[COMMITTED] ada: Fix internal error on address of element of packed array component

[COMMITTED] ada: Fix internal error on address of element of packed array component

[Marc Poulhiès]

From: Eric Botcazou <ebotcazou@adacore.com>

This occurs when the component is part of a discriminated type and its
offset depends on a discriminant, the problem being that the front-end
generates an incomplete Bit_Position attribute reference.

gcc/ada/

	* exp_pakd.adb (Get_Base_And_Bit_Offset): Use the full component
	reference instead of just the selector name for 'Bit_Position.

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

---
 gcc/ada/exp_pakd.adb | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/exp_pakd.adb b/gcc/ada/exp_pakd.adb
index c3908a54538..ad12aec1e23 100644
--- a/gcc/ada/exp_pakd.adb
+++ b/gcc/ada/exp_pakd.adb
@@ -2112,8 +2112,8 @@ package body Exp_Pakd is
 
       --  We build up an expression serially that has the form
 
-      --    linear-subscript * component_size       for each array reference
-      --      +  field'Bit_Position                 for each record field
+      --    linear-subscript * component_size     for each array component ref
+      --      +  pref.component'Bit_Position      for each record component ref
       --      +  ...
 
       loop
@@ -2135,7 +2135,7 @@ package body Exp_Pakd is
          elsif Nkind (Base) = N_Selected_Component then
             Term :=
               Make_Attribute_Reference (Loc,
-                Prefix         => Selector_Name (Base),
+                Prefix         => Base,
                 Attribute_Name => Name_Bit_Position);
 
          else
-- 
2.42.0