[PATCH] D113782: [SLP]Improve cost model for the shuffled extracts.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:5425
+            } while (E == getTreeEntry(Base));
+          }
+          FirstUsers.push_back(VU);
----------------
ABataev wrote:
> RKSimon wrote:
> > Should this be put inside the while() loop before the break? AFAICT that's the only time that cast<InsertElementInst>(Base) is valid.
> No, not quite so. It can be insertelement also if `ScalarToTreeEntry.count(Base)` is true, i.e. there is a tree entry for this insertelement in the graph.
I don't quite follow, this is what I had in mind:

```
// Find the insertvector, vectorized in tree, if any.
Value *Base = VU;
while (isa<InsertElementInst>(Base)) {
  if (ScalarToTreeEntry.count(Base)) {
    VU = Base;

    // Build the mask for the vectorized insertelement instructions.
    if (const TreeEntry *E = getTreeEntry(Base)) {
      do {
        int Idx = E->findLaneForValue(Base);
        ShuffleMask.back()[Idx] = Idx;
        Base = cast<InsertElementInst>(Base)->getOperand(0);
      } while (E == getTreeEntry(Base));
    }
    break;
  }
  Base = cast<InsertElementInst>(Base)->getOperand(0);
}
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113782/new/

https://reviews.llvm.org/D113782