[clang] nonblocking/nonallocating attributes (was: nolock/noalloc) (PR #84983)

[via cfe-commits]

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@@ -4429,6 +4433,218 @@ class FunctionNoProtoType : public FunctionType, public llvm::FoldingSetNode {
   }
 };
 
+// ------------------------------------------------------------------------------
+
+// TODO: Should FunctionEffect be located elsewhere, where Decl is not
+// forward-declared?
+class Decl;
+class CXXMethodDecl;
+class FunctionEffectSet;
+class TypeSourceInfo;
+
+/// Represents an abstract function effect.
+class FunctionEffect {
+public:
+  /// Identifies the particular type of effect.
+  enum class Type {
+    None = 0,
+    NonBlocking,
+    NonAllocating,
+  };
+
+  /// Flags describing behaviors of the effect.
+  // (Why not a struct with bitfields? There's one function that would like to
+  // test a caller-specified bit. There are some potential optimizations that
+  // would OR together the bits of multiple effects.)
+  using Flags = unsigned;
+  enum FlagBit : unsigned {
+    // Can verification inspect callees' implementations? (e.g. nonblocking:
+    // yes, tcb+types: no)
+    FE_InferrableOnCallees = 0x1,
+
+    // Language constructs which effects can diagnose as disallowed.
+    FE_ExcludeThrow = 0x2,
+    FE_ExcludeCatch = 0x4,
+    FE_ExcludeObjCMessageSend = 0x8,
+    FE_ExcludeStaticLocalVars = 0x10,
+    FE_ExcludeThreadLocalVars = 0x20
+  };
+
+  /// Describes the result of effects differing between a base class's virtual
+  /// method and an overriding method in a subclass.
+  enum class OverrideResult {
+    Ignore,
+    Warn,
+    Propagate // Base method's effects are merged with those of the override.
+  };
+
+private:
+  // For uniqueness, currently only Type_ is significant.
+
+  LLVM_PREFERRED_TYPE(Type)
+  unsigned Type_ : 2;
+  Flags Flags_ : 8; // A constant function of Type but cached here.
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Sirraide wrote:

nit: minor style issue: I don’t think we use trailing underscores; maybe you can find different names for these members?

https://github.com/llvm/llvm-project/pull/84983