Re: [PATCH] parisc: Prevent using same register as soure and target in extru/shr

[Helge Deller <deller@gmx.de>]

On 5/18/22 08:57, Sven Schnelle wrote:
> Helge Deller <deller@gmx.de> writes:
>
>> On 5/17/22 14:49, Helge Deller wrote:
>>> In 2004 Randolph added the shr() assembly macro and noted that the
>>> source and target register could not be the same.
>>>
>>> I did not find any confindence in the docs for this restriction. Maybe
>>> it's related that on PA2.0 the upper bits may be clobbered?
>>
>> Looking at the generated kernel code from C-files, I'll find all over usages of
>> 	extru source, x,y,  target
>> where source and target are the same register.
>> So, at least for 32-bit this restriction can't be true.
>
> I did a quick objdump on the 64 bit HP-UX kernel and that one also uses
> extrd/extrw where target and source are the same register. So i don't
> think that restriction is true.

Thanks for checking!
Maybe it's meant that it clobbers when running *32-bit* code on PA2.0?
Just a thought...

Helge