+ return res;
+}
+
+static be_insn_t *chordal_scan_insn(be_chordal_alloc_env_t *env, ir_node *irn)
+{
+ be_insn_env_t ie;
+
+ ie.ignore_colors = env->chordal_env->ignore_colors;
+ ie.aenv = env->chordal_env->birg->main_env->arch_env;
+ ie.obst = &env->chordal_env->obst;
+ ie.cls = env->chordal_env->cls;
+ return be_scan_insn(&ie, irn);
+}
+
+static void pair_up_operands(const be_chordal_alloc_env_t *alloc_env, be_insn_t *insn)
+{
+ const be_chordal_env_t *env = alloc_env->chordal_env;
+
+ int n_uses = be_insn_n_uses(insn);
+ int n_defs = be_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) {
+ be_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 be_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);
+ }
+ }