[llvm] [SelectionDAG] Merge consecutive loads feeding as shuffle operands (PR #207303)

[Sushant Gokhale via llvm-commits]

sushgokh wrote:

> > > Please split the PR into two commits with the first having only the new tests. Doing this makes it much simpler to understand the effects of the code changes.
> > 
> > 
> > Done. PR #207368
> 
> For clarity I didn't mean a separate PR. I'm fine with keeping all the change in a single PR, but having it spread across two commits means you can see the effects of the code changes by selecting only those commits when reviewing.

ok. So should I add the initial tests to this PR or its fine for  now having separate PR ? If separate PR is approved, I will rebase this

https://github.com/llvm/llvm-project/pull/207303