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34098846 WJ |
1 | /* Data flow analysis for GNU compiler. |
2 | Copyright (C) 1987, 1988 Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GNU CC. | |
5 | ||
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 | ||
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. | |
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. */ | |
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, | |
87 | reg_live_length, reg_n_calls_crosses and reg_basic_block. */ | |
88 | \f | |
89 | #include <stdio.h> | |
90 | #include "config.h" | |
91 | #include "rtl.h" | |
92 | #include "basic-block.h" | |
93 | #include "regs.h" | |
94 | #include "hard-reg-set.h" | |
95 | #include "flags.h" | |
96 | ||
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 | ||
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 | ||
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 | ||
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. | |
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. | |
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 | ||
161 | int *reg_n_calls_crossed; | |
162 | ||
163 | /* Indexed by N, gives the uid of the first insn that mentions reg N, | |
164 | provided that reg is local to one basic block. | |
165 | The value here is undefined otherwise. */ | |
166 | ||
167 | rtx *reg_first_use; | |
168 | ||
169 | /* Total number of instructions at which (REG n) is live. | |
170 | The larger this is, the less priority (REG n) gets for | |
171 | allocation in a real register. | |
172 | This information remains valid for the rest of the compilation | |
173 | of the current function; it is used to control register allocation. | |
174 | ||
175 | local-alloc.c may alter this number to change the priority. | |
176 | ||
177 | Negative values are special. | |
178 | -1 is used to mark a pseudo reg which has a constant or memory equivalent | |
179 | and is used infrequently enough that it should not get a hard register. | |
180 | -2 is used to mark a pseudo reg for a parameter, when a frame pointer | |
181 | is not required. global-alloc.c makes an allocno for this but does | |
182 | not try to assign a hard register to it. */ | |
183 | ||
184 | int *reg_live_length; | |
185 | ||
186 | /* Element N is the next insn that uses (hard or pseudo) register number N | |
187 | within the current basic block; or zero, if there is no such insn. | |
188 | This is valid only during the final backward scan in propagate_block. */ | |
189 | ||
190 | static rtx *reg_next_use; | |
191 | ||
192 | /* Size of a regset for the current function, | |
193 | in (1) bytes and (2) elements. */ | |
194 | ||
195 | int regset_bytes; | |
196 | int regset_size; | |
197 | ||
198 | /* Element N is first insn in basic block N. | |
199 | This info lasts until we finish compiling the function. */ | |
200 | ||
201 | rtx *basic_block_head; | |
202 | ||
203 | /* Element N is last insn in basic block N. | |
204 | This info lasts until we finish compiling the function. */ | |
205 | ||
206 | rtx *basic_block_end; | |
207 | ||
208 | /* Element N is a regset describing the registers live | |
209 | at the start of basic block N. | |
210 | This info lasts until we finish compiling the function. */ | |
211 | ||
212 | regset *basic_block_live_at_start; | |
213 | ||
214 | /* Regset of regs live when calls to `setjmp'-like functions happen. */ | |
215 | ||
216 | regset regs_live_at_setjmp; | |
217 | ||
218 | /* Element N is nonzero if control can drop into basic block N | |
219 | from the preceding basic block. Freed after life_analysis. */ | |
220 | ||
221 | static char *basic_block_drops_in; | |
222 | ||
223 | /* Element N is depth within loops of basic block number N. | |
224 | Freed after life_analysis. */ | |
225 | ||
226 | static short *basic_block_loop_depth; | |
227 | ||
228 | /* Element N nonzero if basic block N can actually be reached. | |
229 | Vector exists only during find_basic_blocks. */ | |
230 | ||
231 | static char *block_live_static; | |
232 | ||
233 | /* Depth within loops of basic block being scanned for lifetime analysis, | |
234 | plus one. This is the weight attached to references to registers. */ | |
235 | ||
236 | static int loop_depth; | |
237 | \f | |
238 | /* Define AUTO_INC_DEC if machine has any kind of incrementing | |
239 | or decrementing addressing. */ | |
240 | ||
241 | #ifdef HAVE_PRE_DECREMENT | |
242 | #define AUTO_INC_DEC | |
243 | #endif | |
244 | ||
245 | #ifdef HAVE_PRE_INCREMENT | |
246 | #define AUTO_INC_DEC | |
247 | #endif | |
248 | ||
249 | #ifdef HAVE_POST_DECREMENT | |
250 | #define AUTO_INC_DEC | |
251 | #endif | |
252 | ||
253 | #ifdef HAVE_POST_INCREMENT | |
254 | #define AUTO_INC_DEC | |
255 | #endif | |
256 | ||
257 | /* Forward declarations */ | |
258 | static void find_basic_blocks (); | |
259 | static void life_analysis (); | |
260 | static void mark_label_ref (); | |
261 | void allocate_for_life_analysis (); /* Used also in stupid_life_analysis */ | |
262 | static void init_regset_vector (); | |
263 | static void propagate_block (); | |
264 | static void mark_set_regs (); | |
265 | static void mark_used_regs (); | |
266 | static int insn_dead_p (); | |
267 | static int libcall_dead_p (); | |
268 | static int try_pre_increment (); | |
269 | static int try_pre_increment_1 (); | |
270 | static rtx find_use_as_address (); | |
271 | void dump_flow_info (); | |
272 | \f | |
273 | /* Find basic blocks of the current function and perform data flow analysis. | |
274 | F is the first insn of the function and NREGS the number of register numbers | |
275 | in use. */ | |
276 | ||
277 | void | |
278 | flow_analysis (f, nregs, file) | |
279 | rtx f; | |
280 | int nregs; | |
281 | FILE *file; | |
282 | { | |
283 | register rtx insn; | |
284 | register int i; | |
285 | register int max_uid = 0; | |
286 | ||
287 | /* Count the basic blocks. Also find maximum insn uid value used. */ | |
288 | ||
289 | { | |
290 | register RTX_CODE prev_code = JUMP_INSN; | |
291 | register RTX_CODE code; | |
292 | ||
293 | for (insn = f, i = 0; insn; insn = NEXT_INSN (insn)) | |
294 | { | |
295 | code = GET_CODE (insn); | |
296 | if (INSN_UID (insn) > max_uid) | |
297 | max_uid = INSN_UID (insn); | |
298 | if (code == CODE_LABEL | |
299 | || (prev_code != INSN && prev_code != CALL_INSN | |
300 | && prev_code != CODE_LABEL | |
301 | && (code == INSN || code == CALL_INSN || code == JUMP_INSN))) | |
302 | i++; | |
303 | if (code != NOTE) | |
304 | prev_code = code; | |
305 | } | |
306 | } | |
307 | ||
308 | /* Allocate some tables that last till end of compiling this function | |
309 | and some needed only in find_basic_blocks and life_analysis. */ | |
310 | ||
311 | n_basic_blocks = i; | |
312 | basic_block_head = (rtx *) oballoc (n_basic_blocks * sizeof (rtx)); | |
313 | basic_block_end = (rtx *) oballoc (n_basic_blocks * sizeof (rtx)); | |
314 | basic_block_drops_in = (char *) alloca (n_basic_blocks); | |
315 | basic_block_loop_depth = (short *) alloca (n_basic_blocks * sizeof (short)); | |
316 | uid_block_number = (short *) alloca ((max_uid + 1) * sizeof (short)); | |
317 | uid_volatile = (char *) alloca (max_uid + 1); | |
318 | bzero (uid_volatile, max_uid + 1); | |
319 | ||
320 | find_basic_blocks (f); | |
321 | life_analysis (f, nregs); | |
322 | if (file) | |
323 | dump_flow_info (file); | |
324 | ||
325 | basic_block_drops_in = 0; | |
326 | uid_block_number = 0; | |
327 | basic_block_loop_depth = 0; | |
328 | } | |
329 | \f | |
330 | /* Find all basic blocks of the function whose first insn is F. | |
331 | Store the correct data in the tables that describe the basic blocks, | |
332 | set up the chains of references for each CODE_LABEL, and | |
333 | delete any entire basic blocks that cannot be reached. */ | |
334 | ||
335 | static void | |
336 | find_basic_blocks (f) | |
337 | rtx f; | |
338 | { | |
339 | register rtx insn; | |
340 | register int i; | |
341 | ||
342 | /* Initialize the ref chain of each label to 0. */ | |
343 | /* Record where all the blocks start and end and their depth in loops. */ | |
344 | /* For each insn, record the block it is in. */ | |
345 | ||
346 | { | |
347 | register RTX_CODE prev_code = JUMP_INSN; | |
348 | register RTX_CODE code; | |
349 | int depth = 1; | |
350 | ||
351 | for (insn = f, i = -1; insn; insn = NEXT_INSN (insn)) | |
352 | { | |
353 | code = GET_CODE (insn); | |
354 | if (code == NOTE) | |
355 | { | |
356 | if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_BEG) | |
357 | depth++; | |
358 | else if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_LOOP_END) | |
359 | depth--; | |
360 | } | |
361 | else if (code == CODE_LABEL | |
362 | || (prev_code != INSN && prev_code != CALL_INSN | |
363 | && prev_code != CODE_LABEL | |
364 | && (code == INSN || code == CALL_INSN || code == JUMP_INSN))) | |
365 | { | |
366 | basic_block_head[++i] = insn; | |
367 | basic_block_end[i] = insn; | |
368 | basic_block_loop_depth[i] = depth; | |
369 | if (code == CODE_LABEL) | |
370 | LABEL_REFS (insn) = insn; | |
371 | } | |
372 | else if (code == INSN || code == CALL_INSN || code == JUMP_INSN) | |
373 | basic_block_end[i] = insn; | |
374 | BLOCK_NUM (insn) = i; | |
375 | if (code != NOTE) | |
376 | prev_code = code; | |
377 | } | |
378 | if (i + 1 != n_basic_blocks) | |
379 | abort (); | |
380 | } | |
381 | ||
382 | /* Record which basic blocks control can drop in to. */ | |
383 | ||
384 | { | |
385 | register int i; | |
386 | for (i = 0; i < n_basic_blocks; i++) | |
387 | { | |
388 | register rtx insn = PREV_INSN (basic_block_head[i]); | |
389 | /* TEMP1 is used to avoid a bug in Sequent's compiler. */ | |
390 | register int temp1; | |
391 | while (insn && GET_CODE (insn) == NOTE) | |
392 | insn = PREV_INSN (insn); | |
393 | temp1 = insn && GET_CODE (insn) != BARRIER; | |
394 | basic_block_drops_in[i] = temp1; | |
395 | } | |
396 | } | |
397 | ||
398 | /* Now find which basic blocks can actually be reached | |
399 | and put all jump insns' LABEL_REFS onto the ref-chains | |
400 | of their target labels. */ | |
401 | ||
402 | if (n_basic_blocks > 0) | |
403 | { | |
404 | register char *block_live = (char *) alloca (n_basic_blocks); | |
405 | register char *block_marked = (char *) alloca (n_basic_blocks); | |
406 | int something_marked = 1; | |
407 | ||
408 | /* Initialize with just block 0 reachable and no blocks marked. */ | |
409 | ||
410 | bzero (block_live, n_basic_blocks); | |
411 | bzero (block_marked, n_basic_blocks); | |
412 | block_live[0] = 1; | |
413 | block_live_static = block_live; | |
414 | ||
415 | /* Pass over all blocks, marking each block that is reachable | |
416 | and has not yet been marked. | |
417 | Keep doing this until, in one pass, no blocks have been marked. | |
418 | Then blocks_live and blocks_marked are identical and correct. | |
419 | In addition, all jumps actually reachable have been marked. */ | |
420 | ||
421 | while (something_marked) | |
422 | { | |
423 | something_marked = 0; | |
424 | for (i = 0; i < n_basic_blocks; i++) | |
425 | if (block_live[i] && !block_marked[i]) | |
426 | { | |
427 | block_marked[i] = 1; | |
428 | something_marked = 1; | |
429 | if (i + 1 < n_basic_blocks && basic_block_drops_in[i + 1]) | |
430 | block_live[i + 1] = 1; | |
431 | insn = basic_block_end[i]; | |
432 | if (GET_CODE (insn) == JUMP_INSN) | |
433 | mark_label_ref (PATTERN (insn), insn, 0); | |
434 | } | |
435 | } | |
436 | ||
437 | /* Now delete the code for any basic blocks that can't be reached. | |
438 | They can occur because jump_optimize does not recognize | |
439 | unreachable loops as unreachable. */ | |
440 | ||
441 | for (i = 0; i < n_basic_blocks; i++) | |
442 | if (!block_live[i]) | |
443 | { | |
444 | insn = basic_block_head[i]; | |
445 | while (1) | |
446 | { | |
447 | if (GET_CODE (insn) == BARRIER) | |
448 | abort (); | |
449 | if (GET_CODE (insn) != NOTE) | |
450 | { | |
451 | PUT_CODE (insn, NOTE); | |
452 | NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED; | |
453 | NOTE_SOURCE_FILE (insn) = 0; | |
454 | } | |
455 | if (insn == basic_block_end[i]) | |
456 | { | |
457 | /* BARRIERs are between basic blocks, not part of one. | |
458 | Delete a BARRIER if the preceding jump is deleted. | |
459 | We cannot alter a BARRIER into a NOTE | |
460 | because it is too short; but we can really delete | |
461 | it because it is not part of a basic block. */ | |
462 | if (NEXT_INSN (insn) != 0 | |
463 | && GET_CODE (NEXT_INSN (insn)) == BARRIER) | |
464 | delete_insn (NEXT_INSN (insn)); | |
465 | break; | |
466 | } | |
467 | insn = NEXT_INSN (insn); | |
468 | } | |
469 | /* Each time we delete some basic blocks, | |
470 | see if there is a jump around them that is | |
471 | being turned into a no-op. If so, delete it. */ | |
472 | ||
473 | if (block_live[i - 1]) | |
474 | { | |
475 | register int j; | |
476 | for (j = i; j < n_basic_blocks; j++) | |
477 | if (block_live[j]) | |
478 | { | |
479 | rtx label; | |
480 | insn = basic_block_end[i - 1]; | |
481 | if (GET_CODE (insn) == JUMP_INSN | |
482 | /* An unconditional jump is the only possibility | |
483 | we must check for, since a conditional one | |
484 | would make these blocks live. */ | |
485 | && simplejump_p (insn) | |
486 | && (label = XEXP (SET_SRC (PATTERN (insn)), 0), 1) | |
487 | && INSN_UID (label) != 0 | |
488 | && BLOCK_NUM (label) == j) | |
489 | { | |
490 | PUT_CODE (insn, NOTE); | |
491 | NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED; | |
492 | NOTE_SOURCE_FILE (insn) = 0; | |
493 | if (GET_CODE (NEXT_INSN (insn)) != BARRIER) | |
494 | abort (); | |
495 | delete_insn (NEXT_INSN (insn)); | |
496 | } | |
497 | break; | |
498 | } | |
499 | } | |
500 | } | |
501 | } | |
502 | } | |
503 | \f | |
504 | /* Check expression X for label references; | |
505 | if one is found, add INSN to the label's chain of references. | |
506 | ||
507 | CHECKDUP means check for and avoid creating duplicate references | |
508 | from the same insn. Such duplicates do no serious harm but | |
509 | can slow life analysis. CHECKDUP is set only when duplicates | |
510 | are likely. */ | |
511 | ||
512 | static void | |
513 | mark_label_ref (x, insn, checkdup) | |
514 | rtx x, insn; | |
515 | int checkdup; | |
516 | { | |
517 | register RTX_CODE code = GET_CODE (x); | |
518 | register int i; | |
519 | register char *fmt; | |
520 | ||
521 | if (code == LABEL_REF) | |
522 | { | |
523 | register rtx label = XEXP (x, 0); | |
524 | register rtx y; | |
525 | if (GET_CODE (label) != CODE_LABEL) | |
526 | abort (); | |
527 | /* If the label was never emitted, this insn is junk, | |
528 | but avoid a crash trying to refer to BLOCK_NUM (label). | |
529 | This can happen as a result of a syntax error | |
530 | and a diagnostic has already been printed. */ | |
531 | if (INSN_UID (label) == 0) | |
532 | return; | |
533 | CONTAINING_INSN (x) = insn; | |
534 | /* if CHECKDUP is set, check for duplicate ref from same insn | |
535 | and don't insert. */ | |
536 | if (checkdup) | |
537 | for (y = LABEL_REFS (label); y != label; y = LABEL_NEXTREF (y)) | |
538 | if (CONTAINING_INSN (y) == insn) | |
539 | return; | |
540 | LABEL_NEXTREF (x) = LABEL_REFS (label); | |
541 | LABEL_REFS (label) = x; | |
542 | block_live_static[BLOCK_NUM (label)] = 1; | |
543 | return; | |
544 | } | |
545 | ||
546 | fmt = GET_RTX_FORMAT (code); | |
547 | for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) | |
548 | { | |
549 | if (fmt[i] == 'e') | |
550 | mark_label_ref (XEXP (x, i), insn, 0); | |
551 | if (fmt[i] == 'E') | |
552 | { | |
553 | register int j; | |
554 | for (j = 0; j < XVECLEN (x, i); j++) | |
555 | mark_label_ref (XVECEXP (x, i, j), insn, 1); | |
556 | } | |
557 | } | |
558 | } | |
559 | \f | |
560 | /* Determine the which registers are live at the start of each | |
561 | basic block of the function whose first insn is F. | |
562 | NREGS is the number of registers used in F. | |
563 | We allocate the vector basic_block_live_at_start | |
564 | and the regsets that it points to, and fill them with the data. | |
565 | regset_size and regset_bytes are also set here. */ | |
566 | ||
567 | static void | |
568 | life_analysis (f, nregs) | |
569 | rtx f; | |
570 | int nregs; | |
571 | { | |
572 | register regset tem; | |
573 | int first_pass; | |
574 | int changed; | |
575 | /* For each basic block, a bitmask of regs | |
576 | live on exit from the block. */ | |
577 | regset *basic_block_live_at_end; | |
578 | /* For each basic block, a bitmask of regs | |
579 | live on entry to a successor-block of this block. | |
580 | If this does not match basic_block_live_at_end, | |
581 | that must be updated, and the block must be rescanned. */ | |
582 | regset *basic_block_new_live_at_end; | |
583 | /* For each basic block, a bitmask of regs | |
584 | whose liveness at the end of the basic block | |
585 | can make a difference in which regs are live on entry to the block. | |
586 | These are the regs that are set within the basic block, | |
587 | possibly excluding those that are used after they are set. */ | |
588 | regset *basic_block_significant; | |
589 | register int i; | |
590 | rtx insn; | |
591 | ||
592 | struct obstack flow_obstack; | |
593 | ||
594 | obstack_init (&flow_obstack); | |
595 | ||
596 | max_regno = nregs; | |
597 | ||
598 | bzero (regs_ever_live, sizeof regs_ever_live); | |
599 | ||
600 | /* Allocate and zero out many data structures | |
601 | that will record the data from lifetime analysis. */ | |
602 | ||
603 | allocate_for_life_analysis (); | |
604 | ||
605 | reg_next_use = (rtx *) alloca (nregs * sizeof (rtx)); | |
606 | bzero (reg_next_use, nregs * sizeof (rtx)); | |
607 | ||
608 | /* Set up several regset-vectors used internally within this function. | |
609 | Their meanings are documented above, with their declarations. */ | |
610 | ||
611 | basic_block_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset)); | |
612 | /* Don't use alloca since that leads to a crash rather than an error message | |
613 | if there isn't enough space. | |
614 | Don't use oballoc since we may need to allocate other things during | |
615 | this function on the temporary obstack. */ | |
616 | tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes); | |
617 | bzero (tem, n_basic_blocks * regset_bytes); | |
618 | init_regset_vector (basic_block_live_at_end, tem, n_basic_blocks, regset_bytes); | |
619 | ||
620 | basic_block_new_live_at_end = (regset *) alloca (n_basic_blocks * sizeof (regset)); | |
621 | tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes); | |
622 | bzero (tem, n_basic_blocks * regset_bytes); | |
623 | init_regset_vector (basic_block_new_live_at_end, tem, n_basic_blocks, regset_bytes); | |
624 | ||
625 | basic_block_significant = (regset *) alloca (n_basic_blocks * sizeof (regset)); | |
626 | tem = (regset) obstack_alloc (&flow_obstack, n_basic_blocks * regset_bytes); | |
627 | bzero (tem, n_basic_blocks * regset_bytes); | |
628 | init_regset_vector (basic_block_significant, tem, n_basic_blocks, regset_bytes); | |
629 | ||
630 | /* Record which insns refer to any volatile memory | |
631 | or for any reason can't be deleted just because they are dead stores. | |
632 | Also, delete any insns that copy a register to itself. */ | |
633 | ||
634 | for (insn = f; insn; insn = NEXT_INSN (insn)) | |
635 | { | |
636 | enum rtx_code code1 = GET_CODE (insn); | |
637 | if (code1 == CALL_INSN) | |
638 | INSN_VOLATILE (insn) = 1; | |
639 | else if (code1 == INSN || code1 == JUMP_INSN) | |
640 | { | |
641 | if (GET_CODE (PATTERN (insn)) == SET | |
642 | && GET_CODE (SET_DEST (PATTERN (insn))) == REG | |
643 | && GET_CODE (SET_SRC (PATTERN (insn))) == REG | |
644 | && REGNO (SET_DEST (PATTERN (insn))) == | |
645 | REGNO (SET_SRC (PATTERN (insn)))) | |
646 | { | |
647 | PUT_CODE (insn, NOTE); | |
648 | NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED; | |
649 | NOTE_SOURCE_FILE (insn) = 0; | |
650 | } | |
651 | else if (GET_CODE (PATTERN (insn)) != USE) | |
652 | INSN_VOLATILE (insn) = volatile_refs_p (PATTERN (insn)); | |
653 | /* A SET that makes space on the stack cannot be dead. | |
654 | (Such SETs occur only for allocating variable-size data, | |
655 | so they will always have a PLUS or MINUS according to the | |
656 | direction of stack growth.) | |
657 | Even if this function never uses this stack pointer value, | |
658 | signal handlers do! */ | |
659 | else if (code1 == INSN && GET_CODE (PATTERN (insn)) == SET | |
660 | && SET_DEST (PATTERN (insn)) == stack_pointer_rtx | |
661 | #ifdef STACK_GROWS_DOWNWARD | |
662 | && GET_CODE (SET_SRC (PATTERN (insn))) == MINUS | |
663 | #else | |
664 | && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS | |
665 | #endif | |
666 | && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx) | |
667 | INSN_VOLATILE (insn) = 1; | |
668 | } | |
669 | } | |
670 | ||
671 | if (n_basic_blocks > 0) | |
672 | #ifdef EXIT_IGNORE_STACK | |
673 | if (! (EXIT_IGNORE_STACK) || ! frame_pointer_needed) | |
674 | #endif | |
675 | { | |
676 | /* If exiting needs the right stack value, | |
677 | consider the stack pointer live at the end of the function. */ | |
678 | basic_block_live_at_end[n_basic_blocks - 1] | |
679 | [STACK_POINTER_REGNUM / REGSET_ELT_BITS] | |
680 | |= 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS); | |
681 | basic_block_new_live_at_end[n_basic_blocks - 1] | |
682 | [STACK_POINTER_REGNUM / REGSET_ELT_BITS] | |
683 | |= 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS); | |
684 | } | |
685 | ||
686 | /* Propagate life info through the basic blocks | |
687 | around the graph of basic blocks. | |
688 | ||
689 | This is a relaxation process: each time a new register | |
690 | is live at the end of the basic block, we must scan the block | |
691 | to determine which registers are, as a consequence, live at the beginning | |
692 | of that block. These registers must then be marked live at the ends | |
693 | of all the blocks that can transfer control to that block. | |
694 | The process continues until it reaches a fixed point. */ | |
695 | ||
696 | first_pass = 1; | |
697 | changed = 1; | |
698 | while (changed) | |
699 | { | |
700 | changed = 0; | |
701 | for (i = n_basic_blocks - 1; i >= 0; i--) | |
702 | { | |
703 | int consider = first_pass; | |
704 | int must_rescan = first_pass; | |
705 | register int j; | |
706 | ||
707 | /* Set CONSIDER if this block needs thinking about at all | |
708 | (that is, if the regs live now at the end of it | |
709 | are not the same as were live at the end of it when | |
710 | we last thought about it). | |
711 | Set must_rescan if it needs to be thought about | |
712 | instruction by instruction (that is, if any additional | |
713 | reg that is live at the end now but was not live there before | |
714 | is one of the significant regs of this basic block). */ | |
715 | ||
716 | for (j = 0; j < regset_size; j++) | |
717 | { | |
718 | register int x = basic_block_new_live_at_end[i][j] | |
719 | & ~basic_block_live_at_end[i][j]; | |
720 | if (x) | |
721 | consider = 1; | |
722 | if (x & basic_block_significant[i][j]) | |
723 | { | |
724 | must_rescan = 1; | |
725 | consider = 1; | |
726 | break; | |
727 | } | |
728 | } | |
729 | ||
730 | if (! consider) | |
731 | continue; | |
732 | ||
733 | /* The live_at_start of this block may be changing, | |
734 | so another pass will be required after this one. */ | |
735 | changed = 1; | |
736 | ||
737 | if (! must_rescan) | |
738 | { | |
739 | /* No complete rescan needed; | |
740 | just record those variables newly known live at end | |
741 | as live at start as well. */ | |
742 | for (j = 0; j < regset_size; j++) | |
743 | { | |
744 | register int x = basic_block_new_live_at_end[i][j] | |
745 | & ~basic_block_live_at_end[i][j]; | |
746 | basic_block_live_at_start[i][j] |= x; | |
747 | basic_block_live_at_end[i][j] |= x; | |
748 | } | |
749 | } | |
750 | else | |
751 | { | |
752 | /* Update the basic_block_live_at_start | |
753 | by propagation backwards through the block. */ | |
754 | bcopy (basic_block_new_live_at_end[i], | |
755 | basic_block_live_at_end[i], regset_bytes); | |
756 | bcopy (basic_block_live_at_end[i], | |
757 | basic_block_live_at_start[i], regset_bytes); | |
758 | propagate_block (basic_block_live_at_start[i], | |
759 | basic_block_head[i], basic_block_end[i], 0, | |
760 | first_pass ? basic_block_significant[i] : 0, | |
761 | i); | |
762 | } | |
763 | ||
764 | { | |
765 | register rtx jump, head; | |
766 | /* Update the basic_block_new_live_at_end's of the block | |
767 | that falls through into this one (if any). */ | |
768 | head = basic_block_head[i]; | |
769 | jump = PREV_INSN (head); | |
770 | if (basic_block_drops_in[i]) | |
771 | { | |
772 | register int from_block = BLOCK_NUM (jump); | |
773 | register int j; | |
774 | for (j = 0; j < regset_size; j++) | |
775 | basic_block_new_live_at_end[from_block][j] | |
776 | |= basic_block_live_at_start[i][j]; | |
777 | } | |
778 | /* Update the basic_block_new_live_at_end's of | |
779 | all the blocks that jump to this one. */ | |
780 | if (GET_CODE (head) == CODE_LABEL) | |
781 | for (jump = LABEL_REFS (head); | |
782 | jump != head; | |
783 | jump = LABEL_NEXTREF (jump)) | |
784 | { | |
785 | register int from_block = BLOCK_NUM (CONTAINING_INSN (jump)); | |
786 | register int j; | |
787 | for (j = 0; j < regset_size; j++) | |
788 | basic_block_new_live_at_end[from_block][j] | |
789 | |= basic_block_live_at_start[i][j]; | |
790 | } | |
791 | } | |
792 | #ifdef USE_C_ALLOCA | |
793 | alloca (0); | |
794 | #endif | |
795 | } | |
796 | first_pass = 0; | |
797 | } | |
798 | ||
799 | #if 0 /* This seems unnecessary; life at start of function shouldn't | |
800 | mean that the reg is live in more than one basic block. */ | |
801 | ||
802 | /* Process the regs live at the beginning of the function. | |
803 | Mark them as not local to any one basic block. */ | |
804 | ||
805 | if (n_basic_blocks > 0) | |
806 | for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++) | |
807 | if (basic_block_live_at_start[0][i / REGSET_ELT_BITS] | |
808 | & (1 << (i % REGSET_ELT_BITS))) | |
809 | reg_basic_block[i] = REG_BLOCK_GLOBAL; | |
810 | #endif | |
811 | ||
812 | /* Now the life information is accurate. | |
813 | Make one more pass over each basic block | |
814 | to delete dead stores, create autoincrement addressing | |
815 | and record how many times each register is used, is set, or dies. | |
816 | ||
817 | To save time, we operate directly in basic_block_live_at_end[i], | |
818 | thus destroying it (in fact, converting it into a copy of | |
819 | basic_block_live_at_start[i]). This is ok now because | |
820 | basic_block_live_at_end[i] is no longer used past this point. */ | |
821 | ||
822 | for (i = 0; i < n_basic_blocks; i++) | |
823 | { | |
824 | propagate_block (basic_block_live_at_end[i], | |
825 | basic_block_head[i], basic_block_end[i], 1, 0, i); | |
826 | #ifdef USE_C_ALLOCA | |
827 | alloca (0); | |
828 | #endif | |
829 | } | |
830 | ||
831 | #if 0 | |
832 | /* Something live during a setjmp should not be put in a register | |
833 | on certain machines which restore regs from stack frames | |
834 | rather than from the jmpbuf. | |
835 | But we don't need to do this for the user's variables, since | |
836 | ANSI says only volatile variables need this. */ | |
837 | #ifdef LONGJMP_RESTORE_FROM_STACK | |
838 | for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++) | |
839 | if (regs_live_at_setjmp[i / REGSET_ELT_BITS] & (1 << (i % REGSET_ELT_BITS)) | |
840 | && regno_reg_rtx[i] != 0 && ! REG_USERVAR_P (regno_reg_rtx[i])) | |
841 | { | |
842 | reg_live_length[i] = -1; | |
843 | reg_basic_block[i] = -1; | |
844 | } | |
845 | #endif | |
846 | #endif | |
847 | ||
848 | /* We have a problem with any pseudoreg that | |
849 | lives across the setjmp. ANSI says that if a | |
850 | user variable does not change in value | |
851 | between the setjmp and the longjmp, then the longjmp preserves it. | |
852 | This includes longjmp from a place where the pseudo appears dead. | |
853 | (In principle, the value still exists if it is in scope.) | |
854 | If the pseudo goes in a hard reg, some other value may occupy | |
855 | that hard reg where this pseudo is dead, thus clobbering the pseudo. | |
856 | Conclusion: such a pseudo must not go in a hard reg. */ | |
857 | for (i = FIRST_PSEUDO_REGISTER; i < nregs; i++) | |
858 | if (regs_live_at_setjmp[i / REGSET_ELT_BITS] & (1 << (i % REGSET_ELT_BITS)) | |
859 | && regno_reg_rtx[i] != 0) | |
860 | { | |
861 | reg_live_length[i] = -1; | |
862 | reg_basic_block[i] = -1; | |
863 | } | |
864 | ||
865 | obstack_free (&flow_obstack, 0); | |
866 | } | |
867 | \f | |
868 | /* Subroutines of life analysis. */ | |
869 | ||
870 | /* Allocate the permanent data structures that represent the results | |
871 | of life analysis. Not static since used also for stupid life analysis. */ | |
872 | ||
873 | void | |
874 | allocate_for_life_analysis () | |
875 | { | |
876 | register int i; | |
877 | register regset tem; | |
878 | ||
879 | regset_size = ((max_regno + REGSET_ELT_BITS - 1) / REGSET_ELT_BITS); | |
880 | regset_bytes = regset_size * sizeof (*(regset)0); | |
881 | ||
882 | reg_n_refs = (short *) oballoc (max_regno * sizeof (short)); | |
883 | bzero (reg_n_refs, max_regno * sizeof (short)); | |
884 | ||
885 | reg_n_sets = (short *) oballoc (max_regno * sizeof (short)); | |
886 | bzero (reg_n_sets, max_regno * sizeof (short)); | |
887 | ||
888 | reg_n_deaths = (short *) oballoc (max_regno * sizeof (short)); | |
889 | bzero (reg_n_deaths, max_regno * sizeof (short)); | |
890 | ||
891 | reg_first_use = (rtx *) oballoc (max_regno * sizeof (rtx)); | |
892 | bzero (reg_first_use, max_regno * sizeof (rtx)); | |
893 | ||
894 | reg_live_length = (int *) oballoc (max_regno * sizeof (int)); | |
895 | bzero (reg_live_length, max_regno * sizeof (int)); | |
896 | ||
897 | reg_n_calls_crossed = (int *) oballoc (max_regno * sizeof (int)); | |
898 | bzero (reg_n_calls_crossed, max_regno * sizeof (int)); | |
899 | ||
900 | reg_basic_block = (short *) oballoc (max_regno * sizeof (short)); | |
901 | for (i = 0; i < max_regno; i++) | |
902 | reg_basic_block[i] = REG_BLOCK_UNKNOWN; | |
903 | ||
904 | basic_block_live_at_start = (regset *) oballoc (n_basic_blocks * sizeof (regset)); | |
905 | tem = (regset) oballoc (n_basic_blocks * regset_bytes); | |
906 | bzero (tem, n_basic_blocks * regset_bytes); | |
907 | init_regset_vector (basic_block_live_at_start, tem, n_basic_blocks, regset_bytes); | |
908 | ||
909 | regs_live_at_setjmp = (regset) oballoc (regset_bytes); | |
910 | bzero (regs_live_at_setjmp, regset_bytes); | |
911 | } | |
912 | ||
913 | /* Make each element of VECTOR point at a regset, | |
914 | taking the space for all those regsets from SPACE. | |
915 | SPACE is of type regset, but it is really as long as NELTS regsets. | |
916 | BYTES_PER_ELT is the number of bytes in one regset. */ | |
917 | ||
918 | static void | |
919 | init_regset_vector (vector, space, nelts, bytes_per_elt) | |
920 | regset *vector; | |
921 | regset space; | |
922 | int nelts; | |
923 | int bytes_per_elt; | |
924 | { | |
925 | register int i; | |
926 | register regset p = space; | |
927 | ||
928 | for (i = 0; i < nelts; i++) | |
929 | { | |
930 | vector[i] = p; | |
931 | p += bytes_per_elt / sizeof (*p); | |
932 | } | |
933 | } | |
934 | \f | |
935 | /* Compute the registers live at the beginning of a basic block | |
936 | from those live at the end. | |
937 | ||
938 | When called, OLD contains those live at the end. | |
939 | On return, it contains those live at the beginning. | |
940 | FIRST and LAST are the first and last insns of the basic block. | |
941 | ||
942 | FINAL is nonzero if we are doing the final pass which is not | |
943 | for computing the life info (since that has already been done) | |
944 | but for acting on it. On this pass, we delete dead stores, | |
945 | set up the logical links and dead-variables lists of instructions, | |
946 | and merge instructions for autoincrement and autodecrement addresses. | |
947 | ||
948 | SIGNIFICANT is nonzero only the first time for each basic block. | |
949 | If it is nonzero, it points to a regset in which we store | |
950 | a 1 for each register that is set within the block. | |
951 | ||
952 | BNUM is the number of the basic block. */ | |
953 | ||
954 | static void | |
955 | propagate_block (old, first, last, final, significant, bnum) | |
956 | register regset old; | |
957 | rtx first; | |
958 | rtx last; | |
959 | int final; | |
960 | regset significant; | |
961 | int bnum; | |
962 | { | |
963 | register rtx insn; | |
964 | rtx prev; | |
965 | regset live; | |
966 | regset dead; | |
967 | ||
968 | /* The following variables are used only if FINAL is nonzero. */ | |
969 | /* This vector gets one element for each reg that has been live | |
970 | at any point in the basic block that has been scanned so far. | |
971 | SOMETIMES_MAX says how many elements are in use so far. | |
972 | In each element, OFFSET is the byte-number within a regset | |
973 | for the register described by the element, and BIT is a mask | |
974 | for that register's bit within the byte. */ | |
975 | register struct foo { short offset; short bit; } *regs_sometimes_live; | |
976 | int sometimes_max = 0; | |
977 | /* This regset has 1 for each reg that we have seen live so far. | |
978 | It and REGS_SOMETIMES_LIVE are updated together. */ | |
979 | regset maxlive; | |
980 | ||
981 | loop_depth = basic_block_loop_depth[bnum]; | |
982 | ||
983 | dead = (regset) alloca (regset_bytes); | |
984 | live = (regset) alloca (regset_bytes); | |
985 | ||
986 | if (final) | |
987 | { | |
988 | register int i, offset, bit; | |
989 | ||
990 | maxlive = (regset) alloca (regset_bytes); | |
991 | bcopy (old, maxlive, regset_bytes); | |
992 | regs_sometimes_live | |
993 | = (struct foo *) alloca (max_regno * sizeof (struct foo)); | |
994 | ||
995 | /* Process the regs live at the end of the block. | |
996 | Enter them in MAXLIVE and REGS_SOMETIMES_LIVE. | |
997 | Also mark them as not local to any one basic block. */ | |
998 | ||
999 | for (offset = 0, i = 0; offset < regset_size; offset++) | |
1000 | for (bit = 1; bit; bit <<= 1, i++) | |
1001 | { | |
1002 | if (i == max_regno) | |
1003 | break; | |
1004 | if (old[offset] & bit) | |
1005 | { | |
1006 | reg_basic_block[i] = REG_BLOCK_GLOBAL; | |
1007 | regs_sometimes_live[sometimes_max].offset = offset; | |
1008 | regs_sometimes_live[sometimes_max].bit = i % REGSET_ELT_BITS; | |
1009 | sometimes_max++; | |
1010 | } | |
1011 | } | |
1012 | } | |
1013 | ||
1014 | /* Include any notes at the end of the block in the scan. | |
1015 | This is in case the block ends with a call to setjmp. */ | |
1016 | ||
1017 | while (NEXT_INSN (last) != 0 && GET_CODE (NEXT_INSN (last)) == NOTE) | |
1018 | last = NEXT_INSN (last); | |
1019 | ||
1020 | /* Scan the block an insn at a time from end to beginning. */ | |
1021 | ||
1022 | for (insn = last; ; insn = prev) | |
1023 | { | |
1024 | prev = PREV_INSN (insn); | |
1025 | ||
1026 | /* If this is a call to `setjmp' et al, | |
1027 | warn if any non-volatile datum is live. */ | |
1028 | ||
1029 | if (final && GET_CODE (insn) == NOTE | |
1030 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP) | |
1031 | { | |
1032 | int i; | |
1033 | for (i = 0; i < regset_size; i++) | |
1034 | regs_live_at_setjmp[i] |= old[i]; | |
1035 | } | |
1036 | ||
1037 | /* Update the life-status of regs for this insn. | |
1038 | First DEAD gets which regs are set in this insn | |
1039 | then LIVE gets which regs are used in this insn. | |
1040 | Then the regs live before the insn | |
1041 | are those live after, with DEAD regs turned off, | |
1042 | and then LIVE regs turned on. */ | |
1043 | ||
1044 | if (GET_CODE (insn) == INSN | |
1045 | || GET_CODE (insn) == JUMP_INSN | |
1046 | || GET_CODE (insn) == CALL_INSN) | |
1047 | { | |
1048 | register int i; | |
1049 | rtx note = find_reg_note (insn, REG_RETVAL, 0); | |
1050 | ||
1051 | /* If an instruction consists of just dead store(s) on final pass, | |
1052 | "delete" it by turning it into a NOTE of type NOTE_INSN_DELETED. | |
1053 | We could really delete it with delete_insn, but that | |
1054 | can cause trouble for first or last insn in a basic block. */ | |
1055 | if (final && insn_dead_p (PATTERN (insn), old, 1) | |
1056 | /* Don't delete something that refers to volatile storage! */ | |
1057 | && ! INSN_VOLATILE (insn)) | |
1058 | { | |
1059 | rtx oldpat = PATTERN (insn); | |
1060 | PUT_CODE (insn, NOTE); | |
1061 | NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED; | |
1062 | NOTE_SOURCE_FILE (insn) = 0; | |
1063 | /* If this insn is copying the return value from a library call, | |
1064 | delete the entire library call. */ | |
1065 | if (note && libcall_dead_p (oldpat, old)) | |
1066 | { | |
1067 | rtx first = XEXP (note, 0); | |
1068 | rtx prev = insn; | |
1069 | while (INSN_DELETED_P (first)) | |
1070 | first = NEXT_INSN (first); | |
1071 | while (prev != first) | |
1072 | { | |
1073 | prev = PREV_INSN (prev); | |
1074 | PUT_CODE (prev, NOTE); | |
1075 | NOTE_LINE_NUMBER (prev) = NOTE_INSN_DELETED; | |
1076 | NOTE_SOURCE_FILE (prev) = 0; | |
1077 | } | |
1078 | } | |
1079 | goto flushed; | |
1080 | } | |
1081 | ||
1082 | for (i = 0; i < regset_size; i++) | |
1083 | { | |
1084 | dead[i] = 0; /* Faster than bzero here */ | |
1085 | live[i] = 0; /* since regset_size is usually small */ | |
1086 | } | |
1087 | ||
1088 | /* See if this is an increment or decrement that can be | |
1089 | merged into a following memory address. */ | |
1090 | #ifdef AUTO_INC_DEC | |
1091 | { | |
1092 | register rtx x = PATTERN (insn); | |
1093 | /* Does this instruction increment or decrement a register? */ | |
1094 | if (final && GET_CODE (x) == SET | |
1095 | && GET_CODE (SET_DEST (x)) == REG | |
1096 | && (GET_CODE (SET_SRC (x)) == PLUS | |
1097 | || GET_CODE (SET_SRC (x)) == MINUS) | |
1098 | && XEXP (SET_SRC (x), 0) == SET_DEST (x) | |
1099 | && GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT | |
1100 | /* Ok, look for a following memory ref we can combine with. | |
1101 | If one is found, change the memory ref to a PRE_INC | |
1102 | or PRE_DEC, cancel this insn, and return 1. | |
1103 | Return 0 if nothing has been done. */ | |
1104 | && try_pre_increment_1 (insn)) | |
1105 | goto flushed; | |
1106 | } | |
1107 | #endif /* AUTO_INC_DEC */ | |
1108 | ||
1109 | /* If this is not the final pass, and this insn is copying the | |
1110 | value of a library call and it's dead, don't scan the | |
1111 | insns that perform the library call, so that the call's | |
1112 | arguments are not marked live. */ | |
1113 | if (note && insn_dead_p (PATTERN (insn), old, 1) | |
1114 | && libcall_dead_p (PATTERN (insn), old)) | |
1115 | { | |
1116 | /* Mark the dest reg as `significant'. */ | |
1117 | mark_set_regs (old, dead, PATTERN (insn), 0, significant); | |
1118 | ||
1119 | insn = XEXP (note, 0); | |
1120 | prev = PREV_INSN (insn); | |
1121 | } | |
1122 | else if (GET_CODE (PATTERN (insn)) == SET | |
1123 | && SET_DEST (PATTERN (insn)) == stack_pointer_rtx | |
1124 | && GET_CODE (SET_SRC (PATTERN (insn))) == PLUS | |
1125 | && XEXP (SET_SRC (PATTERN (insn)), 0) == stack_pointer_rtx | |
1126 | && GET_CODE (XEXP (SET_SRC (PATTERN (insn)), 1)) == CONST_INT) | |
1127 | /* We have an insn to pop a constant amount off the stack. | |
1128 | (Such insns use PLUS regardless of the direction of the stack, | |
1129 | and any insn to adjust the stack by a constant is always a pop.) | |
1130 | These insns, if not dead stores, have no effect on life. */ | |
1131 | ; | |
1132 | else | |
1133 | { | |
1134 | /* LIVE gets the regs used in INSN; DEAD gets those set by it. */ | |
1135 | mark_set_regs (old, dead, PATTERN (insn), final ? insn : 0, | |
1136 | significant); | |
1137 | mark_used_regs (old, live, PATTERN (insn), final, insn); | |
1138 | ||
1139 | /* Update OLD for the registers used or set. */ | |
1140 | for (i = 0; i < regset_size; i++) | |
1141 | { | |
1142 | old[i] &= ~dead[i]; | |
1143 | old[i] |= live[i]; | |
1144 | } | |
1145 | ||
1146 | if (GET_CODE (insn) == CALL_INSN) | |
1147 | { | |
1148 | register int i; | |
1149 | ||
1150 | /* Each call clobbers all call-clobbered regs. | |
1151 | Note that the function-value reg is one of these, and | |
1152 | mark_set_regs has already had a chance to handle it. */ | |
1153 | for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) | |
1154 | if (call_used_regs[i]) | |
1155 | dead[i / REGSET_ELT_BITS] |= | |
1156 | (1 << (i % REGSET_ELT_BITS)); | |
1157 | ||
1158 | /* The stack ptr is used (honorarily) by a CALL insn. */ | |
1159 | live[STACK_POINTER_REGNUM / REGSET_ELT_BITS] | |
1160 | |= (1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS)); | |
1161 | } | |
1162 | ||
1163 | /* Update OLD for the registers used or set. */ | |
1164 | for (i = 0; i < regset_size; i++) | |
1165 | { | |
1166 | old[i] &= ~dead[i]; | |
1167 | old[i] |= live[i]; | |
1168 | } | |
1169 | ||
1170 | if (GET_CODE (insn) == CALL_INSN && final) | |
1171 | { | |
1172 | /* Any regs live at the time of a call instruction | |
1173 | must not go in a register clobbered by calls. | |
1174 | Find all regs now live and record this for them. */ | |
1175 | ||
1176 | register struct foo *p = regs_sometimes_live; | |
1177 | ||
1178 | for (i = 0; i < sometimes_max; i++, p++) | |
1179 | if (old[p->offset] & (1 << p->bit)) | |
1180 | reg_n_calls_crossed[p->offset * REGSET_ELT_BITS + p->bit]+= 1; | |
1181 | } | |
1182 | } | |
1183 | ||
1184 | /* On final pass, add any additional sometimes-live regs | |
1185 | into MAXLIVE and REGS_SOMETIMES_LIVE. | |
1186 | Also update counts of how many insns each reg is live at. */ | |
1187 | ||
1188 | if (final) | |
1189 | { | |
1190 | for (i = 0; i < regset_size; i++) | |
1191 | { | |
1192 | register int diff = live[i] & ~maxlive[i]; | |
1193 | ||
1194 | if (diff) | |
1195 | { | |
1196 | register int regno; | |
1197 | maxlive[i] |= diff; | |
1198 | for (regno = 0; diff && regno < REGSET_ELT_BITS; regno++) | |
1199 | if (diff & (1 << regno)) | |
1200 | { | |
1201 | regs_sometimes_live[sometimes_max].offset = i; | |
1202 | regs_sometimes_live[sometimes_max].bit = regno; | |
1203 | diff &= ~ (1 << regno); | |
1204 | sometimes_max++; | |
1205 | } | |
1206 | } | |
1207 | } | |
1208 | ||
1209 | { | |
1210 | register struct foo *p = regs_sometimes_live; | |
1211 | for (i = 0; i < sometimes_max; i++, p++) | |
1212 | { | |
1213 | if (old[p->offset] & (1 << p->bit)) | |
1214 | reg_live_length[p->offset * REGSET_ELT_BITS + p->bit]++; | |
1215 | } | |
1216 | } | |
1217 | } | |
1218 | } | |
1219 | flushed: ; | |
1220 | if (insn == first) | |
1221 | break; | |
1222 | } | |
1223 | } | |
1224 | \f | |
1225 | /* Return 1 if X (the body of an insn, or part of it) is just dead stores | |
1226 | (SET expressions whose destinations are registers dead after the insn). | |
1227 | NEEDED is the regset that says which regs are alive after the insn. */ | |
1228 | ||
1229 | static int | |
1230 | insn_dead_p (x, needed, strict_low_ok) | |
1231 | rtx x; | |
1232 | regset needed; | |
1233 | int strict_low_ok; | |
1234 | { | |
1235 | register RTX_CODE code = GET_CODE (x); | |
1236 | #if 0 | |
1237 | /* Make sure insns to set the stack pointer are never deleted. */ | |
1238 | needed[STACK_POINTER_REGNUM / REGSET_ELT_BITS] | |
1239 | |= 1 << (STACK_POINTER_REGNUM % REGSET_ELT_BITS); | |
1240 | #endif | |
1241 | ||
1242 | /* If setting something that's a reg or part of one, | |
1243 | see if that register's altered value will be live. */ | |
1244 | ||
1245 | if (code == SET) | |
1246 | { | |
1247 | register rtx r = SET_DEST (x); | |
1248 | /* A SET that is a subroutine call cannot be dead. */ | |
1249 | if (GET_CODE (SET_SRC (x)) == CALL) | |
1250 | return 0; | |
1251 | while (GET_CODE (r) == SUBREG | |
1252 | || (strict_low_ok && GET_CODE (r) == STRICT_LOW_PART) | |
1253 | || GET_CODE (r) == ZERO_EXTRACT | |
1254 | || GET_CODE (r) == SIGN_EXTRACT) | |
1255 | r = SUBREG_REG (r); | |
1256 | if (GET_CODE (r) == REG) | |
1257 | { | |
1258 | register int regno = REGNO (r); | |
1259 | register int offset = regno / REGSET_ELT_BITS; | |
1260 | register int bit = 1 << (regno % REGSET_ELT_BITS); | |
1261 | return (! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]) | |
1262 | && (needed[offset] & bit) == 0); | |
1263 | } | |
1264 | } | |
1265 | /* If performing several activities, | |
1266 | insn is dead if each activity is individually dead. | |
1267 | Also, CLOBBERs and USEs can be ignored; a CLOBBER or USE | |
1268 | that's inside a PARALLEL doesn't make the insn worth keeping. */ | |
1269 | else if (code == PARALLEL) | |
1270 | { | |
1271 | register int i = XVECLEN (x, 0); | |
1272 | for (i--; i >= 0; i--) | |
1273 | { | |
1274 | rtx elt = XVECEXP (x, 0, i); | |
1275 | if (!insn_dead_p (elt, needed, strict_low_ok) | |
1276 | && GET_CODE (elt) != CLOBBER | |
1277 | && GET_CODE (elt) != USE) | |
1278 | return 0; | |
1279 | } | |
1280 | return 1; | |
1281 | } | |
1282 | /* We do not check CLOBBER or USE here. | |
1283 | An insn consisting of just a CLOBBER or just a USE | |
1284 | should not be deleted. */ | |
1285 | return 0; | |
1286 | } | |
1287 | ||
1288 | /* If X is the last insn in a libcall, and assuming X is dead, | |
1289 | return 1 if the entire library call is dead. | |
1290 | This is true if the source of X is a dead register | |
1291 | (as well as the destination, which we tested already). | |
1292 | If this insn doesn't just copy a register, then we don't | |
1293 | have an ordinary libcall. In that case, cse could not have | |
1294 | managed to substitute the source for the dest later on, | |
1295 | so we can assume the libcall is dead. */ | |
1296 | ||
1297 | static int | |
1298 | libcall_dead_p (x, needed) | |
1299 | rtx x; | |
1300 | regset needed; | |
1301 | { | |
1302 | register RTX_CODE code = GET_CODE (x); | |
1303 | ||
1304 | if (code == SET) | |
1305 | { | |
1306 | register rtx r = SET_SRC (x); | |
1307 | if (GET_CODE (r) == REG) | |
1308 | { | |
1309 | register int regno = REGNO (r); | |
1310 | register int offset = regno / REGSET_ELT_BITS; | |
1311 | register int bit = 1 << (regno % REGSET_ELT_BITS); | |
1312 | return (needed[offset] & bit) == 0; | |
1313 | } | |
1314 | } | |
1315 | return 1; | |
1316 | } | |
1317 | ||
1318 | /* Return 1 if register REGNO was used before it was set. | |
1319 | In other words, if it is live at function entry. */ | |
1320 | ||
1321 | int | |
1322 | regno_uninitialized (regno) | |
1323 | int regno; | |
1324 | { | |
1325 | if (n_basic_blocks == 0) | |
1326 | return 0; | |
1327 | ||
1328 | return (basic_block_live_at_start[0][regno / REGSET_ELT_BITS] | |
1329 | & (1 << (regno % REGSET_ELT_BITS))); | |
1330 | } | |
1331 | ||
1332 | /* 1 if register REGNO was alive at a place where `setjmp' was called | |
1333 | and was set more than once. Such regs may be clobbered by `longjmp'. */ | |
1334 | ||
1335 | int | |
1336 | regno_clobbered_at_setjmp (regno) | |
1337 | int regno; | |
1338 | { | |
1339 | return (reg_n_sets[regno] > 1 | |
1340 | && (regs_live_at_setjmp[regno / REGSET_ELT_BITS] | |
1341 | & (1 << (regno % REGSET_ELT_BITS)))); | |
1342 | } | |
1343 | \f | |
1344 | /* Process the registers that are set within X. | |
1345 | Their bits are set to 1 in the regset DEAD, | |
1346 | because they are dead prior to this insn. | |
1347 | ||
1348 | If INSN is nonzero, it is the insn being processed | |
1349 | and the fact that it is nonzero implies this is the FINAL pass | |
1350 | in propagate_block. In this case, various info about register | |
1351 | usage is stored, LOG_LINKS fields of insns are set up. */ | |
1352 | ||
1353 | static void mark_set_1 (); | |
1354 | ||
1355 | static void | |
1356 | mark_set_regs (needed, dead, x, insn, significant) | |
1357 | regset needed; | |
1358 | regset dead; | |
1359 | rtx x; | |
1360 | rtx insn; | |
1361 | regset significant; | |
1362 | { | |
1363 | register RTX_CODE code = GET_CODE (x); | |
1364 | ||
1365 | if (code == SET || code == CLOBBER) | |
1366 | mark_set_1 (needed, dead, x, insn, significant); | |
1367 | else if (code == PARALLEL) | |
1368 | { | |
1369 | register int i; | |
1370 | for (i = XVECLEN (x, 0) - 1; i >= 0; i--) | |
1371 | { | |
1372 | code = GET_CODE (XVECEXP (x, 0, i)); | |
1373 | if (code == SET || code == CLOBBER) | |
1374 | mark_set_1 (needed, dead, XVECEXP (x, 0, i), insn, significant); | |
1375 | } | |
1376 | } | |
1377 | } | |
1378 | ||
1379 | /* Process a single SET rtx, X. */ | |
1380 | ||
1381 | static void | |
1382 | mark_set_1 (needed, dead, x, insn, significant) | |
1383 | regset needed; | |
1384 | regset dead; | |
1385 | rtx x; | |
1386 | rtx insn; | |
1387 | regset significant; | |
1388 | { | |
1389 | register int regno; | |
1390 | register rtx reg = SET_DEST (x); | |
1391 | int subreg_p = 0; | |
1392 | ||
1393 | if (reg == 0) | |
1394 | return; | |
1395 | /* Modifying just one hardware register of a multi-reg value | |
1396 | or just a byte field of a register | |
1397 | does not mean the value from before this insn is now dead. | |
1398 | But it does mean liveness of that register at the end of the block | |
1399 | is significant. */ | |
1400 | while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT | |
1401 | || GET_CODE (reg) == SIGN_EXTRACT | |
1402 | || GET_CODE (reg) == STRICT_LOW_PART) | |
1403 | { | |
1404 | if (GET_CODE (reg) == ZERO_EXTRACT | |
1405 | || GET_CODE (reg) == SIGN_EXTRACT | |
1406 | || (GET_CODE (reg) == SUBREG | |
1407 | && REG_SIZE (SUBREG_REG (reg)) > REG_SIZE (reg))) | |
1408 | subreg_p = 1; | |
1409 | ||
1410 | reg = XEXP (reg, 0); | |
1411 | } | |
1412 | ||
1413 | if (GET_CODE (reg) == REG | |
1414 | && (regno = REGNO (reg), regno != FRAME_POINTER_REGNUM) | |
1415 | && regno != ARG_POINTER_REGNUM | |
1416 | && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])) | |
1417 | /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */ | |
1418 | { | |
1419 | register int offset = regno / REGSET_ELT_BITS; | |
1420 | register int bit = 1 << (regno % REGSET_ELT_BITS); | |
1421 | int is_needed = 0; | |
1422 | ||
1423 | /* Mark it as a significant register for this basic block. */ | |
1424 | if (significant) | |
1425 | significant[offset] |= bit; | |
1426 | /* That's all we do, if we are setting only part of the register. */ | |
1427 | if (subreg_p) | |
1428 | return; | |
1429 | ||
1430 | /* If entire register being set, mark it as as dead before this insn. */ | |
1431 | dead[offset] |= bit; | |
1432 | /* A hard reg in a wide mode may really be multiple registers. | |
1433 | If so, mark all of them just like the first. */ | |
1434 | if (regno < FIRST_PSEUDO_REGISTER) | |
1435 | { | |
1436 | int n; | |
1437 | ||
1438 | /* Nothing below is needed for the stack pointer; get out asap. | |
1439 | Eg, log links aren't needed, since combine won't use them. */ | |
1440 | if (regno == STACK_POINTER_REGNUM) | |
1441 | return; | |
1442 | ||
1443 | n = HARD_REGNO_NREGS (regno, GET_MODE (reg)); | |
1444 | while (--n > 0) | |
1445 | { | |
1446 | dead[(regno + n) / REGSET_ELT_BITS] | |
1447 | |= 1 << ((regno + n) % REGSET_ELT_BITS); | |
1448 | if (significant) | |
1449 | significant[(regno + n) / REGSET_ELT_BITS] | |
1450 | |= 1 << ((regno + n) % REGSET_ELT_BITS); | |
1451 | is_needed |= (needed[(regno + n) / REGSET_ELT_BITS] | |
1452 | & 1 << ((regno + n) % REGSET_ELT_BITS)); | |
1453 | } | |
1454 | } | |
1455 | /* Additional data to record if this is the final pass. */ | |
1456 | if (insn) | |
1457 | { | |
1458 | register rtx y = reg_next_use[regno]; | |
1459 | register int blocknum = BLOCK_NUM (insn); | |
1460 | ||
1461 | /* If this is a hard reg, record this function uses the reg. | |
1462 | `combine.c' will get confused if LOG_LINKs are made | |
1463 | for hard regs. */ | |
1464 | ||
1465 | if (regno < FIRST_PSEUDO_REGISTER) | |
1466 | { | |
1467 | register int i; | |
1468 | i = HARD_REGNO_NREGS (regno, GET_MODE (reg)); | |
1469 | if (i == 0) | |
1470 | i = 1; | |
1471 | do | |
1472 | regs_ever_live[regno + --i] = 1; | |
1473 | while (i > 0); | |
1474 | ||
1475 | if (! ((needed[offset] & bit) || is_needed)) | |
1476 | { | |
1477 | /* Note that dead stores have already been deleted if poss. | |
1478 | If we get here, we have found a dead store that cannot | |
1479 | be eliminated (because the insn does something useful). | |
1480 | Indicate this by marking the reg set as dying here. */ | |
1481 | REG_NOTES (insn) | |
1482 | = gen_rtx (EXPR_LIST, REG_DEAD, | |
1483 | reg, REG_NOTES (insn)); | |
1484 | reg_n_deaths[REGNO (reg)]++; | |
1485 | } | |
1486 | return; | |
1487 | } | |
1488 | ||
1489 | /* Keep track of which basic blocks each reg appears in. */ | |
1490 | ||
1491 | if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN) | |
1492 | reg_basic_block[regno] = blocknum; | |
1493 | else if (reg_basic_block[regno] != blocknum) | |
1494 | reg_basic_block[regno] = REG_BLOCK_GLOBAL; | |
1495 | ||
1496 | /* Record first insn to use this reg. */ | |
1497 | reg_first_use[regno] = insn; | |
1498 | ||
1499 | /* Count (weighted) references, stores, etc. */ | |
1500 | reg_n_refs[regno] += loop_depth; | |
1501 | reg_n_sets[regno]++; | |
1502 | /* The next use is no longer "next", since a store intervenes. */ | |
1503 | reg_next_use[regno] = 0; | |
1504 | /* The insns where a reg is live are normally counted elsewhere, | |
1505 | but we want the count to include the insn where the reg is set, | |
1506 | and the normal counting mechanism would not count it. */ | |
1507 | reg_live_length[regno]++; | |
1508 | if ((needed[offset] & bit) || is_needed) | |
1509 | { | |
1510 | /* Make a logical link from the next following insn | |
1511 | that uses this register, back to this insn. | |
1512 | The following insns have already been processed. */ | |
1513 | if (y && (BLOCK_NUM (y) == blocknum)) | |
1514 | LOG_LINKS (y) | |
1515 | = gen_rtx (INSN_LIST, VOIDmode, insn, LOG_LINKS (y)); | |
1516 | } | |
1517 | else | |
1518 | { | |
1519 | /* Note that dead stores have already been deleted when possible | |
1520 | If we get here, we have found a dead store that cannot | |
1521 | be eliminated (because the same insn does something useful). | |
1522 | Indicate this by marking the reg being set as dying here. */ | |
1523 | REG_NOTES (insn) | |
1524 | = gen_rtx (EXPR_LIST, REG_DEAD, | |
1525 | reg, REG_NOTES (insn)); | |
1526 | reg_n_deaths[REGNO (reg)]++; | |
1527 | } | |
1528 | } | |
1529 | } | |
1530 | } | |
1531 | \f | |
1532 | /* Scan expression X and store a 1-bit in LIVE for each reg it uses. | |
1533 | This is done assuming the registers needed from X | |
1534 | are those that have 1-bits in NEEDED. | |
1535 | ||
1536 | On the final pass, FINAL is 1. This means try for autoincrement | |
1537 | and count the uses and deaths of each pseudo-reg. | |
1538 | ||
1539 | INSN is the containing instruction. */ | |
1540 | ||
1541 | static void | |
1542 | mark_used_regs (needed, live, x, final, insn) | |
1543 | regset needed; | |
1544 | regset live; | |
1545 | rtx x; | |
1546 | rtx insn; | |
1547 | int final; | |
1548 | { | |
1549 | register RTX_CODE code; | |
1550 | register int regno; | |
1551 | ||
1552 | retry: | |
1553 | code = GET_CODE (x); | |
1554 | switch (code) | |
1555 | { | |
1556 | case LABEL_REF: | |
1557 | case SYMBOL_REF: | |
1558 | case CONST_INT: | |
1559 | case CONST: | |
1560 | case CONST_DOUBLE: | |
1561 | case CC0: | |
1562 | case PC: | |
1563 | case CLOBBER: | |
1564 | case ADDR_VEC: | |
1565 | case ADDR_DIFF_VEC: | |
1566 | case ASM_INPUT: | |
1567 | return; | |
1568 | ||
1569 | #if defined (HAVE_POST_INCREMENT) || defined (HAVE_POST_DECREMENT) | |
1570 | case MEM: | |
1571 | /* Here we detect use of an index register which might | |
1572 | be good for postincrement or postdecrement. */ | |
1573 | if (final) | |
1574 | { | |
1575 | rtx addr = XEXP (x, 0); | |
1576 | register int size = GET_MODE_SIZE (GET_MODE (x)); | |
1577 | ||
1578 | if (GET_CODE (addr) == REG) | |
1579 | { | |
1580 | register rtx y; | |
1581 | regno = REGNO (addr); | |
1582 | /* Is the next use an increment that might make auto-increment? */ | |
1583 | y = reg_next_use[regno]; | |
1584 | if (y && GET_CODE (PATTERN (y)) == SET | |
1585 | && BLOCK_NUM (y) == BLOCK_NUM (insn) | |
1586 | /* Can't add side effects to jumps; if reg is spilled and | |
1587 | reloaded, there's no way to store back the altered value. */ | |
1588 | && GET_CODE (insn) != JUMP_INSN | |
1589 | && (y = SET_SRC (PATTERN (y)), | |
1590 | (0 | |
1591 | #ifdef HAVE_POST_INCREMENT | |
1592 | || GET_CODE (y) == PLUS | |
1593 | #endif | |
1594 | #ifdef HAVE_POST_DECREMENT | |
1595 | || GET_CODE (y) == MINUS | |
1596 | #endif | |
1597 | ) | |
1598 | && XEXP (y, 0) == addr | |
1599 | && GET_CODE (XEXP (y, 1)) == CONST_INT | |
1600 | && INTVAL (XEXP (y, 1)) == size) | |
1601 | && dead_or_set_p (reg_next_use[regno], addr)) | |
1602 | { | |
1603 | rtx use = find_use_as_address (PATTERN (insn), addr, 0); | |
1604 | ||
1605 | /* Make sure this register appears only once in this insn. */ | |
1606 | if (use != 0 && use != (rtx) 1) | |
1607 | { | |
1608 | /* We have found a suitable auto-increment: | |
1609 | do POST_INC around the register here, | |
1610 | and patch out the increment instruction that follows. */ | |
1611 | XEXP (x, 0) | |
1612 | = gen_rtx (GET_CODE (y) == PLUS ? POST_INC : POST_DEC, | |
1613 | Pmode, addr); | |
1614 | /* Record that this insn has an implicit side effect. */ | |
1615 | REG_NOTES (insn) | |
1616 | = gen_rtx (EXPR_LIST, REG_INC, addr, REG_NOTES (insn)); | |
1617 | ||
1618 | /* Modify the old increment-insn to simply copy | |
1619 | the already-incremented value of our register. */ | |
1620 | y = reg_next_use[regno]; | |
1621 | SET_SRC (PATTERN (y)) = addr; | |
1622 | ||
1623 | /* If that makes it a no-op (copying the register | |
1624 | into itself) then change it to a simpler no-op | |
1625 | so it won't appear to be a "use" and a "set" | |
1626 | of this register. */ | |
1627 | if (SET_DEST (PATTERN (y)) == addr) | |
1628 | PATTERN (y) = gen_rtx (USE, VOIDmode, const0_rtx); | |
1629 | ||
1630 | /* Count an extra reference to the reg for the increment. | |
1631 | When a reg is incremented. | |
1632 | spilling it is worse, so we want to make that | |
1633 | less likely. */ | |
1634 | reg_n_refs[regno] += loop_depth; | |
1635 | /* Count the increment as a setting of the register, | |
1636 | even though it isn't a SET in rtl. */ | |
1637 | reg_n_sets[regno]++; | |
1638 | } | |
1639 | } | |
1640 | } | |
1641 | } | |
1642 | break; | |
1643 | #endif /* HAVE_POST_INCREMENT or HAVE_POST_DECREMENT */ | |
1644 | ||
1645 | case REG: | |
1646 | /* See a register other than being set | |
1647 | => mark it as needed. */ | |
1648 | ||
1649 | regno = REGNO (x); | |
1650 | if (regno != FRAME_POINTER_REGNUM) | |
1651 | /* && regno != ARG_POINTER_REGNUM) -- and without this. */ | |
1652 | /* && regno != STACK_POINTER_REGNUM) -- let's try without this. */ | |
1653 | { | |
1654 | register int offset = regno / REGSET_ELT_BITS; | |
1655 | register int bit = 1 << (regno % REGSET_ELT_BITS); | |
1656 | int is_needed = 0; | |
1657 | ||
1658 | live[offset] |= bit; | |
1659 | /* A hard reg in a wide mode may really be multiple registers. | |
1660 | If so, mark all of them just like the first. */ | |
1661 | if (regno < FIRST_PSEUDO_REGISTER) | |
1662 | { | |
1663 | int n; | |
1664 | ||
1665 | /* For stack ptr or arg pointer, | |
1666 | nothing below can be necessary, so waste no more time. */ | |
1667 | if (regno == STACK_POINTER_REGNUM | |
1668 | || regno == ARG_POINTER_REGNUM) | |
1669 | return; | |
1670 | /* No death notes for global register variables; | |
1671 | their values are live after this function exits. */ | |
1672 | if (global_regs[regno]) | |
1673 | return; | |
1674 | ||
1675 | n = HARD_REGNO_NREGS (regno, GET_MODE (x)); | |
1676 | while (--n > 0) | |
1677 | { | |
1678 | live[(regno + n) / REGSET_ELT_BITS] | |
1679 | |= 1 << ((regno + n) % REGSET_ELT_BITS); | |
1680 | is_needed |= (needed[(regno + n) / REGSET_ELT_BITS] | |
1681 | & 1 << ((regno + n) % REGSET_ELT_BITS)); | |
1682 | } | |
1683 | } | |
1684 | if (final) | |
1685 | { | |
1686 | if (regno < FIRST_PSEUDO_REGISTER) | |
1687 | { | |
1688 | /* If a hard reg is being used, | |
1689 | record that this function does use it. */ | |
1690 | ||
1691 | register int i; | |
1692 | i = HARD_REGNO_NREGS (regno, GET_MODE (x)); | |
1693 | if (i == 0) | |
1694 | i = 1; | |
1695 | do | |
1696 | regs_ever_live[regno + --i] = 1; | |
1697 | while (i > 0); | |
1698 | } | |
1699 | else | |
1700 | { | |
1701 | /* Keep track of which basic block each reg appears in. */ | |
1702 | ||
1703 | register int blocknum = BLOCK_NUM (insn); | |
1704 | ||
1705 | if (reg_basic_block[regno] == REG_BLOCK_UNKNOWN) | |
1706 | reg_basic_block[regno] = blocknum; | |
1707 | else if (reg_basic_block[regno] != blocknum) | |
1708 | reg_basic_block[regno] = REG_BLOCK_GLOBAL; | |
1709 | ||
1710 | /* Record the earliest insn that uses this reg, | |
1711 | provided the reg is used only in one basic block. | |
1712 | Do this by recording each insn, and the one that | |
1713 | sticks is the last one scanned (the earliest insn). */ | |
1714 | ||
1715 | reg_first_use[regno] = insn; | |
1716 | ||
1717 | /* Record where each reg is used, so when the reg | |
1718 | is set we know the next insn that uses it. */ | |
1719 | ||
1720 | reg_next_use[regno] = insn; | |
1721 | ||
1722 | /* Count (weighted) number of uses of each reg. */ | |
1723 | ||
1724 | reg_n_refs[regno] += loop_depth; | |
1725 | } | |
1726 | ||
1727 | /* Record and count the insns in which a reg dies. | |
1728 | If it is used in this insn and was dead below the insn | |
1729 | then it dies in this insn. */ | |
1730 | ||
1731 | if (!(needed[offset] & bit) && !is_needed | |
1732 | && ! find_regno_note (insn, REG_DEAD, regno)) | |
1733 | { | |
1734 | REG_NOTES (insn) | |
1735 | = gen_rtx (EXPR_LIST, REG_DEAD, x, REG_NOTES (insn)); | |
1736 | reg_n_deaths[regno]++; | |
1737 | } | |
1738 | } | |
1739 | } | |
1740 | return; | |
1741 | ||
1742 | case SET: | |
1743 | { | |
1744 | register rtx testreg = SET_DEST (x); | |
1745 | int mark_dest = 0; | |
1746 | ||
1747 | /* Storing in STRICT_LOW_PART is like storing in a reg | |
1748 | in that this SET might be dead, so ignore it in TESTREG. | |
1749 | but in some other ways it is like using the reg. */ | |
1750 | /* Storing in a SUBREG or a bit field is like storing the entire | |
1751 | register in that if the register's value is not used | |
1752 | then this SET is not needed. */ | |
1753 | while (GET_CODE (testreg) == STRICT_LOW_PART | |
1754 | || GET_CODE (testreg) == ZERO_EXTRACT | |
1755 | || GET_CODE (testreg) == SIGN_EXTRACT | |
1756 | || GET_CODE (testreg) == SUBREG) | |
1757 | { | |
1758 | /* Modifying a single register in an alternate mode | |
1759 | does not use any of the old value. But these other | |
1760 | ways of storing in a register do use the old value. */ | |
1761 | if (GET_CODE (testreg) == SUBREG | |
1762 | && !(REG_SIZE (SUBREG_REG (testreg)) > REG_SIZE (testreg))) | |
1763 | ; | |
1764 | else | |
1765 | mark_dest = 1; | |
1766 | ||
1767 | testreg = XEXP (testreg, 0); | |
1768 | } | |
1769 | ||
1770 | /* If this is a store into a register, | |
1771 | recursively scan the only value being stored, | |
1772 | and only if the register's value is live after this insn. | |
1773 | If the value being computed here would never be used | |
1774 | then the values it uses don't need to be computed either. */ | |
1775 | ||
1776 | if (GET_CODE (testreg) == REG | |
1777 | && (regno = REGNO (testreg), regno != FRAME_POINTER_REGNUM) | |
1778 | && regno != ARG_POINTER_REGNUM | |
1779 | && ! (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])) | |
1780 | #if 0 /* This was added in 1.25, but screws up death notes for hard regs. | |
1781 | It probably isn't really needed anyway. */ | |
1782 | && (regno >= FIRST_PSEUDO_REGISTER | |
1783 | || INSN_VOLATILE (insn))) | |
1784 | #endif | |
1785 | { | |
1786 | register int offset = regno / REGSET_ELT_BITS; | |
1787 | register int bit = 1 << (regno % REGSET_ELT_BITS); | |
1788 | if ((needed[offset] & bit) | |
1789 | /* If insn refers to volatile, we mustn't delete it, | |
1790 | so its inputs are all needed. */ | |
1791 | || INSN_VOLATILE (insn)) | |
1792 | { | |
1793 | mark_used_regs (needed, live, SET_SRC (x), final, insn); | |
1794 | if (mark_dest) | |
1795 | mark_used_regs (needed, live, SET_DEST (x), final, insn); | |
1796 | } | |
1797 | return; | |
1798 | } | |
1799 | } | |
1800 | break; | |
1801 | } | |
1802 | ||
1803 | /* Recursively scan the operands of this expression. */ | |
1804 | ||
1805 | { | |
1806 | register char *fmt = GET_RTX_FORMAT (code); | |
1807 | register int i; | |
1808 | ||
1809 | for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) | |
1810 | { | |
1811 | if (fmt[i] == 'e') | |
1812 | { | |
1813 | /* Tail recursive case: save a function call level. */ | |
1814 | if (i == 0) | |
1815 | { | |
1816 | x = XEXP (x, 0); | |
1817 | goto retry; | |
1818 | } | |
1819 | mark_used_regs (needed, live, XEXP (x, i), final, insn); | |
1820 | } | |
1821 | else if (fmt[i] == 'E') | |
1822 | { | |
1823 | register int j; | |
1824 | for (j = 0; j < XVECLEN (x, i); j++) | |
1825 | mark_used_regs (needed, live, XVECEXP (x, i, j), final, insn); | |
1826 | } | |
1827 | } | |
1828 | } | |
1829 | } | |
1830 | \f | |
1831 | #ifdef AUTO_INC_DEC | |
1832 | ||
1833 | static int | |
1834 | try_pre_increment_1 (insn) | |
1835 | rtx insn; | |
1836 | { | |
1837 | /* Find the next use of this reg. If in same basic block, | |
1838 | make it do pre-increment or pre-decrement if appropriate. */ | |
1839 | rtx x = PATTERN (insn); | |
1840 | int amount = ((GET_CODE (SET_SRC (x)) == PLUS ? 1 : -1) | |
1841 | * INTVAL (XEXP (SET_SRC (x), 1))); | |
1842 | int regno = REGNO (SET_DEST (x)); | |
1843 | rtx y = reg_next_use[regno]; | |
1844 | if (y != 0 | |
1845 | && BLOCK_NUM (y) == BLOCK_NUM (insn) | |
1846 | && try_pre_increment (y, SET_DEST (PATTERN (insn)), | |
1847 | amount)) | |
1848 | { | |
1849 | /* We have found a suitable auto-increment | |
1850 | and already changed insn Y to do it. | |
1851 | So flush this increment-instruction. */ | |
1852 | PUT_CODE (insn, NOTE); | |
1853 | NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED; | |
1854 | NOTE_SOURCE_FILE (insn) = 0; | |
1855 | /* Count a reference to this reg for the increment | |
1856 | insn we are deleting. When a reg is incremented. | |
1857 | spilling it is worse, so we want to make that | |
1858 | less likely. */ | |
1859 | reg_n_refs[regno] += loop_depth; | |
1860 | reg_n_sets[regno]++; | |
1861 | return 1; | |
1862 | } | |
1863 | return 0; | |
1864 | } | |
1865 | ||
1866 | /* Try to change INSN so that it does pre-increment or pre-decrement | |
1867 | addressing on register REG in order to add AMOUNT to REG. | |
1868 | AMOUNT is negative for pre-decrement. | |
1869 | Returns 1 if the change could be made. | |
1870 | This checks all about the validity of the result of modifying INSN. */ | |
1871 | ||
1872 | static int | |
1873 | try_pre_increment (insn, reg, amount) | |
1874 | rtx insn, reg; | |
1875 | int amount; | |
1876 | { | |
1877 | register rtx use; | |
1878 | ||
1879 | /* Nonzero if we can try to make a pre-increment or pre-decrement. | |
1880 | For example, addl $4,r1; movl (r1),... can become movl +(r1),... */ | |
1881 | int pre_ok = 0; | |
1882 | /* Nonzero if we can try to make a post-increment or post-decrement. | |
1883 | For example, addl $4,r1; movl -4(r1),... can become movl (r1)+,... | |
1884 | It is possible for both PRE_OK and POST_OK to be nonzero if the machine | |
1885 | supports both pre-inc and post-inc, or both pre-dec and post-dec. */ | |
1886 | int post_ok = 0; | |
1887 | ||
1888 | /* Nonzero if the opportunity actually requires post-inc or post-dec. */ | |
1889 | int do_post = 0; | |
1890 | ||
1891 | /* From the sign of increment, see which possibilities are conceivable | |
1892 | on this target machine. */ | |
1893 | #ifdef HAVE_PRE_INCREMENT | |
1894 | if (amount > 0) | |
1895 | pre_ok = 1; | |
1896 | #endif | |
1897 | #ifdef HAVE_POST_INCREMENT | |
1898 | if (amount > 0) | |
1899 | post_ok = 1; | |
1900 | #endif | |
1901 | ||
1902 | #ifdef HAVE_PRE_DECREMENT | |
1903 | if (amount < 0) | |
1904 | pre_ok = 1; | |
1905 | #endif | |
1906 | #ifdef HAVE_POST_DECREMENT | |
1907 | if (amount < 0) | |
1908 | post_ok = 1; | |
1909 | #endif | |
1910 | ||
1911 | if (! (pre_ok || post_ok)) | |
1912 | return 0; | |
1913 | ||
1914 | /* It is not safe to add a side effect to a jump insn | |
1915 | because if the incremented register is spilled and must be reloaded | |
1916 | there would be no way to store the incremented value back in memory. */ | |
1917 | ||
1918 | if (GET_CODE (insn) == JUMP_INSN) | |
1919 | return 0; | |
1920 | ||
1921 | use = 0; | |
1922 | if (pre_ok) | |
1923 | use = find_use_as_address (PATTERN (insn), reg, 0); | |
1924 | if (post_ok && (use == 0 || use == (rtx) 1)) | |
1925 | { | |
1926 | use = find_use_as_address (PATTERN (insn), reg, -amount); | |
1927 | do_post = 1; | |
1928 | } | |
1929 | ||
1930 | if (use == 0 || use == (rtx) 1) | |
1931 | return 0; | |
1932 | ||
1933 | if (GET_MODE_SIZE (GET_MODE (use)) != (amount > 0 ? amount : - amount)) | |
1934 | return 0; | |
1935 | ||
1936 | XEXP (use, 0) = gen_rtx (amount > 0 | |
1937 | ? (do_post ? POST_INC : PRE_INC) | |
1938 | : (do_post ? POST_DEC : PRE_DEC), | |
1939 | Pmode, reg); | |
1940 | ||
1941 | /* Record that this insn now has an implicit side effect on X. */ | |
1942 | REG_NOTES (insn) = gen_rtx (EXPR_LIST, REG_INC, reg, REG_NOTES (insn)); | |
1943 | return 1; | |
1944 | } | |
1945 | ||
1946 | #endif /* AUTO_INC_DEC */ | |
1947 | \f | |
1948 | /* Find the place in the rtx X where REG is used as a memory address. | |
1949 | Return the MEM rtx that so uses it. | |
1950 | If PLUSCONST is nonzero, search instead for a memory address equivalent to | |
1951 | (plus REG (const_int PLUSCONST)). | |
1952 | ||
1953 | If such an address does not appear, return 0. | |
1954 | If REG appears more than once, or is used other than in such an address, | |
1955 | return (rtx)1. */ | |
1956 | ||
1957 | static rtx | |
1958 | find_use_as_address (x, reg, plusconst) | |
1959 | register rtx x; | |
1960 | rtx reg; | |
1961 | int plusconst; | |
1962 | { | |
1963 | enum rtx_code code = GET_CODE (x); | |
1964 | char *fmt = GET_RTX_FORMAT (code); | |
1965 | register int i; | |
1966 | register rtx value = 0; | |
1967 | register rtx tem; | |
1968 | ||
1969 | if (code == MEM && XEXP (x, 0) == reg && plusconst == 0) | |
1970 | return x; | |
1971 | ||
1972 | if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS | |
1973 | && XEXP (XEXP (x, 0), 0) == reg | |
1974 | && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT | |
1975 | && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst) | |
1976 | return x; | |
1977 | ||
1978 | if (code == SIGN_EXTRACT || code == ZERO_EXTRACT) | |
1979 | { | |
1980 | /* If REG occurs inside a MEM used in a bit-field reference, | |
1981 | that is unacceptable. */ | |
1982 | if (find_use_as_address (XEXP (x, 0), reg, 0) != 0) | |
1983 | return (rtx) 1; | |
1984 | } | |
1985 | ||
1986 | if (x == reg) | |
1987 | return (rtx) 1; | |
1988 | ||
1989 | for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) | |
1990 | { | |
1991 | if (fmt[i] == 'e') | |
1992 | { | |
1993 | tem = find_use_as_address (XEXP (x, i), reg, plusconst); | |
1994 | if (value == 0) | |
1995 | value = tem; | |
1996 | else if (tem != 0) | |
1997 | return (rtx) 1; | |
1998 | } | |
1999 | if (fmt[i] == 'E') | |
2000 | { | |
2001 | register int j; | |
2002 | for (j = XVECLEN (x, i) - 1; j >= 0; j--) | |
2003 | { | |
2004 | tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst); | |
2005 | if (value == 0) | |
2006 | value = tem; | |
2007 | else if (tem != 0) | |
2008 | return (rtx) 1; | |
2009 | } | |
2010 | } | |
2011 | } | |
2012 | ||
2013 | return value; | |
2014 | } | |
2015 | \f | |
2016 | /* Write information about registers and basic blocks into FILE. | |
2017 | This is part of making a debugging dump. */ | |
2018 | ||
2019 | void | |
2020 | dump_flow_info (file) | |
2021 | FILE *file; | |
2022 | { | |
2023 | register int i; | |
2024 | static char *reg_class_names[] = REG_CLASS_NAMES; | |
2025 | ||
2026 | fprintf (file, "%d registers.\n", max_regno); | |
2027 | ||
2028 | for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++) | |
2029 | if (reg_n_refs[i]) | |
2030 | { | |
2031 | enum reg_class class; | |
2032 | fprintf (file, "\nRegister %d used %d times across %d insns", | |
2033 | i, reg_n_refs[i], reg_live_length[i]); | |
2034 | if (reg_basic_block[i] >= 0) | |
2035 | fprintf (file, " in block %d", reg_basic_block[i]); | |
2036 | if (reg_n_deaths[i] != 1) | |
2037 | fprintf (file, "; dies in %d places", reg_n_deaths[i]); | |
2038 | if (reg_n_calls_crossed[i] == 1) | |
2039 | fprintf (file, "; crosses 1 call", reg_n_calls_crossed[i]); | |
2040 | else if (reg_n_calls_crossed[i]) | |
2041 | fprintf (file, "; crosses %d calls", reg_n_calls_crossed[i]); | |
2042 | if (PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD) | |
2043 | fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i)); | |
2044 | class = reg_preferred_class (i); | |
2045 | if (class != GENERAL_REGS) | |
2046 | { | |
2047 | if (reg_preferred_or_nothing (i)) | |
2048 | fprintf (file, "; %s or none", reg_class_names[(int) class]); | |
2049 | else | |
2050 | fprintf (file, "; pref %s", reg_class_names[(int) class]); | |
2051 | } | |
2052 | if (REGNO_POINTER_FLAG (i)) | |
2053 | fprintf (file, "; pointer"); | |
2054 | fprintf (file, ".\n"); | |
2055 | } | |
2056 | fprintf (file, "\n%d basic blocks.\n", n_basic_blocks); | |
2057 | for (i = 0; i < n_basic_blocks; i++) | |
2058 | { | |
2059 | register rtx head, jump; | |
2060 | register int regno; | |
2061 | fprintf (file, "\nBasic block %d: first insn %d, last %d.\n", | |
2062 | i, | |
2063 | INSN_UID (basic_block_head[i]), | |
2064 | INSN_UID (basic_block_end[i])); | |
2065 | /* The control flow graph's storage is freed | |
2066 | now when flow_analysis returns. | |
2067 | Don't try to print it if it is gone. */ | |
2068 | if (basic_block_drops_in) | |
2069 | { | |
2070 | fprintf (file, "Reached from blocks: "); | |
2071 | head = basic_block_head[i]; | |
2072 | if (GET_CODE (head) == CODE_LABEL) | |
2073 | for (jump = LABEL_REFS (head); | |
2074 | jump != head; | |
2075 | jump = LABEL_NEXTREF (jump)) | |
2076 | { | |
2077 | register int from_block = BLOCK_NUM (CONTAINING_INSN (jump)); | |
2078 | fprintf (file, " %d", from_block); | |
2079 | } | |
2080 | if (basic_block_drops_in[i]) | |
2081 | fprintf (file, " previous"); | |
2082 | } | |
2083 | fprintf (file, "\nRegisters live at start:"); | |
2084 | for (regno = 0; regno < max_regno; regno++) | |
2085 | { | |
2086 | register int offset = regno / REGSET_ELT_BITS; | |
2087 | register int bit = 1 << (regno % REGSET_ELT_BITS); | |
2088 | if (basic_block_live_at_start[i][offset] & bit) | |
2089 | fprintf (file, " %d", regno); | |
2090 | } | |
2091 | fprintf (file, "\n"); | |
2092 | } | |
2093 | fprintf (file, "\n"); | |
2094 | } |