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

fusl/src/math/__rem_pio2.c

Index: fusl/src/math/__rem_pio2.c
diff --git a/fusl/src/math/__rem_pio2.c b/fusl/src/math/__rem_pio2.c
new file mode 100644
index 0000000000000000000000000000000000000000..d403f81c792217a195d9680d9356eec17f734f41
--- /dev/null
+++ b/fusl/src/math/__rem_pio2.c
@@ -0,0 +1,177 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ *
+ * Optimized by Bruce D. Evans.
+ */
+/* __rem_pio2(x,y)
+ *
+ * return the remainder of x rem pi/2 in y[0]+y[1]
+ * 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  33 bit of pi/2
+ * pio2_1t:  pi/2 - pio2_1
+ * pio2_2:   second 33 bit of pi/2
+ * pio2_2t:  pi/2 - (pio2_1+pio2_2)
+ * pio2_3:   third  33 bit of pi/2
+ * pio2_3t:  pi/2 - (pio2_1+pio2_2+pio2_3)
+ */
+static const double
+toint   = 1.5/EPS,
+invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
+pio2_1  = 1.57079632673412561417e+00, /* 0x3FF921FB, 0x54400000 */
+pio2_1t = 6.07710050650619224932e-11, /* 0x3DD0B461, 0x1A626331 */
+pio2_2  = 6.07710050630396597660e-11, /* 0x3DD0B461, 0x1A600000 */
+pio2_2t = 2.02226624879595063154e-21, /* 0x3BA3198A, 0x2E037073 */
+pio2_3  = 2.02226624871116645580e-21, /* 0x3BA3198A, 0x2E000000 */
+pio2_3t = 8.47842766036889956997e-32; /* 0x397B839A, 0x252049C1 */
+
+/* caller must handle the case when reduction is not needed: |x| ~<= pi/4 */
+int __rem_pio2(double x, double *y)
+{
+	union {double f; uint64_t i;} u = {x};
+	double_t z,w,t,r,fn;
+	double tx[3],ty[2];
+	uint32_t ix;
+	int sign, n, ex, ey, i;
+
+	sign = u.i>>63;
+	ix = u.i>>32 & 0x7fffffff;
+	if (ix <= 0x400f6a7a) {  /* |x| ~<= 5pi/4 */
+		if ((ix & 0xfffff) == 0x921fb)  /* |x| ~= pi/2 or 2pi/2 */
+			goto medium;  /* cancellation -- use medium case */
+		if (ix <= 0x4002d97c) {  /* |x| ~<= 3pi/4 */
+			if (!sign) {
+				z = x - pio2_1;  /* one round good to 85 bits */
+				y[0] = z - pio2_1t;
+				y[1] = (z-y[0]) - pio2_1t;
+				return 1;
+			} else {
+				z = x + pio2_1;
+				y[0] = z + pio2_1t;
+				y[1] = (z-y[0]) + pio2_1t;
+				return -1;
+			}
+		} else {
+			if (!sign) {
+				z = x - 2*pio2_1;
+				y[0] = z - 2*pio2_1t;
+				y[1] = (z-y[0]) - 2*pio2_1t;
+				return 2;
+			} else {
+				z = x + 2*pio2_1;
+				y[0] = z + 2*pio2_1t;
+				y[1] = (z-y[0]) + 2*pio2_1t;
+				return -2;
+			}
+		}
+	}
+	if (ix <= 0x401c463b) {  /* |x| ~<= 9pi/4 */
+		if (ix <= 0x4015fdbc) {  /* |x| ~<= 7pi/4 */
+			if (ix == 0x4012d97c)  /* |x| ~= 3pi/2 */
+				goto medium;
+			if (!sign) {
+				z = x - 3*pio2_1;
+				y[0] = z - 3*pio2_1t;
+				y[1] = (z-y[0]) - 3*pio2_1t;
+				return 3;
+			} else {
+				z = x + 3*pio2_1;
+				y[0] = z + 3*pio2_1t;
+				y[1] = (z-y[0]) + 3*pio2_1t;
+				return -3;
+			}
+		} else {
+			if (ix == 0x401921fb)  /* |x| ~= 4pi/2 */
+				goto medium;
+			if (!sign) {
+				z = x - 4*pio2_1;
+				y[0] = z - 4*pio2_1t;
+				y[1] = (z-y[0]) - 4*pio2_1t;
+				return 4;
+			} else {
+				z = x + 4*pio2_1;
+				y[0] = z + 4*pio2_1t;
+				y[1] = (z-y[0]) + 4*pio2_1t;
+				return -4;
+			}
+		}
+	}
+	if (ix < 0x413921fb) {  /* |x| ~< 2^20*(pi/2), medium size */
+medium:
+		/* rint(x/(pi/2)), Assume round-to-nearest. */
+		fn = (double_t)x*invpio2 + toint - toint;
+		n = (int32_t)fn;
+		r = x - fn*pio2_1;
+		w = fn*pio2_1t;  /* 1st round, good to 85 bits */
+		y[0] = r - w;
+		u.f = y[0];
+		ey = u.i>>52 & 0x7ff;
+		ex = ix>>20;
+		if (ex - ey > 16) { /* 2nd round, good to 118 bits */
+			t = r;
+			w = fn*pio2_2;
+			r = t - w;
+			w = fn*pio2_2t - ((t-r)-w);
+			y[0] = r - w;
+			u.f = y[0];
+			ey = u.i>>52 & 0x7ff;
+			if (ex - ey > 49) {  /* 3rd round, good to 151 bits, covers all cases */
+				t = r;
+				w = fn*pio2_3;
+				r = t - w;
+				w = fn*pio2_3t - ((t-r)-w);
+				y[0] = r - w;
+			}
+		}
+		y[1] = (r - y[0]) - w;
+		return n;
+	}
+	/*
+	 * all other (large) arguments
+	 */
+	if (ix >= 0x7ff00000) {  /* x is inf or NaN */
+		y[0] = y[1] = x - x;
+		return 0;
+	}
+	/* set z = scalbn(|x|,-ilogb(x)+23) */
+	u.f = x;
+	u.i &= (uint64_t)-1>>12;
+	u.i |= (uint64_t)(0x3ff + 23)<<52;
+	z = u.f;
+	for (i=0; i < 2; i++) {
+		tx[i] = (double)(int32_t)z;
+		z     = (z-tx[i])*0x1p24;
+	}
+	tx[i] = z;
+	/* skip zero terms, first term is non-zero */
+	while (tx[i] == 0.0)
+		i--;
+	n = __rem_pio2_large(tx,ty,(int)(ix>>20)-(0x3ff+23),i+1,1);
+	if (sign) {
+		y[0] = -ty[0];
+		y[1] = -ty[1];
+		return -n;
+	}
+	y[0] = ty[0];
+	y[1] = ty[1];
+	return n;
+}