Provide baseline for experimental GC implementation.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index c3eb5bf4402b3b7dc20a4bece79e3be4794f0567..40f10a1a47871cb1c1a5a737ac5f8a866b8d0bb3 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -1971,12 +1971,16 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
   // Store last subject and last input.
   __ movq(rax, Operand(rsp, kSubjectOffset));
   __ movq(FieldOperand(rbx, RegExpImpl::kLastSubjectOffset), rax);
+#ifdef ENABLE_CARDMARKING_WRITE_BARRIER
   __ movq(rcx, rbx);
   __ RecordWrite(rcx, RegExpImpl::kLastSubjectOffset, rax, rdi);
+#endif
   __ movq(rax, Operand(rsp, kSubjectOffset));
   __ movq(FieldOperand(rbx, RegExpImpl::kLastInputOffset), rax);
+#ifdef ENABLE_CARDMARKING_WRITE_BARRIER
   __ movq(rcx, rbx);
   __ RecordWrite(rcx, RegExpImpl::kLastInputOffset, rax, rdi);
+#endif
 
   // Get the static offsets vector filled by the native regexp code.
   __ movq(rcx, ExternalReference::address_of_static_offsets_vector());