3 * File name: testprograms/array-heap_example.c
4 * Purpose: Show representation of dynamically allocated array.
5 * Author: Goetz Lindenmaier
9 * Copyright: (c) 1999-2003 Universität Karlsruhe
10 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
22 * variables of imperative programs.
23 * It constructs the IR for the following program:
29 * a = malloc(sizeof(a[10]));
33 * The array is placed on the heap. The pointer to the array that
34 * is a local variable is represented as a dataflow edge.
35 * There are two ways to model allocation to the heap in programs with
36 * explicit memory allocation:
37 * 1. Model the calls to malloc and free as simple procedure (of compiler
38 * known procedures returning a pointer. This is the simpler way of
39 * generating FIRM, but restricts the information that can be deduced
41 * 2. Insert an Alloc node. A later pass can lower this to the compiler
42 * known function. This makes the allocation explicit in FIRM, supporting
44 * A problem is modeling free. There is no free node in FIRM. Is this
45 * a necessary extension?
46 * This example shows the second alternative, where the size of the array
47 * is explicitly computed.
50 #define OPTIMIZE_NODE 0
55 /* describes the method main */
60 /* describes types defined by the language */
63 /* describes the array and its fields. */
64 type *array_type; /* the type information for the array */
65 entity *array_ent; /* the entity representing a field of the array */
67 /* Needed while finding the element size. */
69 ir_mode *elt_type_mode;
73 /* holds the graph and nodes. */
75 ir_node *array, *array_ptr, *c3, *elt, *val, *x;
79 /* make basic type information for primitive type int.
80 In Sather primitive types are represented by a class.
81 This is the modeling appropriate for other languages.
82 Mode_i says that all integers shall be implemented as a
83 32 bit integer value. */
84 prim_t_int = new_type_primitive(new_id_from_chars ("int", 3), mode_Is);
86 printf("\nCreating an IR graph: ARRAY-HEAP_EXAMPLE...\n");
88 /* first build procedure main */
89 owner = get_glob_type();
90 proc_main = new_type_method(new_id_from_chars("ARRAY-HEAP_EXAMPLE_main", 23), 0, 1);
91 set_method_res_type(proc_main, 0, (type *)prim_t_int);
92 proc_main_e = new_entity ((type*)owner, new_id_from_chars("ARRAY-HEAP_EXAMPLE_main", 23), (type *)proc_main);
94 /* make type information for the array and set the bounds */
98 current_ir_graph = get_const_code_irg();
99 array_type = new_type_array(new_id_from_chars("a", 1), N_DIMS, prim_t_int);
100 set_array_bounds(array_type, 0,
101 new_Const(mode_Iu, new_tarval_from_long (L_BOUND, mode_Iu)),
102 new_Const(mode_Iu, new_tarval_from_long (U_BOUND, mode_Iu)));
103 /* As the array is accessed by Sel nodes, we need information about
104 the entity the node selects. Entities of an array are it's elements
105 which are, in this case, integers. */
106 main_irg = new_ir_graph (proc_main_e, 4);
107 array_ent = get_array_element_entity(array_type);
109 /* Allocate the array. All program known variables that
110 are not modeled by dataflow edges need an explicit allocate node.
111 If the variable shall be placed on the stack, set stack_alloc. */
112 /* first compute size in bytes. */
113 elt_type = get_array_element_type(array_type);
114 elt_type_mode = get_type_mode(elt_type);
115 /* better: read bounds out of array type information */
116 size = (U_BOUND - L_BOUND + 1) * get_mode_size_bytes(elt_type_mode);
117 /* make constant representing the size */
118 arr_size = new_Const(mode_Iu, new_tarval_from_long (size, mode_Iu));
119 /* allocate and generate the Proj nodes. */
120 array = new_Alloc(get_store(), arr_size, (type*)array_type, stack_alloc);
121 set_store(new_Proj(array, mode_M, 0)); /* make the changed memory visible */
122 array_ptr = new_Proj(array, mode_P, 2); /* remember the pointer to the array */
124 /* Now the "real" program: */
125 /* Load element 3 of the array. For this first generate the pointer to this
126 array element by a select node. (Alternative: increase array pointer
127 by (three * elt_size), but this complicates some optimizations. The
128 type information accessible via the entity allows to generate the
129 pointer increment later. */
130 c3 = new_Const (mode_Iu, new_tarval_from_long (3, mode_Iu));
134 elt = new_Sel(get_store(), array_ptr, 1, in, array_ent);
136 val = new_Load(get_store(), elt, mode_Is);
137 set_store(new_Proj(val, mode_M, 0));
138 val = new_Proj(val, mode_Is, 2);
140 /* return the result of procedure main */
145 x = new_Return (get_store (), 1, in);
147 mature_immBlock (get_irg_current_block(main_irg));
149 /* complete the end_block */
150 add_immBlock_pred (get_irg_end_block(main_irg), x);
151 mature_immBlock (get_irg_end_block(main_irg));
153 finalize_cons (main_irg);
155 printf("Optimizing ...\n");
156 dead_node_elimination(main_irg);
158 /* verify the graph */
161 printf("Dumping the graph and a type graph.\n");
162 char *dump_file_suffix = "";
163 dump_ir_block_graph (main_irg, dump_file_suffix);
164 dump_type_graph(main_irg, dump_file_suffix);
165 dump_all_types(dump_file_suffix);
166 printf("use xvcg to view these graphs:\n");
167 printf("/ben/goetz/bin/xvcg GRAPHNAME\n\n");