Re: [RFA] dwarf2expr.c: Prepare for eventual DW_OP_piece support

[Daniel Jacobowitz <drow at mvista dot com>]

On Wed, Apr 23, 2003 at 06:13:52PM -0700, Kevin Buettner wrote:
> On Apr 23,  6:05pm, Kevin Buettner wrote:
> 
> > ... prepares execute_stack_op() for eventual DW_OP_piece
> > support.
> 
> I have a patch which adds _limited_ DW_OP_piece support.  It finds the
> various "pieces" (all of which must be registers) in the location
> expression and then calls an architecture specific method to determine
> whether, given a single register number, gdb can reliably fetch the
> necessary pieces.  The architecture dependent method simply checks to
> make sure that the register numbers (the pieces) are in the correct
> order and it returns the register number that must be used in order to
> properly fetch the pieces (or -1 if it can't be done).
> 
> This support doesn't handle the interesting case of an object being
> split between a register and memory or even of the slightly less
> interesting case of non-contiguous registers, but it will be adequate
> for most DW_OP_piece expressions that gcc will emit in the near
> future.  Anyway... given the limitations outlined above, is there
> interest in having me submit this patch? 

Ah, sounds like our friend the e500.  I think that you should submit
the patch, personally.

Note that we can make GCC emit more DW_OP_piece information in,
probably, a heartbeat or so.  Once GDB's ready for it.  The movement of
ctx->in_reg out of the loop is appropriate only for the limited
DW_OP_piece support you describe above; but it's in the loop for
exactly the reason of values split between registers and memory.  In
order to support this locations need to become more complete objects. 
I have a plan of attack, but no time.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer