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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Mon, 9 Sep 2024 16:30:50 +0300
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On Mon, 09 Sep 2024 12:28:13 GMT
anton@mips.complang.tuwien.ac.at (Anton Ertl) wrote:

> 
> But when changing the length to 63:
> 
> 0000000000000000 <foo1>:
>    0:   c5 fe 6f 06             vmovdqu (%rsi),%ymm0
>    4:   c5 fe 7f 07             vmovdqu %ymm0,(%rdi)
>    8:   c5 fe 6f 4e 1f          vmovdqu 0x1f(%rsi),%ymm1
>    d:   c5 fe 7f 4f 1f          vmovdqu %ymm1,0x1f(%rdi)
>   12:   c5 f8 77                vzeroupper
>   15:   c3                      ret
>   16:   66 2e 0f 1f 84 00 00    cs nopw 0x0(%rax,%rax,1)
>   1d:   00 00 00 
> 
> 0000000000000020 <foo2>:
>   20:   ba 3f 00 00 00          mov    $0x3f,%edx
>   25:   e9 00 00 00 00          jmp    2a <foo2+0xa>
> 
> - anton

An interesting question is which code I want in this case.
In absence of -march options and with -O1|2|3 I want something like
that:

foo2:
movups (%rsi), %xmm0
movups 16(%rsi), %xmm1
movups 32(%rsi), %xmm2
movups 47(%rsi), %xmm3
movups %xmm0, (%rsi)
movups %xmm1, 16(%rsi)
movups %xmm2, 32(%rsi)
movups %xmm3, 47(%rsi)
ret

Without deep thinking I don't see why I would want anything
different for foo1().