[llvm] [PatternMatch] Use m_Not instead of m_c_Xor with m_AllOnes() (PR #96837)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM, but this is not entirely NFC because it replaces some cases that use m_Xor rather than m_c_Xor.

https://github.com/llvm/llvm-project/pull/96837