[gcc r14-7060] ada: Do not count comparison of addresses as a modification

[Marc Poulhi?s]

https://gcc.gnu.org/g:9b7d674fadd07aed242711e91232dbd049ef35be

commit r14-7060-g9b7d674fadd07aed242711e91232dbd049ef35be
Author: Viljar Indus <indus@adacore.com>
Date:   Tue Dec 12 17:03:13 2023 +0200

    ada: Do not count comparison of addresses as a modification
    
    In some extended code we generate comparisons between
    the Addresses of some variables. This causes those
    variables to be considered modified. Whereas in this
    particular scenario the variables are just referenced.
    
    gcc/ada/
    
            * sem_attr.adb: avoid marking a use of the Address attribute
            as a modification of its prefix.

Diff:
---
 gcc/ada/sem_attr.adb | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/sem_attr.adb b/gcc/ada/sem_attr.adb
index a194360a601..f52103f28dd 100644
--- a/gcc/ada/sem_attr.adb
+++ b/gcc/ada/sem_attr.adb
@@ -12133,9 +12133,13 @@ package body Sem_Attr is
             | Attribute_Code_Address
          =>
             --  To be safe, assume that if the address of a variable is taken,
-            --  it may be modified via this address, so note modification.
+            --  it may be modified via this address, so note modification,
+            --  unless the address is compared directly, which should not be
+            --  considered a modification.
 
-            if Is_Variable (P) then
+            if Is_Variable (P)
+              and then Nkind (Parent (N)) not in N_Op_Compare
+            then
                Note_Possible_Modification (P, Sure => False);
             end if;