[X86] Simplify lowerVectorShuffleAsBitMask to handle only integer VT's

[zvi]

Summary

This function is only called with integer VT arguments, so remove code that handles FP vectors.

[andreadb]

Sounds reasonable to me.
In practice, lowerVectorShuffleAsBitMask is only called when the shuffle valuetype is integer. In all other cases, the lowering logic forces a bitcast on the shuffle operands.

llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

 /// \brief Try to emit a bitmask instruction for a shuffle.
 ///
 /// This handles cases where we can model a blend exactly as a bitmask due to
 /// one of the inputs being zeroable.
 static SDValue lowerVectorShuffleAsBitMask(const SDLoc &DL, MVT VT, SDValue V1,
                                            SDValue V2, ArrayRef<int> Mask,
                                            const SmallBitVector &Zeroable,
                                            SelectionDAG &DAG) {
+  assert(!VT.isFloatingPoint() && "Floating point types are not supported");
   MVT EltVT = VT.getVectorElementType();
-  int NumEltBits = EltVT.getSizeInBits();
-  MVT IntEltVT = MVT::getIntegerVT(NumEltBits);
-  SDValue Zero = DAG.getConstant(0, DL, IntEltVT);
-  SDValue AllOnes = DAG.getConstant(APInt::getAllOnesValue(NumEltBits), DL,
-                                    IntEltVT);
-  if (EltVT.isFloatingPoint()) {
-    Zero = DAG.getBitcast(EltVT, Zero);
-    AllOnes = DAG.getBitcast(EltVT, AllOnes);
-  }
+  SDValue Zero = DAG.getConstant(0, DL, EltVT);
+  SDValue AllOnes =
+      DAG.getConstant(APInt::getAllOnesValue(EltVT.getSizeInBits()), DL, EltVT);
   SmallVector<SDValue, 16> VMaskOps(Mask.size(), Zero);
   SDValue V;
   for (int i = 0, Size = Mask.size(); i < Size; ++i) {
     if (Zeroable[i])
       continue;
     if (Mask[i] % Size != i)
       return SDValue(); // Not a blend.
     if (!V)
       V = Mask[i] < Size ? V1 : V2;
     else if (V != (Mask[i] < Size ? V1 : V2))
       return SDValue(); // Can only let one input through the mask.
 
     VMaskOps[i] = AllOnes;
   }
   if (!V)
     return SDValue(); // No non-zeroable elements!
 
   SDValue VMask = DAG.getBuildVector(VT, DL, VMaskOps);
-  V = DAG.getNode(VT.isFloatingPoint()
-                  ? (unsigned) X86ISD::FAND : (unsigned) ISD::AND,
-                  DL, VT, V, VMask);
-  return V;
+  return DAG.getNode(ISD::AND, DL, VT, V, VMask);
 }
 
 /// \brief Try to emit a blend instruction for a shuffle using bit math.
 ///
 /// This is used as a fallback approach when first class blend instructions are
 /// unavailable. Currently it is only suitable for integer vectors, but could
 /// be generalized for floating point vectors if desirable.
 static SDValue lowerVectorShuffleAsBitBlend(const SDLoc &DL, MVT VT, SDValue V1,