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

fusl/src/math/sqrtf.c

+/* origin: FreeBSD /usr/src/lib/msun/src/e_sqrtf.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 tiny = 1.0e-30;
+
+float sqrtf(float x)
+{
+        float z;
+        int32_t sign = (int)0x80000000;
+        int32_t ix,s,q,m,t,i;
+        uint32_t r;
+
+        GET_FLOAT_WORD(ix, x);
+
+        /* take care of Inf and NaN */
+        if ((ix&0x7f800000) == 0x7f800000)
+                return x*x + x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */
+
+        /* take care of zero */
+        if (ix <= 0) {
+                if ((ix&~sign) == 0)
+                        return x;  /* sqrt(+-0) = +-0 */
+                if (ix < 0)
+                        return (x-x)/(x-x);  /* sqrt(-ve) = sNaN */
+        }
+        /* normalize x */
+        m = ix>>23;
+        if (m == 0) {  /* subnormal x */
+                for (i = 0; (ix&0x00800000) == 0; i++)
+                        ix<<=1;
+                m -= i - 1;
+        }
+        m -= 127;  /* unbias exponent */
+        ix = (ix&0x007fffff)|0x00800000;
+        if (m&1)  /* odd m, double x to make it even */
+                ix += ix;
+        m >>= 1;  /* m = [m/2] */
+
+        /* generate sqrt(x) bit by bit */
+        ix += ix;
+        q = s = 0;       /* q = sqrt(x) */
+        r = 0x01000000;  /* r = moving bit from right to left */
+
+        while (r != 0) {
+                t = s + r;
+                if (t <= ix) {
+                        s = t+r;
+                        ix -= t;
+                        q += r;
+                }
+                ix += ix;
+                r >>= 1;
+        }
+
+        /* use floating add to find out rounding direction */
+        if (ix != 0) {
+                z = 1.0f - tiny; /* raise inexact flag */
+                if (z >= 1.0f) {
+                        z = 1.0f + tiny;
+                        if (z > 1.0f)
+                                q += 2;
+                        else
+                                q += q & 1;
+                }
+        }
+        ix = (q>>1) + 0x3f000000;
+        ix += m << 23;
+        SET_FLOAT_WORD(z, ix);
+        return z;
+}