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

src/compiler/x64/instruction-selector-x64.cc

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index 7ec9dd0d96a7bf0eef11359fa18f0f6eea89b590..3f4e2b3b1c9cfb97e391e5fbf356312bd744c0b5 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -283,6 +283,15 @@ ArchOpcode GetStoreOpcode(StoreRepresentation store_rep) {
 
 }  // 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) {
   LoadRepresentation load_rep = LoadRepresentationOf(node->op());
   X64OperandGenerator g(this);