-Warray-bounds breaks bootstrap on i686-linux

[François-Xavier Coudert]

The Fortran front-end fails to build (breaking bootstrap) on i686- 
linux for revision 120949, due to the -Warray-bounds patch at -O2. I  
believe it to be legal:

$ cat a.i
typedef struct gfc_namespace
{
   int default_type[26];
}
gfc_namespace;

void gfc_get_namespace (gfc_namespace *ns)
{
   int i, *ts;

   for (i = 'a'; i <= 'b'; i++)
     {
       ts = &ns->default_type[i - 'a'];
       *ts = ns->default_type[0];
     }
}
$ /home/fxcoudert/svn/debug3/ibin/./prev-gcc/xgcc -B/home/fxcoudert/ 
svn/debug3/ibin/./prev-gcc/ -B/home/fxcoudert/svn/debug3/irun/i686-pc- 
linux-gnu/bin/ -c -O2 -W -Wall a.i
a.i: In function ‘gfc_get_namespace’:
a.i:13: warning: array subscript is above array bounds