This patch changes GET_MODE_PRECISION from an unsigned short
to a poly_uint16.


2017-10-23  Richard Sandiford  <richard.sandif...@linaro.org>
            Alan Hayward  <alan.hayw...@arm.com>
            David Sherwood  <david.sherw...@arm.com>

gcc/
        * machmode.h (mode_precision): Change from unsigned short to
        poly_uint16_pod.
        (mode_to_precision): Return a poly_uint16 rather than an unsigned
        short.
        (GET_MODE_PRECISION): Return a constant if ONLY_FIXED_SIZE_MODES,
        or if measurement_type is not polynomial.
        (HWI_COMPUTABLE_MODE_P): Turn into a function.  Optimize the case
        in which the mode is already known to be a scalar_int_mode.
        * genmodes.c (emit_mode_precision): Change the type of mode_precision
        from unsigned short to poly_uint16_pod.  Use ZERO_COEFFS for the
        initializer.
        * lto-streamer-in.c (lto_input_mode_table): Use bp_unpack_poly_value
        for GET_MODE_PRECISION.
        * lto-streamer-out.c (lto_write_mode_table): Use bp_pack_poly_value
        for GET_MODE_PRECISION.
        * combine.c (update_rsp_from_reg_equal): Treat GET_MODE_PRECISION
        as polynomial.
        (try_combine, find_split_point, combine_simplify_rtx): Likewise.
        (expand_field_assignment, make_extraction): Likewise.
        (make_compound_operation_int, record_dead_and_set_regs_1): Likewise.
        (get_last_value): Likewise.
        * convert.c (convert_to_integer_1): Likewise.
        * cse.c (cse_insn): Likewise.
        * expr.c (expand_expr_real_1): Likewise.
        * lra-constraints.c (simplify_operand_subreg): Likewise.
        * optabs-query.c (can_atomic_load_p): Likewise.
        * optabs.c (expand_atomic_load): Likewise.
        (expand_atomic_store): Likewise.
        * ree.c (combine_reaching_defs): Likewise.
        * rtl.h (partial_subreg_p, paradoxical_subreg_p): Likewise.
        * rtlanal.c (nonzero_bits1, lsb_bitfield_op_p): Likewise.
        * tree.h (type_has_mode_precision_p): Likewise.
        * ubsan.c (instrument_si_overflow): Likewise.

gcc/ada/
        * gcc-interface/misc.c (enumerate_modes): Treat GET_MODE_PRECISION
        as polynomial.

Index: gcc/machmode.h
===================================================================
--- gcc/machmode.h      2017-10-23 17:25:48.620492005 +0100
+++ gcc/machmode.h      2017-10-23 17:25:54.180292158 +0100
@@ -23,7 +23,7 @@ #define HAVE_MACHINE_MODES
 typedef opt_mode<machine_mode> opt_machine_mode;
 
 extern CONST_MODE_SIZE unsigned short mode_size[NUM_MACHINE_MODES];
-extern const unsigned short mode_precision[NUM_MACHINE_MODES];
+extern const poly_uint16_pod mode_precision[NUM_MACHINE_MODES];
 extern const unsigned char mode_inner[NUM_MACHINE_MODES];
 extern const poly_uint16_pod mode_nunits[NUM_MACHINE_MODES];
 extern CONST_MODE_UNIT_SIZE unsigned char mode_unit_size[NUM_MACHINE_MODES];
@@ -535,7 +535,7 @@ mode_to_bits (machine_mode mode)
 
 /* Return the base GET_MODE_PRECISION value for MODE.  */
 
-ALWAYS_INLINE unsigned short
+ALWAYS_INLINE poly_uint16
 mode_to_precision (machine_mode mode)
 {
   return mode_precision[mode];
@@ -604,7 +604,30 @@ #define GET_MODE_BITSIZE(MODE) (mode_to_
 
 /* Get the number of value bits of an object of mode MODE.  */
 
-#define GET_MODE_PRECISION(MODE) (mode_to_precision (MODE))
+#if ONLY_FIXED_SIZE_MODES
+#define GET_MODE_PRECISION(MODE) \
+  ((unsigned short) mode_to_precision (MODE).coeffs[0])
+#else
+ALWAYS_INLINE poly_uint16
+GET_MODE_PRECISION (machine_mode mode)
+{
+  return mode_to_precision (mode);
+}
+
+template<typename T>
+ALWAYS_INLINE typename if_poly<typename T::measurement_type>::t
+GET_MODE_PRECISION (const T &mode)
+{
+  return mode_to_precision (mode);
+}
+
+template<typename T>
+ALWAYS_INLINE typename if_nonpoly<typename T::measurement_type>::t
+GET_MODE_PRECISION (const T &mode)
+{
+  return mode_to_precision (mode).coeffs[0];
+}
+#endif
 
 /* Get the number of integral bits of an object of mode MODE.  */
 extern CONST_MODE_IBIT unsigned char mode_ibit[NUM_MACHINE_MODES];
@@ -863,9 +886,22 @@ #define TRULY_NOOP_TRUNCATION_MODES_P(MO
   (targetm.truly_noop_truncation (GET_MODE_PRECISION (MODE1), \
                                  GET_MODE_PRECISION (MODE2)))
 
-#define HWI_COMPUTABLE_MODE_P(MODE) \
-  (SCALAR_INT_MODE_P (MODE) \
-   && GET_MODE_PRECISION (MODE) <= HOST_BITS_PER_WIDE_INT)
+/* Return true if MODE is a scalar integer mode that fits in a
+   HOST_WIDE_INT.  */
+
+inline bool
+HWI_COMPUTABLE_MODE_P (machine_mode mode)
+{
+  machine_mode mme = mode;
+  return (SCALAR_INT_MODE_P (mme)
+         && mode_to_precision (mme).coeffs[0] <= HOST_BITS_PER_WIDE_INT);
+}
+
+inline bool
+HWI_COMPUTABLE_MODE_P (scalar_int_mode mode)
+{
+  return GET_MODE_PRECISION (mode) <= HOST_BITS_PER_WIDE_INT;
+}
 
 struct int_n_data_t {
   /* These parts are initailized by genmodes output */
Index: gcc/genmodes.c
===================================================================
--- gcc/genmodes.c      2017-10-23 17:25:48.618492077 +0100
+++ gcc/genmodes.c      2017-10-23 17:25:54.178292230 +0100
@@ -1358,13 +1358,14 @@ emit_mode_precision (void)
   int c;
   struct mode_data *m;
 
-  print_decl ("unsigned short", "mode_precision", "NUM_MACHINE_MODES");
+  print_decl ("poly_uint16_pod", "mode_precision", "NUM_MACHINE_MODES");
 
   for_all_modes (c, m)
     if (m->precision != (unsigned int)-1)
-      tagged_printf ("%u", m->precision, m->name);
+      tagged_printf ("{ %u" ZERO_COEFFS " }", m->precision, m->name);
     else
-      tagged_printf ("%u*BITS_PER_UNIT", m->bytesize, m->name);
+      tagged_printf ("{ %u * BITS_PER_UNIT" ZERO_COEFFS " }",
+                    m->bytesize, m->name);
 
   print_closer ();
 }
Index: gcc/lto-streamer-in.c
===================================================================
--- gcc/lto-streamer-in.c       2017-10-23 17:25:48.619492041 +0100
+++ gcc/lto-streamer-in.c       2017-10-23 17:25:54.179292194 +0100
@@ -1605,7 +1605,7 @@ lto_input_mode_table (struct lto_file_de
       enum mode_class mclass
        = bp_unpack_enum (&bp, mode_class, MAX_MODE_CLASS);
       unsigned int size = bp_unpack_value (&bp, 8);
-      unsigned int prec = bp_unpack_value (&bp, 16);
+      poly_uint16 prec = bp_unpack_poly_value (&bp, 16);
       machine_mode inner = (machine_mode) bp_unpack_value (&bp, 8);
       poly_uint16 nunits = bp_unpack_poly_value (&bp, 16);
       unsigned int ibit = 0, fbit = 0;
@@ -1639,7 +1639,7 @@ lto_input_mode_table (struct lto_file_de
                  : mr = GET_MODE_WIDER_MODE (mr).else_void ())
          if (GET_MODE_CLASS (mr) != mclass
              || GET_MODE_SIZE (mr) != size
-             || GET_MODE_PRECISION (mr) != prec
+             || may_ne (GET_MODE_PRECISION (mr), prec)
              || (inner == m
                  ? GET_MODE_INNER (mr) != mr
                  : GET_MODE_INNER (mr) != table[(int) inner])
Index: gcc/lto-streamer-out.c
===================================================================
--- gcc/lto-streamer-out.c      2017-10-23 17:25:48.620492005 +0100
+++ gcc/lto-streamer-out.c      2017-10-23 17:25:54.180292158 +0100
@@ -2773,7 +2773,7 @@ lto_write_mode_table (void)
          bp_pack_value (&bp, m, 8);
          bp_pack_enum (&bp, mode_class, MAX_MODE_CLASS, GET_MODE_CLASS (m));
          bp_pack_value (&bp, GET_MODE_SIZE (m), 8);
-         bp_pack_value (&bp, GET_MODE_PRECISION (m), 16);
+         bp_pack_poly_value (&bp, GET_MODE_PRECISION (m), 16);
          bp_pack_value (&bp, GET_MODE_INNER (m), 8);
          bp_pack_poly_value (&bp, GET_MODE_NUNITS (m), 16);
          switch (GET_MODE_CLASS (m))
Index: gcc/combine.c
===================================================================
--- gcc/combine.c       2017-10-23 17:25:30.702136080 +0100
+++ gcc/combine.c       2017-10-23 17:25:54.176292301 +0100
@@ -1703,7 +1703,7 @@ update_rsp_from_reg_equal (reg_stat_type
   if (rsp->sign_bit_copies != 1)
     {
       num = num_sign_bit_copies (SET_SRC (set), GET_MODE (x));
-      if (reg_equal && num != GET_MODE_PRECISION (GET_MODE (x)))
+      if (reg_equal && may_ne (num, GET_MODE_PRECISION (GET_MODE (x))))
        {
          unsigned int numeq = num_sign_bit_copies (reg_equal, GET_MODE (x));
          if (num == 0 || numeq > num)
@@ -3938,16 +3938,20 @@ try_combine (rtx_insn *i3, rtx_insn *i2,
           && ! (temp_expr = SET_DEST (XVECEXP (newpat, 0, 1)),
                 (REG_P (temp_expr)
                  && reg_stat[REGNO (temp_expr)].nonzero_bits != 0
-                 && GET_MODE_PRECISION (GET_MODE (temp_expr)) < BITS_PER_WORD
-                 && GET_MODE_PRECISION (GET_MODE (temp_expr)) < 
HOST_BITS_PER_INT
+                 && must_lt (GET_MODE_PRECISION (GET_MODE (temp_expr)),
+                             BITS_PER_WORD)
+                 && must_lt (GET_MODE_PRECISION (GET_MODE (temp_expr)),
+                             HOST_BITS_PER_INT)
                  && (reg_stat[REGNO (temp_expr)].nonzero_bits
                      != GET_MODE_MASK (word_mode))))
           && ! (GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) == SUBREG
                 && (temp_expr = SUBREG_REG (SET_DEST (XVECEXP (newpat, 0, 1))),
                     (REG_P (temp_expr)
                      && reg_stat[REGNO (temp_expr)].nonzero_bits != 0
-                     && GET_MODE_PRECISION (GET_MODE (temp_expr)) < 
BITS_PER_WORD
-                     && GET_MODE_PRECISION (GET_MODE (temp_expr)) < 
HOST_BITS_PER_INT
+                     && must_lt (GET_MODE_PRECISION (GET_MODE (temp_expr)),
+                                 BITS_PER_WORD)
+                     && must_lt (GET_MODE_PRECISION (GET_MODE (temp_expr)),
+                                 HOST_BITS_PER_INT)
                      && (reg_stat[REGNO (temp_expr)].nonzero_bits
                          != GET_MODE_MASK (word_mode)))))
           && ! reg_overlap_mentioned_p (SET_DEST (XVECEXP (newpat, 0, 1)),
@@ -5115,8 +5119,9 @@ find_split_point (rtx *loc, rtx_insn *in
          break;
        }
 
-      if (len && pos >= 0
-         && pos + len <= GET_MODE_PRECISION (GET_MODE (inner))
+      if (len
+         && known_subrange_p (pos, len,
+                              0, GET_MODE_PRECISION (GET_MODE (inner)))
          && is_a <scalar_int_mode> (GET_MODE (SET_SRC (x)), &mode))
        {
          /* For unsigned, we have a choice of a shift followed by an
@@ -5982,8 +5987,9 @@ combine_simplify_rtx (rtx x, machine_mod
               && (UINTVAL (XEXP (XEXP (XEXP (x, 0), 0), 1))
                   == (HOST_WIDE_INT_1U << (i + 1)) - 1))
              || (GET_CODE (XEXP (XEXP (x, 0), 0)) == ZERO_EXTEND
-                 && (GET_MODE_PRECISION (GET_MODE (XEXP (XEXP (XEXP (x, 0), 
0), 0)))
-                     == (unsigned int) i + 1))))
+                 && must_eq ((GET_MODE_PRECISION
+                              (GET_MODE (XEXP (XEXP (XEXP (x, 0), 0), 0)))),
+                             (unsigned int) i + 1))))
        return simplify_shift_const
          (NULL_RTX, ASHIFTRT, int_mode,
           simplify_shift_const (NULL_RTX, ASHIFT, int_mode,
@@ -7314,7 +7320,7 @@ expand_field_assignment (const_rtx x)
 {
   rtx inner;
   rtx pos;                     /* Always counts from low bit.  */
-  int len;
+  int len, inner_len;
   rtx mask, cleared, masked;
   scalar_int_mode compute_mode;
 
@@ -7324,8 +7330,10 @@ expand_field_assignment (const_rtx x)
       if (GET_CODE (SET_DEST (x)) == STRICT_LOW_PART
          && GET_CODE (XEXP (SET_DEST (x), 0)) == SUBREG)
        {
+         rtx x0 = XEXP (SET_DEST (x), 0);
+         if (!GET_MODE_PRECISION (GET_MODE (x0)).is_constant (&len))
+           break;
          inner = SUBREG_REG (XEXP (SET_DEST (x), 0));
-         len = GET_MODE_PRECISION (GET_MODE (XEXP (SET_DEST (x), 0)));
          pos = gen_int_mode (subreg_lsb (XEXP (SET_DEST (x), 0)),
                              MAX_MODE_INT);
        }
@@ -7333,33 +7341,30 @@ expand_field_assignment (const_rtx x)
               && CONST_INT_P (XEXP (SET_DEST (x), 1)))
        {
          inner = XEXP (SET_DEST (x), 0);
+         if (!GET_MODE_PRECISION (GET_MODE (inner)).is_constant (&inner_len))
+           break;
+
          len = INTVAL (XEXP (SET_DEST (x), 1));
          pos = XEXP (SET_DEST (x), 2);
 
          /* A constant position should stay within the width of INNER.  */
-         if (CONST_INT_P (pos)
-             && INTVAL (pos) + len > GET_MODE_PRECISION (GET_MODE (inner)))
+         if (CONST_INT_P (pos) && INTVAL (pos) + len > inner_len)
            break;
 
          if (BITS_BIG_ENDIAN)
            {
              if (CONST_INT_P (pos))
-               pos = GEN_INT (GET_MODE_PRECISION (GET_MODE (inner)) - len
-                              - INTVAL (pos));
+               pos = GEN_INT (inner_len - len - INTVAL (pos));
              else if (GET_CODE (pos) == MINUS
                       && CONST_INT_P (XEXP (pos, 1))
-                      && (INTVAL (XEXP (pos, 1))
-                          == GET_MODE_PRECISION (GET_MODE (inner)) - len))
+                      && INTVAL (XEXP (pos, 1)) == inner_len - len)
                /* If position is ADJUST - X, new position is X.  */
                pos = XEXP (pos, 0);
              else
-               {
-                 HOST_WIDE_INT prec = GET_MODE_PRECISION (GET_MODE (inner));
-                 pos = simplify_gen_binary (MINUS, GET_MODE (pos),
-                                            gen_int_mode (prec - len,
-                                                          GET_MODE (pos)),
-                                            pos);
-               }
+               pos = simplify_gen_binary (MINUS, GET_MODE (pos),
+                                          gen_int_mode (inner_len - len,
+                                                        GET_MODE (pos)),
+                                          pos);
            }
        }
 
@@ -7479,7 +7484,7 @@ make_extraction (machine_mode mode, rtx
             bits outside of is_mode, don't look through
             non-paradoxical SUBREGs.  See PR82192.  */
          || (pos_rtx == NULL_RTX
-             && pos + len <= GET_MODE_PRECISION (is_mode))))
+             && must_le (pos + len, GET_MODE_PRECISION (is_mode)))))
     {
       /* If going from (subreg:SI (mem:QI ...)) to (mem:QI ...),
         consider just the QI as the memory to extract from.
@@ -7510,7 +7515,7 @@ make_extraction (machine_mode mode, rtx
              bits outside of is_mode, don't look through
              TRUNCATE.  See PR82192.  */
           && pos_rtx == NULL_RTX
-          && pos + len <= GET_MODE_PRECISION (is_mode))
+          && must_le (pos + len, GET_MODE_PRECISION (is_mode)))
     inner = XEXP (inner, 0);
 
   inner_mode = GET_MODE (inner);
@@ -7557,11 +7562,12 @@ make_extraction (machine_mode mode, rtx
 
       if (MEM_P (inner))
        {
-         HOST_WIDE_INT offset;
+         poly_int64 offset;
 
          /* POS counts from lsb, but make OFFSET count in memory order.  */
          if (BYTES_BIG_ENDIAN)
-           offset = (GET_MODE_PRECISION (is_mode) - len - pos) / BITS_PER_UNIT;
+           offset = bits_to_bytes_round_down (GET_MODE_PRECISION (is_mode)
+                                              - len - pos);
          else
            offset = pos / BITS_PER_UNIT;
 
@@ -7653,7 +7659,7 @@ make_extraction (machine_mode mode, rtx
      other cases, we would only be going outside our object in cases when
      an original shift would have been undefined.  */
   if (MEM_P (inner)
-      && ((pos_rtx == 0 && pos + len > GET_MODE_PRECISION (is_mode))
+      && ((pos_rtx == 0 && may_gt (pos + len, GET_MODE_PRECISION (is_mode)))
          || (pos_rtx != 0 && len != 1)))
     return 0;
 
@@ -8132,8 +8138,10 @@ make_compound_operation_int (scalar_int_
 
          sub = XEXP (XEXP (x, 0), 0);
          machine_mode sub_mode = GET_MODE (sub);
+         int sub_width;
          if ((REG_P (sub) || MEM_P (sub))
-             && GET_MODE_PRECISION (sub_mode) < mode_width)
+             && GET_MODE_PRECISION (sub_mode).is_constant (&sub_width)
+             && sub_width < mode_width)
            {
              unsigned HOST_WIDE_INT mode_mask = GET_MODE_MASK (sub_mode);
              unsigned HOST_WIDE_INT mask;
@@ -8143,8 +8151,7 @@ make_compound_operation_int (scalar_int_
              if ((mask & mode_mask) == mode_mask)
                {
                  new_rtx = make_compound_operation (sub, next_code);
-                 new_rtx = make_extraction (mode, new_rtx, 0, 0,
-                                            GET_MODE_PRECISION (sub_mode),
+                 new_rtx = make_extraction (mode, new_rtx, 0, 0, sub_width,
                                             1, 0, in_code == COMPARE);
                }
            }
@@ -13215,7 +13222,7 @@ record_dead_and_set_regs_1 (rtx dest, co
       else if (GET_CODE (setter) == SET
               && GET_CODE (SET_DEST (setter)) == SUBREG
               && SUBREG_REG (SET_DEST (setter)) == dest
-              && GET_MODE_PRECISION (GET_MODE (dest)) <= BITS_PER_WORD
+              && must_le (GET_MODE_PRECISION (GET_MODE (dest)), BITS_PER_WORD)
               && subreg_lowpart_p (SET_DEST (setter)))
        record_value_for_reg (dest, record_dead_insn,
                              gen_lowpart (GET_MODE (dest),
@@ -13617,8 +13624,8 @@ get_last_value (const_rtx x)
 
   /* If fewer bits were set than what we are asked for now, we cannot use
      the value.  */
-  if (GET_MODE_PRECISION (rsp->last_set_mode)
-      < GET_MODE_PRECISION (GET_MODE (x)))
+  if (may_lt (GET_MODE_PRECISION (rsp->last_set_mode),
+             GET_MODE_PRECISION (GET_MODE (x))))
     return 0;
 
   /* If the value has all its registers valid, return it.  */
Index: gcc/convert.c
===================================================================
--- gcc/convert.c       2017-09-15 14:47:33.181331910 +0100
+++ gcc/convert.c       2017-10-23 17:25:54.176292301 +0100
@@ -731,7 +731,7 @@ convert_to_integer_1 (tree type, tree ex
         type corresponding to its mode, then do a nop conversion
         to TYPE.  */
       else if (TREE_CODE (type) == ENUMERAL_TYPE
-              || outprec != GET_MODE_PRECISION (TYPE_MODE (type)))
+              || may_ne (outprec, GET_MODE_PRECISION (TYPE_MODE (type))))
        {
          expr = convert (lang_hooks.types.type_for_mode
                          (TYPE_MODE (type), TYPE_UNSIGNED (type)), expr);
Index: gcc/cse.c
===================================================================
--- gcc/cse.c   2017-10-23 17:16:50.359529762 +0100
+++ gcc/cse.c   2017-10-23 17:25:54.177292265 +0100
@@ -5231,8 +5231,9 @@ cse_insn (rtx_insn *insn)
              && CONST_INT_P (XEXP (SET_DEST (sets[i].rtl), 1))
              && CONST_INT_P (XEXP (SET_DEST (sets[i].rtl), 2))
              && REG_P (XEXP (SET_DEST (sets[i].rtl), 0))
-             && (GET_MODE_PRECISION (GET_MODE (SET_DEST (sets[i].rtl)))
-                 >= INTVAL (XEXP (SET_DEST (sets[i].rtl), 1)))
+             && (must_ge
+                 (GET_MODE_PRECISION (GET_MODE (SET_DEST (sets[i].rtl))),
+                  INTVAL (XEXP (SET_DEST (sets[i].rtl), 1))))
              && ((unsigned) INTVAL (XEXP (SET_DEST (sets[i].rtl), 1))
                  + (unsigned) INTVAL (XEXP (SET_DEST (sets[i].rtl), 2))
                  <= HOST_BITS_PER_WIDE_INT))
Index: gcc/expr.c
===================================================================
--- gcc/expr.c  2017-10-23 17:25:51.740379860 +0100
+++ gcc/expr.c  2017-10-23 17:25:54.178292230 +0100
@@ -11034,9 +11034,10 @@ expand_expr_real_1 (tree exp, rtx target
        ;
       /* If neither mode is BLKmode, and both modes are the same size
         then we can use gen_lowpart.  */
-      else if (mode != BLKmode && GET_MODE (op0) != BLKmode
-              && (GET_MODE_PRECISION (mode)
-                  == GET_MODE_PRECISION (GET_MODE (op0)))
+      else if (mode != BLKmode
+              && GET_MODE (op0) != BLKmode
+              && must_eq (GET_MODE_PRECISION (mode),
+                          GET_MODE_PRECISION (GET_MODE (op0)))
               && !COMPLEX_MODE_P (GET_MODE (op0)))
        {
          if (GET_CODE (op0) == SUBREG)
Index: gcc/lra-constraints.c
===================================================================
--- gcc/lra-constraints.c       2017-10-23 17:25:42.597708494 +0100
+++ gcc/lra-constraints.c       2017-10-23 17:25:54.179292194 +0100
@@ -1555,7 +1555,8 @@ simplify_operand_subreg (int nop, machin
             missing important data from memory when the inner is wider than
             outer.  This rule only applies to modes that are no wider than
             a word.  */
-         if (!(GET_MODE_PRECISION (mode) != GET_MODE_PRECISION (innermode)
+         if (!(may_ne (GET_MODE_PRECISION (mode),
+                       GET_MODE_PRECISION (innermode))
                && GET_MODE_SIZE (mode) <= UNITS_PER_WORD
                && GET_MODE_SIZE (innermode) <= UNITS_PER_WORD
                && WORD_REGISTER_OPERATIONS)
Index: gcc/optabs-query.c
===================================================================
--- gcc/optabs-query.c  2017-10-23 17:25:48.620492005 +0100
+++ gcc/optabs-query.c  2017-10-23 17:25:54.180292158 +0100
@@ -592,7 +592,7 @@ can_atomic_load_p (machine_mode mode)
   /* If the size of the object is greater than word size on this target,
      then we assume that a load will not be atomic.  Also see
      expand_atomic_load.  */
-  return GET_MODE_PRECISION (mode) <= BITS_PER_WORD;
+  return must_le (GET_MODE_PRECISION (mode), BITS_PER_WORD);
 }
 
 /* Determine whether "1 << x" is relatively cheap in word_mode.  */
Index: gcc/optabs.c
===================================================================
--- gcc/optabs.c        2017-10-23 17:25:48.621491969 +0100
+++ gcc/optabs.c        2017-10-23 17:25:54.181292122 +0100
@@ -6416,7 +6416,7 @@ expand_atomic_load (rtx target, rtx mem,
      emulate a load with a compare-and-swap operation, but the store that
      doing this could result in would be incorrect if this is a volatile
      atomic load or targetting read-only-mapped memory.  */
-  if (GET_MODE_PRECISION (mode) > BITS_PER_WORD)
+  if (may_gt (GET_MODE_PRECISION (mode), BITS_PER_WORD))
     /* If there is no atomic load, leave the library call.  */
     return NULL_RTX;
 
@@ -6490,7 +6490,7 @@ expand_atomic_store (rtx mem, rtx val, e
 
   /* If the size of the object is greater than word size on this target,
      a default store will not be atomic.  */
-  if (GET_MODE_PRECISION (mode) > BITS_PER_WORD)
+  if (may_gt (GET_MODE_PRECISION (mode), BITS_PER_WORD))
     {
       /* If loads are atomic or we are called to provide a __sync builtin,
         we can try a atomic_exchange and throw away the result.  Otherwise,
Index: gcc/ree.c
===================================================================
--- gcc/ree.c   2017-10-23 11:41:25.865934266 +0100
+++ gcc/ree.c   2017-10-23 17:25:54.181292122 +0100
@@ -860,9 +860,9 @@ combine_reaching_defs (ext_cand *cand, c
         as destination register will not affect its reaching uses, which may
         read its value in a larger mode because DEF_INSN implicitly sets it
         in word mode.  */
-      const unsigned int prec
+      poly_int64 prec
        = GET_MODE_PRECISION (GET_MODE (SET_DEST (*dest_sub_rtx)));
-      if (WORD_REGISTER_OPERATIONS && prec < BITS_PER_WORD)
+      if (WORD_REGISTER_OPERATIONS && must_lt (prec, BITS_PER_WORD))
        {
          struct df_link *uses = get_uses (def_insn, src_reg);
          if (!uses)
Index: gcc/rtl.h
===================================================================
--- gcc/rtl.h   2017-10-23 17:18:57.862160702 +0100
+++ gcc/rtl.h   2017-10-23 17:25:54.182292086 +0100
@@ -3033,7 +3033,12 @@ extern poly_uint64 subreg_size_lowpart_o
 inline bool
 partial_subreg_p (machine_mode outermode, machine_mode innermode)
 {
-  return GET_MODE_PRECISION (outermode) < GET_MODE_PRECISION (innermode);
+  /* Modes involved in a subreg must be ordered.  In particular, we must
+     always know at compile time whether the subreg is paradoxical.  */
+  poly_int64 outer_prec = GET_MODE_PRECISION (outermode);
+  poly_int64 inner_prec = GET_MODE_PRECISION (innermode);
+  gcc_checking_assert (ordered_p (outer_prec, inner_prec));
+  return may_lt (outer_prec, inner_prec);
 }
 
 /* Likewise return true if X is a subreg that is smaller than the inner
@@ -3054,7 +3059,12 @@ partial_subreg_p (const_rtx x)
 inline bool
 paradoxical_subreg_p (machine_mode outermode, machine_mode innermode)
 {
-  return GET_MODE_PRECISION (outermode) > GET_MODE_PRECISION (innermode);
+  /* Modes involved in a subreg must be ordered.  In particular, we must
+     always know at compile time whether the subreg is paradoxical.  */
+  poly_int64 outer_prec = GET_MODE_PRECISION (outermode);
+  poly_int64 inner_prec = GET_MODE_PRECISION (innermode);
+  gcc_checking_assert (ordered_p (outer_prec, inner_prec));
+  return may_gt (outer_prec, inner_prec);
 }
 
 /* Return true if X is a paradoxical subreg, false otherwise.  */
Index: gcc/rtlanal.c
===================================================================
--- gcc/rtlanal.c       2017-10-23 17:25:48.622491933 +0100
+++ gcc/rtlanal.c       2017-10-23 17:25:54.182292086 +0100
@@ -4431,6 +4431,7 @@ nonzero_bits1 (const_rtx x, scalar_int_m
   unsigned HOST_WIDE_INT inner_nz;
   enum rtx_code code;
   machine_mode inner_mode;
+  unsigned int inner_width;
   scalar_int_mode xmode;
 
   unsigned int mode_width = GET_MODE_PRECISION (mode);
@@ -4735,8 +4736,9 @@ nonzero_bits1 (const_rtx x, scalar_int_m
         machines, we can compute this from which bits of the inner
         object might be nonzero.  */
       inner_mode = GET_MODE (SUBREG_REG (x));
-      if (GET_MODE_PRECISION (inner_mode) <= BITS_PER_WORD
-         && GET_MODE_PRECISION (inner_mode) <= HOST_BITS_PER_WIDE_INT)
+      if (GET_MODE_PRECISION (inner_mode).is_constant (&inner_width)
+         && inner_width <= BITS_PER_WORD
+         && inner_width <= HOST_BITS_PER_WIDE_INT)
        {
          nonzero &= cached_nonzero_bits (SUBREG_REG (x), mode,
                                          known_x, known_mode, known_ret);
@@ -4752,8 +4754,9 @@ nonzero_bits1 (const_rtx x, scalar_int_m
                   ? val_signbit_known_set_p (inner_mode, nonzero)
                   : extend_op != ZERO_EXTEND)
               || (!MEM_P (SUBREG_REG (x)) && !REG_P (SUBREG_REG (x))))
-             && xmode_width > GET_MODE_PRECISION (inner_mode))
-           nonzero |= (GET_MODE_MASK (xmode) & ~GET_MODE_MASK (inner_mode));
+             && xmode_width > inner_width)
+           nonzero
+             |= (GET_MODE_MASK (GET_MODE (x)) & ~GET_MODE_MASK (inner_mode));
        }
       break;
 
@@ -6068,8 +6071,9 @@ lsb_bitfield_op_p (rtx x)
       machine_mode mode = GET_MODE (XEXP (x, 0));
       HOST_WIDE_INT len = INTVAL (XEXP (x, 1));
       HOST_WIDE_INT pos = INTVAL (XEXP (x, 2));
+      poly_int64 remaining_bits = GET_MODE_PRECISION (mode) - len;
 
-      return (pos == (BITS_BIG_ENDIAN ? GET_MODE_PRECISION (mode) - len : 0));
+      return must_eq (pos, BITS_BIG_ENDIAN ? remaining_bits : 0);
     }
   return false;
 }
Index: gcc/tree.h
===================================================================
--- gcc/tree.h  2017-10-23 17:25:51.773378674 +0100
+++ gcc/tree.h  2017-10-23 17:25:54.183292050 +0100
@@ -5773,7 +5773,7 @@ struct builtin_structptr_type
 inline bool
 type_has_mode_precision_p (const_tree t)
 {
-  return TYPE_PRECISION (t) == GET_MODE_PRECISION (TYPE_MODE (t));
+  return must_eq (TYPE_PRECISION (t), GET_MODE_PRECISION (TYPE_MODE (t)));
 }
 
 #endif  /* GCC_TREE_H  */
Index: gcc/ubsan.c
===================================================================
--- gcc/ubsan.c 2017-10-23 17:18:47.669056745 +0100
+++ gcc/ubsan.c 2017-10-23 17:25:54.183292050 +0100
@@ -1583,7 +1583,8 @@ instrument_si_overflow (gimple_stmt_iter
      Also punt on bit-fields.  */
   if (!INTEGRAL_TYPE_P (lhsinner)
       || TYPE_OVERFLOW_WRAPS (lhsinner)
-      || GET_MODE_BITSIZE (TYPE_MODE (lhsinner)) != TYPE_PRECISION (lhsinner))
+      || may_ne (GET_MODE_BITSIZE (TYPE_MODE (lhsinner)),
+                TYPE_PRECISION (lhsinner)))
     return;
 
   switch (code)
Index: gcc/ada/gcc-interface/misc.c
===================================================================
--- gcc/ada/gcc-interface/misc.c        2017-10-23 17:25:48.617492113 +0100
+++ gcc/ada/gcc-interface/misc.c        2017-10-23 17:25:54.174292373 +0100
@@ -1298,11 +1298,13 @@ enumerate_modes (void (*f) (const char *
          }
 
       /* If no predefined C types were found, register the mode itself.  */
-      int nunits;
-      if (!skip_p && GET_MODE_NUNITS (i).is_constant (&nunits))
+      int nunits, precision;
+      if (!skip_p
+         && GET_MODE_NUNITS (i).is_constant (&nunits)
+         && GET_MODE_PRECISION (i).is_constant (&precision))
        f (GET_MODE_NAME (i), digs, complex_p,
           vector_p ? nunits : 0, float_rep,
-          GET_MODE_PRECISION (i), GET_MODE_BITSIZE (i),
+          precision, GET_MODE_BITSIZE (i),
           GET_MODE_ALIGNMENT (i));
     }
 }

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