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1.1 root 1: /* Data flow analysis for GNU compiler.
1.1.1.2 root 2: Copyright (C) 1987, 1988 Free Software Foundation, Inc.
1.1 root 3:
4: This file is part of GNU CC.
5:
1.1.1.12 root 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 1, or (at your option)
9: any later version.
10:
1.1 root 11: GNU CC is distributed in the hope that it will be useful,
1.1.1.12 root 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.
15:
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. */
1.1 root 19:
20:
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.
25:
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.
29:
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.
33:
34: ** find_basic_blocks **
35:
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.
40:
41: find_basic_blocks also finds any unreachable loops
42: and deletes them.
43:
44: ** life_analysis **
45:
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.
49:
50: ** live-register info **
51:
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.
54:
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
58: of the basic block.
59:
60: To each insn's REG_NOTES is added an element for each register
61: that is live before the insn or set by the insn, but is dead
62: after the insn.
63:
64: To determine which registers are live after any insn, one can
65: start from the beginning of the basic block and scan insns, noting
66: which registers are set by each insn and which die there.
67:
68: ** Other actions of life_analysis **
69:
70: life_analysis sets up the LOG_LINKS fields of insns because the
71: information needed to do so is readily available.
72:
73: life_analysis deletes insns whose only effect is to store a value
74: that is never used.
75:
76: life_analysis notices cases where a reference to a register as
77: a memory address can be combined with a preceding or following
78: incrementation or decrementation of the register. The separate
79: instruction to increment or decrement is deleted and the address
80: is changed to a POST_INC or similar rtx.
81:
82: Each time an incrementing or decrementing address is created,
83: a REG_INC element is added to the insn's REG_NOTES list.
84:
85: life_analysis fills in certain vectors containing information about
86: register usage: reg_n_refs, reg_n_deaths, reg_n_sets,
1.1.1.14! root 87: reg_live_length, reg_n_calls_crosses and reg_basic_block. */
1.1 root 88:
89: #include <stdio.h>
90: #include "config.h"
91: #include "rtl.h"
92: #include "basic-block.h"
93: #include "regs.h"
1.1.1.2 root 94: #include "hard-reg-set.h"
95: #include "flags.h"
1.1 root 96:
1.1.1.14! root 97: #include "obstack.h"
! 98: #define obstack_chunk_alloc xmalloc
! 99: #define obstack_chunk_free free
! 100:
! 101: extern int xmalloc ();
! 102: extern void free ();
! 103:
1.1 root 104: /* Get the basic block number of an insn.
105: This info should not be expected to remain available
106: after the end of life_analysis. */
107:
108: #define BLOCK_NUM(INSN) uid_block_number[INSN_UID (INSN)]
109:
110: /* This is where the BLOCK_NUM values are really stored.
111: This is set up by find_basic_blocks and used there and in life_analysis,
112: and then freed. */
113:
114: static short *uid_block_number;
115:
1.1.1.2 root 116: /* INSN_VOLATILE (insn) is 1 if the insn refers to anything volatile. */
117:
118: #define INSN_VOLATILE(INSN) uid_volatile[INSN_UID (INSN)]
119: static char *uid_volatile;
120:
1.1 root 121: /* Number of basic blocks in the current function. */
122:
123: int n_basic_blocks;
124:
125: /* Maximum register number used in this function, plus one. */
126:
127: int max_regno;
128:
129: /* Indexed by n, gives number of basic block that (REG n) is used in.
1.1.1.10 root 130: If the value is REG_BLOCK_GLOBAL (-2),
131: it means (REG n) is used in more than one basic block.
132: REG_BLOCK_UNKNOWN (-1) means it hasn't been seen yet so we don't know.
1.1 root 133: This information remains valid for the rest of the compilation
134: of the current function; it is used to control register allocation. */
135:
136: short *reg_basic_block;
137:
138: /* Indexed by n, gives number of times (REG n) is used or set, each
139: weighted by its loop-depth.
140: This information remains valid for the rest of the compilation
141: of the current function; it is used to control register allocation. */
142:
143: short *reg_n_refs;
144:
145: /* Indexed by n, gives number of times (REG n) is set.
146: This information remains valid for the rest of the compilation
147: of the current function; it is used to control register allocation. */
148:
149: short *reg_n_sets;
150:
151: /* Indexed by N, gives number of places register N dies.
152: This information remains valid for the rest of the compilation
153: of the current function; it is used to control register allocation. */
154:
155: short *reg_n_deaths;
156:
157: /* Indexed by N, gives 1 if that reg is live across any CALL_INSNs.
158: This information remains valid for the rest of the compilation
159: of the current function; it is used to control register allocation. */
160:
1.1.1.12 root 161: int *reg_n_calls_crossed;
1.1 root 162:
163: /* Total number of instructions at which (REG n) is live.
164: The larger this is, the less priority (REG n) gets for
165: allocation in a real register.
166: This information remains valid for the rest of the compilation
1.1.1.2 root 167: of the current function; it is used to control register allocation.
168:
169: local-alloc.c may alter this number to change the priority.
170:
171: Negative values are special.
172: -1 is used to mark a pseudo reg which has a constant or memory equivalent
173: and is used infrequently enough that it should not get a hard register.
174: -2 is used to mark a pseudo reg for a parameter, when a frame pointer
175: is not required. global-alloc.c makes an allocno for this but does
176: not try to assign a hard register to it. */
1.1 root 177:
178: int *reg_live_length;
179:
180: /* Element N is the next insn that uses (hard or pseudo) register number N
181: within the current basic block; or zero, if there is no such insn.
182: This is valid only during the final backward scan in propagate_block. */
183:
184: static rtx *reg_next_use;
185:
186: /* Size of a regset for the current function,
187: in (1) bytes and (2) elements. */
188:
189: int regset_bytes;
190: int regset_size;
191:
192: /* Element N is first insn in basic block N.
193: This info lasts until we finish compiling the function. */
194:
195: rtx *basic_block_head;
196:
197: /* Element N is last insn in basic block N.
198: This info lasts until we finish compiling the function. */
199:
200: rtx *basic_block_end;
201:
202: /* Element N is a regset describing the registers live
203: at the start of basic block N.
204: This info lasts until we finish compiling the function. */
205:
206: regset *basic_block_live_at_start;
207:
1.1.1.2 root 208: /* Regset of regs live when calls to `setjmp'-like functions happen. */
209:
210: regset regs_live_at_setjmp;
211:
1.1 root 212: /* Element N is nonzero if control can drop into basic block N
213: from the preceding basic block. Freed after life_analysis. */
214:
1.1.1.2 root 215: static char *basic_block_drops_in;
1.1 root 216:
217: /* Element N is depth within loops of basic block number N.
218: Freed after life_analysis. */
219:
1.1.1.2 root 220: static short *basic_block_loop_depth;
1.1 root 221:
222: /* Element N nonzero if basic block N can actually be reached.
223: Vector exists only during find_basic_blocks. */
224:
1.1.1.2 root 225: static char *block_live_static;
1.1 root 226:
227: /* Depth within loops of basic block being scanned for lifetime analysis,
228: plus one. This is the weight attached to references to registers. */
229:
1.1.1.2 root 230: static int loop_depth;
231:
232: /* Define AUTO_INC_DEC if machine has any kind of incrementing
233: or decrementing addressing. */
234:
235: #ifdef HAVE_PRE_DECREMENT
236: #define AUTO_INC_DEC
237: #endif
238:
239: #ifdef HAVE_PRE_INCREMENT
240: #define AUTO_INC_DEC
241: #endif
242:
243: #ifdef HAVE_POST_DECREMENT
244: #define AUTO_INC_DEC
245: #endif
246:
247: #ifdef HAVE_POST_INCREMENT
248: #define AUTO_INC_DEC
249: #endif
1.1 root 250:
251: /* Forward declarations */
252: static void find_basic_blocks ();
253: static void life_analysis ();
254: static void mark_label_ref ();
255: void allocate_for_life_analysis (); /* Used also in stupid_life_analysis */
256: static void init_regset_vector ();
257: static void propagate_block ();
258: static void mark_set_regs ();
259: static void mark_used_regs ();
260: static int insn_dead_p ();
1.1.1.10 root 261: static int libcall_dead_p ();
1.1 root 262: static int try_pre_increment ();
263: static int try_pre_increment_1 ();
264: static rtx find_use_as_address ();
1.1.1.2 root 265: void dump_flow_info ();
1.1 root 266:
267: /* Find basic blocks of the current function and perform data flow analysis.
268: F is the first insn of the function and NREGS the number of register numbers
269: in use. */
270:
271: void
272: flow_analysis (f, nregs, file)
273: rtx f;
274: int nregs;
275: FILE *file;
276: {
277: register rtx insn;
278: register int i;
279: register int max_uid = 0;
280:
281: /* Count the basic blocks. Also find maximum insn uid value used. */
282:
283: {
284: register RTX_CODE prev_code = JUMP_INSN;
285: register RTX_CODE code;
286:
287: for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
288: {
289: code = GET_CODE (insn);
290: if (INSN_UID (insn) > max_uid)
291: max_uid = INSN_UID (insn);
292: if (code == CODE_LABEL
293: || (prev_code != INSN && prev_code != CALL_INSN
294: && prev_code != CODE_LABEL
295: && (code == INSN || code == CALL_INSN || code == JUMP_INSN)))
296: i++;
297: if (code != NOTE)
298: prev_code = code;
299: }
300: }
301:
302: /* Allocate some tables that last till end of compiling this function
303: and some needed only in find_basic_blocks and life_analysis. */
304:
305: n_basic_blocks = i;
306: basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
307: basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx));
308: basic_block_drops_in = (char *) alloca (n_basic_blocks);
309: basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short));
310: uid_block_number = (short *) alloca ((max_uid + 1) * sizeof (short));
1.1.1.2 root 311: uid_volatile = (char *) alloca (max_uid + 1);
312: bzero (uid_volatile, max_uid + 1);
1.1 root 313:
314: find_basic_blocks (f);
315: life_analysis (f, nregs);
316: if (file)
317: dump_flow_info (file);
318:
319: basic_block_drops_in = 0;
320: uid_block_number = 0;
321: basic_block_loop_depth = 0;
322: }
323:
324: /* Find all basic blocks of the function whose first insn is F.
325: Store the correct data in the tables that describe the basic blocks,
326: set up the chains of references for each CODE_LABEL, and
327: delete any entire basic blocks that cannot be reached. */
328:
329: static void
330: find_basic_blocks (f)
331: rtx f;
332: {
333: register rtx insn;
334: register int i;
335:
336: /* Initialize the ref chain of each label to 0. */
337: /* Record where all the blocks start and end and their depth in loops. */
338: /* For each insn, record the block it is in. */
339:
340: {
341: register RTX_CODE prev_code = JUMP_INSN;
342: register RTX_CODE code;
343: int depth = 1;
344:
345: for (insn = f, i = -1; insn; insn = NEXT_INSN (insn))
346: {
347: code = GET_CODE (insn);
348: if (code == NOTE)
349: {
350: if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG)
351: depth++;
352: else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END)
353: depth--;
354: }
355: else if (code == CODE_LABEL
356: || (prev_code != INSN && prev_code != CALL_INSN
357: && prev_code != CODE_LABEL
358: && (code == INSN || code == CALL_INSN || code == JUMP_INSN)))
359: {
360: basic_block_head[++i] = insn;
361: basic_block_end[i] = insn;
362: basic_block_loop_depth[i] = depth;
363: if (code == CODE_LABEL)
364: LABEL_REFS (insn) = insn;
365: }
366: else if (code == INSN || code == CALL_INSN || code == JUMP_INSN)
367: basic_block_end[i] = insn;
368: BLOCK_NUM (insn) = i;
369: if (code != NOTE)
370: prev_code = code;
371: }
1.1.1.4 root 372: if (i + 1 != n_basic_blocks)
373: abort ();
1.1 root 374: }
375:
376: /* Record which basic blocks control can drop in to. */
377:
378: {
379: register int i;
380: for (i = 0; i < n_basic_blocks; i++)
381: {
382: register rtx insn = PREV_INSN (basic_block_head[i]);
1.1.1.2 root 383: /* TEMP1 is used to avoid a bug in Sequent's compiler. */
384: register int temp1;
1.1 root 385: while (insn && GET_CODE (insn) == NOTE)
386: insn = PREV_INSN (insn);
1.1.1.2 root 387: temp1 = insn && GET_CODE (insn) != BARRIER;
388: basic_block_drops_in[i] = temp1;
1.1 root 389: }
390: }
391:
392: /* Now find which basic blocks can actually be reached
393: and put all jump insns' LABEL_REFS onto the ref-chains
394: of their target labels. */
395:
396: if (n_basic_blocks > 0)
397: {
398: register char *block_live = (char *) alloca (n_basic_blocks);
399: register char *block_marked = (char *) alloca (n_basic_blocks);
400: int something_marked = 1;
401:
402: /* Initialize with just block 0 reachable and no blocks marked. */
403:
404: bzero (block_live, n_basic_blocks);
405: bzero (block_marked, n_basic_blocks);
406: block_live[0] = 1;
407: block_live_static = block_live;
408:
409: /* Pass over all blocks, marking each block that is reachable
410: and has not yet been marked.
411: Keep doing this until, in one pass, no blocks have been marked.
412: Then blocks_live and blocks_marked are identical and correct.
413: In addition, all jumps actually reachable have been marked. */
414:
415: while (something_marked)
416: {
417: something_marked = 0;
418: for (i = 0; i < n_basic_blocks; i++)
419: if (block_live[i] && !block_marked[i])
420: {
421: block_marked[i] = 1;
422: something_marked = 1;
423: if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1])
424: block_live[i + 1] = 1;
425: insn = basic_block_end[i];
426: if (GET_CODE (insn) == JUMP_INSN)
427: mark_label_ref (PATTERN (insn), insn, 0);
428: }
429: }
430:
431: /* Now delete the code for any basic blocks that can't be reached.
432: They can occur because jump_optimize does not recognize
433: unreachable loops as unreachable. */
434:
435: for (i = 0; i < n_basic_blocks; i++)
436: if (!block_live[i])
437: {
438: insn = basic_block_head[i];
439: while (1)
440: {
1.1.1.2 root 441: if (GET_CODE (insn) == BARRIER)
442: abort ();
1.1 root 443: if (GET_CODE (insn) != NOTE)
444: {
445: PUT_CODE (insn, NOTE);
446: NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
447: NOTE_SOURCE_FILE (insn) = 0;
448: }
449: if (insn == basic_block_end[i])
1.1.1.2 root 450: {
451: /* BARRIERs are between basic blocks, not part of one.
452: Delete a BARRIER if the preceding jump is deleted.
453: We cannot alter a BARRIER into a NOTE
454: because it is too short; but we can really delete
455: it because it is not part of a basic block. */
456: if (NEXT_INSN (insn) != 0
457: && GET_CODE (NEXT_INSN (insn)) == BARRIER)
458: delete_insn (NEXT_INSN (insn));
459: break;
460: }
1.1 root 461: insn = NEXT_INSN (insn);
462: }
463: /* Each time we delete some basic blocks,
464: see if there is a jump around them that is
465: being turned into a no-op. If so, delete it. */
466:
467: if (block_live[i - 1])
468: {
469: register int j;
470: for (j = i; j < n_basic_blocks; j++)
471: if (block_live[j])
472: {
1.1.1.6 root 473: rtx label;
1.1 root 474: insn = basic_block_end[i - 1];
475: if (GET_CODE (insn) == JUMP_INSN
1.1.1.6 root 476: /* An unconditional jump is the only possibility
477: we must check for, since a conditional one
478: would make these blocks live. */
479: && simplejump_p (insn)
480: && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1)
481: && INSN_UID (label) != 0
482: && BLOCK_NUM (label) == j)
1.1 root 483: {
484: PUT_CODE (insn, NOTE);
485: NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
486: NOTE_SOURCE_FILE (insn) = 0;
1.1.1.2 root 487: if (GET_CODE (NEXT_INSN (insn)) != BARRIER)
488: abort ();
489: delete_insn (NEXT_INSN (insn));
1.1 root 490: }
491: break;
492: }
493: }
494: }
495: }
496: }
497:
498: /* Check expression X for label references;
499: if one is found, add INSN to the label's chain of references.
500:
501: CHECKDUP means check for and avoid creating duplicate references
502: from the same insn. Such duplicates do no serious harm but
503: can slow life analysis. CHECKDUP is set only when duplicates
504: are likely. */
505:
506: static void
507: mark_label_ref (x, insn, checkdup)
508: rtx x, insn;
509: int checkdup;
510: {
511: register RTX_CODE code = GET_CODE (x);
512: register int i;
513: register char *fmt;
514:
515: if (code == LABEL_REF)
516: {
517: register rtx label = XEXP (x, 0);
518: register rtx y;
519: if (GET_CODE (label) != CODE_LABEL)
1.1.1.4 root 520: abort ();
1.1.1.2 root 521: /* If the label was never emitted, this insn is junk,
522: but avoid a crash trying to refer to BLOCK_NUM (label).
523: This can happen as a result of a syntax error
524: and a diagnostic has already been printed. */
525: if (INSN_UID (label) == 0)
526: return;
1.1 root 527: CONTAINING_INSN (x) = insn;
528: /* if CHECKDUP is set, check for duplicate ref from same insn
529: and don't insert. */
530: if (checkdup)
531: for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y))
532: if (CONTAINING_INSN (y) == insn)
533: return;
534: LABEL_NEXTREF (x) = LABEL_REFS (label);
535: LABEL_REFS (label) = x;
536: block_live_static[BLOCK_NUM (label)] = 1;
537: return;
538: }
539:
540: fmt = GET_RTX_FORMAT (code);
541: for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
542: {
543: if (fmt[i] == 'e')
544: mark_label_ref (XEXP (x, i), insn, 0);
545: if (fmt[i] == 'E')
546: {
547: register int j;
548: for (j = 0; j < XVECLEN (x, i); j++)
549: mark_label_ref (XVECEXP (x, i, j), insn, 1);
550: }
551: }
552: }
553:
554: /* Determine the which registers are live at the start of each
555: basic block of the function whose first insn is F.
556: NREGS is the number of registers used in F.
557: We allocate the vector basic_block_live_at_start
558: and the regsets that it points to, and fill them with the data.
559: regset_size and regset_bytes are also set here. */
560:
561: static void
562: life_analysis (f, nregs)
563: rtx f;
564: int nregs;
565: {
566: register regset tem;
567: int first_pass;
568: int changed;
569: /* For each basic block, a bitmask of regs
570: live on exit from the block. */
571: regset *basic_block_live_at_end;
572: /* For each basic block, a bitmask of regs
573: live on entry to a successor-block of this block.
574: If this does not match basic_block_live_at_end,
575: that must be updated, and the block must be rescanned. */
576: regset *basic_block_new_live_at_end;
577: /* For each basic block, a bitmask of regs
578: whose liveness at the end of the basic block
579: can make a difference in which regs are live on entry to the block.
580: These are the regs that are set within the basic block,
581: possibly excluding those that are used after they are set. */
582: regset *basic_block_significant;
583: register int i;
1.1.1.2 root 584: rtx insn;
1.1 root 585:
1.1.1.14! root 586: struct obstack flow_obstack;
! 587:
! 588: obstack_init (&flow_obstack);
! 589:
1.1 root 590: max_regno = nregs;
591:
592: bzero (regs_ever_live, sizeof regs_ever_live);
593:
594: /* Allocate and zero out many data structures
595: that will record the data from lifetime analysis. */
596:
597: allocate_for_life_analysis ();
598:
599: reg_next_use = (rtx *) alloca (nregs * sizeof (rtx));
600: bzero (reg_next_use, nregs * sizeof (rtx));
601:
602: /* Set up several regset-vectors used internally within this function.
603: Their meanings are documented above, with their declarations. */
604:
605: basic_block_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset));
1.1.1.14! root 606: /* Don't use alloca since that leads to a crash rather than an error message
! 607: if there isn't enough space.
! 608: Don't use oballoc since we may need to allocate other things during
! 609: this function on the temporary obstack. */
! 610: tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
1.1 root 611: bzero (tem, n_basic_blocks * regset_bytes);
612: init_regset_vector (basic_block_live_at_end, tem, n_basic_blocks, regset_bytes);
613:
614: basic_block_new_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset));
1.1.1.14! root 615: tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
1.1 root 616: bzero (tem, n_basic_blocks * regset_bytes);
617: init_regset_vector (basic_block_new_live_at_end, tem, n_basic_blocks, regset_bytes);
618:
619: basic_block_significant = (regset *) alloca (n_basic_blocks * sizeof (regset));
1.1.1.14! root 620: tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes);
1.1 root 621: bzero (tem, n_basic_blocks * regset_bytes);
622: init_regset_vector (basic_block_significant, tem, n_basic_blocks, regset_bytes);
623:
1.1.1.4 root 624: /* Record which insns refer to any volatile memory
1.1.1.9 root 625: or for any reason can't be deleted just because they are dead stores.
626: Also, delete any insns that copy a register to itself. */
1.1.1.2 root 627:
628: for (insn = f; insn; insn = NEXT_INSN (insn))
1.1.1.4 root 629: {
630: enum rtx_code code1 = GET_CODE (insn);
631: if (code1 == CALL_INSN)
632: INSN_VOLATILE (insn) = 1;
633: else if (code1 == INSN || code1 == JUMP_INSN)
634: {
1.1.1.9 root 635: if (GET_CODE (PATTERN (insn)) == SET
636: && GET_CODE (SET_DEST (PATTERN (insn))) == REG
637: && GET_CODE (SET_SRC (PATTERN (insn))) == REG
638: && REGNO (SET_DEST (PATTERN (insn))) ==
639: REGNO (SET_SRC (PATTERN (insn))))
640: {
641: PUT_CODE (insn, NOTE);
642: NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
643: NOTE_SOURCE_FILE (insn) = 0;
644: }
645: else if (GET_CODE (PATTERN (insn)) != USE)
1.1.1.4 root 646: INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn));
647: }
1.1.1.6 root 648: /* A SET that makes space on the stack cannot be dead.
1.1.1.10 root 649: (Such SETs occur only for allocating variable-size data,
650: so they will always have a PLUS or MINUS according to the
651: direction of stack growth.)
1.1.1.6 root 652: Even if this function never uses this stack pointer value,
653: signal handlers do! */
654: else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET
655: && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
656: #ifdef STACK_GROWS_DOWNWARD
657: && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS
658: #else
659: && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
660: #endif
661: && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx)
662: INSN_VOLATILE (insn) = 1;
1.1.1.4 root 663: }
1.1.1.2 root 664:
665: if (n_basic_blocks > 0)
666: #ifdef EXIT_IGNORE_STACK
667: if (! (EXIT_IGNORE_STACK) || ! frame_pointer_needed)
668: #endif
669: {
670: /* If exiting needs the right stack value,
671: consider the stack pointer live at the end of the function. */
672: basic_block_live_at_end[n_basic_blocks - 1]
673: [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
674: |= 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
675: basic_block_new_live_at_end[n_basic_blocks - 1]
676: [STACK_POINTER_REGNUM / REGSET_ELT_BITS]
677: |= 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
678: }
679:
1.1 root 680: /* Propagate life info through the basic blocks
681: around the graph of basic blocks.
682:
683: This is a relaxation process: each time a new register
684: is live at the end of the basic block, we must scan the block
685: to determine which registers are, as a consequence, live at the beginning
686: of that block. These registers must then be marked live at the ends
687: of all the blocks that can transfer control to that block.
688: The process continues until it reaches a fixed point. */
689:
690: first_pass = 1;
691: changed = 1;
692: while (changed)
693: {
694: changed = 0;
695: for (i = n_basic_blocks - 1; i >= 0; i--)
696: {
697: int consider = first_pass;
698: int must_rescan = first_pass;
699: register int j;
700:
701: /* Set CONSIDER if this block needs thinking about at all
702: (that is, if the regs live now at the end of it
703: are not the same as were live at the end of it when
704: we last thought about it).
705: Set must_rescan if it needs to be thought about
706: instruction by instruction (that is, if any additional
707: reg that is live at the end now but was not live there before
708: is one of the significant regs of this basic block). */
709:
710: for (j = 0; j < regset_size; j++)
711: {
712: register int x = basic_block_new_live_at_end[i][j]
713: & ~basic_block_live_at_end[i][j];
714: if (x)
715: consider = 1;
716: if (x & basic_block_significant[i][j])
717: {
718: must_rescan = 1;
719: consider = 1;
720: break;
721: }
722: }
723:
724: if (! consider)
725: continue;
726:
727: /* The live_at_start of this block may be changing,
728: so another pass will be required after this one. */
729: changed = 1;
730:
731: if (! must_rescan)
732: {
733: /* No complete rescan needed;
734: just record those variables newly known live at end
735: as live at start as well. */
736: for (j = 0; j < regset_size; j++)
737: {
738: register int x = basic_block_new_live_at_end[i][j]
739: & ~basic_block_live_at_end[i][j];
740: basic_block_live_at_start[i][j] |= x;
741: basic_block_live_at_end[i][j] |= x;
742: }
743: }
744: else
745: {
746: /* Update the basic_block_live_at_start
747: by propagation backwards through the block. */
748: bcopy (basic_block_new_live_at_end[i],
749: basic_block_live_at_end[i], regset_bytes);
750: bcopy (basic_block_live_at_end[i],
751: basic_block_live_at_start[i], regset_bytes);
752: propagate_block (basic_block_live_at_start[i],
753: basic_block_head[i], basic_block_end[i], 0,
754: first_pass ? basic_block_significant[i] : 0,
755: i);
756: }
757:
758: {
759: register rtx jump, head;
760: /* Update the basic_block_new_live_at_end's of the block
761: that falls through into this one (if any). */
762: head = basic_block_head[i];
763: jump = PREV_INSN (head);
764: if (basic_block_drops_in[i])
765: {
1.1.1.14! root 766: register int from_block = BLOCK_NUM (jump);
1.1 root 767: register int j;
768: for (j = 0; j < regset_size; j++)
769: basic_block_new_live_at_end[from_block][j]
770: |= basic_block_live_at_start[i][j];
771: }
772: /* Update the basic_block_new_live_at_end's of
773: all the blocks that jump to this one. */
774: if (GET_CODE (head) == CODE_LABEL)
775: for (jump = LABEL_REFS (head);
776: jump != head;
777: jump = LABEL_NEXTREF (jump))
778: {
1.1.1.14! root 779: register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1.1 root 780: register int j;
781: for (j = 0; j < regset_size; j++)
782: basic_block_new_live_at_end[from_block][j]
783: |= basic_block_live_at_start[i][j];
784: }
785: }
1.1.1.13 root 786: #ifdef USE_C_ALLOCA
787: alloca (0);
788: #endif
1.1 root 789: }
790: first_pass = 0;
791: }
792:
1.1.1.5 root 793: #if 0 /* This seems unnecessary; life at start of function shouldn't
794: mean that the reg is live in more than one basic block. */
795:
1.1.1.2 root 796: /* Process the regs live at the beginning of the function.
797: Mark them as not local to any one basic block. */
798:
799: if (n_basic_blocks > 0)
800: for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
801: if (basic_block_live_at_start[0][i / REGSET_ELT_BITS]
802: & (1 << (i % REGSET_ELT_BITS)))
1.1.1.4 root 803: reg_basic_block[i] = REG_BLOCK_GLOBAL;
1.1.1.5 root 804: #endif
1.1.1.2 root 805:
1.1 root 806: /* Now the life information is accurate.
807: Make one more pass over each basic block
808: to delete dead stores, create autoincrement addressing
809: and record how many times each register is used, is set, or dies.
810:
811: To save time, we operate directly in basic_block_live_at_end[i],
812: thus destroying it (in fact, converting it into a copy of
813: basic_block_live_at_start[i]). This is ok now because
814: basic_block_live_at_end[i] is no longer used past this point. */
815:
816: for (i = 0; i < n_basic_blocks; i++)
817: {
818: propagate_block (basic_block_live_at_end[i],
819: basic_block_head[i], basic_block_end[i], 1, 0, i);
1.1.1.13 root 820: #ifdef USE_C_ALLOCA
821: alloca (0);
822: #endif
1.1 root 823: }
1.1.1.14! root 824:
! 825: /* Something live during a setjmp should not be put in a register
! 826: on certain machines which restore regs from stack frames
! 827: rather than from the jmpbuf.
! 828: But we don't need to do this for the user's variables, since
! 829: ANSI says only volatile variables need this. */
! 830: #ifdef LONGJMP_RESTORE_FROM_STACK
! 831: for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++)
! 832: if (regs_live_at_setjmp[i / REGSET_ELT_BITS] & (1 << (i % REGSET_ELT_BITS))
! 833: && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i]))
! 834: {
! 835: reg_live_length[i] = -1;
! 836: reg_basic_block[i] = -1;
! 837: }
! 838: #endif
! 839:
! 840: obstack_free (&flow_obstack, 0);
1.1 root 841: }
842:
843: /* Subroutines of life analysis. */
844:
845: /* Allocate the permanent data structures that represent the results
846: of life analysis. Not static since used also for stupid life analysis. */
847:
848: void
849: allocate_for_life_analysis ()
850: {
851: register int i;
852: register regset tem;
853:
854: regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS);
855: regset_bytes = regset_size * sizeof (*(regset)0);
856:
857: reg_n_refs = (short *) oballoc (max_regno * sizeof (short));
858: bzero (reg_n_refs, max_regno * sizeof (short));
859:
860: reg_n_sets = (short *) oballoc (max_regno * sizeof (short));
861: bzero (reg_n_sets, max_regno * sizeof (short));
862:
863: reg_n_deaths = (short *) oballoc (max_regno * sizeof (short));
864: bzero (reg_n_deaths, max_regno * sizeof (short));
865:
866: reg_live_length = (int *) oballoc (max_regno * sizeof (int));
867: bzero (reg_live_length, max_regno * sizeof (int));
868:
1.1.1.12 root 869: reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int));
870: bzero (reg_n_calls_crossed, max_regno * sizeof (int));
1.1 root 871:
872: reg_basic_block = (short *) oballoc (max_regno * sizeof (short));
873: for (i = 0; i < max_regno; i++)
1.1.1.4 root 874: reg_basic_block[i] = REG_BLOCK_UNKNOWN;
1.1 root 875:
876: basic_block_live_at_start = (regset *) oballoc (n_basic_blocks * sizeof (regset));
877: tem = (regset) oballoc (n_basic_blocks * regset_bytes);
878: bzero (tem, n_basic_blocks * regset_bytes);
879: init_regset_vector (basic_block_live_at_start, tem, n_basic_blocks, regset_bytes);
1.1.1.2 root 880:
881: regs_live_at_setjmp = (regset) oballoc (regset_bytes);
882: bzero (regs_live_at_setjmp, regset_bytes);
1.1 root 883: }
884:
885: /* Make each element of VECTOR point at a regset,
886: taking the space for all those regsets from SPACE.
887: SPACE is of type regset, but it is really as long as NELTS regsets.
888: BYTES_PER_ELT is the number of bytes in one regset. */
889:
890: static void
891: init_regset_vector (vector, space, nelts, bytes_per_elt)
892: regset *vector;
893: regset space;
894: int nelts;
895: int bytes_per_elt;
896: {
897: register int i;
898: register regset p = space;
899:
900: for (i = 0; i < nelts; i++)
901: {
902: vector[i] = p;
903: p += bytes_per_elt / sizeof (*p);
904: }
905: }
906:
907: /* Compute the registers live at the beginning of a basic block
908: from those live at the end.
909:
910: When called, OLD contains those live at the end.
911: On return, it contains those live at the beginning.
912: FIRST and LAST are the first and last insns of the basic block.
913:
914: FINAL is nonzero if we are doing the final pass which is not
915: for computing the life info (since that has already been done)
916: but for acting on it. On this pass, we delete dead stores,
917: set up the logical links and dead-variables lists of instructions,
918: and merge instructions for autoincrement and autodecrement addresses.
919:
920: SIGNIFICANT is nonzero only the first time for each basic block.
921: If it is nonzero, it points to a regset in which we store
922: a 1 for each register that is set within the block.
923:
924: BNUM is the number of the basic block. */
925:
926: static void
927: propagate_block (old, first, last, final, significant, bnum)
928: register regset old;
929: rtx first;
930: rtx last;
931: int final;
932: regset significant;
933: int bnum;
934: {
935: register rtx insn;
936: rtx prev;
937: regset live;
938: regset dead;
939:
940: /* The following variables are used only if FINAL is nonzero. */
941: /* This vector gets one element for each reg that has been live
942: at any point in the basic block that has been scanned so far.
943: SOMETIMES_MAX says how many elements are in use so far.
944: In each element, OFFSET is the byte-number within a regset
945: for the register described by the element, and BIT is a mask
946: for that register's bit within the byte. */
947: register struct foo { short offset; short bit; } *regs_sometimes_live;
948: int sometimes_max = 0;
949: /* This regset has 1 for each reg that we have seen live so far.
950: It and REGS_SOMETIMES_LIVE are updated together. */
951: regset maxlive;
952:
953: loop_depth = basic_block_loop_depth[bnum];
954:
955: dead = (regset) alloca (regset_bytes);
956: live = (regset) alloca (regset_bytes);
957:
958: if (final)
959: {
960: register int i, offset, bit;
961:
962: maxlive = (regset) alloca (regset_bytes);
963: bcopy (old, maxlive, regset_bytes);
964: regs_sometimes_live
965: = (struct foo *) alloca (max_regno * sizeof (struct foo));
966:
967: /* Process the regs live at the end of the block.
968: Enter them in MAXLIVE and REGS_SOMETIMES_LIVE.
969: Also mark them as not local to any one basic block. */
970:
971: for (offset = 0, i = 0; offset < regset_size; offset++)
972: for (bit = 1; bit; bit <<= 1, i++)
973: {
974: if (i == max_regno)
975: break;
976: if (old[offset] & bit)
977: {
1.1.1.4 root 978: reg_basic_block[i] = REG_BLOCK_GLOBAL;
1.1 root 979: regs_sometimes_live[sometimes_max].offset = offset;
980: regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS;
981: sometimes_max++;
982: }
983: }
984: }
985:
986: /* Scan the block an insn at a time from end to beginning. */
987:
988: for (insn = last; ; insn = prev)
989: {
990: prev = PREV_INSN (insn);
991:
1.1.1.2 root 992: /* If this is a call to `setjmp' et al,
993: warn if any non-volatile datum is live. */
994:
995: if (final && GET_CODE (insn) == NOTE
996: && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
997: {
998: int i;
999: for (i = 0; i < regset_size; i++)
1000: regs_live_at_setjmp[i] |= old[i];
1.1 root 1001: }
1002:
1003: /* Update the life-status of regs for this insn.
1004: First DEAD gets which regs are set in this insn
1005: then LIVE gets which regs are used in this insn.
1006: Then the regs live before the insn
1007: are those live after, with DEAD regs turned off,
1008: and then LIVE regs turned on. */
1009:
1010: if (GET_CODE (insn) == INSN
1011: || GET_CODE (insn) == JUMP_INSN
1012: || GET_CODE (insn) == CALL_INSN)
1013: {
1014: register int i;
1.1.1.2 root 1015: rtx note = find_reg_note (insn, REG_RETVAL, 0);
1016:
1.1 root 1017: /* If an instruction consists of just dead store(s) on final pass,
1018: "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED.
1019: We could really delete it with delete_insn, but that
1020: can cause trouble for first or last insn in a basic block. */
1.1.1.2 root 1021: if (final && insn_dead_p (PATTERN (insn), old, 1)
1022: /* Don't delete something that refers to volatile storage! */
1023: && ! INSN_VOLATILE (insn))
1.1 root 1024: {
1.1.1.10 root 1025: rtx oldpat = PATTERN (insn);
1.1 root 1026: PUT_CODE (insn, NOTE);
1027: NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1028: NOTE_SOURCE_FILE (insn) = 0;
1.1.1.2 root 1029: /* If this insn is copying the return value from a library call,
1030: delete the entire library call. */
1.1.1.10 root 1031: if (note && libcall_dead_p (oldpat, old))
1.1.1.2 root 1032: {
1033: rtx first = XEXP (note, 0);
1034: rtx prev = insn;
1.1.1.9 root 1035: while (INSN_DELETED_P (first))
1.1.1.2 root 1036: first = NEXT_INSN (first);
1037: while (prev != first)
1038: {
1039: prev = PREV_INSN (prev);
1040: PUT_CODE (prev, NOTE);
1041: NOTE_LINE_NUMBER (prev) = NOTE_INSN_DELETED;
1042: NOTE_SOURCE_FILE (prev) = 0;
1043: }
1044: }
1.1 root 1045: goto flushed;
1046: }
1.1.1.2 root 1047:
1048: for (i = 0; i < regset_size; i++)
1.1 root 1049: {
1.1.1.2 root 1050: dead[i] = 0; /* Faster than bzero here */
1051: live[i] = 0; /* since regset_size is usually small */
1052: }
1.1 root 1053:
1.1.1.2 root 1054: /* See if this is an increment or decrement that can be
1055: merged into a following memory address. */
1056: #ifdef AUTO_INC_DEC
1057: {
1058: register rtx x = PATTERN (insn);
1059: /* Does this instruction increment or decrement a register? */
1060: if (final && GET_CODE (x) == SET
1061: && GET_CODE (SET_DEST (x)) == REG
1062: && (GET_CODE (SET_SRC (x)) == PLUS
1063: || GET_CODE (SET_SRC (x)) == MINUS)
1064: && XEXP (SET_SRC (x), 0) == SET_DEST (x)
1065: && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
1066: /* Ok, look for a following memory ref we can combine with.
1067: If one is found, change the memory ref to a PRE_INC
1068: or PRE_DEC, cancel this insn, and return 1.
1069: Return 0 if nothing has been done. */
1070: && try_pre_increment_1 (insn))
1071: goto flushed;
1072: }
1073: #endif /* AUTO_INC_DEC */
1.1 root 1074:
1.1.1.2 root 1075: /* If this is not the final pass, and this insn is copying the
1076: value of a library call and it's dead, don't scan the
1077: insns that perform the library call, so that the call's
1078: arguments are not marked live. */
1.1.1.10 root 1079: if (note && insn_dead_p (PATTERN (insn), old, 1)
1080: && libcall_dead_p (PATTERN (insn), old))
1.1.1.3 root 1081: {
1.1.1.4 root 1082: /* Mark the dest reg as `significant'. */
1083: mark_set_regs (old, dead, PATTERN (insn), 0, significant);
1084:
1.1.1.3 root 1085: insn = XEXP (note, 0);
1086: prev = PREV_INSN (insn);
1087: }
1.1.1.9 root 1088: else if (GET_CODE (PATTERN (insn)) == SET
1089: && SET_DEST (PATTERN (insn)) == stack_pointer_rtx
1.1.1.4 root 1090: && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS
1091: && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx
1092: && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT)
1.1.1.10 root 1093: /* We have an insn to pop a constant amount off the stack.
1094: (Such insns use PLUS regardless of the direction of the stack,
1095: and any insn to adjust the stack by a constant is always a pop.)
1096: These insns, if not dead stores, have no effect on life. */
1.1.1.4 root 1097: ;
1.1.1.2 root 1098: else
1099: {
1100: /* LIVE gets the regs used in INSN; DEAD gets those set by it. */
1.1 root 1101: mark_set_regs (old, dead, PATTERN (insn), final ? insn : 0,
1102: significant);
1.1.1.2 root 1103: mark_used_regs (old, live, PATTERN (insn), final, insn);
1.1 root 1104:
1105: /* Update OLD for the registers used or set. */
1106: for (i = 0; i < regset_size; i++)
1107: {
1108: old[i] &= ~dead[i];
1109: old[i] |= live[i];
1110: }
1111:
1.1.1.2 root 1112: if (GET_CODE (insn) == CALL_INSN)
1113: {
1114: register int i;
1115:
1116: /* Each call clobbers all call-clobbered regs.
1117: Note that the function-value reg is one of these, and
1118: mark_set_regs has already had a chance to handle it. */
1119: for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1120: if (call_used_regs[i])
1.1.1.9 root 1121: dead[i / REGSET_ELT_BITS] |=
1122: (1 << (i % REGSET_ELT_BITS));
1.1.1.2 root 1123:
1124: /* The stack ptr is used (honorarily) by a CALL insn. */
1.1.1.9 root 1125: live[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1.1.1.2 root 1126: |= (1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS));
1.1.1.9 root 1127: }
1.1.1.2 root 1128:
1.1.1.9 root 1129: /* Update OLD for the registers used or set. */
1130: for (i = 0; i < regset_size; i++)
1131: {
1132: old[i] &= ~dead[i];
1133: old[i] |= live[i];
1134: }
1135:
1136: if (GET_CODE (insn) == CALL_INSN && final)
1137: {
1138: /* Any regs live at the time of a call instruction
1139: must not go in a register clobbered by calls.
1140: Find all regs now live and record this for them. */
1141:
1142: register struct foo *p = regs_sometimes_live;
1143:
1144: for (i = 0; i < sometimes_max; i++, p++)
1145: if (old[p->offset] & (1 << p->bit))
1.1.1.12 root 1146: reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1;
1.1.1.2 root 1147: }
1148: }
1149:
1150: /* On final pass, add any additional sometimes-live regs
1151: into MAXLIVE and REGS_SOMETIMES_LIVE.
1152: Also update counts of how many insns each reg is live at. */
1.1 root 1153:
1.1.1.2 root 1154: if (final)
1155: {
1156: for (i = 0; i < regset_size; i++)
1.1 root 1157: {
1.1.1.2 root 1158: register int diff = live[i] & ~maxlive[i];
1.1 root 1159:
1.1.1.2 root 1160: if (diff)
1161: {
1162: register int regno;
1163: maxlive[i] |= diff;
1164: for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++)
1165: if (diff & (1 << regno))
1166: {
1167: regs_sometimes_live[sometimes_max].offset = i;
1168: regs_sometimes_live[sometimes_max].bit = regno;
1169: diff &= ~ (1 << regno);
1170: sometimes_max++;
1171: }
1172: }
1173: }
1.1 root 1174:
1.1.1.2 root 1175: {
1176: register struct foo *p = regs_sometimes_live;
1177: for (i = 0; i < sometimes_max; i++, p++)
1.1 root 1178: {
1.1.1.2 root 1179: if (old[p->offset] & (1 << p->bit))
1180: reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++;
1.1 root 1181: }
1.1.1.2 root 1182: }
1.1 root 1183: }
1184: }
1.1.1.2 root 1185: flushed: ;
1.1 root 1186: if (insn == first)
1187: break;
1188: }
1189: }
1190:
1191: /* Return 1 if X (the body of an insn, or part of it) is just dead stores
1192: (SET expressions whose destinations are registers dead after the insn).
1193: NEEDED is the regset that says which regs are alive after the insn. */
1194:
1195: static int
1.1.1.2 root 1196: insn_dead_p (x, needed, strict_low_ok)
1.1 root 1197: rtx x;
1198: regset needed;
1.1.1.2 root 1199: int strict_low_ok;
1.1 root 1200: {
1201: register RTX_CODE code = GET_CODE (x);
1.1.1.2 root 1202: #if 0
1.1 root 1203: /* Make sure insns to set the stack pointer are never deleted. */
1204: needed[STACK_POINTER_REGNUM / REGSET_ELT_BITS]
1205: |= 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS);
1.1.1.2 root 1206: #endif
1207:
1208: /* If setting something that's a reg or part of one,
1209: see if that register's altered value will be live. */
1210:
1211: if (code == SET)
1.1 root 1212: {
1.1.1.2 root 1213: register rtx r = SET_DEST (x);
1214: /* A SET that is a subroutine call cannot be dead. */
1215: if (GET_CODE (SET_SRC (x)) == CALL)
1216: return 0;
1217: while (GET_CODE (r) == SUBREG
1218: || (strict_low_ok && GET_CODE (r) == STRICT_LOW_PART)
1219: || GET_CODE (r) == ZERO_EXTRACT
1220: || GET_CODE (r) == SIGN_EXTRACT)
1221: r = SUBREG_REG (r);
1222: if (GET_CODE (r) == REG)
1223: {
1224: register int regno = REGNO (r);
1225: register int offset = regno / REGSET_ELT_BITS;
1226: register int bit = 1 << (regno % REGSET_ELT_BITS);
1.1.1.11 root 1227: return (! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1228: && (needed[offset] & bit) == 0);
1.1.1.2 root 1229: }
1.1 root 1230: }
1.1.1.2 root 1231: /* If performing several activities,
1232: insn is dead if each activity is individually dead.
1233: Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE
1234: that's inside a PARALLEL doesn't make the insn worth keeping. */
1235: else if (code == PARALLEL)
1.1 root 1236: {
1237: register int i = XVECLEN (x, 0);
1238: for (i--; i >= 0; i--)
1.1.1.2 root 1239: {
1240: rtx elt = XVECEXP (x, 0, i);
1241: if (!insn_dead_p (elt, needed, strict_low_ok)
1242: && GET_CODE (elt) != CLOBBER
1243: && GET_CODE (elt) != USE)
1244: return 0;
1245: }
1.1 root 1246: return 1;
1247: }
1.1.1.2 root 1248: /* We do not check CLOBBER or USE here.
1249: An insn consisting of just a CLOBBER or just a USE
1250: should not be deleted. */
1.1 root 1251: return 0;
1252: }
1253:
1.1.1.10 root 1254: /* If X is the last insn in a libcall, and assuming X is dead,
1255: return 1 if the entire library call is dead.
1256: This is true if the source of X is a dead register
1257: (as well as the destination, which we tested already).
1258: If this insn doesn't just copy a register, then we don't
1259: have an ordinary libcall. In that case, cse could not have
1260: managed to substitute the source for the dest later on,
1261: so we can assume the libcall is dead. */
1262:
1263: static int
1264: libcall_dead_p (x, needed)
1265: rtx x;
1266: regset needed;
1267: {
1268: register RTX_CODE code = GET_CODE (x);
1269:
1270: if (code == SET)
1271: {
1272: register rtx r = SET_SRC (x);
1273: if (GET_CODE (r) == REG)
1274: {
1275: register int regno = REGNO (r);
1276: register int offset = regno / REGSET_ELT_BITS;
1277: register int bit = 1 << (regno % REGSET_ELT_BITS);
1278: return (needed[offset] & bit) == 0;
1279: }
1280: }
1281: return 1;
1282: }
1283:
1.1.1.2 root 1284: /* Return 1 if register REGNO was used before it was set.
1285: In other words, if it is live at function entry. */
1.1 root 1286:
1.1.1.2 root 1287: int
1288: regno_uninitialized (regno)
1.1 root 1289: int regno;
1290: {
1.1.1.11 root 1291: if (n_basic_blocks == 0)
1292: return 0;
1293:
1.1.1.2 root 1294: return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS]
1295: & (1 << (regno % REGSET_ELT_BITS)));
1296: }
1297:
1298: /* 1 if register REGNO was alive at a place where `setjmp' was called
1299: and was set more than once. Such regs may be clobbered by `longjmp'. */
1300:
1301: int
1302: regno_clobbered_at_setjmp (regno)
1303: int regno;
1304: {
1305: return (reg_n_sets[regno] > 1
1306: && (regs_live_at_setjmp[regno / REGSET_ELT_BITS]
1307: & (1 << (regno % REGSET_ELT_BITS))));
1.1 root 1308: }
1309:
1310: /* Process the registers that are set within X.
1311: Their bits are set to 1 in the regset DEAD,
1312: because they are dead prior to this insn.
1313:
1314: If INSN is nonzero, it is the insn being processed
1315: and the fact that it is nonzero implies this is the FINAL pass
1316: in propagate_block. In this case, various info about register
1317: usage is stored, LOG_LINKS fields of insns are set up. */
1318:
1319: static void mark_set_1 ();
1320:
1321: static void
1322: mark_set_regs (needed, dead, x, insn, significant)
1323: regset needed;
1324: regset dead;
1325: rtx x;
1326: rtx insn;
1327: regset significant;
1328: {
1329: register RTX_CODE code = GET_CODE (x);
1330:
1331: if (code == SET || code == CLOBBER)
1332: mark_set_1 (needed, dead, x, insn, significant);
1333: else if (code == PARALLEL)
1334: {
1335: register int i;
1336: for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
1337: {
1338: code = GET_CODE (XVECEXP (x, 0, i));
1339: if (code == SET || code == CLOBBER)
1340: mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant);
1341: }
1342: }
1343: }
1344:
1345: /* Process a single SET rtx, X. */
1346:
1347: static void
1348: mark_set_1 (needed, dead, x, insn, significant)
1349: regset needed;
1350: regset dead;
1351: rtx x;
1352: rtx insn;
1353: regset significant;
1354: {
1355: register int regno;
1356: register rtx reg = SET_DEST (x);
1.1.1.13 root 1357: int subreg_p = 0;
1.1 root 1358:
1.1.1.2 root 1359: if (reg == 0)
1360: return;
1361:
1.1.1.13 root 1362: if (GET_CODE (reg) == STRICT_LOW_PART)
1363: reg = XEXP (reg, 0);
1364:
1365: if (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
1366: || GET_CODE (reg) == SIGN_EXTRACT)
1.1 root 1367: {
1.1.1.13 root 1368: /* Modifying just one hardware register of a multi-reg value
1369: or just a byte field of a register
1370: does not mean the value from before this insn is now dead.
1371: But it does mean liveness of that register at the end of the block
1372: is significant. */
1.1 root 1373: if (REG_SIZE (SUBREG_REG (reg)) > REG_SIZE (reg))
1.1.1.13 root 1374: subreg_p = 1;
1.1 root 1375:
1376: reg = SUBREG_REG (reg);
1377: }
1378:
1379: if (GET_CODE (reg) == REG
1380: && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM)
1.1.1.11 root 1381: && regno != ARG_POINTER_REGNUM
1382: && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1.1.1.2 root 1383: /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1.1 root 1384: {
1385: register int offset = regno / REGSET_ELT_BITS;
1386: register int bit = 1 << (regno % REGSET_ELT_BITS);
1.1.1.2 root 1387: int is_needed = 0;
1388:
1.1 root 1389: /* Mark it as a significant register for this basic block. */
1390: if (significant)
1391: significant[offset] |= bit;
1.1.1.13 root 1392: /* That's all we do, if we are setting only part of the register. */
1393: if (subreg_p)
1394: return;
1395:
1396: /* If entire register being set, mark it as as dead before this insn. */
1397: dead[offset] |= bit;
1.1.1.2 root 1398: /* A hard reg in a wide mode may really be multiple registers.
1399: If so, mark all of them just like the first. */
1400: if (regno < FIRST_PSEUDO_REGISTER)
1401: {
1.1.1.4 root 1402: int n;
1403:
1404: /* Nothing below is needed for the stack pointer; get out asap.
1405: Eg, log links aren't needed, since combine won't use them. */
1406: if (regno == STACK_POINTER_REGNUM)
1407: return;
1408:
1409: n = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1.1.1.2 root 1410: while (--n > 0)
1411: {
1412: dead[(regno + n) / REGSET_ELT_BITS]
1413: |= 1 << ((regno + n) % REGSET_ELT_BITS);
1414: if (significant)
1415: significant[(regno + n) / REGSET_ELT_BITS]
1416: |= 1 << ((regno + n) % REGSET_ELT_BITS);
1417: is_needed |= (needed[(regno + n) / REGSET_ELT_BITS]
1418: & 1 << ((regno + n) % REGSET_ELT_BITS));
1419: }
1420: }
1.1 root 1421: /* Additional data to record if this is the final pass. */
1422: if (insn)
1423: {
1424: register rtx y = reg_next_use[regno];
1425: register int blocknum = BLOCK_NUM (insn);
1426:
1.1.1.9 root 1427: /* If this is a hard reg, record this function uses the reg.
1428: `combine.c' will get confused if LOG_LINKs are made
1429: for hard regs. */
1.1 root 1430:
1431: if (regno < FIRST_PSEUDO_REGISTER)
1432: {
1433: register int i;
1434: i = HARD_REGNO_NREGS (regno, GET_MODE (reg));
1.1.1.8 root 1435: if (i == 0)
1436: i = 1;
1.1 root 1437: do
1438: regs_ever_live[regno + --i] = 1;
1439: while (i > 0);
1.1.1.4 root 1440:
1441: if (! ((needed[offset] & bit) || is_needed))
1442: {
1443: /* Note that dead stores have already been deleted if poss.
1444: If we get here, we have found a dead store that cannot
1445: be eliminated (because the insn does something useful).
1446: Indicate this by marking the reg set as dying here. */
1447: REG_NOTES (insn)
1448: = gen_rtx (EXPR_LIST, REG_DEAD,
1449: reg, REG_NOTES (insn));
1450: reg_n_deaths[REGNO (reg)]++;
1451: }
1452: return;
1.1 root 1453: }
1454:
1455: /* Keep track of which basic blocks each reg appears in. */
1456:
1.1.1.4 root 1457: if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
1.1 root 1458: reg_basic_block[regno] = blocknum;
1459: else if (reg_basic_block[regno] != blocknum)
1.1.1.4 root 1460: reg_basic_block[regno] = REG_BLOCK_GLOBAL;
1.1 root 1461:
1462: /* Count (weighted) references, stores, etc. */
1463: reg_n_refs[regno] += loop_depth;
1464: reg_n_sets[regno]++;
1.1.1.2 root 1465: /* The next use is no longer "next", since a store intervenes. */
1466: reg_next_use[regno] = 0;
1.1 root 1467: /* The insns where a reg is live are normally counted elsewhere,
1468: but we want the count to include the insn where the reg is set,
1469: and the normal counting mechanism would not count it. */
1470: reg_live_length[regno]++;
1.1.1.2 root 1471: if ((needed[offset] & bit) || is_needed)
1.1 root 1472: {
1473: /* Make a logical link from the next following insn
1474: that uses this register, back to this insn.
1475: The following insns have already been processed. */
1476: if (y && (BLOCK_NUM (y) == blocknum))
1477: LOG_LINKS (y)
1478: = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y));
1479: }
1480: else
1481: {
1482: /* Note that dead stores have already been deleted when possible
1483: If we get here, we have found a dead store that cannot
1484: be eliminated (because the same insn does something useful).
1485: Indicate this by marking the reg being set as dying here. */
1486: REG_NOTES (insn)
1487: = gen_rtx (EXPR_LIST, REG_DEAD,
1488: reg, REG_NOTES (insn));
1.1.1.3 root 1489: reg_n_deaths[REGNO (reg)]++;
1.1 root 1490: }
1491: }
1492: }
1493: }
1494:
1495: /* Scan expression X and store a 1-bit in LIVE for each reg it uses.
1496: This is done assuming the registers needed from X
1497: are those that have 1-bits in NEEDED.
1498:
1.1.1.2 root 1499: On the final pass, FINAL is 1. This means try for autoincrement
1500: and count the uses and deaths of each pseudo-reg.
1501:
1502: INSN is the containing instruction. */
1.1 root 1503:
1504: static void
1.1.1.2 root 1505: mark_used_regs (needed, live, x, final, insn)
1.1 root 1506: regset needed;
1507: regset live;
1508: rtx x;
1509: rtx insn;
1.1.1.2 root 1510: int final;
1.1 root 1511: {
1512: register RTX_CODE code;
1513: register int regno;
1514:
1515: retry:
1516: code = GET_CODE (x);
1517: switch (code)
1518: {
1519: case LABEL_REF:
1520: case SYMBOL_REF:
1521: case CONST_INT:
1522: case CONST:
1.1.1.4 root 1523: case CONST_DOUBLE:
1.1 root 1524: case CC0:
1525: case PC:
1526: case CLOBBER:
1.1.1.4 root 1527: case ADDR_VEC:
1528: case ADDR_DIFF_VEC:
1529: case ASM_INPUT:
1.1 root 1530: return;
1531:
1532: #if defined (HAVE_POST_INCREMENT) || defined (HAVE_POST_DECREMENT)
1533: case MEM:
1534: /* Here we detect use of an index register which might
1535: be good for postincrement or postdecrement. */
1.1.1.2 root 1536: if (final)
1.1 root 1537: {
1538: rtx addr = XEXP (x, 0);
1539: register int size = GET_MODE_SIZE (GET_MODE (x));
1540:
1541: if (GET_CODE (addr) == REG)
1542: {
1543: register rtx y;
1544: regno = REGNO (addr);
1545: /* Is the next use an increment that might make auto-increment? */
1546: y = reg_next_use[regno];
1547: if (y && GET_CODE (PATTERN (y)) == SET
1548: && BLOCK_NUM (y) == BLOCK_NUM (insn)
1549: /* Can't add side effects to jumps; if reg is spilled and
1550: reloaded, there's no way to store back the altered value. */
1551: && GET_CODE (insn) != JUMP_INSN
1552: && (y = SET_SRC (PATTERN (y)),
1553: (0
1554: #ifdef HAVE_POST_INCREMENT
1555: || GET_CODE (y) == PLUS
1556: #endif
1557: #ifdef HAVE_POST_DECREMENT
1558: || GET_CODE (y) == MINUS
1559: #endif
1560: )
1561: && XEXP (y, 0) == addr
1562: && GET_CODE (XEXP (y, 1)) == CONST_INT
1.1.1.2 root 1563: && INTVAL (XEXP (y, 1)) == size)
1564: && dead_or_set_p (reg_next_use[regno], addr))
1.1 root 1565: {
1.1.1.2 root 1566: rtx use = find_use_as_address (PATTERN (insn), addr, 0);
1.1 root 1567:
1568: /* Make sure this register appears only once in this insn. */
1569: if (use != 0 && use != (rtx) 1)
1570: {
1571: /* We have found a suitable auto-increment:
1572: do POST_INC around the register here,
1573: and patch out the increment instruction that follows. */
1574: XEXP (x, 0)
1575: = gen_rtx (GET_CODE (y) == PLUS ? POST_INC : POST_DEC,
1576: Pmode, addr);
1577: /* Record that this insn has an implicit side effect. */
1578: REG_NOTES (insn)
1579: = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn));
1580:
1.1.1.2 root 1581: /* Modify the old increment-insn to simply copy
1582: the already-incremented value of our register. */
1.1 root 1583: y = reg_next_use[regno];
1.1.1.2 root 1584: SET_SRC (PATTERN (y)) = addr;
1585:
1586: /* If that makes it a no-op (copying the register
1587: into itself) then change it to a simpler no-op
1588: so it won't appear to be a "use" and a "set"
1589: of this register. */
1590: if (SET_DEST (PATTERN (y)) == addr)
1591: PATTERN (y) = gen_rtx (USE, VOIDmode, const0_rtx);
1592:
1593: /* Count an extra reference to the reg for the increment.
1594: When a reg is incremented.
1.1 root 1595: spilling it is worse, so we want to make that
1596: less likely. */
1597: reg_n_refs[regno] += loop_depth;
1.1.1.2 root 1598: /* Count the increment as a setting of the register,
1599: even though it isn't a SET in rtl. */
1600: reg_n_sets[regno]++;
1.1 root 1601: }
1602: }
1603: }
1604: }
1605: break;
1606: #endif /* HAVE_POST_INCREMENT or HAVE_POST_DECREMENT */
1607:
1608: case REG:
1609: /* See a register other than being set
1610: => mark it as needed. */
1611:
1612: regno = REGNO (x);
1.1.1.14! root 1613: if (regno != FRAME_POINTER_REGNUM)
! 1614: /* && regno != ARG_POINTER_REGNUM) -- and without this. */
1.1.1.2 root 1615: /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */
1.1 root 1616: {
1617: register int offset = regno / REGSET_ELT_BITS;
1618: register int bit = 1 << (regno % REGSET_ELT_BITS);
1.1.1.2 root 1619: int is_needed = 0;
1620:
1.1 root 1621: live[offset] |= bit;
1.1.1.2 root 1622: /* A hard reg in a wide mode may really be multiple registers.
1623: If so, mark all of them just like the first. */
1624: if (regno < FIRST_PSEUDO_REGISTER)
1625: {
1.1.1.4 root 1626: int n;
1627:
1.1.1.14! root 1628: /* For stack ptr or arg pointer,
! 1629: nothing below can be necessary, so waste no more time. */
! 1630: if (regno == STACK_POINTER_REGNUM
! 1631: || regno == ARG_POINTER_REGNUM)
1.1.1.4 root 1632: return;
1.1.1.12 root 1633: /* No death notes for global register variables;
1634: their values are live after this function exits. */
1635: if (global_regs[regno])
1636: return;
1.1.1.4 root 1637:
1638: n = HARD_REGNO_NREGS (regno, GET_MODE (x));
1.1.1.2 root 1639: while (--n > 0)
1640: {
1641: live[(regno + n) / REGSET_ELT_BITS]
1642: |= 1 << ((regno + n) % REGSET_ELT_BITS);
1643: is_needed |= (needed[(regno + n) / REGSET_ELT_BITS]
1644: & 1 << ((regno + n) % REGSET_ELT_BITS));
1645: }
1646: }
1647: if (final)
1.1 root 1648: {
1649: if (regno < FIRST_PSEUDO_REGISTER)
1650: {
1.1.1.4 root 1651: /* If a hard reg is being used,
1652: record that this function does use it. */
1653:
1.1 root 1654: register int i;
1655: i = HARD_REGNO_NREGS (regno, GET_MODE (x));
1.1.1.8 root 1656: if (i == 0)
1657: i = 1;
1.1 root 1658: do
1659: regs_ever_live[regno + --i] = 1;
1660: while (i > 0);
1661: }
1.1.1.4 root 1662: else
1663: {
1664: /* Keep track of which basic block each reg appears in. */
1.1 root 1665:
1.1.1.4 root 1666: register int blocknum = BLOCK_NUM (insn);
1.1 root 1667:
1.1.1.4 root 1668: if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN)
1669: reg_basic_block[regno] = blocknum;
1670: else if (reg_basic_block[regno] != blocknum)
1671: reg_basic_block[regno] = REG_BLOCK_GLOBAL;
1.1 root 1672:
1.1.1.4 root 1673: /* Record where each reg is used, so when the reg
1674: is set we know the next insn that uses it. */
1.1 root 1675:
1.1.1.4 root 1676: reg_next_use[regno] = insn;
1.1 root 1677:
1.1.1.4 root 1678: /* Count (weighted) number of uses of each reg. */
1.1 root 1679:
1.1.1.4 root 1680: reg_n_refs[regno] += loop_depth;
1681: }
1.1.1.12 root 1682:
1.1 root 1683: /* Record and count the insns in which a reg dies.
1684: If it is used in this insn and was dead below the insn
1685: then it dies in this insn. */
1686:
1.1.1.2 root 1687: if (!(needed[offset] & bit) && !is_needed
1688: && ! find_regno_note (insn, REG_DEAD, regno))
1.1 root 1689: {
1690: REG_NOTES (insn)
1691: = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn));
1692: reg_n_deaths[regno]++;
1693: }
1694: }
1695: }
1696: return;
1697:
1698: case SET:
1699: {
1.1.1.2 root 1700: register rtx testreg = SET_DEST (x);
1701: int mark_dest = 0;
1.1 root 1702:
1.1.1.2 root 1703: /* Storing in STRICT_LOW_PART is like storing in a reg
1704: in that this SET might be dead, so ignore it in TESTREG.
1705: but in some other ways it is like using the reg. */
1706: /* Storing in a SUBREG or a bit field is like storing the entire
1707: register in that if the register's value is not used
1708: then this SET is not needed. */
1709: while (GET_CODE (testreg) == STRICT_LOW_PART
1710: || GET_CODE (testreg) == ZERO_EXTRACT
1711: || GET_CODE (testreg) == SIGN_EXTRACT
1712: || GET_CODE (testreg) == SUBREG)
1713: {
1714: /* Modifying a single register in an alternate mode
1715: does not use any of the old value. But these other
1716: ways of storing in a register do use the old value. */
1717: if (GET_CODE (testreg) == SUBREG
1718: && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg)))
1719: ;
1720: else
1721: mark_dest = 1;
1722:
1723: testreg = XEXP (testreg, 0);
1724: }
1.1 root 1725:
1726: /* If this is a store into a register,
1727: recursively scan the only value being stored,
1728: and only if the register's value is live after this insn.
1729: If the value being computed here would never be used
1730: then the values it uses don't need to be computed either. */
1731:
1.1.1.2 root 1732: if (GET_CODE (testreg) == REG
1733: && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM)
1.1.1.11 root 1734: && regno != ARG_POINTER_REGNUM
1735: && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]))
1.1.1.7 root 1736: #if 0 /* This was added in 1.25, but screws up death notes for hard regs.
1737: It probably isn't really needed anyway. */
1.1.1.6 root 1738: && (regno >= FIRST_PSEUDO_REGISTER
1739: || INSN_VOLATILE (insn)))
1.1.1.7 root 1740: #endif
1.1 root 1741: {
1742: register int offset = regno / REGSET_ELT_BITS;
1743: register int bit = 1 << (regno % REGSET_ELT_BITS);
1.1.1.2 root 1744: if ((needed[offset] & bit)
1745: /* If insn refers to volatile, we mustn't delete it,
1746: so its inputs are all needed. */
1747: || INSN_VOLATILE (insn))
1748: {
1749: mark_used_regs (needed, live, SET_SRC (x), final, insn);
1750: if (mark_dest)
1751: mark_used_regs (needed, live, SET_DEST (x), final, insn);
1752: }
1.1 root 1753: return;
1754: }
1755: }
1756: break;
1757: }
1758:
1759: /* Recursively scan the operands of this expression. */
1760:
1761: {
1762: register char *fmt = GET_RTX_FORMAT (code);
1763: register int i;
1764:
1765: for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1766: {
1767: if (fmt[i] == 'e')
1768: {
1769: /* Tail recursive case: save a function call level. */
1770: if (i == 0)
1771: {
1772: x = XEXP (x, 0);
1773: goto retry;
1774: }
1.1.1.2 root 1775: mark_used_regs (needed, live, XEXP (x, i), final, insn);
1.1 root 1776: }
1.1.1.4 root 1777: else if (fmt[i] == 'E')
1.1 root 1778: {
1779: register int j;
1780: for (j = 0; j < XVECLEN (x, i); j++)
1.1.1.2 root 1781: mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn);
1.1 root 1782: }
1783: }
1784: }
1785: }
1786:
1.1.1.2 root 1787: #ifdef AUTO_INC_DEC
1.1 root 1788:
1789: static int
1790: try_pre_increment_1 (insn)
1791: rtx insn;
1792: {
1793: /* Find the next use of this reg. If in same basic block,
1794: make it do pre-increment or pre-decrement if appropriate. */
1795: rtx x = PATTERN (insn);
1796: int amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1)
1797: * INTVAL (XEXP (SET_SRC (x), 1)));
1798: int regno = REGNO (SET_DEST (x));
1799: rtx y = reg_next_use[regno];
1800: if (y != 0
1801: && BLOCK_NUM (y) == BLOCK_NUM (insn)
1802: && try_pre_increment (y, SET_DEST (PATTERN (insn)),
1803: amount))
1804: {
1805: /* We have found a suitable auto-increment
1806: and already changed insn Y to do it.
1807: So flush this increment-instruction. */
1808: PUT_CODE (insn, NOTE);
1809: NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
1810: NOTE_SOURCE_FILE (insn) = 0;
1811: /* Count a reference to this reg for the increment
1812: insn we are deleting. When a reg is incremented.
1813: spilling it is worse, so we want to make that
1814: less likely. */
1815: reg_n_refs[regno] += loop_depth;
1.1.1.2 root 1816: reg_n_sets[regno]++;
1.1 root 1817: return 1;
1818: }
1819: return 0;
1820: }
1821:
1822: /* Try to change INSN so that it does pre-increment or pre-decrement
1823: addressing on register REG in order to add AMOUNT to REG.
1824: AMOUNT is negative for pre-decrement.
1825: Returns 1 if the change could be made.
1826: This checks all about the validity of the result of modifying INSN. */
1827:
1828: static int
1829: try_pre_increment (insn, reg, amount)
1830: rtx insn, reg;
1831: int amount;
1832: {
1833: register rtx use;
1834:
1.1.1.2 root 1835: /* Nonzero if we can try to make a pre-increment or pre-decrement.
1836: For example, addl $4,r1; movl (r1),... can become movl +(r1),... */
1837: int pre_ok = 0;
1838: /* Nonzero if we can try to make a post-increment or post-decrement.
1839: For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,...
1840: It is possible for both PRE_OK and POST_OK to be nonzero if the machine
1841: supports both pre-inc and post-inc, or both pre-dec and post-dec. */
1842: int post_ok = 0;
1843:
1844: /* Nonzero if the opportunity actually requires post-inc or post-dec. */
1845: int do_post = 0;
1846:
1847: /* From the sign of increment, see which possibilities are conceivable
1848: on this target machine. */
1849: #ifdef HAVE_PRE_INCREMENT
1.1 root 1850: if (amount > 0)
1.1.1.2 root 1851: pre_ok = 1;
1.1 root 1852: #endif
1.1.1.2 root 1853: #ifdef HAVE_POST_INCREMENT
1854: if (amount > 0)
1855: post_ok = 1;
1.1 root 1856: #endif
1857:
1.1.1.2 root 1858: #ifdef HAVE_PRE_DECREMENT
1.1 root 1859: if (amount < 0)
1.1.1.2 root 1860: pre_ok = 1;
1861: #endif
1862: #ifdef HAVE_POST_DECREMENT
1863: if (amount < 0)
1864: post_ok = 1;
1.1 root 1865: #endif
1866:
1.1.1.2 root 1867: if (! (pre_ok || post_ok))
1868: return 0;
1869:
1.1 root 1870: /* It is not safe to add a side effect to a jump insn
1871: because if the incremented register is spilled and must be reloaded
1872: there would be no way to store the incremented value back in memory. */
1873:
1874: if (GET_CODE (insn) == JUMP_INSN)
1875: return 0;
1876:
1.1.1.2 root 1877: use = 0;
1878: if (pre_ok)
1879: use = find_use_as_address (PATTERN (insn), reg, 0);
1880: if (post_ok && (use == 0 || use == (rtx) 1))
1881: {
1882: use = find_use_as_address (PATTERN (insn), reg, -amount);
1883: do_post = 1;
1884: }
1.1 root 1885:
1886: if (use == 0 || use == (rtx) 1)
1887: return 0;
1888:
1889: if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount))
1890: return 0;
1891:
1.1.1.2 root 1892: XEXP (use, 0) = gen_rtx (amount > 0
1893: ? (do_post ? POST_INC : PRE_INC)
1894: : (do_post ? POST_DEC : PRE_DEC),
1.1 root 1895: Pmode, reg);
1896:
1897: /* Record that this insn now has an implicit side effect on X. */
1898: REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn));
1899: return 1;
1900: }
1901:
1.1.1.2 root 1902: #endif /* AUTO_INC_DEC */
1903:
1.1 root 1904: /* Find the place in the rtx X where REG is used as a memory address.
1905: Return the MEM rtx that so uses it.
1.1.1.2 root 1906: If PLUSCONST is nonzero, search instead for a memory address equivalent to
1907: (plus REG (const_int PLUSCONST)).
1908:
1909: If such an address does not appear, return 0.
1910: If REG appears more than once, or is used other than in such an address,
1.1 root 1911: return (rtx)1. */
1912:
1913: static rtx
1.1.1.2 root 1914: find_use_as_address (x, reg, plusconst)
1.1 root 1915: register rtx x;
1916: rtx reg;
1.1.1.2 root 1917: int plusconst;
1.1 root 1918: {
1919: enum rtx_code code = GET_CODE (x);
1920: char *fmt = GET_RTX_FORMAT (code);
1921: register int i;
1922: register rtx value = 0;
1923: register rtx tem;
1924:
1.1.1.2 root 1925: if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)
1.1 root 1926: return x;
1927:
1.1.1.2 root 1928: if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS
1929: && XEXP (XEXP (x, 0), 0) == reg
1930: && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
1931: && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)
1932: return x;
1933:
1934: if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)
1935: {
1936: /* If REG occurs inside a MEM used in a bit-field reference,
1937: that is unacceptable. */
1938: if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)
1939: return (rtx) 1;
1940: }
1941:
1.1 root 1942: if (x == reg)
1943: return (rtx) 1;
1944:
1945: for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1946: {
1947: if (fmt[i] == 'e')
1948: {
1.1.1.2 root 1949: tem = find_use_as_address (XEXP (x, i), reg, plusconst);
1.1 root 1950: if (value == 0)
1951: value = tem;
1952: else if (tem != 0)
1953: return (rtx) 1;
1954: }
1955: if (fmt[i] == 'E')
1956: {
1957: register int j;
1958: for (j = XVECLEN (x, i) - 1; j >= 0; j--)
1959: {
1.1.1.2 root 1960: tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);
1.1 root 1961: if (value == 0)
1962: value = tem;
1963: else if (tem != 0)
1964: return (rtx) 1;
1965: }
1966: }
1967: }
1968:
1969: return value;
1970: }
1971:
1972: /* Write information about registers and basic blocks into FILE.
1973: This is part of making a debugging dump. */
1974:
1.1.1.2 root 1975: void
1.1 root 1976: dump_flow_info (file)
1977: FILE *file;
1978: {
1979: register int i;
1980: static char *reg_class_names[] = REG_CLASS_NAMES;
1981:
1982: fprintf (file, "%d registers.\n", max_regno);
1983:
1984: for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
1985: if (reg_n_refs[i])
1986: {
1987: enum reg_class class;
1988: fprintf (file, "\nRegister %d used %d times across %d insns",
1989: i, reg_n_refs[i], reg_live_length[i]);
1990: if (reg_basic_block[i] >= 0)
1991: fprintf (file, " in block %d", reg_basic_block[i]);
1992: if (reg_n_deaths[i] != 1)
1993: fprintf (file, "; dies in %d places", reg_n_deaths[i]);
1.1.1.12 root 1994: if (reg_n_calls_crossed[i] == 1)
1995: fprintf (file, "; crosses 1 call", reg_n_calls_crossed[i]);
1996: else if (reg_n_calls_crossed[i])
1997: fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]);
1.1 root 1998: if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
1999: fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
2000: class = reg_preferred_class (i);
2001: if (class != GENERAL_REGS)
1.1.1.2 root 2002: {
2003: if (reg_preferred_or_nothing (i))
2004: fprintf (file, "; %s or none", reg_class_names[(int) class]);
2005: else
2006: fprintf (file, "; pref %s", reg_class_names[(int) class]);
2007: }
1.1 root 2008: if (REGNO_POINTER_FLAG (i))
2009: fprintf (file, "; pointer");
2010: fprintf (file, ".\n");
2011: }
2012: fprintf (file, "\n%d basic blocks.\n", n_basic_blocks);
2013: for (i = 0; i < n_basic_blocks; i++)
2014: {
2015: register rtx head, jump;
2016: register int regno;
2017: fprintf (file, "\nBasic block %d: first insn %d, last %d.\n",
2018: i,
2019: INSN_UID (basic_block_head[i]),
2020: INSN_UID (basic_block_end[i]));
2021: /* The control flow graph's storage is freed
2022: now when flow_analysis returns.
2023: Don't try to print it if it is gone. */
2024: if (basic_block_drops_in)
2025: {
2026: fprintf (file, "Reached from blocks: ");
2027: head = basic_block_head[i];
2028: if (GET_CODE (head) == CODE_LABEL)
2029: for (jump = LABEL_REFS (head);
2030: jump != head;
2031: jump = LABEL_NEXTREF (jump))
2032: {
1.1.1.14! root 2033: register int from_block = BLOCK_NUM (CONTAINING_INSN (jump));
1.1 root 2034: fprintf (file, " %d", from_block);
2035: }
2036: if (basic_block_drops_in[i])
2037: fprintf (file, " previous");
2038: }
2039: fprintf (file, "\nRegisters live at start:");
2040: for (regno = 0; regno < max_regno; regno++)
2041: {
2042: register int offset = regno / REGSET_ELT_BITS;
2043: register int bit = 1 << (regno % REGSET_ELT_BITS);
2044: if (basic_block_live_at_start[i][offset] & bit)
2045: fprintf (file, " %d", regno);
2046: }
2047: fprintf (file, "\n");
2048: }
2049: fprintf (file, "\n");
2050: }
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