/* Floating point library in optimized assembly for 8051
 * Copyright (c) 2004, Paul Stoffregen, paul@pjrc.com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This library 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */


#define SDCC_FLOAT_LIB
#include <float.h>


#ifdef FLOAT_ASM_MCS51

// float __fsadd (float a, float b) __reentrant
static void dummy(void) __naked
{
	__asm

	// extract the two inputs, placing them into:
	//      sign     exponent   mantiassa
	//      ----     --------   ---------
	//  a:  sign_a   exp_a      r4/r3/r2
	//  b:  sign_b   exp_b      r7/r6/r5
	//
	// r1: used to extend precision of a's mantissa
	// r0: general purpose loop counter

	.globl	___fsadd
___fsadd:
	lcall	fsgetargs

	.globl	fsadd_direct_entry
fsadd_direct_entry:
	// we're going to extend mantissa to 32 bits temporarily
	mov	r1, #0

	// which exponent is greater?
	mov	a, exp_b
	cjne	a, exp_a, 00005$
	sjmp	00011$
00005$:	jnc	00010$

	// a's exponent was greater, so shift b's mantissa
	lcall	fs_swap_a_b

00010$:
	// b's exponent was greater, so shift a's mantissa
	mov	a, exp_b
	clr	c
	subb	a, exp_a
	lcall	fs_rshift_a	// acc has # of shifts to do

00011$:
	// decide if we need to add or subtract
	// sign_a and sign_b are stored in the flag bits of psw,
	// so this little trick checks if the arguements ave the
	// same sign.
	mov	a, psw
	swap	a
	xrl	a, psw
	jb	acc.1, 00022$

00020$:
	// add the mantissas (both positive or both negative)
	mov	a, r2
	add	a, r5
	mov	r2, a
	mov	a, r3
	addc	a, r6
	mov	r3, a
	mov	a, r4
	addc	a, r7
	mov	r4, a
	// check for overflow past 24 bits
	jnc	00021$
	mov	a, #1
	lcall	fs_rshift_a
	mov	a, r4
	orl	a, #0x80
	mov	r4, a
00021$:
	ljmp	fs_round_and_return



00022$:
	// subtract the mantissas (one of them is negative)
	clr	c
	mov	a, r2
	subb	a, r5
	mov	r2, a
	mov	a, r3
	subb	a, r6
	mov	r3, a
	mov	a, r4
	subb	a, r7
	mov	r4, a
	jnc	00025$
	// if we get a negative result, turn it positive and
	// flip the sign bit
	clr	c
	clr	a
	subb	a, r1
	mov	r1, a
	clr	a
	subb	a, r2
	mov	r2, a
	clr	a
	subb	a, r3
	mov	r3, a
	clr	a
	subb	a, r4
	mov	r4, a
	cpl	sign_a
00025$:
	lcall	fs_normalize_a
	ljmp	fs_round_and_return

	__endasm;
}

#else


/*
** libgcc support for software floating point.
** Copyright (C) 1991 by Pipeline Associates, Inc.  All rights reserved.
** Permission is granted to do *anything* you want with this file,
** commercial or otherwise, provided this message remains intact.  So there!
** I would appreciate receiving any updates/patches/changes that anyone
** makes, and am willing to be the repository for said changes (am I
** making a big mistake?).
**
** Pat Wood
** Pipeline Associates, Inc.
** pipeline!phw@motown.com or
** sun!pipeline!phw or
** uunet!motown!pipeline!phw
*/

union float_long
  {
    float f;
    unsigned long l;
  };

/* add two floats */
float __fsadd (float a1, float a2)
{
  volatile long mant1, mant2;
  volatile union float_long fl1, fl2;
  volatile int exp1, exp2;
  volatile unsigned long sign = 0;

  fl1.f = a1;
  fl2.f = a2;

  /* check for zero args */
  if (!fl1.l)
    return (fl2.f);
  if (!fl2.l)
    return (fl1.f);

  exp1 = EXP (fl1.l);
  exp2 = EXP (fl2.l);

  if (exp1 > exp2 + 25)
    return (fl1.f);
  if (exp2 > exp1 + 25)
    return (fl2.f);

  mant1 = MANT (fl1.l);
  mant2 = MANT (fl2.l);

  if (SIGN (fl1.l))
    mant1 = -mant1;
  if (SIGN (fl2.l))
    mant2 = -mant2;

  if (exp1 > exp2)
    {
      mant2 >>= exp1 - exp2;
    }
  else
    {
      mant1 >>= exp2 - exp1;
      exp1 = exp2;
    }
  mant1 += mant2;

  if (mant1 < 0)
    {
      mant1 = -mant1;
      sign = SIGNBIT;
    }
  else if (!mant1)
    return (0);

  /* normalize */
  while (mant1<HIDDEN) {
    mant1 <<= 1;
    exp1--;
  }

  /* round off */
  while (mant1 & 0xff000000) {
    if (mant1&1)
      mant1 += 2;
    mant1 >>= 1 ;
    exp1++;
  }

  /* turn off hidden bit */
  mant1 &= ~HIDDEN;

  /* pack up and go home */
  fl1.l = PACK (sign, (unsigned long) exp1, mant1);

  return (fl1.f);
}

#endif
