[flang][hlfir] Support type bound procedure in type descriptors

[jeanPerier]

Summary

In hlfir, procedure designators are propagated as fir.box_proc.
Derived type descriptors are compiler generated constant structure
constructors. They contain CFPTR components for the type bound
procedure addresses.
Before being cast to an integer type so that they can be stored
in the CFPTR components, the fir.box_proc addresses must be
obtained with a fir.box_addr.

[clementval]

LGTM

flang/lib/Lower/ConvertConstant.cpp

if (Fortran::semantics::IsBuiltinCPtr(sym)) {
           converter, loc, expr.value()));
       if (addr.getType() == componentTy) {
         // Do nothing. The Ev::Expr was returned as a value that can be
         // inserted directly to the component without an intermediary.
       } else {
         // The Ev::Expr returned is an initializer that is a pointer (e.g.,
         // null) that must be inserted into an intermediate cptr record
         // value's address field, which ought to be an intptr_t on the target.
+        if (addr.getType().isa<fir::BoxProcType>())
+          addr = builder.create<fir::BoxAddrOp>(loc, addr);
         assert((fir::isa_ref_type(addr.getType()) ||
                 addr.getType().isa<mlir::FunctionType>()) &&
                "expect reference type for address field");
         assert(fir::isa_derived(componentTy) &&
                "expect C_PTR, C_FUNPTR to be a record");
         auto cPtrRecTy = componentTy.cast<fir::RecordType>();
         llvm::StringRef addrFieldName = Fortran::lower::builtin::cptrFieldName;
         mlir::Type addrFieldTy = cPtrRecTy.getType(addrFieldName);

flang/test/Lower/HLFIR/type-bound-proc-tdesc.f90

+! Test lowering of type bound procedure in the derived type descriptors (that
+! are compiler generated constant structure constructors).
+! RUN: bbc -emit-fir -hlfir -o - %s | FileCheck %s
+
+module type_bound_proc_tdesc
+  type :: t
+  contains
+    procedure, nopass :: simple => simple_impl
+    procedure, nopass :: return_char => return_char_impl
+  end type
+
+interface
+  function return_char_impl()
+    character(10) :: return_char_impl
+  end function
+  subroutine simple_impl()
+  end subroutine
+end interface
+end
+  use type_bound_proc_tdesc
+  type(t) :: a
+end
+
+! CHECK-LABEL: fir.global {{.*}} @_QMtype_bound_proc_tdescE.v.t
+! CHECK:  fir.address_of(@_QPreturn_char_impl) : (!fir.ref<!fir.char<1,10>>, index) -> !fir.boxchar<1>
+! CHECK:  %[[VAL_8:.*]] = fir.extract_value %{{.*}}, [0 : index] : (tuple<!fir.boxproc<() -> ()>, i64>) -> !fir.boxproc<() -> ()>
+! CHECK:  fir.box_addr %[[VAL_8]] : (!fir.boxproc<() -> ()>) -> (() -> ())
+! ...
+! CHECK:  %[[VAL_25:.*]] = fir.address_of(@_QPsimple_impl) : () -> ()
+! CHECK:  %[[VAL_26:.*]] = fir.emboxproc %[[VAL_25]] : (() -> ()) -> !fir.boxproc<() -> ()>
+! CHECK:  fir.box_addr %[[VAL_26]] : (!fir.boxproc<() -> ()>) -> (() -> ())