1 /* Data flow analysis for GNU compiler.
2 Copyright (C) 1987, 88, 92-96, 1997 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
22 /* This file contains the data flow analysis pass of the compiler.
23 It computes data flow information
24 which tells combine_instructions which insns to consider combining
25 and controls register allocation.
27 Additional data flow information that is too bulky to record
28 is generated during the analysis, and is used at that time to
29 create autoincrement and autodecrement addressing.
31 The first step is dividing the function into basic blocks.
32 find_basic_blocks does this. Then life_analysis determines
33 where each register is live and where it is dead.
35 ** find_basic_blocks **
37 find_basic_blocks divides the current function's rtl
38 into basic blocks. It records the beginnings and ends of the
39 basic blocks in the vectors basic_block_head and basic_block_end,
40 and the number of blocks in n_basic_blocks.
42 find_basic_blocks also finds any unreachable loops
47 life_analysis is called immediately after find_basic_blocks.
48 It uses the basic block information to determine where each
49 hard or pseudo register is live.
51 ** live-register info **
53 The information about where each register is live is in two parts:
54 the REG_NOTES of insns, and the vector basic_block_live_at_start.
56 basic_block_live_at_start has an element for each basic block,
57 and the element is a bit-vector with a bit for each hard or pseudo
58 register. The bit is 1 if the register is live at the beginning
61 Two types of elements can be added to an insn's REG_NOTES.
62 A REG_DEAD note is added to an insn's REG_NOTES for any register
63 that meets both of two conditions: The value in the register is not
64 needed in subsequent insns and the insn does not replace the value in
65 the register (in the case of multi-word hard registers, the value in
66 each register must be replaced by the insn to avoid a REG_DEAD note).
68 In the vast majority of cases, an object in a REG_DEAD note will be
69 used somewhere in the insn. The (rare) exception to this is if an
70 insn uses a multi-word hard register and only some of the registers are
71 needed in subsequent insns. In that case, REG_DEAD notes will be
72 provided for those hard registers that are not subsequently needed.
73 Partial REG_DEAD notes of this type do not occur when an insn sets
74 only some of the hard registers used in such a multi-word operand;
75 omitting REG_DEAD notes for objects stored in an insn is optional and
76 the desire to do so does not justify the complexity of the partial
79 REG_UNUSED notes are added for each register that is set by the insn
80 but is unused subsequently (if every register set by the insn is unused
81 and the insn does not reference memory or have some other side-effect,
82 the insn is deleted instead). If only part of a multi-word hard
83 register is used in a subsequent insn, REG_UNUSED notes are made for
84 the parts that will not be used.
86 To determine which registers are live after any insn, one can
87 start from the beginning of the basic block and scan insns, noting
88 which registers are set by each insn and which die there.
90 ** Other actions of life_analysis **
92 life_analysis sets up the LOG_LINKS fields of insns because the
93 information needed to do so is readily available.
95 life_analysis deletes insns whose only effect is to store a value
98 life_analysis notices cases where a reference to a register as
99 a memory address can be combined with a preceding or following
100 incrementation or decrementation of the register. The separate
101 instruction to increment or decrement is deleted and the address
102 is changed to a POST_INC or similar rtx.
104 Each time an incrementing or decrementing address is created,
105 a REG_INC element is added to the insn's REG_NOTES list.
107 life_analysis fills in certain vectors containing information about
108 register usage: reg_n_refs, reg_n_deaths, reg_n_sets, reg_live_length,
109 reg_n_calls_crosses and reg_basic_block. */
114 #include "basic-block.h"
115 #include "insn-config.h"
117 #include "hard-reg-set.h"
123 #define obstack_chunk_alloc xmalloc
124 #define obstack_chunk_free free
126 /* The contents of the current function definition are allocated
127 in this obstack, and all are freed at the end of the function.
128 For top-level functions, this is temporary_obstack.
129 Separate obstacks are made for nested functions. */
131 extern struct obstack *function_obstack;
133 /* List of labels that must never be deleted. */
134 extern rtx forced_labels;
136 /* Get the basic block number of an insn.
137 This info should not be expected to remain available
138 after the end of life_analysis. */
140 /* This is the limit of the allocated space in the following two arrays. */
142 static int max_uid_for_flow;
144 #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
146 /* This is where the BLOCK_NUM values are really stored.
147 This is set up by find_basic_blocks and used there and in life_analysis,
150 static int *uid_block_number;
152 /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
154 #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
155 static char *uid_volatile;
157 /* Number of basic blocks in the current function. */
161 /* Maximum register number used in this function, plus one. */
165 /* Maximum number of SCRATCH rtx's used in any basic block of this
170 /* Number of SCRATCH rtx's in the current block. */
172 static int num_scratch;
174 /* Indexed by n, giving various register information */
176 reg_info *reg_n_info;
178 /* Element N is the next insn that uses (hard or pseudo) register number N
179 within the current basic block; or zero, if there is no such insn.
180 This is valid only during the final backward scan in propagate_block. */
182 static rtx *reg_next_use;
184 /* Size of a regset for the current function,
185 in (1) bytes and (2) elements. */
190 /* Element N is first insn in basic block N.
191 This info lasts until we finish compiling the function. */
193 rtx *basic_block_head;
195 /* Element N is last insn in basic block N.
196 This info lasts until we finish compiling the function. */
198 rtx *basic_block_end;
200 /* Element N is a regset describing the registers live
201 at the start of basic block N.
202 This info lasts until we finish compiling the function. */
204 regset *basic_block_live_at_start;
206 /* Regset of regs live when calls to `setjmp'-like functions happen. */
208 regset regs_live_at_setjmp;
210 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
211 that have to go in the same hard reg.
212 The first two regs in the list are a pair, and the next two
213 are another pair, etc. */
216 /* Element N is nonzero if control can drop into basic block N
217 from the preceding basic block. Freed after life_analysis. */
219 static char *basic_block_drops_in;
221 /* Element N is depth within loops of the last insn in basic block number N.
222 Freed after life_analysis. */
224 static short *basic_block_loop_depth;
226 /* Element N nonzero if basic block N can actually be reached.
227 Vector exists only during find_basic_blocks. */
229 static char *block_live_static;
231 /* Depth within loops of basic block being scanned for lifetime analysis,
232 plus one. This is the weight attached to references to registers. */
234 static int loop_depth;
236 /* During propagate_block, this is non-zero if the value of CC0 is live. */
240 /* During propagate_block, this contains the last MEM stored into. It
241 is used to eliminate consecutive stores to the same location. */
243 static rtx last_mem_set;
245 /* Set of registers that may be eliminable. These are handled specially
246 in updating regs_ever_live. */
248 static HARD_REG_SET elim_reg_set;
250 /* Forward declarations */
251 static void find_basic_blocks PROTO((rtx, rtx));
252 static void mark_label_ref PROTO((rtx, rtx, int));
253 static void life_analysis PROTO((rtx, int));
254 void allocate_for_life_analysis PROTO((void));
255 void init_regset_vector PROTO((regset *, int, struct obstack *));
256 void free_regset_vector PROTO((regset *, int));
257 static void propagate_block PROTO((regset, rtx, rtx, int,
259 static rtx flow_delete_insn PROTO((rtx));
260 static int insn_dead_p PROTO((rtx, regset, int));
261 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
262 static void mark_set_regs PROTO((regset, regset, rtx,
264 static void mark_set_1 PROTO((regset, regset, rtx,
267 static void find_auto_inc PROTO((regset, rtx, rtx));
268 static int try_pre_increment_1 PROTO((rtx));
269 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
271 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
272 void dump_flow_info PROTO((FILE *));
274 /* Find basic blocks of the current function and perform data flow analysis.
275 F is the first insn of the function and NREGS the number of register numbers
279 flow_analysis (f, nregs, file)
286 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
287 int in_libcall_block = 0;
289 #ifdef ELIMINABLE_REGS
290 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
293 /* Record which registers will be eliminated. We use this in
296 CLEAR_HARD_REG_SET (elim_reg_set);
298 #ifdef ELIMINABLE_REGS
299 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
300 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
302 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
305 /* Count the basic blocks. Also find maximum insn uid value used. */
308 register RTX_CODE prev_code = JUMP_INSN;
309 register RTX_CODE code;
312 max_uid_for_flow = 0;
314 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
317 /* Track when we are inside in LIBCALL block. */
318 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
319 && find_reg_note (insn, REG_LIBCALL, NULL_RTX))
320 in_libcall_block = 1;
322 code = GET_CODE (insn);
323 if (INSN_UID (insn) > max_uid_for_flow)
324 max_uid_for_flow = INSN_UID (insn);
325 if (code == CODE_LABEL
326 || (GET_RTX_CLASS (code) == 'i'
327 && (prev_code == JUMP_INSN
328 || (prev_code == CALL_INSN
329 && (nonlocal_label_list != 0 || eh_region)
330 && ! in_libcall_block)
331 || prev_code == BARRIER)))
334 if (code == CALL_INSN && find_reg_note (insn, REG_RETVAL, NULL_RTX))
339 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
341 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
344 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
345 && find_reg_note (insn, REG_RETVAL, NULL_RTX))
346 in_libcall_block = 0;
351 /* Leave space for insns we make in some cases for auto-inc. These cases
352 are rare, so we don't need too much space. */
353 max_uid_for_flow += max_uid_for_flow / 10;
356 /* Allocate some tables that last till end of compiling this function
357 and some needed only in find_basic_blocks and life_analysis. */
360 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
361 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
362 basic_block_drops_in = (char *) alloca (n_basic_blocks);
363 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
365 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
366 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
367 bzero (uid_volatile, max_uid_for_flow + 1);
369 find_basic_blocks (f, nonlocal_label_list);
370 life_analysis (f, nregs);
372 dump_flow_info (file);
374 basic_block_drops_in = 0;
375 uid_block_number = 0;
376 basic_block_loop_depth = 0;
379 /* Find all basic blocks of the function whose first insn is F.
380 Store the correct data in the tables that describe the basic blocks,
381 set up the chains of references for each CODE_LABEL, and
382 delete any entire basic blocks that cannot be reached.
384 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
387 find_basic_blocks (f, nonlocal_label_list)
388 rtx f, nonlocal_label_list;
392 register char *block_live = (char *) alloca (n_basic_blocks);
393 register char *block_marked = (char *) alloca (n_basic_blocks);
394 /* An array of CODE_LABELs, indexed by UID for the start of the active
395 EH handler for each insn in F. */
396 rtx *active_eh_handler;
397 /* List of label_refs to all labels whose addresses are taken
399 rtx label_value_list;
400 rtx x, note, eh_note;
401 enum rtx_code prev_code, code;
403 int in_libcall_block = 0;
406 active_eh_handler = (rtx *) alloca ((max_uid_for_flow + 1) * sizeof (rtx));
409 label_value_list = 0;
410 block_live_static = block_live;
411 bzero (block_live, n_basic_blocks);
412 bzero (block_marked, n_basic_blocks);
413 bzero (active_eh_handler, (max_uid_for_flow + 1) * sizeof (rtx));
415 /* Initialize with just block 0 reachable and no blocks marked. */
416 if (n_basic_blocks > 0)
419 /* Initialize the ref chain of each label to 0. Record where all the
420 blocks start and end and their depth in loops. For each insn, record
421 the block it is in. Also mark as reachable any blocks headed by labels
422 that must not be deleted. */
424 for (eh_note = NULL_RTX, insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
425 insn; insn = NEXT_INSN (insn))
428 /* Track when we are inside in LIBCALL block. */
429 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
430 && find_reg_note (insn, REG_LIBCALL, NULL_RTX))
431 in_libcall_block = 1;
433 code = GET_CODE (insn);
436 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
438 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
442 /* A basic block starts at label, or after something that can jump. */
443 else if (code == CODE_LABEL
444 || (GET_RTX_CLASS (code) == 'i'
445 && (prev_code == JUMP_INSN
446 || (prev_code == CALL_INSN
447 && (nonlocal_label_list != 0 || eh_note)
448 && ! in_libcall_block)
449 || prev_code == BARRIER)))
451 basic_block_head[++i] = insn;
452 basic_block_end[i] = insn;
453 basic_block_loop_depth[i] = depth;
455 if (code == CODE_LABEL)
457 LABEL_REFS (insn) = insn;
458 /* Any label that cannot be deleted
459 is considered to start a reachable block. */
460 if (LABEL_PRESERVE_P (insn))
465 else if (GET_RTX_CLASS (code) == 'i')
467 basic_block_end[i] = insn;
468 basic_block_loop_depth[i] = depth;
471 if (GET_RTX_CLASS (code) == 'i')
473 /* Make a list of all labels referred to other than by jumps. */
474 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
475 if (REG_NOTE_KIND (note) == REG_LABEL)
476 label_value_list = gen_rtx_EXPR_LIST (VOIDmode, XEXP (note, 0),
480 /* Keep a lifo list of the currently active exception handlers. */
481 if (GET_CODE (insn) == NOTE)
483 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_BEG)
485 for (x = exception_handler_labels; x; x = XEXP (x, 1))
486 if (CODE_LABEL_NUMBER (XEXP (x, 0)) == NOTE_BLOCK_NUMBER (insn))
488 eh_note = gen_rtx_EXPR_LIST (VOIDmode,
489 XEXP (x, 0), eh_note);
495 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EH_REGION_END)
496 eh_note = XEXP (eh_note, 1);
498 /* If we encounter a CALL_INSN, note which exception handler it
499 might pass control to.
501 If doing asynchronous exceptions, record the active EH handler
502 for every insn, since most insns can throw. */
504 && (asynchronous_exceptions
505 || (GET_CODE (insn) == CALL_INSN
506 && ! in_libcall_block)))
507 active_eh_handler[INSN_UID (insn)] = XEXP (eh_note, 0);
509 BLOCK_NUM (insn) = i;
514 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
515 && find_reg_note (insn, REG_RETVAL, NULL_RTX))
516 in_libcall_block = 0;
519 /* During the second pass, `n_basic_blocks' is only an upper bound.
520 Only perform the sanity check for the first pass, and on the second
521 pass ensure `n_basic_blocks' is set to the correct value. */
522 if (pass == 1 && i + 1 != n_basic_blocks)
524 n_basic_blocks = i + 1;
526 /* Record which basic blocks control can drop in to. */
528 for (i = 0; i < n_basic_blocks; i++)
530 for (insn = PREV_INSN (basic_block_head[i]);
531 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
534 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
537 /* Now find which basic blocks can actually be reached
538 and put all jump insns' LABEL_REFS onto the ref-chains
539 of their target labels. */
541 if (n_basic_blocks > 0)
543 int something_marked = 1;
546 /* Pass over all blocks, marking each block that is reachable
547 and has not yet been marked.
548 Keep doing this until, in one pass, no blocks have been marked.
549 Then blocks_live and blocks_marked are identical and correct.
550 In addition, all jumps actually reachable have been marked. */
552 while (something_marked)
554 something_marked = 0;
555 for (i = 0; i < n_basic_blocks; i++)
556 if (block_live[i] && !block_marked[i])
559 something_marked = 1;
560 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
561 block_live[i + 1] = 1;
562 insn = basic_block_end[i];
563 if (GET_CODE (insn) == JUMP_INSN)
564 mark_label_ref (PATTERN (insn), insn, 0);
566 /* If we have any forced labels, mark them as potentially
567 reachable from this block. */
568 for (x = forced_labels; x; x = XEXP (x, 1))
569 if (! LABEL_REF_NONLOCAL_P (x))
570 mark_label_ref (gen_rtx_LABEL_REF (VOIDmode, XEXP (x, 0)),
573 /* Now scan the insns for this block, we may need to make
574 edges for some of them to various non-obvious locations
575 (exception handlers, nonlocal labels, etc). */
576 for (insn = basic_block_head[i];
577 insn != NEXT_INSN (basic_block_end[i]);
578 insn = NEXT_INSN (insn))
580 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
583 /* References to labels in non-jumping insns have
584 REG_LABEL notes attached to them.
586 This can happen for computed gotos; we don't care
587 about them here since the values are also on the
588 label_value_list and will be marked live if we find
589 a live computed goto.
591 This can also happen when we take the address of
592 a label to pass as an argument to __throw. Note
593 throw only uses the value to determine what handler
594 should be called -- ie the label is not used as
595 a jump target, it just marks regions in the code.
597 In theory we should be able to ignore the REG_LABEL
598 notes, but we have to make sure that the label and
599 associated insns aren't marked dead, so we make
600 the block in question live and create an edge from
601 this insn to the label. This is not strictly
602 correct, but it is close enough for now. */
603 for (note = REG_NOTES (insn);
605 note = XEXP (note, 1))
607 if (REG_NOTE_KIND (note) == REG_LABEL)
610 block_live[BLOCK_NUM (x)] = 1;
611 mark_label_ref (gen_rtx_LABEL_REF (VOIDmode, x),
616 /* If this is a computed jump, then mark it as
617 reaching everything on the label_value_list
618 and forced_labels list. */
619 if (computed_jump_p (insn))
621 for (x = label_value_list; x; x = XEXP (x, 1))
622 mark_label_ref (gen_rtx_LABEL_REF (VOIDmode,
626 for (x = forced_labels; x; x = XEXP (x, 1))
627 mark_label_ref (gen_rtx_LABEL_REF (VOIDmode,
632 /* If this is a CALL_INSN, then mark it as reaching
633 the active EH handler for this CALL_INSN. If
634 we're handling asynchronous exceptions mark every
635 insn as reaching the active EH handler.
637 Also mark the CALL_INSN as reaching any nonlocal
639 else if (asynchronous_exceptions
640 || (GET_CODE (insn) == CALL_INSN
641 && ! find_reg_note (insn, REG_RETVAL,
644 if (active_eh_handler[INSN_UID (insn)])
645 mark_label_ref (gen_rtx_LABEL_REF (VOIDmode,
646 active_eh_handler[INSN_UID (insn)]),
649 if (!asynchronous_exceptions)
651 for (x = nonlocal_label_list;
654 mark_label_ref (gen_rtx_LABEL_REF (VOIDmode,
658 /* ??? This could be made smarter:
659 in some cases it's possible to tell that
660 certain calls will not do a nonlocal goto.
662 For example, if the nested functions that
663 do the nonlocal gotos do not have their
664 addresses taken, then only calls to those
665 functions or to other nested functions that
666 use them could possibly do nonlocal gotos. */
673 /* This should never happen. If it does that means we've computed an
674 incorrect flow graph, which can lead to aborts/crashes later in the
675 compiler or incorrect code generation.
677 We used to try and continue here, but that's just asking for trouble
678 later during the compile or at runtime. It's easier to debug the
679 problem here than later! */
680 for (i = 1; i < n_basic_blocks; i++)
681 if (block_live[i] && ! basic_block_drops_in[i]
682 && GET_CODE (basic_block_head[i]) == CODE_LABEL
683 && LABEL_REFS (basic_block_head[i]) == basic_block_head[i])
686 /* Now delete the code for any basic blocks that can't be reached.
687 They can occur because jump_optimize does not recognize
688 unreachable loops as unreachable. */
691 for (i = 0; i < n_basic_blocks; i++)
696 /* Delete the insns in a (non-live) block. We physically delete
697 every non-note insn except the start and end (so
698 basic_block_head/end needn't be updated), we turn the latter
699 into NOTE_INSN_DELETED notes.
700 We use to "delete" the insns by turning them into notes, but
701 we may be deleting lots of insns that subsequent passes would
702 otherwise have to process. Secondly, lots of deleted blocks in
703 a row can really slow down propagate_block since it will
704 otherwise process insn-turned-notes multiple times when it
705 looks for loop begin/end notes. */
706 if (basic_block_head[i] != basic_block_end[i])
708 /* It would be quicker to delete all of these with a single
709 unchaining, rather than one at a time, but we need to keep
711 insn = NEXT_INSN (basic_block_head[i]);
712 while (insn != basic_block_end[i])
714 if (GET_CODE (insn) == BARRIER)
716 else if (GET_CODE (insn) != NOTE)
717 insn = flow_delete_insn (insn);
719 insn = NEXT_INSN (insn);
722 insn = basic_block_head[i];
723 if (GET_CODE (insn) != NOTE)
725 /* Turn the head into a deleted insn note. */
726 if (GET_CODE (insn) == BARRIER)
729 /* If the head of this block is a CODE_LABEL, then it might
730 be the label for an exception handler which can't be
733 We need to remove the label from the exception_handler_label
734 list and remove the associated NOTE_EH_REGION_BEG and
735 NOTE_EH_REGION_END notes. */
736 if (GET_CODE (insn) == CODE_LABEL)
738 rtx x, *prev = &exception_handler_labels;
740 for (x = exception_handler_labels; x; x = XEXP (x, 1))
742 if (XEXP (x, 0) == insn)
744 /* Found a match, splice this label out of the
747 XEXP (x, 1) = NULL_RTX;
748 XEXP (x, 0) = NULL_RTX;
750 /* Now we have to find the EH_BEG and EH_END notes
751 associated with this label and remove them. */
753 for (x = get_insns (); x; x = NEXT_INSN (x))
755 if (GET_CODE (x) == NOTE
756 && ((NOTE_LINE_NUMBER (x)
757 == NOTE_INSN_EH_REGION_BEG)
758 || (NOTE_LINE_NUMBER (x)
759 == NOTE_INSN_EH_REGION_END))
760 && (NOTE_BLOCK_NUMBER (x)
761 == CODE_LABEL_NUMBER (insn)))
763 NOTE_LINE_NUMBER (x) = NOTE_INSN_DELETED;
764 NOTE_SOURCE_FILE (x) = 0;
773 PUT_CODE (insn, NOTE);
774 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
775 NOTE_SOURCE_FILE (insn) = 0;
777 insn = basic_block_end[i];
778 if (GET_CODE (insn) != NOTE)
780 /* Turn the tail into a deleted insn note. */
781 if (GET_CODE (insn) == BARRIER)
783 PUT_CODE (insn, NOTE);
784 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
785 NOTE_SOURCE_FILE (insn) = 0;
787 /* BARRIERs are between basic blocks, not part of one.
788 Delete a BARRIER if the preceding jump is deleted.
789 We cannot alter a BARRIER into a NOTE
790 because it is too short; but we can really delete
791 it because it is not part of a basic block. */
792 if (NEXT_INSN (insn) != 0
793 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
794 delete_insn (NEXT_INSN (insn));
796 /* Each time we delete some basic blocks,
797 see if there is a jump around them that is
798 being turned into a no-op. If so, delete it. */
800 if (block_live[i - 1])
803 for (j = i + 1; j < n_basic_blocks; j++)
807 insn = basic_block_end[i - 1];
808 if (GET_CODE (insn) == JUMP_INSN
809 /* An unconditional jump is the only possibility
810 we must check for, since a conditional one
811 would make these blocks live. */
812 && simplejump_p (insn)
813 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
814 && INSN_UID (label) != 0
815 && BLOCK_NUM (label) == j)
817 PUT_CODE (insn, NOTE);
818 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
819 NOTE_SOURCE_FILE (insn) = 0;
820 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
822 delete_insn (NEXT_INSN (insn));
829 /* There are pathological cases where one function calling hundreds of
830 nested inline functions can generate lots and lots of unreachable
831 blocks that jump can't delete. Since we don't use sparse matrices
832 a lot of memory will be needed to compile such functions.
833 Implementing sparse matrices is a fair bit of work and it is not
834 clear that they win more than they lose (we don't want to
835 unnecessarily slow down compilation of normal code). By making
836 another pass for the pathological case, we can greatly speed up
837 their compilation without hurting normal code. This works because
838 all the insns in the unreachable blocks have either been deleted or
840 Note that we're talking about reducing memory usage by 10's of
841 megabytes and reducing compilation time by several minutes. */
842 /* ??? The choice of when to make another pass is a bit arbitrary,
843 and was derived from empirical data. */
848 n_basic_blocks -= deleted;
849 /* `n_basic_blocks' may not be correct at this point: two previously
850 separate blocks may now be merged. That's ok though as we
851 recalculate it during the second pass. It certainly can't be
852 any larger than the current value. */
858 /* Subroutines of find_basic_blocks. */
860 /* Check expression X for label references;
861 if one is found, add INSN to the label's chain of references.
863 CHECKDUP means check for and avoid creating duplicate references
864 from the same insn. Such duplicates do no serious harm but
865 can slow life analysis. CHECKDUP is set only when duplicates
869 mark_label_ref (x, insn, checkdup)
873 register RTX_CODE code;
877 /* We can be called with NULL when scanning label_value_list. */
882 if (code == LABEL_REF)
884 register rtx label = XEXP (x, 0);
886 if (GET_CODE (label) != CODE_LABEL)
888 /* If the label was never emitted, this insn is junk,
889 but avoid a crash trying to refer to BLOCK_NUM (label).
890 This can happen as a result of a syntax error
891 and a diagnostic has already been printed. */
892 if (INSN_UID (label) == 0)
894 CONTAINING_INSN (x) = insn;
895 /* if CHECKDUP is set, check for duplicate ref from same insn
898 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
899 if (CONTAINING_INSN (y) == insn)
901 LABEL_NEXTREF (x) = LABEL_REFS (label);
902 LABEL_REFS (label) = x;
903 block_live_static[BLOCK_NUM (label)] = 1;
907 fmt = GET_RTX_FORMAT (code);
908 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
911 mark_label_ref (XEXP (x, i), insn, 0);
915 for (j = 0; j < XVECLEN (x, i); j++)
916 mark_label_ref (XVECEXP (x, i, j), insn, 1);
921 /* Delete INSN by patching it out.
922 Return the next insn. */
925 flow_delete_insn (insn)
928 /* ??? For the moment we assume we don't have to watch for NULLs here
929 since the start/end of basic blocks aren't deleted like this. */
930 NEXT_INSN (PREV_INSN (insn)) = NEXT_INSN (insn);
931 PREV_INSN (NEXT_INSN (insn)) = PREV_INSN (insn);
932 return NEXT_INSN (insn);
935 /* Determine which registers are live at the start of each
936 basic block of the function whose first insn is F.
937 NREGS is the number of registers used in F.
938 We allocate the vector basic_block_live_at_start
939 and the regsets that it points to, and fill them with the data.
940 regset_size and regset_bytes are also set here. */
943 life_analysis (f, nregs)
949 /* For each basic block, a bitmask of regs
950 live on exit from the block. */
951 regset *basic_block_live_at_end;
952 /* For each basic block, a bitmask of regs
953 live on entry to a successor-block of this block.
954 If this does not match basic_block_live_at_end,
955 that must be updated, and the block must be rescanned. */
956 regset *basic_block_new_live_at_end;
957 /* For each basic block, a bitmask of regs
958 whose liveness at the end of the basic block
959 can make a difference in which regs are live on entry to the block.
960 These are the regs that are set within the basic block,
961 possibly excluding those that are used after they are set. */
962 regset *basic_block_significant;
966 struct obstack flow_obstack;
968 gcc_obstack_init (&flow_obstack);
972 bzero (regs_ever_live, sizeof regs_ever_live);
974 /* Allocate and zero out many data structures
975 that will record the data from lifetime analysis. */
977 allocate_for_life_analysis ();
979 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
980 bzero ((char *) reg_next_use, nregs * sizeof (rtx));
982 /* Set up several regset-vectors used internally within this function.
983 Their meanings are documented above, with their declarations. */
985 basic_block_live_at_end
986 = (regset *) alloca (n_basic_blocks * sizeof (regset));
988 /* Don't use alloca since that leads to a crash rather than an error message
989 if there isn't enough space.
990 Don't use oballoc since we may need to allocate other things during
991 this function on the temporary obstack. */
992 init_regset_vector (basic_block_live_at_end, n_basic_blocks, &flow_obstack);
994 basic_block_new_live_at_end
995 = (regset *) alloca (n_basic_blocks * sizeof (regset));
996 init_regset_vector (basic_block_new_live_at_end, n_basic_blocks,
999 basic_block_significant
1000 = (regset *) alloca (n_basic_blocks * sizeof (regset));
1001 init_regset_vector (basic_block_significant, n_basic_blocks, &flow_obstack);
1003 /* Record which insns refer to any volatile memory
1004 or for any reason can't be deleted just because they are dead stores.
1005 Also, delete any insns that copy a register to itself. */
1007 for (insn = f; insn; insn = NEXT_INSN (insn))
1009 enum rtx_code code1 = GET_CODE (insn);
1010 if (code1 == CALL_INSN)
1011 INSN_VOLATILE (insn) = 1;
1012 else if (code1 == INSN || code1 == JUMP_INSN)
1014 /* Delete (in effect) any obvious no-op moves. */
1015 if (GET_CODE (PATTERN (insn)) == SET
1016 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
1017 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
1018 && (REGNO (SET_DEST (PATTERN (insn)))
1019 == REGNO (SET_SRC (PATTERN (insn))))
1020 /* Insns carrying these notes are useful later on. */
1021 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1023 PUT_CODE (insn, NOTE);
1024 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1025 NOTE_SOURCE_FILE (insn) = 0;
1027 /* Delete (in effect) any obvious no-op moves. */
1028 else if (GET_CODE (PATTERN (insn)) == SET
1029 && GET_CODE (SET_DEST (PATTERN (insn))) == SUBREG
1030 && GET_CODE (SUBREG_REG (SET_DEST (PATTERN (insn)))) == REG
1031 && GET_CODE (SET_SRC (PATTERN (insn))) == SUBREG
1032 && GET_CODE (SUBREG_REG (SET_SRC (PATTERN (insn)))) == REG
1033 && (REGNO (SUBREG_REG (SET_DEST (PATTERN (insn))))
1034 == REGNO (SUBREG_REG (SET_SRC (PATTERN (insn)))))
1035 && SUBREG_WORD (SET_DEST (PATTERN (insn))) ==
1036 SUBREG_WORD (SET_SRC (PATTERN (insn)))
1037 /* Insns carrying these notes are useful later on. */
1038 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1040 PUT_CODE (insn, NOTE);
1041 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1042 NOTE_SOURCE_FILE (insn) = 0;
1044 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
1046 /* If nothing but SETs of registers to themselves,
1047 this insn can also be deleted. */
1048 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
1050 rtx tem = XVECEXP (PATTERN (insn), 0, i);
1052 if (GET_CODE (tem) == USE
1053 || GET_CODE (tem) == CLOBBER)
1056 if (GET_CODE (tem) != SET
1057 || GET_CODE (SET_DEST (tem)) != REG
1058 || GET_CODE (SET_SRC (tem)) != REG
1059 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
1063 if (i == XVECLEN (PATTERN (insn), 0)
1064 /* Insns carrying these notes are useful later on. */
1065 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
1067 PUT_CODE (insn, NOTE);
1068 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1069 NOTE_SOURCE_FILE (insn) = 0;
1072 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1074 else if (GET_CODE (PATTERN (insn)) != USE)
1075 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
1076 /* A SET that makes space on the stack cannot be dead.
1077 (Such SETs occur only for allocating variable-size data,
1078 so they will always have a PLUS or MINUS according to the
1079 direction of stack growth.)
1080 Even if this function never uses this stack pointer value,
1081 signal handlers do! */
1082 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
1083 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1084 #ifdef STACK_GROWS_DOWNWARD
1085 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
1087 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1089 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
1090 INSN_VOLATILE (insn) = 1;
1094 if (n_basic_blocks > 0)
1095 #ifdef EXIT_IGNORE_STACK
1096 if (! EXIT_IGNORE_STACK
1097 || (! FRAME_POINTER_REQUIRED
1098 && ! current_function_calls_alloca
1099 && flag_omit_frame_pointer))
1102 /* If exiting needs the right stack value,
1103 consider the stack pointer live at the end of the function. */
1104 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1105 STACK_POINTER_REGNUM);
1106 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1107 STACK_POINTER_REGNUM);
1110 /* Mark the frame pointer is needed at the end of the function. If
1111 we end up eliminating it, it will be removed from the live list
1112 of each basic block by reload. */
1114 if (n_basic_blocks > 0)
1116 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1117 FRAME_POINTER_REGNUM);
1118 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1119 FRAME_POINTER_REGNUM);
1120 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1121 /* If they are different, also mark the hard frame pointer as live */
1122 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1],
1123 HARD_FRAME_POINTER_REGNUM);
1124 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1],
1125 HARD_FRAME_POINTER_REGNUM);
1129 /* Mark all global registers and all registers used by the epilogue
1130 as being live at the end of the function since they may be
1131 referenced by our caller. */
1133 if (n_basic_blocks > 0)
1134 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1136 #ifdef EPILOGUE_USES
1137 || EPILOGUE_USES (i)
1141 SET_REGNO_REG_SET (basic_block_live_at_end[n_basic_blocks - 1], i);
1142 SET_REGNO_REG_SET (basic_block_new_live_at_end[n_basic_blocks - 1], i);
1145 /* Propagate life info through the basic blocks
1146 around the graph of basic blocks.
1148 This is a relaxation process: each time a new register
1149 is live at the end of the basic block, we must scan the block
1150 to determine which registers are, as a consequence, live at the beginning
1151 of that block. These registers must then be marked live at the ends
1152 of all the blocks that can transfer control to that block.
1153 The process continues until it reaches a fixed point. */
1160 for (i = n_basic_blocks - 1; i >= 0; i--)
1162 int consider = first_pass;
1163 int must_rescan = first_pass;
1168 /* Set CONSIDER if this block needs thinking about at all
1169 (that is, if the regs live now at the end of it
1170 are not the same as were live at the end of it when
1171 we last thought about it).
1172 Set must_rescan if it needs to be thought about
1173 instruction by instruction (that is, if any additional
1174 reg that is live at the end now but was not live there before
1175 is one of the significant regs of this basic block). */
1177 EXECUTE_IF_AND_COMPL_IN_REG_SET
1178 (basic_block_new_live_at_end[i],
1179 basic_block_live_at_end[i], 0, j,
1182 if (REGNO_REG_SET_P (basic_block_significant[i], j))
1193 /* The live_at_start of this block may be changing,
1194 so another pass will be required after this one. */
1199 /* No complete rescan needed;
1200 just record those variables newly known live at end
1201 as live at start as well. */
1202 IOR_AND_COMPL_REG_SET (basic_block_live_at_start[i],
1203 basic_block_new_live_at_end[i],
1204 basic_block_live_at_end[i]);
1206 IOR_AND_COMPL_REG_SET (basic_block_live_at_end[i],
1207 basic_block_new_live_at_end[i],
1208 basic_block_live_at_end[i]);
1212 /* Update the basic_block_live_at_start
1213 by propagation backwards through the block. */
1214 COPY_REG_SET (basic_block_live_at_end[i],
1215 basic_block_new_live_at_end[i]);
1216 COPY_REG_SET (basic_block_live_at_start[i],
1217 basic_block_live_at_end[i]);
1218 propagate_block (basic_block_live_at_start[i],
1219 basic_block_head[i], basic_block_end[i], 0,
1220 first_pass ? basic_block_significant[i]
1226 register rtx jump, head;
1228 /* Update the basic_block_new_live_at_end's of the block
1229 that falls through into this one (if any). */
1230 head = basic_block_head[i];
1231 if (basic_block_drops_in[i])
1232 IOR_REG_SET (basic_block_new_live_at_end[i-1],
1233 basic_block_live_at_start[i]);
1235 /* Update the basic_block_new_live_at_end's of
1236 all the blocks that jump to this one. */
1237 if (GET_CODE (head) == CODE_LABEL)
1238 for (jump = LABEL_REFS (head);
1240 jump = LABEL_NEXTREF (jump))
1242 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1243 IOR_REG_SET (basic_block_new_live_at_end[from_block],
1244 basic_block_live_at_start[i]);
1254 /* The only pseudos that are live at the beginning of the function are
1255 those that were not set anywhere in the function. local-alloc doesn't
1256 know how to handle these correctly, so mark them as not local to any
1259 if (n_basic_blocks > 0)
1260 EXECUTE_IF_SET_IN_REG_SET (basic_block_live_at_start[0],
1261 FIRST_PSEUDO_REGISTER, i,
1263 REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL;
1266 /* Now the life information is accurate.
1267 Make one more pass over each basic block
1268 to delete dead stores, create autoincrement addressing
1269 and record how many times each register is used, is set, or dies.
1271 To save time, we operate directly in basic_block_live_at_end[i],
1272 thus destroying it (in fact, converting it into a copy of
1273 basic_block_live_at_start[i]). This is ok now because
1274 basic_block_live_at_end[i] is no longer used past this point. */
1278 for (i = 0; i < n_basic_blocks; i++)
1280 propagate_block (basic_block_live_at_end[i],
1281 basic_block_head[i], basic_block_end[i], 1,
1289 /* Something live during a setjmp should not be put in a register
1290 on certain machines which restore regs from stack frames
1291 rather than from the jmpbuf.
1292 But we don't need to do this for the user's variables, since
1293 ANSI says only volatile variables need this. */
1294 #ifdef LONGJMP_RESTORE_FROM_STACK
1295 EXECUTE_IF_SET_IN_REG_SET (regs_live_at_setjmp,
1296 FIRST_PSEUDO_REGISTER, i,
1298 if (regno_reg_rtx[i] != 0
1299 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1301 REG_LIVE_LENGTH (i) = -1;
1302 REG_BASIC_BLOCK (i) = -1;
1308 /* We have a problem with any pseudoreg that
1309 lives across the setjmp. ANSI says that if a
1310 user variable does not change in value
1311 between the setjmp and the longjmp, then the longjmp preserves it.
1312 This includes longjmp from a place where the pseudo appears dead.
1313 (In principle, the value still exists if it is in scope.)
1314 If the pseudo goes in a hard reg, some other value may occupy
1315 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1316 Conclusion: such a pseudo must not go in a hard reg. */
1317 EXECUTE_IF_SET_IN_REG_SET (regs_live_at_setjmp,
1318 FIRST_PSEUDO_REGISTER, i,
1320 if (regno_reg_rtx[i] != 0)
1322 REG_LIVE_LENGTH (i) = -1;
1323 REG_BASIC_BLOCK (i) = -1;
1328 free_regset_vector (basic_block_live_at_end, n_basic_blocks);
1329 free_regset_vector (basic_block_new_live_at_end, n_basic_blocks);
1330 free_regset_vector (basic_block_significant, n_basic_blocks);
1331 basic_block_live_at_end = (regset *)0;
1332 basic_block_new_live_at_end = (regset *)0;
1333 basic_block_significant = (regset *)0;
1335 obstack_free (&flow_obstack, NULL_PTR);
1338 /* Subroutines of life analysis. */
1340 /* Allocate the permanent data structures that represent the results
1341 of life analysis. Not static since used also for stupid life analysis. */
1344 allocate_for_life_analysis ()
1348 /* Recalculate the register space, in case it has grown. Old style
1349 vector oriented regsets would set regset_{size,bytes} here also. */
1350 allocate_reg_info (max_regno, FALSE, FALSE);
1352 /* Because both reg_scan and flow_analysis want to set up the REG_N_SETS
1353 information, explicitly reset it here. The allocation should have
1354 already happened on the previous reg_scan pass. Make sure in case
1355 some more registers were allocated. */
1356 for (i = 0; i < max_regno; i++)
1359 basic_block_live_at_start
1360 = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1361 init_regset_vector (basic_block_live_at_start, n_basic_blocks,
1364 regs_live_at_setjmp = OBSTACK_ALLOC_REG_SET (function_obstack);
1365 CLEAR_REG_SET (regs_live_at_setjmp);
1368 /* Make each element of VECTOR point at a regset. The vector has
1369 NELTS elements, and space is allocated from the ALLOC_OBSTACK
1373 init_regset_vector (vector, nelts, alloc_obstack)
1376 struct obstack *alloc_obstack;
1380 for (i = 0; i < nelts; i++)
1382 vector[i] = OBSTACK_ALLOC_REG_SET (alloc_obstack);
1383 CLEAR_REG_SET (vector[i]);
1387 /* Release any additional space allocated for each element of VECTOR point
1388 other than the regset header itself. The vector has NELTS elements. */
1391 free_regset_vector (vector, nelts)
1397 for (i = 0; i < nelts; i++)
1398 FREE_REG_SET (vector[i]);
1401 /* Compute the registers live at the beginning of a basic block
1402 from those live at the end.
1404 When called, OLD contains those live at the end.
1405 On return, it contains those live at the beginning.
1406 FIRST and LAST are the first and last insns of the basic block.
1408 FINAL is nonzero if we are doing the final pass which is not
1409 for computing the life info (since that has already been done)
1410 but for acting on it. On this pass, we delete dead stores,
1411 set up the logical links and dead-variables lists of instructions,
1412 and merge instructions for autoincrement and autodecrement addresses.
1414 SIGNIFICANT is nonzero only the first time for each basic block.
1415 If it is nonzero, it points to a regset in which we store
1416 a 1 for each register that is set within the block.
1418 BNUM is the number of the basic block. */
1421 propagate_block (old, first, last, final, significant, bnum)
1422 register regset old;
1434 /* The following variables are used only if FINAL is nonzero. */
1435 /* This vector gets one element for each reg that has been live
1436 at any point in the basic block that has been scanned so far.
1437 SOMETIMES_MAX says how many elements are in use so far. */
1438 register int *regs_sometimes_live;
1439 int sometimes_max = 0;
1440 /* This regset has 1 for each reg that we have seen live so far.
1441 It and REGS_SOMETIMES_LIVE are updated together. */
1444 /* The loop depth may change in the middle of a basic block. Since we
1445 scan from end to beginning, we start with the depth at the end of the
1446 current basic block, and adjust as we pass ends and starts of loops. */
1447 loop_depth = basic_block_loop_depth[bnum];
1449 dead = ALLOCA_REG_SET ();
1450 live = ALLOCA_REG_SET ();
1455 /* Include any notes at the end of the block in the scan.
1456 This is in case the block ends with a call to setjmp. */
1458 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1460 /* Look for loop boundaries, we are going forward here. */
1461 last = NEXT_INSN (last);
1462 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1464 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1473 maxlive = ALLOCA_REG_SET ();
1474 COPY_REG_SET (maxlive, old);
1475 regs_sometimes_live = (int *) alloca (max_regno * sizeof (int));
1477 /* Process the regs live at the end of the block.
1478 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1479 Also mark them as not local to any one basic block. */
1480 EXECUTE_IF_SET_IN_REG_SET (old, 0, i,
1482 REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL;
1483 regs_sometimes_live[sometimes_max] = i;
1488 /* Scan the block an insn at a time from end to beginning. */
1490 for (insn = last; ; insn = prev)
1492 prev = PREV_INSN (insn);
1494 if (GET_CODE (insn) == NOTE)
1496 /* Look for loop boundaries, remembering that we are going
1498 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1500 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1503 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1504 Abort now rather than setting register status incorrectly. */
1505 if (loop_depth == 0)
1508 /* If this is a call to `setjmp' et al,
1509 warn if any non-volatile datum is live. */
1511 if (final && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1512 IOR_REG_SET (regs_live_at_setjmp, old);
1515 /* Update the life-status of regs for this insn.
1516 First DEAD gets which regs are set in this insn
1517 then LIVE gets which regs are used in this insn.
1518 Then the regs live before the insn
1519 are those live after, with DEAD regs turned off,
1520 and then LIVE regs turned on. */
1522 else if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1525 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1527 = (insn_dead_p (PATTERN (insn), old, 0)
1528 /* Don't delete something that refers to volatile storage! */
1529 && ! INSN_VOLATILE (insn));
1531 = (insn_is_dead && note != 0
1532 && libcall_dead_p (PATTERN (insn), old, note, insn));
1534 /* If an instruction consists of just dead store(s) on final pass,
1535 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1536 We could really delete it with delete_insn, but that
1537 can cause trouble for first or last insn in a basic block. */
1538 if (final && insn_is_dead)
1540 PUT_CODE (insn, NOTE);
1541 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1542 NOTE_SOURCE_FILE (insn) = 0;
1544 /* CC0 is now known to be dead. Either this insn used it,
1545 in which case it doesn't anymore, or clobbered it,
1546 so the next insn can't use it. */
1549 /* If this insn is copying the return value from a library call,
1550 delete the entire library call. */
1551 if (libcall_is_dead)
1553 rtx first = XEXP (note, 0);
1555 while (INSN_DELETED_P (first))
1556 first = NEXT_INSN (first);
1561 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1562 NOTE_SOURCE_FILE (p) = 0;
1568 CLEAR_REG_SET (dead);
1569 CLEAR_REG_SET (live);
1571 /* See if this is an increment or decrement that can be
1572 merged into a following memory address. */
1575 register rtx x = single_set (insn);
1577 /* Does this instruction increment or decrement a register? */
1579 && GET_CODE (SET_DEST (x)) == REG
1580 && (GET_CODE (SET_SRC (x)) == PLUS
1581 || GET_CODE (SET_SRC (x)) == MINUS)
1582 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1583 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1584 /* Ok, look for a following memory ref we can combine with.
1585 If one is found, change the memory ref to a PRE_INC
1586 or PRE_DEC, cancel this insn, and return 1.
1587 Return 0 if nothing has been done. */
1588 && try_pre_increment_1 (insn))
1591 #endif /* AUTO_INC_DEC */
1593 /* If this is not the final pass, and this insn is copying the
1594 value of a library call and it's dead, don't scan the
1595 insns that perform the library call, so that the call's
1596 arguments are not marked live. */
1597 if (libcall_is_dead)
1599 /* Mark the dest reg as `significant'. */
1600 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1602 insn = XEXP (note, 0);
1603 prev = PREV_INSN (insn);
1605 else if (GET_CODE (PATTERN (insn)) == SET
1606 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1607 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1608 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1609 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1610 /* We have an insn to pop a constant amount off the stack.
1611 (Such insns use PLUS regardless of the direction of the stack,
1612 and any insn to adjust the stack by a constant is always a pop.)
1613 These insns, if not dead stores, have no effect on life. */
1617 /* LIVE gets the regs used in INSN;
1618 DEAD gets those set by it. Dead insns don't make anything
1621 mark_set_regs (old, dead, PATTERN (insn),
1622 final ? insn : NULL_RTX, significant);
1624 /* If an insn doesn't use CC0, it becomes dead since we
1625 assume that every insn clobbers it. So show it dead here;
1626 mark_used_regs will set it live if it is referenced. */
1630 mark_used_regs (old, live, PATTERN (insn), final, insn);
1632 /* Sometimes we may have inserted something before INSN (such as
1633 a move) when we make an auto-inc. So ensure we will scan
1636 prev = PREV_INSN (insn);
1639 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1645 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1647 note = XEXP (note, 1))
1648 if (GET_CODE (XEXP (note, 0)) == USE)
1649 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1652 /* Each call clobbers all call-clobbered regs that are not
1653 global or fixed. Note that the function-value reg is a
1654 call-clobbered reg, and mark_set_regs has already had
1655 a chance to handle it. */
1657 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1658 if (call_used_regs[i] && ! global_regs[i]
1660 SET_REGNO_REG_SET (dead, i);
1662 /* The stack ptr is used (honorarily) by a CALL insn. */
1663 SET_REGNO_REG_SET (live, STACK_POINTER_REGNUM);
1665 /* Calls may also reference any of the global registers,
1666 so they are made live. */
1667 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1669 mark_used_regs (old, live,
1670 gen_rtx_REG (reg_raw_mode[i], i),
1673 /* Calls also clobber memory. */
1677 /* Update OLD for the registers used or set. */
1678 AND_COMPL_REG_SET (old, dead);
1679 IOR_REG_SET (old, live);
1681 if (GET_CODE (insn) == CALL_INSN && final)
1683 /* Any regs live at the time of a call instruction
1684 must not go in a register clobbered by calls.
1685 Find all regs now live and record this for them. */
1687 register int *p = regs_sometimes_live;
1689 for (i = 0; i < sometimes_max; i++, p++)
1690 if (REGNO_REG_SET_P (old, *p))
1691 REG_N_CALLS_CROSSED (*p)++;
1695 /* On final pass, add any additional sometimes-live regs
1696 into MAXLIVE and REGS_SOMETIMES_LIVE.
1697 Also update counts of how many insns each reg is live at. */
1704 EXECUTE_IF_AND_COMPL_IN_REG_SET
1705 (live, maxlive, 0, regno,
1707 regs_sometimes_live[sometimes_max++] = regno;
1708 SET_REGNO_REG_SET (maxlive, regno);
1711 p = regs_sometimes_live;
1712 for (i = 0; i < sometimes_max; i++)
1715 if (REGNO_REG_SET_P (old, regno))
1716 REG_LIVE_LENGTH (regno)++;
1725 FREE_REG_SET (dead);
1726 FREE_REG_SET (live);
1728 FREE_REG_SET (maxlive);
1730 if (num_scratch > max_scratch)
1731 max_scratch = num_scratch;
1734 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1735 (SET expressions whose destinations are registers dead after the insn).
1736 NEEDED is the regset that says which regs are alive after the insn.
1738 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1741 insn_dead_p (x, needed, call_ok)
1746 register RTX_CODE code = GET_CODE (x);
1747 /* If setting something that's a reg or part of one,
1748 see if that register's altered value will be live. */
1752 register rtx r = SET_DEST (x);
1753 /* A SET that is a subroutine call cannot be dead. */
1754 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1758 if (GET_CODE (r) == CC0)
1762 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1763 && rtx_equal_p (r, last_mem_set))
1766 while (GET_CODE (r) == SUBREG
1767 || GET_CODE (r) == STRICT_LOW_PART
1768 || GET_CODE (r) == ZERO_EXTRACT
1769 || GET_CODE (r) == SIGN_EXTRACT)
1772 if (GET_CODE (r) == REG)
1774 register int regno = REGNO (r);
1776 /* Don't delete insns to set global regs. */
1777 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1778 /* Make sure insns to set frame pointer aren't deleted. */
1779 || regno == FRAME_POINTER_REGNUM
1780 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1781 || regno == HARD_FRAME_POINTER_REGNUM
1783 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1784 /* Make sure insns to set arg pointer are never deleted
1785 (if the arg pointer isn't fixed, there will be a USE for
1786 it, so we can treat it normally). */
1787 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1789 || REGNO_REG_SET_P (needed, regno))
1792 /* If this is a hard register, verify that subsequent words are
1794 if (regno < FIRST_PSEUDO_REGISTER)
1796 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1799 if (REGNO_REG_SET_P (needed, regno+n))
1806 /* If performing several activities,
1807 insn is dead if each activity is individually dead.
1808 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1809 that's inside a PARALLEL doesn't make the insn worth keeping. */
1810 else if (code == PARALLEL)
1812 register int i = XVECLEN (x, 0);
1813 for (i--; i >= 0; i--)
1815 rtx elt = XVECEXP (x, 0, i);
1816 if (!insn_dead_p (elt, needed, call_ok)
1817 && GET_CODE (elt) != CLOBBER
1818 && GET_CODE (elt) != USE)
1823 /* We do not check CLOBBER or USE here.
1824 An insn consisting of just a CLOBBER or just a USE
1825 should not be deleted. */
1829 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1830 return 1 if the entire library call is dead.
1831 This is true if X copies a register (hard or pseudo)
1832 and if the hard return reg of the call insn is dead.
1833 (The caller should have tested the destination of X already for death.)
1835 If this insn doesn't just copy a register, then we don't
1836 have an ordinary libcall. In that case, cse could not have
1837 managed to substitute the source for the dest later on,
1838 so we can assume the libcall is dead.
1840 NEEDED is the bit vector of pseudoregs live before this insn.
1841 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1844 libcall_dead_p (x, needed, note, insn)
1850 register RTX_CODE code = GET_CODE (x);
1854 register rtx r = SET_SRC (x);
1855 if (GET_CODE (r) == REG)
1857 rtx call = XEXP (note, 0);
1860 /* Find the call insn. */
1861 while (call != insn && GET_CODE (call) != CALL_INSN)
1862 call = NEXT_INSN (call);
1864 /* If there is none, do nothing special,
1865 since ordinary death handling can understand these insns. */
1869 /* See if the hard reg holding the value is dead.
1870 If this is a PARALLEL, find the call within it. */
1871 call = PATTERN (call);
1872 if (GET_CODE (call) == PARALLEL)
1874 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1875 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1876 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1879 /* This may be a library call that is returning a value
1880 via invisible pointer. Do nothing special, since
1881 ordinary death handling can understand these insns. */
1885 call = XVECEXP (call, 0, i);
1888 return insn_dead_p (call, needed, 1);
1894 /* Return 1 if register REGNO was used before it was set.
1895 In other words, if it is live at function entry.
1896 Don't count global register variables or variables in registers
1897 that can be used for function arg passing, though. */
1900 regno_uninitialized (regno)
1903 if (n_basic_blocks == 0
1904 || (regno < FIRST_PSEUDO_REGISTER
1905 && (global_regs[regno] || FUNCTION_ARG_REGNO_P (regno))))
1908 return REGNO_REG_SET_P (basic_block_live_at_start[0], regno);
1911 /* 1 if register REGNO was alive at a place where `setjmp' was called
1912 and was set more than once or is an argument.
1913 Such regs may be clobbered by `longjmp'. */
1916 regno_clobbered_at_setjmp (regno)
1919 if (n_basic_blocks == 0)
1922 return ((REG_N_SETS (regno) > 1
1923 || REGNO_REG_SET_P (basic_block_live_at_start[0], regno))
1924 && REGNO_REG_SET_P (regs_live_at_setjmp, regno));
1927 /* Process the registers that are set within X.
1928 Their bits are set to 1 in the regset DEAD,
1929 because they are dead prior to this insn.
1931 If INSN is nonzero, it is the insn being processed
1932 and the fact that it is nonzero implies this is the FINAL pass
1933 in propagate_block. In this case, various info about register
1934 usage is stored, LOG_LINKS fields of insns are set up. */
1937 mark_set_regs (needed, dead, x, insn, significant)
1944 register RTX_CODE code = GET_CODE (x);
1946 if (code == SET || code == CLOBBER)
1947 mark_set_1 (needed, dead, x, insn, significant);
1948 else if (code == PARALLEL)
1951 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1953 code = GET_CODE (XVECEXP (x, 0, i));
1954 if (code == SET || code == CLOBBER)
1955 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1960 /* Process a single SET rtx, X. */
1963 mark_set_1 (needed, dead, x, insn, significant)
1971 register rtx reg = SET_DEST (x);
1973 /* Modifying just one hardware register of a multi-reg value
1974 or just a byte field of a register
1975 does not mean the value from before this insn is now dead.
1976 But it does mean liveness of that register at the end of the block
1979 Within mark_set_1, however, we treat it as if the register is
1980 indeed modified. mark_used_regs will, however, also treat this
1981 register as being used. Thus, we treat these insns as setting a
1982 new value for the register as a function of its old value. This
1983 cases LOG_LINKS to be made appropriately and this will help combine. */
1985 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1986 || GET_CODE (reg) == SIGN_EXTRACT
1987 || GET_CODE (reg) == STRICT_LOW_PART)
1988 reg = XEXP (reg, 0);
1990 /* If we are writing into memory or into a register mentioned in the
1991 address of the last thing stored into memory, show we don't know
1992 what the last store was. If we are writing memory, save the address
1993 unless it is volatile. */
1994 if (GET_CODE (reg) == MEM
1995 || (GET_CODE (reg) == REG
1996 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1999 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
2000 /* There are no REG_INC notes for SP, so we can't assume we'll see
2001 everything that invalidates it. To be safe, don't eliminate any
2002 stores though SP; none of them should be redundant anyway. */
2003 && ! reg_mentioned_p (stack_pointer_rtx, reg))
2006 if (GET_CODE (reg) == REG
2007 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
2008 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2009 && regno != HARD_FRAME_POINTER_REGNUM
2011 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2012 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2014 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
2015 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
2017 int some_needed = REGNO_REG_SET_P (needed, regno);
2018 int some_not_needed = ! some_needed;
2020 /* Mark it as a significant register for this basic block. */
2022 SET_REGNO_REG_SET (significant, regno);
2024 /* Mark it as as dead before this insn. */
2025 SET_REGNO_REG_SET (dead, regno);
2027 /* A hard reg in a wide mode may really be multiple registers.
2028 If so, mark all of them just like the first. */
2029 if (regno < FIRST_PSEUDO_REGISTER)
2033 /* Nothing below is needed for the stack pointer; get out asap.
2034 Eg, log links aren't needed, since combine won't use them. */
2035 if (regno == STACK_POINTER_REGNUM)
2038 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
2041 int regno_n = regno + n;
2042 int needed_regno = REGNO_REG_SET_P (needed, regno_n);
2044 SET_REGNO_REG_SET (significant, regno_n);
2046 SET_REGNO_REG_SET (dead, regno_n);
2047 some_needed |= needed_regno;
2048 some_not_needed |= ! needed_regno;
2051 /* Additional data to record if this is the final pass. */
2054 register rtx y = reg_next_use[regno];
2055 register int blocknum = BLOCK_NUM (insn);
2057 /* If this is a hard reg, record this function uses the reg. */
2059 if (regno < FIRST_PSEUDO_REGISTER)
2062 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
2064 for (i = regno; i < endregno; i++)
2066 /* The next use is no longer "next", since a store
2068 reg_next_use[i] = 0;
2070 regs_ever_live[i] = 1;
2076 /* The next use is no longer "next", since a store
2078 reg_next_use[regno] = 0;
2080 /* Keep track of which basic blocks each reg appears in. */
2082 if (REG_BASIC_BLOCK (regno) == REG_BLOCK_UNKNOWN)
2083 REG_BASIC_BLOCK (regno) = blocknum;
2084 else if (REG_BASIC_BLOCK (regno) != blocknum)
2085 REG_BASIC_BLOCK (regno) = REG_BLOCK_GLOBAL;
2087 /* Count (weighted) references, stores, etc. This counts a
2088 register twice if it is modified, but that is correct. */
2089 REG_N_SETS (regno)++;
2091 REG_N_REFS (regno) += loop_depth;
2093 /* The insns where a reg is live are normally counted
2094 elsewhere, but we want the count to include the insn
2095 where the reg is set, and the normal counting mechanism
2096 would not count it. */
2097 REG_LIVE_LENGTH (regno)++;
2100 if (! some_not_needed)
2102 /* Make a logical link from the next following insn
2103 that uses this register, back to this insn.
2104 The following insns have already been processed.
2106 We don't build a LOG_LINK for hard registers containing
2107 in ASM_OPERANDs. If these registers get replaced,
2108 we might wind up changing the semantics of the insn,
2109 even if reload can make what appear to be valid assignments
2111 if (y && (BLOCK_NUM (y) == blocknum)
2112 && (regno >= FIRST_PSEUDO_REGISTER
2113 || asm_noperands (PATTERN (y)) < 0))
2115 = gen_rtx_INSN_LIST (VOIDmode, insn, LOG_LINKS (y));
2117 else if (! some_needed)
2119 /* Note that dead stores have already been deleted when possible
2120 If we get here, we have found a dead store that cannot
2121 be eliminated (because the same insn does something useful).
2122 Indicate this by marking the reg being set as dying here. */
2124 = gen_rtx_EXPR_LIST (REG_UNUSED, reg, REG_NOTES (insn));
2125 REG_N_DEATHS (REGNO (reg))++;
2129 /* This is a case where we have a multi-word hard register
2130 and some, but not all, of the words of the register are
2131 needed in subsequent insns. Write REG_UNUSED notes
2132 for those parts that were not needed. This case should
2137 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
2139 if (!REGNO_REG_SET_P (needed, regno + i))
2141 = gen_rtx_EXPR_LIST (REG_UNUSED,
2142 gen_rtx_REG (reg_raw_mode[regno + i],
2148 else if (GET_CODE (reg) == REG)
2149 reg_next_use[regno] = 0;
2151 /* If this is the last pass and this is a SCRATCH, show it will be dying
2152 here and count it. */
2153 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2156 = gen_rtx_EXPR_LIST (REG_UNUSED, reg, REG_NOTES (insn));
2163 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2167 find_auto_inc (needed, x, insn)
2172 rtx addr = XEXP (x, 0);
2173 HOST_WIDE_INT offset = 0;
2176 /* Here we detect use of an index register which might be good for
2177 postincrement, postdecrement, preincrement, or predecrement. */
2179 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2180 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2182 if (GET_CODE (addr) == REG)
2185 register int size = GET_MODE_SIZE (GET_MODE (x));
2188 int regno = REGNO (addr);
2190 /* Is the next use an increment that might make auto-increment? */
2191 if ((incr = reg_next_use[regno]) != 0
2192 && (set = single_set (incr)) != 0
2193 && GET_CODE (set) == SET
2194 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2195 /* Can't add side effects to jumps; if reg is spilled and
2196 reloaded, there's no way to store back the altered value. */
2197 && GET_CODE (insn) != JUMP_INSN
2198 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2199 && XEXP (y, 0) == addr
2200 && GET_CODE (XEXP (y, 1)) == CONST_INT
2202 #ifdef HAVE_POST_INCREMENT
2203 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2205 #ifdef HAVE_POST_DECREMENT
2206 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2208 #ifdef HAVE_PRE_INCREMENT
2209 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2211 #ifdef HAVE_PRE_DECREMENT
2212 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2215 /* Make sure this reg appears only once in this insn. */
2216 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2217 use != 0 && use != (rtx) 1))
2219 rtx q = SET_DEST (set);
2220 enum rtx_code inc_code = (INTVAL (XEXP (y, 1)) == size
2221 ? (offset ? PRE_INC : POST_INC)
2222 : (offset ? PRE_DEC : POST_DEC));
2224 if (dead_or_set_p (incr, addr))
2226 /* This is the simple case. Try to make the auto-inc. If
2227 we can't, we are done. Otherwise, we will do any
2228 needed updates below. */
2229 if (! validate_change (insn, &XEXP (x, 0),
2230 gen_rtx_fmt_e (inc_code, Pmode, addr),
2234 else if (GET_CODE (q) == REG
2235 /* PREV_INSN used here to check the semi-open interval
2237 && ! reg_used_between_p (q, PREV_INSN (insn), incr)
2238 /* We must also check for sets of q as q may be
2239 a call clobbered hard register and there may
2240 be a call between PREV_INSN (insn) and incr. */
2241 && ! reg_set_between_p (q, PREV_INSN (insn), incr))
2243 /* We have *p followed sometime later by q = p+size.
2244 Both p and q must be live afterward,
2245 and q is not used between INSN and it's assignment.
2246 Change it to q = p, ...*q..., q = q+size.
2247 Then fall into the usual case. */
2251 emit_move_insn (q, addr);
2252 insns = get_insns ();
2255 /* If anything in INSNS have UID's that don't fit within the
2256 extra space we allocate earlier, we can't make this auto-inc.
2257 This should never happen. */
2258 for (temp = insns; temp; temp = NEXT_INSN (temp))
2260 if (INSN_UID (temp) > max_uid_for_flow)
2262 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2265 /* If we can't make the auto-inc, or can't make the
2266 replacement into Y, exit. There's no point in making
2267 the change below if we can't do the auto-inc and doing
2268 so is not correct in the pre-inc case. */
2270 validate_change (insn, &XEXP (x, 0),
2271 gen_rtx_fmt_e (inc_code, Pmode, q),
2273 validate_change (incr, &XEXP (y, 0), q, 1);
2274 if (! apply_change_group ())
2277 /* We now know we'll be doing this change, so emit the
2278 new insn(s) and do the updates. */
2279 emit_insns_before (insns, insn);
2281 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2282 basic_block_head[BLOCK_NUM (insn)] = insns;
2284 /* INCR will become a NOTE and INSN won't contain a
2285 use of ADDR. If a use of ADDR was just placed in
2286 the insn before INSN, make that the next use.
2287 Otherwise, invalidate it. */
2288 if (GET_CODE (PREV_INSN (insn)) == INSN
2289 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2290 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2291 reg_next_use[regno] = PREV_INSN (insn);
2293 reg_next_use[regno] = 0;
2298 /* REGNO is now used in INCR which is below INSN, but
2299 it previously wasn't live here. If we don't mark
2300 it as needed, we'll put a REG_DEAD note for it
2301 on this insn, which is incorrect. */
2302 SET_REGNO_REG_SET (needed, regno);
2304 /* If there are any calls between INSN and INCR, show
2305 that REGNO now crosses them. */
2306 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2307 if (GET_CODE (temp) == CALL_INSN)
2308 REG_N_CALLS_CROSSED (regno)++;
2313 /* If we haven't returned, it means we were able to make the
2314 auto-inc, so update the status. First, record that this insn
2315 has an implicit side effect. */
2318 = gen_rtx_EXPR_LIST (REG_INC, addr, REG_NOTES (insn));
2320 /* Modify the old increment-insn to simply copy
2321 the already-incremented value of our register. */
2322 if (! validate_change (incr, &SET_SRC (set), addr, 0))
2325 /* If that makes it a no-op (copying the register into itself) delete
2326 it so it won't appear to be a "use" and a "set" of this
2328 if (SET_DEST (set) == addr)
2330 PUT_CODE (incr, NOTE);
2331 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2332 NOTE_SOURCE_FILE (incr) = 0;
2335 if (regno >= FIRST_PSEUDO_REGISTER)
2337 /* Count an extra reference to the reg. When a reg is
2338 incremented, spilling it is worse, so we want to make
2339 that less likely. */
2340 REG_N_REFS (regno) += loop_depth;
2342 /* Count the increment as a setting of the register,
2343 even though it isn't a SET in rtl. */
2344 REG_N_SETS (regno)++;
2349 #endif /* AUTO_INC_DEC */
2351 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2352 This is done assuming the registers needed from X
2353 are those that have 1-bits in NEEDED.
2355 On the final pass, FINAL is 1. This means try for autoincrement
2356 and count the uses and deaths of each pseudo-reg.
2358 INSN is the containing instruction. If INSN is dead, this function is not
2362 mark_used_regs (needed, live, x, final, insn)
2369 register RTX_CODE code;
2374 code = GET_CODE (x);
2395 /* If we are clobbering a MEM, mark any registers inside the address
2397 if (GET_CODE (XEXP (x, 0)) == MEM)
2398 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2402 /* Invalidate the data for the last MEM stored, but only if MEM is
2403 something that can be stored into. */
2404 if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
2405 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
2406 ; /* needn't clear last_mem_set */
2412 find_auto_inc (needed, x, insn);
2417 if (GET_CODE (SUBREG_REG (x)) == REG
2418 && REGNO (SUBREG_REG (x)) >= FIRST_PSEUDO_REGISTER
2419 && (GET_MODE_SIZE (GET_MODE (x))
2420 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))))
2421 REG_CHANGES_SIZE (REGNO (SUBREG_REG (x))) = 1;
2423 /* While we're here, optimize this case. */
2426 /* In case the SUBREG is not of a register, don't optimize */
2427 if (GET_CODE (x) != REG)
2429 mark_used_regs (needed, live, x, final, insn);
2433 /* ... fall through ... */
2436 /* See a register other than being set
2437 => mark it as needed. */
2441 int some_needed = REGNO_REG_SET_P (needed, regno);
2442 int some_not_needed = ! some_needed;
2444 SET_REGNO_REG_SET (live, regno);
2446 /* A hard reg in a wide mode may really be multiple registers.
2447 If so, mark all of them just like the first. */
2448 if (regno < FIRST_PSEUDO_REGISTER)
2452 /* For stack ptr or fixed arg pointer,
2453 nothing below can be necessary, so waste no more time. */
2454 if (regno == STACK_POINTER_REGNUM
2455 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2456 || regno == HARD_FRAME_POINTER_REGNUM
2458 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2459 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2461 || regno == FRAME_POINTER_REGNUM)
2463 /* If this is a register we are going to try to eliminate,
2464 don't mark it live here. If we are successful in
2465 eliminating it, it need not be live unless it is used for
2466 pseudos, in which case it will have been set live when
2467 it was allocated to the pseudos. If the register will not
2468 be eliminated, reload will set it live at that point. */
2470 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2471 regs_ever_live[regno] = 1;
2474 /* No death notes for global register variables;
2475 their values are live after this function exits. */
2476 if (global_regs[regno])
2479 reg_next_use[regno] = insn;
2483 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2486 int regno_n = regno + n;
2487 int needed_regno = REGNO_REG_SET_P (needed, regno_n);
2489 SET_REGNO_REG_SET (live, regno_n);
2490 some_needed |= needed_regno;
2491 some_not_needed |= ! needed_regno;
2496 /* Record where each reg is used, so when the reg
2497 is set we know the next insn that uses it. */
2499 reg_next_use[regno] = insn;
2501 if (regno < FIRST_PSEUDO_REGISTER)
2503 /* If a hard reg is being used,
2504 record that this function does use it. */
2506 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2510 regs_ever_live[regno + --i] = 1;
2515 /* Keep track of which basic block each reg appears in. */
2517 register int blocknum = BLOCK_NUM (insn);
2519 if (REG_BASIC_BLOCK (regno) == REG_BLOCK_UNKNOWN)
2520 REG_BASIC_BLOCK (regno) = blocknum;
2521 else if (REG_BASIC_BLOCK (regno) != blocknum)
2522 REG_BASIC_BLOCK (regno) = REG_BLOCK_GLOBAL;
2524 /* Count (weighted) number of uses of each reg. */
2526 REG_N_REFS (regno) += loop_depth;
2529 /* Record and count the insns in which a reg dies.
2530 If it is used in this insn and was dead below the insn
2531 then it dies in this insn. If it was set in this insn,
2532 we do not make a REG_DEAD note; likewise if we already
2533 made such a note. */
2536 && ! dead_or_set_p (insn, x)
2538 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2542 /* Check for the case where the register dying partially
2543 overlaps the register set by this insn. */
2544 if (regno < FIRST_PSEUDO_REGISTER
2545 && HARD_REGNO_NREGS (regno, GET_MODE (x)) > 1)
2547 int n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2549 some_needed |= dead_or_set_regno_p (insn, regno + n);
2552 /* If none of the words in X is needed, make a REG_DEAD
2553 note. Otherwise, we must make partial REG_DEAD notes. */
2557 = gen_rtx_EXPR_LIST (REG_DEAD, x, REG_NOTES (insn));
2558 REG_N_DEATHS (regno)++;
2564 /* Don't make a REG_DEAD note for a part of a register
2565 that is set in the insn. */
2567 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2569 if (!REGNO_REG_SET_P (needed, regno + i)
2570 && ! dead_or_set_regno_p (insn, regno + i))
2572 = gen_rtx_EXPR_LIST (REG_DEAD,
2573 gen_rtx_REG (reg_raw_mode[regno + i],
2584 register rtx testreg = SET_DEST (x);
2587 /* If storing into MEM, don't show it as being used. But do
2588 show the address as being used. */
2589 if (GET_CODE (testreg) == MEM)
2593 find_auto_inc (needed, testreg, insn);
2595 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2596 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2600 /* Storing in STRICT_LOW_PART is like storing in a reg
2601 in that this SET might be dead, so ignore it in TESTREG.
2602 but in some other ways it is like using the reg.
2604 Storing in a SUBREG or a bit field is like storing the entire
2605 register in that if the register's value is not used
2606 then this SET is not needed. */
2607 while (GET_CODE (testreg) == STRICT_LOW_PART
2608 || GET_CODE (testreg) == ZERO_EXTRACT
2609 || GET_CODE (testreg) == SIGN_EXTRACT
2610 || GET_CODE (testreg) == SUBREG)
2612 if (GET_CODE (testreg) == SUBREG
2613 && GET_CODE (SUBREG_REG (testreg)) == REG
2614 && REGNO (SUBREG_REG (testreg)) >= FIRST_PSEUDO_REGISTER
2615 && (GET_MODE_SIZE (GET_MODE (testreg))
2616 != GET_MODE_SIZE (GET_MODE (SUBREG_REG (testreg)))))
2617 REG_CHANGES_SIZE (REGNO (SUBREG_REG (testreg))) = 1;
2619 /* Modifying a single register in an alternate mode
2620 does not use any of the old value. But these other
2621 ways of storing in a register do use the old value. */
2622 if (GET_CODE (testreg) == SUBREG
2623 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2628 testreg = XEXP (testreg, 0);
2631 /* If this is a store into a register,
2632 recursively scan the value being stored. */
2634 if (GET_CODE (testreg) == REG
2635 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2636 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2637 && regno != HARD_FRAME_POINTER_REGNUM
2639 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2640 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2643 /* We used to exclude global_regs here, but that seems wrong.
2644 Storing in them is like storing in mem. */
2646 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2648 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2655 /* If exiting needs the right stack value, consider this insn as
2656 using the stack pointer. In any event, consider it as using
2657 all global registers and all registers used by return. */
2659 #ifdef EXIT_IGNORE_STACK
2660 if (! EXIT_IGNORE_STACK
2661 || (! FRAME_POINTER_REQUIRED
2662 && ! current_function_calls_alloca
2663 && flag_omit_frame_pointer))
2665 SET_REGNO_REG_SET (live, STACK_POINTER_REGNUM);
2667 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2669 #ifdef EPILOGUE_USES
2670 || EPILOGUE_USES (i)
2673 SET_REGNO_REG_SET (live, i);
2680 /* Recursively scan the operands of this expression. */
2683 register char *fmt = GET_RTX_FORMAT (code);
2686 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2690 /* Tail recursive case: save a function call level. */
2696 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2698 else if (fmt[i] == 'E')
2701 for (j = 0; j < XVECLEN (x, i); j++)
2702 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2711 try_pre_increment_1 (insn)
2714 /* Find the next use of this reg. If in same basic block,
2715 make it do pre-increment or pre-decrement if appropriate. */
2716 rtx x = single_set (insn);
2717 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2718 * INTVAL (XEXP (SET_SRC (x), 1)));
2719 int regno = REGNO (SET_DEST (x));
2720 rtx y = reg_next_use[regno];
2722 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2723 /* Don't do this if the reg dies, or gets set in y; a standard addressing
2724 mode would be better. */
2725 && ! dead_or_set_p (y, SET_DEST (x))
2726 && try_pre_increment (y, SET_DEST (x), amount))
2728 /* We have found a suitable auto-increment
2729 and already changed insn Y to do it.
2730 So flush this increment-instruction. */
2731 PUT_CODE (insn, NOTE);
2732 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2733 NOTE_SOURCE_FILE (insn) = 0;
2734 /* Count a reference to this reg for the increment
2735 insn we are deleting. When a reg is incremented.
2736 spilling it is worse, so we want to make that
2738 if (regno >= FIRST_PSEUDO_REGISTER)
2740 REG_N_REFS (regno) += loop_depth;
2741 REG_N_SETS (regno)++;
2748 /* Try to change INSN so that it does pre-increment or pre-decrement
2749 addressing on register REG in order to add AMOUNT to REG.
2750 AMOUNT is negative for pre-decrement.
2751 Returns 1 if the change could be made.
2752 This checks all about the validity of the result of modifying INSN. */
2755 try_pre_increment (insn, reg, amount)
2757 HOST_WIDE_INT amount;
2761 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2762 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2764 /* Nonzero if we can try to make a post-increment or post-decrement.
2765 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2766 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2767 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2770 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2773 /* From the sign of increment, see which possibilities are conceivable
2774 on this target machine. */
2775 #ifdef HAVE_PRE_INCREMENT
2779 #ifdef HAVE_POST_INCREMENT
2784 #ifdef HAVE_PRE_DECREMENT
2788 #ifdef HAVE_POST_DECREMENT
2793 if (! (pre_ok || post_ok))
2796 /* It is not safe to add a side effect to a jump insn
2797 because if the incremented register is spilled and must be reloaded
2798 there would be no way to store the incremented value back in memory. */
2800 if (GET_CODE (insn) == JUMP_INSN)
2805 use = find_use_as_address (PATTERN (insn), reg, 0);
2806 if (post_ok && (use == 0 || use == (rtx) 1))
2808 use = find_use_as_address (PATTERN (insn), reg, -amount);
2812 if (use == 0 || use == (rtx) 1)
2815 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2818 /* See if this combination of instruction and addressing mode exists. */
2819 if (! validate_change (insn, &XEXP (use, 0),
2820 gen_rtx_fmt_e (amount > 0
2821 ? (do_post ? POST_INC : PRE_INC)
2822 : (do_post ? POST_DEC : PRE_DEC),
2826 /* Record that this insn now has an implicit side effect on X. */
2827 REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_INC, reg, REG_NOTES (insn));
2831 #endif /* AUTO_INC_DEC */
2833 /* Find the place in the rtx X where REG is used as a memory address.
2834 Return the MEM rtx that so uses it.
2835 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2836 (plus REG (const_int PLUSCONST)).
2838 If such an address does not appear, return 0.
2839 If REG appears more than once, or is used other than in such an address,
2843 find_use_as_address (x, reg, plusconst)
2846 HOST_WIDE_INT plusconst;
2848 enum rtx_code code = GET_CODE (x);
2849 char *fmt = GET_RTX_FORMAT (code);
2851 register rtx value = 0;
2854 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2857 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2858 && XEXP (XEXP (x, 0), 0) == reg
2859 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2860 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2863 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2865 /* If REG occurs inside a MEM used in a bit-field reference,
2866 that is unacceptable. */
2867 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2868 return (rtx) (HOST_WIDE_INT) 1;
2872 return (rtx) (HOST_WIDE_INT) 1;
2874 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2878 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2882 return (rtx) (HOST_WIDE_INT) 1;
2887 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2889 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2893 return (rtx) (HOST_WIDE_INT) 1;
2901 /* Write information about registers and basic blocks into FILE.
2902 This is part of making a debugging dump. */
2905 dump_flow_info (file)
2909 static char *reg_class_names[] = REG_CLASS_NAMES;
2911 fprintf (file, "%d registers.\n", max_regno);
2913 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2916 enum reg_class class, altclass;
2917 fprintf (file, "\nRegister %d used %d times across %d insns",
2918 i, REG_N_REFS (i), REG_LIVE_LENGTH (i));
2919 if (REG_BASIC_BLOCK (i) >= 0)
2920 fprintf (file, " in block %d", REG_BASIC_BLOCK (i));
2921 if (REG_N_DEATHS (i) != 1)
2922 fprintf (file, "; dies in %d places", REG_N_DEATHS (i));
2923 if (REG_N_CALLS_CROSSED (i) == 1)
2924 fprintf (file, "; crosses 1 call");
2925 else if (REG_N_CALLS_CROSSED (i))
2926 fprintf (file, "; crosses %d calls", REG_N_CALLS_CROSSED (i));
2927 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2928 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2929 class = reg_preferred_class (i);
2930 altclass = reg_alternate_class (i);
2931 if (class != GENERAL_REGS || altclass != ALL_REGS)
2933 if (altclass == ALL_REGS || class == ALL_REGS)
2934 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2935 else if (altclass == NO_REGS)
2936 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2938 fprintf (file, "; pref %s, else %s",
2939 reg_class_names[(int) class],
2940 reg_class_names[(int) altclass]);
2942 if (REGNO_POINTER_FLAG (i))
2943 fprintf (file, "; pointer");
2944 fprintf (file, ".\n");
2946 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2947 for (i = 0; i < n_basic_blocks; i++)
2949 register rtx head, jump;
2951 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2953 INSN_UID (basic_block_head[i]),
2954 INSN_UID (basic_block_end[i]));
2955 /* The control flow graph's storage is freed
2956 now when flow_analysis returns.
2957 Don't try to print it if it is gone. */
2958 if (basic_block_drops_in)
2960 fprintf (file, "Reached from blocks: ");
2961 head = basic_block_head[i];
2962 if (GET_CODE (head) == CODE_LABEL)
2963 for (jump = LABEL_REFS (head);
2965 jump = LABEL_NEXTREF (jump))
2967 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2968 fprintf (file, " %d", from_block);
2970 if (basic_block_drops_in[i])
2971 fprintf (file, " previous");
2973 fprintf (file, "\nRegisters live at start:");
2974 for (regno = 0; regno < max_regno; regno++)
2975 if (REGNO_REG_SET_P (basic_block_live_at_start[i], regno))
2976 fprintf (file, " %d", regno);
2977 fprintf (file, "\n");
2979 fprintf (file, "\n");
2983 /* Like print_rtl, but also print out live information for the start of each
2987 print_rtl_with_bb (outf, rtx_first)
2991 register rtx tmp_rtx;
2994 fprintf (outf, "(nil)\n");
2999 enum bb_state { NOT_IN_BB, IN_ONE_BB, IN_MULTIPLE_BB };
3000 int max_uid = get_max_uid ();
3001 int *start = (int *) alloca (max_uid * sizeof (int));
3002 int *end = (int *) alloca (max_uid * sizeof (int));
3003 char *in_bb_p = (char *) alloca (max_uid * sizeof (enum bb_state));
3005 for (i = 0; i < max_uid; i++)
3007 start[i] = end[i] = -1;
3008 in_bb_p[i] = NOT_IN_BB;
3011 for (i = n_basic_blocks-1; i >= 0; i--)
3014 start[INSN_UID (basic_block_head[i])] = i;
3015 end[INSN_UID (basic_block_end[i])] = i;
3016 for (x = basic_block_head[i]; x != NULL_RTX; x = NEXT_INSN (x))
3018 in_bb_p[ INSN_UID(x)]
3019 = (in_bb_p[ INSN_UID(x)] == NOT_IN_BB)
3020 ? IN_ONE_BB : IN_MULTIPLE_BB;
3021 if (x == basic_block_end[i])
3026 for (tmp_rtx = rtx_first; NULL != tmp_rtx; tmp_rtx = NEXT_INSN (tmp_rtx))
3028 if ((bb = start[INSN_UID (tmp_rtx)]) >= 0)
3030 fprintf (outf, ";; Start of basic block %d, registers live:",
3033 EXECUTE_IF_SET_IN_REG_SET (basic_block_live_at_start[bb], 0, i,
3035 fprintf (outf, " %d", i);
3036 if (i < FIRST_PSEUDO_REGISTER)
3037 fprintf (outf, " [%s]",
3043 if (in_bb_p[ INSN_UID(tmp_rtx)] == NOT_IN_BB
3044 && GET_CODE (tmp_rtx) != NOTE
3045 && GET_CODE (tmp_rtx) != BARRIER)
3046 fprintf (outf, ";; Insn is not within a basic block\n");
3047 else if (in_bb_p[ INSN_UID(tmp_rtx)] == IN_MULTIPLE_BB)
3048 fprintf (outf, ";; Insn is in multiple basic blocks\n");
3050 print_rtl_single (outf, tmp_rtx);
3052 if ((bb = end[INSN_UID (tmp_rtx)]) >= 0)
3053 fprintf (outf, ";; End of basic block %d\n", bb);
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