RFR: Revert "macro assembler's enqueue barrier register allocation"

[Roman Kennke]

Yes please. I want to see the orginal failure again. :-)

Roman


> This causes bad failures in testing. We would redo it after this revert:
> 
> diff -r c75a645eeb04 src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp
> --- a/src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp	Tue Jun 19 12:19:15
> 2018 +0200
> +++ b/src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp	Tue Jun 19 14:34:20
> 2018 +0200
> @@ -474,11 +474,8 @@
>      // __ push_callee_saved_registers();
>      __ subptr(rsp, 2 * Interpreter::stackElementSize);
>      __ movdbl(Address(rsp, 0), xmm0);
> -    if (dst != c_rarg0) {
> -      __ mov(c_rarg0, dst);
> -    }
> 
> -    satb_write_barrier_pre(masm, noreg, c_rarg0, r15_thread, tmp, true, false);
> +    satb_write_barrier_pre(masm, noreg, dst, r15_thread, tmp, true, false);
>      __ movdbl(xmm0, Address(rsp, 0));
>      __ addptr(rsp, 2 * Interpreter::stackElementSize);
>      //__ pop_callee_saved_registers();
> 
> Testing x86_64 build
> 
> Thanks,
> -Aleksey
> 
>