Initial import

libc/math/sqrtf.c

@@ -0,0 +1,83 @@
+/* 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 "libc/math/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;
+	SET_FLOAT_WORD(z, ix + ((uint32_t)m << 23));
+	return z;
+}