Reapply "[analyzer] Remove constraints on dead symbols as part of removeDeadBindings."

Previously, we'd just keep constraints around forever, which means we'd
never be able to merge paths that differed only in constraints on dead
symbols.

Because we now allow constraints on symbolic expressions, not just single
symbols, this requires changing SymExpr::symbol_iterator to include
intermediate symbol nodes in its traversal, not just the SymbolData leaf
nodes.

This depends on the previous commit to be correct. Originally applied in
r163444, reverted in r164275, now being re-applied.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164622 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 29 insertions, 9 deletions

diff --git a/lib/StaticAnalyzer/Core/ProgramState.cpp b/lib/StaticAnalyzer/Core/ProgramState.cpp
index ed128ef00d..56c6c04df0 100644
--- a/lib/StaticAnalyzer/Core/ProgramState.cpp
+++ b/lib/StaticAnalyzer/Core/ProgramState.cpp
@@ -106,8 +106,9 @@ ProgramStateManager::removeDeadBindings(ProgramStateRef state,
                                                    SymReaper);
   NewState.setStore(newStore);
   SymReaper.setReapedStore(newStore);
-  
-  return getPersistentState(NewState);
+
+  ProgramStateRef Result = getPersistentState(NewState);
+  return ConstraintMgr->removeDeadBindings(Result, SymReaper);
 }
 
 ProgramStateRef ProgramState::bindCompoundLiteral(const CompoundLiteralExpr *CL,
@@ -686,7 +687,9 @@ bool ProgramState::isTainted(SymbolRef Sym, TaintTagType Kind) const {
   bool Tainted = false;
   for (SymExpr::symbol_iterator SI = Sym->symbol_begin(), SE =Sym->symbol_end();
        SI != SE; ++SI) {
-    assert(isa<SymbolData>(*SI));
+    if (!isa<SymbolData>(*SI))
+      continue;
+    
     const TaintTagType *Tag = get<TaintMap>(*SI);
     Tainted = (Tag && *Tag == Kind);
 
diff --git a/lib/StaticAnalyzer/Core/SymbolManager.cpp b/lib/StaticAnalyzer/Core/SymbolManager.cpp
index 87b4ba315e..5334b03b3f 100644
--- a/lib/StaticAnalyzer/Core/SymbolManager.cpp
+++ b/lib/StaticAnalyzer/Core/SymbolManager.cpp
@@ -117,21 +117,17 @@ bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
 
 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
   itr.push_back(SE);
-  while (!isa<SymbolData>(itr.back())) expand();
 }
 
 SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
   assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
-  assert(isa<SymbolData>(itr.back()));
-  itr.pop_back();
-  if (!itr.empty())
-    while (!isa<SymbolData>(itr.back())) expand();
+  expand();
   return *this;
 }
 
 SymbolRef SymExpr::symbol_iterator::operator*() {
   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
-  return cast<SymbolData>(itr.back());
+  return itr.back();
 }
 
 void SymExpr::symbol_iterator::expand() {
diff --git a/test/Analysis/traversal-path-unification.c b/test/Analysis/traversal-path-unification.c
new file mode 100644
index 0000000000..0a45f48a01
--- /dev/null
+++ b/test/Analysis/traversal-path-unification.c
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,debug.DumpTraversal %s | FileCheck %s
+
+int a();
+int b();
+int c();
+
+void testRemoveDeadBindings() {
+  int i = a();
+  if (i)
+    a();
+  else
+    b();
+
+  // At this point the symbol bound to 'i' is dead.
+  // The effects of a() and b() are identical (they both invalidate globals).
+  // We should unify the two paths here and only get one end-of-path node.
+  c();
+}
+
+// CHECK: --END PATH--
+// CHECK-NOT: --END PATH--
\ No newline at end of file