musl/src/math/nextafterf.c

/* origin: FreeBSD /usr/src/lib/msun/src/s_nextafterf.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"

float nextafterf(float x, float y)
{
	volatile float t;
	int32_t hx,hy,ix,iy;

	GET_FLOAT_WORD(hx, x);
	GET_FLOAT_WORD(hy, y);
	ix = hx & 0x7fffffff;  /* |x| */
	iy = hy & 0x7fffffff;  /* |y| */

	if (ix > 0x7f800000 || /* x is nan */
	    iy > 0x7f800000)   /* y is nan */
		return x+y;
	if (x == y)            /* x == y */
		return y;
	if (ix == 0) {         /* x == 0 */
		SET_FLOAT_WORD(x, (hy&0x80000000)|1); /* return +-minsubnormal */
		/* raise underflow flag */
		t = x*x;
		if (t == x)
			return t;
		return x;
	}
	if (hx >= 0) {         /* x > 0 */
		if (hx > hy) {             /* x > y, x -= ulp */
			hx--;
		} else {                   /* x < y, x += ulp */
			hx++;
		}
	} else {               /* x < 0 */
		if (hy >= 0 || hx > hy) {  /* x < y, x -= ulp */
			hx--;
		} else {                   /* x > y, x += ulp */
			hx++;
		}
	}
	hy = hx & 0x7f800000;
	if (hy >= 0x7f800000)  /* overflow */
		return x+x;
	if (hy < 0x00800000) { /* underflow */
		/* raise underflow flag */
		t = x*x;
		if (t != x) {
			SET_FLOAT_WORD(y, hx);
			return y;
		}
	}
	SET_FLOAT_WORD(x, hx);
	return x;
}