Thanks, everyone for the testing and feedback. I've now updated the remaining prebuilt compilers and officially released 5.8 on GitHub. There is a fixes-5.8 branch but that currently just reflects master.
I'm pleased that the 32-bit under 64-bit version has proved so successful. It has involved some quite substantial changes to the storage management in the run-time system and there are still too many special cases in the code. In comparison, the differences between the 32-bit and 64-bit native address versions are quite minor.
Still, this version should be able to cope with most processors for the foreseeable future.
David