Add a "fork" of musl as //fusl.

fusl/src/math/expf.c

Index: fusl/src/math/expf.c
diff --git a/fusl/src/math/expf.c b/fusl/src/math/expf.c
new file mode 100644
index 0000000000000000000000000000000000000000..16e9afe62a21cbd09d6845f8076fb37e4fa5a560
--- /dev/null
+++ b/fusl/src/math/expf.c
@@ -0,0 +1,81 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_expf.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.
+ * ====================================================
+ */
+
+#include "libm.h"
+
+static const float
+half[2] = {0.5,-0.5},
+ln2hi   = 6.9314575195e-1f,  /* 0x3f317200 */
+ln2lo   = 1.4286067653e-6f,  /* 0x35bfbe8e */
+invln2  = 1.4426950216e+0f,  /* 0x3fb8aa3b */
+/*
+ * Domain [-0.34568, 0.34568], range ~[-4.278e-9, 4.447e-9]:
+ * |x*(exp(x)+1)/(exp(x)-1) - p(x)| < 2**-27.74
+ */
+P1 =  1.6666625440e-1f, /*  0xaaaa8f.0p-26 */
+P2 = -2.7667332906e-3f; /* -0xb55215.0p-32 */
+
+float expf(float x)
+{
+	float_t hi, lo, c, xx, y;
+	int k, sign;
+	uint32_t hx;
+
+	GET_FLOAT_WORD(hx, x);
+	sign = hx >> 31;   /* sign bit of x */
+	hx &= 0x7fffffff;  /* high word of |x| */
+
+	/* special cases */
+	if (hx >= 0x42aeac50) {  /* if |x| >= -87.33655f or NaN */
+		if (hx >= 0x42b17218 && !sign) {  /* x >= 88.722839f */
+			/* overflow */
+			x *= 0x1p127f;
+			return x;
+		}
+		if (sign) {
+			/* underflow */
+			FORCE_EVAL(-0x1p-149f/x);
+			if (hx >= 0x42cff1b5)  /* x <= -103.972084f */
+				return 0;
+		}
+	}
+
+	/* argument reduction */
+	if (hx > 0x3eb17218) {  /* if |x| > 0.5 ln2 */
+		if (hx > 0x3f851592)  /* if |x| > 1.5 ln2 */
+			k = invln2*x + half[sign];
+		else
+			k = 1 - sign - sign;
+		hi = x - k*ln2hi;  /* k*ln2hi is exact here */
+		lo = k*ln2lo;
+		x = hi - lo;
+	} else if (hx > 0x39000000) {  /* |x| > 2**-14 */
+		k = 0;
+		hi = x;
+		lo = 0;
+	} else {
+		/* raise inexact */
+		FORCE_EVAL(0x1p127f + x);
+		return 1 + x;
+	}
+
+	/* x is now in primary range */
+	xx = x*x;
+	c = x - xx*(P1+xx*P2);
+	y = 1 + (x*c/(2-c) - lo + hi);
+	if (k == 0)
+		return y;
+	return scalbnf(y, k);
+}