Don't expand bswap with shuffle of illegal vector type.

[arsenm]

Summary

Vector operations are legalized after types, so it isn't
OK to introduce a new illegal type. On R600, an i32 vector and
shuffle is always legal, but the produced vNi8 vector is not.

This is already covered by the existing R600 bswap test
combined with a future patch which exposes this problem.

[arsenm]

Ping

lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

SDValue VectorLegalizer::ExpandSEXTINREG(SDValue Op) {
   Op = Op.getOperand(0);
   Op =   DAG.getNode(ISD::SHL, DL, VT, Op, ShiftSz);
   return DAG.getNode(ISD::SRA, DL, VT, Op, ShiftSz);
 }
 
 SDValue VectorLegalizer::ExpandBSWAP(SDValue Op) {
   EVT VT = Op.getValueType();
 
+  int ScalarSizeInBytes = VT.getScalarSizeInBits() / 8;
+  int NElts = VT.getVectorNumElements();
+  int NShuffleElts = ScalarSizeInBytes * NElts;
+  EVT ByteVT = EVT::getVectorVT(*DAG.getContext(), MVT::i8, NShuffleElts);
+
+  // Don't create a shuffle on an illegal type.
+  if (!TLI.isTypeLegal(ByteVT))
+    return DAG.UnrollVectorOp(Op.getNode());
+
   // Generate a byte wise shuffle mask for the BSWAP.
   SmallVector<int, 16> ShuffleMask;
-  int ScalarSizeInBytes = VT.getScalarSizeInBits() / 8;
-  for (int I = 0, E = VT.getVectorNumElements(); I != E; ++I)
+  for (int I = 0; I != NElts; ++I) {
     for (int J = ScalarSizeInBytes - 1; J >= 0; --J)
       ShuffleMask.push_back((I * ScalarSizeInBytes) + J);
-
-  EVT ByteVT = EVT::getVectorVT(*DAG.getContext(), MVT::i8, ShuffleMask.size());
+  }
 
   // Only emit a shuffle if the mask is legal.
   if (!TLI.isShuffleMaskLegal(ShuffleMask, ByteVT))
     return DAG.UnrollVectorOp(Op.getNode());
 
   SDLoc DL(Op);
   Op = DAG.getNode(ISD::BITCAST, DL, ByteVT, Op.getOperand(0));
   Op = DAG.getVectorShuffle(ByteVT, DL, Op, DAG.getUNDEF(ByteVT),