ip2k.h

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

   their hard registers were needed for spill registers.  If this
   macro returns nonzero for those classes, those pseudos will only
   be allocated by `global.c', which knows how to reallocate the
   pseudo to another register.  If there would not be another
   register available for reallocation, you should not change the
   definition of this macro since the only effect of such a
   definition would be to slow down register allocation.  */

#define CLASS_MAX_NREGS(CLASS, MODE)   GET_MODE_SIZE (MODE)
/* A C expression for the maximum number of consecutive registers of
   class CLASS needed to hold a value of mode MODE.

   This is closely related to the macro `HARD_REGNO_NREGS'.  In fact,
   the value of the macro `CLASS_MAX_NREGS (CLASS, MODE)' should be
   the maximum value of `HARD_REGNO_NREGS (REGNO, MODE)' for all
   REGNO values in the class CLASS.

   This macro helps control the handling of multiple-word values in
   the reload pass.  */

#define CONST_OK_FOR_LETTER_P(VALUE, C)				\
  ((C) == 'I' ? (VALUE) >= -255 && (VALUE) <= -1 :		\
   (C) == 'J' ? (VALUE) >= 0 && (VALUE) <= 7 :			\
   (C) == 'K' ? (VALUE) >= 0 && (VALUE) <= 127 :		\
   (C) == 'L' ? (VALUE) > 0 && (VALUE) < 128:			\
   (C) == 'M' ? (VALUE) == -1:					\
   (C) == 'N' ? (VALUE) == 1:					\
   (C) == 'O' ? (VALUE) == 0:					\
   (C) == 'P' ? (VALUE) >= 0 && (VALUE) <= 255:			\
   0)

/* A C expression that defines the machine-dependent operand
   constraint letters (`I', `J', `K', ... `P') that specify
   particular ranges of integer values.  If C is one of those
   letters, the expression should check that VALUE, an integer, is in
   the appropriate range and return 1 if so, 0 otherwise.  If C is
   not one of those letters, the value should be 0 regardless of
   VALUE.  */

#define CONST_DOUBLE_OK_FOR_LETTER_P(VALUE, C) 0

/* `CONST_DOUBLE_OK_FOR_LETTER_P (VALUE, C)'
   A C expression that defines the machine-dependent operand
   constraint letters that specify particular ranges of
   `const_double' values (`G' or `H').

   If C is one of those letters, the expression should check that
   VALUE, an RTX of code `const_double', is in the appropriate range
   and return 1 if so, 0 otherwise.  If C is not one of those
   letters, the value should be 0 regardless of VALUE.

   `const_double' is used for all floating-point constants and for
   `DImode' fixed-point constants.  A given letter can accept either
   or both kinds of values.  It can use `GET_MODE' to distinguish
   between these kinds.  */

#define EXTRA_CONSTRAINT(X, C) ip2k_extra_constraint (X, C)

/* A C expression that defines the optional machine-dependent
   constraint letters (``Q', `R', `S', `T', `U') that can'
   be used to segregate specific types of operands, usually memory
   references, for the target machine.  Normally this macro will not
   be defined.  If it is required for a particular target machine, it
   should return 1 if VALUE corresponds to the operand type
   represented by the constraint letter C.  If C is not defined as an
   extra constraint, the value returned should be 0 regardless of
   VALUE.

   For example, on the ROMP, load instructions cannot have their
   output in r0 if the memory reference contains a symbolic address.
   Constraint letter `Q' is defined as representing a memory address
   that does *not* contain a symbolic address.  An alternative is
   specified with a `Q' constraint on the input and `r' on the
   output.  The next alternative specifies `m' on the input and a
   register class that does not include r0 on the output.  */

/* This is an undocumented variable which describes
   how GCC will pop a data.  */
#define STACK_POP_CODE PRE_INC

#define STACK_PUSH_CODE POST_DEC
/* This macro defines the operation used when something is pushed on
   the stack.  In RTL, a push operation will be `(set (mem
   (STACK_PUSH_CODE (reg sp))) ...)'
  
   The choices are `PRE_DEC', `POST_DEC', `PRE_INC', and `POST_INC'.
   Which of these is correct depends on the stack direction and on
   whether the stack pointer points to the last item on the stack or
   whether it points to the space for the next item on the stack.
  
   The default is `PRE_DEC' when `STACK_GROWS_DOWNWARD' is defined,
   which is almost always right, and `PRE_INC' otherwise, which is
   often wrong.  */


#define STACK_CHECK_BUILTIN	1
/* Prologue code will do stack checking as necessary.  */
  
#define STARTING_FRAME_OFFSET (0)	
/* Offset from the frame pointer to the first local variable slot to
   be allocated.

   If `FRAME_GROWS_DOWNWARD', find the next slot's offset by
   subtracting the first slot's length from `STARTING_FRAME_OFFSET'.
   Otherwise, it is found by adding the length of the first slot to
   the value `STARTING_FRAME_OFFSET'.  */

#define FRAME_GROWS_DOWNWARD	1
#define STACK_GROWS_DOWNWARD	1

/* On IP2K arg pointer is virtual and resolves to either SP or FP
   after we've resolved what registers are saved (fp chain, return
   pc, etc.  */

#define FIRST_PARM_OFFSET(FUNDECL) 0
/* Offset from the argument pointer register to the first argument's
   address.  On some machines it may depend on the data type of the
   function.

   If `ARGS_GROW_DOWNWARD', this is the offset to the location above
   the first argument's address.  */

/* `STACK_DYNAMIC_OFFSET (FUNDECL)'
   Offset from the stack pointer register to an item dynamically
   allocated on the stack, e.g., by `alloca'.

   The default value for this macro is `STACK_POINTER_OFFSET' plus the
   length of the outgoing arguments.  The default is correct for most
   machines.  See `function.c' for details.  */

#define STACK_POINTER_OFFSET 1
/* IP2K stack is post-decremented, so 0(sp) is address of open space
   and 1(sp) is offset to the location avobe the forst location at which
   outgoing arguments are placed.  */

#define STACK_BOUNDARY 8
/* Define this macro if there is a guaranteed alignment for the stack
   pointer on this machine.  The definition is a C expression for the
   desired alignment (measured in bits).  This value is used as a
   default if PREFERRED_STACK_BOUNDARY is not defined.  */

#define STACK_POINTER_REGNUM REG_SP
/* The register number of the stack pointer register, which must also
   be a fixed register according to `FIXED_REGISTERS'.  On most
   machines, the hardware determines which register this is.  */

#define FRAME_POINTER_REGNUM REG_VFP
/* The register number of the frame pointer register, which is used to
   access automatic variables in the stack frame.  On some machines,
   the hardware determines which register this is.  On other
   machines, you can choose any register you wish for this purpose.  */

#define HARD_FRAME_POINTER_REGNUM REG_FP

#define ARG_POINTER_REGNUM  REG_AP
/* The register number of the arg pointer register, which is used to
   access the function's argument list.  On some machines, this is
   the same as the frame pointer register.  On some machines, the
   hardware determines which register this is.  On other machines,
   you can choose any register you wish for this purpose.  If this is
   not the same register as the frame pointer register, then you must
   mark it as a fixed register according to `FIXED_REGISTERS', or
   arrange to be able to eliminate it (*note Elimination::.).  */

/* We don't really want to support nested functions.  But we'll crash
   in various testsuite tests if we don't at least define the register
   to contain the static chain. The return value register is about as
   bad a place as any for this.  */

#define STATIC_CHAIN_REGNUM	REG_RESULT
/* Register numbers used for passing a function's static chain
   pointer.  If register windows are used, the register number as
   seen by the called function is `STATIC_CHAIN_INCOMING_REGNUM',
   while the register number as seen by the calling function is
   `STATIC_CHAIN_REGNUM'.  If these registers are the same,
   `STATIC_CHAIN_INCOMING_REGNUM' need not be defined.

   The static chain register need not be a fixed register.

   If the static chain is passed in memory, these macros should not be
   defined; instead, the next two macros should be defined.  */

#define FRAME_POINTER_REQUIRED (!flag_omit_frame_pointer)
/* A C expression which is nonzero if a function must have and use a
   frame pointer.  This expression is evaluated  in the reload pass.
   If its value is nonzero the function will have a frame pointer.

   The expression can in principle examine the current function and
   decide according to the facts, but on most machines the constant 0
   or the constant 1 suffices.  Use 0 when the machine allows code to
   be generated with no frame pointer, and doing so saves some time
   or space.  Use 1 when there is no possible advantage to avoiding a
   frame pointer.

   In certain cases, the compiler does not know how to produce valid
   code without a frame pointer.  The compiler recognizes those cases
   and automatically gives the function a frame pointer regardless of
   what `FRAME_POINTER_REQUIRED' says.  You don't need to worry about
   them.

   In a function that does not require a frame pointer, the frame
   pointer register can be allocated for ordinary usage, unless you
   mark it as a fixed register.  See `FIXED_REGISTERS' for more
   information.  */

#define ELIMINABLE_REGS	{ 					\
        {ARG_POINTER_REGNUM, STACK_POINTER_REGNUM},		\
	{ARG_POINTER_REGNUM, HARD_FRAME_POINTER_REGNUM},	\
	{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM},		\
	{FRAME_POINTER_REGNUM, HARD_FRAME_POINTER_REGNUM},	\
	{HARD_FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM},	\
}
/* If defined, this macro specifies a table of register pairs used to
   eliminate unneeded registers that point into the stack frame.  If
   it is not defined, the only elimination attempted by the compiler
   is to replace references to the frame pointer with references to
   the stack pointer.

   The definition of this macro is a list of structure
   initializations, each of which specifies an original and
   replacement register.

   On some machines, the position of the argument pointer is not
   known until the compilation is completed.  In such a case, a
   separate hard register must be used for the argument pointer.
   This register can be eliminated by replacing it with either the
   frame pointer or the argument pointer, depending on whether or not
   the frame pointer has been eliminated.

   In this case, you might specify:
   #define ELIMINABLE_REGS  \
   {{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM}, \
   {ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM}, \
   {FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM}}

   Note that the elimination of the argument pointer with the stack
   pointer is specified first since that is the preferred elimination.  */


#define CAN_ELIMINATE(FROM, TO) 				\
  ((FROM) == HARD_FRAME_POINTER_REGNUM				\
   ? (flag_omit_frame_pointer && !frame_pointer_needed) : 1)
/* Don't eliminate FP unless we EXPLICITLY_ASKED  */

/* A C expression that returns nonzero if the compiler is allowed to
   try to replace register number FROM-REG with register number
   TO-REG.  This macro need only be defined if `ELIMINABLE_REGS' is
   defined, and will usually be the constant 1, since most of the
   cases preventing register elimination are things that the compiler
   already knows about.  */

#define INITIAL_ELIMINATION_OFFSET(FROM, TO, OFFSET) \
  ((OFFSET) = ip2k_init_elim_offset ((FROM), (TO)))

/* This macro is similar to `INITIAL_FRAME_POINTER_OFFSET'.  It
   specifies the initial difference between the specified pair of
   registers.  This macro must be defined if `ELIMINABLE_REGS' is
   defined.  */

#define RETURN_ADDR_RTX(COUNT, X) \
  (((COUNT) == 0) ? gen_rtx_REG (HImode, REG_CALLH) : NULL_RTX)
/*   A C expression whose value is RTL representing the value of the
     return address for the frame COUNT steps up from the current
     frame, after the prologue.  FRAMEADDR is the frame pointer of the
     COUNT frame, or the frame pointer of the COUNT - 1 frame if
     `RETURN_ADDR_IN_PREVIOUS_FRAME' is defined.

     The value of the expression must always be the correct address when
     COUNT is zero, but may be `NULL_RTX' if there is not way to
     determine the return address of other frames.  */

#define PUSH_ROUNDING(NPUSHED) (NPUSHED)
/* A C expression that is the number of bytes actually pushed onto the
   stack when an instruction attempts to push NPUSHED bytes.

   If the target machine does not have a push instruction, do not
   define this macro.  That directs GNU CC to use an alternate
   strategy: to allocate the entire argument block and then store the
   arguments into it.

   On some machines, the definition

   #define PUSH_ROUNDING(BYTES) (BYTES)

   will suffice.  But on other machines, instructions that appear to
   push one byte actually push two bytes in an attempt to maintain
   alignment.  Then the definition should be

   #define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1)  */

#define RETURN_POPS_ARGS(FUNDECL,FUNTYPE,SIZE) \
  ip2k_return_pops_args ((FUNDECL), (FUNTYPE), (SIZE))
/* A C expression that should indicate the number of bytes of its own
   arguments that a function pops on returning, or 0 if the function
   pops no arguments and the caller must therefore pop them all after
   the function returns.

   FUNDECL is a C variable whose value is a tree node that describes
   the function in question.  Normally it is a node of type
   `FUNCTION_DECL' that describes the declaration of the function.
   From this you can obtain the DECL_MACHINE_ATTRIBUTES of the
   function.