add fdlibm

git-svn-id: http://svn2.nishi.boats/svn/milsko/trunk@557 b9cfdab3-6d41-4d17-bbe4-086880011989

external/fdlibm/s_nextafter.c

@@ -0,0 +1,76 @@
+
+/* @(#)s_nextafter.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+/* IEEE functions
+ *	nextafter(x,y)
+ *	return the next machine floating-point number of x in the
+ *	direction toward y.
+ *   Special cases:
+ */
+
+#include "math.h"
+
+double nextafter(double x, double y) {
+	int	 hx, hy, ix, iy;
+	unsigned lx, ly;
+
+	hx = __HI(x);	      /* high word of x */
+	lx = __LO(x);	      /* low  word of x */
+	hy = __HI(y);	      /* high word of y */
+	ly = __LO(y);	      /* low  word of y */
+	ix = hx & 0x7fffffff; /* |x| */
+	iy = hy & 0x7fffffff; /* |y| */
+
+	if(((ix >= 0x7ff00000) && ((ix - 0x7ff00000) | lx) != 0) || /* x is nan */
+	   ((iy >= 0x7ff00000) && ((iy - 0x7ff00000) | ly) != 0))   /* y is nan */
+		return x + y;
+	if(x == y) return x;		   /* x=y, return x */
+	if((ix | lx) == 0) {		   /* x == 0 */
+		__HI(x) = hy & 0x80000000; /* return +-minsubnormal */
+		__LO(x) = 1;
+		y	= x * x;
+		if(y == x) return y;
+		else
+			return x; /* raise underflow flag */
+	}
+	if(hx >= 0) {					   /* x > 0 */
+		if(hx > hy || ((hx == hy) && (lx > ly))) { /* x > y, x -= ulp */
+			if(lx == 0) hx -= 1;
+			lx -= 1;
+		} else { /* x < y, x += ulp */
+			lx += 1;
+			if(lx == 0) hx += 1;
+		}
+	} else {						      /* x < 0 */
+		if(hy >= 0 || hx > hy || ((hx == hy) && (lx > ly))) { /* x < y, x -= ulp */
+			if(lx == 0) hx -= 1;
+			lx -= 1;
+		} else { /* x > y, x += ulp */
+			lx += 1;
+			if(lx == 0) hx += 1;
+		}
+	}
+	hy = hx & 0x7ff00000;
+	if(hy >= 0x7ff00000) return x + x; /* overflow  */
+	if(hy < 0x00100000) {		   /* underflow */
+		y = x * x;
+		if(y != x) { /* raise underflow flag */
+			__HI(y) = hx;
+			__LO(y) = lx;
+			return y;
+		}
+	}
+	__HI(x) = hx;
+	__LO(x) = lx;
+	return x;
+}