[COMMITTED] ada: Fix internal error on misaligned component with variable nominal size

["Marc Poulhiès" <poulhies@adacore.com>]

From: Eric Botcazou <ebotcazou@adacore.com>

The back-end cannot handle this kind of components even when they are small.

gcc/ada/

	* exp_util.adb (Component_May_Be_Bit_Aligned): Do not return false
	for a small component of a record type with a variant part.

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

---
 gcc/ada/exp_util.adb | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/exp_util.adb b/gcc/ada/exp_util.adb
index b2542d4ae59..2e6a1cf892e 100644
--- a/gcc/ada/exp_util.adb
+++ b/gcc/ada/exp_util.adb
@@ -4989,12 +4989,15 @@ package body Exp_Util is
          return False;
 
       --  If we know that we have a small (at most the maximum integer size)
-      --  record or bit-packed array, then everything is fine, since the back
-      --  end can handle these cases correctly, except if a slice is involved.
+      --  bit-packed array or record without variant part, then everything is
+      --  fine, since the back end can handle these cases correctly, except if
+      --  a slice is involved.
 
       elsif Known_Esize (Comp)
         and then Esize (Comp) <= System_Max_Integer_Size
-        and then (Is_Record_Type (UT) or else Is_Bit_Packed_Array (UT))
+        and then (Is_Bit_Packed_Array (UT)
+                   or else (Is_Record_Type (UT)
+                             and then not Has_Variant_Part (UT)))
         and then not For_Slice
       then
          return False;
-- 
2.40.0