On Fri, Oct 10, 2014 at 7:25 PM, Jeff Law <l...@redhat.com> wrote: >>>>> This message revives an old thread [1], where the miscompilation of >>>>> gfortran >>>>> on alpha was found that that resulted in: >>> >>> >>> [...] >>> >>>> As said in the audit trail of the bugreport I think that the caller >>>> of alpha_set_memflags is wrong in applying MEM flags from the _source_ >>>> operand to MEMs generated for the RMW sequence for the destination. >>>> >>>> It would be better to fix that instead. >>> >>> >>> Please see comment #6 of the referred PR [1] for further analysis and >>> ammended testcase. The testcase and analysis will show a "native" read >>> passing possibly aliasing store. >> >> >> Attached v2 patch implements the same approach in all alias.c places >> that declare MEM_READONLY_P operands as never aliasing. >> >> 2014-10-10 Uros Bizjak <ubiz...@gmail.com> >> >> * alias.c (true_dependence_1): Do not exit early for MEM_READONLY_P >> references when alignment ANDs are involved. >> (write_dependence_p): Ditto. >> (may_alias_p): Ditto. >> >> Patch was boostrapped and regression tested on x86_64-linux-gnu and >> alpha-linux-gnu. Unfortunately, there are still failures remaining in >> gfortran testsuite due to independent RTL infrastructure problem with >> VALUEs leaking into aliasing detecting functions [2], [3]. >> >> The patch was discussed and OK'd by Richi in the PR audit trail. If >> there are no objections from RTL maintainers, I plan to commit it to >> the mainline early next week. >> >> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63483 >> [2] https://gcc.gnu.org/ml/gcc/2014-10/msg00060.html >> [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63475 > > No objection. In fact, after reading everything it's pretty obvious to me > that a /u MEM must be considered as potentially conflicting with writes that > are implemented as RMW sequences to deal with the lack of byte access > support.
Thanks, I went ahead and commit the patch to SVN mainline. I wonder, if they should be also committed to release branches? > The escaping VALUE stuff is still in my queue. Great, I can test them on alpha native, there are many gfortran testsuite failures due to this problem. Thanks, Uros.
