diff --git a/library/compiler-builtins/libm/.github/workflows/main.yml b/library/compiler-builtins/libm/.github/workflows/main.yml
index 7e371d6136da..35b307f77116 100644
--- a/library/compiler-builtins/libm/.github/workflows/main.yml
+++ b/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/test-multiprecision \
-          --all-targets
+    - run: cargo clippy --all --all-features --all-targets
 
   builtins:
     name: Check use with compiler-builtins
@@ -241,7 +238,7 @@ jobs:
           fi
 
           LIBM_EXTENSIVE_TESTS="$CHANGED" cargo t \
-            --features test-multiprecision,unstable \
+            --features build-mpfr,unstable \
             --profile release-checked \
             -- extensive
       - name: Print test logs if available
diff --git a/library/compiler-builtins/libm/CONTRIBUTING.md b/library/compiler-builtins/libm/CONTRIBUTING.md
index aadcdf03618e..ba7f78ca014c 100644
--- a/library/compiler-builtins/libm/CONTRIBUTING.md
+++ b/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/test-multiprecision,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.
diff --git a/library/compiler-builtins/libm/ci/run.sh b/library/compiler-builtins/libm/ci/run.sh
index 244a22a076de..35b84809fa2c 100755
--- a/library/compiler-builtins/libm/ci/run.sh
+++ b/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.
@@ -44,11 +52,11 @@ case "$target" in
     # Targets that aren't cross compiled work fine
     # FIXME(ci): we should be able to enable aarch64 Linux here once GHA
     # support rolls out.
-    x86_64*) extra_flags="$extra_flags --features libm-test/test-multiprecision" ;;
-    i686*) extra_flags="$extra_flags --features libm-test/test-multiprecision" ;;
-    i586*) extra_flags="$extra_flags --features libm-test/test-multiprecision --features gmp-mpfr-sys/force-cross" ;;
+    x86_64*) extra_flags="$extra_flags --features libm-test/build-mpfr" ;;
+    i686*) extra_flags="$extra_flags --features libm-test/build-mpfr" ;;
+    i586*) extra_flags="$extra_flags --features libm-test/build-mpfr --features gmp-mpfr-sys/force-cross" ;;
     # Apple aarch64 is native
-    aarch64*apple*) extra_flags="$extra_flags --features libm-test/test-multiprecision" ;;
+    aarch64*apple*) extra_flags="$extra_flags --features libm-test/build-mpfr" ;;
 esac
 
 # FIXME: `STATUS_DLL_NOT_FOUND` testing macros on CI.
@@ -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
 
diff --git a/library/compiler-builtins/libm/crates/libm-test/Cargo.toml b/library/compiler-builtins/libm/crates/libm-test/Cargo.toml
index 621e587c56da..d3f18ab3e5bc 100644
--- a/library/compiler-builtins/libm/crates/libm-test/Cargo.toml
+++ b/library/compiler-builtins/libm/crates/libm-test/Cargo.toml
@@ -5,14 +5,14 @@ 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"]
 
 # Generate tests which are random inputs and the outputs are calculated with
 # musl libc.
-test-multiprecision = ["dep:az", "dep:rug", "dep:gmp-mpfr-sys"]
+build-mpfr = ["dep:az", "dep:rug", "dep:gmp-mpfr-sys"]
 
 # Build our own musl for testing and benchmarks
 build-musl = ["dep:musl-math-sys"]
diff --git a/library/compiler-builtins/libm/crates/libm-test/src/lib.rs b/library/compiler-builtins/libm/crates/libm-test/src/lib.rs
index 6e7017f093c3..cb89f1c8ba7f 100644
--- a/library/compiler-builtins/libm/crates/libm-test/src/lib.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/src/lib.rs
@@ -5,7 +5,7 @@
 pub mod domain;
 mod f8_impl;
 pub mod gen;
-#[cfg(feature = "test-multiprecision")]
+#[cfg(feature = "build-mpfr")]
 pub mod mpfloat;
 mod num;
 pub mod op;
diff --git a/library/compiler-builtins/libm/crates/libm-test/src/run_cfg.rs b/library/compiler-builtins/libm/crates/libm-test/src/run_cfg.rs
index 48a654caaf8f..4a52091fe8d2 100644
--- a/library/compiler-builtins/libm/crates/libm-test/src/run_cfg.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/src/run_cfg.rs
@@ -126,7 +126,7 @@ impl TestEnv {
         let id = ctx.fn_ident;
         let op = id.math_op();
 
-        let will_run_mp = cfg!(feature = "test-multiprecision");
+        let will_run_mp = cfg!(feature = "build-mpfr");
 
         // Tests are pretty slow on non-64-bit targets, x86 MacOS, and targets that run in QEMU. Start
         // with a reduced number on these platforms.
diff --git a/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs b/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs
index e2766cfdabd7..2d8856e166e4 100644
--- a/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/tests/multiprecision.rs
@@ -1,6 +1,6 @@
 //! Test with "infinite precision"
 
-#![cfg(feature = "test-multiprecision")]
+#![cfg(feature = "build-mpfr")]
 
 use libm_test::domain::HasDomain;
 use libm_test::gen::random::RandomInput;
diff --git a/library/compiler-builtins/libm/crates/libm-test/tests/z_extensive/main.rs b/library/compiler-builtins/libm/crates/libm-test/tests/z_extensive/main.rs
index 3a2af88bd83b..5448cb6eaa5b 100644
--- a/library/compiler-builtins/libm/crates/libm-test/tests/z_extensive/main.rs
+++ b/library/compiler-builtins/libm/crates/libm-test/tests/z_extensive/main.rs
@@ -1,14 +1,14 @@
 //! `main` is just a wrapper to handle configuration.
 
-#[cfg(not(feature = "test-multiprecision"))]
+#[cfg(not(feature = "build-mpfr"))]
 fn main() {
     eprintln!("multiprecision not enabled; skipping extensive tests");
 }
 
-#[cfg(feature = "test-multiprecision")]
+#[cfg(feature = "build-mpfr")]
 mod run;
 
-#[cfg(feature = "test-multiprecision")]
+#[cfg(feature = "build-mpfr")]
 fn main() {
     run::run();
 }