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Editorial Team
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Asked: 2026-06-18T05:22:19+00:00

I am learning neon and found a line of code as the following: DATA

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I am learning neon and found a line of code as the following: 

DATA            .req r0  
vld1.16         {d16, d17, d18, d19}, [DATA, :128]!

I can not find any information about what the :128 means. In RealView Compilation Tools® Version 3.1 Assembler Guide, immediate value in vldn’s address register is not defined,
even if :128 means #128. What is the difference between :128 and #128? What does :128 mean exactly in this instruction?

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1 Answer

  1. Editorial Team

    The assembler syntax for that instruction according to the ARM Architecture Reference Manual is:

    VLD1<c><q>.<size> <list>, [<Rn>{@<align>}]!

    So it looks like your :128 means @128 from that context.

    <align> The alignment. It can be one of:

    …

    128 16-byte alignment, available only if <list> contains two or four registers.

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