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Date: Fri, 21 Oct 2022 13:30:08 +0100
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Subject: Re: [PATCH 9/15] arm: Set again stack pointer as CFA reg when popping
 if necessary
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To: Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>,
 Andrea Corallo <Andrea.Corallo@arm.com>
Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>, nd <nd@arm.com>,
 Andrea Corallo via Gcc-patches <gcc-patches@gcc.gnu.org>
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On 27/09/2022 16:24, Kyrylo Tkachov via Gcc-patches wrote:
> 
> 
>> -----Original Message-----
>> From: Andrea Corallo <andrea.corallo@arm.com>
>> Sent: Tuesday, September 27, 2022 11:06 AM
>> To: Kyrylo Tkachov <Kyrylo.Tkachov@arm.com>
>> Cc: Andrea Corallo via Gcc-patches <gcc-patches@gcc.gnu.org>; Richard
>> Earnshaw <Richard.Earnshaw@arm.com>; nd <nd@arm.com>
>> Subject: Re: [PATCH 9/15] arm: Set again stack pointer as CFA reg when
>> popping if necessary
>>
>> Kyrylo Tkachov <Kyrylo.Tkachov@arm.com> writes:
>>
>>> Hi Andrea,
>>>
>>>> -----Original Message-----
>>>> From: Gcc-patches <gcc-patches-
>>>> bounces+kyrylo.tkachov=arm.com@gcc.gnu.org> On Behalf Of Andrea
>>>> Corallo via Gcc-patches
>>>> Sent: Friday, August 12, 2022 4:34 PM
>>>> To: Andrea Corallo via Gcc-patches <gcc-patches@gcc.gnu.org>
>>>> Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>; nd <nd@arm.com>
>>>> Subject: [PATCH 9/15] arm: Set again stack pointer as CFA reg when
>> popping
>>>> if necessary
>>>>
>>>> Hi all,
>>>>
>>>> this patch enables 'arm_emit_multi_reg_pop' to set again the stack
>>>> pointer as CFA reg when popping if this is necessary.
>>>>
>>>
>>>  From what I can tell from similar functions this is correct, but could you
>> elaborate on why this change is needed for my understanding please?
>>> Thanks,
>>> Kyrill
>>
>> Hi Kyrill,
>>
>> sure, if the frame pointer was set, than it is the current CFA register.
>> If we request to adjust the current CFA register offset indicating it
>> being SP (while it's actually FP) that is indeed not correct and the
>> incoherence we will be detected by an assertion in the dwarf emission
>> machinery.
> 
> Thanks,  the patch is ok
> Kyrill
> 
>>
>> Best Regards
>>
>>    Andrea

Hmm, wait.  Why would a multi-reg pop be updating the stack pointer? 
Please can you show a code sequence where this is needed.

R.