Re: Question on attribute save-restore in reg elements (target descriptions).

[Daniel Jacobowitz <drow at false dot org>]

On Fri, May 09, 2008 at 04:41:58PM -0500, Anmol P. Paralkar wrote:
> Hello,
>
>  Per Appendix F, Sec. F.2.5 Registers, of the GDB User Manual:
>
>  save-restore
>
>     Whether the register should be preserved across inferior function
>     calls; this must be either yes or no. The default is yes, which
>     is appropriate for most registers except for some system control
>     registers; this is not related to the target's ABI.
>
>  In our target description file, we have a lot of special purpose
>  registers about which nothing might be assumed either way, so in
>  addition to 'yes' and 'no', can we have an "unspecified" value to
>  this attribute, (say, denoted by '?')? In what way does GDB use this
>  information?

GDB uses this information to make a decision, so clearly it can not be
unspecified - GDB would have to do something unspecified...

When the user types "print foo()" GDB will save and restore those
registers which are marked with save-restore="yes".  Generally this
is what you want for GPRs but not what you want for global system
state like coprocessor control registers.

-- 
Daniel Jacobowitz
CodeSourcery