fix shift by #64 by special casing
Cover more ReservedValues
implement SLI
More special casing for shift #64, this time take into account Signed
shifts which still need to be done.
ensure mask ULL for SLI ops
Fix another special case:
  - ensure we use add2 for extended results
  - special case for shift 64.
Make sure we sign-extend if doing sign specific extended calculations