title: Why is llvm considered unsuitable for implementing a JIT?
body: <p>Many dynamic languages implement (or want to implement) a JIT Compiler in order to speed up their execution times. Inevitably, someone from the peanut gallery asks why they don't use LLVM. The answer is often, "LLVM is unsuitable for building a JIT." (For Example, Armin Rigo's comment <a href="http://morepypy.blogspot.com/2008/04/float-operations-for-jit.html?showComment=1208773800000#c6322995253226647458">here.</a>)</p>
  
  <p><strong>Why is LLVM Unsuitable for building a JIT?</strong></p>
  
  <p>Note: I know LLVM has its own JIT. If LLVM used to be unsuitable, but now is suitable, please say what changed. I'm not talking about running LLVM Bytecode on the LLVM JIT, I'm talking about using the LLVM libraries to implement a JIT for a dynamic language.</p>