GCC GENERIC
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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.
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GCC GENERIC
- 1. GENERIC Kai
- 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
- 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; }