/*---------------------------------------------------------------------------+
   |  reg_compare.c                                                            |
   |                                                                           |
   | Compare two floating point registers                                      |
   |                                                                           |
   | Copyright (C) 1992,1993,1994,1997                                         |
   |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
   |                  E-mail   billm@suburbia.net                              |
   |                                                                           |
   |                                                                           |
   +---------------------------------------------------------------------------*/
  
  /*---------------------------------------------------------------------------+
   | compare() is the core FPU_REG comparison function                         |
   +---------------------------------------------------------------------------*/
  
  #include "fpu_system.h"
  #include "exception.h"
  #include "fpu_emu.h"
  #include "control_w.h"
  #include "status_w.h"

  static int compare(FPU_REG const *b, int tagb)
  {

  	int diff, exp0, expb;
  	u_char st0_tag;
  	FPU_REG *st0_ptr;
  	FPU_REG x, y;
  	u_char st0_sign, signb = getsign(b);
  
  	st0_ptr = &st(0);
  	st0_tag = FPU_gettag0();
  	st0_sign = getsign(st0_ptr);
  
  	if (tagb == TAG_Special)
  		tagb = FPU_Special(b);
  	if (st0_tag == TAG_Special)
  		st0_tag = FPU_Special(st0_ptr);
  
  	if (((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
  	    || ((tagb != TAG_Valid) && (tagb != TW_Denormal))) {
  		if (st0_tag == TAG_Zero) {
  			if (tagb == TAG_Zero)
  				return COMP_A_eq_B;
  			if (tagb == TAG_Valid)
  				return ((signb ==
  					 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
  			if (tagb == TW_Denormal)
  				return ((signb ==
  					 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
  				    | COMP_Denormal;
  		} else if (tagb == TAG_Zero) {
  			if (st0_tag == TAG_Valid)
  				return ((st0_sign ==
  					 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
  			if (st0_tag == TW_Denormal)
  				return ((st0_sign ==
  					 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
  				    | COMP_Denormal;
  		}
  
  		if (st0_tag == TW_Infinity) {
  			if ((tagb == TAG_Valid) || (tagb == TAG_Zero))
  				return ((st0_sign ==
  					 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
  			else if (tagb == TW_Denormal)
  				return ((st0_sign ==
  					 SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
  				    | COMP_Denormal;
  			else if (tagb == TW_Infinity) {
  				/* The 80486 book says that infinities can be equal! */
  				return (st0_sign == signb) ? COMP_A_eq_B :
  				    ((st0_sign ==
  				      SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
  			}
  			/* Fall through to the NaN code */
  		} else if (tagb == TW_Infinity) {
  			if ((st0_tag == TAG_Valid) || (st0_tag == TAG_Zero))
  				return ((signb ==
  					 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
  			if (st0_tag == TW_Denormal)
  				return ((signb ==
  					 SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
  				    | COMP_Denormal;
  			/* Fall through to the NaN code */
  		}
  
  		/* The only possibility now should be that one of the arguments
  		   is a NaN */
  		if ((st0_tag == TW_NaN) || (tagb == TW_NaN)) {
  			int signalling = 0, unsupported = 0;
  			if (st0_tag == TW_NaN) {
  				signalling =
  				    (st0_ptr->sigh & 0xc0000000) == 0x80000000;
  				unsupported = !((exponent(st0_ptr) == EXP_OVER)
  						&& (st0_ptr->
  						    sigh & 0x80000000));
  			}
  			if (tagb == TW_NaN) {
  				signalling |=
  				    (b->sigh & 0xc0000000) == 0x80000000;
  				unsupported |= !((exponent(b) == EXP_OVER)
  						 && (b->sigh & 0x80000000));
  			}
  			if (signalling || unsupported)
  				return COMP_No_Comp | COMP_SNaN | COMP_NaN;
  			else
  				/* Neither is a signaling NaN */
  				return COMP_No_Comp | COMP_NaN;
  		}
  
  		EXCEPTION(EX_Invalid);

  	}

  	if (st0_sign != signb) {
  		return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
  		    | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
  		       COMP_Denormal : 0);

  	}

  	if ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) {
  		FPU_to_exp16(st0_ptr, &x);
  		FPU_to_exp16(b, &y);
  		st0_ptr = &x;
  		b = &y;
  		exp0 = exponent16(st0_ptr);
  		expb = exponent16(b);
  	} else {
  		exp0 = exponent(st0_ptr);
  		expb = exponent(b);

  	}

  
  #ifdef PARANOID

  	if (!(st0_ptr->sigh & 0x80000000))
  		EXCEPTION(EX_Invalid);
  	if (!(b->sigh & 0x80000000))
  		EXCEPTION(EX_Invalid);

  #endif /* PARANOID */

  	diff = exp0 - expb;
  	if (diff == 0) {
  		diff = st0_ptr->sigh - b->sigh;	/* Works only if ms bits are
  						   identical */
  		if (diff == 0) {
  			diff = st0_ptr->sigl > b->sigl;
  			if (diff == 0)
  				diff = -(st0_ptr->sigl < b->sigl);
  		}

  	}

  	if (diff > 0) {
  		return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
  		    | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
  		       COMP_Denormal : 0);
  	}
  	if (diff < 0) {
  		return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
  		    | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
  		       COMP_Denormal : 0);
  	}

  	return COMP_A_eq_B
  	    | (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
  	       COMP_Denormal : 0);
  
  }

  
  /* This function requires that st(0) is not empty */
  int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
  {

  	int f = 0, c;
  
  	c = compare(loaded_data, loaded_tag);
  
  	if (c & COMP_NaN) {
  		EXCEPTION(EX_Invalid);
  		f = SW_C3 | SW_C2 | SW_C0;
  	} else
  		switch (c & 7) {
  		case COMP_A_lt_B:
  			f = SW_C0;
  			break;
  		case COMP_A_eq_B:
  			f = SW_C3;
  			break;
  		case COMP_A_gt_B:
  			f = 0;
  			break;
  		case COMP_No_Comp:
  			f = SW_C3 | SW_C2 | SW_C0;
  			break;

  #ifdef PARANOID

  		default:
  			EXCEPTION(EX_INTERNAL | 0x121);
  			f = SW_C3 | SW_C2 | SW_C0;
  			break;

  #endif /* PARANOID */

  		}
  	setcc(f);
  	if (c & COMP_Denormal) {
  		return denormal_operand() < 0;
  	}
  	return 0;

  }

  static int compare_st_st(int nr)
  {

  	int f = 0, c;
  	FPU_REG *st_ptr;
  
  	if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
  		setcc(SW_C3 | SW_C2 | SW_C0);
  		/* Stack fault */
  		EXCEPTION(EX_StackUnder);
  		return !(control_word & CW_Invalid);
  	}
  
  	st_ptr = &st(nr);
  	c = compare(st_ptr, FPU_gettagi(nr));
  	if (c & COMP_NaN) {
  		setcc(SW_C3 | SW_C2 | SW_C0);
  		EXCEPTION(EX_Invalid);
  		return !(control_word & CW_Invalid);
  	} else
  		switch (c & 7) {
  		case COMP_A_lt_B:
  			f = SW_C0;
  			break;
  		case COMP_A_eq_B:
  			f = SW_C3;
  			break;
  		case COMP_A_gt_B:
  			f = 0;
  			break;
  		case COMP_No_Comp:
  			f = SW_C3 | SW_C2 | SW_C0;
  			break;

  #ifdef PARANOID

  		default:
  			EXCEPTION(EX_INTERNAL | 0x122);
  			f = SW_C3 | SW_C2 | SW_C0;
  			break;

  #endif /* PARANOID */

  		}
  	setcc(f);
  	if (c & COMP_Denormal) {
  		return denormal_operand() < 0;
  	}
  	return 0;

  }

  static int compare_u_st_st(int nr)
  {

  	int f = 0, c;
  	FPU_REG *st_ptr;
  
  	if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
  		setcc(SW_C3 | SW_C2 | SW_C0);
  		/* Stack fault */
  		EXCEPTION(EX_StackUnder);
  		return !(control_word & CW_Invalid);

  	}

  
  	st_ptr = &st(nr);
  	c = compare(st_ptr, FPU_gettagi(nr));
  	if (c & COMP_NaN) {
  		setcc(SW_C3 | SW_C2 | SW_C0);
  		if (c & COMP_SNaN) {	/* This is the only difference between
  					   un-ordered and ordinary comparisons */
  			EXCEPTION(EX_Invalid);
  			return !(control_word & CW_Invalid);
  		}
  		return 0;
  	} else
  		switch (c & 7) {
  		case COMP_A_lt_B:
  			f = SW_C0;
  			break;
  		case COMP_A_eq_B:
  			f = SW_C3;
  			break;
  		case COMP_A_gt_B:
  			f = 0;
  			break;
  		case COMP_No_Comp:
  			f = SW_C3 | SW_C2 | SW_C0;
  			break;

  #ifdef PARANOID

  		default:
  			EXCEPTION(EX_INTERNAL | 0x123);
  			f = SW_C3 | SW_C2 | SW_C0;
  			break;
  #endif /* PARANOID */
  		}
  	setcc(f);
  	if (c & COMP_Denormal) {
  		return denormal_operand() < 0;
  	}
  	return 0;

  }
  
  /*---------------------------------------------------------------------------*/
  
  void fcom_st(void)
  {

  	/* fcom st(i) */
  	compare_st_st(FPU_rm);

  }

  void fcompst(void)
  {

  	/* fcomp st(i) */
  	if (!compare_st_st(FPU_rm))
  		FPU_pop();

  }

  void fcompp(void)
  {

  	/* fcompp */
  	if (FPU_rm != 1) {
  		FPU_illegal();
  		return;
  	}
  	if (!compare_st_st(1))
  		poppop();

  }

  void fucom_(void)
  {

  	/* fucom st(i) */
  	compare_u_st_st(FPU_rm);

  
  }

  void fucomp(void)
  {

  	/* fucomp st(i) */
  	if (!compare_u_st_st(FPU_rm))
  		FPU_pop();

  }

  void fucompp(void)
  {

  	/* fucompp */
  	if (FPU_rm == 1) {
  		if (!compare_u_st_st(1))
  			poppop();
  	} else
  		FPU_illegal();

  }