[PATCH] D104156: [DAGCombine][X86][ARM] EXTRACT_SUBVECTOR(VECTOR_SHUFFLE(?,?,Mask)) -> VECTOR_SHUFFLE(EXTRACT_SUBVECTOR(?, ?), EXTRACT_SUBVECTOR(?, ?), Mask')

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:20752
+    if (!TLI.isExtractSubvectorCheap(NarrowVT, WideVT, Index))
+      return SDValue();
+    SDValue IndexC = DAG.getVectorIdxConstant(Index, DL);
----------------
Do the isExtractSubvectorCheap tests in their own all_of() check before we start creating nodes? It helps stop oneuse failures in later folds if this fails.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D104156/new/

https://reviews.llvm.org/D104156