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 predecessor pos is a backedge in the interprozeduralem view. */
43 int is_inter_backedge(ir_node *n, int pos);
44 /** Returns true if the predecessor pos is a backedge in the intraprocedural view. */
45 int is_intra_backedge(ir_node *n, int pos);
46 /** Returns non-zero if the predecessor pos is a backedge. */
47 int is_backedge (ir_node *n, int pos);
48 /** Marks edge pos as a backedge. */
49 void set_backedge (ir_node *n, int pos);
50 /** Marks edge pos as a non-backedge. */
51 void set_not_backedge (ir_node *n, int pos);
52 /** Returns non-zero if n has backedges. */
53 int has_backedges (ir_node *n);
54 /** Clears all backedge information. */
55 void clear_backedges (ir_node *n);
57 /* ------------------------------------------------------------------- */
59 * The loops data structure.
61 * The loops data structure represents circles in the intermediate
62 * representation. It does not represent loops in the terms of a
64 * Each ir_graph can contain one outermost loop data structure.
65 * loop is the entry point to the nested loops.
66 * The loop data structure contains a field indicating the depth of
67 * the loop within the nesting. Further it contains a list of the
68 * loops with nesting depth -1. Finally it contains a list of all
71 * @todo We could add a field pointing from a node to the containing loop,
72 * this would cost a lot of memory, though.
74 /* ------------------------------------------------------------------- */
75 #ifndef _IR_LOOP_TYPEDEF_
76 #define _IR_LOOP_TYPEDEF_
77 typedef struct ir_loop ir_loop;
80 /** Loop elements: loop nodes and ir nodes */
82 firm_kind *kind; /**< is either k_ir_node or k_ir_loop */
83 ir_node *node; /**< Pointer to an ir_node element */
84 ir_loop *son; /**< Pointer to an ir_loop element */
87 int is_ir_loop(const void *thing);
89 /** Set the outermost loop in ir graph as basic access to loop tree. */
90 void set_irg_loop(ir_graph *irg, ir_loop *l);
92 /* Returns the root loop info (if exists) for an irg. */
93 ir_loop *get_irg_loop(ir_graph *irg);
95 /** Returns the loop n is contained in. NULL if node is in no loop. */
96 ir_loop *get_irn_loop(const ir_node *n);
98 /** Returns outer loop, itself if outermost. */
99 ir_loop *get_loop_outer_loop (const ir_loop *loop);
100 /** Returns nesting depth of this loop */
101 int get_loop_depth (const ir_loop *loop);
103 /* Sons are the inner loops contained in this loop. */
104 /** Returns the number of inner loops */
105 int get_loop_n_sons (const ir_loop *loop);
107 /** Returns the pos`th son loop (inner loop) of a loop.
108 Returns NULL if there is not a pos`th loop_node. */
109 ir_loop *get_loop_son (ir_loop *loop, int pos);
111 /** Returns the number of nodes contained in loop. */
112 int get_loop_n_nodes (ir_loop *loop);
114 /** Returns the pos`th ir_node of a loop.
115 Returns NULL if there is not a pos`th ir_node. */
116 ir_node *get_loop_node (ir_loop *loop, int pos);
118 /** Returns the number of elements contained in loop. */
119 int get_loop_n_elements (const ir_loop *loop);
121 /** Returns a loop element. A loop element can be interpreted as a
122 kind pointer, an ir_node* or an ir_loop*. */
123 loop_element get_loop_element (const ir_loop *loop, int pos);
125 /** Returns the element number of the loop son in loop.
126 * Returns -1 if not found. O(|elements|). */
127 int get_loop_element_pos(const ir_loop *loop, void *le);
129 /** Returns a unique node number for the loop node to make output
130 readable. If libfirm_debug is not set it returns the loop cast to
132 int get_loop_loop_nr(const ir_loop *loop);
134 /** A field to connect additional information to a loop. Only valid
135 if libfirm_debug is set, else returns NULL. */
136 void set_loop_link (ir_loop *loop, void *link);
137 void *get_loop_link (const ir_loop *loop);
139 /* ------------------------------------------------------------------- */
140 /* Constructing and destructing the loop/backedge information. */
141 /* ------------------------------------------------------------------- */
143 /** Constructs backedge information and loop tree for a graph in intraprocedural view.
145 * The algorithm views the program representation as a pure graph.
146 * It assumes that only block and phi nodes may be loop headers.
147 * The resulting loop tree is a possible visiting order for dataflow
150 * This algorithm destoyes the link field of block nodes.
152 * @returns Maximal depth of loop tree.
155 * One assumes, the Phi nodes in a block with a backedge have backedges
156 * at the same positions as the block. This is not the case, as
157 * the scc algorithms does not respect the program semantics in this case.
158 * Take a swap in a loop (t = i; i = j; j = t;) This results in two Phi
159 * nodes. They form a cycle. Once the scc algorithm deleted one of the
160 * edges, the cycle is removed. The second Phi node does not get a
163 /* @@@ Well, maybe construct_loop_information or analyze_loops ? */
164 int construct_backedges(ir_graph *irg);
166 /** Constructs backedges for all irgs in interprocedural view.
168 * @see As construct_backedges(), but for interprocedural view.
171 * All loops in the graph will be marked as such, not only
172 * realizeable loops and recursions in the program. E.g., if the
173 * same funcion is called twice, there is a loop between the first
174 * function return and the second call.
176 * @returns Maximal depth of loop tree.
178 int construct_ip_backedges(void);
180 /** Construct loop tree only for control flow.
182 * This constructs loop information resembling the program structure.
183 * It is useful for loop optimizations and analyses, as, e.g., finding
184 * iteration variables or loop invariant code motion.
186 * This algorithm computes only back edge information for Block nodes, not
189 * This algorithm destoyes the link field of block nodes.
191 * @returns Maximal depth of loop tree.
193 int construct_cf_backedges(ir_graph *irg);
195 /** Construct interprocedural loop tree for control flow.
197 * @see construct_cf_backedges() and construct_ip_backedges().
199 int construct_ip_cf_backedges (void);
201 /** Removes all loop information.
202 * Resets all backedges. Works for any construction algorithm.
204 void free_loop_information(ir_graph *irg);
205 void free_all_loop_information (void);
210 /* ------------------------------------------------------------------- */
211 /* Simple analyses based on the loop information */
212 /* ------------------------------------------------------------------- */
214 /** Test whether a value is loop invariant.
216 * @param n The node to be tested.
217 * @param block A block node.
219 * Returns non-zero, if the node n is not changed in the loop block
220 * belongs to or in inner loops of this block. */
221 int is_loop_invariant(ir_node *n, ir_node *block);
224 #endif /* _IRLOOP_H_ */