Re: [PATCH v2 02/13] regcache: Add functions suitable for regset_supply/collect.

Omair Javaid
2014-07-07T09:32:53Z

On 25 June 2014 21:48, Andreas Arnez <arnez@linux.vnet.ibm.com> wrote:
> These functions are intended to suit all targets that don't require too
> special logic in their regset supply/collect methods. Having such
> generic functions helps reducing target-specific complexity.
>
> gdb/
> * regcache.c: Include "regset.h".
> (regcache_supply_regset, regcache_collect_regset): New functions.
> * regcache.h (struct regcache_map_entry): New structure.
> (REGCACHE_MAP_SKIP_BYTES): New enum value.
> (regcache_supply_regset, regcache_collect_regset): New prototypes.
> ---
> gdb/regcache.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> gdb/regcache.h | 44 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 110 insertions(+)
>
> diff --git a/gdb/regcache.c b/gdb/regcache.c
> index 5ee90b0..78fd962 100644
> --- a/gdb/regcache.c
> +++ b/gdb/regcache.c
> @@ -30,6 +30,7 @@
> #include "exceptions.h"
> #include "remote.h"
> #include "valprint.h"
> +#include "regset.h"
>
> /*
> * DATA STRUCTURE
> @@ -1068,6 +1069,71 @@ regcache_raw_collect (const struct regcache *regcache, int regnum, void *buf)
> memcpy (buf, regbuf, size);
> }
>
> +/* Supply register REGNUM from BUF to REGCACHE, using the register map
> + in REGSET. If REGNUM is -1, do this for all registers in
> + REGSET. */
> +
> +void
> +regcache_supply_regset (const struct regset *regset,
> + struct regcache *regcache,
> + int regnum, const void *buf, size_t size)
> +{
> + const struct regcache_map_entry *map = regset->regmap;
> + int offs = 0;
> + int i, count;
> +
> + for (i = 0; (count = map[i].count) != 0; i++)
> + {
> + int regno = map[i].regno;
> +
> + if (regno == REGCACHE_MAP_SKIP_BYTES)
> + offs += count;
> + else
> + for (; count--; regno++)
> + {
> + int new_offs = offs + regcache->descr->sizeof_register[regno];
> +
> + if (new_offs <= size && (regnum == -1 || regnum == regno))
> + regcache_raw_supply (regcache, regno,
> + buf ? (const gdb_byte *) buf + offs
> + : NULL);
> + offs = new_offs;
> + }
> + }
> +}
> +
> +/* Collect register REGNUM from REGCACHE to BUF, using the register
> + map in REGSET. If REGNUM is -1, do this for all registers in
> + REGSET. */
> +
> +void
> +regcache_collect_regset (const struct regset *regset,
> + const struct regcache *regcache,
> + int regnum, void *buf, size_t size)
> +{
> + const struct regcache_map_entry *map = regset->regmap;
> + int offs = 0;
> + int i, count;
> +
> + for (i = 0; (count = map[i].count) != 0; i++)
> + {
> + int regno = map[i].regno;
> +
> + if (regno == REGCACHE_MAP_SKIP_BYTES)
> + offs += count;
> + else
> + for (; count--; regno++)
> + {
> + int new_offs = offs + regcache->descr->sizeof_register[regno];
> +
> + if (new_offs <= size && (regnum == -1 || regnum == regno))
> + regcache_raw_collect (regcache, regno,
> + (gdb_byte *) buf + offs);
> + offs = new_offs;
> + }
> + }
> +}
> +
>
> /* Special handling for register PC. */
>
> diff --git a/gdb/regcache.h b/gdb/regcache.h
> index 8423f57..73ee043 100644
> --- a/gdb/regcache.h
> +++ b/gdb/regcache.h
> @@ -147,6 +147,50 @@ extern void regcache_raw_supply (struct regcache *regcache,
> extern void regcache_raw_collect (const struct regcache *regcache,
> int regnum, void *buf);
>
> +/* Mapping between register numbers and offsets in a buffer, for use
> + in the '*regset' functions below. In an array of
> + 'regcache_map_entry' each element is interpreted like follows:
> +
> + - If 'regno' is a register number: Map register 'regno' to the
> + current offset (starting with 0) and increase the current offset
> + by the register's size. Repeat this with consecutive register
> + numbers up to 'regno+count-1'.
> +
> + - If 'regno' is REGCACHE_MAP_SKIP_BYTES: Add 'count' to the current
> + offset.
> +
> + - If count=0: End of the map. */
> +
> +struct regcache_map_entry
> +{
> + int count;
> + int regno;
> +};
> +
> +/* Special value for the 'regno' field in the struct above. */
> +
> +enum
> + {
> + REGCACHE_MAP_SKIP_BYTES = -1,
> + };
> +
> +/* Transfer a set of registers (as described by REGSET) between
> + REGCACHE and BUF. If REGNUM == -1, transfer all registers
> + belonging to the regset, otherwise just the register numbered
> + REGNUM. The REGSET's 'regmap' field must point to an array of
> + 'struct regcache_map_entry'.
> +
> + These functions are suitable for the 'regset_supply' and
> + 'regset_collect' fields in a regset structure. */
> +
> +extern void regcache_supply_regset (const struct regset *regset,
> + struct regcache *regcache,
> + int regnum, const void *buf,
> + size_t size);
> +extern void regcache_collect_regset (const struct regset *regset,
> + const struct regcache *regcache,
> + int regnum, void *buf, size_t size);
> +
>
> /* The type of a register. This function is slightly more efficient
> then its gdbarch vector counterpart since it returns a precomputed
> --
> 1.8.4.2
>

Is there a way around avoiding the loop in supply/collect where regnum
!= -1? It should be more efficient in cases where we are looking for a
register with regnum > 0.