[Vm-dev] What happens with named primitives in CM ?

[Andreas Raab]

See the comment in Interpreter>>primitiveExternalCall.

primitiveExternalCall
     "Call an external primitive. The external primitive methods
     contain as first literal an array consisting of:
     * The module name (String | Symbol)
     * The function name (String | Symbol)
     * The session ID (SmallInteger) [OBSOLETE]
     * The function index (Integer) in the externalPrimitiveTable
     For fast failures the primitive index of any method where the
     external prim is not found is rewritten in the method cache
     with zero. This allows for ultra fast responses as long as the
     method stays in the cache.
     The fast failure response relies on lkupClass being properly
     set. This is done in
     #addToMethodCacheSel:class:method:primIndex: to
     compensate for execution of methods that are looked up in a
     superclass (such as in primitivePerformAt).
     With the latest modifications (e.g., actually flushing the
     function addresses from the VM), the session ID is obsolete.
     But for backward compatibility it is still kept around. Also, a
     failed lookup is reported specially. If a method has been
     looked up and not been found, the function address is stored
     as -1 (e.g., the SmallInteger -1 to distinguish from
     16rFFFFFFFF which may be returned from the lookup).
     It is absolutely okay to remove the rewrite if we run into any
     problems later on. It has an approximate speed difference of
     30% per failed primitive call which may be noticable but if,
     for any reasons, we run into problems (like with J3) we can
     always remove the rewrite.
     "


On 5/23/2011 10:03, Mariano Martinez Peck wrote:
>   
>
>
> Hi folks. I was inspecting for example the CM of  Integer >> 
> #bitAnd:   and the first literal is an array like this: 
> #(#LargeIntegers #primDigitBitAnd 0 17)
>
> I understand the first and the second elements, but I don't the third 
> and the fourth. What are they? (0 and 17) because then even seem to 
> change their value.
>
> I am asking because I am serializing CompiledMethod and then at 
> materialization time I am putting just two zeros for the moment. But I 
> am not sure what they mean.
>
> Thanks in advance,
>
> -- 
> Mariano
> http://marianopeck.wordpress.com
>
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