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

[Jon Roelofs via cfe-commits]

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@@ -2397,6 +2397,1262 @@ class UnsafeBufferUsageReporter : public UnsafeBufferUsageHandler {
 };
 } // namespace
 
+// =============================================================================
+
+namespace FXAnalysis {
+
+enum class DiagnosticID : uint8_t {
+  None = 0, // sentinel for an empty Diagnostic
+  Throws,
+  Catches,
+  CallsObjC,
+  AllocatesMemory,
+  HasStaticLocal,
+  AccessesThreadLocal,
+
+  // These only apply to callees, where the analysis stops at the Decl
+  DeclDisallowsInference,
+
+  CallsDeclWithoutEffect,
+  CallsExprWithoutEffect,
+};
+
+// Holds an effect diagnosis, potentially for the entire duration of the
+// analysis phase, in order to refer to it when explaining why a caller has been
+// made unsafe by a callee.
+struct Diagnostic {
+  FunctionEffect Effect;
+  DiagnosticID ID = DiagnosticID::None;
+  SourceLocation Loc;
+  const Decl *Callee = nullptr; // only valid for Calls*
+
+  Diagnostic() = default;
+
+  Diagnostic(const FunctionEffect &Effect, DiagnosticID ID, SourceLocation Loc,
+             const Decl *Callee = nullptr)
+      : Effect(Effect), ID(ID), Loc(Loc), Callee(Callee) {}
+};
+
+enum class SpecialFuncType : uint8_t { None, OperatorNew, OperatorDelete };
+enum class CallType {
+  // unknown: probably function pointer
+  Unknown,
+  Function,
+  Virtual,
+  Block
+};
+
+// Return whether a function's effects CAN be verified.
+// The question of whether it SHOULD be verified is independent.
+static bool functionIsVerifiable(const FunctionDecl *FD) {
+  if (!(FD->hasBody() || FD->isInlined())) {
+    // externally defined; we couldn't verify if we wanted to.
+    return false;
+  }
+  if (FD->isTrivial()) {
+    // Otherwise `struct x { int a; };` would have an unverifiable default
+    // constructor.
+    return true;
+  }
+  return true;
+}
+
+/// A mutable set of FunctionEffect, for use in places where any conditions
+/// have been resolved or can be ignored.
+class EffectSet {
+  // This implementation optimizes footprint, since we hold one of these for
+  // every function visited, which, due to inference, can be many more functions
+  // than have declared effects.
+
+  template <typename T, typename SizeT, SizeT Capacity> struct FixedVector {
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jroelofs wrote:

did `llvm::SmallVector` end up having too much overhead for this?

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