vax.h

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

      else if (GET_CODE (SET_DEST (EXP)) != ZERO_EXTRACT	\
	       && GET_CODE (SET_DEST (EXP)) != PC)		\
	{							\
	  cc_status.flags = 0;					\
	  /* The integer operations below don't set carry or	\
	     set it in an incompatible way.  That's ok though	\
	     as the Z bit is all we need when doing unsigned	\
	     comparisons on the result of these insns (since	\
	     they're always with 0).  Set CC_NO_OVERFLOW to	\
	     generate the correct unsigned branches.  */	\
	  switch (GET_CODE (SET_SRC (EXP)))			\
	    {							\
	    case NEG:						\
	      if (GET_MODE_CLASS (GET_MODE (EXP)) == MODE_FLOAT)\
	 	break;						\
	    case AND:						\
	    case IOR:						\
	    case XOR:						\
	    case NOT:						\
	    case MEM:						\
	    case REG:						\
	      cc_status.flags = CC_NO_OVERFLOW;			\
	      break;						\
	    default:						\
	      break;						\
	    }							\
	  cc_status.value1 = SET_DEST (EXP);			\
	  cc_status.value2 = SET_SRC (EXP); } }			\
  else if (GET_CODE (EXP) == PARALLEL				\
	   && GET_CODE (XVECEXP (EXP, 0, 0)) == SET)		\
    {								\
      if (GET_CODE (SET_SRC (XVECEXP (EXP, 0, 0))) == CALL)	\
	CC_STATUS_INIT;					        \
      else if (GET_CODE (SET_DEST (XVECEXP (EXP, 0, 0))) != PC) \
	{ cc_status.flags = 0;					\
	  cc_status.value1 = SET_DEST (XVECEXP (EXP, 0, 0));	\
	  cc_status.value2 = SET_SRC (XVECEXP (EXP, 0, 0)); }   \
      else							\
	/* PARALLELs whose first element sets the PC are aob,   \
	   sob insns.  They do change the cc's.  */		\
	CC_STATUS_INIT; }					\
  else CC_STATUS_INIT;						\
  if (cc_status.value1 && GET_CODE (cc_status.value1) == REG	\
      && cc_status.value2					\
      && reg_overlap_mentioned_p (cc_status.value1, cc_status.value2))	\
    cc_status.value2 = 0;					\
  if (cc_status.value1 && GET_CODE (cc_status.value1) == MEM	\
      && cc_status.value2					\
      && GET_CODE (cc_status.value2) == MEM)			\
    cc_status.value2 = 0; }
/* Actual condition, one line up, should be that value2's address
   depends on value1, but that is too much of a pain.  */

#define OUTPUT_JUMP(NORMAL, FLOAT, NO_OV)  \
{ if (cc_status.flags & CC_NO_OVERFLOW)				\
    return NO_OV;						\
  return NORMAL; }

/* Control the assembler format that we output.  */

/* Output at beginning of assembler file.  */
/* When debugging, we want to output an extra dummy label so that gas
   can distinguish between D_float and G_float prior to processing the
   .stabs directive identifying type double.  */

#define ASM_FILE_START(FILE) \
  do {								\
    fputs (ASM_APP_OFF, FILE);					\
    if (write_symbols == DBX_DEBUG)				\
      fprintf (FILE, "___vax_%c_doubles:\n", ASM_DOUBLE_CHAR);	\
  } while (0)


/* Output to assembler file text saying following lines
   may contain character constants, extra white space, comments, etc.  */

#define ASM_APP_ON "#APP\n"

/* Output to assembler file text saying following lines
   no longer contain unusual constructs.  */

#define ASM_APP_OFF "#NO_APP\n"

/* Output before read-only data.  */

#define TEXT_SECTION_ASM_OP "\t.text"

/* Output before writable data.  */

#define DATA_SECTION_ASM_OP "\t.data"

/* How to refer to registers in assembler output.
   This sequence is indexed by compiler's hard-register-number (see above).
   The register names will be prefixed by REGISTER_PREFIX, if any.  */

#define REGISTER_PREFIX ""
#define REGISTER_NAMES \
{"r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", \
 "r9", "r10", "r11", "ap", "fp", "sp", "pc"}

/* This is BSD, so it wants DBX format.  */

#define DBX_DEBUGGING_INFO 1

/* Do not break .stabs pseudos into continuations.  */

#define DBX_CONTIN_LENGTH 0

/* This is the char to use for continuation (in case we need to turn
   continuation back on).  */

#define DBX_CONTIN_CHAR '?'

/* Don't use the `xsfoo;' construct in DBX output; this system
   doesn't support it.  */

#define DBX_NO_XREFS

/* Output the .stabs for a C `static' variable in the data section.  */
#define DBX_STATIC_STAB_DATA_SECTION

/* VAX specific: which type character is used for type double?  */

#define ASM_DOUBLE_CHAR (TARGET_G_FLOAT ? 'g' : 'd')

/* This is how to output a command to make the user-level label named NAME
   defined for reference from other files.  */

/* Globalizing directive for a label.  */
#define GLOBAL_ASM_OP ".globl "

/* The prefix to add to user-visible assembler symbols.  */

#define USER_LABEL_PREFIX "_"

/* This is how to output an internal numbered label where
   PREFIX is the class of label and NUM is the number within the class.  */

#define ASM_OUTPUT_INTERNAL_LABEL(FILE,PREFIX,NUM)	\
  fprintf (FILE, "%s%d:\n", PREFIX, NUM)

/* This is how to store into the string LABEL
   the symbol_ref name of an internal numbered label where
   PREFIX is the class of label and NUM is the number within the class.
   This is suitable for output with `assemble_name'.  */

#define ASM_GENERATE_INTERNAL_LABEL(LABEL,PREFIX,NUM)	\
  sprintf (LABEL, "*%s%d", PREFIX, NUM)

/* This is how to output an insn to push a register on the stack.
   It need not be very fast code.  */

#define ASM_OUTPUT_REG_PUSH(FILE,REGNO)  \
  fprintf (FILE, "\tpushl %s\n", reg_names[REGNO])

/* This is how to output an insn to pop a register from the stack.
   It need not be very fast code.  */

#define ASM_OUTPUT_REG_POP(FILE,REGNO)  \
  fprintf (FILE, "\tmovl (%s)+,%s\n", reg_names[STACK_POINTER_REGNUM], \
	   reg_names[REGNO])

/* This is how to output an element of a case-vector that is absolute.
   (The VAX does not use such vectors,
   but we must define this macro anyway.)  */

#define ASM_OUTPUT_ADDR_VEC_ELT(FILE, VALUE)		\
  do							\
    {							\
      char label[256];					\
      ASM_GENERATE_INTERNAL_LABEL (label, "L", (VALUE));\
      fprintf (FILE, "\t.long ");			\
      assemble_name (FILE, label);			\
      fprintf (FILE, "\n");				\
    }							\
  while (0)

/* This is how to output an element of a case-vector that is relative.  */

#define ASM_OUTPUT_ADDR_DIFF_ELT(FILE, BODY, VALUE, REL)	\
  do								\
    {								\
      char label[256];						\
      ASM_GENERATE_INTERNAL_LABEL (label, "L", (VALUE));	\
      fprintf (FILE, "\t.word ");				\
      assemble_name (FILE, label);				\
      ASM_GENERATE_INTERNAL_LABEL (label, "L", (REL));		\
      fprintf (FILE, "-");					\
      assemble_name (FILE, label);				\
      fprintf (FILE, "\n");					\
    }								\
  while (0)

/* This is how to output an assembler line
   that says to advance the location counter
   to a multiple of 2**LOG bytes.  */

#define ASM_OUTPUT_ALIGN(FILE,LOG)  \
  fprintf (FILE, "\t.align %d\n", (LOG))

/* This is how to output an assembler line
   that says to advance the location counter by SIZE bytes.  */

#define ASM_OUTPUT_SKIP(FILE,SIZE)  \
  fprintf (FILE, "\t.space %u\n", (SIZE))

/* This says how to output an assembler line
   to define a global common symbol.  */

#define ASM_OUTPUT_COMMON(FILE, NAME, SIZE, ROUNDED)  \
( fputs (".comm ", (FILE)),			\
  assemble_name ((FILE), (NAME)),		\
  fprintf ((FILE), ",%u\n", (ROUNDED)))

/* This says how to output an assembler line
   to define a local common symbol.  */

#define ASM_OUTPUT_LOCAL(FILE, NAME, SIZE, ROUNDED)  \
( fputs (".lcomm ", (FILE)),			\
  assemble_name ((FILE), (NAME)),		\
  fprintf ((FILE), ",%u\n", (ROUNDED)))

/* Store in OUTPUT a string (made with alloca) containing
   an assembler-name for a local static variable named NAME.
   LABELNO is an integer which is different for each call.  */

#define ASM_FORMAT_PRIVATE_NAME(OUTPUT, NAME, LABELNO)	\
( (OUTPUT) = (char *) alloca (strlen ((NAME)) + 10),	\
  sprintf ((OUTPUT), "%s.%d", (NAME), (LABELNO)))

/* Print an instruction operand X on file FILE.
   CODE is the code from the %-spec that requested printing this operand;
   if `%z3' was used to print operand 3, then CODE is 'z'.

VAX operand formatting codes:

 letter	   print
   C	reverse branch condition
   D	64-bit immediate operand
   B	the low 8 bits of the complement of a constant operand
   H	the low 16 bits of the complement of a constant operand
   M	a mask for the N highest bits of a word
   N	the complement of a constant integer operand
   P	constant operand plus 1
   R	32 - constant operand
   b	the low 8 bits of a negated constant operand
   h	the low 16 bits of a negated constant operand
   #	'd' or 'g' depending on whether dfloat or gfloat is used
   |	register prefix  */

/* The purpose of D is to get around a quirk or bug in VAX assembler
   whereby -1 in a 64-bit immediate operand means 0x00000000ffffffff,
   which is not a 64-bit minus one.  */

#define PRINT_OPERAND_PUNCT_VALID_P(CODE)				\
  ((CODE) == '#' || (CODE) == '|')

#define PRINT_OPERAND(FILE, X, CODE)  \
{ if (CODE == '#') fputc (ASM_DOUBLE_CHAR, FILE);			\
  else if (CODE == '|')							\
    fputs (REGISTER_PREFIX, FILE);					\
  else if (CODE == 'C')							\
    fputs (rev_cond_name (X), FILE);					\
  else if (CODE == 'D' && GET_CODE (X) == CONST_INT && INTVAL (X) < 0)	\
    fprintf (FILE, "$0xffffffff%08x", INTVAL (X));			\
  else if (CODE == 'P' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", INTVAL (X) + 1);				\
  else if (CODE == 'N' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", ~ INTVAL (X));				\
  /* rotl instruction cannot deal with negative arguments.  */		\
  else if (CODE == 'R' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", 32 - INTVAL (X));				\
  else if (CODE == 'H' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", 0xffff & ~ INTVAL (X));			\
  else if (CODE == 'h' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", (short) - INTVAL (x));			\
  else if (CODE == 'B' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", 0xff & ~ INTVAL (X));				\
  else if (CODE == 'b' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", 0xff & - INTVAL (X));				\
  else if (CODE == 'M' && GET_CODE (X) == CONST_INT)			\
    fprintf (FILE, "$%d", ~((1 << INTVAL (x)) - 1));			\
  else if (GET_CODE (X) == REG)						\
    fprintf (FILE, "%s", reg_names[REGNO (X)]);				\
  else if (GET_CODE (X) == MEM)						\
    output_address (XEXP (X, 0));					\
  else if (GET_CODE (X) == CONST_DOUBLE && GET_MODE (X) == SFmode)	\
    { char dstr[30];							\
      real_to_decimal (dstr, CONST_DOUBLE_REAL_VALUE (X),		\
		       sizeof (dstr), 0, 1);				\
      fprintf (FILE, "$0f%s", dstr); }					\
  else if (GET_CODE (X) == CONST_DOUBLE && GET_MODE (X) == DFmode)	\
    { char dstr[30];							\
      real_to_decimal (dstr, CONST_DOUBLE_REAL_VALUE (X),		\
		       sizeof (dstr), 0, 1);				\
      fprintf (FILE, "$0%c%s", ASM_DOUBLE_CHAR, dstr); }		\
  else { putc ('$', FILE); output_addr_const (FILE, X); }}

/* Print a memory operand whose address is X, on file FILE.
   This uses a function in output-vax.c.  */

#define PRINT_OPERAND_ADDRESS(FILE, ADDR)  \
 print_operand_address (FILE, ADDR)

/* This is a blatent lie.  However, it's good enough, since we don't
   actually have any code whatsoever for which this isn't overridden
   by the proper FDE definition.  */
#define INCOMING_RETURN_ADDR_RTX gen_rtx_REG (Pmode, PC_REGNUM)