Combine the incremental-marking write barrier and the remembered-set...

src/ia32/full-codegen-ia32.cc

 // Copyright 2011 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 3075 matching lines @@
   // Swap elements.  Use object and temp as scratch registers.
   __ mov(object, Operand(index_1, 0));
   __ mov(temp,   Operand(index_2, 0));
   __ mov(Operand(index_2, 0), object);
   __ mov(Operand(index_1, 0), temp);
 
   Label new_space;
   __ InNewSpace(elements, temp, equal, &new_space);
 
   __ mov(object, elements);
-  __ RecordWriteHelper(object, index_1, temp, kDontSaveFPRegs);
-  __ RecordWriteHelper(elements, index_2, temp, kDontSaveFPRegs);
+  // Since we are swapping two objects, the incremental marker is not disturbed,
+  // so we don't call the stub that handles this.  TODO(gc): Optimize by
+  // checking the scan_on_scavenge flag, probably by calling the stub.
+  __ RememberedSetHelper(object, index_1, temp, kDontSaveFPRegs);
+  __ RememberedSetHelper(elements, index_2, temp, kDontSaveFPRegs);
 
   __ bind(&new_space);
 
   // We are done. Drop elements from the stack, and return undefined.
   __ add(Operand(esp), Immediate(3 * kPointerSize));
   __ mov(eax, Factory::undefined_value());
   __ jmp(&done);
 
   __ bind(&slow_case);
   __ CallRuntime(Runtime::kSwapElements, 3);
@@ skipping 1155 matching lines @@
   // And return.
   __ ret(0);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32