[Polly][REFACTOR] Simplify the SCoP detection interface a bit

[sebpop]

LGTM.

include/polly/ScopDetection.h

private:
 
   /// @brief Check if a region is a Scop.
   ///
   /// @param Context The context of scop detection.
   ///
   /// @return True if R is a Scop, false otherwise.
   bool isValidRegion(DetectionContext &Context) const;
 
-  /// @brief Check if a region is a Scop.
-  ///
-  /// @param Context The context of scop detection.
-  ///
-  /// @return True if R is a Scop, false otherwise.
-  bool isValidRegion(Region &R) const;
-
   /// @brief Check if a call instruction can be part of a Scop.
   ///
   /// @param CI The call instruction to check.
   /// @return True if the call instruction is valid, false otherwise.
   static bool isValidCallInst(CallInst &CI);
 
   /// @brief Check if a value is invariant in the region Reg.
   ///

lib/Analysis/ScopDetection.cpp

inline bool ScopDetection::invalid(DetectionContext &Context, bool Assert,
 
   return false;
 }
 
 bool ScopDetection::isMaxRegionInScop(const Region &R, bool Verify) const {
   if (!ValidRegions.count(&R))
     return false;
 
-  if (Verify)
-    return isValidRegion(const_cast<Region &>(R));
+  if (Verify) {
+    DetectionContext Context(const_cast<Region &>(R), *AA, false /*verifying*/);
+    return isValidRegion(Context);
+  }
 
   return true;
 }
 
 std::string ScopDetection::regionIsInvalidBecause(const Region *R) const {
   if (!RejectLogs.count(R))
     return "";
 
static unsigned eraseAllChildren(ScopDetection::RegionSet &Regs,
   }
   return Count;
 }
 
 void ScopDetection::findScops(Region &R) {
   if (!DetectRegionsWithoutLoops && regionWithoutLoops(R, LI))
     return;
 
-  bool IsValidRegion = isValidRegion(R);
-  bool HasErrors = RejectLogs.count(&R) > 0;
+  DetectionContext Context(R, *AA, false /*verifying*/);
+  bool RegionIsValid = isValidRegion(Context);
+  bool HasErrors = !RegionIsValid || Context.Log.size() > 0;
 
-  if (IsValidRegion && !HasErrors) {
+  if (PollyTrackFailures && HasErrors)
+    RejectLogs.insert(std::make_pair(&R, Context.Log));
+
+  if (!HasErrors) {
     ++ValidRegion;
     ValidRegions.insert(&R);
     return;
   }
 
   for (auto &SubRegion : R)
     findScops(*SubRegion);
 
if (BasicBlock *Exit = R.getExit()) {
     BasicBlock::iterator I = Exit->begin();
     if (I != Exit->end() && isa<PHINode>(*I))
       return invalid<ReportPHIinExit>(Context, /*Assert=*/true, I);
   }
 
   return true;
 }
 
-bool ScopDetection::isValidRegion(Region &R) const {
-  DetectionContext Context(R, *AA, false /*verifying*/);
-
-  bool RegionIsValid = isValidRegion(Context);
-  bool HasErrors = !RegionIsValid || Context.Log.size() > 0;
-
-  if (PollyTrackFailures && HasErrors)
-    RejectLogs.insert(std::make_pair(&R, Context.Log));
-
-  return RegionIsValid;
-}
-
 bool ScopDetection::isValidRegion(DetectionContext &Context) const {
   Region &R = Context.CurRegion;
 
   DEBUG(dbgs() << "Checking region: " << R.getNameStr() << "\n\t");
 
   if (R.isTopLevelRegion()) {
     DEBUG(dbgs() << "Top level region is invalid\n");
     return false;