VM: Reland Inline instance object hash code into object header on 64bit.

runtime/vm/intermediate_language_dbc.cc

 // Copyright (c) 2016, 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_DBC.
 #if defined(TARGET_ARCH_DBC)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/cpu.h"
@@ skipping 994 matching lines @@
                  Location::RequiresRegister(),
                  LocationSummary::kCall) {
   if (ArgumentCount() == 1) {
     // Allocate with type arguments.
     if (compiler->is_optimizing()) {
       // If we're optimizing, try a streamlined fastpath.
       const intptr_t instance_size = cls().instance_size();
       Isolate* isolate = Isolate::Current();
       if (Heap::IsAllocatableInNewSpace(instance_size) &&
           !cls().TraceAllocation(isolate)) {
-        uword tags = 0;
+        uint32_t tags = 0;
         tags = RawObject::SizeTag::update(instance_size, tags);
         ASSERT(cls().id() != kIllegalCid);
         tags = RawObject::ClassIdTag::update(cls().id(), tags);
         if (Smi::IsValid(tags)) {
           const intptr_t tags_kidx =
               __ AddConstant(Smi::Handle(Smi::New(tags)));
           __ AllocateTOpt(locs()->out(0).reg(), tags_kidx);
           __ Nop(cls().type_arguments_field_offset());
         }
       }
@@ skipping 13 matching lines @@
   } else if (compiler->is_optimizing()) {
     // If we're optimizing, try a streamlined fastpath.
     const intptr_t instance_size = cls().instance_size();
     Isolate* isolate = Isolate::Current();
     if (Heap::IsAllocatableInNewSpace(instance_size) &&
         !cls().TraceAllocation(isolate)) {
       uword tags = 0;
       tags = RawObject::SizeTag::update(instance_size, tags);
       ASSERT(cls().id() != kIllegalCid);
       tags = RawObject::ClassIdTag::update(cls().id(), tags);
+      // tags also has the initial zero hash code on 64 bit.
       if (Smi::IsValid(tags)) {
         const intptr_t tags_kidx = __ AddConstant(Smi::Handle(Smi::New(tags)));
         __ AllocateOpt(locs()->out(0).reg(), tags_kidx);
       }
     }
     const intptr_t kidx = __ AddConstant(cls());
     __ Allocate(kidx);
     compiler->AddCurrentDescriptor(RawPcDescriptors::kOther, Thread::kNoDeoptId,
                                    token_pos());
     compiler->RecordSafepoint(locs());
@@ skipping 591 matching lines @@
   ASSERT(from_representation() == kUnboxedDouble);
   const Register value = locs()->in(0).reg();
   const Register out = locs()->out(0).reg();
   const intptr_t instance_size = compiler->double_class().instance_size();
   Isolate* isolate = Isolate::Current();
   ASSERT(Heap::IsAllocatableInNewSpace(instance_size));
   if (!compiler->double_class().TraceAllocation(isolate)) {
     uword tags = 0;
     tags = RawObject::SizeTag::update(instance_size, tags);
     tags = RawObject::ClassIdTag::update(compiler->double_class().id(), tags);
+    // tags also has the initial zero hash code on 64 bit.
     if (Smi::IsValid(tags)) {
       const intptr_t tags_kidx = __ AddConstant(Smi::Handle(Smi::New(tags)));
       __ AllocateOpt(out, tags_kidx);
     }
   }
   const intptr_t kidx = __ AddConstant(compiler->double_class());
   __ Allocate(kidx);
   compiler->AddCurrentDescriptor(RawPcDescriptors::kOther, Thread::kNoDeoptId,
                                  token_pos());
   compiler->RecordSafepoint(locs());
@@ skipping 394 matching lines @@
   }
   __ IfULe(length, index);
   compiler->EmitDeopt(deopt_id(), ICData::kDeoptCheckArrayBound,
                       (generalized_ ? ICData::kGeneralized : 0) |
                           (licm_hoisted_ ? ICData::kHoisted : 0));
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC