* Set of registers that may be eliminable. These are handled specially
277 in updating regs_ever_live. */
279 static HARD_REG_SET elim_reg_set;
281 /* Forward declarations */
282 static void find_basic_blocks ();
283 static void life_analysis ();
284 static void mark_label_ref ();
285 void allocate_for_life_analysis (); /* Used also in stupid_life_analysis */
286 static void init_regset_vector ();
287 static void propagate_block ();
288 static void mark_set_regs ();
289 static void mark_used_regs ();
290 static int insn_dead_p ();
291 static int libcall_dead_p ();
292 static int try_pre_increment ();
293 static int try_pre_increment_1 ();
294 static rtx find_use_as_address ();
295 void dump_flow_info ();
297 /* Find basic blocks of the current function and perform data flow analysis.
298 F is the first insn of the function and NREGS the number of register numbers
302 flow_analysis (f, nregs, file)
309 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
311 #ifdef ELIMINABLE_REGS
312 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
315 /* Record which registers will be eliminated. We use this in
318 CLEAR_HARD_REG_SET (elim_reg_set);
320 #ifdef ELIMINABLE_REGS
321 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
322 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
324 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
327 /* Count the basic blocks. Also find maximum insn uid value used. */
330 register RTX_CODE prev_code = JUMP_INSN;
331 register RTX_CODE code;
333 max_uid_for_flow = 0;
335 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
337 code = GET_CODE (insn);
338 if (INSN_UID (insn) > max_uid_for_flow)
339 max_uid_for_flow = INSN_UID (insn);
340 if (code == CODE_LABEL
341 || (GET_RTX_CLASS (code) == 'i'
342 && (prev_code == JUMP_INSN
343 || (prev_code == CALL_INSN
344 && nonlocal_label_list != 0)
345 || prev_code == BARRIER)))
353 /* Leave space for insns we make in some cases for auto-inc. These cases
354 are rare, so we don't need too much space. */
355 max_uid_for_flow += max_uid_for_flow / 10;
358 /* Allocate some tables that last till end of compiling this function
359 and some needed only in find_basic_blocks and life_analysis. */
362 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
363 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
364 basic_block_drops_in = (char *) alloca (n_basic_blocks);
365 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
367 = (short *) alloca ((max_uid_for_flow + 1) * sizeof (short));
368 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
369 bzero (uid_volatile, max_uid_for_flow + 1);
371 find_basic_blocks (f, nonlocal_label_list);
372 life_analysis (f, nregs);
374 dump_flow_info (file);
376 basic_block_drops_in = 0;
377 uid_block_number = 0;
378 basic_block_loop_depth = 0;
381 /* Find all basic blocks of the function whose first insn is F.
382 Store the correct data in the tables that describe the basic blocks,
383 set up the chains of references for each CODE_LABEL, and
384 delete any entire basic blocks that cannot be reached.
386 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
389 find_basic_blocks (f, nonlocal_label_list)
390 rtx f, nonlocal_label_list;
394 register char *block_live = (char *) alloca (n_basic_blocks);
395 register char *block_marked = (char *) alloca (n_basic_blocks);
396 /* List of label_refs to all labels whose addresses are taken
398 rtx label_value_list = 0;
400 block_live_static = block_live;
401 bzero (block_live, n_basic_blocks);
402 bzero (block_marked, n_basic_blocks);
404 /* Initialize with just block 0 reachable and no blocks marked. */
405 if (n_basic_blocks > 0)
408 /* Initialize the ref chain of each label to 0. */
409 /* Record where all the blocks start and end and their depth in loops. */
410 /* For each insn, record the block it is in. */
411 /* Also mark as reachable any blocks headed by labels that
412 must not be deleted. */
415 register RTX_CODE prev_code = JUMP_INSN;
416 register RTX_CODE code;
419 for (insn = f, i = -1; insn; insn = NEXT_INSN (insn))
421 code = GET_CODE (insn);
424 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
426 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
429 /* A basic block starts at label, or after something that can jump. */
430 else if (code == CODE_LABEL
431 || (GET_RTX_CLASS (code) == 'i'
432 && (prev_code == JUMP_INSN
433 || (prev_code == CALL_INSN
434 && nonlocal_label_list != 0)
435 || prev_code == BARRIER)))
437 basic_block_head[++i] = insn;
438 basic_block_end[i] = insn;
439 basic_block_loop_depth[i] = depth;
440 if (code == CODE_LABEL)
442 LABEL_REFS (insn) = insn;
443 /* Any label that cannot be deleted
444 is considered to start a reachable block. */
445 if (LABEL_PRESERVE_P (insn))
449 else if (GET_RTX_CLASS (code) == 'i')
451 basic_block_end[i] = insn;
452 basic_block_loop_depth[i] = depth;
455 /* Make a list of all labels referred to other than by jumps. */
456 if (code == INSN || code == CALL_INSN)
458 rtx note = find_reg_note (insn, REG_LABEL, NULL_RTX);
460 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
464 BLOCK_NUM (insn) = i;
466 /* Don't separate a CALL_INSN from following CLOBBER insns. This is
467 a kludge that will go away when each CALL_INSN records its
471 && ! (prev_code == CALL_INSN && code == INSN
472 && GET_CODE (PATTERN (insn)) == CLOBBER))
475 if (i + 1 != n_basic_blocks)
479 /* Don't delete the labels (in this function)
480 that are referenced by non-jump instructions. */
483 for (x = label_value_list; x; x = XEXP (x, 1))
484 if (! LABEL_REF_NONLOCAL_P (x))
485 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
488 /* Record which basic blocks control can drop in to. */
492 for (i = 0; i < n_basic_blocks; i++)
494 register rtx insn = PREV_INSN (basic_block_head[i]);
495 /* TEMP1 is used to avoid a bug in Sequent's compiler. */
497 while (insn && GET_CODE (insn) == NOTE)
498 insn = PREV_INSN (insn);
499 temp1 = insn && GET_CODE (insn) != BARRIER;
500 basic_block_drops_in[i] = temp1;
504 /* Now find which basic blocks can actually be reached
505 and put all jump insns' LABEL_REFS onto the ref-chains
506 of their target labels. */
508 if (n_basic_blocks > 0)
510 int something_marked = 1;
512 /* Find all indirect jump insns and mark them as possibly jumping
513 to all the labels whose addresses are explicitly used.
514 This is because, when there are computed gotos,
515 we can't tell which labels they jump to, of all the possibilities. */
517 for (insn = f; insn; insn = NEXT_INSN (insn))
518 if (GET_CODE (insn) == JUMP_INSN
519 && GET_CODE (PATTERN (insn)) == SET
520 && SET_DEST (PATTERN (insn)) == pc_rtx
521 && (GET_CODE (SET_SRC (PATTERN (insn))) == REG
522 || GET_CODE (SET_SRC (PATTERN (insn))) == MEM))
525 for (x = label_value_list; x; x = XEXP (x, 1))
526 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
528 for (x = forced_labels; x; x = XEXP (x, 1))
529 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
533 /* Find all call insns and mark them as possibly jumping
534 to all the nonlocal goto handler labels. */
536 for (insn = f; insn; insn = NEXT_INSN (insn))
537 if (GET_CODE (insn) == CALL_INSN)
540 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
541 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
543 /* ??? This could be made smarter:
544 in some cases it's possible to tell that certain
545 calls will not do a nonlocal goto.
547 For example, if the nested functions that do the
548 nonlocal gotos do not have their addresses taken, then
549 only calls to those functions or to other nested
550 functions that use them could possibly do nonlocal
554 /* Pass over all blocks, marking each block that is reachable
555 and has not yet been marked.
556 Keep doing this until, in one pass, no blocks have been marked.
557 Then blocks_live and blocks_marked are identical and correct.
558 In addition, all jumps actually reachable have been marked. */
560 while (something_marked)
562 something_marked = 0;
563 for (i = 0; i < n_basic_blocks; i++)
564 if (block_live[i] && !block_marked[i])
567 something_marked = 1;
568 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
569 block_live[i + 1] = 1;
570 insn = basic_block_end[i];
571 if (GET_CODE (insn) == JUMP_INSN)
572 mark_label_ref (PATTERN (insn), insn, 0);
576 /* Now delete the code for any basic blocks that can't be reached.
577 They can occur because jump_optimize does not recognize
578 unreachable loops as unreachable. */
580 for (i = 0; i < n_basic_blocks; i++)
583 insn = basic_block_head[i];
586 if (GET_CODE (insn) == BARRIER)
588 if (GET_CODE (insn) != NOTE)
590 PUT_CODE (insn, NOTE);
591 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
592 NOTE_SOURCE_FILE (insn) = 0;
594 if (insn == basic_block_end[i])
596 /* BARRIERs are between basic blocks, not part of one.
597 Delete a BARRIER if the preceding jump is deleted.
598 We cannot alter a BARRIER into a NOTE
599 because it is too short; but we can really delete
600 it because it is not part of a basic block. */
601 if (NEXT_INSN (insn) != 0
602 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
603 delete_insn (NEXT_INSN (insn));
606 insn = NEXT_INSN (insn);
608 /* Each time we delete some basic blocks,
609 see if there is a jump around them that is
610 being turned into a no-op. If so, delete it. */
612 if (block_live[i - 1])
615 for (j = i; j < n_basic_blocks; j++)
619 insn = basic_block_end[i - 1];
620 if (GET_CODE (insn) == JUMP_INSN
621 /* An unconditional jump is the only possibility
622 we must check for, since a conditional one
623 would make these blocks live. */
624 && simplejump_p (insn)
625 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
626 && INSN_UID (label) != 0
627 && BLOCK_NUM (label) == j)
629 PUT_CODE (insn, NOTE);
630 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
631 NOTE_SOURCE_FILE (insn) = 0;
632 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
634 delete_insn (NEXT_INSN (insn));
643 /* Check expression X for label references;
644 if one is found, add INSN to the label's chain of references.
646 CHECKDUP means check for and avoid creating duplicate references
647 from the same insn. Such duplicates do no serious harm but
648 can slow life analysis. CHECKDUP is set only when duplicates
652 mark_label_ref (x, insn, checkdup)
656 register RTX_CODE code;
660 /* We can be called with NULL when scanning label_value_list. */
665 if (code == LABEL_REF)
667 register rtx label = XEXP (x, 0);
669 if (GET_CODE (label) != CODE_LABEL)
671 /* If the label was never emitted, this insn is junk,
672 but avoid a crash trying to refer to BLOCK_NUM (label).
673 This can happen as a result of a syntax error
674 and a diagnostic has already been printed. */
675 if (INSN_UID (label) == 0)
677 CONTAINING_INSN (x) = insn;
678 /* if CHECKDUP is set, check for duplicate ref from same insn
681 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
682 if (CONTAINING_INSN (y) == insn)
684 LABEL_NEXTREF (x) = LABEL_REFS (label);
685 LABEL_REFS (label) = x;
686 block_live_static[BLOCK_NUM (label)] = 1;
690 fmt = GET_RTX_FORMAT (code);
691 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
694 mark_label_ref (XEXP (x, i), insn, 0);
698 for (j = 0; j < XVECLEN (x, i); j++)
699 mark_label_ref (XVECEXP (x, i, j), insn, 1);
704 /* Determine which registers are live at the start of each
705 basic block of the function whose first insn is F.
706 NREGS is the number of registers used in F.
707 We allocate the vector basic_block_live_at_start
708 and the regsets that it points to, and fill them with the data.
709 regset_size and regset_bytes are also set here. */
712 life_analysis (f, nregs)
719 /* For each basic block, a bitmask of regs
720 live on exit from the block. */
721 regset *basic_block_live_at_end;
722 /* For each basic block, a bitmask of regs
723 live on entry to a successor-block of this block.
724 If this does not match basic_block_live_at_end,
725 that must be updated, and the block must be rescanned. */
726 regset *basic_block_new_live_at_end;
727 /* For each basic block, a bitmask of regs
728 whose liveness at the end of the basic block
729 can make a difference in which regs are live on entry to the block.
730 These are the regs that are set within the basic block,
731 possibly excluding those that are used after they are set. */
732 regset *basic_block_significant;
736 struct obstack flow_obstack;
738 gcc_obstack_init (&flow_obstack);
742 bzero (regs_ever_live, sizeof regs_ever_live);
744 /* Allocate and zero out many data structures
745 that will record the data from lifetime analysis. */
747 allocate_for_life_analysis ();
749 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
750 bzero (reg_next_use, nregs * sizeof (rtx));
752 /* Set up several regset-vectors used internally within this function.
753 Their meanings are documented above, with their declarations. */
755 basic_block_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset));
756 /* Don't use alloca since that leads to a crash rather than an error message
757 if there isn't enough space.
758 Don't use oballoc since we may need to allocate other things during
759 this function on the temporary obstack. */
760 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
761 bzero (tem, n_basic_blocks * regset_bytes);
762 init_regset_vector (basic_block_live_at_end, tem, n_basic_blocks, regset_bytes);
764 basic_block_new_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset));
765 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
766 bzero (tem, n_basic_blocks * regset_bytes);
767 init_regset_vector (basic_block_new_live_at_end, tem, n_basic_blocks, regset_bytes);
769 basic_block_significant = (regset *) alloca (n_basic_blocks * sizeof (regset));
770 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
771 bzero (tem, n_basic_blocks * regset_bytes);
772 init_regset_vector (basic_block_significant, tem, n_basic_blocks, regset_bytes);
774 /* Record which insns refer to any volatile memory
775 or for any reason can't be deleted just because they are dead stores.
776 Also, delete any insns that copy a register to itself. */
778 for (insn = f; insn; insn = NEXT_INSN (insn))
780 enum rtx_code code1 = GET_CODE (insn);
781 if (code1 == CALL_INSN)
782 INSN_VOLATILE (insn) = 1;
783 else if (code1 == INSN || code1 == JUMP_INSN)
785 /* Delete (in effect) any obvious no-op moves. */
786 if (GET_CODE (PATTERN (insn)) == SET
787 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
788 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
789 && REGNO (SET_DEST (PATTERN (insn))) ==
790 REGNO (SET_SRC (PATTERN (insn)))
791 /* Insns carrying these notes are useful later on. */
792 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
794 PUT_CODE (insn, NOTE);
795 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
796 NOTE_SOURCE_FILE (insn) = 0;
798 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
800 /* If nothing but SETs of registers to themselves,
801 this insn can also be deleted. */
802 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
804 rtx tem = XVECEXP (PATTERN (insn), 0, i);
806 if (GET_CODE (tem) == USE
807 || GET_CODE (tem) == CLOBBER)
810 if (GET_CODE (tem) != SET
811 || GET_CODE (SET_DEST (tem)) != REG
812 || GET_CODE (SET_SRC (tem)) != REG
813 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
817 if (i == XVECLEN (PATTERN (insn), 0)
818 /* Insns carrying these notes are useful later on. */
819 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
821 PUT_CODE (insn, NOTE);
822 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
823 NOTE_SOURCE_FILE (insn) = 0;
826 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
828 else if (GET_CODE (PATTERN (insn)) != USE)
829 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
830 /* A SET that makes space on the stack cannot be dead.
831 (Such SETs occur only for allocating variable-size data,
832 so they will always have a PLUS or MINUS according to the
833 direction of stack growth.)
834 Even if this function never uses this stack pointer value,
835 signal handlers do! */
836 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
837 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
838 #ifdef STACK_GROWS_DOWNWARD
839 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
841 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
843 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
844 INSN_VOLATILE (insn) = 1;
848 if (n_basic_blocks > 0)
849 #ifdef EXIT_IGNORE_STACK
850 if (! EXIT_IGNORE_STACK
851 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
854 /* If exiting needs the right stack value,
855 consider the stack pointer live at the end of the function. */
856 basic_block_live_at_end[n_basic_blocks - 1]
857 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
858 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
859 basic_block_new_live_at_end[n_basic_blocks - 1]
860 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
861 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
864 /* Mark all global registers as being live at the end of the function
865 since they may be referenced by our caller. */
867 if (n_basic_blocks > 0)
868 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
871 basic_block_live_at_end[n_basic_blocks - 1]
872 [i / REGSET_ELT_BITS]
873 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
874 basic_block_new_live_at_end[n_basic_blocks - 1]
875 [i / REGSET_ELT_BITS]
876 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
879 /* Propagate life info through the basic blocks
880 around the graph of basic blocks.
882 This is a relaxation process: each time a new register
883 is live at the end of the basic block, we must scan the block
884 to determine which registers are, as a consequence, live at the beginning
885 of that block. These registers must then be marked live at the ends
886 of all the blocks that can transfer control to that block.
887 The process continues until it reaches a fixed point. */
894 for (i = n_basic_blocks - 1; i >= 0; i--)
896 int consider = first_pass;
897 int must_rescan = first_pass;
902 /* Set CONSIDER if this block needs thinking about at all
903 (that is, if the regs live now at the end of it
904 are not the same as were live at the end of it when
905 we last thought about it).
906 Set must_rescan if it needs to be thought about
907 instruction by instruction (that is, if any additional
908 reg that is live at the end now but was not live there before
909 is one of the significant regs of this basic block). */
911 for (j = 0; j < regset_size; j++)
913 register REGSET_ELT_TYPE x
914 = (basic_block_new_live_at_end[i][j]
915 & ~basic_block_live_at_end[i][j]);
918 if (x & basic_block_significant[i][j])
930 /* The live_at_start of this block may be changing,
931 so another pass will be required after this one. */
936 /* No complete rescan needed;
937 just record those variables newly known live at end
938 as live at start as well. */
939 for (j = 0; j < regset_size; j++)
941 register REGSET_ELT_TYPE x
942 = (basic_block_new_live_at_end[i][j]
943 & ~basic_block_live_at_end[i][j]);
944 basic_block_live_at_start[i][j] |= x;
945 basic_block_live_at_end[i][j] |= x;
950 /* Update the basic_block_live_at_start
951 by propagation backwards through the block. */
952 bcopy (basic_block_new_live_at_end[i],
953 basic_block_live_at_end[i], regset_bytes);
954 bcopy (basic_block_live_at_end[i],
955 basic_block_live_at_start[i], regset_bytes);
956 propagate_block (basic_block_live_at_start[i],
957 basic_block_head[i], basic_block_end[i], 0,
958 first_pass ? basic_block_significant[i]
964 register rtx jump, head;
965 /* Update the basic_block_new_live_at_end's of the block
966 that falls through into this one (if any). */
967 head = basic_block_head[i];
968 jump = PREV_INSN (head);
969 if (basic_block_drops_in[i])
971 register int from_block = BLOCK_NUM (jump);
973 for (j = 0; j < regset_size; j++)
974 basic_block_new_live_at_end[from_block][j]
975 |= basic_block_live_at_start[i][j];
977 /* Update the basic_block_new_live_at_end's of
978 all the blocks that jump to this one. */
979 if (GET_CODE (head) == CODE_LABEL)
980 for (jump = LABEL_REFS (head);
982 jump = LABEL_NEXTREF (jump))
984 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
986 for (j = 0; j < regset_size; j++)
987 basic_block_new_live_at_end[from_block][j]
988 |= basic_block_live_at_start[i][j];
998 /* The only pseudos that are live at the beginning of the function are
999 those that were not set anywhere in the function. local-alloc doesn't
1000 know how to handle these correctly, so mark them as not local to any
1003 if (n_basic_blocks > 0)
1004 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1005 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1006 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1007 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1009 /* Now the life information is accurate.
1010 Make one more pass over each basic block
1011 to delete dead stores, create autoincrement addressing
1012 and record how many times each register is used, is set, or dies.
1014 To save time, we operate directly in basic_block_live_at_end[i],
1015 thus destroying it (in fact, converting it into a copy of
1016 basic_block_live_at_start[i]). This is ok now because
1017 basic_block_live_at_end[i] is no longer used past this point. */
1021 for (i = 0; i < n_basic_blocks; i++)
1023 propagate_block (basic_block_live_at_end[i],
1024 basic_block_head[i], basic_block_end[i], 1,
1032 /* Something live during a setjmp should not be put in a register
1033 on certain machines which restore regs from stack frames
1034 rather than from the jmpbuf.
1035 But we don't need to do this for the user's variables, since
1036 ANSI says only volatile variables need this. */
1037 #ifdef LONGJMP_RESTORE_FROM_STACK
1038 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1039 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1040 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1041 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1043 reg_live_length[i] = -1;
1044 reg_basic_block[i] = -1;
1049 /* We have a problem with any pseudoreg that
1050 lives across the setjmp. ANSI says that if a
1051 user variable does not change in value
1052 between the setjmp and the longjmp, then the longjmp preserves it.
1053 This includes longjmp from a place where the pseudo appears dead.
1054 (In principle, the value still exists if it is in scope.)
1055 If the pseudo goes in a hard reg, some other value may occupy
1056 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1057 Conclusion: such a pseudo must not go in a hard reg. */
1058 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1059 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1060 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1061 && regno_reg_rtx[i] != 0)
1063 reg_live_length[i] = -1;
1064 reg_basic_block[i] = -1;
1067 obstack_free (&flow_obstack, NULL_PTR);
1070 /* Subroutines of life analysis. */
1072 /* Allocate the permanent data structures that represent the results
1073 of life analysis. Not static since used also for stupid life analysis. */
1076 allocate_for_life_analysis ()
1079 register regset tem;
1081 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1082 regset_bytes = regset_size * sizeof (*(regset)0);
1084 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1085 bzero (reg_n_refs, max_regno * sizeof (int));
1087 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1088 bzero (reg_n_sets, max_regno * sizeof (short));
1090 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1091 bzero (reg_n_deaths, max_regno * sizeof (short));
1093 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1094 bzero (reg_live_length, max_regno * sizeof (int));
1096 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1097 bzero (reg_n_calls_crossed, max_regno * sizeof (int));
1099 reg_basic_block = (short *) oballoc (max_regno * sizeof (short));
1100 for (i = 0; i < max_regno; i++)
1101 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1103 basic_block_live_at_start = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1104 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1105 bzero (tem, n_basic_blocks * regset_bytes);
1106 init_regset_vector (basic_block_live_at_start, tem, n_basic_blocks, regset_bytes);
1108 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1109 bzero (regs_live_at_setjmp, regset_bytes);
1112 /* Make each element of VECTOR point at a regset,
1113 taking the space for all those regsets from SPACE.
1114 SPACE is of type regset, but it is really as long as NELTS regsets.
1115 BYTES_PER_ELT is the number of bytes in one regset. */
1118 init_regset_vector (vector, space, nelts, bytes_per_elt)
1125 register regset p = space;
1127 for (i = 0; i < nelts; i++)
1130 p += bytes_per_elt / sizeof (*p);
1134 /* Compute the registers live at the beginning of a basic block
1135 from those live at the end.
1137 When called, OLD contains those live at the end.
1138 On return, it contains those live at the beginning.
1139 FIRST and LAST are the first and last insns of the basic block.
1141 FINAL is nonzero if we are doing the final pass which is not
1142 for computing the life info (since that has already been done)
1143 but for acting on it. On this pass, we delete dead stores,
1144 set up the logical links and dead-variables lists of instructions,
1145 and merge instructions for autoincrement and autodecrement addresses.
1147 SIGNIFICANT is nonzero only the first time for each basic block.
1148 If it is nonzero, it points to a regset in which we store
1149 a 1 for each register that is set within the block.
1151 BNUM is the number of the basic block. */
1154 propagate_block (old, first, last, final, significant, bnum)
1155 register regset old;
1167 /* The following variables are used only if FINAL is nonzero. */
1168 /* This vector gets one element for each reg that has been live
1169 at any point in the basic block that has been scanned so far.
1170 SOMETIMES_MAX says how many elements are in use so far.
1171 In each element, OFFSET is the byte-number within a regset
1172 for the register described by the element, and BIT is a mask
1173 for that register's bit within the byte. */
1174 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1175 int sometimes_max = 0;
1176 /* This regset has 1 for each reg that we have seen live so far.
1177 It and REGS_SOMETIMES_LIVE are updated together. */
1180 /* The loop depth may change in the middle of a basic block. Since we
1181 scan from end to beginning, we start with the depth at the end of the
1182 current basic block, and adjust as we pass ends and starts of loops. */
1183 loop_depth = basic_block_loop_depth[bnum];
1185 dead = (regset) alloca (regset_bytes);
1186 live = (regset) alloca (regset_bytes);
1191 /* Include any notes at the end of the block in the scan.
1192 This is in case the block ends with a call to setjmp. */
1194 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1196 /* Look for loop boundaries, we are going forward here. */
1197 last = NEXT_INSN (last);
1198 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1200 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1206 register int i, offset;
1207 REGSET_ELT_TYPE bit;
1210 maxlive = (regset) alloca (regset_bytes);
1211 bcopy (old, maxlive, regset_bytes);
1213 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1215 /* Process the regs live at the end of the block.
1216 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1217 Also mark them as not local to any one basic block. */
1219 for (offset = 0, i = 0; offset < regset_size; offset++)
1220 for (bit = 1; bit; bit <<= 1, i++)
1224 if (old[offset] & bit)
1226 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1227 regs_sometimes_live[sometimes_max].offset = offset;
1228 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1234 /* Scan the block an insn at a time from end to beginning. */
1236 for (insn = last; ; insn = prev)
1238 prev = PREV_INSN (insn);
1240 /* Look for loop boundaries, remembering that we are going backwards. */
1241 if (GET_CODE (insn) == NOTE
1242 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1244 else if (GET_CODE (insn) == NOTE
1245 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1248 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1249 Abort now rather than setting register status incorrectly. */
1250 if (loop_depth == 0)
1253 /* If this is a call to `setjmp' et al,
1254 warn if any non-volatile datum is live. */
1256 if (final && GET_CODE (insn) == NOTE
1257 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1260 for (i = 0; i < regset_size; i++)
1261 regs_live_at_setjmp[i] |= old[i];
1264 /* Update the life-status of regs for this insn.
1265 First DEAD gets which regs are set in this insn
1266 then LIVE gets which regs are used in this insn.
1267 Then the regs live before the insn
1268 are those live after, with DEAD regs turned off,
1269 and then LIVE regs turned on. */
1271 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1274 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1276 = (insn_dead_p (PATTERN (insn), old, 0)
1277 /* Don't delete something that refers to volatile storage! */
1278 && ! INSN_VOLATILE (insn));
1280 = (insn_is_dead && note != 0
1281 && libcall_dead_p (PATTERN (insn), old, note, insn));
1283 /* If an instruction consists of just dead store(s) on final pass,
1284 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1285 We could really delete it with delete_insn, but that
1286 can cause trouble for first or last insn in a basic block. */
1287 if (final && insn_is_dead)
1289 PUT_CODE (insn, NOTE);
1290 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1291 NOTE_SOURCE_FILE (insn) = 0;
1293 /* CC0 is now known to be dead. Either this insn used it,
1294 in which case it doesn't anymore, or clobbered it,
1295 so the next insn can't use it. */
1298 /* If this insn is copying the return value from a library call,
1299 delete the entire library call. */
1300 if (libcall_is_dead)
1302 rtx first = XEXP (note, 0);
1304 while (INSN_DELETED_P (first))
1305 first = NEXT_INSN (first);
1310 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1311 NOTE_SOURCE_FILE (p) = 0;
1317 for (i = 0; i < regset_size; i++)
1319 dead[i] = 0; /* Faster than bzero here */
1320 live[i] = 0; /* since regset_size is usually small */
1323 /* See if this is an increment or decrement that can be
1324 merged into a following memory address. */
1327 register rtx x = PATTERN (insn);
1328 /* Does this instruction increment or decrement a register? */
1329 if (final && GET_CODE (x) == SET
1330 && GET_CODE (SET_DEST (x)) == REG
1331 && (GET_CODE (SET_SRC (x)) == PLUS
1332 || GET_CODE (SET_SRC (x)) == MINUS)
1333 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1334 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1335 /* Ok, look for a following memory ref we can combine with.
1336 If one is found, change the memory ref to a PRE_INC
1337 or PRE_DEC, cancel this insn, and return 1.
1338 Return 0 if nothing has been done. */
1339 && try_pre_increment_1 (insn))
1342 #endif /* AUTO_INC_DEC */
1344 /* If this is not the final pass, and this insn is copying the
1345 value of a library call and it's dead, don't scan the
1346 insns that perform the library call, so that the call's
1347 arguments are not marked live. */
1348 if (libcall_is_dead)
1350 /* Mark the dest reg as `significant'. */
1351 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1353 insn = XEXP (note, 0);
1354 prev = PREV_INSN (insn);
1356 else if (GET_CODE (PATTERN (insn)) == SET
1357 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1358 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1359 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1360 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1361 /* We have an insn to pop a constant amount off the stack.
1362 (Such insns use PLUS regardless of the direction of the stack,
1363 and any insn to adjust the stack by a constant is always a pop.)
1364 These insns, if not dead stores, have no effect on life. */
1368 /* LIVE gets the regs used in INSN;
1369 DEAD gets those set by it. Dead insns don't make anything
1372 mark_set_regs (old, dead, PATTERN (insn),
1373 final ? insn : NULL_RTX, significant);
1375 /* If an insn doesn't use CC0, it becomes dead since we
1376 assume that every insn clobbers it. So show it dead here;
1377 mark_used_regs will set it live if it is referenced. */
1381 mark_used_regs (old, live, PATTERN (insn), final, insn);
1383 /* Sometimes we may have inserted something before INSN (such as
1384 a move) when we make an auto-inc. So ensure we will scan
1387 prev = PREV_INSN (insn);
1390 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1394 /* Each call clobbers all call-clobbered regs that are not
1395 global. Note that the function-value reg is a
1396 call-clobbered reg, and mark_set_regs has already had
1397 a chance to handle it. */
1399 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1400 if (call_used_regs[i] && ! global_regs[i])
1401 dead[i / REGSET_ELT_BITS]
1402 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1404 /* The stack ptr is used (honorarily) by a CALL insn. */
1405 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1406 |= ((REGSET_ELT_TYPE) 1
1407 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1409 /* Calls may also reference any of the global registers,
1410 so they are made live. */
1412 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1414 live[i / REGSET_ELT_BITS]
1415 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1417 /* Calls also clobber memory. */
1421 /* Update OLD for the registers used or set. */
1422 for (i = 0; i < regset_size; i++)
1428 if (GET_CODE (insn) == CALL_INSN && final)
1430 /* Any regs live at the time of a call instruction
1431 must not go in a register clobbered by calls.
1432 Find all regs now live and record this for them. */
1434 register struct sometimes *p = regs_sometimes_live;
1436 for (i = 0; i < sometimes_max; i++, p++)
1437 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1438 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1442 /* On final pass, add any additional sometimes-live regs
1443 into MAXLIVE and REGS_SOMETIMES_LIVE.
1444 Also update counts of how many insns each reg is live at. */
1448 for (i = 0; i < regset_size; i++)
1450 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1456 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1457 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1459 regs_sometimes_live[sometimes_max].offset = i;
1460 regs_sometimes_live[sometimes_max].bit = regno;
1461 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1468 register struct sometimes *p = regs_sometimes_live;
1469 for (i = 0; i < sometimes_max; i++, p++)
1471 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1472 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1482 if (num_scratch > max_scratch)
1483 max_scratch = num_scratch;
1486 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1487 (SET expressions whose destinations are registers dead after the insn).
1488 NEEDED is the regset that says which regs are alive after the insn.
1490 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1493 insn_dead_p (x, needed, call_ok)
1498 register RTX_CODE code = GET_CODE (x);
1499 /* If setting something that's a reg or part of one,
1500 see if that register's altered value will be live. */
1504 register rtx r = SET_DEST (x);
1505 /* A SET that is a subroutine call cannot be dead. */
1506 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1510 if (GET_CODE (r) == CC0)
1514 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1515 && rtx_equal_p (r, last_mem_set))
1518 while (GET_CODE (r) == SUBREG
1519 || GET_CODE (r) == STRICT_LOW_PART
1520 || GET_CODE (r) == ZERO_EXTRACT
1521 || GET_CODE (r) == SIGN_EXTRACT)
1524 if (GET_CODE (r) == REG)
1526 register int regno = REGNO (r);
1527 register int offset = regno / REGSET_ELT_BITS;
1528 register REGSET_ELT_TYPE bit
1529 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1531 /* Don't delete insns to set global regs. */
1532 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1533 /* Make sure insns to set frame pointer aren't deleted. */
1534 || regno == FRAME_POINTER_REGNUM
1535 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1536 /* Make sure insns to set arg pointer are never deleted
1537 (if the arg pointer isn't fixed, there will be a USE for
1538 it, so we can treat it normally). */
1539 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1541 || (needed[offset] & bit) != 0)
1544 /* If this is a hard register, verify that subsequent words are
1546 if (regno < FIRST_PSEUDO_REGISTER)
1548 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1551 if ((needed[(regno + n) / REGSET_ELT_BITS]
1552 & ((REGSET_ELT_TYPE) 1
1553 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1560 /* If performing several activities,
1561 insn is dead if each activity is individually dead.
1562 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1563 that's inside a PARALLEL doesn't make the insn worth keeping. */
1564 else if (code == PARALLEL)
1566 register int i = XVECLEN (x, 0);
1567 for (i--; i >= 0; i--)
1569 rtx elt = XVECEXP (x, 0, i);
1570 if (!insn_dead_p (elt, needed, call_ok)
1571 && GET_CODE (elt) != CLOBBER
1572 && GET_CODE (elt) != USE)
1577 /* We do not check CLOBBER or USE here.
1578 An insn consisting of just a CLOBBER or just a USE
1579 should not be deleted. */
1583 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1584 return 1 if the entire library call is dead.
1585 This is true if X copies a register (hard or pseudo)
1586 and if the hard return reg of the call insn is dead.
1587 (The caller should have tested the destination of X already for death.)
1589 If this insn doesn't just copy a register, then we don't
1590 have an ordinary libcall. In that case, cse could not have
1591 managed to substitute the source for the dest later on,
1592 so we can assume the libcall is dead.
1594 NEEDED is the bit vector of pseudoregs live before this insn.
1595 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1598 libcall_dead_p (x, needed, note, insn)
1604 register RTX_CODE code = GET_CODE (x);
1608 register rtx r = SET_SRC (x);
1609 if (GET_CODE (r) == REG)
1611 rtx call = XEXP (note, 0);
1614 /* Find the call insn. */
1615 while (call != insn && GET_CODE (call) != CALL_INSN)
1616 call = NEXT_INSN (call);
1618 /* If there is none, do nothing special,
1619 since ordinary death handling can understand these insns. */
1623 /* See if the hard reg holding the value is dead.
1624 If this is a PARALLEL, find the call within it. */
1625 call = PATTERN (call);
1626 if (GET_CODE (call) == PARALLEL)
1628 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1629 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1630 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1636 call = XVECEXP (call, 0, i);
1639 return insn_dead_p (call, needed, 1);
1645 /* Return 1 if register REGNO was used before it was set.
1646 In other words, if it is live at function entry.
1647 Don't count global regster variables, though. */
1650 regno_uninitialized (regno)
1653 if (n_basic_blocks == 0 || global_regs[regno])
1656 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1657 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1660 /* 1 if register REGNO was alive at a place where `setjmp' was called
1661 and was set more than once or is an argument.
1662 Such regs may be clobbered by `longjmp'. */
1665 regno_clobbered_at_setjmp (regno)
1668 if (n_basic_blocks == 0)
1671 return ((reg_n_sets[regno] > 1
1672 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1673 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1674 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1675 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1678 /* Process the registers that are set within X.
1679 Their bits are set to 1 in the regset DEAD,
1680 because they are dead prior to this insn.
1682 If INSN is nonzero, it is the insn being processed
1683 and the fact that it is nonzero implies this is the FINAL pass
1684 in propagate_block. In this case, various info about register
1685 usage is stored, LOG_LINKS fields of insns are set up. */
1687 static void mark_set_1 ();
1690 mark_set_regs (needed, dead, x, insn, significant)
1697 register RTX_CODE code = GET_CODE (x);
1699 if (code == SET || code == CLOBBER)
1700 mark_set_1 (needed, dead, x, insn, significant);
1701 else if (code == PARALLEL)
1704 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1706 code = GET_CODE (XVECEXP (x, 0, i));
1707 if (code == SET || code == CLOBBER)
1708 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1713 /* Process a single SET rtx, X. */
1716 mark_set_1 (needed, dead, x, insn, significant)
1724 register rtx reg = SET_DEST (x);
1726 /* Modifying just one hardware register of a multi-reg value
1727 or just a byte field of a register
1728 does not mean the value from before this insn is now dead.
1729 But it does mean liveness of that register at the end of the block
1732 Within mark_set_1, however, we treat it as if the register is
1733 indeed modified. mark_used_regs will, however, also treat this
1734 register as being used. Thus, we treat these insns as setting a
1735 new value for the register as a function of its old value. This
1736 cases LOG_LINKS to be made appropriately and this will help combine. */
1738 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1739 || GET_CODE (reg) == SIGN_EXTRACT
1740 || GET_CODE (reg) == STRICT_LOW_PART)
1741 reg = XEXP (reg, 0);
1743 /* If we are writing into memory or into a register mentioned in the
1744 address of the last thing stored into memory, show we don't know
1745 what the last store was. If we are writing memory, save the address
1746 unless it is volatile. */
1747 if (GET_CODE (reg) == MEM
1748 || (GET_CODE (reg) == REG
1749 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1752 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1753 /* There are no REG_INC notes for SP, so we can't assume we'll see
1754 everything that invalidates it. To be safe, don't eliminate any
1755 stores though SP; none of them should be redundant anyway. */
1756 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1759 if (GET_CODE (reg) == REG
1760 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1761 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1762 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1764 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1765 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1767 register int offset = regno / REGSET_ELT_BITS;
1768 register REGSET_ELT_TYPE bit
1769 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1770 REGSET_ELT_TYPE all_needed = (needed[offset] & bit);
1771 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
1773 /* Mark it as a significant register for this basic block. */
1775 significant[offset] |= bit;
1777 /* Mark it as as dead before this insn. */
1778 dead[offset] |= bit;
1780 /* A hard reg in a wide mode may really be multiple registers.
1781 If so, mark all of them just like the first. */
1782 if (regno < FIRST_PSEUDO_REGISTER)
1786 /* Nothing below is needed for the stack pointer; get out asap.
1787 Eg, log links aren't needed, since combine won't use them. */
1788 if (regno == STACK_POINTER_REGNUM)
1791 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1795 significant[(regno + n) / REGSET_ELT_BITS]
1796 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1797 dead[(regno + n) / REGSET_ELT_BITS]
1798 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1800 |= (needed[(regno + n) / REGSET_ELT_BITS]
1801 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1803 &= (needed[(regno + n) / REGSET_ELT_BITS]
1804 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1807 /* Additional data to record if this is the final pass. */
1810 register rtx y = reg_next_use[regno];
1811 register int blocknum = BLOCK_NUM (insn);
1813 /* If this is a hard reg, record this function uses the reg. */
1815 if (regno < FIRST_PSEUDO_REGISTER)
1818 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
1820 for (i = regno; i < endregno; i++)
1822 regs_ever_live[i] = 1;
1828 /* Keep track of which basic blocks each reg appears in. */
1830 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
1831 reg_basic_block[regno] = blocknum;
1832 else if (reg_basic_block[regno] != blocknum)
1833 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
1835 /* Count (weighted) references, stores, etc. This counts a
1836 register twice if it is modified, but that is correct. */
1837 reg_n_sets[regno]++;
1839 reg_n_refs[regno] += loop_depth;
1841 /* The insns where a reg is live are normally counted
1842 elsewhere, but we want the count to include the insn
1843 where the reg is set, and the normal counting mechanism
1844 would not count it. */
1845 reg_live_length[regno]++;
1848 /* The next use is no longer "next", since a store intervenes. */
1849 reg_next_use[regno] = 0;
1853 /* Make a logical link from the next following insn
1854 that uses this register, back to this insn.
1855 The following insns have already been processed.
1857 We don't build a LOG_LINK for hard registers containing
1858 in ASM_OPERANDs. If these registers get replaced,
1859 we might wind up changing the semantics of the insn,
1860 even if reload can make what appear to be valid assignments
1862 if (y && (BLOCK_NUM (y) == blocknum)
1863 && (regno >= FIRST_PSEUDO_REGISTER
1864 || asm_noperands (PATTERN (y)) < 0))
1866 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
1868 else if (! some_needed)
1870 /* Note that dead stores have already been deleted when possible
1871 If we get here, we have found a dead store that cannot
1872 be eliminated (because the same insn does something useful).
1873 Indicate this by marking the reg being set as dying here. */
1875 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
1876 reg_n_deaths[REGNO (reg)]++;
1880 /* This is a case where we have a multi-word hard register
1881 and some, but not all, of the words of the register are
1882 needed in subsequent insns. Write REG_UNUSED notes
1883 for those parts that were not needed. This case should
1888 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
1890 if ((needed[(regno + i) / REGSET_ELT_BITS]
1891 & ((REGSET_ELT_TYPE) 1
1892 << ((regno + i) % REGSET_ELT_BITS))) == 0)
1894 = gen_rtx (EXPR_LIST, REG_UNUSED,
1895 gen_rtx (REG, word_mode, regno + i),
1901 /* If this is the last pass and this is a SCRATCH, show it will be dying
1902 here and count it. */
1903 else if (GET_CODE (reg) == SCRATCH && insn != 0)
1906 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
1913 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
1917 find_auto_inc (needed, x, insn)
1922 rtx addr = XEXP (x, 0);
1925 /* Here we detect use of an index register which might be good for
1926 postincrement, postdecrement, preincrement, or predecrement. */
1928 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
1929 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
1931 if (GET_CODE (addr) == REG)
1934 register int size = GET_MODE_SIZE (GET_MODE (x));
1937 int regno = REGNO (addr);
1939 /* Is the next use an increment that might make auto-increment? */
1940 incr = reg_next_use[regno];
1941 if (incr && GET_CODE (PATTERN (incr)) == SET
1942 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
1943 /* Can't add side effects to jumps; if reg is spilled and
1944 reloaded, there's no way to store back the altered value. */
1945 && GET_CODE (insn) != JUMP_INSN
1946 && (y = SET_SRC (PATTERN (incr)), GET_CODE (y) == PLUS)
1947 && XEXP (y, 0) == addr
1948 && GET_CODE (XEXP (y, 1)) == CONST_INT
1950 #ifdef HAVE_POST_INCREMENT
1951 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
1953 #ifdef HAVE_POST_DECREMENT
1954 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
1956 #ifdef HAVE_PRE_INCREMENT
1957 || (INTVAL (XEXP (y, 1)) == size && offset == size)
1959 #ifdef HAVE_PRE_DECREMENT
1960 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
1963 /* Make sure this reg appears only once in this insn. */
1964 && (use = find_use_as_address (PATTERN (insn), addr, offset),
1965 use != 0 && use != (rtx) 1))
1968 rtx q = SET_DEST (PATTERN (incr));
1970 if (dead_or_set_p (incr, addr))
1972 else if (GET_CODE (q) == REG && ! reg_used_between_p (q, insn, incr))
1974 /* We have *p followed by q = p+size.
1975 Both p and q must be live afterward,
1976 and q must be dead before.
1977 Change it to q = p, ...*q..., q = q+size.
1978 Then fall into the usual case. */
1982 emit_move_insn (q, addr);
1983 insns = get_insns ();
1986 /* If anything in INSNS have UID's that don't fit within the
1987 extra space we allocate earlier, we can't make this auto-inc.
1988 This should never happen. */
1989 for (temp = insns; temp; temp = NEXT_INSN (temp))
1991 if (INSN_UID (temp) > max_uid_for_flow)
1993 BLOCK_NUM (temp) = BLOCK_NUM (insn);
1996 emit_insns_before (insns, insn);
1998 if (basic_block_head[BLOCK_NUM (insn)] == insn)
1999 basic_block_head[BLOCK_NUM (insn)] = insns;
2004 /* INCR will become a NOTE and INSN won't contain a
2005 use of ADDR. If a use of ADDR was just placed in
2006 the insn before INSN, make that the next use.
2007 Otherwise, invalidate it. */
2008 if (GET_CODE (PREV_INSN (insn)) == INSN
2009 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2010 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2011 reg_next_use[regno] = PREV_INSN (insn);
2013 reg_next_use[regno] = 0;
2019 /* REGNO is now used in INCR which is below INSN, but
2020 it previously wasn't live here. If we don't mark
2021 it as needed, we'll put a REG_DEAD note for it
2022 on this insn, which is incorrect. */
2023 needed[regno / REGSET_ELT_BITS]
2024 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2026 /* If there are any calls between INSN and INCR, show
2027 that REGNO now crosses them. */
2028 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2029 if (GET_CODE (temp) == CALL_INSN)
2030 reg_n_calls_crossed[regno]++;
2035 /* We have found a suitable auto-increment: do POST_INC around
2036 the register here, and patch out the increment instruction
2038 XEXP (x, 0) = gen_rtx ((INTVAL (XEXP (y, 1)) == size
2039 ? (offset ? PRE_INC : POST_INC)
2040 : (offset ? PRE_DEC : POST_DEC)),
2043 /* Record that this insn has an implicit side effect. */
2045 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2047 /* Modify the old increment-insn to simply copy
2048 the already-incremented value of our register. */
2049 SET_SRC (PATTERN (incr)) = addr;
2050 /* Indicate insn must be re-recognized. */
2051 INSN_CODE (incr) = -1;
2053 /* If that makes it a no-op (copying the register into itself)
2054 then delete it so it won't appear to be a "use" and a "set"
2055 of this register. */
2056 if (SET_DEST (PATTERN (incr)) == addr)
2058 PUT_CODE (incr, NOTE);
2059 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2060 NOTE_SOURCE_FILE (incr) = 0;
2063 if (regno >= FIRST_PSEUDO_REGISTER)
2065 /* Count an extra reference to the reg. When a reg is
2066 incremented, spilling it is worse, so we want to make
2067 that less likely. */
2068 reg_n_refs[regno] += loop_depth;
2069 /* Count the increment as a setting of the register,
2070 even though it isn't a SET in rtl. */
2071 reg_n_sets[regno]++;
2077 #endif /* AUTO_INC_DEC */
2079 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2080 This is done assuming the registers needed from X
2081 are those that have 1-bits in NEEDED.
2083 On the final pass, FINAL is 1. This means try for autoincrement
2084 and count the uses and deaths of each pseudo-reg.
2086 INSN is the containing instruction. If INSN is dead, this function is not
2090 mark_used_regs (needed, live, x, final, insn)
2097 register RTX_CODE code;
2102 code = GET_CODE (x);
2124 /* Invalidate the data for the last MEM stored. We could do this only
2125 if the addresses conflict, but this doesn't seem worthwhile. */
2130 find_auto_inc (needed, x, insn);
2135 /* See a register other than being set
2136 => mark it as needed. */
2140 register int offset = regno / REGSET_ELT_BITS;
2141 register REGSET_ELT_TYPE bit
2142 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2143 int all_needed = (needed[offset] & bit) != 0;
2144 int some_needed = (needed[offset] & bit) != 0;
2146 live[offset] |= bit;
2147 /* A hard reg in a wide mode may really be multiple registers.
2148 If so, mark all of them just like the first. */
2149 if (regno < FIRST_PSEUDO_REGISTER)
2153 /* For stack ptr or fixed arg pointer,
2154 nothing below can be necessary, so waste no more time. */
2155 if (regno == STACK_POINTER_REGNUM
2156 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2157 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2159 || regno == FRAME_POINTER_REGNUM)
2161 /* If this is a register we are going to try to eliminate,
2162 don't mark it live here. If we are successful in
2163 eliminating it, it need not be live unless it is used for
2164 pseudos, in which case it will have been set live when
2165 it was allocated to the pseudos. If the register will not
2166 be eliminated, reload will set it live at that point. */
2168 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2169 regs_ever_live[regno] = 1;
2172 /* No death notes for global register variables;
2173 their values are live after this function exits. */
2174 if (global_regs[regno])
2177 reg_next_use[regno] = insn;
2181 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2184 live[(regno + n) / REGSET_ELT_BITS]
2185 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2187 |= (needed[(regno + n) / REGSET_ELT_BITS]
2188 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2190 &= (needed[(regno + n) / REGSET_ELT_BITS]
2191 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2196 /* Record where each reg is used, so when the reg
2197 is set we know the next insn that uses it. */
2199 reg_next_use[regno] = insn;
2201 if (regno < FIRST_PSEUDO_REGISTER)
2203 /* If a hard reg is being used,
2204 record that this function does use it. */
2206 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2210 regs_ever_live[regno + --i] = 1;
2215 /* Keep track of which basic block each reg appears in. */
2217 register int blocknum = BLOCK_NUM (insn);
2219 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2220 reg_basic_block[regno] = blocknum;
2221 else if (reg_basic_block[regno] != blocknum)
2222 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2224 /* Count (weighted) number of uses of each reg. */
2226 reg_n_refs[regno] += loop_depth;
2229 /* Record and count the insns in which a reg dies.
2230 If it is used in this insn and was dead below the insn
2231 then it dies in this insn. If it was set in this insn,
2232 we do not make a REG_DEAD note; likewise if we already
2233 made such a note. */
2236 && ! dead_or_set_p (insn, x)
2238 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2242 /* If none of the words in X is needed, make a REG_DEAD
2243 note. Otherwise, we must make partial REG_DEAD notes. */
2247 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2248 reg_n_deaths[regno]++;
2254 /* Don't make a REG_DEAD note for a part of a register
2255 that is set in the insn. */
2257 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2259 if ((needed[(regno + i) / REGSET_ELT_BITS]
2260 & ((REGSET_ELT_TYPE) 1
2261 << ((regno + i) % REGSET_ELT_BITS))) == 0
2262 && ! dead_or_set_regno_p (insn, regno + i))
2264 = gen_rtx (EXPR_LIST, REG_DEAD,
2265 gen_rtx (REG, word_mode, regno + i),
2275 register rtx testreg = SET_DEST (x);
2278 /* If storing into MEM, don't show it as being used. But do
2279 show the address as being used. */
2280 if (GET_CODE (testreg) == MEM)
2284 find_auto_inc (needed, testreg, insn);
2286 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2287 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2291 /* Storing in STRICT_LOW_PART is like storing in a reg
2292 in that this SET might be dead, so ignore it in TESTREG.
2293 but in some other ways it is like using the reg.
2295 Storing in a SUBREG or a bit field is like storing the entire
2296 register in that if the register's value is not used
2297 then this SET is not needed. */
2298 while (GET_CODE (testreg) == STRICT_LOW_PART
2299 || GET_CODE (testreg) == ZERO_EXTRACT
2300 || GET_CODE (testreg) == SIGN_EXTRACT
2301 || GET_CODE (testreg) == SUBREG)
2303 /* Modifying a single register in an alternate mode
2304 does not use any of the old value. But these other
2305 ways of storing in a register do use the old value. */
2306 if (GET_CODE (testreg) == SUBREG
2307 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2312 testreg = XEXP (testreg, 0);
2315 /* If this is a store into a register,
2316 recursively scan the value being stored. */
2318 if (GET_CODE (testreg) == REG
2319 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2320 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2321 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2324 /* We used to exclude global_regs here, but that seems wrong.
2325 Storing in them is like storing in mem. */
2327 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2329 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2336 /* If exiting needs the right stack value, consider this insn as
2337 using the stack pointer. In any event, consider it as using
2338 all global registers. */
2340 #ifdef EXIT_IGNORE_STACK
2341 if (! EXIT_IGNORE_STACK
2342 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2344 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2345 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2347 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2349 live[i / REGSET_ELT_BITS]
2350 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2354 /* Recursively scan the operands of this expression. */
2357 register char *fmt = GET_RTX_FORMAT (code);
2360 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2364 /* Tail recursive case: save a function call level. */
2370 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2372 else if (fmt[i] == 'E')
2375 for (j = 0; j < XVECLEN (x, i); j++)
2376 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2385 try_pre_increment_1 (insn)
2388 /* Find the next use of this reg. If in same basic block,
2389 make it do pre-increment or pre-decrement if appropriate. */
2390 rtx x = PATTERN (insn);
2391 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2392 * INTVAL (XEXP (SET_SRC (x), 1)));
2393 int regno = REGNO (SET_DEST (x));
2394 rtx y = reg_next_use[regno];
2396 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2397 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2400 /* We have found a suitable auto-increment
2401 and already changed insn Y to do it.
2402 So flush this increment-instruction. */
2403 PUT_CODE (insn, NOTE);
2404 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2405 NOTE_SOURCE_FILE (insn) = 0;
2406 /* Count a reference to this reg for the increment
2407 insn we are deleting. When a reg is incremented.
2408 spilling it is worse, so we want to make that
2410 if (regno >= FIRST_PSEUDO_REGISTER)
2412 reg_n_refs[regno] += loop_depth;
2413 reg_n_sets[regno]++;
2420 /* Try to change INSN so that it does pre-increment or pre-decrement
2421 addressing on register REG in order to add AMOUNT to REG.
2422 AMOUNT is negative for pre-decrement.
2423 Returns 1 if the change could be made.
2424 This checks all about the validity of the result of modifying INSN. */
2427 try_pre_increment (insn, reg, amount)
2429 HOST_WIDE_INT amount;
2433 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2434 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2436 /* Nonzero if we can try to make a post-increment or post-decrement.
2437 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2438 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2439 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2442 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2445 /* From the sign of increment, see which possibilities are conceivable
2446 on this target machine. */
2447 #ifdef HAVE_PRE_INCREMENT
2451 #ifdef HAVE_POST_INCREMENT
2456 #ifdef HAVE_PRE_DECREMENT
2460 #ifdef HAVE_POST_DECREMENT
2465 if (! (pre_ok || post_ok))
2468 /* It is not safe to add a side effect to a jump insn
2469 because if the incremented register is spilled and must be reloaded
2470 there would be no way to store the incremented value back in memory. */
2472 if (GET_CODE (insn) == JUMP_INSN)
2477 use = find_use_as_address (PATTERN (insn), reg, 0);
2478 if (post_ok && (use == 0 || use == (rtx) 1))
2480 use = find_use_as_address (PATTERN (insn), reg, -amount);
2484 if (use == 0 || use == (rtx) 1)
2487 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2490 XEXP (use, 0) = gen_rtx (amount > 0
2491 ? (do_post ? POST_INC : PRE_INC)
2492 : (do_post ? POST_DEC : PRE_DEC),
2495 /* Record that this insn now has an implicit side effect on X. */
2496 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2500 #endif /* AUTO_INC_DEC */
2502 /* Find the place in the rtx X where REG is used as a memory address.
2503 Return the MEM rtx that so uses it.
2504 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2505 (plus REG (const_int PLUSCONST)).
2507 If such an address does not appear, return 0.
2508 If REG appears more than once, or is used other than in such an address,
2512 find_use_as_address (x, reg, plusconst)
2517 enum rtx_code code = GET_CODE (x);
2518 char *fmt = GET_RTX_FORMAT (code);
2520 register rtx value = 0;
2523 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2526 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2527 && XEXP (XEXP (x, 0), 0) == reg
2528 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2529 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2532 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2534 /* If REG occurs inside a MEM used in a bit-field reference,
2535 that is unacceptable. */
2536 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2537 return (rtx) (HOST_WIDE_INT) 1;
2541 return (rtx) (HOST_WIDE_INT) 1;
2543 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2547 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2551 return (rtx) (HOST_WIDE_INT) 1;
2556 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2558 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2562 return (rtx) (HOST_WIDE_INT) 1;
2570 /* Write information about registers and basic blocks into FILE.
2571 This is part of making a debugging dump. */
2574 dump_flow_info (file)
2578 static char *reg_class_names[] = REG_CLASS_NAMES;
2580 fprintf (file, "%d registers.\n", max_regno);
2582 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2585 enum reg_class class, altclass;
2586 fprintf (file, "\nRegister %d used %d times across %d insns",
2587 i, reg_n_refs[i], reg_live_length[i]);
2588 if (reg_basic_block[i] >= 0)
2589 fprintf (file, " in block %d", reg_basic_block[i]);
2590 if (reg_n_deaths[i] != 1)
2591 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2592 if (reg_n_calls_crossed[i] == 1)
2593 fprintf (file, "; crosses 1 call");
2594 else if (reg_n_calls_crossed[i])
2595 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2596 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2597 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2598 class = reg_preferred_class (i);
2599 altclass = reg_alternate_class (i);
2600 if (class != GENERAL_REGS || altclass != ALL_REGS)
2602 if (altclass == ALL_REGS || class == ALL_REGS)
2603 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2604 else if (altclass == NO_REGS)
2605 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2607 fprintf (file, "; pref %s, else %s",
2608 reg_class_names[(int) class],
2609 reg_class_names[(int) altclass]);
2611 if (REGNO_POINTER_FLAG (i))
2612 fprintf (file, "; pointer");
2613 fprintf (file, ".\n");
2615 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2616 for (i = 0; i < n_basic_blocks; i++)
2618 register rtx head, jump;
2620 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2622 INSN_UID (basic_block_head[i]),
2623 INSN_UID (basic_block_end[i]));
2624 /* The control flow graph's storage is freed
2625 now when flow_analysis returns.
2626 Don't try to print it if it is gone. */
2627 if (basic_block_drops_in)
2629 fprintf (file, "Reached from blocks: ");
2630 head = basic_block_head[i];
2631 if (GET_CODE (head) == CODE_LABEL)
2632 for (jump = LABEL_REFS (head);
2634 jump = LABEL_NEXTREF (jump))
2636 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2637 fprintf (file, " %d", from_block);
2639 if (basic_block_drops_in[i])
2640 fprintf (file, " previous");
2642 fprintf (file, "\nRegisters live at start:");
2643 for (regno = 0; regno < max_regno; regno++)
2645 register int offset = regno / REGSET_ELT_BITS;
2646 register REGSET_ELT_TYPE bit
2647 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2648 if (basic_block_live_at_start[i][offset] & bit)
2649 fprintf (file, " %d", regno);
2651 fprintf (file, "\n");
2653 fprintf (file, "\n");