[Vm-dev] understanding slang inlining

[Nicolas Cellier]

Hi all,
I have practically solved
https://github.com/OpenSmalltalk/opensmalltalk-vm/issues/443 for
passing/returning struct by value on X64SysV FFI.

I still have a few cases of packed struct or union to handle, but I know
how to handle them and finish the job.

Practically, but not yet... There is an issue that I can't easily solve:
slang inlining.

The generated code works on fast VM, but not debug nor assert...
It does not work because #ffiCalloutTo:SpecOnStack:in: is not inlined.
Since it uses sender's alloca as stack pointer (where FFI argVector was
marshalled), it obviously will mess the stack if not inlined!

The code is not inlined because a sub-function sends a recursive message .
Unfortunately I have to check struct alignment for correctly determining
the type of 8-byte registers, and algorithm for checking struct alignment
is recursive because we must first check alignment of sub-struct....

Having a recursive function should not be a problem, just don't inline it,
but invoke it.
Unfortunately, our strategy is to inline only sends that can be completely
inlined (and recursively for every sub-send).

So I'm currently blocked...
I'd like to specify to not inquire further sends that explicitely refuse to
be inlined, maybe in the unless block in checkForCompletenessIn:

parseTree
        nodesDo:
            [:node|
             ...snip...]
        unless:
            [:node|
            node isSend
            and: [node selector == #cCode:inSmalltalk:
               * or: [node explicitelyRefuseToBeInlined*
                or: [aCodeGen isAssertSelector: node selector]]]].

Thoughts?
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