[clang] [llvm] [InstCombine] Canonicalize `(sitofp x)` -> `(uitofp x)` if `x >= 0` (PR #82404)

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goldsteinn wrote:

> Heads up: we noticed at google that this is causing the following test to fail:
> 
> https://github.com/google/swiftshader/blob/master/tests/ReactorUnitTests/ReactorUnitTests.cpp#L1312
> 
> I need to put a more proper reproducer, but thought that at least posting the heads-up might be faster to unblock us and maybe the problem is clear. I see that adding a flag vs reverting is already brought up in the last comment, what's the plan for that ?

Reverted with: https://github.com/llvm/llvm-project/commit/6960ace534c4021301dd5a9933ca06ba96edea23

If you can get the repro though, that would still be useful for when I revisit.

https://github.com/llvm/llvm-project/pull/82404