Update verification for unchecked_ownership

Author: meg-gupta

lib/SIL/Verifier/SILOwnershipVerifier.cpp

@@ -346,6 +346,10 @@ bool SILValueOwnershipChecker::gatherUsers(
     Operand *op = uses.pop_back_val();
     SILInstruction *user = op->getUser();
 
+    if (isa<UncheckedOwnershipInst>(user)) {
+      continue;
+    }
+
     // If this op is a type dependent operand, skip it. It is not interesting
     // from an ownership perspective.
     if (user->isTypeDependentOperand(*op))

lib/SIL/Verifier/SILVerifier.cpp

@@ -6711,6 +6711,11 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
             "Result and operand must have the same type, today.");
   }
 
+  void checkUncheckedOwnershipInst(UncheckedOwnershipInst *uoi) {
+    require(F.getModule().getStage() == SILStage::Raw,
+            "unchecked_ownership is valid only in raw SIL");
+  }
+
   void checkAllocPackMetadataInst(AllocPackMetadataInst *apmi) {
     require(apmi->getIntroducer()->mayRequirePackMetadata(*apmi->getFunction()),
             "Introduces instruction of kind which cannot emit on-stack pack "