diff --git a/flang/lib/Lower/IO.cpp b/flang/lib/Lower/IO.cpp
--- a/flang/lib/Lower/IO.cpp
+++ b/flang/lib/Lower/IO.cpp
@@ -161,7 +161,7 @@
 static mlir::func::FuncOp getIORuntimeFunc(mlir::Location loc,
                                            fir::FirOpBuilder &builder) {
   llvm::StringRef name = getName<E>();
-  auto func = builder.getNamedFunction(name);
+  mlir::func::FuncOp func = builder.getNamedFunction(name);
   if (func)
     return func;
   auto funTy = getTypeModel<E>()(builder.getContext());
@@ -179,7 +179,8 @@
                             Fortran::lower::StatementContext &stmtCtx) {
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
   if (csi.ioMsg) {
-    auto getIoMsg = getIORuntimeFunc<mkIOKey(GetIoMsg)>(loc, builder);
+    mlir::func::FuncOp getIoMsg =
+        getIORuntimeFunc<mkIOKey(GetIoMsg)>(loc, builder);
     builder.create<fir::CallOp>(
         loc, getIoMsg,
         mlir::ValueRange{
@@ -189,7 +190,8 @@
             builder.createConvert(loc, getIoMsg.getFunctionType().getInput(2),
                                   fir::getLen(*csi.ioMsg))});
   }
-  auto endIoStatement = getIORuntimeFunc<mkIOKey(EndIoStatement)>(loc, builder);
+  mlir::func::FuncOp endIoStatement =
+      getIORuntimeFunc<mkIOKey(EndIoStatement)>(loc, builder);
   auto call = builder.create<fir::CallOp>(loc, endIoStatement,
                                           mlir::ValueRange{cookie});
   mlir::Value iostat = call.getResult(0);
@@ -478,7 +480,8 @@
     if (!expr)
       fir::emitFatalError(loc, "internal error: could not get evaluate::Expr");
     mlir::Type itemTy = converter.genType(*expr);
-    auto outputFunc = getOutputFunc(loc, builder, itemTy, isFormatted);
+    mlir::func::FuncOp outputFunc =
+        getOutputFunc(loc, builder, itemTy, isFormatted);
     mlir::Type argType = outputFunc.getFunctionType().getInput(1);
     assert((isFormatted || argType.isa<fir::BoxType>()) &&
            "expect descriptor for unformatted IO runtime");
@@ -625,7 +628,7 @@
     if (Fortran::evaluate::HasVectorSubscript(*expr)) {
       auto vectorSubscriptBox =
           Fortran::lower::genVectorSubscriptBox(loc, converter, stmtCtx, *expr);
-      auto inputFunc = getInputFunc(
+      mlir::func::FuncOp inputFunc = getInputFunc(
           loc, builder, vectorSubscriptBox.getElementType(), isFormatted);
       const bool mustBox =
           inputFunc.getFunctionType().getInput(1).isa<fir::BoxType>();
@@ -651,7 +654,8 @@
       continue;
     }
     mlir::Type itemTy = converter.genType(*expr);
-    auto inputFunc = getInputFunc(loc, builder, itemTy, isFormatted);
+    mlir::func::FuncOp inputFunc =
+        getInputFunc(loc, builder, itemTy, isFormatted);
     auto itemExv = inputFunc.getFunctionType().getInput(1).isa<fir::BoxType>()
                        ? converter.genExprBox(loc, *expr, stmtCtx)
                        : converter.genExprAddr(loc, expr, stmtCtx);
@@ -873,7 +877,7 @@
                            const B &spec) {
   Fortran::lower::StatementContext localStatementCtx;
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-  auto ioFunc = getIORuntimeFunc<A>(loc, builder);
+  mlir::func::FuncOp ioFunc = getIORuntimeFunc<A>(loc, builder);
   mlir::FunctionType ioFuncTy = ioFunc.getFunctionType();
   mlir::Value expr = fir::getBase(converter.genExprValue(
       loc, Fortran::semantics::GetExpr(spec.v), localStatementCtx));
@@ -890,7 +894,7 @@
                             const B &spec) {
   Fortran::lower::StatementContext localStatementCtx;
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-  auto ioFunc = getIORuntimeFunc<A>(loc, builder);
+  mlir::func::FuncOp ioFunc = getIORuntimeFunc<A>(loc, builder);
   mlir::FunctionType ioFuncTy = ioFunc.getFunctionType();
   std::tuple<mlir::Value, mlir::Value, mlir::Value> tup =
       lowerStringLit(converter, loc, localStatementCtx, spec,
@@ -922,7 +926,7 @@
   Fortran::lower::StatementContext localStatementCtx;
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
   // has an extra KIND argument
-  auto ioFunc = getIORuntimeFunc<mkIOKey(SetFile)>(loc, builder);
+  mlir::func::FuncOp ioFunc = getIORuntimeFunc<mkIOKey(SetFile)>(loc, builder);
   mlir::FunctionType ioFuncTy = ioFunc.getFunctionType();
   std::tuple<mlir::Value, mlir::Value, mlir::Value> tup =
       lowerStringLit(converter, loc, localStatementCtx, spec,
@@ -1093,7 +1097,8 @@
             std::get_if<Fortran::parser::IoControlSpec::Size>(&spec.u)) {
 
       fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-      auto ioFunc = getIORuntimeFunc<mkIOKey(GetSize)>(loc, builder);
+      mlir::func::FuncOp ioFunc =
+          getIORuntimeFunc<mkIOKey(GetSize)>(loc, builder);
       auto sizeValue =
           builder.create<fir::CallOp>(loc, ioFunc, mlir::ValueRange{cookie})
               .getResult(0);
@@ -1218,7 +1223,8 @@
   if (!csi.hasAnyConditionSpec())
     return;
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-  auto enableHandlers = getIORuntimeFunc<mkIOKey(EnableHandlers)>(loc, builder);
+  mlir::func::FuncOp enableHandlers =
+      getIORuntimeFunc<mkIOKey(EnableHandlers)>(loc, builder);
   mlir::Type boolType = enableHandlers.getFunctionType().getInput(1);
   auto boolValue = [&](bool specifierIsPresent) {
     return builder.create<mlir::arith::ConstantOp>(
@@ -1549,7 +1555,7 @@
   // overflow when passed to the IO runtime, check that the unit number is
   // in range before calling the BeginXXX.
   if (rawUnitWidth > runtimeArgWidth) {
-    auto check =
+    mlir::func::FuncOp check =
         rawUnitWidth <= 64
             ? getIORuntimeFunc<mkIOKey(CheckUnitNumberInRange64)>(loc, builder)
             : getIORuntimeFunc<mkIOKey(CheckUnitNumberInRange128)>(loc,
@@ -1625,7 +1631,7 @@
   Fortran::lower::StatementContext stmtCtx;
   mlir::Location loc = converter.getCurrentLocation();
   ConditionSpecInfo csi = lowerErrorSpec(converter, loc, stmt.v);
-  auto beginFunc = getIORuntimeFunc<K>(loc, builder);
+  mlir::func::FuncOp beginFunc = getIORuntimeFunc<K>(loc, builder);
   mlir::FunctionType beginFuncTy = beginFunc.getFunctionType();
   mlir::Value unit = genIOUnitNumber(
       converter, loc, getExpr<Fortran::parser::FileUnitNumber>(stmt),
@@ -1678,7 +1684,8 @@
             std::get_if<Fortran::parser::ConnectSpec::Newunit>(&spec.u)) {
       Fortran::lower::StatementContext stmtCtx;
       fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-      auto ioFunc = getIORuntimeFunc<mkIOKey(GetNewUnit)>(loc, builder);
+      mlir::func::FuncOp ioFunc =
+          getIORuntimeFunc<mkIOKey(GetNewUnit)>(loc, builder);
       mlir::FunctionType ioFuncTy = ioFunc.getFunctionType();
       const auto *var = Fortran::semantics::GetExpr(newunit->v);
       mlir::Value addr = builder.createConvert(
@@ -1745,9 +1752,9 @@
   mlir::Location loc = converter.getCurrentLocation();
   ConditionSpecInfo csi = lowerErrorSpec(converter, loc, stmt.v);
   bool hasId = hasSpec<Fortran::parser::IdExpr>(stmt);
-  auto beginFunc = hasId
-                       ? getIORuntimeFunc<mkIOKey(BeginWait)>(loc, builder)
-                       : getIORuntimeFunc<mkIOKey(BeginWaitAll)>(loc, builder);
+  mlir::func::FuncOp beginFunc =
+      hasId ? getIORuntimeFunc<mkIOKey(BeginWait)>(loc, builder)
+            : getIORuntimeFunc<mkIOKey(BeginWaitAll)>(loc, builder);
   mlir::FunctionType beginFuncTy = beginFunc.getFunctionType();
   mlir::Value unit = genIOUnitNumber(
       converter, loc, getExpr<Fortran::parser::FileUnitNumber>(stmt),
@@ -1913,9 +1920,9 @@
   }
 
   // Generate the begin data transfer function call.
-  auto ioFunc = getBeginDataTransferFunc<isInput>(loc, builder, isFormatted,
-                                                  isList || isNml, isInternal,
-                                                  isInternalWithDesc, isAsync);
+  mlir::func::FuncOp ioFunc = getBeginDataTransferFunc<isInput>(
+      loc, builder, isFormatted, isList || isNml, isInternal,
+      isInternalWithDesc, isAsync);
   llvm::SmallVector<mlir::Value> ioArgs;
   genBeginDataTransferCallArgs<hasIOCtrl>(
       ioArgs, converter, loc, stmt, ioFunc.getFunctionType(), isFormatted,
@@ -2026,7 +2033,8 @@
       Fortran::parser::InquireSpec::CharVar::Kind::Iomsg)
     return {};
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-  auto specFunc = getIORuntimeFunc<mkIOKey(InquireCharacter)>(loc, builder);
+  mlir::func::FuncOp specFunc =
+      getIORuntimeFunc<mkIOKey(InquireCharacter)>(loc, builder);
   mlir::FunctionType specFuncTy = specFunc.getFunctionType();
   const auto *varExpr = Fortran::semantics::GetExpr(
       std::get<Fortran::parser::ScalarDefaultCharVariable>(var.t));
@@ -2055,7 +2063,8 @@
       Fortran::parser::InquireSpec::IntVar::Kind::Iostat)
     return {};
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
-  auto specFunc = getIORuntimeFunc<mkIOKey(InquireInteger64)>(loc, builder);
+  mlir::func::FuncOp specFunc =
+      getIORuntimeFunc<mkIOKey(InquireInteger64)>(loc, builder);
   mlir::FunctionType specFuncTy = specFunc.getFunctionType();
   const auto *varExpr = Fortran::semantics::GetExpr(
       std::get<Fortran::parser::ScalarIntVariable>(var.t));
@@ -2091,7 +2100,7 @@
   bool pendId =
       idExpr &&
       logVarKind == Fortran::parser::InquireSpec::LogVar::Kind::Pending;
-  auto specFunc =
+  mlir::func::FuncOp specFunc =
       pendId ? getIORuntimeFunc<mkIOKey(InquirePendingId)>(loc, builder)
              : getIORuntimeFunc<mkIOKey(InquireLogical)>(loc, builder);
   mlir::FunctionType specFuncTy = specFunc.getFunctionType();
diff --git a/flang/lib/Lower/Mangler.cpp b/flang/lib/Lower/Mangler.cpp
--- a/flang/lib/Lower/Mangler.cpp
+++ b/flang/lib/Lower/Mangler.cpp
@@ -57,12 +57,13 @@
 
 static const Fortran::semantics::Symbol *
 findInterfaceIfSeperateMP(const Fortran::semantics::Symbol &symbol) {
-  const auto &scope = symbol.owner();
+  const Fortran::semantics::Scope &scope = symbol.owner();
   if (symbol.attrs().test(Fortran::semantics::Attr::MODULE) &&
       scope.IsSubmodule()) {
     // FIXME symbol from MpSubprogramStmt do not seem to have
     // Attr::MODULE set.
-    const auto *iface = scope.parent().FindSymbol(symbol.name());
+    const Fortran::semantics::Symbol *iface =
+        scope.parent().FindSymbol(symbol.name());
     assert(iface && "Separate module procedure must be declared");
     return iface;
   }
@@ -108,10 +109,11 @@
             // Separate module subprograms must be mangled according to the
             // scope where they were declared (the symbol we have is the
             // definition).
-            const auto *interface = &ultimateSymbol;
+            const Fortran::semantics::Symbol *interface = &ultimateSymbol;
             if (const auto *mpIface = findInterfaceIfSeperateMP(ultimateSymbol))
               interface = mpIface;
-            auto modNames = moduleNames(*interface);
+            llvm::SmallVector<llvm::StringRef> modNames =
+                moduleNames(*interface);
             return fir::NameUniquer::doProcedure(modNames, hostName(*interface),
                                                  symbolName);
           },
@@ -129,16 +131,18 @@
                                                  symbolName);
           },
           [&](const Fortran::semantics::ObjectEntityDetails &) {
-            auto modNames = moduleNames(ultimateSymbol);
-            auto optHost = hostName(ultimateSymbol);
+            llvm::SmallVector<llvm::StringRef> modNames =
+                moduleNames(ultimateSymbol);
+            llvm::Optional<llvm::StringRef> optHost = hostName(ultimateSymbol);
             if (Fortran::semantics::IsNamedConstant(ultimateSymbol))
               return fir::NameUniquer::doConstant(modNames, optHost,
                                                   symbolName);
             return fir::NameUniquer::doVariable(modNames, optHost, symbolName);
           },
           [&](const Fortran::semantics::NamelistDetails &) {
-            auto modNames = moduleNames(ultimateSymbol);
-            auto optHost = hostName(ultimateSymbol);
+            llvm::SmallVector<llvm::StringRef> modNames =
+                moduleNames(ultimateSymbol);
+            llvm::Optional<llvm::StringRef> optHost = hostName(ultimateSymbol);
             return fir::NameUniquer::doNamelistGroup(modNames, optHost,
                                                      symbolName);
           },
@@ -159,21 +163,25 @@
 std::string Fortran::lower::mangle::mangleName(
     const Fortran::semantics::DerivedTypeSpec &derivedType) {
   // Resolve host and module association before mangling
-  const auto &ultimateSymbol = derivedType.typeSymbol().GetUltimate();
-  auto symbolName = toStringRef(ultimateSymbol.name());
-  auto modNames = moduleNames(ultimateSymbol);
-  auto optHost = hostName(ultimateSymbol);
+  const Fortran::semantics::Symbol &ultimateSymbol =
+      derivedType.typeSymbol().GetUltimate();
+  llvm::StringRef symbolName = toStringRef(ultimateSymbol.name());
+  llvm::SmallVector<llvm::StringRef> modNames = moduleNames(ultimateSymbol);
+  llvm::Optional<llvm::StringRef> optHost = hostName(ultimateSymbol);
   llvm::SmallVector<std::int64_t> kinds;
   for (const auto &param :
        Fortran::semantics::OrderParameterDeclarations(ultimateSymbol)) {
     const auto &paramDetails =
         param->get<Fortran::semantics::TypeParamDetails>();
     if (paramDetails.attr() == Fortran::common::TypeParamAttr::Kind) {
-      const auto *paramValue = derivedType.FindParameter(param->name());
+      const Fortran::semantics::ParamValue *paramValue =
+          derivedType.FindParameter(param->name());
       assert(paramValue && "derived type kind parameter value not found");
-      auto paramExpr = paramValue->GetExplicit();
+      const Fortran::semantics::MaybeIntExpr paramExpr =
+          paramValue->GetExplicit();
       assert(paramExpr && "derived type kind param not explicit");
-      auto init = Fortran::evaluate::ToInt64(paramValue->GetExplicit());
+      std::optional<int64_t> init =
+          Fortran::evaluate::ToInt64(paramValue->GetExplicit());
       assert(init && "derived type kind param is not constant");
       kinds.emplace_back(*init);
     }
@@ -273,7 +281,7 @@
   name.append(intrinsic.str()).append(".");
   assert(funTy.getNumResults() == 1 && "only function mangling supported");
   name.append(typeToString(funTy.getResult(0)));
-  auto e = funTy.getNumInputs();
+  unsigned e = funTy.getNumInputs();
   for (decltype(e) i = 0; i < e; ++i)
     name.append(".").append(typeToString(funTy.getInput(i)));
   return name;