OS_PlatformFeatures 34 not aware of CBZ & CBNZ ?

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David1664
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OS_PlatformFeatures 34 not aware of CBZ & CBNZ ?

Post by David1664 » Wed Jan 22, 2020 9:25 pm

I wanted to ask this over at the ROOL forum, but I've given up trying to log-in over there!

I'm just curious as to why the ARMv6T2-introduced instructions CBZ and CBNZ aren't included among the list of flags returned by the SWI call OS_PlatformFeatures 34? Did someone forget to include them? :)

https://www.riscosopen.org/wiki/documen ... 34%20Flags

I wasn't aware of those instructions until I compiled some C code which performs fast modulo division (X modulo 2^n-1), and examined the assembly dump.


David.
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IanS
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Re: OS_PlatformFeatures 34 not aware of CBZ & CBNZ ?

Post by IanS » Wed Jan 22, 2020 9:45 pm

Aren't they Thumb instructions?

"information about Thumb modes is not reported"

David1664
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Re: OS_PlatformFeatures 34 not aware of CBZ & CBNZ ?

Post by David1664 » Wed Jan 22, 2020 9:58 pm

IanS wrote:
Wed Jan 22, 2020 9:45 pm
Aren't they Thumb instructions?

"information about Thumb modes is not reported"
Thank you! That would explain it.

(I obviously didn't read the docs carefully enough.)

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helpful
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Re: OS_PlatformFeatures 34 not aware of CBZ & CBNZ ?

Post by helpful » Thu Jan 23, 2020 2:49 am

David1664 wrote:
Wed Jan 22, 2020 9:25 pm
I wanted to ask this over at the ROOL forum, but I've given up trying to log-in over there!
The "trick" to logging in to the ROOL forum is to always go to the top level page https://www.riscosopen.org/ and click on Log In from there, before then visiting the forum pages. If you've already been to the site then you will need to clear the cookies, or restart the browser, or open the site in a private tab!

Bryan.
RISC OS User Group Of London - http://www.rougol.jellybaby.net/
RISC OS London Show - http://www.riscoslondonshow.co.uk/

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