Re: ARM frame fp is not always FP_REGNUM

[Andrew Cagney <ac131313@cygnus.com>]

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.

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

	Andrew
From aoliva@redhat.com Mon Jul 03 22:53:00 2000
From: Alexandre Oliva <aoliva@redhat.com>
To: Andrew Cagney <ac131313@cygnus.com>
Cc: gdb-patches@sourceware.cygnus.com
Subject: Re: ARM frame fp is not always FP_REGNUM
Date: Mon, 03 Jul 2000 22:53:00 -0000
Message-id: <or1z1afnle.fsf@guarana.lsd.ic.unicamp.br>
References: <orn1jyfpso.fsf@guarana.lsd.ic.unicamp.br> <39617827.29D15730@cygnus.com>
X-SW-Source: 2000-07/msg00021.html
Content-length: 673

On Jul  4, 2000, Andrew Cagney <ac131313@cygnus.com> wrote:

> FP_REGNUM refers to GDB's internal frame-handle / frame-pointer /
> frame-base variable.

On ARM, it's register 11, which is a real register.  But SP_REGNUM is
register 13.  Then, when framereg == 13 in EXTRA_FRAME_INFO, `info
regs' will display the value of r13 for r11, and the actual value of
r11 cannot be obtained.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me