GCC source code Analysis, Build_pointer_type () function analysis

function = Build (addr_expr, Build_pointer_type (Tree_type (function)),
function);

Continue to analyze this sentence of the previous article.

/* Constructors for pointer, array and function types.
(Record_type, Union_type and Enumeral_type nodes are
Constructed by Language-dependent code, isn't here.) */

/* Construct, lay out and return the type of pointers to To_type.
If such a type has already been constructed, reuse it. */

Tree
Build_pointer_type (To_type)
Tree To_type;
{
Register Tree t = type_pointer_to (To_type);

/* Below is the result of Debug_tree (To_type);

<function_type 956e8
Type <integer_type 824d0 int permanent SI
Size &LT;INTEGER_CST 8254c literal permanent 4
Align Size_unit 8 sep_unit symtab 0
Sep <integer_cst 8251c literal permanent-2147483648 precision min <integer_cst 8251c-2147483648>
Max &LT;INTEGER_CST 82534 literal permanent 2147483647
Pointer_to_this <pointer_type 88b4c> chain <integer_type 825bc* char>
Permanent EP
Size &LT;INTEGER_CST 82dd8 type <integer_type 82848* unsigned int> literal permanent 8
Align Size_unit 8 sep_unit 0 Symtab 0
Arg-types <tree_list 95698 Permanent
Value <pointer_type 9117c type <integer_type 91130* char>
Permanent unsigned SI size &LT;INTEGER_CST 8254c 4>
Align Size_unit 8 sep_unit symtab 0
Chain <function_type 912c0>
Chain <function_type 959b0>
*/

Register struct Obstack *ambient_obstack = current_obstack;
Register struct Obstack *ambient_saveable_obstack = saveable_obstack;

/* First, if we already has a type for pointers to To_type, use it. */

if (t)
return t;

/* We need a new one.  If To_type is permanent, make this permanent too. */
if (Tree_permanent (To_type))
{
Current_obstack = &permanent_obstack;
Saveable_obstack = &permanent_obstack;
}

t = Make_node (Pointer_type);

/* Below is the result of debug_tree (t);

<pointer_type 98f48 Permanent VOID
Align 1 size_unit 1 Sep_unit 0 symtab 0
*/

Tree_type (t) = To_type;

/* Below is the result of debug_tree (t);

<pointer_type 98f48
Type <function_type 956e8
Type <integer_type 824d0 int permanent SI
Size &LT;INTEGER_CST 8254c literal permanent 4
Align Size_unit 8 sep_unit symtab 0
Sep <integer_cst 8251c literal permanent-2147483648 precision min <integer_cst 8251c-2147483648>
Max &LT;INTEGER_CST 82534 literal permanent 2147483647
Pointer_to_this <pointer_type 88b4c> chain <integer_type 825bc* char>
Permanent EP
Size &LT;INTEGER_CST 82DD8 literal permanent 8
Align Size_unit 8 sep_unit 0 Symtab 0
Arg-types <tree_list 95698 Permanent value <pointer_type 9117c>
Chain <function_type 959b0>
Permanent VOID
Align 1 size_unit 1 Sep_unit 0 symtab 0

*/
/* Record This type as the pointer to To_type. */
Type_pointer_to (To_type) = t;

/*

<function_type 956e8
Type <integer_type 824d0 int permanent SI
Size &LT;INTEGER_CST 8254c literal permanent 4
Align Size_unit 8 sep_unit symtab 0
Sep <integer_cst 8251c literal permanent-2147483648 precision min <integer_cst 8251c-2147483648>
Max &LT;INTEGER_CST 82534 literal permanent 2147483647
Pointer_to_this <pointer_type 88b4c> chain <integer_type 825bc* char>
Permanent EP
Size &LT;INTEGER_CST 82dd8 type <integer_type 82848* unsigned int> literal permanent 8
Align Size_unit 8 sep_unit 0 Symtab 0
Arg-types <tree_list 95698 Permanent
Value <pointer_type 9117c type <integer_type 91130* char>
Permanent unsigned SI size &LT;INTEGER_CST 8254c 4>
Align Size_unit 8 sep_unit symtab 0
Chain <function_type 912c0>
pointer_to_this <pointer_type 98f48>Chain <function_type 959b0>

*/

/* Lay out the type. This function have many callers that is concerned
With Expression-construction, and this simplifies them all.
Also, it guarantees the type_size is permanent if the TYPE is. */
Layout_type (t);

Current_obstack = Ambient_obstack;
Saveable_obstack = Ambient_saveable_obstack;
return t;
}

<pointer_type 98f48
Type <function_type 956e8
Type <integer_type 824d0 int permanent SI
Size &LT;INTEGER_CST 8254c literal permanent 4
Align Size_unit 8 sep_unit symtab 0
Sep <integer_cst 8251c literal permanent-2147483648 precision min <integer_cst 8251c-2147483648>
Max &LT;INTEGER_CST 82534 literal permanent 2147483647
Pointer_to_this <pointer_type 88b4c> chain <integer_type 825bc* char>
Permanent EP
Size &LT;INTEGER_CST 82DD8 literal permanent 8
Align Size_unit 8 sep_unit 0 Symtab 0
Arg-types <tree_list 95698 Permanent value <pointer_type 9117c>
pointer_to_this <pointer_type 98f48> chain <function_type 959b0>
Permanent unsigned SI size &LT;INTEGER_CST 8254c 4>
Align Size_unit 8 sep_unit symtab 0

GCC source code Analysis, Build_pointer_type () function analysis