[LLVMdev] [cfe-dev] Very slow performance of lli on x86

[Garrison Venn]

Granted I'm not up on using bit code files, but I don't believe the  
debug build affects whether or not the jit is used (non-interpretive  
mode). Ignoring other debug build effects on the efficiency of the  
jitted code, it would be interesting if you also could measure the  
time to jit--don't actually execute the 10000 iteration. I don't  
believe this would explain the time scale shown, but it should have  
some effect. To my mind, the proffered time scale also implies  
interpretive mode which you might be able to force to see if this is  
the culprit. I'll help test when you supply the build (make files).

Garrison

On Nov 15, 2009, at 2:55, Prasanth J wrote:

> Sorry i really forgot to mention one thing. I downloaded the X86  
> binaries of llvm+clang and llvm-gcc from llvm download site. i hope  
> that is not a debug build.
>
> Prasanth J
>
>
>
>
>
> On Sun, Nov 15, 2009 at 1:22 PM, Prasanth J <j.prasanth.j at gmail.com>  
> wrote:
> 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
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