- Add a size field to the header.

vm/stub_code_ia32.cc

Index: vm/stub_code_ia32.cc
===================================================================
--- vm/stub_code_ia32.cc	(revision 2918)
+++ vm/stub_code_ia32.cc	(working copy)
@@ -647,6 +647,7 @@
     // 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));
@@ -666,6 +667,9 @@
                        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()));
@@ -673,14 +677,34 @@
     __ 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);
@@ -693,6 +717,7 @@
 
     // Done allocating and initializing the array.
     // EAX: new object.
+    // EDX: Array length as Smi (preserved for the caller.)
     __ ret();
   }
 
@@ -977,8 +1002,26 @@
     __ 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).
@@ -1111,7 +1154,9 @@
       __ 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);
@@ -1129,7 +1174,9 @@
     // 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 =
@@ -1277,7 +1324,9 @@
     // 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.
@@ -1300,7 +1349,9 @@
       // 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));