mmix.h

gcc-you can use this code to learn something about gcc, and inquire further into linux,

   call-clobbered; we'll put arguments in $16 and up, and we need $15 for
   the MMIX register-stack "hole".  */
#define CALL_USED_REGISTERS \
 { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, \
   1, 1, 1, 1, 1, 1, 1 \
 }

#define CONDITIONAL_REGISTER_USAGE mmix_conditional_register_usage ()

/* No INCOMING_REGNO or OUTGOING_REGNO, since those macros are not usable
   for MMIX: it doesn't have a fixed register window size.  FIXME: Perhaps
   we should say something about $0..$15 may sometimes be the incoming
   $16..$31.  Those macros need better documentation; it looks like
   they're just bogus and that FUNCTION_INCOMING_ARG_REGNO_P and
   FUNCTION_OUTGOING_VALUE should be used where they're used.  For the
   moment, do nothing; things seem to work anyway.  */

/* Defining LOCAL_REGNO is necessary in presence of prologue/epilogue,
   else GCC will be confused that those registers aren't saved and
   restored.  */
#define LOCAL_REGNO(REGNO) mmix_local_regno (REGNO)

/* Node: Allocation Order */

/* We should allocate registers from 0 to 31 by increasing number, because
   I think that's what people expect.  Beyond that, just use
   call-clobbered global registers first, then call-clobbered special
   registers.  Last, the fixed registers.  */
#define MMIX_MMIXWARE_ABI_REG_ALLOC_ORDER	\
 { 0, 1, 2, 3, 4, 5, 6, 7,			\
   8, 9, 10, 11, 12, 13, 14, 15,		\
   16, 17, 18, 19, 20, 21, 22, 23,		\
   24, 25, 26, 27, 28, 29, 30, 31,    		\
						\
   252, 251, 250, 249, 248, 247, 		\
						\
   253,						\
						\
   258, 260, 259,				\
						\
   32, 33, 34, 35, 36, 37, 38, 39,		\
   40, 41, 42, 43, 44, 45, 46, 47,		\
   48, 49, 50, 51, 52, 53, 54, 55,		\
   56, 57, 58, 59, 60, 61, 62, 63,		\
   64, 65, 66, 67, 68, 69, 70, 71,		\
   72, 73, 74, 75, 76, 77, 78, 79,		\
   80, 81, 82, 83, 84, 85, 86, 87,		\
   88, 89, 90, 91, 92, 93, 94, 95,		\
   96, 97, 98, 99, 100, 101, 102, 103,		\
   104, 105, 106, 107, 108, 109, 110, 111,	\
   112, 113, 114, 115, 116, 117, 118, 119,	\
   120, 121, 122, 123, 124, 125, 126, 127,	\
   128, 129, 130, 131, 132, 133, 134, 135,	\
   136, 137, 138, 139, 140, 141, 142, 143,	\
   144, 145, 146, 147, 148, 149, 150, 151,	\
   152, 153, 154, 155, 156, 157, 158, 159,	\
   160, 161, 162, 163, 164, 165, 166, 167,	\
   168, 169, 170, 171, 172, 173, 174, 175,	\
   176, 177, 178, 179, 180, 181, 182, 183,	\
   184, 185, 186, 187, 188, 189, 190, 191,	\
   192, 193, 194, 195, 196, 197, 198, 199,	\
   200, 201, 202, 203, 204, 205, 206, 207,	\
   208, 209, 210, 211, 212, 213, 214, 215,	\
   216, 217, 218, 219, 220, 221, 222, 223,	\
   224, 225, 226, 227, 228, 229, 230, 231,	\
   232, 233, 234, 235, 236, 237, 238, 239,	\
   240, 241, 242, 243, 244, 245, 246,		\
						\
   254, 255, 256, 257, 261, 262			\
 }

/* As a convenience, we put this nearby, for ease of comparison.
   First, call-clobbered registers in reverse order of assignment as
   parameters (also the top ones; not because they're parameters, but
   for continuity).

   Second, saved registers that go on the register-stack.

   Third, special registers rH, rR and rJ.  They should not normally be
   allocated, but since they're call-clobbered, it is cheaper to use one
   of them than using a call-saved register for a call-clobbered use,
   assuming it is referenced a very limited number of times.  Other global
   and fixed registers come next; they are never allocated.  */
#define MMIX_GNU_ABI_REG_ALLOC_ORDER		\
 { 252, 251, 250, 249, 248, 247, 246,		\
   245, 244, 243, 242, 241, 240, 239, 238,	\
   237, 236, 235, 234, 233, 232, 231,		\
						\
   0, 1, 2, 3, 4, 5, 6, 7,			\
   8, 9, 10, 11, 12, 13, 14, 15,		\
   16, 17, 18, 19, 20, 21, 22, 23,		\
   24, 25, 26, 27, 28, 29, 30, 31,		\
						\
   253,						\
						\
   258, 260, 259,				\
						\
   32, 33, 34, 35, 36, 37, 38, 39,		\
   40, 41, 42, 43, 44, 45, 46, 47,		\
   48, 49, 50, 51, 52, 53, 54, 55,		\
   56, 57, 58, 59, 60, 61, 62, 63,		\
   64, 65, 66, 67, 68, 69, 70, 71,		\
   72, 73, 74, 75, 76, 77, 78, 79,		\
   80, 81, 82, 83, 84, 85, 86, 87,		\
   88, 89, 90, 91, 92, 93, 94, 95,		\
   96, 97, 98, 99, 100, 101, 102, 103,		\
   104, 105, 106, 107, 108, 109, 110, 111,	\
   112, 113, 114, 115, 116, 117, 118, 119,	\
   120, 121, 122, 123, 124, 125, 126, 127,	\
   128, 129, 130, 131, 132, 133, 134, 135,	\
   136, 137, 138, 139, 140, 141, 142, 143,	\
   144, 145, 146, 147, 148, 149, 150, 151,	\
   152, 153, 154, 155, 156, 157, 158, 159,	\
   160, 161, 162, 163, 164, 165, 166, 167,	\
   168, 169, 170, 171, 172, 173, 174, 175,	\
   176, 177, 178, 179, 180, 181, 182, 183,	\
   184, 185, 186, 187, 188, 189, 190, 191,	\
   192, 193, 194, 195, 196, 197, 198, 199,	\
   200, 201, 202, 203, 204, 205, 206, 207,	\
   208, 209, 210, 211, 212, 213, 214, 215,	\
   216, 217, 218, 219, 220, 221, 222, 223,	\
   224, 225, 226, 227, 228, 229, 230,		\
						\
   254, 255, 256, 257, 261, 262			\
 }

/* The default one.  */
#define REG_ALLOC_ORDER MMIX_MMIXWARE_ABI_REG_ALLOC_ORDER

/* Node: Values in Registers */

#define HARD_REGNO_NREGS(REGNO, MODE)            	\
   ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1)  	\
    / UNITS_PER_WORD)

#define HARD_REGNO_MODE_OK(REGNO, MODE) 1

/* Note that no register can really be accessed in single-float mode, so
   we *can* say 1 here.  FIXME:  Will TRT happen for single-float, or do
   we have to punt to libgcc1.asm?  */
#define MODES_TIEABLE_P(MODE1, MODE2) 1


/* Node: Leaf Functions */
/* (empty) */


/* Node: Register Classes */

enum reg_class
 {
   NO_REGS, GENERAL_REGS, REMAINDER_REG, HIMULT_REG,
   SYSTEM_REGS, ALL_REGS, LIM_REG_CLASSES
 };

#define N_REG_CLASSES (int) LIM_REG_CLASSES

#define REG_CLASS_NAMES						\
 {"NO_REGS", "GENERAL_REGS", "REMAINDER_REG", "HIMULT_REG",	\
  "SYSTEM_REGS", "ALL_REGS"}

/* Note that the contents of each item is always 32 bits.  */
#define REG_CLASS_CONTENTS			\
 {{0, 0, 0, 0, 0, 0, 0, 0, 0},			\
  {~0, ~0, ~0, ~0, ~0, ~0, ~0, ~0, 0x20},	\
  {0, 0, 0, 0, 0, 0, 0, 0, 0x10},		\
  {0, 0, 0, 0, 0, 0, 0, 0, 4},			\
  {0, 0, 0, 0, 0, 0, 0, 0, 0x7f},		\
  {~0, ~0, ~0, ~0, ~0, ~0, ~0, ~0, 0x7f}}

#define REGNO_REG_CLASS(REGNO)					\
 ((REGNO) <= MMIX_LAST_GENERAL_REGISTER				\
  || (REGNO) == MMIX_ARG_POINTER_REGNUM				\
  ? GENERAL_REGS						\
  : (REGNO) == MMIX_REMAINDER_REGNUM ? REMAINDER_REG		\
  : (REGNO) == MMIX_HIMULT_REGNUM ? HIMULT_REG : SYSTEM_REGS)

#define BASE_REG_CLASS GENERAL_REGS

#define INDEX_REG_CLASS GENERAL_REGS

#define REG_CLASS_FROM_LETTER(CHAR)		\
 ((CHAR) == 'x' ? SYSTEM_REGS			\
  : (CHAR) == 'y' ? REMAINDER_REG		\
  : (CHAR) == 'z' ? HIMULT_REG : NO_REGS)

#define REGNO_OK_FOR_BASE_P(REGNO)				\
 ((REGNO) <= MMIX_LAST_GENERAL_REGISTER				\
  || (REGNO) == MMIX_ARG_POINTER_REGNUM				\
  || (reg_renumber[REGNO] > 0					\
      && reg_renumber[REGNO] <= MMIX_LAST_GENERAL_REGISTER))

#define REGNO_OK_FOR_INDEX_P(REGNO) REGNO_OK_FOR_BASE_P (REGNO)

#define PREFERRED_RELOAD_CLASS(X, CLASS) \
 mmix_preferred_reload_class (X, CLASS)

#define PREFERRED_OUTPUT_RELOAD_CLASS(X, CLASS) \
 mmix_preferred_output_reload_class (X, CLASS)

#define SECONDARY_INPUT_RELOAD_CLASS(CLASS, MODE, X) \
 mmix_secondary_reload_class (CLASS, MODE, X, 1)

#define SECONDARY_OUTPUT_RELOAD_CLASS(CLASS, MODE, X) \
 mmix_secondary_reload_class (CLASS, MODE, X, 0)

#define CLASS_MAX_NREGS(CLASS, MODE) HARD_REGNO_NREGS (CLASS, MODE)

#define CONST_OK_FOR_LETTER_P(VALUE, C)	\
 mmix_const_ok_for_letter_p (VALUE, C)

#define EXTRA_CONSTRAINT(VALUE, C)	\
 mmix_extra_constraint (VALUE, C, MMIX_REG_OK_STRICT)

/* Do we need anything serious here?  Yes, any FLOT constant.  */
#define CONST_DOUBLE_OK_FOR_LETTER_P(VALUE, C)			\
 mmix_const_double_ok_for_letter_p (VALUE, C)


/* Node: Frame Layout */

#define STACK_GROWS_DOWNWARD
#define FRAME_GROWS_DOWNWARD

#define STARTING_FRAME_OFFSET \
  mmix_starting_frame_offset ()

#define FIRST_PARM_OFFSET(FUNDECL) 0

#define DYNAMIC_CHAIN_ADDRESS(FRAMEADDR) \
 mmix_dynamic_chain_address (FRAMEADDR)

/* FIXME: It seems RETURN_ADDR_OFFSET is undocumented.  */

#define SETUP_FRAME_ADDRESSES() \
 mmix_setup_frame_addresses ()

#define RETURN_ADDR_RTX(COUNT, FRAME)		\
 mmix_return_addr_rtx (COUNT, FRAME)

/* It's in rJ before we store it somewhere.  */
#define INCOMING_RETURN_ADDR_RTX \
 gen_rtx_REG (Pmode, MMIX_INCOMING_RETURN_ADDRESS_REGNUM)

/* FIXME: This does not seem properly documented or cross-indexed.
   Nowhere except in the code does it say it *has* to be in the range
   0..255, or else it will be truncated.  That goes for the default too.  */
#define DWARF_FRAME_RETURN_COLUMN \
 DWARF_FRAME_REGNUM (MMIX_INCOMING_RETURN_ADDRESS_REGNUM)

/* No return address is stored there.  */
#define INCOMING_FRAME_SP_OFFSET 0

/* Node: Stack Checking */
/* (empty) */


/* Node: Exception Handling */

#define EH_RETURN_DATA_REGNO(N) \
 mmix_eh_return_data_regno (N)

#define EH_RETURN_STACKADJ_RTX \
 mmix_eh_return_stackadj_rtx ()

#define EH_RETURN_HANDLER_RTX \
 mmix_eh_return_handler_rtx ()

#define ASM_PREFERRED_EH_DATA_FORMAT(CODE, GLOBAL) \
 mmix_asm_preferred_eh_data_format (CODE, GLOBAL)

/* Node: Frame Registers */
#define STACK_POINTER_REGNUM MMIX_STACK_POINTER_REGNUM

/* Perhaps we can use HARD_FRAME_POINTER_REGNUM and decide later on
   what register we want to use.  */
#define FRAME_POINTER_REGNUM MMIX_FRAME_POINTER_REGNUM
#define ARG_POINTER_REGNUM MMIX_ARG_POINTER_REGNUM

#define STATIC_CHAIN_REGNUM MMIX_STATIC_CHAIN_REGNUM


/* Node: Elimination */
/* FIXME: Is this requirement built-in?  Anyway, we should try to get rid
   of it; we can deduce the value.  */
#define FRAME_POINTER_REQUIRED (nonlocal_goto_stack_level != NULL_RTX)

/* The frame-pointer is stored in a location that either counts to the
   offset of incoming parameters, or that counts to the offset of the
   frame, so we can't use a single offset.  We therefore eliminate those
   two separately.  */
#define ELIMINABLE_REGS				\
 {{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM},	\
  {ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM},	\
  {FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM}}

/* We need not worry about when the frame-pointer is required for other
   reasons; GCC takes care of those cases.  */
#define CAN_ELIMINATE(FROM, TO) 1

#define INITIAL_ELIMINATION_OFFSET(FROM, TO, OFFSET) \
 (OFFSET) = mmix_initial_elimination_offset (FROM, TO)


/* Node: Stack Arguments */

#define ACCUMULATE_OUTGOING_ARGS 1

#define RETURN_POPS_ARGS(FUNDECL, FUNTYPE, STACKSIZE) 0


/* Node: Register Arguments */
#define FUNCTION_ARG(CUM, MODE, TYPE, NAMED)	\
 mmix_function_arg (&(CUM), MODE, TYPE, NAMED, 0)

#define FUNCTION_INCOMING_ARG(CUM, MODE, TYPE, NAMED)	\
 mmix_function_arg (&(CUM), MODE, TYPE, NAMED, 1)

#define FUNCTION_ARG_PASS_BY_REFERENCE(CUM, MODE, TYPE, NAMED)	\
 mmix_function_arg_pass_by_reference (&(CUM), MODE, TYPE, NAMED)

/* This *sounds* good, but does not seem to be implemented correctly to
   be a win; at least it wasn't in 2.7.2.  FIXME: Check and perhaps
   replace with a big comment.
   The definition needs to match or be a subset of
   FUNCTION_ARG_PASS_BY_REFERENCE, since not all callers check that before
   usage.  Watch lots of C++ test-cases fail if set to 1, for example
   g++.dg/init/byval1.C.  */
#define FUNCTION_ARG_CALLEE_COPIES(CUM, MODE, TYPE, NAMED) \
 mmix_function_arg_pass_by_reference (&(CUM), MODE, TYPE, NAMED)

typedef struct { int regs; int lib; } CUMULATIVE_ARGS;

#define INIT_CUMULATIVE_ARGS(CUM, FNTYPE, LIBNAME, INDIRECT)	\
 ((CUM).regs = 0, (CUM).lib = ((LIBNAME) != 0))

#define FUNCTION_ARG_ADVANCE(CUM, MODE, TYPE, NAMED)		\
 ((CUM).regs							\
  = ((MUST_PASS_IN_STACK (MODE, TYPE))				\
     || (MMIX_FUNCTION_ARG_SIZE (MODE, TYPE) > 8		\
	 && !TARGET_LIBFUNC && !(CUM).lib))			\
  ? (MMIX_MAX_ARGS_IN_REGS) + 1					\
  : (CUM).regs + (7 + (MMIX_FUNCTION_ARG_SIZE (MODE, TYPE))) / 8)

#define FUNCTION_ARG_REGNO_P(REGNO)		\
 mmix_function_arg_regno_p (REGNO, 0)

#define FUNCTION_INCOMING_ARG_REGNO_P(REGNO)		\
 mmix_function_arg_regno_p (REGNO, 1)


/* Node: Register Arguments */

#define FUNCTION_VALUE(VALTYPE, FUNC)  \
 gen_rtx_REG (TYPE_MODE (VALTYPE), MMIX_RETURN_VALUE_REGNUM)

/* This needs to take care of the register hole for complex return values.  */
#define FUNCTION_OUTGOING_VALUE(VALTYPE, FUNC)  \
 mmix_function_outgoing_value (VALTYPE, FUNC)

#define LIBCALL_VALUE(MODE) \
 gen_rtx_REG (MODE, MMIX_RETURN_VALUE_REGNUM)

#define FUNCTION_VALUE_REGNO_P(REGNO) \
 mmix_function_value_regno_p (REGNO)


/* Node: Aggregate Return */

#define STRUCT_VALUE_REGNUM MMIX_STRUCT_VALUE_REGNUM


/* Node: Caller Saves */
/* (empty) */


/* Node: Function Entry */

/* See mmix.c for TARGET_ASM_FUNCTION_PROLOGUE and
   TARGET_ASM_FUNCTION_EPILOGUE.  */

/* We need to say that the epilogue uses the return address, so the
   initial-value machinery restores it.  FIXME: Some targets
   conditionalize on "reload_completed &&".  Investigate difference.