> > On Tue, 19 Jan 2016, Jan Hubicka wrote: > > > > > Hi, > > > here is updated patch. It has same effect as the former version. > > > > > > Bootstrapped/regtested x86_64-linux, OK? > > > > But what about the comment? > > > > We track no > > information on whether given type is used or not, so we have > > to keep them even when not emitting debug information, > > otherwise we may end up remapping variables and their (local) > > types in different orders depending on whether debug > > information is being generated. */ > > > > which suggests that the TYPE_DECLs somehow "order" remapping > > of local types and that is somehow important (maybe for VLA > > types which refer to locals). OTOH local vars are also > > duplicated in order before copying stmts (which may introduce > > differences because of seeing debug stmts or not refering to > > decls/types). > > The original patch is here: > https://gcc.gnu.org/ml/gcc-patches/2011-01/msg01344.html > my understand is that it is all about DECL_UID being stable with -g0 > and -g. My patch does not change that becuase I drop ignored and redundant > typedefs even with -g.
Alexandre, aslo your original mail mentions: > Anyhow, it seems to me that dropping local type decls from lexical > scopes doesn't buy us much, and even though it is indeed a sledgehammer, > as richi put it, this fixes the problem, and I can't envision other > simpler solutions that wouldn't risk running into the problems mentioned > above, so... > Regstrapped on x86_64-linux-gnu and i686-pc-linux-gnu. Ok to install? > One solution I do envision, which might help, would be to try to figure > out which types are unused, and discard those. Say, scan all variables > within a lexical scope (including nested blocks), deciding which ones > can be discarded, and then, as we move out of the nesting, we can > decide, from last to first, which types are unused, and mark as used > types refereced from retained variables and other types that are used, > removing those that, when reached during this backward scan, remain > marked as unused. Or something along these lines, taking nested > functions into account, if needed, and anything else I may have missed > ;-) dropping the type_decls definitly buys us a memory with LTO and firefox. How hard would be to implement the prunning of dead TYPE_DECLs as you suggest? Honza > > Honza
