[KeyedLoadIC] Support Smi "handlers" for element loads

This is an experiment as far as performance is concerned. If Smi-configured
element loading directly from the dispatcher stub is fast enough, then we
can stop compiling LoadFastElementStubs (and drop the corresponding code).

Review-Url: https://codereview.chromium.org/2180273002
Cr-Commit-Position: refs/heads/master@{#38377}

src/code-stub-assembler.h

@@ -509,9 +509,6 @@ class CodeStubAssembler : public compiler::CodeAssembler {
                              Variable* var_handler, Label* if_miss,
                              int unroll_count);
 
-  void HandleLoadICHandlerCase(const LoadICParameters* p,
-                               compiler::Node* handler, Label* miss);
-
   compiler::Node* StubCachePrimaryOffset(compiler::Node* name,
                                          compiler::Node* map);
 
@@ -552,6 +549,19 @@ class CodeStubAssembler : public compiler::CodeAssembler {
       compiler::Node* value);
 
  private:
+  enum ElementSupport { kOnlyProperties, kSupportElements };
+
+  void HandleLoadICHandlerCase(
+      const LoadICParameters* p, compiler::Node* handler, Label* miss,
+      ElementSupport support_elements = kOnlyProperties);
+  void EmitBoundsCheck(compiler::Node* object, compiler::Node* elements,
+                       compiler::Node* intptr_key, compiler::Node* is_jsarray,
+                       Label* miss);
+  void EmitElementLoad(compiler::Node* object, compiler::Node* elements,
+                       compiler::Node* elements_kind, compiler::Node* key,
+                       Label* if_hole, Label* rebox_double,
+                       Variable* var_double_value, Label* miss);
+
   compiler::Node* ElementOffsetFromIndex(compiler::Node* index,
                                          ElementsKind kind, ParameterMode mode,
                                          int base_size = 0);

src/field-index-inl.h

@@ -6,6 +6,7 @@
 #define V8_FIELD_INDEX_INL_H_
 
 #include "src/field-index.h"
+#include "src/ic/handler-configuration.h"
 
 namespace v8 {
 namespace internal {
@@ -88,7 +89,7 @@ inline int FieldIndex::GetLoadByFieldIndex() const {
 // FieldIndex object from it.
 // static
 inline FieldIndex FieldIndex::ForLoadByFieldOffset(Map* map, int offset) {
-  DCHECK(offset & 1);  // Property marker (as opposed to element).
+  DCHECK(LoadHandlerTypeBit::decode(offset) == kLoadICHandlerForProperties);
   bool is_inobject = FieldOffsetIsInobject::decode(offset);
   bool is_double = FieldOffsetIsDouble::decode(offset);
   int field_index = FieldOffsetOffset::decode(offset) >> kPointerSizeLog2;
@@ -114,7 +115,7 @@ inline int FieldIndex::GetLoadByFieldOffset() const {
   return FieldOffsetIsInobject::encode(is_inobject()) |
          FieldOffsetIsDouble::encode(is_double()) |
          FieldOffsetOffset::encode(index() << kPointerSizeLog2) |
-         1;  // Property marker (as opposed to element).
+         LoadHandlerTypeBit::encode(kLoadICHandlerForProperties);
 }
 
 inline FieldIndex FieldIndex::ForDescriptor(Map* map, int descriptor_index) {

src/field-index.h

@@ -81,13 +81,6 @@ class FieldIndex final {
   }
   bool operator!=(FieldIndex const& other) const { return !(*this == other); }
 
-  // For GetLoadByFieldOffset.
-  class FieldOffsetIsInobject : public BitField<bool, 1, 1> {};
-  class FieldOffsetIsDouble : public BitField<bool, 2, 1> {};
-  class FieldOffsetOffset : public BitField<int, 3, 27> {};
-  // Make sure we don't overflow into the sign bit.
-  STATIC_ASSERT(FieldOffsetOffset::kNext <= kSmiValueSize - 1);
-
  private:
   FieldIndex(bool is_inobject, int local_index, bool is_double,
              int inobject_properties, int first_inobject_property_offset,

src/ic/handler-compiler.cc

@@ -6,6 +6,7 @@
 
 #include "src/field-type.h"
 #include "src/ic/call-optimization.h"
+#include "src/ic/handler-configuration.h"
 #include "src/ic/ic-inl.h"
 #include "src/ic/ic.h"
 #include "src/isolate-inl.h"
@@ -577,7 +578,7 @@ Handle<Code> NamedStoreHandlerCompiler::CompileStoreCallback(
 #undef __
 
 // static
-Handle<Code> ElementHandlerCompiler::GetKeyedLoadHandler(
+Handle<Object> ElementHandlerCompiler::GetKeyedLoadHandler(
     Handle<Map> receiver_map, Isolate* isolate) {
   if (receiver_map->has_indexed_interceptor() &&
       !receiver_map->GetIndexedInterceptor()->getter()->IsUndefined(isolate) &&
@@ -610,10 +611,18 @@ Handle<Code> ElementHandlerCompiler::GetKeyedLoadHandler(
   bool convert_hole_to_undefined =
       is_js_array && elements_kind == FAST_HOLEY_ELEMENTS &&
       *receiver_map == isolate->get_initial_js_array_map(elements_kind);
-  TRACE_HANDLER_STATS(isolate, KeyedLoadIC_LoadFastElementStub);
-  return LoadFastElementStub(isolate, is_js_array, elements_kind,
-                             convert_hole_to_undefined)
-      .GetCode();
+  if (FLAG_tf_load_ic_stub) {
+    int config = KeyedLoadElementsKind::encode(elements_kind) |
+                 KeyedLoadConvertHole::encode(convert_hole_to_undefined) |
+                 KeyedLoadIsJsArray::encode(is_js_array) |
+                 LoadHandlerTypeBit::encode(kLoadICHandlerForElements);
+    return handle(Smi::FromInt(config), isolate);
+  } else {
+    TRACE_HANDLER_STATS(isolate, KeyedLoadIC_LoadFastElementStub);
+    return LoadFastElementStub(isolate, is_js_array, elements_kind,
+                               convert_hole_to_undefined)
+        .GetCode();
+  }
 }
 
 void ElementHandlerCompiler::CompileElementHandlers(

src/ic/handler-compiler.h

@@ -279,8 +279,8 @@ class ElementHandlerCompiler : public PropertyHandlerCompiler {
 
   virtual ~ElementHandlerCompiler() {}
 
-  static Handle<Code> GetKeyedLoadHandler(Handle<Map> receiver_map,
-                                          Isolate* isolate);
+  static Handle<Object> GetKeyedLoadHandler(Handle<Map> receiver_map,
+                                            Isolate* isolate);
   void CompileElementHandlers(MapHandleList* receiver_maps,
                               List<Handle<Object>>* handlers);
 

src/ic/handler-configuration.h

+// Copyright 2016 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.
+
+#ifndef V8_IC_HANDLER_CONFIGURATION_H_
+#define V8_IC_HANDLER_CONFIGURATION_H_
+
+#include "src/elements-kind.h"
+#include "src/globals.h"
+#include "src/utils.h"
+
+namespace v8 {
+namespace internal {
+
+enum LoadHandlerType {
+  kLoadICHandlerForElements = 0,
+  kLoadICHandlerForProperties = 1
+};
+
+class LoadHandlerTypeBit : public BitField<bool, 0, 1> {};
+
+// Encoding for configuration Smis for property loads:
+class FieldOffsetIsInobject
+    : public BitField<bool, LoadHandlerTypeBit::kNext, 1> {};
+class FieldOffsetIsDouble
+    : public BitField<bool, FieldOffsetIsInobject::kNext, 1> {};
+class FieldOffsetOffset : public BitField<int, FieldOffsetIsDouble::kNext, 27> {
+};
+// Make sure we don't overflow into the sign bit.
+STATIC_ASSERT(FieldOffsetOffset::kNext <= kSmiValueSize - 1);
+
+// Encoding for configuration Smis for elements loads:
+class KeyedLoadIsJsArray : public BitField<bool, LoadHandlerTypeBit::kNext, 1> {
+};
+class KeyedLoadConvertHole
+    : public BitField<bool, KeyedLoadIsJsArray::kNext, 1> {};
+class KeyedLoadElementsKind
+    : public BitField<ElementsKind, KeyedLoadConvertHole::kNext, 8> {};
+// Make sure we don't overflow into the sign bit.
+STATIC_ASSERT(KeyedLoadElementsKind::kNext <= kSmiValueSize - 1);
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_IC_HANDLER_CONFIGURATION_H_

src/ic/ic.cc

@@ -1328,7 +1328,7 @@ void KeyedLoadIC::UpdateLoadElement(Handle<HeapObject> receiver) {
   TargetMaps(&target_receiver_maps);
 
   if (target_receiver_maps.length() == 0) {
-    Handle<Code> handler =
+    Handle<Object> handler =
         ElementHandlerCompiler::GetKeyedLoadHandler(receiver_map, isolate());
     return ConfigureVectorState(Handle<Name>(), receiver_map, handler);
   }
@@ -1357,7 +1357,7 @@ void KeyedLoadIC::UpdateLoadElement(Handle<HeapObject> receiver) {
       IsMoreGeneralElementsKindTransition(
           target_receiver_maps.at(0)->elements_kind(),
           Handle<JSObject>::cast(receiver)->GetElementsKind())) {
-    Handle<Code> handler =
+    Handle<Object> handler =
         ElementHandlerCompiler::GetKeyedLoadHandler(receiver_map, isolate());
     return ConfigureVectorState(Handle<Name>(), receiver_map, handler);
   }