* arch-utils.h (legacy_register_to_value): Declare.

* arch-utils.h (legacy_register_to_value): Declare.
(legacy_value_to_register): Declare.
(legacy_convert_register_p): Declare.
* arch-utils.c (legacy_register_to_value): New function.
(legacy_value_to_register): New function.
(legacy_convert_register_p): New function.

* gdbarch.sh (REGISTER_TO_VALUE): Define.
(VALUE_TO_REGISTER): Define.
(CONVERT_REGISTER_P): Define.
* gdbarch.h, gdbarch.c: Regenerate.

* valops.c (value_assign): Use CONVERT_REGISTER_P and
VALUE_TO_REGISTER.
* findvar.c (value_from_register): Use REGISTER_TO_VALUE and
CONVERT_REGISTER_P.

* gdbint.texinfo (Target Architecture Definition): Document
REGISTER_TO_VALUE and VALUE_TO_REGISTER and CONVERT_REGISTER_P.
(Target Architecture Definition): Revise section `Using Different
Register and Memory Data Representations'.  Add section `Raw and
Virtual Register Representations'.