llvm-project

61836654 - [X86] combineEXTRACT_SUBVECTOR - fold extractions from UNPCK nodes.

[X86] combineEXTRACT_SUBVECTOR - fold extractions from UNPCK nodes. Allow subvector extraction as long as at least one operand extraction is free. Refactor existing cases into a switch statement to allow easier reuse + future expansion.