Improve polymorphic loads on single slots.

src/hydrogen-instructions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 68 matching lines @@
   V(CallKeyed)                                 \
   V(CallKnownGlobal)                           \
   V(CallNamed)                                 \
   V(CallNew)                                   \
   V(CallRuntime)                               \
   V(CallStub)                                  \
   V(Change)                                    \
   V(CheckFunction)                             \
   V(CheckInstanceType)                         \
   V(CheckMap)                                  \
+  V(CheckMapSet)                               \
   V(CheckNonSmi)                               \
   V(CheckPrototypeMaps)                        \
   V(CheckSmi)                                  \
   V(ClampToUint8)                              \
   V(ClassOfTestAndBranch)                      \
   V(CompareIDAndBranch)                        \
   V(CompareGeneric)                            \
   V(CompareObjectEqAndBranch)                  \
   V(CompareMap)                                \
   V(CompareConstantEqAndBranch)                \
@@ skipping 1944 matching lines @@
         (b->mode() == mode() || !has_element_transitions_);
   }
 
  private:
   bool has_element_transitions_;
   Handle<Map> map_;
   CompareMapMode mode_;
 };
 
 
+class HCheckMapSet: public HTemplateInstruction<1> {

[danno, 2012/03/09 11:52:58]

Please merge with HCheckMap as discussed

[Michael Starzinger, 2012/03/12 11:37:11]

Done. HCheckMap now works with a SmallMapList backing structure and has two
constructors, one taking a single map and the other a set of maps. Also added a
static helper to construct HCheckMaps which allow transitions.

+ public:
+  HCheckMapSet(HValue* value, SmallMapList* map_set) : map_set_(map_set) {
+    map_set->Sort();
+    SetOperandAt(0, value);
+    set_representation(Representation::Tagged());
+    SetFlag(kUseGVN);
+    SetGVNFlag(kDependsOnMaps);
+    SetGVNFlag(kDependsOnElementsKind);
+  }
+
+  virtual Representation RequiredInputRepresentation(int index) {
+    return Representation::Tagged();
+  }
+  virtual void PrintDataTo(StringStream* stream);
+
+  HValue* value() { return OperandAt(0); }
+  SmallMapList* map_set() const { return map_set_; }
+
+  DECLARE_CONCRETE_INSTRUCTION(CheckMapSet)
+
+ protected:
+  virtual bool DataEquals(HValue* other) {

[danno, 2012/03/09 11:52:58]

Fast case single maps by just comparing b->map_set() == map_set()

[Michael Starzinger, 2012/03/12 11:37:11]

The backing SmallMapList cannot be compared by reference. But it already has all
the necessary fast-case code for singletons implemented. So I think relying on
the below loop being executed just once should be efficient enough.

+    HCheckMapSet* b = HCheckMapSet::cast(other);
+    // Relies on the fact that map_set has been sorted before.
+    if (map_set_->length() != b->map_set()->length()) return false;
+    for (int i = 0; i < map_set_->length(); i++) {
+      if (!map_set_->at(i).is_identical_to(b->map_set()->at(i))) return false;
+    }
+    return true;
+  }
+
+ private:
+  SmallMapList* map_set_;
+};
+
+
 class HCheckFunction: public HUnaryOperation {
  public:
   HCheckFunction(HValue* value, Handle<JSFunction> function)
       : HUnaryOperation(value), target_(function) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
@@ skipping 2714 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(LoadFieldByIndex);
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_