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

[Doug Wyatt via cfe-commits]

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@@ -4914,6 +4920,78 @@ class FunctionEffectsRef {
   void dump(llvm::raw_ostream &OS) const;
 };
 
+/// A mutable set of FunctionEffect::Kind.
+class FunctionEffectKindSet {
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dougsonos wrote:

I agree that this can and should use `std::bitset` instead of reinventing it, as a representation, but that doesn't help with the problem of iterating through the set bits, and a lot of code wants to iterate through these sets.

The only alternative I can think of is a `for_each()` method. Sometimes that can be messier than it's worth and sometimes it is better than a special iterator. Will try it.

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