pdp11.c

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

    output_asm_insn ("add $2,%0", &addreg1);

  /* Do that word.  */
  output_asm_insn (singlemove_string (latehalf), latehalf);

  /* Undo the adds we just did.  */
  if (addreg0)
    output_asm_insn ("sub $2,%0", &addreg0);
  if (addreg1)
    output_asm_insn ("sub $2,%0", &addreg1);

  return "";
}
/* Output assembler code to perform a quadword move insn
   with operands OPERANDS.  */

const char *
output_move_quad (operands)
     rtx *operands;
{
  enum { REGOP, OFFSOP, MEMOP, PUSHOP, POPOP, CNSTOP, RNDOP } optype0, optype1;
  rtx latehalf[2];
  rtx addreg0 = 0, addreg1 = 0;

  output_asm_insn(";/* movdi/df: %1 -> %0 */", operands);
  
  if (REG_P (operands[0]))
    optype0 = REGOP;
  else if (offsettable_memref_p (operands[0]))
    optype0 = OFFSOP;
  else if (GET_CODE (XEXP (operands[0], 0)) == POST_INC)
    optype0 = POPOP;
  else if (GET_CODE (XEXP (operands[0], 0)) == PRE_DEC)
    optype0 = PUSHOP;
  else if (GET_CODE (operands[0]) == MEM)
    optype0 = MEMOP;
  else
    optype0 = RNDOP;

  if (REG_P (operands[1]))
    optype1 = REGOP;
  else if (CONSTANT_P (operands[1])
	   || GET_CODE (operands[1]) == CONST_DOUBLE)
    optype1 = CNSTOP;
  else if (offsettable_memref_p (operands[1]))
    optype1 = OFFSOP;
  else if (GET_CODE (XEXP (operands[1], 0)) == POST_INC)
    optype1 = POPOP;
  else if (GET_CODE (XEXP (operands[1], 0)) == PRE_DEC)
    optype1 = PUSHOP;
  else if (GET_CODE (operands[1]) == MEM)
    optype1 = MEMOP;
  else
    optype1 = RNDOP;

  /* Check for the cases that the operand constraints are not
     supposed to allow to happen.  Abort if we get one,
     because generating code for these cases is painful.  */

  if (optype0 == RNDOP || optype1 == RNDOP)
    abort ();
  
  /* check if we move a CPU reg to an FPU reg, or vice versa! */
  if (optype0 == REGOP && optype1 == REGOP)
      /* bogus - 64 bit cannot reside in CPU! */
      if (CPU_REG_P(REGNO(operands[0]))
	  || CPU_REG_P (REGNO(operands[1])))
	  abort();
  
  if (optype0 == REGOP || optype1 == REGOP)
  {
      /* check for use of clrd???? 
         if you ever allow ac4 and ac5 (now we require secondary load) 
	 you must check whether 
	 you want to load into them or store from them - 
	 then dump ac0 into $help$ movce ac4/5 to ac0, do the 
	 store from ac0, and restore ac0 - if you can find 
	 an unused ac[0-3], use that and you save a store and a load!*/

      if (FPU_REG_P(REGNO(operands[0])))
      {
	  if (GET_CODE(operands[1]) == CONST_DOUBLE)
	  {
	      REAL_VALUE_TYPE r;
	      REAL_VALUE_FROM_CONST_DOUBLE (r, operands[1]);

	      if (REAL_VALUES_EQUAL (r, dconst0))
		  return "{clrd|clrf} %0";
	  }
	      
	  return "{ldd|movf} %1, %0";
      }
      
      if (FPU_REG_P(REGNO(operands[1])))
	  return "{std|movf} %1, %0";
  }
      
  /* If one operand is decrementing and one is incrementing
     decrement the former register explicitly
     and change that operand into ordinary indexing.  */

  if (optype0 == PUSHOP && optype1 == POPOP)
    {
      operands[0] = XEXP (XEXP (operands[0], 0), 0);
      output_asm_insn ("sub $8,%0", operands);
      operands[0] = gen_rtx_MEM (DImode, operands[0]);
      optype0 = OFFSOP;
    }
  if (optype0 == POPOP && optype1 == PUSHOP)
    {
      operands[1] = XEXP (XEXP (operands[1], 0), 0);
      output_asm_insn ("sub $8,%1", operands);
      operands[1] = gen_rtx_MEM (SImode, operands[1]);
      optype1 = OFFSOP;
    }

  /* If an operand is an unoffsettable memory ref, find a register
     we can increment temporarily to make it refer to the second word.  */

  if (optype0 == MEMOP)
    addreg0 = find_addr_reg (XEXP (operands[0], 0));

  if (optype1 == MEMOP)
    addreg1 = find_addr_reg (XEXP (operands[1], 0));

  /* Ok, we can do one word at a time.
     Normally we do the low-numbered word first,
     but if either operand is autodecrementing then we
     do the high-numbered word first.

     In either case, set up in LATEHALF the operands to use
     for the high-numbered word and in some cases alter the
     operands in OPERANDS to be suitable for the low-numbered word.  */

  if (optype0 == REGOP)
    latehalf[0] = gen_rtx_REG (SImode, REGNO (operands[0]) + 2);
  else if (optype0 == OFFSOP)
    latehalf[0] = adjust_address (operands[0], SImode, 4);
  else
    latehalf[0] = operands[0];

  if (optype1 == REGOP)
    latehalf[1] = gen_rtx_REG (SImode, REGNO (operands[1]) + 2);
  else if (optype1 == OFFSOP)
    latehalf[1] = adjust_address (operands[1], SImode, 4);
  else if (optype1 == CNSTOP)
    {
      if (GET_CODE (operands[1]) == CONST_DOUBLE)
	{
	    /* floats only. not yet supported!

	     -- compute it into PDP float format, - internally,
	     just use IEEE and ignore possible problems ;-)

	     we might get away with it !!!! */

	    abort();
	    
#ifndef HOST_WORDS_BIG_ENDIAN
	  latehalf[1] = GEN_INT (CONST_DOUBLE_LOW (operands[1]));
	  operands[1] = GEN_INT	(CONST_DOUBLE_HIGH (operands[1]));
#else /* HOST_WORDS_BIG_ENDIAN */
	  latehalf[1] = GEN_INT (CONST_DOUBLE_HIGH (operands[1]));
	  operands[1] = GEN_INT (CONST_DOUBLE_LOW (operands[1]));
#endif /* HOST_WORDS_BIG_ENDIAN */
	}
      else if (GET_CODE(operands[1]) == CONST_INT)
	{
	  latehalf[1] = GEN_INT (0);
	}
      else
	abort();
    }
  else
    latehalf[1] = operands[1];

  /* If insn is effectively movd N(sp),-(sp) then we will do the
     high word first.  We should use the adjusted operand 1 (which is N+4(sp))
     for the low word as well, to compensate for the first decrement of sp.  */
  if (optype0 == PUSHOP
      && REGNO (XEXP (XEXP (operands[0], 0), 0)) == STACK_POINTER_REGNUM
      && reg_overlap_mentioned_p (stack_pointer_rtx, operands[1]))
    operands[1] = latehalf[1];

  /* If one or both operands autodecrementing,
     do the two words, high-numbered first.  */

  /* Likewise,  the first move would clobber the source of the second one,
     do them in the other order.  This happens only for registers;
     such overlap can't happen in memory unless the user explicitly
     sets it up, and that is an undefined circumstance.  */

  if (optype0 == PUSHOP || optype1 == PUSHOP
      || (optype0 == REGOP && optype1 == REGOP
	  && REGNO (operands[0]) == REGNO (latehalf[1])))
    {
      /* Make any unoffsettable addresses point at high-numbered word.  */
      if (addreg0)
	output_asm_insn ("add $4,%0", &addreg0);
      if (addreg1)
	output_asm_insn ("add $4,%0", &addreg1);

      /* Do that word.  */
      output_asm_insn(output_move_double(latehalf), latehalf);

      /* Undo the adds we just did.  */
      if (addreg0)
	output_asm_insn ("sub $4,%0", &addreg0);
      if (addreg1)
	output_asm_insn ("sub $4,%0", &addreg1);

      /* Do low-numbered word.  */
      return output_move_double (operands);
    }

  /* Normal case: do the two words, low-numbered first.  */

  output_asm_insn (output_move_double (operands), operands);

  /* Make any unoffsettable addresses point at high-numbered word.  */
  if (addreg0)
    output_asm_insn ("add $4,%0", &addreg0);
  if (addreg1)
    output_asm_insn ("add $4,%0", &addreg1);

  /* Do that word.  */
  output_asm_insn (output_move_double (latehalf), latehalf);

  /* Undo the adds we just did.  */
  if (addreg0)
    output_asm_insn ("sub $4,%0", &addreg0);
  if (addreg1)
    output_asm_insn ("sub $4,%0", &addreg1);

  return "";
}


/* Return a REG that occurs in ADDR with coefficient 1.
   ADDR can be effectively incremented by incrementing REG.  */

static rtx
find_addr_reg (addr)
     rtx addr;
{
  while (GET_CODE (addr) == PLUS)
    {
      if (GET_CODE (XEXP (addr, 0)) == REG)
	addr = XEXP (addr, 0);
      if (GET_CODE (XEXP (addr, 1)) == REG)
	addr = XEXP (addr, 1);
      if (CONSTANT_P (XEXP (addr, 0)))
	addr = XEXP (addr, 1);
      if (CONSTANT_P (XEXP (addr, 1)))
	addr = XEXP (addr, 0);
    }
  if (GET_CODE (addr) == REG)
    return addr;
  return 0;
}

/* Output an ascii string.  */
void
output_ascii (file, p, size)
     FILE *file;
     const char *p;
     int size;
{
  int i;

  /* This used to output .byte "string", which doesn't work with the UNIX
     assembler and I think not with DEC ones either.  */
  fprintf (file, "\t.byte ");

  for (i = 0; i < size; i++)
    {
      register int c = p[i];
      if (c < 0)
	c += 256;
      fprintf (file, "%#o", c);
      if (i < size - 1)
	putc (',', file);
    }
  putc ('\n', file);
}


/* --- stole from out-vax, needs changes */

void
print_operand_address (file, addr)
     FILE *file;
     register rtx addr;
{
  register rtx reg1, reg2, breg, ireg;
  rtx offset;

 retry:

  switch (GET_CODE (addr))
    {
    case MEM:
      if (TARGET_UNIX_ASM)
	fprintf (file, "*");
      else
	fprintf (file, "@");
      addr = XEXP (addr, 0);
      goto retry;

    case REG:
      fprintf (file, "(%s)", reg_names[REGNO (addr)]);
      break;

    case PRE_MODIFY:
    case PRE_DEC:
      fprintf (file, "-(%s)", reg_names[REGNO (XEXP (addr, 0))]);
      break;

    case POST_MODIFY:
    case POST_INC:
      fprintf (file, "(%s)+", reg_names[REGNO (XEXP (addr, 0))]);
      break;

    case PLUS:
      reg1 = 0;	reg2 = 0;
      ireg = 0;	breg = 0;
      offset = 0;
      if (CONSTANT_ADDRESS_P (XEXP (addr, 0))
	  || GET_CODE (XEXP (addr, 0)) == MEM)
	{
	  offset = XEXP (addr, 0);
	  addr = XEXP (addr, 1);
	}
      else if (CONSTANT_ADDRESS_P (XEXP (addr, 1))
	       || GET_CODE (XEXP (addr, 1)) == MEM)
	{
	  offset = XEXP (addr, 1);
	  addr = XEXP (addr, 0);
	}
      if (GET_CODE (addr) != PLUS)
	;
      else if (GET_CODE (XEXP (addr, 0)) == MULT)
	{
	  reg1 = XEXP (addr, 0);
	  addr = XEXP (addr, 1);
	}
      else if (GET_CODE (XEXP (addr, 1)) == MULT)
	{
	  reg1 = XEXP (addr, 1);
	  addr = XEXP (addr, 0);
	}
      else if (GET_CODE (XEXP (addr, 0)) == REG)
	{
	  reg1 = XEXP (addr, 0);
	  addr = XEXP (addr, 1);
	}
      else if (GET_CODE (XEXP (addr, 1)) == REG)
	{
	  reg1 = XEXP (addr, 1);
	  addr = XEXP (addr, 0);
	}
      if (GET_CODE (addr) == REG || GET_CODE (addr) == MULT)
	{
	  if (reg1 == 0)
	    reg1 = addr;
	  else
	    reg2 = addr;
	  addr = 0;
	}
      if (offset != 0)
	{
	  if (addr != 0) abort ();
	  addr = offset;
	}
      if (reg1 != 0 && GET_CODE (reg1) == MULT)
	{
	  breg = reg2;
	  ireg = reg1;
	}
      else if (reg2 != 0 && GET_CODE (reg2) == MULT)
	{
	  breg = reg1;
	  ireg = reg2;
	}
      else if (reg2 != 0 || GET_CODE (addr) == MEM)
	{
	  breg = reg2;
	  ireg = reg1;
	}
      else
	{
	  breg = reg1;
	  ireg = reg2;
	}
      if (addr != 0)
	output_address (addr);
      if (breg != 0)
	{
	  if (GET_CODE (breg) != REG)
	    abort ();
	  fprintf (file, "(%s)", reg_names[REGNO (breg)]);
	}
      if (ireg != 0)
	{
	  if (GET_CODE (ireg) == MULT)
	    ireg = XEXP (ireg, 0);
	  if (GET_CODE (ireg) != REG)
	    abort ();
	  abort();
	  fprintf (file, "[%s]", reg_names[REGNO (ireg)]);
	}
      break;

    default:
      output_addr_const_pdp11 (file, addr);
    }
}

/* Target hook to assemble integer objects.  We need to use the
   pdp-specific version of output_addr_const.  */

static bool
pdp11_assemble_integer (x, size, aligned_p)
     rtx x;
     unsigned int size;
     int aligned_p;
{
  if (aligned_p)
    switch (size)
      {
      case 1:
	fprintf (asm_out_file, "\t.byte\t");
	output_addr_const_pdp11 (asm_out_file, x);
	fprintf (asm_out_file, " /* char */\n");
	return true;

      case 2:
	fprintf (asm_out_file, TARGET_UNIX_ASM ? "\t" : "\t.word\t");
	output_addr_const_pdp11 (asm_out_file, x);
	fprintf (asm_out_file, " /* short */\n");
	return true;
      }
  return default_assemble_integer (x, size, aligned_p);
}


/* register move costs, indexed by regs */

static const int move_costs[N_REG_CLASSES][N_REG_CLASSES] = 
{
             /* NO  MUL  GEN  LFPU  NLFPU FPU ALL */

/* NO */     {  0,   0,   0,    0,    0,    0,   0},
/* MUL */    {  0,   2,   2,   10,   22,   22,  22},
/* GEN */    {  0,   2,   2,   10,   22,   22,  22},
/* LFPU */   {  0,  10,  10,    2,    2,    2,  10},
/* NLFPU */  {  0,  22,  22,    2,    2,    2,  22},
/* FPU */    {  0,  22,  22,    2,    2,    2,  22},
/* ALL */    {  0,  22,  22,   10,   22,   22,  22}
}  ;


/* -- note that some moves are tremendously expensive, 
   because they require lots of tricks! do we have to 
   charge the costs incurred by secondary reload class 
   -- as we do here with 22 -- or not ? */

int 
register_move_cost(c1, c2)
  enum reg_class c1, c2;
{
    return move_costs[(int)c1][(int)c2];
}

const char *
output_jump(pos, neg, length)
  const char *pos, *neg;
  int length;
{
    static int x = 0;
    
    static char buf[1000];

#if 0
/* currently we don't need this, because the tstdf and cmpdf 
   copy the condition code immediately, and other float operations are not 
   yet recognized as changing the FCC - if so, then the length-cost of all
   jump insns increases by one, because we have to potentially copy the 
   FCC! */
    if (cc_status.flags & CC_IN_FPU)
	output_asm_insn("cfcc", NULL);
#endif
	
    switch (length)
    {
      case 1:
	
	strcpy(buf, pos);
	strcat(buf, " %l0");
	
	return buf;
	
      case 3:
	
	sprintf(buf, "%s JMP_%d\n\tjmp %%l0\nJMP_%d:", neg, x, x);
	
	x++;
	
	return buf;
	
      default:
	
	abort();
    }
    
}

void
notice_update_cc_on_set(exp, insn)
  rtx exp;
  rtx insn ATTRIBUTE_UNUSED;
{
    if (GET_CODE (SET_DEST (exp)) == CC0)
    { 
	cc_status.flags = 0;					
	cc_status.value1 = SET_DEST (exp);			
	cc_status.value2 = SET_SRC (exp);			

/*
	if (GET_MODE(SET_SRC(exp)) == DFmode)
	    cc_status.flags |= CC_IN_FPU;
*/	
    }							
    else if ((GET_CODE (SET_DEST (exp)) == REG		
	      || GET_CODE (SET_DEST (exp)) == MEM)		
	     && GET_CODE (SET_SRC (exp)) != PC		
	     && (GET_MODE (SET_DEST(exp)) == HImode		
		 || GET_MODE (SET_DEST(exp)) == QImode)	
		&& (GET_CODE (SET_SRC(exp)) == PLUS		
		    || GET_CODE (SET_SRC(exp)) == MINUS	
		    || GET_CODE (SET_SRC(exp)) == AND