Revert #69280

[ecstatic-morse]

Resolves #69313 by reverting #69280.

After #69280, #[rustc_args_required_const(2)] is required on the declaration of simd_shuffle intrinsics. This is allowed breakage, since you can't define platform intrinsics on stable. However, the latest release of the widely used packed_simd crate defines these intrinsics without the requisite attribute. Since there's no urgency to merge #69280, let's revert it. We can reconsider when rust-lang/packed_simd#278 is included in a point release of packed_simd.

r? @petrochenkov

[pnkfelix]

@ecstatic-morse shouldn't this also add a regression test for #69313, so we don't hit it again when someone re-attempts doing #69280 ?

[ecstatic-morse]

@pnkfelix simd-intrinsics-generic-elements will ICE in the same way as that issue.

I knew there could be breakage due to #69280. This breakage is allowed since defining simd_shuffle requires platform_intrinsics. However, I missed that this was done in packed_simd as well as stdarch, and it seemed impolite to break everyone using packed_simd with zero notice.

We should do a crater run before retrying #69280, although I suspect there will be a lot of regressions due to pinned versions of packed_simd.

[petrochenkov]

@bors r+

[bors]

📌 Commit 16790ae has been approved by petrochenkov

[bors]

⌛ Testing commit 16790ae with merge 0753459...

[bors]

☀️ Test successful - checks-azure
Approved by: petrochenkov
Pushing 0753459 to master...