[flang] Use SmallPtrSet directly instead of SmallSet (NFC)

I'm trying to remove the redirection in SmallSet.h:

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

to make it clear that we are using SmallPtrSet.  There are only
handful places that rely on this redirection.

This patch replaces SmallSet to SmallPtrSet where the element type is
a pointer.

Author: kazutakahirata

flang/include/flang/Lower/Support/Utils.h

@@ -101,7 +101,7 @@ void privatizeSymbol(
     lower::AbstractConverter &converter, fir::FirOpBuilder &firOpBuilder,
     lower::SymMap &symTable,
     llvm::SetVector<const semantics::Symbol *> &allPrivatizedSymbols,
-    llvm::SmallSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
+    llvm::SmallPtrSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
     const semantics::Symbol *symToPrivatize, OperandsStructType *clauseOps);
 
 } // end namespace Fortran::lower

flang/lib/Lower/Bridge.cpp

@@ -2066,7 +2066,8 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     // complete.
     bool useDelayedPriv = enableDelayedPrivatization && doConcurrentLoopOp;
     llvm::SetVector<const Fortran::semantics::Symbol *> allPrivatizedSymbols;
-    llvm::SmallSet<const Fortran::semantics::Symbol *, 16> mightHaveReadHostSym;
+    llvm::SmallPtrSet<const Fortran::semantics::Symbol *, 16>
+        mightHaveReadHostSym;
 
     for (const Fortran::semantics::Symbol *symToPrivatize : info.localSymList) {
       if (useDelayedPriv) {

flang/lib/Lower/OpenMP/DataSharingProcessor.h

@@ -107,7 +107,7 @@ class DataSharingProcessor {
   lower::pft::Evaluation &eval;
   bool shouldCollectPreDeterminedSymbols;
   bool useDelayedPrivatization;
-  llvm::SmallSet<const semantics::Symbol *, 16> mightHaveReadHostSym;
+  llvm::SmallPtrSet<const semantics::Symbol *, 16> mightHaveReadHostSym;
   lower::SymMap &symTable;
   bool isTargetPrivatization;
   OMPConstructSymbolVisitor visitor;

flang/lib/Lower/PFTBuilder.cpp

@@ -1742,11 +1742,11 @@ struct SymbolDependenceAnalysis {
                                layeredVarList[i].end());
   }
 
-  llvm::SmallSet<const semantics::Symbol *, 32> seen;
+  llvm::SmallPtrSet<const semantics::Symbol *, 32> seen;
   std::vector<Fortran::lower::pft::VariableList> layeredVarList;
-  llvm::SmallSet<const semantics::Symbol *, 32> aliasSyms;
+  llvm::SmallPtrSet<const semantics::Symbol *, 32> aliasSyms;
   /// Set of scopes that have been analyzed for aliases.
-  llvm::SmallSet<const semantics::Scope *, 4> analyzedScopes;
+  llvm::SmallPtrSet<const semantics::Scope *, 4> analyzedScopes;
   std::vector<Fortran::lower::pft::Variable::AggregateStore> stores;
 };
 } // namespace

flang/lib/Lower/Support/Utils.cpp

@@ -654,7 +654,7 @@ void privatizeSymbol(
     lower::AbstractConverter &converter, fir::FirOpBuilder &firOpBuilder,
     lower::SymMap &symTable,
     llvm::SetVector<const semantics::Symbol *> &allPrivatizedSymbols,
-    llvm::SmallSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
+    llvm::SmallPtrSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
     const semantics::Symbol *symToPrivatize, OperandsStructType *clauseOps) {
   constexpr bool isDoConcurrent =
       std::is_same_v<OpType, fir::LocalitySpecifierOp>;
@@ -846,7 +846,7 @@ privatizeSymbol<mlir::omp::PrivateClauseOp, mlir::omp::PrivateClauseOps>(
     lower::AbstractConverter &converter, fir::FirOpBuilder &firOpBuilder,
     lower::SymMap &symTable,
     llvm::SetVector<const semantics::Symbol *> &allPrivatizedSymbols,
-    llvm::SmallSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
+    llvm::SmallPtrSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
     const semantics::Symbol *symToPrivatize,
     mlir::omp::PrivateClauseOps *clauseOps);
 
@@ -855,7 +855,7 @@ privatizeSymbol<fir::LocalitySpecifierOp, fir::LocalitySpecifierOperands>(
     lower::AbstractConverter &converter, fir::FirOpBuilder &firOpBuilder,
     lower::SymMap &symTable,
     llvm::SetVector<const semantics::Symbol *> &allPrivatizedSymbols,
-    llvm::SmallSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
+    llvm::SmallPtrSet<const semantics::Symbol *, 16> &mightHaveReadHostSym,
     const semantics::Symbol *symToPrivatize,
     fir::LocalitySpecifierOperands *clauseOps);
 

flang/lib/Optimizer/HLFIR/Transforms/LowerHLFIROrderedAssignments.cpp

@@ -96,7 +96,7 @@ struct MaskedArrayExpr {
   /// hlfir.elemental_addr that form the elemental tree producing
   /// the expression value. hlfir.elemental that produce values
   /// used inside transformational operations are not part of this set.
-  llvm::SmallSet<mlir::Operation *, 4> elementalParts{};
+  llvm::SmallPtrSet<mlir::Operation *, 4> elementalParts{};
   /// Was generateNoneElementalPart called?
   bool noneElementalPartWasGenerated = false;
   /// Is this expression the mask expression of the outer where statement?

flang/lib/Optimizer/HLFIR/Transforms/ScheduleOrderedAssignments.cpp

@@ -137,7 +137,7 @@ class Scheduler {
   // Schedule being built.
   hlfir::Schedule schedule;
   /// Leaf regions that have been saved so far.
-  llvm::SmallSet<mlir::Region *, 16> savedRegions;
+  llvm::SmallPtrSet<mlir::Region *, 16> savedRegions;
   /// Is schedule.back() a schedule that is only saving region with read
   /// effects?
   bool currentRunIsReadOnly = false;