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 /* Now delete the code for any basic blocks that can't be reached.
612 They can occur because jump_optimize does not recognize
613 unreachable loops as unreachable. */
615 for (i = 0; i < n_basic_blocks; i++)
618 insn = basic_block_head[i];
621 if (GET_CODE (insn) == BARRIER)
623 if (GET_CODE (insn) != NOTE)
625 PUT_CODE (insn, NOTE);
626 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
627 NOTE_SOURCE_FILE (insn) = 0;
629 if (insn == basic_block_end[i])
631 /* BARRIERs are between basic blocks, not part of one.
632 Delete a BARRIER if the preceding jump is deleted.
633 We cannot alter a BARRIER into a NOTE
634 because it is too short; but we can really delete
635 it because it is not part of a basic block. */
636 if (NEXT_INSN (insn) != 0
637 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
638 delete_insn (NEXT_INSN (insn));
641 insn = NEXT_INSN (insn);
643 /* Each time we delete some basic blocks,
644 see if there is a jump around them that is
645 being turned into a no-op. If so, delete it. */
647 if (block_live[i - 1])
650 for (j = i; j < n_basic_blocks; j++)
654 insn = basic_block_end[i - 1];
655 if (GET_CODE (insn) == JUMP_INSN
656 /* An unconditional jump is the only possibility
657 we must check for, since a conditional one
658 would make these blocks live. */
659 && simplejump_p (insn)
660 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
661 && INSN_UID (label) != 0
662 && BLOCK_NUM (label) == j)
664 PUT_CODE (insn, NOTE);
665 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
666 NOTE_SOURCE_FILE (insn) = 0;
667 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
669 delete_insn (NEXT_INSN (insn));
678 /* Return 1 if X contain a REG or MEM that is not in the constant pool. */
684 enum rtx_code code = GET_CODE (x);
690 && ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
691 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))))
694 fmt = GET_RTX_FORMAT (code);
695 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
698 && uses_reg_or_mem (XEXP (x, i)))
702 for (j = 0; j < XVECLEN (x, i); j++)
703 if (uses_reg_or_mem (XVECEXP (x, i, j)))
710 /* Check expression X for label references;
711 if one is found, add INSN to the label's chain of references.
713 CHECKDUP means check for and avoid creating duplicate references
714 from the same insn. Such duplicates do no serious harm but
715 can slow life analysis. CHECKDUP is set only when duplicates
719 mark_label_ref (x, insn, checkdup)
723 register RTX_CODE code;
727 /* We can be called with NULL when scanning label_value_list. */
732 if (code == LABEL_REF)
734 register rtx label = XEXP (x, 0);
736 if (GET_CODE (label) != CODE_LABEL)
738 /* If the label was never emitted, this insn is junk,
739 but avoid a crash trying to refer to BLOCK_NUM (label).
740 This can happen as a result of a syntax error
741 and a diagnostic has already been printed. */
742 if (INSN_UID (label) == 0)
744 CONTAINING_INSN (x) = insn;
745 /* if CHECKDUP is set, check for duplicate ref from same insn
748 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
749 if (CONTAINING_INSN (y) == insn)
751 LABEL_NEXTREF (x) = LABEL_REFS (label);
752 LABEL_REFS (label) = x;
753 block_live_static[BLOCK_NUM (label)] = 1;
757 fmt = GET_RTX_FORMAT (code);
758 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
761 mark_label_ref (XEXP (x, i), insn, 0);
765 for (j = 0; j < XVECLEN (x, i); j++)
766 mark_label_ref (XVECEXP (x, i, j), insn, 1);
771 /* Determine which registers are live at the start of each
772 basic block of the function whose first insn is F.
773 NREGS is the number of registers used in F.
774 We allocate the vector basic_block_live_at_start
775 and the regsets that it points to, and fill them with the data.
776 regset_size and regset_bytes are also set here. */
779 life_analysis (f, nregs)
786 /* For each basic block, a bitmask of regs
787 live on exit from the block. */
788 regset *basic_block_live_at_end;
789 /* For each basic block, a bitmask of regs
790 live on entry to a successor-block of this block.
791 If this does not match basic_block_live_at_end,
792 that must be updated, and the block must be rescanned. */
793 regset *basic_block_new_live_at_end;
794 /* For each basic block, a bitmask of regs
795 whose liveness at the end of the basic block
796 can make a difference in which regs are live on entry to the block.
797 These are the regs that are set within the basic block,
798 possibly excluding those that are used after they are set. */
799 regset *basic_block_significant;
803 struct obstack flow_obstack;
805 gcc_obstack_init (&flow_obstack);
809 bzero (regs_ever_live, sizeof regs_ever_live);
811 /* Allocate and zero out many data structures
812 that will record the data from lifetime analysis. */
814 allocate_for_life_analysis ();
816 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
817 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
819 /* Set up several regset-vectors used internally within this function.
820 Their meanings are documented above, with their declarations. */
822 basic_block_live_at_end
823 = (regset *) alloca (n_basic_blocks * sizeof (regset));
825 /* Don't use alloca since that leads to a crash rather than an error message
826 if there isn't enough space.
827 Don't use oballoc since we may need to allocate other things during
828 this function on the temporary obstack. */
829 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
830 bzero ((char *) tem, n_basic_blocks * regset_bytes);
831 init_regset_vector (basic_block_live_at_end, tem,
832 n_basic_blocks, regset_bytes);
834 basic_block_new_live_at_end
835 = (regset *) alloca (n_basic_blocks * sizeof (regset));
836 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
837 bzero ((char *) tem, n_basic_blocks * regset_bytes);
838 init_regset_vector (basic_block_new_live_at_end, tem,
839 n_basic_blocks, regset_bytes);
841 basic_block_significant
842 = (regset *) alloca (n_basic_blocks * sizeof (regset));
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_significant, tem,
846 n_basic_blocks, regset_bytes);
848 /* Record which insns refer to any volatile memory
849 or for any reason can't be deleted just because they are dead stores.
850 Also, delete any insns that copy a register to itself. */
852 for (insn = f; insn; insn = NEXT_INSN (insn))
854 enum rtx_code code1 = GET_CODE (insn);
855 if (code1 == CALL_INSN)
856 INSN_VOLATILE (insn) = 1;
857 else if (code1 == INSN || code1 == JUMP_INSN)
859 /* Delete (in effect) any obvious no-op moves. */
860 if (GET_CODE (PATTERN (insn)) == SET
861 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
862 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
863 && REGNO (SET_DEST (PATTERN (insn))) ==
864 REGNO (SET_SRC (PATTERN (insn)))
865 /* Insns carrying these notes are useful later on. */
866 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
868 PUT_CODE (insn, NOTE);
869 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
870 NOTE_SOURCE_FILE (insn) = 0;
872 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
874 /* If nothing but SETs of registers to themselves,
875 this insn can also be deleted. */
876 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
878 rtx tem = XVECEXP (PATTERN (insn), 0, i);
880 if (GET_CODE (tem) == USE
881 || GET_CODE (tem) == CLOBBER)
884 if (GET_CODE (tem) != SET
885 || GET_CODE (SET_DEST (tem)) != REG
886 || GET_CODE (SET_SRC (tem)) != REG
887 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
891 if (i == XVECLEN (PATTERN (insn), 0)
892 /* Insns carrying these notes are useful later on. */
893 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
895 PUT_CODE (insn, NOTE);
896 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
897 NOTE_SOURCE_FILE (insn) = 0;
900 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
902 else if (GET_CODE (PATTERN (insn)) != USE)
903 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
904 /* A SET that makes space on the stack cannot be dead.
905 (Such SETs occur only for allocating variable-size data,
906 so they will always have a PLUS or MINUS according to the
907 direction of stack growth.)
908 Even if this function never uses this stack pointer value,
909 signal handlers do! */
910 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
911 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
912 #ifdef STACK_GROWS_DOWNWARD
913 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
915 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
917 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
918 INSN_VOLATILE (insn) = 1;
922 if (n_basic_blocks > 0)
923 #ifdef EXIT_IGNORE_STACK
924 if (! EXIT_IGNORE_STACK
925 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
928 /* If exiting needs the right stack value,
929 consider the stack pointer live at the end of the function. */
930 basic_block_live_at_end[n_basic_blocks - 1]
931 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
932 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
933 basic_block_new_live_at_end[n_basic_blocks - 1]
934 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
935 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
938 /* Mark the frame pointer is needed at the end of the function. If
939 we end up eliminating it, it will be removed from the live list
940 of each basic block by reload. */
942 if (n_basic_blocks > 0)
944 basic_block_live_at_end[n_basic_blocks - 1]
945 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
946 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
947 basic_block_new_live_at_end[n_basic_blocks - 1]
948 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
949 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
950 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
951 /* If they are different, also mark the hard frame pointer as live */
952 basic_block_live_at_end[n_basic_blocks - 1]
953 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
954 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
956 basic_block_new_live_at_end[n_basic_blocks - 1]
957 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
958 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
963 /* Mark all global registers as being live at the end of the function
964 since they may be referenced by our caller. */
966 if (n_basic_blocks > 0)
967 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
970 basic_block_live_at_end[n_basic_blocks - 1]
971 [i / REGSET_ELT_BITS]
972 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
973 basic_block_new_live_at_end[n_basic_blocks - 1]
974 [i / REGSET_ELT_BITS]
975 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
978 /* Propagate life info through the basic blocks
979 around the graph of basic blocks.
981 This is a relaxation process: each time a new register
982 is live at the end of the basic block, we must scan the block
983 to determine which registers are, as a consequence, live at the beginning
984 of that block. These registers must then be marked live at the ends
985 of all the blocks that can transfer control to that block.
986 The process continues until it reaches a fixed point. */
993 for (i = n_basic_blocks - 1; i >= 0; i--)
995 int consider = first_pass;
996 int must_rescan = first_pass;
1001 /* Set CONSIDER if this block needs thinking about at all
1002 (that is, if the regs live now at the end of it
1003 are not the same as were live at the end of it when
1004 we last thought about it).
1005 Set must_rescan if it needs to be thought about
1006 instruction by instruction (that is, if any additional
1007 reg that is live at the end now but was not live there before
1008 is one of the significant regs of this basic block). */
1010 for (j = 0; j < regset_size; j++)
1012 register REGSET_ELT_TYPE x
1013 = (basic_block_new_live_at_end[i][j]
1014 & ~basic_block_live_at_end[i][j]);
1017 if (x & basic_block_significant[i][j])
1029 /* The live_at_start of this block may be changing,
1030 so another pass will be required after this one. */
1035 /* No complete rescan needed;
1036 just record those variables newly known live at end
1037 as live at start as well. */
1038 for (j = 0; j < regset_size; j++)
1040 register REGSET_ELT_TYPE x
1041 = (basic_block_new_live_at_end[i][j]
1042 & ~basic_block_live_at_end[i][j]);
1043 basic_block_live_at_start[i][j] |= x;
1044 basic_block_live_at_end[i][j] |= x;
1049 /* Update the basic_block_live_at_start
1050 by propagation backwards through the block. */
1051 bcopy ((char *) basic_block_new_live_at_end[i],
1052 (char *) basic_block_live_at_end[i], regset_bytes);
1053 bcopy ((char *) basic_block_live_at_end[i],
1054 (char *) basic_block_live_at_start[i], regset_bytes);
1055 propagate_block (basic_block_live_at_start[i],
1056 basic_block_head[i], basic_block_end[i], 0,
1057 first_pass ? basic_block_significant[i]
1063 register rtx jump, head;
1064 /* Update the basic_block_new_live_at_end's of the block
1065 that falls through into this one (if any). */
1066 head = basic_block_head[i];
1067 jump = PREV_INSN (head);
1068 if (basic_block_drops_in[i])
1070 register int from_block = BLOCK_NUM (jump);
1072 for (j = 0; j < regset_size; j++)
1073 basic_block_new_live_at_end[from_block][j]
1074 |= basic_block_live_at_start[i][j];
1076 /* Update the basic_block_new_live_at_end's of
1077 all the blocks that jump to this one. */
1078 if (GET_CODE (head) == CODE_LABEL)
1079 for (jump = LABEL_REFS (head);
1081 jump = LABEL_NEXTREF (jump))
1083 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1085 for (j = 0; j < regset_size; j++)
1086 basic_block_new_live_at_end[from_block][j]
1087 |= basic_block_live_at_start[i][j];
1097 /* The only pseudos that are live at the beginning of the function are
1098 those that were not set anywhere in the function. local-alloc doesn't
1099 know how to handle these correctly, so mark them as not local to any
1102 if (n_basic_blocks > 0)
1103 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1104 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1105 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1106 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1108 /* Now the life information is accurate.
1109 Make one more pass over each basic block
1110 to delete dead stores, create autoincrement addressing
1111 and record how many times each register is used, is set, or dies.
1113 To save time, we operate directly in basic_block_live_at_end[i],
1114 thus destroying it (in fact, converting it into a copy of
1115 basic_block_live_at_start[i]). This is ok now because
1116 basic_block_live_at_end[i] is no longer used past this point. */
1120 for (i = 0; i < n_basic_blocks; i++)
1122 propagate_block (basic_block_live_at_end[i],
1123 basic_block_head[i], basic_block_end[i], 1,
1131 /* Something live during a setjmp should not be put in a register
1132 on certain machines which restore regs from stack frames
1133 rather than from the jmpbuf.
1134 But we don't need to do this for the user's variables, since
1135 ANSI says only volatile variables need this. */
1136 #ifdef LONGJMP_RESTORE_FROM_STACK
1137 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1138 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1139 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1140 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1142 reg_live_length[i] = -1;
1143 reg_basic_block[i] = -1;
1148 /* We have a problem with any pseudoreg that
1149 lives across the setjmp. ANSI says that if a
1150 user variable does not change in value
1151 between the setjmp and the longjmp, then the longjmp preserves it.
1152 This includes longjmp from a place where the pseudo appears dead.
1153 (In principle, the value still exists if it is in scope.)
1154 If the pseudo goes in a hard reg, some other value may occupy
1155 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1156 Conclusion: such a pseudo must not go in a hard reg. */
1157 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1158 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1159 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1160 && regno_reg_rtx[i] != 0)
1162 reg_live_length[i] = -1;
1163 reg_basic_block[i] = -1;
1166 obstack_free (&flow_obstack, NULL_PTR);
1169 /* Subroutines of life analysis. */
1171 /* Allocate the permanent data structures that represent the results
1172 of life analysis. Not static since used also for stupid life analysis. */
1175 allocate_for_life_analysis ()
1178 register regset tem;
1180 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1181 regset_bytes = regset_size * sizeof (*(regset)0);
1183 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1184 bzero ((char *) reg_n_refs, max_regno * sizeof (int));
1186 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1187 bzero ((char *) reg_n_sets, max_regno * sizeof (short));
1189 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1190 bzero ((char *) reg_n_deaths, max_regno * sizeof (short));
1192 reg_changes_size = (char *) oballoc (max_regno * sizeof (char));
1193 bzero (reg_changes_size, max_regno * sizeof (char));;
1195 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1196 bzero ((char *) reg_live_length, max_regno * sizeof (int));
1198 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1199 bzero ((char *) reg_n_calls_crossed, max_regno * sizeof (int));
1201 reg_basic_block = (int *) oballoc (max_regno * sizeof (int));
1202 for (i = 0; i < max_regno; i++)
1203 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1205 basic_block_live_at_start
1206 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1207 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1208 bzero ((char *) tem, n_basic_blocks * regset_bytes);
1209 init_regset_vector (basic_block_live_at_start, tem,
1210 n_basic_blocks, regset_bytes);
1212 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1213 bzero ((char *) regs_live_at_setjmp, regset_bytes);
1216 /* Make each element of VECTOR point at a regset,
1217 taking the space for all those regsets from SPACE.
1218 SPACE is of type regset, but it is really as long as NELTS regsets.
1219 BYTES_PER_ELT is the number of bytes in one regset. */
1222 init_regset_vector (vector, space, nelts, bytes_per_elt)
1229 register regset p = space;
1231 for (i = 0; i < nelts; i++)
1234 p += bytes_per_elt / sizeof (*p);
1238 /* Compute the registers live at the beginning of a basic block
1239 from those live at the end.
1241 When called, OLD contains those live at the end.
1242 On return, it contains those live at the beginning.
1243 FIRST and LAST are the first and last insns of the basic block.
1245 FINAL is nonzero if we are doing the final pass which is not
1246 for computing the life info (since that has already been done)
1247 but for acting on it. On this pass, we delete dead stores,
1248 set up the logical links and dead-variables lists of instructions,
1249 and merge instructions for autoincrement and autodecrement addresses.
1251 SIGNIFICANT is nonzero only the first time for each basic block.
1252 If it is nonzero, it points to a regset in which we store
1253 a 1 for each register that is set within the block.
1255 BNUM is the number of the basic block. */
1258 propagate_block (old, first, last, final, significant, bnum)
1259 register regset old;
1271 /* The following variables are used only if FINAL is nonzero. */
1272 /* This vector gets one element for each reg that has been live
1273 at any point in the basic block that has been scanned so far.
1274 SOMETIMES_MAX says how many elements are in use so far.
1275 In each element, OFFSET is the byte-number within a regset
1276 for the register described by the element, and BIT is a mask
1277 for that register's bit within the byte. */
1278 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1279 int sometimes_max = 0;
1280 /* This regset has 1 for each reg that we have seen live so far.
1281 It and REGS_SOMETIMES_LIVE are updated together. */
1284 /* The loop depth may change in the middle of a basic block. Since we
1285 scan from end to beginning, we start with the depth at the end of the
1286 current basic block, and adjust as we pass ends and starts of loops. */
1287 loop_depth = basic_block_loop_depth[bnum];
1289 dead = (regset) alloca (regset_bytes);
1290 live = (regset) alloca (regset_bytes);
1295 /* Include any notes at the end of the block in the scan.
1296 This is in case the block ends with a call to setjmp. */
1298 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1300 /* Look for loop boundaries, we are going forward here. */
1301 last = NEXT_INSN (last);
1302 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1304 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1310 register int i, offset;
1311 REGSET_ELT_TYPE bit;
1314 maxlive = (regset) alloca (regset_bytes);
1315 bcopy ((char *) old, (char *) maxlive, regset_bytes);
1317 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1319 /* Process the regs live at the end of the block.
1320 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1321 Also mark them as not local to any one basic block. */
1323 for (offset = 0, i = 0; offset < regset_size; offset++)
1324 for (bit = 1; bit; bit <<= 1, i++)
1328 if (old[offset] & bit)
1330 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1331 regs_sometimes_live[sometimes_max].offset = offset;
1332 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1338 /* Scan the block an insn at a time from end to beginning. */
1340 for (insn = last; ; insn = prev)
1342 prev = PREV_INSN (insn);
1344 /* Look for loop boundaries, remembering that we are going backwards. */
1345 if (GET_CODE (insn) == NOTE
1346 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1348 else if (GET_CODE (insn) == NOTE
1349 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1352 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1353 Abort now rather than setting register status incorrectly. */
1354 if (loop_depth == 0)
1357 /* If this is a call to `setjmp' et al,
1358 warn if any non-volatile datum is live. */
1360 if (final && GET_CODE (insn) == NOTE
1361 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1364 for (i = 0; i < regset_size; i++)
1365 regs_live_at_setjmp[i] |= old[i];
1368 /* Update the life-status of regs for this insn.
1369 First DEAD gets which regs are set in this insn
1370 then LIVE gets which regs are used in this insn.
1371 Then the regs live before the insn
1372 are those live after, with DEAD regs turned off,
1373 and then LIVE regs turned on. */
1375 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1378 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1380 = (insn_dead_p (PATTERN (insn), old, 0)
1381 /* Don't delete something that refers to volatile storage! */
1382 && ! INSN_VOLATILE (insn));
1384 = (insn_is_dead && note != 0
1385 && libcall_dead_p (PATTERN (insn), old, note, insn));
1387 /* If an instruction consists of just dead store(s) on final pass,
1388 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1389 We could really delete it with delete_insn, but that
1390 can cause trouble for first or last insn in a basic block. */
1391 if (final && insn_is_dead)
1393 PUT_CODE (insn, NOTE);
1394 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1395 NOTE_SOURCE_FILE (insn) = 0;
1397 /* CC0 is now known to be dead. Either this insn used it,
1398 in which case it doesn't anymore, or clobbered it,
1399 so the next insn can't use it. */
1402 /* If this insn is copying the return value from a library call,
1403 delete the entire library call. */
1404 if (libcall_is_dead)
1406 rtx first = XEXP (note, 0);
1408 while (INSN_DELETED_P (first))
1409 first = NEXT_INSN (first);
1414 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1415 NOTE_SOURCE_FILE (p) = 0;
1421 for (i = 0; i < regset_size; i++)
1423 dead[i] = 0; /* Faster than bzero here */
1424 live[i] = 0; /* since regset_size is usually small */
1427 /* See if this is an increment or decrement that can be
1428 merged into a following memory address. */
1431 register rtx x = PATTERN (insn);
1432 /* Does this instruction increment or decrement a register? */
1433 if (final && GET_CODE (x) == SET
1434 && GET_CODE (SET_DEST (x)) == REG
1435 && (GET_CODE (SET_SRC (x)) == PLUS
1436 || GET_CODE (SET_SRC (x)) == MINUS)
1437 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1438 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1439 /* Ok, look for a following memory ref we can combine with.
1440 If one is found, change the memory ref to a PRE_INC
1441 or PRE_DEC, cancel this insn, and return 1.
1442 Return 0 if nothing has been done. */
1443 && try_pre_increment_1 (insn))
1446 #endif /* AUTO_INC_DEC */
1448 /* If this is not the final pass, and this insn is copying the
1449 value of a library call and it's dead, don't scan the
1450 insns that perform the library call, so that the call's
1451 arguments are not marked live. */
1452 if (libcall_is_dead)
1454 /* Mark the dest reg as `significant'. */
1455 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1457 insn = XEXP (note, 0);
1458 prev = PREV_INSN (insn);
1460 else if (GET_CODE (PATTERN (insn)) == SET
1461 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1462 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1463 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1464 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1465 /* We have an insn to pop a constant amount off the stack.
1466 (Such insns use PLUS regardless of the direction of the stack,
1467 and any insn to adjust the stack by a constant is always a pop.)
1468 These insns, if not dead stores, have no effect on life. */
1472 /* LIVE gets the regs used in INSN;
1473 DEAD gets those set by it. Dead insns don't make anything
1476 mark_set_regs (old, dead, PATTERN (insn),
1477 final ? insn : NULL_RTX, significant);
1479 /* If an insn doesn't use CC0, it becomes dead since we
1480 assume that every insn clobbers it. So show it dead here;
1481 mark_used_regs will set it live if it is referenced. */
1485 mark_used_regs (old, live, PATTERN (insn), final, insn);
1487 /* Sometimes we may have inserted something before INSN (such as
1488 a move) when we make an auto-inc. So ensure we will scan
1491 prev = PREV_INSN (insn);
1494 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1500 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1502 note = XEXP (note, 1))
1503 if (GET_CODE (XEXP (note, 0)) == USE)
1504 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1507 /* Each call clobbers all call-clobbered regs that are not
1508 global. Note that the function-value reg is a
1509 call-clobbered reg, and mark_set_regs has already had
1510 a chance to handle it. */
1512 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1513 if (call_used_regs[i] && ! global_regs[i])
1514 dead[i / REGSET_ELT_BITS]
1515 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1517 /* The stack ptr is used (honorarily) by a CALL insn. */
1518 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1519 |= ((REGSET_ELT_TYPE) 1
1520 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1522 /* Calls may also reference any of the global registers,
1523 so they are made live. */
1524 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1526 mark_used_regs (old, live,
1527 gen_rtx (REG, reg_raw_mode[i], i),
1530 /* Calls also clobber memory. */
1534 /* Update OLD for the registers used or set. */
1535 for (i = 0; i < regset_size; i++)
1541 if (GET_CODE (insn) == CALL_INSN && final)
1543 /* Any regs live at the time of a call instruction
1544 must not go in a register clobbered by calls.
1545 Find all regs now live and record this for them. */
1547 register struct sometimes *p = regs_sometimes_live;
1549 for (i = 0; i < sometimes_max; i++, p++)
1550 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1551 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1555 /* On final pass, add any additional sometimes-live regs
1556 into MAXLIVE and REGS_SOMETIMES_LIVE.
1557 Also update counts of how many insns each reg is live at. */
1561 for (i = 0; i < regset_size; i++)
1563 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1569 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1570 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1572 regs_sometimes_live[sometimes_max].offset = i;
1573 regs_sometimes_live[sometimes_max].bit = regno;
1574 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1581 register struct sometimes *p = regs_sometimes_live;
1582 for (i = 0; i < sometimes_max; i++, p++)
1584 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1585 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1595 if (num_scratch > max_scratch)
1596 max_scratch = num_scratch;
1599 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1600 (SET expressions whose destinations are registers dead after the insn).
1601 NEEDED is the regset that says which regs are alive after the insn.
1603 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1606 insn_dead_p (x, needed, call_ok)
1611 register RTX_CODE code = GET_CODE (x);
1612 /* If setting something that's a reg or part of one,
1613 see if that register's altered value will be live. */
1617 register rtx r = SET_DEST (x);
1618 /* A SET that is a subroutine call cannot be dead. */
1619 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1623 if (GET_CODE (r) == CC0)
1627 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1628 && rtx_equal_p (r, last_mem_set))
1631 while (GET_CODE (r) == SUBREG
1632 || GET_CODE (r) == STRICT_LOW_PART
1633 || GET_CODE (r) == ZERO_EXTRACT
1634 || GET_CODE (r) == SIGN_EXTRACT)
1637 if (GET_CODE (r) == REG)
1639 register int regno = REGNO (r);
1640 register int offset = regno / REGSET_ELT_BITS;
1641 register REGSET_ELT_TYPE bit
1642 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1644 /* Don't delete insns to set global regs. */
1645 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1646 /* Make sure insns to set frame pointer aren't deleted. */
1647 || regno == FRAME_POINTER_REGNUM
1648 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1649 || regno == HARD_FRAME_POINTER_REGNUM
1651 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1652 /* Make sure insns to set arg pointer are never deleted
1653 (if the arg pointer isn't fixed, there will be a USE for
1654 it, so we can treat it normally). */
1655 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1657 || (needed[offset] & bit) != 0)
1660 /* If this is a hard register, verify that subsequent words are
1662 if (regno < FIRST_PSEUDO_REGISTER)
1664 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1667 if ((needed[(regno + n) / REGSET_ELT_BITS]
1668 & ((REGSET_ELT_TYPE) 1
1669 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1676 /* If performing several activities,
1677 insn is dead if each activity is individually dead.
1678 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1679 that's inside a PARALLEL doesn't make the insn worth keeping. */
1680 else if (code == PARALLEL)
1682 register int i = XVECLEN (x, 0);
1683 for (i--; i >= 0; i--)
1685 rtx elt = XVECEXP (x, 0, i);
1686 if (!insn_dead_p (elt, needed, call_ok)
1687 && GET_CODE (elt) != CLOBBER
1688 && GET_CODE (elt) != USE)
1693 /* We do not check CLOBBER or USE here.
1694 An insn consisting of just a CLOBBER or just a USE
1695 should not be deleted. */
1699 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1700 return 1 if the entire library call is dead.
1701 This is true if X copies a register (hard or pseudo)
1702 and if the hard return reg of the call insn is dead.
1703 (The caller should have tested the destination of X already for death.)
1705 If this insn doesn't just copy a register, then we don't
1706 have an ordinary libcall. In that case, cse could not have
1707 managed to substitute the source for the dest later on,
1708 so we can assume the libcall is dead.
1710 NEEDED is the bit vector of pseudoregs live before this insn.
1711 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1714 libcall_dead_p (x, needed, note, insn)
1720 register RTX_CODE code = GET_CODE (x);
1724 register rtx r = SET_SRC (x);
1725 if (GET_CODE (r) == REG)
1727 rtx call = XEXP (note, 0);
1730 /* Find the call insn. */
1731 while (call != insn && GET_CODE (call) != CALL_INSN)
1732 call = NEXT_INSN (call);
1734 /* If there is none, do nothing special,
1735 since ordinary death handling can understand these insns. */
1739 /* See if the hard reg holding the value is dead.
1740 If this is a PARALLEL, find the call within it. */
1741 call = PATTERN (call);
1742 if (GET_CODE (call) == PARALLEL)
1744 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1745 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1746 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1749 /* This may be a library call that is returning a value
1750 via invisible pointer. Do nothing special, since
1751 ordinary death handling can understand these insns. */
1755 call = XVECEXP (call, 0, i);
1758 return insn_dead_p (call, needed, 1);
1764 /* Return 1 if register REGNO was used before it was set.
1765 In other words, if it is live at function entry.
1766 Don't count global regster variables, though. */
1769 regno_uninitialized (regno)
1772 if (n_basic_blocks == 0
1773 || (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1776 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1777 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1780 /* 1 if register REGNO was alive at a place where `setjmp' was called
1781 and was set more than once or is an argument.
1782 Such regs may be clobbered by `longjmp'. */
1785 regno_clobbered_at_setjmp (regno)
1788 if (n_basic_blocks == 0)
1791 return ((reg_n_sets[regno] > 1
1792 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1793 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1794 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1795 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1798 /* Process the registers that are set within X.
1799 Their bits are set to 1 in the regset DEAD,
1800 because they are dead prior to this insn.
1802 If INSN is nonzero, it is the insn being processed
1803 and the fact that it is nonzero implies this is the FINAL pass
1804 in propagate_block. In this case, various info about register
1805 usage is stored, LOG_LINKS fields of insns are set up. */
1808 mark_set_regs (needed, dead, x, insn, significant)
1815 register RTX_CODE code = GET_CODE (x);
1817 if (code == SET || code == CLOBBER)
1818 mark_set_1 (needed, dead, x, insn, significant);
1819 else if (code == PARALLEL)
1822 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1824 code = GET_CODE (XVECEXP (x, 0, i));
1825 if (code == SET || code == CLOBBER)
1826 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1831 /* Process a single SET rtx, X. */
1834 mark_set_1 (needed, dead, x, insn, significant)
1842 register rtx reg = SET_DEST (x);
1844 /* Modifying just one hardware register of a multi-reg value
1845 or just a byte field of a register
1846 does not mean the value from before this insn is now dead.
1847 But it does mean liveness of that register at the end of the block
1850 Within mark_set_1, however, we treat it as if the register is
1851 indeed modified. mark_used_regs will, however, also treat this
1852 register as being used. Thus, we treat these insns as setting a
1853 new value for the register as a function of its old value. This
1854 cases LOG_LINKS to be made appropriately and this will help combine. */
1856 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1857 || GET_CODE (reg) == SIGN_EXTRACT
1858 || GET_CODE (reg) == STRICT_LOW_PART)
1859 reg = XEXP (reg, 0);
1861 /* If we are writing into memory or into a register mentioned in the
1862 address of the last thing stored into memory, show we don't know
1863 what the last store was. If we are writing memory, save the address
1864 unless it is volatile. */
1865 if (GET_CODE (reg) == MEM
1866 || (GET_CODE (reg) == REG
1867 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1870 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1871 /* There are no REG_INC notes for SP, so we can't assume we'll see
1872 everything that invalidates it. To be safe, don't eliminate any
1873 stores though SP; none of them should be redundant anyway. */
1874 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1877 if (GET_CODE (reg) == REG
1878 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1879 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1880 && regno != HARD_FRAME_POINTER_REGNUM
1882 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1883 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1885 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1886 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1888 register int offset = regno / REGSET_ELT_BITS;
1889 register REGSET_ELT_TYPE bit
1890 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1891 REGSET_ELT_TYPE all_needed = (needed[offset] & bit);
1892 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
1894 /* Mark it as a significant register for this basic block. */
1896 significant[offset] |= bit;
1898 /* Mark it as as dead before this insn. */
1899 dead[offset] |= bit;
1901 /* A hard reg in a wide mode may really be multiple registers.
1902 If so, mark all of them just like the first. */
1903 if (regno < FIRST_PSEUDO_REGISTER)
1907 /* Nothing below is needed for the stack pointer; get out asap.
1908 Eg, log links aren't needed, since combine won't use them. */
1909 if (regno == STACK_POINTER_REGNUM)
1912 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1916 significant[(regno + n) / REGSET_ELT_BITS]
1917 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1918 dead[(regno + n) / REGSET_ELT_BITS]
1919 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1921 |= (needed[(regno + n) / REGSET_ELT_BITS]
1922 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1924 &= (needed[(regno + n) / REGSET_ELT_BITS]
1925 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1928 /* Additional data to record if this is the final pass. */
1931 register rtx y = reg_next_use[regno];
1932 register int blocknum = BLOCK_NUM (insn);
1934 /* The next use is no longer "next", since a store intervenes. */
1935 reg_next_use[regno] = 0;
1937 /* If this is a hard reg, record this function uses the reg. */
1939 if (regno < FIRST_PSEUDO_REGISTER)
1942 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
1944 for (i = regno; i < endregno; i++)
1946 regs_ever_live[i] = 1;
1952 /* Keep track of which basic blocks each reg appears in. */
1954 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
1955 reg_basic_block[regno] = blocknum;
1956 else if (reg_basic_block[regno] != blocknum)
1957 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
1959 /* Count (weighted) references, stores, etc. This counts a
1960 register twice if it is modified, but that is correct. */
1961 reg_n_sets[regno]++;
1963 reg_n_refs[regno] += loop_depth;
1965 /* The insns where a reg is live are normally counted
1966 elsewhere, but we want the count to include the insn
1967 where the reg is set, and the normal counting mechanism
1968 would not count it. */
1969 reg_live_length[regno]++;
1974 /* Make a logical link from the next following insn
1975 that uses this register, back to this insn.
1976 The following insns have already been processed.
1978 We don't build a LOG_LINK for hard registers containing
1979 in ASM_OPERANDs. If these registers get replaced,
1980 we might wind up changing the semantics of the insn,
1981 even if reload can make what appear to be valid assignments
1983 if (y && (BLOCK_NUM (y) == blocknum)
1984 && (regno >= FIRST_PSEUDO_REGISTER
1985 || asm_noperands (PATTERN (y)) < 0))
1987 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
1989 else if (! some_needed)
1991 /* Note that dead stores have already been deleted when possible
1992 If we get here, we have found a dead store that cannot
1993 be eliminated (because the same insn does something useful).
1994 Indicate this by marking the reg being set as dying here. */
1996 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
1997 reg_n_deaths[REGNO (reg)]++;
2001 /* This is a case where we have a multi-word hard register
2002 and some, but not all, of the words of the register are
2003 needed in subsequent insns. Write REG_UNUSED notes
2004 for those parts that were not needed. This case should
2009 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2011 if ((needed[(regno + i) / REGSET_ELT_BITS]
2012 & ((REGSET_ELT_TYPE) 1
2013 << ((regno + i) % REGSET_ELT_BITS))) == 0)
2015 = gen_rtx (EXPR_LIST, REG_UNUSED,
2016 gen_rtx (REG, reg_raw_mode[regno + i],
2022 else if (GET_CODE (reg) == REG)
2023 reg_next_use[regno] = 0;
2025 /* If this is the last pass and this is a SCRATCH, show it will be dying
2026 here and count it. */
2027 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2030 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2037 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2041 find_auto_inc (needed, x, insn)
2046 rtx addr = XEXP (x, 0);
2047 HOST_WIDE_INT offset = 0;
2050 /* Here we detect use of an index register which might be good for
2051 postincrement, postdecrement, preincrement, or predecrement. */
2053 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2054 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2056 if (GET_CODE (addr) == REG)
2059 register int size = GET_MODE_SIZE (GET_MODE (x));
2062 int regno = REGNO (addr);
2064 /* Is the next use an increment that might make auto-increment? */
2065 if ((incr = reg_next_use[regno]) != 0
2066 && (set = single_set (incr)) != 0
2067 && GET_CODE (set) == SET
2068 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2069 /* Can't add side effects to jumps; if reg is spilled and
2070 reloaded, there's no way to store back the altered value. */
2071 && GET_CODE (insn) != JUMP_INSN
2072 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2073 && XEXP (y, 0) == addr
2074 && GET_CODE (XEXP (y, 1)) == CONST_INT
2076 #ifdef HAVE_POST_INCREMENT
2077 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2079 #ifdef HAVE_POST_DECREMENT
2080 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2082 #ifdef HAVE_PRE_INCREMENT
2083 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2085 #ifdef HAVE_PRE_DECREMENT
2086 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2089 /* Make sure this reg appears only once in this insn. */
2090 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2091 use != 0 && use != (rtx) 1))
2093 rtx q = SET_DEST (set);
2094 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2095 ? (offset ? PRE_INC : POST_INC)
2096 : (offset ? PRE_DEC : POST_DEC));
2098 if (dead_or_set_p (incr, addr))
2100 /* This is the simple case. Try to make the auto-inc. If
2101 we can't, we are done. Otherwise, we will do any
2102 needed updates below. */
2103 if (! validate_change (insn, &XEXP (x, 0),
2104 gen_rtx (inc_code, Pmode, addr),
2108 else if (GET_CODE (q) == REG
2109 /* PREV_INSN used here to check the semi-open interval
2111 && ! reg_used_between_p (q, PREV_INSN (insn), incr))
2113 /* We have *p followed sometime later by q = p+size.
2114 Both p and q must be live afterward,
2115 and q is not used between INSN and it's assignment.
2116 Change it to q = p, ...*q..., q = q+size.
2117 Then fall into the usual case. */
2121 emit_move_insn (q, addr);
2122 insns = get_insns ();
2125 /* If anything in INSNS have UID's that don't fit within the
2126 extra space we allocate earlier, we can't make this auto-inc.
2127 This should never happen. */
2128 for (temp = insns; temp; temp = NEXT_INSN (temp))
2130 if (INSN_UID (temp) > max_uid_for_flow)
2132 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2135 /* If we can't make the auto-inc, or can't make the
2136 replacement into Y, exit. There's no point in making
2137 the change below if we can't do the auto-inc and doing
2138 so is not correct in the pre-inc case. */
2140 validate_change (insn, &XEXP (x, 0),
2141 gen_rtx (inc_code, Pmode, q),
2143 validate_change (incr, &XEXP (y, 0), q, 1);
2144 if (! apply_change_group ())
2147 /* We now know we'll be doing this change, so emit the
2148 new insn(s) and do the updates. */
2149 emit_insns_before (insns, insn);
2151 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2152 basic_block_head[BLOCK_NUM (insn)] = insns;
2154 /* INCR will become a NOTE and INSN won't contain a
2155 use of ADDR. If a use of ADDR was just placed in
2156 the insn before INSN, make that the next use.
2157 Otherwise, invalidate it. */
2158 if (GET_CODE (PREV_INSN (insn)) == INSN
2159 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2160 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2161 reg_next_use[regno] = PREV_INSN (insn);
2163 reg_next_use[regno] = 0;
2168 /* REGNO is now used in INCR which is below INSN, but
2169 it previously wasn't live here. If we don't mark
2170 it as needed, we'll put a REG_DEAD note for it
2171 on this insn, which is incorrect. */
2172 needed[regno / REGSET_ELT_BITS]
2173 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2175 /* If there are any calls between INSN and INCR, show
2176 that REGNO now crosses them. */
2177 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2178 if (GET_CODE (temp) == CALL_INSN)
2179 reg_n_calls_crossed[regno]++;
2182 /* If we haven't returned, it means we were able to make the
2183 auto-inc, so update the status. First, record that this insn
2184 has an implicit side effect. */
2187 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2189 /* Modify the old increment-insn to simply copy
2190 the already-incremented value of our register. */
2191 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2194 /* If that makes it a no-op (copying the register into itself) delete
2195 it so it won't appear to be a "use" and a "set" of this
2197 if (SET_DEST (set) == addr)
2199 PUT_CODE (incr, NOTE);
2200 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2201 NOTE_SOURCE_FILE (incr) = 0;
2204 if (regno >= FIRST_PSEUDO_REGISTER)
2206 /* Count an extra reference to the reg. When a reg is
2207 incremented, spilling it is worse, so we want to make
2208 that less likely. */
2209 reg_n_refs[regno] += loop_depth;
2211 /* Count the increment as a setting of the register,
2212 even though it isn't a SET in rtl. */
2213 reg_n_sets[regno]++;
2218 #endif /* AUTO_INC_DEC */
2220 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2221 This is done assuming the registers needed from X
2222 are those that have 1-bits in NEEDED.
2224 On the final pass, FINAL is 1. This means try for autoincrement
2225 and count the uses and deaths of each pseudo-reg.
2227 INSN is the containing instruction. If INSN is dead, this function is not
2231 mark_used_regs (needed, live, x, final, insn)
2238 register RTX_CODE code;
2243 code = GET_CODE (x);
2264 /* If we are clobbering a MEM, mark any registers inside the address
2266 if (GET_CODE (XEXP (x, 0)) == MEM)
2267 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2271 /* Invalidate the data for the last MEM stored. We could do this only
2272 if the addresses conflict, but this doesn't seem worthwhile. */
2277 find_auto_inc (needed, x, insn);
2282 if (GET_CODE (SUBREG_REG (x)) == REG
2283 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2284 && (GET_MODE_SIZE (GET_MODE (x))
2285 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
2286 && (INTEGRAL_MODE_P (GET_MODE (x))
2287 || INTEGRAL_MODE_P (GET_MODE (SUBREG_REG (x)))))
2288 reg_changes_size[REGNO (SUBREG_REG (x))] = 1;
2290 /* While we're here, optimize this case. */
2293 /* ... fall through ... */
2296 /* See a register other than being set
2297 => mark it as needed. */
2301 register int offset = regno / REGSET_ELT_BITS;
2302 register REGSET_ELT_TYPE bit
2303 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2304 REGSET_ELT_TYPE all_needed = needed[offset] & bit;
2305 REGSET_ELT_TYPE some_needed = needed[offset] & bit;
2307 live[offset] |= bit;
2308 /* A hard reg in a wide mode may really be multiple registers.
2309 If so, mark all of them just like the first. */
2310 if (regno < FIRST_PSEUDO_REGISTER)
2314 /* For stack ptr or fixed arg pointer,
2315 nothing below can be necessary, so waste no more time. */
2316 if (regno == STACK_POINTER_REGNUM
2317 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2318 || regno == HARD_FRAME_POINTER_REGNUM
2320 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2321 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2323 || regno == FRAME_POINTER_REGNUM)
2325 /* If this is a register we are going to try to eliminate,
2326 don't mark it live here. If we are successful in
2327 eliminating it, it need not be live unless it is used for
2328 pseudos, in which case it will have been set live when
2329 it was allocated to the pseudos. If the register will not
2330 be eliminated, reload will set it live at that point. */
2332 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2333 regs_ever_live[regno] = 1;
2336 /* No death notes for global register variables;
2337 their values are live after this function exits. */
2338 if (global_regs[regno])
2341 reg_next_use[regno] = insn;
2345 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2348 live[(regno + n) / REGSET_ELT_BITS]
2349 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2351 |= (needed[(regno + n) / REGSET_ELT_BITS]
2352 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2354 &= (needed[(regno + n) / REGSET_ELT_BITS]
2355 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2360 /* Record where each reg is used, so when the reg
2361 is set we know the next insn that uses it. */
2363 reg_next_use[regno] = insn;
2365 if (regno < FIRST_PSEUDO_REGISTER)
2367 /* If a hard reg is being used,
2368 record that this function does use it. */
2370 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2374 regs_ever_live[regno + --i] = 1;
2379 /* Keep track of which basic block each reg appears in. */
2381 register int blocknum = BLOCK_NUM (insn);
2383 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2384 reg_basic_block[regno] = blocknum;
2385 else if (reg_basic_block[regno] != blocknum)
2386 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2388 /* Count (weighted) number of uses of each reg. */
2390 reg_n_refs[regno] += loop_depth;
2393 /* Record and count the insns in which a reg dies.
2394 If it is used in this insn and was dead below the insn
2395 then it dies in this insn. If it was set in this insn,
2396 we do not make a REG_DEAD note; likewise if we already
2397 made such a note. */
2400 && ! dead_or_set_p (insn, x)
2402 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2406 /* Check for the case where the register dying partially
2407 overlaps the register set by this insn. */
2408 if (regno < FIRST_PSEUDO_REGISTER
2409 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2411 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2413 some_needed |= dead_or_set_regno_p (insn, regno + n);
2416 /* If none of the words in X is needed, make a REG_DEAD
2417 note. Otherwise, we must make partial REG_DEAD notes. */
2421 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2422 reg_n_deaths[regno]++;
2428 /* Don't make a REG_DEAD note for a part of a register
2429 that is set in the insn. */
2431 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2433 if ((needed[(regno + i) / REGSET_ELT_BITS]
2434 & ((REGSET_ELT_TYPE) 1
2435 << ((regno + i) % REGSET_ELT_BITS))) == 0
2436 && ! dead_or_set_regno_p (insn, regno + i))
2438 = gen_rtx (EXPR_LIST, REG_DEAD,
2439 gen_rtx (REG, reg_raw_mode[regno + i],
2450 register rtx testreg = SET_DEST (x);
2453 /* If storing into MEM, don't show it as being used. But do
2454 show the address as being used. */
2455 if (GET_CODE (testreg) == MEM)
2459 find_auto_inc (needed, testreg, insn);
2461 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2462 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2466 /* Storing in STRICT_LOW_PART is like storing in a reg
2467 in that this SET might be dead, so ignore it in TESTREG.
2468 but in some other ways it is like using the reg.
2470 Storing in a SUBREG or a bit field is like storing the entire
2471 register in that if the register's value is not used
2472 then this SET is not needed. */
2473 while (GET_CODE (testreg) == STRICT_LOW_PART
2474 || GET_CODE (testreg) == ZERO_EXTRACT
2475 || GET_CODE (testreg) == SIGN_EXTRACT
2476 || GET_CODE (testreg) == SUBREG)
2478 /* Modifying a single register in an alternate mode
2479 does not use any of the old value. But these other
2480 ways of storing in a register do use the old value. */
2481 if (GET_CODE (testreg) == SUBREG
2482 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2487 testreg = XEXP (testreg, 0);
2490 /* If this is a store into a register,
2491 recursively scan the value being stored. */
2493 if (GET_CODE (testreg) == REG
2494 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2495 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2496 && regno != HARD_FRAME_POINTER_REGNUM
2498 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2499 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2502 /* We used to exclude global_regs here, but that seems wrong.
2503 Storing in them is like storing in mem. */
2505 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2507 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2514 /* If exiting needs the right stack value, consider this insn as
2515 using the stack pointer. In any event, consider it as using
2516 all global registers. */
2518 #ifdef EXIT_IGNORE_STACK
2519 if (! EXIT_IGNORE_STACK
2520 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2522 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2523 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2525 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2527 live[i / REGSET_ELT_BITS]
2528 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2532 /* Recursively scan the operands of this expression. */
2535 register char *fmt = GET_RTX_FORMAT (code);
2538 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2542 /* Tail recursive case: save a function call level. */
2548 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2550 else if (fmt[i] == 'E')
2553 for (j = 0; j < XVECLEN (x, i); j++)
2554 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2563 try_pre_increment_1 (insn)
2566 /* Find the next use of this reg. If in same basic block,
2567 make it do pre-increment or pre-decrement if appropriate. */
2568 rtx x = PATTERN (insn);
2569 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2570 * INTVAL (XEXP (SET_SRC (x), 1)));
2571 int regno = REGNO (SET_DEST (x));
2572 rtx y = reg_next_use[regno];
2574 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2575 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2576 mode would be better. */
2577 && ! dead_or_set_p (y, SET_DEST (x))
2578 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2581 /* We have found a suitable auto-increment
2582 and already changed insn Y to do it.
2583 So flush this increment-instruction. */
2584 PUT_CODE (insn, NOTE);
2585 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2586 NOTE_SOURCE_FILE (insn) = 0;
2587 /* Count a reference to this reg for the increment
2588 insn we are deleting. When a reg is incremented.
2589 spilling it is worse, so we want to make that
2591 if (regno >= FIRST_PSEUDO_REGISTER)
2593 reg_n_refs[regno] += loop_depth;
2594 reg_n_sets[regno]++;
2601 /* Try to change INSN so that it does pre-increment or pre-decrement
2602 addressing on register REG in order to add AMOUNT to REG.
2603 AMOUNT is negative for pre-decrement.
2604 Returns 1 if the change could be made.
2605 This checks all about the validity of the result of modifying INSN. */
2608 try_pre_increment (insn, reg, amount)
2610 HOST_WIDE_INT amount;
2614 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2615 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2617 /* Nonzero if we can try to make a post-increment or post-decrement.
2618 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2619 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2620 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2623 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2626 /* From the sign of increment, see which possibilities are conceivable
2627 on this target machine. */
2628 #ifdef HAVE_PRE_INCREMENT
2632 #ifdef HAVE_POST_INCREMENT
2637 #ifdef HAVE_PRE_DECREMENT
2641 #ifdef HAVE_POST_DECREMENT
2646 if (! (pre_ok || post_ok))
2649 /* It is not safe to add a side effect to a jump insn
2650 because if the incremented register is spilled and must be reloaded
2651 there would be no way to store the incremented value back in memory. */
2653 if (GET_CODE (insn) == JUMP_INSN)
2658 use = find_use_as_address (PATTERN (insn), reg, 0);
2659 if (post_ok && (use == 0 || use == (rtx) 1))
2661 use = find_use_as_address (PATTERN (insn), reg, -amount);
2665 if (use == 0 || use == (rtx) 1)
2668 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2671 /* See if this combination of instruction and addressing mode exists. */
2672 if (! validate_change (insn, &XEXP (use, 0),
2674 ? (do_post ? POST_INC : PRE_INC)
2675 : (do_post ? POST_DEC : PRE_DEC),
2679 /* Record that this insn now has an implicit side effect on X. */
2680 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2684 #endif /* AUTO_INC_DEC */
2686 /* Find the place in the rtx X where REG is used as a memory address.
2687 Return the MEM rtx that so uses it.
2688 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2689 (plus REG (const_int PLUSCONST)).
2691 If such an address does not appear, return 0.
2692 If REG appears more than once, or is used other than in such an address,
2696 find_use_as_address (x, reg, plusconst)
2699 HOST_WIDE_INT plusconst;
2701 enum rtx_code code = GET_CODE (x);
2702 char *fmt = GET_RTX_FORMAT (code);
2704 register rtx value = 0;
2707 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2710 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2711 && XEXP (XEXP (x, 0), 0) == reg
2712 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2713 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2716 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2718 /* If REG occurs inside a MEM used in a bit-field reference,
2719 that is unacceptable. */
2720 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2721 return (rtx) (HOST_WIDE_INT) 1;
2725 return (rtx) (HOST_WIDE_INT) 1;
2727 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2731 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2735 return (rtx) (HOST_WIDE_INT) 1;
2740 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2742 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2746 return (rtx) (HOST_WIDE_INT) 1;
2754 /* Write information about registers and basic blocks into FILE.
2755 This is part of making a debugging dump. */
2758 dump_flow_info (file)
2762 static char *reg_class_names[] = REG_CLASS_NAMES;
2764 fprintf (file, "%d registers.\n", max_regno);
2766 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2769 enum reg_class class, altclass;
2770 fprintf (file, "\nRegister %d used %d times across %d insns",
2771 i, reg_n_refs[i], reg_live_length[i]);
2772 if (reg_basic_block[i] >= 0)
2773 fprintf (file, " in block %d", reg_basic_block[i]);
2774 if (reg_n_deaths[i] != 1)
2775 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2776 if (reg_n_calls_crossed[i] == 1)
2777 fprintf (file, "; crosses 1 call");
2778 else if (reg_n_calls_crossed[i])
2779 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2780 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2781 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2782 class = reg_preferred_class (i);
2783 altclass = reg_alternate_class (i);
2784 if (class != GENERAL_REGS || altclass != ALL_REGS)
2786 if (altclass == ALL_REGS || class == ALL_REGS)
2787 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2788 else if (altclass == NO_REGS)
2789 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2791 fprintf (file, "; pref %s, else %s",
2792 reg_class_names[(int) class],
2793 reg_class_names[(int) altclass]);
2795 if (REGNO_POINTER_FLAG (i))
2796 fprintf (file, "; pointer");
2797 fprintf (file, ".\n");
2799 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2800 for (i = 0; i < n_basic_blocks; i++)
2802 register rtx head, jump;
2804 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2806 INSN_UID (basic_block_head[i]),
2807 INSN_UID (basic_block_end[i]));
2808 /* The control flow graph's storage is freed
2809 now when flow_analysis returns.
2810 Don't try to print it if it is gone. */
2811 if (basic_block_drops_in)
2813 fprintf (file, "Reached from blocks: ");
2814 head = basic_block_head[i];
2815 if (GET_CODE (head) == CODE_LABEL)
2816 for (jump = LABEL_REFS (head);
2818 jump = LABEL_NEXTREF (jump))
2820 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2821 fprintf (file, " %d", from_block);
2823 if (basic_block_drops_in[i])
2824 fprintf (file, " previous");
2826 fprintf (file, "\nRegisters live at start:");
2827 for (regno = 0; regno < max_regno; regno++)
2829 register int offset = regno / REGSET_ELT_BITS;
2830 register REGSET_ELT_TYPE bit
2831 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2832 if (basic_block_live_at_start[i][offset] & bit)
2833 fprintf (file, " %d", regno);
2835 fprintf (file, "\n");
2837 fprintf (file, "\n");