[polly] Don't count scops in a global variable.

[efriedma]

Summary

Global variables aren't thread-safe.

[Meinersbur]

And I thought we got rid of such globals some time ago.

LGTM.

polly/include/polly/ScopDetection.h

public:
   };
 
   /// Helper data structure to collect statistics about loop counts.
   struct LoopStats {
     int NumLoops;
     int MaxDepth;
   };
 
+  int NextScopID = 0;
+  int getNextID() { return NextScopID++; }
+
 private:
   //===--------------------------------------------------------------------===//
 
   /// Analyses used
   //@{
   const DominatorTree &DT;
   ScalarEvolution &SE;
   LoopInfo &LI;

polly/include/polly/ScopInfo.h

private:
   DominatorTree *DT;
 
   /// The underlying Region.
   Region &R;
 
   /// The name of the SCoP (identical to the regions 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.
   //
   // This owns all the MemoryAccess objects of the Scop created in this pass.
   AccFuncVector AccessFunctions;
 
   /// Flag to indicate that the scheduler actually optimized the SCoP.
   bool IsOptimized = false;
 
private:
   /// scalar.
   DenseMap<const ScopArrayInfo *, SmallVector<MemoryAccess *, 4>> ValueUseAccs;
 
   /// List of all incoming values (write MemoryAccess) of a MemoryKind::PHI or
   /// MemoryKind::ExitPHI scalar.
   DenseMap<const ScopArrayInfo *, SmallVector<MemoryAccess *, 4>>
       PHIIncomingAccs;
 
-  /// Return the ID for a new Scop within a function
-  static int getNextID(std::string ParentFunc);
-
   /// Scop constructor; invoked from ScopBuilder::buildScop.
   Scop(Region &R, ScalarEvolution &SE, LoopInfo &LI, DominatorTree &DT,
-       ScopDetection::DetectionContext &DC, OptimizationRemarkEmitter &ORE);
+       ScopDetection::DetectionContext &DC, OptimizationRemarkEmitter &ORE,
+       int ID);
 
   //@}
 
   /// Initialize this ScopBuilder.
   void init(AliasAnalysis &AA, AssumptionCache &AC, DominatorTree &DT,
             LoopInfo &LI);
 
   /// Add parameter constraints to @p C that imply a non-empty domain.

polly/lib/Analysis/ScopBuilder.cpp

for (auto &Inst : *S->getRegion().getExit()) {
       for (auto &Op : Inst.operands())
         verifyUse(S, Op, LI);
     }
   }
 }
 #endif
 
 void ScopBuilder::buildScop(Region &R, AssumptionCache &AC) {
-  scop.reset(new Scop(R, SE, LI, DT, *SD.getDetectionContext(&R), ORE));
+  scop.reset(new Scop(R, SE, LI, DT, *SD.getDetectionContext(&R), ORE,
+                      SD.getNextID()));
 
   buildStmts(R);
 
   // Create all invariant load instructions first. These are categorized as
   // 'synthesizable', therefore are not part of any ScopStmt but need to be
   // created somewhere.
   const InvariantLoadsSetTy &RIL = scop->getRequiredInvariantLoads();
   for (BasicBlock *BB : scop->getRegion().blocks()) {

polly/lib/Analysis/ScopInfo.cpp

isl::set Scop::getDomainConditions(BasicBlock *BB) const {
 
   auto &RI = *R.getRegionInfo();
   auto *BBR = RI.getRegionFor(BB);
   while (BBR->getEntry() == BB)
     BBR = BBR->getParent();
   return getDomainConditions(BBR->getEntry());
 }
 
-int Scop::NextScopID = 0;
-
-std::string Scop::CurrentFunc;
-
-int Scop::getNextID(std::string ParentFunc) {
-  if (ParentFunc != CurrentFunc) {
-    CurrentFunc = ParentFunc;
-    NextScopID = 0;
-  }
-  return NextScopID++;
-}
-
 Scop::Scop(Region &R, ScalarEvolution &ScalarEvolution, LoopInfo &LI,
            DominatorTree &DT, ScopDetection::DetectionContext &DC,
-           OptimizationRemarkEmitter &ORE)
+           OptimizationRemarkEmitter &ORE, int ID)
     : IslCtx(isl_ctx_alloc(), isl_ctx_free), SE(&ScalarEvolution), DT(&DT),
       R(R), name(None), HasSingleExitEdge(R.getExitingBlock()), DC(DC),
-      ORE(ORE), Affinator(this, LI),
-      ID(getNextID((*R.getEntry()->getParent()).getName().str())) {
+      ORE(ORE), Affinator(this, LI), ID(ID) {
   if (IslOnErrorAbort)
     isl_options_set_on_error(getIslCtx().get(), ISL_ON_ERROR_ABORT);
   buildContext();
 }
 
 Scop::~Scop() = default;
 
 void Scop::removeFromStmtMap(ScopStmt &Stmt) {