LLVM select

select i1 <condition>, <datatype> <var>, <datatype> <var>

  %3 = select i1 %1, i64 -1, i64 %2

• The condition is in i1 as its a boolean, it only needs one bit.
• If %1 is true, then the value of %3 is -1
• If %1 is false, then the value of %3 is %2