Hello Simon, b0534f7 [1] and the subsequent reversion f0fcc41d7 touched `includes/CodeGen.Platform.hs`, the former removing a panic in the case of `globalRegMaybe` being undefined for a platform and replacing it with `Nothing`. Recently I've found that my ARM builds (with -fllvm) crash at this panic whereas they did not as of the 7.8 release. Given that b0534f7 was reverted this is no doubt due to another change that I haven't identified yet. Do you have any idea what is happening here? I'm currently attempting to build with a workaround setting `globalRegMaybe _ = Nothing`, although this smells suspicously like what would happen in the unregisterized case. My other hypothesis is that MACHREGS_arm should be added to the #if MACHREGS_i386 || MACHREGS_x86_64 || MACHREGS_sparc || MACHREGS_powerpc which smells more like what a registerised architecture should do and it seems the requisite macros are defined for ARM in `stg/MachRegs.h`. Whatever happens for ARM should probably also happen for AArch64. How should `globalRegMaybe` and `freeReg` be defined for platforms that rely exclusively on the LLVM backend? Both ARM and AArch64 appear to be doing the wrong thing at present. Cheers, - Ben [1] https://github.com/ghc/ghc/commit/b0534f78a73f972e279eed4447a5687bd6a8308e#d...