Revert of [turbofan] Add support for copy-on-write element stores.

src/compiler/effect-control-linearizer.cc

Index: src/compiler/effect-control-linearizer.cc
diff --git a/src/compiler/effect-control-linearizer.cc b/src/compiler/effect-control-linearizer.cc
index b9924afeb46b29178647f89cca861cf9ac510a9e..766a2e5818f779ee8d6d7db21f7f35c1f35539d1 100644
--- a/src/compiler/effect-control-linearizer.cc
+++ b/src/compiler/effect-control-linearizer.cc
@@ -723,9 +723,6 @@
     case IrOpcode::kPlainPrimitiveToFloat64:
       state = LowerPlainPrimitiveToFloat64(node, *effect, *control);
       break;
-    case IrOpcode::kEnsureWritableFastElements:
-      state = LowerEnsureWritableFastElements(node, *effect, *control);
-      break;
     case IrOpcode::kTransitionElementsKind:
       state = LowerTransitionElementsKind(node, *effect, *control);
       break;
@@ -2590,59 +2587,6 @@
   effect = graph()->NewNode(common()->EffectPhi(2), etrue0, efalse0, control);
   value = graph()->NewNode(common()->Phi(MachineRepresentation::kFloat64, 2),
                            vtrue0, vfalse0, control);
-  return ValueEffectControl(value, effect, control);
-}
-
-EffectControlLinearizer::ValueEffectControl
-EffectControlLinearizer::LowerEnsureWritableFastElements(Node* node,
-                                                         Node* effect,
-                                                         Node* control) {
-  Node* object = node->InputAt(0);
-  Node* elements = node->InputAt(1);
-
-  // Load the current map of {elements}.
-  Node* elements_map = effect =
-      graph()->NewNode(simplified()->LoadField(AccessBuilder::ForMap()),
-                       elements, effect, control);
-
-  // Check if {elements} is not a copy-on-write FixedArray.
-  Node* check = graph()->NewNode(machine()->WordEqual(), elements_map,
-                                 jsgraph()->FixedArrayMapConstant());
-  Node* branch =
-      graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control);
-
-  // Nothing to do if the {elements} are not copy-on-write.
-  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
-  Node* etrue = effect;
-  Node* vtrue = elements;
-
-  // We need to take a copy of the {elements} and set them up for {object}.
-  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
-  Node* efalse = effect;
-  Node* vfalse;
-  {
-    // We need to create a copy of the {elements} for {object}.
-    Operator::Properties properties = Operator::kEliminatable;
-    Callable callable = CodeFactory::CopyFixedArray(isolate());
-    CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
-    CallDescriptor const* const desc = Linkage::GetStubCallDescriptor(
-        isolate(), graph()->zone(), callable.descriptor(), 0, flags,
-        properties);
-    vfalse = efalse = graph()->NewNode(
-        common()->Call(desc), jsgraph()->HeapConstant(callable.code()),
-        elements, jsgraph()->NoContextConstant(), efalse);
-
-    // Store the new {elements} into {object}.
-    efalse = graph()->NewNode(
-        simplified()->StoreField(AccessBuilder::ForJSObjectElements()), object,
-        vfalse, efalse, if_false);
-  }
-
-  control = graph()->NewNode(common()->Merge(2), if_true, if_false);
-  effect = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, control);
-  Node* value = graph()->NewNode(
-      common()->Phi(MachineRepresentation::kTagged, 2), vtrue, vfalse, control);
-
   return ValueEffectControl(value, effect, control);
 }