Add a RISCV64 variable to cpu that indicates both the presence
of RISC-V extensions and performance information about the underlying
RISC-V cores. The variable is only populated with non false values on
Linux. The detection code first attempts to use the riscv_hwprobe
syscall introduced in Linux 6.4, falling back to HWCAP if riscv_hwprobe
is not supported. The patch can detect the C, V, Zba, Zbb and Zbs
extensions. V, Zba, Zbb and Zbs can only be detected on a 6.5 kernel
or later (without backports).
Updates golang/go#61416
Change-Id: I40f92724ee3d337c06bdc559ff0b18a8f6bfda9f
Reviewed-on: https://go-review.googlesource.com/c/sys/+/605815
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Joel Sing <joel@sing.id.au>
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>
The GODEBUG environment variable can be used to disable usage of
specific processor features of Go programs that use the sys/cpu package.
This is useful for testing and benchmarking different code paths that
are guarded by sys/cpu variable checks.
Use of processor features can not be enabled through GODEBUG.
To disable usage of AVX and SSE41 cpu features on GOARCH amd64 use:
GODEBUG=cpu.avx=off,cpu.sse41=off
The special "all" option can be used to disable all options:
GODEBUG=all=off
This aligns the support of GODEBUG for sys/cpu with existing support
for GODEBUG in the Go standard library package internal/cpu.
Fixesgolang/go#33963
Change-Id: I618b71af397bf06c57a49b2a300d032a16d05664
Reviewed-on: https://go-review.googlesource.com/c/sys/+/245237
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
