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Date: Fri, 04 Nov 2005 19:09:00 -0000
From: Michael Snyder <msnyder@redhat.com>
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CC: mysea000@163.com
Subject: Re: who can explain the pseudo-registers and its mechanism to me?thanks
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"ayang" <mysea000 at 163 dot com> wrote:
 > hello,
 >      I am puzzled by the the pseudo-registers and its mechanism when 
I > read the gdb source.It is not described in gdbint.who can explain 
the > pseudo-registers and its mechanism to me?thanks.

Pseudo-registers are fake registers that do not exist
(at least as represented) on the target.  The basic distinction
is that gdb fetches the values of "real" registers from the
target, but computes or composes the values of "pseudo" registers
locally.  An example might be a double-wide pseudo-register
that is composed from the values of two ordinary registers.
GDB fetches the values of the two ordinary registers, but
then combines them to produce the value of the pseudo-register.

If a user changes the value of the pseudo-register, it may
be necessary for gdb to change the target values from which
the pseudo-register was composed.