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[deliverable/binutils-gdb.git] / gdb / prologue-value.c
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7d30c22d 1/* Prologue value handling for GDB.
e2882c85 2 Copyright (C) 2003-2018 Free Software Foundation, Inc.
7d30c22d
JB
3
4 This file is part of GDB.
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
a9762ec7 8 the Free Software Foundation; either version 3 of the License, or
7d30c22d
JB
9 (at your option) any later version.
10
11 This program 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
0df8b418 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
7d30c22d
JB
18
19#include "defs.h"
7d30c22d
JB
20#include "prologue-value.h"
21#include "regcache.h"
22
23\f
24/* Constructors. */
25
26pv_t
27pv_unknown (void)
28{
29 pv_t v = { pvk_unknown, 0, 0 };
30
31 return v;
32}
33
34
35pv_t
36pv_constant (CORE_ADDR k)
37{
38 pv_t v;
39
40 v.kind = pvk_constant;
41 v.reg = -1; /* for debugging */
42 v.k = k;
43
44 return v;
45}
46
47
48pv_t
49pv_register (int reg, CORE_ADDR k)
50{
51 pv_t v;
52
53 v.kind = pvk_register;
54 v.reg = reg;
55 v.k = k;
56
57 return v;
58}
59
60
61\f
62/* Arithmetic operations. */
63
64/* If one of *A and *B is a constant, and the other isn't, swap the
65 values as necessary to ensure that *B is the constant. This can
66 reduce the number of cases we need to analyze in the functions
67 below. */
68static void
69constant_last (pv_t *a, pv_t *b)
70{
71 if (a->kind == pvk_constant
72 && b->kind != pvk_constant)
73 {
74 pv_t temp = *a;
75 *a = *b;
76 *b = temp;
77 }
78}
79
80
81pv_t
82pv_add (pv_t a, pv_t b)
83{
84 constant_last (&a, &b);
85
86 /* We can add a constant to a register. */
87 if (a.kind == pvk_register
88 && b.kind == pvk_constant)
89 return pv_register (a.reg, a.k + b.k);
90
91 /* We can add a constant to another constant. */
92 else if (a.kind == pvk_constant
93 && b.kind == pvk_constant)
94 return pv_constant (a.k + b.k);
95
96 /* Anything else we don't know how to add. We don't have a
97 representation for, say, the sum of two registers, or a multiple
98 of a register's value (adding a register to itself). */
99 else
100 return pv_unknown ();
101}
102
103
104pv_t
105pv_add_constant (pv_t v, CORE_ADDR k)
106{
107 /* Rather than thinking of all the cases we can and can't handle,
108 we'll just let pv_add take care of that for us. */
109 return pv_add (v, pv_constant (k));
110}
111
112
113pv_t
114pv_subtract (pv_t a, pv_t b)
115{
116 /* This isn't quite the same as negating B and adding it to A, since
117 we don't have a representation for the negation of anything but a
118 constant. For example, we can't negate { pvk_register, R1, 10 },
119 but we do know that { pvk_register, R1, 10 } minus { pvk_register,
120 R1, 5 } is { pvk_constant, <ignored>, 5 }.
121
122 This means, for example, that we could subtract two stack
123 addresses; they're both relative to the original SP. Since the
124 frame pointer is set based on the SP, its value will be the
125 original SP plus some constant (probably zero), so we can use its
126 value just fine, too. */
127
128 constant_last (&a, &b);
129
130 /* We can subtract two constants. */
131 if (a.kind == pvk_constant
132 && b.kind == pvk_constant)
133 return pv_constant (a.k - b.k);
134
135 /* We can subtract a constant from a register. */
136 else if (a.kind == pvk_register
137 && b.kind == pvk_constant)
138 return pv_register (a.reg, a.k - b.k);
139
140 /* We can subtract a register from itself, yielding a constant. */
141 else if (a.kind == pvk_register
142 && b.kind == pvk_register
143 && a.reg == b.reg)
144 return pv_constant (a.k - b.k);
145
146 /* We don't know how to subtract anything else. */
147 else
148 return pv_unknown ();
149}
150
151
152pv_t
153pv_logical_and (pv_t a, pv_t b)
154{
155 constant_last (&a, &b);
156
157 /* We can 'and' two constants. */
158 if (a.kind == pvk_constant
159 && b.kind == pvk_constant)
160 return pv_constant (a.k & b.k);
161
162 /* We can 'and' anything with the constant zero. */
163 else if (b.kind == pvk_constant
164 && b.k == 0)
165 return pv_constant (0);
166
167 /* We can 'and' anything with ~0. */
168 else if (b.kind == pvk_constant
169 && b.k == ~ (CORE_ADDR) 0)
170 return a;
171
172 /* We can 'and' a register with itself. */
173 else if (a.kind == pvk_register
174 && b.kind == pvk_register
175 && a.reg == b.reg
176 && a.k == b.k)
177 return a;
178
179 /* Otherwise, we don't know. */
180 else
181 return pv_unknown ();
182}
183
184
185\f
186/* Examining prologue values. */
187
188int
189pv_is_identical (pv_t a, pv_t b)
190{
191 if (a.kind != b.kind)
192 return 0;
193
194 switch (a.kind)
195 {
196 case pvk_unknown:
197 return 1;
198 case pvk_constant:
199 return (a.k == b.k);
200 case pvk_register:
201 return (a.reg == b.reg && a.k == b.k);
202 default:
f3574227 203 gdb_assert_not_reached ("unexpected prologue value kind");
7d30c22d
JB
204 }
205}
206
207
208int
209pv_is_constant (pv_t a)
210{
211 return (a.kind == pvk_constant);
212}
213
214
215int
216pv_is_register (pv_t a, int r)
217{
218 return (a.kind == pvk_register
219 && a.reg == r);
220}
221
222
223int
224pv_is_register_k (pv_t a, int r, CORE_ADDR k)
225{
226 return (a.kind == pvk_register
227 && a.reg == r
228 && a.k == k);
229}
230
231
232enum pv_boolean
233pv_is_array_ref (pv_t addr, CORE_ADDR size,
234 pv_t array_addr, CORE_ADDR array_len,
235 CORE_ADDR elt_size,
236 int *i)
237{
238 /* Note that, since .k is a CORE_ADDR, and CORE_ADDR is unsigned, if
239 addr is *before* the start of the array, then this isn't going to
240 be negative... */
241 pv_t offset = pv_subtract (addr, array_addr);
242
243 if (offset.kind == pvk_constant)
244 {
245 /* This is a rather odd test. We want to know if the SIZE bytes
246 at ADDR don't overlap the array at all, so you'd expect it to
247 be an || expression: "if we're completely before || we're
248 completely after". But with unsigned arithmetic, things are
249 different: since it's a number circle, not a number line, the
250 right values for offset.k are actually one contiguous range. */
251 if (offset.k <= -size
252 && offset.k >= array_len * elt_size)
253 return pv_definite_no;
254 else if (offset.k % elt_size != 0
255 || size != elt_size)
256 return pv_maybe;
257 else
258 {
259 *i = offset.k / elt_size;
260 return pv_definite_yes;
261 }
262 }
263 else
264 return pv_maybe;
265}
266
267
268\f
269/* Areas. */
270
271
272/* A particular value known to be stored in an area.
273
274 Entries form a ring, sorted by unsigned offset from the area's base
275 register's value. Since entries can straddle the wrap-around point,
276 unsigned offsets form a circle, not a number line, so the list
277 itself is structured the same way --- there is no inherent head.
278 The entry with the lowest offset simply follows the entry with the
279 highest offset. Entries may abut, but never overlap. The area's
280 'entry' pointer points to an arbitrary node in the ring. */
f7b7ed97 281struct pv_area::area_entry
7d30c22d
JB
282{
283 /* Links in the doubly-linked ring. */
284 struct area_entry *prev, *next;
285
286 /* Offset of this entry's address from the value of the base
287 register. */
288 CORE_ADDR offset;
289
290 /* The size of this entry. Note that an entry may wrap around from
291 the end of the address space to the beginning. */
292 CORE_ADDR size;
293
294 /* The value stored here. */
295 pv_t value;
296};
297
298
f7b7ed97 299/* See prologue-value.h. */
7d30c22d 300
f7b7ed97
TT
301pv_area::pv_area (int base_reg, int addr_bit)
302 : m_base_reg (base_reg),
303 /* Remember that shift amounts equal to the type's width are
304 undefined. */
305 m_addr_mask (((((CORE_ADDR) 1 << (addr_bit - 1)) - 1) << 1) | 1),
306 m_entry (nullptr)
7d30c22d 307{
7d30c22d
JB
308}
309
f7b7ed97 310/* See prologue-value.h. */
7d30c22d 311
f7b7ed97
TT
312void
313pv_area::clear_entries ()
7d30c22d 314{
f7b7ed97 315 struct area_entry *e = m_entry;
7d30c22d
JB
316
317 if (e)
318 {
319 /* This needs to be a do-while loop, in order to actually
320 process the node being checked for in the terminating
321 condition. */
322 do
323 {
324 struct area_entry *next = e->next;
ad3bbd48 325
7d30c22d 326 xfree (e);
08f08ce6 327 e = next;
7d30c22d 328 }
f7b7ed97 329 while (e != m_entry);
7d30c22d 330
f7b7ed97 331 m_entry = 0;
7d30c22d
JB
332 }
333}
334
335
f7b7ed97 336pv_area::~pv_area ()
7d30c22d 337{
f7b7ed97 338 clear_entries ();
7d30c22d
JB
339}
340
341
f7b7ed97 342/* See prologue-value.h. */
7d30c22d 343
a900ff72 344bool
f7b7ed97 345pv_area::store_would_trash (pv_t addr)
7d30c22d
JB
346{
347 /* It may seem odd that pvk_constant appears here --- after all,
348 that's the case where we know the most about the address! But
349 pv_areas are always relative to a register, and we don't know the
350 value of the register, so we can't compare entry addresses to
351 constants. */
352 return (addr.kind == pvk_unknown
353 || addr.kind == pvk_constant
f7b7ed97 354 || (addr.kind == pvk_register && addr.reg != m_base_reg));
7d30c22d
JB
355}
356
357
f7b7ed97 358/* See prologue-value.h. */
7d30c22d 359
f7b7ed97
TT
360struct pv_area::area_entry *
361pv_area::find_entry (CORE_ADDR offset)
7d30c22d 362{
f7b7ed97 363 struct area_entry *e = m_entry;
7d30c22d
JB
364
365 if (! e)
366 return 0;
367
368 /* If the next entry would be better than the current one, then scan
369 forward. Since we use '<' in this loop, it always terminates.
370
371 Note that, even setting aside the addr_mask stuff, we must not
372 simplify this, in high school algebra fashion, to
373 (e->next->offset < e->offset), because of the way < interacts
374 with wrap-around. We have to subtract offset from both sides to
375 make sure both things we're comparing are on the same side of the
376 discontinuity. */
f7b7ed97
TT
377 while (((e->next->offset - offset) & m_addr_mask)
378 < ((e->offset - offset) & m_addr_mask))
7d30c22d
JB
379 e = e->next;
380
381 /* If the previous entry would be better than the current one, then
382 scan backwards. */
f7b7ed97
TT
383 while (((e->prev->offset - offset) & m_addr_mask)
384 < ((e->offset - offset) & m_addr_mask))
7d30c22d
JB
385 e = e->prev;
386
387 /* In case there's some locality to the searches, set the area's
388 pointer to the entry we've found. */
f7b7ed97 389 m_entry = e;
7d30c22d
JB
390
391 return e;
392}
393
394
f7b7ed97
TT
395/* See prologue-value.h. */
396
397int
398pv_area::overlaps (struct area_entry *entry, CORE_ADDR offset, CORE_ADDR size)
7d30c22d
JB
399{
400 /* Think carefully about wrap-around before simplifying this. */
f7b7ed97
TT
401 return (((entry->offset - offset) & m_addr_mask) < size
402 || ((offset - entry->offset) & m_addr_mask) < entry->size);
7d30c22d
JB
403}
404
405
f7b7ed97
TT
406/* See prologue-value.h. */
407
7d30c22d 408void
f7b7ed97 409pv_area::store (pv_t addr, CORE_ADDR size, pv_t value)
7d30c22d
JB
410{
411 /* Remove any (potentially) overlapping entries. */
f7b7ed97
TT
412 if (store_would_trash (addr))
413 clear_entries ();
7d30c22d
JB
414 else
415 {
416 CORE_ADDR offset = addr.k;
f7b7ed97 417 struct area_entry *e = find_entry (offset);
7d30c22d
JB
418
419 /* Delete all entries that we would overlap. */
f7b7ed97 420 while (e && overlaps (e, offset, size))
7d30c22d
JB
421 {
422 struct area_entry *next = (e->next == e) ? 0 : e->next;
ad3bbd48 423
7d30c22d
JB
424 e->prev->next = e->next;
425 e->next->prev = e->prev;
426
427 xfree (e);
428 e = next;
429 }
430
431 /* Move the area's pointer to the next remaining entry. This
432 will also zero the pointer if we've deleted all the entries. */
f7b7ed97 433 m_entry = e;
7d30c22d
JB
434 }
435
f7b7ed97 436 /* Now, there are no entries overlapping us, and m_entry is
7d30c22d
JB
437 either zero or pointing at the closest entry after us. We can
438 just insert ourselves before that.
439
440 But if we're storing an unknown value, don't bother --- that's
441 the default. */
442 if (value.kind == pvk_unknown)
443 return;
444 else
445 {
446 CORE_ADDR offset = addr.k;
8d749320 447 struct area_entry *e = XNEW (struct area_entry);
ad3bbd48 448
7d30c22d
JB
449 e->offset = offset;
450 e->size = size;
451 e->value = value;
452
f7b7ed97 453 if (m_entry)
7d30c22d 454 {
f7b7ed97
TT
455 e->prev = m_entry->prev;
456 e->next = m_entry;
7d30c22d
JB
457 e->prev->next = e->next->prev = e;
458 }
459 else
460 {
461 e->prev = e->next = e;
f7b7ed97 462 m_entry = e;
7d30c22d
JB
463 }
464 }
465}
466
467
f7b7ed97
TT
468/* See prologue-value.h. */
469
7d30c22d 470pv_t
f7b7ed97 471pv_area::fetch (pv_t addr, CORE_ADDR size)
7d30c22d
JB
472{
473 /* If we have no entries, or we can't decide how ADDR relates to the
474 entries we do have, then the value is unknown. */
f7b7ed97
TT
475 if (! m_entry
476 || store_would_trash (addr))
7d30c22d
JB
477 return pv_unknown ();
478 else
479 {
480 CORE_ADDR offset = addr.k;
f7b7ed97 481 struct area_entry *e = find_entry (offset);
7d30c22d
JB
482
483 /* If this entry exactly matches what we're looking for, then
484 we're set. Otherwise, say it's unknown. */
485 if (e->offset == offset && e->size == size)
486 return e->value;
487 else
488 return pv_unknown ();
489 }
490}
491
492
f7b7ed97
TT
493/* See prologue-value.h. */
494
a900ff72 495bool
f7b7ed97 496pv_area::find_reg (struct gdbarch *gdbarch, int reg, CORE_ADDR *offset_p)
7d30c22d 497{
f7b7ed97 498 struct area_entry *e = m_entry;
7d30c22d
JB
499
500 if (e)
501 do
502 {
503 if (e->value.kind == pvk_register
504 && e->value.reg == reg
505 && e->value.k == 0
506 && e->size == register_size (gdbarch, reg))
507 {
508 if (offset_p)
509 *offset_p = e->offset;
a900ff72 510 return true;
7d30c22d
JB
511 }
512
513 e = e->next;
514 }
f7b7ed97 515 while (e != m_entry);
7d30c22d 516
a900ff72 517 return false;
7d30c22d
JB
518}
519
520
f7b7ed97
TT
521/* See prologue-value.h. */
522
7d30c22d 523void
f7b7ed97
TT
524pv_area::scan (void (*func) (void *closure,
525 pv_t addr,
526 CORE_ADDR size,
527 pv_t value),
528 void *closure)
7d30c22d 529{
f7b7ed97 530 struct area_entry *e = m_entry;
7d30c22d
JB
531 pv_t addr;
532
533 addr.kind = pvk_register;
f7b7ed97 534 addr.reg = m_base_reg;
7d30c22d
JB
535
536 if (e)
537 do
538 {
539 addr.k = e->offset;
540 func (closure, addr, e->size, e->value);
541 e = e->next;
542 }
f7b7ed97 543 while (e != m_entry);
7d30c22d 544}
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