[Patch] OpenMP/Fortran: Fix handling of 'declare target' with 'link' clause [PR11555]

[Patch] OpenMP/Fortran: Fix handling of 'declare target' with 'link' clause [PR11555]

[Tobias Burnus]

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Hi all,

it turned out that 'declare target' with 'link' clause was broken in multiple ways.

The main fix is the attached patch, i.e. namely pushing the variables already to
the offload-vars list already in the FE.

When implementing it, I noticed:
* C has a similar issue when using nested functions, which is
   a GNU extension →https://gcc.gnu.org/115574

* When doing partial mapping of arrays (which is one of the reasons for 'link'),
   offsets are mishandled in Fortran (not tested in C), see FIXME in the patch)
   There: arr2(10) should print 10 but with map(arr2(10:)) it prints 19.
   (I will file a PR about this).

* It might happen that linked variables do not get linked. I have not investigated
   why, but 'arr2' gives link errors – while 'arr' works.
   See FIXME in the patch. (I will file a PR about this)

* For COMMON blocks, map(/common/) is rejected,https://gcc.gnu.org/PR115577

* When then mapping map(a,b,c) which is identical for 'common /mycom/ a,b,c',
   it fails to link the device side as the 'mycom_' symbol cannot be found on the
   device side.  (I will file a PR about this)

As COMMON as issues, an alternative would be to defer the trans-common.cc
changes to a later patch.

Comments, questions, concerns?

Tobias

PS: Tested with nvptx offloading with a page-migration supporting system with
nvptx and GCN offloading configured and no new fails observed.

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OpenMP/Fortran: Fix handling of 'declare target' with 'link' clause [PR11555]

Contrary to a normal 'declare target', the 'declare target link' attribute
also needs to set node->offloadable and push the offload_vars in the front end.

Linked variables require that the data is mapped. For module variables, this
can happen anywhere. For variables in an external subprograms or the main
programm, this can only happen in the either that program itself or in an
internal subprogram. - Whether a variable is just normally mapped or linked then
becomes relevant if a device routine exists that can access that variable,
i.e. an internal procedure has then to be marked as declare target.

	PR fortran/115559

gcc/fortran/ChangeLog:

	* trans-common.cc (build_common_decl): Add 'omp declare target' and
	'omp declare target link' variables to offload_vars.
	* trans-decl.cc (add_attributes_to_decl): Likewise; update args and
	call decl_attributes.
	(get_proc_pointer_decl, gfc_get_extern_function_decl,
	build_function_decl): Update calls.
	(gfc_get_symbol_decl): Likewise; move after 'DECL_STATIC (t)=1'
	to avoid errors with symtab_node::get_create.

libgomp/ChangeLog:

	* testsuite/libgomp.fortran/declare-target-link.f90: New test.

 gcc/fortran/trans-common.cc                        |  21 ++++
 gcc/fortran/trans-decl.cc                          |  81 +++++++++-----
 .../libgomp.fortran/declare-target-link.f90        | 119 +++++++++++++++++++++
 3 files changed, 195 insertions(+), 26 deletions(-)

diff --git a/gcc/fortran/trans-common.cc b/gcc/fortran/trans-common.cc
index 5f44e7bd663..e714342c3c0 100644
--- a/gcc/fortran/trans-common.cc
+++ b/gcc/fortran/trans-common.cc
@@ -98,6 +98,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "coretypes.h"
 #include "tm.h"
 #include "tree.h"
+#include "cgraph.h"
+#include "context.h"
+#include "omp-offload.h"
 #include "gfortran.h"
 #include "trans.h"
 #include "stringpool.h"
@@ -497,6 +500,24 @@ build_common_decl (gfc_common_head *com, tree union_type, bool is_init)
 	  = tree_cons (get_identifier ("omp declare target"),
 		       omp_clauses, DECL_ATTRIBUTES (decl));
 
+      if (com->omp_declare_target_link || com->omp_declare_target)
+	{
+	  /* Add to offload_vars; get_create does so for omp_declare_target,
+	     omp_declare_target_link requires manual work.  */
+	  gcc_assert (symtab_node::get (decl) == 0);
+	  symtab_node *node = symtab_node::get_create (decl);
+	  if (node != NULL && com->omp_declare_target_link)
+	    {
+	      node->offloadable = 1;
+	      if (ENABLE_OFFLOADING)
+		{
+		  g->have_offload = true;
+		  if (is_a <varpool_node *> (node))
+		    vec_safe_push (offload_vars, decl);
+		}
+	    }
+	}
+
       /* Place the back end declaration for this common block in
          GLOBAL_BINDING_LEVEL.  */
       gfc_map_of_all_commons[identifier] = pushdecl_top_level (decl);
diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index 8d4f06a4e1d..4067dd6ed77 100644
--- a/gcc/fortran/trans-decl.cc
+++ b/gcc/fortran/trans-decl.cc
@@ -46,7 +46,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "trans-stmt.h"
 #include "gomp-constants.h"
 #include "gimplify.h"
+#include "context.h"
 #include "omp-general.h"
+#include "omp-offload.h"
 #include "attr-fnspec.h"
 #include "tree-iterator.h"
 #include "dependency.h"
@@ -1470,19 +1472,18 @@ gfc_add_assign_aux_vars (gfc_symbol * sym)
 }
 
 
-static tree
-add_attributes_to_decl (symbol_attribute sym_attr, tree list)
+static void
+add_attributes_to_decl (tree *decl_p, const gfc_symbol *sym)
 {
   unsigned id;
-  tree attr;
+  tree list = NULL_TREE;
+  symbol_attribute sym_attr = sym->attr;
 
   for (id = 0; id < EXT_ATTR_NUM; id++)
     if (sym_attr.ext_attr & (1 << id) && ext_attr_list[id].middle_end_name)
       {
-	attr = build_tree_list (
-		 get_identifier (ext_attr_list[id].middle_end_name),
-				 NULL_TREE);
-	list = chainon (list, attr);
+	tree ident = get_identifier (ext_attr_list[id].middle_end_name);
+	list = tree_cons (ident, NULL_TREE, list);
       }
 
   tree clauses = NULL_TREE;
@@ -1545,6 +1546,7 @@ add_attributes_to_decl (symbol_attribute sym_attr, tree list)
       clauses = c;
     }
 
+  bool has_declare = true;
   if (sym_attr.omp_declare_target_link
       || sym_attr.oacc_declare_link)
     list = tree_cons (get_identifier ("omp declare target link"),
@@ -1556,12 +1558,45 @@ add_attributes_to_decl (symbol_attribute sym_attr, tree list)
 	   || sym_attr.oacc_declare_device_resident)
     list = tree_cons (get_identifier ("omp declare target"),
 		      clauses, list);
+  else
+    has_declare = false;
 
   if (sym_attr.omp_declare_target_indirect)
     list = tree_cons (get_identifier ("omp declare target indirect"),
 		      clauses, list);
 
-  return list;
+  decl_attributes (decl_p, list, 0);
+
+  if (has_declare
+      && VAR_P (*decl_p)
+      && sym->ns->proc_name->attr.flavor != FL_MODULE)
+    {
+      has_declare = false;
+      for (gfc_namespace* ns = sym->ns->contained; ns; ns = ns->sibling)
+	if (ns->proc_name->attr.omp_declare_target)
+	  {
+	    has_declare = true;
+	    break;
+	  }
+    }
+
+  if (has_declare && VAR_P (*decl_p) && has_declare)
+    {
+      /* Add to offload_vars; get_create does so for omp_declare_target,
+	 omp_declare_target_link requires manual work.  */
+      gcc_assert (symtab_node::get (*decl_p) == 0);
+      symtab_node *node = symtab_node::get_create (*decl_p);
+      if (node != NULL && sym_attr.omp_declare_target_link)
+	{
+	  node->offloadable = 1;
+	  if (ENABLE_OFFLOADING)
+	    {
+	      g->have_offload = true;
+	      if (is_a <varpool_node *> (node))
+		vec_safe_push (offload_vars, *decl_p);
+	    }
+	}
+    }
 }
 
 
@@ -1576,7 +1611,6 @@ gfc_get_symbol_decl (gfc_symbol * sym)
 {
   tree decl;
   tree length = NULL_TREE;
-  tree attributes;
   int byref;
   bool intrinsic_array_parameter = false;
   bool fun_or_res;
@@ -1861,12 +1895,6 @@ gfc_get_symbol_decl (gfc_symbol * sym)
   decl = build_decl (gfc_get_location (&sym->declared_at),
 		     VAR_DECL, gfc_sym_identifier (sym), gfc_sym_type (sym));
 
-  /* Add attributes to variables.  Functions are handled elsewhere.  */
-  attributes = add_attributes_to_decl (sym->attr, NULL_TREE);
-  decl_attributes (&decl, attributes, 0);
-  if (sym->ts.deferred && VAR_P (length))
-    decl_attributes (&length, attributes, 0);
-
   /* Symbols from modules should have their assembler names mangled.
      This is done here rather than in gfc_finish_var_decl because it
      is different for string length variables.  */
@@ -2032,6 +2060,12 @@ gfc_get_symbol_decl (gfc_symbol * sym)
 	TREE_READONLY (decl) = 1;
     }
 
+  /* Add attributes to variables.  Functions are handled elsewhere.  */
+  add_attributes_to_decl (&decl, sym);
+
+  if (sym->ts.deferred && VAR_P (length))
+    decl_attributes (&length, DECL_ATTRIBUTES (decl), 0);
+
   return decl;
 }
 
@@ -2068,7 +2102,6 @@ static tree
 get_proc_pointer_decl (gfc_symbol *sym)
 {
   tree decl;
-  tree attributes;
 
   if (sym->module || sym->fn_result_spec)
     {
@@ -2148,8 +2181,7 @@ get_proc_pointer_decl (gfc_symbol *sym)
       && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)))
     set_decl_tls_model (decl, decl_default_tls_model (decl));
 
-  attributes = add_attributes_to_decl (sym->attr, NULL_TREE);
-  decl_attributes (&decl, attributes, 0);
+  add_attributes_to_decl (&decl, sym);
 
   return decl;
 }
@@ -2163,7 +2195,6 @@ gfc_get_extern_function_decl (gfc_symbol * sym, gfc_actual_arglist *actual_args,
 {
   tree type;
   tree fndecl;
-  tree attributes;
   gfc_expr e;
   gfc_intrinsic_sym *isym;
   gfc_expr argexpr;
@@ -2361,8 +2392,7 @@ module_sym:
   DECL_EXTERNAL (fndecl) = 1;
   TREE_PUBLIC (fndecl) = 1;
 
-  attributes = add_attributes_to_decl (sym->attr, NULL_TREE);
-  decl_attributes (&fndecl, attributes, 0);
+  add_attributes_to_decl (&fndecl, sym);
 
   gfc_set_decl_assembler_name (fndecl, mangled_name);
 
@@ -2421,7 +2451,7 @@ module_sym:
 static void
 build_function_decl (gfc_symbol * sym, bool global)
 {
-  tree fndecl, type, attributes;
+  tree fndecl, type;
   symbol_attribute attr;
   tree result_decl;
   gfc_formal_arglist *f;
@@ -2472,15 +2502,14 @@ build_function_decl (gfc_symbol * sym, bool global)
   if (sym->attr.referenced || sym->attr.entry_master)
     TREE_USED (fndecl) = 1;
 
-  attributes = add_attributes_to_decl (attr, NULL_TREE);
-  decl_attributes (&fndecl, attributes, 0);
+  add_attributes_to_decl (&fndecl, sym);
 
   /* Figure out the return type of the declared function, and build a
      RESULT_DECL for it.  If this is a subroutine with alternate
      returns, build a RESULT_DECL for it.  */
   result_decl = NULL_TREE;
   /* TODO: Shouldn't this just be TREE_TYPE (TREE_TYPE (fndecl)).  */
-  if (attr.function)
+  if (sym->attr.function)
     {
       if (gfc_return_by_reference (sym))
 	type = void_type_node;
@@ -2527,7 +2556,7 @@ build_function_decl (gfc_symbol * sym, bool global)
   /* Set attributes for PURE functions. A call to a PURE function in the
      Fortran 95 sense is both pure and without side effects in the C
      sense.  */
-  if (attr.pure || attr.implicit_pure)
+  if (sym->attr.pure || sym->attr.implicit_pure)
     {
       /* TODO: check if a pure SUBROUTINE has no INTENT(OUT) arguments
 	 including an alternate return. In that case it can also be
diff --git a/libgomp/testsuite/libgomp.fortran/declare-target-link.f90 b/libgomp/testsuite/libgomp.fortran/declare-target-link.f90
new file mode 100644
index 00000000000..5243fe09002
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/declare-target-link.f90
@@ -0,0 +1,119 @@
+! { dg-additional-options "-Wall" }
+! PR fortran/115559
+
+module m
+   integer :: A
+   !$omp declare target link(A)
+end module m
+
+subroutine f
+  implicit none (type, external)
+  integer, save :: x, y  ! { dg-warning "Unused variable 'y' declared" }
+  !$omp declare target link(x, y)
+
+  ! note: y is not 'link' as gfortran doesn't regard it as used
+  x = 6
+  call ii
+
+contains
+  subroutine k
+    !$omp declare target
+     use m
+     A = 5
+  end
+  subroutine ii
+    integer :: res
+    !$omp target map(x) map(from: res)
+      call k()
+      call ll()
+      res = get()
+    !$omp end target
+    ! print *, res
+    if (res /= 6 + 7 + 5) &
+      stop 1
+  end
+  subroutine ll
+    !$omp declare target
+    x = x + 7
+  end
+  integer function get()
+     use m
+     !$omp declare target
+     get = x + A
+  end
+end
+
+
+subroutine sub
+  implicit none (type, external)
+  integer, save :: arr(100), arr2(1:4)
+  !$omp declare target link(arr,arr2)
+
+  call mapit
+  call device1
+  call re_mapit
+  call device2
+contains
+  subroutine mapit
+    integer :: i
+    arr = [(i, i=1,100)]
+    ! FIXME: map(arr(10:50)) mapping causes offset issues:
+    ! i.e. accessing arr(10) later accesses the 19th not the 10th element!
+    ! !$omp target enter data map(to:arr(10:50)) map(alloc: arr2(1:4))
+    !$omp target enter data map(to:arr) map(alloc: arr2(1:4)) ! Workaround: mapp all of 'arr'
+  end subroutine
+  subroutine re_mapit
+    integer :: i
+    !$omp target exit data map(from:arr(10:50)) map(delete: arr2)
+
+    if (any (arr(1:9) /= [(i, i=1,9)])) stop 2
+    if (any (arr(10:50) /= [(3-10*i, i=10,50)])) stop 3
+    if (any (arr(51:100) /= [(i, i=51,100)])) stop 4
+  end subroutine
+
+  subroutine device1
+    integer :: res
+    !$omp target map(from:res)
+      res = run_device1()
+    !$omp end target
+    print *, res
+    ! FIXME: arr2 not link mapped
+    ! if (res /= -11436) stop 5
+    if (res /= -11546) stop 5 ! FIXME
+  end
+  integer function run_device1()
+    !$omp declare target
+    integer :: i
+    run_device1 = -99
+    ! FIXME: arr2 not link mapped
+    !   arr2 = [11,22,33,44]
+    if (any (arr(10:50) /= [(i, i=10,50)])) then
+      run_device1 = arr(11)
+      return
+    end if
+    ! FIXME:
+    ! run_device1 = sum(arr(10:13) + arr2)
+    run_device1 = sum(arr(10:13) ) ! FIXME
+    do i = 10, 50
+      arr(i) = 3 - 10 * arr(i)
+    end do
+    run_device1 = run_device1 + sum(arr(15:50))
+  end
+  subroutine device2
+  end
+  integer function run_device2()
+    !$omp declare target
+    run_device2 = -99
+  end
+end
+
+
+use m
+implicit none (type, external)
+external f
+external sub
+
+!$omp target enter data map(alloc: A)
+call f()
+call sub
+end