use stable aarch64 intrinsics (#50)

Author: srijs

.github/workflows/ci.yml

@@ -8,9 +8,6 @@ on:
     branches:
       - master
 
-env:
-  MSRV: "1.63.0"
-
 jobs:
   stable:
     name: stable
@@ -51,8 +48,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - name: Get MSRV from Cargo.toml
+        id: msrv
+        run: echo "version=$(grep '^rust-version' Cargo.toml | sed 's/rust-version = "\(.*\)"/\1/')" >> $GITHUB_OUTPUT
       - name: Install Rust
-        run: rustup update $MSRV && rustup default $MSRV
+        run: rustup update ${{ steps.msrv.outputs.version }} && rustup default ${{ steps.msrv.outputs.version }}
       - name: Test in debug mode
         run: cargo test --no-fail-fast
       - name: Test in release mode

Cargo.toml

@@ -12,6 +12,7 @@ repository = "https://github.com/srijs/rust-crc32fast"
 readme = "README.md"
 keywords = ["hash", "crc", "crc32", "simd", "fast"]
 categories = ["algorithms", "no-std"]
+rust-version = "1.63"
 
 [dependencies]
 cfg-if = "1.0"

README.md

@@ -73,8 +73,6 @@ Note: Because runtime CPU feature detection requires OS support, the specialized
 This feature flag enables unstable features that are only available on the `nightly` channel. Keep in mind that when enabling this feature flag, you
 might experience breaking changes when updating compiler versions.
 
-Currently, enabling this feature flag will make the optimized `aarch64` implementation available.
-
 ## License
 
 This project is licensed under either of

build.rs

@@ -0,0 +1,27 @@
+use std::{env, process::Command};
+
+fn main() {
+    if let Some(minor_version) = minor_rustc_version() {
+        // rustc 1.80 stabilized ARM CRC32 intrinsics:
+        // https://doc.rust-lang.org/nightly/core/arch/aarch64/fn.__crc32d.html
+        if minor_version >= 80 {
+            println!("cargo:rustc-cfg=stable_arm_crc32_intrinsics");
+            println!("cargo:rustc-check-cfg=cfg(stable_arm_crc32_intrinsics)");
+        }
+    }
+}
+
+fn minor_rustc_version() -> Option<u32> {
+    Command::new(env::var_os("RUSTC")?)
+        .arg("--version")
+        .output()
+        .ok()
+        .and_then(|output| {
+            std::str::from_utf8(&output.stdout).ok().and_then(|output| {
+                output
+                    .split('.')
+                    .nth(1)
+                    .and_then(|minor_version| minor_version.parse().ok())
+            })
+        })
+}

src/specialized/mod.rs

@@ -5,7 +5,7 @@ cfg_if! {
     ))] {
         mod pclmulqdq;
         pub use self::pclmulqdq::State;
-    } else if #[cfg(all(feature = "nightly", target_arch = "aarch64"))] {
+    } else if #[cfg(all(stable_arm_crc32_intrinsics, target_arch = "aarch64"))] {
         mod aarch64;
         pub use self::aarch64::State;
     } else {