[LLVMdev] JIT bug?

[Evan Cheng]

Are you really running the JIT? IT seems like you are just using the  
static compiler.

Unless the code is using some idiom that we happen to miss badly, it's  
uncommon to see this kind of performance issue. What's the  
optimization level you are building the benchmark at? Anyway, please  
file a bug about the performance issues. If the source code is freely  
available, someone can download it and try it out.

Thanks,

Evan

On Jun 18, 2008, at 2:35 PM, Torvald Riegel wrote:

> Hi,
>
> I see sth that to me looks like a JIT bug. The program is the KMeans  
> benchmark
> from the STAMP benchmark suite (http://stamp.stanford.edu).
> Overwrite ./common/Defines.common.mk with the attached files to make  
> CC/LD
> customizable.
>
> in ./kmeans, for
> ./kmeans -m40 -n40 -t0.00001 -i inputs/random-n65536-d32-c16.txt -p  
> 1 :
>
> make -f Makefile.seq clean
>
> CC='llvm-gcc' LD='llvm-gcc -lm' make -f Makefile.seq
> -->works, but is slower than gcc (35s vs 16s on my Intel 32b system)
>
> CC='llvm-gcc -emit-llvm' LD='llvm-ld -lm' make -f Makefile.seq
> --> does not work (lot's of NaN's in the output, and much faster  
> (11s))
>
> CC='llvm-gcc -emit-llvm' LD='llvm-ld -lm -disable-opt' make -f  
> Makefile.seq
> --> does not work either
>
> CC='llvm-gcc -emit-llvm' LD='llvm-ld -lm -disable-opt -native' make - 
> f -->
> looks as if it would work (and is faster, 16s)
>
> CC='llvm-gcc -emit-llvm' LD='llvm-ld -lm -native' make -f Makefile.seq
> --> looks as if it would work (and is faster, 16s)
>
> CC='llvm-gcc -emit-llvm' LD='llvm-ld -link-as-library' make -f  
> Makefile.seq
> llc -f -o kmeans.s kmeans
> gcc -o kmeans kmeans.s -lm -lpthread
> --> looks as if it would work (and is faster, 16s)
>
> Any suggestions? Is this a known limitation? Is there more information
> necessary (eg, for a bug report)?
>
> thanks,
> Torvald
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