[LLVMdev] Packages

[Chris Lattner]

> I've done a little more thinking about this (putting source definitions
> into bytecode/assembler) files. Despite my previous assertions to the
> contrary, using the LLVM type and constant global declarations in the
> source definitions section is a little limiting because (a) it limits
> the choices for source compiler writers, (b) it might imply a larger
> amount of information than would otherwise be possible, and (c) it
> implies a contract between LLVM and source compiler writers that LLVM
> shouldn't have to support.

Again, reiterating from my more complete response in the previous mail,
I'm still thinking it is "too early" to support this.  :)

> So, here's what I suggest:
>
>      1. LLVM supports a named section that contains a BLOB. LLVM doesn't
>         care about the contents of the BLOB but will assist in its
>         maintenance (see below). To LLVM its a name and a chunk of data.
>      2. The name of the section is to allow information from different
>         compilers to be distinguished.
>      3. LLVM provides a C++ class that represents the named blob. I'll
>         call this class "ExtraInfo".
>      4. Source compiler writers can subclass ExtraInfo to their heart's
>         content.
>      6. During compilation, any ExtraInfo subclasses created by the
>         source compiler are attached to the Module object and the
>         maintenance provided in 5 is invoked automatically as
>         optimizations occur.

All of this is trivially implementable...

>      5. The ExtraInfo class supports pure virtual methods that are
>         invoked by LLVM to notify its subclass(es) when an optimization
>         causes a function, type or global variable to be deleted. No
>         other notifications should be necessary.

This sounds _extremely_ limited.  What if the optimizer deletes arguments
to functions?  Presumably your information will have to be updated, right?
What if it specializes the function because every caller has some
property?

-Chris

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