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, gives number of places register N dies.
181 This information remains valid for the rest of the compilation
182 of the current function; it is used to control register allocation. */
186 /* Indexed by N, gives 1 if that reg is live across any CALL_INSNs.
187 This information remains valid for the rest of the compilation
188 of the current function; it is used to control register allocation. */
190 int *reg_n_calls_crossed;
192 /* Total number of instructions at which (REG n) is live.
193 The larger this is, the less priority (REG n) gets for
194 allocation in a real register.
195 This information remains valid for the rest of the compilation
196 of the current function; it is used to control register allocation.
198 local-alloc.c may alter this number to change the priority.
200 Negative values are special.
201 -1 is used to mark a pseudo reg which has a constant or memory equivalent
202 and is used infrequently enough that it should not get a hard register.
203 -2 is used to mark a pseudo reg for a parameter, when a frame pointer
204 is not required. global.c makes an allocno for this but does
205 not try to assign a hard register to it. */
207 int *reg_live_length;
209 /* Element N is the next insn that uses (hard or pseudo) register number N
210 within the current basic block; or zero, if there is no such insn.
211 This is valid only during the final backward scan in propagate_block. */
213 static rtx *reg_next_use;
215 /* Size of a regset for the current function,
216 in (1) bytes and (2) elements. */
221 /* Element N is first insn in basic block N.
222 This info lasts until we finish compiling the function. */
224 rtx *basic_block_head;
226 /* Element N is last insn in basic block N.
227 This info lasts until we finish compiling the function. */
229 rtx *basic_block_end;
231 /* Element N is a regset describing the registers live
232 at the start of basic block N.
233 This info lasts until we finish compiling the function. */
235 regset *basic_block_live_at_start;
237 /* Regset of regs live when calls to `setjmp'-like functions happen. */
239 regset regs_live_at_setjmp;
241 /* List made of EXPR_LIST rtx's which gives pairs of pseudo registers
242 that have to go in the same hard reg.
243 The first two regs in the list are a pair, and the next two
244 are another pair, etc. */
247 /* Element N is nonzero if control can drop into basic block N
248 from the preceding basic block. Freed after life_analysis. */
250 static char *basic_block_drops_in;
252 /* Element N is depth within loops of the last insn in basic block number N.
253 Freed after life_analysis. */
255 static short *basic_block_loop_depth;
257 /* Element N nonzero if basic block N can actually be reached.
258 Vector exists only during find_basic_blocks. */
260 static char *block_live_static;
262 /* Depth within loops of basic block being scanned for lifetime analysis,
263 plus one. This is the weight attached to references to registers. */
265 static int loop_depth;
267 /* During propagate_block, this is non-zero if the value of CC0 is live. */
271 /* During propagate_block, this contains the last MEM stored into. It
272 is used to eliminate consecutive stores to the same location. */
274 static rtx last_mem_set;
276 /* Set of registers that may be eliminable. These are handled specially
277 in updating regs_ever_live. */
279 static HARD_REG_SET elim_reg_set;
281 /* Forward declarations */
282 static void find_basic_blocks PROTO((rtx, rtx));
283 static int uses_reg_or_mem PROTO((rtx));
284 static void mark_label_ref PROTO((rtx, rtx, int));
285 static void life_analysis PROTO((rtx, int));
286 void allocate_for_life_analysis PROTO((void));
287 static void init_regset_vector PROTO((regset *, regset, int, int));
288 static void propagate_block PROTO((regset, rtx, rtx, int,
290 static int insn_dead_p PROTO((rtx, regset, int));
291 static int libcall_dead_p PROTO((rtx, regset, rtx, rtx));
292 static void mark_set_regs PROTO((regset, regset, rtx,
294 static void mark_set_1 PROTO((regset, regset, rtx,
296 static void find_auto_inc PROTO((regset, rtx, rtx));
297 static void mark_used_regs PROTO((regset, regset, rtx, int, rtx));
298 static int try_pre_increment_1 PROTO((rtx));
299 static int try_pre_increment PROTO((rtx, rtx, HOST_WIDE_INT));
300 static rtx find_use_as_address PROTO((rtx, rtx, HOST_WIDE_INT));
301 void dump_flow_info PROTO((FILE *));
303 /* Find basic blocks of the current function and perform data flow analysis.
304 F is the first insn of the function and NREGS the number of register numbers
308 flow_analysis (f, nregs, file)
315 rtx nonlocal_label_list = nonlocal_label_rtx_list ();
317 #ifdef ELIMINABLE_REGS
318 static struct {int from, to; } eliminables[] = ELIMINABLE_REGS;
321 /* Record which registers will be eliminated. We use this in
324 CLEAR_HARD_REG_SET (elim_reg_set);
326 #ifdef ELIMINABLE_REGS
327 for (i = 0; i < sizeof eliminables / sizeof eliminables[0]; i++)
328 SET_HARD_REG_BIT (elim_reg_set, eliminables[i].from);
330 SET_HARD_REG_BIT (elim_reg_set, FRAME_POINTER_REGNUM);
333 /* Count the basic blocks. Also find maximum insn uid value used. */
336 register RTX_CODE prev_code = JUMP_INSN;
337 register RTX_CODE code;
339 max_uid_for_flow = 0;
341 for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
343 code = GET_CODE (insn);
344 if (INSN_UID (insn) > max_uid_for_flow)
345 max_uid_for_flow = INSN_UID (insn);
346 if (code == CODE_LABEL
347 || (GET_RTX_CLASS (code) == 'i'
348 && (prev_code == JUMP_INSN
349 || (prev_code == CALL_INSN
350 && nonlocal_label_list != 0)
351 || prev_code == BARRIER)))
359 /* Leave space for insns we make in some cases for auto-inc. These cases
360 are rare, so we don't need too much space. */
361 max_uid_for_flow += max_uid_for_flow / 10;
364 /* Allocate some tables that last till end of compiling this function
365 and some needed only in find_basic_blocks and life_analysis. */
368 basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
369 basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
370 basic_block_drops_in = (char *) alloca (n_basic_blocks);
371 basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
373 = (int *) alloca ((max_uid_for_flow + 1) * sizeof (int));
374 uid_volatile = (char *) alloca (max_uid_for_flow + 1);
375 bzero (uid_volatile, max_uid_for_flow + 1);
377 find_basic_blocks (f, nonlocal_label_list);
378 life_analysis (f, nregs);
380 dump_flow_info (file);
382 basic_block_drops_in = 0;
383 uid_block_number = 0;
384 basic_block_loop_depth = 0;
387 /* Find all basic blocks of the function whose first insn is F.
388 Store the correct data in the tables that describe the basic blocks,
389 set up the chains of references for each CODE_LABEL, and
390 delete any entire basic blocks that cannot be reached.
392 NONLOCAL_LABEL_LIST is the same local variable from flow_analysis. */
395 find_basic_blocks (f, nonlocal_label_list)
396 rtx f, nonlocal_label_list;
400 register char *block_live = (char *) alloca (n_basic_blocks);
401 register char *block_marked = (char *) alloca (n_basic_blocks);
402 /* List of label_refs to all labels whose addresses are taken
404 rtx label_value_list = 0;
406 enum rtx_code prev_code, code;
409 block_live_static = block_live;
410 bzero (block_live, n_basic_blocks);
411 bzero (block_marked, n_basic_blocks);
413 /* Initialize with just block 0 reachable and no blocks marked. */
414 if (n_basic_blocks > 0)
417 /* Initialize the ref chain of each label to 0. Record where all the
418 blocks start and end and their depth in loops. For each insn, record
419 the block it is in. Also mark as reachable any blocks headed by labels
420 that must not be deleted. */
422 for (insn = f, i = -1, prev_code = JUMP_INSN, depth = 1;
423 insn; insn = NEXT_INSN (insn))
425 code = GET_CODE (insn);
428 if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
430 else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
434 /* A basic block starts at label, or after something that can jump. */
435 else if (code == CODE_LABEL
436 || (GET_RTX_CLASS (code) == 'i'
437 && (prev_code == JUMP_INSN
438 || (prev_code == CALL_INSN
439 && nonlocal_label_list != 0)
440 || prev_code == BARRIER)))
442 basic_block_head[++i] = insn;
443 basic_block_end[i] = insn;
444 basic_block_loop_depth[i] = depth;
446 if (code == CODE_LABEL)
448 LABEL_REFS (insn) = insn;
449 /* Any label that cannot be deleted
450 is considered to start a reachable block. */
451 if (LABEL_PRESERVE_P (insn))
456 else if (GET_RTX_CLASS (code) == 'i')
458 basic_block_end[i] = insn;
459 basic_block_loop_depth[i] = depth;
462 if (GET_RTX_CLASS (code) == 'i')
464 /* Make a list of all labels referred to other than by jumps. */
465 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
466 if (REG_NOTE_KIND (note) == REG_LABEL)
467 label_value_list = gen_rtx (EXPR_LIST, VOIDmode, XEXP (note, 0),
471 BLOCK_NUM (insn) = i;
477 if (i + 1 != n_basic_blocks)
480 /* Don't delete the labels (in this function)
481 that are referenced by non-jump instructions. */
483 for (x = label_value_list; x; x = XEXP (x, 1))
484 if (! LABEL_REF_NONLOCAL_P (x))
485 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
487 for (x = forced_labels; x; x = XEXP (x, 1))
488 if (! LABEL_REF_NONLOCAL_P (x))
489 block_live[BLOCK_NUM (XEXP (x, 0))] = 1;
491 /* Record which basic blocks control can drop in to. */
493 for (i = 0; i < n_basic_blocks; i++)
495 for (insn = PREV_INSN (basic_block_head[i]);
496 insn && GET_CODE (insn) == NOTE; insn = PREV_INSN (insn))
499 basic_block_drops_in[i] = insn && GET_CODE (insn) != BARRIER;
502 /* Now find which basic blocks can actually be reached
503 and put all jump insns' LABEL_REFS onto the ref-chains
504 of their target labels. */
506 if (n_basic_blocks > 0)
508 int something_marked = 1;
510 /* Find all indirect jump insns and mark them as possibly jumping to all
511 the labels whose addresses are explicitly used. This is because,
512 when there are computed gotos, we can't tell which labels they jump
513 to, of all the possibilities.
515 Tablejumps and casesi insns are OK and we can recognize them by
516 a (use (label_ref)). */
518 for (insn = f; insn; insn = NEXT_INSN (insn))
519 if (GET_CODE (insn) == JUMP_INSN)
521 rtx pat = PATTERN (insn);
522 int computed_jump = 0;
524 if (GET_CODE (pat) == PARALLEL)
526 int len = XVECLEN (pat, 0);
527 int has_use_labelref = 0;
529 for (i = len - 1; i >= 0; i--)
530 if (GET_CODE (XVECEXP (pat, 0, i)) == USE
531 && (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
533 has_use_labelref = 1;
535 if (! has_use_labelref)
536 for (i = len - 1; i >= 0; i--)
537 if (GET_CODE (XVECEXP (pat, 0, i)) == SET
538 && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
539 && uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
542 else if (GET_CODE (pat) == SET
543 && SET_DEST (pat) == pc_rtx
544 && uses_reg_or_mem (SET_SRC (pat)))
549 for (x = label_value_list; x; x = XEXP (x, 1))
550 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
553 for (x = forced_labels; x; x = XEXP (x, 1))
554 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
559 /* Find all call insns and mark them as possibly jumping
560 to all the nonlocal goto handler labels. */
562 for (insn = f; insn; insn = NEXT_INSN (insn))
563 if (GET_CODE (insn) == CALL_INSN)
565 for (x = nonlocal_label_list; x; x = XEXP (x, 1))
566 /* Don't try marking labels that
567 were deleted as unreferenced. */
568 if (GET_CODE (XEXP (x, 0)) == CODE_LABEL)
569 mark_label_ref (gen_rtx (LABEL_REF, VOIDmode, XEXP (x, 0)),
572 /* ??? This could be made smarter:
573 in some cases it's possible to tell that certain
574 calls will not do a nonlocal goto.
576 For example, if the nested functions that do the
577 nonlocal gotos do not have their addresses taken, then
578 only calls to those functions or to other nested
579 functions that use them could possibly do nonlocal
583 /* Pass over all blocks, marking each block that is reachable
584 and has not yet been marked.
585 Keep doing this until, in one pass, no blocks have been marked.
586 Then blocks_live and blocks_marked are identical and correct.
587 In addition, all jumps actually reachable have been marked. */
589 while (something_marked)
591 something_marked = 0;
592 for (i = 0; i < n_basic_blocks; i++)
593 if (block_live[i] && !block_marked[i])
596 something_marked = 1;
597 if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
598 block_live[i + 1] = 1;
599 insn = basic_block_end[i];
600 if (GET_CODE (insn) == JUMP_INSN)
601 mark_label_ref (PATTERN (insn), insn, 0);
605 /* Now delete the code for any basic blocks that can't be reached.
606 They can occur because jump_optimize does not recognize
607 unreachable loops as unreachable. */
609 for (i = 0; i < n_basic_blocks; i++)
612 insn = basic_block_head[i];
615 if (GET_CODE (insn) == BARRIER)
617 if (GET_CODE (insn) != NOTE)
619 PUT_CODE (insn, NOTE);
620 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
621 NOTE_SOURCE_FILE (insn) = 0;
623 if (insn == basic_block_end[i])
625 /* BARRIERs are between basic blocks, not part of one.
626 Delete a BARRIER if the preceding jump is deleted.
627 We cannot alter a BARRIER into a NOTE
628 because it is too short; but we can really delete
629 it because it is not part of a basic block. */
630 if (NEXT_INSN (insn) != 0
631 && GET_CODE (NEXT_INSN (insn)) == BARRIER)
632 delete_insn (NEXT_INSN (insn));
635 insn = NEXT_INSN (insn);
637 /* Each time we delete some basic blocks,
638 see if there is a jump around them that is
639 being turned into a no-op. If so, delete it. */
641 if (block_live[i - 1])
644 for (j = i; j < n_basic_blocks; j++)
648 insn = basic_block_end[i - 1];
649 if (GET_CODE (insn) == JUMP_INSN
650 /* An unconditional jump is the only possibility
651 we must check for, since a conditional one
652 would make these blocks live. */
653 && simplejump_p (insn)
654 && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
655 && INSN_UID (label) != 0
656 && BLOCK_NUM (label) == j)
658 PUT_CODE (insn, NOTE);
659 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
660 NOTE_SOURCE_FILE (insn) = 0;
661 if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
663 delete_insn (NEXT_INSN (insn));
672 /* Return 1 if X contain a REG or MEM that is not in the constant pool. */
678 enum rtx_code code = GET_CODE (x);
684 && ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
685 && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))))
688 fmt = GET_RTX_FORMAT (code);
689 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
692 && uses_reg_or_mem (XEXP (x, i)))
696 for (j = 0; j < XVECLEN (x, i); j++)
697 if (uses_reg_or_mem (XVECEXP (x, i, j)))
704 /* Check expression X for label references;
705 if one is found, add INSN to the label's chain of references.
707 CHECKDUP means check for and avoid creating duplicate references
708 from the same insn. Such duplicates do no serious harm but
709 can slow life analysis. CHECKDUP is set only when duplicates
713 mark_label_ref (x, insn, checkdup)
717 register RTX_CODE code;
721 /* We can be called with NULL when scanning label_value_list. */
726 if (code == LABEL_REF)
728 register rtx label = XEXP (x, 0);
730 if (GET_CODE (label) != CODE_LABEL)
732 /* If the label was never emitted, this insn is junk,
733 but avoid a crash trying to refer to BLOCK_NUM (label).
734 This can happen as a result of a syntax error
735 and a diagnostic has already been printed. */
736 if (INSN_UID (label) == 0)
738 CONTAINING_INSN (x) = insn;
739 /* if CHECKDUP is set, check for duplicate ref from same insn
742 for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
743 if (CONTAINING_INSN (y) == insn)
745 LABEL_NEXTREF (x) = LABEL_REFS (label);
746 LABEL_REFS (label) = x;
747 block_live_static[BLOCK_NUM (label)] = 1;
751 fmt = GET_RTX_FORMAT (code);
752 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
755 mark_label_ref (XEXP (x, i), insn, 0);
759 for (j = 0; j < XVECLEN (x, i); j++)
760 mark_label_ref (XVECEXP (x, i, j), insn, 1);
765 /* Determine which registers are live at the start of each
766 basic block of the function whose first insn is F.
767 NREGS is the number of registers used in F.
768 We allocate the vector basic_block_live_at_start
769 and the regsets that it points to, and fill them with the data.
770 regset_size and regset_bytes are also set here. */
773 life_analysis (f, nregs)
780 /* For each basic block, a bitmask of regs
781 live on exit from the block. */
782 regset *basic_block_live_at_end;
783 /* For each basic block, a bitmask of regs
784 live on entry to a successor-block of this block.
785 If this does not match basic_block_live_at_end,
786 that must be updated, and the block must be rescanned. */
787 regset *basic_block_new_live_at_end;
788 /* For each basic block, a bitmask of regs
789 whose liveness at the end of the basic block
790 can make a difference in which regs are live on entry to the block.
791 These are the regs that are set within the basic block,
792 possibly excluding those that are used after they are set. */
793 regset *basic_block_significant;
797 struct obstack flow_obstack;
799 gcc_obstack_init (&flow_obstack);
803 bzero (regs_ever_live, sizeof regs_ever_live);
805 /* Allocate and zero out many data structures
806 that will record the data from lifetime analysis. */
808 allocate_for_life_analysis ();
810 reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
811 bzero (reg_next_use, nregs * sizeof (rtx));
813 /* Set up several regset-vectors used internally within this function.
814 Their meanings are documented above, with their declarations. */
816 basic_block_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset));
817 /* Don't use alloca since that leads to a crash rather than an error message
818 if there isn't enough space.
819 Don't use oballoc since we may need to allocate other things during
820 this function on the temporary obstack. */
821 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
822 bzero (tem, n_basic_blocks * regset_bytes);
823 init_regset_vector (basic_block_live_at_end, tem, n_basic_blocks, regset_bytes);
825 basic_block_new_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset));
826 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
827 bzero (tem, n_basic_blocks * regset_bytes);
828 init_regset_vector (basic_block_new_live_at_end, tem, n_basic_blocks, regset_bytes);
830 basic_block_significant = (regset *) alloca (n_basic_blocks * sizeof (regset));
831 tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
832 bzero (tem, n_basic_blocks * regset_bytes);
833 init_regset_vector (basic_block_significant, tem, n_basic_blocks, regset_bytes);
835 /* Record which insns refer to any volatile memory
836 or for any reason can't be deleted just because they are dead stores.
837 Also, delete any insns that copy a register to itself. */
839 for (insn = f; insn; insn = NEXT_INSN (insn))
841 enum rtx_code code1 = GET_CODE (insn);
842 if (code1 == CALL_INSN)
843 INSN_VOLATILE (insn) = 1;
844 else if (code1 == INSN || code1 == JUMP_INSN)
846 /* Delete (in effect) any obvious no-op moves. */
847 if (GET_CODE (PATTERN (insn)) == SET
848 && GET_CODE (SET_DEST (PATTERN (insn))) == REG
849 && GET_CODE (SET_SRC (PATTERN (insn))) == REG
850 && REGNO (SET_DEST (PATTERN (insn))) ==
851 REGNO (SET_SRC (PATTERN (insn)))
852 /* Insns carrying these notes are useful later on. */
853 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
855 PUT_CODE (insn, NOTE);
856 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
857 NOTE_SOURCE_FILE (insn) = 0;
859 else if (GET_CODE (PATTERN (insn)) == PARALLEL)
861 /* If nothing but SETs of registers to themselves,
862 this insn can also be deleted. */
863 for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
865 rtx tem = XVECEXP (PATTERN (insn), 0, i);
867 if (GET_CODE (tem) == USE
868 || GET_CODE (tem) == CLOBBER)
871 if (GET_CODE (tem) != SET
872 || GET_CODE (SET_DEST (tem)) != REG
873 || GET_CODE (SET_SRC (tem)) != REG
874 || REGNO (SET_DEST (tem)) != REGNO (SET_SRC (tem)))
878 if (i == XVECLEN (PATTERN (insn), 0)
879 /* Insns carrying these notes are useful later on. */
880 && ! find_reg_note (insn, REG_EQUAL, NULL_RTX))
882 PUT_CODE (insn, NOTE);
883 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
884 NOTE_SOURCE_FILE (insn) = 0;
887 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
889 else if (GET_CODE (PATTERN (insn)) != USE)
890 INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
891 /* A SET that makes space on the stack cannot be dead.
892 (Such SETs occur only for allocating variable-size data,
893 so they will always have a PLUS or MINUS according to the
894 direction of stack growth.)
895 Even if this function never uses this stack pointer value,
896 signal handlers do! */
897 else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
898 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
899 #ifdef STACK_GROWS_DOWNWARD
900 && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
902 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
904 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
905 INSN_VOLATILE (insn) = 1;
909 if (n_basic_blocks > 0)
910 #ifdef EXIT_IGNORE_STACK
911 if (! EXIT_IGNORE_STACK
912 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
915 /* If exiting needs the right stack value,
916 consider the stack pointer live at the end of the function. */
917 basic_block_live_at_end[n_basic_blocks - 1]
918 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
919 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
920 basic_block_new_live_at_end[n_basic_blocks - 1]
921 [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
922 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
925 /* Mark the frame pointer is needed at the end of the function. If
926 we end up eliminating it, it will be removed from the live list
927 of each basic block by reload. */
929 if (n_basic_blocks > 0)
931 basic_block_live_at_end[n_basic_blocks - 1]
932 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
933 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
934 basic_block_new_live_at_end[n_basic_blocks - 1]
935 [FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
936 |= (REGSET_ELT_TYPE) 1 << (FRAME_POINTER_REGNUM % REGSET_ELT_BITS);
937 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
938 /* If they are different, also mark the hard frame pointer as live */
939 basic_block_live_at_end[n_basic_blocks - 1]
940 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
941 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
943 basic_block_new_live_at_end[n_basic_blocks - 1]
944 [HARD_FRAME_POINTER_REGNUM / REGSET_ELT_BITS]
945 |= (REGSET_ELT_TYPE) 1 << (HARD_FRAME_POINTER_REGNUM
950 /* Mark all global registers as being live at the end of the function
951 since they may be referenced by our caller. */
953 if (n_basic_blocks > 0)
954 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
957 basic_block_live_at_end[n_basic_blocks - 1]
958 [i / REGSET_ELT_BITS]
959 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
960 basic_block_new_live_at_end[n_basic_blocks - 1]
961 [i / REGSET_ELT_BITS]
962 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
965 /* Propagate life info through the basic blocks
966 around the graph of basic blocks.
968 This is a relaxation process: each time a new register
969 is live at the end of the basic block, we must scan the block
970 to determine which registers are, as a consequence, live at the beginning
971 of that block. These registers must then be marked live at the ends
972 of all the blocks that can transfer control to that block.
973 The process continues until it reaches a fixed point. */
980 for (i = n_basic_blocks - 1; i >= 0; i--)
982 int consider = first_pass;
983 int must_rescan = first_pass;
988 /* Set CONSIDER if this block needs thinking about at all
989 (that is, if the regs live now at the end of it
990 are not the same as were live at the end of it when
991 we last thought about it).
992 Set must_rescan if it needs to be thought about
993 instruction by instruction (that is, if any additional
994 reg that is live at the end now but was not live there before
995 is one of the significant regs of this basic block). */
997 for (j = 0; j < regset_size; j++)
999 register REGSET_ELT_TYPE x
1000 = (basic_block_new_live_at_end[i][j]
1001 & ~basic_block_live_at_end[i][j]);
1004 if (x & basic_block_significant[i][j])
1016 /* The live_at_start of this block may be changing,
1017 so another pass will be required after this one. */
1022 /* No complete rescan needed;
1023 just record those variables newly known live at end
1024 as live at start as well. */
1025 for (j = 0; j < regset_size; j++)
1027 register REGSET_ELT_TYPE x
1028 = (basic_block_new_live_at_end[i][j]
1029 & ~basic_block_live_at_end[i][j]);
1030 basic_block_live_at_start[i][j] |= x;
1031 basic_block_live_at_end[i][j] |= x;
1036 /* Update the basic_block_live_at_start
1037 by propagation backwards through the block. */
1038 bcopy (basic_block_new_live_at_end[i],
1039 basic_block_live_at_end[i], regset_bytes);
1040 bcopy (basic_block_live_at_end[i],
1041 basic_block_live_at_start[i], regset_bytes);
1042 propagate_block (basic_block_live_at_start[i],
1043 basic_block_head[i], basic_block_end[i], 0,
1044 first_pass ? basic_block_significant[i]
1050 register rtx jump, head;
1051 /* Update the basic_block_new_live_at_end's of the block
1052 that falls through into this one (if any). */
1053 head = basic_block_head[i];
1054 jump = PREV_INSN (head);
1055 if (basic_block_drops_in[i])
1057 register int from_block = BLOCK_NUM (jump);
1059 for (j = 0; j < regset_size; j++)
1060 basic_block_new_live_at_end[from_block][j]
1061 |= basic_block_live_at_start[i][j];
1063 /* Update the basic_block_new_live_at_end's of
1064 all the blocks that jump to this one. */
1065 if (GET_CODE (head) == CODE_LABEL)
1066 for (jump = LABEL_REFS (head);
1068 jump = LABEL_NEXTREF (jump))
1070 register int from_block = BLOCK_NUM (CONTAINING_INSN (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];
1084 /* The only pseudos that are live at the beginning of the function are
1085 those that were not set anywhere in the function. local-alloc doesn't
1086 know how to handle these correctly, so mark them as not local to any
1089 if (n_basic_blocks > 0)
1090 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1091 if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
1092 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1093 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1095 /* Now the life information is accurate.
1096 Make one more pass over each basic block
1097 to delete dead stores, create autoincrement addressing
1098 and record how many times each register is used, is set, or dies.
1100 To save time, we operate directly in basic_block_live_at_end[i],
1101 thus destroying it (in fact, converting it into a copy of
1102 basic_block_live_at_start[i]). This is ok now because
1103 basic_block_live_at_end[i] is no longer used past this point. */
1107 for (i = 0; i < n_basic_blocks; i++)
1109 propagate_block (basic_block_live_at_end[i],
1110 basic_block_head[i], basic_block_end[i], 1,
1118 /* Something live during a setjmp should not be put in a register
1119 on certain machines which restore regs from stack frames
1120 rather than from the jmpbuf.
1121 But we don't need to do this for the user's variables, since
1122 ANSI says only volatile variables need this. */
1123 #ifdef LONGJMP_RESTORE_FROM_STACK
1124 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1125 if (regs_live_at_setjmp[i / REGSET_ELT_BITS]
1126 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS))
1127 && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
1129 reg_live_length[i] = -1;
1130 reg_basic_block[i] = -1;
1135 /* We have a problem with any pseudoreg that
1136 lives across the setjmp. ANSI says that if a
1137 user variable does not change in value
1138 between the setjmp and the longjmp, then the longjmp preserves it.
1139 This includes longjmp from a place where the pseudo appears dead.
1140 (In principle, the value still exists if it is in scope.)
1141 If the pseudo goes in a hard reg, some other value may occupy
1142 that hard reg where this pseudo is dead, thus clobbering the pseudo.
1143 Conclusion: such a pseudo must not go in a hard reg. */
1144 for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
1145 if ((regs_live_at_setjmp[i / REGSET_ELT_BITS]
1146 & ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS)))
1147 && regno_reg_rtx[i] != 0)
1149 reg_live_length[i] = -1;
1150 reg_basic_block[i] = -1;
1153 obstack_free (&flow_obstack, NULL_PTR);
1156 /* Subroutines of life analysis. */
1158 /* Allocate the permanent data structures that represent the results
1159 of life analysis. Not static since used also for stupid life analysis. */
1162 allocate_for_life_analysis ()
1165 register regset tem;
1167 regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
1168 regset_bytes = regset_size * sizeof (*(regset)0);
1170 reg_n_refs = (int *) oballoc (max_regno * sizeof (int));
1171 bzero (reg_n_refs, max_regno * sizeof (int));
1173 reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
1174 bzero (reg_n_sets, max_regno * sizeof (short));
1176 reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
1177 bzero (reg_n_deaths, max_regno * sizeof (short));
1179 reg_live_length = (int *) oballoc (max_regno * sizeof (int));
1180 bzero (reg_live_length, max_regno * sizeof (int));
1182 reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
1183 bzero (reg_n_calls_crossed, max_regno * sizeof (int));
1185 reg_basic_block = (int *) oballoc (max_regno * sizeof (int));
1186 for (i = 0; i < max_regno; i++)
1187 reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1189 basic_block_live_at_start = (regset *) oballoc (n_basic_blocks * sizeof (regset));
1190 tem = (regset) oballoc (n_basic_blocks * regset_bytes);
1191 bzero (tem, n_basic_blocks * regset_bytes);
1192 init_regset_vector (basic_block_live_at_start, tem, n_basic_blocks, regset_bytes);
1194 regs_live_at_setjmp = (regset) oballoc (regset_bytes);
1195 bzero (regs_live_at_setjmp, regset_bytes);
1198 /* Make each element of VECTOR point at a regset,
1199 taking the space for all those regsets from SPACE.
1200 SPACE is of type regset, but it is really as long as NELTS regsets.
1201 BYTES_PER_ELT is the number of bytes in one regset. */
1204 init_regset_vector (vector, space, nelts, bytes_per_elt)
1211 register regset p = space;
1213 for (i = 0; i < nelts; i++)
1216 p += bytes_per_elt / sizeof (*p);
1220 /* Compute the registers live at the beginning of a basic block
1221 from those live at the end.
1223 When called, OLD contains those live at the end.
1224 On return, it contains those live at the beginning.
1225 FIRST and LAST are the first and last insns of the basic block.
1227 FINAL is nonzero if we are doing the final pass which is not
1228 for computing the life info (since that has already been done)
1229 but for acting on it. On this pass, we delete dead stores,
1230 set up the logical links and dead-variables lists of instructions,
1231 and merge instructions for autoincrement and autodecrement addresses.
1233 SIGNIFICANT is nonzero only the first time for each basic block.
1234 If it is nonzero, it points to a regset in which we store
1235 a 1 for each register that is set within the block.
1237 BNUM is the number of the basic block. */
1240 propagate_block (old, first, last, final, significant, bnum)
1241 register regset old;
1253 /* The following variables are used only if FINAL is nonzero. */
1254 /* This vector gets one element for each reg that has been live
1255 at any point in the basic block that has been scanned so far.
1256 SOMETIMES_MAX says how many elements are in use so far.
1257 In each element, OFFSET is the byte-number within a regset
1258 for the register described by the element, and BIT is a mask
1259 for that register's bit within the byte. */
1260 register struct sometimes { short offset; short bit; } *regs_sometimes_live;
1261 int sometimes_max = 0;
1262 /* This regset has 1 for each reg that we have seen live so far.
1263 It and REGS_SOMETIMES_LIVE are updated together. */
1266 /* The loop depth may change in the middle of a basic block. Since we
1267 scan from end to beginning, we start with the depth at the end of the
1268 current basic block, and adjust as we pass ends and starts of loops. */
1269 loop_depth = basic_block_loop_depth[bnum];
1271 dead = (regset) alloca (regset_bytes);
1272 live = (regset) alloca (regset_bytes);
1277 /* Include any notes at the end of the block in the scan.
1278 This is in case the block ends with a call to setjmp. */
1280 while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE)
1282 /* Look for loop boundaries, we are going forward here. */
1283 last = NEXT_INSN (last);
1284 if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_BEG)
1286 else if (NOTE_LINE_NUMBER (last) == NOTE_INSN_LOOP_END)
1292 register int i, offset;
1293 REGSET_ELT_TYPE bit;
1296 maxlive = (regset) alloca (regset_bytes);
1297 bcopy (old, maxlive, regset_bytes);
1299 = (struct sometimes *) alloca (max_regno * sizeof (struct sometimes));
1301 /* Process the regs live at the end of the block.
1302 Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
1303 Also mark them as not local to any one basic block. */
1305 for (offset = 0, i = 0; offset < regset_size; offset++)
1306 for (bit = 1; bit; bit <<= 1, i++)
1310 if (old[offset] & bit)
1312 reg_basic_block[i] = REG_BLOCK_GLOBAL;
1313 regs_sometimes_live[sometimes_max].offset = offset;
1314 regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
1320 /* Scan the block an insn at a time from end to beginning. */
1322 for (insn = last; ; insn = prev)
1324 prev = PREV_INSN (insn);
1326 /* Look for loop boundaries, remembering that we are going backwards. */
1327 if (GET_CODE (insn) == NOTE
1328 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
1330 else if (GET_CODE (insn) == NOTE
1331 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
1334 /* If we have LOOP_DEPTH == 0, there has been a bookkeeping error.
1335 Abort now rather than setting register status incorrectly. */
1336 if (loop_depth == 0)
1339 /* If this is a call to `setjmp' et al,
1340 warn if any non-volatile datum is live. */
1342 if (final && GET_CODE (insn) == NOTE
1343 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
1346 for (i = 0; i < regset_size; i++)
1347 regs_live_at_setjmp[i] |= old[i];
1350 /* Update the life-status of regs for this insn.
1351 First DEAD gets which regs are set in this insn
1352 then LIVE gets which regs are used in this insn.
1353 Then the regs live before the insn
1354 are those live after, with DEAD regs turned off,
1355 and then LIVE regs turned on. */
1357 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1360 rtx note = find_reg_note (insn, REG_RETVAL, NULL_RTX);
1362 = (insn_dead_p (PATTERN (insn), old, 0)
1363 /* Don't delete something that refers to volatile storage! */
1364 && ! INSN_VOLATILE (insn));
1366 = (insn_is_dead && note != 0
1367 && libcall_dead_p (PATTERN (insn), old, note, insn));
1369 /* If an instruction consists of just dead store(s) on final pass,
1370 "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1371 We could really delete it with delete_insn, but that
1372 can cause trouble for first or last insn in a basic block. */
1373 if (final && insn_is_dead)
1375 PUT_CODE (insn, NOTE);
1376 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1377 NOTE_SOURCE_FILE (insn) = 0;
1379 /* CC0 is now known to be dead. Either this insn used it,
1380 in which case it doesn't anymore, or clobbered it,
1381 so the next insn can't use it. */
1384 /* If this insn is copying the return value from a library call,
1385 delete the entire library call. */
1386 if (libcall_is_dead)
1388 rtx first = XEXP (note, 0);
1390 while (INSN_DELETED_P (first))
1391 first = NEXT_INSN (first);
1396 NOTE_LINE_NUMBER (p) = NOTE_INSN_DELETED;
1397 NOTE_SOURCE_FILE (p) = 0;
1403 for (i = 0; i < regset_size; i++)
1405 dead[i] = 0; /* Faster than bzero here */
1406 live[i] = 0; /* since regset_size is usually small */
1409 /* See if this is an increment or decrement that can be
1410 merged into a following memory address. */
1413 register rtx x = PATTERN (insn);
1414 /* Does this instruction increment or decrement a register? */
1415 if (final && GET_CODE (x) == SET
1416 && GET_CODE (SET_DEST (x)) == REG
1417 && (GET_CODE (SET_SRC (x)) == PLUS
1418 || GET_CODE (SET_SRC (x)) == MINUS)
1419 && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1420 && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1421 /* Ok, look for a following memory ref we can combine with.
1422 If one is found, change the memory ref to a PRE_INC
1423 or PRE_DEC, cancel this insn, and return 1.
1424 Return 0 if nothing has been done. */
1425 && try_pre_increment_1 (insn))
1428 #endif /* AUTO_INC_DEC */
1430 /* If this is not the final pass, and this insn is copying the
1431 value of a library call and it's dead, don't scan the
1432 insns that perform the library call, so that the call's
1433 arguments are not marked live. */
1434 if (libcall_is_dead)
1436 /* Mark the dest reg as `significant'. */
1437 mark_set_regs (old, dead, PATTERN (insn), NULL_RTX, significant);
1439 insn = XEXP (note, 0);
1440 prev = PREV_INSN (insn);
1442 else if (GET_CODE (PATTERN (insn)) == SET
1443 && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1444 && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1445 && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1446 && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1447 /* We have an insn to pop a constant amount off the stack.
1448 (Such insns use PLUS regardless of the direction of the stack,
1449 and any insn to adjust the stack by a constant is always a pop.)
1450 These insns, if not dead stores, have no effect on life. */
1454 /* LIVE gets the regs used in INSN;
1455 DEAD gets those set by it. Dead insns don't make anything
1458 mark_set_regs (old, dead, PATTERN (insn),
1459 final ? insn : NULL_RTX, significant);
1461 /* If an insn doesn't use CC0, it becomes dead since we
1462 assume that every insn clobbers it. So show it dead here;
1463 mark_used_regs will set it live if it is referenced. */
1467 mark_used_regs (old, live, PATTERN (insn), final, insn);
1469 /* Sometimes we may have inserted something before INSN (such as
1470 a move) when we make an auto-inc. So ensure we will scan
1473 prev = PREV_INSN (insn);
1476 if (! insn_is_dead && GET_CODE (insn) == CALL_INSN)
1482 for (note = CALL_INSN_FUNCTION_USAGE (insn);
1484 note = XEXP (note, 1))
1485 if (GET_CODE (XEXP (note, 0)) == USE)
1486 mark_used_regs (old, live, SET_DEST (XEXP (note, 0)),
1489 /* Each call clobbers all call-clobbered regs that are not
1490 global. Note that the function-value reg is a
1491 call-clobbered reg, and mark_set_regs has already had
1492 a chance to handle it. */
1494 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1495 if (call_used_regs[i] && ! global_regs[i])
1496 dead[i / REGSET_ELT_BITS]
1497 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1499 /* The stack ptr is used (honorarily) by a CALL insn. */
1500 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1501 |= ((REGSET_ELT_TYPE) 1
1502 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1504 /* Calls may also reference any of the global registers,
1505 so they are made live. */
1507 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1509 live[i / REGSET_ELT_BITS]
1510 |= ((REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS));
1512 /* Calls also clobber memory. */
1516 /* Update OLD for the registers used or set. */
1517 for (i = 0; i < regset_size; i++)
1523 if (GET_CODE (insn) == CALL_INSN && final)
1525 /* Any regs live at the time of a call instruction
1526 must not go in a register clobbered by calls.
1527 Find all regs now live and record this for them. */
1529 register struct sometimes *p = regs_sometimes_live;
1531 for (i = 0; i < sometimes_max; i++, p++)
1532 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1533 reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1537 /* On final pass, add any additional sometimes-live regs
1538 into MAXLIVE and REGS_SOMETIMES_LIVE.
1539 Also update counts of how many insns each reg is live at. */
1543 for (i = 0; i < regset_size; i++)
1545 register REGSET_ELT_TYPE diff = live[i] & ~maxlive[i];
1551 for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1552 if (diff & ((REGSET_ELT_TYPE) 1 << regno))
1554 regs_sometimes_live[sometimes_max].offset = i;
1555 regs_sometimes_live[sometimes_max].bit = regno;
1556 diff &= ~ ((REGSET_ELT_TYPE) 1 << regno);
1563 register struct sometimes *p = regs_sometimes_live;
1564 for (i = 0; i < sometimes_max; i++, p++)
1566 if (old[p->offset] & ((REGSET_ELT_TYPE) 1 << p->bit))
1567 reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1577 if (num_scratch > max_scratch)
1578 max_scratch = num_scratch;
1581 /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1582 (SET expressions whose destinations are registers dead after the insn).
1583 NEEDED is the regset that says which regs are alive after the insn.
1585 Unless CALL_OK is non-zero, an insn is needed if it contains a CALL. */
1588 insn_dead_p (x, needed, call_ok)
1593 register RTX_CODE code = GET_CODE (x);
1594 /* If setting something that's a reg or part of one,
1595 see if that register's altered value will be live. */
1599 register rtx r = SET_DEST (x);
1600 /* A SET that is a subroutine call cannot be dead. */
1601 if (! call_ok && GET_CODE (SET_SRC (x)) == CALL)
1605 if (GET_CODE (r) == CC0)
1609 if (GET_CODE (r) == MEM && last_mem_set && ! MEM_VOLATILE_P (r)
1610 && rtx_equal_p (r, last_mem_set))
1613 while (GET_CODE (r) == SUBREG
1614 || GET_CODE (r) == STRICT_LOW_PART
1615 || GET_CODE (r) == ZERO_EXTRACT
1616 || GET_CODE (r) == SIGN_EXTRACT)
1619 if (GET_CODE (r) == REG)
1621 register int regno = REGNO (r);
1622 register int offset = regno / REGSET_ELT_BITS;
1623 register REGSET_ELT_TYPE bit
1624 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1626 /* Don't delete insns to set global regs. */
1627 if ((regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1628 /* Make sure insns to set frame pointer aren't deleted. */
1629 || regno == FRAME_POINTER_REGNUM
1630 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1631 || regno == HARD_FRAME_POINTER_REGNUM
1633 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1634 /* Make sure insns to set arg pointer are never deleted
1635 (if the arg pointer isn't fixed, there will be a USE for
1636 it, so we can treat it normally). */
1637 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1639 || (needed[offset] & bit) != 0)
1642 /* If this is a hard register, verify that subsequent words are
1644 if (regno < FIRST_PSEUDO_REGISTER)
1646 int n = HARD_REGNO_NREGS (regno, GET_MODE (r));
1649 if ((needed[(regno + n) / REGSET_ELT_BITS]
1650 & ((REGSET_ELT_TYPE) 1
1651 << ((regno + n) % REGSET_ELT_BITS))) != 0)
1658 /* If performing several activities,
1659 insn is dead if each activity is individually dead.
1660 Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1661 that's inside a PARALLEL doesn't make the insn worth keeping. */
1662 else if (code == PARALLEL)
1664 register int i = XVECLEN (x, 0);
1665 for (i--; i >= 0; i--)
1667 rtx elt = XVECEXP (x, 0, i);
1668 if (!insn_dead_p (elt, needed, call_ok)
1669 && GET_CODE (elt) != CLOBBER
1670 && GET_CODE (elt) != USE)
1675 /* We do not check CLOBBER or USE here.
1676 An insn consisting of just a CLOBBER or just a USE
1677 should not be deleted. */
1681 /* If X is the pattern of the last insn in a libcall, and assuming X is dead,
1682 return 1 if the entire library call is dead.
1683 This is true if X copies a register (hard or pseudo)
1684 and if the hard return reg of the call insn is dead.
1685 (The caller should have tested the destination of X already for death.)
1687 If this insn doesn't just copy a register, then we don't
1688 have an ordinary libcall. In that case, cse could not have
1689 managed to substitute the source for the dest later on,
1690 so we can assume the libcall is dead.
1692 NEEDED is the bit vector of pseudoregs live before this insn.
1693 NOTE is the REG_RETVAL note of the insn. INSN is the insn itself. */
1696 libcall_dead_p (x, needed, note, insn)
1702 register RTX_CODE code = GET_CODE (x);
1706 register rtx r = SET_SRC (x);
1707 if (GET_CODE (r) == REG)
1709 rtx call = XEXP (note, 0);
1712 /* Find the call insn. */
1713 while (call != insn && GET_CODE (call) != CALL_INSN)
1714 call = NEXT_INSN (call);
1716 /* If there is none, do nothing special,
1717 since ordinary death handling can understand these insns. */
1721 /* See if the hard reg holding the value is dead.
1722 If this is a PARALLEL, find the call within it. */
1723 call = PATTERN (call);
1724 if (GET_CODE (call) == PARALLEL)
1726 for (i = XVECLEN (call, 0) - 1; i >= 0; i--)
1727 if (GET_CODE (XVECEXP (call, 0, i)) == SET
1728 && GET_CODE (SET_SRC (XVECEXP (call, 0, i))) == CALL)
1731 /* This may be a library call that is returning a value
1732 via invisible pointer. Do nothing special, since
1733 ordinary death handling can understand these insns. */
1737 call = XVECEXP (call, 0, i);
1740 return insn_dead_p (call, needed, 1);
1746 /* Return 1 if register REGNO was used before it was set.
1747 In other words, if it is live at function entry.
1748 Don't count global regster variables, though. */
1751 regno_uninitialized (regno)
1754 if (n_basic_blocks == 0
1755 || (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1758 return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1759 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS)));
1762 /* 1 if register REGNO was alive at a place where `setjmp' was called
1763 and was set more than once or is an argument.
1764 Such regs may be clobbered by `longjmp'. */
1767 regno_clobbered_at_setjmp (regno)
1770 if (n_basic_blocks == 0)
1773 return ((reg_n_sets[regno] > 1
1774 || (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1775 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))))
1776 && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1777 & ((REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS))));
1780 /* Process the registers that are set within X.
1781 Their bits are set to 1 in the regset DEAD,
1782 because they are dead prior to this insn.
1784 If INSN is nonzero, it is the insn being processed
1785 and the fact that it is nonzero implies this is the FINAL pass
1786 in propagate_block. In this case, various info about register
1787 usage is stored, LOG_LINKS fields of insns are set up. */
1790 mark_set_regs (needed, dead, x, insn, significant)
1797 register RTX_CODE code = GET_CODE (x);
1799 if (code == SET || code == CLOBBER)
1800 mark_set_1 (needed, dead, x, insn, significant);
1801 else if (code == PARALLEL)
1804 for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1806 code = GET_CODE (XVECEXP (x, 0, i));
1807 if (code == SET || code == CLOBBER)
1808 mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1813 /* Process a single SET rtx, X. */
1816 mark_set_1 (needed, dead, x, insn, significant)
1824 register rtx reg = SET_DEST (x);
1826 /* Modifying just one hardware register of a multi-reg value
1827 or just a byte field of a register
1828 does not mean the value from before this insn is now dead.
1829 But it does mean liveness of that register at the end of the block
1832 Within mark_set_1, however, we treat it as if the register is
1833 indeed modified. mark_used_regs will, however, also treat this
1834 register as being used. Thus, we treat these insns as setting a
1835 new value for the register as a function of its old value. This
1836 cases LOG_LINKS to be made appropriately and this will help combine. */
1838 while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1839 || GET_CODE (reg) == SIGN_EXTRACT
1840 || GET_CODE (reg) == STRICT_LOW_PART)
1841 reg = XEXP (reg, 0);
1843 /* If we are writing into memory or into a register mentioned in the
1844 address of the last thing stored into memory, show we don't know
1845 what the last store was. If we are writing memory, save the address
1846 unless it is volatile. */
1847 if (GET_CODE (reg) == MEM
1848 || (GET_CODE (reg) == REG
1849 && last_mem_set != 0 && reg_overlap_mentioned_p (reg, last_mem_set)))
1852 if (GET_CODE (reg) == MEM && ! side_effects_p (reg)
1853 /* There are no REG_INC notes for SP, so we can't assume we'll see
1854 everything that invalidates it. To be safe, don't eliminate any
1855 stores though SP; none of them should be redundant anyway. */
1856 && ! reg_mentioned_p (stack_pointer_rtx, reg))
1859 if (GET_CODE (reg) == REG
1860 && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1861 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
1862 && regno != HARD_FRAME_POINTER_REGNUM
1864 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
1865 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
1867 && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1868 /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1870 register int offset = regno / REGSET_ELT_BITS;
1871 register REGSET_ELT_TYPE bit
1872 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
1873 REGSET_ELT_TYPE all_needed = (needed[offset] & bit);
1874 REGSET_ELT_TYPE some_needed = (needed[offset] & bit);
1876 /* Mark it as a significant register for this basic block. */
1878 significant[offset] |= bit;
1880 /* Mark it as as dead before this insn. */
1881 dead[offset] |= bit;
1883 /* A hard reg in a wide mode may really be multiple registers.
1884 If so, mark all of them just like the first. */
1885 if (regno < FIRST_PSEUDO_REGISTER)
1889 /* Nothing below is needed for the stack pointer; get out asap.
1890 Eg, log links aren't needed, since combine won't use them. */
1891 if (regno == STACK_POINTER_REGNUM)
1894 n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1898 significant[(regno + n) / REGSET_ELT_BITS]
1899 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1900 dead[(regno + n) / REGSET_ELT_BITS]
1901 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
1903 |= (needed[(regno + n) / REGSET_ELT_BITS]
1904 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1906 &= (needed[(regno + n) / REGSET_ELT_BITS]
1907 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
1910 /* Additional data to record if this is the final pass. */
1913 register rtx y = reg_next_use[regno];
1914 register int blocknum = BLOCK_NUM (insn);
1916 /* The next use is no longer "next", since a store intervenes. */
1917 reg_next_use[regno] = 0;
1919 /* If this is a hard reg, record this function uses the reg. */
1921 if (regno < FIRST_PSEUDO_REGISTER)
1924 int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
1926 for (i = regno; i < endregno; i++)
1928 regs_ever_live[i] = 1;
1934 /* Keep track of which basic blocks each reg appears in. */
1936 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
1937 reg_basic_block[regno] = blocknum;
1938 else if (reg_basic_block[regno] != blocknum)
1939 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
1941 /* Count (weighted) references, stores, etc. This counts a
1942 register twice if it is modified, but that is correct. */
1943 reg_n_sets[regno]++;
1945 reg_n_refs[regno] += loop_depth;
1947 /* The insns where a reg is live are normally counted
1948 elsewhere, but we want the count to include the insn
1949 where the reg is set, and the normal counting mechanism
1950 would not count it. */
1951 reg_live_length[regno]++;
1956 /* Make a logical link from the next following insn
1957 that uses this register, back to this insn.
1958 The following insns have already been processed.
1960 We don't build a LOG_LINK for hard registers containing
1961 in ASM_OPERANDs. If these registers get replaced,
1962 we might wind up changing the semantics of the insn,
1963 even if reload can make what appear to be valid assignments
1965 if (y && (BLOCK_NUM (y) == blocknum)
1966 && (regno >= FIRST_PSEUDO_REGISTER
1967 || asm_noperands (PATTERN (y)) < 0))
1969 = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
1971 else if (! some_needed)
1973 /* Note that dead stores have already been deleted when possible
1974 If we get here, we have found a dead store that cannot
1975 be eliminated (because the same insn does something useful).
1976 Indicate this by marking the reg being set as dying here. */
1978 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
1979 reg_n_deaths[REGNO (reg)]++;
1983 /* This is a case where we have a multi-word hard register
1984 and some, but not all, of the words of the register are
1985 needed in subsequent insns. Write REG_UNUSED notes
1986 for those parts that were not needed. This case should
1991 for (i = HARD_REGNO_NREGS (regno, GET_MODE (reg)) - 1;
1993 if ((needed[(regno + i) / REGSET_ELT_BITS]
1994 & ((REGSET_ELT_TYPE) 1
1995 << ((regno + i) % REGSET_ELT_BITS))) == 0)
1997 = gen_rtx (EXPR_LIST, REG_UNUSED,
1998 gen_rtx (REG, word_mode, regno + i),
2003 else if (GET_CODE (reg) == REG)
2004 reg_next_use[regno] = 0;
2006 /* If this is the last pass and this is a SCRATCH, show it will be dying
2007 here and count it. */
2008 else if (GET_CODE (reg) == SCRATCH && insn != 0)
2011 = gen_rtx (EXPR_LIST, REG_UNUSED, reg, REG_NOTES (insn));
2018 /* X is a MEM found in INSN. See if we can convert it into an auto-increment
2022 find_auto_inc (needed, x, insn)
2027 rtx addr = XEXP (x, 0);
2028 HOST_WIDE_INT offset = 0;
2031 /* Here we detect use of an index register which might be good for
2032 postincrement, postdecrement, preincrement, or predecrement. */
2034 if (GET_CODE (addr) == PLUS && GET_CODE (XEXP (addr, 1)) == CONST_INT)
2035 offset = INTVAL (XEXP (addr, 1)), addr = XEXP (addr, 0);
2037 if (GET_CODE (addr) == REG)
2040 register int size = GET_MODE_SIZE (GET_MODE (x));
2043 int regno = REGNO (addr);
2045 /* Is the next use an increment that might make auto-increment? */
2046 if ((incr = reg_next_use[regno]) != 0
2047 && (set = single_set (incr)) != 0
2048 && GET_CODE (set) == SET
2049 && BLOCK_NUM (incr) == BLOCK_NUM (insn)
2050 /* Can't add side effects to jumps; if reg is spilled and
2051 reloaded, there's no way to store back the altered value. */
2052 && GET_CODE (insn) != JUMP_INSN
2053 && (y = SET_SRC (set), GET_CODE (y) == PLUS)
2054 && XEXP (y, 0) == addr
2055 && GET_CODE (XEXP (y, 1)) == CONST_INT
2057 #ifdef HAVE_POST_INCREMENT
2058 || (INTVAL (XEXP (y, 1)) == size && offset == 0)
2060 #ifdef HAVE_POST_DECREMENT
2061 || (INTVAL (XEXP (y, 1)) == - size && offset == 0)
2063 #ifdef HAVE_PRE_INCREMENT
2064 || (INTVAL (XEXP (y, 1)) == size && offset == size)
2066 #ifdef HAVE_PRE_DECREMENT
2067 || (INTVAL (XEXP (y, 1)) == - size && offset == - size)
2070 /* Make sure this reg appears only once in this insn. */
2071 && (use = find_use_as_address (PATTERN (insn), addr, offset),
2072 use != 0 && use != (rtx) 1))
2075 rtx q = SET_DEST (set);
2077 if (dead_or_set_p (incr, addr))
2079 else if (GET_CODE (q) == REG
2080 /* PREV_INSN used here to check the semi-open interval
2082 && ! reg_used_between_p (q, PREV_INSN (insn), incr))
2084 /* We have *p followed sometime later by q = p+size.
2085 Both p and q must be live afterward,
2086 and q is not used between INSN and it's assignment.
2087 Change it to q = p, ...*q..., q = q+size.
2088 Then fall into the usual case. */
2092 emit_move_insn (q, addr);
2093 insns = get_insns ();
2096 /* If anything in INSNS have UID's that don't fit within the
2097 extra space we allocate earlier, we can't make this auto-inc.
2098 This should never happen. */
2099 for (temp = insns; temp; temp = NEXT_INSN (temp))
2101 if (INSN_UID (temp) > max_uid_for_flow)
2103 BLOCK_NUM (temp) = BLOCK_NUM (insn);
2106 emit_insns_before (insns, insn);
2108 if (basic_block_head[BLOCK_NUM (insn)] == insn)
2109 basic_block_head[BLOCK_NUM (insn)] = insns;
2114 /* INCR will become a NOTE and INSN won't contain a
2115 use of ADDR. If a use of ADDR was just placed in
2116 the insn before INSN, make that the next use.
2117 Otherwise, invalidate it. */
2118 if (GET_CODE (PREV_INSN (insn)) == INSN
2119 && GET_CODE (PATTERN (PREV_INSN (insn))) == SET
2120 && SET_SRC (PATTERN (PREV_INSN (insn))) == addr)
2121 reg_next_use[regno] = PREV_INSN (insn);
2123 reg_next_use[regno] = 0;
2129 /* REGNO is now used in INCR which is below INSN, but
2130 it previously wasn't live here. If we don't mark
2131 it as needed, we'll put a REG_DEAD note for it
2132 on this insn, which is incorrect. */
2133 needed[regno / REGSET_ELT_BITS]
2134 |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2136 /* If there are any calls between INSN and INCR, show
2137 that REGNO now crosses them. */
2138 for (temp = insn; temp != incr; temp = NEXT_INSN (temp))
2139 if (GET_CODE (temp) == CALL_INSN)
2140 reg_n_calls_crossed[regno]++;
2144 /* If we have found a suitable auto-increment, do
2145 POST_INC around the register here, and patch out the
2146 increment instruction that follows. */
2147 && validate_change (insn, &XEXP (x, 0),
2148 gen_rtx ((INTVAL (XEXP (y, 1)) == size
2149 ? (offset ? PRE_INC : POST_INC)
2150 : (offset ? PRE_DEC : POST_DEC)),
2153 /* Record that this insn has an implicit side effect. */
2155 = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
2157 /* Modify the old increment-insn to simply copy
2158 the already-incremented value of our register. */
2159 SET_SRC (set) = addr;
2160 /* Indicate insn must be re-recognized. */
2161 INSN_CODE (incr) = -1;
2163 /* If that makes it a no-op (copying the register into itself)
2164 then delete it so it won't appear to be a "use" and a "set"
2165 of this register. */
2166 if (SET_DEST (set) == addr)
2168 PUT_CODE (incr, NOTE);
2169 NOTE_LINE_NUMBER (incr) = NOTE_INSN_DELETED;
2170 NOTE_SOURCE_FILE (incr) = 0;
2173 if (regno >= FIRST_PSEUDO_REGISTER)
2175 /* Count an extra reference to the reg. When a reg is
2176 incremented, spilling it is worse, so we want to make
2177 that less likely. */
2178 reg_n_refs[regno] += loop_depth;
2179 /* Count the increment as a setting of the register,
2180 even though it isn't a SET in rtl. */
2181 reg_n_sets[regno]++;
2187 #endif /* AUTO_INC_DEC */
2189 /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
2190 This is done assuming the registers needed from X
2191 are those that have 1-bits in NEEDED.
2193 On the final pass, FINAL is 1. This means try for autoincrement
2194 and count the uses and deaths of each pseudo-reg.
2196 INSN is the containing instruction. If INSN is dead, this function is not
2200 mark_used_regs (needed, live, x, final, insn)
2207 register RTX_CODE code;
2212 code = GET_CODE (x);
2233 /* If we are clobbering a MEM, mark any registers inside the address
2235 if (GET_CODE (XEXP (x, 0)) == MEM)
2236 mark_used_regs (needed, live, XEXP (XEXP (x, 0), 0), final, insn);
2240 /* Invalidate the data for the last MEM stored. We could do this only
2241 if the addresses conflict, but this doesn't seem worthwhile. */
2246 find_auto_inc (needed, x, insn);
2251 /* See a register other than being set
2252 => mark it as needed. */
2256 register int offset = regno / REGSET_ELT_BITS;
2257 register REGSET_ELT_TYPE bit
2258 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2259 REGSET_ELT_TYPE all_needed = needed[offset] & bit;
2260 REGSET_ELT_TYPE some_needed = needed[offset] & bit;
2262 live[offset] |= bit;
2263 /* A hard reg in a wide mode may really be multiple registers.
2264 If so, mark all of them just like the first. */
2265 if (regno < FIRST_PSEUDO_REGISTER)
2269 /* For stack ptr or fixed arg pointer,
2270 nothing below can be necessary, so waste no more time. */
2271 if (regno == STACK_POINTER_REGNUM
2272 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2273 || regno == HARD_FRAME_POINTER_REGNUM
2275 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2276 || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2278 || regno == FRAME_POINTER_REGNUM)
2280 /* If this is a register we are going to try to eliminate,
2281 don't mark it live here. If we are successful in
2282 eliminating it, it need not be live unless it is used for
2283 pseudos, in which case it will have been set live when
2284 it was allocated to the pseudos. If the register will not
2285 be eliminated, reload will set it live at that point. */
2287 if (! TEST_HARD_REG_BIT (elim_reg_set, regno))
2288 regs_ever_live[regno] = 1;
2291 /* No death notes for global register variables;
2292 their values are live after this function exits. */
2293 if (global_regs[regno])
2296 reg_next_use[regno] = insn;
2300 n = HARD_REGNO_NREGS (regno, GET_MODE (x));
2303 live[(regno + n) / REGSET_ELT_BITS]
2304 |= (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS);
2306 |= (needed[(regno + n) / REGSET_ELT_BITS]
2307 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2309 &= (needed[(regno + n) / REGSET_ELT_BITS]
2310 & (REGSET_ELT_TYPE) 1 << ((regno + n) % REGSET_ELT_BITS));
2315 /* Record where each reg is used, so when the reg
2316 is set we know the next insn that uses it. */
2318 reg_next_use[regno] = insn;
2320 if (regno < FIRST_PSEUDO_REGISTER)
2322 /* If a hard reg is being used,
2323 record that this function does use it. */
2325 i = HARD_REGNO_NREGS (regno, GET_MODE (x));
2329 regs_ever_live[regno + --i] = 1;
2334 /* Keep track of which basic block each reg appears in. */
2336 register int blocknum = BLOCK_NUM (insn);
2338 if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
2339 reg_basic_block[regno] = blocknum;
2340 else if (reg_basic_block[regno] != blocknum)
2341 reg_basic_block[regno] = REG_BLOCK_GLOBAL;
2343 /* Count (weighted) number of uses of each reg. */
2345 reg_n_refs[regno] += loop_depth;
2348 /* Record and count the insns in which a reg dies.
2349 If it is used in this insn and was dead below the insn
2350 then it dies in this insn. If it was set in this insn,
2351 we do not make a REG_DEAD note; likewise if we already
2352 made such a note. */
2355 && ! dead_or_set_p (insn, x)
2357 && (regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
2361 /* If none of the words in X is needed, make a REG_DEAD
2362 note. Otherwise, we must make partial REG_DEAD notes. */
2366 = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
2367 reg_n_deaths[regno]++;
2373 /* Don't make a REG_DEAD note for a part of a register
2374 that is set in the insn. */
2376 for (i = HARD_REGNO_NREGS (regno, GET_MODE (x)) - 1;
2378 if ((needed[(regno + i) / REGSET_ELT_BITS]
2379 & ((REGSET_ELT_TYPE) 1
2380 << ((regno + i) % REGSET_ELT_BITS))) == 0
2381 && ! dead_or_set_regno_p (insn, regno + i))
2383 = gen_rtx (EXPR_LIST, REG_DEAD,
2384 gen_rtx (REG, word_mode, regno + i),
2394 register rtx testreg = SET_DEST (x);
2397 /* If storing into MEM, don't show it as being used. But do
2398 show the address as being used. */
2399 if (GET_CODE (testreg) == MEM)
2403 find_auto_inc (needed, testreg, insn);
2405 mark_used_regs (needed, live, XEXP (testreg, 0), final, insn);
2406 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2410 /* Storing in STRICT_LOW_PART is like storing in a reg
2411 in that this SET might be dead, so ignore it in TESTREG.
2412 but in some other ways it is like using the reg.
2414 Storing in a SUBREG or a bit field is like storing the entire
2415 register in that if the register's value is not used
2416 then this SET is not needed. */
2417 while (GET_CODE (testreg) == STRICT_LOW_PART
2418 || GET_CODE (testreg) == ZERO_EXTRACT
2419 || GET_CODE (testreg) == SIGN_EXTRACT
2420 || GET_CODE (testreg) == SUBREG)
2422 /* Modifying a single register in an alternate mode
2423 does not use any of the old value. But these other
2424 ways of storing in a register do use the old value. */
2425 if (GET_CODE (testreg) == SUBREG
2426 && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
2431 testreg = XEXP (testreg, 0);
2434 /* If this is a store into a register,
2435 recursively scan the value being stored. */
2437 if (GET_CODE (testreg) == REG
2438 && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
2439 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
2440 && regno != HARD_FRAME_POINTER_REGNUM
2442 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
2443 && ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
2446 /* We used to exclude global_regs here, but that seems wrong.
2447 Storing in them is like storing in mem. */
2449 mark_used_regs (needed, live, SET_SRC (x), final, insn);
2451 mark_used_regs (needed, live, SET_DEST (x), final, insn);
2458 /* If exiting needs the right stack value, consider this insn as
2459 using the stack pointer. In any event, consider it as using
2460 all global registers. */
2462 #ifdef EXIT_IGNORE_STACK
2463 if (! EXIT_IGNORE_STACK
2464 || (! FRAME_POINTER_REQUIRED && flag_omit_frame_pointer))
2466 live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
2467 |= (REGSET_ELT_TYPE) 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
2469 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2471 live[i / REGSET_ELT_BITS]
2472 |= (REGSET_ELT_TYPE) 1 << (i % REGSET_ELT_BITS);
2476 /* Recursively scan the operands of this expression. */
2479 register char *fmt = GET_RTX_FORMAT (code);
2482 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2486 /* Tail recursive case: save a function call level. */
2492 mark_used_regs (needed, live, XEXP (x, i), final, insn);
2494 else if (fmt[i] == 'E')
2497 for (j = 0; j < XVECLEN (x, i); j++)
2498 mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
2507 try_pre_increment_1 (insn)
2510 /* Find the next use of this reg. If in same basic block,
2511 make it do pre-increment or pre-decrement if appropriate. */
2512 rtx x = PATTERN (insn);
2513 HOST_WIDE_INT amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
2514 * INTVAL (XEXP (SET_SRC (x), 1)));
2515 int regno = REGNO (SET_DEST (x));
2516 rtx y = reg_next_use[regno];
2518 && BLOCK_NUM (y) == BLOCK_NUM (insn)
2519 && try_pre_increment (y, SET_DEST (PATTERN (insn)),
2522 /* We have found a suitable auto-increment
2523 and already changed insn Y to do it.
2524 So flush this increment-instruction. */
2525 PUT_CODE (insn, NOTE);
2526 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
2527 NOTE_SOURCE_FILE (insn) = 0;
2528 /* Count a reference to this reg for the increment
2529 insn we are deleting. When a reg is incremented.
2530 spilling it is worse, so we want to make that
2532 if (regno >= FIRST_PSEUDO_REGISTER)
2534 reg_n_refs[regno] += loop_depth;
2535 reg_n_sets[regno]++;
2542 /* Try to change INSN so that it does pre-increment or pre-decrement
2543 addressing on register REG in order to add AMOUNT to REG.
2544 AMOUNT is negative for pre-decrement.
2545 Returns 1 if the change could be made.
2546 This checks all about the validity of the result of modifying INSN. */
2549 try_pre_increment (insn, reg, amount)
2551 HOST_WIDE_INT amount;
2555 /* Nonzero if we can try to make a pre-increment or pre-decrement.
2556 For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
2558 /* Nonzero if we can try to make a post-increment or post-decrement.
2559 For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
2560 It is possible for both PRE_OK and POST_OK to be nonzero if the machine
2561 supports both pre-inc and post-inc, or both pre-dec and post-dec. */
2564 /* Nonzero if the opportunity actually requires post-inc or post-dec. */
2567 /* From the sign of increment, see which possibilities are conceivable
2568 on this target machine. */
2569 #ifdef HAVE_PRE_INCREMENT
2573 #ifdef HAVE_POST_INCREMENT
2578 #ifdef HAVE_PRE_DECREMENT
2582 #ifdef HAVE_POST_DECREMENT
2587 if (! (pre_ok || post_ok))
2590 /* It is not safe to add a side effect to a jump insn
2591 because if the incremented register is spilled and must be reloaded
2592 there would be no way to store the incremented value back in memory. */
2594 if (GET_CODE (insn) == JUMP_INSN)
2599 use = find_use_as_address (PATTERN (insn), reg, 0);
2600 if (post_ok && (use == 0 || use == (rtx) 1))
2602 use = find_use_as_address (PATTERN (insn), reg, -amount);
2606 if (use == 0 || use == (rtx) 1)
2609 if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
2612 /* See if this combination of instruction and addressing mode exists. */
2613 if (! validate_change (insn, &XEXP (use, 0),
2615 ? (do_post ? POST_INC : PRE_INC)
2616 : (do_post ? POST_DEC : PRE_DEC),
2620 /* Record that this insn now has an implicit side effect on X. */
2621 REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
2625 #endif /* AUTO_INC_DEC */
2627 /* Find the place in the rtx X where REG is used as a memory address.
2628 Return the MEM rtx that so uses it.
2629 If PLUSCONST is nonzero, search instead for a memory address equivalent to
2630 (plus REG (const_int PLUSCONST)).
2632 If such an address does not appear, return 0.
2633 If REG appears more than once, or is used other than in such an address,
2637 find_use_as_address (x, reg, plusconst)
2640 HOST_WIDE_INT plusconst;
2642 enum rtx_code code = GET_CODE (x);
2643 char *fmt = GET_RTX_FORMAT (code);
2645 register rtx value = 0;
2648 if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
2651 if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
2652 && XEXP (XEXP (x, 0), 0) == reg
2653 && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
2654 && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
2657 if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
2659 /* If REG occurs inside a MEM used in a bit-field reference,
2660 that is unacceptable. */
2661 if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
2662 return (rtx) (HOST_WIDE_INT) 1;
2666 return (rtx) (HOST_WIDE_INT) 1;
2668 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2672 tem = find_use_as_address (XEXP (x, i), reg, plusconst);
2676 return (rtx) (HOST_WIDE_INT) 1;
2681 for (j = XVECLEN (x, i) - 1; j >= 0; j--)
2683 tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
2687 return (rtx) (HOST_WIDE_INT) 1;
2695 /* Write information about registers and basic blocks into FILE.
2696 This is part of making a debugging dump. */
2699 dump_flow_info (file)
2703 static char *reg_class_names[] = REG_CLASS_NAMES;
2705 fprintf (file, "%d registers.\n", max_regno);
2707 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
2710 enum reg_class class, altclass;
2711 fprintf (file, "\nRegister %d used %d times across %d insns",
2712 i, reg_n_refs[i], reg_live_length[i]);
2713 if (reg_basic_block[i] >= 0)
2714 fprintf (file, " in block %d", reg_basic_block[i]);
2715 if (reg_n_deaths[i] != 1)
2716 fprintf (file, "; dies in %d places", reg_n_deaths[i]);
2717 if (reg_n_calls_crossed[i] == 1)
2718 fprintf (file, "; crosses 1 call");
2719 else if (reg_n_calls_crossed[i])
2720 fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
2721 if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
2722 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2723 class = reg_preferred_class (i);
2724 altclass = reg_alternate_class (i);
2725 if (class != GENERAL_REGS || altclass != ALL_REGS)
2727 if (altclass == ALL_REGS || class == ALL_REGS)
2728 fprintf (file, "; pref %s", reg_class_names[(int) class]);
2729 else if (altclass == NO_REGS)
2730 fprintf (file, "; %s or none", reg_class_names[(int) class]);
2732 fprintf (file, "; pref %s, else %s",
2733 reg_class_names[(int) class],
2734 reg_class_names[(int) altclass]);
2736 if (REGNO_POINTER_FLAG (i))
2737 fprintf (file, "; pointer");
2738 fprintf (file, ".\n");
2740 fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2741 for (i = 0; i < n_basic_blocks; i++)
2743 register rtx head, jump;
2745 fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2747 INSN_UID (basic_block_head[i]),
2748 INSN_UID (basic_block_end[i]));
2749 /* The control flow graph's storage is freed
2750 now when flow_analysis returns.
2751 Don't try to print it if it is gone. */
2752 if (basic_block_drops_in)
2754 fprintf (file, "Reached from blocks: ");
2755 head = basic_block_head[i];
2756 if (GET_CODE (head) == CODE_LABEL)
2757 for (jump = LABEL_REFS (head);
2759 jump = LABEL_NEXTREF (jump))
2761 register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
2762 fprintf (file, " %d", from_block);
2764 if (basic_block_drops_in[i])
2765 fprintf (file, " previous");
2767 fprintf (file, "\nRegisters live at start:");
2768 for (regno = 0; regno < max_regno; regno++)
2770 register int offset = regno / REGSET_ELT_BITS;
2771 register REGSET_ELT_TYPE bit
2772 = (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);
2773 if (basic_block_live_at_start[i][offset] & bit)
2774 fprintf (file, " %d", regno);
2776 fprintf (file, "\n");
2778 fprintf (file, "\n");