On Sun, Dec 20, 2020 at 6:43 PM Martin Sebor <mse...@gmail.com> wrote: > > On 12/19/20 12:48 AM, Richard Biener via Gcc-patches wrote: > > On December 19, 2020 1:55:02 AM GMT+01:00, Martin Sebor via Gcc-patches > > <gcc-patches@gcc.gnu.org> wrote: > >> To keep tree expressions stored by the front end in attribute > >> access for nontrivial VLA bounds from getting corrupted during > >> Gimplification and to avoid breaking the preconditions verified > >> by the LTO streamer that no such trees exist in the IL, > >> the attached patch replaces those bounds with a string > >> representation of those expressions (as STRING_CST). It also > >> tweaks the pretty-printer to improve the formatting of the VLA > >> bounds and avoid inserting spurious spaces in some cases. > >> > >> The strings are only used by the front end to verify that > >> redeclarations of the same function match in the form and bounds > >> of their VLA arguments, and they're not needed in the middle end. > >> I considered removing them just before the front end finishes but > >> I couldn't find an efficient way to do that. Is there some data > >> structure that stores all function declarations in a translation > >> unit? If there is, then traversing it and removing the attribute > >> arguments might also be an option, either in addition to this > >> change or in lieu of it. > > > > There is the free lang data pass in tree.c which walks all reachable tree > > nodes. > > You said in response to Honza's suggestion in pr97172 to do that: > > The frontend needs to make sure no frontend specific tree codes > leak into GENERIC so GENERICization is the place where the FE > should clear those. FLD is too late and doing it there would > be a hack. > > Are you now saying you've had a change of heart and that doing it > there isn't a hack after all?
Well, removing a FE specific attribute [when having non-constant arg] might be OK there. But note you asked for a "pass over all tree nodes" thing and I just pointed out free-lang-data. Doing the STRING_CST is certainly less fragile since the SSA names created at gimplification time could even be ggc_freed when no longer used in the IL. Richard. > Martin > > >> The patch was tested on x86_64-linux. > >> > >> Martin > > >
