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flat assembler > Windows > AVX how ymm0 to xmm0 ?

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Roman



Joined: 21 Apr 2012
Posts: 467
32 bit program.
I know ymm0 store 256 bits and xmm0 store 128 bits
In my task i use all xmm0 to xmm7 registers. And i want store xmm0 result in ymm0.
I want do this:
Code:
movups xmm0,DQWORD [vector4]
movaps ymm0,xmm0
.... some code...
movaps xmm0,ymm0
    

How do this ?

And second question. ymm0 and xmm0 is the different registers ?
Post 11 Jan 2019, 08:33
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Roman



Joined: 21 Apr 2012
Posts: 467
I found Vperm2f128 and Vinsertf128
Post 11 Jan 2019, 12:41
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 7207
Location: Kraków, Poland
Roman wrote:
And second question. ymm0 and xmm0 is the different registers ?
XMM0 is the lower half of YMM0 (which in turn is the lower half of ZMM0 on AVX-512-capable CPU).

Also, the upper half is automatically zeroed when you modify XMM0 with an AVX instruction (one that uses VEX encoding, they have mnemonics prepended with V letter), but it is not touched when you alter XMM0 with a classic SSE instruction.
Post 11 Jan 2019, 12:43
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Furs



Joined: 04 Mar 2016
Posts: 1386
Roman wrote:
And second question. ymm0 and xmm0 is the different registers ?
It's like rax and eax, same register, lower half. Zero-extended when using AVX instructions (not SSE tho).
Post 11 Jan 2019, 21:03
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