[llvm] [DAG] isKnownNeverZero - add ISD::SHL DemandedElts handling and tests (PR #183772)

[via llvm-commits]

Joeljm1 wrote:

> please keep an eye on the CI because known-never-zero.ll is still failing - and many of those codegen changes from your regeneration don't look right

Could u confirm if llvm/utils/update_llc_test_checks.py is the script to generate?? 
also i was using git clang-format HEAD~1 as in the doc and it was alway telling "no modified files to format" but also trying clang-format --style=LLVM -i SelectionDAG.cpp changes a lot of other code to so not sure on which to use.

I am sorry for asking a lot. This seems like it should have been a quick task. Sorry for taking a lot of time for it

https://github.com/llvm/llvm-project/pull/183772