Sharing of descriptor arrays.

src/arm/macro-assembler-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3685 matching lines @@
   bind(&done);
 }
 
 
 void MacroAssembler::LoadInstanceDescriptors(Register map,
                                              Register descriptors,
                                              Register scratch) {
   Register temp = descriptors;
   ldr(temp, FieldMemOperand(map, Map::kTransitionsOrBackPointerOffset));
 
-  Label ok, fail;
+  Label ok, fail, load_from_back_pointer;
   CheckMap(temp,
            scratch,
            isolate()->factory()->fixed_array_map(),
            &fail,
            DONT_DO_SMI_CHECK);
-  ldr(descriptors, FieldMemOperand(temp, TransitionArray::kDescriptorsOffset));
+  ldr(temp, FieldMemOperand(temp, TransitionArray::kDescriptorsPointerOffset));
+  ldr(descriptors, FieldMemOperand(temp, JSGlobalPropertyCell::kValueOffset));
   jmp(&ok);
+
   bind(&fail);
+  CompareRoot(temp, Heap::kUndefinedValueRootIndex);
+  b(ne, &load_from_back_pointer);
   mov(descriptors, Operand(FACTORY->empty_descriptor_array()));
+  jmp(&ok);
+
+  bind(&load_from_back_pointer);
+  ldr(temp, FieldMemOperand(temp, Map::kTransitionsOrBackPointerOffset));
+  ldr(temp, FieldMemOperand(temp, TransitionArray::kDescriptorsPointerOffset));
+  ldr(descriptors, FieldMemOperand(temp, JSGlobalPropertyCell::kValueOffset));
+
   bind(&ok);
 }
 
 
+void MacroAssembler::NumberOfOwnDescriptors(Register dst, Register map) {
+  ldr(dst, FieldMemOperand(map, Map::kBitFieldOffset));
+  DecodeField<Map::NumberOfOwnDescriptorsBits>(dst);
+}
+
+
 void MacroAssembler::EnumLength(Register dst, Register map) {
   STATIC_ASSERT(Map::EnumLengthBits::kShift == 0);
   ldr(dst, FieldMemOperand(map, Map::kBitField3Offset));
   and_(dst, dst, Operand(Smi::FromInt(Map::EnumLengthBits::kMask)));
 }
 
 
 void MacroAssembler::CheckEnumCache(Register null_value, Label* call_runtime) {
   Register  empty_fixed_array_value = r6;
   LoadRoot(empty_fixed_array_value, Heap::kEmptyFixedArrayRootIndex);
@@ skipping 91 matching lines @@
 void CodePatcher::EmitCondition(Condition cond) {
   Instr instr = Assembler::instr_at(masm_.pc_);
   instr = (instr & ~kCondMask) | cond;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM