nonblocking/nonallocating attributes: 2nd pass caller/callee analysis

clang/include/clang/AST/Type.h

@@ -48,6 +48,7 @@
 #include "llvm/Support/PointerLikeTypeTraits.h"
 #include "llvm/Support/TrailingObjects.h"
 #include "llvm/Support/type_traits.h"
+#include <bitset>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
@@ -118,6 +119,8 @@ class EnumDecl;
 class Expr;
 class ExtQualsTypeCommonBase;
 class FunctionDecl;
+class FunctionEffectsRef;
+class FunctionEffectKindSet;
 class FunctionEffectSet;
 class IdentifierInfo;
 class NamedDecl;
@@ -4774,26 +4777,30 @@ class FunctionEffect {
   /// The description printed in diagnostics, e.g. 'nonblocking'.
   StringRef name() const;
 
-  /// Return true if the effect is allowed to be inferred on the callee,
-  /// which is either a FunctionDecl or BlockDecl.
+  /// Determine whether the effect is allowed to be inferred on the callee,
+  /// which is either a FunctionDecl or BlockDecl. If the returned optional
+  /// is empty, inference is permitted; otherwise it holds the effect which
+  /// blocked inference.
   /// Example: This allows nonblocking(false) to prevent inference for the
   /// function.
-  bool canInferOnFunction(const Decl &Callee) const;
+  std::optional<FunctionEffect>
+  effectProhibitingInference(const Decl &Callee,
+                             FunctionEffectKindSet CalleeFX) const;
 
   // Return false for success. When true is returned for a direct call, then the
   // FE_InferrableOnCallees flag may trigger inference rather than an immediate
   // diagnostic. Caller should be assumed to have the effect (it may not have it
   // explicitly when inferring).
   bool shouldDiagnoseFunctionCall(bool Direct,
-                                  ArrayRef<FunctionEffect> CalleeFX) const;
+                                  FunctionEffectKindSet CalleeFX) const;
 
-  friend bool operator==(const FunctionEffect &LHS, const FunctionEffect &RHS) {
+  friend bool operator==(FunctionEffect LHS, FunctionEffect RHS) {
     return LHS.FKind == RHS.FKind;
   }
-  friend bool operator!=(const FunctionEffect &LHS, const FunctionEffect &RHS) {
+  friend bool operator!=(FunctionEffect LHS, FunctionEffect RHS) {
     return !(LHS == RHS);
   }
-  friend bool operator<(const FunctionEffect &LHS, const FunctionEffect &RHS) {
+  friend bool operator<(FunctionEffect LHS, FunctionEffect RHS) {
     return LHS.FKind < RHS.FKind;
   }
 };
@@ -4822,8 +4829,7 @@ struct FunctionEffectWithCondition {
   EffectConditionExpr Cond;
 
   FunctionEffectWithCondition() = default;
-  FunctionEffectWithCondition(const FunctionEffect &E,
-                              const EffectConditionExpr &C)
+  FunctionEffectWithCondition(FunctionEffect E, const EffectConditionExpr &C)
       : Effect(E), Cond(C) {}
 
   /// Return a textual description of the effect, and its condition, if any.
@@ -4932,6 +4938,78 @@ class FunctionEffectsRef {
   void dump(llvm::raw_ostream &OS) const;
 };
 
+/// A mutable set of FunctionEffect::Kind.
+class FunctionEffectKindSet {
+  // For now this only needs to be a bitmap.
+  constexpr static size_t EndBitPos = 8;
+  using KindBitsT = std::bitset<EndBitPos>;
+
+  KindBitsT KindBits{};
+
+  explicit FunctionEffectKindSet(KindBitsT KB) : KindBits(KB) {}
+
+  constexpr static size_t kindToPos(FunctionEffect::Kind K) {
+    return size_t(K);
+  }
+
+public:
+  FunctionEffectKindSet() = default;
+  explicit FunctionEffectKindSet(FunctionEffectsRef FX) { insert(FX); }
+
+  // Iterates through the bits which are set.
+  class iterator {
+    const FunctionEffectKindSet *Outer = nullptr;
+    size_t Idx = 0;
+
+    // If Idx does not reference a set bit, advance it until it does,
+    // or until it reaches EndBitPos.
+    void advanceToNextSetBit() {
+      while (Idx < EndBitPos && !Outer->KindBits.test(Idx))
+        ++Idx;
+    }
+
+  public:
+    iterator();
+    iterator(const FunctionEffectKindSet &O, size_t I) : Outer(&O), Idx(I) {
+      advanceToNextSetBit();
+    }
+    bool operator==(const iterator &Other) const { return Idx == Other.Idx; }
+    bool operator!=(const iterator &Other) const { return Idx != Other.Idx; }
+
+    iterator operator++() {
+      ++Idx;
+      advanceToNextSetBit();
+      return *this;
+    }
+
+    FunctionEffect operator*() const {
+      assert(Idx < EndBitPos);
+      return FunctionEffect(FunctionEffect::Kind(Idx));
+    }
+  };
+
+  iterator begin() const { return iterator(*this, 0); }
+  iterator end() const { return iterator(*this, EndBitPos); }
+
+  void insert(FunctionEffect Effect) { KindBits.set(kindToPos(Effect.kind())); }
+  void insert(FunctionEffectsRef FX) {
+    for (FunctionEffect Item : FX.effects())
+      insert(Item);
+  }
+  void insert(FunctionEffectKindSet Set) { KindBits |= Set.KindBits; }
+
+  bool empty() const { return KindBits.none(); }
+  bool contains(const FunctionEffect::Kind EK) const {
+    return KindBits.test(kindToPos(EK));
+  }
+  void dump(llvm::raw_ostream &OS) const;
+
+  static FunctionEffectKindSet difference(FunctionEffectKindSet LHS,
+                                          FunctionEffectKindSet RHS) {
+    return FunctionEffectKindSet(LHS.KindBits & ~RHS.KindBits);
+  }
+};
+
 /// A mutable set of FunctionEffects and possibly conditions attached to them.
 /// Used to compare and merge effects on declarations.
 ///

clang/include/clang/Basic/DiagnosticGroups.td

@@ -1557,6 +1557,7 @@ def UnsafeBufferUsage : DiagGroup<"unsafe-buffer-usage", [UnsafeBufferUsageInCon
 // Warnings and notes related to the function effects system underlying
 // the nonblocking and nonallocating attributes.
 def FunctionEffects : DiagGroup<"function-effects">;
+def PerfConstraintImpliesNoexcept : DiagGroup<"perf-constraint-implies-noexcept">;
 
 // Warnings and notes InstallAPI verification.
 def InstallAPIViolation : DiagGroup<"installapi-violation">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10950,6 +10950,51 @@ def warn_imp_cast_drops_unaligned : Warning<
   InGroup<DiagGroup<"unaligned-qualifier-implicit-cast">>;
 
 // Function effects
+def warn_func_effect_violation : Warning<
+  "'%0' %select{function|constructor|destructor|lambda|block|constructor's member initializer}1 "
+  "must not %select{allocate or deallocate memory|throw or catch exceptions|"
+  "have static local variables|use thread-local variables|access ObjC methods or properties}2">,
+  InGroup<FunctionEffects>;
+def note_func_effect_violation : Note<
+  "%select{function|constructor|destructor|lambda|block|member initializer}0 "
+  "cannot be inferred '%1' because it "
+  "%select{allocates or deallocates memory|throws or catches exceptions|"
+  "has a static local variable|uses a thread-local variable|"
+  "accesses an ObjC method or property}2">;
+def warn_func_effect_calls_func_without_effect : Warning<
+  "'%0' %select{function|constructor|destructor|lambda|block|constructor's member initializer}1 "
+  "must not call non-'%0' "
+  "%select{function|constructor|destructor|lambda|block}2 "
+  "'%3'">,
+  InGroup<FunctionEffects>;
+def note_func_effect_calls_func_without_effect : Note<
+  "%select{function|constructor|destructor|lambda|block|member initializer}0 "
+  "cannot be inferred '%1' because it calls non-'%1' "
+  "%select{function|constructor|destructor|lambda|block}2 "
+  "'%3'">;
+def warn_func_effect_calls_expr_without_effect : Warning<
+  "'%0' %select{function|constructor|destructor|lambda|block|constructor's member initializer}1 "
+  "must not call non-'%0' expression">,
+  InGroup<FunctionEffects>;
+def note_func_effect_call_extern : Note<
+  "declaration cannot be inferred '%0' because it has no definition in this translation unit">;
+def note_func_effect_call_disallows_inference : Note<
+  "%select{function|constructor|destructor|lambda|block}0 "
+  "does not permit inference of '%1' because it is declared '%2'">;
+def note_func_effect_call_indirect : Note<
+  "%select{virtual method|function pointer}0 cannot be inferred '%1'">;
+def warn_perf_constraint_implies_noexcept : Warning<
+  "'%0' function should be declared noexcept">,
+  InGroup<PerfConstraintImpliesNoexcept>;
+
+// FIXME: It would be nice if we could provide fuller template expansion notes.
+def note_func_effect_from_template : Note<
+  "in template expansion here">;
+def note_func_effect_in_constructor : Note<
+  "in%select{| implicit}0 constructor here">;
+def note_in_evaluating_default_argument : Note<
+  "in evaluating default argument here">;
+
 // spoofing nonblocking/nonallocating
 def warn_invalid_add_func_effects : Warning<
   "attribute '%0' should not be added via type conversion">,