I suppose both "would" and "have" are more of auxiliary/helping verbs in the phrase: "You would have done the same thing". Am I right?
You are right. Would is always an auxiliary verb. Most grammarians call it a modal auxiliary, but the term defective auxiliary is also used.
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You are right. Would is always an auxiliary verb. Most grammarians call it a modal auxiliary, but the term defective auxiliary is also used. Have is part of the infinitive have done. All modal auxiliaries must be followed by an infinitive, of which there are two in the active voice and another two in the passive.
CB