x86_32 build and test failures after JDK-8228369 (Shenandoah: Refactor LRB C1 stubs)

/home/shade/trunks/jdk-jdk/src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp: In member function 'void ShenandoahBarrierSetAssembler::generate_c1_load_reference_barrier_runtime_stub(StubAssembler*)':
/home/shade/trunks/jdk-jdk/src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp:901:24: error: 'c_rarg0' was not declared in this scope
   __ load_parameter(0, c_rarg0);
                        ^~~~~~~