[gcc r12-1679] [Ada] Disable wrong computation of offsets within multidimensional arrays

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:05447313c9acb24e0fad6305ad333077707de9ba

commit r12-1679-g05447313c9acb24e0fad6305ad333077707de9ba
Author: Piotr Trojanek <trojanek@adacore.com>
Date:   Fri Mar 26 09:36:49 2021 +0100

    [Ada] Disable wrong computation of offsets within multidimensional arrays
    
    gcc/ada/
    
            * sem_util.adb (Indexed_Component_Bit_Offset): Return an unknown
            offset for components within multidimensional arrays; remove
            redundant parens.

Diff:
---
 gcc/ada/sem_util.adb | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
index 2e102b93497..44a568404ad 100644
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -14827,6 +14827,12 @@ package body Sem_Util is
          return No_Uint;
       end if;
 
+      --  Do not attempt to compute offsets within multi-dimensional arrays
+
+      if Present (Next_Index (Ind)) then
+         return No_Uint;
+      end if;
+
       if Nkind (Ind) = N_Subtype_Indication then
          Ind := Constraint (Ind);
 
@@ -14843,7 +14849,7 @@ package body Sem_Util is
 
       --  Return the scaled offset
 
-      return Off * (Expr_Value (Exp) - Expr_Value (Low_Bound ((Ind))));
+      return Off * (Expr_Value (Exp) - Expr_Value (Low_Bound (Ind)));
    end Indexed_Component_Bit_Offset;
 
    -----------------------------