[analyzer][NFC] Introduce CallDescriptionSets

Sometimes we only want to decide if some function is called, and we
don't care which of the set.
This `CallDescriptionSet` will have the same behavior, except
instead of `lookup()` returning a pointer to the mapped value,
the `contains()` returns `bool`.
Internally, it uses the `CallDescriptionMap<bool>` for implementing the
behavior. It is preferred, to reuse the generic
`CallDescriptionMap::lookup()` logic, instead of duplicating it.
The generic version might be improved by implementing a hash lookup or
something along those lines.

Reviewed By: martong, Szelethus

Differential Revision: https://reviews.llvm.org/D113589

Author: Balazs Benics

clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h

@@ -88,6 +88,8 @@ class CallDescription {
 /// An immutable map from CallDescriptions to arbitrary data. Provides a unified
 /// way for checkers to react on function calls.
 template <typename T> class CallDescriptionMap {
+  friend class CallDescriptionSet;
+
   // Some call descriptions aren't easily hashable (eg., the ones with qualified
   // names in which some sections are omitted), so let's put them
   // in a simple vector and use linear lookup.
@@ -118,6 +120,21 @@ template <typename T> class CallDescriptionMap {
   }
 };
 
+/// An immutable set of CallDescriptions.
+/// Checkers can efficiently decide if a given CallEvent matches any
+/// CallDescription in the set.
+class CallDescriptionSet {
+  CallDescriptionMap<bool /*unused*/> Impl = {};
+
+public:
+  CallDescriptionSet(std::initializer_list<CallDescription> &&List);
+
+  CallDescriptionSet(const CallDescriptionSet &) = delete;
+  CallDescriptionSet &operator=(const CallDescription &) = delete;
+
+  LLVM_NODISCARD bool contains(const CallEvent &Call) const;
+};
+
 } // namespace ento
 } // namespace clang
 

clang/lib/StaticAnalyzer/Core/CallDescription.cpp

@@ -46,3 +46,14 @@ ento::CallDescription::CallDescription(
     Optional<unsigned> RequiredArgs /*= None*/,
     Optional<size_t> RequiredParams /*= None*/)
     : CallDescription(0, QualifiedName, RequiredArgs, RequiredParams) {}
+
+ento::CallDescriptionSet::CallDescriptionSet(
+    std::initializer_list<CallDescription> &&List) {
+  Impl.LinearMap.reserve(List.size());
+  for (const CallDescription &CD : List)
+    Impl.LinearMap.push_back({CD, /*unused*/ true});
+}
+
+bool ento::CallDescriptionSet::contains(const CallEvent &Call) const {
+  return static_cast<bool>(Impl.lookup(Call));
+}