[PATCH] D70484: [ARM,MVE] Add an InstCombine rule permitting VPNOT.

[Simon Tatham via Phabricator via llvm-commits]

simon_tatham created this revision.
simon_tatham added reviewers: ostannard, MarkMurrayARM, dmgreen.
Herald added subscribers: llvm-commits, hiraditya, kristof.beyls.
Herald added a project: LLVM.

If a user writing C code using the ACLE MVE intrinsics generates a
predicate and then complements it, then the resulting IR will use the
`pred_v2i` IR intrinsic to turn some `<n x i1>` vector into a 16-bit
integer; complement that integer; and convert back. This will generate
machine code that moves the predicate out of the `P0` register,
complements it in an integer GPR, and moves it back in again.

This InstCombine rule replaces `i2v(~v2i(x))` with a direct complement
of the original predicate vector, which we can already instruction-
select as the VPNOT instruction which complements P0 in place.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70484

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/CodeGen/Thumb2/mve-vpt-from-intrinsics.ll
  llvm/test/Transforms/InstCombine/ARM/mve-v2i2v.ll

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