Enable VPCLMULQDQ support on Rust 1.89+

[onethumb]

The Problem

We're currently gating VPCLMULQDQ support (for a ~2X throughput improvement on modern x86_64 platforms) behind the vpclmulqdq feature flag since AVX512 hasn't been stable.

Stable AVX512 support just landed for Rust 1.89.0, so we'd like to start using it.

The Solution

Replace the vpclmulqdq feature flag with rustversion for Rust 1.89+ so we can safely use it.

Changes

• Deprecate the vpclmulqdq feature flag and remove all of its usage
• Add rustversion support and gate all AVX512 usage for Rust 1.89+

Planned version bump

• Which: MINOR
• Why: non-breaking performance improvement

Links

• https://releases.rs/docs/1.89.0/

Notes

I'll wait to merge and ship this until 1.89 becomes stable on August 7, 2025.

[Copilot]

Pull Request Overview

This PR enables AVX512 support with stable Rust 1.89+ by replacing the legacy vpclmulqdq feature flag with rustversion conditionals. Key changes include:

• Updating attribute directives across CRC32 and architecture modules to use rustversion.
• Removing the vpclmulqdq cfg-gates from multiple files.
• Adjusting Cargo.toml to reflect the deprecation of the vpclmulqdq feature.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/crc32/fusion/x86.rs	Replaced commented rustversion attributes with active ones, removing vpclmulqdq cfgs.
src/arch/x86.rs	Updated attribute directives by removing vpclmulqdq cfgs.
src/arch/vpclmulqdq.rs	Removed vpclmulqdq cfg-gate; now fully gated by rustversion.
src/arch/mod.rs	Adjusted conditional definitions for update functions based on rustversion.
Cargo.toml	Added rustversion dependency and updated the vpclmulqdq feature comment.

Comments suppressed due to low confidence (1)

src/arch/mod.rs:49

• [nitpick] Multiple definitions of the 'update' function are conditionally compiled with similar logic; consider refactoring to reduce duplication and improve readability.

pub(crate) unsafe fn update(state: u64, bytes: &[u8], params: CrcParams) -> u64 {

[Copilot]

Correct the spelling 'depreated' to 'deprecated' in the feature flag comment.

Suggested change

	vpclmulqdq = [] # depreated, VPCLMULQDQ stabilized in Rust 1.89.0
	vpclmulqdq = [] # deprecated, VPCLMULQDQ stabilized in Rust 1.89.0

[jg15]

What will happen if this program is run on a x86_64 platform that does not support vpclmulqdq (or other platform-specific instructions)?
I assume we should gracefully fall back to the most efficient set of instructions that the given processor supports.
Do we need to query the CPU features before choosing which algorithm to attempt?
Perhaps using something like this macro https://doc.rust-lang.org/std/macro.is_x86_feature_detected.html

[onethumb]

@jg15

What will happen if this program is run on a x86_64 platform that does not support vpclmulqdq (or other platform-specific instructions)? I assume we should gracefully fall back to the most efficient set of instructions that the given processor supports. Do we need to query the CPU features before choosing which algorithm to attempt? Perhaps using something like this macro https://doc.rust-lang.org/std/macro.is_x86_feature_detected.html

It does currently gracefully degrade: VPCLMULQDQ -> AVX2 -> SSE -> software-based table lookup. It does so using both conditional compilation attributes and runtime functions like is_x86_feature_detected() and is_aarch64_feature_detected(), and I've tested it across a wide range of systems which have a wide variety of features. The intended degradation works as designed across all the systems I've tested to date.

If you have a system which doesn't work properly, or doesn't degrade to the correct target, I'd love to know what CPU it is so I can test it. 👍