code review 133740043: cmd/6a: add MOVDQA and MOVDQU instructions

cmd/6a: add MOVDQA and MOVDQU instructions

Move aligned (or unaligned) double quadword.

[stephan.lachowsky, 2014-08-21 21:09:56]

Hello golang-codereviews@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[gobot, 2014-08-21 23:33:39]

R=rsc@golang.org (assigned by dave@cheney.net)

[josharian, 2014-08-21 23:59:53]

Naive questions:

It looks like MOVDQU and MOVDQA are already covered by MOVOU and MOVO
respectively. And after applying this CL, I assembled:

TEXT test(SB),$0
	MOVOU	X0, 0(DI)
	MOVO	X0, 0(DI)
	MOVDQA	X0, 0(DI)
	MOVDQU	X0, 0(DI)

which yielded f3 0f 7f 07 66 0f 7f 07 66 0f 00 07 f3 0f 00 07. According to
http://www.onlinedisassembler.com/odaweb/, this disassembles to:

f30f7f07	movdqu XMMWORD PTR [rdi],xmm0	
660f7f07	movdqa XMMWORD PTR [rdi],xmm0	
66	data16	
0f0007	sldt   WORD PTR [rdi]	
f30f0007	repz sldt WORD PTR [rdi]	
 
So it looks like the new encoding is not correct. Or have I misused MOVDQA and
MOVDQU?

[rsc, 2014-08-22 00:45:41]

I believe these are already present, as MOVO and MOVOU.
The O stands for octo-word.

[stephan.lachowsky, 2014-08-22 01:30:33]

You are both correct. These already exist, and the encoding for the register to
memory direction is incorrect.

Is it worth adding MOVDQ synonyms? If not this change is withdrawn.
> On 21 Aug 2014, at 05:45 pm, rsc@golang.org wrote:
> 
> I believe these are already present, as MOVO and MOVOU.
> The O stands for octo-word.
> 
> 
> https://codereview.appspot.com/133740043/

[rsc, 2014-08-22 01:54:15]

No, I'd rather not add the aliases. We don't try to match all the Intel
names.

[gobot, 2014-12-19 05:12:30]

R=close

To the author of this CL:

The Go project has moved to Gerrit Code Review.

If this CL should be continued, please see the latest version of
https://golang.org/doc/contribute.html for instructions on
how to set up Git and the Go project's Gerrit codereview plugin,
and then create a new change with your current code.

If there has been discussion on this CL, please give a link to it
(golang.org/cl/133740043 is best) in the description in your
new CL.

Thanks very much.