[llvm] LICM: hoist BO assoc when (C1 op LV) op C2 (PR #106999)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> You can just assert that the op is commutative (after the associativity check). In general, all associative ops we support are also commutative.

Little confused by this. Aren't `FAdd` and `FMul` commutative, but not associative?

```cpp
  bool isAssociative() const LLVM_READONLY;
  static bool isAssociative(unsigned Opcode) {
    return Opcode == And || Opcode == Or || Opcode == Xor ||
           Opcode == Add || Opcode == Mul;
  }

  bool isCommutative() const LLVM_READONLY;
  static bool isCommutative(unsigned Opcode) {
    switch (Opcode) {
    case Add: case FAdd:
    case Mul: case FMul:
    case And: case Or: case Xor:
      return true;
    default:
      return false;
  }
  }
```

https://github.com/llvm/llvm-project/pull/106999