[clang-tidy] Optimize misc-confusable-identifiers

Main performance issue in this check were caused by many
calls to getPrimaryContext and constant walk up to declaration
contexts using getParent. Also there were issue with forallBases
that is slow.

Profiled with perf and tested on open-source project Cataclysm-DDA.
Before changes check took 27320 seconds, after changes 3682 seconds.
That's 86.5% reduction. More optimizations are still possible in this
check.

Reviewed By: serge-sans-paille

Differential Revision: https://reviews.llvm.org/D151051

Author: PiotrZSL

clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.cpp

@@ -45,7 +45,7 @@ ConfusableIdentifierCheck::~ConfusableIdentifierCheck() = default;
 // We're skipping 1. and 3. for the sake of simplicity, but this can lead to
 // false positive.
 
-std::string ConfusableIdentifierCheck::skeleton(StringRef Name) {
+static std::string skeleton(StringRef Name) {
   using namespace llvm;
   std::string SName = Name.str();
   std::string Skeleton;
@@ -89,75 +89,107 @@ std::string ConfusableIdentifierCheck::skeleton(StringRef Name) {
   return Skeleton;
 }
 
-static bool mayShadowImpl(const NamedDecl *ND0, const NamedDecl *ND1) {
-  const DeclContext *DC0 = ND0->getDeclContext()->getPrimaryContext();
-  const DeclContext *DC1 = ND1->getDeclContext()->getPrimaryContext();
+static bool mayShadowImpl(const DeclContext *DC0, const DeclContext *DC1) {
+  return DC0 && DC0 == DC1;
+}
 
-  if (isa<TemplateTypeParmDecl>(ND0) || isa<TemplateTypeParmDecl>(ND0))
-    return true;
+static bool mayShadowImpl(const NamedDecl *ND0, const NamedDecl *ND1) {
+  return isa<TemplateTypeParmDecl>(ND0) || isa<TemplateTypeParmDecl>(ND1);
+}
 
-  while (DC0->isTransparentContext())
-    DC0 = DC0->getParent();
-  while (DC1->isTransparentContext())
-    DC1 = DC1->getParent();
+static bool isMemberOf(const ConfusableIdentifierCheck::ContextInfo *DC0,
+                       const ConfusableIdentifierCheck::ContextInfo *DC1) {
+  if (DC0->Bases.empty())
+    return false;
+  return llvm::is_contained(DC1->Bases, DC0->PrimaryContext);
+}
 
-  if (DC0->Equals(DC1))
+static bool enclosesContext(const ConfusableIdentifierCheck::ContextInfo *DC0,
+                            const ConfusableIdentifierCheck::ContextInfo *DC1) {
+  if (DC0->PrimaryContext == DC1->PrimaryContext)
     return true;
 
-  return false;
+  return llvm::is_contained(DC0->PrimaryContexts, DC1->PrimaryContext) ||
+         llvm::is_contained(DC1->PrimaryContexts, DC0->PrimaryContext);
 }
 
-static bool isMemberOf(const NamedDecl *ND, const CXXRecordDecl *RD) {
-  const DeclContext *NDParent = ND->getDeclContext();
-  if (!NDParent || !isa<CXXRecordDecl>(NDParent))
-    return false;
-  if (NDParent == RD)
+static bool mayShadow(const NamedDecl *ND0,
+                      const ConfusableIdentifierCheck::ContextInfo *DC0,
+                      const NamedDecl *ND1,
+                      const ConfusableIdentifierCheck::ContextInfo *DC1) {
+  if (!DC0->Bases.empty() && ND1->getAccess() != AS_private &&
+      isMemberOf(DC1, DC0))
     return true;
-  return !RD->forallBases(
-      [NDParent](const CXXRecordDecl *Base) { return NDParent != Base; });
+  if (!DC1->Bases.empty() && ND0->getAccess() != AS_private &&
+      isMemberOf(DC0, DC1))
+    return true;
+
+  return enclosesContext(DC0, DC1) &&
+         (mayShadowImpl(ND0, ND1) || mayShadowImpl(DC0->NonTransparentContext,
+                                                   DC1->NonTransparentContext));
 }
 
-static bool mayShadow(const NamedDecl *ND0, const NamedDecl *ND1) {
+const ConfusableIdentifierCheck::ContextInfo *
+ConfusableIdentifierCheck::getContextInfo(const DeclContext *DC) {
+  const DeclContext *PrimaryContext = DC->getPrimaryContext();
+  auto It = ContextInfos.find(PrimaryContext);
+  if (It != ContextInfos.end())
+    return &It->second;
+
+  ContextInfo &Info = ContextInfos[PrimaryContext];
+  Info.PrimaryContext = PrimaryContext;
+  Info.NonTransparentContext = PrimaryContext;
+
+  while (Info.NonTransparentContext->isTransparentContext()) {
+    Info.NonTransparentContext = Info.NonTransparentContext->getParent();
+    if (!Info.NonTransparentContext)
+      break;
+  }
 
-  const DeclContext *DC0 = ND0->getDeclContext()->getPrimaryContext();
-  const DeclContext *DC1 = ND1->getDeclContext()->getPrimaryContext();
+  if (Info.NonTransparentContext)
+    Info.NonTransparentContext =
+        Info.NonTransparentContext->getPrimaryContext();
 
-  if (const CXXRecordDecl *RD0 = dyn_cast<CXXRecordDecl>(DC0)) {
-    RD0 = RD0->getDefinition();
-    if (RD0 && ND1->getAccess() != AS_private && isMemberOf(ND1, RD0))
-      return true;
+  while (DC) {
+    if (!isa<LinkageSpecDecl>(DC) && !isa<ExportDecl>(DC))
+      Info.PrimaryContexts.push_back(DC->getPrimaryContext());
+    DC = DC->getParent();
   }
-  if (const CXXRecordDecl *RD1 = dyn_cast<CXXRecordDecl>(DC1)) {
-    RD1 = RD1->getDefinition();
-    if (RD1 && ND0->getAccess() != AS_private && isMemberOf(ND0, RD1))
-      return true;
+
+  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(PrimaryContext)) {
+    RD = RD->getDefinition();
+    if (RD) {
+      Info.Bases.push_back(RD);
+      RD->forallBases([&](const CXXRecordDecl *Base) {
+        Info.Bases.push_back(Base);
+        return false;
+      });
+    }
   }
 
-  if (DC0->Encloses(DC1))
-    return mayShadowImpl(ND0, ND1);
-  if (DC1->Encloses(DC0))
-    return mayShadowImpl(ND1, ND0);
-  return false;
+  return &Info;
 }
 
 void ConfusableIdentifierCheck::check(
     const ast_matchers::MatchFinder::MatchResult &Result) {
   if (const auto *ND = Result.Nodes.getNodeAs<NamedDecl>("nameddecl")) {
     if (IdentifierInfo *NDII = ND->getIdentifier()) {
+      const ContextInfo *Info = getContextInfo(ND->getDeclContext());
       StringRef NDName = NDII->getName();
-      llvm::SmallVector<const NamedDecl *> &Mapped = Mapper[skeleton(NDName)];
-      for (const NamedDecl *OND : Mapped) {
-        const IdentifierInfo *ONDII = OND->getIdentifier();
-        if (mayShadow(ND, OND)) {
+      llvm::SmallVector<Entry> &Mapped = Mapper[skeleton(NDName)];
+      for (const Entry &E : Mapped) {
+        const IdentifierInfo *ONDII = E.Declaration->getIdentifier();
+        if (mayShadow(ND, Info, E.Declaration, E.Info)) {
           StringRef ONDName = ONDII->getName();
           if (ONDName != NDName) {
-            diag(ND->getLocation(), "%0 is confusable with %1") << ND << OND;
-            diag(OND->getLocation(), "other declaration found here",
+            diag(ND->getLocation(), "%0 is confusable with %1")
+                << ND << E.Declaration;
+            diag(E.Declaration->getLocation(), "other declaration found here",
                  DiagnosticIDs::Note);
           }
         }
       }
-      Mapped.push_back(ND);
+      Mapped.push_back({ND, Info});
     }
   }
 }

clang-tools-extra/clang-tidy/misc/ConfusableIdentifierCheck.h

@@ -11,6 +11,7 @@
 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MISC_CONFUSABLE_IDENTIFIER_CHECK_H
 
 #include "../ClangTidyCheck.h"
+#include <unordered_map>
 
 namespace clang::tidy::misc {
 
@@ -26,9 +27,23 @@ class ConfusableIdentifierCheck : public ClangTidyCheck {
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 
+  struct ContextInfo {
+    const DeclContext *PrimaryContext;
+    const DeclContext *NonTransparentContext;
+    llvm::SmallVector<const DeclContext *> PrimaryContexts;
+    llvm::SmallVector<const CXXRecordDecl *> Bases;
+  };
+
 private:
-  std::string skeleton(StringRef);
-  llvm::StringMap<llvm::SmallVector<const NamedDecl *>> Mapper;
+  struct Entry {
+    const NamedDecl *Declaration;
+    const ContextInfo *Info;
+  };
+
+  const ContextInfo *getContextInfo(const DeclContext *DC);
+
+  llvm::StringMap<llvm::SmallVector<Entry>> Mapper;
+  std::unordered_map<const DeclContext *, ContextInfo> ContextInfos;
 };
 
 } // namespace clang::tidy::misc