1 /* Copyright (C) 1998 - 2000 by Universitaet Karlsruhe
4 * Authors: Goetz Lindenmaier
17 * variables of imperative programs.
18 * It constructs the IR for the following program:
24 * a = malloc(sizeof(a[10]));
28 * The array is placed on the heap. The pointer to the array that
29 * is a local variable is represented as a dataflow edge.
30 * There are two ways to model allocation to the heap in programs with
31 * explicit memory allocation:
32 * 1. Model the calls to malloc and free as simple procedure (of compiler
33 * known procedures returning a pointer. This is the simpler way of
34 * generating FIRM, but restricts the information that can be deduced
36 * 2. Insert an Alloc node. A later pass can lower this to the compiler
37 * known function. This makes the allocation explicit in FIRM, supporting
39 * A problem is modeling free. There is no free node in FIRM. Is this
40 * a necessary extension?
41 * This example shows the second alternative, where the size of the array
42 * is explicitly computed.
45 #define OPTIMIZE_NODE 0
50 /* describes the method main */
55 /* describes types defined by the language */
58 /* describes the array and its fields. */
59 type *array_type; /* the type information for the array */
60 entity *array_ent; /* the entity representing a field of the array */
62 /* Needed while finding the element size. */
64 ir_mode *elt_type_mode;
68 /* holds the graph and nodes. */
70 ir_node *array, *array_ptr, *c3, *elt, *val, *x;
74 /* make basic type information for primitive type int.
75 In Sather primitive types are represented by a class.
76 This is the modeling appropriate for other languages.
77 Mode_i says that all integers shall be implemented as a
78 32 bit integer value. */
79 prim_t_int = new_type_primitive(id_from_str ("int", 3), mode_Is);
81 printf("\nCreating an IR graph: ARRAY-HEAP_EXAMPLE...\n");
83 /* first build procedure main */
84 owner = get_glob_type();
85 proc_main = new_type_method(id_from_str("ARRAY-HEAP_EXAMPLE_main", 23), 0, 1);
86 set_method_res_type(proc_main, 0, (type *)prim_t_int);
87 proc_main_e = new_entity ((type*)owner, id_from_str ("ARRAY-HEAP_EXAMPLE_main", 23), (type *)proc_main);
89 /* make type information for the array and set the bounds */
93 current_ir_graph = get_const_code_irg();
94 array_type = new_type_array(id_from_str("a", 1), N_DIMS, prim_t_int);
95 set_array_bounds(array_type, 0,
96 new_Const(mode_Iu, new_tarval_from_long (L_BOUND, mode_Iu)),
97 new_Const(mode_Iu, new_tarval_from_long (U_BOUND, mode_Iu)));
98 /* As the array is accessed by Sel nodes, we need information about
99 the entity the node selects. Entities of an array are it's elements
100 which are, in this case, integers. */
101 main_irg = new_ir_graph (proc_main_e, 4);
102 array_ent = get_array_element_entity(array_type);
104 /* Allocate the array. All program known variables that
105 are not modeled by dataflow edges need an explicit allocate node.
106 If the variable shall be placed on the stack, set stack_alloc. */
107 /* first compute size in bytes. */
108 elt_type = get_array_element_type(array_type);
109 elt_type_mode = get_type_mode(elt_type);
110 /* better: read bounds out of array type information */
111 size = (U_BOUND - L_BOUND + 1) * get_mode_size_bytes(elt_type_mode);
112 /* make constant representing the size */
113 arr_size = new_Const(mode_Iu, new_tarval_from_long (size, mode_Iu));
114 /* allocate and generate the Proj nodes. */
115 array = new_Alloc(get_store(), arr_size, (type*)array_type, stack_alloc);
116 set_store(new_Proj(array, mode_M, 0)); /* make the changed memory visible */
117 array_ptr = new_Proj(array, mode_P, 2); /* remember the pointer to the array */
119 /* Now the "real" program: */
120 /* Load element 3 of the array. For this first generate the pointer to this
121 array element by a select node. (Alternative: increase array pointer
122 by (three * elt_size), but this complicates some optimizations. The
123 type information accessible via the entity allows to generate the
124 pointer increment later. */
125 c3 = new_Const (mode_Iu, new_tarval_from_long (3, mode_Iu));
129 elt = new_Sel(get_store(), array_ptr, 1, in, array_ent);
131 val = new_Load(get_store(), elt);
132 set_store(new_Proj(val, mode_M, 0));
133 val = new_Proj(val, mode_Is, 2);
135 /* return the result of procedure main */
140 x = new_Return (get_store (), 1, in);
142 mature_block (get_irg_current_block(main_irg));
144 /* complete the end_block */
145 add_in_edge (get_irg_end_block(main_irg), x);
146 mature_block (get_irg_end_block(main_irg));
148 finalize_cons (main_irg);
150 printf("Optimizing ...\n");
151 dead_node_elimination(main_irg);
153 /* verify the graph */
156 printf("Dumping the graph and a type graph.\n");
157 dump_ir_block_graph (main_irg);
158 dump_type_graph(main_irg);
160 printf("use xvcg to view these graphs:\n");
161 printf("/ben/goetz/bin/xvcg GRAPHNAME\n\n");