Re: [Sablevm-developer] pc++ to skip preparation address in (GET|PUT)(FIELD|STATIC)

[Chris P. <chr...@ma...>]

>>I notice that instructions.m4.c in staging@r1503 no longer has a pc++ to 
>>skip the preparation address at the beginning of (GET|PUT)(FIELD|STATIC).
>>    
>>
>Right.
>
>  
>
>>How does this address get skipped in the switch interpreter without 
>>inlinability testing?
>>
>>You have a some _svmf_no_inlining_increment_pc() function, but it's only 
>>turned on / defined for inlinability testing.
>>
>>The other instructions like INVOKE<X> still have the pc++ at the 
>>beginning.  I checked in prepare_code.c and the preparation address is 
>>still being used, I'm just wondering where it gets skipped ...
>>    
>>
>First see two_modes.list - it list all two-mode instructions.
>
>Then see instructions_preparation.m4.c - there's all logic (or magic)
>there. See m4svm_mark_start_and_skip macro which has two versions.
>You're mainly interested in m4svm_mark_start_and_skip_normal.
>
>For any two-modes bytecode it generates this code:
>
>  if (SVM_INLINEABLE_$1 != SVM_INTRP_FLAG_INLINEABLE) pc++; 
>
>Note, that the result of the comparison is known at comile time
>as both values are #defines so no real conditional here.
>Also note, that it depends on the value of SVM_INLINEABLE_$1 of
>certain bytecode for certain architecture so we don't hardcode
>pc++ usage in two_modes.list.
>
>And for non-inlined engines it does pc++ for all two-modes instructions.
>
>  
>

Thanks for the explanation.  I put the above text in my 
instructions_preparation.m4.c working copy.  It's not in my sandbox yet, 
but will be tomorrow.

I think you should move your inlining stuff out of prepare_code.c into a 
separate file like "inlinability.c" or something, and just put it above 
prepare_code.c in libsablevm.c.  The file is pushing 10000 lines now and 
your stuff doesn't tie in directly as one of the phases called in 
_svmf_prepare_code().  Just my opinion ...

I'll let you know how things go tomorrow.  I wrote up some short coding 
guidelines today, mostly based on the existing code, that I think would 
help everyone (especially newcomers), but I'll wait till I'm done to 
mail them.

Cheers,
Chris