1 files changed, 36 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/libm/src/math/atanh.rs b/vendor/compiler_builtins/libm/src/math/atanh.rs
new file mode 100644
index 000000000..79a989c42
--- /dev/null
+++ b/vendor/compiler_builtins/libm/src/math/atanh.rs
@@ -0,0 +1,36 @@
+use super::log1p;
+
+/* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */
+/// Inverse hyperbolic tangent (f64)
+///
+/// Calculates the inverse hyperbolic tangent of `x`.
+/// Is defined as `log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2`.
+pub fn atanh(x: f64) -> f64 {
+    let u = x.to_bits();
+    let e = ((u >> 52) as usize) & 0x7ff;
+    let sign = (u >> 63) != 0;
+
+    /* |x| */
+    let mut y = f64::from_bits(u & 0x7fff_ffff_ffff_ffff);
+
+    if e < 0x3ff - 1 {
+        if e < 0x3ff - 32 {
+            /* handle underflow */
+            if e == 0 {
+                force_eval!(y as f32);
+            }
+        } else {
+            /* |x| < 0.5, up to 1.7ulp error */
+            y = 0.5 * log1p(2.0 * y + 2.0 * y * y / (1.0 - y));
+        }
+    } else {
+        /* avoid overflow */
+        y = 0.5 * log1p(2.0 * (y / (1.0 - y)));
+    }
+
+    if sign {
+        -y
+    } else {
+        y
+    }
+}