http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56572
--- Comment #5 from Richard Henderson <rth at gcc dot gnu.org> --- Yes, removing nested transactions (when possible) is worth doing. The problem is not just with ipa_inline, but also with early_inline. Indeed, for an example this small, I would have expected early_inline to have already nested f into g between lower_tm and ipa_tm. I think I'd always intended that ipa_tm delete nested transations as it saw them, since _even if_ f isn't inlined into g, the transational clone of f (which g should call) also should not have the nested transaction. I.e. inside a transactional clone we know we must be within an outer transaction. As a sort of pass-within-a-pass, we're already walking the transaction tree, and the blocks therein, in order to transform calls. I would think it would be easy enough to add a similar pass-within-a-pass to walk the transaction tree and delete nested transactions. Hopefully we could do this before actually creating the uninstrumented path. I think moving the creation of the uninstrumented path after ipa_inline is probably a mistake. The inliner makes decisions e.g. based on the number of calls to a function. If we double the number of calls with the creation of the uninst path, that could significantly change the decisions that ipa_inline would make. r~
