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

Mon Dec 6 10:29:11 PST 2021

lebedev.ri added inline comments.

================
Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:20833
+    // Profitability check: only deal with extractions from the first subvector.
+    if (OpSubvecIdx != 0)
+      return SDValue();
----------------
RKSimon wrote:
> Why do we need this and isExtractSubvectorCheap ?
Because the test changes were somewhat less controversial with that check.

Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D104156