arc.c

gcc-2.95.3 Linux下最常用的C编译器

arc_print_operand_address (file, addr)
     FILE *file;
     rtx addr;
{
  register rtx base, index = 0;
  int offset = 0;

  switch (GET_CODE (addr))
    {
    case REG :
      fputs (reg_names[REGNO (addr)], file);
      break;
    case SYMBOL_REF :
      if (/*???*/ 0 && SYMBOL_REF_FLAG (addr))
	{
	  fprintf (file, "%%st(");
	  output_addr_const (file, addr);
	  fprintf (file, ")");
	}
      else
	output_addr_const (file, addr);
      break;
    case PLUS :
      if (GET_CODE (XEXP (addr, 0)) == CONST_INT)
	offset = INTVAL (XEXP (addr, 0)), base = XEXP (addr, 1);
      else if (GET_CODE (XEXP (addr, 1)) == CONST_INT)
	offset = INTVAL (XEXP (addr, 1)), base = XEXP (addr, 0);
      else
	base = XEXP (addr, 0), index = XEXP (addr, 1);
      if (GET_CODE (base) != REG)
	abort ();
      fputs (reg_names[REGNO (base)], file);
      if (index == 0)
	{
	  if (offset != 0)
	    fprintf (file, ",%d", offset);
	}
      else if (GET_CODE (index) == REG)
	fprintf (file, ",%s", reg_names[REGNO (index)]);
      else if (GET_CODE (index) == SYMBOL_REF)
	fputc (',', file), output_addr_const (file, index);
      else
	abort ();
      break;
    case PRE_INC :
    case PRE_DEC :
      /* We shouldn't get here as we've lost the mode of the memory object
	 (which says how much to inc/dec by.  */
      abort ();
      break;
    default :
      output_addr_const (file, addr);
      break;
    }
}

/* Update compare/branch separation marker.  */

static void
record_cc_ref (insn)
     rtx insn;
{
  last_insn_set_cc_p = current_insn_set_cc_p;

  switch (get_attr_cond (insn))
    {
    case COND_SET :
    case COND_SET_ZN :
    case COND_SET_ZNC :
      if (get_attr_length (insn) == 1)
	current_insn_set_cc_p = 1;
      else
	current_insn_set_cc_p = 0;
      break;
    default :
      current_insn_set_cc_p = 0;
      break;
    }
}

/* Conditional execution support.

   This is based on the ARM port but for now is much simpler.

   A finite state machine takes care of noticing whether or not instructions
   can be conditionally executed, and thus decrease execution time and code
   size by deleting branch instructions.  The fsm is controlled by
   final_prescan_insn, and controls the actions of PRINT_OPERAND.  The patterns
   in the .md file for the branch insns also have a hand in this.  */

/* The state of the fsm controlling condition codes are:
   0: normal, do nothing special
   1: don't output this insn
   2: don't output this insn
   3: make insns conditional
   4: make insns conditional

   State transitions (state->state by whom, under what condition):
   0 -> 1 final_prescan_insn, if insn is conditional branch
   0 -> 2 final_prescan_insn, if the `target' is an unconditional branch
   1 -> 3 branch patterns, after having not output the conditional branch
   2 -> 4 branch patterns, after having not output the conditional branch
   3 -> 0 ASM_OUTPUT_INTERNAL_LABEL, if the `target' label is reached
          (the target label has CODE_LABEL_NUMBER equal to
	  arc_ccfsm_target_label).
   4 -> 0 final_prescan_insn, if `target' unconditional branch is reached

   If the jump clobbers the conditions then we use states 2 and 4.

   A similar thing can be done with conditional return insns.

   We also handle separating branches from sets of the condition code.
   This is done here because knowledge of the ccfsm state is required,
   we may not be outputting the branch.  */

void
arc_final_prescan_insn (insn, opvec, noperands)
     rtx insn;
     rtx *opvec;
     int noperands;
{
  /* BODY will hold the body of INSN.  */
  register rtx body = PATTERN (insn);

  /* This will be 1 if trying to repeat the trick (ie: do the `else' part of
     an if/then/else), and things need to be reversed.  */
  int reverse = 0;

  /* If we start with a return insn, we only succeed if we find another one. */
  int seeking_return = 0;
  
  /* START_INSN will hold the insn from where we start looking.  This is the
     first insn after the following code_label if REVERSE is true.  */
  rtx start_insn = insn;

  /* Update compare/branch separation marker.  */
  record_cc_ref (insn);

  /* Allow -mdebug-ccfsm to turn this off so we can see how well it does.
     We can't do this in macro FINAL_PRESCAN_INSN because its called from
     final_scan_insn which has `optimize' as a local.  */
  if (optimize < 2 || TARGET_NO_COND_EXEC)
    return;

  /* If in state 4, check if the target branch is reached, in order to
     change back to state 0.  */
  if (arc_ccfsm_state == 4)
    {
      if (insn == arc_ccfsm_target_insn)
	{
	  arc_ccfsm_target_insn = NULL;
	  arc_ccfsm_state = 0;
	}
      return;
    }

  /* If in state 3, it is possible to repeat the trick, if this insn is an
     unconditional branch to a label, and immediately following this branch
     is the previous target label which is only used once, and the label this
     branch jumps to is not too far off.  Or in other words "we've done the
     `then' part, see if we can do the `else' part."  */
  if (arc_ccfsm_state == 3)
    {
      if (simplejump_p (insn))
	{
	  start_insn = next_nonnote_insn (start_insn);
	  if (GET_CODE (start_insn) == BARRIER)
	    {
	      /* ??? Isn't this always a barrier?  */
	      start_insn = next_nonnote_insn (start_insn);
	    }
	  if (GET_CODE (start_insn) == CODE_LABEL
	      && CODE_LABEL_NUMBER (start_insn) == arc_ccfsm_target_label
	      && LABEL_NUSES (start_insn) == 1)
	    reverse = TRUE;
	  else
	    return;
	}
      else if (GET_CODE (body) == RETURN)
        {
	  start_insn = next_nonnote_insn (start_insn);
	  if (GET_CODE (start_insn) == BARRIER)
	    start_insn = next_nonnote_insn (start_insn);
	  if (GET_CODE (start_insn) == CODE_LABEL
	      && CODE_LABEL_NUMBER (start_insn) == arc_ccfsm_target_label
	      && LABEL_NUSES (start_insn) == 1)
	    {
	      reverse = TRUE;
	      seeking_return = 1;
	    }
	  else
	    return;
        }
      else
	return;
    }

  if (GET_CODE (insn) != JUMP_INSN)
    return;

  /* This jump might be paralleled with a clobber of the condition codes,
     the jump should always come first.  */
  if (GET_CODE (body) == PARALLEL && XVECLEN (body, 0) > 0)
    body = XVECEXP (body, 0, 0);

  if (reverse
      || (GET_CODE (body) == SET && GET_CODE (SET_DEST (body)) == PC
	  && GET_CODE (SET_SRC (body)) == IF_THEN_ELSE))
    {
      int insns_skipped = 0, fail = FALSE, succeed = FALSE;
      /* Flag which part of the IF_THEN_ELSE is the LABEL_REF.  */
      int then_not_else = TRUE;
      /* Nonzero if next insn must be the target label.  */
      int next_must_be_target_label_p;
      rtx this_insn = start_insn, label = 0;

      /* Register the insn jumped to.  */
      if (reverse)
        {
	  if (!seeking_return)
	    label = XEXP (SET_SRC (body), 0);
        }
      else if (GET_CODE (XEXP (SET_SRC (body), 1)) == LABEL_REF)
	label = XEXP (XEXP (SET_SRC (body), 1), 0);
      else if (GET_CODE (XEXP (SET_SRC (body), 2)) == LABEL_REF)
	{
	  label = XEXP (XEXP (SET_SRC (body), 2), 0);
	  then_not_else = FALSE;
	}
      else if (GET_CODE (XEXP (SET_SRC (body), 1)) == RETURN)
	seeking_return = 1;
      else if (GET_CODE (XEXP (SET_SRC (body), 2)) == RETURN)
        {
	  seeking_return = 1;
	  then_not_else = FALSE;
        }
      else
	abort ();

      /* See how many insns this branch skips, and what kind of insns.  If all
	 insns are okay, and the label or unconditional branch to the same
	 label is not too far away, succeed.  */
      for (insns_skipped = 0, next_must_be_target_label_p = FALSE;
	   !fail && !succeed && insns_skipped < MAX_INSNS_SKIPPED;
	   insns_skipped++)
	{
	  rtx scanbody;

	  this_insn = next_nonnote_insn (this_insn);
	  if (!this_insn)
	    break;

	  if (next_must_be_target_label_p)
	    {
	      if (GET_CODE (this_insn) == BARRIER)
		continue;
	      if (GET_CODE (this_insn) == CODE_LABEL
		  && this_insn == label)
		{
		  arc_ccfsm_state = 1;
		  succeed = TRUE;
		}
	      else
		fail = TRUE;
	      break;
	    }

	  scanbody = PATTERN (this_insn);

	  switch (GET_CODE (this_insn))
	    {
	    case CODE_LABEL:
	      /* Succeed if it is the target label, otherwise fail since
		 control falls in from somewhere else.  */
	      if (this_insn == label)
		{
		  arc_ccfsm_state = 1;
		  succeed = TRUE;
		}
	      else
		fail = TRUE;
	      break;

	    case BARRIER:
	      /* Succeed if the following insn is the target label.
		 Otherwise fail.  
		 If return insns are used then the last insn in a function 
		 will be a barrier. */
	      next_must_be_target_label_p = TRUE;
	      break;

	    case CALL_INSN:
	      /* Can handle a call insn if there are no insns after it.
		 IE: The next "insn" is the target label.  We don't have to
		 worry about delay slots as such insns are SEQUENCE's inside
		 INSN's.  ??? It is possible to handle such insns though.  */
	      if (get_attr_cond (this_insn) == COND_CANUSE)
		next_must_be_target_label_p = TRUE;
	      else
		fail = TRUE;
	      break;

	    case JUMP_INSN:
      	      /* If this is an unconditional branch to the same label, succeed.
		 If it is to another label, do nothing.  If it is conditional,
		 fail.  */
	      /* ??? Probably, the test for the SET and the PC are unnecessary. */

	      if (GET_CODE (scanbody) == SET
		  && GET_CODE (SET_DEST (scanbody)) == PC)
		{
		  if (GET_CODE (SET_SRC (scanbody)) == LABEL_REF
		      && XEXP (SET_SRC (scanbody), 0) == label && !reverse)
		    {
		      arc_ccfsm_state = 2;
		      succeed = TRUE;
		    }
		  else if (GET_CODE (SET_SRC (scanbody)) == IF_THEN_ELSE)
		    fail = TRUE;
		}
	      else if (GET_CODE (scanbody) == RETURN
		       && seeking_return)
	        {
		  arc_ccfsm_state = 2;
		  succeed = TRUE;
	        }
	      else if (GET_CODE (scanbody) == PARALLEL)
	        {
		  if (get_attr_cond (this_insn) != COND_CANUSE)
		    fail = TRUE;
		}
	      break;

	    case INSN:
	      /* We can only do this with insns that can use the condition
		 codes (and don't set them).  */
	      if (GET_CODE (scanbody) == SET
		  || GET_CODE (scanbody) == PARALLEL)
		{
		  if (get_attr_cond (this_insn) != COND_CANUSE)
		    fail = TRUE;
		}
	      /* We can't handle other insns like sequences.  */
	      else
		fail = TRUE;
	      break;

	    default:
	      break;
	    }
	}

      if (succeed)
	{
	  if ((!seeking_return) && (arc_ccfsm_state == 1 || reverse))
	    arc_ccfsm_target_label = CODE_LABEL_NUMBER (label);
	  else if (seeking_return || arc_ccfsm_state == 2)
	    {
	      while (this_insn && GET_CODE (PATTERN (this_insn)) == USE)
	        {
		  this_insn = next_nonnote_insn (this_insn);
		  if (this_insn && (GET_CODE (this_insn) == BARRIER
				    || GET_CODE (this_insn) == CODE_LABEL))
		    abort ();
	        }
	      if (!this_insn)
	        {
		  /* Oh dear! we ran off the end, give up.  */
		  insn_extract (insn);
		  arc_ccfsm_state = 0;
		  arc_ccfsm_target_insn = NULL;
		  return;
	        }
	      arc_ccfsm_target_insn = this_insn;
	    }
	  else
	    abort ();

	  /* If REVERSE is true, ARM_CURRENT_CC needs to be inverted from
	     what it was.  */
	  if (!reverse)
	    arc_ccfsm_current_cc = get_arc_condition_code (XEXP (SET_SRC (body),
								 0));

	  if (reverse || then_not_else)
	    arc_ccfsm_current_cc = ARC_INVERSE_CONDITION_CODE (arc_ccfsm_current_cc);
	}

      /* Restore recog_operand.  Getting the attributes of other insns can
	 destroy this array, but final.c assumes that it remains intact
	 across this call; since the insn has been recognized already we
	 call insn_extract direct. */
      insn_extract (insn);
    }
}

/* Record that we are currently outputting label NUM with prefix PREFIX.
   It it's the label we're looking for, reset the ccfsm machinery.

   Called from ASM_OUTPUT_INTERNAL_LABEL.  */

void
arc_ccfsm_at_label (prefix, num)
     char *prefix;
     int num;
{
  if (arc_ccfsm_state == 3 && arc_ccfsm_target_label == num
      && !strcmp (prefix, "L"))
    {
      arc_ccfsm_state = 0;
      arc_ccfsm_target_insn = NULL_RTX;
    }
}

/* See if the current insn, which is a conditional branch, is to be
   deleted.  */

int
arc_ccfsm_branch_deleted_p ()
{
  if (arc_ccfsm_state == 1 || arc_ccfsm_state == 2)
    return 1;
  return 0;
}

/* Record a branch isn't output because subsequent insns can be
   conditionalized.  */

void
arc_ccfsm_record_branch_deleted ()
{
  /* Indicate we're conditionalizing insns now.  */
  arc_ccfsm_state += 2;

  /* If the next insn is a subroutine call, we still need a nop between the
     cc setter and user.  We need to undo the effect of calling record_cc_ref
     for the just deleted branch.  */
  current_insn_set_cc_p = last_insn_set_cc_p;
}