-@c Copyright (c) 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
-@c Free Software Foundation, Inc.
+@c Copyright (c) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
+@c 2009 Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
Occasionally, a particular tree slot (like an operand to an expression,
or a particular field in a declaration) will be referred to as
-``reserved for the back end.'' These slots are used to store RTL when
+``reserved for the back end''. These slots are used to store RTL when
the tree is converted to RTL for use by the GCC back end. However, if
that process is not taking place (e.g., if the front end is being hooked
up to an intelligent editor), then those slots may be used by the
@tindex TYPE_MIN_VALUE
@tindex TYPE_MAX_VALUE
@tindex REAL_TYPE
+@tindex FIXED_POINT_TYPE
@tindex COMPLEX_TYPE
@tindex ENUMERAL_TYPE
@tindex BOOLEAN_TYPE
@findex TYPENAME_TYPE_FULLNAME
@findex TYPE_FIELDS
@findex TYPE_PTROBV_P
+@findex TYPE_CANONICAL
+@findex TYPE_STRUCTURAL_EQUALITY_P
+@findex SET_TYPE_STRUCTURAL_EQUALITY
All types have corresponding tree nodes. However, you should not assume
that there is exactly one tree node corresponding to each type. There
-are often several nodes each of which correspond to the same type.
+are often multiple nodes corresponding to the same type.
For the most part, different kinds of types have different tree codes.
(For example, pointer types use a @code{POINTER_TYPE} code while arrays
@item TYPE_NAME
This macro returns a declaration (in the form of a @code{TYPE_DECL}) for
-the type. (Note this macro does @emph{not} return a
+the type. (Note this macro does @emph{not} return an
@code{IDENTIFIER_NODE}, as you might expect, given its name!) You can
look at the @code{DECL_NAME} of the @code{TYPE_DECL} to obtain the
actual name of the type. The @code{TYPE_NAME} will be @code{NULL_TREE}
may use @code{TYPE_PTROBV_P} to test for a pointer to object type as
well as @code{void *}.
+@item TYPE_CANONICAL
+This macro returns the ``canonical'' type for the given type
+node. Canonical types are used to improve performance in the C++ and
+Objective-C++ front ends by allowing efficient comparison between two
+type nodes in @code{same_type_p}: if the @code{TYPE_CANONICAL} values
+of the types are equal, the types are equivalent; otherwise, the types
+are not equivalent. The notion of equivalence for canonical types is
+the same as the notion of type equivalence in the language itself. For
+instance,
+
+When @code{TYPE_CANONICAL} is @code{NULL_TREE}, there is no canonical
+type for the given type node. In this case, comparison between this
+type and any other type requires the compiler to perform a deep,
+``structural'' comparison to see if the two type nodes have the same
+form and properties.
+
+The canonical type for a node is always the most fundamental type in
+the equivalence class of types. For instance, @code{int} is its own
+canonical type. A typedef @code{I} of @code{int} will have @code{int}
+as its canonical type. Similarly, @code{I*}@ and a typedef @code{IP}@
+(defined to @code{I*}) will has @code{int*} as their canonical
+type. When building a new type node, be sure to set
+@code{TYPE_CANONICAL} to the appropriate canonical type. If the new
+type is a compound type (built from other types), and any of those
+other types require structural equality, use
+@code{SET_TYPE_STRUCTURAL_EQUALITY} to ensure that the new type also
+requires structural equality. Finally, if for some reason you cannot
+guarantee that @code{TYPE_CANONICAL} will point to the canonical type,
+use @code{SET_TYPE_STRUCTURAL_EQUALITY} to make sure that the new
+type--and any type constructed based on it--requires structural
+equality. If you suspect that the canonical type system is
+miscomparing types, pass @code{--param verify-canonical-types=1} to
+the compiler or configure with @code{--enable-checking} to force the
+compiler to verify its canonical-type comparisons against the
+structural comparisons; the compiler will then print any warnings if
+the canonical types miscompare.
+
+@item TYPE_STRUCTURAL_EQUALITY_P
+This predicate holds when the node requires structural equality
+checks, e.g., when @code{TYPE_CANONICAL} is @code{NULL_TREE}.
+
+@item SET_TYPE_STRUCTURAL_EQUALITY
+This macro states that the type node it is given requires structural
+equality checks, e.g., it sets @code{TYPE_CANONICAL} to
+@code{NULL_TREE}.
+
@item same_type_p
This predicate takes two types as input, and holds if they are the same
type. For example, if one type is a @code{typedef} for the other, or
@item INTEGER_TYPE
Used to represent the various integral types, including @code{char},
@code{short}, @code{int}, @code{long}, and @code{long long}. This code
-is not used for enumeration types, nor for the @code{bool} type. Note
-that GCC's @code{CHAR_TYPE} node is @emph{not} used to represent
-@code{char}. The @code{TYPE_PRECISION} is the number of bits used in
+is not used for enumeration types, nor for the @code{bool} type.
+The @code{TYPE_PRECISION} is the number of bits used in
the representation, represented as an @code{unsigned int}. (Note that
in the general case this is not the same value as @code{TYPE_SIZE};
suppose that there were a 24-bit integer type, but that alignment
double} types. The number of bits in the floating-point representation
is given by @code{TYPE_PRECISION}, as in the @code{INTEGER_TYPE} case.
+@item FIXED_POINT_TYPE
+Used to represent the @code{short _Fract}, @code{_Fract}, @code{long
+_Fract}, @code{long long _Fract}, @code{short _Accum}, @code{_Accum},
+@code{long _Accum}, and @code{long long _Accum} types. The number of bits
+in the fixed-point representation is given by @code{TYPE_PRECISION},
+as in the @code{INTEGER_TYPE} case. There may be padding bits, fractional
+bits and integral bits. The number of fractional bits is given by
+@code{TYPE_FBIT}, and the number of integral bits is given by @code{TYPE_IBIT}.
+The fixed-point type is unsigned if @code{TYPE_UNSIGNED} holds; otherwise,
+it is signed.
+The fixed-point type is saturating if @code{TYPE_SATURATING} holds; otherwise,
+it is not saturating.
+
@item COMPLEX_TYPE
Used to represent GCC built-in @code{__complex__} data types. The
@code{TREE_TYPE} is the type of the real and imaginary parts.
@findex CLASSTYPE_DECLARED_CLASS
@findex TYPE_BINFO
@findex BINFO_TYPE
-@findex TREE_VIA_PUBLIC
-@findex TREE_VIA_PROTECTED
-@findex TREE_VIA_PRIVATE
@findex TYPE_FIELDS
@findex TYPE_VFIELD
@findex TYPE_METHODS
Every class has an associated @dfn{binfo}, which can be obtained with
@code{TYPE_BINFO}. Binfos are used to represent base-classes. The
binfo given by @code{TYPE_BINFO} is the degenerate case, whereby every
-class is considered to be its own base-class. The base classes for a
-particular binfo can be obtained with @code{BINFO_BASETYPES}. These
-base-classes are themselves binfos. The class type associated with a
-binfo is given by @code{BINFO_TYPE}. It is always the case that
-@code{BINFO_TYPE (TYPE_BINFO (x))} is the same type as @code{x}, up to
-qualifiers. However, it is not always the case that @code{TYPE_BINFO
-(BINFO_TYPE (y))} is always the same binfo as @code{y}. The reason is
-that if @code{y} is a binfo representing a base-class @code{B} of a
-derived class @code{D}, then @code{BINFO_TYPE (y)} will be @code{B},
-and @code{TYPE_BINFO (BINFO_TYPE (y))} will be @code{B} as its own
-base-class, rather than as a base-class of @code{D}.
-
-The @code{BINFO_BASETYPES} is a @code{TREE_VEC} (@pxref{Containers}).
-Base types appear in left-to-right order in this vector. You can tell
-whether or @code{public}, @code{protected}, or @code{private}
-inheritance was used by using the @code{TREE_VIA_PUBLIC},
-@code{TREE_VIA_PROTECTED}, and @code{TREE_VIA_PRIVATE} macros. Each of
-these macros takes a @code{BINFO} and is true if and only if the
-indicated kind of inheritance was used. If @code{TREE_VIA_VIRTUAL}
-holds of a binfo, then its @code{BINFO_TYPE} was inherited from
-virtually.
+class is considered to be its own base-class. The base binfos for a
+particular binfo are held in a vector, whose length is obtained with
+@code{BINFO_N_BASE_BINFOS}. The base binfos themselves are obtained
+with @code{BINFO_BASE_BINFO} and @code{BINFO_BASE_ITERATE}. To add a
+new binfo, use @code{BINFO_BASE_APPEND}. The vector of base binfos can
+be obtained with @code{BINFO_BASE_BINFOS}, but normally you do not need
+to use that. The class type associated with a binfo is given by
+@code{BINFO_TYPE}. It is not always the case that @code{BINFO_TYPE
+(TYPE_BINFO (x))}, because of typedefs and qualified types. Neither is
+it the case that @code{TYPE_BINFO (BINFO_TYPE (y))} is the same binfo as
+@code{y}. The reason is that if @code{y} is a binfo representing a
+base-class @code{B} of a derived class @code{D}, then @code{BINFO_TYPE
+(y)} will be @code{B}, and @code{TYPE_BINFO (BINFO_TYPE (y))} will be
+@code{B} as its own base-class, rather than as a base-class of @code{D}.
+
+The access to a base type can be found with @code{BINFO_BASE_ACCESS}.
+This will produce @code{access_public_node}, @code{access_private_node}
+or @code{access_protected_node}. If bases are always public,
+@code{BINFO_BASE_ACCESSES} may be @code{NULL}.
+
+@code{BINFO_VIRTUAL_P} is used to specify whether the binfo is inherited
+virtually or not. The other flags, @code{BINFO_MARKED_P} and
+@code{BINFO_FLAG_1} to @code{BINFO_FLAG_6} can be used for language
+specific use.
The following macros can be used on a tree node representing a class-type.
@ftable @code
@item LOCAL_CLASS_P
-This predicate holds if the class is local class @emph{i.e.} declared
+This predicate holds if the class is local class @emph{i.e.}@: declared
inside a function body.
@item TYPE_POLYMORPHIC_P
(represented by @code{FUNCTION_DECL} nodes), which are described in
@ref{Functions}.
+@menu
+* Working with declarations:: Macros and functions that work on
+declarations.
+* Internal structure:: How declaration nodes are represented.
+@end menu
+
+@node Working with declarations
+@subsection Working with declarations
+
Some macros can be used with any kind of declaration. These include:
@ftable @code
@item DECL_NAME
@item FIELD_DECL
These nodes represent non-static data members. The @code{DECL_SIZE} and
-@code{DECL_ALIGN} behave as for @code{VAR_DECL} nodes. The
-@code{DECL_FIELD_BITPOS} gives the first bit used for this field, as an
-@code{INTEGER_CST}. These values are indexed from zero, where zero
-indicates the first bit in the object.
-
-If @code{DECL_C_BIT_FIELD} holds, this field is a bit-field.
+@code{DECL_ALIGN} behave as for @code{VAR_DECL} nodes.
+The position of the field within the parent record is specified by a
+combination of three attributes. @code{DECL_FIELD_OFFSET} is the position,
+counting in bytes, of the @code{DECL_OFFSET_ALIGN}-bit sized word containing
+the bit of the field closest to the beginning of the structure.
+@code{DECL_FIELD_BIT_OFFSET} is the bit offset of the first bit of the field
+within this word; this may be nonzero even for fields that are not bit-fields,
+since @code{DECL_OFFSET_ALIGN} may be greater than the natural alignment
+of the field's type.
+
+If @code{DECL_C_BIT_FIELD} holds, this field is a bit-field. In a bit-field,
+@code{DECL_BIT_FIELD_TYPE} also contains the type that was originally
+specified for it, while DECL_TYPE may be a modified type with lesser precision,
+according to the size of the bit field.
@item NAMESPACE_DECL
@xref{Namespaces}.
@end table
+@node Internal structure
+@subsection Internal structure
+
+@code{DECL} nodes are represented internally as a hierarchy of
+structures.
+
+@menu
+* Current structure hierarchy:: The current DECL node structure
+hierarchy.
+* Adding new DECL node types:: How to add a new DECL node to a
+frontend.
+@end menu
+
+@node Current structure hierarchy
+@subsubsection Current structure hierarchy
+
+@table @code
+
+@item struct tree_decl_minimal
+This is the minimal structure to inherit from in order for common
+@code{DECL} macros to work. The fields it contains are a unique ID,
+source location, context, and name.
+
+@item struct tree_decl_common
+This structure inherits from @code{struct tree_decl_minimal}. It
+contains fields that most @code{DECL} nodes need, such as a field to
+store alignment, machine mode, size, and attributes.
+
+@item struct tree_field_decl
+This structure inherits from @code{struct tree_decl_common}. It is
+used to represent @code{FIELD_DECL}.
+
+@item struct tree_label_decl
+This structure inherits from @code{struct tree_decl_common}. It is
+used to represent @code{LABEL_DECL}.
+
+@item struct tree_translation_unit_decl
+This structure inherits from @code{struct tree_decl_common}. It is
+used to represent @code{TRANSLATION_UNIT_DECL}.
+
+@item struct tree_decl_with_rtl
+This structure inherits from @code{struct tree_decl_common}. It
+contains a field to store the low-level RTL associated with a
+@code{DECL} node.
+
+@item struct tree_result_decl
+This structure inherits from @code{struct tree_decl_with_rtl}. It is
+used to represent @code{RESULT_DECL}.
+
+@item struct tree_const_decl
+This structure inherits from @code{struct tree_decl_with_rtl}. It is
+used to represent @code{CONST_DECL}.
+
+@item struct tree_parm_decl
+This structure inherits from @code{struct tree_decl_with_rtl}. It is
+used to represent @code{PARM_DECL}.
+
+@item struct tree_decl_with_vis
+This structure inherits from @code{struct tree_decl_with_rtl}. It
+contains fields necessary to store visibility information, as well as
+a section name and assembler name.
+
+@item struct tree_var_decl
+This structure inherits from @code{struct tree_decl_with_vis}. It is
+used to represent @code{VAR_DECL}.
+
+@item struct tree_function_decl
+This structure inherits from @code{struct tree_decl_with_vis}. It is
+used to represent @code{FUNCTION_DECL}.
+
+@end table
+@node Adding new DECL node types
+@subsubsection Adding new DECL node types
+
+Adding a new @code{DECL} tree consists of the following steps
+
+@table @asis
+
+@item Add a new tree code for the @code{DECL} node
+For language specific @code{DECL} nodes, there is a @file{.def} file
+in each frontend directory where the tree code should be added.
+For @code{DECL} nodes that are part of the middle-end, the code should
+be added to @file{tree.def}.
+
+@item Create a new structure type for the @code{DECL} node
+These structures should inherit from one of the existing structures in
+the language hierarchy by using that structure as the first member.
+
+@smallexample
+struct tree_foo_decl
+@{
+ struct tree_decl_with_vis common;
+@}
+@end smallexample
+
+Would create a structure name @code{tree_foo_decl} that inherits from
+@code{struct tree_decl_with_vis}.
+
+For language specific @code{DECL} nodes, this new structure type
+should go in the appropriate @file{.h} file.
+For @code{DECL} nodes that are part of the middle-end, the structure
+type should go in @file{tree.h}.
+
+@item Add a member to the tree structure enumerator for the node
+For garbage collection and dynamic checking purposes, each @code{DECL}
+node structure type is required to have a unique enumerator value
+specified with it.
+For language specific @code{DECL} nodes, this new enumerator value
+should go in the appropriate @file{.def} file.
+For @code{DECL} nodes that are part of the middle-end, the enumerator
+values are specified in @file{treestruct.def}.
+
+@item Update @code{union tree_node}
+In order to make your new structure type usable, it must be added to
+@code{union tree_node}.
+For language specific @code{DECL} nodes, a new entry should be added
+to the appropriate @file{.h} file of the form
+@smallexample
+ struct tree_foo_decl GTY ((tag ("TS_VAR_DECL"))) foo_decl;
+@end smallexample
+For @code{DECL} nodes that are part of the middle-end, the additional
+member goes directly into @code{union tree_node} in @file{tree.h}.
+
+@item Update dynamic checking info
+In order to be able to check whether accessing a named portion of
+@code{union tree_node} is legal, and whether a certain @code{DECL} node
+contains one of the enumerated @code{DECL} node structures in the
+hierarchy, a simple lookup table is used.
+This lookup table needs to be kept up to date with the tree structure
+hierarchy, or else checking and containment macros will fail
+inappropriately.
+
+For language specific @code{DECL} nodes, their is an @code{init_ts}
+function in an appropriate @file{.c} file, which initializes the lookup
+table.
+Code setting up the table for new @code{DECL} nodes should be added
+there.
+For each @code{DECL} tree code and enumerator value representing a
+member of the inheritance hierarchy, the table should contain 1 if
+that tree code inherits (directly or indirectly) from that member.
+Thus, a @code{FOO_DECL} node derived from @code{struct decl_with_rtl},
+and enumerator value @code{TS_FOO_DECL}, would be set up as follows
+@smallexample
+tree_contains_struct[FOO_DECL][TS_FOO_DECL] = 1;
+tree_contains_struct[FOO_DECL][TS_DECL_WRTL] = 1;
+tree_contains_struct[FOO_DECL][TS_DECL_COMMON] = 1;
+tree_contains_struct[FOO_DECL][TS_DECL_MINIMAL] = 1;
+@end smallexample
+
+For @code{DECL} nodes that are part of the middle-end, the setup code
+goes into @file{tree.c}.
+
+@item Add macros to access any new fields and flags
+
+Each added field or flag should have a macro that is used to access
+it, that performs appropriate checking to ensure only the right type of
+@code{DECL} nodes access the field.
+
+These macros generally take the following form
+@smallexample
+#define FOO_DECL_FIELDNAME(NODE) FOO_DECL_CHECK(NODE)->foo_decl.fieldname
+@end smallexample
+However, if the structure is simply a base class for further
+structures, something like the following should be used
+@smallexample
+#define BASE_STRUCT_CHECK(T) CONTAINS_STRUCT_CHECK(T, TS_BASE_STRUCT)
+#define BASE_STRUCT_FIELDNAME(NODE) \
+ (BASE_STRUCT_CHECK(NODE)->base_struct.fieldname
+@end smallexample
+
+@end table
+
+
@c ---------------------------------------------------------------------
@c Functions
@c ---------------------------------------------------------------------
@findex OVL_NEXT
A function is represented by a @code{FUNCTION_DECL} node. A set of
-overloaded functions is sometimes represented by a @code{OVERLOAD} node.
+overloaded functions is sometimes represented by an @code{OVERLOAD} node.
An @code{OVERLOAD} node is not a declaration, so none of the
@samp{DECL_} macros should be used on an @code{OVERLOAD}. An
referenced @code{VAR_DECL}. If the @code{DECL_CONTEXT} for the
referenced @code{VAR_DECL} is not the same as the function currently
being processed, and neither @code{DECL_EXTERNAL} nor
-@code{DECL_STATIC} hold, then the reference is to a local variable in
+@code{TREE_STATIC} hold, then the reference is to a local variable in
a containing function, and the back end must take appropriate action.
@menu
@findex DECL_GLOBAL_CTOR_P
@findex DECL_GLOBAL_DTOR_P
@findex GLOBAL_INIT_PRIORITY
+@findex DECL_FUNCTION_SPECIFIC_TARGET
+@findex DECL_FUNCTION_SPECIFIC_OPTIMIZATION
The following macros and functions can be used on a @code{FUNCTION_DECL}:
@ftable @code
@item TYPE_NOTHROW_P
This predicate holds when the exception-specification of its arguments
-if of the form `@code{()}'.
+is of the form `@code{()}'.
@item DECL_ARRAY_DELETE_OPERATOR_P
This predicate holds if the function an overloaded
@code{operator delete[]}.
+@item DECL_FUNCTION_SPECIFIC_TARGET
+This macro returns a tree node that holds the target options that are
+to be used to compile this particular function or @code{NULL_TREE} if
+the function is to be compiled with the target options specified on
+the command line.
+
+@item DECL_FUNCTION_SPECIFIC_OPTIMIZATION
+This macro returns a tree node that holds the optimization options
+that are to be used to compile this particular function or
+@code{NULL_TREE} if the function is to be compiled with the
+optimization options specified on the command line.
@end ftable
@c ---------------------------------------------------------------------
@findex IF_COND
@findex THEN_CLAUSE
@findex ELSE_CLAUSE
-@tindex RETURN_INIT
@tindex RETURN_STMT
@findex RETURN_EXPR
@tindex SUBOBJECT
@{
case IF_STMT:
process_stmt (THEN_CLAUSE (stmt));
- /* More processing here. */
+ /* @r{More processing here.} */
break;
@dots{}
@code{IDENTIFIER_NODE} giving the name of the label can be obtained from
the @code{LABEL_DECL} with @code{DECL_NAME}.
-@item RETURN_INIT
+@item RETURN_EXPR
-If the function uses the G++ ``named return value'' extension, meaning
-that the function has been defined like:
-@smallexample
-S f(int) return s @{@dots{}@}
-@end smallexample
-then there will be a @code{RETURN_INIT}. There is never a named
-returned value for a constructor. The first argument to the
-@code{RETURN_INIT} is the name of the object returned; the second
-argument is the initializer for the object. The object is initialized
-when the @code{RETURN_INIT} is encountered. The object referred to is
-the actual object returned; this extension is a manual way of doing the
-``return-value optimization.'' Therefore, the object must actually be
-constructed in the place where the object will be returned.
-
-@item RETURN_STMT
-
-Used to represent a @code{return} statement. The @code{RETURN_EXPR} is
-the expression returned; it will be @code{NULL_TREE} if the statement
-was just
+Used to represent a @code{return} statement. Operand 0 represents the
+value to return. It should either be the @code{RESULT_DECL} for the
+containing function, or a @code{MODIFY_EXPR} or @code{INIT_EXPR}
+setting the function's @code{RESULT_DECL}. It will be
+@code{NULL_TREE} if the statement was just
@smallexample
return;
@end smallexample
@item SWITCH_STMT
-Used to represent a @code{switch} statement. The @code{SWITCH_COND} is
-the expression on which the switch is occurring. See the documentation
+Used to represent a @code{switch} statement. The @code{SWITCH_STMT_COND}
+is the expression on which the switch is occurring. See the documentation
for an @code{IF_STMT} for more information on the representation used
-for the condition. The @code{SWITCH_BODY} is the body of the switch
-statement. The @code{SWITCH_TYPE} is the original type of switch
+for the condition. The @code{SWITCH_STMT_BODY} is the body of the switch
+statement. The @code{SWITCH_STMT_TYPE} is the original type of switch
expression as given in the source, before any compiler conversions.
@item TRY_BLOCK
@findex tree_int_cst_lt
@findex tree_int_cst_equal
@tindex REAL_CST
+@tindex FIXED_CST
@tindex COMPLEX_CST
@tindex VECTOR_CST
@tindex STRING_CST
@tindex NON_LVALUE_EXPR
@tindex NOP_EXPR
@tindex CONVERT_EXPR
+@tindex FIXED_CONVERT_EXPR
@tindex THROW_EXPR
@tindex LSHIFT_EXPR
@tindex RSHIFT_EXPR
@tindex TRUTH_AND_EXPR
@tindex TRUTH_OR_EXPR
@tindex TRUTH_XOR_EXPR
+@tindex POINTER_PLUS_EXPR
@tindex PLUS_EXPR
@tindex MINUS_EXPR
@tindex MULT_EXPR
@tindex EXACT_DIV_EXPR
@tindex ARRAY_REF
@tindex ARRAY_RANGE_REF
+@tindex TARGET_MEM_REF
@tindex LT_EXPR
@tindex LE_EXPR
@tindex GT_EXPR
@tindex TARGET_EXPR
@tindex AGGR_INIT_EXPR
@tindex VA_ARG_EXPR
+@tindex OMP_PARALLEL
+@tindex OMP_FOR
+@tindex OMP_SECTIONS
+@tindex OMP_SINGLE
+@tindex OMP_SECTION
+@tindex OMP_MASTER
+@tindex OMP_ORDERED
+@tindex OMP_CRITICAL
+@tindex OMP_RETURN
+@tindex OMP_CONTINUE
+@tindex OMP_ATOMIC
+@tindex OMP_CLAUSE
+@tindex VEC_LSHIFT_EXPR
+@tindex VEC_RSHIFT_EXPR
+@tindex VEC_WIDEN_MULT_HI_EXPR
+@tindex VEC_WIDEN_MULT_LO_EXPR
+@tindex VEC_UNPACK_HI_EXPR
+@tindex VEC_UNPACK_LO_EXPR
+@tindex VEC_UNPACK_FLOAT_HI_EXPR
+@tindex VEC_UNPACK_FLOAT_LO_EXPR
+@tindex VEC_PACK_TRUNC_EXPR
+@tindex VEC_PACK_SAT_EXPR
+@tindex VEC_PACK_FIX_TRUNC_EXPR
+@tindex VEC_EXTRACT_EVEN_EXPR
+@tindex VEC_EXTRACT_ODD_EXPR
+@tindex VEC_INTERLEAVE_HIGH_EXPR
+@tindex VEC_INTERLEAVE_LOW_EXPR
The internal representation for expressions is for the most part quite
straightforward. However, there are a few facts that one must bear in
acyclic graph. (For example there may be many references to the integer
constant zero throughout the source program; many of these will be
represented by the same expression node.) You should not rely on
-certain kinds of node being shared, nor should rely on certain kinds of
+certain kinds of node being shared, nor should you rely on certain kinds of
nodes being unshared.
The following macros can be used with all expression nodes:
@noindent
As this example indicates, the operands are zero-indexed.
+All the expressions starting with @code{OMP_} represent directives and
+clauses used by the OpenMP API @w{@uref{http://www.openmp.org/}}.
+
The table below begins with constants, moves on to unary expressions,
then proceeds to binary expressions, and concludes with various other
kinds of expressions:
FIXME: Talk about how to obtain representations of this constant, do
comparisons, and so forth.
+@item FIXED_CST
+
+These nodes represent fixed-point constants. The type of these constants
+is obtained with @code{TREE_TYPE}. @code{TREE_FIXED_CST_PTR} points to
+a @code{struct fixed_value}; @code{TREE_FIXED_CST} returns the structure
+itself. @code{struct fixed_value} contains @code{data} with the size of two
+@code{HOST_BITS_PER_WIDE_INT} and @code{mode} as the associated fixed-point
+machine mode for @code{data}.
+
@item COMPLEX_CST
These nodes are used to represent complex number constants, that is a
@code{__complex__} whose parts are constant nodes. The
@item TRUTH_NOT_EXPR
These nodes represent logical negation, and will always have integral
-(or boolean) type. The operand is the value being negated.
+(or boolean) type. The operand is the value being negated. The type
+of the operand and that of the result are always of @code{BOOLEAN_TYPE}
+or @code{INTEGER_TYPE}.
@item PREDECREMENT_EXPR
@itemx PREINCREMENT_EXPR
@item FIX_TRUNC_EXPR
These nodes represent conversion of a floating-point value to an
-integer. The single operand will have a floating-point type, while the
+integer. The single operand will have a floating-point type, while
the complete expression will have an integral (or boolean) type. The
operand is rounded towards zero.
conversion is never represented by a @code{CONVERT_EXPR}; instead, the
function calls are made explicit.
+@item FIXED_CONVERT_EXPR
+These nodes are used to represent conversions that involve fixed-point
+values. For example, from a fixed-point value to another fixed-point value,
+from an integer to a fixed-point value, from a fixed-point value to an
+integer, from a floating-point value to a fixed-point value, or from
+a fixed-point value to a floating-point value.
+
@item THROW_EXPR
These nodes represent @code{throw} expressions. The single operand is
an expression for the code that should be executed to throw the
high-order bits should be zero-filled when the expression has unsigned
type and filled with the sign bit when the expression has signed type.
Note that the result is undefined if the second operand is larger
-than the first operand's type size.
+than or equal to the first operand's type size.
@item BIT_IOR_EXPR
@item TRUTH_ANDIF_EXPR
@itemx TRUTH_ORIF_EXPR
-These nodes represent logical and and logical or, respectively. These
-operators are not strict; i.e., the second operand is evaluated only if
-the value of the expression is not determined by evaluation of the first
-operand. The type of the operands, and the result type, is always of
-boolean or integral type.
+These nodes represent logical ``and'' and logical ``or'', respectively.
+These operators are not strict; i.e., the second operand is evaluated
+only if the value of the expression is not determined by evaluation of
+the first operand. The type of the operands and that of the result are
+always of @code{BOOLEAN_TYPE} or @code{INTEGER_TYPE}.
@item TRUTH_AND_EXPR
@itemx TRUTH_OR_EXPR
They are strict; both arguments are always evaluated. There are no
corresponding operators in C or C++, but the front end will sometimes
generate these expressions anyhow, if it can tell that strictness does
-not matter.
+not matter. The type of the operands and that of the result are
+always of @code{BOOLEAN_TYPE} or @code{INTEGER_TYPE}.
+
+@itemx POINTER_PLUS_EXPR
+This node represents pointer arithmetic. The first operand is always
+a pointer/reference type. The second operand is always an unsigned
+integer type compatible with sizetype. This is the only binary
+arithmetic operand that can operate on pointer types.
@itemx PLUS_EXPR
@itemx MINUS_EXPR
result. @code{TRUNC_DIV_EXPR} rounds towards zero, @code{FLOOR_DIV_EXPR}
rounds towards negative infinity, @code{CEIL_DIV_EXPR} rounds towards
positive infinity and @code{ROUND_DIV_EXPR} rounds to the closest integer.
-Integer division in C and C++ is truncating, i.e@. @code{TRUNC_DIV_EXPR}.
+Integer division in C and C++ is truncating, i.e.@: @code{TRUNC_DIV_EXPR}.
The behavior of these operations on signed arithmetic overflow, when
dividing the minimum signed integer by minus one, is controlled by the
The integer modulus of two operands @code{a} and @code{b} is
defined as @code{a - (a/b)*b} where the division calculated using
the corresponding division operator. Hence for @code{TRUNC_MOD_EXPR}
-this definition assumes division using truncation towards zero, i.e@.
+this definition assumes division using truncation towards zero, i.e.@:
@code{TRUNC_DIV_EXPR}. Integer remainder in C and C++ uses truncating
-division, i.e@. @code{TRUNC_MOD_EXPR}.
+division, i.e.@: @code{TRUNC_MOD_EXPR}.
@item EXACT_DIV_EXPR
The @code{EXACT_DIV_EXPR} code is used to represent integer divisions where
the second is the index. To calculate the address of the memory
accessed, you must scale the index by the size of the type of the array
elements. The type of these expressions must be the type of a component of
-the array.
+the array. The third and fourth operands are used after gimplification
+to represent the lower bound and component size but should not be used
+directly; call @code{array_ref_low_bound} and @code{array_ref_element_size}
+instead.
@item ARRAY_RANGE_REF
These nodes represent access to a range (or ``slice'') of an array. The
type is the same as that of the first operand. The range of that array
type determines the amount of data these expressions access.
+@item TARGET_MEM_REF
+These nodes represent memory accesses whose address directly map to
+an addressing mode of the target architecture. The first argument
+is @code{TMR_SYMBOL} and must be a @code{VAR_DECL} of an object with
+a fixed address. The second argument is @code{TMR_BASE} and the
+third one is @code{TMR_INDEX}. The fourth argument is
+@code{TMR_STEP} and must be an @code{INTEGER_CST}. The fifth
+argument is @code{TMR_OFFSET} and must be an @code{INTEGER_CST}.
+Any of the arguments may be NULL if the appropriate component
+does not appear in the address. Address of the @code{TARGET_MEM_REF}
+is determined in the following way.
+
+@smallexample
+&TMR_SYMBOL + TMR_BASE + TMR_INDEX * TMR_STEP + TMR_OFFSET
+@end smallexample
+
+The sixth argument is the reference to the original memory access, which
+is preserved for the purposes of the RTL alias analysis. The seventh
+argument is a tag representing the results of tree level alias analysis.
+
@item LT_EXPR
@itemx LE_EXPR
@itemx GT_EXPR
@item INIT_EXPR
These nodes are just like @code{MODIFY_EXPR}, but are used only when a
-variable is initialized, rather than assigned to subsequently.
+variable is initialized, rather than assigned to subsequently. This
+means that we can assume that the target of the initialization is not
+used in computing its own value; any reference to the lhs in computing
+the rhs is undefined.
@item COMPONENT_REF
These nodes represent non-static data member accesses. The first
operand is the object (rather than a pointer to it); the second operand
-is the @code{FIELD_DECL} for the data member.
+is the @code{FIELD_DECL} for the data member. The third operand represents
+the byte offset of the field, but should not be used directly; call
+@code{component_ref_field_offset} instead.
@item COMPOUND_EXPR
These nodes represent comma-expressions. The first operand is an
@item CALL_EXPR
These nodes are used to represent calls to functions, including
-non-static member functions. The first operand is a pointer to the
+non-static member functions. @code{CALL_EXPR}s are implemented as
+expression nodes with a variable number of operands. Rather than using
+@code{TREE_OPERAND} to extract them, it is preferable to use the
+specialized accessor macros and functions that operate specifically on
+@code{CALL_EXPR} nodes.
+
+@code{CALL_EXPR_FN} returns a pointer to the
function to call; it is always an expression whose type is a
-@code{POINTER_TYPE}. The second argument is a @code{TREE_LIST}. The
-arguments to the call appear left-to-right in the list. The
-@code{TREE_VALUE} of each list node contains the expression
-corresponding to that argument. (The value of @code{TREE_PURPOSE} for
-these nodes is unspecified, and should be ignored.) For non-static
+@code{POINTER_TYPE}.
+
+The number of arguments to the call is returned by @code{call_expr_nargs},
+while the arguments themselves can be accessed with the @code{CALL_EXPR_ARG}
+macro. The arguments are zero-indexed and numbered left-to-right.
+You can iterate over the arguments using @code{FOR_EACH_CALL_EXPR_ARG}, as in:
+
+@smallexample
+tree call, arg;
+call_expr_arg_iterator iter;
+FOR_EACH_CALL_EXPR_ARG (arg, iter, call)
+ /* arg is bound to successive arguments of call. */
+ @dots{};
+@end smallexample
+
+For non-static
member functions, there will be an operand corresponding to the
@code{this} pointer. There will always be expressions corresponding to
all of the arguments, even if the function is declared with default
arguments and some arguments are not explicitly provided at the call
sites.
+@code{CALL_EXPR}s also have a @code{CALL_EXPR_STATIC_CHAIN} operand that
+is used to implement nested functions. This operand is otherwise null.
+
@item STMT_EXPR
These nodes are used to represent GCC's statement-expression extension.
The statement-expression extension allows code like this:
@smallexample
int f() @{ return (@{ int j; j = 3; j + 7; @}); @}
@end smallexample
-In other words, an sequence of statements may occur where a single
+In other words, a sequence of statements may occur where a single
expression would normally appear. The @code{STMT_EXPR} node represents
such an expression. The @code{STMT_EXPR_STMT} gives the statement
contained in the expression. The value of the expression is the value
If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is an
@code{ARRAY_TYPE}, then the @code{TREE_PURPOSE} of each element in the
-@code{TREE_LIST} will be an @code{INTEGER_CST}. This constant indicates
-which element of the array (indexed from zero) is being assigned to;
-again, the @code{TREE_VALUE} is the corresponding initializer. If the
-@code{TREE_PURPOSE} is @code{NULL_TREE}, then the initializer is for the
-next available array element.
+@code{TREE_LIST} will be an @code{INTEGER_CST} or a @code{RANGE_EXPR} of
+two @code{INTEGER_CST}s. A single @code{INTEGER_CST} indicates which
+element of the array (indexed from zero) is being assigned to. A
+@code{RANGE_EXPR} indicates an inclusive range of elements to
+initialize. In both cases the @code{TREE_VALUE} is the corresponding
+initializer. It is re-evaluated for each element of a
+@code{RANGE_EXPR}. If the @code{TREE_PURPOSE} is @code{NULL_TREE}, then
+the initializer is for the next available array element.
In the front end, you should not depend on the fields appearing in any
particular order. However, in the middle end, fields must appear in
represented. Unrepresented fields will be set to zero.
@item COMPOUND_LITERAL_EXPR
-@findex COMPOUND_LITERAL_EXPR_DECL_STMT
+@findex COMPOUND_LITERAL_EXPR_DECL_EXPR
@findex COMPOUND_LITERAL_EXPR_DECL
These nodes represent ISO C99 compound literals. The
-@code{COMPOUND_LITERAL_EXPR_DECL_STMT} is a @code{DECL_STMT}
+@code{COMPOUND_LITERAL_EXPR_DECL_EXPR} is a @code{DECL_EXPR}
containing an anonymous @code{VAR_DECL} for
the unnamed object represented by the compound literal; the
@code{DECL_INITIAL} of that @code{VAR_DECL} is a @code{CONSTRUCTOR}
An @code{AGGR_INIT_EXPR} represents the initialization as the return
value of a function call, or as the result of a constructor. An
@code{AGGR_INIT_EXPR} will only appear as a full-expression, or as the
-second operand of a @code{TARGET_EXPR}. The first operand to the
-@code{AGGR_INIT_EXPR} is the address of a function to call, just as in
-a @code{CALL_EXPR}. The second operand are the arguments to pass that
-function, as a @code{TREE_LIST}, again in a manner similar to that of
-a @code{CALL_EXPR}.
+second operand of a @code{TARGET_EXPR}. @code{AGGR_INIT_EXPR}s have
+a representation similar to that of @code{CALL_EXPR}s. You can use
+the @code{AGGR_INIT_EXPR_FN} and @code{AGGR_INIT_EXPR_ARG} macros to access
+the function to call and the arguments to pass.
If @code{AGGR_INIT_VIA_CTOR_P} holds of the @code{AGGR_INIT_EXPR}, then
-the initialization is via a constructor call. The address of the third
-operand of the @code{AGGR_INIT_EXPR}, which is always a @code{VAR_DECL},
+the initialization is via a constructor call. The address of the
+@code{AGGR_INIT_EXPR_SLOT} operand, which is always a @code{VAR_DECL},
is taken, and this value replaces the first argument in the argument
list.
Its @code{TREE_TYPE} yields the tree representation for @code{type} and
its sole argument yields the representation for @code{ap}.
+@item OMP_PARALLEL
+
+Represents @code{#pragma omp parallel [clause1 @dots{} clauseN]}. It
+has four operands:
+
+Operand @code{OMP_PARALLEL_BODY} is valid while in GENERIC and
+High GIMPLE forms. It contains the body of code to be executed
+by all the threads. During GIMPLE lowering, this operand becomes
+@code{NULL} and the body is emitted linearly after
+@code{OMP_PARALLEL}.
+
+Operand @code{OMP_PARALLEL_CLAUSES} is the list of clauses
+associated with the directive.
+
+Operand @code{OMP_PARALLEL_FN} is created by
+@code{pass_lower_omp}, it contains the @code{FUNCTION_DECL}
+for the function that will contain the body of the parallel
+region.
+
+Operand @code{OMP_PARALLEL_DATA_ARG} is also created by
+@code{pass_lower_omp}. If there are shared variables to be
+communicated to the children threads, this operand will contain
+the @code{VAR_DECL} that contains all the shared values and
+variables.
+
+@item OMP_FOR
+
+Represents @code{#pragma omp for [clause1 @dots{} clauseN]}. It
+has 5 operands:
+
+Operand @code{OMP_FOR_BODY} contains the loop body.
+
+Operand @code{OMP_FOR_CLAUSES} is the list of clauses
+associated with the directive.
+
+Operand @code{OMP_FOR_INIT} is the loop initialization code of
+the form @code{VAR = N1}.
+
+Operand @code{OMP_FOR_COND} is the loop conditional expression
+of the form @code{VAR @{<,>,<=,>=@} N2}.
+
+Operand @code{OMP_FOR_INCR} is the loop index increment of the
+form @code{VAR @{+=,-=@} INCR}.
+
+Operand @code{OMP_FOR_PRE_BODY} contains side-effect code from
+operands @code{OMP_FOR_INIT}, @code{OMP_FOR_COND} and
+@code{OMP_FOR_INC}. These side-effects are part of the
+@code{OMP_FOR} block but must be evaluated before the start of
+loop body.
+
+The loop index variable @code{VAR} must be a signed integer variable,
+which is implicitly private to each thread. Bounds
+@code{N1} and @code{N2} and the increment expression
+@code{INCR} are required to be loop invariant integer
+expressions that are evaluated without any synchronization. The
+evaluation order, frequency of evaluation and side-effects are
+unspecified by the standard.
+
+@item OMP_SECTIONS
+
+Represents @code{#pragma omp sections [clause1 @dots{} clauseN]}.
+
+Operand @code{OMP_SECTIONS_BODY} contains the sections body,
+which in turn contains a set of @code{OMP_SECTION} nodes for
+each of the concurrent sections delimited by @code{#pragma omp
+section}.
+
+Operand @code{OMP_SECTIONS_CLAUSES} is the list of clauses
+associated with the directive.
+
+@item OMP_SECTION
+
+Section delimiter for @code{OMP_SECTIONS}.
+
+@item OMP_SINGLE
+
+Represents @code{#pragma omp single}.
+
+Operand @code{OMP_SINGLE_BODY} contains the body of code to be
+executed by a single thread.
+
+Operand @code{OMP_SINGLE_CLAUSES} is the list of clauses
+associated with the directive.
+
+@item OMP_MASTER
+
+Represents @code{#pragma omp master}.
+
+Operand @code{OMP_MASTER_BODY} contains the body of code to be
+executed by the master thread.
+
+@item OMP_ORDERED
+
+Represents @code{#pragma omp ordered}.
+
+Operand @code{OMP_ORDERED_BODY} contains the body of code to be
+executed in the sequential order dictated by the loop index
+variable.
+
+@item OMP_CRITICAL
+
+Represents @code{#pragma omp critical [name]}.
+
+Operand @code{OMP_CRITICAL_BODY} is the critical section.
+
+Operand @code{OMP_CRITICAL_NAME} is an optional identifier to
+label the critical section.
+
+@item OMP_RETURN
+
+This does not represent any OpenMP directive, it is an artificial
+marker to indicate the end of the body of an OpenMP@. It is used
+by the flow graph (@code{tree-cfg.c}) and OpenMP region
+building code (@code{omp-low.c}).
+
+@item OMP_CONTINUE
+
+Similarly, this instruction does not represent an OpenMP
+directive, it is used by @code{OMP_FOR} and
+@code{OMP_SECTIONS} to mark the place where the code needs to
+loop to the next iteration (in the case of @code{OMP_FOR}) or
+the next section (in the case of @code{OMP_SECTIONS}).
+
+In some cases, @code{OMP_CONTINUE} is placed right before
+@code{OMP_RETURN}. But if there are cleanups that need to
+occur right after the looping body, it will be emitted between
+@code{OMP_CONTINUE} and @code{OMP_RETURN}.
+
+@item OMP_ATOMIC
+
+Represents @code{#pragma omp atomic}.
+
+Operand 0 is the address at which the atomic operation is to be
+performed.
+
+Operand 1 is the expression to evaluate. The gimplifier tries
+three alternative code generation strategies. Whenever possible,
+an atomic update built-in is used. If that fails, a
+compare-and-swap loop is attempted. If that also fails, a
+regular critical section around the expression is used.
+
+@item OMP_CLAUSE
+
+Represents clauses associated with one of the @code{OMP_} directives.
+Clauses are represented by separate sub-codes defined in
+@file{tree.h}. Clauses codes can be one of:
+@code{OMP_CLAUSE_PRIVATE}, @code{OMP_CLAUSE_SHARED},
+@code{OMP_CLAUSE_FIRSTPRIVATE},
+@code{OMP_CLAUSE_LASTPRIVATE}, @code{OMP_CLAUSE_COPYIN},
+@code{OMP_CLAUSE_COPYPRIVATE}, @code{OMP_CLAUSE_IF},
+@code{OMP_CLAUSE_NUM_THREADS}, @code{OMP_CLAUSE_SCHEDULE},
+@code{OMP_CLAUSE_NOWAIT}, @code{OMP_CLAUSE_ORDERED},
+@code{OMP_CLAUSE_DEFAULT}, and @code{OMP_CLAUSE_REDUCTION}. Each code
+represents the corresponding OpenMP clause.
+
+Clauses associated with the same directive are chained together
+via @code{OMP_CLAUSE_CHAIN}. Those clauses that accept a list
+of variables are restricted to exactly one, accessed with
+@code{OMP_CLAUSE_VAR}. Therefore, multiple variables under the
+same clause @code{C} need to be represented as multiple @code{C} clauses
+chained together. This facilitates adding new clauses during
+compilation.
+
+@item VEC_LSHIFT_EXPR
+@itemx VEC_RSHIFT_EXPR
+These nodes represent whole vector left and right shifts, respectively.
+The first operand is the vector to shift; it will always be of vector type.
+The second operand is an expression for the number of bits by which to
+shift. Note that the result is undefined if the second operand is larger
+than or equal to the first operand's type size.
+
+@item VEC_WIDEN_MULT_HI_EXPR
+@itemx VEC_WIDEN_MULT_LO_EXPR
+These nodes represent widening vector multiplication of the high and low
+parts of the two input vectors, respectively. Their operands are vectors
+that contain the same number of elements (@code{N}) of the same integral type.
+The result is a vector that contains half as many elements, of an integral type
+whose size is twice as wide. In the case of @code{VEC_WIDEN_MULT_HI_EXPR} the
+high @code{N/2} elements of the two vector are multiplied to produce the
+vector of @code{N/2} products. In the case of @code{VEC_WIDEN_MULT_LO_EXPR} the
+low @code{N/2} elements of the two vector are multiplied to produce the
+vector of @code{N/2} products.
+
+@item VEC_UNPACK_HI_EXPR
+@itemx VEC_UNPACK_LO_EXPR
+These nodes represent unpacking of the high and low parts of the input vector,
+respectively. The single operand is a vector that contains @code{N} elements
+of the same integral or floating point type. The result is a vector
+that contains half as many elements, of an integral or floating point type
+whose size is twice as wide. In the case of @code{VEC_UNPACK_HI_EXPR} the
+high @code{N/2} elements of the vector are extracted and widened (promoted).
+In the case of @code{VEC_UNPACK_LO_EXPR} the low @code{N/2} elements of the
+vector are extracted and widened (promoted).
+
+@item VEC_UNPACK_FLOAT_HI_EXPR
+@itemx VEC_UNPACK_FLOAT_LO_EXPR
+These nodes represent unpacking of the high and low parts of the input vector,
+where the values are converted from fixed point to floating point. The
+single operand is a vector that contains @code{N} elements of the same
+integral type. The result is a vector that contains half as many elements
+of a floating point type whose size is twice as wide. In the case of
+@code{VEC_UNPACK_HI_EXPR} the high @code{N/2} elements of the vector are
+extracted, converted and widened. In the case of @code{VEC_UNPACK_LO_EXPR}
+the low @code{N/2} elements of the vector are extracted, converted and widened.
+
+@item VEC_PACK_TRUNC_EXPR
+This node represents packing of truncated elements of the two input vectors
+into the output vector. Input operands are vectors that contain the same
+number of elements of the same integral or floating point type. The result
+is a vector that contains twice as many elements of an integral or floating
+point type whose size is half as wide. The elements of the two vectors are
+demoted and merged (concatenated) to form the output vector.
+
+@item VEC_PACK_SAT_EXPR
+This node represents packing of elements of the two input vectors into the
+output vector using saturation. Input operands are vectors that contain
+the same number of elements of the same integral type. The result is a
+vector that contains twice as many elements of an integral type whose size
+is half as wide. The elements of the two vectors are demoted and merged
+(concatenated) to form the output vector.
+
+@item VEC_PACK_FIX_TRUNC_EXPR
+This node represents packing of elements of the two input vectors into the
+output vector, where the values are converted from floating point
+to fixed point. Input operands are vectors that contain the same number
+of elements of a floating point type. The result is a vector that contains
+twice as many elements of an integral type whose size is half as wide. The
+elements of the two vectors are merged (concatenated) to form the output
+vector.
+
+@item VEC_EXTRACT_EVEN_EXPR
+@itemx VEC_EXTRACT_ODD_EXPR
+These nodes represent extracting of the even/odd elements of the two input
+vectors, respectively. Their operands and result are vectors that contain the
+same number of elements of the same type.
+
+@item VEC_INTERLEAVE_HIGH_EXPR
+@itemx VEC_INTERLEAVE_LOW_EXPR
+These nodes represent merging and interleaving of the high/low elements of the
+two input vectors, respectively. The operands and the result are vectors that
+contain the same number of elements (@code{N}) of the same type.
+In the case of @code{VEC_INTERLEAVE_HIGH_EXPR}, the high @code{N/2} elements of
+the first input vector are interleaved with the high @code{N/2} elements of the
+second input vector. In the case of @code{VEC_INTERLEAVE_LOW_EXPR}, the low
+@code{N/2} elements of the first input vector are interleaved with the low
+@code{N/2} elements of the second input vector.
+
@end table
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