File : repinfo.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- R E P I N F O --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1999-2014, 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- --
13 -- ware Foundation; either version 3, 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. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 -- This package contains the routines to handle back annotation of the
33 -- tree to fill in representation information, and also the routine used
34 -- by -gnatR to print this information. This unit is used both in the
35 -- compiler and in ASIS (it is used in ASIS as part of the implementation
36 -- of the data decomposition annex).
37
38 with Types; use Types;
39 with Uintp; use Uintp;
40
41 package Repinfo is
42
43 --------------------------------
44 -- Representation Information --
45 --------------------------------
46
47 -- The representation information of interest here is size and
48 -- component information for arrays and records. For primitive
49 -- types, the front end computes the Esize and RM_Size fields of
50 -- the corresponding entities as constant non-negative integers,
51 -- and the Uint values are stored directly in these fields.
52
53 -- For composite types, there are three cases:
54
55 -- 1. In some cases the front end knows the values statically,
56 -- for example in the case where representation clauses or
57 -- pragmas specify the values.
58
59 -- 2. If Backend_Layout is True, then the backend is responsible
60 -- for layout of all types and objects not laid out by the
61 -- front end. This includes all dynamic values, and also
62 -- static values (e.g. record sizes) when not set by the
63 -- front end.
64
65 -- 3. If Backend_Layout is False, then the front end lays out
66 -- all data, according to target dependent size and alignment
67 -- information, creating dynamic inlinable functions where
68 -- needed in the case of sizes not known till runtime.
69
70 -----------------------------
71 -- Back-Annotation by Gigi --
72 -----------------------------
73
74 -- The following interface is used by gigi if Backend_Layout is True
75
76 -- As part of the processing in gigi, the types are laid out and
77 -- appropriate values computed for the sizes and component positions
78 -- and sizes of records and arrays.
79
80 -- The back-annotation circuit in gigi is responsible for updating the
81 -- relevant fields in the tree to reflect these computations, as follows:
82
83 -- For E_Array_Type entities, the Component_Size field
84
85 -- For all record and array types and subtypes, the Esize field,
86 -- which contains the Size (more accurately the Object_SIze) value
87 -- for the type or subtype.
88
89 -- For E_Component and E_Discriminant entities, the Esize (size
90 -- of component) and Component_Bit_Offset fields. Note that gigi
91 -- does not back annotate Normalized_Position/First_Bit.
92
93 -- There are three cases to consider:
94
95 -- 1. The value is constant. In this case, the back annotation works
96 -- by simply storing the non-negative universal integer value in
97 -- the appropriate field corresponding to this constant size.
98
99 -- 2. The value depends on variables other than discriminants of the
100 -- current record. In this case, the value is not known, even if
101 -- the complete data of the record is available, and gigi marks
102 -- this situation by storing the special value No_Uint.
103
104 -- 3. The value depends on the discriminant values for the current
105 -- record. In this case, gigi back annotates the field with a
106 -- representation of the expression for computing the value in
107 -- terms of the discriminants. A negative Uint value is used to
108 -- represent the value of such an expression, as explained in
109 -- the following section.
110
111 -- Note: the extended back-annotation for the dynamic case is needed only
112 -- for -gnatR3 output, and for proper operation of the ASIS DDA. Since it
113 -- can be expensive to do this back annotation (for discriminated records
114 -- with many variable length arrays), we only do the full back annotation
115 -- in -gnatR3 mode, or ASIS mode. In any other mode, the back-end just sets
116 -- the value to Uint_Minus_1, indicating that the value of the attribute
117 -- depends on discriminant information, but not giving further details.
118
119 -- GCC expressions are represented with a Uint value that is negative.
120 -- See the body of this package for details on the representation used.
121
122 -- One other case in which gigi back annotates GCC expressions is in
123 -- the Present_Expr field of an N_Variant node. This expression which
124 -- will always depend on discriminants, and hence always be represented
125 -- as a negative Uint value, provides an expression which, when evaluated
126 -- with a given set of discriminant values, indicates whether the variant
127 -- is present for that set of values (result is True, i.e. non-zero) or
128 -- not present (result is False, i.e. zero). Again, the full annotation of
129 -- this field is done only in -gnatR3 mode or in ASIS mode, and in other
130 -- modes, the value is set to Uint_Minus_1.
131
132 subtype Node_Ref is Uint;
133 -- Subtype used for negative Uint values used to represent nodes
134
135 subtype Node_Ref_Or_Val is Uint;
136 -- Subtype used for values that can either be a Node_Ref (negative)
137 -- or a value (non-negative)
138
139 type TCode is range 0 .. 28;
140 -- Type used on Ada side to represent DEFTREECODE values defined in
141 -- tree.def. Only a subset of these tree codes can actually appear.
142 -- The names are the names from tree.def in Ada casing.
143
144 -- name code description operands
145
146 Cond_Expr : constant TCode := 1; -- conditional 3
147 Plus_Expr : constant TCode := 2; -- addition 2
148 Minus_Expr : constant TCode := 3; -- subtraction 2
149 Mult_Expr : constant TCode := 4; -- multiplication 2
150 Trunc_Div_Expr : constant TCode := 5; -- truncating division 2
151 Ceil_Div_Expr : constant TCode := 6; -- division rounding up 2
152 Floor_Div_Expr : constant TCode := 7; -- division rounding down 2
153 Trunc_Mod_Expr : constant TCode := 8; -- mod for trunc_div 2
154 Ceil_Mod_Expr : constant TCode := 9; -- mod for ceil_div 2
155 Floor_Mod_Expr : constant TCode := 10; -- mod for floor_div 2
156 Exact_Div_Expr : constant TCode := 11; -- exact div 2
157 Negate_Expr : constant TCode := 12; -- negation 1
158 Min_Expr : constant TCode := 13; -- minimum 2
159 Max_Expr : constant TCode := 14; -- maximum 2
160 Abs_Expr : constant TCode := 15; -- absolute value 1
161 Truth_Andif_Expr : constant TCode := 16; -- Boolean and then 2
162 Truth_Orif_Expr : constant TCode := 17; -- Boolean or else 2
163 Truth_And_Expr : constant TCode := 18; -- Boolean and 2
164 Truth_Or_Expr : constant TCode := 19; -- Boolean or 2
165 Truth_Xor_Expr : constant TCode := 20; -- Boolean xor 2
166 Truth_Not_Expr : constant TCode := 21; -- Boolean not 1
167 Lt_Expr : constant TCode := 22; -- comparison < 2
168 Le_Expr : constant TCode := 23; -- comparison <= 2
169 Gt_Expr : constant TCode := 24; -- comparison > 2
170 Ge_Expr : constant TCode := 25; -- comparison >= 2
171 Eq_Expr : constant TCode := 26; -- comparison = 2
172 Ne_Expr : constant TCode := 27; -- comparison /= 2
173 Bit_And_Expr : constant TCode := 28; -- Binary and 2
174
175 -- The following entry is used to represent a discriminant value in
176 -- the tree. It has a special tree code that does not correspond
177 -- directly to a gcc node. The single operand is the number of the
178 -- discriminant in the record (1 = first discriminant).
179
180 Discrim_Val : constant TCode := 0; -- discriminant value 1
181
182 ------------------------
183 -- The gigi Interface --
184 ------------------------
185
186 -- The following declarations are for use by gigi for back annotation
187
188 function Create_Node
189 (Expr : TCode;
190 Op1 : Node_Ref_Or_Val;
191 Op2 : Node_Ref_Or_Val := No_Uint;
192 Op3 : Node_Ref_Or_Val := No_Uint) return Node_Ref;
193 -- Creates a node using the tree code defined by Expr and from one to three
194 -- operands as required (unused operands set as shown to No_Uint) Note that
195 -- this call can be used to create a discriminant reference by using (Expr
196 -- => Discrim_Val, Op1 => discriminant_number).
197
198 function Create_Discrim_Ref (Discr : Entity_Id) return Node_Ref;
199 -- Creates a reference to the discriminant whose entity is Discr
200
201 --------------------------------------------------------
202 -- Front-End Interface for Dynamic Size/Offset Values --
203 --------------------------------------------------------
204
205 -- If Backend_Layout is False, then the front-end deals with all
206 -- dynamic size and offset fields. There are two cases:
207
208 -- 1. The value can be computed at the time of type freezing, and
209 -- is stored in a run-time constant. In this case, the field
210 -- contains a reference to this entity. In the case of sizes
211 -- the value stored is the size in storage units, since dynamic
212 -- sizes are always a multiple of storage units.
213
214 -- 2. The size/offset depends on the value of discriminants at
215 -- run-time. In this case, the front end builds a function to
216 -- compute the value. This function has a single parameter
217 -- which is the discriminated record object in question. Any
218 -- references to discriminant values are simply references to
219 -- the appropriate discriminant in this single argument, and
220 -- to compute the required size/offset value at run time, the
221 -- code generator simply constructs a call to the function
222 -- with the appropriate argument. The size/offset field in
223 -- this case contains a reference to the function entity.
224 -- Note that as for case 1, if such a function is used to
225 -- return a size, then the size in storage units is returned,
226 -- not the size in bits.
227
228 -- The interface here allows these created entities to be referenced
229 -- using negative Unit values, so that they can be stored in the
230 -- appropriate size and offset fields in the tree.
231
232 -- In the case of components, if the location of the component is static,
233 -- then all four fields (Component_Bit_Offset, Normalized_Position, Esize,
234 -- and Normalized_First_Bit) are set to appropriate values. In the case of
235 -- a non-static component location, Component_Bit_Offset is not used and
236 -- is left set to Unknown. Normalized_Position and Normalized_First_Bit
237 -- are set appropriately.
238
239 subtype SO_Ref is Uint;
240 -- Type used to represent a Uint value that represents a static or
241 -- dynamic size/offset value (non-negative if static, negative if
242 -- the size value is dynamic).
243
244 subtype Dynamic_SO_Ref is Uint;
245 -- Type used to represent a negative Uint value used to store
246 -- a dynamic size/offset value.
247
248 function Is_Dynamic_SO_Ref (U : SO_Ref) return Boolean;
249 pragma Inline (Is_Dynamic_SO_Ref);
250 -- Given a SO_Ref (Uint) value, returns True iff the SO_Ref value
251 -- represents a dynamic Size/Offset value (i.e. it is negative).
252
253 function Is_Static_SO_Ref (U : SO_Ref) return Boolean;
254 pragma Inline (Is_Static_SO_Ref);
255 -- Given a SO_Ref (Uint) value, returns True iff the SO_Ref value
256 -- represents a static Size/Offset value (i.e. it is non-negative).
257
258 function Create_Dynamic_SO_Ref (E : Entity_Id) return Dynamic_SO_Ref;
259 -- Given the Entity_Id for a constant (case 1), the Node_Id for an
260 -- expression (case 2), or the Entity_Id for a function (case 3),
261 -- this function returns a (negative) Uint value that can be used
262 -- to retrieve the entity or expression for later use.
263
264 function Get_Dynamic_SO_Entity (U : Dynamic_SO_Ref) return Entity_Id;
265 -- Retrieve the Node_Id or Entity_Id stored by a previous call to
266 -- Create_Dynamic_SO_Ref. The approach is that the front end makes
267 -- the necessary Create_Dynamic_SO_Ref calls to associate the node
268 -- and entity id values and the back end makes Get_Dynamic_SO_Ref
269 -- calls to retrieve them.
270
271 --------------------
272 -- ASIS_Interface --
273 --------------------
274
275 type Discrim_List is array (Pos range <>) of Uint;
276 -- Type used to represent list of discriminant values
277
278 function Rep_Value
279 (Val : Node_Ref_Or_Val;
280 D : Discrim_List) return Uint;
281 -- Given the contents of a First_Bit_Position or Esize field containing
282 -- a node reference (i.e. a negative Uint value) and D, the list of
283 -- discriminant values, returns the interpreted value of this field.
284 -- For convenience, Rep_Value will take a non-negative Uint value
285 -- as an argument value, and return it unmodified. A No_Uint value is
286 -- also returned unmodified.
287
288 procedure Tree_Read;
289 -- Initializes internal tables from current tree file using the relevant
290 -- Table.Tree_Read routines.
291
292 ------------------------
293 -- Compiler Interface --
294 ------------------------
295
296 procedure List_Rep_Info (Bytes_Big_Endian : Boolean);
297 -- Procedure to list representation information. Bytes_Big_Endian is the
298 -- value from Ttypes (Repinfo cannot have a dependency on Ttypes).
299
300 procedure Tree_Write;
301 -- Writes out internal tables to current tree file using the relevant
302 -- Table.Tree_Write routines.
303
304 --------------------------
305 -- Debugging Procedures --
306 --------------------------
307
308 procedure List_GCC_Expression (U : Node_Ref_Or_Val);
309 -- Prints out given expression in symbolic form. Constants are listed
310 -- in decimal numeric form, Discriminants are listed with a # followed
311 -- by the discriminant number, and operators are output in appropriate
312 -- symbolic form No_Uint displays as two question marks. The output is
313 -- on a single line but has no line return after it. This procedure is
314 -- useful only if operating in backend layout mode.
315
316 procedure lgx (U : Node_Ref_Or_Val);
317 -- In backend layout mode, this is like List_GCC_Expression, but
318 -- includes a line return at the end. If operating in front end
319 -- layout mode, then the name of the entity for the size (either
320 -- a function of a variable) is listed followed by a line return.
321
322 end Repinfo;