Re: [RFC] "info registers" is misleading

[Richard Earnshaw <rearnsha at arm dot com>]

msnyder@redhat.com said:
> This is an old old issue.  The frame pointer register is special.
> Info registers does not show the actual value of the fp register -- it
> shows the virtual frame pointer (the address of the function's stack
> frame).  Usually it's the same value -- unles you're in a frameless
> function (ie. one that does not use the frame pointer register).

> Now that we have pseudo-registers, we've talked about  adding a
> pseudo-frame-pointer register and using it for FP_REGNUM, so that the
> "real" frame pointer register can always display its real value. 

Indeed.  It isn't even confined to Thumb code.  If you have ARM code 
compiled with -fomit-frame-pointer, then gdb will confuse the 
stack-pointer and frame-pointer registers.  Very hard to work out what is 
happening, especially if you want to force a register.

If we add extra gloop to "info registers" for printing out the 
pseudo-frame-pointer register, then please don't call it "fp" (or at least 
allow a target to provide its own name): "fp" is a well-known alias on the 
arm (defined by the APCS) for r11.  Users should be able to use fp as the 
ARM register r11 and will get confused if it represents anything else.

R.