Llvm.Opcode

`sig
type t =
Invalid
| Ret
| Br
| Switch
| IndirectBr
| Invoke
| Invalid2
| Unreachable
| Add
| FAdd
| Sub
| FSub
| Mul
| FMul
| UDiv
| SDiv
| FDiv
| URem
| SRem
| FRem
| Shl
| LShr
| AShr
| And
| Or
| Xor
| Alloca
| Load
| Store
| GetElementPtr
| Trunc
| ZExt
| SExt
| FPToUI
| FPToSI
| UIToFP
| SIToFP
| FPTrunc
| FPExt
| PtrToInt
| IntToPtr
| BitCast
| ICmp
| FCmp
| PHI
| Call
| Select
| UserOp1
| UserOp2
| VAArg
| ExtractElement
| InsertElement
| ShuffleVector
| ExtractValue
| InsertValue
| Fence
| AtomicCmpXchg
| AtomicRMW
| Resume
| LandingPad
| AddrSpaceCast
| CleanupRet
| CatchRet
| CatchPad
| CleanupPad
| CatchSwitch
| FNeg
| CallBr
| Freeze
end`