[clang] nonblocking/nonallocating attributes: 2nd pass caller/callee analysis (PR #99656)

[Doug Wyatt via cfe-commits]

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@@ -4940,6 +4955,78 @@ class FunctionEffectsRef {
   void dump(llvm::raw_ostream &OS) const;
 };
 
+/// A mutable set of FunctionEffect::Kind.
+class FunctionEffectKindSet {
+  // For now this only needs to be a bitmap.
+  constexpr static size_t EndBitPos = 8;
+  using KindBitsT = std::bitset<EndBitPos>;
+
+  KindBitsT KindBits{};
+
+  explicit FunctionEffectKindSet(KindBitsT KB) : KindBits(KB) {}
+
+  constexpr static size_t kindToPos(FunctionEffect::Kind K) {
+    return static_cast<size_t>(K);
+  }
+
+public:
+  FunctionEffectKindSet() = default;
+  explicit FunctionEffectKindSet(FunctionEffectsRef FX) { insert(FX); }
+
+  // Iterates through the bits which are set.
+  class iterator {
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dougsonos wrote:

Wow, it still builds when private, but I don't understand. Apparently the `for` loops which walk through this thing aren't being foiled by the privateness of the iterator.

https://github.com/llvm/llvm-project/pull/99656