compiler/stdc/math/s_nexttowardf.c

   1 /*
   2  * ====================================================
   3  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   4  *
   5  * Developed at SunPro, a Sun Microsystems, Inc. business.
   6  * Permission to use, copy, modify, and distribute this
   7  * software is freely granted, provided that this notice
   8  * is preserved.
   9  * ====================================================
  10  */
  11
  12 #ifndef lint
  13 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_nexttowardf.c,v 1.1 2005/03/07 04:57:38 das Exp $";
  14 #endif
  15
  16 #include <float.h>
  17
  18 #include "fpmath.h"
  19 #include "math.h"
  20 #include "math_private.h"
  21
  22 #define LDBL_INFNAN_EXP (LDBL_MAX_EXP * 2 - 1)
  23
  24 float
  25 nexttowardf(float x, long double y)
  26 {
  27         union IEEEl2bits uy;
  28         volatile float t;
  29         int32_t hx,ix;
  30
  31         GET_FLOAT_WORD(hx,x);
  32         ix = hx&0x7fffffff;             /* |x| */
  33         uy.e = y;
  34
  35         if((ix>0x7f800000) ||
  36            (uy.bits.exp == LDBL_INFNAN_EXP &&
  37             ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
  38            return x+y;  /* x or y is nan */
  39         if(x==y) return (float)y;               /* x=y, return y */
  40         if(ix==0) {                             /* x == 0 */
  41             SET_FLOAT_WORD(x,(uy.bits.sign<<31)|1);/* return +-minsubnormal */
  42             t = x*x;
  43             if(t==x) return t; else return x;   /* raise underflow flag */
  44         }
  45         if(hx>=0 ^ x < y)                       /* x -= ulp */
  46             hx -= 1;
  47         else                                    /* x += ulp */
  48             hx += 1;
  49         ix = hx&0x7f800000;
  50         if(ix>=0x7f800000) return x+x;  /* overflow  */
  51         if(ix<0x00800000) {             /* underflow */
  52             t = x*x;
  53             if(t!=x) {          /* raise underflow flag */
  54                 SET_FLOAT_WORD(y,hx);
  55                 return y;
  56             }
  57         }
  58         SET_FLOAT_WORD(x,hx);
  59         return x;
  60 }