Improve hashCode for closures

runtime/lib/function.cc

Index: runtime/lib/function.cc
diff --git a/runtime/lib/function.cc b/runtime/lib/function.cc
index cf6e29813f2795baaafb582b6969b5f1d8f29bae..e87914aac7174d882f4afce7ba6bc18151ee9068 100644
--- a/runtime/lib/function.cc
+++ b/runtime/lib/function.cc
@@ -68,11 +68,30 @@ DEFINE_NATIVE_ENTRY(Closure_equals, 2) {
   return Bool::False().raw();
 }
 
-DEFINE_NATIVE_ENTRY(Closure_hashCode, 1) {
+DEFINE_NATIVE_ENTRY(Closure_calculateHashCode, 1) {

[rmacnak, 2017/07/19 01:00:24]

computeHash

(Compare String and Type)

[alexmarkov, 2017/07/19 17:54:19]

Done.

   const Closure& receiver =
       Closure::CheckedHandle(zone, arguments->NativeArgAt(0));
   const Function& func = Function::Handle(zone, receiver.function());
-  return func.GetClosureHashCode();
+  intptr_t result = func.GetClosureHashCode();
+  if (func.IsImplicitInstanceClosureFunction()) {
+    // Calculate identityHashCode of cached closure receiver and
+    // combine it with function's hash code.
+    const Context& context = Context::Handle(zone, receiver.context());
+    const Object& recv = Object::Handle(zone, context.At(0));
+    ASSERT(recv.IsInstance());
+    const Object& recvHash =
+        Object::Handle(zone, Instance::Cast(recv).IdentityHashCode());
+    if (recvHash.IsInteger()) {
+      result = result ^ static_cast<intptr_t>(

[rmacnak, 2017/07/19 01:00:24]

Please use CombineHashes and FinalizeHash

[alexmarkov, 2017/07/19 17:54:19]

Done.

+                            Integer::Cast(recvHash).AsTruncatedInt64Value());
+    }
+  }
+  // Finalize hash value like for strings so that it fits into a smi.
+  result += result << 3;
+  result ^= result >> 11;
+  result += result << 15;
+  result &= ((static_cast<intptr_t>(1) << String::kHashBits) - 1);
+  return Smi::New(result);
 }
 
 DEFINE_NATIVE_ENTRY(Closure_clone, 1) {