[llvm] [IA]: Construct (de)interleave4 out of (de)interleave2 (PR #89276)

[Matthew Devereau via llvm-commits]

================
@@ -3155,8 +3155,9 @@ class TargetLoweringBase {
   ///
   /// \p DI is the deinterleave intrinsic.
   /// \p LI is the accompanying load instruction
----------------
MDevereau wrote:

The comments on these 2 functions look outdated. It would be nice to explain what DeadInsts should look like going into and out of the function given it's a reference to a vector.

https://github.com/llvm/llvm-project/pull/89276