[all-commits] [llvm/llvm-project] 4e2b53: [X86] Add tests for optimizing out zero-check in i...

[goldsteinn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4e2b532cb94150cddbc095e167a62f0b38538cc0
      https://github.com/llvm/llvm-project/commit/4e2b532cb94150cddbc095e167a62f0b38538cc0
  Author: Noah Goldstein <goldstein.w.n at gmail.com>
  Date:   2023-06-12 (Mon, 12 Jun 2023)

  Changed paths:
    A llvm/test/CodeGen/X86/ispow2.ll

  Log Message:
  -----------
  [X86] Add tests for optimizing out zero-check in is_pow2 setcc pattern; NFC

Differential Revision: https://reviews.llvm.org/D152674


  Commit: 5c8188c7bc524c3e4ea22762645fcbe43042aee9
      https://github.com/llvm/llvm-project/commit/5c8188c7bc524c3e4ea22762645fcbe43042aee9
  Author: Noah Goldstein <goldstein.w.n at gmail.com>
  Date:   2023-06-12 (Mon, 12 Jun 2023)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    M llvm/test/CodeGen/X86/ispow2.ll

  Log Message:
  -----------
  [DAGCombine] Use `IsKnownNeverZero` to see if we need zero-check in is_pow2 setcc patern

`ctpop(X) eq/ne 1` is checking if X is a non-zero power of 2. Power of
2 check including zero is `(X & (X-1)) eq/ne 0` and unfortunately
there is no good pattern for checking a power of 2 while excluding
zero. So, when lowering `ctpop(X) eq/ne 1`, explicitly check
`IsKnownNeverZero(X)` to maybe be able to optimize out the extra zero
check.

We need this explicitly as DAGCombiner does not re-analyze provable
setcc nodes, and the middle-end never finds it beneficially to broaden
`ctpop(X) eq/ne 1` -> `ctpop(X) ule/ugt 1` (power of 2 including
zero).

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D152675


  Commit: 758ffdbfccff95a5e4b6bf9eaf227e27ca6ea116
      https://github.com/llvm/llvm-project/commit/758ffdbfccff95a5e4b6bf9eaf227e27ca6ea116
  Author: Noah Goldstein <goldstein.w.n at gmail.com>
  Date:   2023-06-12 (Mon, 12 Jun 2023)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

  Log Message:
  -----------
  [InstCombine] Factor out power of 2 comparison patterns to helper; NFC

Differential Revision: https://reviews.llvm.org/D152728


Compare: https://github.com/llvm/llvm-project/compare/314d18141615...758ffdbfccff