[llvm] [RISCV] Support 3-argument associative add for transformAddShlImm (PR #86883)

[Philip Reames via llvm-commits]

preames wrote:

> Does this work on the real example https://godbolt.org/z/fxc688sbG

On that example?  Not even a little bit.

However, it does cover these two:

```
long foo32(long fillUpAttacks[64][8], int i, int j) {
  return fillUpAttacks[i][j];
}

long foo(long fillUpAttacks[64][8], long i, long j) {
  return fillUpAttacks[i][j];
}

```

https://github.com/llvm/llvm-project/pull/86883