If you heat ice, it melts.
If the weather is fine, I sit outside.
If the weather is fine, I will sit outside.
If the weather is fine, I am going to sit outside.
If I win one more time, I will have beaten the record.
If it will help, I can offer you some advice.
If it will help, I will offer you some advice.
If I were stronger, I would move those logs.
If I were stronger, I would have moved those logs.
If I had worked harder, I would be rich by now.
If I had worked harder, I would have become rich.
If it was hot in those days, I went swimming.
If I said that yesterday, I did not mean it.
If he said that, he is a fool.
If he said that, I will complain.
If you have passed the exam already, you have done well.
If you have passed the exam already, you are very clever.
If you have passed the exam already, you will be very successful.
If there had been a death in the village, the flags flew at half-mast the next day.
If the war had indeed begun, there was no indication of it.
If the war had indeed begun, we had not been informed.
If the patient would die without the operation, you are justified in performing it.
If the patient would die without the operation, you would be justified in performing it.
If the patient would have died without the operation, you were justified in performing it.
If the patient would have died without the operation, you would have been justified in performing it.
Source: TFD.