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 /** Returns non-zero if the predecessor pos is a backedge. */
46 int is_backedge (ir_node *n, int pos);
47 /** Remarks that edge pos is a backedge. */
48 void set_backedge (ir_node *n, int pos);
49 /** Remarks that edge pos is not a backedge. */
50 void set_not_backedge (ir_node *n, int pos);
51 /** Returns non-zero if n has backedges. */
52 int has_backedges (ir_node *n);
53 /** Sets backedge information to zero. */
54 void clear_backedges (ir_node *n);
56 /* ------------------------------------------------------------------- */
58 * The loops datastructure.
60 * The loops datastructure represents circles in the intermediate
61 * representation. It does not represent loops in the terms of a
63 * Each ir_graph can contain one outermost loop datastructure.
64 * loop is the entry point to the nested loops.
65 * The loop datastructure contains a field indicating the depth of
66 * the loop within the nesting. Further it contains a list of the
67 * loops with nesting depth -1. Finally it contains a list of all
70 * @todo We could add a field pointing from a node to the containing loop,
71 * this would cost a lot of memory, though.
73 /* ------------------------------------------------------------------- */
74 typedef struct ir_loop ir_loop;
76 /** Loop elements: loop nodes and ir nodes */
78 firm_kind *kind; /**< is either k_ir_node or k_ir_loop */
79 ir_node *node; /**< Pointer to an ir_node element */
80 ir_loop *son; /**< Pointer to an ir_loop element */
83 int is_ir_loop(const void *thing);
85 /** Set the outermost loop in ir graph as basic access to loop tree. */
86 void set_irg_loop(ir_graph *irg, ir_loop *l);
88 /* Returns the root loop info (if exists) for an irg. */
89 ir_loop *get_irg_loop(ir_graph *irg);
91 /** Returns the loop n is contained in. NULL if node is in no loop. */
92 ir_loop *get_irn_loop(ir_node *n);
94 /** Returns outer loop, itself if outermost. */
95 ir_loop *get_loop_outer_loop (ir_loop *loop);
96 /** Returns nesting depth of this loop */
97 int get_loop_depth (ir_loop *loop);
99 /* Sons are the inner loops contained in this loop. */
100 /** Returns the number of inner loops */
101 int get_loop_n_sons (ir_loop *loop);
103 /** Returns the pos`th son loop (inner loop) of a loop.
104 Returns NULL if there is not a pos`th loop_node. */
105 ir_loop *get_loop_son (ir_loop *loop, int pos);
107 /** Returns the number of nodes contained in loop. */
108 int get_loop_n_nodes (ir_loop *loop);
110 /** Returns the pos`th ir_node of a loop.
111 Returns NULL if there is not a pos`th ir_node. */
112 ir_node *get_loop_node (ir_loop *loop, int pos);
114 /** Returns the number of elements contained in loop. */
115 int get_loop_n_elements (ir_loop *loop);
116 /** Returns a loop element. A loop element can be interpreted as a
117 kind pointer, an ir_node* or an ir_loop*. */
118 loop_element get_loop_element (ir_loop *loop, int pos);
120 /** Returns the element number of the loop son in loop.
121 * Returns -1 if not found. O(|elements|). */
122 int get_loop_element_pos(ir_loop *loop, void *le);
124 /** Returns a unique node number for the loop node to make output
125 readable. If libfirm_debug is not set it returns the loop cast to
127 int get_loop_loop_nr(ir_loop *loop);
129 /** A field to connect additional information to a loop. Only valid
130 if libfirm_debug is set, else returns NULL. */
131 void set_loop_link (ir_loop *loop, void *link);
132 void *get_loop_link (const ir_loop *loop);
134 /* ------------------------------------------------------------------- */
135 /* Constructing and destructing the loop/backedge information. */
136 /* ------------------------------------------------------------------- */
138 /** Constructs backedge information and loop tree for a graph in intraprocedural view.
140 * The algorithm views the program representation as a pure graph.
141 * It assumes that only block and phi nodes may be loop headers.
142 * The resulting loop tree is a possible visiting order for dataflow
145 * @returns Maximal depth of loop tree.
148 * One assumes, the Phi nodes in a block with a backedge have backedges
149 * at the same positions as the block. This is not the case, as
150 * the scc algorithms does not respect the program semantics in this case.
151 * Take a swap in a loop (t = i; i = j; j = t;) This results in two Phi
152 * nodes. They form a cycle. Once the scc algorithm deleted one of the
153 * edges, the cycle is removed. The second Phi node does not get a
156 /* @@@ Well, maybe construct_loop_information or analyze_loops ? */
157 int construct_backedges(ir_graph *irg);
159 /** Constructs backedges for all irgs in interprocedural view.
161 * @see As construct_backedges(), but for interprocedural view.
164 * All loops in the graph will be marked as such, not only
165 * realizeable loops and recursions in the program. E.g., if the
166 * same funcion is called twice, there is a loop between the first
167 * function return and the second call.
169 * @returns Maximal depth of loop tree.
171 int construct_ip_backedges(void);
173 /** Construct loop tree only for control flow.
175 * This constructs loop information resembling the program structure.
176 * It is useful for loop optimizations and analyses, as, e.g., finding
177 * iteration variables or loop invariant code motion.
179 * This algorithm computes only back edge information for Block nodes, not
182 * @returns Maximal depth of loop tree. */
183 int construct_cf_backedges(ir_graph *irg);
185 /** Construct interprocedural loop tree for control flow.
187 * @see construct_cf_backedges() and construct_ip_backedges().
189 int construct_ip_cf_backedges (void);
191 /** Removes all loop information.
192 * Resets all backedges. Works for any construction algorithm.
194 void free_loop_information(ir_graph *irg);
195 void free_all_loop_information (void);
200 /* ------------------------------------------------------------------- */
201 /* Simple analyses based on the loop information */
202 /* ------------------------------------------------------------------- */
204 /** Test whether a value is loop invariant.
206 * @param n The node to be tested.
207 * @param block A block node.
209 * Returns non-zero, if the node n is not changed in the loop block
210 * belongs to or in inner loops of this block. */
211 int is_loop_invariant(ir_node *n, ir_node *block);
214 #endif /* _IRLOOP_H_ */