Re: [PATCH] [DWARF] Fix hierarchy of debug information for offload kernels.

[Richard Biener <richard.guenther@gmail.com>]

On Thu, Jul 15, 2021 at 12:35 PM Hafiz Abid Qadeer
<abid_qadeer@mentor.com> wrote:
>
> On 15/07/2021 11:33, Thomas Schwinge wrote:
> >
> >> Note that the "parent" should be abstract but I don't think dwarf has a
> >> way to express a fully abstract parent of a concrete instance child - or
> >> at least how GCC expresses this causes consumers to "misinterpret"
> >> that.  I wonder if adding a DW_AT_declaration to the late DWARF
> >> emitted "parent" would fix things as well here?
> >
> > (I suppose not, Abid?)
> >
>
> Yes, adding DW_AT_declaration does not fix the problem.

Does emitting

DW_TAG_compile_unit
  DW_AT_name    ("<artificial>")

  DW_TAG_subprogram // notional parent function (foo) with no code range
    DW_AT_declaration 1
a:    DW_TAG_subprogram // offload function foo._omp_fn.0
      DW_AT_declaration 1

  DW_TAG_subprogram // offload function
  DW_AT_abstract_origin a
...

do the trick?  The following would do this, flattening function definitions
for the concrete copies:

diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 82783c4968b..a9c8bc43e88 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -6076,6 +6076,11 @@ maybe_create_die_with_external_ref (tree decl)
   /* Peel types in the context stack.  */
   while (ctx && TYPE_P (ctx))
     ctx = TYPE_CONTEXT (ctx);
+  /* For functions peel the context up to namespace/TU scope.  The abstract
+     copies reveal the true nesting.  */
+  if (TREE_CODE (decl) == FUNCTION_DECL)
+    while (ctx && TREE_CODE (ctx) == FUNCTION_DECL)
+      ctx = DECL_CONTEXT (ctx);
   /* Likewise namespaces in case we do not want to emit DIEs for them.  */
   if (debug_info_level <= DINFO_LEVEL_TERSE)
     while (ctx && TREE_CODE (ctx) == NAMESPACE_DECL)
@@ -6099,8 +6104,7 @@ maybe_create_die_with_external_ref (tree decl)
        /* Leave function local entities parent determination to when
           we process scope vars.  */
        ;
-      else
-       parent = lookup_decl_die (ctx);
+      parent = lookup_decl_die (ctx);
     }
   else
     /* In some cases the FEs fail to set DECL_CONTEXT properly.



>
> --
> Hafiz Abid Qadeer
> Mentor, a Siemens Business