gcc/double-int.h

   1 /* Operations with long integers.
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it
   7 under the terms of the GNU General Public License as published by the
   8 Free Software Foundation; either version 2, or (at your option) any
   9 later version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT
  12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to the Free
  18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301, USA.  */
  20
  21 #ifndef DOUBLE_INT_H
  22 #define DOUBLE_INT_H
  23
  24 /* A large integer is currently represented as a pair of HOST_WIDE_INTs.
  25    It therefore represents a number with precision of
  26    2 * HOST_BITS_PER_WIDE_INT bits (it is however possible that the
  27    internal representation will change, if numbers with greater precision
  28    are needed, so the users should not rely on it).  The representation does
  29    not contain any information about signedness of the represented value, so
  30    it can be used to represent both signed and unsigned numbers.  For
  31    operations where the results depend on signedness (division, comparisons),
  32    it must be specified separately.  For each such operation, there are three
  33    versions of the function -- double_int_op, that takes an extra UNS argument
  34    giving the signedness of the values, and double_int_sop and double_int_uop
  35    that stand for its specializations for signed and unsigned values.
  36
  37    You may also represent with numbers in smaller precision using double_int.
  38    You however need to use double_int_ext (that fills in the bits of the
  39    number over the prescribed precision with zeros or with the sign bit) before
  40    operations that do not perform arithmetics modulo 2^precision (comparisons,
  41    division), and possibly before storing the results, if you want to keep
  42    them in some canonical form).  In general, the signedness of double_int_ext
  43    should match the signedness of the operation.
  44
  45    ??? The components of double_int differ in signedness mostly for
  46    historical reasons (they replace an older structure used to represent
  47    numbers with precision wigher than HOST_WIDE_INT).  It might be less
  48    confusing to have them both signed or both unsigned.  */
  49
  50 typedef struct
  51 {
  52   unsigned HOST_WIDE_INT low;
  53   HOST_WIDE_INT high;
  54 } double_int;
  55
  56 union tree_node;
  57
  58 /* Constructors and conversions.  */
  59
  60 union tree_node *double_int_to_tree (union tree_node *, double_int);
  61 double_int tree_to_double_int (union tree_node *tree);
  62
  63 /* Constructs double_int from integer CST.  The bits over the precision of
  64    HOST_WIDE_INT are filled with the sign bit.  */
  65
  66 static inline double_int
  67 shwi_to_double_int (HOST_WIDE_INT cst)
  68 {
  69   double_int r;
  70
  71   r.low = (unsigned HOST_WIDE_INT) cst;
  72   r.high = cst < 0 ? -1 : 0;
  73
  74   return r;
  75 }
  76
  77 /* Some useful constants.  */
  78
  79 #define double_int_minus_one (shwi_to_double_int (-1))
  80 #define double_int_zero (shwi_to_double_int (0))
  81 #define double_int_one (shwi_to_double_int (1))
  82 #define double_int_two (shwi_to_double_int (2))
  83 #define double_int_ten (shwi_to_double_int (10))
  84
  85 /* Constructs double_int from unsigned integer CST.  The bits over the
  86    precision of HOST_WIDE_INT are filled with zeros.  */
  87
  88 static inline double_int
  89 uhwi_to_double_int (unsigned HOST_WIDE_INT cst)
  90 {
  91   double_int r;
  92
  93   r.low = cst;
  94   r.high = 0;
  95
  96   return r;
  97 }
  98
  99 /* The following operations perform arithmetics modulo 2^precision,
 100    so you do not need to call double_int_ext between them, even if
 101    you are representing numbers with precision less than
 102    2 * HOST_BITS_PER_WIDE_INT bits.  */
 103
 104 double_int double_int_mul (double_int, double_int);
 105 double_int double_int_add (double_int, double_int);
 106 double_int double_int_neg (double_int);
 107
 108 /* You must ensure that double_int_ext is called on the operands
 109    of the following operations, if the precision of the numbers
 110    is less than 2 * HOST_BITS_PER_WIDE_INT bits.  */
 111 bool double_int_fits_in_hwi_p (double_int, bool);
 112 bool double_int_fits_in_shwi_p (double_int);
 113 bool double_int_fits_in_uhwi_p (double_int);
 114 HOST_WIDE_INT double_int_to_shwi (double_int);
 115 unsigned HOST_WIDE_INT double_int_to_uhwi (double_int);
 116 double_int double_int_div (double_int, double_int, bool, unsigned);
 117 double_int double_int_sdiv (double_int, double_int, unsigned);
 118 double_int double_int_udiv (double_int, double_int, unsigned);
 119 bool double_int_negative_p (double_int);
 120 int double_int_cmp (double_int, double_int, bool);
 121 int double_int_scmp (double_int, double_int);
 122 int double_int_ucmp (double_int, double_int);
 123 void dump_double_int (FILE *, double_int, bool);
 124
 125 /* Zero and sign extension of numbers in smaller precisions.  */
 126
 127 double_int double_int_ext (double_int, unsigned, bool);
 128 double_int double_int_sext (double_int, unsigned);
 129 double_int double_int_zext (double_int, unsigned);
 130
 131 #define ALL_ONES (~((unsigned HOST_WIDE_INT) 0))
 132
 133 /* The operands of the following comparison functions must be processed
 134    with double_int_ext, if their precision is less than
 135    2 * HOST_BITS_PER_WIDE_INT bits.  */
 136
 137 /* Returns true if CST is zero.  */
 138
 139 static inline bool
 140 double_int_zero_p (double_int cst)
 141 {
 142   return cst.low == 0 && cst.high == 0;
 143 }
 144
 145 /* Returns true if CST is one.  */
 146
 147 static inline bool
 148 double_int_one_p (double_int cst)
 149 {
 150   return cst.low == 1 && cst.high == 0;
 151 }
 152
 153 /* Returns true if CST is minus one.  */
 154
 155 static inline bool
 156 double_int_minus_one_p (double_int cst)
 157 {
 158   return (cst.low == ALL_ONES && cst.high == -1);
 159 }
 160
 161 /* Returns true if CST1 == CST2.  */
 162
 163 static inline bool
 164 double_int_equal_p (double_int cst1, double_int cst2)
 165 {
 166   return cst1.low == cst2.low && cst1.high == cst2.high;
 167 }
 168
 169 #endif /* DOUBLE_INT_H */