RFR(M) 8155980: ARM InterpreterMacroAssembler::get_method_counters() should not be saving callee saved registers

[Max Ockner]

Hi Chris,

This looks good to me.

As a side note, and from the perspective of someone who has been digging 
in x86 rather than arm, I wonder if register saving can be rolled into 
call_VM as is done in x86. It would certainly smooth over some of the 
stylistic differences between the platforms.

Thanks,
Max

On 1/6/2017 6:14 PM, Chris Plummer wrote:
> Hello,
>
> Please review the following arm changes. They will be pushed to JDK 10 
> only (when it opens).
>
> https://bugs.openjdk.java.net/browse/JDK-8155980
> http://cr.openjdk.java.net/~cjplummer/8155980/webrev.02/webrev.hotspot
>
> JDK-8012544 added a bunch of callee register saving to 
> InterpreterMacroAssembler::get_method_counters() around the call_VM() 
> call. The reason is because there are a couple of callers of 
> get_method_counters() that need to have r0 and r3 preserved. 
> get_method_counters() should not be responsible for having to save 
> callee saved registers. It does not know which ones are in use when it 
> is called, so it can't do this efficiently. In fact 2 of the 4 callers 
> of get_method_counters() do not need any registers saved. For this 
> reason the callee of get_method_counters() should be responsible for 
> saving callee registers.
>
> This solution would have been been pretty straight forward, except 
> that AARCH64 does not allow SP to go above extended_sp, so when 
> setting up extended_sp I needed to make sure there will be room for 
> the 2 registers that need to be pushed. extended_sp is mainly based on 
> max_stack() for the method, plus an extra slot for jsr292 and 
> exception handling (but not both at the same time). So the fix here is 
> mostly about making sure there are always at least 2 extra slots for 
> pushing the 2 registers.
>
> Here are the changes:
>
> interp_masm_arm.cpp
>   -No longer save/restore registers in get_method_counters():
>
> templateTable_arm.cpp:
>   -Save/restore Rdisp and R3_bytecode to stack around calls to 
> get_method_counters.
>
> abstractinterpreter__arm.cpp::
>   -Properly account for extra 2 slots needed on AARCH64 when creating 
> a frame
>    in layout_activation()
>   -Note I switched to using method->constMethod()->max_stack() because
>    method->max_stack() includes Method::extra_stack_entries(), and I 
> want to
>    account for Method::extra_stack_entries() separately.
>
> templateInterpreterGenerator_arm.cpp:
>   -Properly account for extra 2 slots needed on AARCH64 when creating 
> a frame
>    in generate_normal_entry().
>
> I've tested the following with -Xcomp and with -Xmixed on arm32 and 
> arm64:
>
>   Kitchensink
>   vm.mlvm
>   :jdk_svc
>   :hotspot_runtime
>   :hotspot_serviceability
>   :hotspot_compiler
>   :jdk_lang
>   :jdk_util
>
> I also tested the test case from JDK-8012544.
>
> thanks,
>
> Chris
>
>