[gcc r9-8894] c: Fix ICE with _Atomic side-effect in nested fn param decls [PR94842]

[gcc r9-8894] c: Fix ICE with _Atomic side-effect in nested fn param decls [PR94842]

[Jakub Jelinek]

https://gcc.gnu.org/g:b66139a3ba159473432edabb983c62219a28590d

commit r9-8894-gb66139a3ba159473432edabb983c62219a28590d
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Apr 30 21:48:30 2020 +0200

    c: Fix ICE with _Atomic side-effect in nested fn param decls [PR94842]
    
    If there are _Atomic side-effects in the parameter declarations
    of non-nested function, when they are parsed, current_function_decl is
    NULL, the create_artificial_label created labels during build_atomic* are
    then adjusted by store_parm_decls through set_labels_context_r callback.
    Unfortunately, if such thing happens in nested function parameter
    declarations, while those decls are parsed current_function_decl is the
    parent function (and am not sure it is a good idea to temporarily clear it,
    some code perhaps should be aware it is in a nested function, or it can
    refer to variables from the parent function etc.) and that means
    store_param_decls through set_labels_context_r doesn't adjust anything.
    As those labels are emitted in the nested function body rather than in the
    parent, I think it is ok to override the context in those cases.
    
    2020-04-30  Jakub Jelinek  <jakub@redhat.com>
    
            PR c/94842
            * c-decl.c (set_labels_context_r): In addition to context-less
            LABEL_DECLs adjust also LABEL_DECLs with context equal to
            parent function if any.
            (store_parm_decls): Adjust comment.
    
            * gcc.dg/pr94842.c: New test.
    
    (cherry picked from commit 61fb8963c22d91152a9c46a3512307bef3b3d7f7)

Diff:
---
 gcc/c/c-decl.c                 | 15 +++++++++++----
 gcc/testsuite/gcc.dg/pr94842.c | 11 +++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index caa2b75ac6d..80071112130 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -9464,15 +9464,18 @@ store_parm_decls_from (struct c_arg_info *arg_info)
   store_parm_decls ();
 }
 
-/* Called by walk_tree to look for and update context-less labels.  */
+/* Called by walk_tree to look for and update context-less labels
+   or labels with context in the parent function.  */
 
 static tree
 set_labels_context_r (tree *tp, int *walk_subtrees, void *data)
 {
+  tree ctx = static_cast<tree>(data);
   if (TREE_CODE (*tp) == LABEL_EXPR
-      && DECL_CONTEXT (LABEL_EXPR_LABEL (*tp)) == NULL_TREE)
+      && (DECL_CONTEXT (LABEL_EXPR_LABEL (*tp)) == NULL_TREE
+	  || DECL_CONTEXT (LABEL_EXPR_LABEL (*tp)) == DECL_CONTEXT (ctx)))
     {
-      DECL_CONTEXT (LABEL_EXPR_LABEL (*tp)) = static_cast<tree>(data);
+      DECL_CONTEXT (LABEL_EXPR_LABEL (*tp)) = ctx;
       *walk_subtrees = 0;
     }
 
@@ -9543,7 +9546,11 @@ store_parm_decls (void)
 	 gotos, labels, etc.  Because at that time the function decl
 	 for F has not been created yet, those labels do not have any
 	 function context.  But we have the fndecl now, so update the
-	 labels accordingly.  gimplify_expr would crash otherwise.  */
+	 labels accordingly.  gimplify_expr would crash otherwise.
+	 Or with nested functions the labels could be created with parent
+	 function's context, while when the statement is emitted at the
+	 start of the nested function, it needs the nested function's
+	 context.  */
       walk_tree_without_duplicates (&arg_info->pending_sizes,
 				    set_labels_context_r, fndecl);
       add_stmt (arg_info->pending_sizes);
diff --git a/gcc/testsuite/gcc.dg/pr94842.c b/gcc/testsuite/gcc.dg/pr94842.c
new file mode 100644
index 00000000000..33d9d42644c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94842.c
@@ -0,0 +1,11 @@
+/* PR c/94842 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+_Atomic float x = 5;
+
+void
+foo (void)
+{
+  void bar (float y[(int) (x += 2)]) {}
+}