[llvm] [GlobalIsel] Combine G_EXTRACT_VECTOR_ELT (PR #85321)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

We have now named opcodes for extract/insert subvector, but we fail to select the intrinsics:
https://github.com/llvm/llvm-project/blob/2a547f0f6c6b456342b9bfad38787f54f265fc96/llvm/test/CodeGen/AArch64/extract-vector-elt.ll#L809

https://github.com/llvm/llvm-project/pull/85321