main/gcc/ada/set_targ.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E T _ T A R G                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2013-2014, 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- --
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  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 --
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  18 -- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 --  This package handles setting target dependent parameters. If the -gnatet
  27 --  switch is not set, then these values are taken from the back end (via the
  28 --  routines in Get_Targ, and the enumerate_modes routine in misc.c). If the
  29 --  switch is set, then the values are read from the target.atp file in the
  30 --  current directory (usually written with the Write_Target_Dependent_Values
  31 --  procedure defined in this package).
  32
  33 --  Note that all these values return sizes of C types with corresponding
  34 --  names. This allows GNAT to define the corresponding Ada types to have
  35 --  the same representation. There is one exception: the representation
  36 --  of Wide_Character_Type uses twice the size of a C char, instead of the
  37 --  size of wchar_t, since this corresponds to expected Ada usage.
  38
  39 with Einfo; use Einfo;
  40 with Types; use Types;
  41
  42 package Set_Targ is
  43
  44    -----------------------------
  45    -- Target-Dependent Values --
  46    -----------------------------
  47
  48    --  The following is a table of target dependent values. In normal operation
  49    --  these values are set by calling the appropriate C backend routines that
  50    --  interface to back end routines that determine target characteristics.
  51
  52    --  If the -gnateT switch is used, then any values that are read from the
  53    --  file target.atp in the current directory overwrite values set from the
  54    --  back end. This is used by tools other than the compiler, e.g. to do
  55    --  semantic analysis of programs that will run on some other target than
  56    --  the machine on which the tool is run.
  57
  58    --  Note: fields marked with a question mark are boolean fields, where a
  59    --  value of 0 is False, and a value of 1 is True.
  60
  61    Bits_BE                    : Nat; -- Bits stored big-endian?
  62    Bits_Per_Unit              : Pos; -- Bits in a storage unit
  63    Bits_Per_Word              : Pos; -- Bits in a word
  64    Bytes_BE                   : Nat; -- Bytes stored big-endian?
  65    Char_Size                  : Pos; -- Standard.Character'Size
  66    Double_Float_Alignment     : Nat; -- Alignment of double float
  67    Double_Scalar_Alignment    : Nat; -- Alignment of double length scalar
  68    Double_Size                : Pos; -- Standard.Long_Float'Size
  69    Float_Size                 : Pos; -- Standard.Float'Size
  70    Float_Words_BE             : Nat; -- Float words stored big-endian?
  71    Int_Size                   : Pos; -- Standard.Integer'Size
  72    Long_Double_Size           : Pos; -- Standard.Long_Long_Float'Size
  73    Long_Long_Size             : Pos; -- Standard.Long_Long_Integer'Size
  74    Long_Size                  : Pos; -- Standard.Long_Integer'Size
  75    Maximum_Alignment          : Pos; -- Maximum permitted alignment
  76    Max_Unaligned_Field        : Pos; -- Maximum size for unaligned bit field
  77    Pointer_Size               : Pos; -- System.Address'Size
  78    Short_Enums                : Nat; -- Foreign enums use short size?
  79    Short_Size                 : Pos; -- Standard.Short_Integer'Size
  80    Strict_Alignment           : Nat; -- Strict alignment?
  81    System_Allocator_Alignment : Nat; -- Alignment for malloc calls
  82    Wchar_T_Size               : Pos; -- Interfaces.C.wchar_t'Size
  83    Words_BE                   : Nat; -- Words stored big-endian?
  84
  85    -------------------------------------
  86    -- Registered Floating-Point Types --
  87    -------------------------------------
  88
  89    --  This table contains the list of modes supported by the back-end as
  90    --  provided by the back end routine enumerate_modes in misc.c. Note that
  91    --  we only store floating-point modes (see Register_Float_Type).
  92
  93    type FPT_Mode_Entry is record
  94       NAME      : String_Ptr;     -- Name of mode (no null character at end)
  95       DIGS      : Natural;        -- Digits for floating-point type
  96       FLOAT_REP : Float_Rep_Kind; -- Float representation
  97       PRECISION : Natural;        -- Precision in bits
  98       SIZE      : Natural;        -- Size in bits
  99       ALIGNMENT : Natural;        -- Alignment in bits
 100    end record;
 101
 102    FPT_Mode_Table : array (1 .. 1000) of FPT_Mode_Entry;
 103    Num_FPT_Modes  : Natural := 0;
 104    --  Table containing the supported modes and number of entries
 105
 106    -----------------
 107    -- Subprograms --
 108    -----------------
 109
 110    procedure Write_Target_Dependent_Values;
 111    --  This routine writes the file target.atp in the current directory with
 112    --  the values of the global target parameters as listed above, and as set
 113    --  by prior calls to Initialize/Read_Target_Dependent_Values. The format
 114    --  of the target.atp file is as follows
 115    --
 116    --    First come the values of the variables defined in this spec:
 117    --
 118    --      One line per value
 119    --
 120    --        name  value
 121    --
 122    --      where name is the name of the parameter, spelled out in full,
 123    --      and cased as in the above list, and value is an unsigned decimal
 124    --      integer. Two or more blanks separates the name from the value.
 125    --
 126    --      All the variables must be present, in alphabetical order (i.e. the
 127    --      same order as the declarations in this spec).
 128    --
 129    --   Then there is a blank line to separate the two parts of the file. Then
 130    --   come the lines showing the floating-point types to be registered.
 131    --
 132    --     One line per registered mode
 133    --
 134    --       name  digs float_rep precision alignment
 135    --
 136    --     where name is the string name of the type (which can have single
 137    --     spaces embedded in the name (e.g. long double). The name is followed
 138    --     by at least two blanks. The following fields are as described above
 139    --     for a Mode_Entry (where float_rep is I/V/A for IEEE-754-Binary,
 140    --     Vax_Native, AAMP), fields are separated by at least one blank, and
 141    --     a LF character immediately follows the alignment field.
 142    --
 143    --     ??? We do not write the size for backward compatibility reasons,
 144    --     which means that target.atp will not be a complete description for
 145    --     the very peculiar cases where the size cannot be computed from the
 146    --     precision and the alignment by the formula:
 147    --
 148    --       size := (precision + alignment - 1) / alignment * alignment
 149
 150 end Set_Targ;