[Bug middle-end/37135] [4.3/4.4 Regression] code size increase for bit-fields assignment

["jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from jakub at gcc dot gnu dot org  2008-11-21 15:29 -------
4.4 compiles this (at least at -O2) into:
        movb    $70, conf
        movb    $-78, conf+1
        movb    $83, conf+2
        movb    $80, conf+3
so this looks then as a dup of PR22141.  Testcase without the unnecessary
enum etc.:
union U
{
  struct
  {
    unsigned f1 : 4;
    unsigned f2 : 4;
    unsigned f3 : 4;
    unsigned f4 : 4;
    unsigned f5 : 4;
    unsigned f6 : 4;
    unsigned f7 : 4;
    unsigned f8 : 4;
  } f;
  unsigned g;
} u;

const union U def = { .f = { .f1 = 6, .f2 = 4, .f3 = 2, .f4 = 11,
     .f5 = 3, .f6 = 5, .f7 = 0, .f8 = 5 } };

void fn1 (void)
{
  u = def;
}

void fn3 (union U *);
void fn2 (void)
{
  union U v = def;
  fn3 (&v);
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37135