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

[via cfe-commits]

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@@ -4719,8 +4719,9 @@ class FunctionEffect {
     NonBlocking = 1,
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Sirraide wrote:

Something I only thought about just now: is `None` ever actually used? Otherwise, we should probably just remove it and start at 0 so we don’t have to do this `- 1` and `+ 1` dance below, because that seems like a recipe for disaster in terms of off-by-one errors.

(Even if it is used, we should probably just use `std::optional<FunctionEffect::Kind>` instead)

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