SIL: fix: SILCloner doesn't create SILUndefs correctly and add verification for that

cloned SILUndefs ended up with the wrong parent function

Author: eeckstein

include/swift/SIL/SILCloner.h

@@ -592,9 +592,7 @@ SILCloner<ImplClass>::getMappedValue(SILValue Value) {
   // If we have undef, just remap the type.
   if (auto *U = dyn_cast<SILUndef>(Value)) {
     auto type = getOpType(U->getType());
-    ValueBase *undef =
-        (type == U->getType() ? U : SILUndef::get(Builder.getFunction(), type));
-    return SILValue(undef);
+    return SILUndef::get(Builder.getFunction(), type);
   }
 
   llvm_unreachable("Unmapped value while cloning?");

lib/SIL/Verifier/SILVerifier.cpp

@@ -1263,6 +1263,10 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
                 "instruction isn't dominated by its bb argument operand");
       }
 
+      if (auto *undef = dyn_cast<SILUndef>(operand.get())) {
+        require(undef->getParent() == BB->getParent(), "SILUndef in wrong function");
+      }
+
       require(operand.getUser() == I,
               "instruction's operand's owner isn't the instruction");
       require(isOperandInValueUses(&operand), "operand value isn't used by operand");