[NFC][PowerPC] Return early if the element type is not byte-sized in combineBVOfConsecutiveLoads

[ZhangKang]

Summary

Based on the Eli Friedman's comments in https://reviews.llvm.org/D60811 , we'd better return early if the element type is not byte-sized in combineBVOfConsecutiveLoads.

[efriedma]

LGTM

llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp

 /// of the vector type if the loads are consecutive. If the loads are
 /// consecutive but in descending order, a shuffle is added at the end
 /// to reorder the vector.
 static SDValue combineBVOfConsecutiveLoads(SDNode *N, SelectionDAG &DAG) {
   assert(N->getOpcode() == ISD::BUILD_VECTOR &&
          "Should be called with a BUILD_VECTOR node");
 
   SDLoc dl(N);
+
+  // Return early for non byte-sized type, as they can't be consecutive.
+  if (!N->getValueType(0).getVectorElementType().isByteSized())
+    return SDValue();
+
   bool InputsAreConsecutiveLoads = true;
   bool InputsAreReverseConsecutive = true;
   unsigned ElemSize = N->getValueType(0).getScalarType().getStoreSize();
   SDValue FirstInput = N->getOperand(0);
   bool IsRoundOfExtLoad = false;
 
   if (FirstInput.getOpcode() == ISD::FP_ROUND &&
       FirstInput.getOperand(0).getOpcode() == ISD::LOAD) {