cse.c

早期freebsd实现

  ? ((((int) REG << 7) + reg_qty[REGNO (X)]) % NBUCKETS)	\
  : canon_hash (X, M) % NBUCKETS)

/* Determine whether register number N is considered a fixed register for CSE.
   It is desirable to replace other regs with fixed regs, to reduce need for
   non-fixed hard regs.
   A reg wins if it is either the frame pointer or designated as fixed,
   but not if it is an overlapping register.  */
#ifdef OVERLAPPING_REGNO_P
#define FIXED_REGNO_P(N)  \
  (((N) == FRAME_POINTER_REGNUM || fixed_regs[N])	\
   && ! OVERLAPPING_REGNO_P ((N)))
#else
#define FIXED_REGNO_P(N)  \
  ((N) == FRAME_POINTER_REGNUM || fixed_regs[N])
#endif

/* Compute cost of X, as stored in the `cost' field of a table_elt.  Fixed
   hard registers are the cheapest with a cost of 0.  Next come pseudos
   with a cost of one and other hard registers with a cost of 2.  Aside
   from these special cases, call `rtx_cost'.  */

#define COST(X)						\
  (GET_CODE (X) == REG					\
   ? (REGNO (X) >= FIRST_PSEUDO_REGISTER ? 1		\
      : (FIXED_REGNO_P (REGNO (X))			\
	 && REGNO_REG_CLASS (REGNO (X)) != NO_REGS) ? 0	\
      : 2)						\
   : rtx_cost (X, SET) * 2)

/* Determine if the quantity number for register X represents a valid index
   into the `qty_...' variables.  */

#define REGNO_QTY_VALID_P(N) (reg_qty[N] != (N))

static struct table_elt *table[NBUCKETS];

/* Chain of `struct table_elt's made so far for this function
   but currently removed from the table.  */

static struct table_elt *free_element_chain;

/* Number of `struct table_elt' structures made so far for this function.  */

static int n_elements_made;

/* Maximum value `n_elements_made' has had so far in this compilation
   for functions previously processed.  */

static int max_elements_made;

/* Surviving equivalence class when two equivalence classes are merged 
   by recording the effects of a jump in the last insn.  Zero if the
   last insn was not a conditional jump.  */

static struct table_elt *last_jump_equiv_class;

/* Set to the cost of a constant pool reference if one was found for a
   symbolic constant.  If this was found, it means we should try to
   convert constants into constant pool entries if they don't fit in
   the insn.  */

static int constant_pool_entries_cost;

/* Bits describing what kind of values in memory must be invalidated
   for a particular instruction.  If all three bits are zero,
   no memory refs need to be invalidated.  Each bit is more powerful
   than the preceding ones, and if a bit is set then the preceding
   bits are also set.

   Here is how the bits are set:
   Pushing onto the stack invalidates only the stack pointer,
   writing at a fixed address invalidates only variable addresses,
   writing in a structure element at variable address
     invalidates all but scalar variables,
   and writing in anything else at variable address invalidates everything.  */

struct write_data
{
  int sp : 1;			/* Invalidate stack pointer. */
  int var : 1;			/* Invalidate variable addresses.  */
  int nonscalar : 1;		/* Invalidate all but scalar variables.  */
  int all : 1;			/* Invalidate all memory refs.  */
};

/* Nonzero if X has the form (PLUS frame-pointer integer).  We check for
   virtual regs here because the simplify_*_operation routines are called
   by integrate.c, which is called before virtual register instantiation.  */

#define FIXED_BASE_PLUS_P(X)					\
  ((X) == frame_pointer_rtx || (X) == arg_pointer_rtx		\
   || (X) == virtual_stack_vars_rtx				\
   || (X) == virtual_incoming_args_rtx				\
   || (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 1)) == CONST_INT \
       && (XEXP (X, 0) == frame_pointer_rtx			\
	   || XEXP (X, 0) == arg_pointer_rtx			\
	   || XEXP (X, 0) == virtual_stack_vars_rtx		\
	   || XEXP (X, 0) == virtual_incoming_args_rtx)))

/* Similar, but also allows reference to the stack pointer.

   This used to include FIXED_BASE_PLUS_P, however, we can't assume that
   arg_pointer_rtx by itself is nonzero, because on at least one machine,
   the i960, the arg pointer is zero when it is unused.  */

#define NONZERO_BASE_PLUS_P(X)					\
  ((X) == frame_pointer_rtx					\
   || (X) == virtual_stack_vars_rtx				\
   || (X) == virtual_incoming_args_rtx				\
   || (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 1)) == CONST_INT \
       && (XEXP (X, 0) == frame_pointer_rtx			\
	   || XEXP (X, 0) == arg_pointer_rtx			\
	   || XEXP (X, 0) == virtual_stack_vars_rtx		\
	   || XEXP (X, 0) == virtual_incoming_args_rtx))	\
   || (X) == stack_pointer_rtx					\
   || (X) == virtual_stack_dynamic_rtx				\
   || (X) == virtual_outgoing_args_rtx				\
   || (GET_CODE (X) == PLUS && GET_CODE (XEXP (X, 1)) == CONST_INT \
       && (XEXP (X, 0) == stack_pointer_rtx			\
	   || XEXP (X, 0) == virtual_stack_dynamic_rtx		\
	   || XEXP (X, 0) == virtual_outgoing_args_rtx)))

static struct table_elt *lookup ();
static void free_element ();

static int insert_regs ();
static void rehash_using_reg ();
static void remove_invalid_refs ();
static int exp_equiv_p ();
int refers_to_p ();
int refers_to_mem_p ();
static void invalidate_from_clobbers ();
static int safe_hash ();
static int canon_hash ();
static rtx fold_rtx ();
static rtx equiv_constant ();
static void record_jump_cond ();
static void note_mem_written ();
static int cse_rtx_addr_varies_p ();
static enum rtx_code find_comparison_args ();
static void cse_insn ();
static void cse_set_around_loop ();

/* Return an estimate of the cost of computing rtx X.
   One use is in cse, to decide which expression to keep in the hash table.
   Another is in rtl generation, to pick the cheapest way to multiply.
   Other uses like the latter are expected in the future.  */

/* Return the right cost to give to an operation
   to make the cost of the corresponding register-to-register instruction
   N times that of a fast register-to-register instruction.  */

#define COSTS_N_INSNS(N) ((N) * 4 - 2)

int
rtx_cost (x, outer_code)
     rtx x;
     enum rtx_code outer_code;
{
  register int i, j;
  register enum rtx_code code;
  register char *fmt;
  register int total;

  if (x == 0)
    return 0;

  /* Compute the default costs of certain things.
     Note that RTX_COSTS can override the defaults.  */

  code = GET_CODE (x);
  switch (code)
    {
    case MULT:
      /* Count multiplication by 2**n as a shift,
	 because if we are considering it, we would output it as a shift.  */
      if (GET_CODE (XEXP (x, 1)) == CONST_INT
	  && exact_log2 (INTVAL (XEXP (x, 1))) >= 0)
	total = 2;
      else
	total = COSTS_N_INSNS (5);
      break;
    case DIV:
    case UDIV:
    case MOD:
    case UMOD:
      total = COSTS_N_INSNS (7);
      break;
    case USE:
      /* Used in loop.c and combine.c as a marker.  */
      total = 0;
      break;
    case ASM_OPERANDS:
      /* We don't want these to be used in substitutions because
	 we have no way of validating the resulting insn.  So assign
	 anything containing an ASM_OPERANDS a very high cost.  */
      total = 1000;
      break;
    default:
      total = 2;
    }

  switch (code)
    {
    case REG:
      return 1;
    case SUBREG:
      /* If we can't tie these modes, make this expensive.  The larger
	 the mode, the more expensive it is.  */
      if (! MODES_TIEABLE_P (GET_MODE (x), GET_MODE (SUBREG_REG (x))))
	return COSTS_N_INSNS (2
			      + GET_MODE_SIZE (GET_MODE (x)) / UNITS_PER_WORD);
      return 2;
#ifdef RTX_COSTS
      RTX_COSTS (x, code, outer_code);
#endif 
      CONST_COSTS (x, code, outer_code);
    }

  /* Sum the costs of the sub-rtx's, plus cost of this operation,
     which is already in total.  */

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    if (fmt[i] == 'e')
      total += rtx_cost (XEXP (x, i), code);
    else if (fmt[i] == 'E')
      for (j = 0; j < XVECLEN (x, i); j++)
	total += rtx_cost (XVECEXP (x, i, j), code);

  return total;
}

/* Clear the hash table and initialize each register with its own quantity,
   for a new basic block.  */

static void
new_basic_block ()
{
  register int i;

  next_qty = max_reg;

  bzero (reg_tick, max_reg * sizeof (int));

  bcopy (all_minus_one, reg_in_table, max_reg * sizeof (int));
  bcopy (consec_ints, reg_qty, max_reg * sizeof (int));
  CLEAR_HARD_REG_SET (hard_regs_in_table);

  /* The per-quantity values used to be initialized here, but it is
     much faster to initialize each as it is made in `make_new_qty'.  */

  for (i = 0; i < NBUCKETS; i++)
    {
      register struct table_elt *this, *next;
      for (this = table[i]; this; this = next)
	{
	  next = this->next_same_hash;
	  free_element (this);
	}
    }

  bzero (table, sizeof table);

  prev_insn = 0;

#ifdef HAVE_cc0
  prev_insn_cc0 = 0;
#endif
}

/* Say that register REG contains a quantity not in any register before
   and initialize that quantity.  */

static void
make_new_qty (reg)
     register int reg;
{
  register int q;

  if (next_qty >= max_qty)
    abort ();

  q = reg_qty[reg] = next_qty++;
  qty_first_reg[q] = reg;
  qty_last_reg[q] = reg;
  qty_const[q] = qty_const_insn[q] = 0;
  qty_comparison_code[q] = UNKNOWN;

  reg_next_eqv[reg] = reg_prev_eqv[reg] = -1;
}

/* Make reg NEW equivalent to reg OLD.
   OLD is not changing; NEW is.  */

static void
make_regs_eqv (new, old)
     register int new, old;
{
  register int lastr, firstr;
  register int q = reg_qty[old];

  /* Nothing should become eqv until it has a "non-invalid" qty number.  */
  if (! REGNO_QTY_VALID_P (old))
    abort ();

  reg_qty[new] = q;
  firstr = qty_first_reg[q];
  lastr = qty_last_reg[q];

  /* Prefer fixed hard registers to anything.  Prefer pseudo regs to other
     hard regs.  Among pseudos, if NEW will live longer than any other reg
     of the same qty, and that is beyond the current basic block,
     make it the new canonical replacement for this qty.  */
  if (! (firstr < FIRST_PSEUDO_REGISTER && FIXED_REGNO_P (firstr))
      /* Certain fixed registers might be of the class NO_REGS.  This means
	 that not only can they not be allocated by the compiler, but
	 they cannot be used in substitutions or canonicalizations
	 either.  */
      && (new >= FIRST_PSEUDO_REGISTER || REGNO_REG_CLASS (new) != NO_REGS)
      && ((new < FIRST_PSEUDO_REGISTER && FIXED_REGNO_P (new))
	  || (new >= FIRST_PSEUDO_REGISTER
	      && (firstr < FIRST_PSEUDO_REGISTER
		  || ((uid_cuid[regno_last_uid[new]] > cse_basic_block_end
		       || (uid_cuid[regno_first_uid[new]]
			   < cse_basic_block_start))
		      && (uid_cuid[regno_last_uid[new]]
			  > uid_cuid[regno_last_uid[firstr]]))))))
    {
      reg_prev_eqv[firstr] = new;
      reg_next_eqv[new] = firstr;
      reg_prev_eqv[new] = -1;
      qty_first_reg[q] = new;
    }
  else
    {
      /* If NEW is a hard reg (known to be non-fixed), insert at end.
	 Otherwise, insert before any non-fixed hard regs that are at the
	 end.  Registers of class NO_REGS cannot be used as an
	 equivalent for anything.  */
      while (lastr < FIRST_PSEUDO_REGISTER && reg_prev_eqv[lastr] >= 0
	     && (REGNO_REG_CLASS (lastr) == NO_REGS || ! FIXED_REGNO_P (lastr))
	     && new >= FIRST_PSEUDO_REGISTER)
	lastr = reg_prev_eqv[lastr];
      reg_next_eqv[new] = reg_next_eqv[lastr];
      if (reg_next_eqv[lastr] >= 0)
	reg_prev_eqv[reg_next_eqv[lastr]] = new;
      else
	qty_last_reg[q] = new;
      reg_next_eqv[lastr] = new;
      reg_prev_eqv[new] = lastr;
    }
}

/* Remove REG from its equivalence class.  */

static void
delete_reg_equiv (reg)
     register int reg;
{
  register int n = reg_next_eqv[reg];
  register int p = reg_prev_eqv[reg];
  register int q = reg_qty[reg];

  /* If invalid, do nothing.  N and P above are undefined in that case.  */
  if (q == reg)
    return;

  if (n != -1)
    reg_prev_eqv[n] = p;
  else
    qty_last_reg[q] = p;
  if (p != -1)
    reg_next_eqv[p] = n;
  else
    qty_first_reg[q] = n;

  reg_qty[reg] = reg;
}

/* Remove any invalid expressions from the hash table
   that refer to any of the registers contained in expression X.

   Make sure that newly inserted references to those registers
   as subexpressions will be considered valid.

   mention_regs is not called when a register itself
   is being stored in the table.

   Return 1 if we have done something that may have changed the hash code
   of X.  */

static int
mention_regs (x)
     rtx x;
{
  register enum rtx_code code;
  register int i, j;
  register char *fmt;
  register int changed = 0;

  if (x == 0)
    return 0;

  code = GET_CODE (x);
  if (code == REG)
    {
      register int regno = REGNO (x);
      register int endregno
	= regno + (regno >= FIRST_PSEUDO_REGISTER ? 1
		   : HARD_REGNO_NREGS (regno, GET_MODE (x)));
      int i;

      for (i = regno; i < endregno; i++)
	{
	  if (reg_in_table[i] >= 0 && reg_in_table[i] != reg_tick[i])
	    remove_invalid_refs (i);

	  reg_in_table[i] = reg_tick[i];
	}

      return 0;
    }

  /* If X is a comparison or a COMPARE and either operand is a register
     that does not have a quantity, give it one.  This is so that a later
     call to record_jump_equiv won't cause X to be assigned a different
     hash code and not found in the table after that call.

     It is not necessary to do this here, since rehash_using_reg can