[llvm] [Reland][ValueTracking] Improve Bitcast handling to match SDAG (PR #145223)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> > Can you please add a test for a case that was previously miscompiled?
> 
> I'm trying to reduce [this](https://%5Bmartin.st/temp/loopfilter_sse2-preproc.c%5D(https://martin.st/temp/loopfilter_sse2-preproc.c)), but I'm not sure what the miscompile was

You could diff and see which bit gives a different output compared with the previous, broken version of this change.

https://github.com/llvm/llvm-project/pull/145223