[analyzer] Do not run visitors until the fixpoint, run only once.

In the current implementation, we run visitors until the fixed point is
reached.
That is, if a visitor adds another visitor, the currently processed path
is destroyed, all diagnostics is discarded, and it is regenerated again,
until it's no longer modified.
This pattern has a few negative implications:

 - This loop does not even guarantee to terminate.
   E.g. just imagine two visitors bouncing a diagnostics around.
 - Performance-wise, e.g. for sqlite3 all visitors are being re-run at
   least 10 times for some bugs.
   We have already seen a few reports where it leads to timeouts.
 - If we want to add more computationally intense visitors, this will
   become worse.
 - From architectural standpoint, the current layout requires copying
   visitors, which is conceptually wrong, and can be annoying (e.g. no
   unique_ptr on visitors allowed).

The proposed change is a much simpler architecture: the outer loop
processes nodes upwards, and whenever the visitor is added it only
processes current nodes and above, thus guaranteeing termination.

Differential Revision: https://reviews.llvm.org/D47856

llvm-svn: 335666

1 files changed, 3 insertions, 4 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
index 039bc08c5c2..bd657340fcf 100644
--- a/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/ValistChecker.cpp
@@ -69,7 +69,7 @@ private:
                             bool IsCopy) const;
   void checkVAListEndCall(const CallEvent &Call, CheckerContext &C) const;
 
-  class ValistBugVisitor : public BugReporterVisitorImpl<ValistBugVisitor> {
+  class ValistBugVisitor : public BugReporterVisitor {
   public:
     ValistBugVisitor(const MemRegion *Reg, bool IsLeak = false)
         : Reg(Reg), IsLeak(IsLeak) {}
@@ -78,7 +78,7 @@ private:
       ID.AddPointer(&X);
       ID.AddPointer(Reg);
     }
-    std::unique_ptr<PathDiagnosticPiece>
+    std::shared_ptr<PathDiagnosticPiece>
     getEndPath(BugReporterContext &BRC, const ExplodedNode *EndPathNode,
                BugReport &BR) override {
       if (!IsLeak)
@@ -87,8 +87,7 @@ private:
       PathDiagnosticLocation L = PathDiagnosticLocation::createEndOfPath(
           EndPathNode, BRC.getSourceManager());
       // Do not add the statement itself as a range in case of leak.
-      return llvm::make_unique<PathDiagnosticEventPiece>(L, BR.getDescription(),
-                                                         false);
+      return std::make_shared<PathDiagnosticEventPiece>(L, BR.getDescription(), false);
     }
     std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
                                                    const ExplodedNode *PrevN,