Source to src/cpu/m68k.h


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/*
  * UAE - The Un*x Amiga Emulator
  *
  * MC68000 emulation - machine dependent bits
  *
  * Copyright 1996 Bernd Schmidt
  * Copyright 2004-2005 Richard Drummond
  */

 /*
  * Machine dependent structure for holding the 68k CCR flags
  */
struct flag_struct {
    unsigned int cznv;
    unsigned int x;
};

extern struct flag_struct regflags;

/*
 * The bits in the cznv field in the above structure are assigned to
 * allow the easy mirroring of the x86 condition flags. (For example,
 * from the AX register - the x86 overflow flag can be copied to AL
 * with a setto %AL instr and the other flags copied to AH with an
 * lahf instr).
 *
 * The 68k CZNV flags are thus assinged in cznv as:
 *
 * <--AL-->  <--AH-->
 * 76543210  FEDCBA98 --------- ---------
 * xxxxxxxV  NZxxxxxC xxxxxxxxx xxxxxxxxx
 */

#define FLAGBIT_N	15
#define FLAGBIT_Z	14
#define FLAGBIT_C	8
#define FLAGBIT_V	0
#define FLAGBIT_X	8

#define FLAGVAL_N	(1 << FLAGBIT_N)
#define FLAGVAL_Z 	(1 << FLAGBIT_Z)
#define FLAGVAL_C	(1 << FLAGBIT_C)
#define FLAGVAL_V	(1 << FLAGBIT_V)
#define FLAGVAL_X	(1 << FLAGBIT_X)

#define SET_ZFLG(y)	(regflags.cznv = (regflags.cznv & ~FLAGVAL_Z) | (((y) ? 1 : 0) << FLAGBIT_Z))
#define SET_CFLG(y)	(regflags.cznv = (regflags.cznv & ~FLAGVAL_C) | (((y) ? 1 : 0) << FLAGBIT_C))
#define SET_VFLG(y)	(regflags.cznv = (regflags.cznv & ~FLAGVAL_V) | (((y) ? 1 : 0) << FLAGBIT_V))
#define SET_NFLG(y)	(regflags.cznv = (regflags.cznv & ~FLAGVAL_N) | (((y) ? 1 : 0) << FLAGBIT_N))
#define SET_XFLG(y)	(regflags.x    = ((y) ? 1 : 0) << FLAGBIT_X)

#define GET_ZFLG()	((regflags.cznv >> FLAGBIT_Z) & 1)
#define GET_CFLG()	((regflags.cznv >> FLAGBIT_C) & 1)
#define GET_VFLG()	((regflags.cznv >> FLAGBIT_V) & 1)
#define GET_NFLG()	((regflags.cznv >> FLAGBIT_N) & 1)
#define GET_XFLG()	((regflags.x    >> FLAGBIT_X) & 1)

#define CLEAR_CZNV()	(regflags.cznv  = 0)
#define GET_CZNV()	(regflags.cznv)
#define IOR_CZNV(X)	(regflags.cznv |= (X))
#define SET_CZNV(X)	(regflags.cznv  = (X))

#define COPY_CARRY() (regflags.x = regflags.cznv)


/*
 * Test CCR condition
 */
STATIC_INLINE int cctrue (int cc)
{
    uae_u32 cznv = regflags.cznv;

    switch (cc) {
	case 0:  return 1;								/*				T  */
	case 1:  return 0;								/*				F  */
	case 2:  return (cznv & (FLAGVAL_C | FLAGVAL_Z)) == 0;				/* !CFLG && !ZFLG		HI */
	case 3:  return (cznv & (FLAGVAL_C | FLAGVAL_Z)) != 0;				/*  CFLG || ZFLG		LS */
	case 4:  return (cznv & FLAGVAL_C) == 0;					/* !CFLG			CC */
	case 5:  return (cznv & FLAGVAL_C) != 0;					/*  CFLG			CS */
	case 6:  return (cznv & FLAGVAL_Z) == 0;					/* !ZFLG			NE */
	case 7:  return (cznv & FLAGVAL_Z) != 0;					/*  ZFLG			EQ */
	case 8:  return (cznv & FLAGVAL_V) == 0;					/* !VFLG			VC */
	case 9:  return (cznv & FLAGVAL_V) != 0;					/*  VFLG			VS */
	case 10: return (cznv & FLAGVAL_N) == 0;					/* !NFLG			PL */
	case 11: return (cznv & FLAGVAL_N) != 0;					/*  NFLG			MI */
	case 12: return (((cznv << (FLAGBIT_N - FLAGBIT_V)) ^ cznv) & FLAGVAL_N) == 0;	/*  NFLG == VFLG		GE */
	case 13: return (((cznv << (FLAGBIT_N - FLAGBIT_V)) ^ cznv) & FLAGVAL_N) != 0;	/*  NFLG != VFLG		LT */
	case 14: cznv &= (FLAGVAL_N | FLAGVAL_Z | FLAGVAL_V);				/* ZFLG && (NFLG == VFLG)	GT */
		 return (((cznv << (FLAGBIT_N - FLAGBIT_V)) ^ cznv) & (FLAGVAL_N | FLAGVAL_Z)) == 0;
	case 15: cznv &= (FLAGVAL_N | FLAGVAL_Z | FLAGVAL_V);				/* ZFLG && (NFLG != VFLG)	LE */
		 return (((cznv << (FLAGBIT_N - FLAGBIT_V)) ^ cznv) & (FLAGVAL_N | FLAGVAL_Z)) != 0;
    }
    return 0;
}