Factor out super-class and interface array subtype checks into a stub.

runtime/vm/stub_code_ia32.cc

Index: runtime/vm/stub_code_ia32.cc
===================================================================
--- runtime/vm/stub_code_ia32.cc	(revision 5920)
+++ runtime/vm/stub_code_ia32.cc	(working copy)
@@ -1755,6 +1755,85 @@
   __ jmp(&StubCode::OneArgCheckInlineCacheLabel());
 }
 
+
+// Check if an instance class is a subtype of class/interface using simple
+// superchain and interface array traversal. Does not take type parameters into
+// account.
+// EAX: instance.
+// EDX: class/interface to test against (is class of instance a subtype of it).
+// Result in EDX: 1 is subtype, 0 maybe not.
+// Destroys EBX, ECX.
+void StubCode::GenerateIsSubTypeStub(Assembler* assembler) {
+  const Immediate raw_null =
+      Immediate(reinterpret_cast<intptr_t>(Object::null()));
+  Label test_class, not_found, found, class_loaded_in_ECX, smi_value;
+  __ EnterFrame(0);
+  __ testl(EAX, Immediate(kSmiTagMask));
+  __ j(ZERO, &smi_value, Assembler::kNearJump);
+  __ movl(ECX, FieldAddress(EAX, Object::class_offset()));
+  __ jmp(&class_loaded_in_ECX, Assembler::kNearJump);
+  __ Bind(&smi_value);
+  __ movl(ECX, FieldAddress(CTX, Context::isolate_offset()));
+  __ movl(ECX, Address(ECX, Isolate::object_store_offset()));
+  __ movl(ECX, Address(ECX, ObjectStore::smi_class_offset()));
+  __ Bind(&class_loaded_in_ECX);
+
+  __ movzxb(EBX, FieldAddress(EDX, Class::is_interface_offset()));
+  // Check if we are comparing against class or interface.
+  __ cmpl(EBX, Immediate(0));
+  __ j(EQUAL, &test_class, Assembler::kNearJump);
+
+  // Get interfaces array from instance class.
+  __ movl(EBX, FieldAddress(ECX, Class::interfaces_offset()));
+  __ cmpl(EBX, raw_null);
+  __ j(EQUAL, &not_found, Assembler::kNearJump);
+  __ movl(EDI, FieldAddress(EBX, Array::length_offset()));
+  // EDI: array index.
+  // EBX: interface array.
+  // EDX: interface searched
+  Label array_loop;
+  __ Bind(&array_loop);
+  __ subl(EDI, Immediate(Smi::RawValue(1)));
+  // __ cmpl(EDI, Immediate(0));
+  __ j(LESS, &not_found, Assembler::kNearJump);
+  // EDI is Smi therefore TIMES_2 instead of TIMES_4.
+  // Get type from array.
+  __ movl(ECX, FieldAddress(EBX, EDI, TIMES_2, Array::data_offset()));
+  __ movl(ECX, FieldAddress(ECX, Type::type_class_offset()));
+  __ cmpl(ECX, EDX);
+  __ j(EQUAL, &found, Assembler::kNearJump);
+  __ jmp(&array_loop, Assembler::kNearJump);
+
+  __ Bind(&not_found);
+  __ xorl(EAX, EAX);
+  __ LeaveFrame();
+  __ ret();
+
+  __ Bind(&found);
+  __ movl(EAX, Immediate(1));
+  __ LeaveFrame();
+  __ ret();
+
+  __ Bind(&test_class);
+  // EDX: test class.
+  __ cmpl(ECX, EDX);
+  __ j(EQUAL, &found, Assembler::kNearJump);
+
+  // Check superclasses using a loop (faster than runtime call).
+  Label super_loop;
+  __ Bind(&super_loop);
+  // ECX: class -> super.
+  __ movl(ECX, FieldAddress(ECX, Class::super_type_offset()));
+  // The supertype of Object is a null object.
+  __ cmpl(ECX, raw_null);
+  __ j(EQUAL, &not_found, Assembler::kNearJump);
+  __ movl(ECX, FieldAddress(ECX, Type::type_class_offset()));
+  __ cmpl(EDX, ECX);
+  __ j(NOT_EQUAL, &super_loop, Assembler::kNearJump);
+  __ jmp(&found, Assembler::kNearJump);
+}
+
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32