ARMV7a: selected processor does not support requested special purpose register

ARMV7a: selected processor does not support requested special purpose register

[Umesh Kalappa]

Hi All,

We have problem to compile the following asm
https://godbolt.org/z/hejMPoW69

and asm error out with the subject message .

Is mrs for float special register not valid on cortex-a9 ?

Thank you
~Umesh

Re: ARMV7a: selected processor does not support requested special purpose register

[Richard Earnshaw]

On 03/10/2022 15:41, Umesh Kalappa via Binutils wrote:
> Hi All,
> 
> We have problem to compile the following asm
> https://godbolt.org/z/hejMPoW69
> 
> and asm error out with the subject message .
> 
> Is mrs for float special register not valid on cortex-a9 ?
> 
> Thank you
> ~Umesh

that's because the instruction you want is

vmrs r4, fpscr

R.

Re: ARMV7a: selected processor does not support requested special purpose register

[Richard Earnshaw]

On 03/10/2022 16:48, Richard Earnshaw via Binutils wrote:
> 
> 
> On 03/10/2022 15:41, Umesh Kalappa via Binutils wrote:
>> Hi All,
>>
>> We have problem to compile the following asm
>> https://godbolt.org/z/hejMPoW69
>>
>> and asm error out with the subject message .
>>
>> Is mrs for float special register not valid on cortex-a9 ?
>>
>> Thank you
>> ~Umesh
> 
> that's because the instruction you want is
> 
> vmrs r4, fpscr
> 
> R.

Also note that the fmrrs mnemonic is not part of the UAL (unified 
assembly language) specification - it was deprecated a long time ago. 
The correct names these days all start with a V - the disassembler 
output shows the modern form.

The legacy name for vmrs was fmrx.

R.

Re: ARMV7a: selected processor does not support requested special purpose register

[Umesh Kalappa]

Thank you Richard for the information and do you please point us to
the reference ,which states the same ?

Quick grep doesn't helped us ,Thank you again
~Umesh

On Mon, Oct 3, 2022 at 9:24 PM Richard Earnshaw
<Richard.Earnshaw@foss.arm.com> wrote:
>
>
>
> On 03/10/2022 16:48, Richard Earnshaw via Binutils wrote:
> >
> >
> > On 03/10/2022 15:41, Umesh Kalappa via Binutils wrote:
> >> Hi All,
> >>
> >> We have problem to compile the following asm
> >> https://godbolt.org/z/hejMPoW69
> >>
> >> and asm error out with the subject message .
> >>
> >> Is mrs for float special register not valid on cortex-a9 ?
> >>
> >> Thank you
> >> ~Umesh
> >
> > that's because the instruction you want is
> >
> > vmrs r4, fpscr
> >
> > R.
>
> Also note that the fmrrs mnemonic is not part of the UAL (unified
> assembly language) specification - it was deprecated a long time ago.
> The correct names these days all start with a V - the disassembler
> output shows the modern form.
>
> The legacy name for vmrs was fmrx.
>
> R.

Re: ARMV7a: selected processor does not support requested special purpose register

[Richard Earnshaw]

On 04/10/2022 05:26, Umesh Kalappa wrote:
> Thank you Richard for the information and do you please point us to
> the reference ,which states the same ?
> 
> Quick grep doesn't helped us ,Thank you again
> ~Umesh
> 
> On Mon, Oct 3, 2022 at 9:24 PM Richard Earnshaw
> <Richard.Earnshaw@foss.arm.com> wrote:
>>
>>
>>
>> On 03/10/2022 16:48, Richard Earnshaw via Binutils wrote:
>>>
>>>
>>> On 03/10/2022 15:41, Umesh Kalappa via Binutils wrote:
>>>> Hi All,
>>>>
>>>> We have problem to compile the following asm
>>>> https://godbolt.org/z/hejMPoW69
>>>>
>>>> and asm error out with the subject message .
>>>>
>>>> Is mrs for float special register not valid on cortex-a9 ?
>>>>
>>>> Thank you
>>>> ~Umesh
>>>
>>> that's because the instruction you want is
>>>
>>> vmrs r4, fpscr
>>>
>>> R.
>>
>> Also note that the fmrrs mnemonic is not part of the UAL (unified
>> assembly language) specification - it was deprecated a long time ago.
>> The correct names these days all start with a V - the disassembler
>> output shows the modern form.
>>
>> The legacy name for vmrs was fmrx.
>>
>> R.

You won't find (well are extremely unlikely to find) any documentation 
for the legacy mnemonics online - the reference I have is from the ARMv5 
ARM ARM from nearly 20 years ago, which was in paper form.

The current UAL syntax is documented in the Arm ARM, which you can 
download from developer.arm.com - follow the links to the architecture.

There's also a fairly good list of the mapping between the legacy 
mnemonics and UAL for VFP here:
https://developer.arm.com/documentation/ddi0406/b/Application-Level-Architecture/Instruction-Details/Alphabetical-list-of-instructions/F---former-VFP-instruction-mnemonics-

R.

Re: ARMV7a: selected processor does not support requested special purpose register

[Joseph Myers]

On Tue, 4 Oct 2022, Richard Earnshaw via Binutils wrote:

> You won't find (well are extremely unlikely to find) any documentation for the
> legacy mnemonics online - the reference I have is from the ARMv5 ARM ARM from
> nearly 20 years ago, which was in paper form.

It seems DDI0100I (v6 ARM) is still online: 
https://documentation-service.arm.com/static/5f8dacc8f86e16515cdb865a

-- 
Joseph S. Myers
joseph@codesourcery.com