[PATCH] D54698: [SelectionDAG] Initial support for FSHL/FSHR funnel shift opcodes (PR39467)

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:7001
+  unsigned RotOpc = IsFSHL ? ISD::ROTL : ISD::ROTR;
+  if (N0 == N1 && hasOperation(RotOpc, VT))
+    return DAG.getNode(RotOpc, SDLoc(N), VT, N0, N2);
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Similar to what the DAG builder code does, would it make sense to also check for the reverse direction rotate here?


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Comment at: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:5744
+    auto FunnelOpcode = IsFSHL ? ISD::FSHL : ISD::FSHR;
+    if (TLI.isOperationLegalOrCustom(FunnelOpcode, VT)) {
+      setValue(&I, DAG.getNode(FunnelOpcode, sdl, VT, X, Y, Z));
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Would it be possible to unconditionally create FSHL/FSHR here, drop the expansion code below and rely on the expansion in DAG legalization only?


Repository:
  rL LLVM

https://reviews.llvm.org/D54698