[PATCH] [analyzer] Fix inefficiency in dead symbol removal

[Pavel Labath]

  Ah, yes, I forgot about that.

  I added a separate set to track the (region, store) pairs (or pairs of anything, if it is ever needed).

Hi jordan_rose,

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

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D1398?vs=3466&id=3521#toc

Files:
  include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
  lib/StaticAnalyzer/Core/ProgramState.cpp

Index: include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
===================================================================
--- include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
+++ include/clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h
@@ -799,15 +799,18 @@
 /// SymbolVisitor.
 class ScanReachableSymbols {
   typedef llvm::DenseMap<const void*, unsigned> VisitedItems;
+  typedef llvm::DenseMap<std::pair<const void*, const void*>, unsigned> VisitedPairs;
 
   VisitedItems visited;
+  VisitedPairs visitedPairs;
   ProgramStateRef state;
   SymbolVisitor &visitor;
 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);
Index: lib/StaticAnalyzer/Core/ProgramState.cpp
===================================================================
--- lib/StaticAnalyzer/Core/ProgramState.cpp
+++ lib/StaticAnalyzer/Core/ProgramState.cpp
@@ -526,6 +526,20 @@
   return getPersistentState(NewState);
 }
 
+bool ScanReachableSymbols::scan(nonloc::LazyCompoundVal val) {
+  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();
+  unsigned &isVisited = visitedPairs[std::make_pair(R, val.getStore())];
+  if (isVisited)
+    return true;
+  isVisited = 1;
+
+  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))
@@ -570,16 +584,8 @@
     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());
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