+ const be_chordal_env_t *env = alloc_env->chordal_env;
+
+ int n_uses = insn_n_uses(insn);
+ int n_defs = insn_n_defs(insn);
+ bitset_t *bs = bitset_alloca(env->cls->n_regs);
+ bipartite_t *bp = bipartite_new(n_defs, n_uses);
+ int *pairing = alloca(MAX(n_defs, n_uses) * sizeof(pairing[0]));
+
+ int i, j;
+
+ /*
+ For each out operand, try to find an in operand which can be assigned the
+ same register as the out operand.
+ */
+ for(j = 0; j < insn->use_start; ++j) {
+ operand_t *out_op = &insn->ops[j];
+
+ /* Try to find an in operand which has ... */
+ for(i = insn->use_start; i < insn->n_ops; ++i) {
+ const operand_t *op = &insn->ops[i];
+
+ /*
+ The in operand can only be paired with a def, if the node defining the
+ operand's value does not interfere with the instruction itself. That
+ would mean, that it is live at the instruction, so no result of the instruction
+ can have the same register as the operand.
+
+ Furthermore, tow operands can be paired, if the admissible registers
+ of one are a subset of the other's. We record the operand whose constraints
+ count in the decisive array.
+ */
+ if(!values_interfere(op->irn, op->carrier)) {
+ if(get_decisive_partner_regs(bs, out_op, op))
+ bipartite_add(bp, j, i - insn->use_start);
+ }
+ }
+ }
+
+ /* Compute the pairing. */
+ bipartite_matching(bp, pairing);
+ for(i = 0; i < insn->use_start; ++i) {
+ int p = pairing[i] + insn->use_start;
+
+ if(p >= insn->use_start) {
+ insn->ops[i].partner = &insn->ops[p];
+ insn->ops[p].partner = &insn->ops[i];
+ }
+ }
+
+ bipartite_free(bp);
+}
+
+
+static ir_node *pre_process_constraints(be_chordal_alloc_env_t *alloc_env, insn_t **the_insn)
+{
+ be_chordal_env_t *env = alloc_env->chordal_env;
+ const arch_env_t *aenv = env->birg->main_env->arch_env;
+ insn_t *insn = *the_insn;
+ ir_node *bl = get_nodes_block(insn->irn);
+ ir_node *copy = NULL;
+ ir_node *perm = NULL;
+ bitset_t *out_constr = bitset_alloca(env->cls->n_regs);
+ bitset_t *bs = bitset_alloca(env->cls->n_regs);
+ DEBUG_ONLY(firm_dbg_module_t *dbg = alloc_env->constr_dbg;)
+