gcc/tree.def

   1 /* This file contains the definitions and documentation for the
   2    tree codes used in the GNU C compiler.
   3    Copyright (C) 1987, 1988, 1993 Free Software Foundation, Inc.
   4
   5 This file is part of GNU CC.
   6
   7 GNU CC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GNU CC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU CC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  20
  21
  22 /* The third argument can be:
  23    "x" for an exceptional code (fits no category).
  24    "t" for a type object code.
  25    "b" for a lexical block.
  26    "c" for codes for constants.
  27    "d" for codes for declarations (also serving as variable refs).
  28    "r" for codes for references to storage.
  29    "<" for codes for comparison expressions.
  30    "1" for codes for unary arithmetic expressions.
  31    "2" for codes for binary arithmetic expressions.
  32    "s" for codes for expressions with inherent side effects.
  33    "e" for codes for other kinds of expressions.  */
  34
  35 /* For `r', `e', `<', `1', `2', `s' and `x' nodes,
  36    the 4th element is the number of argument slots to allocate.
  37    This determines the size of the tree node object.  */
  38
  39 /* Any erroneous construct is parsed into a node of this type.
  40    This type of node is accepted without complaint in all contexts
  41    by later parsing activities, to avoid multiple error messages
  42    for one error.
  43    No fields in these nodes are used except the TREE_CODE.  */
  44 DEFTREECODE (ERROR_MARK, "error_mark", "x", 0)
  45
  46 /* Used to represent a name (such as, in the DECL_NAME of a decl node).
  47    Internally it looks like a STRING_CST node.
  48    There is only one IDENTIFIER_NODE ever made for any particular name.
  49    Use `get_identifier' to get it (or create it, the first time).  */
  50 DEFTREECODE (IDENTIFIER_NODE, "identifier_node", "x", -1)
  51
  52 /* Used to hold information to identify an operator (or combination
  53    of two operators) considered as a `noun' rather than a `verb'.
  54    The first operand is encoded in the TREE_TYPE field.  */
  55 DEFTREECODE (OP_IDENTIFIER, "op_identifier", "x", 2)
  56
  57 /* Has the TREE_VALUE and TREE_PURPOSE fields.  */
  58 /* These nodes are made into lists by chaining through the
  59    TREE_CHAIN field.  The elements of the list live in the
  60    TREE_VALUE fields, while TREE_PURPOSE fields are occasionally
  61    used as well to get the effect of Lisp association lists.  */
  62 DEFTREECODE (TREE_LIST, "tree_list", "x", 2)
  63
  64 /* These nodes contain an array of tree nodes.  */
  65 DEFTREECODE (TREE_VEC, "tree_vec", "x", 2)
  66
  67 /* A symbol binding block.  These are arranged in a tree,
  68    where the BLOCK_SUBBLOCKS field contains a chain of subblocks
  69    chained through the BLOCK_CHAIN field.
  70    BLOCK_SUPERCONTEXT points to the parent block.
  71      For a block which represents the outermost scope of a function, it
  72      points to the FUNCTION_DECL node.
  73    BLOCK_VARS points to a chain of decl nodes.
  74    BLOCK_TYPE_TAGS points to a chain of types which have their own names.
  75    BLOCK_CHAIN points to the next BLOCK at the same level.
  76    BLOCK_ABSTRACT_ORIGIN points to the original (abstract) tree node which
  77    this block is an instance of, or else is NULL to indicate that this
  78    block is not an instance of anything else.  When non-NULL, the value
  79    could either point to another BLOCK node or it could point to a
  80    FUNCTION_DECL node (e.g. in the case of a block representing the
  81    outermost scope of a particular inlining of a function).
  82    BLOCK_ABSTRACT is non-zero if the block represents an abstract
  83    instance of a block (i.e. one which is nested within an abstract
  84    instance of a inline function. */
  85 DEFTREECODE (BLOCK, "block", "b", 0)
  86 \f
  87 /* Each data type is represented by a tree node whose code is one of
  88    the following:  */
  89 /* Each node that represents a data type has a component TYPE_SIZE
  90    containing a tree that is an expression for the size in bits.
  91    The TYPE_MODE contains the machine mode for values of this type.
  92    The TYPE_POINTER_TO field contains a type for a pointer to this type,
  93      or zero if no such has been created yet.
  94    The TYPE_NEXT_VARIANT field is used to chain together types
  95      that are variants made by type modifiers such as "const" and "volatile".
  96    The TYPE_MAIN_VARIANT field, in any member of such a chain,
  97      points to the start of the chain.
  98    The TYPE_NONCOPIED_PARTS field is a list specifying which parts
  99      of an object of this type should *not* be copied by assignment.
 100      The TREE_PURPOSE of each element is the offset of the part
 101      and the TREE_VALUE is the size in bits of the part.
 102    The TYPE_NAME field contains info on the name used in the program
 103      for this type (for GDB symbol table output).  It is either a
 104      TYPE_DECL node, for types that are typedefs, or an IDENTIFIER_NODE
 105      in the case of structs, unions or enums that are known with a tag,
 106      or zero for types that have no special name.
 107    The TYPE_CONTEXT for any sort of type which could have a name or
 108     which could have named members (e.g. tagged types in C/C++) will
 109     point to the node which represents the scope of the given type, or
 110     will be NULL_TREE if the type has "file scope".  For most types, this
 111     will point to a BLOCK node or a FUNCTION_DECL node, but it could also
 112     point to a FUNCTION_TYPE node (for types whose scope is limited to the
 113     formal parameter list of some function type specification) or it
 114     could point to a RECORD_TYPE, UNION_TYPE or QUAL_UNION_TYPE node
 115     (for C++ "member" types).
 116     For non-tagged-types, TYPE_CONTEXT need not be set to anything in
 117     particular, since any type which is of some type category  (e.g.
 118     an array type or a function type) which cannot either have a name
 119     itself or have named members doesn't really have a "scope" per se.
 120   The TREE_CHAIN field is used as a forward-references to names for
 121     ENUMERAL_TYPE, RECORD_TYPE, UNION_TYPE, and QUAL_UNION_TYPE nodes;
 122     see below.  */
 123
 124 DEFTREECODE (VOID_TYPE, "void_type", "t", 0)    /* The void type in C */
 125
 126 /* Integer types in all languages, including char in C.
 127    Also used for sub-ranges of other discrete types.
 128    Has components TYPE_MIN_VALUE, TYPE_MAX_VALUE (expressions, inclusive)
 129    and TYPE_PRECISION (number of bits used by this type).
 130    In the case of a subrange type in Pascal, the TREE_TYPE
 131    of this will point at the supertype (another INTEGER_TYPE,
 132    or an ENUMERAL_TYPE, CHAR_TYPE, or BOOLEAN_TYPE).
 133    Otherwise, the TREE_TYPE is zero.  */
 134 DEFTREECODE (INTEGER_TYPE, "integer_type", "t", 0)
 135
 136 /* C's float and double.  Different floating types are distinguished
 137    by machine mode and by the TYPE_SIZE and the TYPE_PRECISION.  */
 138 DEFTREECODE (REAL_TYPE, "real_type", "t", 0)
 139
 140 /* Complex number types.  The TREE_TYPE field is the data type
 141    of the real and imaginary parts.  */
 142 DEFTREECODE (COMPLEX_TYPE, "complex_type", "t", 0)
 143
 144 /* C enums.  The type node looks just like an INTEGER_TYPE node.
 145    The symbols for the values of the enum type are defined by
 146    CONST_DECL nodes, but the type does not point to them;
 147    however, the TYPE_VALUES is a list in which each element's TREE_PURPOSE
 148    is a name and the TREE_VALUE is the value (an INTEGER_CST node).  */
 149 /* A forward reference `enum foo' when no enum named foo is defined yet
 150    has zero (a null pointer) in its TYPE_SIZE.  The tag name is in
 151    the TYPE_NAME field.  If the type is later defined, the normal
 152    fields are filled in.
 153    RECORD_TYPE, UNION_TYPE, and QUAL_UNION_TYPE forward refs are
 154    treated similarly.  */
 155 DEFTREECODE (ENUMERAL_TYPE, "enumeral_type", "t", 0)
 156
 157 /* Pascal's boolean type (true or false are the only values);
 158    no special fields needed.  */
 159 DEFTREECODE (BOOLEAN_TYPE, "boolean_type", "t", 0)
 160
 161 /* CHAR in Pascal; not used in C.
 162    No special fields needed.  */
 163 DEFTREECODE (CHAR_TYPE, "char_type", "t", 0)
 164
 165 /* All pointer-to-x types have code POINTER_TYPE.
 166    The TREE_TYPE points to the node for the type pointed to.  */
 167 DEFTREECODE (POINTER_TYPE, "pointer_type", "t", 0)
 168
 169 /* An offset is a pointer relative to an object.
 170    The TREE_TYPE field is the type of the object at the offset.
 171    The TYPE_OFFSET_BASETYPE points to the node for the type of object
 172    that the offset is relative to.  */
 173 DEFTREECODE (OFFSET_TYPE, "offset_type", "t", 0)
 174
 175 /* A reference is like a pointer except that it is coerced
 176    automatically to the value it points to.  Used in C++.  */
 177 DEFTREECODE (REFERENCE_TYPE, "reference_type", "t", 0)
 178
 179 /* METHOD_TYPE is the type of a function which takes an extra first
 180    argument for "self", which is not present in the declared argument list.
 181    The TREE_TYPE is the return type of the method.  The TYPE_METHOD_BASETYPE
 182    is the type of "self".  TYPE_ARG_TYPES is the real argument list, which
 183    includes the hidden argument for "self".  */
 184 DEFTREECODE (METHOD_TYPE, "method_type", "t", 0)
 185
 186 /* Used for Pascal; details not determined right now.  */
 187 DEFTREECODE (FILE_TYPE, "file_type", "t", 0)
 188
 189 /* Types of arrays.  Special fields:
 190    TREE_TYPE              Type of an array element.
 191    TYPE_DOMAIN            Type to index by.
 192                             Its range of values specifies the array length.
 193    TYPE_SEP               Expression for units from one elt to the next.
 194    TYPE_SEP_UNIT          Number of bits in a unit for previous.
 195  The field TYPE_POINTER_TO (TREE_TYPE (array_type)) is always nonzero
 196  and holds the type to coerce a value of that array type to in C.
 197  TYPE_STRING_FLAG indicates a string (in contrast to an array of chars)
 198  in languages (such as Chill) that make a distinction. */
 199 /* Array types in C or Pascal */
 200 DEFTREECODE (ARRAY_TYPE, "array_type", "t", 0)
 201
 202 /* Types of sets for Pascal.  Special fields are the same as
 203    in an array type.  The target type is always a boolean type.  */
 204 DEFTREECODE (SET_TYPE, "set_type", "t", 0)
 205
 206 /* Struct in C, or record in Pascal.  */
 207 /* Special fields:
 208    TYPE_FIELDS  chain of FIELD_DECLs for the fields of the struct.
 209    A few may need to be added for Pascal.  */
 210 /* See the comment above, before ENUMERAL_TYPE, for how
 211    forward references to struct tags are handled in C.  */
 212 DEFTREECODE (RECORD_TYPE, "record_type", "t", 0)
 213
 214 /* Union in C.  Like a struct, except that the offsets of the fields
 215    will all be zero.  */
 216 /* See the comment above, before ENUMERAL_TYPE, for how
 217    forward references to union tags are handled in C.  */
 218 DEFTREECODE (UNION_TYPE, "union_type", "t", 0)  /* C union type */
 219
 220 /* Similar to UNION_TYPE, except that the expressions in DECL_QUALIFIER
 221    in each FIELD_DECL determine what the union contains.  The first
 222    field whose DECL_QUALIFIER expression is true is deemed to occupy
 223    the union.  */
 224 DEFTREECODE (QUAL_UNION_TYPE, "qual_union_type", "t", 0)
 225
 226 /* Type of functions.  Special fields:
 227    TREE_TYPE                type of value returned.
 228    TYPE_ARG_TYPES      list of types of arguments expected.
 229         this list is made of TREE_LIST nodes.
 230    Types of "Procedures" in languages where they are different from functions
 231    have code FUNCTION_TYPE also, but then TREE_TYPE is zero or void type.  */
 232 DEFTREECODE (FUNCTION_TYPE, "function_type", "t", 0)
 233
 234 /* This is a language-specific kind of type.
 235    Its meaning is defined by the language front end.
 236    layout_type does not know how to lay this out,
 237    so the front-end must do so manually.  */
 238 DEFTREECODE (LANG_TYPE, "lang_type", "t", 0)
 239 \f
 240 /* Expressions */
 241
 242 /* First, the constants.  */
 243
 244 /* Contents are in TREE_INT_CST_LOW and TREE_INT_CST_HIGH fields,
 245    32 bits each, giving us a 64 bit constant capability.
 246    Note: constants of type char in Pascal are INTEGER_CST,
 247    and so are pointer constants such as nil in Pascal or NULL in C.
 248    `(int *) 1' in C also results in an INTEGER_CST.  */
 249 DEFTREECODE (INTEGER_CST, "integer_cst", "c", 2)
 250
 251 /* Contents are in TREE_REAL_CST field.  Also there is TREE_CST_RTL.  */
 252 DEFTREECODE (REAL_CST, "real_cst", "c", 3)
 253
 254 /* Contents are in TREE_REALPART and TREE_IMAGPART fields,
 255    whose contents are other constant nodes.
 256    Also there is TREE_CST_RTL.  */
 257 DEFTREECODE (COMPLEX_CST, "complex_cst", "c", 3)
 258
 259 /* Contents are TREE_STRING_LENGTH and TREE_STRING_POINTER fields.
 260    Also there is TREE_CST_RTL.  */
 261 DEFTREECODE (STRING_CST, "string_cst", "c", 3)
 262
 263 /* Declarations.  All references to names are represented as ..._DECL nodes.
 264    The decls in one binding context are chained through the TREE_CHAIN field.
 265    Each DECL has a DECL_NAME field which contains an IDENTIFIER_NODE.
 266     (Some decls, most often labels, may have zero as the DECL_NAME).
 267    DECL_CONTEXT points to the node representing the context in which
 268     this declaration has its scope.  For FIELD_DECLs, this is the
 269     RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE node that the field
 270     is a member of.  For VAR_DECL, PARM_DECL, FUNCTION_DECL, LABEL_DECL,
 271     and CONST_DECL nodes, this points to the FUNCTION_DECL for the
 272     containing function, or else yields NULL_TREE if the given decl
 273     has "file scope".
 274    DECL_ABSTRACT_ORIGIN, if non-NULL, points to the original (abstract)
 275     ..._DECL node of which this decl is an (inlined or template expanded)
 276     instance.
 277    The TREE_TYPE field holds the data type of the object, when relevant.
 278     LABEL_DECLs have no data type.  For TYPE_DECL, the TREE_TYPE field
 279     contents are the type whose name is being declared.
 280    The DECL_ALIGN, DECL_SIZE,
 281     and DECL_MODE fields exist in decl nodes just as in type nodes.
 282     They are unused in LABEL_DECL, TYPE_DECL and CONST_DECL nodes.
 283
 284    DECL_OFFSET holds an integer number of bits offset for the location.
 285    DECL_VOFFSET holds an expression for a variable offset; it is
 286    to be multiplied by DECL_VOFFSET_UNIT (an integer).
 287    These fields are relevant only in FIELD_DECLs and PARM_DECLs.
 288
 289    DECL_INITIAL holds the value to initialize a variable to,
 290    or the value of a constant.  For a function, it holds the body
 291    (a node of type BLOCK representing the function's binding contour
 292    and whose body contains the function's statements.)  For a LABEL_DECL
 293    in C, it is a flag, nonzero if the label's definition has been seen.
 294
 295    PARM_DECLs use a special field:
 296    DECL_ARG_TYPE is the type in which the argument is actually
 297     passed, which may be different from its type within the function.
 298
 299    FUNCTION_DECLs use four special fields:
 300    DECL_ARGUMENTS holds a chain of PARM_DECL nodes for the arguments.
 301    DECL_RESULT holds a RESULT_DECL node for the value of a function,
 302     or it is 0 for a function that returns no value.
 303     (C functions returning void have zero here.)
 304    DECL_RESULT_TYPE holds the type in which the result is actually
 305     returned.  This is usually the same as the type of DECL_RESULT,
 306     but (1) it may be a wider integer type and
 307     (2) it remains valid, for the sake of inlining, even after the
 308     function's compilation is done.
 309    DECL_FUNCTION_CODE is a code number that is nonzero for
 310     built-in functions.  Its value is an enum built_in_function
 311     that says which built-in function it is.
 312
 313    DECL_SOURCE_FILE holds a filename string and DECL_SOURCE_LINE
 314    holds a line number.  In some cases these can be the location of
 315    a reference, if no definition has been seen.
 316
 317    DECL_ABSTRACT is non-zero if the decl represents an abstract instance
 318    of a decl (i.e. one which is nested within an abstract instance of a
 319    inline function.  */
 320
 321 DEFTREECODE (FUNCTION_DECL, "function_decl", "d", 0)
 322 DEFTREECODE (LABEL_DECL, "label_decl", "d", 0)
 323 DEFTREECODE (CONST_DECL, "const_decl", "d", 0)
 324 DEFTREECODE (TYPE_DECL, "type_decl", "d", 0)
 325 DEFTREECODE (VAR_DECL, "var_decl", "d", 0)
 326 DEFTREECODE (PARM_DECL, "parm_decl", "d", 0)
 327 DEFTREECODE (RESULT_DECL, "result_decl", "d", 0)
 328 DEFTREECODE (FIELD_DECL, "field_decl", "d", 0)
 329 \f
 330 /* References to storage.  */
 331
 332 /* Value is structure or union component.
 333    Operand 0 is the structure or union (an expression);
 334    operand 1 is the field (a node of type FIELD_DECL).  */
 335 DEFTREECODE (COMPONENT_REF, "component_ref", "r", 2)
 336
 337 /* Reference to a group of bits within an object.  Similar to COMPONENT_REF
 338    except the position is given explicitly rather than via a FIELD_DECL.
 339    Operand 0 is the structure or union expression;
 340    operand 1 is a tree giving the number of bits being referenced;
 341    operand 2 is a tree giving the position of the first referenced bit.
 342    The field can be either a signed or unsigned field;
 343    TREE_UNSIGNED says which.  */
 344 DEFTREECODE (BIT_FIELD_REF, "bit_field_ref", "r", 3)
 345
 346 /* C unary `*' or Pascal `^'.  One operand, an expression for a pointer.  */
 347 DEFTREECODE (INDIRECT_REF, "indirect_ref", "r", 1)
 348
 349 /* Reference to the contents of an offset
 350    (a value whose type is an OFFSET_TYPE).
 351    Operand 0 is the object within which the offset is taken.
 352    Operand 1 is the offset.  */
 353 DEFTREECODE (OFFSET_REF, "offset_ref", "r", 2)
 354
 355 /* Pascal `^` on a file.  One operand, an expression for the file.  */
 356 DEFTREECODE (BUFFER_REF, "buffer_ref", "r", 1)
 357
 358 /* Array indexing in languages other than C.
 359    Operand 0 is the array; operand 1 is a list of indices
 360    stored as a chain of TREE_LIST nodes.  */
 361 DEFTREECODE (ARRAY_REF, "array_ref", "r", 2)
 362
 363 /* Constructor: return an aggregate value made from specified components.
 364    In C, this is used only for structure and array initializers.
 365    The first "operand" is really a pointer to the RTL,
 366    for constant constructors only.
 367    The second operand is a list of component values
 368    made out of a chain of TREE_LIST nodes.  */
 369 DEFTREECODE (CONSTRUCTOR, "constructor", "e", 2)
 370
 371 /* The expression types are mostly straightforward,
 372    with the fourth argument of DEFTREECODE saying
 373    how many operands there are.
 374    Unless otherwise specified, the operands are expressions.  */
 375
 376 /* Contains two expressions to compute, one followed by the other.
 377    the first value is ignored.  The second one's value is used.  */
 378 DEFTREECODE (COMPOUND_EXPR, "compound_expr", "e", 2)
 379
 380 /* Assignment expression.  Operand 0 is the what to set; 1, the new value.  */
 381 DEFTREECODE (MODIFY_EXPR, "modify_expr", "e", 2)
 382
 383 /* Initialization expression.  Operand 0 is the variable to initialize;
 384    Operand 1 is the initializer.  */
 385 DEFTREECODE (INIT_EXPR, "init_expr", "e", 2)
 386
 387 /* For TARGET_EXPR, operand 0 is the target of an initialization,
 388    operand 1 is the initializer for the target,
 389    and operand 2 is the cleanup for this node, if any.  */
 390 DEFTREECODE (TARGET_EXPR, "target_expr", "e", 3)
 391
 392 /* Conditional expression ( ... ? ... : ...  in C).
 393    Operand 0 is the condition.
 394    Operand 1 is the then-value.
 395    Operand 2 is the else-value.  */
 396 DEFTREECODE (COND_EXPR, "cond_expr", "e", 3)
 397
 398 /* Declare local variables, including making RTL and allocating space.
 399    Operand 0 is a chain of VAR_DECL nodes for the variables.
 400    Operand 1 is the body, the expression to be computed using
 401    the variables.  The value of operand 1 becomes that of the BIND_EXPR.
 402    Operand 2 is the BLOCK that corresponds to these bindings
 403    for debugging purposes.  If this BIND_EXPR is actually expanded,
 404    that sets the TREE_USED flag in the BLOCK.
 405
 406    The BIND_EXPR is not responsible for informing parsers
 407    about these variables.  If the body is coming from the input file,
 408    then the code that creates the BIND_EXPR is also responsible for
 409    informing the parser of the variables.
 410
 411    If the BIND_EXPR is ever expanded, its TREE_USED flag is set.
 412    This tells the code for debugging symbol tables not to ignore the BIND_EXPR.
 413    If the BIND_EXPR should be output for debugging but will not be expanded,
 414    set the TREE_USED flag by hand.
 415
 416    In order for the BIND_EXPR to be known at all, the code that creates it
 417    must also install it as a subblock in the tree of BLOCK
 418    nodes for the function.  */
 419 DEFTREECODE (BIND_EXPR, "bind_expr", "e", 3)
 420
 421 /* Function call.  Operand 0 is the function.
 422    Operand 1 is the argument list, a list of expressions
 423    made out of a chain of TREE_LIST nodes.
 424    There is no operand 2.  That slot is used for the
 425    CALL_EXPR_RTL macro (see preexpand_calls).  */
 426 DEFTREECODE (CALL_EXPR, "call_expr", "e", 3)
 427
 428 /* Call a method.  Operand 0 is the method, whose type is a METHOD_TYPE.
 429    Operand 1 is the expression for "self".
 430    Operand 2 is the list of explicit arguments.  */
 431 DEFTREECODE (METHOD_CALL_EXPR, "method_call_expr", "e", 4)
 432
 433 /* Specify a value to compute along with its corresponding cleanup.
 434    Operand 0 argument is an expression whose value needs a cleanup.
 435    Operand 1 is an RTL_EXPR which will eventually represent that value.
 436    Operand 2 is the cleanup expression for the object.
 437      The RTL_EXPR is used in this expression, which is how the expression
 438      manages to act on the proper value.
 439    The cleanup is executed by the first enclosing CLEANUP_POINT_EXPR, if
 440    it exists, otherwise it is the responsibility of the caller to manually
 441    call expand_cleanups_to, as needed.  */
 442 DEFTREECODE (WITH_CLEANUP_EXPR, "with_cleanup_expr", "e", 3)
 443
 444 /* Specify a cleanup point.
 445    Operand 0 is the expression that has cleanups that we want ensure are
 446    cleaned up.  */
 447 DEFTREECODE (CLEANUP_POINT_EXPR, "cleanup_point_expr", "e", 1)
 448
 449 /* The following two codes are used in languages that have types where
 450    the position and/or sizes of fields vary from object to object of the
 451    same type, i.e., where some other field in the object contains a value
 452    that is used in the computation of another field's offset or size.
 453
 454    For example, a record type with a discriminant in Ada is such a type.
 455    This mechanism is also used to create "fat pointers" for unconstrained
 456    array types in Ada; the fat pointer is a structure one of whose fields is
 457    a pointer to the actual array type and the other field is a pointer to a
 458    template, which is a structure containing the bounds of the array.  The
 459    bounds in the type pointed to by the first field in the fat pointer refer
 460    to the values in the template.
 461
 462    These "self-references" are doing using a PLACEHOLDER_EXPR.  This is a
 463    node that will later be replaced with the object being referenced.  Its type
 464    is that of the object and selects which object to use from a chain of
 465    references (see below).
 466
 467    When we wish to evaluate a size or offset, we check it is contains a
 468    placeholder.  If it does, we construct a WITH_RECORD_EXPR that contains
 469    both the expression we wish to evaluate and an expression within which the
 470    object may be found.  The latter expression is the object itself in
 471    the simple case of an Ada record with discriminant, but it can be the
 472    array in the case of an unconstrained array.
 473
 474    In the latter case, we need the fat pointer, because the bounds of the
 475    array can only be accessed from it.  However, we rely here on the fact that
 476    the expression for the array contains the dereference of the fat pointer
 477    that obtained the array pointer.
 478
 479    Accordingly, when looking for the object to substitute in place of
 480    a PLACEHOLDER_EXPR, we look down the first operand of the expression
 481    passed as the second operand to WITH_RECORD_EXPR until we find something
 482    of the desired type or reach a constant.  */
 483
 484 /* Denotes a record to later be supplied with a WITH_RECORD_EXPR when
 485    evaluating this expression.  The type of this expression is used to
 486    find the record to replace it.  */
 487 DEFTREECODE (PLACEHOLDER_EXPR, "placeholder_expr", "x", 0)
 488
 489 /* Provide an expression that references a record to be used in place
 490    of a PLACEHOLDER_EXPR.  The record to be used is the record within
 491    operand 1 that has the same type as the PLACEHOLDER_EXPR in
 492    operand 0.  */
 493 DEFTREECODE (WITH_RECORD_EXPR, "with_record_expr", "e", 2)
 494
 495 /* Simple arithmetic.  Operands must have the same machine mode
 496    and the value shares that mode.  */
 497 DEFTREECODE (PLUS_EXPR, "plus_expr", "2", 2)
 498 DEFTREECODE (MINUS_EXPR, "minus_expr", "2", 2)
 499 DEFTREECODE (MULT_EXPR, "mult_expr", "2", 2)
 500
 501 /* Division for integer result that rounds the quotient toward zero.  */
 502 /* Operands must have the same machine mode.
 503    In principle they may be real, but that is not currently supported.
 504    The result is always fixed point, and it has the same type as the
 505    operands if they are fixed point.   */
 506 DEFTREECODE (TRUNC_DIV_EXPR, "trunc_div_expr", "2", 2)
 507
 508 /* Division for integer result that rounds the quotient toward infinity.  */
 509 DEFTREECODE (CEIL_DIV_EXPR, "ceil_div_expr", "2", 2)
 510
 511 /* Division for integer result that rounds toward minus infinity.  */
 512 DEFTREECODE (FLOOR_DIV_EXPR, "floor_div_expr", "2", 2)
 513
 514 /* Division for integer result that rounds toward nearest integer.  */
 515 DEFTREECODE (ROUND_DIV_EXPR, "round_div_expr", "2", 2)
 516
 517 /* Four kinds of remainder that go with the four kinds of division.  */
 518 DEFTREECODE (TRUNC_MOD_EXPR, "trunc_mod_expr", "2", 2)
 519 DEFTREECODE (CEIL_MOD_EXPR, "ceil_mod_expr", "2", 2)
 520 DEFTREECODE (FLOOR_MOD_EXPR, "floor_mod_expr", "2", 2)
 521 DEFTREECODE (ROUND_MOD_EXPR, "round_mod_expr", "2", 2)
 522
 523 /* Division for real result.  The two operands must have the same type.
 524    In principle they could be integers, but currently only real
 525    operands are supported.  The result must have the same type
 526    as the operands.  */
 527 DEFTREECODE (RDIV_EXPR, "rdiv_expr", "2", 2)
 528
 529 /* Division which is not supposed to need rounding.
 530    Used for pointer subtraction in C.  */
 531 DEFTREECODE (EXACT_DIV_EXPR, "exact_div_expr", "2", 2)
 532
 533 /* Conversion of real to fixed point: four ways to round,
 534    like the four ways to divide.
 535    CONVERT_EXPR can also be used to convert a real to an integer,
 536    and that is what is used in languages that do not have ways of
 537    specifying which of these is wanted.  Maybe these are not needed.  */
 538 DEFTREECODE (FIX_TRUNC_EXPR, "fix_trunc_expr", "1", 1)
 539 DEFTREECODE (FIX_CEIL_EXPR, "fix_ceil_expr", "1", 1)
 540 DEFTREECODE (FIX_FLOOR_EXPR, "fix_floor_expr", "1", 1)
 541 DEFTREECODE (FIX_ROUND_EXPR, "fix_round_expr", "1", 1)
 542
 543 /* Conversion of an integer to a real.  */
 544 DEFTREECODE (FLOAT_EXPR, "float_expr", "1", 1)
 545
 546 /* Exponentiation.  Operands may have any types;
 547    constraints on value type are not known yet.  */
 548 DEFTREECODE (EXPON_EXPR, "expon_expr", "2", 2)
 549
 550 /* Unary negation.  Value has same type as operand.  */
 551 DEFTREECODE (NEGATE_EXPR, "negate_expr", "1", 1)
 552
 553 DEFTREECODE (MIN_EXPR, "min_expr", "2", 2)
 554 DEFTREECODE (MAX_EXPR, "max_expr", "2", 2)
 555 DEFTREECODE (ABS_EXPR, "abs_expr", "1", 1)
 556 DEFTREECODE (FFS_EXPR, "ffs_expr", "1", 1)
 557
 558 /* Shift operations for shift and rotate.
 559    Shift is supposed to mean logical shift if done on an
 560    unsigned type, arithmetic shift on a signed type.
 561    The second operand is the number of bits to
 562    shift by, and must always have mode SImode.
 563    The result has the same mode as the first operand.  */
 564 DEFTREECODE (LSHIFT_EXPR, "alshift_expr", "2", 2)
 565 DEFTREECODE (RSHIFT_EXPR, "arshift_expr", "2", 2)
 566 DEFTREECODE (LROTATE_EXPR, "lrotate_expr", "2", 2)
 567 DEFTREECODE (RROTATE_EXPR, "rrotate_expr", "2", 2)
 568
 569 /* Bitwise operations.  Operands have same mode as result.  */
 570 DEFTREECODE (BIT_IOR_EXPR, "bit_ior_expr", "2", 2)
 571 DEFTREECODE (BIT_XOR_EXPR, "bit_xor_expr", "2", 2)
 572 DEFTREECODE (BIT_AND_EXPR, "bit_and_expr", "2", 2)
 573 DEFTREECODE (BIT_ANDTC_EXPR, "bit_andtc_expr", "2", 2)
 574 DEFTREECODE (BIT_NOT_EXPR, "bit_not_expr", "1", 1)
 575
 576 /* Combination of boolean values or of integers considered only
 577    as zero or nonzero.  ANDIF and ORIF allow the second operand
 578    not to be computed if the value of the expression is determined
 579    from the first operand.  AND, OR, and XOR always compute the second
 580    operand whether its value is needed or not (for side effects).  */
 581 DEFTREECODE (TRUTH_ANDIF_EXPR, "truth_andif_expr", "e", 2)
 582 DEFTREECODE (TRUTH_ORIF_EXPR, "truth_orif_expr", "e", 2)
 583 DEFTREECODE (TRUTH_AND_EXPR, "truth_and_expr", "e", 2)
 584 DEFTREECODE (TRUTH_OR_EXPR, "truth_or_expr", "e", 2)
 585 DEFTREECODE (TRUTH_XOR_EXPR, "truth_xor_expr", "e", 2)
 586 DEFTREECODE (TRUTH_NOT_EXPR, "truth_not_expr", "e", 1)
 587
 588 /* Relational operators.
 589    `EQ_EXPR' and `NE_EXPR' are allowed for any types.
 590    The others are allowed only for integer (or pointer or enumeral)
 591    or real types.
 592    In all cases the operands will have the same type,
 593    and the value is always the type used by the language for booleans.  */
 594 DEFTREECODE (LT_EXPR, "lt_expr", "<", 2)
 595 DEFTREECODE (LE_EXPR, "le_expr", "<", 2)
 596 DEFTREECODE (GT_EXPR, "gt_expr", "<", 2)
 597 DEFTREECODE (GE_EXPR, "ge_expr", "<", 2)
 598 DEFTREECODE (EQ_EXPR, "eq_expr", "<", 2)
 599 DEFTREECODE (NE_EXPR, "ne_expr", "<", 2)
 600
 601 /* Operations for Pascal sets.  Not used now.  */
 602 DEFTREECODE (IN_EXPR, "in_expr", "2", 2)
 603 DEFTREECODE (SET_LE_EXPR, "set_le_expr", "<", 2)
 604 DEFTREECODE (CARD_EXPR, "card_expr", "1", 1)
 605 DEFTREECODE (RANGE_EXPR, "range_expr", "2", 2)
 606
 607 /* Represents a conversion of type of a value.
 608    All conversions, including implicit ones, must be
 609    represented by CONVERT_EXPR nodes.  */
 610 DEFTREECODE (CONVERT_EXPR, "convert_expr", "1", 1)
 611
 612 /* Represents a conversion expected to require no code to be generated.  */
 613 DEFTREECODE (NOP_EXPR, "nop_expr", "1", 1)
 614
 615 /* Value is same as argument, but guaranteed not an lvalue.  */
 616 DEFTREECODE (NON_LVALUE_EXPR, "non_lvalue_expr", "1", 1)
 617
 618 /* Represents something we computed once and will use multiple times.
 619    First operand is that expression.  Second is the function decl
 620    in which the SAVE_EXPR was created.  The third operand is the RTL,
 621    nonzero only after the expression has been computed.  */
 622 DEFTREECODE (SAVE_EXPR, "save_expr", "e", 3)
 623
 624 /* Represents something whose RTL has already been expanded
 625    as a sequence which should be emitted when this expression is expanded.
 626    The first operand is the RTL to emit.  It is the first of a chain of insns.
 627    The second is the RTL expression for the result.  */
 628 DEFTREECODE (RTL_EXPR, "rtl_expr", "e", 2)
 629
 630 /* & in C.  Value is the address at which the operand's value resides.
 631    Operand may have any mode.  Result mode is Pmode.  */
 632 DEFTREECODE (ADDR_EXPR, "addr_expr", "e", 1)
 633
 634 /* Non-lvalue reference or pointer to an object.  */
 635 DEFTREECODE (REFERENCE_EXPR, "reference_expr", "e", 1)
 636
 637 /* Operand is a function constant; result is a function variable value
 638    of typeEPmode.  Used only for languages that need static chains.  */
 639 DEFTREECODE (ENTRY_VALUE_EXPR, "entry_value_expr", "e", 1)
 640
 641 /* Given two real or integer operands of the same type,
 642    returns a complex value of the corresponding complex type.  */
 643 DEFTREECODE (COMPLEX_EXPR, "complex_expr", "2", 2)
 644
 645 /* Complex conjugate of operand.  Used only on complex types.
 646    The value has the same type as the operand.  */
 647 DEFTREECODE (CONJ_EXPR, "conj_expr", "1", 1)
 648
 649 /* Used only on an operand of complex type, these return
 650    a value of the corresponding component type.  */
 651 DEFTREECODE (REALPART_EXPR, "realpart_expr", "1", 1)
 652 DEFTREECODE (IMAGPART_EXPR, "imagpart_expr", "1", 1)
 653
 654 /* Nodes for ++ and -- in C.
 655    The second arg is how much to increment or decrement by.
 656    For a pointer, it would be the size of the object pointed to.  */
 657 DEFTREECODE (PREDECREMENT_EXPR, "predecrement_expr", "e", 2)
 658 DEFTREECODE (PREINCREMENT_EXPR, "preincrement_expr", "e", 2)
 659 DEFTREECODE (POSTDECREMENT_EXPR, "postdecrement_expr", "e", 2)
 660 DEFTREECODE (POSTINCREMENT_EXPR, "postincrement_expr", "e", 2)
 661 \f
 662 /* These types of expressions have no useful value,
 663    and always have side effects.  */
 664
 665 /* A label definition, encapsulated as a statement.
 666    Operand 0 is the LABEL_DECL node for the label that appears here.
 667    The type should be void and the value should be ignored.  */
 668 DEFTREECODE (LABEL_EXPR, "label_expr", "s", 1)
 669
 670 /* GOTO.  Operand 0 is a LABEL_DECL node.
 671    The type should be void and the value should be ignored.  */
 672 DEFTREECODE (GOTO_EXPR, "goto_expr", "s", 1)
 673
 674 /* RETURN.  Evaluates operand 0, then returns from the current function.
 675    Presumably that operand is an assignment that stores into the
 676    RESULT_DECL that hold the value to be returned.
 677    The operand may be null.
 678    The type should be void and the value should be ignored.  */
 679 DEFTREECODE (RETURN_EXPR, "return_expr", "s", 1)
 680
 681 /* Exit the inner most loop conditionally.  Operand 0 is the condition.
 682    The type should be void and the value should be ignored.  */
 683 DEFTREECODE (EXIT_EXPR, "exit_expr", "s", 1)
 684
 685 /* A loop.  Operand 0 is the body of the loop.
 686    It must contain an EXIT_EXPR or is an infinite loop.
 687    The type should be void and the value should be ignored.  */
 688 DEFTREECODE (LOOP_EXPR, "loop_expr", "s", 1)
 689
 690 /*
 691 Local variables:
 692 mode:c
 693 version-control: t
 694 End:
 695 */