diff --git a/include/flang/Optimizer/Builder/BoxValue.h b/include/flang/Optimizer/Builder/BoxValue.h
new file mode 100644
index 0000000..ef84dfd
--- /dev/null
+++ b/include/flang/Optimizer/Builder/BoxValue.h
@@ -0,0 +1,472 @@
+//===-- BoxValue.h -- internal box values -----------------------*- C++ -*-===//
+//
+// 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/
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_OPTIMIZER_BUILDER_BOXVALUE_H
+#define FORTRAN_OPTIMIZER_BUILDER_BOXVALUE_H
+
+#include "flang/Optimizer/Dialect/FIRType.h"
+#include "flang/Optimizer/Support/FatalError.h"
+#include "flang/Optimizer/Support/Matcher.h"
+#include "mlir/IR/OperationSupport.h"
+#include "mlir/IR/Value.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/raw_ostream.h"
+#include <utility>
+
+namespace fir {
+class CharBoxValue;
+class ArrayBoxValue;
+class CharArrayBoxValue;
+class ProcBoxValue;
+class MutableBoxValue;
+class BoxValue;
+
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const CharBoxValue &);
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const ArrayBoxValue &);
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const CharArrayBoxValue &);
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const ProcBoxValue &);
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const MutableBoxValue &);
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const BoxValue &);
+
+//===----------------------------------------------------------------------===//
+//
+// Boxed values
+//
+// Define a set of containers used internally by the lowering bridge to keep
+// track of extended values associated with a Fortran subexpression. These
+// associations are maintained during the construction of FIR.
+//
+//===----------------------------------------------------------------------===//
+
+/// Most expressions of intrinsic type can be passed unboxed. Their properties
+/// are known statically.
+using UnboxedValue = mlir::Value;
+
+/// Abstract base class.
+class AbstractBox {
+public:
+  AbstractBox() = delete;
+  AbstractBox(mlir::Value addr) : addr{addr} {}
+
+  /// FIXME: this comment is not true anymore since genLoad
+  /// is loading constant length characters. What is the impact  /// ?
+  /// An abstract box always contains a memory reference to a value.
+  mlir::Value getAddr() const { return addr; }
+
+protected:
+  mlir::Value addr;
+};
+
+/// Expressions of CHARACTER type have an associated, possibly dynamic LEN
+/// value.
+class CharBoxValue : public AbstractBox {
+public:
+  CharBoxValue(mlir::Value addr, mlir::Value len)
+      : AbstractBox{addr}, len{len} {
+    if (addr && addr.getType().template isa<fir::BoxCharType>())
+      fir::emitFatalError(addr.getLoc(),
+                          "BoxChar should not be in CharBoxValue");
+  }
+
+  CharBoxValue clone(mlir::Value newBase) const { return {newBase, len}; }
+
+  /// Convenience alias to get the memory reference to the buffer.
+  mlir::Value getBuffer() const { return getAddr(); }
+
+  mlir::Value getLen() const { return len; }
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &,
+                                       const CharBoxValue &);
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this; }
+
+protected:
+  mlir::Value len;
+};
+
+/// Abstract base class.
+/// Expressions of type array have at minimum a shape. These expressions may
+/// have lbound attributes (dynamic values) that affect the interpretation of
+/// indexing expressions.
+class AbstractArrayBox {
+public:
+  AbstractArrayBox() = default;
+  AbstractArrayBox(llvm::ArrayRef<mlir::Value> extents,
+                   llvm::ArrayRef<mlir::Value> lbounds)
+      : extents{extents.begin(), extents.end()}, lbounds{lbounds.begin(),
+                                                         lbounds.end()} {}
+
+  // Every array has extents that describe its shape.
+  const llvm::SmallVectorImpl<mlir::Value> &getExtents() const {
+    return extents;
+  }
+
+  // An array expression may have user-defined lower bound values.
+  // If this vector is empty, the default in all dimensions is `1`.
+  const llvm::SmallVectorImpl<mlir::Value> &getLBounds() const {
+    return lbounds;
+  }
+
+  bool lboundsAllOne() const { return lbounds.empty(); }
+  std::size_t rank() const { return extents.size(); }
+
+protected:
+  llvm::SmallVector<mlir::Value, 4> extents;
+  llvm::SmallVector<mlir::Value, 4> lbounds;
+};
+
+/// Expressions with rank > 0 have extents. They may also have lbounds that are
+/// not 1.
+class ArrayBoxValue : public AbstractBox, public AbstractArrayBox {
+public:
+  ArrayBoxValue(mlir::Value addr, llvm::ArrayRef<mlir::Value> extents,
+                llvm::ArrayRef<mlir::Value> lbounds = {})
+      : AbstractBox{addr}, AbstractArrayBox{extents, lbounds} {}
+
+  ArrayBoxValue clone(mlir::Value newBase) const {
+    return {newBase, extents, lbounds};
+  }
+
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &,
+                                       const ArrayBoxValue &);
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this; }
+};
+
+/// Expressions of type CHARACTER and with rank > 0.
+class CharArrayBoxValue : public CharBoxValue, public AbstractArrayBox {
+public:
+  CharArrayBoxValue(mlir::Value addr, mlir::Value len,
+                    llvm::ArrayRef<mlir::Value> extents,
+                    llvm::ArrayRef<mlir::Value> lbounds = {})
+      : CharBoxValue{addr, len}, AbstractArrayBox{extents, lbounds} {}
+
+  CharArrayBoxValue clone(mlir::Value newBase) const {
+    return {newBase, len, extents, lbounds};
+  }
+
+  CharBoxValue cloneElement(mlir::Value newBase) const {
+    return {newBase, len};
+  }
+
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &,
+                                       const CharArrayBoxValue &);
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this; }
+};
+
+/// Expressions that are procedure POINTERs may need a set of references to
+/// variables in the host scope.
+class ProcBoxValue : public AbstractBox {
+public:
+  ProcBoxValue(mlir::Value addr, mlir::Value context)
+      : AbstractBox{addr}, hostContext{context} {}
+
+  ProcBoxValue clone(mlir::Value newBase) const {
+    return {newBase, hostContext};
+  }
+
+  mlir::Value getHostContext() const { return hostContext; }
+
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &,
+                                       const ProcBoxValue &);
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this; }
+
+protected:
+  mlir::Value hostContext;
+};
+
+/// Base class for values associated to a fir.box or fir.ref<fir.box>.
+class AbstractIrBox : public AbstractBox, public AbstractArrayBox {
+public:
+  AbstractIrBox(mlir::Value addr) : AbstractBox{addr} {}
+  AbstractIrBox(mlir::Value addr, llvm::ArrayRef<mlir::Value> lbounds,
+                llvm::ArrayRef<mlir::Value> extents)
+      : AbstractBox{addr}, AbstractArrayBox(extents, lbounds) {}
+  /// Get the fir.box<type> part of the address type.
+  fir::BoxType getBoxTy() const {
+    auto type = getAddr().getType();
+    if (auto pointedTy = fir::dyn_cast_ptrEleTy(type))
+      type = pointedTy;
+    return type.cast<fir::BoxType>();
+  }
+  /// Return the part of the address type after memory and box types. That is
+  /// the element type, maybe wrapped in a fir.array type.
+  mlir::Type getBaseTy() const {
+    return fir::dyn_cast_ptrOrBoxEleTy(getBoxTy());
+  }
+
+  /// Return the memory type of the data address inside the box:
+  /// - for fir.box<fir.ptr<T>>, return fir.ptr<T>
+  /// - for fir.box<fir.heap<T>>, return fir.heap<T>
+  /// - for fir.box<T>, return fir.ref<T>
+  mlir::Type getMemTy() const {
+    auto ty = getBoxTy().getEleTy();
+    if (fir::isa_ref_type(ty))
+      return ty;
+    return fir::ReferenceType::get(ty);
+  }
+
+  /// Get the scalar type related to the described entity
+  mlir::Type getEleTy() const {
+    auto type = getBaseTy();
+    if (auto seqTy = type.dyn_cast<fir::SequenceType>())
+      return seqTy.getEleTy();
+    return type;
+  }
+
+  /// Is the entity an array or an assumed rank ?
+  bool hasRank() const { return getBaseTy().isa<fir::SequenceType>(); }
+  /// Is this an assumed rank ?
+  bool hasAssumedRank() const {
+    auto seqTy = getBaseTy().dyn_cast<fir::SequenceType>();
+    return seqTy && seqTy.hasUnknownShape();
+  }
+  /// Returns the rank of the entity. Beware that zero will be returned for
+  /// both scalars and assumed rank.
+  unsigned rank() const {
+    if (auto seqTy = getBaseTy().dyn_cast<fir::SequenceType>())
+      return seqTy.getDimension();
+    return 0;
+  }
+  /// Is this a character entity ?
+  bool isCharacter() const { return fir::isa_char(getEleTy()); };
+  /// Is this a derived type entity ?
+  bool isDerived() const { return getEleTy().isa<fir::RecordType>(); };
+
+  bool isDerivedWithLengthParameters() const {
+    auto record = getEleTy().dyn_cast<fir::RecordType>();
+    return record && record.getNumLenParams() != 0;
+  };
+  /// Is this a CLASS(*)/TYPE(*) ?
+  bool isUnlimitedPolymorphic() const {
+    return getEleTy().isa<mlir::NoneType>();
+  }
+};
+
+/// An entity described by a fir.box value that cannot be read into
+/// another ExtendedValue category, either because the fir.box may be an
+/// absent optional and we need to wait until the user is referencing it
+/// to read it, or because it contains important information that cannot
+/// be exposed in FIR (e.g. non contiguous byte stride).
+/// It may also store explicit bounds or length parameters that were specified
+/// for the entity.
+class BoxValue : public AbstractIrBox {
+public:
+  BoxValue(mlir::Value addr) : AbstractIrBox{addr} { assert(verify()); }
+  BoxValue(mlir::Value addr, llvm::ArrayRef<mlir::Value> lbounds,
+           llvm::ArrayRef<mlir::Value> explicitParams,
+           llvm::ArrayRef<mlir::Value> explicitExtents = {})
+      : AbstractIrBox{addr, lbounds, explicitExtents},
+        explicitParams{explicitParams.begin(), explicitParams.end()} {
+    assert(verify());
+  }
+  // TODO: check contiguous attribute of addr
+  bool isContiguous() const { return false; }
+
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &, const BoxValue &);
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this; }
+
+  llvm::ArrayRef<mlir::Value> getLBounds() const { return lbounds; }
+
+  // The extents member is not guaranteed to be field for arrays. It is only
+  // guaranteed to be field for explicit shape arrays. In general,
+  // explicit-shape will not come as descriptors, so this field will be empty in
+  // most cases. The exception are derived types with length parameters and
+  // polymorphic dummy argument arrays. It may be possible for the explicit
+  // extents to conflict with the shape information that is in the box according
+  // to 15.5.2.11 sequence association rules.
+  llvm::ArrayRef<mlir::Value> getExplicitExtents() const { return extents; }
+
+  llvm::ArrayRef<mlir::Value> getExplicitParameters() const {
+    return explicitParams;
+  }
+
+protected:
+  // Verify constructor invariants.
+  bool verify() const;
+
+  // Only field when the BoxValue has explicit length parameters.
+  // Otherwise, the length parameters are in the fir.box.
+  llvm::SmallVector<mlir::Value, 2> explicitParams;
+};
+
+/// Set of variables (addresses) holding the allocatable properties. These may
+/// be empty in case it is not deemed safe to duplicate the descriptor
+/// information locally (For instance, a volatile allocatable will always be
+/// lowered to a descriptor to preserve the integrity of the entity and its
+/// associated properties. As such, all references to the entity and its
+/// property will go through the descriptor explicitly.).
+class MutableProperties {
+public:
+  bool isEmpty() const { return !addr; }
+  mlir::Value addr;
+  llvm::SmallVector<mlir::Value, 2> extents;
+  llvm::SmallVector<mlir::Value, 2> lbounds;
+  /// Only keep track of the deferred length parameters through variables, since
+  /// they are the only ones that can change as per the deferred type parameters
+  /// definition in F2018 standard section 3.147.12.2.
+  /// Non-deferred values are returned by
+  /// MutableBoxValue.nonDeferredLenParams().
+  llvm::SmallVector<mlir::Value, 2> deferredParams;
+};
+
+/// MutableBoxValue is used for entities that are represented by the address of
+/// a box. This is intended to be used for entities whose base address, shape
+/// and type are not constant in the entity lifetime (e.g Allocatables and
+/// Pointers).
+class MutableBoxValue : public AbstractIrBox {
+public:
+  /// Create MutableBoxValue given the address \p addr of the box and the non
+  /// deferred length parameters \p lenParameters. The non deferred length
+  /// parameters must always be provided, even if they are constant and already
+  /// reflected in the address type.
+  MutableBoxValue(mlir::Value addr, mlir::ValueRange lenParameters,
+                  MutableProperties mutableProperties)
+      : AbstractIrBox(addr), lenParams{lenParameters.begin(),
+                                       lenParameters.end()},
+        mutableProperties{mutableProperties} {
+    // Currently only accepts fir.(ref/ptr/heap)<fir.box<type>> mlir::Value for
+    // the address. This may change if we accept
+    // fir.(ref/ptr/heap)<fir.heap<type>> for scalar without length parameters.
+    assert(verify() &&
+           "MutableBoxValue requires mem ref to fir.box<fir.[heap|ptr]<type>>");
+  }
+  /// Is this a Fortran pointer ?
+  bool isPointer() const {
+    return getBoxTy().getEleTy().isa<fir::PointerType>();
+  }
+  /// Is this an allocatable ?
+  bool isAllocatable() const {
+    return getBoxTy().getEleTy().isa<fir::HeapType>();
+  }
+  /// Does this entity have any non deferred length parameters ?
+  bool hasNonDeferredLenParams() const { return !lenParams.empty(); }
+  /// Return the non deferred length parameters.
+  llvm::ArrayRef<mlir::Value> nonDeferredLenParams() const { return lenParams; }
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &,
+                                       const MutableBoxValue &);
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this; }
+
+  /// Set of variables is used instead of a descriptor to hold the entity
+  /// properties instead of a fir.ref<fir.box<>>.
+  bool isDescribedByVariables() const { return !mutableProperties.isEmpty(); }
+
+  const MutableProperties &getMutableProperties() const {
+    return mutableProperties;
+  }
+
+protected:
+  /// Validate the address type form in the constructor.
+  bool verify() const;
+  /// Hold the non-deferred length parameter values  (both for characters and
+  /// derived). Non-deferred length parameters cannot change dynamically, as
+  /// opposed to deferred type parameters (3.147.12.2).
+  llvm::SmallVector<mlir::Value, 2> lenParams;
+  /// Set of variables holding the extents, lower bounds and
+  /// base address when it is deemed safe to work with these variables rather
+  /// than directly with a descriptor.
+  MutableProperties mutableProperties;
+};
+
+class ExtendedValue;
+
+/// Get the base value of an extended value. Every type of extended value has a
+/// base value or is null.
+mlir::Value getBase(const ExtendedValue &exv);
+
+/// Get the LEN property value of an extended value. CHARACTER values have a LEN
+/// property.
+mlir::Value getLen(const ExtendedValue &exv);
+
+/// Pretty-print an extended value.
+llvm::raw_ostream &operator<<(llvm::raw_ostream &, const ExtendedValue &);
+
+/// Return a clone of the extended value `exv` with the base value `base`
+/// substituted.
+ExtendedValue substBase(const ExtendedValue &exv, mlir::Value base);
+
+/// Is the extended value `exv` an array?
+bool isArray(const ExtendedValue &exv);
+
+/// Get the type parameters for `exv`.
+llvm::SmallVector<mlir::Value> getTypeParams(const ExtendedValue &exv);
+
+/// An extended value is a box of values pertaining to a discrete entity. It is
+/// used in lowering to track all the runtime values related to an entity. For
+/// example, an entity may have an address in memory that contains its value(s)
+/// as well as various attribute values that describe the shape and starting
+/// indices if it is an array entity.
+class ExtendedValue : public details::matcher<ExtendedValue> {
+public:
+  using VT =
+      std::variant<UnboxedValue, CharBoxValue, ArrayBoxValue, CharArrayBoxValue,
+                   ProcBoxValue, BoxValue, MutableBoxValue>;
+
+  ExtendedValue() : box{UnboxedValue{}} {}
+  template <typename A, typename = std::enable_if_t<
+                            !std::is_same_v<std::decay_t<A>, ExtendedValue>>>
+  constexpr ExtendedValue(A &&a) : box{std::forward<A>(a)} {
+    if (const auto *b = getUnboxed()) {
+      if (*b) {
+        auto type = b->getType();
+        if (type.template isa<fir::BoxCharType>())
+          fir::emitFatalError(b->getLoc(), "BoxChar should be unboxed");
+        if (auto refType = type.template dyn_cast<fir::ReferenceType>())
+          type = refType.getEleTy();
+        if (auto seqType = type.template dyn_cast<fir::SequenceType>())
+          type = seqType.getEleTy();
+        if (fir::isa_char(type))
+          fir::emitFatalError(b->getLoc(),
+                              "character buffer should be in CharBoxValue");
+      }
+    }
+  }
+
+  template <typename A>
+  constexpr const A *getBoxOf() const {
+    return std::get_if<A>(&box);
+  }
+
+  constexpr const CharBoxValue *getCharBox() const {
+    return getBoxOf<CharBoxValue>();
+  }
+
+  constexpr const UnboxedValue *getUnboxed() const {
+    return getBoxOf<UnboxedValue>();
+  }
+
+  unsigned rank() const {
+    return match([](const fir::UnboxedValue &box) -> unsigned { return 0; },
+                 [](const fir::CharBoxValue &box) -> unsigned { return 0; },
+                 [](const fir::ProcBoxValue &box) -> unsigned { return 0; },
+                 [](const auto &box) -> unsigned { return box.rank(); });
+  }
+
+  /// LLVM style debugging of extended values
+  LLVM_DUMP_METHOD void dump() const { llvm::errs() << *this << '\n'; }
+
+  friend llvm::raw_ostream &operator<<(llvm::raw_ostream &,
+                                       const ExtendedValue &);
+
+  const VT &matchee() const { return box; }
+
+private:
+  VT box;
+};
+
+/// Is the extended value `exv` unboxed and non-null?
+inline bool isUnboxedValue(const ExtendedValue &exv) {
+  return exv.match(
+      [](const fir::UnboxedValue &box) { return box ? true : false; },
+      [](const auto &) { return false; });
+}
+} // namespace fir
+
+#endif // FORTRAN_OPTIMIZER_BUILDER_BOXVALUE_H
diff --git a/include/flang/Optimizer/Builder/FIRBuilder.h b/include/flang/Optimizer/Builder/FIRBuilder.h
index 5984055..4710e02 100644
--- a/include/flang/Optimizer/Builder/FIRBuilder.h
+++ b/include/flang/Optimizer/Builder/FIRBuilder.h
@@ -23,6 +23,7 @@
 #include "mlir/IR/BuiltinOps.h"
 
 namespace fir {
+class ExtendedValue;
 
 //===----------------------------------------------------------------------===//
 // FirOpBuilder
@@ -55,6 +56,9 @@
   /// Create a sequence of `eleTy` with `rank` dimensions of unknown size.
   mlir::Type getVarLenSeqTy(mlir::Type eleTy, unsigned rank = 1);
 
+  /// Get character length type
+  mlir::Type getCharacterLengthType() { return getIndexType(); }
+
   /// Get the integer type whose bit width corresponds to the width of pointer
   /// types, or is bigger.
   mlir::Type getIntPtrType() {
@@ -266,9 +270,14 @@
 
 namespace fir::factory {
 
-//===--------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
 // String literal helper helpers
-//===--------------------------------------------------------------------===//
+//===----------------------------------------------------------------------===//
+
+/// Create a !fir.char<1> string literal global and returns a
+/// fir::CharBoxValue with its address and length.
+fir::ExtendedValue createStringLiteral(fir::FirOpBuilder &, mlir::Location,
+                                       llvm::StringRef string);
 
 /// Unique a compiler generated identifier. A short prefix should be provided
 /// to hint at the origin of the identifier.
@@ -278,6 +287,9 @@
 // Location helpers
 //===----------------------------------------------------------------------===//
 
+/// Generate a string literal containing the file name and return its address
+mlir::Value locationToFilename(fir::FirOpBuilder &, mlir::Location);
+
 /// Generate a constant of the given type with the location line number
 mlir::Value locationToLineNo(fir::FirOpBuilder &, mlir::Location, mlir::Type);
 
diff --git a/include/flang/Optimizer/Dialect/FIRType.h b/include/flang/Optimizer/Dialect/FIRType.h
index 82c4a43..e0f0e29 100644
--- a/include/flang/Optimizer/Dialect/FIRType.h
+++ b/include/flang/Optimizer/Dialect/FIRType.h
@@ -138,6 +138,22 @@
 /// of unknown rank or type.
 bool isa_unknown_size_box(mlir::Type t);
 
+/// Returns true iff `t` is a fir.char type and has an unknown length.
+inline bool characterWithDynamicLen(mlir::Type t) {
+  if (auto charTy = t.dyn_cast<fir::CharacterType>())
+    return charTy.hasDynamicLen();
+  return false;
+}
+
+/// Returns true iff `seqTy` has either an unknown shape or a non-constant shape
+/// (where rank > 0).
+inline bool sequenceWithNonConstantShape(fir::SequenceType seqTy) {
+  return seqTy.hasUnknownShape() || !seqTy.hasConstantShape();
+}
+
+/// Returns true iff the type `t` does not have a constant size.
+bool hasDynamicSize(mlir::Type t);
+
 /// If `t` is a SequenceType return its element type, otherwise return `t`.
 inline mlir::Type unwrapSequenceType(mlir::Type t) {
   if (auto seqTy = t.dyn_cast<fir::SequenceType>())
diff --git a/include/flang/Optimizer/Support/Matcher.h b/include/flang/Optimizer/Support/Matcher.h
new file mode 100644
index 0000000..da1d7c2
--- /dev/null
+++ b/include/flang/Optimizer/Support/Matcher.h
@@ -0,0 +1,35 @@
+//===-- Optimizer/Support/Matcher.h -----------------------------*- C++ -*-===//
+//
+// 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/
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_OPTIMIZER_SUPPORT_MATCHER_H
+#define FORTRAN_OPTIMIZER_SUPPORT_MATCHER_H
+
+#include <variant>
+
+// Boilerplate CRTP class for a simplified type-casing syntactic sugar. This
+// lets one write pattern matchers using a more compact syntax.
+namespace fir::details {
+// clang-format off
+template<class... Ts> struct matches : Ts... { using Ts::operator()...; };
+template<class... Ts> matches(Ts...) -> matches<Ts...>;
+template<typename N> struct matcher {
+  template<typename... Ts> auto match(Ts... ts) {
+    return std::visit(matches{ts...}, static_cast<N*>(this)->matchee());
+  }
+  template<typename... Ts> auto match(Ts... ts) const {
+    return std::visit(matches{ts...}, static_cast<N const*>(this)->matchee());
+  }
+};
+// clang-format on
+} // namespace fir::details
+
+#endif // FORTRAN_OPTIMIZER_SUPPORT_MATCHER_H
diff --git a/lib/Optimizer/Builder/BoxValue.cpp b/lib/Optimizer/Builder/BoxValue.cpp
new file mode 100644
index 0000000..0b713ec
--- /dev/null
+++ b/lib/Optimizer/Builder/BoxValue.cpp
@@ -0,0 +1,228 @@
+//===-- BoxValue.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
+//
+//===----------------------------------------------------------------------===//
+//
+// Pretty printers for box values, etc.
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Optimizer/Builder/BoxValue.h"
+#include "mlir/IR/BuiltinTypes.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "flang-box-value"
+
+mlir::Value fir::getBase(const fir::ExtendedValue &exv) {
+  return exv.match([](const fir::UnboxedValue &x) { return x; },
+                   [](const auto &x) { return x.getAddr(); });
+}
+
+mlir::Value fir::getLen(const fir::ExtendedValue &exv) {
+  return exv.match(
+      [](const fir::CharBoxValue &x) { return x.getLen(); },
+      [](const fir::CharArrayBoxValue &x) { return x.getLen(); },
+      [](const fir::BoxValue &) -> mlir::Value {
+        llvm::report_fatal_error("Need to read len from BoxValue Exv");
+      },
+      [](const fir::MutableBoxValue &) -> mlir::Value {
+        llvm::report_fatal_error("Need to read len from MutableBoxValue Exv");
+      },
+      [](const auto &) { return mlir::Value{}; });
+}
+
+fir::ExtendedValue fir::substBase(const fir::ExtendedValue &exv,
+                                  mlir::Value base) {
+  return exv.match(
+      [=](const fir::UnboxedValue &x) { return fir::ExtendedValue(base); },
+      [=](const fir::BoxValue &) -> fir::ExtendedValue {
+        llvm::report_fatal_error("TODO: substbase of BoxValue");
+      },
+      [=](const fir::MutableBoxValue &) -> fir::ExtendedValue {
+        llvm::report_fatal_error("TODO: substbase of MutableBoxValue");
+      },
+      [=](const auto &x) { return fir::ExtendedValue(x.clone(base)); });
+}
+
+llvm::SmallVector<mlir::Value> fir::getTypeParams(const ExtendedValue &exv) {
+  using RT = llvm::SmallVector<mlir::Value>;
+  auto baseTy = fir::getBase(exv).getType();
+  if (auto t = fir::dyn_cast_ptrEleTy(baseTy))
+    baseTy = t;
+  baseTy = fir::unwrapSequenceType(baseTy);
+  if (!fir::hasDynamicSize(baseTy))
+    return {}; // type has constant size, no type parameters needed
+  [[maybe_unused]] auto loc = fir::getBase(exv).getLoc();
+  return exv.match(
+      [](const fir::CharBoxValue &x) -> RT { return {x.getLen()}; },
+      [](const fir::CharArrayBoxValue &x) -> RT { return {x.getLen()}; },
+      [&](const fir::BoxValue &) -> RT {
+        LLVM_DEBUG(mlir::emitWarning(
+            loc, "TODO: box value is missing type parameters"));
+        return {};
+      },
+      [&](const fir::MutableBoxValue &) -> RT {
+        // In this case, the type params may be bound to the variable in an
+        // ALLOCATE statement as part of a type-spec.
+        LLVM_DEBUG(mlir::emitWarning(
+            loc, "TODO: mutable box value is missing type parameters"));
+        return {};
+      },
+      [](const auto &) -> RT { return {}; });
+}
+
+bool fir::isArray(const fir::ExtendedValue &exv) {
+  return exv.match(
+      [](const fir::ArrayBoxValue &) { return true; },
+      [](const fir::CharArrayBoxValue &) { return true; },
+      [](const fir::BoxValue &box) { return box.hasRank(); },
+      [](const fir::MutableBoxValue &box) { return box.hasRank(); },
+      [](auto) { return false; });
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::CharBoxValue &box) {
+  return os << "boxchar { addr: " << box.getAddr() << ", len: " << box.getLen()
+            << " }";
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::ArrayBoxValue &box) {
+  os << "boxarray { addr: " << box.getAddr();
+  if (box.getLBounds().size()) {
+    os << ", lbounds: [";
+    llvm::interleaveComma(box.getLBounds(), os);
+    os << "]";
+  } else {
+    os << ", lbounds: all-ones";
+  }
+  os << ", shape: [";
+  llvm::interleaveComma(box.getExtents(), os);
+  return os << "]}";
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::CharArrayBoxValue &box) {
+  os << "boxchararray { addr: " << box.getAddr() << ", len : " << box.getLen();
+  if (box.getLBounds().size()) {
+    os << ", lbounds: [";
+    llvm::interleaveComma(box.getLBounds(), os);
+    os << "]";
+  } else {
+    os << " lbounds: all-ones";
+  }
+  os << ", shape: [";
+  llvm::interleaveComma(box.getExtents(), os);
+  return os << "]}";
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::ProcBoxValue &box) {
+  return os << "boxproc: { procedure: " << box.getAddr()
+            << ", context: " << box.hostContext << "}";
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::BoxValue &box) {
+  os << "box: { value: " << box.getAddr();
+  if (box.lbounds.size()) {
+    os << ", lbounds: [";
+    llvm::interleaveComma(box.lbounds, os);
+    os << "]";
+  }
+  if (!box.explicitParams.empty()) {
+    os << ", explicit type params: [";
+    llvm::interleaveComma(box.explicitParams, os);
+    os << "]";
+  }
+  if (!box.extents.empty()) {
+    os << ", explicit extents: [";
+    llvm::interleaveComma(box.extents, os);
+    os << "]";
+  }
+  return os << "}";
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::MutableBoxValue &box) {
+  os << "mutablebox: { addr: " << box.getAddr();
+  if (!box.lenParams.empty()) {
+    os << ", non deferred type params: [";
+    llvm::interleaveComma(box.lenParams, os);
+    os << "]";
+  }
+  const auto &properties = box.mutableProperties;
+  if (!properties.isEmpty()) {
+    os << ", mutableProperties: { addr: " << properties.addr;
+    if (!properties.lbounds.empty()) {
+      os << ", lbounds: [";
+      llvm::interleaveComma(properties.lbounds, os);
+      os << "]";
+    }
+    if (!properties.extents.empty()) {
+      os << ", shape: [";
+      llvm::interleaveComma(properties.extents, os);
+      os << "]";
+    }
+    if (!properties.deferredParams.empty()) {
+      os << ", deferred type params: [";
+      llvm::interleaveComma(properties.deferredParams, os);
+      os << "]";
+    }
+    os << "}";
+  }
+  return os << "}";
+}
+
+llvm::raw_ostream &fir::operator<<(llvm::raw_ostream &os,
+                                   const fir::ExtendedValue &exv) {
+  exv.match([&](const auto &value) { os << value; });
+  return os;
+}
+
+/// Debug verifier for MutableBox ctor. There is no guarantee that this will
+/// always be called, so it should not have any functional side effects,
+/// the const is here to enforce that.
+bool fir::MutableBoxValue::verify() const {
+  auto type = fir::dyn_cast_ptrEleTy(getAddr().getType());
+  if (!type)
+    return false;
+  auto box = type.dyn_cast<fir::BoxType>();
+  if (!box)
+    return false;
+  auto eleTy = box.getEleTy();
+  if (!eleTy.isa<fir::PointerType>() && !eleTy.isa<fir::HeapType>())
+    return false;
+
+  auto nParams = lenParams.size();
+  if (isCharacter()) {
+    if (nParams > 1)
+      return false;
+  } else if (!isDerived()) {
+    if (nParams != 0)
+      return false;
+  }
+  return true;
+}
+
+/// Debug verifier for BoxValue ctor. There is no guarantee this will
+/// always be called.
+bool fir::BoxValue::verify() const {
+  if (!addr.getType().isa<fir::BoxType>())
+    return false;
+  if (!lbounds.empty() && lbounds.size() != rank())
+    return false;
+  // Explicit extents are here to cover cases where an explicit-shape dummy
+  // argument comes as a fir.box. This can only happen with derived types and
+  // unlimited polymorphic.
+  if (!extents.empty() && !(isDerived() || isUnlimitedPolymorphic()))
+    return false;
+  if (!extents.empty() && extents.size() != rank())
+    return false;
+  if (isCharacter() && explicitParams.size() > 1)
+    return false;
+  return true;
+}
diff --git a/lib/Optimizer/Builder/CMakeLists.txt b/lib/Optimizer/Builder/CMakeLists.txt
index c000c98..f4aafeb 100644
--- a/lib/Optimizer/Builder/CMakeLists.txt
+++ b/lib/Optimizer/Builder/CMakeLists.txt
@@ -1,5 +1,6 @@
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 add_flang_library(FIRBuilder
+  BoxValue.cpp
   DoLoopHelper.cpp
   FIRBuilder.cpp
 
diff --git a/lib/Optimizer/Builder/FIRBuilder.cpp b/lib/Optimizer/Builder/FIRBuilder.cpp
index 22e77d4..ab060af 100644
--- a/lib/Optimizer/Builder/FIRBuilder.cpp
+++ b/lib/Optimizer/Builder/FIRBuilder.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Optimizer/Builder/FIRBuilder.h"
+#include "flang/Optimizer/Builder/BoxValue.h"
 #include "flang/Optimizer/Dialect/FIROpsSupport.h"
 #include "flang/Optimizer/Support/FatalError.h"
 #include "flang/Optimizer/Support/InternalNames.h"
@@ -207,6 +208,16 @@
       nm.append(".").append(llvm::toHex(name)));
 }
 
+mlir::Value fir::factory::locationToFilename(fir::FirOpBuilder &builder,
+                                             mlir::Location loc) {
+  if (auto flc = loc.dyn_cast<mlir::FileLineColLoc>()) {
+    // must be encoded as asciiz, C string
+    auto fn = flc.getFilename().str() + '\0';
+    return fir::getBase(createStringLiteral(builder, loc, fn));
+  }
+  return builder.createNullConstant(loc);
+}
+
 mlir::Value fir::factory::locationToLineNo(fir::FirOpBuilder &builder,
                                            mlir::Location loc,
                                            mlir::Type type) {
@@ -214,3 +225,24 @@
     return builder.createIntegerConstant(loc, type, flc.getLine());
   return builder.createIntegerConstant(loc, type, 0);
 }
+
+fir::ExtendedValue fir::factory::createStringLiteral(fir::FirOpBuilder &builder,
+                                                     mlir::Location loc,
+                                                     llvm::StringRef str) {
+  std::string globalName = fir::factory::uniqueCGIdent("cl", str);
+  auto type = fir::CharacterType::get(builder.getContext(), 1, str.size());
+  auto global = builder.getNamedGlobal(globalName);
+  if (!global)
+    global = builder.createGlobalConstant(
+        loc, type, globalName,
+        [&](fir::FirOpBuilder &builder) {
+          auto stringLitOp = builder.createStringLitOp(loc, str);
+          builder.create<fir::HasValueOp>(loc, stringLitOp);
+        },
+        builder.createLinkOnceLinkage());
+  auto addr = builder.create<fir::AddrOfOp>(loc, global.resultType(),
+                                            global.getSymbol());
+  auto len = builder.createIntegerConstant(
+      loc, builder.getCharacterLengthType(), str.size());
+  return fir::CharBoxValue{addr, len};
+}
diff --git a/lib/Optimizer/Dialect/FIROps.cpp b/lib/Optimizer/Dialect/FIROps.cpp
index 287cc6a..64174b8 100644
--- a/lib/Optimizer/Dialect/FIROps.cpp
+++ b/lib/Optimizer/Dialect/FIROps.cpp
@@ -1311,6 +1311,10 @@
 // GlobalLenOp
 //===----------------------------------------------------------------------===//
 
+mlir::Type fir::GlobalOp::resultType() {
+  return wrapAllocaResultType(getType());
+}
+
 static mlir::ParseResult parseGlobalLenOp(mlir::OpAsmParser &parser,
                                           mlir::OperationState &result) {
   llvm::StringRef fieldName;
diff --git a/lib/Optimizer/Dialect/FIRType.cpp b/lib/Optimizer/Dialect/FIRType.cpp
index fb3fba6..e020048 100644
--- a/lib/Optimizer/Dialect/FIRType.cpp
+++ b/lib/Optimizer/Dialect/FIRType.cpp
@@ -218,6 +218,34 @@
       .Default([](mlir::Type) { return mlir::Type{}; });
 }
 
+static bool hasDynamicSize(fir::RecordType recTy) {
+  for (auto field : recTy.getTypeList()) {
+    if (auto arr = field.second.dyn_cast<fir::SequenceType>()) {
+      if (sequenceWithNonConstantShape(arr))
+        return true;
+    } else if (characterWithDynamicLen(field.second)) {
+      return true;
+    } else if (auto rec = field.second.dyn_cast<fir::RecordType>()) {
+      if (hasDynamicSize(rec))
+        return true;
+    }
+  }
+  return false;
+}
+
+bool hasDynamicSize(mlir::Type t) {
+  if (auto arr = t.dyn_cast<fir::SequenceType>()) {
+    if (sequenceWithNonConstantShape(arr))
+      return true;
+    t = arr.getEleTy();
+  }
+  if (characterWithDynamicLen(t))
+    return true;
+  if (auto rec = t.dyn_cast<fir::RecordType>())
+    return hasDynamicSize(rec);
+  return false;
+}
+
 } // namespace fir
 
 namespace {
diff --git a/unittests/Optimizer/Builder/FIRBuilderTest.cpp b/unittests/Optimizer/Builder/FIRBuilderTest.cpp
index 06b4575..2942477 100644
--- a/unittests/Optimizer/Builder/FIRBuilderTest.cpp
+++ b/unittests/Optimizer/Builder/FIRBuilderTest.cpp
@@ -8,6 +8,7 @@
 
 #include "flang/Optimizer/Builder/FIRBuilder.h"
 #include "gtest/gtest.h"
+#include "flang/Optimizer/Builder/BoxValue.h"
 #include "flang/Optimizer/Support/InitFIR.h"
 #include "flang/Optimizer/Support/KindMapping.h"
 
@@ -243,3 +244,77 @@
       builder, builder.getUnknownLoc(), builder.getI64Type());
   checkIntegerConstant(line, builder.getI64Type(), 0);
 }
+
+TEST_F(FIRBuilderTest, hasDynamicSize) {
+  auto builder = getBuilder();
+  auto type = fir::CharacterType::get(builder.getContext(), 1, 16);
+  EXPECT_FALSE(fir::hasDynamicSize(type));
+  EXPECT_TRUE(fir::SequenceType::getUnknownExtent());
+  auto seqTy = builder.getVarLenSeqTy(builder.getI64Type(), 10);
+  EXPECT_TRUE(fir::hasDynamicSize(seqTy));
+  EXPECT_FALSE(fir::hasDynamicSize(builder.getI64Type()));
+}
+
+TEST_F(FIRBuilderTest, locationToFilename) {
+  auto builder = getBuilder();
+  auto loc =
+      mlir::FileLineColLoc::get(builder.getIdentifier("file1.f90"), 10, 5);
+  mlir::Value locToFile = fir::factory::locationToFilename(builder, loc);
+  auto addrOp = dyn_cast<fir::AddrOfOp>(locToFile.getDefiningOp());
+  auto symbol = addrOp.symbol().getRootReference().getValue();
+  auto global = builder.getNamedGlobal(symbol);
+  auto stringLitOps = global.getRegion().front().getOps<fir::StringLitOp>();
+  EXPECT_TRUE(llvm::hasSingleElement(stringLitOps));
+  for (auto stringLit : stringLitOps) {
+    EXPECT_EQ(10, stringLit.getSize().cast<mlir::IntegerAttr>().getValue());
+    EXPECT_TRUE(stringLit.getValue().isa<StringAttr>());
+    EXPECT_EQ(0,
+        strcmp("file1.f90\0",
+            stringLit.getValue()
+                .dyn_cast<StringAttr>()
+                .getValue()
+                .str()
+                .c_str()));
+  }
+}
+
+TEST_F(FIRBuilderTest, createStringLitOp) {
+  auto builder = getBuilder();
+  llvm::StringRef data("mystringlitdata");
+  auto loc = builder.getUnknownLoc();
+  auto op = builder.createStringLitOp(loc, data);
+  EXPECT_EQ(15, op.getSize().cast<mlir::IntegerAttr>().getValue());
+  EXPECT_TRUE(op.getValue().isa<StringAttr>());
+  EXPECT_EQ(data, op.getValue().dyn_cast<StringAttr>().getValue());
+}
+
+TEST_F(FIRBuilderTest, createStringLiteral) {
+  auto builder = getBuilder();
+  auto loc = builder.getUnknownLoc();
+  llvm::StringRef strValue("onestringliteral");
+  auto strLit = fir::factory::createStringLiteral(builder, loc, strValue);
+  EXPECT_EQ(0u, strLit.rank());
+  EXPECT_TRUE(strLit.getCharBox() != nullptr);
+  auto *charBox = strLit.getCharBox();
+  EXPECT_FALSE(fir::isArray(*charBox));
+  checkIntegerConstant(charBox->getLen(), builder.getCharacterLengthType(), 16);
+  auto generalGetLen = fir::getLen(strLit);
+  checkIntegerConstant(generalGetLen, builder.getCharacterLengthType(), 16);
+  auto addr = charBox->getBuffer();
+  EXPECT_TRUE(mlir::isa<fir::AddrOfOp>(addr.getDefiningOp()));
+  auto addrOp = dyn_cast<fir::AddrOfOp>(addr.getDefiningOp());
+  auto symbol = addrOp.symbol().getRootReference().getValue();
+  auto global = builder.getNamedGlobal(symbol);
+  EXPECT_EQ(
+      builder.createLinkOnceLinkage().getValue(), global.linkName().getValue());
+  EXPECT_EQ(fir::CharacterType::get(builder.getContext(), 1, strValue.size()),
+      global.type());
+
+  auto stringLitOps = global.getRegion().front().getOps<fir::StringLitOp>();
+  EXPECT_TRUE(llvm::hasSingleElement(stringLitOps));
+  for (auto stringLit : stringLitOps) {
+    EXPECT_EQ(16, stringLit.getSize().cast<mlir::IntegerAttr>().getValue());
+    EXPECT_TRUE(stringLit.getValue().isa<StringAttr>());
+    EXPECT_EQ(strValue, stringLit.getValue().dyn_cast<StringAttr>().getValue());
+  }
+}