[Transforms][Scalar] Delete unused code

Author: gmh5225

llvm/lib/Transforms/Scalar/BDCE.cpp

@@ -97,9 +97,6 @@ static bool bitTrackingDCE(Function &F, DemandedBits &DB) {
     if (I.mayHaveSideEffects() && I.use_empty())
       continue;
 
-    if (I.isVolatile() && !I.isPHINodeOrSelectInstOrSwitchInst())
-      continue;
-
     // Remove instructions that are dead, either because they were not reached
     // during analysis or have no demanded bits.
     if (DB.isInstructionDead(&I) ||