Enable build-mpfr and build-musl by default

Most users who are developing this crate are likely running on a Unix
system, since there isn't much to test against otherwise. For
convenience, enable the features required to run these tests by default.

library/compiler-builtins/libm/.github/workflows/main.yml

@@ -131,10 +131,7 @@ jobs:
     - uses: Swatinem/rust-cache@v2
     - name: Download musl source
       run: ./ci/download-musl.sh
-    - run: |
-        cargo clippy --all \
-          --features libm-test/build-musl,libm-test/build-mpfr \
-          --all-targets
+    - run: cargo clippy --all --all-features --all-targets
 
   builtins:
     name: Check use with compiler-builtins

library/compiler-builtins/libm/CONTRIBUTING.md

@@ -62,15 +62,12 @@ Check [PR #65] for an example.
 Normal tests can be executed with:
 
 ```sh
-cargo test
+# `--release` ables more test cases
+cargo test --release
 ```
 
-If you'd like to run tests with randomized inputs that get compared against
-infinite-precision results, run:
-
-```sh
-cargo test --features libm-test/build-mpfr,libm-test/build-musl --release
-```
+If you are on a system that cannot build musl or MPFR, passing
+`--no-default-features` will run some limited tests.
 
 The multiprecision tests use the [`rug`] crate for bindings to MPFR. MPFR can
 be difficult to build on non-Unix systems, refer to [`gmp_mpfr_sys`] for help.

library/compiler-builtins/libm/ci/run.sh

@@ -14,7 +14,15 @@ if [ -z "$target" ]; then
     target="$host_target"
 fi
 
-extra_flags=""
+# We enumerate features manually.
+extra_flags="--no-default-features"
+
+# Enable arch-specific routines when available.
+extra_flags="$extra_flags --features arch"
+
+# Always enable `unstable-float` since it expands available API but does not
+# change any implementations.
+extra_flags="$extra_flags --features unstable-float"
 
 # We need to specifically skip tests for musl-math-sys on systems that can't
 # build musl since otherwise `--all` will activate it.
@@ -57,14 +65,8 @@ case "$target" in
     *windows-gnu) extra_flags="$extra_flags --exclude libm-macros" ;;
 esac
 
-# Make sure we can build with overriding features. We test the indibidual
-# features it controls separately.
-cargo check --no-default-features
-cargo check --features "force-soft-floats"
-
-# Always enable `unstable-float` since it expands available API but does not
-# change any implementations.
-extra_flags="$extra_flags --features unstable-float"
+# Make sure we can build with overriding features.
+cargo check -p libm --no-default-features
 
 if [ "${BUILD_ONLY:-}" = "1" ]; then
     cmd="cargo build --target $target --package libm"
@@ -80,11 +82,14 @@ else
     $cmd --features unstable-intrinsics
     $cmd --features unstable-intrinsics --benches
     
-    # Test the same in release mode, which also increases coverage.
+    # Test the same in release mode, which also increases coverage. Also ensure
+    # the soft float routines are checked.
     $cmd --profile release-checked 
+    $cmd --profile release-checked --features force-soft-floats
     $cmd --profile release-checked --features unstable-intrinsics
     $cmd --profile release-checked --features unstable-intrinsics --benches
 
-    ENSURE_NO_PANIC=1 cargo build --target "$target" --release
+    # Ensure that the routines do not panic.
+    ENSURE_NO_PANIC=1 cargo build -p libm --target "$target" --no-default-features --release
 fi
 

library/compiler-builtins/libm/crates/libm-test/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 publish = false
 
 [features]
-default = ["unstable-float"]
+default = ["build-mpfr", "build-musl", "unstable-float"]
 
 # Propagated from libm because this affects which functions we test.
 unstable-float = ["libm/unstable-float", "rug?/nightly-float"]