Interesting that Crystal did worse than Java even on many non-GC-stress-test benchmarks. I wasn't expecting that.

Some theories as to sources of the slowness:

- The Boehm GC is so much worse that it accounts for bad performance even on benchmarks that don't stress it.

- Crystal's polymorphic calls don't use inline caches and JIT speculation so they aren't as fast as Java's.

- LLVM isn't as good at bounds check elimination as Java because C++ doesn't need it.

- The Crystal code used reference types where it normally would use value types, and Java really has a better code generator for this sort of object-oriented code.