Mark simd_shuffle intrinsics as rustc_args_required_const

[ecstatic-morse]

This change was made in stdarch but not packed_simd. See rust-lang/rust#69280 for background.

[GabrielMajeri]

I've tried running cargo test with this PR checked-out, and it gave an error with

error[E0658]: this is an internal attribute that will never be stable
  --> src/codegen/llvm.rs:13:5
   |
13 |     #[rustc_args_required_const(2)]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #29642 <https://github.com/rust-lang/rust/issues/29642> for more information
   = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable

I guess adding #![feature(rustc_attrs)] should fix this.

[GabrielMajeri]

I've checked it out locally and all tests passed. @gnzlbg is it ok to merge?

[ecstatic-morse]

ping @gnzlbg

[hsivonen]

@ecstatic-morse, why was this closed without merging?

[ecstatic-morse]

Just due to inactivity. I'm not sure how to move it forward.

[ecstatic-morse]

It seems @workingjubilee might be maintaining this repo now? This is still relevant.

[Lokathor]

The crate is being moved into long-term maintenance mode. Unless this is critical to keeping the crate building, we are unlikely to handle any particular issue.

New work by the Portable SIMD Project Group (not yet announced) is going into a fresh crate so that we can examine each part as it goes into the crate.

[ecstatic-morse]

It's critical to keeping this crate building.

[Lokathor]

(oops, this is already a pr, not an issue. my bad, we'll probably review and accept it)

[workingjubilee]

Hello! Fixing this is tentatively on the docket, but what does the numeric parameter to the attribute mean?

[Lokathor]

It's the arg index within the argument list.

[workingjubilee]

Oh! Then this is obviously correct.

[stefson]

hey there, this is a friendly note to everyone that rustc_args_required_const was removed in rust-1.54, and this will most likely lead to compile errors. At least the version of packed_sim that firefox pulls into its source tree doesn't compile anymore.

corresponding rust bug/pullrequest: rust-lang/rust#85110

[hsivonen]

At least the version of packed_sim that firefox pulls into its source tree doesn't compile anymore.

I'm in the process of cherry-picking the relevant packed_simd patches to Firefox.