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/* This file contains the definitions and documentation for the

   tree codes used in GCC.

   Copyright (C) 1987, 1988, 1993, 1995, 1997, 1998, 2000, 2001, 2004, 2005,

   2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under

the terms of the GNU General Public License as published by the Free

Software Foundation; either version 3, or (at your option) any later

version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY

WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

for more details.

You should have received a copy of the GNU General Public License

along with GCC; see the file COPYING3.  If not see

.  */

/* For tcc_references, tcc_expression, tcc_comparison, tcc_unary,

   tcc_binary, and tcc_statement nodes, which use struct tree_exp, the

   4th element is the number of argument slots to allocate.  This

   determines the size of the tree node object.  Other nodes use

   different structures, and the size is determined by the tree_union

   member structure; the 4th element should be zero.  Languages that

   define language-specific tcc_exceptional or tcc_constant codes must

   define the tree_size langhook to say how big they are.

   These tree codes have been sorted so that the macros in tree.h that

   check for various tree codes are optimized into range checks.  This

   gives a measurable performance improvement.  When adding a new

   code, consider its placement in relation to the other codes.  */

/* Any erroneous construct is parsed into a node of this type.

   This type of node is accepted without complaint in all contexts

   by later parsing activities, to avoid multiple error messages

   for one error.

   No fields in these nodes are used except the TREE_CODE.  */

DEFTREECODE (ERROR_MARK, "error_mark", tcc_exceptional, 0)

/* Used to represent a name (such as, in the DECL_NAME of a decl node).

   Internally it looks like a STRING_CST node.

   There is only one IDENTIFIER_NODE ever made for any particular name.

   Use `get_identifier' to get it (or create it, the first time).  */

DEFTREECODE (IDENTIFIER_NODE, "identifier_node", tcc_exceptional, 0)

/* Has the TREE_VALUE and TREE_PURPOSE fields.  */

/* These nodes are made into lists by chaining through the

   TREE_CHAIN field.  The elements of the list live in the

   TREE_VALUE fields, while TREE_PURPOSE fields are occasionally

   used as well to get the effect of Lisp association lists.  */

DEFTREECODE (TREE_LIST, "tree_list", tcc_exceptional, 0)

/* These nodes contain an array of tree nodes.  */

DEFTREECODE (TREE_VEC, "tree_vec", tcc_exceptional, 0)

/* A symbol binding block.  These are arranged in a tree,

   where the BLOCK_SUBBLOCKS field contains a chain of subblocks

   chained through the BLOCK_CHAIN field.

   BLOCK_SUPERCONTEXT points to the parent block.

     For a block which represents the outermost scope of a function, it

     points to the FUNCTION_DECL node.

   BLOCK_VARS points to a chain of decl nodes.

   BLOCK_CHAIN points to the next BLOCK at the same level.

   BLOCK_ABSTRACT_ORIGIN points to the original (abstract) tree node which

   this block is an instance of, or else is NULL to indicate that this

   block is not an instance of anything else.  When non-NULL, the value

   could either point to another BLOCK node or it could point to a

   FUNCTION_DECL node (e.g. in the case of a block representing the

   outermost scope of a particular inlining of a function).

   BLOCK_ABSTRACT is nonzero if the block represents an abstract

   instance of a block (i.e. one which is nested within an abstract

   instance of an inline function).

   TREE_ASM_WRITTEN is nonzero if the block was actually referenced

   in the generated assembly.  */

DEFTREECODE (BLOCK, "block", tcc_exceptional, 0)

/* Each data type is represented by a tree node whose code is one of

   the following:  */

/* Each node that represents a data type has a component TYPE_SIZE

   containing a tree that is an expression for the size in bits.

   The TYPE_MODE contains the machine mode for values of this type.

   The TYPE_POINTER_TO field contains a type for a pointer to this type,

     or zero if no such has been created yet.

   The TYPE_NEXT_VARIANT field is used to chain together types

     that are variants made by type modifiers such as "const" and "volatile".

   The TYPE_MAIN_VARIANT field, in any member of such a chain,

     points to the start of the chain.

   The TYPE_NAME field contains info on the name used in the program

     for this type (for GDB symbol table output).  It is either a

     TYPE_DECL node, for types that are typedefs, or an IDENTIFIER_NODE

     in the case of structs, unions or enums that are known with a tag,

     or zero for types that have no special name.

   The TYPE_CONTEXT for any sort of type which could have a name or

    which could have named members (e.g. tagged types in C/C++) will

    point to the node which represents the scope of the given type, or

    will be NULL_TREE if the type has "file scope".  For most types, this

    will point to a BLOCK node or a FUNCTION_DECL node, but it could also

    point to a FUNCTION_TYPE node (for types whose scope is limited to the

    formal parameter list of some function type specification) or it

    could point to a RECORD_TYPE, UNION_TYPE or QUAL_UNION_TYPE node

    (for C++ "member" types).

    For non-tagged-types, TYPE_CONTEXT need not be set to anything in

    particular, since any type which is of some type category  (e.g.

    an array type or a function type) which cannot either have a name

    itself or have named members doesn't really have a "scope" per se.

  The TREE_CHAIN field is used as a forward-references to names for

    ENUMERAL_TYPE, RECORD_TYPE, UNION_TYPE, and QUAL_UNION_TYPE nodes;

    see below.  */

/* The ordering of the following codes is optimized for the checking

   macros in tree.h.  Changing the order will degrade the speed of the

   compiler.  OFFSET_TYPE, ENUMERAL_TYPE, BOOLEAN_TYPE, INTEGER_TYPE,

   REAL_TYPE, POINTER_TYPE.  */

/* An offset is a pointer relative to an object.

   The TREE_TYPE field is the type of the object at the offset.

   The TYPE_OFFSET_BASETYPE points to the node for the type of object

   that the offset is relative to.  */

DEFTREECODE (OFFSET_TYPE, "offset_type", tcc_type, 0)

/* C enums.  The type node looks just like an INTEGER_TYPE node.

   The symbols for the values of the enum type are defined by

   CONST_DECL nodes, but the type does not point to them;

   however, the TYPE_VALUES is a list in which each element's TREE_PURPOSE

   is a name and the TREE_VALUE is the value (an INTEGER_CST node).  */

/* A forward reference `enum foo' when no enum named foo is defined yet

   has zero (a null pointer) in its TYPE_SIZE.  The tag name is in

   the TYPE_NAME field.  If the type is later defined, the normal

   fields are filled in.

   RECORD_TYPE, UNION_TYPE, and QUAL_UNION_TYPE forward refs are

   treated similarly.  */

DEFTREECODE (ENUMERAL_TYPE, "enumeral_type", tcc_type, 0)

/* Boolean type (true or false are the only values).  Looks like an

   INTEGRAL_TYPE.  */

DEFTREECODE (BOOLEAN_TYPE, "boolean_type", tcc_type, 0)

/* Integer types in all languages, including char in C.

   Also used for sub-ranges of other discrete types.

   Has components TYPE_MIN_VALUE, TYPE_MAX_VALUE (expressions, inclusive)

   and TYPE_PRECISION (number of bits used by this type).

   In the case of a subrange type in Pascal, the TREE_TYPE

   of this will point at the supertype (another INTEGER_TYPE,

   or an ENUMERAL_TYPE or BOOLEAN_TYPE).

   Otherwise, the TREE_TYPE is zero.  */

DEFTREECODE (INTEGER_TYPE, "integer_type", tcc_type, 0)

/* C's float and double.  Different floating types are distinguished

   by machine mode and by the TYPE_SIZE and the TYPE_PRECISION.  */

DEFTREECODE (REAL_TYPE, "real_type", tcc_type, 0)

/* The ordering of the following codes is optimized for the checking

   macros in tree.h.  Changing the order will degrade the speed of the

   compiler.  POINTER_TYPE, REFERENCE_TYPE.  Note that this range

   overlaps the previous range of ordered types.  */

/* All pointer-to-x types have code POINTER_TYPE.

   The TREE_TYPE points to the node for the type pointed to.  */

DEFTREECODE (POINTER_TYPE, "pointer_type", tcc_type, 0)

/* A reference is like a pointer except that it is coerced

   automatically to the value it points to.  Used in C++.  */

DEFTREECODE (REFERENCE_TYPE, "reference_type", tcc_type, 0)

/* The C++ decltype(nullptr) type.  */

DEFTREECODE (NULLPTR_TYPE, "nullptr_type", tcc_type, 0)

/* _Fract and _Accum types in Embedded-C.  Different fixed-point types

   are distinguished by machine mode and by the TYPE_SIZE and the

   TYPE_PRECISION.  */

DEFTREECODE (FIXED_POINT_TYPE, "fixed_point_type", tcc_type, 0)

/* The ordering of the following codes is optimized for the checking

   macros in tree.h.  Changing the order will degrade the speed of the

   compiler.  COMPLEX_TYPE, VECTOR_TYPE, ARRAY_TYPE.  */

/* Complex number types.  The TREE_TYPE field is the data type

   of the real and imaginary parts.  It must be of scalar

   arithmetic type, not including pointer type.  */

DEFTREECODE (COMPLEX_TYPE, "complex_type", tcc_type, 0)

/* Vector types.  The TREE_TYPE field is the data type of the vector

   elements.  The TYPE_PRECISION field is the number of subparts of

   the vector.  */

DEFTREECODE (VECTOR_TYPE, "vector_type", tcc_type, 0)

/* The ordering of the following codes is optimized for the checking

   macros in tree.h.  Changing the order will degrade the speed of the

   compiler.  ARRAY_TYPE, RECORD_TYPE, UNION_TYPE, QUAL_UNION_TYPE.

   Note that this range overlaps the previous range.  */

/* Types of arrays.  Special fields:

   TREE_TYPE              Type of an array element.

   TYPE_DOMAIN            Type to index by.

                            Its range of values specifies the array length.

 The field TYPE_POINTER_TO (TREE_TYPE (array_type)) is always nonzero

 and holds the type to coerce a value of that array type to in C.

 TYPE_STRING_FLAG indicates a string (in contrast to an array of chars)

 in languages (such as Chill) that make a distinction.  */

/* Array types in C or Pascal */

DEFTREECODE (ARRAY_TYPE, "array_type", tcc_type, 0)

/* Struct in C, or record in Pascal.  */

/* Special fields:

   TYPE_FIELDS  chain of FIELD_DECLs for the fields of the struct,

     and VAR_DECLs, TYPE_DECLs and CONST_DECLs for record-scope variables,

     types and enumerators.

   A few may need to be added for Pascal.  */

/* See the comment above, before ENUMERAL_TYPE, for how

   forward references to struct tags are handled in C.  */

DEFTREECODE (RECORD_TYPE, "record_type", tcc_type, 0)

/* Union in C.  Like a struct, except that the offsets of the fields

   will all be zero.  */

/* See the comment above, before ENUMERAL_TYPE, for how

   forward references to union tags are handled in C.  */

DEFTREECODE (UNION_TYPE, "union_type", tcc_type, 0)     /* C union type */

/* Similar to UNION_TYPE, except that the expressions in DECL_QUALIFIER

   in each FIELD_DECL determine what the union contains.  The first

   field whose DECL_QUALIFIER expression is true is deemed to occupy

   the union.  */

DEFTREECODE (QUAL_UNION_TYPE, "qual_union_type", tcc_type, 0)

/* The ordering of the following codes is optimized for the checking

   macros in tree.h.  Changing the order will degrade the speed of the

   compiler.  VOID_TYPE, FUNCTION_TYPE, METHOD_TYPE.  */

/* The void type in C */

DEFTREECODE (VOID_TYPE, "void_type", tcc_type, 0)

/* Type of functions.  Special fields:

   TREE_TYPE                type of value returned.

   TYPE_ARG_TYPES      list of types of arguments expected.

        this list is made of TREE_LIST nodes.

   Types of "Procedures" in languages where they are different from functions

   have code FUNCTION_TYPE also, but then TREE_TYPE is zero or void type.  */

DEFTREECODE (FUNCTION_TYPE, "function_type", tcc_type, 0)

/* METHOD_TYPE is the type of a function which takes an extra first

   argument for "self", which is not present in the declared argument list.

   The TREE_TYPE is the return type of the method.  The TYPE_METHOD_BASETYPE

   is the type of "self".  TYPE_ARG_TYPES is the real argument list, which

   includes the hidden argument for "self".  */

DEFTREECODE (METHOD_TYPE, "method_type", tcc_type, 0)

/* This is a language-specific kind of type.

   Its meaning is defined by the language front end.

   layout_type does not know how to lay this out,

   so the front-end must do so manually.  */

DEFTREECODE (LANG_TYPE, "lang_type", tcc_type, 0)

/* Expressions */

/* First, the constants.  */

/* Contents are in TREE_INT_CST_LOW and TREE_INT_CST_HIGH fields,

   32 bits each, giving us a 64 bit constant capability.  INTEGER_CST

   nodes can be shared, and therefore should be considered read only.

   They should be copied, before setting a flag such as TREE_OVERFLOW.

   If an INTEGER_CST has TREE_OVERFLOW already set, it is known to be unique.

   INTEGER_CST nodes are created for the integral types, for pointer

   types and for vector and float types in some circumstances.  */

DEFTREECODE (INTEGER_CST, "integer_cst", tcc_constant, 0)

/* Contents are in TREE_REAL_CST field.  */

DEFTREECODE (REAL_CST, "real_cst", tcc_constant, 0)

/* Contents are in TREE_FIXED_CST field.  */

DEFTREECODE (FIXED_CST, "fixed_cst", tcc_constant, 0)

/* Contents are in TREE_REALPART and TREE_IMAGPART fields,

   whose contents are other constant nodes.  */

DEFTREECODE (COMPLEX_CST, "complex_cst", tcc_constant, 0)

/* Contents are in TREE_VECTOR_CST_ELTS field.  */

DEFTREECODE (VECTOR_CST, "vector_cst", tcc_constant, 0)

/* Contents are TREE_STRING_LENGTH and the actual contents of the string.  */

DEFTREECODE (STRING_CST, "string_cst", tcc_constant, 0)

/* Declarations.  All references to names are represented as ..._DECL

   nodes.  The decls in one binding context are chained through the

   TREE_CHAIN field.  Each DECL has a DECL_NAME field which contains

   an IDENTIFIER_NODE.  (Some decls, most often labels, may have zero

   as the DECL_NAME).  DECL_CONTEXT points to the node representing

   the context in which this declaration has its scope.  For

   FIELD_DECLs, this is the RECORD_TYPE, UNION_TYPE, or

   QUAL_UNION_TYPE node that the field is a member of.  For VAR_DECL,

   PARM_DECL, FUNCTION_DECL, LABEL_DECL, and CONST_DECL nodes, this

   points to either the FUNCTION_DECL for the containing function, the

   RECORD_TYPE or UNION_TYPE for the containing type, or NULL_TREE or

   a TRANSLATION_UNIT_DECL if the given decl has "file scope".

   DECL_ABSTRACT_ORIGIN, if non-NULL, points to the original (abstract)

    ..._DECL node of which this decl is an (inlined or template expanded)

    instance.

   The TREE_TYPE field holds the data type of the object, when relevant.

    LABEL_DECLs have no data type.  For TYPE_DECL, the TREE_TYPE field

    contents are the type whose name is being declared.

   The DECL_ALIGN, DECL_SIZE,

    and DECL_MODE fields exist in decl nodes just as in type nodes.

    They are unused in LABEL_DECL, TYPE_DECL and CONST_DECL nodes.

   DECL_FIELD_BIT_OFFSET holds an integer number of bits offset for

   the location.  DECL_VOFFSET holds an expression for a variable

   offset; it is to be multiplied by DECL_VOFFSET_UNIT (an integer).

   These fields are relevant only in FIELD_DECLs and PARM_DECLs.

   DECL_INITIAL holds the value to initialize a variable to,

   or the value of a constant.  For a function, it holds the body

   (a node of type BLOCK representing the function's binding contour

   and whose body contains the function's statements.)  For a LABEL_DECL

   in C, it is a flag, nonzero if the label's definition has been seen.

   PARM_DECLs use a special field:

   DECL_ARG_TYPE is the type in which the argument is actually

    passed, which may be different from its type within the function.

   FUNCTION_DECLs use four special fields:

   DECL_ARGUMENTS holds a chain of PARM_DECL nodes for the arguments.

   DECL_RESULT holds a RESULT_DECL node for the value of a function.

    The DECL_RTL field is 0 for a function that returns no value.

    (C functions returning void have zero here.)

    The TREE_TYPE field is the type in which the result is actually

    returned.  This is usually the same as the return type of the

    FUNCTION_DECL, but it may be a wider integer type because of

    promotion.

   DECL_FUNCTION_CODE is a code number that is nonzero for

    built-in functions.  Its value is an enum built_in_function

    that says which built-in function it is.

   DECL_SOURCE_FILE holds a filename string and DECL_SOURCE_LINE

   holds a line number.  In some cases these can be the location of

   a reference, if no definition has been seen.

   DECL_ABSTRACT is nonzero if the decl represents an abstract instance

   of a decl (i.e. one which is nested within an abstract instance of a

   inline function.  */

DEFTREECODE (FUNCTION_DECL, "function_decl", tcc_declaration, 0)

DEFTREECODE (LABEL_DECL, "label_decl", tcc_declaration, 0)

/* The ordering of the following codes is optimized for the checking

   macros in tree.h.  Changing the order will degrade the speed of the

   compiler.  FIELD_DECL, VAR_DECL, CONST_DECL, PARM_DECL,

   TYPE_DECL.  */

DEFTREECODE (FIELD_DECL, "field_decl", tcc_declaration, 0)

DEFTREECODE (VAR_DECL, "var_decl", tcc_declaration, 0)

DEFTREECODE (CONST_DECL, "const_decl", tcc_declaration, 0)

DEFTREECODE (PARM_DECL, "parm_decl", tcc_declaration, 0)

DEFTREECODE (TYPE_DECL, "type_decl", tcc_declaration, 0)

DEFTREECODE (RESULT_DECL, "result_decl", tcc_declaration, 0)

/* A "declaration" of a debug temporary.  It should only appear in

   DEBUG stmts.  */

DEFTREECODE (DEBUG_EXPR_DECL, "debug_expr_decl", tcc_declaration, 0)

/* A namespace declaration.  Namespaces appear in DECL_CONTEXT of other

   _DECLs, providing a hierarchy of names.  */

DEFTREECODE (NAMESPACE_DECL, "namespace_decl", tcc_declaration, 0)

/* A declaration import.

   The C++ FE uses this to represent a using-directive; eg:

   "using namespace foo".

   But it could be used to represent any declaration import construct.

   Whenever a declaration import appears in a lexical block, the BLOCK node

   representing that lexical block in GIMPLE will contain an IMPORTED_DECL

   node, linked via BLOCK_VARS accessor of the said BLOCK.

   For a given NODE which code is IMPORTED_DECL,

   IMPORTED_DECL_ASSOCIATED_DECL (NODE) accesses the imported declaration.  */

DEFTREECODE (IMPORTED_DECL, "imported_decl", tcc_declaration, 0)

/* A translation unit.  This is not technically a declaration, since it

   can't be looked up, but it's close enough.  */

DEFTREECODE (TRANSLATION_UNIT_DECL, "translation_unit_decl",\

             tcc_declaration, 0)

/* References to storage.  */

/* The ordering of the following codes is optimized for the classification

   in handled_component_p.  Keep them in a consecutive group.  */

/* Value is structure or union component.

   Operand 0 is the structure or union (an expression).

   Operand 1 is the field (a node of type FIELD_DECL).

   Operand 2, if present, is the value of DECL_FIELD_OFFSET, measured

   in units of DECL_OFFSET_ALIGN / BITS_PER_UNIT.  */

DEFTREECODE (COMPONENT_REF, "component_ref", tcc_reference, 3)

/* Reference to a group of bits within an object.  Similar to COMPONENT_REF

   except the position is given explicitly rather than via a FIELD_DECL.

   Operand 0 is the structure or union expression;

   operand 1 is a tree giving the constant number of bits being referenced;

   operand 2 is a tree giving the constant position of the first referenced bit.

   The result type width has to match the number of bits referenced.

   If the result type is integral, its signedness specifies how it is extended

   to its mode width.  */

DEFTREECODE (BIT_FIELD_REF, "bit_field_ref", tcc_reference, 3)

/* Array indexing.

   Operand 0 is the array; operand 1 is a (single) array index.

   Operand 2, if present, is a copy of TYPE_MIN_VALUE of the index.

   Operand 3, if present, is the element size, measured in units of

   the alignment of the element type.  */

DEFTREECODE (ARRAY_REF, "array_ref", tcc_reference, 4)

/* Likewise, except that the result is a range ("slice") of the array.  The

   starting index of the resulting array is taken from operand 1 and the size

   of the range is taken from the type of the expression.  */

DEFTREECODE (ARRAY_RANGE_REF, "array_range_ref", tcc_reference, 4)

/* Used only on an operand of complex type, these return

   a value of the corresponding component type.  */

DEFTREECODE (REALPART_EXPR, "realpart_expr", tcc_reference, 1)

DEFTREECODE (IMAGPART_EXPR, "imagpart_expr", tcc_reference, 1)

/* Represents viewing something of one type as being of a second type.

   This corresponds to an "Unchecked Conversion" in Ada and roughly to

   the idiom *(type2 *)&X in C.  The only operand is the value to be

   viewed as being of another type.  It is undefined if the type of the

   input and of the expression have different sizes.

   This code may also be used within the LHS of a MODIFY_EXPR, in which

   case no actual data motion may occur.  TREE_ADDRESSABLE will be set in

   this case and GCC must abort if it could not do the operation without

   generating insns.  */

DEFTREECODE (VIEW_CONVERT_EXPR, "view_convert_expr", tcc_reference, 1)

/* C unary `*' or Pascal `^'.  One operand, an expression for a pointer.  */

DEFTREECODE (INDIRECT_REF, "indirect_ref", tcc_reference, 1)

/* Used to represent lookup in a virtual method table which is dependent on

   the runtime type of an object.  Operands are:

   OBJ_TYPE_REF_EXPR: An expression that evaluates the value to use.

   OBJ_TYPE_REF_OBJECT: Is the object on whose behalf the lookup is

   being performed.  Through this the optimizers may be able to statically

   determine the dynamic type of the object.

   OBJ_TYPE_REF_TOKEN: An integer index to the virtual method table.  */

DEFTREECODE (OBJ_TYPE_REF, "obj_type_ref", tcc_expression, 3)

/* Constructor: return an aggregate value made from specified components.

   In C, this is used only for structure and array initializers.

   The operand is a sequence of component values made out of a VEC of

   struct constructor_elt.

   For ARRAY_TYPE:

   The field INDEX of each constructor_elt is the corresponding index.

   If the index is a RANGE_EXPR, it is a short-hand for many nodes,

   one for each index in the range.  (If the corresponding field VALUE

   has side-effects, they are evaluated once for each element.  Wrap the

   value in a SAVE_EXPR if you want to evaluate side effects only once.)

   For RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE:

   The field INDEX of each node is a FIELD_DECL.  */

DEFTREECODE (CONSTRUCTOR, "constructor", tcc_exceptional, 0)

/* The expression types are mostly straightforward, with the fourth argument

   of DEFTREECODE saying how many operands there are.

   Unless otherwise specified, the operands are expressions and the

   types of all the operands and the expression must all be the same.  */

/* Contains two expressions to compute, one followed by the other.

   the first value is ignored.  The second one's value is used.  The

   type of the first expression need not agree with the other types.  */

DEFTREECODE (COMPOUND_EXPR, "compound_expr", tcc_expression, 2)

/* Assignment expression.  Operand 0 is the what to set; 1, the new value.  */

DEFTREECODE (MODIFY_EXPR, "modify_expr", tcc_expression, 2)

/* Initialization expression.  Operand 0 is the variable to initialize;

   Operand 1 is the initializer.  This differs from MODIFY_EXPR in that any

   reference to the referent of operand 0 within operand 1 is undefined.  */

DEFTREECODE (INIT_EXPR, "init_expr", tcc_expression, 2)

/* For TARGET_EXPR, operand 0 is the target of an initialization,

   operand 1 is the initializer for the target, which may be void

     if simply expanding it initializes the target.

   operand 2 is the cleanup for this node, if any.

   operand 3 is the saved initializer after this node has been

   expanded once; this is so we can re-expand the tree later.  */

DEFTREECODE (TARGET_EXPR, "target_expr", tcc_expression, 4)

/* Conditional expression ( ... ? ... : ...  in C).

   Operand 0 is the condition.

   Operand 1 is the then-value.

   Operand 2 is the else-value.

   Operand 0 may be of any type.

   Operand 1 must have the same type as the entire expression, unless

   it unconditionally throws an exception, in which case it should

   have VOID_TYPE.  The same constraints apply to operand 2.  The

   condition in operand 0 must be of integral type.

   In cfg gimple, if you do not have a selection expression, operands

   1 and 2 are NULL.  The operands are then taken from the cfg edges. */

DEFTREECODE (COND_EXPR, "cond_expr", tcc_expression, 3)

/* Vector conditional expression. It is like COND_EXPR, but with

   vector operands.

   A = VEC_COND_EXPR ( X < Y, B, C)

   means

   for (i=0; i

     A[i] = X[i] < Y[i] ? B[i] : C[i];

*/

DEFTREECODE (VEC_COND_EXPR, "vec_cond_expr", tcc_expression, 3)

/* Vector permutation expression.  A = VEC_PERM_EXPR means

   N = length(mask)

   foreach i in N:

     M = mask[i] % (2*N)

     A = M < N ? v0[M] : v1[M-N]

   V0 and V1 are vectors of the same type.  MASK is an integer-typed

   vector.  The number of MASK elements must be the same with the

   number of elements in V0 and V1.  The size of the inner type

   of the MASK and of the V0 and V1 must be the same.

*/

DEFTREECODE (VEC_PERM_EXPR, "vec_perm_expr", tcc_expression, 3)

/* Declare local variables, including making RTL and allocating space.

   BIND_EXPR_VARS is a chain of VAR_DECL nodes for the variables.

   BIND_EXPR_BODY is the body, the expression to be computed using

   the variables.  The value of operand 1 becomes that of the BIND_EXPR.

   BIND_EXPR_BLOCK is the BLOCK that corresponds to these bindings

   for debugging purposes.  If this BIND_EXPR is actually expanded,

   that sets the TREE_USED flag in the BLOCK.

   The BIND_EXPR is not responsible for informing parsers

   about these variables.  If the body is coming from the input file,

   then the code that creates the BIND_EXPR is also responsible for

   informing the parser of the variables.

   If the BIND_EXPR is ever expanded, its TREE_USED flag is set.

   This tells the code for debugging symbol tables not to ignore the BIND_EXPR.

   If the BIND_EXPR should be output for debugging but will not be expanded,

   set the TREE_USED flag by hand.

   In order for the BIND_EXPR to be known at all, the code that creates it

   must also install it as a subblock in the tree of BLOCK

   nodes for the function.  */

DEFTREECODE (BIND_EXPR, "bind_expr", tcc_expression, 3)

/* Function call.  CALL_EXPRs are represented by variably-sized expression

   nodes.  There are at least three fixed operands.  Operand 0 is an

   INTEGER_CST node containing the total operand count, the number of

   arguments plus 3.  Operand 1 is the function, while operand 2 is

   is static chain argument, or NULL.  The remaining operands are the

   arguments to the call.  */

DEFTREECODE (CALL_EXPR, "call_expr", tcc_vl_exp, 3)

/* Specify a value to compute along with its corresponding cleanup.

   Operand 0 is the cleanup expression.

   The cleanup is executed by the first enclosing CLEANUP_POINT_EXPR,

   which must exist.  This differs from TRY_CATCH_EXPR in that operand 1

   is always evaluated when cleanups are run.  */

DEFTREECODE (WITH_CLEANUP_EXPR, "with_cleanup_expr", tcc_expression, 1)

/* Specify a cleanup point.

   Operand 0 is an expression that may have cleanups.  If it does, those

   cleanups are executed after the expression is expanded.

   Note that if the expression is a reference to storage, it is forced out

   of memory before the cleanups are run.  This is necessary to handle

   cases where the cleanups modify the storage referenced; in the

   expression 't.i', if 't' is a struct with an integer member 'i' and a

   cleanup which modifies 'i', the value of the expression depends on

   whether the cleanup is run before or after 't.i' is evaluated.  When

   expand_expr is run on 't.i', it returns a MEM.  This is not good enough;

   the value of 't.i' must be forced out of memory.

   As a consequence, the operand of a CLEANUP_POINT_EXPR must not have

   BLKmode, because it will not be forced out of memory.  */

DEFTREECODE (CLEANUP_POINT_EXPR, "cleanup_point_expr", tcc_expression, 1)

/* The following code is used in languages that have types where some

   field in an object of the type contains a value that is used in the

   computation of another field's offset or size and/or the size of the

   type.  The positions and/or sizes of fields can vary from object to

   object of the same type or even for one and the same object within

   its scope.

   Record types with discriminants in Ada or schema types in Pascal are

   examples of such types.  This mechanism is also used to create "fat

   pointers" for unconstrained array types in Ada; the fat pointer is a

   structure one of whose fields is a pointer to the actual array type

   and the other field is a pointer to a template, which is a structure

   containing the bounds of the array.  The bounds in the type pointed

   to by the first field in the fat pointer refer to the values in the

   template.

   When you wish to construct such a type you need "self-references"

   that allow you to reference the object having this type from the

   TYPE node, i.e. without having a variable instantiating this type.

   Such a "self-references" is done using a PLACEHOLDER_EXPR.  This is

   a node that will later be replaced with the object being referenced.

   Its type is that of the object and selects which object to use from

   a chain of references (see below).  No other slots are used in the

   PLACEHOLDER_EXPR.

   For example, if your type FOO is a RECORD_TYPE with a field BAR,

   and you need the value of .BAR to calculate TYPE_SIZE

   (FOO), just substitute  above with a PLACEHOLDER_EXPR

   whose TREE_TYPE is FOO.  Then construct your COMPONENT_REF with

   the PLACEHOLDER_EXPR as the first operand (which has the correct

   type).  Later, when the size is needed in the program, the back-end

   will find this PLACEHOLDER_EXPR and generate code to calculate the

   actual size at run-time.  In the following, we describe how this

   calculation is done.

   When we wish to evaluate a size or offset, we check whether it contains a

   PLACEHOLDER_EXPR.  If it does, we call substitute_placeholder_in_expr

   passing both that tree and an expression within which the object may be

   found.  The latter expression is the object itself in the simple case of

   an Ada record with discriminant, but it can be the array in the case of an

   unconstrained array.

   In the latter case, we need the fat pointer, because the bounds of

   the array can only be accessed from it.  However, we rely here on the

   fact that the expression for the array contains the dereference of

   the fat pointer that obtained the array pointer.  */

/* Denotes a record to later be substituted before evaluating this expression.

   The type of this expression is used to find the record to replace it.  */

DEFTREECODE (PLACEHOLDER_EXPR, "placeholder_expr", tcc_exceptional, 0)

/* Simple arithmetic.  */

DEFTREECODE (PLUS_EXPR, "plus_expr", tcc_binary, 2)

DEFTREECODE (MINUS_EXPR, "minus_expr", tcc_binary, 2)

DEFTREECODE (MULT_EXPR, "mult_expr", tcc_binary, 2)

/* Pointer addition.  The first operand is always a pointer and the

   second operand is an integer of type sizetype.  */

DEFTREECODE (POINTER_PLUS_EXPR, "pointer_plus_expr", tcc_binary, 2)

/* Highpart multiplication.  For an integral type with precision B,

   returns bits [2B-1, B] of the full 2*B product.  */

DEFTREECODE (MULT_HIGHPART_EXPR, "mult_highpart_expr", tcc_binary, 2)

/* Division for integer result that rounds the quotient toward zero.  */

DEFTREECODE (TRUNC_DIV_EXPR, "trunc_div_expr", tcc_binary, 2)

/* Division for integer result that rounds the quotient toward infinity.  */

DEFTREECODE (CEIL_DIV_EXPR, "ceil_div_expr", tcc_binary, 2)

/* Division for integer result that rounds toward minus infinity.  */

DEFTREECODE (FLOOR_DIV_EXPR, "floor_div_expr", tcc_binary, 2)

/* Division for integer result that rounds toward nearest integer.  */

DEFTREECODE (ROUND_DIV_EXPR, "round_div_expr", tcc_binary, 2)

/* Four kinds of remainder that go with the four kinds of division.  */

DEFTREECODE (TRUNC_MOD_EXPR, "trunc_mod_expr", tcc_binary, 2)

DEFTREECODE (CEIL_MOD_EXPR, "ceil_mod_expr", tcc_binary, 2)

DEFTREECODE (FLOOR_MOD_EXPR, "floor_mod_expr", tcc_binary, 2)

DEFTREECODE (ROUND_MOD_EXPR, "round_mod_expr", tcc_binary, 2)

/* Division for real result.  */

DEFTREECODE (RDIV_EXPR, "rdiv_expr", tcc_binary, 2)

/* Division which is not supposed to need rounding.

   Used for pointer subtraction in C.  */

DEFTREECODE (EXACT_DIV_EXPR, "exact_div_expr", tcc_binary, 2)

/* Conversion of real to fixed point by truncation.  */

DEFTREECODE (FIX_TRUNC_EXPR, "fix_trunc_expr", tcc_unary, 1)

/* Conversion of an integer to a real.  */

DEFTREECODE (FLOAT_EXPR, "float_expr", tcc_unary, 1)

/* Unary negation.  */

DEFTREECODE (NEGATE_EXPR, "negate_expr", tcc_unary, 1)

/* Minimum and maximum values.  When used with floating point, if both

   operands are zeros, or if either operand is NaN, then it is unspecified

   which of the two operands is returned as the result.  */

DEFTREECODE (MIN_EXPR, "min_expr", tcc_binary, 2)

DEFTREECODE (MAX_EXPR, "max_expr", tcc_binary, 2)

/* Represents the absolute value of the operand.

   An ABS_EXPR must have either an INTEGER_TYPE or a REAL_TYPE.  The

   operand of the ABS_EXPR must have the same type.  */

DEFTREECODE (ABS_EXPR, "abs_expr", tcc_unary, 1)

/* Shift operations for shift and rotate.

   Shift means logical shift if done on an

   unsigned type, arithmetic shift if done on a signed type.

   The second operand is the number of bits to

   shift by; it need not be the same type as the first operand and result.

   Note that the result is undefined if the second operand is larger

   than or equal to the first operand's type size.

   The first operand of a shift can have either an integer or a

   (non-integer) fixed-point type.  We follow the ISO/IEC TR 18037:2004

   semantics for the latter.

   Rotates are defined for integer types only.  */

DEFTREECODE (LSHIFT_EXPR, "lshift_expr", tcc_binary, 2)

DEFTREECODE (RSHIFT_EXPR, "rshift_expr", tcc_binary, 2)

DEFTREECODE (LROTATE_EXPR, "lrotate_expr", tcc_binary, 2)

DEFTREECODE (RROTATE_EXPR, "rrotate_expr", tcc_binary, 2)

/* Bitwise operations.  Operands have same mode as result.  */

DEFTREECODE (BIT_IOR_EXPR, "bit_ior_expr", tcc_binary, 2)

DEFTREECODE (BIT_XOR_EXPR, "bit_xor_expr", tcc_binary, 2)

DEFTREECODE (BIT_AND_EXPR, "bit_and_expr", tcc_binary, 2)

DEFTREECODE (BIT_NOT_EXPR, "bit_not_expr", tcc_unary, 1)

/* ANDIF and ORIF allow the second operand not to be computed if the

   value of the expression is determined from the first operand.  AND,

   OR, and XOR always compute the second operand whether its value is

   needed or not (for side effects).  The operand may have

   BOOLEAN_TYPE or INTEGER_TYPE.  In either case, the argument will be

   either zero or one.  For example, a TRUTH_NOT_EXPR will never have

   an INTEGER_TYPE VAR_DECL as its argument; instead, a NE_EXPR will be

   used to compare the VAR_DECL to zero, thereby obtaining a node with

   value zero or one.  */

DEFTREECODE (TRUTH_ANDIF_EXPR, "truth_andif_expr", tcc_expression, 2)

DEFTREECODE (TRUTH_ORIF_EXPR, "truth_orif_expr", tcc_expression, 2)

DEFTREECODE (TRUTH_AND_EXPR, "truth_and_expr", tcc_expression, 2)

DEFTREECODE (TRUTH_OR_EXPR, "truth_or_expr", tcc_expression, 2)

DEFTREECODE (TRUTH_XOR_EXPR, "truth_xor_expr", tcc_expression, 2)

DEFTREECODE (TRUTH_NOT_EXPR, "truth_not_expr", tcc_expression, 1)

/* Relational operators.

   `EQ_EXPR' and `NE_EXPR' are allowed for any types.

   The others are allowed only for integer (or pointer or enumeral)

   or real types.

   In all cases the operands will have the same type,

   and the value is either the type used by the language for booleans

   or an integer vector type of the same size and with the same number

   of elements as the comparison operands.  True for a vector of

   comparison results has all bits set while false is equal to zero.  */

DEFTREECODE (LT_EXPR, "lt_expr", tcc_comparison, 2)

DEFTREECODE (LE_EXPR, "le_expr", tcc_comparison, 2)

DEFTREECODE (GT_EXPR, "gt_expr", tcc_comparison, 2)

DEFTREECODE (GE_EXPR, "ge_expr", tcc_comparison, 2)

DEFTREECODE (EQ_EXPR, "eq_expr", tcc_comparison, 2)

DEFTREECODE (NE_EXPR, "ne_expr", tcc_comparison, 2)

/* Additional relational operators for floating point unordered.  */

DEFTREECODE (UNORDERED_EXPR, "unordered_expr", tcc_comparison, 2)

DEFTREECODE (ORDERED_EXPR, "ordered_expr", tcc_comparison, 2)

/* These are equivalent to unordered or ...  */

DEFTREECODE (UNLT_EXPR, "unlt_expr", tcc_comparison, 2)

DEFTREECODE (UNLE_EXPR, "unle_expr", tcc_comparison, 2)

DEFTREECODE (UNGT_EXPR, "ungt_expr", tcc_comparison, 2)

DEFTREECODE (UNGE_EXPR, "unge_expr", tcc_comparison, 2)

DEFTREECODE (UNEQ_EXPR, "uneq_expr", tcc_comparison, 2)

/* This is the reverse of uneq_expr.  */

DEFTREECODE (LTGT_EXPR, "ltgt_expr", tcc_comparison, 2)

DEFTREECODE (RANGE_EXPR, "range_expr", tcc_binary, 2)

/* Represents a re-association barrier for floating point expressions

   like explicit parenthesis in fortran.  */

DEFTREECODE (PAREN_EXPR, "paren_expr", tcc_unary, 1)

/* Represents a conversion of type of a value.

   All conversions, including implicit ones, must be

   represented by CONVERT_EXPR or NOP_EXPR nodes.  */

DEFTREECODE (CONVERT_EXPR, "convert_expr", tcc_unary, 1)

/* Conversion of a pointer value to a pointer to a different

   address space.  */

DEFTREECODE (ADDR_SPACE_CONVERT_EXPR, "addr_space_convert_expr", tcc_unary, 1)

/* Conversion of a fixed-point value to an integer, a real, or a fixed-point

   value.  Or conversion of a fixed-point value from an integer, a real, or

   a fixed-point value.  */

DEFTREECODE (FIXED_CONVERT_EXPR, "fixed_convert_expr", tcc_unary, 1)

/* Represents a conversion expected to require no code to be generated.  */

DEFTREECODE (NOP_EXPR, "nop_expr", tcc_unary, 1)

/* Value is same as argument, but guaranteed not an lvalue.  */

DEFTREECODE (NON_LVALUE_EXPR, "non_lvalue_expr", tcc_unary, 1)

/* A COMPOUND_LITERAL_EXPR represents a literal that is placed in a DECL.  The

   COMPOUND_LITERAL_EXPR_DECL_EXPR is the a DECL_EXPR containing the decl

   for the anonymous object represented by the COMPOUND_LITERAL;

   the DECL_INITIAL of that decl is the CONSTRUCTOR that initializes

   the compound literal.  */

DEFTREECODE (COMPOUND_LITERAL_EXPR, "compound_literal_expr", tcc_expression, 1)

/* Represents something we computed once and will use multiple times.

   First operand is that expression.  After it is evaluated once, it

   will be replaced by the temporary variable that holds the value.  */

DEFTREECODE (SAVE_EXPR, "save_expr", tcc_expression, 1)

/* & in C.  Value is the address at which the operand's value resides.

   Operand may have any mode.  Result mode is Pmode.  */

DEFTREECODE (ADDR_EXPR, "addr_expr", tcc_expression, 1)

/* Operand0 is a function constant; result is part N of a function

   descriptor of type ptr_mode.  */

DEFTREECODE (FDESC_EXPR, "fdesc_expr", tcc_expression, 2)

/* Given two real or integer operands of the same type,

   returns a complex value of the corresponding complex type.  */

DEFTREECODE (COMPLEX_EXPR, "complex_expr", tcc_binary, 2)

/* Complex conjugate of operand.  Used only on complex types.  */

DEFTREECODE (CONJ_EXPR, "conj_expr", tcc_unary, 1)

/* Nodes for ++ and -- in C.

   The second arg is how much to increment or decrement by.

   For a pointer, it would be the size of the object pointed to.  */

DEFTREECODE (PREDECREMENT_EXPR, "predecrement_expr", tcc_expression, 2)

DEFTREECODE (PREINCREMENT_EXPR, "preincrement_expr", tcc_expression, 2)

DEFTREECODE (POSTDECREMENT_EXPR, "postdecrement_expr", tcc_expression, 2)

DEFTREECODE (POSTINCREMENT_EXPR, "postincrement_expr", tcc_expression, 2)

/* Used to implement `va_arg'.  */

DEFTREECODE (VA_ARG_EXPR, "va_arg_expr", tcc_expression, 1)

/* Evaluate operand 1.  If and only if an exception is thrown during

   the evaluation of operand 1, evaluate operand 2.

   This differs from TRY_FINALLY_EXPR in that operand 2 is not evaluated

   on a normal or jump exit, only on an exception.  */

DEFTREECODE (TRY_CATCH_EXPR, "try_catch_expr", tcc_statement, 2)

/* Evaluate the first operand.

   The second operand is a cleanup expression which is evaluated

   on any exit (normal, exception, or jump out) from this expression.  */

DEFTREECODE (TRY_FINALLY_EXPR, "try_finally", tcc_statement, 2)

/* These types of expressions have no useful value,

   and always have side effects.  */

/* Used to represent a local declaration. The operand is DECL_EXPR_DECL.  */

DEFTREECODE (DECL_EXPR, "decl_expr", tcc_statement, 1)

/* A label definition, encapsulated as a statement.

   Operand 0 is the LABEL_DECL node for the label that appears here.

   The type should be void and the value should be ignored.  */

DEFTREECODE (LABEL_EXPR, "label_expr", tcc_statement, 1)

/* GOTO.  Operand 0 is a LABEL_DECL node or an expression.

   The type should be void and the value should be ignored.  */

DEFTREECODE (GOTO_EXPR, "goto_expr", tcc_statement, 1)

/* RETURN.  Evaluates operand 0, then returns from the current function.

   Presumably that operand is an assignment that stores into the

   RESULT_DECL that hold the value to be returned.

   The operand may be null.

   The type should be void and the value should be ignored.  */

DEFTREECODE (RETURN_EXPR, "return_expr", tcc_statement, 1)

/* Exit the inner most loop conditionally.  Operand 0 is the condition.

   The type should be void and the value should be ignored.  */

DEFTREECODE (EXIT_EXPR, "exit_expr", tcc_statement, 1)

/* A loop.  Operand 0 is the body of the loop.

   It must contain an EXIT_EXPR or is an infinite loop.

   The type should be void and the value should be ignored.  */

DEFTREECODE (LOOP_EXPR, "loop_expr", tcc_statement, 1)

/* Switch expression.

   TREE_TYPE is the original type of the condition, before any

   language required type conversions.  It may be NULL, in which case

   the original type and final types are assumed to be the same.

   Operand 0 is the expression used to perform the branch,

   Operand 1 is the body of the switch, which probably contains

     CASE_LABEL_EXPRs.  It may also be NULL, in which case operand 2

     must not be NULL.

   Operand 2 is either NULL_TREE or a TREE_VEC of the CASE_LABEL_EXPRs

     of all the cases.  */

DEFTREECODE (SWITCH_EXPR, "switch_expr", tcc_statement, 3)

/* Used to represent a case label.

   Operand 0 is CASE_LOW.  It may be NULL_TREE, in which case the label

     is a 'default' label.

   Operand 1 is CASE_HIGH.  If it is NULL_TREE, the label is a simple

     (one-value) case label.  If it is non-NULL_TREE, the case is a range.

   Operand 2 is CASE_LABEL, which is is the corresponding LABEL_DECL.

   Operand 4 is CASE_CHAIN.  This operand is only used in tree-cfg.c to

     speed up the lookup of case labels which use a particular edge in

     the control flow graph.  */

DEFTREECODE (CASE_LABEL_EXPR, "case_label_expr", tcc_statement, 4)

/* Used to represent an inline assembly statement.  ASM_STRING returns a

   STRING_CST for the instruction (e.g., "mov x, y"). ASM_OUTPUTS,

   ASM_INPUTS, and ASM_CLOBBERS represent the outputs, inputs, and clobbers

   for the statement.  ASM_LABELS, if present, indicates various destinations

   for the asm; labels cannot be combined with outputs.  */

DEFTREECODE (ASM_EXPR, "asm_expr", tcc_statement, 5)

/* Variable references for SSA analysis.  New SSA names are created every

   time a variable is assigned a new value.  The SSA builder uses SSA_NAME

   nodes to implement SSA versioning.  */

DEFTREECODE (SSA_NAME, "ssa_name", tcc_exceptional, 0)

/* Used to represent a typed exception handler.  CATCH_TYPES is the type (or

   list of types) handled, and CATCH_BODY is the code for the handler.  */

DEFTREECODE (CATCH_EXPR, "catch_expr", tcc_statement, 2)

/* Used to represent an exception specification.  EH_FILTER_TYPES is a list

   of allowed types, and EH_FILTER_FAILURE is an expression to evaluate on

   failure.  */

DEFTREECODE (EH_FILTER_EXPR, "eh_filter_expr", tcc_statement, 2)

/* Node used for describing a property that is known at compile

   time.  */

DEFTREECODE (SCEV_KNOWN, "scev_known", tcc_expression, 0)

/* Node used for describing a property that is not known at compile

   time.  */

DEFTREECODE (SCEV_NOT_KNOWN, "scev_not_known", tcc_expression, 0)

/* Polynomial chains of recurrences.

   Under the form: cr = {CHREC_LEFT (cr), +, CHREC_RIGHT (cr)}.  */

DEFTREECODE (POLYNOMIAL_CHREC, "polynomial_chrec", tcc_expression, 3)

/* Used to chain children of container statements together.

   Use the interface in tree-iterator.h to access this node.  */

DEFTREECODE (STATEMENT_LIST, "statement_list", tcc_exceptional, 0)

/* Predicate assertion.  Artificial expression generated by the optimizers

   to keep track of predicate values.  This expression may only appear on

   the RHS of assignments.

   Given X = ASSERT_EXPR , the optimizers can infer

   two things: