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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- L A Y O U T --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 2000-2019, Free Software Foundation, Inc. --
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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17 -- for more details. You should have received a copy of the GNU General --
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18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
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19 -- http://www.gnu.org/licenses for a complete copy of the license. --
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20 -- --
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21 -- GNAT was originally developed by the GNAT team at New York University. --
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22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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23 -- --
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24 ------------------------------------------------------------------------------
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25
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26 -- This package does front-end layout of types and objects. The result is
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27 -- to annotate the tree with information on size and alignment of types
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28 -- and objects. How much layout is performed depends on the setting of the
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29 -- target dependent parameter Frontend_Layout.
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30
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31 with Types; use Types;
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32
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33 package Layout is
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34
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35 -- The following procedures are called from Freeze, so all entities
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36 -- for types and objects that get frozen (which should be all such
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37 -- entities which are seen by the back end) will get laid out by one
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38 -- of these two procedures.
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39
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40 procedure Layout_Type (E : Entity_Id);
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41 -- This procedure may set or adjust the fields Esize, RM_Size and
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42 -- Alignment in the non-generic type or subtype entity E. If the
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43 -- Frontend_Layout switch is True, then it is guaranteed that all
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44 -- three fields will be properly set on return. Regardless of the
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45 -- Frontend_Layout value, it is guaranteed that all discrete types
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46 -- will have both Esize and RM_Size fields set on return (since
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47 -- these are static values). Note that Layout_Type is not called
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48 -- for generic types, since these play no part in code generation,
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49 -- and hence representation aspects are irrelevant.
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50
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51 procedure Layout_Object (E : Entity_Id);
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52 -- E is either a variable (E_Variable), a constant (E_Constant),
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53 -- a loop parameter (E_Loop_Parameter), or a formal parameter of
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54 -- a non-generic subprogram (E_In_Parameter, E_In_Out_Parameter,
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55 -- or E_Out_Parameter). This procedure may set or adjust the
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56 -- Esize and Alignment fields of E. If Frontend_Layout is True,
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57 -- then it is guaranteed that both fields will be properly set
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58 -- on return. If the Esize is still unknown in the latter case,
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59 -- it means that the object must be allocated dynamically, since
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60 -- its length is not known at compile time.
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61
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62 -- The following are utility routines, called from various places
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63
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64 procedure Adjust_Esize_Alignment (E : Entity_Id);
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65 -- E is the entity for a type or object. This procedure checks that the
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66 -- size and alignment are compatible, and if not either gives an error
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67 -- message if they cannot be adjusted or else adjusts them appropriately.
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68
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69 procedure Set_Discrete_RM_Size (Def_Id : Entity_Id);
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70 -- Set proper RM_Size for discrete size, this is normally the minimum
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71 -- number of bits to accommodate the range given, except in the case
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72 -- where the subtype statically matches the first subtype, in which
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73 -- case the size must be copied from the first subtype. For generic
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74 -- types, the RM_Size is simply set to zero. This routine also sets
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75 -- the Is_Constrained flag in Def_Id.
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76
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77 procedure Set_Elem_Alignment (E : Entity_Id; Align : Nat := 0);
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78 -- The front end always sets alignments for elementary types by calling
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79 -- this procedure. Note that we have to do this for discrete types (since
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80 -- the Alignment attribute is static), so we might as well do it for all
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81 -- elementary types, as the processing is the same. If Align is nonzero,
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82 -- it is an external alignment setting that we must respect.
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83
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84 end Layout;
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