[gcc(refs/users/aoliva/heads/testme)] make_type_from_size: avoid TYPE_DEBUG_TYPE / TREE_TYPE loops

[Alexandre Oliva]

https://gcc.gnu.org/g:0c598db8978a3569bd250a67ac52b7a88d544041

commit 0c598db8978a3569bd250a67ac52b7a88d544041
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Fri Jun 28 05:35:58 2024 -0300

    make_type_from_size: avoid TYPE_DEBUG_TYPE / TREE_TYPE loops
    
    Before make_type_from_size links a preexisting type to the
    newly-created narrower type to use the latter for debug information
    purposes, make sure that won't form a loop: if the type didn't have
    TREE_TYPE set, the new type will link back to the original type,
    rather than to the type's base type, and then modified_type_die would
    recurse indefinitely between them.
    
    
    for  gcc/ada/ChangeLog
    
            * gcc-interface/utils.cc (make_type_from_size): Avoid forming
            loops.

Diff:
---
 gcc/ada/gcc-interface/utils.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/gcc-interface/utils.cc b/gcc/ada/gcc-interface/utils.cc
index daf8d7ccdc5..b46e035e1d4 100644
--- a/gcc/ada/gcc-interface/utils.cc
+++ b/gcc/ada/gcc-interface/utils.cc
@@ -1427,10 +1427,12 @@ make_type_from_size (tree type, tree size_tree, bool for_biased)
       /* Enable us to avoid creating the same narrower type multiple
 	 times, and avoid duplication in debug information, by mapping
 	 the wider type to the narrower version.  If biasing is
-	 different, we use the narrower type for debug information.  */
+	 different, we use the narrower type for debug information.
+	 Be careful to avoid forming loops.  */
       if (TYPE_CAN_HAVE_DEBUG_TYPE_P (type)
 	  && !TYPE_DEBUG_TYPE (type)
-	  && biased_p == for_biased)
+	  && biased_p == for_biased
+	  && TREE_TYPE (new_type) != type)
 	SET_TYPE_DEBUG_TYPE (type, new_type);
 
       return new_type;