reload1.c

早期freebsd实现

		     gen_rtx (REG, Pmode, FRAME_POINTER_REGNUM),
		     gen_rtx (REG, Pmode, i));
      /* This way, we make sure that reg+reg is an offsettable address.  */
      tem = plus_constant (tem, 4);

      if (memory_address_p (QImode, tem))
	{
	  double_reg_address_ok = 1;
	  break;
	}
    }

  /* Initialize obstack for our rtl allocation. */
  gcc_obstack_init (&reload_obstack);
  reload_firstobj = (char *) obstack_alloc (&reload_obstack, 0);

#ifdef HAVE_SECONDARY_RELOADS

  /* Initialize the optabs for doing special input and output reloads.  */

  for (i = 0; i < NUM_MACHINE_MODES; i++)
    reload_in_optab[i] = reload_out_optab[i] = CODE_FOR_nothing;

#ifdef HAVE_reload_inqi
  if (HAVE_reload_inqi)
    reload_in_optab[(int) QImode] = CODE_FOR_reload_inqi;
#endif
#ifdef HAVE_reload_inhi
  if (HAVE_reload_inhi)
    reload_in_optab[(int) HImode] = CODE_FOR_reload_inhi;
#endif
#ifdef HAVE_reload_insi
  if (HAVE_reload_insi)
    reload_in_optab[(int) SImode] = CODE_FOR_reload_insi;
#endif
#ifdef HAVE_reload_indi
  if (HAVE_reload_indi)
    reload_in_optab[(int) DImode] = CODE_FOR_reload_indi;
#endif
#ifdef HAVE_reload_inti
  if (HAVE_reload_inti)
    reload_in_optab[(int) TImode] = CODE_FOR_reload_inti;
#endif
#ifdef HAVE_reload_insf
  if (HAVE_reload_insf)
    reload_in_optab[(int) SFmode] = CODE_FOR_reload_insf;
#endif
#ifdef HAVE_reload_indf
  if (HAVE_reload_indf)
    reload_in_optab[(int) DFmode] = CODE_FOR_reload_indf;
#endif
#ifdef HAVE_reload_inxf
  if (HAVE_reload_inxf)
    reload_in_optab[(int) XFmode] = CODE_FOR_reload_inxf;
#endif
#ifdef HAVE_reload_intf
  if (HAVE_reload_intf)
    reload_in_optab[(int) TFmode] = CODE_FOR_reload_intf;
#endif

#ifdef HAVE_reload_outqi
  if (HAVE_reload_outqi)
    reload_out_optab[(int) QImode] = CODE_FOR_reload_outqi;
#endif
#ifdef HAVE_reload_outhi
  if (HAVE_reload_outhi)
    reload_out_optab[(int) HImode] = CODE_FOR_reload_outhi;
#endif
#ifdef HAVE_reload_outsi
  if (HAVE_reload_outsi)
    reload_out_optab[(int) SImode] = CODE_FOR_reload_outsi;
#endif
#ifdef HAVE_reload_outdi
  if (HAVE_reload_outdi)
    reload_out_optab[(int) DImode] = CODE_FOR_reload_outdi;
#endif
#ifdef HAVE_reload_outti
  if (HAVE_reload_outti)
    reload_out_optab[(int) TImode] = CODE_FOR_reload_outti;
#endif
#ifdef HAVE_reload_outsf
  if (HAVE_reload_outsf)
    reload_out_optab[(int) SFmode] = CODE_FOR_reload_outsf;
#endif
#ifdef HAVE_reload_outdf
  if (HAVE_reload_outdf)
    reload_out_optab[(int) DFmode] = CODE_FOR_reload_outdf;
#endif
#ifdef HAVE_reload_outxf
  if (HAVE_reload_outxf)
    reload_out_optab[(int) XFmode] = CODE_FOR_reload_outxf;
#endif
#ifdef HAVE_reload_outtf
  if (HAVE_reload_outtf)
    reload_out_optab[(int) TFmode] = CODE_FOR_reload_outtf;
#endif

#endif /* HAVE_SECONDARY_RELOADS */

}

/* Main entry point for the reload pass, and only entry point
   in this file.

   FIRST is the first insn of the function being compiled.

   GLOBAL nonzero means we were called from global_alloc
   and should attempt to reallocate any pseudoregs that we
   displace from hard regs we will use for reloads.
   If GLOBAL is zero, we do not have enough information to do that,
   so any pseudo reg that is spilled must go to the stack.

   DUMPFILE is the global-reg debugging dump file stream, or 0.
   If it is nonzero, messages are written to it to describe
   which registers are seized as reload regs, which pseudo regs
   are spilled from them, and where the pseudo regs are reallocated to.

   Return value is nonzero if reload failed
   and we must not do any more for this function.  */

int
reload (first, global, dumpfile)
     rtx first;
     int global;
     FILE *dumpfile;
{
  register int class;
  register int i;
  register rtx insn;
  register struct elim_table *ep;

  int something_changed;
  int something_needs_reloads;
  int something_needs_elimination;
  int new_basic_block_needs;
  enum reg_class caller_save_spill_class = NO_REGS;
  int caller_save_group_size = 1;

  /* Nonzero means we couldn't get enough spill regs.  */
  int failure = 0;

  /* The basic block number currently being processed for INSN.  */
  int this_block;

  /* Make sure even insns with volatile mem refs are recognizable.  */
  init_recog ();

  /* Enable find_equiv_reg to distinguish insns made by reload.  */
  reload_first_uid = get_max_uid ();

  for (i = 0; i < N_REG_CLASSES; i++)
    basic_block_needs[i] = 0;

#ifdef SECONDARY_MEMORY_NEEDED
  /* Initialize the secondary memory table.  */
  clear_secondary_mem ();
#endif

  /* Remember which hard regs appear explicitly
     before we merge into `regs_ever_live' the ones in which
     pseudo regs have been allocated.  */
  bcopy (regs_ever_live, regs_explicitly_used, sizeof regs_ever_live);

  /* We don't have a stack slot for any spill reg yet.  */
  bzero (spill_stack_slot, sizeof spill_stack_slot);
  bzero (spill_stack_slot_width, sizeof spill_stack_slot_width);

  /* Initialize the save area information for caller-save, in case some
     are needed.  */
  init_save_areas ();

  /* Compute which hard registers are now in use
     as homes for pseudo registers.
     This is done here rather than (eg) in global_alloc
     because this point is reached even if not optimizing.  */

  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
    mark_home_live (i);

  /* Make sure that the last insn in the chain
     is not something that needs reloading.  */
  emit_note (NULL_PTR, NOTE_INSN_DELETED);

  /* Find all the pseudo registers that didn't get hard regs
     but do have known equivalent constants or memory slots.
     These include parameters (known equivalent to parameter slots)
     and cse'd or loop-moved constant memory addresses.

     Record constant equivalents in reg_equiv_constant
     so they will be substituted by find_reloads.
     Record memory equivalents in reg_mem_equiv so they can
     be substituted eventually by altering the REG-rtx's.  */

  reg_equiv_constant = (rtx *) alloca (max_regno * sizeof (rtx));
  bzero (reg_equiv_constant, max_regno * sizeof (rtx));
  reg_equiv_memory_loc = (rtx *) alloca (max_regno * sizeof (rtx));
  bzero (reg_equiv_memory_loc, max_regno * sizeof (rtx));
  reg_equiv_mem = (rtx *) alloca (max_regno * sizeof (rtx));
  bzero (reg_equiv_mem, max_regno * sizeof (rtx));
  reg_equiv_init = (rtx *) alloca (max_regno * sizeof (rtx));
  bzero (reg_equiv_init, max_regno * sizeof (rtx));
  reg_equiv_address = (rtx *) alloca (max_regno * sizeof (rtx));
  bzero (reg_equiv_address, max_regno * sizeof (rtx));
  reg_max_ref_width = (int *) alloca (max_regno * sizeof (int));
  bzero (reg_max_ref_width, max_regno * sizeof (int));

  /* Look for REG_EQUIV notes; record what each pseudo is equivalent to.
     Also find all paradoxical subregs
     and find largest such for each pseudo.  */

  for (insn = first; insn; insn = NEXT_INSN (insn))
    {
      rtx set = single_set (insn);

      if (set != 0 && GET_CODE (SET_DEST (set)) == REG)
	{
	  rtx note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
	  if (note
#ifdef LEGITIMATE_PIC_OPERAND_P
	      && (! CONSTANT_P (XEXP (note, 0)) || ! flag_pic
		  || LEGITIMATE_PIC_OPERAND_P (XEXP (note, 0)))
#endif
	      )
	    {
	      rtx x = XEXP (note, 0);
	      i = REGNO (SET_DEST (set));
	      if (i > LAST_VIRTUAL_REGISTER)
		{
		  if (GET_CODE (x) == MEM)
		    reg_equiv_memory_loc[i] = x;
		  else if (CONSTANT_P (x))
		    {
		      if (LEGITIMATE_CONSTANT_P (x))
			reg_equiv_constant[i] = x;
		      else
			reg_equiv_memory_loc[i]
			  = force_const_mem (GET_MODE (SET_DEST (set)), x);
		    }
		  else
		    continue;

		  /* If this register is being made equivalent to a MEM
		     and the MEM is not SET_SRC, the equivalencing insn
		     is one with the MEM as a SET_DEST and it occurs later.
		     So don't mark this insn now.  */
		  if (GET_CODE (x) != MEM
		      || rtx_equal_p (SET_SRC (set), x))
		    reg_equiv_init[i] = insn;
		}
	    }
	}

      /* If this insn is setting a MEM from a register equivalent to it,
	 this is the equivalencing insn.  */
      else if (set && GET_CODE (SET_DEST (set)) == MEM
	       && GET_CODE (SET_SRC (set)) == REG
	       && reg_equiv_memory_loc[REGNO (SET_SRC (set))]
	       && rtx_equal_p (SET_DEST (set),
			       reg_equiv_memory_loc[REGNO (SET_SRC (set))]))
	reg_equiv_init[REGNO (SET_SRC (set))] = insn;

      if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
	scan_paradoxical_subregs (PATTERN (insn));
    }

  /* Does this function require a frame pointer?  */

  frame_pointer_needed = (! flag_omit_frame_pointer
#ifdef EXIT_IGNORE_STACK
			  /* ?? If EXIT_IGNORE_STACK is set, we will not save
			     and restore sp for alloca.  So we can't eliminate
			     the frame pointer in that case.  At some point,
			     we should improve this by emitting the
			     sp-adjusting insns for this case.  */
			  || (current_function_calls_alloca
			      && EXIT_IGNORE_STACK)
#endif
			  || FRAME_POINTER_REQUIRED);

  num_eliminable = 0;

  /* Initialize the table of registers to eliminate.  The way we do this
     depends on how the eliminable registers were defined.  */
#ifdef ELIMINABLE_REGS
  for (ep = reg_eliminate; ep < &reg_eliminate[NUM_ELIMINABLE_REGS]; ep++)
    {
      ep->can_eliminate = ep->can_eliminate_previous
	= (CAN_ELIMINATE (ep->from, ep->to)
	   && (ep->from != FRAME_POINTER_REGNUM || ! frame_pointer_needed));
    }
#else
  reg_eliminate[0].can_eliminate = reg_eliminate[0].can_eliminate_previous
    = ! frame_pointer_needed;
#endif

  /* Count the number of eliminable registers and build the FROM and TO
     REG rtx's.  Note that code in gen_rtx will cause, e.g.,
     gen_rtx (REG, Pmode, STACK_POINTER_REGNUM) to equal stack_pointer_rtx.
     We depend on this.  */
  for (ep = reg_eliminate; ep < &reg_eliminate[NUM_ELIMINABLE_REGS]; ep++)
    {
      num_eliminable += ep->can_eliminate;
      ep->from_rtx = gen_rtx (REG, Pmode, ep->from);
      ep->to_rtx = gen_rtx (REG, Pmode, ep->to);
    }

  num_labels = max_label_num () - get_first_label_num ();

  /* Allocate the tables used to store offset information at labels.  */
  offsets_known_at = (char *) alloca (num_labels);
  offsets_at
    = (int (*)[NUM_ELIMINABLE_REGS])
      alloca (num_labels * NUM_ELIMINABLE_REGS * sizeof (int));

  offsets_known_at -= get_first_label_num ();
  offsets_at -= get_first_label_num ();

  /* Alter each pseudo-reg rtx to contain its hard reg number.
     Assign stack slots to the pseudos that lack hard regs or equivalents.
     Do not touch virtual registers.  */

  for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++)
    alter_reg (i, -1);

  /* Round size of stack frame to BIGGEST_ALIGNMENT.  This must be done here
     because the stack size may be a part of the offset computation for
     register elimination.   */
  assign_stack_local (BLKmode, 0, 0);

  /* If we have some registers we think can be eliminated, scan all insns to
     see if there is an insn that sets one of these registers to something
     other than itself plus a constant.  If so, the register cannot be
     eliminated.  Doing this scan here eliminates an extra pass through the
     main reload loop in the most common case where register elimination
     cannot be done.  */
  for (insn = first; insn && num_eliminable; insn = NEXT_INSN (insn))
    if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
	|| GET_CODE (insn) == CALL_INSN)
      note_stores (PATTERN (insn), mark_not_eliminable);

#ifndef REGISTER_CONSTRAINTS
  /* If all the pseudo regs have hard regs,
     except for those that are never referenced,
     we know that no reloads are needed.  */
  /* But that is not true if there are register constraints, since
     in that case some pseudos might be in the wrong kind of hard reg.  */

  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
    if (reg_renumber[i] == -1 && reg_n_refs[i] != 0)
      break;

  if (i == max_regno && num_eliminable == 0 && ! caller_save_needed)
    return;
#endif

  /* Compute the order of preference for hard registers to spill.
     Store them by decreasing preference in potential_reload_regs.  */

  order_regs_for_reload ();

  /* So far, no hard regs have been spilled.  */
  n_spills = 0;
  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    spill_reg_order[i] = -1;

  /* On most machines, we can't use any register explicitly used in the
     rtl as a spill register.  But on some, we have to.  Those will have
     taken care to keep the life of hard regs as short as possible.  */