For some reason, clang 6 crashes with a stack overflow on PGO + LTO on
Linux 64 bits. Clang 7 doesn't, but has other problems.
After some bisecting, I found the following:
- r322684 is the first revision that is broken on the release_60 branch.
- that revision is a cherry pick of r322313 from trunk, which is
similarly broken.
- trunk was fixed by r322325, which, funnily enough, predates when
r322313 was cherry-picked.
While the change from r322325 is relatively large, mixing multiple
different changes in a single commit, there also haven't been
significant changes to the same file on trunk since (one macro name
change, one documentation change, and a change related to debug info),
which would tend to indicate the change is not going to break anything,
or at least not more than upgrading to clang 7 would.
The exact part that fixes the issue could probably be found in this
large commit, but I didn't feel like digging into it further considering
the above.
Mike Hommey