thumb.c

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  if (len >= 8)
    {
      emit_insn (gen_movmem8b (out, in));
      len -= 8;
    }
  if (len >= 4)
    {
      rtx reg = gen_reg_rtx (SImode);
      emit_insn (gen_movsi (reg, gen_rtx (MEM, SImode, in)));
      emit_insn (gen_movsi (gen_rtx (MEM, SImode, out), reg));
      len -= 4;
      offset += 4;
    }
  if (len >= 2)
    {
      rtx reg = gen_reg_rtx (HImode);
      emit_insn (gen_movhi (reg, gen_rtx (MEM, HImode, 
					  plus_constant (in, offset))));
      emit_insn (gen_movhi (gen_rtx (MEM, HImode, plus_constant (out, offset)),
			    reg));
      len -= 2;
      offset += 2;
    }
  if (len)
    {
      rtx reg = gen_reg_rtx (QImode);
      emit_insn (gen_movqi (reg, gen_rtx (MEM, QImode,
					  plus_constant (in, offset))));
      emit_insn (gen_movqi (gen_rtx (MEM, QImode, plus_constant (out, offset)),
			    reg));
    }
}


/* Routines for reloading */

void
thumb_reload_out_si (operands)
     rtx operands;
{
  abort ();
}

/* Return non-zero if FUNC must be entered in ARM mode.  */
int
is_called_in_ARM_mode (func)
     tree func;
{
  if (TREE_CODE (func) != FUNCTION_DECL)
    abort ();

  /* Ignore the problem about functions whoes address is taken.  */
  if (TARGET_CALLEE_INTERWORKING && TREE_PUBLIC (func))
    return TRUE;

  return FALSE;
}


/* Routines for emitting code */

void
final_prescan_insn(insn)
     rtx insn;
{
  extern int *insn_addresses;

  if (flag_print_asm_name)
    fprintf (asm_out_file, "%s 0x%04x\n", ASM_COMMENT_START,
	     insn_addresses[INSN_UID (insn)]);
}


static void thumb_pushpop ( FILE *, int, int ); /* Forward declaration.  */

#ifdef __GNUC__
inline
#endif
static int
number_of_first_bit_set (mask)
     int mask;
{
  int bit;

  for (bit = 0;
       (mask & (1 << bit)) == 0;
       ++ bit)
    continue;

  return bit;
}

#define ARG_1_REGISTER   0
#define ARG_2_REGISTER   1
#define ARG_3_REGISTER   2
#define ARG_4_REGISTER   3
#define WORK_REGISTER    7
#define FRAME_POINTER	11
#define IP_REGISTER	12
#define STACK_POINTER	STACK_POINTER_REGNUM
#define LINK_REGISTER	14
#define PROGRAM_COUNTER 15

/* Generate code to return from a thumb function.  If
   'reg_containing_return_addr' is -1, then the return address is
   actually on the stack, at the stack pointer.  */
static void
thumb_exit (f, reg_containing_return_addr)
     FILE * f;
     int    reg_containing_return_addr;
{
  int regs_available_for_popping;
  int regs_to_pop;
  int pops_needed;
  int reg;
  int available;
  int required;
  int mode;
  int size;
  int restore_a4 = FALSE;

  /* Compute the registers we need to pop.  */
  regs_to_pop = 0;
  pops_needed = 0;
  
  if (reg_containing_return_addr == -1)
    {
      regs_to_pop |= 1 << LINK_REGISTER;
      ++ pops_needed;
    }

  if (TARGET_BACKTRACE)
    {
      /* Restore frame pointer and stack pointer.  */
      regs_to_pop |= (1 << FRAME_POINTER) | (1 << STACK_POINTER);
      pops_needed += 2;
    }

  /* If there is nothing to pop then just emit the BX instruction and return.*/
  if (pops_needed == 0)
    {
      asm_fprintf (f, "\tbx\t%s\n", reg_names [reg_containing_return_addr]);

      return;
    }

  /* Otherwise if we are not supporting interworking and we have not created
     a backtrace structure and the function was not entered in ARM mode then
     just pop the return address straight into the PC. */
  else if (   ! TARGET_THUMB_INTERWORK
	   && ! TARGET_BACKTRACE
	   && ! is_called_in_ARM_mode (current_function_decl))
    {
      asm_fprintf (f, "\tpop\t{pc}\n" );

      return;
    }

  /* Find out how many of the (return) argument registers we can corrupt. */
  regs_available_for_popping = 0;
  
#ifdef RTX_CODE
  /* If we can deduce the registers used from the function's return value.
     This is more reliable that examining regs_ever_live[] because that
     will be set if the register is ever used in the function, not just if
     the register is used to hold a return value.  */

  if (current_function_return_rtx != 0)
      mode = GET_MODE (current_function_return_rtx);
  else
#endif
      mode = DECL_MODE (DECL_RESULT (current_function_decl));

  size = GET_MODE_SIZE (mode);

  if (size == 0)
    {
      /* In a void function we can use any argument register.
	 In a function that returns a structure on the stack
	 we can use the second and third argument registers.  */
      if (mode == VOIDmode)
	regs_available_for_popping =
	    (1 << ARG_1_REGISTER)
	  | (1 << ARG_2_REGISTER)
	  | (1 << ARG_3_REGISTER);
      else
	regs_available_for_popping =
	    (1 << ARG_2_REGISTER)
	  | (1 << ARG_3_REGISTER);
    }
  else if (size <= 4) regs_available_for_popping =
			  (1 << ARG_2_REGISTER)
			| (1 << ARG_3_REGISTER);
  else if (size <= 8) regs_available_for_popping =
			(1 << ARG_3_REGISTER);
  
  /* Match registers to be popped with registers into which we pop them.  */
  for (available = regs_available_for_popping,
       required  = regs_to_pop;
       required != 0 && available != 0;
       available &= ~(available & - available),
       required  &= ~(required  & - required))
    -- pops_needed;

  /* If we have any popping registers left over, remove them.  */
  if (available > 0)
    regs_available_for_popping &= ~ available;
  
  /* Otherwise if we need another popping register we can use
     the fourth argument register.  */
  else if (pops_needed)
    {
      /* If we have not found any free argument registers and
	 reg a4 contains the return address, we must move it.  */
      if (regs_available_for_popping == 0
	  && reg_containing_return_addr == ARG_4_REGISTER)
	{
	  asm_fprintf (f, "\tmov\t%s, %s\n",
		       reg_names [LINK_REGISTER], reg_names [ARG_4_REGISTER]);
	  reg_containing_return_addr = LINK_REGISTER;
	}
      else if (size > 12)
	{
	  /* Register a4 is being used to hold part of the return value,
	     but we have dire need of a free, low register.  */
	  restore_a4 = TRUE;
	  
	  asm_fprintf (f, "\tmov\t%s, %s\n",
		       reg_names [IP_REGISTER], reg_names [ARG_4_REGISTER]);
	}
      
      if (reg_containing_return_addr != ARG_4_REGISTER)
	{
	  /* The fourth argument register is available.  */
	  regs_available_for_popping |= 1 << ARG_4_REGISTER;
	  
	  -- pops_needed;
	}
    }

  /* Pop as many registers as we can.  */
  thumb_pushpop (f, regs_available_for_popping, FALSE);

  /* Process the registers we popped.  */
  if (reg_containing_return_addr == -1)
    {
      /* The return address was popped into the lowest numbered register.  */
      regs_to_pop &= ~ (1 << LINK_REGISTER);
      
      reg_containing_return_addr =
	number_of_first_bit_set (regs_available_for_popping);

      /* Remove this register for the mask of available registers, so that
         the return address will not be corrupted by futher pops.  */
      regs_available_for_popping &= ~ (1 << reg_containing_return_addr);
    }

  /* If we popped other registers then handle them here.  */
  if (regs_available_for_popping)
    {
      int frame_pointer;
      
      /* Work out which register currently contains the frame pointer.  */
      frame_pointer = number_of_first_bit_set (regs_available_for_popping);

      /* Move it into the correct place.  */
      asm_fprintf (f, "\tmov\tfp, %s\n", reg_names [frame_pointer]);

      /* (Temporarily) remove it from the mask of popped registers.  */
      regs_available_for_popping &= ~ (1 << frame_pointer);
      regs_to_pop &= ~ (1 << FRAME_POINTER);
      
      if (regs_available_for_popping)
	{
	  int stack_pointer;
	  
	  /* We popped the stack pointer as well, find the register that
	     contains it.*/
	  stack_pointer = number_of_first_bit_set (regs_available_for_popping);

	  /* Move it into the stack register.  */
	  asm_fprintf (f, "\tmov\tsp, %s\n", reg_names [stack_pointer]);
	  
	  /* At this point we have popped all necessary registers, so
	     do not worry about restoring regs_available_for_popping
	     to its correct value:

	     assert (pops_needed == 0)
	     assert (regs_available_for_popping == (1 << frame_pointer))
	     assert (regs_to_pop == (1 << STACK_POINTER))  */
	}
      else
	{
	  /* Since we have just move the popped value into the frame
	     pointer, the popping register is available for reuse, and
	     we know that we still have the stack pointer left to pop.  */
	  regs_available_for_popping |= (1 << frame_pointer);
	}
    }
  
  /* If we still have registers left on the stack, but we no longer have
     any registers into which we can pop them, then we must move the return
     address into the link register and make available the register that
     contained it.  */
  if (regs_available_for_popping == 0 && pops_needed > 0)
    {
      regs_available_for_popping |= 1 << reg_containing_return_addr;
      
      asm_fprintf (f, "\tmov\t%s, %s\n",
		   reg_names [LINK_REGISTER],
		   reg_names [reg_containing_return_addr]);
      
      reg_containing_return_addr = LINK_REGISTER;
    }

  /* If we have registers left on the stack then pop some more.
     We know that at most we will want to pop FP and SP.  */
  if (pops_needed > 0)
    {
      int  popped_into;
      int  move_to;
      
      thumb_pushpop (f, regs_available_for_popping, FALSE);

      /* We have popped either FP or SP.
	 Move whichever one it is into the correct register.  */
      popped_into = number_of_first_bit_set (regs_available_for_popping);
      move_to     = number_of_first_bit_set (regs_to_pop);

      asm_fprintf (f, "\tmov\t%s, %s\n",
		   reg_names [move_to], reg_names [popped_into]);

      regs_to_pop &= ~ (1 << move_to);

      -- pops_needed;
    }
  
  /* If we still have not popped everything then we must have only
     had one register available to us and we are now popping the SP.  */
  if (pops_needed > 0)
    {
      int  popped_into;
      
      thumb_pushpop (f, regs_available_for_popping, FALSE);

      popped_into = number_of_first_bit_set (regs_available_for_popping);

      asm_fprintf (f, "\tmov\tsp, %s\n", reg_names [popped_into]);

      /*
	assert (regs_to_pop == (1 << STACK_POINTER))
	assert (pops_needed == 1)
      */
    }

  /* If necessary restore the a4 register.  */
  if (restore_a4)
    {
      if (reg_containing_return_addr != LINK_REGISTER)
	{
	  asm_fprintf (f, "\tmov\t%s, %s\n",
		       reg_names [LINK_REGISTER], reg_names [ARG_4_REGISTER]);
	  reg_containing_return_addr = LINK_REGISTER;
	}
    
      asm_fprintf (f, "\tmov\t%s, %s\n",
		   reg_names [ARG_4_REGISTER], reg_names [IP_REGISTER]);
    }
  
  /* Return to caller.  */
  asm_fprintf (f, "\tbx\t%s\n", reg_names [reg_containing_return_addr]);
}

/* Emit code to push or pop registers to or from the stack.  */
static void
thumb_pushpop (f, mask, push)
     FILE * f;
     int mask;
     int push;
{
  int regno;
  int lo_mask = mask & 0xFF;

  if (lo_mask == 0 && ! push && (mask & (1 << 15)))
    {
      /* Special case.  Do not generate a POP PC statement here, do it in
	 thumb_exit() */
      
      thumb_exit (f, -1);
      return;
    }
      
  asm_fprintf (f, "\t%s\t{", push ? "push" : "pop");

  /* Look at the low registers first.  */
  
  for (regno = 0; regno < 8; regno ++, lo_mask >>= 1)
    {
      if (lo_mask & 1)
	{
	  asm_fprintf (f, reg_names[regno]);
	  
	  if ((lo_mask & ~1) != 0)
	    asm_fprintf (f, ", ");
	}
    }
  
  if (push && (mask & (1 << 14)))
    {
      /* Catch pushing the LR.  */

      if (mask & 0xFF)
	asm_fprintf (f, ", ");
      
      asm_fprintf (f, reg_names[14]);
    }
  else if (!push && (mask & (1 << 15)))
    {
      /* Catch popping the PC.  */
      
      if (TARGET_THUMB_INTERWORK || TARGET_BACKTRACE)
	{
	  /* The PC is never poped directly, instead
	     it is popped into r3 and then BX is used. */
	  
	  asm_fprintf (f, "}\n");

	  thumb_exit (f, -1);

	  return;
	}
      else
	{
	  if (mask & 0xFF)
	    asm_fprintf (f, ", ");
	  
	  asm_fprintf (f, reg_names[15]);
	}
    }
       
  asm_fprintf (f, "}\n");
}

/* Returns non-zero if the current function contains a far jump */

int
far_jump_used_p (void)
{
  rtx insn;
  
  for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
    {
      if (GET_CODE (insn) == JUMP_INSN
	  /* Ignore tablejump patterns.  */
	  && GET_CODE (PATTERN (insn)) != ADDR_VEC
	  && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC
	  && get_attr_far_jump (insn) == FAR_JUMP_YES)
	return 1;
    }

  return 0;
}

static int return_used_this_function = 0;

char *
output_return ()
{
  int regno;
  int live_regs_mask = 0;

  return_used_this_function = 1;

  for (regno = 0; regno < 8; regno++)
    if (regs_ever_live[regno] && ! call_used_regs[regno])
      live_regs_mask |= 1 << regno;

  if (live_regs_mask == 0)
    {
      if (leaf_function_p () && ! far_jump_used_p())
	{
	  thumb_exit (asm_out_file, 14);	      
	}
      else if (   TARGET_THUMB_INTERWORK
	       || TARGET_BACKTRACE
	       || is_called_in_ARM_mode (current_function_decl))
	{
	  thumb_exit (asm_out_file, -1);
	}
      else
	asm_fprintf (asm_out_file, "\tpop\t{pc}\n");
    }
  else
    {
      asm_fprintf (asm_out_file,  "\tpop\t{");
      
      for (regno = 0; live_regs_mask; regno ++, live_regs_mask >>= 1)
	if (live_regs_mask & 1)
	  {