Expose the support module publicly with a test feature

library/compiler-builtins/libm/Cargo.toml

@@ -26,6 +26,9 @@ unstable = ["unstable-intrinsics"]
 # Enable calls to functions in `core::intrinsics`
 unstable-intrinsics = []
 
+# Make some internal things public for testing.
+unstable-test-support = []
+
 # Used to prevent using any intrinsics or arch-specific code.
 #
 # HACK: this is a negative feature which is generally a bad idea in Cargo, but

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

@@ -13,6 +13,7 @@ bench = false
 # Duplicated from libm's Cargo.toml
 unstable = []
 unstable-intrinsics = []
+unstable-test-support = []
 checked = []
 force-soft-floats = []
 

library/compiler-builtins/libm/src/math/mod.rs

@@ -74,9 +74,16 @@ macro_rules! div {
     };
 }
 
-// Private modules
+// `support` may be public for testing
 #[macro_use]
+#[cfg(feature = "unstable-test-support")]
+pub mod support;
+
+#[macro_use]
+#[cfg(not(feature = "unstable-test-support"))]
 mod support;
+
+// Private modules
 mod arch;
 mod expo2;
 mod fenv;