[llvm] [SLP] Use known bits of each value in computeMinimumValueSizes (PR #82013)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> > There is a general rework of the whole analysis #78976
> 
> Oh, interesting! Hadn't seen that previously. Once you're back in the office, can we sink up? I'd had a broader rewrite of this code in mind myself.

I'm back, we can talk later today/Monday/etc.

https://github.com/llvm/llvm-project/pull/82013