[gcc r15-5693] ada: Do not use ATTR_ADDR_EXPR for 'Unrestricted_Access

[Marc Poulhi?s via Gcc-cvs]

https://gcc.gnu.org/g:ae7c0475f108f14cabcc1613df449670b1e9d1a2

commit r15-5693-gae7c0475f108f14cabcc1613df449670b1e9d1a2
Author: Eric Botcazou <ebotca...@adacore.come>
Date:   Mon Nov 11 11:16:26 2024 +0100

    ada: Do not use ATTR_ADDR_EXPR for 'Unrestricted_Access
    
    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.

Diff:
---
 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 5d971c1681d6..3aa41253d74c 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);