openmp: Fix up cloning of dynamic C++ initializers for OpenMP target [PR119370]

The following testcase ICEs, because we emit the dynamic initialization twice,
once for host and once for target initialization, and although we use
copy_tree_body_r to unshare it, e.g. for the array initializers it can contain
TARGET_EXPRs with local temporaries (or local temporaries alone).
Now, these temporaries were created when current_function_decl was NULL,
they are outside of any particular function, so they have DECL_CONTEXT NULL.
That is normally fine, gimple_add_tmp_var will set DECL_CONTEXT for them
later on to the host __static_init* function into which they are gimplified.
The problem is that the copy_tree_body_r cloning happens before that (and has
to, gimplification is destructive and so we couldn't gimplify the same tree
again in __omp_static_init* function) and uses auto_var_in_fn_p to see what
needs to be remapped.  But that means it doesn't remap temporaries with
NULL DECL_CONTEXT and having the same temporaries in two different functions
results in ICEs (sure, one can e.g. use parent function's temporaries in a
nested function).

The following patch just arranges to set DECL_CONTEXT on the temporaries
to the host dynamic initialization function, so that they get remapped.
If gimplification cared whether DECL_CONTEXT is NULL or not, we could
remember those that we've changed in a vector and undo it afterwards,
but seems it doesn't really care.

2025-03-20  Jakub Jelinek  <jakub@redhat.com>

	PR c++/119370
	* decl2.cc (set_context_for_auto_vars_r): New function.
	(emit_partial_init_fini_fn): Call walk_tree with that function
	on &init before walk_tree with copy_tree_body_r.

	* g++.dg/gomp/pr119370.C: New test.

(cherry picked from commit e0b3eeb67f6d3bfe95591d8fb0c7dfd3f1b3b4ef)

diff --git a/gcc/cp/ChangeLog.omp b/gcc/cp/ChangeLog.omp
index 659c56a282adc7e6cb4385a48369d0d726ab320e..4cc1ad2df527ea98e48a7865d71434fbd6468e8c 100644 (file)
--- a/gcc/cp/ChangeLog.omp
+++ b/gcc/cp/ChangeLog.omp
@@ -1,5 +1,13 @@
 2025-04-25  Thomas Schwinge  <tschwinge@baylibre.com>
 
+       Backported from trunk:
+       2025-03-20  Jakub Jelinek  <jakub@redhat.com>
+
+       PR c++/119370
+       * decl2.cc (set_context_for_auto_vars_r): New function.
+       (emit_partial_init_fini_fn): Call walk_tree with that function
+       on &init before walk_tree with copy_tree_body_r.
+
        Backported from trunk:
        2025-02-25  Jakub Jelinek  <jakub@redhat.com>
 

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index b1754fb8f6c27370f808eb575281d79e47b0c982..02e1bfff979b9ed9b57707784361b5645b9d25f7 100644 (file)
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -4398,6 +4398,23 @@ one_static_initialization_or_destruction (bool initp, tree decl, tree init,
   DECL_STATIC_FUNCTION_P (current_function_decl) = 0;
 }
 
+/* Helper for emit_partial_init_fini_fn OpenMP target handling, called via
+   walk_tree.  Set DECL_CONTEXT on any automatic temporaries which still
+   have it NULL to id->src_fn, so that later copy_tree_body_r can remap those.
+   Otherwise DECL_CONTEXT would be set only during gimplification of the host
+   fn and when copy_tree_body_r doesn't remap those, we'd ICE during the
+   target fn gimplification because the same automatic VAR_DECL can't be
+   used in multiple functions (with the exception of nested functions).  */
+
+static tree
+set_context_for_auto_vars_r (tree *tp, int *, void *data)
+{
+  copy_body_data *id = (copy_body_data *) data;
+  if (auto_var_in_fn_p (*tp, NULL_TREE) && DECL_ARTIFICIAL (*tp))
+    DECL_CONTEXT (*tp) = id->src_fn;
+  return NULL_TREE;
+}
+
 /* Generate code to do the initialization or destruction of the decls in VARS,
    a TREE_LIST of VAR_DECL with static storage duration.
    Whether initialization or destruction is performed is specified by INITP.  */
@@ -4451,6 +4468,7 @@ emit_partial_init_fini_fn (bool initp, unsigned priority, tree vars,
          id.transform_new_cfg = true;
          id.transform_return_to_modify = false;
          id.eh_lp_nr = 0;
+         walk_tree (&init, set_context_for_auto_vars_r, &id, NULL);
          walk_tree (&init, copy_tree_body_r, &id, NULL);
        }
       /* Do one initialization or destruction.  */

diff --git a/gcc/testsuite/ChangeLog.omp b/gcc/testsuite/ChangeLog.omp
index d13b5d1f42871c1b2b02fc44c478e84f18ab66aa..af82bfa9262fed6b2471705ca25e6c0fb5079d05 100644 (file)
--- a/gcc/testsuite/ChangeLog.omp
+++ b/gcc/testsuite/ChangeLog.omp
@@ -1,5 +1,11 @@
 2025-04-25  Thomas Schwinge  <tschwinge@baylibre.com>
 
+       Backported from trunk:
+       2025-03-20  Jakub Jelinek  <jakub@redhat.com>
+
+       PR c++/119370
+       * g++.dg/gomp/pr119370.C: New test.
+
        Backported from trunk:
        2025-02-25  Jakub Jelinek  <jakub@redhat.com>
 

diff --git a/gcc/testsuite/g++.dg/gomp/pr119370.C b/gcc/testsuite/g++.dg/gomp/pr119370.C
new file mode 100644 (file)
index 0000000..9ecc9b7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/gomp/pr119370.C
@@ -0,0 +1,10 @@
+// PR c++/119370
+// { dg-do compile }
+
+#pragma omp declare target
+struct S {
+  int s;
+  S () : s (0) {}
+};
+S a[2];
+#pragma omp end declare target