Revert of [Atomics] Remove Atomics code stubs; use TF ops

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index a68da487fc198a8e8dd94e6534034af228f5cdfe..a917328650a45af6e39bc1b3033e3ec2cad893b1 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -1180,11 +1180,6 @@
       MarkAsWord32(NodeProperties::FindProjection(node, 0));
       MarkAsWord32(NodeProperties::FindProjection(node, 1));
       return VisitWord32PairSar(node);
-    case IrOpcode::kAtomicLoad: {
-      LoadRepresentation type = LoadRepresentationOf(node->op());
-      MarkAsRepresentation(type.representation(), node);
-      return VisitAtomicLoad(node);
-    }
     default:
       V8_Fatal(__FILE__, __LINE__, "Unexpected operator #%d:%s @ node #%d",
                node->opcode(), node->op()->mnemonic(), node->id());