[Atomics] Make Atomics.store a builtin using TF

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 b1af3e56d89e106ac159e6cc623643e771b99770..e494dd1d1f83db33c6f5a391f1353cd6d757b605 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -2029,6 +2029,44 @@ void InstructionSelector::VisitAtomicLoad(Node* node) {
   VisitLoad(node);
 }
 
+void InstructionSelector::VisitAtomicStore(Node* node) {
+  X64OperandGenerator g(this);
+  Node* base = node->InputAt(0);
+  Node* index = node->InputAt(1);
+  Node* value = node->InputAt(2);
+
+  MachineRepresentation rep = AtomicStoreRepresentationOf(node->op());
+  ArchOpcode opcode = kArchNop;
+  switch (rep) {
+    case MachineRepresentation::kWord8:
+      opcode = kX64Xchgb;
+      break;
+    case MachineRepresentation::kWord16:
+      opcode = kX64Xchgw;
+      break;
+    case MachineRepresentation::kWord32:
+      opcode = kX64Xchgl;
+      break;
+    default:
+      UNREACHABLE();
+      return;
+  }
+  AddressingMode addressing_mode;
+  InstructionOperand inputs[4];
+  size_t input_count = 0;
+  inputs[input_count++] = g.UseUniqueRegister(base);
+  if (g.CanBeImmediate(index)) {
+    inputs[input_count++] = g.UseImmediate(index);
+    addressing_mode = kMode_MRI;
+  } else {
+    inputs[input_count++] = g.UseUniqueRegister(index);
+    addressing_mode = kMode_MR1;
+  }
+  inputs[input_count++] = g.UseUniqueRegister(value);
+  InstructionCode code = opcode | AddressingModeField::encode(addressing_mode);
+  Emit(code, 0, static_cast<InstructionOperand*>(nullptr), input_count, inputs);
+}
+
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {