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

[Eric Christopher]

> 
> 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