Yeah, given that observing a variable at the Perl level could cause SV upgrades within an opcode, maybe it's better to say the challenges are:

• Polymorphic data structures at the C level; with
• SV upgrades in opcodes; leading to
• Large opcode function sizes

We're not talking about JITting a five line Smalltalk method that's monomorphic across 80% of calls here. It would surprise me if the average opcode didn't expand to a size larger—and quite a few basic blocks more‐than LLVM wants to try to JIT.