[all-commits] [llvm/llvm-project] ac4f30: [InstCombine] add test for miscompile in dropRedun...

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  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ac4f30ac49aafc1ab31b7090f8d69662686a6cfc
      https://github.com/llvm/llvm-project/commit/ac4f30ac49aafc1ab31b7090f8d69662686a6cfc
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2021-09-29 (Wed, 29 Sep 2021)

  Changed paths:
    M llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll

  Log Message:
  -----------
  [InstCombine] add test for miscompile in dropRedundantMaskingOfLeftShiftInput(); NFC (PR51351)


  Commit: d3e2067c7c42200d487f7339e10b1e613576abef
      https://github.com/llvm/llvm-project/commit/d3e2067c7c42200d487f7339e10b1e613576abef
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2021-09-29 (Wed, 29 Sep 2021)

  Changed paths:
    M llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll
    M llvm/test/Transforms/InstSimplify/shift.ll

  Log Message:
  -----------
  [InstSimplify] add tests for (-1 << x) s>> x; NFC


  Commit: ea56dcb73012f65e6ffb1c320c97c6fbf45480e0
      https://github.com/llvm/llvm-project/commit/ea56dcb73012f65e6ffb1c320c97c6fbf45480e0
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2021-09-29 (Wed, 29 Sep 2021)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
    M llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll

  Log Message:
  -----------
  [InstCombine] fix miscompile from dropRedundantMaskingOfLeftShiftInput()

The test is from https://llvm.org/PR51351.

There are 2 related logic bugs from over-generalizing "lshr" to "any shr",
but I'm not sure how to expose the difference for "MaskC" because instsimplify
already folds ashr of -1.

I'll extend instsimplify to catch the MaskD pattern as a follow-up, but this
patch should be enough to avoid the miscompile.


Compare: https://github.com/llvm/llvm-project/compare/9886f21bc138...ea56dcb73012