If you had told me in the 90s when Microsoft was king that someday "proprietary" would be used to describe a completely open-source, documented, published technology that its creator encourages others to adopt, I would have laughed and said it's impossible.
> NaCl is weak at handling dynamically generated code
They got it working for x86 (http://static.googleusercontent.com/external_content/untrust...) and it's currently just not prioritized for PNaCl AFAIK.
> PNaCl from what I recall relies on LLVM which is yet to demonstrate low latency code generation performance
Sounds like the kind of problem that can be addressed once other much bigger problems are solved. It's not like any such problem would be fundamental or insurmountable.
> in contrast to older more mature code generators such as TAOS, LuaJit.
I don't know about TAOS but LuaJIT 2.0 (with it's completely rewritten code generator) is only 5 years old compared to LLVM's 12 years. Even LuaJIT 1 is only 7-8 years old.