Add TODO to performExtractVectorEltCombine()

Author: chrisjbris

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -14680,6 +14680,8 @@ SITargetLowering::performExtractVectorEltCombine(SDNode *N,
   // depending on the shift operand. See e.g. performSraCombine().
   // This combine ensures that the optimisation is compatible with v2i32
   // legalised AND.
+  // TODO: Consider if additional improvements can be made by generalising to
+  // other constants and vector types.
   if (VecVT == MVT::v2i32 && Vec->getOpcode() == ISD::AND &&
       Vec->getOperand(1)->getOpcode() == ISD::BUILD_VECTOR) {
     SDValue BV = Vec->getOperand(1);