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 int insn_dead_p PROTO((rtx, regset, int));
297 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
298 static void mark_set_regs PROTO((regset, regset, rtx,
300 static void mark_set_1 PROTO((regset, regset, rtx,
302 static void find_auto_inc PROTO((regset, rtx, rtx));
303 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
304 static int try_pre_increment_1 PROTO((rtx));
305 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
306 static rtx find_use_as_address PROTO((rtx, rtx, HOST_WIDE_INT));
307 void dump_flow_info PROTO((FILE *));
309 /* Find basic blocks of the current function and perform data flow analysis.
310 F is the first insn of the function and NREGS the number of register numbers
314 flow_analysis (f, nregs, file)
321 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
323 #ifdef ELIMINABLE_REGS
324 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
327 /* Record which registers will be eliminated. We use this in
330 CLEAR_HARD_REG_SET (elim_reg_set);
332 #ifdef ELIMINABLE_REGS
333 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
334 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
336 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
339 /* Count the basic blocks. Also find maximum insn uid value used. */
342 register RTX_CODE prev_code = JUMP_INSN;
343 register RTX_CODE code;
345 max_uid_for_flow = 0;
347 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
349 code = GET_CODE (insn);
350 if (INSN_UID (insn) > max_uid_for_flow)
351 max_uid_for_flow = INSN_UID (insn);
352 if (code == CODE_LABEL
353 || (GET_RTX_CLASS (code) == 'i'
354 && (prev_code == JUMP_INSN
355 || (prev_code == CALL_INSN
356 && nonlocal_label_list != 0)
357 || prev_code == BARRIER)))
365 /* Leave space for insns we make in some cases for auto-inc. These cases
366 are rare, so we don't need too much space. */
367 max_uid_for_flow += max_uid_for_flow / 10;
370 /* Allocate some tables that last till end of compiling this function
371 and some needed only in find_basic_blocks and life_analysis. */
374 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
375 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
376 basic_block_drops_in = (char *) alloca (n_basic_blocks);
377 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
379 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
380 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
381 bzero (uid_volatile, max_uid_for_flow + 1);
383 find_basic_blocks (f, nonlocal_label_list);
384 life_analysis (f, nregs);
386 dump_flow_info (file);
388 basic_block_drops_in = 0;
389 uid_block_number = 0;
390 basic_block_loop_depth = 0;
393 /* Find all basic blocks of the function whose first insn is F.
394 Store the correct data in the tables that describe the basic blocks,
395 set up the chains of references for each CODE_LABEL, and
396 delete any entire basic blocks that cannot be reached.
398 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
401 find_basic_blocks (f, nonlocal_label_list)
402 rtx f, nonlocal_label_list;
406 register char *block_live = (char *) alloca (n_basic_blocks);
407 register char *block_marked = (char *) alloca (n_basic_blocks);
408 /* List of label_refs to all labels whose addresses are taken
410 rtx label_value_list = 0;
412 enum rtx_code prev_code, code;
415 block_live_static = block_live;
416 bzero (block_live, n_basic_blocks);
417 bzero (block_marked, n_basic_blocks);
419 /* Initialize with just block 0 reachable and no blocks marked. */
420 if (n_basic_blocks > 0)
423 /* Initialize the ref chain of each label to 0. Record where all the
424 blocks start and end and their depth in loops. For each insn, record
425 the block it is in. Also mark as reachable any blocks headed by labels
426 that must not be deleted. */
428 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
429 insn; insn = NEXT_INSN (insn))
431 code = GET_CODE (insn);
434 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
436 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
440 /* A basic block starts at label, or after something that can jump. */
441 else if (code == CODE_LABEL
442 || (GET_RTX_CLASS (code) == 'i'
443 && (prev_code == JUMP_INSN
444 || (prev_code == CALL_INSN
445 && nonlocal_label_list != 0)
446 || prev_code == BARRIER)))
448 basic_block_head[++i] = insn;
449 basic_block_end[i] = insn;
450 basic_block_loop_depth[i] = depth;
452 if (code == CODE_LABEL)
454 LABEL_REFS (insn) = insn;
455 /* Any label that cannot be deleted
456 is considered to start a reachable block. */
457 if (LABEL_PRESERVE_P (insn))
462 else if (GET_RTX_CLASS (code) == 'i')
464 basic_block_end[i] = insn;
465 basic_block_loop_depth[i] = depth;
468 if (GET_RTX_CLASS (code) == 'i')
470 /* Make a list of all labels referred to other than by jumps. */
471 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
472 if (REG_NOTE_KIND (note) == REG_LABEL)
473 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
477 BLOCK_NUM (insn) = i;
483 if (i + 1 != n_basic_blocks)
486 /* Don't delete the labels (in this function)
487 that are referenced by non-jump instructions. */
489 for (x = label_value_list; x; x = XEXP (x, 1))
490 if (! LABEL_REF_NONLOCAL_P (x))
491 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
493 for (x = forced_labels; x; x = XEXP (x, 1))
494 if (! LABEL_REF_NONLOCAL_P (x))
495 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
497 /* Record which basic blocks control can drop in to. */
499 for (i = 0; i < n_basic_blocks; i++)
501 for (insn = PREV_INSN (basic_block_head[i]);
502 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
505 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
508 /* Now find which basic blocks can actually be reached
509 and put all jump insns' LABEL_REFS onto the ref-chains
510 of their target labels. */
512 if (n_basic_blocks > 0)
514 int something_marked = 1;
516 /* Find all indirect jump insns and mark them as possibly jumping to all
517 the labels whose addresses are explicitly used. This is because,
518 when there are computed gotos, we can't tell which labels they jump
519 to, of all the possibilities.
521 Tablejumps and casesi insns are OK and we can recognize them by
522 a (use (label_ref)). */
524 for (insn = f; insn; insn = NEXT_INSN (insn))
525 if (GET_CODE (insn) == JUMP_INSN)
527 rtx pat = PATTERN (insn);
528 int computed_jump = 0;
530 if (GET_CODE (pat) == PARALLEL)
532 int len = XVECLEN (pat, 0);
533 int has_use_labelref = 0;
535 for (i = len - 1; i >= 0; i--)
536 if (GET_CODE (XVECEXP (pat, 0, i)) == USE
537 && (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
539 has_use_labelref = 1;
541 if (! has_use_labelref)
542 for (i = len - 1; i >= 0; i--)
543 if (GET_CODE (XVECEXP (pat, 0, i)) == SET
544 && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
545 && uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
548 else if (GET_CODE (pat) == SET
549 && SET_DEST (pat) == pc_rtx
550 && uses_reg_or_mem (SET_SRC (pat)))
555 for (x = label_value_list; x; x = XEXP (x, 1))
556 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
559 for (x = forced_labels; x; x = XEXP (x, 1))
560 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
565 /* Find all call insns and mark them as possibly jumping
566 to all the nonlocal goto handler labels. */
568 for (insn = f; insn; insn = NEXT_INSN (insn))
569 if (GET_CODE (insn) == CALL_INSN)
571 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
572 /* Don't try marking labels that
573 were deleted as unreferenced. */
574 if (GET_CODE (XEXP (x, 0)) == CODE_LABEL)
575 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
578 /* ??? This could be made smarter:
579 in some cases it's possible to tell that certain
580 calls will not do a nonlocal goto.
582 For example, if the nested functions that do the
583 nonlocal gotos do not have their addresses taken, then
584 only calls to those functions or to other nested
585 functions that use them could possibly do nonlocal
589 /* Pass over all blocks, marking each block that is reachable
590 and has not yet been marked.
591 Keep doing this until, in one pass, no blocks have been marked.
592 Then blocks_live and blocks_marked are identical and correct.
593 In addition, all jumps actually reachable have been marked. */
595 while (something_marked)
597 something_marked = 0;
598 for (i = 0; i < n_basic_blocks; i++)
599 if (block_live[i] && !block_marked[i])
602 something_marked = 1;
603 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
604 block_live[i + 1] = 1;
605 insn = basic_block_end[i];
606 if (GET_CODE (insn) == JUMP_INSN)
607 mark_label_ref (PATTERN (insn), insn, 0);
611 /* ??? See if we have a "live" basic block that is not reachable.
612 This can happen if it is headed by a label that is preserved or
613 in one of the label lists, but no call or computed jump is in
614 the loop. It's not clear if we can delete the block or not,
615 but don't for now. However, we will mess up register status if
616 it remains unreachable, so add a fake reachability from the
619 for (i = 1; i < n_basic_blocks; i++)
620 if (block_live[i] && ! basic_block_drops_in[i]
621 && GET_CODE (basic_block_head[i]) == CODE_LABEL
622 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
623 basic_block_drops_in[i] = 1;
625 /* Now delete the code for any basic blocks that can't be reached.
626 They can occur because jump_optimize does not recognize
627 unreachable loops as unreachable. */
629 for (i = 0; i < n_basic_blocks; i++)
632 insn = basic_block_head[i];
635 if (GET_CODE (insn) == BARRIER)
637 if (GET_CODE (insn) != NOTE)
639 PUT_CODE (insn, NOTE);
640 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
641 NOTE_SOURCE_FILE (insn) = 0;
643 if (insn == basic_block_end[i])
645 /* BARRIERs are between basic blocks, not part of one.
646 Delete a BARRIER if the preceding jump is deleted.
647 We cannot alter a BARRIER into a NOTE
648 because it is too short; but we can really delete
649 it because it is not part of a basic block. */
650 if (NEXT_INSN (insn) != 0
651 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
652 delete_insn (NEXT_INSN (insn));
655 insn = NEXT_INSN (insn);
657 /* Each time we delete some basic blocks,
658 see if there is a jump around them that is
659 being turned into a no-op. If so, delete it. */
661 if (block_live[i - 1])
664 for (j = i; j < n_basic_blocks; j++)
668 insn = basic_block_end[i - 1];
669 if (GET_CODE (insn) == JUMP_INSN
670 /* An unconditional jump is the only possibility
671 we must check for, since a conditional one
672 would make these blocks live. */
673 && simplejump_p (insn)
674 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
675 && INSN_UID (label) != 0
676 && BLOCK_NUM (label) == j)
678 PUT_CODE (insn, NOTE);
679 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
680 NOTE_SOURCE_FILE (insn) = 0;
681 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
683 delete_insn (NEXT_INSN (insn));
692 /* Return 1 if X contain a REG or MEM that is not in the constant pool. */
698 enum rtx_code code = GET_CODE (x);
704 && ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
705 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))))
708 fmt = GET_RTX_FORMAT (code);
709 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
712 && uses_reg_or_mem (XEXP (x, i)))
716 for (j = 0; j < XVECLEN (x, i); j++)
717 if (uses_reg_or_mem (XVECEXP (x, i, j)))
724 /* Check expression X for label references;
725 if one is found, add INSN to the label's chain of references.
727 CHECKDUP means check for and avoid creating duplicate references
728 from the same insn. Such duplicates do no serious harm but
729 can slow life analysis. CHECKDUP is set only when duplicates
733 mark_label_ref (x, insn, checkdup)
737 register RTX_CODE code;
741 /* We can be called with NULL when scanning label_value_list. */
746 if (code == LABEL_REF)
748 register rtx label = XEXP (x, 0);
750 if (GET_CODE (label) != CODE_LABEL)
752 /* If the label was never emitted, this insn is junk,
753 but avoid a crash trying to refer to BLOCK_NUM (label).
754 This can happen as a result of a syntax error
755 and a diagnostic has already been printed. */
756 if (INSN_UID (label) == 0)
758 CONTAINING_INSN (x) = insn;
759 /* if CHECKDUP is set, check for duplicate ref from same insn
762 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
763 if (CONTAINING_INSN (y) == insn)
765 LABEL_NEXTREF (x) = LABEL_REFS (label);
766 LABEL_REFS (label) = x;
767 block_live_static[BLOCK_NUM (label)] = 1;
771 fmt = GET_RTX_FORMAT (code);
772 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
775 mark_label_ref (XEXP (x, i), insn, 0);
779 for (j = 0; j < XVECLEN (x, i); j++)
780 mark_label_ref (XVECEXP (x, i, j), insn, 1);
785 /* Determine which registers are live at the start of each
786 basic block of the function whose first insn is F.
787 NREGS is the number of registers used in F.
788 We allocate the vector basic_block_live_at_start
789 and the regsets that it points to, and fill them with the data.
790 regset_size and regset_bytes are also set here. */
793 life_analysis (f, nregs)
800 /* For each basic block, a bitmask of regs
801 live on exit from the block. */
802 regset *basic_block_live_at_end;
803 /* For each basic block, a bitmask of regs
804 live on entry to a successor-block of this block.
805 If this does not match basic_block_live_at_end,
806 that must be updated, and the block must be rescanned. */
807 regset *basic_block_new_live_at_end;
808 /* For each basic block, a bitmask of regs
809 whose liveness at the end of the basic block
810 can make a difference in which regs are live on entry to the block.
811 These are the regs that are set within the basic block,
812 possibly excluding those that are used after they are set. */
813 regset *basic_block_significant;
817 struct obstack flow_obstack;
819 gcc_obstack_init (&flow_obstack);
823 bzero (regs_ever_live, sizeof regs_ever_live);
825 /* Allocate and zero out many data structures
826 that will record the data from lifetime analysis. */
828 allocate_for_life_analysis ();
830 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
831 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
833 /* Set up several regset-vectors used internally within this function.
834 Their meanings are documented above, with their declarations. */
836 basic_block_live_at_end
837 = (regset *) alloca (n_basic_blocks * sizeof (regset));
839 /* Don't use alloca since that leads to a crash rather than an error message
840 if there isn't enough space.
841 Don't use oballoc since we may need to allocate other things during
842 this function on the temporary obstack. */
843 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
844 bzero ((char *) tem, n_basic_blocks * regset_bytes);
845 init_regset_vector (basic_block_live_at_end, tem,
846 n_basic_blocks, regset_bytes);
848 basic_block_new_live_at_end
849 = (regset *) alloca (n_basic_blocks * sizeof (regset));
850 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
851 bzero ((char *) tem, n_basic_blocks * regset_bytes);
852 init_regset_vector (basic_block_new_live_at_end, tem,
853 n_basic_blocks, regset_bytes);
855 basic_block_significant
856 = (regset *) alloca (n_basic_blocks * sizeof (regset));
857 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
858 bzero ((char *) tem, n_basic_blocks * regset_bytes);
859 init_regset_vector (basic_block_significant, tem,
860 n_basic_blocks, regset_bytes);
862 /* Record which insns refer to any volatile memory
863 or for any reason can't be deleted just because they are dead stores.
864 Also, delete any insns that copy a register to itself. */
866 for (insn = f; insn; insn = NEXT_INSN (insn))
868 enum rtx_code code1 = GET_CODE (insn);
869 if (code1 == CALL_INSN)
870 INSN_VOLATILE (insn) = 1;
871 else if (code1 == INSN || code1 == JUMP_INSN)
873 /* Delete (in effect) any obvious no-op moves. */
874 if (GET_CODE (PATTERN (insn)) == SET
875 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
876 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
877 && REGNO (SET_DEST (PATTERN (insn))) ==
878 REGNO (SET_SRC (PATTERN (insn)))
879 /* Insns carrying these notes are useful later on. */
880 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
882 PUT_CODE (insn, NOTE);
883 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
884 NOTE_SOURCE_FILE (insn) = 0;
886 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
888 /* If nothing but SETs of registers to themselves,
889 this insn can also be deleted. */
890 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
892 rtx tem = XVECEXP (PATTERN (insn), 0, i);
894 if (GET_CODE (tem) == USE
895 || GET_CODE (tem) == CLOBBER)
898 if (GET_CODE (tem) != SET
899 || GET_CODE (SET_DEST (tem)) != REG
900 || GET_CODE (SET_SRC (tem)) != REG
901 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
905 if (i == XVECLEN (PATTERN (insn), 0)
906 /* Insns carrying these notes are useful later on. */
907 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
909 PUT_CODE (insn, NOTE);
910 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
911 NOTE_SOURCE_FILE (insn) = 0;
914 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
916 else if (GET_CODE (PATTERN (insn)) != USE)
917 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
918 /* A SET that makes space on the stack cannot be dead.
919 (Such SETs occur only for allocating variable-size data,
920 so they will always have a PLUS or MINUS according to the
921 direction of stack growth.)
922 Even if this function never uses this stack pointer value,
923 signal handlers do! */
924 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
925 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
926 #ifdef STACK_GROWS_DOWNWARD
927 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
929 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
931 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
932 INSN_VOLATILE (insn) = 1;
936 if (n_basic_blocks > 0)
937 #ifdef EXIT_IGNORE_STACK
938 if (! EXIT_IGNORE_STACK
939 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
942 /* If exiting needs the right stack value,
943 consider the stack pointer live at the end of the function. */
944 basic_block_live_at_end[n_basic_blocks - 1]
945 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
946 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
947 basic_block_new_live_at_end[n_basic_blocks - 1]
948 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
949 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
952 /* Mark the frame pointer is needed at the end of the function. If
953 we end up eliminating it, it will be removed from the live list
954 of each basic block by reload. */
956 if (n_basic_blocks > 0)
958 basic_block_live_at_end[n_basic_blocks - 1]
959 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
960 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
961 basic_block_new_live_at_end[n_basic_blocks - 1]
962 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
963 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
964 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
965 /* If they are different, also mark the hard frame pointer as live */
966 basic_block_live_at_end[n_basic_blocks - 1]
967 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
968 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
970 basic_block_new_live_at_end[n_basic_blocks - 1]
971 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
972 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
977 /* Mark all global registers as being live at the end of the function
978 since they may be referenced by our caller. */
980 if (n_basic_blocks > 0)
981 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
984 basic_block_live_at_end[n_basic_blocks - 1]
985 [i / REGSET_ELT_BITS]
986 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
987 basic_block_new_live_at_end[n_basic_blocks - 1]
988 [i / REGSET_ELT_BITS]
989 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
992 /* Propagate life info through the basic blocks
993 around the graph of basic blocks.
995 This is a relaxation process: each time a new register
996 is live at the end of the basic block, we must scan the block
997 to determine which registers are, as a consequence, live at the beginning
998 of that block. These registers must then be marked live at the ends
999 of all the blocks that can transfer control to that block.
1000 The process continues until it reaches a fixed point. */
1007 for (i = n_basic_blocks - 1; i >= 0; i--)
1009 int consider = first_pass;
1010 int must_rescan = first_pass;
1015 /* Set CONSIDER if this block needs thinking about at all
1016 (that is, if the regs live now at the end of it
1017 are not the same as were live at the end of it when
1018 we last thought about it).
1019 Set must_rescan if it needs to be thought about
1020 instruction by instruction (that is, if any additional
1021 reg that is live at the end now but was not live there before
1022 is one of the significant regs of this basic block). */
1024 for (j = 0; j < regset_size; j++)
1026 register REGSET_ELT_TYPE x
1027 = (basic_block_new_live_at_end[i][j]
1028 & ~basic_block_live_at_end[i][j]);
1031 if (x & basic_block_significant[i][j])
1043 /* The live_at_start of this block may be changing,
1044 so another pass will be required after this one. */
1049 /* No complete rescan needed;
1050 just record those variables newly known live at end
1051 as live at start as well. */
1052 for (j = 0; j < regset_size; j++)
1054 register REGSET_ELT_TYPE x
1055 = (basic_block_new_live_at_end[i][j]
1056 & ~basic_block_live_at_end[i][j]);
1057 basic_block_live_at_start[i][j] |= x;
1058 basic_block_live_at_end[i][j] |= x;
1063 /* Update the basic_block_live_at_start
1064 by propagation backwards through the block. */
1065 bcopy ((char *) basic_block_new_live_at_end[i],
1066 (char *) basic_block_live_at_end[i], regset_bytes);
1067 bcopy ((char *) basic_block_live_at_end[i],
1068 (char *) basic_block_live_at_start[i], regset_bytes);
1069 propagate_block (basic_block_live_at_start[i],
1070 basic_block_head[i], basic_block_end[i], 0,
1071 first_pass ? basic_block_significant[i]
1077 register rtx jump, head;
1079 /* Update the basic_block_new_live_at_end's of the block
1080 that falls through into this one (if any). */
1081 head = basic_block_head[i];
1082 if (basic_block_drops_in[i])
1085 for (j = 0; j < regset_size; j++)
1086 basic_block_new_live_at_end[i-1][j]
1087 |= basic_block_live_at_start[i][j];
1090 /* Update the basic_block_new_live_at_end's of
1091 all the blocks that jump to this one. */
1092 if (GET_CODE (head) == CODE_LABEL)
1093 for (jump = LABEL_REFS (head);
1095 jump = LABEL_NEXTREF (jump))
1097 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1099 for (j = 0; j < regset_size; j++)
1100 basic_block_new_live_at_end[from_block][j]
1101 |= basic_block_live_at_start[i][j];
1111 /* The only pseudos that are live at the beginning of the function are
1112 those that were not set anywhere in the function. local-alloc doesn't
1113 know how to handle these correctly, so mark them as not local to any
1116 if (n_basic_blocks > 0)
1117 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1118 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1119 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1120 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1122 /* Now the life information is accurate.
1123 Make one more pass over each basic block
1124 to delete dead stores, create autoincrement addressing
1125 and record how many times each register is used, is set, or dies.
1127 To save time, we operate directly in basic_block_live_at_end[i],
1128 thus destroying it (in fact, converting it into a copy of
1129 basic_block_live_at_start[i]). This is ok now because
1130 basic_block_live_at_end[i] is no longer used past this point. */
1134 for (i = 0; i < n_basic_blocks; i++)
1136 propagate_block (basic_block_live_at_end[i],
1137 basic_block_head[i], basic_block_end[i], 1,
1145 /* Something live during a setjmp should not be put in a register
1146 on certain machines which restore regs from stack frames
1147 rather than from the jmpbuf.
1148 But we don't need to do this for the user's variables, since
1149 ANSI says only volatile variables need this. */
1150 #ifdef LONGJMP_RESTORE_FROM_STACK
1151 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1152 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1153 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1154 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1156 reg_live_length[i] = -1;
1157 reg_basic_block[i] = -1;
1162 /* We have a problem with any pseudoreg that
1163 lives across the setjmp. ANSI says that if a
1164 user variable does not change in value
1165 between the setjmp and the longjmp, then the longjmp preserves it.
1166 This includes longjmp from a place where the pseudo appears dead.
1167 (In principle, the value still exists if it is in scope.)
1168 If the pseudo goes in a hard reg, some other value may occupy
1169 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1170 Conclusion: such a pseudo must not go in a hard reg. */
1171 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1172 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1173 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1174 && regno_reg_rtx[i] != 0)
1176 reg_live_length[i] = -1;
1177 reg_basic_block[i] = -1;
1180 obstack_free (&flow_obstack, NULL_PTR);
1183 /* Subroutines of life analysis. */
1185 /* Allocate the permanent data structures that represent the results
1186 of life analysis. Not static since used also for stupid life analysis. */
1189 allocate_for_life_analysis ()
1192 register regset tem;
1194 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1195 regset_bytes = regset_size * sizeof (*(regset)0);
1197 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1198 bzero ((char *) reg_n_refs, max_regno * sizeof (int));
1200 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1201 bzero ((char *) reg_n_sets, max_regno * sizeof (short));
1203 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1204 bzero ((char *) reg_n_deaths, max_regno * sizeof (short));
1206 reg_changes_size = (char *) oballoc (max_regno * sizeof (char));
1207 bzero (reg_changes_size, max_regno * sizeof (char));;
1209 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1210 bzero ((char *) reg_live_length, max_regno * sizeof (int));
1212 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1213 bzero ((char *) reg_n_calls_crossed, max_regno * sizeof (int));
1215 reg_basic_block = (int *) oballoc (max_regno * sizeof (int));
1216 for (i = 0; i < max_regno; i++)
1217 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1219 basic_block_live_at_start
1220 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1221 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1222 bzero ((char *) tem, n_basic_blocks * regset_bytes);
1223 init_regset_vector (basic_block_live_at_start, tem,
1224 n_basic_blocks, regset_bytes);
1226 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1227 bzero ((char *) regs_live_at_setjmp, regset_bytes);
1230 /* Make each element of VECTOR point at a regset,
1231 taking the space for all those regsets from SPACE.
1232 SPACE is of type regset, but it is really as long as NELTS regsets.
1233 BYTES_PER_ELT is the number of bytes in one regset. */
1236 init_regset_vector (vector, space, nelts, bytes_per_elt)
1243 register regset p = space;
1245 for (i = 0; i < nelts; i++)
1248 p += bytes_per_elt / sizeof (*p);
1252 /* Compute the registers live at the beginning of a basic block
1253 from those live at the end.
1255 When called, OLD contains those live at the end.
1256 On return, it contains those live at the beginning.
1257 FIRST and LAST are the first and last insns of the basic block.
1259 FINAL is nonzero if we are doing the final pass which is not
1260 for computing the life info (since that has already been done)
1261 but for acting on it. On this pass, we delete dead stores,
1262 set up the logical links and dead-variables lists of instructions,
1263 and merge instructions for autoincrement and autodecrement addresses.
1265 SIGNIFICANT is nonzero only the first time for each basic block.
1266 If it is nonzero, it points to a regset in which we store
1267 a 1 for each register that is set within the block.
1269 BNUM is the number of the basic block. */
1272 propagate_block (old, first, last, final, significant, bnum)
1273 register regset old;
1285 /* The following variables are used only if FINAL is nonzero. */
1286 /* This vector gets one element for each reg that has been live
1287 at any point in the basic block that has been scanned so far.
1288 SOMETIMES_MAX says how many elements are in use so far.
1289 In each element, OFFSET is the byte-number within a regset
1290 for the register described by the element, and BIT is a mask
1291 for that register's bit within the byte. */
1292 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1293 int sometimes_max = 0;
1294 /* This regset has 1 for each reg that we have seen live so far.
1295 It and REGS_SOMETIMES_LIVE are updated together. */
1298 /* The loop depth may change in the middle of a basic block. Since we
1299 scan from end to beginning, we start with the depth at the end of the
1300 current basic block, and adjust as we pass ends and starts of loops. */
1301 loop_depth = basic_block_loop_depth[bnum];
1303 dead = (regset) alloca (regset_bytes);
1304 live = (regset) alloca (regset_bytes);
1309 /* Include any notes at the end of the block in the scan.
1310 This is in case the block ends with a call to setjmp. */
1312 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1314 /* Look for loop boundaries, we are going forward here. */
1315 last = NEXT_INSN (last);
1316 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1318 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1324 register int i, offset;
1325 REGSET_ELT_TYPE bit;
1328 maxlive = (regset) alloca (regset_bytes);
1329 bcopy ((char *) old, (char *) maxlive, regset_bytes);
1331 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1333 /* Process the regs live at the end of the block.
1334 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1335 Also mark them as not local to any one basic block. */
1337 for (offset = 0, i = 0; offset < regset_size; offset++)
1338 for (bit = 1; bit; bit <<= 1, i++)
1342 if (old[offset] & bit)
1344 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1345 regs_sometimes_live[sometimes_max].offset = offset;
1346 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1352 /* Scan the block an insn at a time from end to beginning. */
1354 for (insn = last; ; insn = prev)
1356 prev = PREV_INSN (insn);
1358 /* Look for loop boundaries, remembering that we are going backwards. */
1359 if (GET_CODE (insn) == NOTE
1360 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1362 else if (GET_CODE (insn) == NOTE
1363 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1366 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1367 Abort now rather than setting register status incorrectly. */
1368 if (loop_depth == 0)
1371 /* If this is a call to `setjmp' et al,
1372 warn if any non-volatile datum is live. */
1374 if (final && GET_CODE (insn) == NOTE
1375 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1378 for (i = 0; i < regset_size; i++)
1379 regs_live_at_setjmp[i] |= old[i];
1382 /* Update the life-status of regs for this insn.
1383 First DEAD gets which regs are set in this insn
1384 then LIVE gets which regs are used in this insn.
1385 Then the regs live before the insn
1386 are those live after, with DEAD regs turned off,
1387 and then LIVE regs turned on. */
1389 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1392 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1394 = (insn_dead_p (PATTERN (insn), old, 0)
1395 /* Don't delete something that refers to volatile storage! */
1396 && ! INSN_VOLATILE (insn));
1398 = (insn_is_dead && note != 0
1399 && libcall_dead_p (PATTERN (insn), old, note, insn));
1401 /* If an instruction consists of just dead store(s) on final pass,
1402 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1403 We could really delete it with delete_insn, but that
1404 can cause trouble for first or last insn in a basic block. */
1405 if (final && insn_is_dead)
1407 PUT_CODE (insn, NOTE);
1408 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1409 NOTE_SOURCE_FILE (insn) = 0;
1411 /* CC0 is now known to be dead. Either this insn used it,
1412 in which case it doesn't anymore, or clobbered it,
1413 so the next insn can't use it. */
1416 /* If this insn is copying the return value from a library call,
1417 delete the entire library call. */
1418 if (libcall_is_dead)
1420 rtx first = XEXP (note, 0);
1422 while (INSN_DELETED_P (first))
1423 first = NEXT_INSN (first);
1428 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1429 NOTE_SOURCE_FILE (p) = 0;
1435 for (i = 0; i < regset_size; i++)
1437 dead[i] = 0; /* Faster than bzero here */
1438 live[i] = 0; /* since regset_size is usually small */
1441 /* See if this is an increment or decrement that can be
1442 merged into a following memory address. */
1445 register rtx x = PATTERN (insn);
1446 /* Does this instruction increment or decrement a register? */
1447 if (final && GET_CODE (x) == SET
1448 && GET_CODE (SET_DEST (x)) == REG
1449 && (GET_CODE (SET_SRC (x)) == PLUS
1450 || GET_CODE (SET_SRC (x)) == MINUS)
1451 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1452 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1453 /* Ok, look for a following memory ref we can combine with.
1454 If one is found, change the memory ref to a PRE_INC
1455 or PRE_DEC, cancel this insn, and return 1.
1456 Return 0 if nothing has been done. */
1457 && try_pre_increment_1 (insn))
1460 #endif /* AUTO_INC_DEC */
1462 /* If this is not the final pass, and this insn is copying the
1463 value of a library call and it's dead, don't scan the
1464 insns that perform the library call, so that the call's
1465 arguments are not marked live. */
1466 if (libcall_is_dead)
1468 /* Mark the dest reg as `significant'. */
1469 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1471 insn = XEXP (note, 0);
1472 prev = PREV_INSN (insn);
1474 else if (GET_CODE (PATTERN (insn)) == SET
1475 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1476 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1477 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1478 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1479 /* We have an insn to pop a constant amount off the stack.
1480 (Such insns use PLUS regardless of the direction of the stack,
1481 and any insn to adjust the stack by a constant is always a pop.)
1482 These insns, if not dead stores, have no effect on life. */
1486 /* LIVE gets the regs used in INSN;
1487 DEAD gets those set by it. Dead insns don't make anything
1490 mark_set_regs (old, dead, PATTERN (insn),
1491 final ? insn : NULL_RTX, significant);
1493 /* If an insn doesn't use CC0, it becomes dead since we
1494 assume that every insn clobbers it. So show it dead here;
1495 mark_used_regs will set it live if it is referenced. */
1499 mark_used_regs (old, live, PATTERN (insn), final, insn);
1501 /* Sometimes we may have inserted something before INSN (such as
1502 a move) when we make an auto-inc. So ensure we will scan
1505 prev = PREV_INSN (insn);
1508 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1514 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1516 note = XEXP (note, 1))
1517 if (GET_CODE (XEXP (note, 0)) == USE)
1518 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1521 /* Each call clobbers all call-clobbered regs that are not
1522 global. Note that the function-value reg is a
1523 call-clobbered reg, and mark_set_regs has already had
1524 a chance to handle it. */
1526 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1527 if (call_used_regs[i] && ! global_regs[i])
1528 dead[i / REGSET_ELT_BITS]
1529 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1531 /* The stack ptr is used (honorarily) by a CALL insn. */
1532 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1533 |= ((REGSET_ELT_TYPE) 1
1534 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1536 /* Calls may also reference any of the global registers,
1537 so they are made live. */
1538 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1540 mark_used_regs (old, live,
1541 gen_rtx (REG, reg_raw_mode[i], i),
1544 /* Calls also clobber memory. */
1548 /* Update OLD for the registers used or set. */
1549 for (i = 0; i < regset_size; i++)
1555 if (GET_CODE (insn) == CALL_INSN && final)
1557 /* Any regs live at the time of a call instruction
1558 must not go in a register clobbered by calls.
1559 Find all regs now live and record this for them. */
1561 register struct sometimes *p = regs_sometimes_live;
1563 for (i = 0; i < sometimes_max; i++, p++)
1564 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1565 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1569 /* On final pass, add any additional sometimes-live regs
1570 into MAXLIVE and REGS_SOMETIMES_LIVE.
1571 Also update counts of how many insns each reg is live at. */
1575 for (i = 0; i < regset_size; i++)
1577 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1583 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1584 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1586 regs_sometimes_live[sometimes_max].offset = i;
1587 regs_sometimes_live[sometimes_max].bit = regno;
1588 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1595 register struct sometimes *p = regs_sometimes_live;
1596 for (i = 0; i < sometimes_max; i++, p++)
1598 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1599 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1609 if (num_scratch > max_scratch)
1610 max_scratch = num_scratch;
1613 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1614 (SET expressions whose destinations are registers dead after the insn).
1615 NEEDED is the regset that says which regs are alive after the insn.
1617 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1620 insn_dead_p (x, needed, call_ok)
1625 register RTX_CODE code = GET_CODE (x);
1626 /* If setting something that's a reg or part of one,
1627 see if that register's altered value will be live. */
1631 register rtx r = SET_DEST (x);
1632 /* A SET that is a subroutine call cannot be dead. */
1633 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1637 if (GET_CODE (r) == CC0)
1641 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1642 && rtx_equal_p (r, last_mem_set))
1645 while (GET_CODE (r) == SUBREG
1646 || GET_CODE (r) == STRICT_LOW_PART
1647 || GET_CODE (r) == ZERO_EXTRACT
1648 || GET_CODE (r) == SIGN_EXTRACT)
1651 if (GET_CODE (r) == REG)
1653 register int regno = REGNO (r);
1654 register int offset = regno / REGSET_ELT_BITS;
1655 register REGSET_ELT_TYPE bit
1656 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1658 /* Don't delete insns to set global regs. */
1659 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1660 /* Make sure insns to set frame pointer aren't deleted. */
1661 || regno == FRAME_POINTER_REGNUM
1662 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1663 || regno == HARD_FRAME_POINTER_REGNUM
1665 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1666 /* Make sure insns to set arg pointer are never deleted
1667 (if the arg pointer isn't fixed, there will be a USE for
1668 it, so we can treat it normally). */
1669 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1671 || (needed[offset] & bit) != 0)
1674 /* If this is a hard register, verify that subsequent words are
1676 if (regno < FIRST_PSEUDO_REGISTER)
1678 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1681 if ((needed[(regno + n) / REGSET_ELT_BITS]
1682 & ((REGSET_ELT_TYPE) 1
1683 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1690 /* If performing several activities,
1691 insn is dead if each activity is individually dead.
1692 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1693 that's inside a PARALLEL doesn't make the insn worth keeping. */
1694 else if (code == PARALLEL)
1696 register int i = XVECLEN (x, 0);
1697 for (i--; i >= 0; i--)
1699 rtx elt = XVECEXP (x, 0, i);
1700 if (!insn_dead_p (elt, needed, call_ok)
1701 && GET_CODE (elt) != CLOBBER
1702 && GET_CODE (elt) != USE)
1707 /* We do not check CLOBBER or USE here.
1708 An insn consisting of just a CLOBBER or just a USE
1709 should not be deleted. */
1713 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1714 return 1 if the entire library call is dead.
1715 This is true if X copies a register (hard or pseudo)
1716 and if the hard return reg of the call insn is dead.
1717 (The caller should have tested the destination of X already for death.)
1719 If this insn doesn't just copy a register, then we don't
1720 have an ordinary libcall. In that case, cse could not have
1721 managed to substitute the source for the dest later on,
1722 so we can assume the libcall is dead.
1724 NEEDED is the bit vector of pseudoregs live before this insn.
1725 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1728 libcall_dead_p (x, needed, note, insn)
1734 register RTX_CODE code = GET_CODE (x);
1738 register rtx r = SET_SRC (x);
1739 if (GET_CODE (r) == REG)
1741 rtx call = XEXP (note, 0);
1744 /* Find the call insn. */
1745 while (call != insn && GET_CODE (call) != CALL_INSN)
1746 call = NEXT_INSN (call);
1748 /* If there is none, do nothing special,
1749 since ordinary death handling can understand these insns. */
1753 /* See if the hard reg holding the value is dead.
1754 If this is a PARALLEL, find the call within it. */
1755 call = PATTERN (call);
1756 if (GET_CODE (call) == PARALLEL)
1758 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1759 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1760 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1763 /* This may be a library call that is returning a value
1764 via invisible pointer. Do nothing special, since
1765 ordinary death handling can understand these insns. */
1769 call = XVECEXP (call, 0, i);
1772 return insn_dead_p (call, needed, 1);
1778 /* Return 1 if register REGNO was used before it was set.
1779 In other words, if it is live at function entry.
1780 Don't count global regster variables, though. */
1783 regno_uninitialized (regno)
1786 if (n_basic_blocks == 0
1787 || (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1790 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1791 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1794 /* 1 if register REGNO was alive at a place where `setjmp' was called
1795 and was set more than once or is an argument.
1796 Such regs may be clobbered by `longjmp'. */
1799 regno_clobbered_at_setjmp (regno)
1802 if (n_basic_blocks == 0)
1805 return ((reg_n_sets[regno] > 1
1806 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1807 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1808 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1809 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1812 /* Process the registers that are set within X.
1813 Their bits are set to 1 in the regset DEAD,
1814 because they are dead prior to this insn.
1816 If INSN is nonzero, it is the insn being processed
1817 and the fact that it is nonzero implies this is the FINAL pass
1818 in propagate_block. In this case, various info about register
1819 usage is stored, LOG_LINKS fields of insns are set up. */
1822 mark_set_regs (needed, dead, x, insn, significant)
1829 register RTX_CODE code = GET_CODE (x);
1831 if (code == SET || code == CLOBBER)
1832 mark_set_1 (needed, dead, x, insn, significant);
1833 else if (code == PARALLEL)
1836 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1838 code = GET_CODE (XVECEXP (x, 0, i));
1839 if (code == SET || code == CLOBBER)
1840 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1845 /* Process a single SET rtx, X. */
1848 mark_set_1 (needed, dead, x, insn, significant)
1856 register rtx reg = SET_DEST (x);
1858 /* Modifying just one hardware register of a multi-reg value
1859 or just a byte field of a register
1860 does not mean the value from before this insn is now dead.
1861 But it does mean liveness of that register at the end of the block
1864 Within mark_set_1, however, we treat it as if the register is
1865 indeed modified. mark_used_regs will, however, also treat this
1866 register as being used. Thus, we treat these insns as setting a
1867 new value for the register as a function of its old value. This
1868 cases LOG_LINKS to be made appropriately and this will help combine. */
1870 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1871 || GET_CODE (reg) == SIGN_EXTRACT
1872 || GET_CODE (reg) == STRICT_LOW_PART)
1873 reg = XEXP (reg, 0);
1875 /* If we are writing into memory or into a register mentioned in the
1876 address of the last thing stored into memory, show we don't know
1877 what the last store was. If we are writing memory, save the address
1878 unless it is volatile. */
1879 if (GET_CODE (reg) == MEM
1880 || (GET_CODE (reg) == REG
1881 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1884 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1885 /* There are no REG_INC notes for SP, so we can't assume we'll see
1886 everything that invalidates it. To be safe, don't eliminate any
1887 stores though SP; none of them should be redundant anyway. */
1888 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1891 if (GET_CODE (reg) == REG
1892 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1893 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1894 && regno != HARD_FRAME_POINTER_REGNUM
1896 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1897 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1899 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1900 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1902 register int offset = regno / REGSET_ELT_BITS;
1903 register REGSET_ELT_TYPE bit
1904 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1905 REGSET_ELT_TYPE all_needed = (needed[offset] & bit);
1906 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
1908 /* Mark it as a significant register for this basic block. */
1910 significant[offset] |= bit;
1912 /* Mark it as as dead before this insn. */
1913 dead[offset] |= bit;
1915 /* A hard reg in a wide mode may really be multiple registers.
1916 If so, mark all of them just like the first. */
1917 if (regno < FIRST_PSEUDO_REGISTER)
1921 /* Nothing below is needed for the stack pointer; get out asap.
1922 Eg, log links aren't needed, since combine won't use them. */
1923 if (regno == STACK_POINTER_REGNUM)
1926 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1930 significant[(regno + n) / REGSET_ELT_BITS]
1931 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1932 dead[(regno + n) / REGSET_ELT_BITS]
1933 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1935 |= (needed[(regno + n) / REGSET_ELT_BITS]
1936 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1938 &= (needed[(regno + n) / REGSET_ELT_BITS]
1939 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1942 /* Additional data to record if this is the final pass. */
1945 register rtx y = reg_next_use[regno];
1946 register int blocknum = BLOCK_NUM (insn);
1948 /* The next use is no longer "next", since a store intervenes. */
1949 reg_next_use[regno] = 0;
1951 /* If this is a hard reg, record this function uses the reg. */
1953 if (regno < FIRST_PSEUDO_REGISTER)
1956 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
1958 for (i = regno; i < endregno; i++)
1960 regs_ever_live[i] = 1;
1966 /* Keep track of which basic blocks each reg appears in. */
1968 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
1969 reg_basic_block[regno] = blocknum;
1970 else if (reg_basic_block[regno] != blocknum)
1971 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
1973 /* Count (weighted) references, stores, etc. This counts a
1974 register twice if it is modified, but that is correct. */
1975 reg_n_sets[regno]++;
1977 reg_n_refs[regno] += loop_depth;
1979 /* The insns where a reg is live are normally counted
1980 elsewhere, but we want the count to include the insn
1981 where the reg is set, and the normal counting mechanism
1982 would not count it. */
1983 reg_live_length[regno]++;
1988 /* Make a logical link from the next following insn
1989 that uses this register, back to this insn.
1990 The following insns have already been processed.
1992 We don't build a LOG_LINK for hard registers containing
1993 in ASM_OPERANDs. If these registers get replaced,
1994 we might wind up changing the semantics of the insn,
1995 even if reload can make what appear to be valid assignments
1997 if (y && (BLOCK_NUM (y) == blocknum)
1998 && (regno >= FIRST_PSEUDO_REGISTER
1999 || asm_noperands (PATTERN (y)) < 0))
2001 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
2003 else if (! some_needed)
2005 /* Note that dead stores have already been deleted when possible
2006 If we get here, we have found a dead store that cannot
2007 be eliminated (because the same insn does something useful).
2008 Indicate this by marking the reg being set as dying here. */
2010 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2011 reg_n_deaths[REGNO (reg)]++;
2015 /* This is a case where we have a multi-word hard register
2016 and some, but not all, of the words of the register are
2017 needed in subsequent insns. Write REG_UNUSED notes
2018 for those parts that were not needed. This case should
2023 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2025 if ((needed[(regno + i) / REGSET_ELT_BITS]
2026 & ((REGSET_ELT_TYPE) 1
2027 << ((regno + i) % REGSET_ELT_BITS))) == 0)
2029 = gen_rtx (EXPR_LIST, REG_UNUSED,
2030 gen_rtx (REG, reg_raw_mode[regno + i],
2036 else if (GET_CODE (reg) == REG)
2037 reg_next_use[regno] = 0;
2039 /* If this is the last pass and this is a SCRATCH, show it will be dying
2040 here and count it. */
2041 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2044 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2051 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2055 find_auto_inc (needed, x, insn)
2060 rtx addr = XEXP (x, 0);
2061 HOST_WIDE_INT offset = 0;
2064 /* Here we detect use of an index register which might be good for
2065 postincrement, postdecrement, preincrement, or predecrement. */
2067 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2068 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2070 if (GET_CODE (addr) == REG)
2073 register int size = GET_MODE_SIZE (GET_MODE (x));
2076 int regno = REGNO (addr);
2078 /* Is the next use an increment that might make auto-increment? */
2079 if ((incr = reg_next_use[regno]) != 0
2080 && (set = single_set (incr)) != 0
2081 && GET_CODE (set) == SET
2082 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2083 /* Can't add side effects to jumps; if reg is spilled and
2084 reloaded, there's no way to store back the altered value. */
2085 && GET_CODE (insn) != JUMP_INSN
2086 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2087 && XEXP (y, 0) == addr
2088 && GET_CODE (XEXP (y, 1)) == CONST_INT
2090 #ifdef HAVE_POST_INCREMENT
2091 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2093 #ifdef HAVE_POST_DECREMENT
2094 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2096 #ifdef HAVE_PRE_INCREMENT
2097 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2099 #ifdef HAVE_PRE_DECREMENT
2100 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2103 /* Make sure this reg appears only once in this insn. */
2104 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2105 use != 0 && use != (rtx) 1))
2107 rtx q = SET_DEST (set);
2108 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2109 ? (offset ? PRE_INC : POST_INC)
2110 : (offset ? PRE_DEC : POST_DEC));
2112 if (dead_or_set_p (incr, addr))
2114 /* This is the simple case. Try to make the auto-inc. If
2115 we can't, we are done. Otherwise, we will do any
2116 needed updates below. */
2117 if (! validate_change (insn, &XEXP (x, 0),
2118 gen_rtx (inc_code, Pmode, addr),
2122 else if (GET_CODE (q) == REG
2123 /* PREV_INSN used here to check the semi-open interval
2125 && ! reg_used_between_p (q, PREV_INSN (insn), incr))
2127 /* We have *p followed sometime later by q = p+size.
2128 Both p and q must be live afterward,
2129 and q is not used between INSN and it's assignment.
2130 Change it to q = p, ...*q..., q = q+size.
2131 Then fall into the usual case. */
2135 emit_move_insn (q, addr);
2136 insns = get_insns ();
2139 /* If anything in INSNS have UID's that don't fit within the
2140 extra space we allocate earlier, we can't make this auto-inc.
2141 This should never happen. */
2142 for (temp = insns; temp; temp = NEXT_INSN (temp))
2144 if (INSN_UID (temp) > max_uid_for_flow)
2146 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2149 /* If we can't make the auto-inc, or can't make the
2150 replacement into Y, exit. There's no point in making
2151 the change below if we can't do the auto-inc and doing
2152 so is not correct in the pre-inc case. */
2154 validate_change (insn, &XEXP (x, 0),
2155 gen_rtx (inc_code, Pmode, q),
2157 validate_change (incr, &XEXP (y, 0), q, 1);
2158 if (! apply_change_group ())
2161 /* We now know we'll be doing this change, so emit the
2162 new insn(s) and do the updates. */
2163 emit_insns_before (insns, insn);
2165 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2166 basic_block_head[BLOCK_NUM (insn)] = insns;
2168 /* INCR will become a NOTE and INSN won't contain a
2169 use of ADDR. If a use of ADDR was just placed in
2170 the insn before INSN, make that the next use.
2171 Otherwise, invalidate it. */
2172 if (GET_CODE (PREV_INSN (insn)) == INSN
2173 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2174 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2175 reg_next_use[regno] = PREV_INSN (insn);
2177 reg_next_use[regno] = 0;
2182 /* REGNO is now used in INCR which is below INSN, but
2183 it previously wasn't live here. If we don't mark
2184 it as needed, we'll put a REG_DEAD note for it
2185 on this insn, which is incorrect. */
2186 needed[regno / REGSET_ELT_BITS]
2187 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2189 /* If there are any calls between INSN and INCR, show
2190 that REGNO now crosses them. */
2191 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2192 if (GET_CODE (temp) == CALL_INSN)
2193 reg_n_calls_crossed[regno]++;
2196 /* If we haven't returned, it means we were able to make the
2197 auto-inc, so update the status. First, record that this insn
2198 has an implicit side effect. */
2201 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2203 /* Modify the old increment-insn to simply copy
2204 the already-incremented value of our register. */
2205 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2208 /* If that makes it a no-op (copying the register into itself) delete
2209 it so it won't appear to be a "use" and a "set" of this
2211 if (SET_DEST (set) == addr)
2213 PUT_CODE (incr, NOTE);
2214 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2215 NOTE_SOURCE_FILE (incr) = 0;
2218 if (regno >= FIRST_PSEUDO_REGISTER)
2220 /* Count an extra reference to the reg. When a reg is
2221 incremented, spilling it is worse, so we want to make
2222 that less likely. */
2223 reg_n_refs[regno] += loop_depth;
2225 /* Count the increment as a setting of the register,
2226 even though it isn't a SET in rtl. */
2227 reg_n_sets[regno]++;
2232 #endif /* AUTO_INC_DEC */
2234 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2235 This is done assuming the registers needed from X
2236 are those that have 1-bits in NEEDED.
2238 On the final pass, FINAL is 1. This means try for autoincrement
2239 and count the uses and deaths of each pseudo-reg.
2241 INSN is the containing instruction. If INSN is dead, this function is not
2245 mark_used_regs (needed, live, x, final, insn)
2252 register RTX_CODE code;
2257 code = GET_CODE (x);
2278 /* If we are clobbering a MEM, mark any registers inside the address
2280 if (GET_CODE (XEXP (x, 0)) == MEM)
2281 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2285 /* Invalidate the data for the last MEM stored. We could do this only
2286 if the addresses conflict, but this doesn't seem worthwhile. */
2291 find_auto_inc (needed, x, insn);
2296 if (GET_CODE (SUBREG_REG (x)) == REG
2297 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2298 && (GET_MODE_SIZE (GET_MODE (x))
2299 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
2300 && (INTEGRAL_MODE_P (GET_MODE (x))
2301 || INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (x)))))
2302 reg_changes_size[REGNO (SUBREG_REG (x))] = 1;
2304 /* While we're here, optimize this case. */
2307 /* ... fall through ... */
2310 /* See a register other than being set
2311 => mark it as needed. */
2315 register int offset = regno / REGSET_ELT_BITS;
2316 register REGSET_ELT_TYPE bit
2317 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2318 REGSET_ELT_TYPE all_needed = needed[offset] & bit;
2319 REGSET_ELT_TYPE some_needed = needed[offset] & bit;
2321 live[offset] |= bit;
2322 /* A hard reg in a wide mode may really be multiple registers.
2323 If so, mark all of them just like the first. */
2324 if (regno < FIRST_PSEUDO_REGISTER)
2328 /* For stack ptr or fixed arg pointer,
2329 nothing below can be necessary, so waste no more time. */
2330 if (regno == STACK_POINTER_REGNUM
2331 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2332 || regno == HARD_FRAME_POINTER_REGNUM
2334 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2335 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2337 || regno == FRAME_POINTER_REGNUM)
2339 /* If this is a register we are going to try to eliminate,
2340 don't mark it live here. If we are successful in
2341 eliminating it, it need not be live unless it is used for
2342 pseudos, in which case it will have been set live when
2343 it was allocated to the pseudos. If the register will not
2344 be eliminated, reload will set it live at that point. */
2346 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2347 regs_ever_live[regno] = 1;
2350 /* No death notes for global register variables;
2351 their values are live after this function exits. */
2352 if (global_regs[regno])
2355 reg_next_use[regno] = insn;
2359 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2362 live[(regno + n) / REGSET_ELT_BITS]
2363 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2365 |= (needed[(regno + n) / REGSET_ELT_BITS]
2366 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2368 &= (needed[(regno + n) / REGSET_ELT_BITS]
2369 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2374 /* Record where each reg is used, so when the reg
2375 is set we know the next insn that uses it. */
2377 reg_next_use[regno] = insn;
2379 if (regno < FIRST_PSEUDO_REGISTER)
2381 /* If a hard reg is being used,
2382 record that this function does use it. */
2384 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2388 regs_ever_live[regno + --i] = 1;
2393 /* Keep track of which basic block each reg appears in. */
2395 register int blocknum = BLOCK_NUM (insn);
2397 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2398 reg_basic_block[regno] = blocknum;
2399 else if (reg_basic_block[regno] != blocknum)
2400 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2402 /* Count (weighted) number of uses of each reg. */
2404 reg_n_refs[regno] += loop_depth;
2407 /* Record and count the insns in which a reg dies.
2408 If it is used in this insn and was dead below the insn
2409 then it dies in this insn. If it was set in this insn,
2410 we do not make a REG_DEAD note; likewise if we already
2411 made such a note. */
2414 && ! dead_or_set_p (insn, x)
2416 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2420 /* Check for the case where the register dying partially
2421 overlaps the register set by this insn. */
2422 if (regno < FIRST_PSEUDO_REGISTER
2423 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2425 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2427 some_needed |= dead_or_set_regno_p (insn, regno + n);
2430 /* If none of the words in X is needed, make a REG_DEAD
2431 note. Otherwise, we must make partial REG_DEAD notes. */
2435 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2436 reg_n_deaths[regno]++;
2442 /* Don't make a REG_DEAD note for a part of a register
2443 that is set in the insn. */
2445 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2447 if ((needed[(regno + i) / REGSET_ELT_BITS]
2448 & ((REGSET_ELT_TYPE) 1
2449 << ((regno + i) % REGSET_ELT_BITS))) == 0
2450 && ! dead_or_set_regno_p (insn, regno + i))
2452 = gen_rtx (EXPR_LIST, REG_DEAD,
2453 gen_rtx (REG, reg_raw_mode[regno + i],
2464 register rtx testreg = SET_DEST (x);
2467 /* If storing into MEM, don't show it as being used. But do
2468 show the address as being used. */
2469 if (GET_CODE (testreg) == MEM)
2473 find_auto_inc (needed, testreg, insn);
2475 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2476 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2480 /* Storing in STRICT_LOW_PART is like storing in a reg
2481 in that this SET might be dead, so ignore it in TESTREG.
2482 but in some other ways it is like using the reg.
2484 Storing in a SUBREG or a bit field is like storing the entire
2485 register in that if the register's value is not used
2486 then this SET is not needed. */
2487 while (GET_CODE (testreg) == STRICT_LOW_PART
2488 || GET_CODE (testreg) == ZERO_EXTRACT
2489 || GET_CODE (testreg) == SIGN_EXTRACT
2490 || GET_CODE (testreg) == SUBREG)
2492 /* Modifying a single register in an alternate mode
2493 does not use any of the old value. But these other
2494 ways of storing in a register do use the old value. */
2495 if (GET_CODE (testreg) == SUBREG
2496 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2501 testreg = XEXP (testreg, 0);
2504 /* If this is a store into a register,
2505 recursively scan the value being stored. */
2507 if (GET_CODE (testreg) == REG
2508 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2509 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2510 && regno != HARD_FRAME_POINTER_REGNUM
2512 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2513 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2516 /* We used to exclude global_regs here, but that seems wrong.
2517 Storing in them is like storing in mem. */
2519 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2521 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2528 /* If exiting needs the right stack value, consider this insn as
2529 using the stack pointer. In any event, consider it as using
2530 all global registers. */
2532 #ifdef EXIT_IGNORE_STACK
2533 if (! EXIT_IGNORE_STACK
2534 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2536 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2537 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2539 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2541 live[i / REGSET_ELT_BITS]
2542 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2546 /* Recursively scan the operands of this expression. */
2549 register char *fmt = GET_RTX_FORMAT (code);
2552 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2556 /* Tail recursive case: save a function call level. */
2562 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2564 else if (fmt[i] == 'E')
2567 for (j = 0; j < XVECLEN (x, i); j++)
2568 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2577 try_pre_increment_1 (insn)
2580 /* Find the next use of this reg. If in same basic block,
2581 make it do pre-increment or pre-decrement if appropriate. */
2582 rtx x = PATTERN (insn);
2583 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2584 * INTVAL (XEXP (SET_SRC (x), 1)));
2585 int regno = REGNO (SET_DEST (x));
2586 rtx y = reg_next_use[regno];
2588 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2589 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2590 mode would be better. */
2591 && ! dead_or_set_p (y, SET_DEST (x))
2592 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2595 /* We have found a suitable auto-increment
2596 and already changed insn Y to do it.
2597 So flush this increment-instruction. */
2598 PUT_CODE (insn, NOTE);
2599 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2600 NOTE_SOURCE_FILE (insn) = 0;
2601 /* Count a reference to this reg for the increment
2602 insn we are deleting. When a reg is incremented.
2603 spilling it is worse, so we want to make that
2605 if (regno >= FIRST_PSEUDO_REGISTER)
2607 reg_n_refs[regno] += loop_depth;
2608 reg_n_sets[regno]++;
2615 /* Try to change INSN so that it does pre-increment or pre-decrement
2616 addressing on register REG in order to add AMOUNT to REG.
2617 AMOUNT is negative for pre-decrement.
2618 Returns 1 if the change could be made.
2619 This checks all about the validity of the result of modifying INSN. */
2622 try_pre_increment (insn, reg, amount)
2624 HOST_WIDE_INT amount;
2628 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2629 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2631 /* Nonzero if we can try to make a post-increment or post-decrement.
2632 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2633 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2634 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2637 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2640 /* From the sign of increment, see which possibilities are conceivable
2641 on this target machine. */
2642 #ifdef HAVE_PRE_INCREMENT
2646 #ifdef HAVE_POST_INCREMENT
2651 #ifdef HAVE_PRE_DECREMENT
2655 #ifdef HAVE_POST_DECREMENT
2660 if (! (pre_ok || post_ok))
2663 /* It is not safe to add a side effect to a jump insn
2664 because if the incremented register is spilled and must be reloaded
2665 there would be no way to store the incremented value back in memory. */
2667 if (GET_CODE (insn) == JUMP_INSN)
2672 use = find_use_as_address (PATTERN (insn), reg, 0);
2673 if (post_ok && (use == 0 || use == (rtx) 1))
2675 use = find_use_as_address (PATTERN (insn), reg, -amount);
2679 if (use == 0 || use == (rtx) 1)
2682 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2685 /* See if this combination of instruction and addressing mode exists. */
2686 if (! validate_change (insn, &XEXP (use, 0),
2688 ? (do_post ? POST_INC : PRE_INC)
2689 : (do_post ? POST_DEC : PRE_DEC),
2693 /* Record that this insn now has an implicit side effect on X. */
2694 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2698 #endif /* AUTO_INC_DEC */
2700 /* Find the place in the rtx X where REG is used as a memory address.
2701 Return the MEM rtx that so uses it.
2702 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2703 (plus REG (const_int PLUSCONST)).
2705 If such an address does not appear, return 0.
2706 If REG appears more than once, or is used other than in such an address,
2710 find_use_as_address (x, reg, plusconst)
2713 HOST_WIDE_INT plusconst;
2715 enum rtx_code code = GET_CODE (x);
2716 char *fmt = GET_RTX_FORMAT (code);
2718 register rtx value = 0;
2721 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2724 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2725 && XEXP (XEXP (x, 0), 0) == reg
2726 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2727 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2730 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2732 /* If REG occurs inside a MEM used in a bit-field reference,
2733 that is unacceptable. */
2734 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2735 return (rtx) (HOST_WIDE_INT) 1;
2739 return (rtx) (HOST_WIDE_INT) 1;
2741 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2745 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2749 return (rtx) (HOST_WIDE_INT) 1;
2754 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2756 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2760 return (rtx) (HOST_WIDE_INT) 1;
2768 /* Write information about registers and basic blocks into FILE.
2769 This is part of making a debugging dump. */
2772 dump_flow_info (file)
2776 static char *reg_class_names[] = REG_CLASS_NAMES;
2778 fprintf (file, "%d registers.\n", max_regno);
2780 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2783 enum reg_class class, altclass;
2784 fprintf (file, "\nRegister %d used %d times across %d insns",
2785 i, reg_n_refs[i], reg_live_length[i]);
2786 if (reg_basic_block[i] >= 0)
2787 fprintf (file, " in block %d", reg_basic_block[i]);
2788 if (reg_n_deaths[i] != 1)
2789 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2790 if (reg_n_calls_crossed[i] == 1)
2791 fprintf (file, "; crosses 1 call");
2792 else if (reg_n_calls_crossed[i])
2793 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2794 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2795 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2796 class = reg_preferred_class (i);
2797 altclass = reg_alternate_class (i);
2798 if (class != GENERAL_REGS || altclass != ALL_REGS)
2800 if (altclass == ALL_REGS || class == ALL_REGS)
2801 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2802 else if (altclass == NO_REGS)
2803 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2805 fprintf (file, "; pref %s, else %s",
2806 reg_class_names[(int) class],
2807 reg_class_names[(int) altclass]);
2809 if (REGNO_POINTER_FLAG (i))
2810 fprintf (file, "; pointer");
2811 fprintf (file, ".\n");
2813 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2814 for (i = 0; i < n_basic_blocks; i++)
2816 register rtx head, jump;
2818 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2820 INSN_UID (basic_block_head[i]),
2821 INSN_UID (basic_block_end[i]));
2822 /* The control flow graph's storage is freed
2823 now when flow_analysis returns.
2824 Don't try to print it if it is gone. */
2825 if (basic_block_drops_in)
2827 fprintf (file, "Reached from blocks: ");
2828 head = basic_block_head[i];
2829 if (GET_CODE (head) == CODE_LABEL)
2830 for (jump = LABEL_REFS (head);
2832 jump = LABEL_NEXTREF (jump))
2834 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2835 fprintf (file, " %d", from_block);
2837 if (basic_block_drops_in[i])
2838 fprintf (file, " previous");
2840 fprintf (file, "\nRegisters live at start:");
2841 for (regno = 0; regno < max_regno; regno++)
2843 register int offset = regno / REGSET_ELT_BITS;
2844 register REGSET_ELT_TYPE bit
2845 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2846 if (basic_block_live_at_start[i][offset] & bit)
2847 fprintf (file, " %d", regno);
2849 fprintf (file, "\n");
2851 fprintf (file, "\n");