FTB

Format: FTB dest, source

Phase0: FTB FT3, (S2|FT2)

Phase1: -

Phase2: -

Description: Find top bit set, starting from the MSB – Where result is MSB=31 down to LSB=0

Return -1 if no bits set.
Table 1. Example:
c = 0;
while ((unsigned)S2>>c) ++c;
    FT3 = c-1;