[X86] Remove scaleVectorShuffleBlendMask and use APIntOps::ScaleBitMask directly.

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -10589,15 +10589,6 @@ static bool matchShuffleAsBlend(MVT VT, SDValue V1, SDValue V2,
   return true;
 }
 
-static uint64_t scaleVectorShuffleBlendMask(uint64_t BlendMask, int Size,
-                                            int Scale) {
-  uint64_t ScaledMask = 0;
-  for (int i = 0; i != Size; ++i)
-    if (BlendMask & (1ull << i))
-      ScaledMask |= ((1ull << Scale) - 1) << (i * Scale);
-  return ScaledMask;
-}
-
 /// Try to emit a blend instruction for a shuffle.
 ///
 /// This doesn't do any checks for the availability of instructions for blending
@@ -40539,14 +40530,15 @@ static SDValue combineTargetShuffle(SDValue N, const SDLoc &DL,
       MVT SrcVT = N0.getOperand(0).getSimpleValueType();
       if ((VT.getScalarSizeInBits() % SrcVT.getScalarSizeInBits()) == 0 &&
           SrcVT.getScalarSizeInBits() >= 32) {
-        unsigned BlendMask = N.getConstantOperandVal(2);
         unsigned Size = VT.getVectorNumElements();
-        unsigned Scale = VT.getScalarSizeInBits() / SrcVT.getScalarSizeInBits();
-        BlendMask = scaleVectorShuffleBlendMask(BlendMask, Size, Scale);
+        unsigned NewSize = SrcVT.getVectorNumElements();
+        APInt BlendMask = N.getConstantOperandAPInt(2).zextOrTrunc(Size);
+        APInt NewBlendMask = APIntOps::ScaleBitMask(BlendMask, NewSize);
         return DAG.getBitcast(
             VT, DAG.getNode(X86ISD::BLENDI, DL, SrcVT, N0.getOperand(0),
                             N1.getOperand(0),
-                            DAG.getTargetConstant(BlendMask, DL, MVT::i8)));
+                            DAG.getTargetConstant(NewBlendMask.getZExtValue(),
+                                                  DL, MVT::i8)));
       }
     }
     return SDValue();