[polly] [ScopInfo] Don't pre-compute the name of the Scop's region.

[efriedma]

Summary

This gets very expensive for basic blocks which don't have a name: it calls printAsOperand, which numbers the entire module. We don't normally need the name anyway, though, so don't compute it by default.

[Meinersbur]

LGTM.

Is there a cost in that the name is not cached anymore? Is it used even if -polly-use-llvm-names is not given?

[efriedma]

With the old pass manager, the only place that actually uses the result of getName() is some debug dumps in include/llvm/IR/PassManager.h. With the new pass manager, it looks like ScopPass.h/ScopPass.cpp call getName() unconditionally... but the result is still only used for debug dumps.

[grosser]

Very useful!

Best,
Tobias

polly/trunk/include/polly/ScopInfo.h

private:
   std::shared_ptr<isl_ctx> IslCtx;
 
   ScalarEvolution *SE;
   DominatorTree *DT;
 
   /// The underlying Region.
   Region &R;
 
-  /// The name of the SCoP (identical to the regions name)
-  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; }
+  const StringRef getName() const { return R.getNameStr(); }
 
   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(); }
 

polly/trunk/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), 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;