[clang] [alpha.webkit.UncountedCallArgsChecker] Detect & ignore trivial function calls. (PR #81808)

[Artem Dergachev via cfe-commits]

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@@ -222,4 +223,210 @@ bool isPtrConversion(const FunctionDecl *F) {
   return false;
 }
 
+bool isSingleton(const FunctionDecl *F) {
+  assert(F);
+  // FIXME: check # of params == 1
+  if (auto *MethodDecl = dyn_cast<CXXMethodDecl>(F)) {
+    if (!MethodDecl->isStatic())
+      return false;
+  }
+  const auto &Name = safeGetName(F);
+  std::string SingletonStr = "singleton";
+  auto index = Name.find(SingletonStr);
+  return index != std::string::npos &&
+         index == Name.size() - SingletonStr.size();
+}
+
+// We only care about statements so let's use the simple
+// (non-recursive) visitor.
+class TrivialFunctionAnalysisVisitor
+    : public ConstStmtVisitor<TrivialFunctionAnalysisVisitor, bool> {
+
+  // Returns false if at least one child is non-trivial.
+  bool VisitChildren(const Stmt *S) {
+    for (const Stmt *Child : S->children()) {
+      if (Child && !Visit(Child))
+        return false;
+    }
+
+    return true;
+  }
+
+public:
+  using CacheTy = TrivialFunctionAnalysis::CacheTy;
+
+  TrivialFunctionAnalysisVisitor(CacheTy &Cache) : Cache(Cache) {}
+
+  bool VisitStmt(const Stmt *S) {
+    // All statements are non-trivial unless overriden later.
+    // Don't even recurse into children by default.
+    return false;
+  }
+
+  bool VisitCompoundStmt(const CompoundStmt *CS) {
+    // A compound statement is allowed as long each individual sub-statement
+    // is trivial.
+    return VisitChildren(CS);
+  }
+
+  bool VisitReturnStmt(const ReturnStmt *RS) {
+    // A return statement is allowed as long as the return value is trivial.
+    return Visit(RS->getRetValue());
+  }
+
+  bool VisitDeclStmt(const DeclStmt *DS) { return VisitChildren(DS); }
+  bool VisitDoStmt(const DoStmt *DS) { return VisitChildren(DS); }
+  bool VisitIfStmt(const IfStmt *IS) { return VisitChildren(IS); }
+  bool VisitSwitchStmt(const SwitchStmt *SS) { return VisitChildren(SS); }
+  bool VisitCaseStmt(const CaseStmt *CS) { return VisitChildren(CS); }
+  bool VisitDefaultStmt(const DefaultStmt *DS) { return VisitChildren(DS); }
+
+  bool VisitUnaryOperator(const UnaryOperator *UO) {
+    // Operator '*' and '!' are allowed as long as the operand is trivial.
+    if (UO->getOpcode() == UO_Deref || UO->getOpcode() == UO_LNot)
+      return Visit(UO->getSubExpr());
+
+    // Other operators are non-trivial.
+    return false;
+  }
+
+  bool VisitBinaryOperator(const BinaryOperator *BO) {
+    // Binary operators are trivial if their operands are trivial.
+    return Visit(BO->getLHS()) && Visit(BO->getRHS());
+  }
+
+  bool VisitConditionalOperator(const ConditionalOperator *CO) {
+    // Ternary operators are trivial if their conditions & values are trivial.
+    return VisitChildren(CO);
+  }
+
+  bool VisitDeclRefExpr(const DeclRefExpr *DRE) {
+    if (auto *decl = DRE->getDecl()) {
+      if (isa<ParmVarDecl>(decl))
+        return true;
+    }
+    return false;
+  }
+
+  bool VisitStaticAssertDecl(const StaticAssertDecl *SAD) {
+    // Any static_assert is considered trivial.
+    return true;
+  }
+
+  bool VisitCallExpr(const CallExpr *CE) {
+    if (auto *MCE = dyn_cast<CXXMemberCallExpr>(CE))
+      return VisitCXXMemberCallExpr(MCE);
----------------
haoNoQ wrote:

This happens automatically, you don't need to do that manually. The visitor calls the most specialized user-defined method. (If it's not user-defined, it's defined by default to call the slightly less specialized method.)

On the other hand, it might make sense to call `VisitCallExpr()` from inside `VisitCXXMemberCallExpr()` to reuse some code. (Or you can define a common method called by both.)

https://github.com/llvm/llvm-project/pull/81808