[LLVMdev] Re: Why JITC?

Chris Lattner sabre at nondot.org
Tue Aug 8 20:28:07 PDT 2006


On Tue, 8 Aug 2006, Mike Hearn wrote:
> On Mon, 07 Aug 2006 13:56:48 -0500, Andrew Lenharth wrote:
>> Granted, LLVM currently doesn't really do much of this, but the
>> infastructure is there to do so.
>
> Right, but you can get this by doing profile directed optimisation during
> development so end users/production systems don't have the overhead. Also

LLVM has infrastructure to support that as well.  If it makes more sense 
for your application, use it.  LLVM doesn't force you to use the JIT, it 
works perfectly fine as a static compiler.

-chris

> it seems to me that at some point the bookkeeping and analysis overhead
> for these optimisations would reduce performance of the program by more
> than they improve it. Eg keeping track of which calls are candidates for
> inlining may increase memory usage, so increasing swapping or decreasing
> cache utilisation, so losing you more performance than it gains.
>
> thanks -mike
>
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-Chris

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