- fix SimplifyCFG

Author: eeckstein

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -3703,10 +3703,11 @@ bool SimplifyCFG::simplifyArgument(SILBasicBlock *BB, unsigned i) {
     return simplifySwitchEnumToSelectEnum(BB, i, A);
 
   // For now, just focus on cases where there is a single use.
-  if (!A->hasOneUse())
+  SILValue argVal = lookThroughBorrowedFromUser(A);
+  if (!argVal->hasOneUse())
     return false;
 
-  auto *Use = *lookThroughBorrowedFromUser(A)->use_begin();
+  auto *Use = *argVal->use_begin();
   auto *User = Use->getUser();
 
   auto disableInOSSA = [](SingleValueInstruction *inst) {