gcc/libgcc/config/libbid/bid128_quantize.c

/* Copyright (C) 2007  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 2, or (at your option) any later
version.

In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file.  (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)

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.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.  */

#define BID_128RES
#include "bid_internal.h"

BID128_FUNCTION_ARG2 (bid128_quantize, x, y)

     UINT256 CT;
     UINT128 CX, CY, T, CX2, CR, Stemp, res, REM_H, C2N;
     UINT64 sign_x, sign_y, remainder_h, carry, CY64, valid_x;
     int_float tempx;
     int exponent_x, exponent_y, digits_x, extra_digits, amount;
     int expon_diff, total_digits, bin_expon_cx, rmode, status;

valid_x = unpack_BID128_value (&sign_x, &exponent_x, &CX, x);

  // unpack arguments, check for NaN or Infinity
if (!unpack_BID128_value (&sign_y, &exponent_y, &CY, y)) {
    // y is Inf. or NaN
#ifdef SET_STATUS_FLAGS
if ((x.w[1] & SNAN_MASK64) == SNAN_MASK64)	// y is sNaN
  __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif

    // test if y is NaN
if ((y.w[1] & 0x7c00000000000000ull) == 0x7c00000000000000ull) {
#ifdef SET_STATUS_FLAGS
  if ((y.w[1] & 0x7e00000000000000ull) == 0x7e00000000000000ull) {
    // set status flags
    __set_status_flags (pfpsf, INVALID_EXCEPTION);
  }
#endif
  if ((x.w[1] & 0x7c00000000000000ull) != 0x7c00000000000000ull) {
    res.w[1] = CY.w[1] & QUIET_MASK64;
    res.w[0] = CY.w[0];
  } else {
    res.w[1] = CX.w[1] & QUIET_MASK64;
    res.w[0] = CX.w[0];
  }
  BID_RETURN (res);
}
    // y is Infinity?
if ((y.w[1] & 0x7800000000000000ull) == 0x7800000000000000ull) {
  // check if x is not Inf.
  if (((x.w[1] & 0x7c00000000000000ull) < 0x7800000000000000ull)) {
    // return NaN 
#ifdef SET_STATUS_FLAGS
    // set status flags
    __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
    res.w[1] = 0x7c00000000000000ull;
    res.w[0] = 0;
    BID_RETURN (res);
  } else
    if (((x.w[1] & 0x7c00000000000000ull) <= 0x7800000000000000ull)) {
    res.w[1] = CX.w[1] & QUIET_MASK64;
    res.w[0] = CX.w[0];
    BID_RETURN (res);
  }
}

}

if (!valid_x) {
  // test if x is NaN or Inf
  if ((x.w[1] & 0x7c00000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
    // set status flags
    __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
    res.w[1] = 0x7c00000000000000ull;
    res.w[0] = 0;
    BID_RETURN (res);
  } else if ((x.w[1] & 0x7c00000000000000ull) == 0x7c00000000000000ull) {
    if ((x.w[1] & 0x7e00000000000000ull) == 0x7e00000000000000ull) {
#ifdef SET_STATUS_FLAGS
      // set status flags
      __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
    }
    res.w[1] = CX.w[1] & QUIET_MASK64;
    res.w[0] = CX.w[0];
    BID_RETURN (res);
  }
  if (!CX.w[1] && !CX.w[0]) {
    get_BID128_very_fast (&res, sign_x, exponent_y, CX);
    BID_RETURN (res);
  }
}
  // get number of decimal digits in coefficient_x
if (CX.w[1]) {
  tempx.d = (float) CX.w[1];
  bin_expon_cx = ((tempx.i >> 23) & 0xff) - 0x7f + 64;
} else {
  tempx.d = (float) CX.w[0];
  bin_expon_cx = ((tempx.i >> 23) & 0xff) - 0x7f;
}

digits_x = estimate_decimal_digits[bin_expon_cx];
if (CX.w[1] > power10_table_128[digits_x].w[1]
    || (CX.w[1] == power10_table_128[digits_x].w[1]
	&& CX.w[0] >= power10_table_128[digits_x].w[0]))
  digits_x++;

expon_diff = exponent_x - exponent_y;
total_digits = digits_x + expon_diff;

if ((UINT32) total_digits <= 34) {
  if (expon_diff >= 0) {
    T = power10_table_128[expon_diff];
    __mul_128x128_low (CX2, T, CX);
    get_BID128_very_fast (&res, sign_x, exponent_y, CX2);
    BID_RETURN (res);
  }
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
  rmode = rnd_mode;
  if (sign_x && (unsigned) (rmode - 1) < 2)
    rmode = 3 - rmode;
#else
  rmode = 0;
#endif
#else
  rmode = 0;
#endif
  // must round off -expon_diff digits
  extra_digits = -expon_diff;
  __add_128_128 (CX, CX, round_const_table_128[rmode][extra_digits]);

  // get P*(2^M[extra_digits])/10^extra_digits
  __mul_128x128_to_256 (CT, CX, reciprocals10_128[extra_digits]);

  // now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
  amount = recip_scale[extra_digits];
  CX2.w[0] = CT.w[2];
  CX2.w[1] = CT.w[3];
  if (amount >= 64) {
    CR.w[1] = 0;
    CR.w[0] = CX2.w[1] >> (amount - 64);
  } else {
    __shr_128 (CR, CX2, amount);
  }

#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
  if (rnd_mode == 0)
#endif
    if (CR.w[0] & 1) {
      // check whether fractional part of initial_P/10^extra_digits is 
      // exactly .5 this is the same as fractional part of 
      // (initial_P + 0.5*10^extra_digits)/10^extra_digits is exactly zero

      // get remainder
      if (amount >= 64) {
	remainder_h = CX2.w[0] | (CX2.w[1] << (128 - amount));
      } else
	remainder_h = CX2.w[0] << (64 - amount);

      // test whether fractional part is 0
      if (!remainder_h
	  && (CT.w[1] < reciprocals10_128[extra_digits].w[1]
	      || (CT.w[1] == reciprocals10_128[extra_digits].w[1]
		  && CT.w[0] < reciprocals10_128[extra_digits].w[0]))) {
	CR.w[0]--;
      }
    }
#endif

#ifdef SET_STATUS_FLAGS
  status = INEXACT_EXCEPTION;

  // get remainder
  if (amount >= 64) {
    REM_H.w[1] = (CX2.w[1] << (128 - amount));
    REM_H.w[0] = CX2.w[0];
  } else {
    REM_H.w[1] = CX2.w[0] << (64 - amount);
    REM_H.w[0] = 0;
  }

  switch (rmode) {
  case ROUNDING_TO_NEAREST:
  case ROUNDING_TIES_AWAY:
    // test whether fractional part is 0
    if (REM_H.w[1] == 0x8000000000000000ull && !REM_H.w[0]
	&& (CT.w[1] < reciprocals10_128[extra_digits].w[1]
	    || (CT.w[1] == reciprocals10_128[extra_digits].w[1]
		&& CT.w[0] < reciprocals10_128[extra_digits].w[0])))
      status = EXACT_STATUS;
    break;
  case ROUNDING_DOWN:
  case ROUNDING_TO_ZERO:
    if (!(REM_H.w[1] | REM_H.w[0])
	&& (CT.w[1] < reciprocals10_128[extra_digits].w[1]
	    || (CT.w[1] == reciprocals10_128[extra_digits].w[1]
		&& CT.w[0] < reciprocals10_128[extra_digits].w[0])))
      status = EXACT_STATUS;
    break;
  default:
    // round up
    __add_carry_out (Stemp.w[0], CY64, CT.w[0],
		     reciprocals10_128[extra_digits].w[0]);
    __add_carry_in_out (Stemp.w[1], carry, CT.w[1],
			reciprocals10_128[extra_digits].w[1], CY64);
    if (amount < 64) {
      C2N.w[1] = 0;
      C2N.w[0] = ((UINT64) 1) << amount;
      REM_H.w[0] = REM_H.w[1] >> (64 - amount);
      REM_H.w[1] = 0;
    } else {
      C2N.w[1] = ((UINT64) 1) << (amount - 64);
      C2N.w[0] = 0;
      REM_H.w[1] >>= (128 - amount);
    }
    REM_H.w[0] += carry;
    if (REM_H.w[0] < carry)
      REM_H.w[1]++;
    if (__unsigned_compare_ge_128 (REM_H, C2N))
      status = EXACT_STATUS;
  }

  __set_status_flags (pfpsf, status);

#endif
  get_BID128_very_fast (&res, sign_x, exponent_y, CR);
  BID_RETURN (res);
}
if (total_digits < 0) {
  CR.w[1] = CR.w[0] = 0;
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
  rmode = rnd_mode;
  if (sign_x && (unsigned) (rmode - 1) < 2)
    rmode = 3 - rmode;
  if (rmode == ROUNDING_UP)
    CR.w[0] = 1;
#endif
#endif
#ifdef SET_STATUS_FLAGS
  __set_status_flags (pfpsf, INEXACT_EXCEPTION);
#endif
  get_BID128_very_fast (&res, sign_x, exponent_y, CR);
  BID_RETURN (res);
}
  // else  more than 34 digits in coefficient
#ifdef SET_STATUS_FLAGS
__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
res.w[1] = 0x7c00000000000000ull;
res.w[0] = 0;
BID_RETURN (res);

}