[llvm] [VPlan] Allow recursive narrowing in interleave group narrowing. (PR #167310)

[Ramkumar Ramachandra via llvm-commits]

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artagnon wrote:

We're only check the opcode here, and not the operands themselves, so I think this could miscompile an example with different operands.

https://github.com/llvm/llvm-project/pull/167310