r188677 - [analyzer] Fix inefficiency in dead symbol removal

[Pavel Labath]

Author: labath
Date: Mon Aug 19 10:23:34 2013
New Revision: 188677

URL: http://llvm.org/viewvc/llvm-project?rev=188677&view=rev
Log:
[analyzer] Fix inefficiency in dead symbol removal

Summary:
ScanReachableSymbols uses a "visited" set to avoid scanning the same object
twice. However, it did not use the optimization for LazyCompoundVal objects,
which resulted in exponential complexity for long chains of temporary objects.
Adding this resulted in a decrease of analysis time from >3h to 3 seconds for
some files.

Reviewers: jordan_rose

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1398

Modified:
    cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
    cfe/trunk/lib/StaticAnalyzer/Core/ProgramState.cpp

Modified: cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h?rev=188677&r1=188676&r2=188677&view=diff
==============================================================================
--- cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h (original)
+++ cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h Mon Aug 19 10:23:34 2013
@@ -798,7 +798,7 @@ CB ProgramState::scanReachableSymbols(co
 /// A Utility class that allows to visit the reachable symbols using a custom
 /// SymbolVisitor.
 class ScanReachableSymbols {
-  typedef llvm::DenseMap<const void*, unsigned> VisitedItems;
+  typedef llvm::DenseSet<const void*> VisitedItems;
 
   VisitedItems visited;
   ProgramStateRef state;
@@ -808,6 +808,7 @@ public:
   ScanReachableSymbols(ProgramStateRef st, SymbolVisitor& v)
     : state(st), visitor(v) {}
 
+  bool scan(nonloc::LazyCompoundVal val);
   bool scan(nonloc::CompoundVal val);
   bool scan(SVal val);
   bool scan(const MemRegion *R);

Modified: cfe/trunk/lib/StaticAnalyzer/Core/ProgramState.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/ProgramState.cpp?rev=188677&r1=188676&r2=188677&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/ProgramState.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Core/ProgramState.cpp Mon Aug 19 10:23:34 2013
@@ -526,6 +526,19 @@ ProgramStateRef ProgramStateManager::rem
   return getPersistentState(NewState);
 }
 
+bool ScanReachableSymbols::scan(nonloc::LazyCompoundVal val) {
+  bool wasVisited = !visited.insert(val.getCVData()).second;
+  if (wasVisited)
+    return true;
+
+  StoreManager &StoreMgr = state->getStateManager().getStoreManager();
+  // FIXME: We don't really want to use getBaseRegion() here because pointer
+  // arithmetic doesn't apply, but scanReachableSymbols only accepts base
+  // regions right now.
+  const MemRegion *R = val.getRegion()->getBaseRegion();
+  return StoreMgr.scanReachableSymbols(val.getStore(), R, *this);
+}
+
 bool ScanReachableSymbols::scan(nonloc::CompoundVal val) {
   for (nonloc::CompoundVal::iterator I=val.begin(), E=val.end(); I!=E; ++I)
     if (!scan(*I))
@@ -535,10 +548,9 @@ bool ScanReachableSymbols::scan(nonloc::
 }
 
 bool ScanReachableSymbols::scan(const SymExpr *sym) {
-  unsigned &isVisited = visited[sym];
-  if (isVisited)
+  bool wasVisited = !visited.insert(sym).second;
+  if (wasVisited)
     return true;
-  isVisited = 1;
   
   if (!visitor.VisitSymbol(sym))
     return false;
@@ -570,16 +582,8 @@ bool ScanReachableSymbols::scan(SVal val
     return scan(X->getRegion());
 
   if (Optional<nonloc::LazyCompoundVal> X =
-          val.getAs<nonloc::LazyCompoundVal>()) {
-    StoreManager &StoreMgr = state->getStateManager().getStoreManager();
-    // FIXME: We don't really want to use getBaseRegion() here because pointer
-    // arithmetic doesn't apply, but scanReachableSymbols only accepts base
-    // regions right now.
-    if (!StoreMgr.scanReachableSymbols(X->getStore(),
-                                       X->getRegion()->getBaseRegion(),
-                                       *this))
-      return false;
-  }
+          val.getAs<nonloc::LazyCompoundVal>())
+    return scan(*X);
 
   if (Optional<nonloc::LocAsInteger> X = val.getAs<nonloc::LocAsInteger>())
     return scan(X->getLoc());
@@ -600,11 +604,9 @@ bool ScanReachableSymbols::scan(const Me
   if (isa<MemSpaceRegion>(R))
     return true;
   
-  unsigned &isVisited = visited[R];
-  if (isVisited)
+  bool wasVisited = !visited.insert(R).second;
+  if (wasVisited)
     return true;
-  isVisited = 1;
-  
   
   if (!visitor.VisitMemRegion(R))
     return false;