1 files changed, 31 insertions, 0 deletions
diff --git a/library/compiler-builtins/libm/src/math/fabsf128.rs b/library/compiler-builtins/libm/src/math/fabsf128.rs
new file mode 100644
index 00000000000..46429ca4940
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/fabsf128.rs
@@ -0,0 +1,31 @@
+/// Absolute value (magnitude) (f128)
+///
+/// Calculates the absolute value (magnitude) of the argument `x`,
+/// by direct manipulation of the bit representation of `x`.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn fabsf128(x: f128) -> f128 {
+    super::generic::fabs(x)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn sanity_check() {
+        assert_eq!(fabsf128(-1.0), 1.0);
+        assert_eq!(fabsf128(2.8), 2.8);
+    }
+
+    /// The spec: https://en.cppreference.com/w/cpp/numeric/math/fabs
+    #[test]
+    fn spec_tests() {
+        assert!(fabsf128(f128::NAN).is_nan());
+        for f in [0.0, -0.0].iter().copied() {
+            assert_eq!(fabsf128(f), 0.0);
+        }
+        for f in [f128::INFINITY, f128::NEG_INFINITY].iter().copied() {
+            assert_eq!(fabsf128(f), f128::INFINITY);
+        }
+    }
+}