[Atomics] Remove Atomics code stubs; use TF ops

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 dd99e89296c28ebb1ce17504f112fc467fd96a6e..dba3d9b2309b5085e623125173bde7e28b8fdeaf 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -2024,6 +2024,14 @@ void InstructionSelector::VisitFloat64InsertHighWord32(Node* node) {
        g.UseRegister(left), g.Use(right));
 }
 
+void InstructionSelector::VisitAtomicLoad(Node* node) {
+  LoadRepresentation load_rep = LoadRepresentationOf(node->op());
+  DCHECK(load_rep.representation() == MachineRepresentation::kWord8 ||
+         load_rep.representation() == MachineRepresentation::kWord16 ||
+         load_rep.representation() == MachineRepresentation::kWord32);
+  USE(load_rep);
+  VisitLoad(node);
+}
 
 // static
 MachineOperatorBuilder::Flags