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NEON-How to shift the whole D or Q to left or right?

Note: This was originally posted on 12th July 2012 at http://forums.arm.com

Hello

Base on NEON instuction set, I can find the VSHL or VSHR to perform shift operation. But it is just for every element.

How can I shift the whole D or Q register to left or right?

For instance, if D = 0x0001020304050607, when it shift right 8 bit, it should become D=0x0000010203040506.

Best Regards,
Alan Chen

Alan Chen over 12 years ago

Note: This was originally posted on 16th July 2012 at http://forums.arm.com

Thank you.

But could you write one example and let me konw how I can use VEXT to implement byte shift?

And if I can use VEXT to shift two bytes in one instruction?
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Etienne SOBOLE over 12 years ago

Note: This was originally posted on 12th July 2012 at http://forums.arm.com

Hello
Base on NEON instuction set, I can find the VSHL or VSHR to perform shift operation. But it is just for every element.
How can I shift the whole D or Q register to left or right?
For instance, if D = 0x0001020304050607, when it shift right 8 bit, it should become D=0x0000010203040506.

Best Regards,
Alan Chen

For byte shifting you can use VEXT instruction
For bit shifting, I not sur you can do that with a simple instruction !

Etienne
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Peter Harris over 12 years ago

Note: This was originally posted on 16th July 2012 at http://forums.arm.com

Use the same principle as a rotate (shown in the manual), but feed in a register of zeros for one or other of the registers, depending which way you are shifting.

http://infocenter.ar...h/CIHGAEFI.html

HTH,
Iso
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