Below is the rumored benchmark for the Galaxy S8. For reference the s7 Edge scores a single core score of 1911 and a multi score of 5620. So almost no increase in single core performance but multicore benchmark shows a 7 percent increase in performance.
|Mar 06, 2017||Samsung Galaxy S7 edgeARMv8 1586 MHz (8 cores)||Android 64-bit||1911||5620|
source – slashleaks.com