[llvm] [VPlan] Extend cse to eliminate redundant widened loads (PR #212543)

[Ramkumar Ramachandra via llvm-commits]

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artagnon wrote:

Could simply add:

```
if (auto *EarlierLoad = dyn_cast<VPWidenLoadRecipe>(V)) {
  MemoryLocation *Loc = vputils::getMemoryLoacation(*EarlierLoad);
  if (!canCSEWithNoAliasCheck(*Loc, EarlierLoad, cast<VPWidenLoadRecipe>(Def))
    continue;
}
```

here, and remove the earlier special-case? I don't think Loc can ever be null for a VPWidenLoadRecipe? I think we should use the memory location of the earlier load technically?

https://github.com/llvm/llvm-project/pull/212543