[Bug bootstrap/80779] MPX bootstrap does not work on real hardware supporting that

[aivchenk at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80779

--- Comment #2 from Alexander Ivchenko <aivchenk at gcc dot gnu.org> ---
I made some progress a while back with that, mostly by adding
__attribute__((bnd_legacy)) just as in Martin's patches. I don't like that
approach though, as it does not look natural. The two thinks that I found are:

1) There are cases where we have union at the end of the struct, where one
field of the union is a flexible array. I marked those fields of the struct
with corresponding attribute, but, probably, more natural would be to add that
by default when "-fchkp-flexible-struct-trailing-arrays" option is used. We
have a lot of false positives because of that

2) I found a real bounds violation :) In ipa-chkp.c in
chkp_map_attr_arg_indexes  there is a "idx = indexes[idx - 1] + 1;" in the
loop. Here, "idx" may be zero