_REG_R2
gr[_REG_R2] = (__greg_t)&sfp->sf_uc;
gr[_REG_R2] = r->r[2];
r->r[2] = gr[_REG_R2];
gr[_REG_R2] = tf->tf_r2;
tf->tf_r2 = gr[_REG_R2];