Re: [whopr] Design/implementation alternatives for the driver and WPA

["Rafael Espindola" <espindola at google dot com>]

> Is there a specific reason you don't use the LLVM LTO interface?  It seems
> to be roughly the same as your proposed interface:
>
> a) it has a simple C interface like your proposed one
> b) it is already implemented in one system linker (Apple's), so GCC would
> just provide its own linker plugin and it would work on apple platforms
> c) it is richer than your interface
> d) it is battle tested, and exists today
> e) it is completely independent of llvm (by design)
> f) it is fully documented: http://llvm.org/docs/LinkTimeOptimization.html
>
> Is there something specific you don't like about the LLVM interface?


We are still discussing how we are going to implement, so the API is
still not final. Some things that have been pointed out:

*) Plugins could have other uses and the naming used on the LLVM LTO
interface is LTO specific.
*) We have a normal symbol table on the .o files. It is not clear if
we should assume that it will always be the case. If so, we don't need
the API part that handles that.
*) How do you handle the case of multiple symbols with the same name
(say a weak and a strong one)? lto_codegen_add_must_preserve_symbol
has a char* argument. How does it know which symbol we are talking
about?
*) To save memory, one option is to have the plugin exec WPA and WPA
exec the linker again with the new objects. In this case the api
should be a bit different.


> -Chris
>


Cheers,
-- 
Rafael Avila de Espindola

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