[go] internal/runtime/sys: improve DIT assembly

[Roland Shoemaker (Gerrit)]

Roland Shoemaker submitted the change

Change information

Commit message:

internal/runtime/sys: improve DIT assembly

In EnableDIT, if DIT is already enabled, return early instead of
executing MSR and DSB/ISB, since they are not particularly cheap
instructions.

Also, if we have support for the SB (Speculation Barrier) instruction,
use it instead of DSB+ISB when enabling DIT, since SB is cheaper.

Change-Id: I1b3ecbd95ed42bfd10d646125704abf4e80b6d2e

Reviewed-on: https://go-review.googlesource.com/c/go/+/729800

Reviewed-by: Keith Randall <k...@google.com>

Reviewed-by: Keith Randall <k...@golang.org>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Files:

• M src/internal/runtime/sys/dit_arm64.go
• M src/internal/runtime/sys/dit_arm64.s

Change size: S

Delta: 2 files changed, 11 insertions(+), 3 deletions(-)

Branch: refs/heads/master

Submit Requirements:

• Code-Review: +2 by Keith Randall, +1 by Keith Randall
• TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

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Gerrit

Gerrit-MessageType: merged

Gerrit-Project: go

Gerrit-Branch: master

Gerrit-Change-Id: I1b3ecbd95ed42bfd10d646125704abf4e80b6d2e

Gerrit-Change-Number: 729800

Gerrit-PatchSet: 8

Gerrit-Owner: Roland Shoemaker <rol...@golang.org>

Gerrit-Reviewer: Austin Clements <aus...@google.com>

Gerrit-Reviewer: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Gerrit-Reviewer: Keith Randall <k...@golang.org>

Gerrit-Reviewer: Keith Randall <k...@google.com>

Gerrit-Reviewer: Roland Shoemaker <rol...@golang.org>

Gerrit-CC: Gopher Robot <go...@golang.org>