[PATCH] D126782: [AArch64] Look through bitcast when looking for extract_high subvector

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: SjoerdMeijer, samtebbs, jaykang10, sdesmalen.
Herald added subscribers: steven.zhang, hiraditya, kristof.beyls.
Herald added a project: All.
dmgreen requested review of this revision.
Herald added a project: LLVM.

Since D61806 <https://reviews.llvm.org/D61806>, DAGCombiner has folded `subvector_extract(bitcast(..))` to `bitcast(subvector_extract(..))`, which would place a bitcast between a subvector_extract and the operation that could be converted to a "high" neon instruction (like smull2).  This adds better matching for the subvector_extract, through the tablegen extract_high PatFrags to optionally skip the bitcast under little ending, still matchings an extract of the high half of the input vector.

I didn't update the extract_high of a duplicate patterns, as the ComplexPattern need names operands. I did add a extract_high_dup_v8i16 PatFrag to abstract away the common code, which can be extended in a future patch.


https://reviews.llvm.org/D126782

Files:
  llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
  llvm/lib/Target/AArch64/AArch64InstrFormats.td
  llvm/lib/Target/AArch64/AArch64InstrInfo.td
  llvm/test/CodeGen/AArch64/highextractbitcast.ll

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