Comment by kragen

Sure, to find contiguous chunks of 6 slots within a single word, you can do

    t &= t << 1;
    t &= t << 2;
    t &= t << 2;

and that sort of thing is pretty appealing, but you lose the ability to know what size an object is just by looking at an address, and it's still a lot slower than scanning for an open slot in a page of 5× bigger objects.

Should I assume from your use of uint32_t that you're targeting embedded ARM microcontrollers?