[llvm] [SandboxIR] Add setOperand() and RAUW,RUWIf,RUOW (PR #98410)

[Arthur Eubanks via llvm-commits]

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@@ -180,6 +206,19 @@ bool User::classof(const Value *From) {
   }
 }
 
+void User::setOperand(unsigned OperandIdx, Value *Operand) {
+  if (!isa<llvm::User>(Val))
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aeubanks wrote:

and that's sorta already covered by the `cast<llvm::User>` below, but I guess a nicer error message is good

https://github.com/llvm/llvm-project/pull/98410