Only the shifts with applicable SSE2 instructions are implemented here: PSRL* (for ushr) only has 16-64 bit instructions and PSRA* (for sshr) only has 16-32 bit instructions.
Only the shifts with applicable SSE2 instructions are implemented here: PSRL* (for ushr) only has 16-64 bit instructions and PSRA* (for sshr) only has 16-32 bit instructions.