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      1 /*	$NetBSD: s_nexttowardf.c,v 1.5 2024/05/05 14:06:47 riastradh Exp $	*/
      2 
      3 /*
      4  * ====================================================
      5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      6  *
      7  * Developed at SunPro, a Sun Microsystems, Inc. business.
      8  * Permission to use, copy, modify, and distribute this
      9  * software is freely granted, provided that this notice
     10  * is preserved.
     11  * ====================================================
     12  */
     13 
     14 #include <sys/cdefs.h>
     15 #if 0
     16 __FBSDID("$FreeBSD: src/lib/msun/src/s_nexttowardf.c,v 1.3 2011/02/10 07:38:38 das Exp $");
     17 #else
     18 __RCSID("$NetBSD: s_nexttowardf.c,v 1.5 2024/05/05 14:06:47 riastradh Exp $");
     19 #endif
     20 
     21 #include <string.h>
     22 #include <float.h>
     23 #include <machine/ieee.h>
     24 
     25 #include "math.h"
     26 #include "math_private.h"
     27 
     28 /*
     29  * On ports where long double is just double, reuse the ieee_double_u
     30  * union as if it were ieee_ext_u -- broken-down components of (long)
     31  * double values.
     32  */
     33 #ifndef __HAVE_LONG_DOUBLE
     34 #define	ieee_ext_u	ieee_double_u
     35 #define	extu_ld		dblu_d
     36 #define	extu_ext	dblu_dbl
     37 #define	ext_sign	dbl_sign
     38 #define	ext_exp		dbl_exp
     39 #define	ext_frach	dbl_frach
     40 #define	ext_fracl	dbl_fracl
     41 #define	EXT_EXP_INFNAN	DBL_EXP_INFNAN
     42 #define	LDBL_NBIT	0
     43 #endif
     44 
     45 /*
     46  * XXX We should arrange to define LDBL_NBIT unconditionally in the
     47  * appropriate MD header file.
     48  */
     49 #ifdef LDBL_IMPLICIT_NBIT
     50 #define	LDBL_NBIT	0
     51 #endif
     52 
     53 float
     54 nexttowardf(float x, long double y)
     55 {
     56 	volatile float t;
     57 	int32_t hx,ix;
     58 	union ieee_ext_u uy;
     59 
     60 	GET_FLOAT_WORD(hx,x);
     61 	ix = hx&0x7fffffff;		/* |x| */
     62 
     63 	memset(&uy, 0, sizeof(uy));
     64 	uy.extu_ld = y;
     65 	uy.extu_ext.ext_frach &= ~LDBL_NBIT;
     66 
     67 	if((ix>0x7f800000) ||
     68 	   (uy.extu_ext.ext_exp == EXT_EXP_INFNAN &&
     69 	    (uy.extu_ext.ext_frach | uy.extu_ext.ext_fracl) != 0))
     70 	   return x+y;	/* x or y is nan */
     71 	if(x==y) return (float)y;		/* x=y, return y */
     72 	if(ix==0) {				/* x == 0 */
     73 	    SET_FLOAT_WORD(x,(uy.extu_ext.ext_sign<<31)|1);/* return +-minsubnormal */
     74 	    t = x*x;
     75 	    if(t==x) return t; else return x;	/* raise underflow flag */
     76 	}
     77 	if((hx >= 0) ^ (x < y))			/* x -= ulp */
     78 	    hx -= 1;
     79 	else					/* x += ulp */
     80 	    hx += 1;
     81 	ix = hx&0x7f800000;
     82 	if(ix>=0x7f800000) return x+x;	/* overflow  */
     83 	if(ix<0x00800000) {		/* underflow */
     84 	    t = x*x;
     85 	    if(t!=x) {		/* raise underflow flag */
     86 	        SET_FLOAT_WORD(x,hx);
     87 		return x;
     88 	    }
     89 	}
     90 	SET_FLOAT_WORD(x,hx);
     91 	return x;
     92 }
     93