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

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

Index: src/compiler/arm/instruction-selector-arm.cc
diff --git a/src/compiler/arm/instruction-selector-arm.cc b/src/compiler/arm/instruction-selector-arm.cc
index 8d11c1d82647a98a63146f29db11e568097f5449..ef0bb6800e4933ecf905a65f3ca03558760db289 100644
--- a/src/compiler/arm/instruction-selector-arm.cc
+++ b/src/compiler/arm/instruction-selector-arm.cc
@@ -1814,29 +1814,6 @@
        g.UseRegister(right));
 }
 
-void InstructionSelector::VisitAtomicLoad(Node* node) {
-  LoadRepresentation load_rep = LoadRepresentationOf(node->op());
-  ArmOperandGenerator g(this);
-  Node* base = node->InputAt(0);
-  Node* index = node->InputAt(1);
-  ArchOpcode opcode = kArchNop;
-  switch (load_rep.representation()) {
-    case MachineRepresentation::kWord8:
-      opcode = load_rep.IsSigned() ? kAtomicLoadInt8 : kAtomicLoadUint8;
-      break;
-    case MachineRepresentation::kWord16:
-      opcode = load_rep.IsSigned() ? kAtomicLoadInt16 : kAtomicLoadUint16;
-      break;
-    case MachineRepresentation::kWord32:
-      opcode = kAtomicLoadWord32;
-      break;
-    default:
-      UNREACHABLE();
-      return;
-  }
-  Emit(opcode | AddressingModeField::encode(kMode_Offset_RR),
-       g.DefineAsRegister(node), g.UseRegister(base), g.UseRegister(index));
-}
 
 // static
 MachineOperatorBuilder::Flags