1 /* Prologue value handling for GDB.
2 Copyright (C) 2003-2016 Free Software Foundation, Inc.
4 This file is part of GDB.
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
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
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.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
20 #include "prologue-value.h"
29 pv_t v
= { pvk_unknown
, 0, 0 };
36 pv_constant (CORE_ADDR k
)
40 v
.kind
= pvk_constant
;
41 v
.reg
= -1; /* for debugging */
49 pv_register (int reg
, CORE_ADDR k
)
53 v
.kind
= pvk_register
;
62 /* Arithmetic operations. */
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
69 constant_last (pv_t
*a
, pv_t
*b
)
71 if (a
->kind
== pvk_constant
72 && b
->kind
!= pvk_constant
)
82 pv_add (pv_t a
, pv_t b
)
84 constant_last (&a
, &b
);
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
);
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
);
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). */
100 return pv_unknown ();
105 pv_add_constant (pv_t v
, CORE_ADDR k
)
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
));
114 pv_subtract (pv_t a
, pv_t b
)
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 }.
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. */
128 constant_last (&a
, &b
);
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
);
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
);
140 /* We can subtract a register from itself, yielding a constant. */
141 else if (a
.kind
== pvk_register
142 && b
.kind
== pvk_register
144 return pv_constant (a
.k
- b
.k
);
146 /* We don't know how to subtract anything else. */
148 return pv_unknown ();
153 pv_logical_and (pv_t a
, pv_t b
)
155 constant_last (&a
, &b
);
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
);
162 /* We can 'and' anything with the constant zero. */
163 else if (b
.kind
== pvk_constant
165 return pv_constant (0);
167 /* We can 'and' anything with ~0. */
168 else if (b
.kind
== pvk_constant
169 && b
.k
== ~ (CORE_ADDR
) 0)
172 /* We can 'and' a register with itself. */
173 else if (a
.kind
== pvk_register
174 && b
.kind
== pvk_register
179 /* Otherwise, we don't know. */
181 return pv_unknown ();
186 /* Examining prologue values. */
189 pv_is_identical (pv_t a
, pv_t b
)
191 if (a
.kind
!= b
.kind
)
201 return (a
.reg
== b
.reg
&& a
.k
== b
.k
);
203 gdb_assert_not_reached ("unexpected prologue value kind");
209 pv_is_constant (pv_t a
)
211 return (a
.kind
== pvk_constant
);
216 pv_is_register (pv_t a
, int r
)
218 return (a
.kind
== pvk_register
224 pv_is_register_k (pv_t a
, int r
, CORE_ADDR k
)
226 return (a
.kind
== pvk_register
233 pv_is_array_ref (pv_t addr
, CORE_ADDR size
,
234 pv_t array_addr
, CORE_ADDR array_len
,
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
241 pv_t offset
= pv_subtract (addr
, array_addr
);
243 if (offset
.kind
== pvk_constant
)
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
259 *i
= offset
.k
/ elt_size
;
260 return pv_definite_yes
;
272 /* A particular value known to be stored in an area.
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. */
283 /* Links in the doubly-linked ring. */
284 struct area_entry
*prev
, *next
;
286 /* Offset of this entry's address from the value of the base
290 /* The size of this entry. Note that an entry may wrap around from
291 the end of the address space to the beginning. */
294 /* The value stored here. */
301 /* This area's base register. */
304 /* The mask to apply to addresses, to make the wrap-around happen at
308 /* An element of the doubly-linked ring of entries, or zero if we
310 struct area_entry
*entry
;
315 make_pv_area (int base_reg
, int addr_bit
)
317 struct pv_area
*a
= XNEW (struct pv_area
);
319 memset (a
, 0, sizeof (*a
));
321 a
->base_reg
= base_reg
;
324 /* Remember that shift amounts equal to the type's width are
326 a
->addr_mask
= ((((CORE_ADDR
) 1 << (addr_bit
- 1)) - 1) << 1) | 1;
332 /* Delete all entries from AREA. */
334 clear_entries (struct pv_area
*area
)
336 struct area_entry
*e
= area
->entry
;
340 /* This needs to be a do-while loop, in order to actually
341 process the node being checked for in the terminating
345 struct area_entry
*next
= e
->next
;
350 while (e
!= area
->entry
);
358 free_pv_area (struct pv_area
*area
)
360 clear_entries (area
);
366 do_free_pv_area_cleanup (void *arg
)
368 free_pv_area ((struct pv_area
*) arg
);
373 make_cleanup_free_pv_area (struct pv_area
*area
)
375 return make_cleanup (do_free_pv_area_cleanup
, (void *) area
);
380 pv_area_store_would_trash (struct pv_area
*area
, pv_t addr
)
382 /* It may seem odd that pvk_constant appears here --- after all,
383 that's the case where we know the most about the address! But
384 pv_areas are always relative to a register, and we don't know the
385 value of the register, so we can't compare entry addresses to
387 return (addr
.kind
== pvk_unknown
388 || addr
.kind
== pvk_constant
389 || (addr
.kind
== pvk_register
&& addr
.reg
!= area
->base_reg
));
393 /* Return a pointer to the first entry we hit in AREA starting at
394 OFFSET and going forward.
396 This may return zero, if AREA has no entries.
398 And since the entries are a ring, this may return an entry that
399 entirely precedes OFFSET. This is the correct behavior: depending
400 on the sizes involved, we could still overlap such an area, with
402 static struct area_entry
*
403 find_entry (struct pv_area
*area
, CORE_ADDR offset
)
405 struct area_entry
*e
= area
->entry
;
410 /* If the next entry would be better than the current one, then scan
411 forward. Since we use '<' in this loop, it always terminates.
413 Note that, even setting aside the addr_mask stuff, we must not
414 simplify this, in high school algebra fashion, to
415 (e->next->offset < e->offset), because of the way < interacts
416 with wrap-around. We have to subtract offset from both sides to
417 make sure both things we're comparing are on the same side of the
419 while (((e
->next
->offset
- offset
) & area
->addr_mask
)
420 < ((e
->offset
- offset
) & area
->addr_mask
))
423 /* If the previous entry would be better than the current one, then
425 while (((e
->prev
->offset
- offset
) & area
->addr_mask
)
426 < ((e
->offset
- offset
) & area
->addr_mask
))
429 /* In case there's some locality to the searches, set the area's
430 pointer to the entry we've found. */
437 /* Return non-zero if the SIZE bytes at OFFSET would overlap ENTRY;
438 return zero otherwise. AREA is the area to which ENTRY belongs. */
440 overlaps (struct pv_area
*area
,
441 struct area_entry
*entry
,
445 /* Think carefully about wrap-around before simplifying this. */
446 return (((entry
->offset
- offset
) & area
->addr_mask
) < size
447 || ((offset
- entry
->offset
) & area
->addr_mask
) < entry
->size
);
452 pv_area_store (struct pv_area
*area
,
457 /* Remove any (potentially) overlapping entries. */
458 if (pv_area_store_would_trash (area
, addr
))
459 clear_entries (area
);
462 CORE_ADDR offset
= addr
.k
;
463 struct area_entry
*e
= find_entry (area
, offset
);
465 /* Delete all entries that we would overlap. */
466 while (e
&& overlaps (area
, e
, offset
, size
))
468 struct area_entry
*next
= (e
->next
== e
) ? 0 : e
->next
;
470 e
->prev
->next
= e
->next
;
471 e
->next
->prev
= e
->prev
;
477 /* Move the area's pointer to the next remaining entry. This
478 will also zero the pointer if we've deleted all the entries. */
482 /* Now, there are no entries overlapping us, and area->entry is
483 either zero or pointing at the closest entry after us. We can
484 just insert ourselves before that.
486 But if we're storing an unknown value, don't bother --- that's
488 if (value
.kind
== pvk_unknown
)
492 CORE_ADDR offset
= addr
.k
;
493 struct area_entry
*e
= XNEW (struct area_entry
);
501 e
->prev
= area
->entry
->prev
;
502 e
->next
= area
->entry
;
503 e
->prev
->next
= e
->next
->prev
= e
;
507 e
->prev
= e
->next
= e
;
515 pv_area_fetch (struct pv_area
*area
, pv_t addr
, CORE_ADDR size
)
517 /* If we have no entries, or we can't decide how ADDR relates to the
518 entries we do have, then the value is unknown. */
520 || pv_area_store_would_trash (area
, addr
))
521 return pv_unknown ();
524 CORE_ADDR offset
= addr
.k
;
525 struct area_entry
*e
= find_entry (area
, offset
);
527 /* If this entry exactly matches what we're looking for, then
528 we're set. Otherwise, say it's unknown. */
529 if (e
->offset
== offset
&& e
->size
== size
)
532 return pv_unknown ();
538 pv_area_find_reg (struct pv_area
*area
,
539 struct gdbarch
*gdbarch
,
543 struct area_entry
*e
= area
->entry
;
548 if (e
->value
.kind
== pvk_register
549 && e
->value
.reg
== reg
551 && e
->size
== register_size (gdbarch
, reg
))
554 *offset_p
= e
->offset
;
560 while (e
!= area
->entry
);
567 pv_area_scan (struct pv_area
*area
,
568 void (*func
) (void *closure
,
574 struct area_entry
*e
= area
->entry
;
577 addr
.kind
= pvk_register
;
578 addr
.reg
= area
->base_reg
;
584 func (closure
, addr
, e
->size
, e
->value
);
587 while (e
!= area
->entry
);
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