Speed up check by using a recursive visitor.

[sbenza]

Summary

Use a recursive visitor instead of forEachDescendant() matcher.
The latter requires several layers of virtual function calls for each node and
it is more expensive than the visitor.
Benchmark results show improvement of ~6% walltime in clang-tidy.

[alexfh]

LG. Thank you!

clang-tidy/readability/FunctionSizeCheck.cpp

25

nit: clang-format -style=file

[sbenza]

Reformat code

clang-tidy/readability/FunctionSizeCheck.h

 ///     statements. The default is `-1` (ignore the number of branches).
 class FunctionSizeCheck : public ClangTidyCheck {
 public:
   FunctionSizeCheck(StringRef Name, ClangTidyContext *Context);
 
   void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
-  void onEndOfTranslationUnit() override;
 
 private:
-  struct FunctionInfo {
-    FunctionInfo() : Lines(0), Statements(0), Branches(0) {}
-    unsigned Lines;
-    unsigned Statements;
-    unsigned Branches;
-  };
-
   const unsigned LineThreshold;
   const unsigned StatementThreshold;
   const unsigned BranchThreshold;
-
-  llvm::DenseMap<const FunctionDecl *, FunctionInfo> FunctionInfos;
 };
 
 } // namespace readability
 } // namespace tidy
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_FUNCTIONSIZECHECK_H

clang-tidy/readability/FunctionSizeCheck.cpp

 //===--- FunctionSize.cpp - clang-tidy ------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "FunctionSizeCheck.h"
+#include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace readability {
 
+class FunctionASTVisitor : public RecursiveASTVisitor<FunctionASTVisitor> {
+  using Base = RecursiveASTVisitor<FunctionASTVisitor>;
+
+public:
+  bool TraverseStmt(Stmt *Node) {
+    if (!Node)
+      return Base::TraverseStmt(Node);
+
+    if (TrackedParent.back() && !isa<CompoundStmt>(Node))
+      ++Info.Statements;
+
+    switch (Node->getStmtClass()) {
+    case Stmt::IfStmtClass:
+    case Stmt::WhileStmtClass:
+    case Stmt::DoStmtClass:
+    case Stmt::CXXForRangeStmtClass:
+    case Stmt::ForStmtClass:
+    case Stmt::SwitchStmtClass:
+      ++Info.Branches;
+    // fallthrough
+    case Stmt::CompoundStmtClass:
+      TrackedParent.push_back(true);
+      break;
+    default:
+      TrackedParent.push_back(false);
+      break;
+    }
+
+    Base::TraverseStmt(Node);
+
+    TrackedParent.pop_back();
+    return true;
+  }
+
+  bool TraverseDecl(Decl *Node) {
+    TrackedParent.push_back(false);
+    Base::TraverseDecl(Node);
+    TrackedParent.pop_back();
+    return true;
+  }
+
+  struct FunctionInfo {
+    FunctionInfo() : Lines(0), Statements(0), Branches(0) {}
+    unsigned Lines;
+    unsigned Statements;
+    unsigned Branches;
+  };
+  FunctionInfo Info;
+  std::vector<bool> TrackedParent;
+};
+
 FunctionSizeCheck::FunctionSizeCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
       LineThreshold(Options.get("LineThreshold", -1U)),
       StatementThreshold(Options.get("StatementThreshold", 800U)),
       BranchThreshold(Options.get("BranchThreshold", -1U)) {}
 
 void FunctionSizeCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "LineThreshold", LineThreshold);
   Options.store(Opts, "StatementThreshold", StatementThreshold);
   Options.store(Opts, "BranchThreshold", BranchThreshold);
 }
 
 void FunctionSizeCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(
-      functionDecl(
-          unless(isInstantiated()),
-          forEachDescendant(
-              stmt(unless(compoundStmt()),
-                   hasParent(stmt(anyOf(compoundStmt(), ifStmt(),
-                                        anyOf(whileStmt(), doStmt(),
-                                              cxxForRangeStmt(), forStmt())))))
-                  .bind("stmt"))).bind("func"),
-      this);
+  Finder->addMatcher(functionDecl(unless(isInstantiated())).bind("func"), this);
 }
 
 void FunctionSizeCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
 
-  FunctionInfo &FI = FunctionInfos[Func];
+  FunctionASTVisitor Visitor;
+  Visitor.TraverseDecl(const_cast<FunctionDecl *>(Func));
+  auto &FI = Visitor.Info;
+
+  if (FI.Statements == 0)
+    return;
 
   // Count the lines including whitespace and comments. Really simple.
-  if (!FI.Lines) {
-    if (const Stmt *Body = Func->getBody()) {
-      SourceManager *SM = Result.SourceManager;
-      if (SM->isWrittenInSameFile(Body->getLocStart(), Body->getLocEnd())) {
-        FI.Lines = SM->getSpellingLineNumber(Body->getLocEnd()) -
-                   SM->getSpellingLineNumber(Body->getLocStart());
-      }
-    }
-  }
-
-  const auto *Statement = Result.Nodes.getNodeAs<Stmt>("stmt");
-  ++FI.Statements;
-
-  // TODO: switch cases, gotos
-  if (isa<IfStmt>(Statement) || isa<WhileStmt>(Statement) ||
-      isa<ForStmt>(Statement) || isa<SwitchStmt>(Statement) ||
-      isa<DoStmt>(Statement) || isa<CXXForRangeStmt>(Statement))
-    ++FI.Branches;
-}
 
-void FunctionSizeCheck::onEndOfTranslationUnit() {
-  // If we're above the limit emit a warning.
-  for (const auto &P : FunctionInfos) {
-    const FunctionInfo &FI = P.second;
-    if (FI.Lines > LineThreshold || FI.Statements > StatementThreshold ||
-        FI.Branches > BranchThreshold) {
-      diag(P.first->getLocation(),
-           "function %0 exceeds recommended size/complexity thresholds")
-          << P.first;
-    }
+    diag(Func->getLocation(),
+        << Func;
 
-    if (FI.Lines > LineThreshold) {
-      diag(P.first->getLocation(),
-           "%0 lines including whitespace and comments (threshold %1)",
-           DiagnosticIDs::Note)
-          << FI.Lines << LineThreshold;
-    }
+    diag(Func->getLocation(),
 
-    if (FI.Statements > StatementThreshold) {
-      diag(P.first->getLocation(), "%0 statements (threshold %1)",
-           DiagnosticIDs::Note)
-          << FI.Statements << StatementThreshold;
-    }
+    diag(Func->getLocation(), "%0 statements (threshold %1)",
 
-    if (FI.Branches > BranchThreshold) {
-      diag(P.first->getLocation(), "%0 branches (threshold %1)",
-           DiagnosticIDs::Note)
-          << FI.Branches << BranchThreshold;
-    }
-  }
+    diag(Func->getLocation(), "%0 branches (threshold %1)", DiagnosticIDs::Note)
 
-  FunctionInfos.clear();
-}
-
 } // namespace readability
 } // namespace tidy
 } // namespace clang