[llvm] r199244 - Reapply "LTO: add API to set strategy for -internalize"

[Nick Kledzik]

On Apr 2, 2014, at 1:22 PM, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
>>> 
>>> Have you found a case where the extra calls are actually noticeable?
>> 
>> Probably not.  Since my approach directly modelled what the linker wants, and
>> certainly wasn't going to be slower, I never profiled.  (Sorry I missed that
>> that conversation; I arrived too late.)
>> 
>> Nick, did you do any profiling of this?

Rafael,

Duncan and I came up with this API addition during discussions of why ld -r had some failure cases with bitcode.  We eventually mapped out that the linker has a couple of modes in which changes how symbols of different visibility are handled.  That model of modes led to this API. 

ld64 does not use the new API yet.

But, given that this can be implemented with extreme usage of lto_codegen_add_must_preserve_symbol(), we should just do that (that is, don’t do a premature optimization).  

Also, given that lld is coming and may do things differently.  No need to invest in a short lived new API.


Duncan: I think I can do this all in the linker without a new API.

-Nick