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

[Chris Plummer]

Hi Max,

I took a quick look at the x86 call_VM() code and didn't see any 
register saving. Can you point me to it?

thanks,

Chris

On 1/9/17 8:09 AM, Max Ockner wrote:
> 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
>>
>>
>