PoC: add no-std libm tests to CI

.github/workflows/ci.yml

@@ -219,6 +219,25 @@ jobs:
       - name: cargo test
         run: cargo test --workspace --locked --all-features --no-fail-fast --target ${{ matrix.platform.target }}
 
+  test-stable-libm:
+    name: cargo test (libm, no_std)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: install stable toolchain
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ env.RUST_STABLE_VER }}
+
+      - name: restore cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          save-if: ${{ github.event_name != 'merge_group' }}
+
+      - name: cargo test
+        run: cargo test -p fearless_simd_tests --locked --no-default-features --features libm --no-fail-fast
+
   test-sde:
     name: cargo test in an emulator
     runs-on: ${{ matrix.platform.os }}

Cargo.toml

@@ -69,7 +69,7 @@ clippy.wildcard_dependencies = "warn"
 clippy.uninlined_format_args = "allow"
 
 [workspace.dependencies]
-fearless_simd = { path = "fearless_simd" }
+fearless_simd = { path = "fearless_simd", default-features = false }
 fearless_simd_dev_macros = { path = "fearless_simd_dev_macros" }
 proc-macro2 = "1.0.95"
 syn = { version = "2.0.101", features = ["full", "extra-traits"] }

fearless_simd_tests/Cargo.toml

@@ -19,6 +19,11 @@ path = "tests/mod.rs"
 [lints]
 workspace = true
 
+[features]
+default = ["std"]
+std = ["fearless_simd/std"]
+libm = ["fearless_simd/libm"]
+
 [dependencies]
-fearless_simd = { workspace = true, features = ["std"] }
+fearless_simd = { workspace = true }
 fearless_simd_dev_macros = { workspace = true }

fearless_simd_tests/tests/mod.rs

@@ -27,6 +27,7 @@ fn generic_cast<S: Simd>(x: S::f32s) -> S::u32s {
     dead_code,
     reason = "The `UNSUPPORTED_LEVEL_MESSAGE` is only used in some cfgs."
 )]
+#[cfg(any(feature = "std", target_arch = "wasm32"))]
 #[test]
 fn supports_highest_level() {
     const UNSUPPORTED_LEVEL_MESSAGE: &str = "This means that some of the other tests in this run may be false positives, that is, they have been marked as succeeding even though they would actually fail if they could run.\n\