I sent a paper to a top-tier computer-science conference, it was rejected and I got several useful suggestions for improvement. I improved the paper accordingly and I consider to submit it to the same conference in the following year. It is likely that the paper will be reviewed by the same referees.
When sending a revised paper to a journal, the authors should indicate where exactly they revised the paper, so that the referees do not have to read everything again. Should I do the same in this case? If so, how can I indicate to the referees the locations in which I corrected the paper according to their comments from previous year?
My concern is that, if I do not indicate where I revised the paper, the referees might think "we have already reviewed this paper and rejected it last year, and it looks similar, so we should reject it again".
I would not recommend stating that it's a revised paper for several reasons:
Contrary to your assumption, it is not likely to be reviewed by the same people. Typically, each topic in a large computer science conference may be covered by many reviewers, and they get assigned either arbitrarily or by a bidding process. With a few reviewers assigned from a large pool, there might or might not be overlap, but the majority will likely not have seen the prior version.
Computer science conferences, unlike journals, do not tend to provide a "comments to reviewers" section in their submissions. Trying to wedge that in will likely make your submission stand out in a bad way, putting the idea of rejection in your reviewers' heads.
If you've really done a strong set of revisions, it should be pretty obvious that the paper has changed a lot even to a reviewer who's seen it before.
In short: I see no particular positives and several negatives for such a declaration.