[premain] need help merging g1BarrierSetC2.cpp

[Andrew Dinn]

Hi Ioi,

I believe I have worked out what was causing the aarch64 code to break. 
A call from archived C2 code to 
G1BarrierSetRuntime::write_ref_field_pre_entry was not being relocated 
and so we ended up jumping to an address in the old VM 0xffff76c77578 
rather than the correct address in the new VM 0xfffff4c77578.

This was happening because the C2 barrier code was refactored to use 
some new helper methods and one of them, 
generate_c2_barrier_runtime_call, failed to load its branch target using 
a RuntimeAddress wrapper

     static void generate_c2_barrier_runtime_call(MacroAssembler* masm, 
G1BarrierStubC2* stub, const Register arg, const address runtime_path) {
       SaveLiveRegisters save_registers(masm, stub);
       if (c_rarg0 != arg) {
         __ mov(c_rarg0, arg);
       }
       __ mov(c_rarg1, rthread);
       __ mov(rscratch1, runtime_path);
       __ blr(rscratch1);
     }


The mov to rscratch1 above needs to be replaced with

   __ lea(rscratch1, RuntimeAddress(runtime_path));

I have pushed a patch to the branch in my repo and with this patch the 
ExcludedClasses, JavacBench, MicronautFirstApp, HelidonQuickStart and 
SpringPetclinic tests all passed.

I am not sure what is breaking x86 but it is not the same problem -- the 
x86 implementation of generate_c2_barrier_runtime_call is defined 
correctly as follows:

     static void generate_c2_barrier_runtime_call(MacroAssembler* masm, 
G1BarrierStubC2* stub, const Register arg, const address runtime_path) {
     #ifdef _LP64
       SaveLiveRegisters save_registers(masm, stub);
       if (c_rarg0 != arg) {
         __ mov(c_rarg0, arg);
       }
       __ mov(c_rarg1, r15_thread);
       // rax is a caller-saved, non-argument-passing register, so it 
does not
       // interfere with c_rarg0 or c_rarg1. If it contained any live 
value before
       // entering this stub, it is saved at this point, and restored 
after the
       // call. If it did not contain any live value, it is free to be 
used. In
       // either case, it is safe to use it here as a call scratch register.
       __ call(RuntimeAddress(runtime_path), rax);
     #else
       Unimplemented();
     #endif // _LP64
     }

I will move on now to debugging the problems on x86.

regards,


Andrew Dinn
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