Hi everyone,

Can someone help me with running llvm-exegesis tool on x86_64? I saw that I need libpfm library, but I’m still getting segmentation fault when I try to run the tool. Is there anything else I need to do (build llvm on some specific way) ?
This is how I tried to run this tool: llvm-exegesis -mode=latency -opcode-name=ADD64rr


Hi Luka,

Which CPU and OS are you running? Most linux distros seem to have an old version of libpfm - I’ve had more luck (better CPU support) by using the trunk version from

Also, are running the tool with sudo?


Hi Simon,

I updated my OS to Ubuntu 18.04.1, and now it works fine. I’m not sure what was the issue on Ubuntu 16.04.10


Hi Luka, some distributions require you to allow perf event access (see https://reviews.llvm.org/D47572), have you done that ?

Hi Clement,

I updated my OS from Ubuntu 16.04.10 to Ubuntu 18.04.1, and now it works fine.