Tracking Issue for LoongArch CRC Intrinsics

[heiher]

This is a tracking issue for the CRC intrinsics on LoongArch64.
No feature gate is required for this issue, since the CRC instructions are part of the base LoongArch64 v1.0 ISA.
CRC instructions are only defined for the LoongArch64 ISA and are not available on LoongArch32.

Public API

The stdarch_loongarch_crc feature exposes 8 functions, note that these do not require a target feature to call:

/// Calculate the CRC value using the IEEE 802.3 polynomial (0xEDB88320)
pub fn crc_w_b_w(a: i8, b: i32) -> i32

/// Calculate the CRC value using the IEEE 802.3 polynomial (0xEDB88320)
pub fn crc_w_h_w(a: i16, b: i32) -> i32

/// Calculate the CRC value using the IEEE 802.3 polynomial (0xEDB88320)
pub fn crc_w_w_w(a: i32, b: i32) -> i32

/// Calculate the CRC value using the IEEE 802.3 polynomial (0xEDB88320)
pub fn crc_w_d_w(a: i64, b: i32) -> i32 

/// Calculate the CRC value using the Castagnoli polynomial (0x82F63B78)
pub fn crcc_w_b_w(a: i8, b: i32) -> i32

/// Calculate the CRC value using the Castagnoli polynomial (0x82F63B78)
pub fn crcc_w_h_w(a: i16, b: i32) -> i32

/// Calculate the CRC value using the Castagnoli polynomial (0x82F63B78)
pub fn crcc_w_w_w(a: i32, b: i32) -> i32

/// Calculate the CRC value using the Castagnoli polynomial (0x82F63B78)
pub fn crcc_w_d_w(a: i64, b: i32) -> i32

Steps

• Implement the RFC (cc @rust-lang/XXX -- can anyone write up mentoring
  instructions?)
• Adjust documentation (see instructions on rustc-dev-guide)
• Style updates for any new syntax (nightly-style-procedure)
  • Style team decision on new formatting
  • Formatting for new syntax has been added to the Style Guide
  • (non-blocking) Formatting has been implemented in rustfmt
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

• list all the "unresolved questions" found in the RFC to ensure they are
  not forgotten.

Implementation history

• core_arch: Add LoongArch basic intrinsics stdarch#1688
• Several fixes to the loongarch CRC intrinsics stdarch#2136

[folkertdev]

Specifically this tracking issue was made just so that we can FCP the stabilization here. @heiher is our target maintainer for the loongarch targets.

The stabilization PR is at rust-lang/stdarch#2137, the functions are very similar to the crc intrinsics on aarch64 from #117215.

[Amanieu]

@rfcbot merge libs-api

[Amanieu]

@rfcbot merge libs-api

[rust-rfcbot]

Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @the8472

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.