gdtoa/_ldbl_util.c

   1 /*
   2  * Copyright (c) 2004 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http:www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #include <sys/cdefs.h>
  25 #include <stdint.h>
  26 #include <strings.h>
  27 #include <float.h>
  28 #include <math.h>
  29 #include <alloca.h>
  30
  31 #include "fpmath.h"
  32
  33 #define BITS64          64
  34 #define DBL_BIAS        (DBL_MAX_EXP - 1)
  35 #define DBL_SUBEXP      (-DBL_BIAS + 1)
  36 #define LL_BITS         (8 * sizeof(int64_t))
  37 #define LL_HIGHBIT      (1LL << 63)
  38
  39 __private_extern__ void
  40 _ldbl2array32dd(union IEEEl2bits u, uint32_t *a)
  41 {
  42         int bit, shift, highbit, dexp;
  43         uint64_t a64[2];
  44         int64_t t64;
  45
  46         bzero(a64, sizeof(a64));
  47
  48         switch (__fpclassifyd(u.d[0])) {
  49         case FP_NORMAL:
  50                 a64[1] = (1LL << (LDBL_MANT_DIG - BITS64 - 1));
  51                 /* drop through */
  52         case FP_SUBNORMAL:
  53                 a64[1] |= ((uint64_t)u.bits.manh >> (BITS64 - LDBL_MANL_SIZE));
  54                 a64[0] = ((uint64_t)u.bits.manh << LDBL_MANL_SIZE);
  55                 break;
  56         default:
  57                 goto done;
  58         }
  59
  60         dexp = (int)u.bits.exp - (int)u.bits.exp2;
  61         /*
  62          * if the tail double is so small to not fit in LDBL_MANT_DIG bits,
  63          * then just skip it.
  64          */
  65         if (dexp >= LDBL_MANT_DIG)
  66                 goto done;
  67
  68         switch (__fpclassifyd(u.d[1])) {
  69         case FP_NORMAL:
  70                 bit = LDBL_MANT_DIG - dexp - 1;
  71                 t64 = (1LL << bit);
  72                 break;
  73         case FP_SUBNORMAL:
  74                 bit = LDBL_MANT_DIG - (int)u.bits.exp;
  75                 t64 = 0;
  76                 break;
  77         default:
  78                 goto done;
  79         }
  80         shift = LDBL_MANL_SIZE - bit - 1;
  81         if (shift >= 0)
  82                 t64 |= (u.bits.manl >> shift);
  83         else
  84                 t64 |= (u.bits.manl << (-shift));
  85         highbit = ((a64[0] & LL_HIGHBIT) != 0);
  86         if (u.bits.sign == u.bits.sign2) {
  87                 a64[0] += t64;
  88                 if (highbit && !(a64[0] & LL_HIGHBIT))  /* carry */
  89                         a64[1]++;
  90         } else {
  91                 a64[0] -= t64;
  92                 if (!highbit && (a64[0] & LL_HIGHBIT))  /* borrow */
  93                         a64[1]--;
  94         }
  95
  96         done:
  97         a[0] = (uint32_t)a64[0];
  98         a[1] = (uint32_t)(a64[0] >> 32);
  99         a[2] = (uint32_t)a64[1];
 100         a[3] = (uint32_t)(a64[1] >> 32);
 101 }