libgcc/config/libbid/bid64_scalb.c

   1 /* Copyright (C) 2007-2017 Free Software Foundation, Inc.
   2
   3 This file is part of GCC.
   4
   5 GCC is free software; you can redistribute it and/or modify it under
   6 the terms of the GNU General Public License as published by the Free
   7 Software Foundation; either version 3, or (at your option) any later
   8 version.
   9
  10 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  11 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13 for more details.
  14
  15 Under Section 7 of GPL version 3, you are granted additional
  16 permissions described in the GCC Runtime Library Exception, version
  17 3.1, as published by the Free Software Foundation.
  18
  19 You should have received a copy of the GNU General Public License and
  20 a copy of the GCC Runtime Library Exception along with this program;
  21 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  22 <http://www.gnu.org/licenses/>.  */
  23
  24 #include "bid_internal.h"
  25
  26 #define MAX_FORMAT_DIGITS     16
  27 #define DECIMAL_EXPONENT_BIAS 398
  28 #define MAX_DECIMAL_EXPONENT  767
  29
  30 #if DECIMAL_CALL_BY_REFERENCE
  31
  32 void
  33 bid64_scalb (UINT64 * pres, UINT64 * px,
  34              int *pn _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
  35              _EXC_INFO_PARAM) {
  36   UINT64 x;
  37   int n;
  38 #else
  39
  40 UINT64
  41 bid64_scalb (UINT64 x,
  42              int n _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
  43              _EXC_INFO_PARAM) {
  44 #endif
  45   UINT64 sign_x, coefficient_x, res;
  46   SINT64 exp64;
  47   int exponent_x, rmode;
  48
  49 #if DECIMAL_CALL_BY_REFERENCE
  50 #if !DECIMAL_GLOBAL_ROUNDING
  51   _IDEC_round rnd_mode = *prnd_mode;
  52 #endif
  53   x = *px;
  54   n = *pn;
  55 #endif
  56
  57   // unpack arguments, check for NaN or Infinity
  58   if (!unpack_BID64 (&sign_x, &exponent_x, &coefficient_x, x)) {
  59     // x is Inf. or NaN or 0
  60 #ifdef SET_STATUS_FLAGS
  61     if ((x & SNAN_MASK64) == SNAN_MASK64)       // y is sNaN
  62       __set_status_flags (pfpsf, INVALID_EXCEPTION);
  63 #endif
  64     if (coefficient_x)
  65       res = coefficient_x & QUIET_MASK64;
  66         else {
  67        exp64 = (SINT64) exponent_x + (SINT64) n;
  68            if(exp64<0) exp64=0;
  69            if(exp64>MAX_DECIMAL_EXPONENT) exp64=MAX_DECIMAL_EXPONENT;
  70        exponent_x = exp64;
  71       res = very_fast_get_BID64 (sign_x, exponent_x, coefficient_x);    // 0
  72         }
  73     BID_RETURN (res);
  74   }
  75
  76   exp64 = (SINT64) exponent_x + (SINT64) n;
  77   exponent_x = exp64;
  78
  79   if ((UINT32) exponent_x <= MAX_DECIMAL_EXPONENT) {
  80     res = very_fast_get_BID64 (sign_x, exponent_x, coefficient_x);
  81     BID_RETURN (res);
  82   }
  83   // check for overflow
  84   if (exp64 > MAX_DECIMAL_EXPONENT) {
  85     // try to normalize coefficient
  86     while ((coefficient_x < 1000000000000000ull)
  87            && (exp64 > MAX_DECIMAL_EXPONENT)) {
  88       // coefficient_x < 10^15, scale by 10
  89       coefficient_x = (coefficient_x << 1) + (coefficient_x << 3);
  90       exponent_x--;
  91       exp64--;
  92     }
  93     if (exp64 <= MAX_DECIMAL_EXPONENT) {
  94       res = very_fast_get_BID64 (sign_x, exponent_x, coefficient_x);
  95       BID_RETURN (res);
  96     } else
  97       exponent_x = 0x7fffffff;  // overflow
  98   }
  99   // exponent < 0
 100   // the BID pack routine will round the coefficient
 101   rmode = rnd_mode;
 102   res = get_BID64 (sign_x, exponent_x, coefficient_x, rmode, pfpsf);
 103   BID_RETURN (res);
 104
 105 }