[llvm] [GlobalISel][AArch64] Combine unmerge(G_EXT v, undef) to unmerge(v). (PR #65263)

[Vladislav Dzhidzhoev via llvm-commits]

dzhidzhoev wrote:

> Should be a generic combine. Can you generalize to N unused defs?

G_EXT is an opcode for AArch64's `ext` instruction. Could you please suggest how to generalize it for other targets?


https://github.com/llvm/llvm-project/pull/65263