[PATCH] D109149: [DAG] Fold select_cc setgt X, -1, C, ~C -> xor (ashr X, BW-1), C

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:22873
+        DAG.getConstant(CmpOpVT.getScalarSizeInBits() - 1, DL, CmpOpVT));
+    return DAG.getNode(ISD::XOR, DL, VT, DAG.getSExtOrTrunc(ASR, DL, VT),
+                       DAG.getSExtOrTrunc(CC == ISD::SETLT ? N3 : N2, DL, VT));
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Is it really beneficial if this cast is necessary? Should this check the compared and selected types match (or maybe allow truncate, if it's free)


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D109149/new/

https://reviews.llvm.org/D109149