[PATCH] D66718: [DAGCombiner] (insert_vector_elt (vector_shuffle X, Y), (extract_vector_elt X, N), IdxC) -> (vector_shuffle X, Y)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:16451
+    if (Offset != -1) {
+      SmallVector<int, 16> NewMask(SVN->getMask().begin(), SVN->getMask().end());
+
----------------
You already have this at line 16438:
```
ArrayRef<int> Mask = SVN->getMask()
```


================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:16456
+
+      return DAG.getVectorShuffle(Vec.getValueType(), SDLoc(N),
+                                  Vec.getOperand(0), Vec.getOperand(1),
----------------
You need to check NewMask is legal: if (!TLI.isShuffleMaskLegal(NewMask, Vec.getValueType()))


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D66718/new/

https://reviews.llvm.org/D66718