[llvm] [SandboxIR] Implement UnreachableInst (PR #101856)

[Julius Alexandre via llvm-commits]

medievalghoul wrote:

> Hmm does the test actually pass?
> 
> For the instruction to be created as a `sanbdoxir::UnreachableInst` we need to add the following code in `Value *Context::getOrCreateValueInternal(llvm::Value *LLVMV, llvm::User *U)`:
> 
> ```
>   case llvm::Instruction::Unreachable: {
>     auto *LLVMUnreachable = cast<llvm::UnreachableInst>(LLVMV);
>     It->second = std::unique_ptr<UnreachableInst>(new UnreachableInst(LLVMUnreachable, *this));
>     return It->second.get();
>   }
> ```

Good catch. Interestingly, the test did pass, but I'm not entirely sure why, if the code you sent me is required. It might be a case of "it works on my computer." I made sure to add it.

https://github.com/llvm/llvm-project/pull/101856