cmd/compile: intrinsify math/bits.RotateLeft{32,64} on all architectures

[mundaym]

#21536 (comment) reminded me about this. Currently the intrinsic is only implemented on amd64, arm64, ppc64 and s390x. We should enable it everywhere. It will need tests in tests/codegen. Could be a good beginner compiler issue to tackle.

CLs so far:

• amd64: https://go-review.googlesource.com/c/go/+/132435
• arm64: https://go-review.googlesource.com/c/go/+/122542
• ppc64: https://go-review.googlesource.com/c/go/+/163760
• s390x: https://go-review.googlesource.com/c/go/+/133035

[josharian]

cc @benshi001 for arm

[odeke-em]

Kindly paging @bmkessler who might also be interested in this issue.

[gopherbot]

Change https://golang.org/cl/182359 mentions this issue: cmd/compile: intrinsify RotateLeft32 on wasm

[gopherbot]

Change https://golang.org/cl/188697 mentions this issue: cmd/compile: optimize ARM's math.bits.RotateLeft32

[gopherbot]

Change https://golang.org/cl/189277 mentions this issue: cmd/compile: optimize 386's math.bits.RotateLeft32

[odeke-em]

Alright, and doing a checkup here on the statuses of the various GOARCHes

GOARCH	CLs	Done
386	89277	✔
amd64	132435	✔
arm	188697	✔
arm64	122542	✔
mips		❌
mips64		❌
mips64le		❌
mipsle		❌
ppc64	163760	✔
ppc64le	163760	✔
s390x	133035	✔
wasm	182359	✔

From the table above, we are currently lacking for the GOARCH variants of mips* and ppc64le.
Kindly pinging you @ceseo, might you have some bandwidth to work on a CL for ppc64le? @cherrymui @randall77 might y'all be available for mips* or have suggestions of other experts? I think we can get this in for Go1.14 :) And thank you everyone who has submitted CLs and reviewed or discussed getting CLs to solve this, great stuff!

[cherrymui]

CL 163760 should cover both ppc64 and ppc64le, right?

On MIPS, the rotate instruction is rather new. We still support older machines. I guess we could do something based on GOMIPS(64) value, but we need to introduce the values first. Two shifts + an OR doesn't sounds too bad.

[laboger]

CL 163760 handles both ppc64le and ppc64. When ppc64x is specified, that means both.

…

On Thu, Oct 17, 2019 at 9:07 AM cherrymui ***@***.***> wrote: CL 163760 should cover both ppc64 and ppc64le, right? On MIPS, the rotate instruction is rather new. We still support older machines. I guess we could do something based on GOMIPS(64) value, but we need to introduce the values first. Two shifts + an OR doesn't sounds too bad. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#31265?email_source=notifications&email_token=ACH7BDATPMDS3OGUPJ25KW3QPBWS3A5CNFSM4HDWR4J2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEBQGSYY#issuecomment-543189347>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACH7BDCQYEPWOO4KKTS3ZF3QPBWS3ANCNFSM4HDWR4JQ> .

[mengzhuo]

CL 163760 should cover both ppc64 and ppc64le, right?

On MIPS, the rotate instruction is rather new. We still support older machines. I guess we could do something based on GOMIPS(64) value, but we need to introduce the values first. Two shifts + an OR doesn't sounds too bad.

The minimal requirement of MIPS64X is MIPS III, which is introduced in 1991 according to Wikipedia.

I'm thinking update Go minimal requirement of MIPS64X to MIPS64 R2 (not MIPS II) as MIPS32X do.

And we can adding compile flag

GOMIPS64=r*

r2 = release 2
r6 = release 6

For the future MIPS64 r6, which is whole new instruction set.

We already had GOMIPS64=hardfloat and won't conflict with r* flag by separate them with comma, i.e. GOMIPS64=hardfloat,r2