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+/* Prologue value handling for GDB.
+ Copyright 2003, 2004, 2005 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to:
+
+ Free Software Foundation, Inc.
+ 51 Franklin St - Fifth Floor
+ Boston, MA 02110-1301
+ USA */
+
+#include "defs.h"
+#include "gdb_string.h"
+#include "gdb_assert.h"
+#include "prologue-value.h"
+#include "regcache.h"
+
+
+/* Constructors. */
+
+pv_t
+pv_unknown (void)
+{
+ pv_t v = { pvk_unknown, 0, 0 };
+
+ return v;
+}
+
+
+pv_t
+pv_constant (CORE_ADDR k)
+{
+ pv_t v;
+
+ v.kind = pvk_constant;
+ v.reg = -1; /* for debugging */
+ v.k = k;
+
+ return v;
+}
+
+
+pv_t
+pv_register (int reg, CORE_ADDR k)
+{
+ pv_t v;
+
+ v.kind = pvk_register;
+ v.reg = reg;
+ v.k = k;
+
+ return v;
+}
+
+
+
+/* Arithmetic operations. */
+
+/* If one of *A and *B is a constant, and the other isn't, swap the
+ values as necessary to ensure that *B is the constant. This can
+ reduce the number of cases we need to analyze in the functions
+ below. */
+static void
+constant_last (pv_t *a, pv_t *b)
+{
+ if (a->kind == pvk_constant
+ && b->kind != pvk_constant)
+ {
+ pv_t temp = *a;
+ *a = *b;
+ *b = temp;
+ }
+}
+
+
+pv_t
+pv_add (pv_t a, pv_t b)
+{
+ constant_last (&a, &b);
+
+ /* We can add a constant to a register. */
+ if (a.kind == pvk_register
+ && b.kind == pvk_constant)
+ return pv_register (a.reg, a.k + b.k);
+
+ /* We can add a constant to another constant. */
+ else if (a.kind == pvk_constant
+ && b.kind == pvk_constant)
+ return pv_constant (a.k + b.k);
+
+ /* Anything else we don't know how to add. We don't have a
+ representation for, say, the sum of two registers, or a multiple
+ of a register's value (adding a register to itself). */
+ else
+ return pv_unknown ();
+}
+
+
+pv_t
+pv_add_constant (pv_t v, CORE_ADDR k)
+{
+ /* Rather than thinking of all the cases we can and can't handle,
+ we'll just let pv_add take care of that for us. */
+ return pv_add (v, pv_constant (k));
+}
+
+
+pv_t
+pv_subtract (pv_t a, pv_t b)
+{
+ /* This isn't quite the same as negating B and adding it to A, since
+ we don't have a representation for the negation of anything but a
+ constant. For example, we can't negate { pvk_register, R1, 10 },
+ but we do know that { pvk_register, R1, 10 } minus { pvk_register,
+ R1, 5 } is { pvk_constant, <ignored>, 5 }.
+
+ This means, for example, that we could subtract two stack
+ addresses; they're both relative to the original SP. Since the
+ frame pointer is set based on the SP, its value will be the
+ original SP plus some constant (probably zero), so we can use its
+ value just fine, too. */
+
+ constant_last (&a, &b);
+
+ /* We can subtract two constants. */
+ if (a.kind == pvk_constant
+ && b.kind == pvk_constant)
+ return pv_constant (a.k - b.k);
+
+ /* We can subtract a constant from a register. */
+ else if (a.kind == pvk_register
+ && b.kind == pvk_constant)
+ return pv_register (a.reg, a.k - b.k);
+
+ /* We can subtract a register from itself, yielding a constant. */
+ else if (a.kind == pvk_register
+ && b.kind == pvk_register
+ && a.reg == b.reg)
+ return pv_constant (a.k - b.k);
+
+ /* We don't know how to subtract anything else. */
+ else
+ return pv_unknown ();
+}
+
+
+pv_t
+pv_logical_and (pv_t a, pv_t b)
+{
+ constant_last (&a, &b);
+
+ /* We can 'and' two constants. */
+ if (a.kind == pvk_constant
+ && b.kind == pvk_constant)
+ return pv_constant (a.k & b.k);
+
+ /* We can 'and' anything with the constant zero. */
+ else if (b.kind == pvk_constant
+ && b.k == 0)
+ return pv_constant (0);
+
+ /* We can 'and' anything with ~0. */
+ else if (b.kind == pvk_constant
+ && b.k == ~ (CORE_ADDR) 0)
+ return a;
+
+ /* We can 'and' a register with itself. */
+ else if (a.kind == pvk_register
+ && b.kind == pvk_register
+ && a.reg == b.reg
+ && a.k == b.k)
+ return a;
+
+ /* Otherwise, we don't know. */
+ else
+ return pv_unknown ();
+}
+
+
+
+/* Examining prologue values. */
+
+int
+pv_is_identical (pv_t a, pv_t b)
+{
+ if (a.kind != b.kind)
+ return 0;
+
+ switch (a.kind)
+ {
+ case pvk_unknown:
+ return 1;
+ case pvk_constant:
+ return (a.k == b.k);
+ case pvk_register:
+ return (a.reg == b.reg && a.k == b.k);
+ default:
+ gdb_assert (0);
+ }
+}
+
+
+int
+pv_is_constant (pv_t a)
+{
+ return (a.kind == pvk_constant);
+}
+
+
+int
+pv_is_register (pv_t a, int r)
+{
+ return (a.kind == pvk_register
+ && a.reg == r);
+}
+
+
+int
+pv_is_register_k (pv_t a, int r, CORE_ADDR k)
+{
+ return (a.kind == pvk_register
+ && a.reg == r
+ && a.k == k);
+}
+
+
+enum pv_boolean
+pv_is_array_ref (pv_t addr, CORE_ADDR size,
+ pv_t array_addr, CORE_ADDR array_len,
+ CORE_ADDR elt_size,
+ int *i)
+{
+ /* Note that, since .k is a CORE_ADDR, and CORE_ADDR is unsigned, if
+ addr is *before* the start of the array, then this isn't going to
+ be negative... */
+ pv_t offset = pv_subtract (addr, array_addr);
+
+ if (offset.kind == pvk_constant)
+ {
+ /* This is a rather odd test. We want to know if the SIZE bytes
+ at ADDR don't overlap the array at all, so you'd expect it to
+ be an || expression: "if we're completely before || we're
+ completely after". But with unsigned arithmetic, things are
+ different: since it's a number circle, not a number line, the
+ right values for offset.k are actually one contiguous range. */
+ if (offset.k <= -size
+ && offset.k >= array_len * elt_size)
+ return pv_definite_no;
+ else if (offset.k % elt_size != 0
+ || size != elt_size)
+ return pv_maybe;
+ else
+ {
+ *i = offset.k / elt_size;
+ return pv_definite_yes;
+ }
+ }
+ else
+ return pv_maybe;
+}
+
+
+
+/* Areas. */
+
+
+/* A particular value known to be stored in an area.
+
+ Entries form a ring, sorted by unsigned offset from the area's base
+ register's value. Since entries can straddle the wrap-around point,
+ unsigned offsets form a circle, not a number line, so the list
+ itself is structured the same way --- there is no inherent head.
+ The entry with the lowest offset simply follows the entry with the
+ highest offset. Entries may abut, but never overlap. The area's
+ 'entry' pointer points to an arbitrary node in the ring. */
+struct area_entry
+{
+ /* Links in the doubly-linked ring. */
+ struct area_entry *prev, *next;
+
+ /* Offset of this entry's address from the value of the base
+ register. */
+ CORE_ADDR offset;
+
+ /* The size of this entry. Note that an entry may wrap around from
+ the end of the address space to the beginning. */
+ CORE_ADDR size;
+
+ /* The value stored here. */
+ pv_t value;
+};
+
+
+struct pv_area
+{
+ /* This area's base register. */
+ int base_reg;
+
+ /* The mask to apply to addresses, to make the wrap-around happen at
+ the right place. */
+ CORE_ADDR addr_mask;
+
+ /* An element of the doubly-linked ring of entries, or zero if we
+ have none. */
+ struct area_entry *entry;
+};
+
+
+struct pv_area *
+make_pv_area (int base_reg)
+{
+ struct pv_area *a = (struct pv_area *) xmalloc (sizeof (*a));
+
+ memset (a, 0, sizeof (*a));
+
+ a->base_reg = base_reg;
+ a->entry = 0;
+
+ /* Remember that shift amounts equal to the type's width are
+ undefined. */
+ a->addr_mask = ((((CORE_ADDR) 1 << (TARGET_ADDR_BIT - 1)) - 1) << 1) | 1;
+
+ return a;
+}
+
+
+/* Delete all entries from AREA. */
+static void
+clear_entries (struct pv_area *area)
+{
+ struct area_entry *e = area->entry;
+
+ if (e)
+ {
+ /* This needs to be a do-while loop, in order to actually
+ process the node being checked for in the terminating
+ condition. */
+ do
+ {
+ struct area_entry *next = e->next;
+ xfree (e);
+ }
+ while (e != area->entry);
+
+ area->entry = 0;
+ }
+}
+
+
+void
+free_pv_area (struct pv_area *area)
+{
+ clear_entries (area);
+ xfree (area);
+}
+
+
+static void
+do_free_pv_area_cleanup (void *arg)
+{
+ free_pv_area ((struct pv_area *) arg);
+}
+
+
+struct cleanup *
+make_cleanup_free_pv_area (struct pv_area *area)
+{
+ return make_cleanup (do_free_pv_area_cleanup, (void *) area);
+}
+
+
+int
+pv_area_store_would_trash (struct pv_area *area, pv_t addr)
+{
+ /* It may seem odd that pvk_constant appears here --- after all,
+ that's the case where we know the most about the address! But
+ pv_areas are always relative to a register, and we don't know the
+ value of the register, so we can't compare entry addresses to
+ constants. */
+ return (addr.kind == pvk_unknown
+ || addr.kind == pvk_constant
+ || (addr.kind == pvk_register && addr.reg != area->base_reg));
+}
+
+
+/* Return a pointer to the first entry we hit in AREA starting at
+ OFFSET and going forward.
+
+ This may return zero, if AREA has no entries.
+
+ And since the entries are a ring, this may return an entry that
+ entirely preceeds OFFSET. This is the correct behavior: depending
+ on the sizes involved, we could still overlap such an area, with
+ wrap-around. */
+static struct area_entry *
+find_entry (struct pv_area *area, CORE_ADDR offset)
+{
+ struct area_entry *e = area->entry;
+
+ if (! e)
+ return 0;
+
+ /* If the next entry would be better than the current one, then scan
+ forward. Since we use '<' in this loop, it always terminates.
+
+ Note that, even setting aside the addr_mask stuff, we must not
+ simplify this, in high school algebra fashion, to
+ (e->next->offset < e->offset), because of the way < interacts
+ with wrap-around. We have to subtract offset from both sides to
+ make sure both things we're comparing are on the same side of the
+ discontinuity. */
+ while (((e->next->offset - offset) & area->addr_mask)
+ < ((e->offset - offset) & area->addr_mask))
+ e = e->next;
+
+ /* If the previous entry would be better than the current one, then
+ scan backwards. */
+ while (((e->prev->offset - offset) & area->addr_mask)
+ < ((e->offset - offset) & area->addr_mask))
+ e = e->prev;
+
+ /* In case there's some locality to the searches, set the area's
+ pointer to the entry we've found. */
+ area->entry = e;
+
+ return e;
+}
+
+
+/* Return non-zero if the SIZE bytes at OFFSET would overlap ENTRY;
+ return zero otherwise. AREA is the area to which ENTRY belongs. */
+static int
+overlaps (struct pv_area *area,
+ struct area_entry *entry,
+ CORE_ADDR offset,
+ CORE_ADDR size)
+{
+ /* Think carefully about wrap-around before simplifying this. */
+ return (((entry->offset - offset) & area->addr_mask) < size
+ || ((offset - entry->offset) & area->addr_mask) < entry->size);
+}
+
+
+void
+pv_area_store (struct pv_area *area,
+ pv_t addr,
+ CORE_ADDR size,
+ pv_t value)
+{
+ /* Remove any (potentially) overlapping entries. */
+ if (pv_area_store_would_trash (area, addr))
+ clear_entries (area);
+ else
+ {
+ CORE_ADDR offset = addr.k;
+ struct area_entry *e = find_entry (area, offset);
+
+ /* Delete all entries that we would overlap. */
+ while (e && overlaps (area, e, offset, size))
+ {
+ struct area_entry *next = (e->next == e) ? 0 : e->next;
+ e->prev->next = e->next;
+ e->next->prev = e->prev;
+
+ xfree (e);
+ e = next;
+ }
+
+ /* Move the area's pointer to the next remaining entry. This
+ will also zero the pointer if we've deleted all the entries. */
+ area->entry = e;
+ }
+
+ /* Now, there are no entries overlapping us, and area->entry is
+ either zero or pointing at the closest entry after us. We can
+ just insert ourselves before that.
+
+ But if we're storing an unknown value, don't bother --- that's
+ the default. */
+ if (value.kind == pvk_unknown)
+ return;
+ else
+ {
+ CORE_ADDR offset = addr.k;
+ struct area_entry *e = (struct area_entry *) xmalloc (sizeof (*e));
+ e->offset = offset;
+ e->size = size;
+ e->value = value;
+
+ if (area->entry)
+ {
+ e->prev = area->entry->prev;
+ e->next = area->entry;
+ e->prev->next = e->next->prev = e;
+ }
+ else
+ {
+ e->prev = e->next = e;
+ area->entry = e;
+ }
+ }
+}
+
+
+pv_t
+pv_area_fetch (struct pv_area *area, pv_t addr, CORE_ADDR size)
+{
+ /* If we have no entries, or we can't decide how ADDR relates to the
+ entries we do have, then the value is unknown. */
+ if (! area->entry
+ || pv_area_store_would_trash (area, addr))
+ return pv_unknown ();
+ else
+ {
+ CORE_ADDR offset = addr.k;
+ struct area_entry *e = find_entry (area, offset);
+
+ /* If this entry exactly matches what we're looking for, then
+ we're set. Otherwise, say it's unknown. */
+ if (e->offset == offset && e->size == size)
+ return e->value;
+ else
+ return pv_unknown ();
+ }
+}
+
+
+int
+pv_area_find_reg (struct pv_area *area,
+ struct gdbarch *gdbarch,
+ int reg,
+ CORE_ADDR *offset_p)
+{
+ struct area_entry *e = area->entry;
+
+ if (e)
+ do
+ {
+ if (e->value.kind == pvk_register
+ && e->value.reg == reg
+ && e->value.k == 0
+ && e->size == register_size (gdbarch, reg))
+ {
+ if (offset_p)
+ *offset_p = e->offset;
+ return 1;
+ }
+
+ e = e->next;
+ }
+ while (e != area->entry);
+
+ return 0;
+}
+
+
+void
+pv_area_scan (struct pv_area *area,
+ void (*func) (void *closure,
+ pv_t addr,
+ CORE_ADDR size,
+ pv_t value),
+ void *closure)
+{
+ struct area_entry *e = area->entry;
+ pv_t addr;
+
+ addr.kind = pvk_register;
+ addr.reg = area->base_reg;
+
+ if (e)
+ do
+ {
+ addr.k = e->offset;
+ func (closure, addr, e->size, e->value);
+ e = e->next;
+ }
+ while (e != area->entry);
+}