sched.c

gcc库的原代码,对编程有很大帮助.

static void
sched_analyze_1 (x, insn)
     rtx x;
     rtx insn;
{
  register int regno;
  register rtx dest = SET_DEST (x);

  if (dest == 0)
    return;

  while (GET_CODE (dest) == STRICT_LOW_PART || GET_CODE (dest) == SUBREG
	 || GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == SIGN_EXTRACT)
    {
      if (GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == SIGN_EXTRACT)
	{
	  /* The second and third arguments are values read by this insn.  */
	  sched_analyze_2 (XEXP (dest, 1), insn);
	  sched_analyze_2 (XEXP (dest, 2), insn);
	}
      dest = SUBREG_REG (dest);
    }

  if (GET_CODE (dest) == REG)
    {
      register int i;

      regno = REGNO (dest);

      /* A hard reg in a wide mode may really be multiple registers.
	 If so, mark all of them just like the first.  */
      if (regno < FIRST_PSEUDO_REGISTER)
	{
	  i = HARD_REGNO_NREGS (regno, GET_MODE (dest));
	  while (--i >= 0)
	    {
	      rtx u;

	      for (u = reg_last_uses[regno+i]; u; u = XEXP (u, 1))
		add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
	      reg_last_uses[regno + i] = 0;
	      if (reg_last_sets[regno + i])
		add_dependence (insn, reg_last_sets[regno + i],
				REG_DEP_OUTPUT);
	      reg_pending_sets[(regno + i) / REGSET_ELT_BITS]
		|= (REGSET_ELT_TYPE) 1 << ((regno + i) % REGSET_ELT_BITS);
	      if ((call_used_regs[i] || global_regs[i])
		  && last_function_call)
		/* Function calls clobber all call_used regs.  */
		add_dependence (insn, last_function_call, REG_DEP_ANTI);
	    }
	}
      else
	{
	  rtx u;

	  for (u = reg_last_uses[regno]; u; u = XEXP (u, 1))
	    add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
	  reg_last_uses[regno] = 0;
	  if (reg_last_sets[regno])
	    add_dependence (insn, reg_last_sets[regno], REG_DEP_OUTPUT);
	  reg_pending_sets[regno / REGSET_ELT_BITS]
	    |= (REGSET_ELT_TYPE) 1 << (regno % REGSET_ELT_BITS);

	  /* Pseudos that are REG_EQUIV to something may be replaced
	     by that during reloading.  We need only add dependencies for
	     the address in the REG_EQUIV note.  */
	  if (! reload_completed
	      && reg_known_equiv_p[regno]
	      && GET_CODE (reg_known_value[regno]) == MEM)
	    sched_analyze_2 (XEXP (reg_known_value[regno], 0), insn);

	  /* Don't let it cross a call after scheduling if it doesn't
	     already cross one.  */
	  if (reg_n_calls_crossed[regno] == 0 && last_function_call)
	    add_dependence (insn, last_function_call, REG_DEP_ANTI);
	}
    }
  else if (GET_CODE (dest) == MEM)
    {
      /* Writing memory.  */

      if (pending_lists_length > 32)
	{
	  /* Flush all pending reads and writes to prevent the pending lists
	     from getting any larger.  Insn scheduling runs too slowly when
	     these lists get long.  The number 32 was chosen because it
	     seems like a reasonable number.  When compiling GCC with itself,
	     this flush occurs 8 times for sparc, and 10 times for m88k using
	     the number 32.  */
	  flush_pending_lists (insn);
	}
      else
	{
	  rtx pending, pending_mem;

	  pending = pending_read_insns;
	  pending_mem = pending_read_mems;
	  while (pending)
	    {
	      /* If a dependency already exists, don't create a new one.  */
	      if (! find_insn_list (XEXP (pending, 0), LOG_LINKS (insn)))
		if (anti_dependence (XEXP (pending_mem, 0), dest))
		  add_dependence (insn, XEXP (pending, 0), REG_DEP_ANTI);

	      pending = XEXP (pending, 1);
	      pending_mem = XEXP (pending_mem, 1);
	    }

	  pending = pending_write_insns;
	  pending_mem = pending_write_mems;
	  while (pending)
	    {
	      /* If a dependency already exists, don't create a new one.  */
	      if (! find_insn_list (XEXP (pending, 0), LOG_LINKS (insn)))
		if (output_dependence (XEXP (pending_mem, 0), dest))
		  add_dependence (insn, XEXP (pending, 0), REG_DEP_OUTPUT);

	      pending = XEXP (pending, 1);
	      pending_mem = XEXP (pending_mem, 1);
	    }

	  if (last_pending_memory_flush)
	    add_dependence (insn, last_pending_memory_flush, REG_DEP_ANTI);

	  add_insn_mem_dependence (&pending_write_insns, &pending_write_mems,
				   insn, dest);
	}
      sched_analyze_2 (XEXP (dest, 0), insn);
    }

  /* Analyze reads.  */
  if (GET_CODE (x) == SET)
    sched_analyze_2 (SET_SRC (x), insn);
}

/* Analyze the uses of memory and registers in rtx X in INSN.  */

static void
sched_analyze_2 (x, insn)
     rtx x;
     rtx insn;
{
  register int i;
  register int j;
  register enum rtx_code code;
  register char *fmt;

  if (x == 0)
    return;

  code = GET_CODE (x);

  switch (code)
    {
    case CONST_INT:
    case CONST_DOUBLE:
    case SYMBOL_REF:
    case CONST:
    case LABEL_REF:
      /* Ignore constants.  Note that we must handle CONST_DOUBLE here
	 because it may have a cc0_rtx in its CONST_DOUBLE_CHAIN field, but
	 this does not mean that this insn is using cc0.  */
      return;

#ifdef HAVE_cc0
    case CC0:
      {
	rtx link, prev;

	/* There may be a note before this insn now, but all notes will
	   be removed before we actually try to schedule the insns, so
	   it won't cause a problem later.  We must avoid it here though.  */

	/* User of CC0 depends on immediately preceding insn.  */
	SCHED_GROUP_P (insn) = 1;

	/* Make a copy of all dependencies on the immediately previous insn,
	   and add to this insn.  This is so that all the dependencies will
	   apply to the group.  Remove an explicit dependence on this insn
	   as SCHED_GROUP_P now represents it.  */

	prev = PREV_INSN (insn);
	while (GET_CODE (prev) == NOTE)
	  prev = PREV_INSN (prev);

	if (find_insn_list (prev, LOG_LINKS (insn)))
	  remove_dependence (insn, prev);

	for (link = LOG_LINKS (prev); link; link = XEXP (link, 1))
	  add_dependence (insn, XEXP (link, 0), REG_NOTE_KIND (link));

	return;
      }
#endif

    case REG:
      {
	int regno = REGNO (x);
	if (regno < FIRST_PSEUDO_REGISTER)
	  {
	    int i;

	    i = HARD_REGNO_NREGS (regno, GET_MODE (x));
	    while (--i >= 0)
	      {
		reg_last_uses[regno + i]
		  = gen_rtx (INSN_LIST, VOIDmode,
			     insn, reg_last_uses[regno + i]);
		if (reg_last_sets[regno + i])
		  add_dependence (insn, reg_last_sets[regno + i], 0);
		if ((call_used_regs[regno + i] || global_regs[regno + i])
		    && last_function_call)
		  /* Function calls clobber all call_used regs.  */
		  add_dependence (insn, last_function_call, REG_DEP_ANTI);
	      }
	  }
	else
	  {
	    reg_last_uses[regno]
	      = gen_rtx (INSN_LIST, VOIDmode, insn, reg_last_uses[regno]);
	    if (reg_last_sets[regno])
	      add_dependence (insn, reg_last_sets[regno], 0);

	    /* Pseudos that are REG_EQUIV to something may be replaced
	       by that during reloading.  We need only add dependencies for
	       the address in the REG_EQUIV note.  */
	    if (! reload_completed
		&& reg_known_equiv_p[regno]
		&& GET_CODE (reg_known_value[regno]) == MEM)
	      sched_analyze_2 (XEXP (reg_known_value[regno], 0), insn);

	    /* If the register does not already cross any calls, then add this
	       insn to the sched_before_next_call list so that it will still
	       not cross calls after scheduling.  */
	    if (reg_n_calls_crossed[regno] == 0)
	      add_dependence (sched_before_next_call, insn, REG_DEP_ANTI);
	  }
	return;
      }

    case MEM:
      {
	/* Reading memory.  */

	rtx pending, pending_mem;

	pending = pending_read_insns;
	pending_mem = pending_read_mems;
	while (pending)
	  {
	    /* If a dependency already exists, don't create a new one.  */
	    if (! find_insn_list (XEXP (pending, 0), LOG_LINKS (insn)))
	      if (read_dependence (XEXP (pending_mem, 0), x))
		add_dependence (insn, XEXP (pending, 0), REG_DEP_ANTI);

	    pending = XEXP (pending, 1);
	    pending_mem = XEXP (pending_mem, 1);
	  }

	pending = pending_write_insns;
	pending_mem = pending_write_mems;
	while (pending)
	  {
	    /* If a dependency already exists, don't create a new one.  */
	    if (! find_insn_list (XEXP (pending, 0), LOG_LINKS (insn)))
	      if (true_dependence (XEXP (pending_mem, 0), x))
		add_dependence (insn, XEXP (pending, 0), 0);

	    pending = XEXP (pending, 1);
	    pending_mem = XEXP (pending_mem, 1);
	  }
	if (last_pending_memory_flush)
	  add_dependence (insn, last_pending_memory_flush, REG_DEP_ANTI);

	/* Always add these dependencies to pending_reads, since
	   this insn may be followed by a write.  */
	add_insn_mem_dependence (&pending_read_insns, &pending_read_mems,
				 insn, x);

	/* Take advantage of tail recursion here.  */
	sched_analyze_2 (XEXP (x, 0), insn);
	return;
      }

    case ASM_OPERANDS:
    case ASM_INPUT:
    case UNSPEC_VOLATILE:
    case TRAP_IF:
      {
	rtx u;

	/* Traditional and volatile asm instructions must be considered to use
	   and clobber all hard registers, all pseudo-registers and all of
	   memory.  So must TRAP_IF and UNSPEC_VOLATILE operations.

	   Consider for instance a volatile asm that changes the fpu rounding
	   mode.  An insn should not be moved across this even if it only uses
	   pseudo-regs because it might give an incorrectly rounded result.  */
	if (code != ASM_OPERANDS || MEM_VOLATILE_P (x))
	  {
	    int max_reg = max_reg_num ();
	    for (i = 0; i < max_reg; i++)
	      {
		for (u = reg_last_uses[i]; u; u = XEXP (u, 1))
		  add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
		reg_last_uses[i] = 0;
		if (reg_last_sets[i])
		  add_dependence (insn, reg_last_sets[i], 0);
	      }
	    reg_pending_sets_all = 1;

	    flush_pending_lists (insn);
	  }

	/* For all ASM_OPERANDS, we must traverse the vector of input operands.
	   We can not just fall through here since then we would be confused
	   by the ASM_INPUT rtx inside ASM_OPERANDS, which do not indicate
	   traditional asms unlike their normal usage.  */

	if (code == ASM_OPERANDS)
	  {
	    for (j = 0; j < ASM_OPERANDS_INPUT_LENGTH (x); j++)
	      sched_analyze_2 (ASM_OPERANDS_INPUT (x, j), insn);
	    return;
	  }
	break;
      }

    case PRE_DEC:
    case POST_DEC:
    case PRE_INC:
    case POST_INC:
      /* These both read and modify the result.  We must handle them as writes
	 to get proper dependencies for following instructions.  We must handle
	 them as reads to get proper dependencies from this to previous
	 instructions.  Thus we need to pass them to both sched_analyze_1
	 and sched_analyze_2.  We must call sched_analyze_2 first in order
	 to get the proper antecedent for the read.  */
      sched_analyze_2 (XEXP (x, 0), insn);
      sched_analyze_1 (x, insn);
      return;
    }

  /* Other cases: walk the insn.  */
  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	sched_analyze_2 (XEXP (x, i), insn);
      else if (fmt[i] == 'E')
	for (j = 0; j < XVECLEN (x, i); j++)
	  sched_analyze_2 (XVECEXP (x, i, j), insn);
    }
}

/* Analyze an INSN with pattern X to find all dependencies.  */

static void
sched_analyze_insn (x, insn, loop_notes)
     rtx x, insn;
     rtx loop_notes;
{
  register RTX_CODE code = GET_CODE (x);
  rtx link;
  int maxreg = max_reg_num ();
  int i;

  if (code == SET || code == CLOBBER)
    sched_analyze_1 (x, insn);
  else if (code == PARALLEL)
    {
      register int i;
      for (i = XVECLEN (x, 0) - 1; i >= 0; i--)
	{
	  code = GET_CODE (XVECEXP (x, 0, i));
	  if (code == SET || code == CLOBBER)
	    sched_analyze_1 (XVECEXP (x, 0, i), insn);
	  else
	    sched_analyze_2 (XVECEXP (x, 0, i), insn);
	}
    }
  else
    sched_analyze_2 (x, insn);

  /* Mark registers CLOBBERED or used by called function.  */
  if (GET_CODE (insn) == CALL_INSN)
    for (link = CALL_INSN_FUNCTION_USAGE (insn); link; link = XEXP (link, 1))
      {
	if (GET_CODE (XEXP (link, 0)) == CLOBBER)
	  sched_analyze_1 (XEXP (link, 0), insn);
	else
	  sched_analyze_2 (XEXP (link, 0), insn);
      }

  /* If there is a LOOP_{BEG,END} note in the middle of a basic block, then
     we must be sure that no instructions are scheduled across it.
     Otherwise, the reg_n_refs info (which depends on loop_depth) would
     become incorrect.  */

  if (loop_notes)
    {
      int max_reg = max_reg_num ();
      rtx link;

      for (i = 0; i < max_reg; i++)
	{
	  rtx u;
	  for (u = reg_last_uses[i]; u; u = XEXP (u, 1))
	    add_dependence (insn, XEXP (u, 0), REG_DEP_ANTI);
	  reg_last_uses[i] = 0;
	  if (reg_last_sets[i])
	    add_dependence (insn, reg_last