m68k.h

gcc库的原代码,对编程有很大帮助.

/* Definitions of target machine for GNU compiler.  Sun 68000/68020 version.
   Copyright (C) 1987, 1988, 1993, 1994, 1995 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


/* Note that some other tm.h files include this one and then override
   many of the definitions that relate to assembler syntax.  */


/* Names to predefine in the preprocessor for this target machine.  */

/* See sun3.h, sun2.h, isi.h for different CPP_PREDEFINES.  */

/* Print subsidiary information on the compiler version in use.  */
#ifdef MOTOROLA
#define TARGET_VERSION fprintf (stderr, " (68k, Motorola syntax)");
#else
#define TARGET_VERSION fprintf (stderr, " (68k, MIT syntax)");
#endif

/* Define SUPPORT_SUN_FPA to include support for generating code for
   the Sun Floating Point Accelerator, an optional product for Sun 3
   machines.  By default, it is not defined.  Avoid defining it unless
   you need to output code for the Sun3+FPA architecture, as it has the
   effect of slowing down the register set operations in hard-reg-set.h
   (total number of registers will exceed number of bits in a long,
   if defined, causing the set operations to expand to loops).
   SUPPORT_SUN_FPA is typically defined in sun3.h.  */

/* Run-time compilation parameters selecting different hardware subsets.  */

extern int target_flags;

/* Macros used in the machine description to test the flags.  */

/* Compile for a 68020 (not a 68000 or 68010).  */
#define TARGET_68020 (target_flags & 1)

/* Compile 68881 insns for floating point (not library calls).  */
#define TARGET_68881 (target_flags & 2)

/* Compile using 68020 bitfield insns.  */
#define TARGET_BITFIELD (target_flags & 4)

/* Compile using rtd insn calling sequence.
   This will not work unless you use prototypes at least
   for all functions that can take varying numbers of args.  */
#define TARGET_RTD (target_flags & 8)

/* Compile passing first two args in regs 0 and 1.
   This exists only to test compiler features that will
   be needed for RISC chips.  It is not usable
   and is not intended to be usable on this cpu.  */
#define TARGET_REGPARM (target_flags & 020)

/* Compile with 16-bit `int'.  */
#define TARGET_SHORT (target_flags & 040)

/* Compile with special insns for Sun FPA.  */
#ifdef SUPPORT_SUN_FPA
#define TARGET_FPA (target_flags & 0100)
#else
#define TARGET_FPA 0
#endif

/* Compile (actually, link) for Sun SKY board.  */
#define TARGET_SKY (target_flags & 0200)

/* Optimize for 68040, but still allow execution on 68020
   (-m68020-40 or -m68040).
   The 68040 will execute all 68030 and 68881/2 instructions, but some
   of them must be emulated in software by the OS.  When TARGET_68040 is
   turned on, these instructions won't be used.  This code will still
   run on a 68030 and 68881/2. */
#define TARGET_68040 (target_flags & 01400)

/* Use the 68040-only fp instructions (-m68040).  */
#define TARGET_68040_ONLY (target_flags & 01000)

/* Macro to define tables used to set the flags.
   This is a list in braces of pairs in braces,
   each pair being { "NAME", VALUE }
   where VALUE is the bits to set or minus the bits to clear.
   An empty string NAME is used to identify the default VALUE.  */

#define TARGET_SWITCHES  \
  { { "68020", -01400},				\
    { "c68020", -01400},			\
    { "68020", 5},				\
    { "c68020", 5},				\
    { "68881", 2},				\
    { "bitfield", 4},				\
    { "68000", -01405},				\
    { "c68000", -01405},			\
    { "soft-float", -01102},			\
    { "nobitfield", -4},			\
    { "rtd", 8},				\
    { "nortd", -8},				\
    { "short", 040},				\
    { "noshort", -040},				\
    { "fpa", 0100},				\
    { "nofpa", -0100},				\
    { "sky", 0200},				\
    { "nosky", -0200},				\
    { "68020-40", 0407},			\
    { "68030", -01400},				\
    { "68030", 5},				\
    { "68040", 01007},				\
    { "68851", 0},	/* Affects *_SPEC and/or GAS.  */	\
    { "no-68851", 0},	/* Affects *_SPEC and/or GAS.  */	\
    { "68302", 0},	/* Affects *_SPEC and/or GAS.  */	\
    { "no-68302", 0},	/* Affects *_SPEC and/or GAS.  */	\
    { "68332", 0},	/* Affects *_SPEC and/or GAS.  */	\
    { "no-68332", 0},	/* Affects *_SPEC and/or GAS.  */	\
    SUBTARGET_SWITCHES				\
    { "", TARGET_DEFAULT}}
/* TARGET_DEFAULT is defined in sun*.h and isi.h, etc.  */

/* This is meant to be redefined in the host dependent files */
#define SUBTARGET_SWITCHES

#ifdef SUPPORT_SUN_FPA
/* Blow away 68881 flag silently on TARGET_FPA (since we can't clear
   any bits in TARGET_SWITCHES above) */
#define OVERRIDE_OPTIONS		\
{					\
  if (TARGET_FPA) target_flags &= ~2;	\
  if (! TARGET_68020 && flag_pic == 2)	\
    error("-fPIC is not currently supported on the 68000 or 68010\n");	\
  SUBTARGET_OVERRIDE_OPTIONS;		\
}
#else
#define OVERRIDE_OPTIONS		\
{					\
  if (! TARGET_68020 && flag_pic == 2)	\
    error("-fPIC is not currently supported on the 68000 or 68010\n");	\
  SUBTARGET_OVERRIDE_OPTIONS;		\
}
#endif /* defined SUPPORT_SUN_FPA */

/* This is meant to be redefined in the host dependent files */
#define SUBTARGET_OVERRIDE_OPTIONS

/* target machine storage layout */

/* Define for XFmode extended real floating point support.
   This will automatically cause REAL_ARITHMETIC to be defined.  */
#define LONG_DOUBLE_TYPE_SIZE 96

/* Define if you don't want extended real, but do want to use the
   software floating point emulator for REAL_ARITHMETIC and
   decimal <-> binary conversion. */
/* #define REAL_ARITHMETIC */

/* Define this if most significant bit is lowest numbered
   in instructions that operate on numbered bit-fields.
   This is true for 68020 insns such as bfins and bfexts.
   We make it true always by avoiding using the single-bit insns
   except in special cases with constant bit numbers.  */
#define BITS_BIG_ENDIAN 1

/* Define this if most significant byte of a word is the lowest numbered.  */
/* That is true on the 68000.  */
#define BYTES_BIG_ENDIAN 1

/* Define this if most significant word of a multiword number is the lowest
   numbered.  */
/* For 68000 we can decide arbitrarily
   since there are no machine instructions for them.
   So let's be consistent.  */
#define WORDS_BIG_ENDIAN 1

/* number of bits in an addressable storage unit */
#define BITS_PER_UNIT 8

/* Width in bits of a "word", which is the contents of a machine register.
   Note that this is not necessarily the width of data type `int';
   if using 16-bit ints on a 68000, this would still be 32.
   But on a machine with 16-bit registers, this would be 16.  */
#define BITS_PER_WORD 32

/* Width of a word, in units (bytes).  */
#define UNITS_PER_WORD 4

/* Width in bits of a pointer.
   See also the macro `Pmode' defined below.  */
#define POINTER_SIZE 32

/* Allocation boundary (in *bits*) for storing arguments in argument list.  */
#define PARM_BOUNDARY (TARGET_SHORT ? 16 : 32)

/* Boundary (in *bits*) on which stack pointer should be aligned.  */
#define STACK_BOUNDARY 16

/* Allocation boundary (in *bits*) for the code of a function.  */
#define FUNCTION_BOUNDARY 16

/* Alignment of field after `int : 0' in a structure.  */
#define EMPTY_FIELD_BOUNDARY 16

/* No data type wants to be aligned rounder than this.  */
#define BIGGEST_ALIGNMENT 16

/* Set this nonzero if move instructions will actually fail to work
   when given unaligned data.  */
#define STRICT_ALIGNMENT 1

#define SELECT_RTX_SECTION(MODE, X)					\
{									\
  if (!flag_pic)							\
    readonly_data_section();						\
  else if (LEGITIMATE_PIC_OPERAND_P (X))				\
    readonly_data_section();						\
  else									\
    data_section();							\
}

/* Define number of bits in most basic integer type.
   (If undefined, default is BITS_PER_WORD).  */

#define INT_TYPE_SIZE (TARGET_SHORT ? 16 : 32)

/* Define these to avoid dependence on meaning of `int'.
   Note that WCHAR_TYPE_SIZE is used in cexp.y,
   where TARGET_SHORT is not available.  */

#define WCHAR_TYPE "long int"
#define WCHAR_TYPE_SIZE 32

/* Standard register usage.  */

/* Number of actual hardware registers.
   The hardware registers are assigned numbers for the compiler
   from 0 to just below FIRST_PSEUDO_REGISTER.
   All registers that the compiler knows about must be given numbers,
   even those that are not normally considered general registers.
   For the 68000, we give the data registers numbers 0-7,
   the address registers numbers 010-017,
   and the 68881 floating point registers numbers 020-027.  */
#ifndef SUPPORT_SUN_FPA
#define FIRST_PSEUDO_REGISTER 24
#else
#define FIRST_PSEUDO_REGISTER 56
#endif

/* This defines the register which is used to hold the offset table for PIC. */
#define PIC_OFFSET_TABLE_REGNUM 13

/* Used to output a (use pic_offset_table_rtx) so that we 
   always save/restore a5 in functions that use PIC relocation
   at *any* time during the compilation process. */
#define FINALIZE_PIC finalize_pic()

#ifndef SUPPORT_SUN_FPA

/* 1 for registers that have pervasive standard uses
   and are not available for the register allocator.
   On the 68000, only the stack pointer is such.  */

#define FIXED_REGISTERS        \
 {/* Data registers.  */       \
  0, 0, 0, 0, 0, 0, 0, 0,      \
                               \
  /* Address registers.  */    \
  0, 0, 0, 0, 0, 0, 0, 1,      \
                               \
  /* Floating point registers  \
     (if available).  */       \
  0, 0, 0, 0, 0, 0, 0, 0 }

/* 1 for registers not available across function calls.
   These must include the FIXED_REGISTERS and also any
   registers that can be used without being saved.
   The latter must include the registers where values are returned
   and the register where structure-value addresses are passed.
   Aside from that, you can include as many other registers as you like.  */
#define CALL_USED_REGISTERS \
 {1, 1, 0, 0, 0, 0, 0, 0,   \
  1, 1, 0, 0, 0, 0, 0, 1,   \
  1, 1, 0, 0, 0, 0, 0, 0 }

#else /* SUPPORT_SUN_FPA */

/* 1 for registers that have pervasive standard uses
   and are not available for the register allocator.
   On the 68000, only the stack pointer is such.  */

/* fpa0 is also reserved so that it can be used to move shit back and
   forth between high fpa regs and everything else. */

#define FIXED_REGISTERS        \
 {/* Data registers.  */       \
  0, 0, 0, 0, 0, 0, 0, 0,      \
                               \
  /* Address registers.  */    \
  0, 0, 0, 0, 0, 0, 0, 1,      \
                               \
  /* Floating point registers  \
     (if available).  */       \
  0, 0, 0, 0, 0, 0, 0, 0,      \
                               \
  /* Sun3 FPA registers.  */   \
  1, 0, 0, 0, 0, 0, 0, 0,      \
  0, 0, 0, 0, 0, 0, 0, 0,      \
  0, 0, 0, 0, 0, 0, 0, 0,      \
  0, 0, 0, 0, 0, 0, 0, 0 }

/* 1 for registers not available across function calls.
   These must include the FIXED_REGISTERS and also any
   registers that can be used without being saved.
   The latter must include the registers where values are returned
   and the register where structure-value addresses are passed.
   Aside from that, you can include as many other registers as you like.  */
#define CALL_USED_REGISTERS \
 {1, 1, 0, 0, 0, 0, 0, 0, \
  1, 1, 0, 0, 0, 0, 0, 1, \
  1, 1, 0, 0, 0, 0, 0, 0, \
  /* FPA registers.  */   \
  1, 1, 1, 1, 0, 0, 0, 0, \
  0, 0, 0, 0, 0, 0, 0, 0, \
  0, 0, 0, 0, 0, 0, 0, 0, \
  0, 0, 0, 0, 0, 0, 0, 0  }

#endif /* defined SUPPORT_SUN_FPA */


/* Make sure everything's fine if we *don't* have a given processor.
   This assumes that putting a register in fixed_regs will keep the
   compiler's mitts completely off it.  We don't bother to zero it out
   of register classes.  If neither TARGET_FPA or TARGET_68881 is set,
   the compiler won't touch since no instructions that use these
   registers will be valid.  */