LLVM Profile Error: Runtime and instrumentation version mismatch : expected 10, but get 8

[ivanrg99]

Hi! Love the project.

I updated my system recently, using the latest llvm package from homebrew and latest rust version. When I now run cargo pgo optimize, I keep getting a LLVM Profile Error: Runtime and instrumentation version mismatch : expected 10, but get 8 error.

My llvm installation is version 19, and running rustc --version --verbose reveals that my rust installation is also using llvm 19:

rustc 1.84.0 (9fc6b4312 2025-01-07)
binary: rustc
commit-hash: 9fc6b43126469e3858e2fe86cafb4f0fd5068869
commit-date: 2025-01-07
host: aarch64-apple-darwin
release: 1.84.0
LLVM version: 19.1.5

Is anyone else facing this issue?

[Kobzol]

Hi, could you please post the output of cargo pgo info? Thanks!

[ivanrg99]

[rustc version]: 1.84.0 is recent enough
[llvm-profdata]: found at /Users/ivan/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/aarch64-apple-darwin/bin/llvm-profdata
[llvm-bolt]: found at /Users/ivan/Downloads/LLVM/build/bin/llvm-bolt
[merge-fdata]: found at /Users/ivan/Downloads/LLVM/build/bin/merge-fdata

I was missing bolt from my llvm install, so I have built it myself from version 19.1.17 of llvm (which is the latest one packaged by brew), but the same error still persists.

[Kobzol]

BOLT shouldn't be at fault here.

I see that you're on macOS. Sadly, PGO doesn't work well for Rust on macOS. I remember seeing similar errors when we tried to PGO the compiler (rustc) itself on macOS, and these issues haven't been resolved yet. So it's probably this long-standing, yet unresolved issue. Someone has been looking at it recently (https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/How.20to.20distribute.20builds.20across.20multiple.20macbooks.3F).

I think that you're going to get the same result, but you could try doing PGO without cargo-pgo (https://doc.rust-lang.org/rustc/profile-guided-optimization.html) to see if that works. If the same error happens without cargo-pgo, then sadly I can't do much here. You could report the issue in the Rust issue tracker though.