[clang] [clang][FlowSensitive] Do a quick check and bail early for massive CFGs (PR #186808)

[Jan Voung via cfe-commits]

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@@ -496,6 +519,14 @@ runTypeErasedDataflowAnalysis(
       MaybeStartingEnv ? *MaybeStartingEnv : InitEnv;
 
   const clang::CFG &CFG = ACFG.getCFG();
+  if (CFG.size() > static_cast<size_t>(MaxBlockVisits)) {
+    if (CFG.size() > NumBlockVisitsIfVisitEachReachableOnce(CFG)) {
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jvoung wrote:

Oops, yes -- fixed the comparison, and added a test.

Added some comments too.

https://github.com/llvm/llvm-project/pull/186808