[PATCH] D33137: [DAGCombiner] use narrow vector ops to eliminate concat/extract (PR32790)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14470
+         "Extract index is not a multiple of the vector length.");
+  if (Extract->getOperand(0).getValueSizeInBits() != VT.getSizeInBits() * 2)
+    return SDValue();
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Could you use isExtractSubvectorCheap instead here?

We might even need a isExtractSubvectorFree option as well...


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14476
+  SDValue BinOp = Extract->getOperand(0);
+  if (BinOp.getOpcode() == ISD::BITCAST)
+    BinOp = BinOp.getOperand(0);
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I'm starting to think that X86ISelLowering's peekThroughBitcasts and peekThroughOneUseBitcasts helpers should be exposed globally.


https://reviews.llvm.org/D33137