[PATCH] D150923: [KnownBits] Factor out and improve the lowbit computation for {u,s}div

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added a comment.

In D150923#4405744 <https://reviews.llvm.org/D150923#4405744>, @chapuni wrote:

> @goldstein.w.n
> I am sorry. As far as I have been investigating, this is not the cause but 1st commit to trigger. The failure was hidden when I added debug codes, heisenbug.
> The failure can be seen in my internal builders.
>
> The failure is;
>
> - Observable for targeting aarch64. PerfReader.cpp sometimes differs.
> - I have not seen for targeting x86-64.
> - I have seen for targeting aarch64, on aarch64-linux and cross on x86_64-linux.
>   - Differs between aarh64-host and x86_64-host (for targeting aarch64)
>   - Differs between stage2 and stage3 on aarch64-linux.

I see, so probably some misuse of knownbits in the aarch64 backend?


Repository:
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  https://reviews.llvm.org/D150923/new/

https://reviews.llvm.org/D150923