http://sourceware.org/ml/gdb-cvs/2009-07/msg00143.html
2009-07-21 Daniel Jacobowitz <dan@codesourcery.com>
Vladimir Prus <vladimir@codesourcery.com>
* valops.c (value_fetch_lazy): Handle bitfields explicitly.
(value_assign): Remove unnecessary FIXME. Honor the container
type of bitfields if possible.
* value.c (struct value): Add parent field.
(value_parent): New function.
(value_free): Free the parent also.
(value_copy): Copy the parent also.
(value_primitive_field): Do not read the contents of a lazy
value to create a child bitfield value. Set bitpos and offset
according to the container type if possible.
(unpack_bits_as_long): Rename from unpack_field_as_long. Take
field_type, bitpos, and bitsize instead of type and fieldno.
(unpack_field_as_long): Use unpack_bits_as_long.
* value.h (value_parent, unpack_bits_as_long): New prototypes.
[ Reverted, backported for Fedora. ]
--- ./gdb/valops.c 2009-08-28 19:27:30.000000000 +0200
+++ ./gdb/valops.c 2009-08-28 19:27:59.000000000 +0200
@@ -689,25 +689,7 @@ value_fetch_lazy (struct value *val)
{
gdb_assert (value_lazy (val));
allocate_value_contents (val);
- if (value_bitsize (val))
- {
- /* To read a lazy bitfield, read the entire enclosing value. This
- prevents reading the same block of (possibly volatile) memory once
- per bitfield. It would be even better to read only the containing
- word, but we have no way to record that just specific bits of a
- value have been fetched. */
- struct type *type = check_typedef (value_type (val));
- enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (type));
- struct value *parent = value_parent (val);
- LONGEST offset = value_offset (val);
- LONGEST num = unpack_bits_as_long (value_type (val),
- value_contents (parent) + offset,
- value_bitpos (val),
- value_bitsize (val));
- int length = TYPE_LENGTH (type);
- store_signed_integer (value_contents_raw (val), length, byte_order, num);
- }
- else if (VALUE_LVAL (val) == lval_memory)
+ if (VALUE_LVAL (val) == lval_memory)
{
CORE_ADDR addr = value_raw_address (val);
@@ -883,20 +865,13 @@ value_assign (struct value *toval, struc
if (value_bitsize (toval))
{
+ /* We assume that the argument to read_memory is in units
+ of host chars. FIXME: Is that correct? */
changed_len = (value_bitpos (toval)
+ value_bitsize (toval)
+ HOST_CHAR_BIT - 1)
/ HOST_CHAR_BIT;
- /* If we can read-modify-write exactly the size of the
- containing type (e.g. short or int) then do so. This
- is safer for volatile bitfields mapped to hardware
- registers. */
- if (changed_len < TYPE_LENGTH (type)
- && TYPE_LENGTH (type) <= (int) sizeof (LONGEST)
- && ((LONGEST) value_address (toval) % TYPE_LENGTH (type)) == 0)
- changed_len = TYPE_LENGTH (type);
-
if (changed_len > (int) sizeof (LONGEST))
error (_("Can't handle bitfields which don't fit in a %d bit word."),
(int) sizeof (LONGEST) * HOST_CHAR_BIT);
--- ./gdb/value.c 2009-08-28 19:27:29.000000000 +0200
+++ ./gdb/value.c 2009-08-28 19:28:34.000000000 +0200
@@ -110,11 +110,6 @@ struct value
gdbarch_bits_big_endian=1 targets, it is the position of the MSB. */
int bitpos;
- /* Only used for bitfields; the containing value. This allows a
- single read from the target when displaying multiple
- bitfields. */
- struct value *parent;
-
/* Frame register value is relative to. This will be described in
the lval enum above as "lval_register". */
struct frame_id frame_id;
@@ -392,12 +387,6 @@ set_value_bitsize (struct value *value,
value->bitsize = bit;
}
-struct value *
-value_parent (struct value *value)
-{
- return value->parent;
-}
-
gdb_byte *
value_contents_raw (struct value *value)
{
@@ -617,11 +606,6 @@ value_free (struct value *val)
if (val->reference_count > 0)
return;
- /* If there's an associated parent value, drop our reference to
- it. */
- if (val->parent != NULL)
- value_free (val->parent);
-
type_decref (val->type);
type_decref (val->enclosing_type);
@@ -750,9 +734,6 @@ value_copy (struct value *arg)
TYPE_LENGTH (value_enclosing_type (arg)));
}
- val->parent = arg->parent;
- if (val->parent)
- value_incref (val->parent);
if (VALUE_LVAL (val) == lval_computed)
{
struct lval_funcs *funcs = val->location.computed.funcs;
@@ -1946,28 +1927,15 @@ value_primitive_field (struct value *arg
if (TYPE_FIELD_BITSIZE (arg_type, fieldno))
{
- /* Create a new value for the bitfield, with bitpos and bitsize
- set. If possible, arrange offset and bitpos so that we can
- do a single aligned read of the size of the containing type.
- Otherwise, adjust offset to the byte containing the first
- bit. Assume that the address, offset, and embedded offset
- are sufficiently aligned. */
- int bitpos = TYPE_FIELD_BITPOS (arg_type, fieldno);
- int container_bitsize = TYPE_LENGTH (type) * 8;
-
- v = allocate_value_lazy (type);
+ v = value_from_longest (type,
+ unpack_field_as_long (arg_type,
+ value_contents (arg1)
+ + offset,
+ fieldno));
+ v->bitpos = TYPE_FIELD_BITPOS (arg_type, fieldno) % 8;
v->bitsize = TYPE_FIELD_BITSIZE (arg_type, fieldno);
- if ((bitpos % container_bitsize) + v->bitsize <= container_bitsize
- && TYPE_LENGTH (type) <= (int) sizeof (LONGEST))
- v->bitpos = bitpos % container_bitsize;
- else
- v->bitpos = bitpos % 8;
- v->offset = value_offset (arg1) + value_embedded_offset (arg1)
- + (bitpos - v->bitpos) / 8;
- v->parent = arg1;
- value_incref (v->parent);
- if (!value_lazy (arg1))
- value_fetch_lazy (v);
+ v->offset = value_offset (arg1) + offset
+ + TYPE_FIELD_BITPOS (arg_type, fieldno) / 8;
}
else if (fieldno < TYPE_N_BASECLASSES (arg_type))
{
@@ -2094,9 +2062,8 @@ value_fn_field (struct value **arg1p, st
}
-/* Unpack a bitfield of the specified FIELD_TYPE, from the anonymous
- object at VALADDR. The bitfield starts at BITPOS bits and contains
- BITSIZE bits.
+/* Unpack a field FIELDNO of the specified TYPE, from the anonymous object at
+ VALADDR.
Extracting bits depends on endianness of the machine. Compute the
number of least significant bits to discard. For big endian machines,
@@ -2110,21 +2077,24 @@ value_fn_field (struct value **arg1p, st
If the field is signed, we also do sign extension. */
LONGEST
-unpack_bits_as_long (struct type *field_type, const gdb_byte *valaddr,
- int bitpos, int bitsize)
+unpack_field_as_long (struct type *type, const gdb_byte *valaddr, int fieldno)
{
- enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (field_type));
+ enum bfd_endian byte_order = gdbarch_byte_order (get_type_arch (type));
ULONGEST val;
ULONGEST valmask;
+ int bitpos = TYPE_FIELD_BITPOS (type, fieldno);
+ int bitsize = TYPE_FIELD_BITSIZE (type, fieldno);
int lsbcount;
+ struct type *field_type;
val = extract_unsigned_integer (valaddr + bitpos / 8,
sizeof (val), byte_order);
+ field_type = TYPE_FIELD_TYPE (type, fieldno);
CHECK_TYPEDEF (field_type);
/* Extract bits. See comment above. */
- if (gdbarch_bits_big_endian (get_type_arch (field_type)))
+ if (gdbarch_bits_big_endian (get_type_arch (type)))
lsbcount = (sizeof val * 8 - bitpos % 8 - bitsize);
else
lsbcount = (bitpos % 8);
@@ -2148,19 +2118,6 @@ unpack_bits_as_long (struct type *field_
return (val);
}
-/* Unpack a field FIELDNO of the specified TYPE, from the anonymous object at
- VALADDR. See unpack_bits_as_long for more details. */
-
-LONGEST
-unpack_field_as_long (struct type *type, const gdb_byte *valaddr, int fieldno)
-{
- int bitpos = TYPE_FIELD_BITPOS (type, fieldno);
- int bitsize = TYPE_FIELD_BITSIZE (type, fieldno);
- struct type *field_type = TYPE_FIELD_TYPE (type, fieldno);
-
- return unpack_bits_as_long (field_type, valaddr, bitpos, bitsize);
-}
-
/* Modify the value of a bitfield. ADDR points to a block of memory in
target byte order; the bitfield starts in the byte pointed to. FIELDVAL
is the desired value of the field, in host byte order. BITPOS and BITSIZE
--- ./gdb/value.h 2009-08-28 19:27:29.000000000 +0200
+++ ./gdb/value.h 2009-08-28 19:27:59.000000000 +0200
@@ -71,12 +71,6 @@ extern void set_value_bitsize (struct va
extern int value_bitpos (struct value *);
extern void set_value_bitpos (struct value *, int bit);
-/* Only used for bitfields; the containing value. This allows a
- single read from the target when displaying multiple
- bitfields. */
-
-struct value *value_parent (struct value *);
-
/* Describes offset of a value within lval of a structure in bytes.
If lval == lval_memory, this is an offset to the address. If lval
== lval_register, this is a further offset from location.address
@@ -330,8 +324,6 @@ extern LONGEST unpack_long (struct type
extern DOUBLEST unpack_double (struct type *type, const gdb_byte *valaddr,
int *invp);
extern CORE_ADDR unpack_pointer (struct type *type, const gdb_byte *valaddr);
-LONGEST unpack_bits_as_long (struct type *field_type, const gdb_byte *valaddr,
- int bitpos, int bitsize);
extern LONGEST unpack_field_as_long (struct type *type,
const gdb_byte *valaddr,
int fieldno);