Re: ARM frame fp is not always FP_REGNUM

[Michael Snyder <msnyder at cygnus dot com>]

Andrew Cagney wrote:
> 
> Alexandre Oliva wrote:
> >
> > read_relative_register_raw_bytes_for_frame() would optimize access to
> > FP_REGNUM by not re-reading it when the value of FP is already known.
> > However, because FP is not always available, sometimes the value of SP
> > is stored in the frame structure as the value of FP.  In this case,
> > reading the value of FP_REGNUM will get you SP instead of the actual
> > value of the FP register.  This patch fixes this bug.  Ok to install?
> 
> I'm not sure about this.
> 
> FP_REGNUM refers to GDB's internal frame-handle / frame-pointer /
> frame-base variable.  It doesn't refer to the ISA register that is seen
> in architectures such as ARM or VAX.  Unfortunatly, some architectures
> have both and this leads to confusion.

Huh???  FP_REGNUM refers to a register.
The "fp" that is displayed by "info registers" sometimes 
refers to gdb's internal pseudo-frame or virtual frame location,
but the constant FP_REGNUM is a real hardware register.

> What exactly is the behavour you're seeing and what behavour are you
> trying to achieve.
> 
>         Andrew