[llvm] [InstCombine] Do not combine shuffle+bitcast if the bitcast is eliminable. (PR #135769)

[Ricardo Jesus via llvm-commits]

rj-jesus wrote:

Hi @nikic, shall I open a PR with the alternative fold as you suggested (bitcast+extractelement+bitcast to shufflevector+bitcast) so that we can compare both approaches, or are you happy for us to block the initial fold (shufflevector+bitcast to bitcast+extractelement) from happening in the first place?

https://github.com/llvm/llvm-project/pull/135769