[PATCH] D106370: [Analyzer][solver][NFC] Add explanatory comments to trivial eq classes

[Gabor Marton via Phabricator via cfe-commits]

martong created this revision.
martong added reviewers: vsavchenko, NoQ, steakhal.
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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106370

Files:
  clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp


Index: clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
+++ clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp
@@ -559,8 +559,20 @@
 
   /// Return a set of class members for the given state.
   LLVM_NODISCARD inline SymbolSet getClassMembers(ProgramStateRef State) const;
+
   /// Return true if the current class is trivial in the given state.
+  // A class is trivial if and only if there is not any member relations stored
+  // to it in State/ClassMembers.
+  // An equivalence class with one member might seem as it does not hold any
+  // meaningful information, i.e. that is a tautology. However, during the
+  // removal of dead symbols we do not remove classes with one member for
+  // resource and performance reasons. Consequently, a class with one member is
+  // not necessarily trivial. It could happen that we have a class with two
+  // members and then during the removal of dead symbols we remove one of its
+  // members. In this case, the class is still non-trivial (it still has the
+  // mappings in ClassMembers), even though it has only one member.
   LLVM_NODISCARD inline bool isTrivial(ProgramStateRef State) const;
+
   /// Return true if the current class is trivial and its only member is dead.
   LLVM_NODISCARD inline bool isTriviallyDead(ProgramStateRef State,
                                              SymbolReaper &Reaper) const;


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