libgcc/config/libbid/bid64_quantize.c

/* Copyright (C) 2007-2014 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/>.  */

#include "bid_internal.h"

#define MAX_FORMAT_DIGITS     16
#define DECIMAL_EXPONENT_BIAS 398
#define MAX_DECIMAL_EXPONENT  767

#if DECIMAL_CALL_BY_REFERENCE

void
bid64_quantize (UINT64 * pres, UINT64 * px,
		UINT64 *
		py _RND_MODE_PARAM _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
		_EXC_INFO_PARAM) {
  UINT64 x, y;
#else

UINT64
bid64_quantize (UINT64 x,
		UINT64 y _RND_MODE_PARAM _EXC_FLAGS_PARAM
		_EXC_MASKS_PARAM _EXC_INFO_PARAM) {
#endif
  UINT128 CT;
  UINT64 sign_x, sign_y, coefficient_x, coefficient_y, remainder_h, C64,
    valid_x;
  UINT64 tmp, carry, res;
  int_float tempx;
  int exponent_x, exponent_y, digits_x, extra_digits, amount, amount2;
  int expon_diff, total_digits, bin_expon_cx;
  unsigned rmode, status;

#if DECIMAL_CALL_BY_REFERENCE
#if !DECIMAL_GLOBAL_ROUNDING
  _IDEC_round rnd_mode = *prnd_mode;
#endif
  x = *px;
  y = *py;
#endif

  valid_x = unpack_BID64 (&sign_x, &exponent_x, &coefficient_x, x);
  // unpack arguments, check for NaN or Infinity
  if (!unpack_BID64 (&sign_y, &exponent_y, &coefficient_y, y)) {
    // Inf. or NaN or 0
#ifdef SET_STATUS_FLAGS
    if ((x & SNAN_MASK64) == SNAN_MASK64)	// y is sNaN
      __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif

    // x=Inf, y=Inf?
    if (((coefficient_x << 1) == 0xf000000000000000ull)
	&& ((coefficient_y << 1) == 0xf000000000000000ull)) {
      res = coefficient_x;
      BID_RETURN (res);
    }
    // Inf or NaN?
    if ((y & 0x7800000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
      if (((y & 0x7e00000000000000ull) == 0x7e00000000000000ull)	// sNaN
	  || (((y & 0x7c00000000000000ull) == 0x7800000000000000ull) &&	//Inf
	      ((x & 0x7c00000000000000ull) < 0x7800000000000000ull)))
	__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
      if ((y & NAN_MASK64) != NAN_MASK64)
	coefficient_y = 0;
      if ((x & NAN_MASK64) != NAN_MASK64) {
	res = 0x7c00000000000000ull | (coefficient_y & QUIET_MASK64);
	if (((y & NAN_MASK64) != NAN_MASK64) && ((x & NAN_MASK64) == 0x7800000000000000ull))
		res = x;
	BID_RETURN (res);
      }
    }
  }
  // unpack arguments, check for NaN or Infinity
  if (!valid_x) {
    // x is Inf. or NaN or 0

    // Inf or NaN?
    if ((x & 0x7800000000000000ull) == 0x7800000000000000ull) {
#ifdef SET_STATUS_FLAGS
      if (((x & 0x7e00000000000000ull) == 0x7e00000000000000ull)	// sNaN
	  || ((x & 0x7c00000000000000ull) == 0x7800000000000000ull))	//Inf 
	__set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
      if ((x & NAN_MASK64) != NAN_MASK64)
	coefficient_x = 0;
      res = 0x7c00000000000000ull | (coefficient_x & QUIET_MASK64);
      BID_RETURN (res);
    }

    res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, 0);
    BID_RETURN (res);
  }
  // get number of decimal digits in coefficient_x
  tempx.d = (float) coefficient_x;
  bin_expon_cx = ((tempx.i >> 23) & 0xff) - 0x7f;
  digits_x = estimate_decimal_digits[bin_expon_cx];
  if (coefficient_x >= power10_table_128[digits_x].w[0])
    digits_x++;

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

  // check range of scaled coefficient
  if ((UINT32) (total_digits + 1) <= 17) {
    if (expon_diff >= 0) {
      coefficient_x *= power10_table_128[expon_diff].w[0];
      res = very_fast_get_BID64 (sign_x, exponent_y, coefficient_x);
      BID_RETURN (res);
    }
    // must round off -expon_diff digits
    extra_digits = -expon_diff;
#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
    coefficient_x += round_const_table[rmode][extra_digits];

    // get P*(2^M[extra_digits])/10^extra_digits
    __mul_64x64_to_128 (CT, coefficient_x,
			reciprocals10_64[extra_digits]);

    // now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
    amount = short_recip_scale[extra_digits];
    C64 = CT.w[1] >> amount;
#ifndef IEEE_ROUND_NEAREST_TIES_AWAY
#ifndef IEEE_ROUND_NEAREST
    if (rnd_mode == 0)
#endif
      if (C64 & 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
	amount2 = 64 - amount;
	remainder_h = 0;
	remainder_h--;
	remainder_h >>= amount2;
	remainder_h = remainder_h & CT.w[1];

	// test whether fractional part is 0
	if (!remainder_h && (CT.w[0] < reciprocals10_64[extra_digits])) {
	  C64--;
	}
      }
#endif

#ifdef SET_STATUS_FLAGS
    status = INEXACT_EXCEPTION;
    // get remainder
    remainder_h = CT.w[1] << (64 - amount);
    switch (rmode) {
    case ROUNDING_TO_NEAREST:
    case ROUNDING_TIES_AWAY:
      // test whether fractional part is 0
      if ((remainder_h == 0x8000000000000000ull)
	  && (CT.w[0] < reciprocals10_64[extra_digits]))
	status = EXACT_STATUS;
      break;
    case ROUNDING_DOWN:
    case ROUNDING_TO_ZERO:
      if (!remainder_h && (CT.w[0] < reciprocals10_64[extra_digits]))
	status = EXACT_STATUS;
      //if(!C64 && rmode==ROUNDING_DOWN) sign_s=sign_y;
      break;
    default:
      // round up
      __add_carry_out (tmp, carry, CT.w[0],
		       reciprocals10_64[extra_digits]);
      if ((remainder_h >> (64 - amount)) + carry >=
	  (((UINT64) 1) << amount))
	status = EXACT_STATUS;
      break;
    }
    __set_status_flags (pfpsf, status);
#endif

    res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, C64);
    BID_RETURN (res);
  }

  if (total_digits < 0) {
#ifdef SET_STATUS_FLAGS
    __set_status_flags (pfpsf, INEXACT_EXCEPTION);
#endif
    C64 = 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)
      C64 = 1;
#endif
#endif
    res = very_fast_get_BID64_small_mantissa (sign_x, exponent_y, C64);
    BID_RETURN (res);
  }
  // else  more than 16 digits in coefficient
#ifdef SET_STATUS_FLAGS
  __set_status_flags (pfpsf, INVALID_EXCEPTION);
#endif
  res = 0x7c00000000000000ull;
  BID_RETURN (res);

}