Reland of [turbofan] Restore basic write barrier elimination.

src/compiler/change-lowering.cc

Index: src/compiler/change-lowering.cc
diff --git a/src/compiler/change-lowering.cc b/src/compiler/change-lowering.cc
index d2afdf5b4e6ebb04d820a2b69fca6d546598e712..26775c071bd024e02687730817541f508bcf0458 100644
--- a/src/compiler/change-lowering.cc
+++ b/src/compiler/change-lowering.cc
@@ -9,7 +9,6 @@
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/simplified-operator.h"
-#include "src/conversions-inl.h"
 
 namespace v8 {
 namespace internal {
@@ -37,38 +36,6 @@
   return NoChange();
 }
 
-namespace {
-
-WriteBarrierKind ComputeWriteBarrierKind(BaseTaggedness base_is_tagged,
-                                         MachineRepresentation representation,
-                                         Node* value) {
-  // TODO(bmeurer): Optimize write barriers based on input.
-  if (base_is_tagged == kTaggedBase &&
-      representation == MachineRepresentation::kTagged) {
-    if (value->opcode() == IrOpcode::kHeapConstant) {
-      return kPointerWriteBarrier;
-    } else if (value->opcode() == IrOpcode::kNumberConstant) {
-      double const number_value = OpParameter<double>(value);
-      if (IsSmiDouble(number_value)) return kNoWriteBarrier;
-      return kPointerWriteBarrier;
-    }
-    return kFullWriteBarrier;
-  }
-  return kNoWriteBarrier;
-}
-
-WriteBarrierKind ComputeWriteBarrierKind(BaseTaggedness base_is_tagged,
-                                         MachineRepresentation representation,
-                                         int field_offset, Node* value) {
-  if (base_is_tagged == kTaggedBase && field_offset == HeapObject::kMapOffset) {
-    // Write barriers for storing maps are cheaper.
-    return kMapWriteBarrier;
-  }
-  return ComputeWriteBarrierKind(base_is_tagged, representation, value);
-}
-
-}  // namespace
-
 Reduction ChangeLowering::ReduceLoadField(Node* node) {
   const FieldAccess& access = FieldAccessOf(node->op());
   Node* offset = jsgraph()->IntPtrConstant(access.offset - access.tag());
@@ -79,14 +46,11 @@
 
 Reduction ChangeLowering::ReduceStoreField(Node* node) {
   const FieldAccess& access = FieldAccessOf(node->op());
-  WriteBarrierKind kind = ComputeWriteBarrierKind(
-      access.base_is_tagged, access.machine_type.representation(),
-      access.offset, node->InputAt(1));
   Node* offset = jsgraph()->IntPtrConstant(access.offset - access.tag());
   node->InsertInput(graph()->zone(), 1, offset);
-  NodeProperties::ChangeOp(node,
-                           machine()->Store(StoreRepresentation(
-                               access.machine_type.representation(), kind)));
+  NodeProperties::ChangeOp(node, machine()->Store(StoreRepresentation(
+                                     access.machine_type.representation(),
+                                     access.write_barrier_kind)));
   return Changed(node);
 }
 
@@ -124,12 +88,9 @@
 Reduction ChangeLowering::ReduceStoreElement(Node* node) {
   const ElementAccess& access = ElementAccessOf(node->op());
   node->ReplaceInput(1, ComputeIndex(access, node->InputAt(1)));
-  NodeProperties::ChangeOp(
-      node, machine()->Store(StoreRepresentation(
-                access.machine_type.representation(),
-                ComputeWriteBarrierKind(access.base_is_tagged,
-                                        access.machine_type.representation(),
-                                        node->InputAt(2)))));
+  NodeProperties::ChangeOp(node, machine()->Store(StoreRepresentation(
+                                     access.machine_type.representation(),
+                                     access.write_barrier_kind)));
   return Changed(node);
 }