Try llvm_readcyclecounter for Rand48.defaultSeed on ARM, x86 linux, SPARC, RISC-V, non-OSX PPC

[n8sh]

RISC-V support for llvm_readcyclecounter was added in LLVM 9.

[kinke]

May I ask how you found this? After a quick glance, it seems it's called exactly twice in the lifetime of a process, when initializing the GC (and its 2 treaps, and Treap being the only Rand48 user).

[n8sh]

I don't remember the context but I might have originally come across it while searching for uses of time. If it's only used twice per process, maybe it would be better to instead submit an upstream patch that removes defaultSeed and uses a pair of constants when initializing the treaps.

[kinke]

Yep that's what I was thinking as well; I doubt these non-deterministic GC treaps are desirable. Pinging @rainers.