gcc11 issue on reference functions

Starting with gcc11, many of the hash reference functions return incorrect results on -O2 and above but pass as at -O1. This may be related to a gcc11 siting [gcc bug 101257](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101257) where IPA is causing a violation of the strict aliasing rules. Commit 9510077 attempts to fix this with attribute(noipa) but can revert if fixed.