[PATCH] D136659: [AliasAnalysis] Introduce getModRefInfoMask() as a generalization of pointsToConstantMemory().

Thu Mar 30 11:16:00 PDT 2023

xry111 added a comment.

In D136659#4233990 <https://reviews.llvm.org/D136659#4233990>, @nikic wrote:

> In D136659#4233968 <https://reviews.llvm.org/D136659#4233968>, @xry111 wrote:
>
>> We observed a crash in Thunderbird built with Rustc using LLVM 16.0.0 (happens with Rustc 1.68.x built with a system LLVM 16, and Rustc nightly 2023-03-25).  See https://bugzilla.mozilla.org/show_bug.cgi?id=1824544.
>>
>> Bisect suggests this change is the first bad commit.
>>
>> Any pointer for diagnose?
>
> Probably the same issue as https://github.com/llvm/llvm-project/issues/58776. It needs a smaller reproducer than "build all of firefox".

Well this is annoying.  When we reported this to Mozilla guys they just believe we are building Thunderbird in a wrong way.  And it seems they have no interest to use a latest Rustc/LLVM in their CI.  We are not Mozilla developers so it seems we cannot review the large code base to find what's wrong...

Are there any tools (test case reducer or UBsan) may help?  Or is it possible to disable this optimization via some RUSTFLAGS as a work around?

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