_REG_R5
gr[_REG_R5] = tf->tf_reg[5];
tf->tf_reg[5] = gr[_REG_R5];
gr[_REG_R5] = tf->tf_r5;
tf->tf_r5 = gr[_REG_R5];
gr[_REG_R5] = tf->tf_r5;
tf->tf_r5 = gr[_REG_R5];
gr[_REG_R5] = tf->tf_r5;
tf->tf_r5 = gr[_REG_R5];
gr[_REG_R5] = luc->luc_mcontext.arm_r5;
luc->luc_mcontext.arm_r5 = gr[_REG_R5];