[all-commits] [llvm/llvm-project] 58b68e: [X86] Don't use popcnt for parity if only bits 7:0...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 58b68e70ebf6308f982426a2618782f473218eed
      https://github.com/llvm/llvm-project/commit/58b68e70ebf6308f982426a2618782f473218eed
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2021-10-06 (Wed, 06 Oct 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/parity.ll

  Log Message:
  -----------
  [X86] Don't use popcnt for parity if only bits 7:0 of the input can be non-zero.

Without popcnt we had a special case for using the parity flag from a single test i8 test instruction if only bits 7:0 could be non-zero. That special case is still useful when we have popcnt.

To reach this special case, we enable custom lowering of parity for i16/i32/i64 even when popcnt is enabled. The check for POPCNT being enabled is now after the special case in LowerPARITY.

Fixes PR52093

Differential Revision: https://reviews.llvm.org/D111249