[llvm] [PowerPC] Exploit xxeval instruction for ternary patterns - part 1 (PR #141733)

[Amy Kwan via llvm-commits]

https://github.com/amy-kwan commented:

We had a discussion of this offline - could we refactor the PR to handle different types and move some of the implementation out of TableGen?

https://github.com/llvm/llvm-project/pull/141733