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 __nexttowardl = nexttowardl
  31 
  32 #include "libm.h"
  33 #include <float.h>                /* LDBL_MAX, LDBL_MIN */
  34 
  35 #if defined(__sparc)
  36 #define n0      0
  37 #define n1      1
  38 #define n2      2
  39 #define n3      3
  40 #define X86PDNRM1(x)
  41 #define INC(px) { \
  42                         if (++px[n3] == 0) \
  43                                 if (++px[n2] == 0) \
  44                                         if (++px[n1] == 0) \
  45                                                 ++px[n0]; \
  46                 }
  47 #define DEC(px) { \
  48                         if (--px[n3] == 0xffffffff) \
  49                                 if (--px[n2] == 0xffffffff) \
  50                                         if (--px[n1] == 0xffffffff) \
  51                                                 --px[n0]; \
  52                 }
  53 #elif defined(__x86)
  54 #define n0      2
  55 #define n1      1
  56 #define n2      0
  57 #define n3      0
  58 /*
  59  * if pseudo-denormal, replace by the equivalent normal
  60  */
  61 #define X86PDNRM1(x)    if (XBIASED_EXP(x) == 0 && (((int *) &x)[1] & \
  62                                 0x80000000) != 0) \
  63                                 ((int *) &x)[2] |= 1
  64 #define INC(px) { \
  65                         if (++px[n2] == 0) \
  66                                 if ((++px[n1] & ~0x80000000) == 0) \
  67                                         px[n1] = 0x80000000, ++px[n0]; \
  68                 }
  69 #define DEC(px) { \
  70                         if (--px[n2] == 0xffffffff) \
  71                                 if (--px[n1] == 0x7fffffff) \
  72                                         if ((--px[n0] & 0x7fff) != 0) \
  73                                                 px[n1] |= 0x80000000; \
  74                 }
  75 #endif
  76 
  77 long double
  78 nexttowardl(long double x, long double y) {
  79         int *px = (int *) &x;
  80         int *py = (int *) &y;
  81 
  82         if (x == y)
  83                 return (y);             /* C99 requirement */
  84         if (x != x || y != y)
  85                 return (x * y);
  86 
  87         if (ISZEROL(x)) {       /* x == 0.0 */
  88                 px[n0] = py[n0] & XSGNMSK;
  89                 px[n1] = px[n2] = 0;
  90                 px[n3] = 1;
  91         } else {
  92                 X86PDNRM1(x);
  93                 if ((px[n0] & XSGNMSK) == 0) {      /* x > 0.0 */
  94                         if (x > y)   /* x > y */
  95                                 DEC(px)
  96                         else
  97                                 INC(px)
  98                 } else {
  99                         if (x < y)   /* x < y */
 100                                 DEC(px)
 101                         else
 102                                 INC(px)
 103                 }
 104         }
 105 #ifndef lint
 106         {
 107                 volatile long double dummy __unused;
 108                 int k = XBIASED_EXP(x);
 109 
 110                 if (k == 0)
 111                         dummy = LDBL_MIN * copysignl(LDBL_MIN, x);
 112                 else if (k == 0x7fff)
 113                         dummy = LDBL_MAX * copysignl(LDBL_MAX, x);
 114         }
 115 #endif
 116         return (x);
 117 }