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?
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 :(.
> > 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
