BIB merge Ada regression

[Laurent Guerby <guerby at acm dot org>]

I updated just after the merge and reran ACATS and got (only :) three 
regressions
(cxa4026,27,30) from just before the merge on x86/linux. It turns
out to be a -O2 miscompilation of Ada.Strings.Search.Index that
can be reduced to the simple source code below.

$ gnatmake -O2 toto.adb
$ ./toto

raised STORAGE_ERROR : stack overflow (or erroneous memory access)
$

(GNAT blurb for  SIGSEGV.)

It works (no crash) at -O0 and -O1, and with a previous build at all 
optimization levels.

Unfortunately I have no working GCC 3.3/4 debugger yet so I can't go
much further right now.

--
Laurent Guerby <guerby@acm.org>

-- reduced from cxa4026
package Toto_P is

   type Character_Mapping_Function is
      access function (From : in Character) return Character;

   function Map_To_Lower_Case (From : Character) return Character;

end Toto_p;

package body Toto_P is

   function Map_To_Lower_Case (From : Character) return Character is
   begin
      return From;
   end Map_To_Lower_Case;

end Toto_p;

with Toto_P; use Toto_P;
procedure Toto is

   function Index2 (Mapping  : in Character_Mapping_Function) return 
Natural is
   begin
      if Mapping.all ('a') = 'a' then
         return 1;
      else
         return 0;
      end if;
   end Index2;

   Map_To_Lower_Case_Ptr : Character_Mapping_Function := 
Map_To_Lower_Case'Access;
   X : Natural := Index2 (Mapping => Map_To_Lower_Case_Ptr);
begin
   null;
end Toto;