usr/src/lib/libm/common/R/nextafterf.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 /*
  26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29
  30 #pragma weak __nextafterf = nextafterf
  31
  32 #include "libm.h"
  33
  34 float
  35 nextafterf(float x, float y) {
  36         float w;
  37         int *pw = (int *) &w;
  38         int *px = (int *) &x;
  39         int *py = (int *) &y;
  40         int ix, iy, iz;
  41
  42         ix = px[0];
  43         iy = py[0];
  44         if ((ix & ~0x80000000) > 0x7f800000)
  45                 return (x * y);         /* + -> * for Cheetah */
  46         if ((iy & ~0x80000000) > 0x7f800000)
  47                 return (y * x);         /* + -> * for Cheetah */
  48         if (ix == iy || (ix | iy) == 0x80000000)
  49                 return (y);             /* C99 requirement */
  50         if ((ix & ~0x80000000) == 0)
  51                 iz = 1 | (iy & 0x80000000);
  52         else if (ix > 0) {
  53                 if (ix > iy)
  54                         iz = ix - 1;
  55                 else
  56                         iz = ix + 1;
  57         } else {
  58                 if (iy < 0 && ix < iy)
  59                         iz = ix + 1;
  60                 else
  61                         iz = ix - 1;
  62         }
  63         pw[0] = iz;
  64         ix = iz & 0x7f800000;
  65         if (ix == 0x7f800000) {
  66                 /* raise overflow */
  67                 volatile float t;
  68
  69                 *(int *) &t = 0x7f7fffff;
  70                 t *= t;
  71         } else if (ix == 0) {
  72                 /* raise underflow */
  73                 volatile float t;
  74
  75                 *(int *) &t = 0x00800000;
  76                 t *= t;
  77         }
  78         return (w);
  79 }