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 #if defined(ELFOBJ)
  31 #pragma weak nearbyintf = __nearbyintf
  32 #endif
  33 
  34 #include "libm.h"
  35 #include "fenv_synonyms.h"
  36 #include <fenv.h>
  37 
  38 float
  39 __nearbyintf(float x) {
  40         union {
  41                 unsigned i;
  42                 float f;
  43         } xx;
  44         unsigned hx, sx, i, frac;
  45         int rm;
  46 
  47         xx.f = x;
  48         sx = xx.i & 0x80000000;
  49         hx = xx.i & ~0x80000000;
  50 
  51         /* handle trivial cases */
  52         if (hx >= 0x4b000000) {      /* x is nan, inf, or already integral */
  53                 if (hx > 0x7f800000) /* x is nan */
  54                         return (x * x);         /* + -> * for Cheetah */
  55                 return (x);
  56         } else if (hx == 0)             /* x is zero */
  57                 return (x);
  58 
  59         /* get the rounding mode */
  60         rm = fegetround();
  61 
  62         /* flip the sense of directed roundings if x is negative */
  63         if (sx && (rm == FE_UPWARD || rm == FE_DOWNWARD))
  64                 rm = (FE_UPWARD + FE_DOWNWARD) - rm;
  65 
  66         /* handle |x| < 1 */
  67         if (hx < 0x3f800000) {
  68                 if (rm == FE_UPWARD || (rm == FE_TONEAREST && hx > 0x3f000000))
  69                         xx.i = sx | 0x3f800000;
  70                 else
  71                         xx.i = sx;
  72                 return (xx.f);
  73         }
  74 
  75         /* round x at the integer bit */
  76         i = 1 << (0x96 - (hx >> 23));
  77         frac = hx & (i - 1);
  78         if (!frac)
  79                 return (x);
  80 
  81         hx &= ~(i - 1);
  82         if (rm == FE_UPWARD || (rm == FE_TONEAREST && (frac > (i >> 1) ||
  83                 (frac == (i >> 1)) && (hx & i))))
  84                 xx.i = sx | (hx + i);
  85         else
  86                 xx.i = sx | hx;
  87         return (xx.f);
  88 }
  89 
  90 #if 0
  91 
  92 /*
  93  * Alternate implementations for SPARC, x86, using fp ops.  These may
  94  * be faster depending on how expensive saving and restoring the fp
  95  * modes and status flags is.
  96  */
  97 
  98 #include "libm.h"
  99 #include "fma.h"
 100 
 101 #if defined(__sparc)
 102 
 103 float
 104 __nearbyintf(float x) {
 105         union {
 106                 unsigned i;
 107                 float f;
 108         } xx, yy;
 109         float z;
 110         unsigned hx, sx, fsr, oldfsr;
 111         int rm;
 112 
 113         xx.f = x;
 114         sx = xx.i & 0x80000000;
 115         hx = xx.i & ~0x80000000;
 116 
 117         /* handle trivial cases */
 118         if (hx >= 0x4b000000)        /* x is nan, inf, or already integral */
 119                 return (x + 0.0f);
 120         else if (hx == 0)       /* x is zero */
 121                 return (x);
 122 
 123         /* save the fsr */
 124         __fenv_getfsr(&oldfsr);
 125 
 126         /* handle |x| < 1 */
 127         if (hx < 0x3f800000) {
 128                 /* flip the sense of directed roundings if x is negative */
 129                 rm = oldfsr >> 30;
 130                 if (sx)
 131                         rm ^= rm >> 1;
 132                 if (rm == FSR_RP || (rm == FSR_RN && hx > 0x3f000000))
 133                         xx.i = sx | 0x3f800000;
 134                 else
 135                         xx.i = sx;
 136                 return (xx.f);
 137         }
 138 
 139         /* clear the inexact trap */
 140         fsr = oldfsr & ~FSR_NXM;
 141         __fenv_setfsr(&fsr);
 142 
 143         /* round x at the integer bit */
 144         yy.i = sx | 0x4b000000;
 145         z = (x + yy.f) - yy.f;
 146 
 147         /* restore the old fsr */
 148         __fenv_setfsr(&oldfsr);
 149 
 150         return (z);
 151 }
 152 
 153 #elif defined(__x86)
 154 
 155 /* inline template */
 156 extern long double frndint(long double);
 157 
 158 float
 159 __nearbyintf(float x) {
 160         long double z;
 161         unsigned oldcwsw, cwsw;
 162 
 163         /* save the control and status words, mask the inexact exception */
 164         __fenv_getcwsw(&oldcwsw);
 165         cwsw = oldcwsw | 0x00200000;
 166         __fenv_setcwsw(&cwsw);
 167 
 168         z = frndint((long double) x);
 169 
 170         /*
 171          * restore the control and status words, preserving all but the
 172          * inexact flag
 173          */
 174         __fenv_getcwsw(&cwsw);
 175         oldcwsw |= (cwsw & 0x1f);
 176         __fenv_setcwsw(&oldcwsw);
 177 
 178         /* note: the value of z is representable in single precision */
 179         return (z);
 180 }
 181 
 182 #else
 183 #error Unknown architecture
 184 #endif
 185 
 186 #endif