loop.c

早期freebsd实现

		  start_sequence ();
		  emit_move_insn (m->set_dest, m->set_src);
		  temp = get_insns ();
		  end_sequence ();

		  add_label_notes (m->set_src, temp);

		  i1 = emit_insns_before (temp, loop_start);
		  if (! find_reg_note (i1, REG_EQUAL, NULL_RTX))
		    REG_NOTES (i1)
		      = gen_rtx (EXPR_LIST,
				 m->is_equiv ? REG_EQUIV : REG_EQUAL,
				 m->set_src, REG_NOTES (i1));

		  if (loop_dump_stream)
		    fprintf (loop_dump_stream, " moved to %d", INSN_UID (i1));

		  /* The more regs we move, the less we like moving them.  */
		  threshold -= 3;
		}
	      else
		{
		  for (count = m->consec; count >= 0; count--)
		    {
		      rtx i1, temp;

		      /* If first insn of libcall sequence, skip to end. */
		      /* Do this at start of loop, since p is guaranteed to 
			 be an insn here.  */
		      if (GET_CODE (p) != NOTE
			  && (temp = find_reg_note (p, REG_LIBCALL, NULL_RTX)))
			p = XEXP (temp, 0);

		      /* If last insn of libcall sequence, move all
			 insns except the last before the loop.  The last
			 insn is handled in the normal manner.  */
		      if (GET_CODE (p) != NOTE
			  && (temp = find_reg_note (p, REG_RETVAL, NULL_RTX)))
			{
			  rtx fn_address = 0;
			  rtx fn_reg = 0;
			  rtx fn_address_insn = 0;

			  first = 0;
			  for (temp = XEXP (temp, 0); temp != p;
			       temp = NEXT_INSN (temp))
			    {
			      rtx body;
			      rtx n;
			      rtx next;

			      if (GET_CODE (temp) == NOTE)
				continue;

			      body = PATTERN (temp);

			      /* Find the next insn after TEMP,
				 not counting USE or NOTE insns.  */
			      for (next = NEXT_INSN (temp); next != p;
				   next = NEXT_INSN (next))
				if (! (GET_CODE (next) == INSN
				       && GET_CODE (PATTERN (next)) == USE)
				    && GET_CODE (next) != NOTE)
				  break;
			      
			      /* If that is the call, this may be the insn
				 that loads the function address.

				 Extract the function address from the insn
				 that loads it into a register.
				 If this insn was cse'd, we get incorrect code.

				 So emit a new move insn that copies the
				 function address into the register that the
				 call insn will use.  flow.c will delete any
				 redundant stores that we have created.  */
			      if (GET_CODE (next) == CALL_INSN
				  && GET_CODE (body) == SET
				  && GET_CODE (SET_DEST (body)) == REG
				  && (n = find_reg_note (temp, REG_EQUAL,
							 NULL_RTX)))
				{
				  fn_reg = SET_SRC (body);
				  if (GET_CODE (fn_reg) != REG)
				    fn_reg = SET_DEST (body);
				  fn_address = XEXP (n, 0);
				  fn_address_insn = temp;
				}
			      /* We have the call insn.
				 If it uses the register we suspect it might,
				 load it with the correct address directly.  */
			      if (GET_CODE (temp) == CALL_INSN
				  && fn_address != 0
				  && reg_referenced_p (fn_reg, body))
				emit_insn_after (gen_move_insn (fn_reg,
								fn_address),
						 fn_address_insn);

			      if (GET_CODE (temp) == CALL_INSN)
				i1 = emit_call_insn_before (body, loop_start);
			      else
				i1 = emit_insn_before (body, loop_start);
			      if (first == 0)
				first = i1;
			      if (temp == fn_address_insn)
				fn_address_insn = i1;
			      REG_NOTES (i1) = REG_NOTES (temp);
			      delete_insn (temp);
			    }
			}
		      if (m->savemode != VOIDmode)
			{
			  /* P sets REG to zero; but we should clear only
			     the bits that are not covered by the mode
			     m->savemode.  */
			  rtx reg = m->set_dest;
			  rtx sequence;
			  rtx tem;
		      
			  start_sequence ();
			  tem = expand_binop
			    (GET_MODE (reg), and_optab, reg,
			     GEN_INT ((((HOST_WIDE_INT) 1
					<< GET_MODE_BITSIZE (m->savemode)))
				      - 1),
			     reg, 1, OPTAB_LIB_WIDEN);
			  if (tem == 0)
			    abort ();
			  if (tem != reg)
			    emit_move_insn (reg, tem);
			  sequence = gen_sequence ();
			  end_sequence ();
			  i1 = emit_insn_before (sequence, loop_start);
			}
		      else if (GET_CODE (p) == CALL_INSN)
			i1 = emit_call_insn_before (PATTERN (p), loop_start);
		      else
			i1 = emit_insn_before (PATTERN (p), loop_start);

		      REG_NOTES (i1) = REG_NOTES (p);

		      if (new_start == 0)
			new_start = i1;

		      if (loop_dump_stream)
			fprintf (loop_dump_stream, " moved to %d",
				 INSN_UID (i1));

#if 0
		      /* This isn't needed because REG_NOTES is copied
			 below and is wrong since P might be a PARALLEL.  */
		      if (REG_NOTES (i1) == 0
			  && ! m->partial /* But not if it's a zero-extend clr. */
			  && ! m->global /* and not if used outside the loop
					    (since it might get set outside).  */
			  && CONSTANT_P (SET_SRC (PATTERN (p))))
			REG_NOTES (i1)
			  = gen_rtx (EXPR_LIST, REG_EQUAL,
				     SET_SRC (PATTERN (p)), REG_NOTES (i1));
#endif

		      /* If library call, now fix the REG_NOTES that contain
			 insn pointers, namely REG_LIBCALL on FIRST
			 and REG_RETVAL on I1.  */
		      if (temp = find_reg_note (i1, REG_RETVAL, NULL_RTX))
			{
			  XEXP (temp, 0) = first;
			  temp = find_reg_note (first, REG_LIBCALL, NULL_RTX);
			  XEXP (temp, 0) = i1;
			}

		      delete_insn (p);
		      do p = NEXT_INSN (p);
		      while (p && GET_CODE (p) == NOTE);
		    }

		  /* The more regs we move, the less we like moving them.  */
		  threshold -= 3;
		}

	      /* Any other movable that loads the same register
		 MUST be moved.  */
	      already_moved[regno] = 1;

	      /* This reg has been moved out of one loop.  */
	      moved_once[regno] = 1;

	      /* The reg set here is now invariant.  */
	      if (! m->partial)
		n_times_set[regno] = 0;

	      m->done = 1;

	      /* Change the length-of-life info for the register
		 to say it lives at least the full length of this loop.
		 This will help guide optimizations in outer loops.  */

	      if (uid_luid[regno_first_uid[regno]] > INSN_LUID (loop_start))
		/* This is the old insn before all the moved insns.
		   We can't use the moved insn because it is out of range
		   in uid_luid.  Only the old insns have luids.  */
		regno_first_uid[regno] = INSN_UID (loop_start);
	      if (uid_luid[regno_last_uid[regno]] < INSN_LUID (end))
		regno_last_uid[regno] = INSN_UID (end);

	      /* Combine with this moved insn any other matching movables.  */

	      if (! m->partial)
		for (m1 = movables; m1; m1 = m1->next)
		  if (m1->match == m)
		    {
		      rtx temp;

		      /* Schedule the reg loaded by M1
			 for replacement so that shares the reg of M.
			 If the modes differ (only possible in restricted
			 circumstances, make a SUBREG.  */
		      if (GET_MODE (m->set_dest) == GET_MODE (m1->set_dest))
			reg_map[m1->regno] = m->set_dest;
		      else
			reg_map[m1->regno]
			  = gen_lowpart_common (GET_MODE (m1->set_dest),
						m->set_dest);
		    
		      /* Get rid of the matching insn
			 and prevent further processing of it.  */
		      m1->done = 1;

		      /* if library call, delete all insn except last, which
			 is deleted below */
		      if (temp = find_reg_note (m1->insn, REG_RETVAL,
						NULL_RTX))
			{
			  for (temp = XEXP (temp, 0); temp != m1->insn;
			       temp = NEXT_INSN (temp))
			    delete_insn (temp);
			}
		      delete_insn (m1->insn);

		      /* Any other movable that loads the same register
			 MUST be moved.  */
		      already_moved[m1->regno] = 1;

		      /* The reg merged here is now invariant,
			 if the reg it matches is invariant.  */
		      if (! m->partial)
			n_times_set[m1->regno] = 0;
		    }
	    }
	  else if (loop_dump_stream)
	    fprintf (loop_dump_stream, "not desirable");
	}
      else if (loop_dump_stream && !m->match)
	fprintf (loop_dump_stream, "not safe");

      if (loop_dump_stream)
	fprintf (loop_dump_stream, "\n");
    }

  if (new_start == 0)
    new_start = loop_start;

  /* Go through all the instructions in the loop, making
     all the register substitutions scheduled in REG_MAP.  */
  for (p = new_start; p != end; p = NEXT_INSN (p))
    if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
	|| GET_CODE (p) == CALL_INSN)
      {
	replace_regs (PATTERN (p), reg_map, nregs, 0);
	replace_regs (REG_NOTES (p), reg_map, nregs, 0);
      }
}

#if 0
/* Scan X and replace the address of any MEM in it with ADDR.
   REG is the address that MEM should have before the replacement.  */

static void
replace_call_address (x, reg, addr)
     rtx x, reg, addr;
{
  register enum rtx_code code;
  register int i;
  register char *fmt;

  if (x == 0)
    return;
  code = GET_CODE (x);
  switch (code)
    {
    case PC:
    case CC0:
    case CONST_INT:
    case CONST_DOUBLE:
    case CONST:
    case SYMBOL_REF:
    case LABEL_REF:
    case REG:
      return;

    case SET:
      /* Short cut for very common case.  */
      replace_call_address (XEXP (x, 1), reg, addr);
      return;

    case CALL:
      /* Short cut for very common case.  */
      replace_call_address (XEXP (x, 0), reg, addr);
      return;

    case MEM:
      /* If this MEM uses a reg other than the one we expected,
	 something is wrong.  */
      if (XEXP (x, 0) != reg)
	abort ();
      XEXP (x, 0) = addr;
      return;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	replace_call_address (XEXP (x, i), reg, addr);
      if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = 0; j < XVECLEN (x, i); j++)
	    replace_call_address (XVECEXP (x, i, j), reg, addr);
	}
    }
}
#endif

/* Return the number of memory refs to addresses that vary
   in the rtx X.  */

static int
count_nonfixed_reads (x)
     rtx x;
{
  register enum rtx_code code;
  register int i;
  register char *fmt;
  int value;

  if (x == 0)
    return 0;

  code = GET_CODE (x);
  switch (code)
    {
    case PC:
    case CC0:
    case CONST_INT:
    case CONST_DOUBLE:
    case CONST:
    case SYMBOL_REF:
    case LABEL_REF:
    case REG:
      return 0;

    case MEM:
      return ((invariant_p (XEXP (x, 0)) != 1)
	      + count_nonfixed_reads (XEXP (x, 0)));
    }

  value = 0;
  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	value += count_nonfixed_reads (XEXP (x, i));
      if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = 0; j < XVECLEN (x, i); j++)
	    value += count_nonfixed_reads (XVECEXP (x, i, j));
	}
    }
  return value;
}


#if 0
/* P is an instruction that sets a register to the result of a ZERO_EXTEND.
   Replace it with an instruction to load just the low bytes
   if the machine supports such an instruction,
   and insert above LOOP_START an instruction to clear the register.  */

static void
constant_high_bytes (p, loop_start)
     rtx p, loop_start;
{
  register rtx new;
  register int insn_code_number;

  /* Try to change (SET (REG ...) (ZERO_EXTEND (..:B ...)))
     to (SET (STRICT_LOW_PART (SUBREG:B (REG...))) ...).  */

  new = gen_rtx (SET, VOIDmode,
		 gen_rtx (STRICT_LOW_PART, VOIDmode,
			  gen_rtx (SUBREG, GET_MODE (XEXP (SET_SRC (PATTERN (p)), 0)),
				   SET_DEST (PATTERN (p)),
				   0)),
		 XEXP (SET_SRC (PATTERN (p)), 0));
  insn_code_number = recog (new, p);

  if (insn_code_number)
    {
      register int i;

      /* Clear destination register before the loop.  */
      emit_insn_before (gen_rtx (SET, VOIDmode,
				 SET_DEST (PATTERN (p)),
				 const0_rtx),
			loop_star