[NFC] Comment on the use of unchecked_ownership

Author: meg-gupta

lib/SILGen/SILGenApply.cpp

@@ -5482,6 +5482,9 @@ ManagedValue SILGenFunction::applyBorrowMutateAccessor(
   if (fn.getFunction()->getConventions().hasGuaranteedResult()) {
     auto selfArg = args.back().getValue();
     if (isa<LoadBorrowInst>(selfArg)) {
+      // unchecked_ownership is used to silence the ownership verifier for
+      // returning a value produced within a load_borrow scope. SILGenCleanup
+      // eliminates it and introduces return_borrow appropriately.
       rawResult = B.createUncheckedOwnership(loc, rawResult);
     }
   }

lib/SILGen/SILGenStmt.cpp

@@ -720,6 +720,9 @@ bool SILGenFunction::emitBorrowOrMutateAccessorResult(
     assert(F.getConventions().hasGuaranteedResult());
     auto regularLoc = RegularLocation::getAutoGeneratedLocation();
     auto load = B.createLoadBorrow(regularLoc, guaranteedAddress).getValue();
+    // unchecked_ownership is used to silence the ownership verifier for
+    // returning a value produced within a load_borrow scope. SILGenCleanup
+    // eliminates it and introduces return_borrow appropriately.
     return B.createUncheckedOwnership(regularLoc, load);
   };