Revert "- Use a hash table to canonicalize instances/arrays to avoid having to iterate over a linea…

runtime/vm/dart_entry.cc

Index: runtime/vm/dart_entry.cc
diff --git a/runtime/vm/dart_entry.cc b/runtime/vm/dart_entry.cc
index ec881ea7f9813f075909d0164089fa729e395dcf..ea55b49e9f7eeaa6d5ca9d714ebfddeb2cd9617f 100644
--- a/runtime/vm/dart_entry.cc
+++ b/runtime/vm/dart_entry.cc
@@ -322,26 +322,23 @@ RawArray* ArgumentsDescriptor::New(intptr_t num_arguments,
   // argument count; the positional argument count; a sequence of (name,
   // position) pairs, sorted by name, for each named optional argument; and
   // a terminating null to simplify iterating in generated code.
-  Thread* thread = Thread::Current();
-  Zone* zone = thread->zone();
   const intptr_t descriptor_len = LengthFor(num_named_args);
-  Array& descriptor = Array::Handle(
-      zone, Array::New(descriptor_len, Heap::kOld));
+  Array& descriptor = Array::Handle(Array::New(descriptor_len, Heap::kOld));
 
   // Set total number of passed arguments.
   descriptor.SetAt(kCountIndex, Smi::Handle(Smi::New(num_arguments)));
   // Set number of positional arguments.
   descriptor.SetAt(kPositionalCountIndex, Smi::Handle(Smi::New(num_pos_args)));
   // Set alphabetically sorted entries for named arguments.
-  String& name = String::Handle(zone);
-  Smi& pos = Smi::Handle(zone);
-  String& previous_name = String::Handle(zone);
-  Smi& previous_pos = Smi::Handle(zone);
+  String& name = String::Handle();
+  Smi& pos = Smi::Handle();
   for (intptr_t i = 0; i < num_named_args; i++) {
     name ^= optional_arguments_names.At(i);
     pos = Smi::New(num_pos_args + i);
     intptr_t insert_index = kFirstNamedEntryIndex + (kNamedEntrySize * i);
     // Shift already inserted pairs with "larger" names.
+    String& previous_name = String::Handle();
+    Smi& previous_pos = Smi::Handle();
     while (insert_index > kFirstNamedEntryIndex) {
       intptr_t previous_index = insert_index - kNamedEntrySize;
       previous_name ^= descriptor.At(previous_index + kNameOffset);
@@ -362,7 +359,7 @@ RawArray* ArgumentsDescriptor::New(intptr_t num_arguments,
 
   // Share the immutable descriptor when possible by canonicalizing it.
   descriptor.MakeImmutable();
-  descriptor ^= descriptor.CheckAndCanonicalize(thread, NULL);
+  descriptor ^= descriptor.CheckAndCanonicalize(NULL);
   ASSERT(!descriptor.IsNull());
   return descriptor.raw();
 }
@@ -382,12 +379,9 @@ RawArray* ArgumentsDescriptor::NewNonCached(intptr_t num_arguments,
   // Build the arguments descriptor array, which consists of the total
   // argument count; the positional argument count; and
   // a terminating null to simplify iterating in generated code.
-  Thread* thread = Thread::Current();
-  Zone* zone = thread->zone();
   const intptr_t descriptor_len = LengthFor(0);
-  Array& descriptor = Array::Handle(
-      zone, Array::New(descriptor_len, Heap::kOld));
-  const Smi& arg_count = Smi::Handle(zone, Smi::New(num_arguments));
+  Array& descriptor = Array::Handle(Array::New(descriptor_len, Heap::kOld));
+  const Smi& arg_count = Smi::Handle(Smi::New(num_arguments));
 
   // Set total number of passed arguments.
   descriptor.SetAt(kCountIndex, arg_count);
@@ -401,7 +395,7 @@ RawArray* ArgumentsDescriptor::NewNonCached(intptr_t num_arguments,
   // Share the immutable descriptor when possible by canonicalizing it.
   descriptor.MakeImmutable();
   if (canonicalize) {
-    descriptor ^= descriptor.CheckAndCanonicalize(thread, NULL);
+    descriptor ^= descriptor.CheckAndCanonicalize(NULL);
   }
   ASSERT(!descriptor.IsNull());
   return descriptor.raw();