VM: [Kernel, Precompiler] Improve Function and Field hashes for objects originating from Kernel.

runtime/vm/precompiler.h

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_PRECOMPILER_H_
 #define RUNTIME_VM_PRECOMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/hash_map.h"
 #include "vm/hash_table.h"
@@ skipping 163 matching lines @@
   }
 
   static inline bool IsKeyEqual(Pair pair, Key key) {
     return (pair->target_name() == key->target_name()) &&
            (pair->args_descriptor() == key->args_descriptor());
   }
 };
 
 typedef DirectChainedHashMap<UnlinkedCallKeyValueTrait> UnlinkedCallSet;
 
+static inline intptr_t SimplePointerHash(void* ptr) {
+  return reinterpret_cast<intptr_t>(ptr) * 2654435761UL;
+}
 
 class FunctionKeyValueTrait {
  public:
   // Typedefs needed for the DirectChainedHashMap template.
   typedef const Function* Key;
   typedef const Function* Value;
   typedef const Function* Pair;
 
   static Key KeyOf(Pair kv) { return kv; }
 
   static Value ValueOf(Pair kv) { return kv; }
 
-  static inline intptr_t Hashcode(Key key) { return key->token_pos().value(); }
+  static inline intptr_t Hashcode(Key key) {
+    // We are using pointer hash for objects originating from Kernel because
+    // Fasta currently does not assign any position information to them.
+    if (key->kernel_function() != NULL) {
+      return SimplePointerHash(key->kernel_function());
+    } else {
+      return key->token_pos().value();
+    }
+  }
 
   static inline bool IsKeyEqual(Pair pair, Key key) {
     return pair->raw() == key->raw();
   }
 };
 
 typedef DirectChainedHashMap<FunctionKeyValueTrait> FunctionSet;
 
 
 class FieldKeyValueTrait {
  public:
   // Typedefs needed for the DirectChainedHashMap template.
   typedef const Field* Key;
   typedef const Field* Value;
   typedef const Field* Pair;
 
   static Key KeyOf(Pair kv) { return kv; }
 
   static Value ValueOf(Pair kv) { return kv; }
 
-  static inline intptr_t Hashcode(Key key) { return key->token_pos().value(); }
+  static inline intptr_t Hashcode(Key key) {
+    // We are using pointer hash for objects originating from Kernel because
+    // Fasta currently does not assign any position information to them.
+    if (key->kernel_field() != NULL) {
+      return SimplePointerHash(key->kernel_field());
+    } else {
+      return key->token_pos().value();
+    }
+  }
 
   static inline bool IsKeyEqual(Pair pair, Key key) {
     return pair->raw() == key->raw();
   }
 };
 
 typedef DirectChainedHashMap<FieldKeyValueTrait> FieldSet;
 
 
 class ClassKeyValueTrait {
@@ skipping 333 matching lines @@
   }
   static RawObject* NewKey(const Function& function) { return function.raw(); }
 };
 
 typedef UnorderedHashSet<FunctionsTraits> UniqueFunctionsSet;
 
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_PRECOMPILER_H_