GENERIC provides a language-independent way to represent program structures and expressions as tree structures. The document outlines the different types of tree nodes used to represent various language elements like declarations, statements, functions, and types. Key nodes include IDENTIFIER_NODE for identifiers, TYPE for type specifications, DECLARATIONS for declarations, STATEMENTS for statements, and FUNCTION_DECL for function definitions. Attributes are represented as TREE_LIST structures and containers can be either TREE_LIST or TREE_VEC nodes.

1. GENERIC
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2. • The purpose of GENERIC is simply to provide a
language-independent way of representing an
entire function in trees.
• A statement is defined as any expression whose
value is ignored.
• A statement will always have TREE_SIDE_EFFECTS
set

3. • You can tell what kind of node a particular tree is
by using the TREE_CODE macro.
• All GENERIC trees have two fields in common.
• TREE_CHAIN
• a pointer be used as a singly-linked list
• TREE_TYPE

4. code & flags
tree type
tree chain
struct tree_base
struct tree_typed
struct tree_common
typedef union tree_node *tree
typedef const union tree_node *const_tree
union tree_node

5. IDENTIFIER_NODE
• There are never two distinct IDENTIFIER_NODEs
representing the same identifier.
• IDENTIFIER_POINTER
• IDENTIFIER_LENGTH

6. Container
• Two kinds of container
• TREE_LIST
• TREE_PURPOSE
• TREE_VALUE
• The next node is found by following the TREE_CHAIN
• TREE_VEC
• TREE_VEC_LENGTH
• TREE_VEC_ELT

7. code & flags
tree type
tree chain
struct tree_base
struct tree_typed
struct tree_common
tree_list
purposetree
valuetree
code & flags
tree type
tree chain
purpose
value
tree_list
NULL_TREE

8. code & flags
tree type
tree chain
struct tree_base
struct tree_typed
struct tree_common
tree_vec
a[1]tree

9. TYPE
• INTEGER_TYPE
• REAL_TYPE
• FIXED_POINT_TYPE
• COMPLEX_TYPE
• ENUMERAL_TYPE
• BOOLEAN_TYPE
• POINTER_TYPE
• REFERENCE_TYPE
• FUNCTION_TYPE
• METHOD_TYPE
• ARRAY_TYPE
• RECORD_TYPE
• UNION_TYPE
• QUAL_UNION_TYPE
• LANG_TYPE
• OFFSET_TYPE

10. Declarations
• LABEL_DECL
• CONST_DECL
• enumeration constants
• RESULT_DECL
• the value returned by a function
• TYPE_DECL
• typedef declarations
• VAR_DECL
• variables with namespace or block scope
• static data members
• PARM_DECL
• a parameter to a function
• DEBUG_EXPR_DECL
• FIELD_DECL
• non-static data members
• NAMESPACE_DECL

11. VAR_DECL
• DECL_SIZE
• DECL_ALIGN
• DECL_THIS_STATIC
• static variable
• DECL_THIS_EXTERN
• extern variable
• DECL_INITIAL
• an expression for the initialiser

12. PARM_DECL
• DECL_ARGUMENTS
• DECL_ARG_TYPE
• the type that will actually be used when a value is
passed to this function

13. Attributes
• TREE_LIST
• TREE_PURPOSE
• the name of the attribute
• TREE_VALUE
• TREE_LIST of the arguments of the attribute
• TREE_CHAIN
• next attribute
• DECL_ATTRIBUTES (tree decl)
• DECL_ATTRIBUTES (tree type)

14. Statements
• ASM_EXPR
• inline assembly
• DECL_EXPR
• a local declaration
• LABEL_EXPR
• GOTO_EXPR
• goto statement
• RETURN_EXPR
• return statement
• LOOP_EXPR
• infinite loop
• EXIT_EXPR
• conditional exit from the nearest LOOP_EXPR
• SWITCH_EXPR
• switch statement
• CASE_LABEL_EXPR
• a case label

15. Blocks
• BIND_EXPR
• BIND_EXPR_VARS
• variables in a block

16. Statement Sequences
• STATEMENT_LIST

17. FUNCTION_DECL
BIND_EXPR
saved_tree
gimplify_stmt
int test_gimple(int param_a, char param_b, float param_c)
{
int local;
local = param_a + param_b;
local = (int)((float)local * param_c);
return local;
}
locus
VOID_TYPE
type
VAR_DECL
operands[0]
INTEGER_TYPE
type
BLOCK
operands[2]
STATEMENT_LIST
operands[1]
DECL_EXPR
head
VAR_DECL
operands[0]
INTEGER_TYPE
type
MODIFY_EXPR
VAR_DECL PLUS_EXPR
operands[0] operands[1]
INTEGER_TYPE
type
NOP_EXPR PARM_DECL
operands[0] operands[1]
PARM_DECL
operands[0]

18. Functions
• A function is represented by a FUNCTION_DECL node.
• DECL_NAME
• DECL_ASSEMBLER_NAME
• DECL_ARGUMENTS
• PARM_DECL for the first argument
• Subsequent PARM_DECL nodes can be obtained by following the TREE_CHAIN links.
• DECL_RESULT
• RESULT_DECL
• DECL_SAVED_TREE
• the complete body of the function
• TREE_TYPE
• FUNCTION_TYPE
• METHOD_TYPE

19. FUNCTION_DECL
FUNCTION_TYPE
PARM_DECL RESULT_DECL
INTEGER_TYPEPARM_DECL
PARM_DECL
type
type arguments result
chain
chain
vec<tree> fnargs
INTEGER_TYPE
initial
gimplify_parameters
INTEGER_TYPE
size_unit
REAL_TYPE
type
REAL_TYPE
initial
int test_gimple(int param_a, char param_b, float param_c)
{
int local;
local = param_a + param_b;
local = (int)((float)local * param_c);
return local;
}