[analyzer][NFC] Remove duplicated work from retain count leak report

[vsavchenko]

Summary

Allocation site is the key location for the leak checker. It is a
uniqueing location for the report and a source of information for
the warning's message.

Before this patch, we calculated and used it twice in bug report and
in bug report visitor. Such duplication is not only harmful
performance-wise (not much, but still), but also design-wise. Because
changing something about the end piece of the report should've been
repeated for description as well.

[NoQ]

Great, thanks!

clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountDiagnostics.cpp

public:
 
   PathDiagnosticPieceRef getEndPath(BugReporterContext &BRC,
                                     const ExplodedNode *N,
                                     PathSensitiveBugReport &BR) override;
 };
 
 class RefLeakReportVisitor : public RefCountReportVisitor {
 public:
-  RefLeakReportVisitor(SymbolRef sym) : RefCountReportVisitor(sym) {}
+  RefLeakReportVisitor(SymbolRef Sym, const MemRegion *FirstBinding)
+      : RefCountReportVisitor(Sym), FirstBinding(FirstBinding) {}
 
   PathDiagnosticPieceRef getEndPath(BugReporterContext &BRC,
                                     const ExplodedNode *N,
                                     PathSensitiveBugReport &BR) override;
+
+private:
+  const MemRegion *FirstBinding;
 };
 
 } // end namespace retaincountchecker
 } // end namespace ento
 } // end namespace clang
 
 
 /// Find the first node with the parent stack frame.

 RefLeakReportVisitor::getEndPath(BugReporterContext &BRC,
                                  const ExplodedNode *EndN,
                                  PathSensitiveBugReport &BR) {
 
   // Tell the BugReporterContext to report cases when the tracked symbol is
   // assigned to different variables, etc.
   BR.markInteresting(Sym);
 
-  // We are reporting a leak.  Walk up the graph to get to the first node where
-  // the symbol appeared, and also get the first VarDecl that tracked object
-  // is stored to.
-  AllocationInfo AllocI = GetAllocationSite(BRC.getStateManager(), EndN, Sym);
-
-  const MemRegion* FirstBinding = AllocI.R;
-  BR.markInteresting(AllocI.InterestingMethodContext);
-
   PathDiagnosticLocation L = cast<RefLeakReport>(BR).getEndOfPath();
 
   std::string sbuf;
   llvm::raw_string_ostream os(sbuf);
 
   os << "Object leaked: ";
 
   Optional<std::string> RegionDescription = describeRegion(FirstBinding);
void RefLeakReport::createDescription(CheckerContext &Ctx) {
   } else {
 
     // If we can't figure out the name, just supply the type information.
     os << " of type '" << getPrettyTypeName(Sym->getType()) << "'";
   }
 }
 
 RefLeakReport::RefLeakReport(const RefCountBug &D, const LangOptions &LOpts,
-                             ExplodedNode *n, SymbolRef sym,
+                             ExplodedNode *N, SymbolRef Sym,
                              CheckerContext &Ctx)
-    : RefCountReport(D, LOpts, n, sym, /*isLeak=*/true) {
+    : RefCountReport(D, LOpts, N, Sym, /*isLeak=*/true) {
 
-  deriveAllocLocation(Ctx, sym);
+  deriveAllocLocation(Ctx, Sym);
   if (!AllocBinding)
-    deriveParamLocation(Ctx, sym);
+    deriveParamLocation(Ctx, Sym);
 
   createDescription(Ctx);
 
-  addVisitor(std::make_unique<RefLeakReportVisitor>(sym));
+  addVisitor(std::make_unique<RefLeakReportVisitor>(Sym, AllocBinding));
 }