+ /*
+ If the current node is a barrier toggle the silent flag.
+ If we are in the start block, we are ought to be silent at the beginning,
+ so the toggling activates the constraint handling but skips the barrier.
+ If we are in the end block we handle the in requirements of the barrier
+ and set the rest to silent.
+ */
+ if(be_is_Barrier(irn))
+ *silent = !*silent;
+
+ if(be_silent)
+ goto end;
+
+ /*
+ Perms inserted before the constraint handling phase are considered to be
+ correctly precolored. These Perms arise during the ABI handling phase.
+ */
+ if(insn->has_constraints) {
+ const arch_env_t *aenv = env->birg->main_env->arch_env;
+ int n_regs = env->cls->n_regs;
+ bitset_t *bs = bitset_alloca(n_regs);
+ ir_node **alloc_nodes = alloca(n_regs * sizeof(alloc_nodes[0]));
+ bipartite_t *bp = bipartite_new(n_regs, n_regs);
+ int *assignment = alloca(n_regs * sizeof(assignment[0]));
+ pmap *partners = pmap_create();
+ DEBUG_ONLY(firm_dbg_module_t *dbg = alloc_env->constr_dbg;)
+
+ int i, n_alloc;
+ long col;
+ const ir_edge_t *edge;
+ ir_node *perm = NULL;
+
+ /*
+ prepare the constraint handling of this node.
+ Perms are constructed and Copies are created for constrained values
+ interfering with the instruction.
+ */
+ perm = pre_process_constraints(alloc_env, &insn);
+
+ /* find suitable in operands to the out operands of the node. */
+ pair_up_operands(alloc_env, insn);
+
+ /*
+ look at the in/out operands and add each operand (and its possible partner)
+ to a bipartite graph (left: nodes with partners, right: admissible colors).
+ */
+ for(i = 0, n_alloc = 0; i < insn->n_ops; ++i) {
+ be_operand_t *op = &insn->ops[i];
+
+ /*
+ If the operand has no partner or the partner has not been marked
+ for allocation, determine the admissible registers and mark it
+ for allocation by associating the node and its partner with the
+ set of admissible registers via a bipartite graph.
+ */
+ if(!op->partner || !pmap_contains(partners, op->partner->carrier)) {
+
+ pmap_insert(partners, op->carrier, op->partner ? op->partner->carrier : NULL);
+ alloc_nodes[n_alloc] = op->carrier;
+
+ DBG((dbg, LEVEL_2, "\tassociating %+F and %+F\n", op->carrier, op->partner ? op->partner->carrier : NULL));
+
+ bitset_clear_all(bs);
+ get_decisive_partner_regs(bs, op, op->partner);
+
+ DBG((dbg, LEVEL_2, "\tallowed registers for %+F: %B\n", op->carrier, bs));
+
+ bitset_foreach(bs, col)
+ bipartite_add(bp, n_alloc, col);
+
+ n_alloc++;