Add alternate version of LiveVariables analysis that does not kill liveness at assignments. This 'relaxed' liveness is useful in path sensitive analysis for situations where the resulting extended liveness allows us to find some bugs.

- Added killAtAssign flag to LiveVariables
- Added relaxed LiveVariables to AnalysisContext with an accessor

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@112306 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 28 insertions, 9 deletions

diff --git a/include/clang/Analysis/Analyses/LiveVariables.h b/include/clang/Analysis/Analyses/LiveVariables.h
index 44ab080acb..237fe14aed 100644
--- a/include/clang/Analysis/Analyses/LiveVariables.h
+++ b/include/clang/Analysis/Analyses/LiveVariables.h
@@ -41,8 +41,9 @@ struct LiveVariables_ValueTypes {
     ObserverTy* Observer;
     ValTy AlwaysLive;
     AnalysisContext *AC;
+    bool killAtAssign;
 
-    AnalysisDataTy() : Observer(NULL), AC(NULL) {}
+    AnalysisDataTy() : Observer(NULL), AC(NULL), killAtAssign(true) {}
   };
 
   //===-----------------------------------------------------===//
@@ -68,7 +69,7 @@ class LiveVariables : public DataflowValues<LiveVariables_ValueTypes,
 public:
   typedef LiveVariables_ValueTypes::ObserverTy ObserverTy;
 
-  LiveVariables(AnalysisContext &AC);
+  LiveVariables(AnalysisContext &AC, bool killAtAssign = true);
 
   /// IsLive - Return true if a variable is live at the end of a
   /// specified block.
diff --git a/include/clang/Analysis/AnalysisContext.h b/include/clang/Analysis/AnalysisContext.h
index 6091db4be9..7d4d25f8b0 100644
--- a/include/clang/Analysis/AnalysisContext.h
+++ b/include/clang/Analysis/AnalysisContext.h
@@ -49,6 +49,7 @@ class AnalysisContext {
   CFG *cfg, *completeCFG;
   bool builtCFG, builtCompleteCFG;
   LiveVariables *liveness;
+  LiveVariables *relaxedLiveness;
   ParentMap *PM;
   PseudoConstantAnalysis *PCA;
   llvm::DenseMap<const BlockDecl*,void*> *ReferencedBlockVars;
@@ -61,7 +62,7 @@ public:
                   bool addehedges = false)
     : D(d), TU(tu), cfg(0), completeCFG(0),
       builtCFG(false), builtCompleteCFG(false),
-      liveness(0), PM(0), PCA(0),
+      liveness(0), relaxedLiveness(0), PM(0), PCA(0),
       ReferencedBlockVars(0), UseUnoptimizedCFG(useUnoptimizedCFG),
       AddEHEdges(addehedges) {}
 
@@ -89,6 +90,7 @@ public:
   ParentMap &getParentMap();
   PseudoConstantAnalysis *getPseudoConstantAnalysis();
   LiveVariables *getLiveVariables();
+  LiveVariables *getRelaxedLiveVariables();
 
   typedef const VarDecl * const * referenced_decls_iterator;
 
diff --git a/lib/Analysis/AnalysisContext.cpp b/lib/Analysis/AnalysisContext.cpp
index 2c337f07c3..884cbc65f4 100644
--- a/lib/Analysis/AnalysisContext.cpp
+++ b/lib/Analysis/AnalysisContext.cpp
@@ -104,6 +104,20 @@ LiveVariables *AnalysisContext::getLiveVariables() {
   return liveness;
 }
 
+LiveVariables *AnalysisContext::getRelaxedLiveVariables() {
+  if (!relaxedLiveness) {
+    CFG *c = getCFG();
+    if (!c)
+      return 0;
+
+    relaxedLiveness = new LiveVariables(*this, false);
+    relaxedLiveness->runOnCFG(*c);
+    relaxedLiveness->runOnAllBlocks(*c, 0, true);
+  }
+
+  return relaxedLiveness;
+}
+
 AnalysisContext *AnalysisContextManager::getContext(const Decl *D,
                                                     idx::TranslationUnit *TU) {
   AnalysisContext *&AC = Contexts[D];
diff --git a/lib/Analysis/LiveVariables.cpp b/lib/Analysis/LiveVariables.cpp
index 3011fd0dee..47b2e3d604 100644
--- a/lib/Analysis/LiveVariables.cpp
+++ b/lib/Analysis/LiveVariables.cpp
@@ -77,12 +77,13 @@ public:
 };
 } // end anonymous namespace
 
-LiveVariables::LiveVariables(AnalysisContext &AC) {  
+LiveVariables::LiveVariables(AnalysisContext &AC, bool killAtAssign) {
   // Register all referenced VarDecls.
   CFG &cfg = *AC.getCFG();
   getAnalysisData().setCFG(cfg);
   getAnalysisData().setContext(AC.getASTContext());
   getAnalysisData().AC = &AC;
+  getAnalysisData().killAtAssign = killAtAssign;
 
   RegisterDecls R(getAnalysisData());
   cfg.VisitBlockStmts(R);
@@ -260,12 +261,13 @@ void TransferFuncs::VisitAssign(BinaryOperator* B) {
     if (DR->getDecl()->getType()->isReferenceType()) {
       VisitDeclRefExpr(DR);
     } else {
-      // Update liveness inforamtion.
-      unsigned bit = AD.getIdx(DR->getDecl());
-      LiveState.getDeclBit(bit) = Dead | AD.AlwaysLive.getDeclBit(bit);
-
-      if (AD.Observer) { AD.Observer->ObserverKill(DR); }
+      if (AD.killAtAssign) {
+        // Update liveness inforamtion.
+        unsigned bit = AD.getIdx(DR->getDecl());
+        LiveState.getDeclBit(bit) = Dead | AD.AlwaysLive.getDeclBit(bit);
 
+        if (AD.Observer) { AD.Observer->ObserverKill(DR); }
+      }
       // Handle things like +=, etc., which also generate "uses"
       // of a variable.  Do this just by visiting the subexpression.
       if (B->getOpcode() != BO_Assign)