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Fast duplicate lane

Etienne SOBOLE
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Note: This was originally posted on 17th April 2013 at http://forums.arm.com

hi.
I have a little problem.

I have as input a Dn register with 8 byte.
[a, b, c, d, e, f, g, h]

I'd like to have 2 Dn Register with
[a, a, b, b, c, c, d, d]
and
[e, e, f, f, g, g, h, h]

The purpose is to try to do that with a minimum number of NEON register.
for the moment the best Way I found is something like


vmovl.u8              Qn, Dn                 @ convert byte to half word
vmul.u16              Qn, Qn, Qx    @ Dx contain 8 * 257


I'm looking for a solution not using extra register !

do you nhave any idea ?
thank's
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  • Offline
    Note: This was originally posted on 22nd April 2013 at http://forums.arm.com

    Ok thank's to everybody.

    I'll try new proposed solution, but it seem's that vzip would be the best solution.
    That was very interesting to se so many differente solution to solve this simple problem !

    @RKSimon : thank's for VSLI, I had never try this instruction ;)
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  • Offline
    Note: This was originally posted on 22nd April 2013 at http://forums.arm.com

    Ok thank's to everybody.

    I'll try new proposed solution, but it seem's that vzip would be the best solution.
    That was very interesting to se so many differente solution to solve this simple problem !

    @RKSimon : thank's for VSLI, I had never try this instruction ;)
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