runtime: improve arm64 memclr

[mrosier-qdt]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.9.2 linux/arm64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

What did you do?

Identified via inspection.

What did you expect to see?

The implementation can be improved by unrolling loops and using sets of ldp and stp instructions.

What did you see instead?

[mrosier-qdt]

The intent of this bug report is to convey the fact that my team and I are developing an improved version of the memclr routine for arm64. We understand the tree opens for performance work in early February.

[mrosier-qdt]

Thanks, @randall77. I'm fairly new to github issue reporting. Google seems to indicate only project owners can assign bugs, correct?

[bradfitz]

We don't really use the Github Assignee feature much. Don't worry about it. Just declare that you're working on it with text as you did above.

[mrosier-qdt]

SGTM. Thanks, Brad.

[gopherbot]

Change https://golang.org/cl/82055 mentions this issue: runtime: improve arm64 memclr implementation.