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What is lane

Note: This was originally posted on 29th July 2013 at http://forums.arm.com

Hi there,
I'm new to the ARM world.
I've encountered ARM instructions which are described as follows:
"Store single 1-element structure from one lane of one register".

I'm not sure what "lane" means ?
The instruction is a store instruction. so it reads from a register and write into the memory.

I'm not even sure I post it in the right forum.
would appreciate every help I can get.

Sincerely,
Hagai

Peter Harris over 12 years ago

Note: This was originally posted on 29th July 2013 at http://forums.arm.com

These descriptions are from the NEON instructions which are SIMD vector instructions. As they are vector instructions one register contains multiple values - each value is assigned a logical lane, starting from lane 0 at the least-significant bits. How many lanes depends on data size (8, 16, 32) and register type (64 or 128-bit).

These store instructions would therefore only store out one lane to memory, and ignore the other contents of the register being stored.

HTH,
Iso
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Bob Boys over 12 years ago

Note: This was originally posted on 2nd August 2013 at http://forums.arm.com

Hello

For a well written introduction to NEON and SIMD in general: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dht0002a/index.html

Or search ARM DHT002a

There are useful diagrams that explain what a lane is.

Bob
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