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Understanding VPf and NEON link

Note: This was originally posted on 14th March 2011 at http://forums.arm.com

I'd like to understand exactly how NEON can be used instead of VPf.

I understand that
FADDS
is now replaced by
VADD.f32

But I have some questions about that.
- Does the 2 syntax have the same memory representation (do they have the same hexadecimal representation) ??? (I guess Yes, but i'd like to be sure)
- FADDS can be conditionnal !!! Can anybody give me an example ?
- if FADDS can be conditionnal then VADD.f32 should be too ! What is the correct syntaxe for a conditionnal VADD.f32
- FADDS is now VADD.f32 and is executed into NEON pipeline. Does it mean that VADD.f32 (and FADDS) execute in 1 cycle instead of 9.

Is I'm right,
FADDD is replaced by VADD.f64 but is not executed into NEON pipeline, so the VPF cycle table must be used !!!
FADDD not seems to be a conditionnal instruction! Are we ok about that ?

Thank's
Etienne

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Etienne SOBOLE over 12 years ago

Note: This was originally posted on 17th March 2011 at http://forums.arm.com

I've made some test about floating point operation.

And...
I've wrote My first post in english (almost english).
http://pulsar.webshaker.net/2011/03/17/optimize-float-operation-on-cortex-a8/

It's clear that using NEON instead of VPf can really increase floating point performance.

My problem is that I do not succeed to activate the FastMode.
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0344k/Chdiihcd.html

Is it a compilation parameters or is it more complicated to activate this mode.
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Etienne SOBOLE over 12 years ago

Note: This was originally posted on 17th March 2011 at http://forums.arm.com

I've made some test about floating point operation.

And...
I've wrote My first post in english (almost english).
http://pulsar.webshaker.net/2011/03/17/optimize-float-operation-on-cortex-a8/

It's clear that using NEON instead of VPf can really increase floating point performance.

My problem is that I do not succeed to activate the FastMode.
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0344k/Chdiihcd.html

Is it a compilation parameters or is it more complicated to activate this mode.
Cancel
Vote up 0 Vote down

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