More bug discussion: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61904
Rearranging optimisation passes reveals a bug. Not really ‘terminal’.
The only thing that seems terminally broken in this story is Linus' ability to communicate on LKML without verbal abuse.
… Which is why it was already fixed upstream, before this email ever happened. Debian just wasn’t up to date.
Per the bug report, it was broken in 4.5.0 and fixed in 4.9.1, which means pretty much everyone, everywhere (minus the gcc-4.2.1 BSDs).
However, the only way to expose the broken behavior came into existence in the 4.8.x branch and the early 4.9.x code, and was patched in both branches and releases were made.