[LLVMdev] runtime optimizations in LLVM

Gordon Henriksen gordonhenriksen at mac.com
Thu Jan 3 15:14:31 PST 2008

Hi Kamal,

On Jan 2, 2008, at 05:57, Kamal R. Prasad wrote:

> (im new to LLVM , so pl excuse if this is a naive q).


> Can someone provide info on what runtime optimizations are done in  

You can use any of LLVM's optimizing transformations in a JIT context.  
There's a list here:


Unlike Java, you're in the driver's seat. You can determine which  
optimizations are applied to your code, and when.

> do you have something along lines of JVM's hotspot feature?

You can recompile a function in the JIT at any time.


However, LLVM does not yet have support frame rewriting; you cannot re- 
optimize and resume a function that is on the call stack.

> How efficient is the optimized code vis-a-vis native code?

It is native code! :) LLVM is also an excellent static compiler (see  
llvm-gcc, clang).

— Gordon

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