[PATCH] D112443: [SelectionDAG] Optimize expansion for rotates/funnel shifts

Mon Oct 25 10:22:52 PDT 2021

craig.topper added inline comments.

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Comment at: llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp:4427
+  // Expand to a pair of funnel shifts.
+  EVT NewShAmtVT = TLI.getShiftAmountTy(HalfVT, DAG.getDataLayout(), false);
+  SDValue NewShAmt = DAG.getAnyExtOrTrunc(ShAmt, DL, NewShAmtVT);
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RKSimon wrote:
> craig.topper wrote:
> > Does passing "false" to this really solve the original problem I raised? That makes getShiftAmountTy use pointer type, but pointer type on some targets is i16 which wouldn't be enough to represent a shift amount for an i65356. Should this instead use the getShiftAmountTyForConstant helper? The name of that function is outdated.
> Sorry I missed that comment on the other phab
I'm working on a patch to fold getShiftAmountTyForConstant into TLI.getShiftAmountTy and then we'll never have to thing about this again.

Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112443/new/

https://reviews.llvm.org/D112443