1 files changed, 36 insertions, 0 deletions
diff --git a/library/compiler-builtins/libm/src/math/cosh.rs b/library/compiler-builtins/libm/src/math/cosh.rs
new file mode 100644
index 00000000000..d2e43fd6cb6
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/cosh.rs
@@ -0,0 +1,36 @@
+use super::{exp, expm1, k_expo2};
+
+/// Hyperbolic cosine (f64)
+///
+/// Computes the hyperbolic cosine of the argument x.
+/// Is defined as `(exp(x) + exp(-x))/2`
+/// Angles are specified in radians.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn cosh(mut x: f64) -> f64 {
+    /* |x| */
+    let mut ix = x.to_bits();
+    ix &= 0x7fffffffffffffff;
+    x = f64::from_bits(ix);
+    let w = ix >> 32;
+
+    /* |x| < log(2) */
+    if w < 0x3fe62e42 {
+        if w < 0x3ff00000 - (26 << 20) {
+            let x1p120 = f64::from_bits(0x4770000000000000);
+            force_eval!(x + x1p120);
+            return 1.;
+        }
+        let t = expm1(x); // exponential minus 1
+        return 1. + t * t / (2. * (1. + t));
+    }
+
+    /* |x| < log(DBL_MAX) */
+    if w < 0x40862e42 {
+        let t = exp(x);
+        /* note: if x>log(0x1p26) then the 1/t is not needed */
+        return 0.5 * (t + 1. / t);
+    }
+
+    /* |x| > log(DBL_MAX) or nan */
+    k_expo2(x)
+}