[llvm] r344403 - [LegalizeVectorTypes] When unrolling in WidenVecRes_Convert, make sure we use the original vector element count. Not min of the widened result type and the possibly widened input type.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Fri Oct 12 12:37:47 2018
New Revision: 344403

URL: http://llvm.org/viewvc/llvm-project?rev=344403&view=rev
Log:
[LegalizeVectorTypes] When unrolling in WidenVecRes_Convert, make sure we use the original vector element count. Not min of the widened result type and the possibly widened input type.

If the input type is widened as well, but we still were forced to unroll, we shouldn't be considering the widened input element count. We should only create as many scalar operations as the original type called for.

This will be important for an upcoming patch.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp?rev=344403&r1=344402&r2=344403&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp Fri Oct 12 12:37:47 2018
@@ -2809,11 +2809,8 @@ SDValue DAGTypeLegalizer::WidenVecRes_Co
     if (WidenNumElts % InVTNumElts == 0) {
       // Widen the input and call convert on the widened input vector.
       unsigned NumConcat = WidenNumElts/InVTNumElts;
-      SmallVector<SDValue, 16> Ops(NumConcat);
+      SmallVector<SDValue, 16> Ops(NumConcat, DAG.getUNDEF(InVT));
       Ops[0] = InOp;
-      SDValue UndefVal = DAG.getUNDEF(InVT);
-      for (unsigned i = 1; i != NumConcat; ++i)
-        Ops[i] = UndefVal;
       SDValue InVec = DAG.getNode(ISD::CONCAT_VECTORS, DL, InWidenVT, Ops);
       if (N->getNumOperands() == 1)
         return DAG.getNode(Opcode, DL, WidenVT, InVec);
@@ -2832,11 +2829,12 @@ SDValue DAGTypeLegalizer::WidenVecRes_Co
   }
 
   // Otherwise unroll into some nasty scalar code and rebuild the vector.
-  SmallVector<SDValue, 16> Ops(WidenNumElts);
   EVT EltVT = WidenVT.getVectorElementType();
-  unsigned MinElts = std::min(InVTNumElts, WidenNumElts);
-  unsigned i;
-  for (i=0; i < MinElts; ++i) {
+  SmallVector<SDValue, 16> Ops(WidenNumElts, DAG.getUNDEF(EltVT));
+  // Use the original element count so we don't do more scalar opts than
+  // necessary.
+  unsigned MinElts = N->getValueType(0).getVectorNumElements();
+  for (unsigned i=0; i < MinElts; ++i) {
     SDValue Val = DAG.getNode(
         ISD::EXTRACT_VECTOR_ELT, DL, InEltVT, InOp,
         DAG.getConstant(i, DL, TLI.getVectorIdxTy(DAG.getDataLayout())));
@@ -2846,10 +2844,6 @@ SDValue DAGTypeLegalizer::WidenVecRes_Co
       Ops[i] = DAG.getNode(Opcode, DL, EltVT, Val, N->getOperand(1), Flags);
   }
 
-  SDValue UndefVal = DAG.getUNDEF(EltVT);
-  for (; i < WidenNumElts; ++i)
-    Ops[i] = UndefVal;
-
   return DAG.getBuildVector(WidenVT, DL, Ops);
 }