[RFC] register_to_value/value_to_register arguments?

[RFC] register_to_value/value_to_register arguments?

[Maciej W. Rozycki]

Hello,

 While doing some changes recently I have come across this inconsistency 
in our internal document when it comes to register_to_value and 
value_to_register gdbarch method arguments (patch below).

 However this rises a question: it is relatively expensive to retrieve 
gdbarch from frame, most target implementations of these methods need it 
and it is already readily available to the caller (retrieved from the very 
frame) -- wouldn't it therefore make sense to pass it along frame?  Why 
wasn't it done like this when the API was changed according to this 
documentation patch?

  Maciej

2012-06-11  Maciej W. Rozycki  <macro@codesourcery.com>

	gdb/doc/
	* gdbint.texinfo (Using Different Register and Memory Data
        Representations): Update gdbarch_register_to_value and
	gdbarch_value_to_register arguments.

gdb-doc-gdbint-regconv.diff
Index: gdb-fsf-trunk-quilt/gdb/doc/gdbint.texinfo
===================================================================
--- gdb-fsf-trunk-quilt.orig/gdb/doc/gdbint.texinfo	2012-06-01 18:42:43.205559049 +0100
+++ gdb-fsf-trunk-quilt/gdb/doc/gdbint.texinfo	2012-06-11 10:17:24.713600380 +0100
@@ -3726,7 +3726,7 @@ If defined, this function should return 
 type, when no conversion is necessary.
 @end deftypefn
 
-@deftypefn {Architecture Function} void gdbarch_register_to_value (struct gdbarch *@var{gdbarch}, int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
+@deftypefn {Architecture Function} void gdbarch_register_to_value (struct gdbarch *@var{gdbarch}, struct frame_info *@var{frame}, int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
 
 Convert the value of register number @var{reg} to a data object of
 type @var{type}.  The buffer at @var{from} holds the register's value
@@ -3745,7 +3745,7 @@ non-zero value.
 
 @end deftypefn
 
-@deftypefn {Architecture Function} void gdbarch_value_to_register (struct gdbarch *@var{gdbarch}, struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
+@deftypefn {Architecture Function} void gdbarch_value_to_register (struct gdbarch *@var{gdbarch}, struct frame_info *@var{frame}, struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
 
 Convert a data value of type @var{type} to register number @var{reg}'
 raw format.

Re: [RFC] register_to_value/value_to_register arguments?

[Eli Zaretskii]

> Date: Mon, 11 Jun 2012 10:36:30 +0100
> From: "Maciej W. Rozycki" <macro@codesourcery.com>
> 
> 2012-06-11  Maciej W. Rozycki  <macro@codesourcery.com>
> 
> 	gdb/doc/
> 	* gdbint.texinfo (Using Different Register and Memory Data
>         Representations): Update gdbarch_register_to_value and
> 	gdbarch_value_to_register arguments.

This patch is OK, thanks.

Re: [RFC] register_to_value/value_to_register arguments?

[Tom Tromey]

>>>>> "Maciej" == Maciej W Rozycki <macro@codesourcery.com> writes:

Maciej>  However this rises a question: it is relatively expensive to
Maciej> retrieve gdbarch from frame, most target implementations of
Maciej> these methods need it and it is already readily available to the
Maciej> caller (retrieved from the very frame) -- wouldn't it therefore
Maciej> make sense to pass it along frame?

It seems to me that the frame's arch is cached, so retrieving it is only
expensive the first time.  Given that, the current approach is clearer
and safer, since there's no possibility of arguments being out of sync.

Tom