gcc/ada/cuintp.c

   1 /****************************************************************************
   2  *                                                                          *
   3  *                        GNAT COMPILER COMPONENTS                          *
   4  *                                                                          *
   5  *                               C U I N T P                                *
   6  *                                                                          *
   7  *                          C Implementation File                           *
   8  *                                                                          *
   9  *          Copyright (C) 1992-2005 Free Software Foundation, Inc.          *
  10  *                                                                          *
  11  * GNAT is free software;  you can  redistribute it  and/or modify it under *
  12  * terms of the  GNU General Public License as published  by the Free Soft- *
  13  * ware  Foundation;  either version 2,  or (at your option) any later ver- *
  14  * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
  15  * OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY *
  16  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License *
  17  * for  more details.  You should have  received  a copy of the GNU General *
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  20  * Boston, MA 02110-1301, USA.                                              *
  21  *                                                                          *
  22  * GNAT was originally developed  by the GNAT team at  New York University. *
  23  * Extensive contributions were provided by Ada Core Technologies Inc.      *
  24  *                                                                          *
  25  ****************************************************************************/
  26
  27 /* This file corresponds to the Ada package body Uintp. It was created
  28    manually from the files uintp.ads and uintp.adb. */
  29
  30 #include "config.h"
  31 #include "system.h"
  32 #include "coretypes.h"
  33 #include "tm.h"
  34 #include "tree.h"
  35 #include "ada.h"
  36 #include "types.h"
  37 #include "uintp.h"
  38 #include "atree.h"
  39 #include "elists.h"
  40 #include "nlists.h"
  41 #include "stringt.h"
  42 #include "fe.h"
  43 #include "gigi.h"
  44 #include "ada-tree.h"
  45
  46 /* Universal integers are represented by the Uint type which is an index into
  47    the Uints_Ptr table containing Uint_Entry values.  A Uint_Entry contains an
  48    index and length for getting the "digits" of the universal integer from the
  49    Udigits_Ptr table.
  50
  51    For efficiency, this method is used only for integer values larger than the
  52    constant Uint_Bias.  If a Uint is less than this constant, then it contains
  53    the integer value itself.  The origin of the Uints_Ptr table is adjusted so
  54    that a Uint value of Uint_Bias indexes the first element.
  55
  56    First define a utility function that operates like build_int_cst for
  57    integral types and does a conversion to floating-point for real types.  */
  58
  59 static tree
  60 build_cst_from_int (tree type, HOST_WIDE_INT low)
  61 {
  62   if (TREE_CODE (type) == REAL_TYPE)
  63     return convert (type, build_int_cst (NULL_TREE, low));
  64   else
  65     return force_fit_type (build_int_cst (type, low), false, false, false);
  66 }
  67
  68 /* Similar to UI_To_Int, but return a GCC INTEGER_CST or REAL_CST node,
  69    depending on whether TYPE is an integral or real type.  Overflow is tested
  70    by the constant-folding used to build the node.  TYPE is the GCC type of
  71    the resulting node.  */
  72
  73 tree
  74 UI_To_gnu (Uint Input, tree type)
  75 {
  76   tree gnu_ret;
  77
  78   /* We might have a TYPE with biased representation and be passed an
  79      unbiased value that doesn't fit.  We always use an unbiased type able
  80      to hold any such possible value for intermediate computations, and
  81      then rely on a conversion back to TYPE to perform the bias adjustment
  82      when need be.  */
  83
  84   int biased_type_p
  85     = (TREE_CODE (type) == INTEGER_TYPE
  86        && TYPE_BIASED_REPRESENTATION_P (type));
  87
  88   tree comp_type = biased_type_p ? get_base_type (type) : type;
  89
  90   if (Input <= Uint_Direct_Last)
  91     gnu_ret = build_cst_from_int (comp_type, Input - Uint_Direct_Bias);
  92   else
  93     {
  94       Int Idx = Uints_Ptr[Input].Loc;
  95       Pos Length = Uints_Ptr[Input].Length;
  96       Int First = Udigits_Ptr[Idx];
  97       tree gnu_base;
  98
  99       gcc_assert (Length > 0);
 100
 101       /* The computations we perform below always require a type at least as
 102          large as an integer not to overflow.  REAL types are always fine, but
 103          INTEGER or ENUMERAL types we are handed may be too short.  We use a
 104          base integer type node for the computations in this case and will
 105          convert the final result back to the incoming type later on.  */
 106
 107       if (TREE_CODE (comp_type) != REAL_TYPE
 108           && TYPE_PRECISION (comp_type) < TYPE_PRECISION (integer_type_node))
 109         comp_type = integer_type_node;
 110
 111       gnu_base = build_cst_from_int (comp_type, Base);
 112
 113       gnu_ret = build_cst_from_int (comp_type, First);
 114       if (First < 0)
 115         for (Idx++, Length--; Length; Idx++, Length--)
 116           gnu_ret = fold (build2 (MINUS_EXPR, comp_type,
 117                                   fold (build2 (MULT_EXPR, comp_type,
 118                                                 gnu_ret, gnu_base)),
 119                                   build_cst_from_int (comp_type,
 120                                                       Udigits_Ptr[Idx])));
 121       else
 122         for (Idx++, Length--; Length; Idx++, Length--)
 123           gnu_ret = fold (build2 (PLUS_EXPR, comp_type,
 124                                   fold (build2 (MULT_EXPR, comp_type,
 125                                                 gnu_ret, gnu_base)),
 126                                   build_cst_from_int (comp_type,
 127                                                       Udigits_Ptr[Idx])));
 128     }
 129
 130   gnu_ret = convert (type, gnu_ret);
 131
 132   /* We don't need any NOP_EXPR or NON_LVALUE_EXPR on GNU_RET.  */
 133   while ((TREE_CODE (gnu_ret) == NOP_EXPR
 134           || TREE_CODE (gnu_ret) == NON_LVALUE_EXPR)
 135          && TREE_TYPE (TREE_OPERAND (gnu_ret, 0)) == TREE_TYPE (gnu_ret))
 136     gnu_ret = TREE_OPERAND (gnu_ret, 0);
 137
 138   return gnu_ret;
 139 }