[SelectionDAG] Remove FIXME and commented out code from 20 years ago. NFC (#150055)

Author: topperc

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -10860,26 +10860,6 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTList,
            (Ops[2]->getAsZExtVal() == 0 || Ops[2]->getAsZExtVal() == 1) &&
            "Invalid STRICT_FP_ROUND!");
     break;
-#if 0
-  // FIXME: figure out how to safely handle things like
-  // int foo(int x) { return 1 << (x & 255); }
-  // int bar() { return foo(256); }
-  case ISD::SRA_PARTS:
-  case ISD::SRL_PARTS:
-  case ISD::SHL_PARTS:
-    if (N3.getOpcode() == ISD::SIGN_EXTEND_INREG &&
-        cast<VTSDNode>(N3.getOperand(1))->getVT() != MVT::i1)
-      return getNode(Opcode, DL, VT, N1, N2, N3.getOperand(0));
-    else if (N3.getOpcode() == ISD::AND)
-      if (ConstantSDNode *AndRHS = dyn_cast<ConstantSDNode>(N3.getOperand(1))) {
-        // If the and is only masking out bits that cannot effect the shift,
-        // eliminate the and.
-        unsigned NumBits = VT.getScalarSizeInBits()*2;
-        if ((AndRHS->getValue() & (NumBits-1)) == NumBits-1)
-          return getNode(Opcode, DL, VT, N1, N2, N3.getOperand(0));
-      }
-    break;
-#endif
   }
 
   // Memoize the node unless it returns a glue result.