[LLVMdev] JIT bug?

[Torvald Riegel]

On Thursday 19 June 2008, Evan Cheng wrote:
> Are you really running the JIT? IT seems like you are just using the
> static compiler.

When using llvm-ld without -native, yes, I'm pretty sure. Besides the lower 
performance in only the first case, cases 2 and 3 also produce incorrect 
output. When the program is llvm-ld'ed with -native or if llc is uses, it 
seems to work fine.

I will check optz levels for the first case again, and file bug(s).

torvald

>
> 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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