[llvm] [LICM] Fold associative binary ops to promote code hoisting (PR #81608)

[Ricardo Jesus via llvm-commits]

rj-jesus wrote:

@amy-kwan @chenzheng1030 Could you please have a look at the failing PowerPC tests below? I can make the transform more restrictive but I'd appreciate some feedback before doing so!
```
  LLVM :: CodeGen/PowerPC/common-chain.ll
  LLVM :: CodeGen/PowerPC/p10-spill-crlt.ll
```

https://github.com/llvm/llvm-project/pull/81608