[LLVMdev] Very slow performance of lli on x86

[Prasanth J]

Hi all,

LLVM is built without debug enabled. Also i am not forcing lli to use
interpreter mode. so i dont think the reason is not because of debug build
or interpreter mode.


*step 1: *
compiled the 3 files (generic_replica.c ,xacc.c and dacc.c) with clang-cc to
llvm bytecode files using -emit-llvm-bc and (-O0/-O3) options
*step 2:*
bytecode obtained from step 1 (generic_replica.bc, xacc.bc and dacc.bc) is
passed to opt tool using (-O0/-O3) options
*step 3:*
optimized bytecode obtained from step 2 (generic_replica.opt.bc, xacc.opt.bc
and dacc.opt.c) is combinde to a single bytecode file (monolith.bc) using
llvm-ld tool
*step 4: *
running monolith.bc for 10000 iterations using lli tool and measured the
time.

I also tried using llvm-gcc for emiting bytecode in step 1 but got almost
the same output. As i have my entire setup in office i cant attach my
makefile today. i will attach my entire setup tom once i get back to office.
Also i will attach the configuration options i used for compiling LLVM. Let
me know in case i am wrong anywhere.

Thanks & Regards,
Prasanth J





On Sun, Nov 15, 2009 at 3:40 AM, Evan Cheng <evan.cheng at apple.com> wrote:

> He is probably using the interpreter on a debug build.
>
> Evan
>
>
> On Nov 14, 2009, at 1:40 PM, Eric Christopher <echristo at apple.com> wrote:
>
>
>>> for -O3 results refer attachment.
>>> time                      clang (-O0)
>>> llvm-gcc(-O0)                   gcc(-O0)
>>> real                      0m10.247s
>>> 0m11.324s                         0m10.963s
>>> user                     0m2.644s
>>> 0m2.478s                          0m2.263s
>>> sys                      0m5.949s
>>> 0m6.000s                          0m5.953s
>>>
>>> llvm-jit
>>> i used clang-cc -O0 -emit-llvm-bc to emit llvm bytecode and then passed
>>> it to opt tool and then linked all bytecode files to single bytecode using
>>> llvm-ld, i used lli tool to run this single bytecode file and noticed the
>>> following output
>>> real      6m33.786s
>>> user      5m12.612s
>>> sys       1m1.205s
>>>
>>> why is lli taking such a loooong time to execute this particular piece of
>>> code.??
>>>
>>
>> Something's wrong on your machine or something. I did the same (but using
>> llvm-gcc for the .ll files).  Using a debug build of current ToT I got this:
>>
>> [ghostwheel:~/Desktop] echristo% time
>> ~/builds/build-llvm-64bit/Debug/bin/lli foo.bc.bc
>> 0.210u 0.010s 0:00.22 100.0%    0+0k 0+0io 0pf+0w
>>
>>
>> That's a 64-bit build, but you'll notice the time difference. That said
>> I'm guessing that there's something missing since it takes no time to
>> execute. Step by step directions on what you did might help.
>>
>> -eric
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>
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