1 files changed, 68 insertions, 0 deletions
diff --git a/library/compiler-builtins/libm/src/math/asinf.rs b/library/compiler-builtins/libm/src/math/asinf.rs
new file mode 100644
index 00000000000..ed685556730
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/asinf.rs
@@ -0,0 +1,68 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_asinf.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+use super::sqrt::sqrt;
+use super::support::Float;
+
+const PIO2: f64 = 1.570796326794896558e+00;
+
+/* coefficients for R(x^2) */
+const P_S0: f32 = 1.6666586697e-01;
+const P_S1: f32 = -4.2743422091e-02;
+const P_S2: f32 = -8.6563630030e-03;
+const Q_S1: f32 = -7.0662963390e-01;
+
+fn r(z: f32) -> f32 {
+    let p = z * (P_S0 + z * (P_S1 + z * P_S2));
+    let q = 1. + z * Q_S1;
+    p / q
+}
+
+/// Arcsine (f32)
+///
+/// Computes the inverse sine (arc sine) of the argument `x`.
+/// Arguments to asin must be in the range -1 to 1.
+/// Returns values in radians, in the range of -pi/2 to pi/2.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn asinf(mut x: f32) -> f32 {
+    let x1p_120 = f64::from_bits(0x3870000000000000); // 0x1p-120 === 2 ^ (-120)
+
+    let hx = x.to_bits();
+    let ix = hx & 0x7fffffff;
+
+    if ix >= 0x3f800000 {
+        /* |x| >= 1 */
+        if ix == 0x3f800000 {
+            /* |x| == 1 */
+            return ((x as f64) * PIO2 + x1p_120) as f32; /* asin(+-1) = +-pi/2 with inexact */
+        }
+        return 0. / (x - x); /* asin(|x|>1) is NaN */
+    }
+
+    if ix < 0x3f000000 {
+        /* |x| < 0.5 */
+        /* if 0x1p-126 <= |x| < 0x1p-12, avoid raising underflow */
+        if (0x00800000..0x39800000).contains(&ix) {
+            return x;
+        }
+        return x + x * r(x * x);
+    }
+
+    /* 1 > |x| >= 0.5 */
+    let z = (1. - Float::abs(x)) * 0.5;
+    let s = sqrt(z as f64);
+    x = (PIO2 - 2. * (s + s * (r(z) as f64))) as f32;
+    if (hx >> 31) != 0 { -x } else { x }
+}