[llvm-dev] MCJit Runtine Performance

Morten Brodersen via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 4 21:12:06 PST 2016

Hi Keno,

I am talking about runtime. The performance of the generated machine 
code. Not the time it takes to lower the IR to machine code.

We typically only JIT once (taking a few secs) and then run the 
generated machine code for hours. So the JIT time (IR -> machine code) 
doesn't impact us.


On 05/02/16 15:58, Keno Fischer wrote:
> Actually, reading over all of this again, I realize I may have made 
> the wrong statement. The runtime regressions we see in julia are 
> actually regressions in how long LLVM itself takes to do the 
> compilation (but since it happens at run time in the JIT case, I think 
> of it as a regression in our running time). We have only noticed 
> occasional regressions in the performance of the generated code (which 
> we are in the process of fixing). Which kind of regression are you 
> talking about, time taken by LLVM or time taken by the LLVM-generated 
> code?
> On Thu, Feb 4, 2016 at 11:44 PM, Rafael EspĂ­ndola 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>     On 4 February 2016 at 22:48, Morten Brodersen via llvm-dev
>     <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>     > Hi Rafael,
>     >
>     > Not easily (llc).
>     >
>     > Is there a way to make MCJit not use the large code model when
>     JIT'ing?
>     >
>     I think Davide started adding support for the small code model.
>     Cheers,
>     Rafael
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>     llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
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