- const ir_node *b1 = get_nodes_block(a);
- const ir_node *b2 = get_nodes_block(b);
- int lo_a, lo_b;
-
- assert(block_dominates(b1, b2));
-
- /*
- * if the two blocks are not equal, a and b can only interfere if a is
- * live in at b2.
- */
- if(b1 != b2 && !is_live_in(b2, a))
- return 0;
-
- lo_a = is_live_end(b2, a);
- lo_b = is_live_end(b2, b);
-
- /*
- * If the two blocks are the same and one value is live out and the
- * definition of the other is after the definition ov the live out
- * value, they interfere.
- */
- if(b1 == b2) {
- int pos_a = sched_get_time_step(a);
- int pos_b = sched_get_time_step(b);
-
- if((pos_a < pos_b && lo_a) || (pos_b < pos_a && lo_b))
- return 1;
- }
-
- /*
- * Now it is left to check, if the sequence from the last use of 'b'
- * (or the end of the block b2, if b is live out)
- * to the def of 'b' contains a use and NOT the def of 'a'. Then they
- * also interfere
- */
- {
- const ir_node *irn;
-
- /* Initialize the liveness. */
- int a_live = lo_a;
- int b_live = lo_b;
-
- /* Go from the end of block b2 and try to detect the liveness. */
- sched_foreach_reverse(b2, irn) {
- int i, n;
-
- /*
- * If the definition of 'a' was found 'a' and 'b' interfere, if
- * 'b' is live here.
- */
- if(irn == a)
- return b_live;
-
- /* Same goes for 'b'. */
- if(irn == b)
- return a_live;
-
- /* If 'a' is not yet live, search for a use. */
- if(!a_live) {
- for(i = 0, n = get_irn_arity(irn); i < n; ++i)
- if(get_irn_n(irn, i) == a) {
- a_live = 1;
- break;
- }
- }
-
- /* Same for 'b' */
- if(!b_live) {
- for(i = 0, n = get_irn_arity(irn); i < n; ++i)
- if(get_irn_n(irn, i) == b) {
- b_live = 1;
- break;
- }
- }
-
- }