2 * Base routines for register allocation.
3 * @author Sebastian Hack
18 #include "besched_t.h"
21 static sched_timestep_t get_time_step(const ir_node *irn)
23 return is_Phi(irn) ? 0 : sched_get_time_step(irn);
26 int value_dominates(const ir_node *a, const ir_node *b)
29 const ir_node *ba = get_block(a);
30 const ir_node *bb = get_block(b);
33 * a and b are not in the same block,
34 * so dominance is determined by the dominance of the blocks.
37 res = block_dominates(ba, bb);
40 * Dominance is determined by the time steps of the schedule.
43 sched_timestep_t as = get_time_step(a);
44 sched_timestep_t bs = get_time_step(b);
52 * Check, if two values interfere.
53 * @param a The first value.
54 * @param b The second value.
55 * @return 1, if a and b interfere, 0 if not.
57 int values_interfere(const be_lv_t *lv, const ir_node *a, const ir_node *b)
59 int a2b = value_dominates(a, b);
60 int b2a = value_dominates(b, a);
62 /* If there is no dominance relation, they do not interfere. */
64 const ir_edge_t *edge;
68 * Adjust a and b so, that a dominates b if
69 * a dominates b or vice versa.
77 bb = get_nodes_block(b);
80 * If a is live end in b's block it is
81 * live at b's definition (a dominates b)
83 if(be_is_live_end(lv, bb, a))
87 * Look at all usages of a.
88 * If there's one usage of a in the block of b, then
89 * we check, if this use is dominated by b, if that's true
90 * a and b interfere. Note that b must strictly dominate the user,
91 * since if b is the last user of in the block, b and a do not
93 * Uses of a not in b's block can be disobeyed, because the
94 * check for a being live at the end of b's block is already
97 foreach_out_edge(a, edge) {
98 const ir_node *user = edge->src;
99 if(get_nodes_block(user) == bb && !is_Phi(user) && b != user && value_dominates(b, user))