compiler ICE on darwin

Does anyone have any insights into why clang ICEs when compiling layer2/RepCylBond.cpp in pymol at any optimization higher than -O0 on darwin?

https://bugs.llvm.org/show_bug.cgi?id=37280

The problem is suppressed with -fno-strict-aliasing so I am wondering if there is some code in that file that could be re-organized to avoid the bug. Unfortunately, the ICE doesn’t seem to indicate what line in the source file triggered the compiler segfault.
Jack
ps Oddly the same reproducer seems to not trigger the issue on x86_64 ubuntu bionic Linux.