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9ae8ffe7 JL |
1 | /* Alias analysis for GNU C |
2 | Copyright (C) 1997 Free Software Foundation, Inc. | |
3 | Contributed by John Carr (jfc@mit.edu). | |
4 | ||
5 | This file is part of GNU CC. | |
6 | ||
7 | GNU CC is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 2, or (at your option) | |
10 | any later version. | |
11 | ||
12 | GNU CC is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with GNU CC; see the file COPYING. If not, write to | |
19 | the Free Software Foundation, 59 Temple Place - Suite 330, | |
20 | Boston, MA 02111-1307, USA. */ | |
21 | ||
22 | #include "config.h" | |
23 | #include "rtl.h" | |
24 | #include "expr.h" | |
25 | #include "regs.h" | |
26 | #include "hard-reg-set.h" | |
27 | #include "flags.h" | |
28 | ||
29 | static rtx canon_rtx PROTO((rtx)); | |
30 | static int rtx_equal_for_memref_p PROTO((rtx, rtx)); | |
31 | static rtx find_symbolic_term PROTO((rtx)); | |
32 | static int memrefs_conflict_p PROTO((int, rtx, int, rtx, | |
33 | HOST_WIDE_INT)); | |
34 | ||
35 | /* Set up all info needed to perform alias analysis on memory references. */ | |
36 | ||
37 | #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X))) | |
38 | ||
39 | /* reg_base_value[N] gives an address to which register N is related. | |
40 | If all sets after the first add or subtract to the current value | |
41 | or otherwise modify it so it does not point to a different top level | |
42 | object, reg_base_value[N] is equal to the address part of the source | |
2a2c8203 JC |
43 | of the first set. |
44 | ||
45 | A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS | |
46 | expressions represent certain special values: function arguments and | |
47 | the stack, frame, and argument pointers. The contents of an address | |
48 | expression are not used (but they are descriptive for debugging); | |
49 | only the address and mode matter. Pointer equality, not rtx_equal_p, | |
50 | determines whether two ADDRESS expressions refer to the same base | |
51 | address. The mode determines whether it is a function argument or | |
52 | other special value. */ | |
53 | ||
9ae8ffe7 | 54 | rtx *reg_base_value; |
ec907dd8 | 55 | rtx *new_reg_base_value; |
9ae8ffe7 JL |
56 | unsigned int reg_base_value_size; /* size of reg_base_value array */ |
57 | #define REG_BASE_VALUE(X) \ | |
58 | (REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0) | |
59 | ||
60 | /* Vector indexed by N giving the initial (unchanging) value known | |
61 | for pseudo-register N. */ | |
62 | rtx *reg_known_value; | |
63 | ||
64 | /* Indicates number of valid entries in reg_known_value. */ | |
65 | static int reg_known_value_size; | |
66 | ||
67 | /* Vector recording for each reg_known_value whether it is due to a | |
68 | REG_EQUIV note. Future passes (viz., reload) may replace the | |
69 | pseudo with the equivalent expression and so we account for the | |
70 | dependences that would be introduced if that happens. */ | |
71 | /* ??? This is a problem only on the Convex. The REG_EQUIV notes created in | |
72 | assign_parms mention the arg pointer, and there are explicit insns in the | |
73 | RTL that modify the arg pointer. Thus we must ensure that such insns don't | |
74 | get scheduled across each other because that would invalidate the REG_EQUIV | |
75 | notes. One could argue that the REG_EQUIV notes are wrong, but solving | |
76 | the problem in the scheduler will likely give better code, so we do it | |
77 | here. */ | |
78 | char *reg_known_equiv_p; | |
79 | ||
2a2c8203 JC |
80 | /* True when scanning insns from the start of the rtl to the |
81 | NOTE_INSN_FUNCTION_BEG note. */ | |
9ae8ffe7 | 82 | |
9ae8ffe7 JL |
83 | static int copying_arguments; |
84 | ||
2a2c8203 JC |
85 | /* Inside SRC, the source of a SET, find a base address. */ |
86 | ||
9ae8ffe7 JL |
87 | static rtx |
88 | find_base_value (src) | |
89 | register rtx src; | |
90 | { | |
91 | switch (GET_CODE (src)) | |
92 | { | |
93 | case SYMBOL_REF: | |
94 | case LABEL_REF: | |
95 | return src; | |
96 | ||
97 | case REG: | |
ec907dd8 JL |
98 | /* If this REG is related to a known base value, return it. */ |
99 | if (reg_base_value[REGNO (src)]) | |
100 | return reg_base_value[REGNO (src)]; | |
101 | ||
2a2c8203 JC |
102 | /* At the start of a function argument registers have known base |
103 | values which may be lost later. Returning an ADDRESS | |
104 | expression here allows optimization based on argument values | |
105 | even when the argument registers are used for other purposes. */ | |
106 | if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments) | |
ec907dd8 | 107 | return new_reg_base_value[REGNO (src)]; |
9ae8ffe7 JL |
108 | return src; |
109 | ||
110 | case MEM: | |
111 | /* Check for an argument passed in memory. Only record in the | |
112 | copying-arguments block; it is too hard to track changes | |
113 | otherwise. */ | |
114 | if (copying_arguments | |
115 | && (XEXP (src, 0) == arg_pointer_rtx | |
116 | || (GET_CODE (XEXP (src, 0)) == PLUS | |
117 | && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) | |
118 | return gen_rtx (ADDRESS, VOIDmode, src); | |
119 | return 0; | |
120 | ||
121 | case CONST: | |
122 | src = XEXP (src, 0); | |
123 | if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS) | |
124 | break; | |
125 | /* fall through */ | |
2a2c8203 | 126 | |
9ae8ffe7 JL |
127 | case PLUS: |
128 | case MINUS: | |
2a2c8203 | 129 | { |
ec907dd8 JL |
130 | rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1); |
131 | ||
132 | /* If either operand is a REG, then see if we already have | |
133 | a known value for it. */ | |
134 | if (GET_CODE (src_0) == REG) | |
135 | { | |
136 | temp = find_base_value (src_0); | |
137 | if (temp) | |
138 | src_0 = temp; | |
139 | } | |
140 | ||
141 | if (GET_CODE (src_1) == REG) | |
142 | { | |
143 | temp = find_base_value (src_1); | |
144 | if (temp) | |
145 | src_1 = temp; | |
146 | } | |
2a2c8203 JC |
147 | |
148 | /* Guess which operand is the base address. | |
149 | ||
ec907dd8 JL |
150 | If either operand is a symbol, then it is the base. If |
151 | either operand is a CONST_INT, then the other is the base. */ | |
2a2c8203 JC |
152 | |
153 | if (GET_CODE (src_1) == CONST_INT | |
154 | || GET_CODE (src_0) == SYMBOL_REF | |
155 | || GET_CODE (src_0) == LABEL_REF | |
156 | || GET_CODE (src_0) == CONST) | |
157 | return find_base_value (src_0); | |
158 | ||
ec907dd8 JL |
159 | if (GET_CODE (src_0) == CONST_INT |
160 | || GET_CODE (src_1) == SYMBOL_REF | |
161 | || GET_CODE (src_1) == LABEL_REF | |
162 | || GET_CODE (src_1) == CONST) | |
163 | return find_base_value (src_1); | |
164 | ||
165 | /* This might not be necessary anymore. | |
166 | ||
167 | If either operand is a REG that is a known pointer, then it | |
168 | is the base. */ | |
2a2c8203 JC |
169 | if (GET_CODE (src_0) == REG && REGNO_POINTER_FLAG (REGNO (src_0))) |
170 | return find_base_value (src_0); | |
171 | ||
172 | if (GET_CODE (src_1) == REG && REGNO_POINTER_FLAG (REGNO (src_1))) | |
173 | return find_base_value (src_1); | |
174 | ||
9ae8ffe7 | 175 | return 0; |
2a2c8203 JC |
176 | } |
177 | ||
178 | case LO_SUM: | |
179 | /* The standard form is (lo_sum reg sym) so look only at the | |
180 | second operand. */ | |
181 | return find_base_value (XEXP (src, 1)); | |
9ae8ffe7 JL |
182 | |
183 | case AND: | |
184 | /* If the second operand is constant set the base | |
185 | address to the first operand. */ | |
2a2c8203 JC |
186 | if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0) |
187 | return find_base_value (XEXP (src, 0)); | |
9ae8ffe7 JL |
188 | return 0; |
189 | ||
190 | case HIGH: | |
2a2c8203 | 191 | return find_base_value (XEXP (src, 0)); |
9ae8ffe7 JL |
192 | } |
193 | ||
194 | return 0; | |
195 | } | |
196 | ||
197 | /* Called from init_alias_analysis indirectly through note_stores. */ | |
198 | ||
199 | /* while scanning insns to find base values, reg_seen[N] is nonzero if | |
200 | register N has been set in this function. */ | |
201 | static char *reg_seen; | |
202 | ||
ec907dd8 JL |
203 | /* */ |
204 | static int unique_id; | |
205 | ||
2a2c8203 JC |
206 | static void |
207 | record_set (dest, set) | |
9ae8ffe7 JL |
208 | rtx dest, set; |
209 | { | |
210 | register int regno; | |
211 | rtx src; | |
212 | ||
213 | if (GET_CODE (dest) != REG) | |
214 | return; | |
215 | ||
216 | regno = REGNO (dest); | |
217 | ||
218 | if (set) | |
219 | { | |
220 | /* A CLOBBER wipes out any old value but does not prevent a previously | |
221 | unset register from acquiring a base address (i.e. reg_seen is not | |
222 | set). */ | |
223 | if (GET_CODE (set) == CLOBBER) | |
224 | { | |
ec907dd8 | 225 | new_reg_base_value[regno] = 0; |
9ae8ffe7 JL |
226 | return; |
227 | } | |
228 | src = SET_SRC (set); | |
229 | } | |
230 | else | |
231 | { | |
9ae8ffe7 JL |
232 | if (reg_seen[regno]) |
233 | { | |
ec907dd8 | 234 | new_reg_base_value[regno] = 0; |
9ae8ffe7 JL |
235 | return; |
236 | } | |
237 | reg_seen[regno] = 1; | |
ec907dd8 | 238 | new_reg_base_value[regno] = gen_rtx (ADDRESS, Pmode, |
9ae8ffe7 JL |
239 | GEN_INT (unique_id++)); |
240 | return; | |
241 | } | |
242 | ||
243 | /* This is not the first set. If the new value is not related to the | |
244 | old value, forget the base value. Note that the following code is | |
245 | not detected: | |
246 | extern int x, y; int *p = &x; p += (&y-&x); | |
247 | ANSI C does not allow computing the difference of addresses | |
248 | of distinct top level objects. */ | |
ec907dd8 | 249 | if (new_reg_base_value[regno]) |
9ae8ffe7 JL |
250 | switch (GET_CODE (src)) |
251 | { | |
2a2c8203 | 252 | case LO_SUM: |
9ae8ffe7 JL |
253 | case PLUS: |
254 | case MINUS: | |
255 | if (XEXP (src, 0) != dest && XEXP (src, 1) != dest) | |
ec907dd8 | 256 | new_reg_base_value[regno] = 0; |
9ae8ffe7 JL |
257 | break; |
258 | case AND: | |
259 | if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT) | |
ec907dd8 | 260 | new_reg_base_value[regno] = 0; |
9ae8ffe7 | 261 | break; |
9ae8ffe7 | 262 | default: |
ec907dd8 | 263 | new_reg_base_value[regno] = 0; |
9ae8ffe7 JL |
264 | break; |
265 | } | |
266 | /* If this is the first set of a register, record the value. */ | |
267 | else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno]) | |
ec907dd8 JL |
268 | && ! reg_seen[regno] && new_reg_base_value[regno] == 0) |
269 | new_reg_base_value[regno] = find_base_value (src); | |
9ae8ffe7 JL |
270 | |
271 | reg_seen[regno] = 1; | |
272 | } | |
273 | ||
274 | /* Called from loop optimization when a new pseudo-register is created. */ | |
275 | void | |
276 | record_base_value (regno, val) | |
277 | int regno; | |
278 | rtx val; | |
279 | { | |
280 | if (!flag_alias_check || regno >= reg_base_value_size) | |
281 | return; | |
282 | if (GET_CODE (val) == REG) | |
283 | { | |
284 | if (REGNO (val) < reg_base_value_size) | |
285 | reg_base_value[regno] = reg_base_value[REGNO (val)]; | |
286 | return; | |
287 | } | |
288 | reg_base_value[regno] = find_base_value (val); | |
289 | } | |
290 | ||
291 | static rtx | |
292 | canon_rtx (x) | |
293 | rtx x; | |
294 | { | |
295 | /* Recursively look for equivalences. */ | |
296 | if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER | |
297 | && REGNO (x) < reg_known_value_size) | |
298 | return reg_known_value[REGNO (x)] == x | |
299 | ? x : canon_rtx (reg_known_value[REGNO (x)]); | |
300 | else if (GET_CODE (x) == PLUS) | |
301 | { | |
302 | rtx x0 = canon_rtx (XEXP (x, 0)); | |
303 | rtx x1 = canon_rtx (XEXP (x, 1)); | |
304 | ||
305 | if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1)) | |
306 | { | |
307 | /* We can tolerate LO_SUMs being offset here; these | |
308 | rtl are used for nothing other than comparisons. */ | |
309 | if (GET_CODE (x0) == CONST_INT) | |
310 | return plus_constant_for_output (x1, INTVAL (x0)); | |
311 | else if (GET_CODE (x1) == CONST_INT) | |
312 | return plus_constant_for_output (x0, INTVAL (x1)); | |
313 | return gen_rtx (PLUS, GET_MODE (x), x0, x1); | |
314 | } | |
315 | } | |
316 | /* This gives us much better alias analysis when called from | |
317 | the loop optimizer. Note we want to leave the original | |
318 | MEM alone, but need to return the canonicalized MEM with | |
319 | all the flags with their original values. */ | |
320 | else if (GET_CODE (x) == MEM) | |
321 | { | |
322 | rtx addr = canon_rtx (XEXP (x, 0)); | |
323 | if (addr != XEXP (x, 0)) | |
324 | { | |
325 | rtx new = gen_rtx (MEM, GET_MODE (x), addr); | |
326 | MEM_VOLATILE_P (new) = MEM_VOLATILE_P (x); | |
327 | RTX_UNCHANGING_P (new) = RTX_UNCHANGING_P (x); | |
328 | MEM_IN_STRUCT_P (new) = MEM_IN_STRUCT_P (x); | |
329 | x = new; | |
330 | } | |
331 | } | |
332 | return x; | |
333 | } | |
334 | ||
335 | /* Return 1 if X and Y are identical-looking rtx's. | |
336 | ||
337 | We use the data in reg_known_value above to see if two registers with | |
338 | different numbers are, in fact, equivalent. */ | |
339 | ||
340 | static int | |
341 | rtx_equal_for_memref_p (x, y) | |
342 | rtx x, y; | |
343 | { | |
344 | register int i; | |
345 | register int j; | |
346 | register enum rtx_code code; | |
347 | register char *fmt; | |
348 | ||
349 | if (x == 0 && y == 0) | |
350 | return 1; | |
351 | if (x == 0 || y == 0) | |
352 | return 0; | |
353 | x = canon_rtx (x); | |
354 | y = canon_rtx (y); | |
355 | ||
356 | if (x == y) | |
357 | return 1; | |
358 | ||
359 | code = GET_CODE (x); | |
360 | /* Rtx's of different codes cannot be equal. */ | |
361 | if (code != GET_CODE (y)) | |
362 | return 0; | |
363 | ||
364 | /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. | |
365 | (REG:SI x) and (REG:HI x) are NOT equivalent. */ | |
366 | ||
367 | if (GET_MODE (x) != GET_MODE (y)) | |
368 | return 0; | |
369 | ||
370 | /* REG, LABEL_REF, and SYMBOL_REF can be compared nonrecursively. */ | |
371 | ||
372 | if (code == REG) | |
373 | return REGNO (x) == REGNO (y); | |
374 | if (code == LABEL_REF) | |
375 | return XEXP (x, 0) == XEXP (y, 0); | |
376 | if (code == SYMBOL_REF) | |
377 | return XSTR (x, 0) == XSTR (y, 0); | |
378 | ||
379 | /* For commutative operations, the RTX match if the operand match in any | |
380 | order. Also handle the simple binary and unary cases without a loop. */ | |
381 | if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c') | |
382 | return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) | |
383 | && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))) | |
384 | || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1)) | |
385 | && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0)))); | |
386 | else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2') | |
387 | return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) | |
388 | && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))); | |
389 | else if (GET_RTX_CLASS (code) == '1') | |
390 | return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)); | |
391 | ||
392 | /* Compare the elements. If any pair of corresponding elements | |
393 | fail to match, return 0 for the whole things. */ | |
394 | ||
395 | fmt = GET_RTX_FORMAT (code); | |
396 | for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) | |
397 | { | |
398 | switch (fmt[i]) | |
399 | { | |
400 | case 'w': | |
401 | if (XWINT (x, i) != XWINT (y, i)) | |
402 | return 0; | |
403 | break; | |
404 | ||
405 | case 'n': | |
406 | case 'i': | |
407 | if (XINT (x, i) != XINT (y, i)) | |
408 | return 0; | |
409 | break; | |
410 | ||
411 | case 'V': | |
412 | case 'E': | |
413 | /* Two vectors must have the same length. */ | |
414 | if (XVECLEN (x, i) != XVECLEN (y, i)) | |
415 | return 0; | |
416 | ||
417 | /* And the corresponding elements must match. */ | |
418 | for (j = 0; j < XVECLEN (x, i); j++) | |
419 | if (rtx_equal_for_memref_p (XVECEXP (x, i, j), XVECEXP (y, i, j)) == 0) | |
420 | return 0; | |
421 | break; | |
422 | ||
423 | case 'e': | |
424 | if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0) | |
425 | return 0; | |
426 | break; | |
427 | ||
428 | case 'S': | |
429 | case 's': | |
430 | if (strcmp (XSTR (x, i), XSTR (y, i))) | |
431 | return 0; | |
432 | break; | |
433 | ||
434 | case 'u': | |
435 | /* These are just backpointers, so they don't matter. */ | |
436 | break; | |
437 | ||
438 | case '0': | |
439 | break; | |
440 | ||
441 | /* It is believed that rtx's at this level will never | |
442 | contain anything but integers and other rtx's, | |
443 | except for within LABEL_REFs and SYMBOL_REFs. */ | |
444 | default: | |
445 | abort (); | |
446 | } | |
447 | } | |
448 | return 1; | |
449 | } | |
450 | ||
451 | /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within | |
452 | X and return it, or return 0 if none found. */ | |
453 | ||
454 | static rtx | |
455 | find_symbolic_term (x) | |
456 | rtx x; | |
457 | { | |
458 | register int i; | |
459 | register enum rtx_code code; | |
460 | register char *fmt; | |
461 | ||
462 | code = GET_CODE (x); | |
463 | if (code == SYMBOL_REF || code == LABEL_REF) | |
464 | return x; | |
465 | if (GET_RTX_CLASS (code) == 'o') | |
466 | return 0; | |
467 | ||
468 | fmt = GET_RTX_FORMAT (code); | |
469 | for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) | |
470 | { | |
471 | rtx t; | |
472 | ||
473 | if (fmt[i] == 'e') | |
474 | { | |
475 | t = find_symbolic_term (XEXP (x, i)); | |
476 | if (t != 0) | |
477 | return t; | |
478 | } | |
479 | else if (fmt[i] == 'E') | |
480 | break; | |
481 | } | |
482 | return 0; | |
483 | } | |
484 | ||
485 | static rtx | |
486 | find_base_term (x) | |
487 | register rtx x; | |
488 | { | |
489 | switch (GET_CODE (x)) | |
490 | { | |
491 | case REG: | |
492 | return REG_BASE_VALUE (x); | |
493 | ||
494 | case HIGH: | |
495 | return find_base_term (XEXP (x, 0)); | |
496 | ||
6d849a2a JL |
497 | case PRE_INC: |
498 | case PRE_DEC: | |
499 | case POST_INC: | |
500 | case POST_DEC: | |
501 | return find_base_term (XEXP (x, 0)); | |
502 | ||
9ae8ffe7 JL |
503 | case CONST: |
504 | x = XEXP (x, 0); | |
505 | if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS) | |
506 | return 0; | |
507 | /* fall through */ | |
508 | case LO_SUM: | |
509 | case PLUS: | |
510 | case MINUS: | |
511 | { | |
512 | rtx tmp = find_base_term (XEXP (x, 0)); | |
513 | if (tmp) | |
514 | return tmp; | |
515 | return find_base_term (XEXP (x, 1)); | |
516 | } | |
517 | ||
518 | case AND: | |
519 | if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT) | |
520 | return REG_BASE_VALUE (XEXP (x, 0)); | |
521 | return 0; | |
522 | ||
523 | case SYMBOL_REF: | |
524 | case LABEL_REF: | |
525 | return x; | |
526 | ||
527 | default: | |
528 | return 0; | |
529 | } | |
530 | } | |
531 | ||
532 | /* Return 0 if the addresses X and Y are known to point to different | |
533 | objects, 1 if they might be pointers to the same object. */ | |
534 | ||
535 | static int | |
536 | base_alias_check (x, y) | |
537 | rtx x, y; | |
538 | { | |
539 | rtx x_base = find_base_term (x); | |
540 | rtx y_base = find_base_term (y); | |
541 | ||
542 | /* If either base address is unknown or the base addresses are equal, | |
543 | nothing is known about aliasing. */ | |
544 | ||
545 | if (x_base == 0 || y_base == 0 || rtx_equal_p (x_base, y_base)) | |
546 | return 1; | |
547 | ||
548 | /* The base addresses of the read and write are different | |
c02f035f RH |
549 | expressions. If they are both symbols and they are not accessed |
550 | via AND, there is no conflict. */ | |
551 | /* XXX: We can bring knowledge of object alignment and offset into | |
552 | play here. For example, on alpha, "char a, b;" can alias one | |
553 | another, though "char a; long b;" cannot. Similarly, offsets | |
554 | into strutures may be brought into play. Given "char a, b[40];", | |
555 | a and b[1] may overlap, but a and b[20] do not. */ | |
9ae8ffe7 | 556 | if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) |
c02f035f RH |
557 | { |
558 | return GET_CODE (x) == AND || GET_CODE (y) == AND; | |
559 | } | |
9ae8ffe7 JL |
560 | |
561 | /* If one address is a stack reference there can be no alias: | |
562 | stack references using different base registers do not alias, | |
563 | a stack reference can not alias a parameter, and a stack reference | |
564 | can not alias a global. */ | |
565 | if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode) | |
566 | || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode)) | |
567 | return 0; | |
568 | ||
569 | if (! flag_argument_noalias) | |
570 | return 1; | |
571 | ||
572 | if (flag_argument_noalias > 1) | |
573 | return 0; | |
574 | ||
575 | /* Weak noalias assertion (arguments are distinct, but may match globals). */ | |
576 | return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode); | |
577 | } | |
578 | ||
579 | /* Return nonzero if X and Y (memory addresses) could reference the | |
580 | same location in memory. C is an offset accumulator. When | |
581 | C is nonzero, we are testing aliases between X and Y + C. | |
582 | XSIZE is the size in bytes of the X reference, | |
583 | similarly YSIZE is the size in bytes for Y. | |
584 | ||
585 | If XSIZE or YSIZE is zero, we do not know the amount of memory being | |
586 | referenced (the reference was BLKmode), so make the most pessimistic | |
587 | assumptions. | |
588 | ||
c02f035f RH |
589 | If XSIZE or YSIZE is negative, we may access memory outside the object |
590 | being referenced as a side effect. This can happen when using AND to | |
591 | align memory references, as is done on the Alpha. | |
592 | ||
9ae8ffe7 JL |
593 | We recognize the following cases of non-conflicting memory: |
594 | ||
595 | (1) addresses involving the frame pointer cannot conflict | |
596 | with addresses involving static variables. | |
597 | (2) static variables with different addresses cannot conflict. | |
598 | ||
599 | Nice to notice that varying addresses cannot conflict with fp if no | |
600 | local variables had their addresses taken, but that's too hard now. */ | |
601 | ||
602 | ||
603 | static int | |
604 | memrefs_conflict_p (xsize, x, ysize, y, c) | |
605 | register rtx x, y; | |
606 | int xsize, ysize; | |
607 | HOST_WIDE_INT c; | |
608 | { | |
609 | if (GET_CODE (x) == HIGH) | |
610 | x = XEXP (x, 0); | |
611 | else if (GET_CODE (x) == LO_SUM) | |
612 | x = XEXP (x, 1); | |
613 | else | |
614 | x = canon_rtx (x); | |
615 | if (GET_CODE (y) == HIGH) | |
616 | y = XEXP (y, 0); | |
617 | else if (GET_CODE (y) == LO_SUM) | |
618 | y = XEXP (y, 1); | |
619 | else | |
620 | y = canon_rtx (y); | |
621 | ||
622 | if (rtx_equal_for_memref_p (x, y)) | |
623 | { | |
c02f035f | 624 | if (xsize <= 0 || ysize <= 0) |
9ae8ffe7 JL |
625 | return 1; |
626 | if (c >= 0 && xsize > c) | |
627 | return 1; | |
628 | if (c < 0 && ysize+c > 0) | |
629 | return 1; | |
630 | return 0; | |
631 | } | |
632 | ||
633 | if (y == frame_pointer_rtx || y == hard_frame_pointer_rtx | |
96286722 | 634 | || y == stack_pointer_rtx || y == arg_pointer_rtx) |
9ae8ffe7 JL |
635 | { |
636 | rtx t = y; | |
637 | int tsize = ysize; | |
638 | y = x; ysize = xsize; | |
639 | x = t; xsize = tsize; | |
640 | } | |
641 | ||
642 | if (x == frame_pointer_rtx || x == hard_frame_pointer_rtx | |
96286722 | 643 | || x == stack_pointer_rtx || x == arg_pointer_rtx) |
9ae8ffe7 JL |
644 | { |
645 | rtx y1; | |
646 | ||
647 | if (CONSTANT_P (y)) | |
648 | return 0; | |
649 | ||
650 | if (GET_CODE (y) == PLUS | |
651 | && canon_rtx (XEXP (y, 0)) == x | |
652 | && (y1 = canon_rtx (XEXP (y, 1))) | |
653 | && GET_CODE (y1) == CONST_INT) | |
654 | { | |
655 | c += INTVAL (y1); | |
c02f035f | 656 | return (xsize <= 0 || ysize <= 0 |
9ae8ffe7 JL |
657 | || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); |
658 | } | |
659 | ||
660 | if (GET_CODE (y) == PLUS | |
661 | && (y1 = canon_rtx (XEXP (y, 0))) | |
662 | && CONSTANT_P (y1)) | |
663 | return 0; | |
664 | ||
665 | return 1; | |
666 | } | |
667 | ||
668 | if (GET_CODE (x) == PLUS) | |
669 | { | |
670 | /* The fact that X is canonicalized means that this | |
671 | PLUS rtx is canonicalized. */ | |
672 | rtx x0 = XEXP (x, 0); | |
673 | rtx x1 = XEXP (x, 1); | |
674 | ||
675 | if (GET_CODE (y) == PLUS) | |
676 | { | |
677 | /* The fact that Y is canonicalized means that this | |
678 | PLUS rtx is canonicalized. */ | |
679 | rtx y0 = XEXP (y, 0); | |
680 | rtx y1 = XEXP (y, 1); | |
681 | ||
682 | if (rtx_equal_for_memref_p (x1, y1)) | |
683 | return memrefs_conflict_p (xsize, x0, ysize, y0, c); | |
684 | if (rtx_equal_for_memref_p (x0, y0)) | |
685 | return memrefs_conflict_p (xsize, x1, ysize, y1, c); | |
686 | if (GET_CODE (x1) == CONST_INT) | |
687 | if (GET_CODE (y1) == CONST_INT) | |
688 | return memrefs_conflict_p (xsize, x0, ysize, y0, | |
689 | c - INTVAL (x1) + INTVAL (y1)); | |
690 | else | |
691 | return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); | |
692 | else if (GET_CODE (y1) == CONST_INT) | |
693 | return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); | |
694 | ||
695 | /* Handle case where we cannot understand iteration operators, | |
696 | but we notice that the base addresses are distinct objects. */ | |
697 | /* ??? Is this still necessary? */ | |
698 | x = find_symbolic_term (x); | |
699 | if (x == 0) | |
700 | return 1; | |
701 | y = find_symbolic_term (y); | |
702 | if (y == 0) | |
703 | return 1; | |
704 | return rtx_equal_for_memref_p (x, y); | |
705 | } | |
706 | else if (GET_CODE (x1) == CONST_INT) | |
707 | return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); | |
708 | } | |
709 | else if (GET_CODE (y) == PLUS) | |
710 | { | |
711 | /* The fact that Y is canonicalized means that this | |
712 | PLUS rtx is canonicalized. */ | |
713 | rtx y0 = XEXP (y, 0); | |
714 | rtx y1 = XEXP (y, 1); | |
715 | ||
716 | if (GET_CODE (y1) == CONST_INT) | |
717 | return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); | |
718 | else | |
719 | return 1; | |
720 | } | |
721 | ||
722 | if (GET_CODE (x) == GET_CODE (y)) | |
723 | switch (GET_CODE (x)) | |
724 | { | |
725 | case MULT: | |
726 | { | |
727 | /* Handle cases where we expect the second operands to be the | |
728 | same, and check only whether the first operand would conflict | |
729 | or not. */ | |
730 | rtx x0, y0; | |
731 | rtx x1 = canon_rtx (XEXP (x, 1)); | |
732 | rtx y1 = canon_rtx (XEXP (y, 1)); | |
733 | if (! rtx_equal_for_memref_p (x1, y1)) | |
734 | return 1; | |
735 | x0 = canon_rtx (XEXP (x, 0)); | |
736 | y0 = canon_rtx (XEXP (y, 0)); | |
737 | if (rtx_equal_for_memref_p (x0, y0)) | |
738 | return (xsize == 0 || ysize == 0 | |
739 | || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); | |
740 | ||
741 | /* Can't properly adjust our sizes. */ | |
742 | if (GET_CODE (x1) != CONST_INT) | |
743 | return 1; | |
744 | xsize /= INTVAL (x1); | |
745 | ysize /= INTVAL (x1); | |
746 | c /= INTVAL (x1); | |
747 | return memrefs_conflict_p (xsize, x0, ysize, y0, c); | |
748 | } | |
749 | } | |
750 | ||
751 | /* Treat an access through an AND (e.g. a subword access on an Alpha) | |
752 | as an access with indeterminate size. */ | |
753 | if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT) | |
c02f035f | 754 | return memrefs_conflict_p (-1, XEXP (x, 0), ysize, y, c); |
9ae8ffe7 | 755 | if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT) |
c02f035f RH |
756 | { |
757 | /* XXX: If we are indexing far enough into the array/structure, we | |
758 | may yet be able to determine that we can not overlap. But we | |
759 | also need to that we are far enough from the end not to overlap | |
760 | a following reference, so we do nothing for now. */ | |
761 | return memrefs_conflict_p (xsize, x, -1, XEXP (y, 0), c); | |
762 | } | |
9ae8ffe7 JL |
763 | |
764 | if (CONSTANT_P (x)) | |
765 | { | |
766 | if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT) | |
767 | { | |
768 | c += (INTVAL (y) - INTVAL (x)); | |
c02f035f | 769 | return (xsize <= 0 || ysize <= 0 |
9ae8ffe7 JL |
770 | || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); |
771 | } | |
772 | ||
773 | if (GET_CODE (x) == CONST) | |
774 | { | |
775 | if (GET_CODE (y) == CONST) | |
776 | return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), | |
777 | ysize, canon_rtx (XEXP (y, 0)), c); | |
778 | else | |
779 | return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), | |
780 | ysize, y, c); | |
781 | } | |
782 | if (GET_CODE (y) == CONST) | |
783 | return memrefs_conflict_p (xsize, x, ysize, | |
784 | canon_rtx (XEXP (y, 0)), c); | |
785 | ||
786 | if (CONSTANT_P (y)) | |
c02f035f RH |
787 | return (xsize < 0 || ysize < 0 |
788 | || (rtx_equal_for_memref_p (x, y) | |
789 | && (xsize == 0 || ysize == 0 | |
790 | || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)))); | |
9ae8ffe7 JL |
791 | |
792 | return 1; | |
793 | } | |
794 | return 1; | |
795 | } | |
796 | ||
797 | /* Functions to compute memory dependencies. | |
798 | ||
799 | Since we process the insns in execution order, we can build tables | |
800 | to keep track of what registers are fixed (and not aliased), what registers | |
801 | are varying in known ways, and what registers are varying in unknown | |
802 | ways. | |
803 | ||
804 | If both memory references are volatile, then there must always be a | |
805 | dependence between the two references, since their order can not be | |
806 | changed. A volatile and non-volatile reference can be interchanged | |
807 | though. | |
808 | ||
fa8b6024 | 809 | A MEM_IN_STRUCT reference at a non-QImode non-AND varying address can never |
9ae8ffe7 JL |
810 | conflict with a non-MEM_IN_STRUCT reference at a fixed address. We must |
811 | allow QImode aliasing because the ANSI C standard allows character | |
812 | pointers to alias anything. We are assuming that characters are | |
fa8b6024 JW |
813 | always QImode here. We also must allow AND addresses, because they may |
814 | generate accesses outside the object being referenced. This is used to | |
815 | generate aligned addresses from unaligned addresses, for instance, the | |
816 | alpha storeqi_unaligned pattern. */ | |
9ae8ffe7 JL |
817 | |
818 | /* Read dependence: X is read after read in MEM takes place. There can | |
819 | only be a dependence here if both reads are volatile. */ | |
820 | ||
821 | int | |
822 | read_dependence (mem, x) | |
823 | rtx mem; | |
824 | rtx x; | |
825 | { | |
826 | return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem); | |
827 | } | |
828 | ||
829 | /* True dependence: X is read after store in MEM takes place. */ | |
830 | ||
831 | int | |
832 | true_dependence (mem, mem_mode, x, varies) | |
833 | rtx mem; | |
834 | enum machine_mode mem_mode; | |
835 | rtx x; | |
836 | int (*varies)(); | |
837 | { | |
838 | rtx x_addr, mem_addr; | |
839 | ||
840 | if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) | |
841 | return 1; | |
842 | ||
843 | x_addr = XEXP (x, 0); | |
844 | mem_addr = XEXP (mem, 0); | |
845 | ||
846 | if (flag_alias_check && ! base_alias_check (x_addr, mem_addr)) | |
847 | return 0; | |
848 | ||
849 | /* If X is an unchanging read, then it can't possibly conflict with any | |
850 | non-unchanging store. It may conflict with an unchanging write though, | |
851 | because there may be a single store to this address to initialize it. | |
852 | Just fall through to the code below to resolve the case where we have | |
853 | both an unchanging read and an unchanging write. This won't handle all | |
854 | cases optimally, but the possible performance loss should be | |
855 | negligible. */ | |
856 | if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem)) | |
857 | return 0; | |
858 | ||
859 | x_addr = canon_rtx (x_addr); | |
860 | mem_addr = canon_rtx (mem_addr); | |
861 | if (mem_mode == VOIDmode) | |
862 | mem_mode = GET_MODE (mem); | |
863 | ||
edaa4ee0 | 864 | if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, |
6d849a2a | 865 | SIZE_FOR_MODE (x), x_addr, 0)) |
9ae8ffe7 JL |
866 | return 0; |
867 | ||
868 | /* If both references are struct references, or both are not, nothing | |
869 | is known about aliasing. | |
870 | ||
871 | If either reference is QImode or BLKmode, ANSI C permits aliasing. | |
872 | ||
873 | If both addresses are constant, or both are not, nothing is known | |
874 | about aliasing. */ | |
875 | if (MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (mem) | |
876 | || mem_mode == QImode || mem_mode == BLKmode | |
57163df0 | 877 | || GET_MODE (x) == QImode || GET_MODE (x) == BLKmode |
fa8b6024 | 878 | || GET_CODE (x_addr) == AND || GET_CODE (mem_addr) == AND |
9ae8ffe7 JL |
879 | || varies (x_addr) == varies (mem_addr)) |
880 | return 1; | |
881 | ||
882 | /* One memory reference is to a constant address, one is not. | |
883 | One is to a structure, the other is not. | |
884 | ||
885 | If either memory reference is a variable structure the other is a | |
886 | fixed scalar and there is no aliasing. */ | |
887 | if ((MEM_IN_STRUCT_P (mem) && varies (mem_addr)) | |
27314274 | 888 | || (MEM_IN_STRUCT_P (x) && varies (x_addr))) |
9ae8ffe7 JL |
889 | return 0; |
890 | ||
891 | return 1; | |
892 | } | |
893 | ||
894 | /* Anti dependence: X is written after read in MEM takes place. */ | |
895 | ||
896 | int | |
897 | anti_dependence (mem, x) | |
898 | rtx mem; | |
899 | rtx x; | |
900 | { | |
901 | if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) | |
902 | return 1; | |
903 | ||
904 | if (flag_alias_check && ! base_alias_check (XEXP (x, 0), XEXP (mem, 0))) | |
905 | return 0; | |
906 | ||
907 | /* If MEM is an unchanging read, then it can't possibly conflict with | |
908 | the store to X, because there is at most one store to MEM, and it must | |
909 | have occurred somewhere before MEM. */ | |
910 | x = canon_rtx (x); | |
911 | mem = canon_rtx (mem); | |
912 | if (RTX_UNCHANGING_P (mem)) | |
913 | return 0; | |
914 | ||
915 | return (memrefs_conflict_p (SIZE_FOR_MODE (mem), XEXP (mem, 0), | |
916 | SIZE_FOR_MODE (x), XEXP (x, 0), 0) | |
917 | && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem) | |
918 | && GET_MODE (mem) != QImode | |
fa8b6024 | 919 | && GET_CODE (XEXP (mem, 0)) != AND |
9ae8ffe7 JL |
920 | && ! MEM_IN_STRUCT_P (x) && ! rtx_addr_varies_p (x)) |
921 | && ! (MEM_IN_STRUCT_P (x) && rtx_addr_varies_p (x) | |
922 | && GET_MODE (x) != QImode | |
fa8b6024 | 923 | && GET_CODE (XEXP (x, 0)) != AND |
9ae8ffe7 JL |
924 | && ! MEM_IN_STRUCT_P (mem) && ! rtx_addr_varies_p (mem))); |
925 | } | |
926 | ||
927 | /* Output dependence: X is written after store in MEM takes place. */ | |
928 | ||
929 | int | |
930 | output_dependence (mem, x) | |
931 | register rtx mem; | |
932 | register rtx x; | |
933 | { | |
934 | if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) | |
935 | return 1; | |
936 | ||
937 | if (flag_alias_check && !base_alias_check (XEXP (x, 0), XEXP (mem, 0))) | |
938 | return 0; | |
939 | ||
940 | x = canon_rtx (x); | |
941 | mem = canon_rtx (mem); | |
942 | return (memrefs_conflict_p (SIZE_FOR_MODE (mem), XEXP (mem, 0), | |
943 | SIZE_FOR_MODE (x), XEXP (x, 0), 0) | |
944 | && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem) | |
945 | && GET_MODE (mem) != QImode | |
fa8b6024 | 946 | && GET_CODE (XEXP (mem, 0)) != AND |
9ae8ffe7 JL |
947 | && ! MEM_IN_STRUCT_P (x) && ! rtx_addr_varies_p (x)) |
948 | && ! (MEM_IN_STRUCT_P (x) && rtx_addr_varies_p (x) | |
949 | && GET_MODE (x) != QImode | |
fa8b6024 | 950 | && GET_CODE (XEXP (x, 0)) != AND |
9ae8ffe7 JL |
951 | && ! MEM_IN_STRUCT_P (mem) && ! rtx_addr_varies_p (mem))); |
952 | } | |
953 | ||
954 | void | |
955 | init_alias_analysis () | |
956 | { | |
957 | int maxreg = max_reg_num (); | |
958 | int changed; | |
959 | register int i; | |
960 | register rtx insn; | |
961 | rtx note; | |
962 | rtx set; | |
963 | ||
964 | reg_known_value_size = maxreg; | |
965 | ||
966 | reg_known_value | |
967 | = (rtx *) oballoc ((maxreg - FIRST_PSEUDO_REGISTER) * sizeof (rtx)) | |
968 | - FIRST_PSEUDO_REGISTER; | |
969 | reg_known_equiv_p = | |
970 | oballoc (maxreg - FIRST_PSEUDO_REGISTER) - FIRST_PSEUDO_REGISTER; | |
971 | bzero ((char *) (reg_known_value + FIRST_PSEUDO_REGISTER), | |
972 | (maxreg-FIRST_PSEUDO_REGISTER) * sizeof (rtx)); | |
973 | bzero (reg_known_equiv_p + FIRST_PSEUDO_REGISTER, | |
974 | (maxreg - FIRST_PSEUDO_REGISTER) * sizeof (char)); | |
975 | ||
976 | if (flag_alias_check) | |
977 | { | |
978 | /* Overallocate reg_base_value to allow some growth during loop | |
979 | optimization. Loop unrolling can create a large number of | |
980 | registers. */ | |
981 | reg_base_value_size = maxreg * 2; | |
982 | reg_base_value = (rtx *)oballoc (reg_base_value_size * sizeof (rtx)); | |
ec907dd8 | 983 | new_reg_base_value = (rtx *)alloca (reg_base_value_size * sizeof (rtx)); |
9ae8ffe7 | 984 | reg_seen = (char *)alloca (reg_base_value_size); |
52b7724b | 985 | bzero ((char *) reg_base_value, reg_base_value_size * sizeof (rtx)); |
ec907dd8 JL |
986 | } |
987 | ||
988 | /* The basic idea is that each pass through this loop will use the | |
989 | "constant" information from the previous pass to propagate alias | |
990 | information through another level of assignments. | |
991 | ||
992 | This could get expensive if the assignment chains are long. Maybe | |
993 | we should throttle the number of iterations, possibly based on | |
994 | the optimization level. | |
995 | ||
996 | We could propagate more information in the first pass by making use | |
997 | of REG_N_SETS to determine immediately that the alias information | |
998 | for a pseudo is "constant". */ | |
999 | changed = 1; | |
1000 | while (changed) | |
1001 | { | |
1002 | /* Assume nothing will change this iteration of the loop. */ | |
1003 | changed = 0; | |
1004 | ||
ec907dd8 JL |
1005 | /* We want to assign the same IDs each iteration of this loop, so |
1006 | start counting from zero each iteration of the loop. */ | |
1007 | unique_id = 0; | |
1008 | ||
1009 | /* We're at the start of the funtion each iteration through the | |
1010 | loop, so we're copying arguments. */ | |
1011 | copying_arguments = 1; | |
9ae8ffe7 | 1012 | |
8072f69c JL |
1013 | /* Only perform initialization of the arrays if we're actually |
1014 | performing alias analysis. */ | |
1015 | if (flag_alias_check) | |
1016 | { | |
1017 | /* Wipe the potential alias information clean for this pass. */ | |
1018 | bzero ((char *) new_reg_base_value, | |
1019 | reg_base_value_size * sizeof (rtx)); | |
1020 | ||
1021 | /* Wipe the reg_seen array clean. */ | |
1022 | bzero ((char *) reg_seen, reg_base_value_size); | |
9ae8ffe7 | 1023 | |
8072f69c JL |
1024 | /* Mark all hard registers which may contain an address. |
1025 | The stack, frame and argument pointers may contain an address. | |
1026 | An argument register which can hold a Pmode value may contain | |
1027 | an address even if it is not in BASE_REGS. | |
1028 | ||
1029 | The address expression is VOIDmode for an argument and | |
1030 | Pmode for other registers. */ | |
9ae8ffe7 JL |
1031 | #ifndef OUTGOING_REGNO |
1032 | #define OUTGOING_REGNO(N) N | |
1033 | #endif | |
8072f69c JL |
1034 | for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
1035 | /* Check whether this register can hold an incoming pointer | |
1036 | argument. FUNCTION_ARG_REGNO_P tests outgoing register | |
1037 | numbers, so translate if necessary due to register windows. */ | |
1038 | if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i)) | |
1039 | && HARD_REGNO_MODE_OK (i, Pmode)) | |
1040 | new_reg_base_value[i] = gen_rtx (ADDRESS, VOIDmode, | |
1041 | gen_rtx (REG, Pmode, i)); | |
1042 | ||
1043 | new_reg_base_value[STACK_POINTER_REGNUM] | |
1044 | = gen_rtx (ADDRESS, Pmode, stack_pointer_rtx); | |
1045 | new_reg_base_value[ARG_POINTER_REGNUM] | |
1046 | = gen_rtx (ADDRESS, Pmode, arg_pointer_rtx); | |
1047 | new_reg_base_value[FRAME_POINTER_REGNUM] | |
1048 | = gen_rtx (ADDRESS, Pmode, frame_pointer_rtx); | |
2a2c8203 | 1049 | #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM |
8072f69c JL |
1050 | new_reg_base_value[HARD_FRAME_POINTER_REGNUM] |
1051 | = gen_rtx (ADDRESS, Pmode, hard_frame_pointer_rtx); | |
2a2c8203 | 1052 | #endif |
8072f69c JL |
1053 | if (struct_value_incoming_rtx |
1054 | && GET_CODE (struct_value_incoming_rtx) == REG) | |
1055 | new_reg_base_value[REGNO (struct_value_incoming_rtx)] | |
1056 | = gen_rtx (ADDRESS, Pmode, struct_value_incoming_rtx); | |
1057 | ||
1058 | if (static_chain_rtx | |
1059 | && GET_CODE (static_chain_rtx) == REG) | |
1060 | new_reg_base_value[REGNO (static_chain_rtx)] | |
1061 | = gen_rtx (ADDRESS, Pmode, static_chain_rtx); | |
1062 | } | |
ec907dd8 JL |
1063 | |
1064 | /* Walk the insns adding values to the new_reg_base_value array. */ | |
1065 | for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) | |
9ae8ffe7 | 1066 | { |
ec907dd8 JL |
1067 | if (flag_alias_check && GET_RTX_CLASS (GET_CODE (insn)) == 'i') |
1068 | { | |
1069 | /* If this insn has a noalias note, process it, Otherwise, | |
1070 | scan for sets. A simple set will have no side effects | |
1071 | which could change the base value of any other register. */ | |
1072 | rtx noalias_note; | |
1073 | if (GET_CODE (PATTERN (insn)) == SET | |
1074 | && (noalias_note = find_reg_note (insn, | |
1075 | REG_NOALIAS, NULL_RTX))) | |
1076 | record_set (SET_DEST (PATTERN (insn)), 0); | |
1077 | else | |
1078 | note_stores (PATTERN (insn), record_set); | |
1079 | } | |
1080 | else if (GET_CODE (insn) == NOTE | |
1081 | && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG) | |
1082 | copying_arguments = 0; | |
1083 | ||
1084 | if ((set = single_set (insn)) != 0 | |
1085 | && GET_CODE (SET_DEST (set)) == REG | |
1086 | && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER | |
1087 | && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0 | |
1088 | && REG_N_SETS (REGNO (SET_DEST (set))) == 1) | |
1089 | || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0) | |
1090 | && GET_CODE (XEXP (note, 0)) != EXPR_LIST) | |
1091 | { | |
1092 | int regno = REGNO (SET_DEST (set)); | |
1093 | reg_known_value[regno] = XEXP (note, 0); | |
1094 | reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV; | |
1095 | } | |
9ae8ffe7 | 1096 | } |
ec907dd8 JL |
1097 | |
1098 | /* Now propagate values from new_reg_base_value to reg_base_value. */ | |
8072f69c JL |
1099 | if (flag_alias_check) |
1100 | for (i = 0; i < reg_base_value_size; i++) | |
1101 | { | |
1102 | if (new_reg_base_value[i] | |
1103 | && new_reg_base_value[i] != reg_base_value[i] | |
1104 | && !rtx_equal_p (new_reg_base_value[i], reg_base_value[i])) | |
1105 | { | |
1106 | reg_base_value[i] = new_reg_base_value[i]; | |
1107 | changed = 1; | |
1108 | } | |
1109 | } | |
9ae8ffe7 JL |
1110 | } |
1111 | ||
1112 | /* Fill in the remaining entries. */ | |
1113 | for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++) | |
1114 | if (reg_known_value[i] == 0) | |
1115 | reg_known_value[i] = regno_reg_rtx[i]; | |
1116 | ||
1117 | if (! flag_alias_check) | |
1118 | return; | |
1119 | ||
1120 | /* Simplify the reg_base_value array so that no register refers to | |
1121 | another register, except to special registers indirectly through | |
1122 | ADDRESS expressions. | |
1123 | ||
1124 | In theory this loop can take as long as O(registers^2), but unless | |
1125 | there are very long dependency chains it will run in close to linear | |
1126 | time. */ | |
1127 | do | |
1128 | { | |
1129 | changed = 0; | |
7557aa98 | 1130 | for (i = 0; i < reg_base_value_size; i++) |
9ae8ffe7 JL |
1131 | { |
1132 | rtx base = reg_base_value[i]; | |
1133 | if (base && GET_CODE (base) == REG) | |
1134 | { | |
1135 | int base_regno = REGNO (base); | |
1136 | if (base_regno == i) /* register set from itself */ | |
1137 | reg_base_value[i] = 0; | |
1138 | else | |
1139 | reg_base_value[i] = reg_base_value[base_regno]; | |
1140 | changed = 1; | |
1141 | } | |
1142 | } | |
1143 | } | |
1144 | while (changed); | |
1145 | ||
ec907dd8 | 1146 | new_reg_base_value = 0; |
9ae8ffe7 JL |
1147 | reg_seen = 0; |
1148 | } | |
1149 | ||
1150 | void | |
1151 | end_alias_analysis () | |
1152 | { | |
1153 | reg_known_value = 0; | |
1154 | reg_base_value = 0; | |
1155 | reg_base_value_size = 0; | |
1156 | } |