Bail out the LiveVariables analysis when the CFG is very large, as

we are encountering some scalability issues with memory usage.   The
appropriate long term fix is to make the analysis more scalable, but
this will at least prevent the analyzer swapping when
analyzing very large functions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159578 91177308-0d34-0410-b5e6-96231b3b80d8

Author: tkremenek

Diff for: lib/Analysis/LiveVariables.cpp

@@ -486,6 +486,11 @@ LiveVariables::computeLiveness(AnalysisDeclContext &AC,
   if (!cfg)
     return 0;
 
+  // The analysis currently has scalability issues for very large CFGs.
+  // Bail out if it looks too large.
+  if (cfg->getNumBlockIDs() > 300000)
+    return 0;
+
   LiveVariablesImpl *LV = new LiveVariablesImpl(AC, killAtAssign);
 
   // Construct the dataflow worklist.  Enqueue the exit block as the

Diff for: lib/StaticAnalyzer/Core/ExprEngineCallAndReturn.cpp

@@ -11,6 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Analysis/Analyses/LiveVariables.h"
 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/Calls.h"
@@ -244,6 +245,11 @@ bool ExprEngine::shouldInlineDecl(const Decl *D, ExplodedNode *Pred) {
   if (isa<CXXConstructorDecl>(D))
     return false;
 
+  // It is possible that the live variables analysis cannot be
+  // run.  If so, bail out.
+  if (!CalleeADC->getAnalysis<RelaxedLiveVariables>())
+    return false;
+
   return true;
 }
 

Diff for: lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp

@@ -523,6 +523,10 @@ void AnalysisConsumer::ActionExprEngine(Decl *D, bool ObjCGCEnabled,
   if (!Mgr->getCFG(D))
     return;
 
+  // See if the LiveVariables analysis scales.
+  if (!Mgr->getAnalysisDeclContext(D)->getAnalysis<RelaxedLiveVariables>())
+    return;
+
   ExprEngine Eng(*Mgr, ObjCGCEnabled, VisitedCallees, &FunctionSummaries);
 
   // Set the graph auditor.