- Add a size field to the header.

vm/stub_code_ia32.cc

 // Copyright (c) 2011, 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"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
 #include "vm/ic_data.h"
@@ skipping 629 matching lines @@
     // ECX: array element type.
     // EDX: Array length as Smi.
     // EDI: Points to new space object.
     __ cmpl(EBX, Address(EDI, Scavenger::end_offset()));
     __ j(ABOVE_EQUAL, &slow_case, Assembler::kNearJump);
 
     // Successfully allocated the object(s), now update top to point to
     // next object start and initialize the object.
     // EAX: potential new object start.
     // EBX: potential next object start.
+    // EDX: Array length as Smi.
     // EDI: Points to new space object.
     __ movl(Address(EDI, Scavenger::top_offset()), EBX);
     __ addl(EAX, Immediate(kHeapObjectTag));
 
     // EAX: new object start as a tagged pointer.
     // EBX: new object end address.
     // ECX: array element type.
     // EDX: Array length as Smi.
 
     // Store the type argument field.
     __ StoreIntoObject(EAX,
                        FieldAddress(EAX, Array::type_arguments_offset()),
                        ECX);
 
     // Set the length field.
     __ StoreIntoObject(EAX,
                        FieldAddress(EAX, Array::length_offset()),
                        EDX);
 
+    // EAX: new object start as a tagged pointer.
+    // EBX: new object end address.
+    // EDX: Array length as Smi.
     // Store class value for array.
     __ movl(ECX, FieldAddress(CTX, Context::isolate_offset()));
     __ movl(ECX, Address(ECX, Isolate::object_store_offset()));
     __ movl(ECX, Address(ECX, ObjectStore::array_class_offset()));
     __ StoreIntoObject(EAX,
                        FieldAddress(EAX, Array::class_offset()),
                        ECX);
-    __ movl(FieldAddress(EAX, Array::tags_offset()), Immediate(0));  // Tags.
+    // Calculate the size tag.
+    // EAX: new object start as a tagged pointer.
+    // EBX: new object end address.
+    // EDX: Array length as Smi.
+    {
+      Label size_tag_overflow, done;
+      __ leal(ECX, Address(EDX, TIMES_2, fixed_size));  // EDX is Smi.
+      ASSERT(kSmiTagShift == 1);
+      __ andl(ECX, Immediate(-kObjectAlignment));
+      __ cmpl(ECX,
+              Immediate(RawObject::SizeTag::kMaxSizeTag));

[siva, 2012/01/04 01:56:03]

Can't this be in one line?

[Ivan Posva, 2012/01/04 07:59:42]

Done.

+      __ j(ABOVE, &size_tag_overflow, Assembler::kNearJump);
+      __ shll(ECX, Immediate(RawObject::kSizeTagBit - kObjectAlignmentLog2));
+      __ movl(FieldAddress(EAX, Array::tags_offset()), ECX);
+      __ jmp(&done);
+
+      __ Bind(&size_tag_overflow);
+      __ movl(FieldAddress(EAX, Array::tags_offset()), Immediate(0));
+      __ Bind(&done);
+    }
 
     // Initialize all array elements to raw_null.
     // EAX: new object start as a tagged pointer.
     // EBX: new object end address.
+    // EDX: Array length as Smi.
+    __ leal(ECX, FieldAddress(EAX, Array::data_offset()));
     // ECX: iterator which initially points to the start of the variable
     // data area to be initialized.
-    __ leal(ECX, FieldAddress(EAX, Array::data_offset()));
     Label done;
     Label init_loop;
     __ Bind(&init_loop);
     __ cmpl(ECX, EBX);
     __ j(ABOVE_EQUAL, &done, Assembler::kNearJump);
     __ movl(Address(ECX, 0), raw_null);
     __ addl(ECX, Immediate(kWordSize));
     __ jmp(&init_loop, Assembler::kNearJump);
     __ Bind(&done);
 
     // Done allocating and initializing the array.
     // EAX: new object.
+    // EDX: Array length as Smi (preserved for the caller.)
     __ ret();
   }
 
   // Unable to allocate the array using the fast inline code, just call
   // into the runtime.
   __ Bind(&slow_case);
   __ EnterFrame(0);
   __ pushl(raw_null);  // Setup space on stack for return value.
   __ pushl(EDX);  // Array length as Smi.
   __ pushl(ECX);  // Element type.
@@ skipping 264 matching lines @@
     __ movl(Address::Absolute(heap->TopAddress()), EBX);
     __ addl(EAX, Immediate(kHeapObjectTag));
 
     // Initialize the class field in the context object.
     // EAX: new object.
     // EDX: number of context variables.
     __ LoadObject(EBX, context_class);  // Load up class field of context.
     __ StoreIntoObject(EAX,
                        FieldAddress(EAX, Context::class_offset()),
                        EBX);
-    __ movl(FieldAddress(EAX, Context::tags_offset()), Immediate(0));  // Tags.
+    // Calculate the size tag.
+    // EAX: new object.
+    // EDX: number of context variables.
+    {
+      Label size_tag_overflow, done;
+      __ leal(EBX, Address(EDX, TIMES_4, fixed_size));
+      __ andl(EBX, Immediate(-kObjectAlignment));
+      __ cmpl(EBX,
+              Immediate(RawObject::SizeTag::kMaxSizeTag));

[siva, 2012/01/04 01:56:03]

Can't this be in one line?

[Ivan Posva, 2012/01/04 07:59:42]

Done.

+      __ j(ABOVE, &size_tag_overflow, Assembler::kNearJump);
+      __ shll(EBX, Immediate(RawObject::kSizeTagBit - kObjectAlignmentLog2));
+      __ movl(FieldAddress(EAX, Context::tags_offset()), EBX);  // Tags.
+      __ jmp(&done);
+
+      __ Bind(&size_tag_overflow);
+      // Set overflow size tag value.
+      __ movl(FieldAddress(EAX, Context::tags_offset()), Immediate(0));
+      __ Bind(&done);

[siva, 2012/01/04 01:56:03]

Can this piece of code which is repeated here and above be factored into a
static method:
GenerateStoreTags(Assembler* assembler, Register size);

[Ivan Posva, 2012/01/04 07:59:42]

We should evaluate that once we are done with setting up all of the tag bits.

+    }
 
     // Setup up number of context variables field.
     // EAX: new object.
     // EDX: number of context variables as integer value (not object).
     __ movl(FieldAddress(EAX, Context::num_variables_offset()), EDX);
 
     // Setup isolate field.
     // Load Isolate pointer from Context structure into EBX.
     // EAX: new object.
     // EDX: number of context variables.
@@ skipping 113 matching lines @@
       __ movl(Address(ECX,
           InstantiatedTypeArguments::uninstantiated_type_arguments_offset()),
               EDI);
       __ movl(EDX, Address(ESP, kInstantiatorTypeArgumentsOffset));
       __ movl(Address(ECX,
           InstantiatedTypeArguments::instantiator_type_arguments_offset()),
               EDX);
       __ LoadObject(EDX,
           Class::ZoneHandle(Object::instantiated_type_arguments_class()));
       __ movl(Address(ECX, Instance::class_offset()), EDX);  // Set its class.
-      __ movl(Address(ECX, Instance::tags_offset()), Immediate(0));  // Tags.
+      // Set the tags.

[siva, 2012/01/04 01:56:03]

ASSERT(type_args_size <= RawObject::SizeTag::kMaxSizeTag);

[Ivan Posva, 2012/01/04 07:59:42]

ditto

+      __ movl(Address(ECX, Instance::tags_offset()),
+              Immediate(RawObject::SizeTag::encode(type_args_size)));
       // Set the new InstantiatedTypeArguments object (ECX) as the type
       // arguments (EDI) of the new object (EAX).
       __ movl(EDI, ECX);
       __ addl(EDI, Immediate(kHeapObjectTag));
       // Set EBX to new object end.
       __ movl(EBX, ECX);
       __ Bind(&type_arguments_ready);
       // EAX: new object.
       // EDI: new object type arguments.
     }
 
     // Initialize the class field in the object.
     // EAX: new object start.
     // EBX: next object start.
     // EDI: new object type arguments (if is_cls_parameterized).
     __ LoadObject(EDX, cls);  // Load class of object to be allocated.
     __ movl(Address(EAX, Instance::class_offset()), EDX);
-    __ movl(Address(EAX, Instance::tags_offset()), Immediate(0));  // Tags.
+    // Set the tags.

[siva, 2012/01/04 01:56:03]

ASSERT(instance_size <= RawObject::SizeTag::kMaxSizeTag);

[Ivan Posva, 2012/01/04 07:59:42]

ditto

+    __ movl(Address(EAX, Instance::tags_offset()),
+            Immediate(RawObject::SizeTag::encode(instance_size)));
 
     // Initialize the remaining words of the object.
     const Immediate raw_null =
         Immediate(reinterpret_cast<intptr_t>(Object::null()));
 
     // EAX: new object start.
     // EBX: next object start.
     // EDX: class of the object to be allocated.
     // First try inlining the initialization without a loop.
     if (instance_size < (kInlineInstanceSize * kWordSize) &&
@@ skipping 127 matching lines @@
 
     // Successfully allocated the object, now update top to point to
     // next object start and initialize the object.
     __ movl(Address::Absolute(heap->TopAddress()), EBX);
 
     // Initialize the class field in the object.
     // EAX: new closure object.
     // ECX: new context object (only if is_implicit_closure).
     __ LoadObject(EDX, cls);  // Load signature class of closure.
     __ movl(Address(EAX, Closure::class_offset()), EDX);
-    __ movl(Address(EAX, Closure::tags_offset()), Immediate(0));  // Tags.
+    // Set the tags.

[siva, 2012/01/04 01:56:03]

ASSERT(closure_size <= RawObject::SizeTag::kMaxSizeTag);

[Ivan Posva, 2012/01/04 07:59:42]

ditto.

+    __ movl(Address(EAX, Closure::tags_offset()),
+            Immediate(RawObject::SizeTag::encode(closure_size)));
 
     // Initialize the function field in the object.
     // EAX: new closure object.
     // ECX: new context object (only if is_implicit_closure).
     // EBX: next object start.
     __ LoadObject(EDX, func);  // Load function of closure to be allocated.
     __ movl(Address(EAX, Closure::function_offset()), EDX);
 
     // Setup the context for this closure.
     if (is_implicit_static_closure) {
       ObjectStore* object_store = Isolate::Current()->object_store();
       ASSERT(object_store != NULL);
       const Context& empty_context =
           Context::ZoneHandle(object_store->empty_context());
       __ LoadObject(EDX, empty_context);
       __ movl(Address(EAX, Closure::context_offset()), EDX);
     } else if (is_implicit_instance_closure) {
       // Initialize the new context capturing the receiver.
 
       // Set the class field to the Context class.
       __ LoadObject(EBX, Class::ZoneHandle(Object::context_class()));
       __ movl(Address(ECX, Context::class_offset()), EBX);
-      __ movl(Address(ECX, Context::tags_offset()), Immediate(0));  // Tags.
+      // Set the tags.

[siva, 2012/01/04 01:56:03]

ASSERT(context_size <= RawObject::SizeTag::kMaxSizeTag);

[Ivan Posva, 2012/01/04 07:59:42]

ditto.

+      __ movl(Address(ECX, Context::tags_offset()),
+              Immediate(RawObject::SizeTag::encode(context_size)));
 
       // Set number of variables field to 1 (for captured receiver).
       __ movl(Address(ECX, Context::num_variables_offset()), Immediate(1));
 
       // Set isolate field to isolate of current context.
       __ movl(EDX, FieldAddress(CTX, Context::isolate_offset()));
       __ movl(Address(ECX, Context::isolate_offset()), EDX);
 
       // Set the parent field to null.
       __ movl(Address(ECX, Context::parent_offset()), raw_null);
@@ skipping 324 matching lines @@
   __ popl(EDX);
   __ popl(ECX);
   __ LeaveFrame();
   // Now call the dynamic function.
   __ jmp(&StubCode::OneArgCheckInlineCacheLabel());
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32