glibc/sysdeps/ieee754/flt-32/s_nearbyintf.c

/* s_rintf.c -- float version of s_rint.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */
/* Adapted for use as nearbyint by Ulrich Drepper <drepper@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 <fenv.h>
#include <math.h>
#include <math-barriers.h>
#include <math_private.h>
#include <libm-alias-float.h>

static const float
TWO23[2]={
  8.3886080000e+06, /* 0x4b000000 */
 -8.3886080000e+06, /* 0xcb000000 */
};

float
__nearbyintf(float x)
{
	fenv_t env;
	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) {
		libc_feholdexceptf (&env);
		w = TWO23[sx] + math_opt_barrier (x);
		t =  w-TWO23[sx];
		math_force_eval (t);
		libc_fesetenvf (&env);
		GET_FLOAT_WORD(i0,t);
		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
		return t;
	    }
	} else {
	    if(__builtin_expect(j0==0x80, 0)) return x+x;	/* inf or NaN */
	    else return x;		/* x is integral */
	}
	libc_feholdexceptf (&env);
	w = TWO23[sx] + math_opt_barrier (x);
	t = w-TWO23[sx];
	math_force_eval (t);
	libc_fesetenvf (&env);
	return t;
}
libm_alias_float (__nearbyint, nearbyint)