https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67153
--- Comment #18 from ncm at cantrip dot org --- It is far from clear to me that gcc-5's choice to put the increment value in a register, and use just one loop body, is wrong. Rather, it appears that an incidental choice in the placement order of basic blocks or register assignment interacts badly with a bug in Haswell branch prediction, value dependency tracking, micro-op cache, or something. An actual fix for this would need to identify and step around Haswell's sensititvity to whichever detail of code generation this program happens upon.
