[llvm] [NFC][AArch64] Refactor AArch64LoopIdiomTransform in preparation for more idioms (PR #78471)

[David Sherwood via llvm-commits]

david-arm wrote:

> Hi, Where these more scenarios come from? How do you consider this question? As i known, there are some scenarios in sub-item 557.xz of SPEC2017 int. Will you consider to support these scenarios?

Yes, some of these new scenarios are in the xz benchmark in SPEC2017. There are loops recognised in blender too, although these are not in hot code. Certainly there are lots of cases in the LLVM test suite where we will transform loops too. To be honest, one of the main benefits of going wide and supporting more loops is to get better test coverage, although hopefully we will see increased performance in more applications as well.

https://github.com/llvm/llvm-project/pull/78471