[flang] Fixed comparison for derived types constants.

[vzakhari]

Summary

The two constants should be equal only if their derived types
are the same. This fixes regression caused by D150380.

[jeanPerier]

Looks good

flang/include/flang/Evaluate/constant.h

Constant(const semantics::DerivedTypeSpec &,
       std::vector<StructureConstructorValues> &&, ConstantSubscripts &&);
   Constant(const semantics::DerivedTypeSpec &,
       std::vector<StructureConstructor> &&, ConstantSubscripts &&);
   CLASS_BOILERPLATE(Constant)
 
   std::optional<StructureConstructor> GetScalarValue() const;
   StructureConstructor At(const ConstantSubscripts &) const;
 
+  bool operator==(const Constant &) const;
   Constant Reshape(ConstantSubscripts &&) const;
   std::size_t CopyFrom(const Constant &source, std::size_t count,
       ConstantSubscripts &resultSubscripts, const std::vector<int> *dimOrder);
 };
 
 FOR_EACH_LENGTHLESS_INTRINSIC_KIND(extern template class ConstantBase, )
 extern template class ConstantBase<SomeDerived, StructureConstructorValues>;
 FOR_EACH_INTRINSIC_KIND(extern template class Constant, )
 
 #define INSTANTIATE_CONSTANT_TEMPLATES \
   FOR_EACH_LENGTHLESS_INTRINSIC_KIND(template class ConstantBase, ) \
   template class ConstantBase<SomeDerived, StructureConstructorValues>; \
   FOR_EACH_INTRINSIC_KIND(template class Constant, )
 } // namespace Fortran::evaluate
 #endif // FORTRAN_EVALUATE_CONSTANT_H_

flang/lib/Evaluate/constant.cpp

Constant<SomeDerived>::GetScalarValue() const {
   }
 }
 
 StructureConstructor Constant<SomeDerived>::At(
     const ConstantSubscripts &index) const {
   return {result().derivedTypeSpec(), values_.at(SubscriptsToOffset(index))};
 }
 
+bool Constant<SomeDerived>::operator==(
+    const Constant<SomeDerived> &that) const {
+  return result().derivedTypeSpec() == that.result().derivedTypeSpec() &&
+      shape() == that.shape() && values_ == that.values_;
+}
+
 auto Constant<SomeDerived>::Reshape(ConstantSubscripts &&dims) const
     -> Constant {
   return {result().derivedTypeSpec(), Base::Reshape(dims), std::move(dims)};
 }
 
 std::size_t Constant<SomeDerived>::CopyFrom(const Constant<SomeDerived> &source,
     std::size_t count, ConstantSubscripts &resultSubscripts,
     const std::vector<int> *dimOrder) {

flang/test/Lower/constant-literal-mangling.f90

 ! Test the names created for globals holding constant literal values
 ! RUN: bbc -emit-fir -o - %s | FileCheck %s
 
 type someType
   integer :: i
 end type
 
 type otherType
   integer :: i
 end type
 
+type emptyType1
+end type emptyType1
+
+type emptyType2
+end type emptyType2
+
   print *, [42, 42]
 ! CHECK: fir.address_of(@_QQro.2xi4.0)
 
   print *, reshape([42, 42, 42, 42, 42, 42], [2,3])
 ! CHECK: fir.address_of(@_QQro.2x3xi4.1)
 
   print *, [42_8, 42_8]
 ! CHECK: fir.address_of(@_QQro.2xi8.2)
! CHECK: fir.address_of(@_QQro.0x4xc1.null.12)
   print *, [Character(2)::]
 ! CHECK: fir.address_of(@_QQro.0x2xc1.null.13)
   print *, [Character(2)::]
 ! CHECK: fir.address_of(@_QQro.0x2xc1.null.13)
 
   print *, [otherType(42)]
 ! CHECK: fir.address_of(@_QQro.1x_QFTothertype.14)
 
+  print *, [emptyType1()]
+  print *, [emptyType2()]
 end
 
 ! CHECK: fir.global internal @_QQro.1x_QFTsometype.10 constant : !fir.array<1x!fir.type<_QFTsometype{i:i32}>> {
 ! CHECK:   %{{.*}} = arith.constant 11 : i32
 ! CHECK: }
 
 ! CHECK: fir.global internal @_QQro.1x_QFTsometype.11 constant : !fir.array<1x!fir.type<_QFTsometype{i:i32}>> {
 ! CHECK:   %{{.*}} = arith.constant 42 : i32