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

fusl/src/math/__rem_pio2f.c

+/* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2f.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Debugged and optimized by Bruce D. Evans.
+ */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+/* __rem_pio2f(x,y)
+ *
+ * return the remainder of x rem pi/2 in *y
+ * use double precision for everything except passing x
+ * use __rem_pio2_large() for large x
+ */
+
+#include "libm.h"
+
+#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
+#define EPS DBL_EPSILON
+#elif FLT_EVAL_METHOD==2
+#define EPS LDBL_EPSILON
+#endif
+
+/*
+ * invpio2:  53 bits of 2/pi
+ * pio2_1:   first 25 bits of pi/2
+ * pio2_1t:  pi/2 - pio2_1
+ */
+static const double
+toint   = 1.5/EPS,
+invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
+pio2_1  = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
+pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
+
+int __rem_pio2f(float x, double *y)
+{
+        union {float f; uint32_t i;} u = {x};
+        double tx[1],ty[1];
+        double_t fn;
+        uint32_t ix;
+        int n, sign, e0;
+
+        ix = u.i & 0x7fffffff;
+        /* 25+53 bit pi is good enough for medium size */
+        if (ix < 0x4dc90fdb) {  /* |x| ~< 2^28*(pi/2), medium size */
+                /* Use a specialized rint() to get fn.  Assume round-to-nearest. */
+                fn = (double_t)x*invpio2 + toint - toint;
+                n  = (int32_t)fn;
+                *y = x - fn*pio2_1 - fn*pio2_1t;
+                return n;
+        }
+        if(ix>=0x7f800000) {  /* x is inf or NaN */
+                *y = x-x;
+                return 0;
+        }
+        /* scale x into [2^23, 2^24-1] */
+        sign = u.i>>31;
+        e0 = (ix>>23) - (0x7f+23);  /* e0 = ilogb(|x|)-23, positive */
+        u.i = ix - (e0<<23);
+        tx[0] = u.f;
+        n  =  __rem_pio2_large(tx,ty,e0,1,0);
+        if (sign) {
+                *y = -ty[0];
+                return -n;
+        }
+        *y = ty[0];
+        return n;
+}