[PATCH] D138846: MC/DC in LLVM Source-Based Code Coverage: LLVM back-end and compiler-rt

Tue Nov 21 08:39:09 PST 2023

zequanwu added a comment.

In D138846#4657195 <https://reviews.llvm.org/D138846#4657195>, @zequanwu wrote:

> In D138846#4657194 <https://reviews.llvm.org/D138846#4657194>, @alanphipps wrote:
>
>> In D138846#4657193 <https://reviews.llvm.org/D138846#4657193>, @zequanwu wrote:
>>
>>> In D138846#4657175 <https://reviews.llvm.org/D138846#4657175>, @hans wrote:
>>>
>>>> We're seeing crashes in `initializeValueProfRuntimeRecord` that bisects to this commit. I think Zequan is investigating: https://bugs.chromium.org/p/chromium/issues/detail?id=1503919
>>>
>>> It turns out to be that our rust code with old version of rustc without this change, so mixture of raw profile versions are used, causing segment fault.
>>
>> Thank you for the update! Is this also the case of the issue @glandium reports above as well?  I think both issues manifested as a ValueProf issue.
>
> I don't know, but I'd suggest to check if all sources compiled with profile runtime are using the llvm version that contains this change. Otherwise, mixed raw profiles versions will cause unexpected behaviour.

I just saw @glandium's earlier comment:

> Code built with older versions of LLVM (e.g. rust) and running with the updated runtime crash at startup with this change.

This is the exact same issue we encountered. Because there is a profile format change, it's expected to update both clang and rustc to use the same version of llvm in order for it to work.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D138846/new/

https://reviews.llvm.org/D138846