Reland of [turbofan] Restore basic write barrier elimination.

src/compiler/change-lowering.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/change-lowering.h"
 
 #include "src/compiler/js-graph.h"
 #include "src/compiler/linkage.h"
 #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 {
 namespace compiler {
 
 ChangeLowering::~ChangeLowering() {}
 
 
 Reduction ChangeLowering::Reduce(Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kLoadField:
       return ReduceLoadField(node);
     case IrOpcode::kStoreField:
       return ReduceStoreField(node);
     case IrOpcode::kLoadElement:
       return ReduceLoadElement(node);
     case IrOpcode::kStoreElement:
       return ReduceStoreElement(node);
     case IrOpcode::kAllocate:
       return ReduceAllocate(node);
     default:
       return NoChange();
   }
   UNREACHABLE();
   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());
   node->InsertInput(graph()->zone(), 1, offset);
   NodeProperties::ChangeOp(node, machine()->Load(access.machine_type));
   return Changed(node);
 }
 
 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);
 }
 
 
 Node* ChangeLowering::ComputeIndex(const ElementAccess& access,
                                    Node* const key) {
   Node* index = key;
   const int element_size_shift =
       ElementSizeLog2Of(access.machine_type.representation());
   if (element_size_shift) {
@@ skipping 17 matching lines @@
 Reduction ChangeLowering::ReduceLoadElement(Node* node) {
   const ElementAccess& access = ElementAccessOf(node->op());
   node->ReplaceInput(1, ComputeIndex(access, node->InputAt(1)));
   NodeProperties::ChangeOp(node, machine()->Load(access.machine_type));
   return Changed(node);
 }
 
 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);
 }
 
 Reduction ChangeLowering::ReduceAllocate(Node* node) {
   PretenureFlag pretenure = OpParameter<PretenureFlag>(node->op());
   Node* target = pretenure == NOT_TENURED
                      ? jsgraph()->AllocateInNewSpaceStubConstant()
                      : jsgraph()->AllocateInOldSpaceStubConstant();
   node->InsertInput(graph()->zone(), 0, target);
   if (!allocate_operator_.is_set()) {
@@ skipping 16 matching lines @@
 }
 
 
 MachineOperatorBuilder* ChangeLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8