[PATCH] D77718: [ARM] Combines for VMOVN

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: SjoerdMeijer, samparker, simon_tatham, ostannard.
Herald added subscribers: hiraditya, kristof.beyls.

This adds two combines for VMOVN, one to fold VMOVN[tb](c, VQMOVNb(a, b)) => VQMOVN[tb](c, b), the other to perform demand bits analysis on the lanes of a VMOVN. We know that only the bottom lanes of the second operand and the top or bottom lanes of the Qd operand are needed in the result, depending on if the VMOVN is bottom or top.


https://reviews.llvm.org/D77718

Files:
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/test/CodeGen/Thumb2/mve-satmul-loops.ll
  llvm/test/CodeGen/Thumb2/mve-vqmovn-combine.ll

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