musl/src/math/rintf.c

/* origin: FreeBSD /usr/src/lib/msun/src/s_rintf.c */
/*
 * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected].
 */
/*
 * ====================================================
 * 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
TWO23[2] = {
  8.3886080000e+06, /* 0x4b000000 */
 -8.3886080000e+06, /* 0xcb000000 */
};

float rintf(float x)
{
	int32_t i0,j0,sx;
	float w,t;

	GET_FLOAT_WORD(i0, x);
	sx = (i0>>31) & 1;
	j0 = ((i0>>23)&0xff) - 0x7f;
	if (j0 < 23) {
		if (j0 < 0) {
			if ((i0&0x7fffffff) == 0)
				return x;
			STRICT_ASSIGN(float, w, TWO23[sx] + x);
			t = w - TWO23[sx];
			GET_FLOAT_WORD(i0, t);
			SET_FLOAT_WORD(t, (i0&0x7fffffff)|(sx<<31));
			return t;
		}
		STRICT_ASSIGN(float, w, TWO23[sx] + x);
		return w - TWO23[sx];
	}
	if (j0 == 0x80)
		return x+x;  /* inf or NaN */
	return x;            /* x is integral */
}