cpu: add GODEBUG options to disable use of instruction set extensions

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.

Fixes golang/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>
15 files changed
tree: 7f9df537c5092f6a17210cd4793e85348c632b62
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. codereview.cfg
  10. cpu/
  11. go.mod
  12. internal/
  13. plan9/
  14. unix/
  15. windows/
README.md

sys

This repository holds supplemental Go packages for low-level interactions with the operating system.

Download/Install

The easiest way to install is to run go get -u golang.org/x/sys. You can also manually git clone the repository to $GOPATH/src/golang.org/x/sys.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the sys repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/sys:” in the subject line, so it is easy to find.