[flang] Lower ArrayRef to hlfir.designate

[jeanPerier]

Summary

Also add support for fir.boxchar in HLFIRTools so that character
designator with none constant lengths can be processed/converted to
fir::ExtendedValue.

Depends on D138121.

[clementval]

LGTM

[vzakhari]

flang/lib/Lower/ConvertExprToHLFIR.cpp

63–106

Can you please use some static size for SmallVector? There is an assertion in SmallVector implementation that may kick in if size of Subsctipt type increases or if the constant limit in SmallVector is changed for whatever reason.

71

I guess you may use LoweredSubscripts here.

[jeanPerier]

Remove LoweredSubscripts alias and use static size in one of
the llvm::SmallVector with bigger data type.

[jeanPerier]

flang/lib/Lower/ConvertExprToHLFIR.cpp

71

Actually the alias is not really needed anymore since it is only used here, I forgot to remove it. But I updated this SmallVector to use a static size, thanks for the tip.

flang/include/flang/Optimizer/Builder/HLFIRTools.h

public:
   }
 
   bool hasLengthParameters() const {
     mlir::Type eleTy = getFortranElementType();
     return eleTy.isa<fir::CharacterType>() ||
            fir::isRecordWithTypeParameters(eleTy);
   }
 
+  bool isCharacter() const {
+    return getFortranElementType().isa<fir::CharacterType>();
+  }
+
   fir::FortranVariableOpInterface getIfVariableInterface() const {
     return this->getDefiningOp<fir::FortranVariableOpInterface>();
   }
 
   // Get the entity as an mlir SSA value containing all the shape, type
   // parameters and dynamic shape information.
   mlir::Value getBase() const { return *this; }
 

 /// In that case, a cleanup function is provided to generate the finalization
 /// code after the end of the fir::ExtendedValue use.
 using CleanupFunction = std::function<void()>;
 std::pair<fir::ExtendedValue, llvm::Optional<CleanupFunction>>
 translateToExtendedValue(mlir::Location loc, fir::FirOpBuilder &builder,
                          Entity entity);
 
 /// Function to translate FortranVariableOpInterface to fir::ExtendedValue.
-/// It does not generate any IR, and is a simple packaging operation.
+/// It may generates IR to unbox fir.boxchar, but has otherwise no side effects
+/// on the IR.
 fir::ExtendedValue
-translateToExtendedValue(fir::FortranVariableOpInterface fortranVariable);
+translateToExtendedValue(mlir::Location loc, fir::FirOpBuilder &builder,
+                         fir::FortranVariableOpInterface fortranVariable);
 
 /// Generate declaration for a fir::ExtendedValue in memory.
 EntityWithAttributes genDeclare(mlir::Location loc, fir::FirOpBuilder &builder,
                                 const fir::ExtendedValue &exv,
                                 llvm::StringRef name,
                                 fir::FortranVariableFlagsAttr flags);
 
 /// If the entity is a variable, load its value (dereference pointers and
 /// allocatables if needed). Do nothing if the entity os already a variable or
 /// if it is not a scalar entity of numerical or logical type.
 Entity loadTrivialScalar(mlir::Location loc, fir::FirOpBuilder &builder,
                          Entity entity);
 
+/// Compute the lower and upper bounds of an entity.
+llvm::SmallVector<std::pair<mlir::Value, mlir::Value>>
+genBounds(mlir::Location loc, fir::FirOpBuilder &builder, Entity entity);
+
+/// Read length parameters into result if this entity has any.
+void genLengthParameters(mlir::Location loc, fir::FirOpBuilder &builder,
+                         Entity entity,
+                         llvm::SmallVectorImpl<mlir::Value> &result);
+
 } // namespace hlfir
 
 #endif // FORTRAN_OPTIMIZER_BUILDER_HLFIRTOOLS_H

flang/lib/Lower/ConvertExprToHLFIR.cpp

 //===-- ConvertExprToHLFIR.cpp --------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // Coding style: https://mlir.llvm.org/getting_started/DeveloperGuide/
 //
 //===----------------------------------------------------------------------===//
 
 #include "flang/Lower/ConvertExprToHLFIR.h"
+#include "flang/Evaluate/shape.h"
 #include "flang/Lower/AbstractConverter.h"
 #include "flang/Lower/ConvertConstant.h"
 #include "flang/Lower/StatementContext.h"
 #include "flang/Lower/SymbolMap.h"
 #include "flang/Optimizer/Builder/Todo.h"
+#include "flang/Optimizer/HLFIR/HLFIROps.h"
 
 namespace {
 
 /// Lower Designators to HLFIR.
 class HlfirDesignatorBuilder {
 public:
   HlfirDesignatorBuilder(mlir::Location loc,
                          Fortran::lower::AbstractConverter &converter,
                          Fortran::lower::SymMap &symMap,
                          Fortran::lower::StatementContext &stmtCtx)
       : converter{converter}, symMap{symMap}, stmtCtx{stmtCtx}, loc{loc} {}
 
   // Character designators variant contains substrings
   using CharacterDesignators =
       decltype(Fortran::evaluate::Designator<Fortran::evaluate::Type<
                    Fortran::evaluate::TypeCategory::Character, 1>>::u);
   hlfir::EntityWithAttributes
   gen(const CharacterDesignators &designatorVariant) {
-    return std::visit([&](const auto &x) { return gen(x); }, designatorVariant);
+    return std::visit(
+        [&](const auto &x) -> hlfir::EntityWithAttributes { return gen(x); },
+        designatorVariant);
   }
   // Character designators variant contains complex parts
   using RealDesignators =
       decltype(Fortran::evaluate::Designator<Fortran::evaluate::Type<
                    Fortran::evaluate::TypeCategory::Real, 4>>::u);
   hlfir::EntityWithAttributes gen(const RealDesignators &designatorVariant) {
-    return std::visit([&](const auto &x) { return gen(x); }, designatorVariant);
+    return std::visit(
+        [&](const auto &x) -> hlfir::EntityWithAttributes { return gen(x); },
+        designatorVariant);
   }
   // All other designators are similar
   using OtherDesignators =
       decltype(Fortran::evaluate::Designator<Fortran::evaluate::Type<
                    Fortran::evaluate::TypeCategory::Integer, 4>>::u);
   hlfir::EntityWithAttributes gen(const OtherDesignators &designatorVariant) {
-    return std::visit([&](const auto &x) { return gen(x); }, designatorVariant);
+    return std::visit(
+        [&](const auto &x) -> hlfir::EntityWithAttributes { return gen(x); },
+        designatorVariant);
   }
 
 private:
-  hlfir::EntityWithAttributes
+  /// Struct that is filled while visiting a part-ref (in the "visit" member
+  /// function) before the top level "gen" generates an hlfir.declare for the
+  /// part ref. It contains the lowered pieces of the part-ref that will
+  /// become the operands of an hlfir.declare.
+  struct PartInfo {
+    fir::FortranVariableOpInterface base;
+    llvm::SmallVector<hlfir::DesignateOp::Subscript, 8> subscripts;
+    mlir::Value resultShape;
+    llvm::SmallVector<mlir::Value> typeParams;
+  };
+
+  /// Generate an hlfir.declare for a part-ref given a filled PartInfo and the
+  /// FIR type for this part-ref.
+  fir::FortranVariableOpInterface genDeclare(mlir::Type resultValueType,
+                                             PartInfo &partInfo) {
+    // Compute hlfir.declare result type.
+    // TODO: ensure polymorphic aspect of base of component  will be
+    // preserved, as well as pointer/allocatable component aspects.
+    mlir::Type resultType;
+    /// Array sections may be non contiguous, so the output must be a box even
+    /// when the extents are static. This can be refined later for cases where
+    /// the output is know to be simply contiguous and that do not have lower
+    /// bounds.
+    auto charType = resultValueType.dyn_cast<fir::CharacterType>();
+    if (charType && charType.hasDynamicLen())
+      resultType =
+          fir::BoxCharType::get(charType.getContext(), charType.getFKind());
+    else if (resultValueType.isa<fir::SequenceType>() ||
+             fir::hasDynamicSize(resultValueType))
+      resultType = fir::BoxType::get(resultValueType);
+    else
+      resultType = fir::ReferenceType::get(resultValueType);
+
+    llvm::Optional<bool> complexPart;
+    llvm::SmallVector<mlir::Value> substring;
+    auto designate = getBuilder().create<hlfir::DesignateOp>(
+        getLoc(), resultType, partInfo.base.getBase(), "",
+        /*componentShape=*/mlir::Value{}, partInfo.subscripts, substring,
+        complexPart, partInfo.resultShape, partInfo.typeParams);
+    return mlir::cast<fir::FortranVariableOpInterface>(
+        designate.getOperation());
+  }
+
+  fir::FortranVariableOpInterface
   gen(const Fortran::evaluate::SymbolRef &symbolRef) {
     if (llvm::Optional<fir::FortranVariableOpInterface> varDef =
             getSymMap().lookupVariableDefinition(symbolRef))
       return *varDef;
     TODO(getLoc(), "lowering symbol to HLFIR");
   }
+
   hlfir::EntityWithAttributes
   gen(const Fortran::evaluate::Component &component) {
     TODO(getLoc(), "lowering component to HLFIR");
   }
+
   hlfir::EntityWithAttributes gen(const Fortran::evaluate::ArrayRef &arrayRef) {
-    TODO(getLoc(), "lowering ArrayRef to HLFIR");
+    PartInfo partInfo;
+    mlir::Type resultType = visit(arrayRef, partInfo);
+    return genDeclare(resultType, partInfo);
   }
+
   hlfir::EntityWithAttributes
   gen(const Fortran::evaluate::CoarrayRef &coarrayRef) {
     TODO(getLoc(), "lowering CoarrayRef to HLFIR");
   }
+
   hlfir::EntityWithAttributes
   gen(const Fortran::evaluate::ComplexPart &complexPart) {
     TODO(getLoc(), "lowering complex part to HLFIR");
   }
+
   hlfir::EntityWithAttributes
   gen(const Fortran::evaluate::Substring &substring) {
     TODO(getLoc(), "lowering substrings to HLFIR");
   }
 
+  mlir::Type visit(const Fortran::evaluate::SymbolRef &symbolRef,
+                   PartInfo &partInfo) {
+    partInfo.base = gen(symbolRef);
+    hlfir::genLengthParameters(getLoc(), getBuilder(), partInfo.base,
+                               partInfo.typeParams);
+    return partInfo.base.getElementOrSequenceType();
+  }
+
+  mlir::Type visit(const Fortran::evaluate::ArrayRef &arrayRef,
+                   PartInfo &partInfo) {
+    mlir::Type baseType;
+    if (const auto *component = arrayRef.base().UnwrapComponent())
+      baseType = visit(*component, partInfo);
+    baseType = visit(arrayRef.base().GetLastSymbol(), partInfo);
+
+    fir::FirOpBuilder &builder = getBuilder();
+    mlir::Location loc = getLoc();
+    mlir::Type idxTy = builder.getIndexType();
+    llvm::SmallVector<std::pair<mlir::Value, mlir::Value>> bounds;
+    auto getBounds = [&](unsigned i) {
+      if (bounds.empty())
+        bounds = hlfir::genBounds(loc, builder, partInfo.base);
+      return bounds[i];
+    };
+    auto frontEndResultShape =
+        Fortran::evaluate::GetShape(converter.getFoldingContext(), arrayRef);
+    llvm::SmallVector<mlir::Value> resultExtents;
+    fir::SequenceType::Shape resultTypeShape;
+    for (auto subscript : llvm::enumerate(arrayRef.subscript())) {
+      if (const auto *triplet =
+              std::get_if<Fortran::evaluate::Triplet>(&subscript.value().u)) {
+        mlir::Value lb, ub;
+        if (const auto &lbExpr = triplet->lower())
+          lb = genSubscript(*lbExpr);
+        else
+          lb = getBounds(subscript.index()).first;
+        if (const auto &ubExpr = triplet->upper())
+          ub = genSubscript(*ubExpr);
+        else
+          ub = getBounds(subscript.index()).second;
+        lb = builder.createConvert(loc, idxTy, lb);
+        ub = builder.createConvert(loc, idxTy, ub);
+        mlir::Value stride = genSubscript(triplet->stride());
+        stride = builder.createConvert(loc, idxTy, stride);
+        mlir::Value extent;
+        // Use constant extent if possible. The main advantage to do this now
+        // is to get the best FIR array types as possible while lowering.
+        if (frontEndResultShape)
+          if (auto maybeI64 = Fortran::evaluate::ToInt64(
+                  frontEndResultShape->at(resultExtents.size()))) {
+            resultTypeShape.push_back(*maybeI64);
+            extent = builder.createIntegerConstant(loc, idxTy, *maybeI64);
+          }
+        if (!extent) {
+          extent = builder.genExtentFromTriplet(loc, lb, ub, stride, idxTy);
+          resultTypeShape.push_back(fir::SequenceType::getUnknownExtent());
+        }
+        partInfo.subscripts.emplace_back(
+            hlfir::DesignateOp::Triplet{lb, ub, stride});
+        resultExtents.push_back(extent);
+      } else {
+        const auto &expr =
+            std::get<Fortran::evaluate::IndirectSubscriptIntegerExpr>(
+                subscript.value().u)
+                .value();
+        if (expr.Rank() > 0)
+          TODO(getLoc(), "vector subscripts in HLFIR");
+        partInfo.subscripts.push_back(genSubscript(expr));
+      }
+    }
+
+    assert(resultExtents.size() == resultTypeShape.size() &&
+           "inconsistent hlfir.designate shape");
+    mlir::Type resultType = baseType.cast<fir::SequenceType>().getEleTy();
+    if (!resultTypeShape.empty()) {
+      resultType = fir::SequenceType::get(resultTypeShape, resultType);
+      partInfo.resultShape = builder.genShape(loc, resultExtents);
+    }
+    return resultType;
+  }
+
+  mlir::Type visit(const Fortran::evaluate::Component &component,
+                   PartInfo &partInfo) {
+    TODO(getLoc(), "lowering component to HLFIR");
+  }
+
+  /// Lower a subscript expression. If it is a scalar subscript that is
+  /// a variable, it is loaded into an integer value.
+  template <typename T>
+  hlfir::EntityWithAttributes
+  genSubscript(const Fortran::evaluate::Expr<T> &expr);
+
   mlir::Location getLoc() const { return loc; }
   Fortran::lower::AbstractConverter &getConverter() { return converter; }
   fir::FirOpBuilder &getBuilder() { return converter.getFirOpBuilder(); }
   Fortran::lower::SymMap &getSymMap() { return symMap; }
   Fortran::lower::StatementContext &getStmtCtx() { return stmtCtx; }
 
   Fortran::lower::AbstractConverter &converter;
   Fortran::lower::SymMap &symMap;
private:
   Fortran::lower::StatementContext &getStmtCtx() { return stmtCtx; }
 
   Fortran::lower::AbstractConverter &converter;
   Fortran::lower::SymMap &symMap;
   Fortran::lower::StatementContext &stmtCtx;
   mlir::Location loc;
 };
 
+template <typename T>
+hlfir::EntityWithAttributes
+HlfirDesignatorBuilder::genSubscript(const Fortran::evaluate::Expr<T> &expr) {
+  auto loweredExpr =
+      HlfirBuilder(getLoc(), getConverter(), getSymMap(), getStmtCtx())
+          .gen(expr);
+  if (!loweredExpr.isArray()) {
+    fir::FirOpBuilder &builder = getBuilder();
+    if (loweredExpr.isVariable())
+      return hlfir::EntityWithAttributes{
+          hlfir::loadTrivialScalar(loc, builder, loweredExpr).getBase()};
+    // Skip constant conversions that litters designators and makes generated
+    // IR harder to read: directly use index constants for constant subscripts.
+    mlir::Type idxTy = builder.getIndexType();
+    if (loweredExpr.getType() != idxTy)
+      if (auto cstIndex = fir::factory::getIntIfConstant(loweredExpr))
+        return hlfir::EntityWithAttributes{
+            builder.createIntegerConstant(getLoc(), idxTy, *cstIndex)};
+  }
+  return loweredExpr;
+}
+
 } // namespace
 
 hlfir::EntityWithAttributes Fortran::lower::convertExprToHLFIR(
     mlir::Location loc, Fortran::lower::AbstractConverter &converter,
     const Fortran::lower::SomeExpr &expr, Fortran::lower::SymMap &symMap,
     Fortran::lower::StatementContext &stmtCtx) {
   return HlfirBuilder(loc, converter, symMap, stmtCtx).gen(expr);
 }

flang/lib/Optimizer/Builder/HLFIRTools.cpp

 getExplicitTypeParams(fir::FortranVariableOpInterface var) {
   llvm::SmallVector<mlir::Value> res;
   mlir::OperandRange range = var.getExplicitTypeParams();
   res.append(range.begin(), range.end());
   return res;
 }
 
 std::pair<fir::ExtendedValue, llvm::Optional<hlfir::CleanupFunction>>
-hlfir::translateToExtendedValue(mlir::Location loc, fir::FirOpBuilder &,
+hlfir::translateToExtendedValue(mlir::Location loc, fir::FirOpBuilder &builder,
                                 hlfir::Entity entity) {
   if (auto variable = entity.getIfVariableInterface())
-    return {hlfir::translateToExtendedValue(variable), {}};
+    return {hlfir::translateToExtendedValue(loc, builder, variable), {}};
   if (entity.isVariable())
     TODO(loc, "HLFIR variable to fir::ExtendedValue without a "
               "FortranVariableOpInterface");
   if (entity.getType().isa<hlfir::ExprType>())
     TODO(loc, "hlfir.expr to fir::ExtendedValue"); // use hlfir.associate
   return {{static_cast<mlir::Value>(entity)}, {}};
 }
 
 mlir::Value hlfir::Entity::getFirBase() const {
   if (fir::FortranVariableOpInterface variable = getIfVariableInterface())
     if (auto declareOp =
             mlir::dyn_cast<hlfir::DeclareOp>(variable.getOperation()))
       return declareOp.getOriginalBase();
   return getBase();
 }
 
 fir::ExtendedValue
-hlfir::translateToExtendedValue(fir::FortranVariableOpInterface variable) {
+hlfir::translateToExtendedValue(mlir::Location loc, fir::FirOpBuilder &builder,
+                                fir::FortranVariableOpInterface variable) {
   /// When going towards FIR, use the original base value to avoid
   /// introducing descriptors at runtime when they are not required.
   mlir::Value firBase = Entity{variable}.getFirBase();
   if (variable.isPointer() || variable.isAllocatable())
     TODO(variable->getLoc(), "pointer or allocatable "
                              "FortranVariableOpInterface to extendedValue");
   if (firBase.getType().isa<fir::BaseBoxType>())
     return fir::BoxValue(firBase, getExplicitLbounds(variable),
                          getExplicitTypeParams(variable));
 
   if (variable.isCharacter()) {
     if (variable.isArray())
       return fir::CharArrayBoxValue(firBase, variable.getExplicitCharLen(),
                                     getExplicitExtents(variable),
                                     getExplicitLbounds(variable));
+    if (auto boxCharType = firBase.getType().dyn_cast<fir::BoxCharType>()) {
+      auto unboxed = builder.create<fir::UnboxCharOp>(
+          loc, fir::ReferenceType::get(boxCharType.getEleTy()),
+          builder.getIndexType(), firBase);
+      return fir::CharBoxValue(unboxed.getResult(0),
+                               variable.getExplicitCharLen());
+    }
     return fir::CharBoxValue(firBase, variable.getExplicitCharLen());
   }
   if (variable.isArray())
     return fir::ArrayBoxValue(firBase, getExplicitExtents(variable),
                               getExplicitLbounds(variable));
   return firBase;
 }
 
hlfir::Entity hlfir::loadTrivialScalar(mlir::Location loc,
   if (entity.isVariable() && entity.isScalar() &&
       fir::isa_trivial(entity.getFortranElementType())) {
     if (entity.isMutableBox())
       TODO(loc, "load pointer/allocatable scalar");
     return Entity{builder.create<fir::LoadOp>(loc, entity)};
   }
   return entity;
 }
+
+static mlir::Value genUBound(mlir::Location loc, fir::FirOpBuilder &builder,
+                             mlir::Value lb, mlir::Value extent,
+                             mlir::Value one) {
+  if (auto constantLb = fir::factory::getIntIfConstant(lb))
+    if (*constantLb == 1)
+      return extent;
+  extent = builder.createConvert(loc, one.getType(), extent);
+  lb = builder.createConvert(loc, one.getType(), lb);
+  auto add = builder.create<mlir::arith::AddIOp>(loc, lb, extent);
+  return builder.create<mlir::arith::SubIOp>(loc, add, one);
+}
+
+llvm::SmallVector<std::pair<mlir::Value, mlir::Value>>
+hlfir::genBounds(mlir::Location loc, fir::FirOpBuilder &builder,
+                 Entity entity) {
+  if (entity.getType().isa<hlfir::ExprType>())
+    TODO(loc, "bounds of expressions in hlfir");
+  auto [exv, cleanup] = translateToExtendedValue(loc, builder, entity);
+  assert(!cleanup && "translation of entity should not yield cleanup");
+  if (const auto *mutableBox = exv.getBoxOf<fir::MutableBoxValue>())
+    exv = fir::factory::genMutableBoxRead(builder, loc, *mutableBox);
+  mlir::Type idxTy = builder.getIndexType();
+  mlir::Value one = builder.createIntegerConstant(loc, idxTy, 1);
+  llvm::SmallVector<std::pair<mlir::Value, mlir::Value>> result;
+  for (unsigned dim = 0; dim < exv.rank(); ++dim) {
+    mlir::Value extent = fir::factory::readExtent(builder, loc, exv, dim);
+    mlir::Value lb = fir::factory::readLowerBound(builder, loc, exv, dim, one);
+    mlir::Value ub = genUBound(loc, builder, lb, extent, one);
+    result.push_back({lb, ub});
+  }
+  return result;
+}
+
+void hlfir::genLengthParameters(mlir::Location loc, fir::FirOpBuilder &builder,
+                                Entity entity,
+                                llvm::SmallVectorImpl<mlir::Value> &result) {
+  if (!entity.hasLengthParameters())
+    return;
+  if (entity.getType().isa<hlfir::ExprType>())
+    // Going through fir::ExtendedValue would create a temp,
+    // which is not desired for an inquiry.
+    TODO(loc, "inquire type parameters of hlfir.expr");
+
+  if (entity.isCharacter()) {
+    auto [exv, cleanup] = translateToExtendedValue(loc, builder, entity);
+    assert(!cleanup && "translation of entity should not yield cleanup");
+    result.push_back(fir::factory::readCharLen(builder, loc, exv));
+    return;
+  }
+  TODO(loc, "inquire PDTs length parameters in HLFIR");
+}

flang/test/Lower/HLFIR/designators.f90

+! Test lowering of designators to HLFIR
+! RUN: bbc -emit-fir -hlfir -o - %s 2>&1 | FileCheck %s
+
+subroutine array_ref(x, n)
+  real :: x(:)
+  integer(8) :: n
+  print *, x(n)
+end subroutine
+! CHECK-LABEL: func.func @_QParray_ref(
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFarray_refEn"} : (!fir.ref<i64>) -> (!fir.ref<i64>, !fir.ref<i64>)
+! CHECK:  %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFarray_refEx"} : (!fir.box<!fir.array<?xf32>>) -> (!fir.box<!fir.array<?xf32>>, !fir.box<!fir.array<?xf32>>)
+! CHECK:  %[[VAL_9:.*]] = fir.load %[[VAL_2]]#0 : !fir.ref<i64>
+! CHECK:  %[[VAL_10:.*]] = hlfir.designate %[[VAL_3]]#0 (%[[VAL_9]])  : (!fir.box<!fir.array<?xf32>>, i64) -> !fir.ref<f32>
+
+subroutine char_array_ref(x, n)
+  character(*) :: x(:)
+  print *, x(10)
+end subroutine
+! CHECK-LABEL: func.func @_QPchar_array_ref(
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFchar_array_refEn"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:  %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFchar_array_refEx"} : (!fir.box<!fir.array<?x!fir.char<1,?>>>) -> (!fir.box<!fir.array<?x!fir.char<1,?>>>, !fir.box<!fir.array<?x!fir.char<1,?>>>)
+! CHECK:  %[[VAL_9:.*]] = fir.box_elesize %[[VAL_3]]#1 : (!fir.box<!fir.array<?x!fir.char<1,?>>>) -> index
+! CHECK:  %[[VAL_10:.*]] = arith.constant 10 : index
+! CHECK:  %[[VAL_11:.*]] = hlfir.designate %[[VAL_3]]#0 (%[[VAL_10]])  typeparams %[[VAL_9]] : (!fir.box<!fir.array<?x!fir.char<1,?>>>, index, index) -> !fir.boxchar<1>
+
+subroutine char_array_ref_cst_len(x, n)
+  character(5) :: x(:)
+  print *, x(10)
+end subroutine
+! CHECK-LABEL: func.func @_QPchar_array_ref_cst_len(
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFchar_array_ref_cst_lenEn"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:  %[[VAL_3:.*]] = arith.constant 5 : index
+! CHECK:  %[[VAL_4:.*]]:2 = hlfir.declare %{{.*}} typeparams %[[VAL_3]] {uniq_name = "_QFchar_array_ref_cst_lenEx"} : (!fir.box<!fir.array<?x!fir.char<1,5>>>, index) -> (!fir.box<!fir.array<?x!fir.char<1,5>>>, !fir.box<!fir.array<?x!fir.char<1,5>>>)
+! CHECK:  %[[VAL_10:.*]] = arith.constant 10 : index
+! CHECK:  %[[VAL_11:.*]] = hlfir.designate %[[VAL_4]]#0 (%[[VAL_10]])  typeparams %[[VAL_3]] : (!fir.box<!fir.array<?x!fir.char<1,5>>>, index, index) -> !fir.ref<!fir.char<1,5>>
+
+subroutine array_section(x)
+  real :: x(10)
+  print *, x(2:8:3)
+end subroutine
+! CHECK-LABEL: func.func @_QParray_section(
+! CHECK:  %[[VAL_1:.*]] = arith.constant 10 : index
+! CHECK:  %[[VAL_2:.*]] = fir.shape %[[VAL_1]] : (index) -> !fir.shape<1>
+! CHECK:  %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}}(%[[VAL_2]]) {uniq_name = "_QFarray_sectionEx"} : (!fir.ref<!fir.array<10xf32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<10xf32>>, !fir.ref<!fir.array<10xf32>>)
+! CHECK:  %[[VAL_9:.*]] = arith.constant 2 : index
+! CHECK:  %[[VAL_10:.*]] = arith.constant 8 : index
+! CHECK:  %[[VAL_11:.*]] = arith.constant 3 : index
+! CHECK:  %[[VAL_12:.*]] = arith.constant 3 : index
+! CHECK:  %[[VAL_13:.*]] = fir.shape %[[VAL_12]] : (index) -> !fir.shape<1>
+! CHECK:  %[[VAL_14:.*]] = hlfir.designate %[[VAL_3]]#0 (%[[VAL_9]]:%[[VAL_10]]:%[[VAL_11]])  shape %[[VAL_13]] : (!fir.ref<!fir.array<10xf32>>, index, index, index, !fir.shape<1>) -> !fir.box<!fir.array<3xf32>>
+
+subroutine array_section_2(x, n)
+  real :: x(:)
+  integer(8) :: n
+  print *, x(n::3)
+end subroutine
+! CHECK-LABEL: func.func @_QParray_section_2(
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFarray_section_2En"} : (!fir.ref<i64>) -> (!fir.ref<i64>, !fir.ref<i64>)
+! CHECK:  %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFarray_section_2Ex"} : (!fir.box<!fir.array<?xf32>>) -> (!fir.box<!fir.array<?xf32>>, !fir.box<!fir.array<?xf32>>)
+! CHECK:  %[[VAL_9:.*]] = fir.load %[[VAL_2]]#0 : !fir.ref<i64>
+! CHECK:  %[[VAL_10:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_11:.*]]:3 = fir.box_dims %[[VAL_3]]#1, %[[VAL_10]] : (!fir.box<!fir.array<?xf32>>, index) -> (index, index, index)
+! CHECK:  %[[VAL_12:.*]] = fir.convert %[[VAL_9]] : (i64) -> index
+! CHECK:  %[[VAL_13:.*]] = arith.constant 3 : index
+! CHECK:  %[[VAL_14:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_15:.*]] = arith.subi %[[VAL_11]]#1, %[[VAL_12]] : index
+! CHECK:  %[[VAL_16:.*]] = arith.addi %[[VAL_15]], %[[VAL_13]] : index
+! CHECK:  %[[VAL_17:.*]] = arith.divsi %[[VAL_16]], %[[VAL_13]] : index
+! CHECK:  %[[VAL_18:.*]] = arith.cmpi sgt, %[[VAL_17]], %[[VAL_14]] : index
+! CHECK:  %[[VAL_19:.*]] = arith.select %[[VAL_18]], %[[VAL_17]], %[[VAL_14]] : index
+! CHECK:  %[[VAL_20:.*]] = fir.shape %[[VAL_19]] : (index) -> !fir.shape<1>
+! CHECK:  %[[VAL_21:.*]] = hlfir.designate %[[VAL_3]]#0 (%[[VAL_12]]:%[[VAL_11]]#1:%[[VAL_13]])  shape %[[VAL_20]] : (!fir.box<!fir.array<?xf32>>, index, index, index, !fir.shape<1>) -> !fir.box<!fir.array<?xf32>>
+
+subroutine char_array_section(x, n)
+  character(*) :: x(:)
+  print *, x(::3)
+end subroutine
+! CHECK-LABEL: func.func @_QPchar_array_section(
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFchar_array_sectionEn"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:  %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFchar_array_sectionEx"} : (!fir.box<!fir.array<?x!fir.char<1,?>>>) -> (!fir.box<!fir.array<?x!fir.char<1,?>>>, !fir.box<!fir.array<?x!fir.char<1,?>>>)
+! CHECK:  %[[VAL_9:.*]] = fir.box_elesize %[[VAL_3]]#1 : (!fir.box<!fir.array<?x!fir.char<1,?>>>) -> index
+! CHECK:  %[[VAL_10:.*]] = arith.constant 1 : index
+! CHECK:  %[[VAL_11:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_12:.*]]:3 = fir.box_dims %[[VAL_3]]#1, %[[VAL_11]] : (!fir.box<!fir.array<?x!fir.char<1,?>>>, index) -> (index, index, index)
+! CHECK:  %[[VAL_13:.*]] = arith.constant 3 : index
+! CHECK:  %[[VAL_14:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_15:.*]] = arith.subi %[[VAL_12]]#1, %[[VAL_10]] : index
+! CHECK:  %[[VAL_16:.*]] = arith.addi %[[VAL_15]], %[[VAL_13]] : index
+! CHECK:  %[[VAL_17:.*]] = arith.divsi %[[VAL_16]], %[[VAL_13]] : index
+! CHECK:  %[[VAL_18:.*]] = arith.cmpi sgt, %[[VAL_17]], %[[VAL_14]] : index
+! CHECK:  %[[VAL_19:.*]] = arith.select %[[VAL_18]], %[[VAL_17]], %[[VAL_14]] : index
+! CHECK:  %[[VAL_20:.*]] = fir.shape %[[VAL_19]] : (index) -> !fir.shape<1>
+! CHECK:  %[[VAL_21:.*]] = hlfir.designate %[[VAL_3]]#0 (%[[VAL_10]]:%[[VAL_12]]#1:%[[VAL_13]])  shape %[[VAL_20]] typeparams %[[VAL_9]] : (!fir.box<!fir.array<?x!fir.char<1,?>>>, index, index, index, !fir.shape<1>, index) -> !fir.box<!fir.array<?x!fir.char<1,?>>>
+
+subroutine char_array_section_cst_len(x, n)
+  character(5) :: x(:)
+  print *, x(::3)
+end subroutine
+! CHECK-LABEL: func.func @_QPchar_array_section_cst_len(
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFchar_array_section_cst_lenEn"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK:  %[[VAL_3:.*]] = arith.constant 5 : index
+! CHECK:  %[[VAL_4:.*]]:2 = hlfir.declare %{{.*}} typeparams %[[VAL_3]] {uniq_name = "_QFchar_array_section_cst_lenEx"} : (!fir.box<!fir.array<?x!fir.char<1,5>>>, index) -> (!fir.box<!fir.array<?x!fir.char<1,5>>>, !fir.box<!fir.array<?x!fir.char<1,5>>>)
+! CHECK:  %[[VAL_10:.*]] = arith.constant 1 : index
+! CHECK:  %[[VAL_11:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_12:.*]]:3 = fir.box_dims %[[VAL_4]]#1, %[[VAL_11]] : (!fir.box<!fir.array<?x!fir.char<1,5>>>, index) -> (index, index, index)
+! CHECK:  %[[VAL_13:.*]] = arith.constant 3 : index
+! CHECK:  %[[VAL_14:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_15:.*]] = arith.subi %[[VAL_12]]#1, %[[VAL_10]] : index
+! CHECK:  %[[VAL_16:.*]] = arith.addi %[[VAL_15]], %[[VAL_13]] : index
+! CHECK:  %[[VAL_17:.*]] = arith.divsi %[[VAL_16]], %[[VAL_13]] : index
+! CHECK:  %[[VAL_18:.*]] = arith.cmpi sgt, %[[VAL_17]], %[[VAL_14]] : index
+! CHECK:  %[[VAL_19:.*]] = arith.select %[[VAL_18]], %[[VAL_17]], %[[VAL_14]] : index
+! CHECK:  %[[VAL_20:.*]] = fir.shape %[[VAL_19]] : (index) -> !fir.shape<1>
+! CHECK:  %[[VAL_21:.*]] = hlfir.designate %[[VAL_4]]#0 (%[[VAL_10]]:%[[VAL_12]]#1:%[[VAL_13]])  shape %[[VAL_20]] typeparams %[[VAL_3]] : (!fir.box<!fir.array<?x!fir.char<1,5>>>, index, index, index, !fir.shape<1>, index) -> !fir.box<!fir.array<?x!fir.char<1,5>>>