- Add a size field to the header.

vm/stub_code_x64.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_X64)
 
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
 #include "vm/ic_data.h"
@@ skipping 553 matching lines @@
 
   if (FLAG_inline_alloc) {
     // Compute the size to be allocated, it is based on the array length
     // and it computed as:
     // RoundedAllocationSize((array_length * kwordSize) + sizeof(RawArray)).
     // Assert that length is a Smi.
     __ testq(R10, Immediate(kSmiTagSize));
     if (FLAG_use_slow_path) {
       __ jmp(&slow_case);
     } else {
-      __ j(NOT_ZERO, &slow_case, Assembler::kNearJump);
+      __ j(NOT_ZERO, &slow_case);
     }
     __ movq(R13, FieldAddress(CTX, Context::isolate_offset()));
     __ movq(R13, Address(R13, Isolate::heap_offset()));
     __ movq(R13, Address(R13, Heap::new_space_offset()));
 
     // Calculate and align allocation size.
     // Load new object start and calculate next object start.
     // RBX: array element type.
     // R10: Array length as Smi.
     // R13: Points to new space object.
     __ movq(RAX, Address(R13, Scavenger::top_offset()));
     intptr_t fixed_size = sizeof(RawArray) + kObjectAlignment - 1;
     __ leaq(R12, Address(R10, TIMES_4, fixed_size));  // R10 is Smi.
     ASSERT(kSmiTagShift == 1);
     __ andq(R12, Immediate(-kObjectAlignment));
     __ leaq(R12, Address(RAX, R12, TIMES_1, 0));
 
     // Check if the allocation fits into the remaining space.
     // RAX: potential new object start.
     // R12: potential next object start.
     // RBX: array element type.
     // R10: Array length as Smi.
     // R13: Points to new space object.
     __ cmpq(R12, Address(R13, Scavenger::end_offset()));
-    __ j(ABOVE_EQUAL, &slow_case, Assembler::kNearJump);
+    __ j(ABOVE_EQUAL, &slow_case);
 
     // Successfully allocated the object(s), now update top to point to
     // next object start and initialize the object.
     // RAX: potential new object start.
     // R12: potential next object start.
     // R13: Points to new space object.
     __ movq(Address(R13, Scavenger::top_offset()), R12);
     __ addq(RAX, Immediate(kHeapObjectTag));
 
     // RAX: new object start as a tagged pointer.
     // R12: new object end address.
     // RBX: array element type.
     // R10: Array length as Smi.
 
     // Store the type argument field.
     __ StoreIntoObject(RAX,
                        FieldAddress(RAX, Array::type_arguments_offset()),
                        RBX);
 
     // Set the length field.
     __ StoreIntoObject(RAX, FieldAddress(RAX, Array::length_offset()), R10);
 
     // Store class value for array.
     __ movq(RBX, FieldAddress(CTX, Context::isolate_offset()));
     __ movq(RBX, Address(RBX, Isolate::object_store_offset()));
     __ movq(RBX, Address(RBX, ObjectStore::array_class_offset()));
     __ StoreIntoObject(RAX, FieldAddress(RAX, Array::class_offset()), RBX);
-    __ movq(FieldAddress(RAX, Array::tags_offset()), Immediate(0));  // Tags.
+    // Calculate the size tag.
+    // RAX: new object start as a tagged pointer.
+    // R12: new object end address.
+    // R10: Array length as Smi.
+    {
+      Label size_tag_overflow, done;
+      __ leaq(RBX, Address(R10, TIMES_2, fixed_size));  // R10 is Smi.
+      ASSERT(kSmiTagShift == 1);
+      __ andq(RBX, Immediate(-kObjectAlignment));
+      __ cmpq(RBX,
+              Immediate(RawObject::SizeTag::kMaxSizeTag));

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

Can this fit in one line?

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

Done.

+      __ j(ABOVE, &size_tag_overflow, Assembler::kNearJump);
+      __ shlq(RBX, Immediate(RawObject::kSizeTagBit - kObjectAlignmentLog2));
+      __ movq(FieldAddress(RAX, Array::tags_offset()), RBX);
+      __ jmp(&done);
+
+      __ Bind(&size_tag_overflow);
+      __ movq(FieldAddress(RAX, Array::tags_offset()), Immediate(0));
+      __ Bind(&done);
+    }
 
     // Initialize all array elements to raw_null.
     // RAX: new object start as a tagged pointer.
     // R12: new object end address.
     // RBX: iterator which initially points to the start of the variable
     // data area to be initialized.
     __ leaq(RBX, FieldAddress(RAX, Array::data_offset()));
     Label done;
     Label init_loop;
     __ Bind(&init_loop);
     __ cmpq(RBX, R12);
     __ j(ABOVE_EQUAL, &done, Assembler::kNearJump);
     __ movq(Address(RBX, 0), raw_null);
     __ addq(RBX, Immediate(kWordSize));
     __ jmp(&init_loop, Assembler::kNearJump);
     __ Bind(&done);
 
     // Done allocating and initializing the array.
     // RAX: new object.
+    // R10: 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);
   __ pushq(raw_null);  // Setup space on stack for return value.
   __ pushq(R10);  // Array length as Smi.
   __ pushq(RBX);  // Element type.
@@ skipping 230 matching lines @@
       __ movq(Address(RCX,
           InstantiatedTypeArguments::uninstantiated_type_arguments_offset()),
               RDI);
       __ movq(RDX, Address(RSP, kInstantiatorTypeArgumentsOffset));
       __ movq(Address(RCX,
           InstantiatedTypeArguments::instantiator_type_arguments_offset()),
               RDX);
       __ LoadObject(RDX,
           Class::ZoneHandle(Object::instantiated_type_arguments_class()));
       __ movq(Address(RCX, Instance::class_offset()), RDX);  // Set its class.
-      __ movq(Address(RCX, 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.

+      __ movq(Address(RCX, Instance::tags_offset()),
+              Immediate(RawObject::SizeTag::encode(type_args_size)));
       // Set the new InstantiatedTypeArguments object (RCX) as the type
       // arguments (RDI) of the new object (RAX).
       __ movq(RDI, RCX);
       __ addq(RDI, Immediate(kHeapObjectTag));
       // Set RBX to new object end.
       __ movq(RBX, RCX);
       __ Bind(&type_arguments_ready);
       // RAX: new object.
       // RDI: new object type arguments.
     }
 
     // Initialize the class field in the object.
     // RAX: new object start.
     // RBX: next object start.
     // RDI: new object type arguments (if is_cls_parameterized).
     __ LoadObject(RDX, cls);  // Load class of object to be allocated.
     __ movq(Address(RAX, Instance::class_offset()), RDX);
-    __ movq(Address(RAX, 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.

+    __ movq(Address(RAX, 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()));
 
     // RAX: new object start.
     // RBX: next object start.
     // RDX: class of the object to be allocated.
     // First try inlining the initialization without a loop.
     if (instance_size < (kInlineInstanceSize * kWordSize) &&
@@ skipping 317 matching lines @@
 }
 
 
 void StubCode::GenerateBreakpointDynamicStub(Assembler* assembler) {
   __ Unimplemented("BreakpointDynamic stub");
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64