Faster code for megamorphic calls fo get:hashCode for Smi and OneByteString

runtime/vm/flow_graph_compiler_x64.cc

 // Copyright (c) 2013, 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.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1310 matching lines @@
     TokenPosition token_pos,
     LocationSummary* locs,
     intptr_t try_index,
     intptr_t slow_path_argument_count) {
   const String& name = String::Handle(zone(), ic_data.target_name());
   const Array& arguments_descriptor =
       Array::ZoneHandle(zone(), ic_data.arguments_descriptor());
   ASSERT(!arguments_descriptor.IsNull() && (arguments_descriptor.Length() > 0));
   const MegamorphicCache& cache = MegamorphicCache::ZoneHandle(zone(),
       MegamorphicCacheTable::Lookup(isolate(), name, arguments_descriptor));
+  __ Comment("MegamorphicCall");
+  // Load receiver into RDI.
+  __ movq(RDI, Address(RSP, (argument_count - 1) * kWordSize));
+  Label done;
+  if (name.raw() == Symbols::hashCode().raw()) {
+    Label try_onebytestring, megamorphic_call;
+    __ Comment("Inlined get:hashCode for Smi and OneByteString");
+    __ testq(RDI, Immediate(kSmiTagMask));
+    __ j(NOT_ZERO, &try_onebytestring, Assembler::kNearJump);  // Non-smi value.
+    __ movq(RAX, RDI);
+    __ jmp(&done, Assembler::kNearJump);
 
-  __ Comment("MegamorphicCall");
-  __ movq(RDI, Address(RSP, (argument_count - 1) * kWordSize));
+    __ Bind(&try_onebytestring);
+    __ CompareClassId(RDI, kOneByteStringCid);
+    __ j(NOT_EQUAL, &megamorphic_call, Assembler::kNearJump);
+    __ movq(RAX, FieldAddress(RDI, String::hash_offset()));
+    __ cmpq(RAX, Immediate(0));
+    __ j(NOT_EQUAL, &done, Assembler::kNearJump);
+
+    __ Bind(&megamorphic_call);
+    __ Comment("Slow case: megamorphic call");
+  }
   __ LoadObject(RBX, cache);
   if (FLAG_use_megamorphic_stub) {
     __ Call(*StubCode::MegamorphicLookup_entry());
   } else  {
     StubCode::EmitMegamorphicLookup(assembler());
   }
   __ call(RCX);
 
+  __ Bind(&done);
   RecordSafepoint(locs, slow_path_argument_count);
   const intptr_t deopt_id_after = Thread::ToDeoptAfter(deopt_id);
   if (FLAG_precompiled_mode) {
     // Megamorphic calls may occur in slow path stubs.
     // If valid use try_index argument.
     if (try_index == CatchClauseNode::kInvalidTryIndex) {
       try_index = CurrentTryIndex();
     }
     pc_descriptors_list()->AddDescriptor(RawPcDescriptors::kOther,
                                          assembler()->CodeSize(),
@@ skipping 498 matching lines @@
   __ movups(reg, Address(RSP, 0));
   __ AddImmediate(RSP, Immediate(kFpuRegisterSize));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64