add vpdpbusd avx512 intrinsic

[folkertdev]

This intrinsic is useful for the adler32 checksum algorithm.

The test attempts to hit a bunch of overflow and truncation cases, and I've validated it on real hardware.

[rustbot]

Thank you for contributing to Miri! A reviewer will take a look at your PR, typically within a week or two.
Please remember to not force-push to the PR branch except when you need to rebase due to a conflict or when the reviewer asks you for it.

[RalfJung]

Thanks for the PR!

I am slightly concerned about slowly growing a huge avx512 file that nobody has an overview of any more.^^ But as long as there's a clear motivation in the form of a core ecosystem crate, I hope that will naturally limit the scope of what we have to support.

View changes since this review

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[folkertdev]

@rustbot ready

[RalfJung]

Suggested change

	/// the corresponding 32-bit integer in `src`, and store the packed 32-bit results in `dst`.
	/// the corresponding 32-bit integer in `src` (using wrapping arithmetic), and store the packed 32-bit results in `dst`.

[RalfJung]

What do you mean by "very likely"? You are fixing all the inputs here, there should be no probabilities.^^

This pairs up with elements in A and B, right? So you can have comments there indicating which ones this is paired up with.

[RalfJung]

This looks great, thanks! Please squash the commits. You can squash manually if there are multiple independent commits you want to preserve, or use ./miri squash (make sure to pick a suitable commit message). Then write @rustbot ready after you force-pushed the squashed PR.

@rustbot author

[folkertdev]

@rustbot ready

resolved