How to select only visible pixels of an underlying layer?

Hi! So basically I need to select ONLY the visible part of an image, which is partially covered by another layer..

For example there is an image with a transparent circle in the middle, and the rest is black, now if I add another layer with a picture (under the previous one), I will want to select only the part of the picture that is in the circle

Don't tell me to use the lasso tool or to do it manually, because the image I want to select is too complex and would take a lot of time