On Fri, 1 Mar 2019, Jakub Jelinek wrote: > On Fri, Mar 01, 2019 at 09:49:03AM +0100, Richard Biener wrote: > > On Fri, 1 Mar 2019, Jakub Jelinek wrote: > > > Some of the builtin folding sets TREE_NO_WARNING flags, which triggers as > > > --enable-checking=fold errors. I think we should allow setting of > > > TREE_NO_WARNING flag when folding, so this patch arranges that. > > > > > > Tested on: > > > ../configure --enable-languages=c,c++,fortran --enable-checking=fold > > > --disable-bootstrap > > > make -jN && make -jN -k check > > > No extra FAILs compared to normal regtest. Ok for trunk? > > > > Hmm, I guess it's OK though for EXPR_P I think we may want the > > TREE_NO_WARNING setter to unshare the tree? Because IIRC it is > > exactly because of tree sharing that we do this kind of checking? > > Maybe, I just wonder if it wouldn't be too expensive. > These TREE_NO_WARNING sets are typically on arguments of builtin functions > so we'd need to unshare the argument (shallow copy) as well as the whole > builtin. Some spots (usually older) in builtins.c do create new trees, > but some TREE_NO_WARNING setting is hidden even in APIs like c_strlen > which actually doesn't return the argument. Plus, many of those functions > that set it are used both during expansion (where supposedly we don't care > about modifying in place) and folding. What a mess?
Uh. > So, do you prefer to drop this patch, or just take the || EXPR_P (expr) > part away from it and let Martin (who has added pretty much all of these > TREE_NO_WARNING) fix it later? c_strlen is probably the oldest with this > issue and most likely very hard to change; the thing is, it is usually used > during expansion and we heavily rely in that case that it modifies it > in-place and thus doesn't warn multiple times. Just use it also in > fold_builtin_strlen :(. No, as said the patch is probably OK (setting TREE_NO_WARNING is harmless from a tree-sharing perspective but still undesired IMHO). Maybe you can add a comment reflecting the above and open a bug so we can eventually revisit this in future. Thanks, Richard. > > > 2019-03-01 Jakub Jelinek <ja...@redhat.com> > > > > > > PR middle-end/89503 > > > * fold-const.c (fold_checksum_tree): Ignore TREE_NO_WARNING bit > > > on DECL_P and EXPR_P. > > Jakub
