3 * File name: ir/ana/irloop_t.h
4 * Purpose: Loop datastructure and access functions.
5 * Author: Goetz Lindenmaier
9 * Copyright: (c) 2002-2003 Universität Karlsruhe
10 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
16 * Computes backedges in the control and data flow.
18 * @author Goetz Lindenmaier
20 * Only Block and Phi/Filter nodes can have incoming backedges.
21 * Constructs loops data structure: indicates loop nesting.
30 /* ------------------------------------------------------------------- */
32 * Backedge information.
34 * Predecessors of Block, Phi and interprocedural Filter nodes can
35 * have backedges. If loop information is computed, this
36 * information is computed, too.
37 * The backedge information can only be used if the graph is not in
38 * phase phase_building.
40 /* ------------------------------------------------------------------- */
42 /** Returns true if the predesessor pos is a backedge. */
43 int is_inter_backedge(ir_node *n, int pos);
44 int is_intra_backedge(ir_node *n, int pos);
45 bool is_backedge (ir_node *n, int pos);
46 /** Remarks that edge pos is a backedge. */
47 void set_backedge (ir_node *n, int pos);
48 /** Remarks that edge pos is not a backedge. */
49 void set_not_backedge (ir_node *n, int pos);
50 /** Returns true if n has backedges. */
51 bool has_backedges (ir_node *n);
52 /** Sets backedge information to zero. */
53 void clear_backedges (ir_node *n);
55 /* ------------------------------------------------------------------- */
57 * The loops datastructure.
59 * The loops datastructure represents circles in the intermediate
60 * representation. It does not represent loops in the terms of a
62 * Each ir_graph can contain one outermost loop datastructure.
63 * loop is the entry point to the nested loops.
64 * The loop datastructure contains a field indicating the depth of
65 * the loop within the nesting. Further it contains a list of the
66 * loops with nesting depth -1. Finally it contains a list of all
69 * @todo We could add a field pointing from a node to the containing loop,
70 * this would cost a lot of memory, though.
72 /* ------------------------------------------------------------------- */
73 typedef struct ir_loop ir_loop;
75 /** Loop elements: loop nodes and ir nodes */
77 firm_kind *kind; /**< is either k_ir_node or k_ir_loop */
78 ir_node *node; /**< Pointer to an ir_node element */
79 ir_loop *son; /**< Pointer to an ir_loop element */
82 int is_ir_loop(const void *thing);
84 /** Set the outermost loop in ir graph as basic access to loop tree. */
85 void set_irg_loop(ir_graph *irg, ir_loop *l);
87 /* Returns the root loop info (if exists) for an irg. */
88 ir_loop *get_irg_loop(ir_graph *irg);
90 /** Returns the loop n is contained in. NULL if node is in no loop. */
91 ir_loop *get_irn_loop(ir_node *n);
93 /** Returns outer loop, itself if outermost. */
94 ir_loop *get_loop_outer_loop (ir_loop *loop);
95 /** Returns nesting depth of this loop */
96 int get_loop_depth (ir_loop *loop);
98 /* Sons are the inner loops contained in this loop. */
99 /** Returns the number of inner loops */
100 int get_loop_n_sons (ir_loop *loop);
102 /** Returns the pos`th son loop (inner loop) of a loop.
103 Returns NULL if there is not a pos`th loop_node. */
104 ir_loop *get_loop_son (ir_loop *loop, int pos);
106 /** Returns the number of nodes contained in loop. */
107 int get_loop_n_nodes (ir_loop *loop);
109 /** Returns the pos`th ir_node of a loop.
110 Returns NULL if there is not a pos`th ir_node. */
111 ir_node *get_loop_node (ir_loop *loop, int pos);
113 /** Returns the number of elements contained in loop. */
114 int get_loop_n_elements (ir_loop *loop);
115 /** Returns a loop element. A loop element can be interpreted as a
116 kind pointer, an ir_node* or an ir_loop*. */
117 loop_element get_loop_element (ir_loop *loop, int pos);
119 /** Returns the element number of the loop son in loop.
120 * Returns -1 if not found. O(#elements). */
121 int get_loop_element_pos(ir_loop *loop, void *le);
123 /** Returns a unique node number for the loop node to make output
124 readable. If libfirm_debug is not set it returns the loop cast to
126 int get_loop_loop_nr(ir_loop *loop);
128 /** A field to connect additional information to a loop. Only valid
129 if libfirm_debug is set, else returns NULL. */
130 void set_loop_link (ir_loop *loop, void *link);
131 void *get_loop_link (const ir_loop *loop);
133 /* ------------------------------------------------------------------- */
134 /* Constructing and destructing the loop/backedge information. */
135 /* ------------------------------------------------------------------- */
137 /** Constructs backedge information and loop tree for a graph in intraprocedural view.
139 * The algorithm views the program representation as a pure graph.
140 * It assumes that only block and phi nodes may be loop headers.
141 * The resulting loop tree is a possible visiting order for dataflow
144 * @returns Maximal depth of loop tree.
147 * One assumes, the Phi nodes in a block with a backedge have backedges
148 * at the same positions as the block. This is not the case, as
149 * the scc algorithms does not respect the program semantics in this case.
150 * Take a swap in a loop (t = i; i = j; j = t;) This results in two Phi
151 * nodes. They form a cycle. Once the scc algorithm deleted one of the
152 * edges, the cycle is removed. The second Phi node does not get a
155 /* @@@ Well, maybe construct_loop_information or analyze_loops ? */
156 int construct_backedges(ir_graph *irg);
158 /** Constructs backedges for all irgs in interprocedural view.
160 * @see As construct_backedges(), but for interprocedural view.
163 * All loops in the graph will be marked as such, not only
164 * realizeable loops and recursions in the program. E.g., if the
165 * same funcion is called twice, there is a loop between the first
166 * function return and the second call.
168 * @returns Maximal depth of loop tree.
170 int construct_ip_backedges(void);
172 /** Construct loop tree only for control flow.
174 * This constructs loop information resembling the program structure.
175 * It is useful for loop optimizations and analyses, as, e.g., finding
176 * iteration variables or loop invariant code motion.
178 * This algorithm computes only back edge information for Block nodes, not
181 * @returns Maximal depth of loop tree. */
182 int construct_cf_backedges(ir_graph *irg);
184 /** Construct interprocedural loop tree for control flow.
186 * @see construct_cf_backedges() and construct_ip_backedges().
188 int construct_ip_cf_backedges (void);
190 /** Removes all loop information.
191 * Resets all backedges. Works for any construction algorithm.
193 void free_loop_information(ir_graph *irg);
194 void free_all_loop_information (void);
199 /* ------------------------------------------------------------------- */
200 /* Simple analyses based on the loop information */
201 /* ------------------------------------------------------------------- */
203 /** Test whether a value is loop invariant.
205 * @param n The node to be tested.
206 * @param block A block node.
208 * Returns true, if the node n is not changed in the loop block
209 * belongs to or in inner loops of this block. */
210 int is_loop_invariant(ir_node *n, ir_node *block);
213 #endif /* _IRLOOP_H_ */