/* IEEE754 floating point arithmetic
   * double precision: common utilities
   */
  /*
   * MIPS floating point support
   * Copyright (C) 1994-2000 Algorithmics Ltd.
   *
   * ########################################################################
   *
   *  This program is free software; you can distribute it and/or modify it
   *  under the terms of the GNU General Public License (Version 2) as
   *  published by the Free Software Foundation.
   *
   *  This program is distributed in the hope 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 this program; if not, write to the Free Software Foundation, Inc.,
   *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
   *
   * ########################################################################
   */
  
  
  #include "ieee754dp.h"
  
  int ieee754dp_class(ieee754dp x)
  {
  	COMPXDP;
  	EXPLODEXDP;
  	return xc;
  }
  
  int ieee754dp_isnan(ieee754dp x)
  {
  	return ieee754dp_class(x) >= IEEE754_CLASS_SNAN;
  }
  
  int ieee754dp_issnan(ieee754dp x)
  {
  	assert(ieee754dp_isnan(x));
  	return ((DPMANT(x) & DP_MBIT(DP_MBITS-1)) == DP_MBIT(DP_MBITS-1));
  }
  
  
  ieee754dp ieee754dp_xcpt(ieee754dp r, const char *op, ...)
  {
  	struct ieee754xctx ax;
  	if (!TSTX())
  		return r;
  
  	ax.op = op;
  	ax.rt = IEEE754_RT_DP;
  	ax.rv.dp = r;
  	va_start(ax.ap, op);
  	ieee754_xcpt(&ax);
  	va_end(ax.ap);
  	return ax.rv.dp;
  }
  
  ieee754dp ieee754dp_nanxcpt(ieee754dp r, const char *op, ...)
  {
  	struct ieee754xctx ax;
  
  	assert(ieee754dp_isnan(r));
  
  	if (!ieee754dp_issnan(r))	/* QNAN does not cause invalid op !! */
  		return r;
  
  	if (!SETANDTESTCX(IEEE754_INVALID_OPERATION)) {
  		/* not enabled convert to a quiet NaN */
  		DPMANT(r) &= (~DP_MBIT(DP_MBITS-1));
  		if (ieee754dp_isnan(r))
  			return r;
  		else
  			return ieee754dp_indef();
  	}
  
  	ax.op = op;
  	ax.rt = 0;
  	ax.rv.dp = r;
  	va_start(ax.ap, op);
  	ieee754_xcpt(&ax);
  	va_end(ax.ap);
  	return ax.rv.dp;
  }
  
  ieee754dp ieee754dp_bestnan(ieee754dp x, ieee754dp y)
  {
  	assert(ieee754dp_isnan(x));
  	assert(ieee754dp_isnan(y));
  
  	if (DPMANT(x) > DPMANT(y))
  		return x;
  	else
  		return y;
  }
  
  
  static u64 get_rounding(int sn, u64 xm)
  {
  	/* inexact must round of 3 bits
  	 */
  	if (xm & (DP_MBIT(3) - 1)) {
  		switch (ieee754_csr.rm) {
  		case IEEE754_RZ:
  			break;
  		case IEEE754_RN:
  			xm += 0x3 + ((xm >> 3) & 1);
  			/* xm += (xm&0x8)?0x4:0x3 */
  			break;
  		case IEEE754_RU:	/* toward +Infinity */
  			if (!sn)	/* ?? */
  				xm += 0x8;
  			break;
  		case IEEE754_RD:	/* toward -Infinity */
  			if (sn) /* ?? */
  				xm += 0x8;
  			break;
  		}
  	}
  	return xm;
  }
  
  
  /* generate a normal/denormal number with over,under handling
   * sn is sign
   * xe is an unbiased exponent
   * xm is 3bit extended precision value.
   */
  ieee754dp ieee754dp_format(int sn, int xe, u64 xm)
  {
  	assert(xm);		/* we don't gen exact zeros (probably should) */
  
  	assert((xm >> (DP_MBITS + 1 + 3)) == 0);	/* no execess */
  	assert(xm & (DP_HIDDEN_BIT << 3));
  
  	if (xe < DP_EMIN) {
  		/* strip lower bits */
  		int es = DP_EMIN - xe;
  
  		if (ieee754_csr.nod) {
  			SETCX(IEEE754_UNDERFLOW);
  			SETCX(IEEE754_INEXACT);
  
  			switch(ieee754_csr.rm) {
  			case IEEE754_RN:
  			case IEEE754_RZ:
  				return ieee754dp_zero(sn);
  			case IEEE754_RU:    /* toward +Infinity */
  				if(sn == 0)
  					return ieee754dp_min(0);
  				else
  					return ieee754dp_zero(1);
  			case IEEE754_RD:    /* toward -Infinity */
  				if(sn == 0)
  					return ieee754dp_zero(0);
  				else
  					return ieee754dp_min(1);
  			}
  		}
  
  		if (xe == DP_EMIN - 1
  				&& get_rounding(sn, xm) >> (DP_MBITS + 1 + 3))
  		{
  			/* Not tiny after rounding */
  			SETCX(IEEE754_INEXACT);
  			xm = get_rounding(sn, xm);
  			xm >>= 1;
  			/* Clear grs bits */
  			xm &= ~(DP_MBIT(3) - 1);
  			xe++;
  		}
  		else {
  			/* sticky right shift es bits
  			 */
  			xm = XDPSRS(xm, es);
  			xe += es;
  			assert((xm & (DP_HIDDEN_BIT << 3)) == 0);
  			assert(xe == DP_EMIN);
  		}
  	}
  	if (xm & (DP_MBIT(3) - 1)) {
  		SETCX(IEEE754_INEXACT);
  		if ((xm & (DP_HIDDEN_BIT << 3)) == 0) {
  			SETCX(IEEE754_UNDERFLOW);
  		}
  
  		/* inexact must round of 3 bits
  		 */
  		xm = get_rounding(sn, xm);
  		/* adjust exponent for rounding add overflowing
  		 */
  		if (xm >> (DP_MBITS + 3 + 1)) {
  			/* add causes mantissa overflow */
  			xm >>= 1;
  			xe++;
  		}
  	}
  	/* strip grs bits */
  	xm >>= 3;
  
  	assert((xm >> (DP_MBITS + 1)) == 0);	/* no execess */
  	assert(xe >= DP_EMIN);
  
  	if (xe > DP_EMAX) {
  		SETCX(IEEE754_OVERFLOW);
  		SETCX(IEEE754_INEXACT);
  		/* -O can be table indexed by (rm,sn) */
  		switch (ieee754_csr.rm) {
  		case IEEE754_RN:
  			return ieee754dp_inf(sn);
  		case IEEE754_RZ:
  			return ieee754dp_max(sn);
  		case IEEE754_RU:	/* toward +Infinity */
  			if (sn == 0)
  				return ieee754dp_inf(0);
  			else
  				return ieee754dp_max(1);
  		case IEEE754_RD:	/* toward -Infinity */
  			if (sn == 0)
  				return ieee754dp_max(0);
  			else
  				return ieee754dp_inf(1);
  		}
  	}
  	/* gen norm/denorm/zero */
  
  	if ((xm & DP_HIDDEN_BIT) == 0) {
  		/* we underflow (tiny/zero) */
  		assert(xe == DP_EMIN);
  		if (ieee754_csr.mx & IEEE754_UNDERFLOW)
  			SETCX(IEEE754_UNDERFLOW);
  		return builddp(sn, DP_EMIN - 1 + DP_EBIAS, xm);
  	} else {
  		assert((xm >> (DP_MBITS + 1)) == 0);	/* no execess */
  		assert(xm & DP_HIDDEN_BIT);
  
  		return builddp(sn, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
  	}
  }