[llvm] [SandboxIR] Implement UnaryInstruction class (PR #101541)

[Thorsten Schütt via llvm-commits]

================
@@ -836,10 +839,26 @@ class BranchInst : public Instruction {
 #endif
 };
 
-class LoadInst final : public Instruction {
+/// An abstract class, parent of unary instructions.
+class UnaryInstruction : public Instruction {
+protected:
+  UnaryInstruction(ClassID ID, Opcode Opc, llvm::Instruction *LLVMI,
+                   Context &Ctx)
+      : Instruction(ID, Opc, LLVMI, Ctx) {}
+
+public:
+  static bool classof(const Instruction *I) {
+    return I->getOpcode() == Instruction::Opcode::Load || isa<CastInst>(I);
+  }
+  static bool classof(const Value *V) {
+    return isa<Instruction>(V) && classof(cast<Instruction>(V));
----------------
tschuett wrote:

isa + cast again?
```
if (Instruction *I = dyn_cast<Instruction>(V))
  return classes(I);
return false;
```

https://github.com/llvm/llvm-project/pull/101541