From: Eric Botcazou <ebotca...@adacore.come>

Unlike for 'Access or 'Unchecked_Access, the Attribute_to_gnu routine passes
ATTR_ADDR_EXPR to build_unary_op for 'Unrestricted_Access, which causes the
processing done in build_unary_op to flatten the reference, in particular to
remove all intermediate (view) conversions, which may be problematic for the
SUBSTITUTE_PLACEHOLDER_IN_EXPR machinery.

gcc/ada/ChangeLog:

        * gcc-interface/trans.cc (Attribute_to_gnu) <Attr_Access>: Do not
        pass ATTR_ADDR_EXPR to build_unary_op for 'Unrestricted_Access.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/gcc-interface/trans.cc | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/gcc-interface/trans.cc b/gcc/ada/gcc-interface/trans.cc
index 5d971c1681d..3aa41253d74 100644
--- a/gcc/ada/gcc-interface/trans.cc
+++ b/gcc/ada/gcc-interface/trans.cc
@@ -1840,10 +1840,15 @@ Attribute_to_gnu (Node_Id gnat_node, tree 
*gnu_result_type_p,
       gcc_assert (TREE_CODE (gnu_prefix) != TYPE_DECL);
 
       gnu_result_type = get_unpadded_type (Etype (gnat_node));
+
+      /* We used to pass ATTR_ADDR_EXPR for Attr_Unrestricted_Access too, but
+        the processing done in build_unary_op for it flattens the reference,
+        in particular removes all intermediate (view) conversions, which may
+        cause SUBSTITUTE_PLACEHOLDER_IN_EXPR to fail to substitute in the
+        bounds of a fat pointer returned for Attr_Unrestricted_Access.  */
       gnu_result
-       = build_unary_op (((attribute == Attr_Address
-                           || attribute == Attr_Unrestricted_Access)
-                          && !Must_Be_Byte_Aligned (gnat_node))
+       = build_unary_op (attribute == Attr_Address
+                         && !Must_Be_Byte_Aligned (gnat_node)
                          ? ATTR_ADDR_EXPR : ADDR_EXPR,
                          gnu_result_type, gnu_prefix);
 
-- 
2.43.0

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