It doesn't help to attach this into a closed bugreport. LTO allows GCC to do a lot more transformations and sometime the transformations hurts the final performance. This is a bug and we will try to fix it. >From information you gave it is however impossible to guess what may possibly >go wrong. If you provide some more analysis about why your program gets slower and attach it into a (new) PR, we will try to take a look.
Honza
