[NewGVN] Use leader for instrinsics with the returned attribute

[ManuelJBrito]

Summary

Intrinsics with the returned attribute are copies of arguments, but those arguments might be equivalent to something. We this patch we now use lookupOperandLeader to try and find a leader for the returned value.

[xbolva00]

Tests?

[kmitropoulou]

A test case will be helpful.

[ManuelJBrito]

This patch isn't really useful, the value will be moved to the correct congruence class regardless. Sorry for wasting your time.

llvm/lib/Transforms/Scalar/NewGVN.cpp

 NewGVN::ExprResult NewGVN::performSymbolicCallEvaluation(Instruction *I) const {
   auto *CI = cast<CallInst>(I);
   if (auto *II = dyn_cast<IntrinsicInst>(I)) {
     // Intrinsics with the returned attribute are copies of arguments.
     if (auto *ReturnedValue = II->getReturnedArgOperand()) {
       if (II->getIntrinsicID() == Intrinsic::ssa_copy)
         if (auto Res = performSymbolicPredicateInfoEvaluation(II))
           return Res;
-      return ExprResult::some(createVariableOrConstant(ReturnedValue));
+      return ExprResult::some(
+          createVariableOrConstant(lookupOperandLeader(ReturnedValue)));
     }
   }
 
   // FIXME: Currently the calls which may access the thread id may
   // be considered as not accessing the memory. But this is
   // problematic for coroutines, since coroutines may resume in a
   // different thread. So we disable the optimization here for the
   // correctness. However, it may block many other correct