[clang] Thread Safety Analysis: Support reentrant capabilities (PR #137133)

[Aaron Puchert via cfe-commits]

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@@ -271,26 +271,32 @@ class CFGWalker {
 // translateAttrExpr needs it, but that should be moved too.
 class CapabilityExpr {
 private:
-  /// The capability expression and whether it's negated.
-  llvm::PointerIntPair<const til::SExpr *, 1, bool> CapExpr;
+  /// The capability expression and flags.
+  llvm::PointerIntPair<const til::SExpr *, 2, unsigned> CapExpr;
 
   /// The kind of capability as specified by @ref CapabilityAttr::getName.
   StringRef CapKind;
 
 public:
-  CapabilityExpr() : CapExpr(nullptr, false) {}
-  CapabilityExpr(const til::SExpr *E, StringRef Kind, bool Neg)
-      : CapExpr(E, Neg), CapKind(Kind) {}
+  static constexpr unsigned FlagNegative = 1u << 0;
+  static constexpr unsigned FlagReentrant = 1u << 1;
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aaronpuchert wrote:

We do, but the question is whether we have 4 possible states or just 3: can a mutex be both [negative](https://clang.llvm.org/docs/ThreadSafetyAnalysis.html#negative) and reentrant? If yes, we have 2×`bool`, otherwise we have something like `enum {Regular, Negative, Reentrant}`.

https://github.com/llvm/llvm-project/pull/137133