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/* reg.h - registers for bcc */
/* Copyright (C) 1992 Bruce Evans */
/*
The compiler generates "addresses" of the form
indirect(indcount) (rx + offset)
where
rx is a machine register (possibly null)
n is the indirection count (possibly 0)
offset is a constant.
It does not support more complicated formats like
indirect(indcount) (rx + index * scale + offset).
The register is coded as bit flag in the storage component of
the symbol structure. This allows groups of registers to be tested
using bitwise "&". Throughout the compiler, the group of these bit
flags has the type reg_t. If there are only a few registers, reg_t
can be an unsigned char. It must be unsigned if the high bit is
used, to avoid sign extension problems. For bootstrapping the compiler
from a compiler with no unsigned char, the unsigned type should be
used instead (with a signifigant waste of storage).
The bit flags should really be defined as ((reg_t) whatever) but
then they would not (necessarily) be constant expressions and couldn't
be used in switch selectors or (worse) preprocessor expressions.
The CONSTANT and GLOBAL (non-) register bits are almost
equivalent. A constant with nonzero indirection is marked as a
GLOBAL and not a CONSTANT. This makes it easier to test for a constant
CONSTANT. Globals which are formed in this way are converted to
constants if their indirection count is reset to 0 (by & operator).
*/
/* register bit flags */
#define NOSTORAGE 0x000 /* structure/union member offsets */
#define CONSTANT 0x001 /* offsets are values */
#define BREG 0x002
#define DREG 0x004
#define INDREG0 0x008
#define INDREG1 0x010
#define INDREG2 0x020
#define LOCAL 0x040
#define GLOBAL 0x080 /* offsets from storage name or 0 */
#define CCREG CONSTANT /* arg to PSHS/PULS functions only */
#ifdef I8088
# ifdef FRAMEPOINTER
# define FRAMEREG LOCAL
# endif
# define STACKREG 0x100
# define DATREG1 0x200
# define DATREG2 0x400
# define DATREG1B 0x800
#endif
#ifdef MC6809
# define DPREG LOCAL /* arg to PSHS/PULS functions only */
# define PCREG GLOBAL /* arg to PSHS/PULS functions only */
#endif
/* data for pushing and pulling registers */
#define MINREGCHAR 'A'
#ifdef I8088
# define FLAGSREGCHAR 'f'
# define pushchar() pushlist(AXREG)
#endif
#ifdef MC6809
# define pushchar() pushlist(BREG)
#endif
/* special registers */
#ifdef I8088
# define ALREG BREG
# define AXREG DREG
# define DXREG DATREG2
# define MULREG DATREG1B
# define SHIFTREG DATREG1B
#endif
#ifdef MC6809
# define XREG INDREG0 /* XREG is special for ABX in index & switch */
# define YREG INDREG2 /* XREG and YREG allow LEA (Z test) in cmp() */
#endif
/* groups of registers */
#define ALLDATREGS (BREG|DREG)
#define CHARREGS BREG
#define MAXREGS 1 /* number of data registers */
#define WORKDATREGS (BREG|DREG)
/* function call and return registers */
#define ARGREG RETURNREG /* for (1st) argument */
#define LONGARGREGS LONGRETURNREGS /* for long or float arg */
#define LONGRETURNREGS (INDREG0|LONGREG2)
#define LONGREG2 DREG
#ifdef I8088
# define LONGRETSPECIAL /* LONGRETURNREGS!=RETURNREG && RETURNREG==LONGREG2 */
# define RETURNREG DREG
#endif
#ifdef MC6809
# define RETURNREG INDREG0
#endif
/* registers which can be pulled as a group with the program counter */
/* to perform an efficient function return */
#ifdef MC6809
#define JUNK1REGS BREG /* 1 bytes locals to discard */
#define JUNK2REGS INDREG2
#define JUNK3REGS (BREG|INDREG2)
#define JUNK4REGS (INDREG1|INDREG2)
#endif
/* registers which can be pushed as a group with the first argument */
/* to perform an efficient function startup */
#ifdef MC6809
# define LOC1REGS CCREG /* 1 bytes local to allocate */
# define LOC2REGS DREG
# define LOC3REGS (CCREG|DREG)
# define LOC4REGS (CCREG|DREG|DPREG)
# endif
/* registers to be used by software operations */
#define OPREG INDREG0 /* 2nd reg for software ops (1st is DREG) */
#define OPWORKREG INDREG2 /* 3rd register for software ops */
/* maximum indirection count for 1 instruction */
#ifdef I8088
# define MAXINDIRECT 1
#endif
#ifdef MC6809
# define MAXINDIRECT 2
#endif
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