FTB_SHI

Format: FTB_SHI dest, source.

Phase0: FTB_SHI FT3, (S2)

Phase1: -

Phase2: -

Description: Find top bit with signal

Find the first 0 from the MSB if the number is negative, else the first 1 from the MSB. Return -1 if no bits set.
Table 1. Example:
c=0;
while ((S2[31] ^ S2)>>c) ++c;
    FT3=c-1;