[Regression] [PATCH] Do not print empty-group regs when printing general ones

[Luis Machado]

On 1/31/20 7:34 AM, Shahab Vahedi wrote:
> This patch was reviewed once (as OK):
> https://sourceware.org/ml/gdb-patches/2020-01/msg00613.html
> 
> Could someone review/merge it?
> 
> 
> Cheers,
> Shahab
> 

FTR, this has broken general register printing for ARM/AArch64. Now 
"info reg" shows nothing.

Given there are already remote stubs, probes and gdbservers running out 
there, this is an undesirable change to have.

I had an IRC chat with Christian and he pointed me at some documentation 
stating empty-group registers should not be printed, but i think this is 
a case where the implementation has diverged from the documentation.

https://sourceware.org/gdb/current/onlinedocs/gdb/Target-Description-Format.html#Target-Description-Format

We could probably patch up any non-standard target description XML's 
from now on, but the existing behavior may have to be preserved.

I haven't investigated this in depth yet to determine what can/should 
change.