compiler/mlib/s_modfl.c

   1 /*-
   2  * Copyright (c) 2007 David Schultz <das@FreeBSD.ORG>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  *
  26  * Derived from s_modf.c, which has the following Copyright:
  27  * ====================================================
  28  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  29  *
  30  * Developed at SunPro, a Sun Microsystems, Inc. business.
  31  * Permission to use, copy, modify, and distribute this
  32  * software is freely granted, provided that this notice
  33  * is preserved.
  34  * ====================================================
  35  *
  36  * $FreeBSD: src/lib/msun/src/s_modfl.c,v 1.1 2007/01/07 07:54:21 das Exp $
  37  */
  38
  39 #include <float.h>
  40 #include <math.h>
  41 #include <stdint.h>
  42
  43 #include "fpmath.h"
  44
  45 #if LDBL_MANL_SIZE > 32
  46 #define MASK    ((uint64_t)-1)
  47 #else
  48 #define MASK    ((uint32_t)-1)
  49 #endif
  50 /* Return the last n bits of a word, representing the fractional part. */
  51 #define GETFRAC(bits, n)        ((bits) & ~(MASK << (n)))
  52 /* The number of fraction bits in manh, not counting the integer bit */
  53 #define HIBITS  (LDBL_MANT_DIG - LDBL_MANL_SIZE)
  54
  55 static const long double zero[] = { 0.0L, -0.0L };
  56
  57 long double
  58 modfl(long double x, long double *iptr)
  59 {
  60         union IEEEl2bits ux;
  61         int e;
  62
  63         ux.e = x;
  64         e = ux.bits.exp - LDBL_MAX_EXP + 1;
  65         if (e < HIBITS) {                       /* Integer part is in manh. */
  66                 if (e < 0) {                    /* |x|<1 */
  67                         *iptr = zero[ux.bits.sign];
  68                         return (x);
  69                 } else {
  70                         if ((GETFRAC(ux.bits.manh, HIBITS - 1 - e) |
  71                              ux.bits.manl) == 0) {      /* X is an integer. */
  72                                 *iptr = x;
  73                                 return (zero[ux.bits.sign]);
  74                         } else {
  75                                 /* Clear all but the top e+1 bits. */
  76                                 ux.bits.manh >>= HIBITS - 1 - e;
  77                                 ux.bits.manh <<= HIBITS - 1 - e;
  78                                 ux.bits.manl = 0;
  79                                 *iptr = ux.e;
  80                                 return (x - ux.e);
  81                         }
  82                 }
  83         } else if (e >= LDBL_MANT_DIG - 1) {    /* x has no fraction part. */
  84                 *iptr = x;
  85                 if (x != x)                     /* Handle NaNs. */
  86                         return (x);
  87                 return (zero[ux.bits.sign]);
  88         } else {                                /* Fraction part is in manl. */
  89                 if (GETFRAC(ux.bits.manl, LDBL_MANT_DIG - 1 - e) == 0) {
  90                         /* x is integral. */
  91                         *iptr = x;
  92                         return (zero[ux.bits.sign]);
  93                 } else {
  94                         /* Clear all but the top e+1 bits. */
  95                         ux.bits.manl >>= LDBL_MANT_DIG - 1 - e;
  96                         ux.bits.manl <<= LDBL_MANT_DIG - 1 - e;
  97                         *iptr = ux.e;
  98                         return (x - ux.e);
  99                 }
 100         }
 101 }