[turbofan] Reland of `Add alignment parameter to StackSlot operator`

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 3ff3f2354cc6af0494a624933b31d5b00d01ddc9..f4e8ea13d2be5c62ed78393fe3a4c9acb87eca5a 100644
--- a/src/compiler/s390/instruction-selector-s390.cc
+++ b/src/compiler/s390/instruction-selector-s390.cc
@@ -702,6 +702,15 @@ void VisitBinOp(InstructionSelector* selector, Node* node,
 
 }  // namespace
 
+void InstructionSelector::VisitStackSlot(Node* node) {
+  StackSlotRepresentation rep = StackSlotRepresentationOf(node->op());
+  int slot = frame_->AllocateSpillSlot(rep.size());
+  OperandGenerator g(this);
+
+  Emit(kArchStackSlot, g.DefineAsRegister(node),
+       sequence()->AddImmediate(Constant(slot)), 0, nullptr);
+}
+
 void InstructionSelector::VisitLoad(Node* node) {
   S390OperandGenerator g(this);
   ArchOpcode opcode = SelectLoadOpcode(node);