[flang] Lower more array character cases

This patch adds more lowering and tests for character array assignment/copy.

This patch is part of the upstreaming effort from fir-dev branch.

Depends on D121300

Reviewed By: PeteSteinfeld, schweitz

Differential Revision: https://reviews.llvm.org/D121301

Co-authored-by: Jean Perier <jperier@nvidia.com>
Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>

flang/include/flang/Lower/ConvertExpr.h

@@ -108,6 +108,16 @@ fir::MutableBoxValue createMutableBox(mlir::Location loc,
                                       AbstractConverter &converter,
                                       const SomeExpr &expr, SymMap &symMap);
 
+/// Create a fir::BoxValue describing the value of \p expr.
+/// If \p expr is a variable without vector subscripts, the fir::BoxValue
+/// described the variable storage. Otherwise, the created fir::BoxValue
+/// describes a temporary storage containing \p expr evaluation, and clean-up
+/// for the temporary is added to the provided StatementContext \p stmtCtx.
+fir::ExtendedValue createBoxValue(mlir::Location loc,
+                                  AbstractConverter &converter,
+                                  const SomeExpr &expr, SymMap &symMap,
+                                  StatementContext &stmtCtx);
+
 /// Lower an array assignment expression.
 ///
 /// 1. Evaluate the lhs to determine the rank and how to form the ArrayLoad

flang/include/flang/Lower/Mangler.h

@@ -13,6 +13,7 @@
 #ifndef FORTRAN_LOWER_MANGLER_H
 #define FORTRAN_LOWER_MANGLER_H
 
+#include "flang/Evaluate/expression.h"
 #include "mlir/IR/BuiltinTypes.h"
 #include "llvm/ADT/StringRef.h"
 #include <string>
@@ -58,6 +59,38 @@ std::string mangleName(const semantics::DerivedTypeSpec &);
 /// Recover the bare name of the original symbol from an internal name.
 std::string demangleName(llvm::StringRef name);
 
+std::string
+mangleArrayLiteral(const uint8_t *addr, size_t size,
+                   const Fortran::evaluate::ConstantSubscripts &shape,
+                   Fortran::common::TypeCategory cat, int kind = 0,
+                   Fortran::common::ConstantSubscript charLen = -1);
+
+template <Fortran::common::TypeCategory TC, int KIND>
+std::string mangleArrayLiteral(
+    const Fortran::evaluate::Constant<Fortran::evaluate::Type<TC, KIND>> &x) {
+  return mangleArrayLiteral(
+      reinterpret_cast<const uint8_t *>(x.values().data()),
+      x.values().size() * sizeof(x.values()[0]), x.shape(), TC, KIND);
+}
+
+template <int KIND>
+std::string
+mangleArrayLiteral(const Fortran::evaluate::Constant<Fortran::evaluate::Type<
+                       Fortran::common::TypeCategory::Character, KIND>> &x) {
+  return mangleArrayLiteral(
+      reinterpret_cast<const uint8_t *>(x.values().data()),
+      x.values().size() * sizeof(x.values()[0]), x.shape(),
+      Fortran::common::TypeCategory::Character, KIND, x.LEN());
+}
+
+inline std::string mangleArrayLiteral(
+    const Fortran::evaluate::Constant<Fortran::evaluate::SomeDerived> &x) {
+  return mangleArrayLiteral(
+      reinterpret_cast<const uint8_t *>(x.values().data()),
+      x.values().size() * sizeof(x.values()[0]), x.shape(),
+      Fortran::common::TypeCategory::Derived);
+}
+
 } // namespace lower::mangle
 } // namespace Fortran