[clang-tools-extra] Replace SmallSet with SmallPtrSet (NFC) (llvm#154365)

This patch replaces SmallSet<T *, N> with SmallPtrSet<T *, N>.  Note
that SmallSet.h "redirects" SmallSet to SmallPtrSet for pointer
element types:

  template <typename PointeeType, unsigned N>
class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N>
{};

We only have 10 instances that rely on this "redirection", with more
than half of them under clang-tools-extra/.  Since the redirection
doesn't improve readability, this patch replaces SmallSet with
SmallPtrSet for pointer element types.

I'm planning to remove the redirection eventually.

Author: kazutakahirata

clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp

@@ -188,7 +188,7 @@ static bool isKnownToHaveValue(const Expr &Cond, const ASTContext &Ctx,
 /// \return true iff all `CallExprs` visited have callees; false otherwise
 ///         indicating there is an unresolved indirect call.
 static bool populateCallees(const Stmt *StmtNode,
-                            llvm::SmallSet<const Decl *, 16> &Callees) {
+                            llvm::SmallPtrSet<const Decl *, 16> &Callees) {
   if (const auto *Call = dyn_cast<CallExpr>(StmtNode)) {
     const Decl *Callee = Call->getDirectCallee();
 
@@ -212,7 +212,7 @@ static bool populateCallees(const Stmt *StmtNode,
 /// returns true iff `SCC` contains `Func` and its' function set overlaps with
 /// `Callees`
 static bool overlap(ArrayRef<CallGraphNode *> SCC,
-                    const llvm::SmallSet<const Decl *, 16> &Callees,
+                    const llvm::SmallPtrSet<const Decl *, 16> &Callees,
                     const Decl *Func) {
   bool ContainsFunc = false, Overlap = false;
 
@@ -264,7 +264,7 @@ static bool hasRecursionOverStaticLoopCondVariables(const Expr *Cond,
   if (!hasStaticLocalVariable(Cond))
     return false;
 
-  llvm::SmallSet<const Decl *, 16> CalleesInLoop;
+  llvm::SmallPtrSet<const Decl *, 16> CalleesInLoop;
 
   if (!populateCallees(LoopStmt, CalleesInLoop)) {
     // If there are unresolved indirect calls, we assume there could

clang-tools-extra/clangd/AST.cpp

@@ -985,7 +985,7 @@ resolveForwardingParameters(const FunctionDecl *D, unsigned MaxDepth) {
     // Recurse on pack parameters
     size_t Depth = 0;
     const FunctionDecl *CurrentFunction = D;
-    llvm::SmallSet<const FunctionTemplateDecl *, 4> SeenTemplates;
+    llvm::SmallPtrSet<const FunctionTemplateDecl *, 4> SeenTemplates;
     if (const auto *Template = D->getPrimaryTemplate()) {
       SeenTemplates.insert(Template);
     }

clang-tools-extra/clangd/XRefs.cpp

@@ -1876,7 +1876,7 @@ static void fillSubTypes(const SymbolID &ID,
   });
 }
 
-using RecursionProtectionSet = llvm::SmallSet<const CXXRecordDecl *, 4>;
+using RecursionProtectionSet = llvm::SmallPtrSet<const CXXRecordDecl *, 4>;
 
 // Extracts parents from AST and populates the type hierarchy item.
 static void fillSuperTypes(const CXXRecordDecl &CXXRD, llvm::StringRef TUPath,

clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp

@@ -181,7 +181,7 @@ struct ExtractionZone {
   bool requiresHoisting(const SourceManager &SM,
                         const HeuristicResolver *Resolver) const {
     // First find all the declarations that happened inside extraction zone.
-    llvm::SmallSet<const Decl *, 1> DeclsInExtZone;
+    llvm::SmallPtrSet<const Decl *, 1> DeclsInExtZone;
     for (auto *RootStmt : RootStmts) {
       findExplicitReferences(
           RootStmt,