[llvm] [PowerPC] Peephole address calculation in TOC memops (PR #76488)

[Qiu Chaofan via llvm-commits]

ecnelises wrote:

> I haven't reviewed this PR yet, but just also wanted give a heads up (in case you were not aware) that my PR (#71485) also touches some parts of the `PeepholePPC64()` function.

I had a quick look. It changes code to `Offset != 0` if block which is still `continue;` so the conflict resolution is trivial.

Also, I tried do the peephole when offset is non-zero, but without change to AsmParser, system assembler will be unhappy with some output assemblies. I left more comments in your PR.

https://github.com/llvm/llvm-project/pull/76488