x/crypto/internal/chacha20: improve performance for ppc64le

[pfsmorigo]

Please answer these questions before submitting your issue. Thanks!

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

Using upstream.

Does this issue reproduce with the latest release?

Yes

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

GOARCH="ppc64le"
GOHOSTARCH="ppc64le"
GOHOSTOS="linux"

What did you do?

I opened this issue in order to submit a patch that adds asm implementation for chacha20 using vector instructions on ppc64le.

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

What did you expect to see?

What did you see instead?

[laboger]

The heading should start with x/crypto/chacha20poly1305:

[gopherbot]

Change https://golang.org/cl/108999 mentions this issue: internal/chacha20: improve performance for ppc64le

[pfsmorigo]

I renamed to "x/crypto/internal/chacha20" since chacha20 is not inside chacha20poly1305 anymore (see commit 4937306)

[pfsmorigo]

@dot-asm Hello Andy, can you add chacha/asm/chacha-ppc.pl to the cryptogams repository? Same as you did for #22637 Thanks!

[pfsmorigo]

Any update @dot-asm?

[gopherbot]

Change https://golang.org/cl/172177 mentions this issue: internal/chacha20: improve performance for ppc64le

[dot-asm]

For reference, the original implementation had face-lift, dramatically improving performance on POWER9, by ~80%. Trouble there is that POWER9 is kind of "allergic" to mixtures of scalar and vector instructions, which original fits-all-ppc is heavily relying on. Since 'go' doesn't seem to be concerned about anything pre-POWER8, it would be sensible to deploy new code path...

[laboger]

@dot-asm Do you mean you have a new power9-only implementation, or that the new implementation works on both power8 and power9?

[dot-asm]

POWER9 was merely a trigger for a change, because it was observed to perform unexpectedly poorly. But the change itself is PowerISA 2.07-based, so that it works on POWER8 and forward. Is it faster on POWER8? Of course, just not as much as on POWER9, only by ~40%.

[laboger]

Due to the deadline for Go 1.13 we will submit it as is for now to get better performance, then convert to the vsx implementation in Go 1.14 to improve further.

[gopherbot]

Change https://golang.org/cl/195959 mentions this issue: internal/chacha20: improve chacha20 performance on ppc64le