Simd

[JunHe77]

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[JunHe77]

@googlebot I signed it!

[google-cla]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
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[JunHe77]

@googlebot I signed it!

[JunHe77]

Rebased to resolve conflict in snappy-internal.h

[JunHe77]

@atdt , would you pls help to review? Thanks.

[pwnall]

@JunHe77 thank you very much for this contribution!

Would you like to address the feedback below, or would you prefer that I take care of it while going through our merge process?

[pwnall]

Thank you for realizing we need these #defines and #includes in the header, for the V128 type alias.

Can you please move this block outside namespaces?

I think that #including C system headers in a C++ namespace is undefined behavior.

[JunHe77]

Thanks for pointing this out, will update.

[pwnall]

Could you please explain the benefit of wrapping _bzhi_u32 with this function?

Until I learn more, I'm inclined to suggest that we remove the abstraction. It's currently used in exactly one place, and it's only defined when SNAPPY_HAVE_BMI2. So, it's effectively a less-known alias for the _bzhi_u32 intrinsic.

[JunHe77]

Well received, will update.

[JunHe77]

Updated. @pwnall , @atdt , would you pls help to review? Thanks a lot.

[pwnall]

@JunHe77 Thank you very much for the revisions!

I'll get this PR through the merge process in our internal repository. When the process completes, the PR will be merged.