Implement optional turbofan UnalignedLoad and UnalignedStore operators

src/compiler/s390/instruction-selector-s390.cc

Index: src/compiler/s390/instruction-selector-s390.cc
diff --git a/src/compiler/s390/instruction-selector-s390.cc b/src/compiler/s390/instruction-selector-s390.cc
index d3fa86149dfdd29e1819f62b240340002837193f..8d5cab6e1c75104b50cc3f2d891cbbd3e3c01e22 100644
--- a/src/compiler/s390/instruction-selector-s390.cc
+++ b/src/compiler/s390/instruction-selector-s390.cc
@@ -315,6 +315,12 @@ void InstructionSelector::VisitStore(Node* node) {
   }
 }
 
+// Architecture supports unaligned access, therefore VisitLoad is used instead
+void InstructionSelector::VisitUnalignedLoad(Node* node) { UNREACHABLE(); }
+
+// Architecture supports unaligned access, therefore VisitStore is used instead
+void InstructionSelector::VisitUnalignedStore(Node* node) { UNREACHABLE(); }
+
 void InstructionSelector::VisitCheckedLoad(Node* node) {
   CheckedLoadRepresentation load_rep = CheckedLoadRepresentationOf(node->op());
   S390OperandGenerator g(this);