reload1.c

这是完整的gcc源代码

	  max_needs[class]--;
	  p = reg_class_superclasses[class];
	  while (*p != LIM_REG_CLASSES)
	    max_needs[(int) *p++]--;

	  if (! counted_for_groups[spill_regs[i]])
	    {
	      if (max_nongroups[class] > 0)
		counted_for_nongroups[spill_regs[i]] = 1;
	      max_nongroups[class]--;
	      p = reg_class_superclasses[class];
	      while (*p != LIM_REG_CLASSES)
		{
		  if (max_nongroups[(int) *p] > 0)
		    counted_for_nongroups[spill_regs[i]] = 1;
		  max_nongroups[(int) *p++]--;
		}
	    }
	}

      /* If all needs are met, we win.  */

      for (i = 0; i < N_REG_CLASSES; i++)
	if (max_needs[i] > 0 || max_groups[i] > 0 || max_nongroups[i] > 0)
	  break;
      if (i == N_REG_CLASSES && !new_basic_block_needs)
	break;

      /* Not all needs are met; must spill more hard regs.  */

      /* If any element of basic_block_needs changed from 0 to 1,
	 re-spill all the regs already spilled.  This may spill
	 additional pseudos that didn't spill before.  */

      if (new_basic_block_needs)
	for (i = 0; i < n_spills; i++)
	  something_changed
	    |= spill_hard_reg (spill_regs[i], global, dumpfile);

      /* Now find more reload regs to satisfy the remaining need
	 Do it by ascending class number, since otherwise a reg
	 might be spilled for a big class and might fail to count
	 for a smaller class even though it belongs to that class.

	 Count spilled regs in `spills', and add entries to
	 `spill_regs' and `spill_reg_order'.  */

      for (class = 0; class < N_REG_CLASSES; class++)
	{
	  /* First get the groups of registers.
	     If we got single registers first, we might fragment
	     possible groups.  */
	  while (max_groups[class] > 0)
	    {
	      /* Groups of size 2 (the only groups used on most machines)
		 are treated specially.  */
	      if (group_size[class] == 2)
		{
		  /* First, look for a register that will complete a group.  */
		  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
		    {
		      int j = potential_reload_regs[i];
		      int other;
		      if (j >= 0 && !fixed_regs[j] && j != FRAME_POINTER_REGNUM
			  && !regs_explicitly_used[j]
			  &&
			  ((j > 0 && (other = j - 1, spill_reg_order[other] >= 0)
			    && TEST_HARD_REG_BIT (reg_class_contents[class], j)
			    && TEST_HARD_REG_BIT (reg_class_contents[class], other)
			    && HARD_REGNO_MODE_OK (other, group_mode[class])
			    && ! counted_for_nongroups[other]
			    /* We don't want one part of another group.
			       We could get "two groups" that overlap!  */
			    && ! counted_for_groups[other])

			   ||
			   (j < FIRST_PSEUDO_REGISTER - 1
			    && (other = j + 1, spill_reg_order[other] >= 0)
			    && TEST_HARD_REG_BIT (reg_class_contents[class], j)
			    && TEST_HARD_REG_BIT (reg_class_contents[class], other)
			    && HARD_REGNO_MODE_OK (j, group_mode[class])
			    && ! counted_for_nongroups[other]
			    && ! counted_for_groups[other])))
			{
			  register enum reg_class *p;

			  /* We have found one that will complete a group,
			     so count off one group as provided.  */
			  max_groups[class]--;
			  p = reg_class_superclasses[class];
			  while (*p != LIM_REG_CLASSES)
			    max_groups[(int) *p++]--;

			  /* Indicate both these regs are part of a group.  */
			  counted_for_groups[j] = 1;
			  counted_for_groups[other] = 1;

			  break;
			}
		    }
		  /* We can't complete a group, so start one.  */
		  if (i == FIRST_PSEUDO_REGISTER)
		    for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
		      {
			int j = potential_reload_regs[i];
			if (j >= 0 && j + 1 < FIRST_PSEUDO_REGISTER
			    && !fixed_regs[j] && j != FRAME_POINTER_REGNUM
			    && spill_reg_order[j] < 0 && spill_reg_order[j + 1] < 0
			    && TEST_HARD_REG_BIT (reg_class_contents[class], j)
			    && TEST_HARD_REG_BIT (reg_class_contents[class], j + 1)
			    && HARD_REGNO_MODE_OK (j, group_mode[class])
			    && ! counted_for_nongroups[j + 1])
			  break;
		      }

		  /* I should be the index in potential_reload_regs
		     of the new reload reg we have found.  */

		  something_changed
		    |= new_spill_reg (i, class, max_needs, 0,
				      global, dumpfile);
		}
	      else
		{
		  /* For groups of more than 2 registers,
		     look for a sufficient sequence of unspilled registers,
		     and spill them all at once.  */
		  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
		    {
		      int j = potential_reload_regs[i];
		      int k;
		      if (j >= 0 && j + 1 < FIRST_PSEUDO_REGISTER
			  && HARD_REGNO_MODE_OK (j, group_mode[class]))
			{
			  /* Check each reg in the sequence.  */
			  for (k = 0; k < group_size[class]; k++)
			    if (! (spill_reg_order[j + k] < 0
				   && !fixed_regs[j + k]
				   && j + k != FRAME_POINTER_REGNUM
				   && TEST_HARD_REG_BIT (reg_class_contents[class], j + k)))
			      break;
			  /* We got a full sequence, so spill them all.  */
			  if (k == group_size[class])
			    {
			      register enum reg_class *p;
			      for (k = 0; k < group_size[class]; k++)
				{
				  int idx;
				  counted_for_groups[j + k] = 1;
				  for (idx = 0; idx < FIRST_PSEUDO_REGISTER; idx++)
				    if (potential_reload_regs[idx] == j + k)
				      break;
				  something_changed
				    |= new_spill_reg (idx, class, max_needs, 0,
						      global, dumpfile);
				}

			      /* We have found one that will complete a group,
				 so count off one group as provided.  */
			      max_groups[class]--;
			      p = reg_class_superclasses[class];
			      while (*p != LIM_REG_CLASSES)
				max_groups[(int) *p++]--;

			      break;
			    }
			}
		    }
		}
	    }

	  /* Now similarly satisfy all need for single registers.  */

	  while (max_needs[class] > 0 || max_nongroups[class] > 0)
	    {
	      /* Consider the potential reload regs that aren't
		 yet in use as reload regs, in order of preference.
		 Find the most preferred one that's in this class.  */

	      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
		if (potential_reload_regs[i] >= 0
		    && TEST_HARD_REG_BIT (reg_class_contents[class],
					  potential_reload_regs[i])
		    /* If this reg will not be available for groups,
		       pick one that does not foreclose possible groups.
		       This is a kludge, and not very general,
		       but it should be sufficient to make the 386 work,
		       and the problem should not occur on machines with
		       more registers.  */
		    && (max_nongroups[class] == 0
			|| possible_group_p (potential_reload_regs[i], max_groups)))
		  break;

	      /* I should be the index in potential_reload_regs
		 of the new reload reg we have found.  */

	      something_changed
		|= new_spill_reg (i, class, max_needs, max_nongroups,
				  global, dumpfile);
	    }
	}
    }

  /* Insert code to save and restore call-clobbered hard regs
     around calls.  */

  if (caller_save_needed)
    save_call_clobbered_regs ();

  /* Now we know for certain whether we have a frame pointer.
     If not, correct all references to go through the stack pointer.
     This must be done before reloading, since reloading could generate
     insns where sp+const cannot validly replace the frame pointer.
     *This will lose if an insn might need more spill regs after
     frame pointer elimination than it needed before.*  */

  if (! frame_pointer_needed)
    eliminate_frame_pointer (first);

  /* Use the reload registers where necessary
     by generating move instructions to move the must-be-register
     values into or out of the reload registers.  */

  if (something_needs_reloads)
    reload_as_needed (first, global);

  /* Now eliminate all pseudo regs by modifying them into
     their equivalent memory references.
     The REG-rtx's for the pseudos are modified in place,
     so all insns that used to refer to them now refer to memory.

     For a reg that has a reg_equiv_address, all those insns
     were changed by reloading so that no insns refer to it any longer;
     but the DECL_RTL of a variable decl may refer to it,
     and if so this causes the debugging info to mention the variable.  */

  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
    {
      rtx addr = 0;
      if (reg_equiv_mem[i])
	addr = XEXP (reg_equiv_mem[i], 0);
      if (reg_equiv_address[i])
	addr = reg_equiv_address[i];
      if (addr)
	{
	  if (! frame_pointer_needed)
	    FIX_FRAME_POINTER_ADDRESS (addr, 0);
	  if (reg_renumber[i] < 0)
	    {
	      rtx reg = regno_reg_rtx[i];
	      XEXP (reg, 0) = addr;
	      REG_USERVAR_P (reg) = 0;
	      PUT_CODE (reg, MEM);
	    }
	  else if (reg_equiv_mem[i])
	    XEXP (reg_equiv_mem[i], 0) = addr;
	}
    }
}

/* Nonzero if, after spilling reg REGNO for non-groups,
   it will still be possible to find a group if we still need one.  */

static int
possible_group_p (regno, max_groups)
     int regno;
     int *max_groups;
{
  int i;
  int group = 0;

  for (i = 0; i < (int) N_REG_CLASSES; i++)
    group |= max_groups[i];

  if (group == 0)
    return 1;

  /* Consider each pair of consecutive registers.  */
  for (i = 0; i < FIRST_PSEUDO_REGISTER - 1; i++)
    {
      if (i == regno || i + 1 == regno)
	continue;

      /* A pair of consecutive regs we can still spill does the trick.  */
      if (spill_reg_order[i] < 0 && spill_reg_order[i + 1] < 0
	  && !regs_explicitly_used[i] && !regs_explicitly_used[i + 1]
	  && !fixed_regs[i] && i != FRAME_POINTER_REGNUM
	  && !fixed_regs[i + 1] && i + 1 != FRAME_POINTER_REGNUM)
	return 1;

      /* A pair of one already spilled and one we can spill does it
	 provided the one already spilled is not otherwise reserved.  */
      if (spill_reg_order[i] < 0 && !regs_explicitly_used[i]
	  && !fixed_regs[i] && i != FRAME_POINTER_REGNUM
	  && spill_reg_order[i + 1] >= 0
	  && !counted_for_groups[i + 1]
	  && !counted_for_nongroups[i + 1])
	return 1;
      if (spill_reg_order[i + 1] < 0 && !regs_explicitly_used[i + 1]
	  && !fixed_regs[i + 1] && i + 1 != FRAME_POINTER_REGNUM
	  && spill_reg_order[i] >= 0
	  && !counted_for_groups[i]
	  && !counted_for_nongroups[i])
	return 1;
    }

  return 0;
}

/* 1 if two machine modes MODE0 and MODE1 are equivalent
   as far as HARD_REGNO_MODE_OK is concerned
   for registers in class CLASS.  */

static int
modes_equiv_for_class_p (mode0, mode1, class)
     enum machine_mode mode0, mode1;
     enum reg_class class;
{
  register int regno;
  for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
    {
      /* If any reg in CLASS allows one mode but not the other, fail.
	 Or if the two modes have different sizes in that reg, fail.  */
      if (TEST_HARD_REG_BIT (reg_class_contents[(int) class], regno)
	  && (HARD_REGNO_MODE_OK (regno, mode0)
	      != HARD_REGNO_MODE_OK (regno, mode1))
	  && (HARD_REGNO_NREGS (regno, mode0)
	      != HARD_REGNO_NREGS (regno, mode1)))
	return 0;
    }
  return 1;
}

/* Add a new register to the tables of available spill-registers
    (as well as spilling all pseudos allocated to the register).
   I is the index of this register in potential_reload_regs.
   CLASS is the regclass whose need is being satisfied.
   MAX_NEEDS and MAX_NONGROUPS are the vectors of needs,
    so that this register can count off against them.
    MAX_NONGROUPS is 0 if this register is part of a group.
   GLOBAL and DUMPFILE are the same as the args that `reload' got.  */

static int
new_spill_reg (i, class, max_needs, max_nongroups, global, dumpfile)
     int i;
     int class;
     int *max_needs;
     int *max_nongroups;
     int global;
     FILE *dumpfile;
{
  register enum reg_class *p;
  int val;
  int regno = potential_reload_regs[i];

  if (i >= FIRST_PSEUDO_REGISTER)
    abort ();	/* Caller failed to find any register.  */

#if 0 /* This causes errors on the 386 for code that works ok.  */
  if (regs_explicitly_used[regno])
    {
      error ("spilling register %s, which is explicitly used",
	     reg_names[regno]);
      error ("(Probably too many explicit register variables");
      error (" are used in this function)");
    }
#endif

  /* Make reg REGNO an additional reload reg.  */

  potential_reload_regs[i] = -1;
  spill_regs[n_spills] = regno;
  spill_reg_order[regno] = n_spills;
  forbidden_regs[regno] = 1;
  if (dumpfile)
    fprintf (dumpfile, "Spilling reg %d.\n", spill_regs[n_spills]);

  /* Clear off the needs we just satisfied.  */

  max_needs[class]--;
  p = reg_class_superclasses[class];
  while (*p != LIM_REG_CLASSES)
    max_needs[(int) *p++]--;

  if (max_nongroups && max_nongroups[class] > 0)
    {
      counted_for_nongroups[regno] = 1;
      max_nongroups[class]--;
      p = reg_class_superclasses[class];
      while (*p != LIM_REG_CLASSES)
	max_nongroups[(int) *p++]--;
    }

  /* Spill every pseudo reg that was allocated to this reg
     or to something that overlaps this reg.  */

  val = spill_hard_reg (spill_regs[n_spills], global, dumpfile);

  regs_ever_live[spill_regs[n_spills]] = 1;