libgcc/config/libbid/bid128_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 #define BID_128RES
  25 #include "bid_internal.h"
  26
  27 #define DECIMAL_EXPONENT_BIAS_128 6176
  28 #define MAX_DECIMAL_EXPONENT_128  12287
  29
  30
  31
  32 BID128_FUNCTION_ARG128_ARGTYPE2 (bid128_scalb, x, int, n)
  33
  34      UINT128 CX, CX2, CX8, res;
  35      SINT64 exp64;
  36      UINT64 sign_x;
  37      int exponent_x, rmode;
  38
  39   // unpack arguments, check for NaN or Infinity
  40 if (!unpack_BID128_value (&sign_x, &exponent_x, &CX, x)) {
  41     // x is Inf. or NaN or 0
  42 #ifdef SET_STATUS_FLAGS
  43 if ((x.w[1] & SNAN_MASK64) == SNAN_MASK64)      // y is sNaN
  44   __set_status_flags (pfpsf, INVALID_EXCEPTION);
  45 #endif
  46 res.w[1] = CX.w[1] & QUIET_MASK64;
  47 res.w[0] = CX.w[0];
  48 if (!CX.w[1]) {
  49        exp64 = (SINT64) exponent_x + (SINT64) n;
  50            if(exp64<0) exp64=0;
  51            if(exp64>MAX_DECIMAL_EXPONENT_128) exp64=MAX_DECIMAL_EXPONENT_128;
  52        exponent_x = exp64;
  53   get_BID128_very_fast (&res, sign_x, exponent_x, CX);
  54 }
  55 BID_RETURN (res);
  56 }
  57
  58 exp64 = (SINT64) exponent_x + (SINT64) n;
  59 exponent_x = exp64;
  60
  61 if ((UINT32) exponent_x <= MAX_DECIMAL_EXPONENT_128) {
  62   get_BID128_very_fast (&res, sign_x, exponent_x, CX);
  63   BID_RETURN (res);
  64 }
  65   // check for overflow
  66 if (exp64 > MAX_DECIMAL_EXPONENT_128) {
  67   if (CX.w[1] < 0x314dc6448d93ull) {
  68     // try to normalize coefficient
  69     do {
  70       CX8.w[1] = (CX.w[1] << 3) | (CX.w[0] >> 61);
  71       CX8.w[0] = CX.w[0] << 3;
  72       CX2.w[1] = (CX.w[1] << 1) | (CX.w[0] >> 63);
  73       CX2.w[0] = CX.w[0] << 1;
  74       __add_128_128 (CX, CX2, CX8);
  75
  76       exponent_x--;
  77       exp64--;
  78     }
  79     while (CX.w[1] < 0x314dc6448d93ull
  80            && exp64 > MAX_DECIMAL_EXPONENT_128);
  81
  82   }
  83   if (exp64 <= MAX_DECIMAL_EXPONENT_128) {
  84     get_BID128_very_fast (&res, sign_x, exponent_x, CX);
  85     BID_RETURN (res);
  86   } else
  87     exponent_x = 0x7fffffff;    // overflow
  88 }
  89   // exponent < 0
  90   // the BID pack routine will round the coefficient
  91 rmode = rnd_mode;
  92 get_BID128 (&res, sign_x, exponent_x, CX, (unsigned int *) &rmode,
  93             pfpsf);
  94 BID_RETURN (res);
  95
  96 }