[turbofan] Restore basic write barrier elimination.

src/compiler/simplified-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/simplified-lowering.h"
 
 #include <limits>
 
+#include "src/address-map.h"
 #include "src/base/bits.h"
 #include "src/code-factory.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/diamond.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/operator-properties.h"
 #include "src/compiler/representation-change.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/compiler/source-position.h"
+#include "src/conversions-inl.h"
 #include "src/objects.h"
 #include "src/type-cache.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // Macro for outputting trace information from representation inference.
 #define TRACE(...)                                      \
   do {                                                  \
@@ skipping 671 matching lines @@
   }
 
   const Operator* Uint32Op(Node* node) {
     return changer_->Uint32OperatorFor(node->opcode());
   }
 
   const Operator* Float64Op(Node* node) {
     return changer_->Float64OperatorFor(node->opcode());
   }
 
+  WriteBarrierKind WriteBarrierKindFor(
+      BaseTaggedness base_taggedness,
+      MachineRepresentation field_representation, Type* field_type,
+      Node* value) {
+    if (base_taggedness == kTaggedBase &&
+        field_representation == MachineRepresentation::kTagged) {
+      Type* value_type = NodeProperties::GetType(value);
+      if (field_type->Is(Type::TaggedSigned()) ||
+          value_type->Is(Type::TaggedSigned())) {
+        // Write barriers are only for stores of heap objects.
+        return kNoWriteBarrier;
+      }
+      if (field_type->Is(Type::BooleanOrNullOrUndefined()) ||
+          value_type->Is(Type::BooleanOrNullOrUndefined())) {
+        // Write barriers are not necessary when storing true, false, null or
+        // undefined, because these special oddballs are always in the root set.
+        return kNoWriteBarrier;
+      }
+      if (value_type->IsConstant() &&
+          value_type->AsConstant()->Value()->IsHeapObject()) {
+        Handle<HeapObject> value_object =
+            Handle<HeapObject>::cast(value_type->AsConstant()->Value());
+        if (value_object->IsMap()) {
+          // Write barriers for storing maps are cheaper.
+          return kMapWriteBarrier;
+        }
+        RootIndexMap root_index_map(jsgraph_->isolate());
+        int root_index = root_index_map.Lookup(*value_object);
+        if (root_index != RootIndexMap::kInvalidRootIndex &&
+            jsgraph_->isolate()->heap()->RootIsImmortalImmovable(root_index)) {
+          // Write barriers are unnecessary for immortal immovable roots.
+          return kNoWriteBarrier;
+        }
+      }
+      if (field_type->Is(Type::TaggedPointer()) ||
+          value_type->Is(Type::TaggedPointer())) {
+        // Write barriers for heap objects are cheaper.
+        return kPointerWriteBarrier;
+      }
+      NumberMatcher m(value);
+      if (m.HasValue()) {
+        if (IsSmiDouble(m.Value())) {
+          // Storing a smi doesn't need a write barrier.
+          return kNoWriteBarrier;
+        }
+        // The NumberConstant will be represented as HeapNumber.
+        return kPointerWriteBarrier;
+      }
+      return kFullWriteBarrier;
+    }
+    return kNoWriteBarrier;
+  }
+
+  WriteBarrierKind WriteBarrierKindFor(
+      BaseTaggedness base_taggedness,
+      MachineRepresentation field_representation, int field_offset,
+      Type* field_type, Node* value) {
+    if (base_taggedness == kTaggedBase &&
+        field_offset == HeapObject::kMapOffset) {
+      return kMapWriteBarrier;
+    }
+    return WriteBarrierKindFor(base_taggedness, field_representation,
+                               field_type, value);
+  }
+
   // Dispatching routine for visiting the node {node} with the usage {use}.
   // Depending on the operator, propagate new usage info to the inputs.
   void VisitNode(Node* node, Truncation truncation,
                  SimplifiedLowering* lowering) {
     switch (node->opcode()) {
       //------------------------------------------------------------------
       // Common operators.
       //------------------------------------------------------------------
       case IrOpcode::kStart:
       case IrOpcode::kDead:
@@ skipping 407 matching lines @@
         SetOutput(node, access.machine_type.representation());
         break;
       }
       case IrOpcode::kStoreField: {
         FieldAccess access = FieldAccessOf(node->op());
         ProcessInput(node, 0, UseInfoForBasePointer(access));
         ProcessInput(node, 1, TruncatingUseInfoFromRepresentation(
                                   access.machine_type.representation()));
         ProcessRemainingInputs(node, 2);
         SetOutput(node, MachineRepresentation::kNone);
+        if (lower()) {
+          WriteBarrierKind write_barrier_kind = WriteBarrierKindFor(
+              access.base_is_tagged, access.machine_type.representation(),
+              access.offset, access.type, node->InputAt(1));
+          if (write_barrier_kind < access.write_barrier_kind) {
+            access.write_barrier_kind = write_barrier_kind;
+            NodeProperties::ChangeOp(
+                node, jsgraph_->simplified()->StoreField(access));
+          }
+        }
         break;
       }
       case IrOpcode::kLoadBuffer: {
         BufferAccess access = BufferAccessOf(node->op());
         ProcessInput(node, 0, UseInfo::PointerInt());        // buffer
         ProcessInput(node, 1, UseInfo::TruncatingWord32());  // offset
         ProcessInput(node, 2, UseInfo::TruncatingWord32());  // length
         ProcessRemainingInputs(node, 3);
 
         MachineRepresentation output;
@@ skipping 45 matching lines @@
       }
       case IrOpcode::kStoreElement: {
         ElementAccess access = ElementAccessOf(node->op());
         ProcessInput(node, 0, UseInfoForBasePointer(access));  // base
         ProcessInput(node, 1, UseInfo::TruncatingWord32());    // index
         ProcessInput(node, 2,
                      TruncatingUseInfoFromRepresentation(
                          access.machine_type.representation()));  // value
         ProcessRemainingInputs(node, 3);
         SetOutput(node, MachineRepresentation::kNone);
+        if (lower()) {
+          WriteBarrierKind write_barrier_kind = WriteBarrierKindFor(
+              access.base_is_tagged, access.machine_type.representation(),
+              access.type, node->InputAt(2));
+          if (write_barrier_kind < access.write_barrier_kind) {
+            access.write_barrier_kind = write_barrier_kind;
+            NodeProperties::ChangeOp(
+                node, jsgraph_->simplified()->StoreElement(access));
+          }
+        }
         break;
       }
       case IrOpcode::kObjectIsCallable:
       case IrOpcode::kObjectIsNumber:
       case IrOpcode::kObjectIsReceiver:
       case IrOpcode::kObjectIsSmi:
       case IrOpcode::kObjectIsString:
       case IrOpcode::kObjectIsUndetectable: {
         ProcessInput(node, 0, UseInfo::AnyTagged());
         SetOutput(node, MachineRepresentation::kBit);
@@ skipping 1159 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoProperties);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8