* DecayOp - array or function to pointer decay. Not shown in C.
* BitCastOp - bit-preserving conversion. Emitted as bit_cast if
necessary.
* ExtendOp - zero- or sign-extending conversion from any integer type to
any wider integer type.
* TruncateOp - truncating conversion from any integer type to any
narrower integer type.
* PtrResizeOp - resizes a pointer without changing its pointee type.
Lauri Vasama