gcc/libgcc/config/libbid/bid128_scalb.c

/* Copyright (C) 2007-2020 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#define BID_128RES
#include "bid_internal.h"

#define DECIMAL_EXPONENT_BIAS_128 6176
#define MAX_DECIMAL_EXPONENT_128  12287



BID128_FUNCTION_ARG128_ARGTYPE2 (bid128_scalb, x, int, n)

     UINT128 CX, CX2, CX8, res;
     SINT64 exp64;
     UINT64 sign_x;
     int exponent_x, rmode;

  // unpack arguments, check for NaN or Infinity
if (!unpack_BID128_value (&sign_x, &exponent_x, &CX, x)) {
    // x is Inf. or NaN or 0
#ifdef SET_STATUS_FLAGS
if ((x.w[1] & SNAN_MASK64) == SNAN_MASK64)	// y is sNaN
  __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res.w[1] = CX.w[1] & QUIET_MASK64;
res.w[0] = CX.w[0];
if (!CX.w[1]) {
       exp64 = (SINT64) exponent_x + (SINT64) n;
	   if(exp64<0) exp64=0;
	   if(exp64>MAX_DECIMAL_EXPONENT_128) exp64=MAX_DECIMAL_EXPONENT_128;
       exponent_x = exp64;
  get_BID128_very_fast (&res, sign_x, exponent_x, CX);
}
BID_RETURN (res);
}

exp64 = (SINT64) exponent_x + (SINT64) n;
exponent_x = exp64;

if ((UINT32) exponent_x <= MAX_DECIMAL_EXPONENT_128) {
  get_BID128_very_fast (&res, sign_x, exponent_x, CX);
  BID_RETURN (res);
}
  // check for overflow
if (exp64 > MAX_DECIMAL_EXPONENT_128) {
  if (CX.w[1] < 0x314dc6448d93ull) {
    // try to normalize coefficient
    do {
      CX8.w[1] = (CX.w[1] << 3) | (CX.w[0] >> 61);
      CX8.w[0] = CX.w[0] << 3;
      CX2.w[1] = (CX.w[1] << 1) | (CX.w[0] >> 63);
      CX2.w[0] = CX.w[0] << 1;
      __add_128_128 (CX, CX2, CX8);

      exponent_x--;
      exp64--;
    }
    while (CX.w[1] < 0x314dc6448d93ull
	   && exp64 > MAX_DECIMAL_EXPONENT_128);

  }
  if (exp64 <= MAX_DECIMAL_EXPONENT_128) {
    get_BID128_very_fast (&res, sign_x, exponent_x, CX);
    BID_RETURN (res);
  } else
    exponent_x = 0x7fffffff;	// overflow
}
  // exponent < 0
  // the BID pack routine will round the coefficient
rmode = rnd_mode;
get_BID128 (&res, sign_x, exponent_x, CX, (unsigned int *) &rmode,
	    pfpsf);
BID_RETURN (res);

}