[Polly] Create Scop name lazily

[philip.pfaffe]

Summary

Creating the Scop name is expensive, because creating the Region name
it's derived from is expensive. So create the name lazily, because getName() is
actually called rarely.

Side note: getName() and getNameStr() return different things. Is this
intentional? Should it be unified?

[grosser]

LGTM. Can you potentially include the old SVN revisions in your commit message?

include/polly/ScopInfo.h

 
 #include "polly/ScopDetection.h"
 #include "polly/Support/SCEVAffinator.h"
 #include "polly/Support/ScopHelper.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Analysis/RegionPass.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/IR/DebugLoc.h"
private:
 
   ScalarEvolution *SE;
   DominatorTree *DT;
 
   /// The underlying Region.
   Region &R;
 
   /// The name of the SCoP (identical to the regions name)
-  std::string name;
+  Optional<std::string> name;
 
   /// The ID to be assigned to the next Scop in a function
   static int NextScopID;
 
   /// The name of the function currently under consideration
   static std::string CurrentFunc;
 
   // Access functions of the SCoP.
public:
   iterator_range<ParameterSetTy::iterator> parameters() const {
     return make_range(Parameters.begin(), Parameters.end());
   }
 
   /// Return whether this scop is empty, i.e. contains no statements that
   /// could be executed.
   bool isEmpty() const { return Stmts.empty(); }
 
-  const StringRef getName() const { return name; }
+  StringRef getName() {
+    if (!name)
+      name = R.getNameStr();
+    return *name;
+  }
 
   using array_iterator = ArrayInfoSetTy::iterator;
   using const_array_iterator = ArrayInfoSetTy::const_iterator;
   using array_range = iterator_range<ArrayInfoSetTy::iterator>;
   using const_array_range = iterator_range<ArrayInfoSetTy::const_iterator>;
 
   inline array_iterator array_begin() { return ScopArrayInfoSet.begin(); }
 

lib/Analysis/ScopInfo.cpp

int Scop::getNextID(std::string ParentFunc) {
   }
   return NextScopID++;
 }
 
 Scop::Scop(Region &R, ScalarEvolution &ScalarEvolution, LoopInfo &LI,
            DominatorTree &DT, ScopDetection::DetectionContext &DC,
            OptimizationRemarkEmitter &ORE)
     : IslCtx(isl_ctx_alloc(), isl_ctx_free), SE(&ScalarEvolution), DT(&DT),
-      R(R), name(R.getNameStr()), HasSingleExitEdge(R.getExitingBlock()),
-      DC(DC), ORE(ORE), Affinator(this, LI),
+      R(R), name(None), HasSingleExitEdge(R.getExitingBlock()), DC(DC),
+      ORE(ORE), Affinator(this, LI),
       ID(getNextID((*R.getEntry()->getParent()).getName().str())) {
   if (IslOnErrorAbort)
     isl_options_set_on_error(getIslCtx().get(), ISL_ON_ERROR_ABORT);
   buildContext();
 }
 
 Scop::~Scop() = default;