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) 1999-2013, 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-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 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 38with Types; use Types; 39with Uintp; use Uintp; 40 41package 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 (yet ???) 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 -- GCC expressions are represented with a Uint value that is negative. 112 -- See the body of this package for details on the representation used. 113 114 -- One other case in which gigi back annotates GCC expressions is in 115 -- the Present_Expr field of an N_Variant node. This expression which 116 -- will always depend on discriminants, and hence always be represented 117 -- as a negative Uint value, provides an expression which, when evaluated 118 -- with a given set of discriminant values, indicates whether the variant 119 -- is present for that set of values (result is True, i.e. non-zero) or 120 -- not present (result is False, i.e. zero). 121 122 subtype Node_Ref is Uint; 123 -- Subtype used for negative Uint values used to represent nodes 124 125 subtype Node_Ref_Or_Val is Uint; 126 -- Subtype used for values that can either be a Node_Ref (negative) 127 -- or a value (non-negative) 128 129 type TCode is range 0 .. 28; 130 -- Type used on Ada side to represent DEFTREECODE values defined in 131 -- tree.def. Only a subset of these tree codes can actually appear. 132 -- The names are the names from tree.def in Ada casing. 133 134 -- name code description operands 135 136 Cond_Expr : constant TCode := 1; -- conditional 3 137 Plus_Expr : constant TCode := 2; -- addition 2 138 Minus_Expr : constant TCode := 3; -- subtraction 2 139 Mult_Expr : constant TCode := 4; -- multiplication 2 140 Trunc_Div_Expr : constant TCode := 5; -- truncating division 2 141 Ceil_Div_Expr : constant TCode := 6; -- division rounding up 2 142 Floor_Div_Expr : constant TCode := 7; -- division rounding down 2 143 Trunc_Mod_Expr : constant TCode := 8; -- mod for trunc_div 2 144 Ceil_Mod_Expr : constant TCode := 9; -- mod for ceil_div 2 145 Floor_Mod_Expr : constant TCode := 10; -- mod for floor_div 2 146 Exact_Div_Expr : constant TCode := 11; -- exact div 2 147 Negate_Expr : constant TCode := 12; -- negation 1 148 Min_Expr : constant TCode := 13; -- minimum 2 149 Max_Expr : constant TCode := 14; -- maximum 2 150 Abs_Expr : constant TCode := 15; -- absolute value 1 151 Truth_Andif_Expr : constant TCode := 16; -- Boolean and then 2 152 Truth_Orif_Expr : constant TCode := 17; -- Boolean or else 2 153 Truth_And_Expr : constant TCode := 18; -- Boolean and 2 154 Truth_Or_Expr : constant TCode := 19; -- Boolean or 2 155 Truth_Xor_Expr : constant TCode := 20; -- Boolean xor 2 156 Truth_Not_Expr : constant TCode := 21; -- Boolean not 1 157 Lt_Expr : constant TCode := 22; -- comparison < 2 158 Le_Expr : constant TCode := 23; -- comparison <= 2 159 Gt_Expr : constant TCode := 24; -- comparison > 2 160 Ge_Expr : constant TCode := 25; -- comparison >= 2 161 Eq_Expr : constant TCode := 26; -- comparison = 2 162 Ne_Expr : constant TCode := 27; -- comparison /= 2 163 Bit_And_Expr : constant TCode := 28; -- Binary and 2 164 165 -- The following entry is used to represent a discriminant value in 166 -- the tree. It has a special tree code that does not correspond 167 -- directly to a gcc node. The single operand is the number of the 168 -- discriminant in the record (1 = first discriminant). 169 170 Discrim_Val : constant TCode := 0; -- discriminant value 1 171 172 ------------------------ 173 -- The gigi Interface -- 174 ------------------------ 175 176 -- The following declarations are for use by gigi for back annotation 177 178 function Create_Node 179 (Expr : TCode; 180 Op1 : Node_Ref_Or_Val; 181 Op2 : Node_Ref_Or_Val := No_Uint; 182 Op3 : Node_Ref_Or_Val := No_Uint) return Node_Ref; 183 -- Creates a node using the tree code defined by Expr and from one to three 184 -- operands as required (unused operands set as shown to No_Uint) Note that 185 -- this call can be used to create a discriminant reference by using (Expr 186 -- => Discrim_Val, Op1 => discriminant_number). 187 188 function Create_Discrim_Ref (Discr : Entity_Id) return Node_Ref; 189 -- Creates a reference to the discriminant whose entity is Discr 190 191 -------------------------------------------------------- 192 -- Front-End Interface for Dynamic Size/Offset Values -- 193 -------------------------------------------------------- 194 195 -- If Backend_Layout is False, then the front-end deals with all 196 -- dynamic size and offset fields. There are two cases: 197 198 -- 1. The value can be computed at the time of type freezing, and 199 -- is stored in a run-time constant. In this case, the field 200 -- contains a reference to this entity. In the case of sizes 201 -- the value stored is the size in storage units, since dynamic 202 -- sizes are always a multiple of storage units. 203 204 -- 2. The size/offset depends on the value of discriminants at 205 -- run-time. In this case, the front end builds a function to 206 -- compute the value. This function has a single parameter 207 -- which is the discriminated record object in question. Any 208 -- references to discriminant values are simply references to 209 -- the appropriate discriminant in this single argument, and 210 -- to compute the required size/offset value at run time, the 211 -- code generator simply constructs a call to the function 212 -- with the appropriate argument. The size/offset field in 213 -- this case contains a reference to the function entity. 214 -- Note that as for case 1, if such a function is used to 215 -- return a size, then the size in storage units is returned, 216 -- not the size in bits. 217 218 -- The interface here allows these created entities to be referenced 219 -- using negative Unit values, so that they can be stored in the 220 -- appropriate size and offset fields in the tree. 221 222 -- In the case of components, if the location of the component is static, 223 -- then all four fields (Component_Bit_Offset, Normalized_Position, Esize, 224 -- and Normalized_First_Bit) are set to appropriate values. In the case of 225 -- a non-static component location, Component_Bit_Offset is not used and 226 -- is left set to Unknown. Normalized_Position and Normalized_First_Bit 227 -- are set appropriately. 228 229 subtype SO_Ref is Uint; 230 -- Type used to represent a Uint value that represents a static or 231 -- dynamic size/offset value (non-negative if static, negative if 232 -- the size value is dynamic). 233 234 subtype Dynamic_SO_Ref is Uint; 235 -- Type used to represent a negative Uint value used to store 236 -- a dynamic size/offset value. 237 238 function Is_Dynamic_SO_Ref (U : SO_Ref) return Boolean; 239 pragma Inline (Is_Dynamic_SO_Ref); 240 -- Given a SO_Ref (Uint) value, returns True iff the SO_Ref value 241 -- represents a dynamic Size/Offset value (i.e. it is negative). 242 243 function Is_Static_SO_Ref (U : SO_Ref) return Boolean; 244 pragma Inline (Is_Static_SO_Ref); 245 -- Given a SO_Ref (Uint) value, returns True iff the SO_Ref value 246 -- represents a static Size/Offset value (i.e. it is non-negative). 247 248 function Create_Dynamic_SO_Ref (E : Entity_Id) return Dynamic_SO_Ref; 249 -- Given the Entity_Id for a constant (case 1), the Node_Id for an 250 -- expression (case 2), or the Entity_Id for a function (case 3), 251 -- this function returns a (negative) Uint value that can be used 252 -- to retrieve the entity or expression for later use. 253 254 function Get_Dynamic_SO_Entity (U : Dynamic_SO_Ref) return Entity_Id; 255 -- Retrieve the Node_Id or Entity_Id stored by a previous call to 256 -- Create_Dynamic_SO_Ref. The approach is that the front end makes 257 -- the necessary Create_Dynamic_SO_Ref calls to associate the node 258 -- and entity id values and the back end makes Get_Dynamic_SO_Ref 259 -- calls to retrieve them. 260 261 -------------------- 262 -- ASIS_Interface -- 263 -------------------- 264 265 type Discrim_List is array (Pos range <>) of Uint; 266 -- Type used to represent list of discriminant values 267 268 function Rep_Value 269 (Val : Node_Ref_Or_Val; 270 D : Discrim_List) return Uint; 271 -- Given the contents of a First_Bit_Position or Esize field containing 272 -- a node reference (i.e. a negative Uint value) and D, the list of 273 -- discriminant values, returns the interpreted value of this field. 274 -- For convenience, Rep_Value will take a non-negative Uint value 275 -- as an argument value, and return it unmodified. A No_Uint value is 276 -- also returned unmodified. 277 278 procedure Tree_Read; 279 -- Initializes internal tables from current tree file using the relevant 280 -- Table.Tree_Read routines. 281 282 ------------------------ 283 -- Compiler Interface -- 284 ------------------------ 285 286 procedure List_Rep_Info (Bytes_Big_Endian : Boolean); 287 -- Procedure to list representation information. Bytes_Big_Endian is the 288 -- value from Ttypes (Repinfo cannot have a dependency on Ttypes). 289 290 procedure Tree_Write; 291 -- Writes out internal tables to current tree file using the relevant 292 -- Table.Tree_Write routines. 293 294 -------------------------- 295 -- Debugging Procedures -- 296 -------------------------- 297 298 procedure List_GCC_Expression (U : Node_Ref_Or_Val); 299 -- Prints out given expression in symbolic form. Constants are listed 300 -- in decimal numeric form, Discriminants are listed with a # followed 301 -- by the discriminant number, and operators are output in appropriate 302 -- symbolic form No_Uint displays as two question marks. The output is 303 -- on a single line but has no line return after it. This procedure is 304 -- useful only if operating in backend layout mode. 305 306 procedure lgx (U : Node_Ref_Or_Val); 307 -- In backend layout mode, this is like List_GCC_Expression, but 308 -- includes a line return at the end. If operating in front end 309 -- layout mode, then the name of the entity for the size (either 310 -- a function of a variable) is listed followed by a line return. 311 312end Repinfo; 313