[rfc] Handle DWARF-2 value pieces residing in *parts* of a register

[Tom Tromey]

>>>>> "Ulrich" == Ulrich Weigand <uweigand@de.ibm.com> writes:

Ulrich> Now, according to the DWARF-2 standard, the location of register pieces
Ulrich> of smaller than full register size is defined by the platform ABI.
Ulrich> For the placement of a small value in a *single* register we have a
Ulrich> gdbarch callback (gdbarch_value_from_register); maybe we need something
Ulrich> like that for value pieces as well.  At the very least, we ought to
Ulrich> you the same default as default_value_from_register does: assume
Ulrich> partial register use implies the least-significant part of the register.

Ulrich> The patch below implements this.

I think this seems reasonable.

It seems straightforward enough to add an arch method if we ever
actually need one.  I wouldn't worry about it unless we already know of
such a machine.

Ulrich> 	a register, assume the least-signficant part is used.

Typo, "significant".

Tom