On Mon, 10 Oct 2011, Jan Hubicka wrote: > > > Actually it seems to me that mangling at WPA makes more sense - you don't > > > get > > > symbol name sensitive on partitioning decisions so things go a bit more > > > consistently. Partitioning depends on global properties of program so any > > > code > > > that depends on particular partitioning decisions will have tendency to > > > randomly break and unbreak. > > > > > > We can not really make any promises about our ability to not mangle > > > particular > > > symbol (for use in asm code or whatever): we need to mangle on the > > > occasion of > > > conflict with another static symbol but also when we decide to promote it > > > hidden. We have no information about another hidden symbol in the non-LTO > > > world. Either linker plugin API needs to be extended by providing us > > > with list > > > of forbidden names or ability to have "hidden in LTO world" visibility or > > > we > > > probably need to start using random seeds on all promoted symbols. > > > (in fact I already do sort of mangling to avoid conflict on comdats that > > > has been > > > brought local and then again promoted global, I just did not noticed it > > > is a general > > > problem back then when I first saw the linker complaining). > > > > Ok, I see why it makes sense on WPA time. But then why not mangle > > during partitioning? I think it still makes sense to avoid mangling local > > decls, if not for debugging experience. > > Yeah, we could do that. Debugging experience is quite good reason (though it > will > also make bogus asm statements magically work and break on random basis. In a > way > just breaking them seems more sensible behaviour to me ;) ).
;) > > We do mangle late when we bring symbols local anyway, no? I also > > seem to remember we mangle at LTO time, too ... > > Hmm, I think we mangle at stream in since we do make hashtables based on > symbol names > that are supposed to be unique, but perhaps I am wrong. I think we do not hash local symbols, so that shouldn't be an issue. > LTO time you mean at compilation time when streaming out? I am not aware of > that. Maybe that changed then or I misremember. Can you try the "obvious" and simply mangle all local statics at partitioning time? (leaving the non-conflict case for a further improvement) Richard.
