global-alloc.c

这是完整的gcc源代码

	 This is ok; we know the size from PSEUDO_REGNO_SIZE.
	 For explicit hard regs, we cannot know the size that way
	 since one hard reg can be used with various sizes.
	 Therefore, we must require that all the hard regs
	 implicitly live as part of a multi-word hard reg
	 are explicitly marked in basic_block_live_at_start.  */

      {
	register int offset, bit;
	register regset old = basic_block_live_at_start[b];
	int ax = 0;

#ifdef HARD_REG_SET
	hard_regs_live = old[0];
#else
	COPY_HARD_REG_SET (hard_regs_live, old);
#endif
	for (offset = 0, i = 0; offset < regset_size; offset++)
	  if (old[offset] == 0)
	    i += HOST_BITS_PER_INT;
	  else
	    for (bit = 1; bit; bit <<= 1, i++)
	      {
		if (i >= max_regno)
		  break;
		if (old[offset] & bit)
		  {
		    register int a = reg_allocno[i];
		    if (a >= 0)
		      {
			SET_ALLOCNO_LIVE (a);
			block_start_allocnos[ax++] = a;
		      }
		    else if ((a = reg_renumber[i]) >= 0)
		      mark_reg_live_nc (a, PSEUDO_REGNO_MODE (i));
		  }
	      }

	/* Record that each allocno now live conflicts with each other
	   allocno now live, and with each hard reg now live.  */

	record_conflicts (block_start_allocnos, ax);
      }

      insn = basic_block_head[b];

      /* Scan the code of this basic block, noting which allocnos
	 and hard regs are born or die.  When one is born,
	 record a conflict with all others currently live.  */

      while (1)
	{
	  register RTX_CODE code = GET_CODE (insn);
	  register rtx link;

	  /* Make regs_set an empty set.  */

	  n_regs_set = 0;

	  if (code == INSN || code == CALL_INSN || code == JUMP_INSN)
	    {
	      /* Mark any registers clobbered by INSN as live,
		 so they conflict with the inputs.  */

	      note_stores (PATTERN (insn), mark_reg_clobber);

	      /* Mark any registers dead after INSN as dead now.  */

	      for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
		if (REG_NOTE_KIND (link) == REG_DEAD)
		  mark_reg_death (XEXP (link, 0));

	      /* Mark any registers set in INSN as live,
		 and mark them as conflicting with all other live regs.
		 Clobbers are processed again, so they conflict with
		 the registers that are set.  */

	      note_stores (PATTERN (insn), mark_reg_store);

	      /* Mark any registers both set and dead after INSN as dead.
		 This is not redundant!
		 A register may be set and killed in the same insn.
		 It is necessary to mark them as live, above, to get
		 the right conflicts within the insn.  */

	      while (n_regs_set > 0)
		if (find_regno_note (insn, REG_DEAD, REGNO (regs_set[--n_regs_set])))
		  mark_reg_death (regs_set[n_regs_set]);

	      /*???The following seems to be incorrect.  */
	      /* Likewise for regs set by incrementation.  */

	      for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
		if (REG_NOTE_KIND (link) == REG_INC
		    && find_regno_note (insn, REG_DEAD, REGNO (XEXP (link, 0))))
		  mark_reg_death (XEXP (link, 0));
	    }

	  if (insn == basic_block_end[b])
	    break;
	  insn = NEXT_INSN (insn);
	}
    }
}

/* Assign a hard register to ALLOCNO; look for one that is the beginning
   of a long enough stretch of hard regs none of which conflicts with ALLOCNO.
   The registers marked in PREFREGS are tried first.

   If ALL_REGS_P is zero, consider only the preferred class of ALLOCNO's reg.
   Otherwise ignore that preferred class.

   If ACCEPT_CALL_CLOBBERED is nonzero, accept a call-clobbered hard reg that
   will have to be saved and restored at calls.

   If we find one, record it in reg_renumber.
   If not, do nothing.  */

static void
find_reg (allocno, losers, all_regs_p, accept_call_clobbered, prefregs)
     int allocno;
     register short *losers;
     int all_regs_p;
     int accept_call_clobbered;
     HARD_REG_SET prefregs;
{
  register int i, prefreg, pass;
#ifdef HARD_REG_SET
  register		/* Declare it register if it's a scalar.  */
#endif
    HARD_REG_SET used;

  enum reg_class class 
    = all_regs_p ? GENERAL_REGS : reg_preferred_class (allocno_reg[allocno]);
  enum machine_mode mode = PSEUDO_REGNO_MODE (allocno_reg[allocno]);

  if (accept_call_clobbered)
    COPY_HARD_REG_SET (used, call_fixed_reg_set);
  else if (reg_n_calls_crossed[allocno_reg[allocno]] == 0)
    COPY_HARD_REG_SET (used, fixed_reg_set);
  else
    COPY_HARD_REG_SET (used, call_used_reg_set);

  /* Some registers should not be allocated in global-alloc.  */
  IOR_HARD_REG_SET (used, no_global_alloc_regs);

  IOR_COMPL_HARD_REG_SET (used, reg_class_contents[(int) class]);
  IOR_HARD_REG_SET (used, hard_reg_conflicts[allocno]);
  if (frame_pointer_needed)
    SET_HARD_REG_BIT (used, FRAME_POINTER_REGNUM);

  AND_COMPL_HARD_REG_SET (prefregs, used);

  /* Try to find a register from the preferred set first. */

  i = -1;
  for (prefreg = 0; prefreg < FIRST_PSEUDO_REGISTER; prefreg++)
    if (TEST_HARD_REG_BIT (prefregs, prefreg)
	&& (losers == 0 || losers[prefreg] < 0)
	&& HARD_REGNO_MODE_OK (prefreg, mode))
      {
	register int j;
	register int lim = prefreg + HARD_REGNO_NREGS (prefreg, mode);
	for (j = prefreg + 1;
	     (j < lim
	      && ! TEST_HARD_REG_BIT (used, j)
	      && (losers == 0 || losers[j] < 0));
	     j++);
	if (j == lim)
	  {
	    i = prefreg;
	    break;
	  }
      }

#if 0
  /* Otherwise try each hard reg to see if it fits.  Do this in two passes.
     In the first pass, skip registers that are prefered by some pseudo to
     give it a better chance of getting one of those registers.  Only if
     we can't get a register when excluding those do we take one of them.  */

  /* This is turned off because it makes worse allocation on the 68020.  */
  for (pass = 0; pass <= 1 && i < 0; pass++)
#endif
  pass = 1;
    for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
      {
#ifdef REG_ALLOC_ORDER
	int regno = reg_alloc_order[i];
#else
	int regno = i;
#endif
	if (! TEST_HARD_REG_BIT (used, regno)
	    && (losers == 0 || losers[regno] < 0)
	    && (pass == 1 || ! TEST_HARD_REG_BIT (regs_someone_prefers, regno))
	    && HARD_REGNO_MODE_OK (regno, mode))
	  {
	    register int j;
	    register int lim = regno + HARD_REGNO_NREGS (regno, mode);
	    for (j = regno + 1;
		 (j < lim
		  && ! TEST_HARD_REG_BIT (used, j)
		  && (losers == 0 || losers[j] < 0));
		 j++);
	    if (j == lim)
	      {
		i = regno;
		break;
	      }
#ifndef REG_ALLOC_ORDER
	    i = j;			/* Skip starting points we know will lose */
#endif
	  }
      }

  /* Did we find a register?  */

  if (i < FIRST_PSEUDO_REGISTER)
    {
      register int lim, j;
      HARD_REG_SET this_reg;

      /* Yes.  Record it as the hard register of this pseudo-reg.  */
      reg_renumber[allocno_reg[allocno]] = i;
      /* For each other pseudo-reg conflicting with this one,
	 mark it as conflicting with the hard regs this one occupies.  */
      CLEAR_HARD_REG_SET (this_reg);
      lim = i + HARD_REGNO_NREGS (i, mode);
      for (j = i; j < lim; j++)
	SET_HARD_REG_BIT (this_reg, j);
      lim = allocno;
      for (j = 0; j < max_allocno; j++)
	if (CONFLICTP (lim, j) || CONFLICTP (j, lim))
	  {
	    IOR_HARD_REG_SET (hard_reg_conflicts[j], this_reg);
	  }
    }
  else if (flag_caller_saves)
    {
      /* Did not find a register.  If it would be profitable to
	 allocate a call-clobbered register and save and restore it
	 around calls, do that.  */
      if (! accept_call_clobbered
	  && reg_n_calls_crossed[allocno_reg[allocno]] != 0
	  && CALLER_SAVE_PROFITABLE (reg_n_refs[allocno_reg[allocno]],
				     reg_n_calls_crossed[allocno_reg[allocno]]))
	{
	  find_reg (allocno, losers, all_regs_p, 1, prefregs);
	  if (reg_renumber[allocno_reg[allocno]] >= 0)
	    caller_save_needed = 1;
	}
    }
}

/* Called from `reload' to look for a hard reg to put pseudo reg REGNO in.
   Perhaps it had previously seemed not worth a hard reg,
   or perhaps its old hard reg has been commandeered for reloads.
   FORBIDDEN_REGS is a vector that indicates certain hard regs
   that may not be used, even if they do not appear to be allocated.
   A nonnegative element means the corresponding hard reg is forbidden.
   If FORBIDDEN_REGS is zero, no regs are forbidden.  */

void
retry_global_alloc (regno, forbidden_regs)
     int regno;
     short *forbidden_regs;
{
  int allocno = reg_allocno[regno];
  if (allocno >= 0)
    {
      /* If we have more than one register class,
	 first try allocating in the class that is cheapest
	 for this pseudo-reg.  If that fails, try any reg.  */
      if (N_REG_CLASSES > 1)
	find_reg (allocno, forbidden_regs, 0, 0,
		  hard_reg_preferences[allocno]);
      if (reg_renumber[regno] < 0
	  && !reg_preferred_or_nothing (regno))
	find_reg (allocno, forbidden_regs, 1, 0,
		  hard_reg_preferences[allocno]);
    }
}

/* Called from reload pass to see if current function's pseudo regs
   require a frame pointer to be allocated and set up.

   Return 1 if so, 0 otherwise.
   We may alter the hard-reg allocation of the pseudo regs
   in order to make the frame pointer unnecessary.
   However, if the value is 1, nothing has been altered.

   Args grant access to some tables used in reload1.c.
   See there for info on them.  */

int
check_frame_pointer_required (reg_equiv_constant, reg_equiv_mem, reg_equiv_address)
     rtx *reg_equiv_constant, *reg_equiv_mem, *reg_equiv_address;
{
  register int i;
  HARD_REG_SET *old_hard_reg_conflicts;
  short *old_reg_renumber;
  char old_regs_ever_live[FIRST_PSEUDO_REGISTER];

  /* If any pseudo reg has no hard reg and no equivalent,
     we must have a frame pointer.  */

  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
    if (reg_renumber[i] < 0 && reg_n_refs[i] > 0
        && reg_equiv_mem[i] == 0 && reg_equiv_constant[i] == 0
	&& reg_equiv_address[i] == 0)
      return 1;

  /* If we might not need a frame pointer,
     try finding a hard reg for any pseudo that has a memory equivalent.
     That is because the memory equivalent probably refers to a frame
     pointer.  */

  old_reg_renumber = (short *) alloca (max_regno * sizeof (short));
  old_hard_reg_conflicts = (HARD_REG_SET *)
    alloca (max_allocno * sizeof (HARD_REG_SET));

  bcopy (reg_renumber, old_reg_renumber, max_regno * sizeof (short));
  bcopy (hard_reg_conflicts, old_hard_reg_conflicts,
	 max_allocno * sizeof (HARD_REG_SET));
  bcopy (regs_ever_live, old_regs_ever_live, sizeof regs_ever_live);

  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
    if (reg_renumber[i] < 0
	&& ((reg_equiv_mem[i]
	     && reg_mentioned_p (frame_pointer_rtx, reg_equiv_mem[i]))
	    || (reg_equiv_address[i]
		&& reg_mentioned_p (frame_pointer_rtx, reg_equiv_address[i]))))
      {
	retry_global_alloc (i, 0);
	/* If we can't find a hard reg for ALL of them,
	   or if a previously unneeded hard reg is used that requires saving,
	   we fail: set all those pseudos back as they were.  */
	if (reg_renumber[i] < 0
	    || (! old_regs_ever_live[reg_renumber[i]]
		&& ! call_used_regs[reg_renumber[i]]))
	  {
	    bcopy (old_reg_renumber, reg_renumber,
		   max_regno * sizeof (short));
	    bcopy (old_hard_reg_conflicts, hard_reg_conflicts,
		   max_allocno * sizeof (HARD_REG_SET));
	    bcopy (old_regs_ever_live, regs_ever_live, sizeof regs_ever_live);
	    return 1;
	  }
	mark_home_live (i);
      }

  return 0;
}

/* Record a conflict between register REGNO
   and everything currently live.
   REGNO must not be a pseudo reg that was allocated
   by local_alloc; such numbers must be translated through
   reg_renumber before calling here.  */

static void
record_one_conflict (regno)
     int regno;
{