[Bug middle-end/68878] [6 Regression] 471.omnetpp in SPEC CPU 2006 is miscompiled with LTO

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68878

--- Comment #8 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
OK, the bug is caused by fact that new decl merging won't merge decls without
symbol table entries. Devirtualization uses them and it means we lose a ctor. 
I have fix for the merging, but it seems to be a latent bug in ipa-cp or
ipa-devirt I need to fix first - it should only cause a drop in number of
devirtualizations, not a wrong code issue.