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function addresses from the VM), the session ID is obsolete.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