[NFC] Consistenly use commented and annotated ScopPass functions

  The changes affect methods that are part of the Pass interface and
  include:
    - Comments that describe the methods purpose.
    - A consistent use of the keywords override and virtual.
  Additionally, the printScop method is now optional and removed from
  SCoP passes that do not implement it.

llvm-svn: 248685
diff --git a/polly/lib/Transform/DeadCodeElimination.cpp b/polly/lib/Transform/DeadCodeElimination.cpp
index 1d5ccbe..f8374d6 100644
--- a/polly/lib/Transform/DeadCodeElimination.cpp
+++ b/polly/lib/Transform/DeadCodeElimination.cpp
@@ -59,9 +59,10 @@
   static char ID;
   explicit DeadCodeElim() : ScopPass(ID) {}
 
+  /// @brief Remove dead iterations from the schedule of @p S.
   bool runOnScop(Scop &S) override;
 
-  void printScop(raw_ostream &OS, Scop &S) const override;
+  /// @brief Register all analyses and transformation required.
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
 private:
@@ -166,8 +167,6 @@
   return eliminateDeadCode(S, DCEPreciseSteps);
 }
 
-void DeadCodeElim::printScop(raw_ostream &, Scop &) const {}
-
 void DeadCodeElim::getAnalysisUsage(AnalysisUsage &AU) const {
   ScopPass::getAnalysisUsage(AU);
   AU.addRequired<DependenceInfo>();