1 files changed, 144 insertions, 0 deletions
diff --git a/vendor/compiler_builtins/libm/src/math/expm1.rs b/vendor/compiler_builtins/libm/src/math/expm1.rs
new file mode 100644
index 000000000..42608509a
--- /dev/null
+++ b/vendor/compiler_builtins/libm/src/math/expm1.rs
@@ -0,0 +1,144 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_expm1.c */
+/*
+ * ====================================================
+ * 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 core::f64;
+
+const O_THRESHOLD: f64 = 7.09782712893383973096e+02; /* 0x40862E42, 0xFEFA39EF */
+const LN2_HI: f64 = 6.93147180369123816490e-01; /* 0x3fe62e42, 0xfee00000 */
+const LN2_LO: f64 = 1.90821492927058770002e-10; /* 0x3dea39ef, 0x35793c76 */
+const INVLN2: f64 = 1.44269504088896338700e+00; /* 0x3ff71547, 0x652b82fe */
+/* Scaled Q's: Qn_here = 2**n * Qn_above, for R(2*z) where z = hxs = x*x/2: */
+const Q1: f64 = -3.33333333333331316428e-02; /* BFA11111 111110F4 */
+const Q2: f64 = 1.58730158725481460165e-03; /* 3F5A01A0 19FE5585 */
+const Q3: f64 = -7.93650757867487942473e-05; /* BF14CE19 9EAADBB7 */
+const Q4: f64 = 4.00821782732936239552e-06; /* 3ED0CFCA 86E65239 */
+const Q5: f64 = -2.01099218183624371326e-07; /* BE8AFDB7 6E09C32D */
+
+/// Exponential, base *e*, of x-1 (f64)
+///
+/// Calculates the exponential of `x` and subtract 1, that is, *e* raised
+/// to the power `x` minus 1 (where *e* is the base of the natural
+/// system of logarithms, approximately 2.71828).
+/// The result is accurate even for small values of `x`,
+/// where using `exp(x)-1` would lose many significant digits.
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn expm1(mut x: f64) -> f64 {
+    let hi: f64;
+    let lo: f64;
+    let k: i32;
+    let c: f64;
+    let mut t: f64;
+    let mut y: f64;
+
+    let mut ui = x.to_bits();
+    let hx = ((ui >> 32) & 0x7fffffff) as u32;
+    let sign = (ui >> 63) as i32;
+
+    /* filter out huge and non-finite argument */
+    if hx >= 0x4043687A {
+        /* if |x|>=56*ln2 */
+        if x.is_nan() {
+            return x;
+        }
+        if sign != 0 {
+            return -1.0;
+        }
+        if x > O_THRESHOLD {
+            x *= f64::from_bits(0x7fe0000000000000);
+            return x;
+        }
+    }
+
+    /* argument reduction */
+    if hx > 0x3fd62e42 {
+        /* if  |x| > 0.5 ln2 */
+        if hx < 0x3FF0A2B2 {
+            /* and |x| < 1.5 ln2 */
+            if sign == 0 {
+                hi = x - LN2_HI;
+                lo = LN2_LO;
+                k = 1;
+            } else {
+                hi = x + LN2_HI;
+                lo = -LN2_LO;
+                k = -1;
+            }
+        } else {
+            k = (INVLN2 * x + if sign != 0 { -0.5 } else { 0.5 }) as i32;
+            t = k as f64;
+            hi = x - t * LN2_HI; /* t*ln2_hi is exact here */
+            lo = t * LN2_LO;
+        }
+        x = hi - lo;
+        c = (hi - x) - lo;
+    } else if hx < 0x3c900000 {
+        /* |x| < 2**-54, return x */
+        if hx < 0x00100000 {
+            force_eval!(x);
+        }
+        return x;
+    } else {
+        c = 0.0;
+        k = 0;
+    }
+
+    /* x is now in primary range */
+    let hfx = 0.5 * x;
+    let hxs = x * hfx;
+    let r1 = 1.0 + hxs * (Q1 + hxs * (Q2 + hxs * (Q3 + hxs * (Q4 + hxs * Q5))));
+    t = 3.0 - r1 * hfx;
+    let mut e = hxs * ((r1 - t) / (6.0 - x * t));
+    if k == 0 {
+        /* c is 0 */
+        return x - (x * e - hxs);
+    }
+    e = x * (e - c) - c;
+    e -= hxs;
+    /* exp(x) ~ 2^k (x_reduced - e + 1) */
+    if k == -1 {
+        return 0.5 * (x - e) - 0.5;
+    }
+    if k == 1 {
+        if x < -0.25 {
+            return -2.0 * (e - (x + 0.5));
+        }
+        return 1.0 + 2.0 * (x - e);
+    }
+    ui = ((0x3ff + k) as u64) << 52; /* 2^k */
+    let twopk = f64::from_bits(ui);
+    if k < 0 || k > 56 {
+        /* suffice to return exp(x)-1 */
+        y = x - e + 1.0;
+        if k == 1024 {
+            y = y * 2.0 * f64::from_bits(0x7fe0000000000000);
+        } else {
+            y = y * twopk;
+        }
+        return y - 1.0;
+    }
+    ui = ((0x3ff - k) as u64) << 52; /* 2^-k */
+    let uf = f64::from_bits(ui);
+    if k < 20 {
+        y = (x - e + (1.0 - uf)) * twopk;
+    } else {
+        y = (x - (e + uf) + 1.0) * twopk;
+    }
+    y
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn sanity_check() {
+        assert_eq!(super::expm1(1.1), 2.0041660239464334);
+    }
+}