[PATCH] D108058: [SelectionDAG] Optimize expansion for rotates/funnel shifts.

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp:4248
+  // Expand to a pair of funnel shifts.
+  EVT NewShAmtVT = TLI.getShiftAmountTy(HalfVT, DAG.getDataLayout());
+  SDValue NewShAmt = DAG.getAnyExtOrTrunc(ShAmt, dl, NewShAmtVT);
----------------
This will pass "true" for the third operand, LegalTypes, which I think makes this call getScalarShiftAmountTy. X86 will always return MVT::i8. That won't be large enough for all valid shift amounts if you're splitting a 1024 bit funnel shift.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D108058/new/

https://reviews.llvm.org/D108058