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

runtime/vm/flow_graph_compiler_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1282 matching lines @@
     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 R0.
   __ LoadFromOffset(R0, SP, (argument_count - 1) * kWordSize);
+  Label done;
+  if (name.raw() == Symbols::hashCode().raw()) {
+    Label megamorphic_call;
+    __ Comment("Inlined get:hashCode for Smi and OneByteString");
+    __ tsti(R0, Immediate(kSmiTagMask));
+    __ b(&done, EQ);  // Is Smi.
+
+    __ CompareClassId(R0, kOneByteStringCid);
+    __ b(&megamorphic_call, NE);
+
+    // Use R5 (cache for megamorphic call) as scratch.
+    __ mov(R5, R0);  // Preserve receiver in R5, result in R0.
+    __ ldr(R0, FieldAddress(R0, String::hash_offset()));
+    __ CompareRegisters(R0, ZR);
+    __ b(&done, NE);
+    __ mov(R0, R5);  // Restore receiver in R0,
+
+    __ Bind(&megamorphic_call);
+    __ Comment("Slow case: megamorphic call");
+  }
+
   __ LoadObject(R5, cache);
   if (FLAG_use_megamorphic_stub) {
     __ BranchLink(*StubCode::MegamorphicLookup_entry());
   } else  {
     StubCode::EmitMegamorphicLookup(assembler());
   }
   __ blr(R1);
 
+  __ 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 591 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   __ PopDouble(reg);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64